BE728112A - - Google Patents

Description

  

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  "Catalysts, their preparation and their use"

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The present invention relates to novel solid catalysts formed by ss-strontium nickel phosphate or strontium nickel pyrophosphate, or mixtures thereof, which are dehydrogenation catalysts, the invention also relating to the preparation of these catalysts.



   The present invention also relates to an improved process for the production of aliphatic conjugated diolefins by dehydrogenation of saturated and olefinically unsaturated hydrocarbons, containing 4 or more carbon atoms in the chain of the molecule, without excessive cracking or other decomposition of the hydrocarbons. carbides. The invention also relates to the dehydrogenation of alkyl aromatics to produce alkenyl aromatics, wherein the alkenyl double bond is conjugated with the unsaturation of the aromatic ring. The dehydrogenation can be carried out in the presence or absence of oxygen and a halogen.



   Processes are known for the dehydrogenation of butene to butadiene, isopentene to isoprene, and ethylbenzene to styrene. The increased demands in the industry for synthetic rubbers and other products prepared from these diolefins have increased the importance of research to find new processes and / or novel catalysts for the production. production of these diolefins. One of the most well-known industrial processes for the production of these diolefins is a dehydrogenation process in which C4-C6 olefins are converted to C4-C diolefins in the presence of a calcium nickel phosphate catalyst.

   This process requires the presence of substantial proportions of water vapor and the periodic regeneration of the catalyst in the presence of water vapor and air. The calcium nickel phosphate catalyst and the processes for its use in chemical reactions. dehydrogenation are described in US Patents 2,442,319 and 2,442,320 issued May 25, 1948 to Britton et al., Patent Nos. 2,456,367 and 2,456,368 issued December 14, 1948 to Britton and also, Patent 2,542,813 issued February 20, 1951 to Heath, and Patent 2,616,081 issued December 10, 1957 to Heath et al.

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   The usual industrial process for the production of butadiene presupposes the use of the characteristics of these patents. More particularly, the industrial process involves passing a stream of normal butylenes and large amounts of water vapor, usually 15 to 20 volumes of water vapor per volume of the hydrocarbons, through a chamber containing a vapor. bed of calcium nickel phosphate catalyst, and maintaining the temperature in this chamber at about 550 to 750 ° C. The mixed vapor effluent, containing the desired diene, is cooled and the unconsumed butylene is separated. , by-products and other impurities Unconsumed butylene, separated from by-products and other impurities, is recycled to the process.



   During use in the dehydrogenation reaction, the calcium nickel phosphate catalyst gradually accumulates small amounts of carbon or non-volatile carbonaceous materials and becomes less selective as a dehydrogenation catalyst. If these carbonaceous deposits are left on the catalyst surface, they lead to accelerated and excessive deposition of carbon, and possibly the formation of a carbon "backfill" in the catalyst bed. Accordingly, the flow of the hydrocarbons is periodically interrupted and the gaseous hydrocarbons are purged from the catalyst bed using water vapor.

   After purging, an oxygen-containing regeneration gas (usually air, although c2 is sometimes used) is fed to the bed along with superheated steam, usually. in a volumetric ratio that providing approximately 1 part of air to 6 parts of water vapor. The regeneration cycle is of an appropriate duration for the oxidation of the carbonaceous deposits and for the return of the catalyst to its first selective activity. The flow of the oxygen-containing gas is then stopped, the catalyst bed is purged with water vapor to rid it of the oxygen-containing gas, and the bed is fed again. of catalyst the starting material containing the olefins, in admixture with superheated steam.



   The operations described above define a current operating cycle, namely: (1) a "process" period, during which the reaction mixture of water vapor and hy-

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 hydrocarbons containing olefins pass through the bed, (2) a "purge" period, during which the gaseous hydrocarbons are separated from the bed by passing only water vapor through it, (3) a "regeneration" period, during which any carbonaceous deposits are removed by combustion with a mixture of water vapor and air or other oxygen-containing gas, and (4) a second period "purge", in which water vapor alone is fed to the bed to remove air or O2 therefrom.



   After many such cycles of operation, the above-mentioned calcium nickel phosphate catalysts gradually lose their catalytic activity for the conversion of olefins to diolefins. In industrial practice, this drop in activity is compensated for by an increase in the temperature of the reacting gases. This production maintenance technique contributes to a decline in catalytic activity and catalyst potency.

   Eventually, the useful life of the catalyst comes to an end, usually with the sudden formation of a carbon backfill which cannot be removed by combustion during the regeneration period and which rapidly grows in the bed, to dimensions. such that a continuation of the operation is impracticable, with the necessary shutdown of the installation. '
Excessive carbon build-up during the later stages of catalyst life, under normal cyclic operation, may result in part from the increased cracking of the hydrocarbons as the temperature is increased to maintain the activity, and may also be partly due to the dust particle effect of the catalyst.

   Such dust can arise from frictional wear and abrasion of the bed of pellets, when large volumes of circulation are suddenly stopped, for example during the switching operations necessary to switch from the "process" period to the process. regeneration period.



   The general use of large volumes of water vapor per volume of hydrocarbon fed during the process results in the production of certain undesirable compounds, such as, for example, carbon monoxide, carbon dioxide, l acetone and methyl ethyl ketone. It is believed that ketones

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 are produced by the reaction of acetylene olefins with water. These ketones must be separated by a separate extraction phase to give a usable butadiene product.



   The undesirable characteristics described above have been overcome by the present invention which relates to the planning, preparation and use of novel catalyst materials containing strontium, nickel and the phosphate radical, the latter. also including the pyrophosphate radical.



  The catalyst is prepared by co-precipitation of a product comprising strontium and nickel atoms chemically combined with the phosphate radical. Strontium nickel phosphates have a ratio of from about 2 to about 20 atoms of strontium per atom of nickel, and from 1 to about 2 atoms of strontium and nickel, in combination, per atom of phosphorus.



   Freshly precipitated strontium nickel phosphates are believed to be amorphous because they do not give an X-ray diffraction pattern.



   When dried at 100-300 C, strontium nickel phosphates, having the atomic ratios defined above, are light, tan-colored materials which show three new patterns of powder on X-rays. The degree of crystallization - nity at this stage depends partially on the temperature and the drying time. Three new phases of the dried material were differentiated by examination of the powder diagrams
One of the crystalline phases of the dried powder was referred to as P-strontium nickel phosphate, because of its isostructural relationship with Whitlockite or ss (Ca) 3 (PO4) 2 The following Table I gives values for ss-strontium nickel phosphate.



   TABLE I X-ray powder diffraction result for ss-strcntium nickel phosphate
 EMI5.1
 
<tb> d <SEP> 1/11 <SEP> (hkl)
<tb> 8.5 <SEP> 5 <SEP> 110 <SEP>
<tb>
<tb> 6.7 <SEP> 8 <SEP> 211
<tb>
<tb> 5.3 <SEP> 25 <SEP> 101
<tb>
<tb> 4.48 <SEP> 10 <SEP> 200
<tb>
<tb> 3.59 <SEP> 25 <SEP> 433
<tb>
 

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 TABLE I (continued)
 EMI6.1
 
<tb> d <SEP> I / I1 <SEP> (hk1)
<tb>
<tb>
<tb>
<tb> 3.41 <SEP> 15 <SEP> 213
<tb>
<tb>
<tb>
<tb>
<tb> 3.35 <SEP> 5 <SEP> 432.422
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 3.27 <SEP> 30 <SEP> 310
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 3.06 <SEP> 10 <SEP> 211
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.97 <SEP> 100 <SEP> = <SEP> Il <SEP> 442, <SEP> 421
<tb>
<tb>
<tb>
<tb>
<tb> 2.83 <SEP> 13 <SEP> 431
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.78 <SEP> 13 <SEP> 411, <SEP> 330,

  543
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 65 <SEP> 63 <SEP> 202
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.59 <SEP> 10 <SEP> 311
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.45 <SEP> 5 <SEP> 321, <SEP> 420
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.36 <SEP> 5 <SEP> 654
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.23 <SEP> 20 <SEP> 633, <SEP> 552, <SEP> 400
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.17 <SEP> 10 <SEP> 664
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2,08 <SEP> 20 <SEP> 632,440
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2.05 <SEP> 15 <SEP> 411.642
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.98 <SEP> 30 <SEP> 622.322, <SEP> 601
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.93 <SEP> 20 <SEP> 776, <SEP> 530
<tb>
<tb>
<tb>
<tb>
<tb> 1.91 <SEP> 15 <SEP> 510
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.85 <SEP> 13 <SEP> 631
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.83 <SEP> 13 <SEP> 223,

  733
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.80 <SEP> 30 <SEP> 332
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.76 <SEP> 15 <SEP> 303, <SEP> 763
<tb>
 In this table and in the following tables giving X-ray diffraction results, d represents the distance between the planes of atoms in the crystal structure, this distance being measured in Angstrom units. These distances are calculated using the well-known Braggs formula n # = 2d sin 0. I / I1 represents the relative intensity of a particular line in the diagram, based on a value of 100 for the most intense line, and hkl are the Miller indices of the lines. Ss-strontium nickel phosphates are not isostructurally related to (Sr) 3 (PO4) 2 because the form 13 of the latter compound is not known.

   This fact is taken as evidence that nickel atoms occupy locations in the crystal lattice, and that strontium p-nickel phosphates actually form a mixed metal phosphate. The

 <Desc / Clms Page number 7>

 
 EMI7.1
 j3-strontium nickel phosphates, {Sr] 3 (normal P04'2 and - ss (Ca) 2 (PO4) 2 all have rhombohedral structures. The lattice constants referred to their respective hexagonal structural units are given. below:

   a c
 EMI7.2
 ! 3 (ca) 3 (P04) 2 10, 43 A 37. 4 A p-strontium phosphate nickel la, 56 "39.5 (Sr) 3 (P04) 2 5.39 19.77
A second crystalline phase new to the dried material is believed to be an acidic nickel strontium phosphate, the structure of which does not correlate with that of any known strontium phosphate. This structure is favored by low temperature precipitation.

   The X-ray powder diagram is given in Table II below;
TABLE II X-ray powder diffraction results for Sr - Ni acid phosphate of unknown structure
 EMI7.3
 
<tb> d <SEP> I / I1
<tb> 9.2 <SEP> 5
<tb>
<tb> 5.8 <SEP> 10
<tb>
<tb> '<SEP> 4.56 <SEP> 25
<tb>
<tb> 4.15 <SEP> 4
<tb>
<tb> 3.96 <SEP> 5
<tb>
<tb> 3.74 <SEP> 100
<tb>
<tb> 3.61 <SEP> 8
<tb>
<tb> 3.36 <SEP> 40
<tb>
<tb> 3,25 <SEP> 50
<tb>
<tb> 3.13 <SEP> 40
<tb>
<tb> 3.02 <SEP> 8
<tb>
<tb> 2.88 <SEP> 40
<tb>
<tb> 2.70 <SEP> 15
<tb>
<tb> 2.62 <SEP> 20
<tb>
<tb> 2.59 <SEP> 6
<tb>
<tb> 2.46 <SEP> 10
<tb>
<tb> 2.45 <SEP> 4
<tb>
<tb> 2.39 <SEP> 5
<tb>
<tb> 2.33 <SEP> 25
<tb>
<tb> 2.27 <SEP> 40
<tb>
<tb> 2.22 <SEP> 20
<tb>
 

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 TABLE 11 (continued)
 EMI8.1
 1-, 1 1 a '. ;

  > l / Ii 1 "
 EMI8.2
 
<tb> 2.19 <SEP> 20
<tb>
<tb> 2.12 <SEP> 5
<tb>
<tb>
<tb> 2.10 <SEP> 5
<tb>
<tb>
<tb>
<tb> 2.04 <SEP> 18
<tb>
<tb>
<tb> 2.03 <SEP> 15
<tb>
<tb>
<tb> 1.94 <SEP> 40
<tb>
<tb>
<tb> 1.90 <SEP> 10
<tb>
<tb>
<tb> 1.86 <SEP> 30
<tb>
<tb>
<tb> 1.84 <SEP> 10
<tb>
<tb> 1.82 <SEP> 6
<tb>
<tb>
<tb>
<tb> 1,805 <SEP> 8
<tb>
<tb>
<tb> 1.78 <SEP> 25 <SEP> - <SEP>
<tb>
<tb>
<tb> 1,735 <SEP> 6
<tb>
<tb>
<tb> 1.69 <SEP> 20
<tb>
 
The third X-ray diffraction pattern occurs most frequently in dried precipitates formed at elevated temperatures. This crystalline phase is believed to be α-strontium nickel acid phosphate. The X-ray powder diagram is defined in the following Table III.



   TABLE III X-ray powder diffraction results for a structure defined as α-strontium nickel acid phosphate
 EMI8.3
 
<tb> d <SEP> I / I1
<tb>
<tb> 7.0 <SEP> 8.0
<tb>
<tb>
<tb> 5.05 <SEP> 8.0
<tb>
<tb>
<tb> 4.84 <SEP> 5.3
<tb>
<tb>
<tb> 4, <SEP> 68 <SEP> 5.3
<tb>
<tb>
<tb> 4.50 <SEP> 5.3
<tb>
<tb>
<tb> 4.40 <SEP> 5.3
<tb>
<tb>
<tb> 4.25 <SEP> 8.0
<tb>
<tb>
<tb> 3.75 <SEP> 8.0
<tb>
<tb>
<tb> 3.48 <SEP> 100.0 <SEP> = <SEP> I1
<tb>
<tb>
<tb> 3.38 <SEP> 8.0
<tb>
<tb> 3.19 <SEP> 13.3
<tb>
<tb>
<tb> 3.02 <SEP> 80.0
<tb>
<tb>
<tb>
<tb> 2.98 <SEP> 33.3
<tb>
 

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 TABLE III (continued).
 EMI9.1
 z = -¯ Id - 'ii, 1 7 ¯ <-, 1 / fi = .Î "-
 EMI9.2
 
<tb> 2.84 <SEP> 40.0
<tb>
<tb>
<tb>
<tb> 2.61 <SEP> 20.0
<tb>
<tb>
<tb>
<tb> 2.52 <SEP> 26.7
<tb>
<tb>
<tb>
<tb>
<tb> 2,

  33 <SEP> 13.3
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 22 <SEP> 8.0
<tb>
<tb>
<tb>
<tb> 2, <SEP> 24 <SEP> 13.3
<tb>
<tb>
<tb>
<tb>
<tb> 2.18 <SEP> 13.3
<tb>
<tb>
<tb>
<tb>
<tb> 2.12 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 2.05 <SEP> 16.0
<tb>
<tb>
<tb>
<tb>
<tb> 1.97 <SEP> 26.7
<tb>
<tb>
<tb>
<tb>
<tb> 1.91 <SEP> 8.0
<tb>
<tb>
<tb>
<tb>
<tb> 1.88 <SEP> la, 7
<tb>
<tb>
<tb>
<tb>
<tb> 1.85 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.82 <SEP> 5.3
<tb>
<tb>
<tb>
<tb> 1.80 <SEP> 20.0
<tb>
<tb>
<tb>
<tb>
<tb> 1.79 <SEP> 8.0
<tb>
<tb>
<tb>
<tb>
<tb> 1.76 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.73 <SEP> 20.0
<tb>
<tb>
<tb>
<tb>
<tb> 1.70 <SEP> 13.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.64 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.60 <SEP> 13.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.54 <SEP> 10.7
<tb>
<tb>
<tb>
<tb> 1.49 <SEP> 8
<tb>
<tb>
<tb>
<tb>
<tb> 1,

  43 <SEP> 10.7
<tb>
<tb>
<tb>
<tb>
<tb> 1.41 <SEP> 10.7
<tb>
<tb>
<tb>
<tb>
<tb> 1.35 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.32 <SEP> 8
<tb>
<tb>
<tb>
<tb>
<tb> 1.30 <SEP> 5.3
<tb>
<tb>
<tb>
<tb> 1.23 <SEP> 8
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 1.21 <SEP> 5.3
<tb>
<tb>
<tb>
<tb> 1.20 <SEP> 5.3
<tb>
<tb>
<tb>
<tb>
<tb> 1.185 <SEP> 10.7
<tb>
 Dried strontium nickel phosphates, prepared by the methods defined below, appeared to be either mainly of the unknown structure defined by the results of Table II, or of the structure of ss-strontium phosphate.

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 nickel of Table I, or of a structure corresponding to mixtures of the two preceding structures.



   The exact structure of all crystal states of dried matter has not been determined. The crystals, when present, can be of any of the three forms described in Tables I, II and III or of a form corresponding to mixtures of the three crystalline states.



   After roasting in steam and air at 450-750 or in a muffle furnace at correspon- ding temperatures, the previous unknown structure of strontium nickel acid phosphate is apparently converted into yet another ma- A new crystalline strontium nickel phosphate, which is isostructural to strontium pyrophosphate. The {3-strontium nickel phosphate in the powder appears to remain of an unaltered crystal structure after roasting. The material which is roasted is very crystalline and it is probable that all phases actually present in concentrations of about 5% or more are detectable by the X-ray diffraction technique.



  The catalytic materials of the present invention, when roasted at 550-750 ° C., give either nickel s-strontium phosphate or nickel strontium pyrophosphate or mixtures of the two crystalline phosphates.



   The X-ray powder diffraction results for strontium nickel pyrophosphate, which is probably produced by converting at least some of the acid phosphates of Tables II and III, are given in the following Table IV,
TABLE IV X-ray powder diffraction result for strontium nickel pyrophosphate
 EMI10.1
 
<tb> d <SEP> ¯¯¯¯ <SEP> I / I1
<tb>
<tb> 5.32 <SEP> 12 <SEP>
<tb>
<tb>
<tb>
<tb> 4.90 <SEP> 15
<tb>
<tb>
<tb>
<tb> 4.20 <SEP> 10
<tb>
<tb>
<tb>
<tb> 3.61 <SEP> 10
<tb>
<tb>
<tb> 3.54 <SEP> 10
<tb>
<tb>
<tb>
<tb> 3.46 <SEP> 42
<tb>
<tb>
<tb>
<tb> 3.43 <SEP> 41
<tb>
<tb>
<tb>
<tb> 3.34 <SEP> 41
<tb>
 

 <Desc / Clms Page number 11>

   TAB @ WATER IV (continued)
 EMI11.1
 . '¯ ¯s, - ..

   ¯ ¯ illl -
 EMI11.2
 
<tb> 3.28 <SEP> 8
<tb>
<tb>
<tb>
<tb> 3.10 <SEP> 100
<tb>
<tb>
<tb>
<tb>
<tb> 3.07 <SEP> 41
<tb>
<tb>
<tb>
<tb>
<tb> 3.00 <SEP> 16
<tb>
<tb>
<tb>
<tb>
<tb> 2.98 <SEP> 25
<tb>
<tb>
<tb>
<tb> 2.90 <SEP> 16
<tb>
<tb>
<tb>
<tb>
<tb> 2.87 <SEP> 13
<tb>
<tb>
<tb>
<tb>
<tb> 2.84 <SEP> 12
<tb>
<tb>
<tb>
<tb>
<tb> 2.77 <SEP> 9 <SEP>
<tb>
<tb>
<tb>
<tb>
<tb> 2.65 <SEP> 24
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 63 <SEP> 10
<tb>
<tb>
<tb>
<tb>
<tb> 2.43 <SEP> 14
<tb>
<tb>
<tb>
<tb>
<tb> 2.40 <SEP> 6
<tb>
<tb>
<tb>
<tb>
<tb> 2.31 <SEP> 15
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 26 <SEP> 8
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 22 <SEP> 6
<tb>
<tb>
<tb>
<tb> 2.18 <SEP> 15
<tb>
<tb>
<tb>
<tb>
<tb> 2.16 <SEP> 22
<tb>
<tb>
<tb>
<tb>
<tb> 2, <SEP> 06 <SEP> 22
<tb>
<tb>
<tb>
<tb>
<tb> 2,

  01 <SEP> 19
<tb>
<tb>
<tb>
<tb>
<tb> 1.92 <SEP> 13
<tb>
 
The general process for making the catalyst is to mix the materials containing strontium, nickel and phsophate in aqueous media in the proportions required to ensure the desired ratio of strontium to nickel, as well as of the combined metals and phosphorus while maintaining the general pH of the reaction system in the range of about 5.0 to about 9.5.



   Particular processes for the preparation of the catalyst are mentioned below.



   One method involves feeding a stream containing a mixture of water soluble nickel and strontium salts and another stream containing an alkaline phosphate, such as ammonium phosphate, to a reactor or precipitator. tation in such amounts that the pH is maintained at the desired value. Another preferred method involves feeding a

 <Desc / Clms Page number 12>

 aqueous solution comprising the required proportions of a strontium compound, a compound of nickel and phosphoric acid, in a reactor as a stream, together with the supply of gaseous or aqueous ammonia as a second current, each current being supplied at such a rate that the desired overall pH of the mixture is maintained.

   Still another preferred method comprises mixing a solution or paste of strontium hydroxide with a solution of a nickel compound in aqueous phosphoric acid, in a reactor, in the amounts necessary to maintain the ratios. defined metal / metal and metal / phosphorus, and also to maintain the overall pH of the mixture at 5.0-9.5. Another process assumes the supply of separate streams of the reactants in quantities suitable for maintaining the proportions of Sr, Ni and P within the limits defined above, and the maintenance of the pH at a value as defined previously, with a material - re alkaline which is preferably NH3 or strontium hydroxide.

   Another method comprises feeding an aqueous solution having the desired ratio of strontium and nickel salts and comprising phosphoric acid, to an aqueous solution of ammonium hydroxide or to an aqueous solution of ammonium hydroxide. amine, until the required pH is reached. Yet another method comprises feeding an aqueous solution comprising the requisite proportion of strontium and nickel salts to a solution of diammonium phosphate until the required pH is reached, or else 1. reverse feeding, that is, feeding the solution of diammonium phosphate to a solution containing the salts of strontium and nickel.



   Strontium nickel phosphate readily forms a flocculating precipitate. The precipitate is separated by known means, for example by filtration, decantation or centrifugation, it is optionally washed and again separated and dried. The dried material is then ground to the required fineness, usually so that such material passes through a 12 mesh screen. The granules obtained are preferably mixed with a small amount of lubricant (1 to 5%). for example graphite, then processed into pellets and roasted. If desired, these granules can be roasted without turning them into pellets.



     - The starting materials that can be used for

 <Desc / Clms Page number 13>

 preparing the catalysts are the water-soluble salts of strontium, for example chloride, bromide, iodide, nitrate, formate, acetate or propionate, strontium compounds which dissolve in aqueous phosphoric acid, for example oxide, bicarbonate or carbonate, or strontium hydroxide in solution or in the form of a paste.



   The salts or compounds of nickel which can be used are bromide, chloride, iodide, nickel nitrate, nickel and ammonium phosphates, or other nickel phosphates, as well as nickel. metallic nickel or compounds which dissolve in aqueous phosphoric acid, for example oxide, bicarbonate, basic carbonate or ordinary carbonate. Solutions of metallic nickel or compounds thereof, which are soluble in aqueous phosphoric acid, are of particular interest for the second and third process mentioned above.



   The source of the phosphate radical can be ortho-phosphoric acid or a phosphoric acid which is totally or partially neutralized with an alkali metal oxide, hydroxide, bicarbonate or carbonate (eg sodium, potassium) or with ammonia or an amine. Suitable water soluble amines are dimethylamine, trimethylamine, ethylamine, diethylamine or triethylamine.



   The catalysts prepared by the processes described above, after roasting at 450-750 C, are very crystalline and contain 0 to 100% nickel ss-strontium phosphate and 0 to 100% nickel strontium pyrophosphate, or mixtures of these two structures.



   The ratio of the sum of nickel and strontium atoms per phosphorus atom is preferably maintained in the range of 1 to 1.65 in the feed streams.



  The strontium / nickel ratio in the feed streams must also be controlled, otherwise the resulting precipitate will not show sufficient catalytic activity for dehydrogenation. If the strontium / nickel ratio in the feed is less than 2/1 or more than 12/1, the catalytic activity decreases somewhat.

   Likewise, the pH of the mixture from which the catalyst precipitates should be controlled, even with the ratio

 <Desc / Clms Page number 14>

 appropriate strontium / nickel and the appropriate ratio of strontium and nickel to phosphorus atoms, a pH significantly below 5.0 or above 9.5 can markedly change the ratio of strontium and nickel to phosphorus atoms in the precipitate. - T of phosphate and thus produce a catalyst of a composition and an activity which differs from what is desired.



   The starting materials, when fed to the reaction chamber, should preferably contain water in an amount such that the paste which forms contains less than 5% by weight, usually less than 2% by weight, of precipitated flocculant nickel strontium phosphate produced. The use of large proportions of water is advantageous because it allows easier and more precise control of the pH value of the reaction mixture than is possible when the reagents are used in a reaction stage. higher concentration.

   However, the reagents can be used in a more concentrated form, if desired:
A preferred method of producing the strontium nickel phosphate catalyst is hereinafter described by considering a mode of continuously forming the catalytic material, employing, as starting materials, gaseous ammonia and solution. aqueous phosphoric acid and strontium and nickel salts, in the relative proportions recommended above and in concentrations slightly lower than those which would give direct precipitation of a metal salt from the solution containing the acid phosphoric. The aqueous solution of phosphoric acid and strontium and n-ckel salts is passed through a stream of water at such a rate that it is diluted with 20 to 40 times its volume of water.

   The resulting diluted solution is fed to a reservoir or other reaction vessel.



  Simultaneously with the introduction of the solution of phosphoric acid and of metallic salts into the tank, gaseous ammonia is introduced therein at a point away from the point of supply of the solution of phosphoric acid and of metallic salts. , and this in an amount suitable for neutralizing the acid with the formation of a mixture having an overall pH value of between 5.0 and 7.5.



  Using well known flow control devices, the flow rates of either or both starting materials can be automatically controlled so as to maintain the flow rate.

 <Desc / Clms Page number 15>

 mixture at a substantially constant pH value.



   When strontium hydroxide is used as an ingredient in the form of a paste or in solution in water, the pH range over which the catalysts can be prepared will vary from 5.0 to 9.5. preferably 7.5 to 9.0.



   The preferred method of preparing the catalyst with strontium hydroxide is to feed into the reactor an aqueous solution or paste of the hydroxide as a stream, and an aqueous solution of the ingredient of nickel. and phosphoric acid as a second stream, while maintaining the overall pH of the reaction within the specified range.



  Another method which can be used is to feed the aqueous solution of the ingredient nickel and phosphoric acid to the strontium hydroxide solution or paste, or alternatively the paste can be fed to the aqueous solution of the strontium hydroxide. ingredient nic- kel and phosphoric acid.



   In accordance with any one of these methods, strontium nickel phosphate is precipitated as a flocculant which is kept in suspension by vigorous stirring.



  As soon as the process has started, that is to say as soon as a paste of flocculating material is formed, precipitation develops in the presence of the nickel strontium phosphate paste or in the presence of the paste of nickel strontium phosphate. strontium hydroxide.



   The starting materials are continuously fed into the reaction vessel causing the flocculant paste to overflow out of the chamber, for example through an overflow line. The overflowing material can be fed directly to a filter but it is preferably passed through a settling tank where the strontium nickel phosphate settles very quickly to form a lower layer which usually occupies 5 to 15%. the volume of dough fed to the tank. In the absence of agitation, the deposit is practically complete after standing for 5 to 30 minutes.

   The use of a settling tank allows the use of the latter as a storage tank for the material, as well as for the mixture of all the insoluble nickel strontium phosphate, produced over a period of one day or over a longer period, so as to obtain a large quantity of product

 <Desc / Clms Page number 16>

 of essentially uniform quality as a whole. The clear supernatant liquid which forms is separated from the relatively dense strontium nickel phosphate paste or slurry precipitated by decantation, and this paste is fed to the filter.



   The filter cake or paste is washed with water to separate soluble impurities. The dense paste obtained as a filter cake usually contains 15 to 30% by weight of precipitated strontium nickel phosphate, the remainder being water. At this point, the precipitate is arently amorphous.



   The filter cake is preferably dried by heating, for example at temperatures of 100 to 400 ° C., until it is substantially free from water. The dried product can be broken up or ground to powder form and used as it is as a catalyst, or it can be mixed, which is preferred, with a lubricant, such as graphite or carbon. bydro-carbon oil, and then compress it into pellets. Frequently, prior to compression of the pelletized material, a small amount (0.2-10% by weight) of chromic oxide (Cr2O3) is mixed therein as a catalytic activator.



  Another method of preparing the catalyst uses an alkaline ammonium phosphate solution which may contain excess ammonia, as one of the streams, and an aqueous solution of strontium and nickel salts (in corresponding proportions. latives corresponding to 2-20 strontium atoms, preferably 3-9 per nickel atom) in the form of the other stream, and the feeding of these two streams into the reaction chamber at relative rates such as the resulting mixture is maintained at pH values of 5.0-7.5.



   Other methods of obtaining the strontium nickel phosphate precipitate are the various batch processes in which one of the feed streams is added directly to a stirred amount of the other. Thus, an aqueous solution of strontium and nickel salts in the proportions defined, together with the phosphoric acid necessary for the precipitation, can be added separately or together with an aqueous solution of. ammonium hydroxide or other base. This addition is stopped when the stoichiometric amounts have been mixed or when the pH of the mixture falls into

 <Desc / Clms Page number 17>

 the range of 5.0 to 7.5.

   Alternatively, the reverse method of addition can be used, whereby ammonium hydroxide solution or other base is added to the phosphoric acid solution containing the strontium and nickel salts. If desired, a phosphoric acid solution of a nickel compound can be added to a strontium hydroxide solution or paste or vice versa. It will be understood that the various starting materials described above are also applicable to each of these batch processes for preparing the catalyst.



  Anything previously contemplated for filtration, washing, drying, etc. can also be used for these process variants.



   The temperature at which the precipitation takes place is not critical and can conveniently be in the range of 0 to 40 ° C, but the temperature is preferably maintained at around ambient conditions.



   Although strontium nickel phosphate obtained in the above manner can be used directly as a catalyst in the dehydrogenation process, when it has been dried, it is preferably mixed with a small amount of graphite or d. 'another separable lubricant, before compressing it into pellets of a more suitable size and shape, for example pellets of approximately cylindrical shape with a diameter of 0.48 cm over a length of. 0.48 cm. In such preparation it should be understood that before the pellet catalyst reaches suitable industrial activity, the binder or lubricant must be separated.

   This is usually accomplished by heating the pellets in a mixture of vapor water and air to a temperature of 450 to 750 ° C to oxidize and separate the binder.



   In the presence of water vapor, the strontium nickel phosphate catalysts thus prepared and roasted, whether in granular form or in the form of pellets, are effective in catalyzing the dehydrogenation of alkyl aromatic hydrocarbons in ss-alkenyl aromatic hydrocarbons, and C4-C6 monoolefins having at least 4 carbon atoms in a chain of the corresponding diolefins. These catalysts are more particularly effective in catalyzing dehydrogenation.

 <Desc / Clms Page number 18>

 nation of ethylbenzene to styrene, n-butylenes to butadiene-1,3, isopentenes to isoprene, and 2,3-dimethyl butenes to 2,3-dimethyl butadiene-1,3.

   These catalysts, in the presence of steam, a source of bromine and a source of molecular oxygen, are capable of continuously dehydrogenating the mono-olefins described above into their corresponding dienes and they are in further capable of dehydrogenating ethyl benzene to styrene and C4-C6 alkanes having at least 4 carbon atoms in a chain, into a mixture of dienes and mono-olefins of the same number of carbon atoms as in the alkane starting point. This is how n-butane is converted to a mixture of n-butylene and butadiene-1,3, 2-methyl butane is converted to a mixture of isoprene and isopentenes, and the 2, 3-dimethyl butane is converted to a mixture of 2,3-dimethyl butadiene-1,3 and 2,3-dimethyl butenes.



   The process for carrying out such dehydrogenation using the strontium nickel phosphate catalyst is generally similar to the prior art processes, in particular to the processes using calcium nickel phosphate catalysts, but with the following exceptions.
1 the proportion of water vapor, when the catalyst of the present invention is used, can be greatly reduced from 20 to 40 volumes of vapor per volume of hydrocarbons which is used in the case of a catalyst of the prior art-,
2 the fraction of the total cycle time which is required for the regeneration phase when the catalyst of the present invention is employed,

   is greatly reduced compared to the fraction of time required with the usual calcium nickel phosphate catalyst;
3 the space velocity of water vapor, which is required during regeneration and which is expressed in volumes of water vapor per volume of catalyst per hour, can be significantly reduced;
The carbonyl separation plant required by the process of the present invention is smaller than with common calcium nickel phosphate;
5 the dehydrogenation temperature can be sharp

 <Desc / Clms Page number 19>

 ment higher when using the catalyst of this:

   invention that when using -calcium nickel- phosphate -
The catalyst of the present invention is also suitable for use in a continuous process, in which oxygen and a source of halogen, such as bromine, are also introduced to provide a continuous process. continuously.



   As a result of these advantages, a more economical production of butadiene is obtained, with a remarkable increase in productivity if the same number of reactors is considered.



   In the production of a diolefin according to the invention, the granular or pelletized catalyst is charged into a reaction chamber and the lubricant, if any, is separated from the catalyst by passing air, or preferably a mixture of roughly equal volumes of air and water vapor, through the catalyst bed at an elevated temperature, for example at 450-750 C. When the lubricant used in the preparation of the catalyst granules is a substance capable of being vaporized (for example a mineral or vegetable oil), the phase of treatment of the catalyst with air can be preceded by a phase of passage of a gas inert, such as nitrogen or carbon dioxide, on the catalyst to vaporize at least a portion of the binding agent from the catalyst granules.

   The crystals formed during roasting are so small that they ordinarily cannot be seen even under a microscope, and the crystallization which occurs during heating of the catalyst is not visible to the naked eye.



   After the catalyst has been released from the lubricant, the catalyst bed is steamed to release it from the air and heated to the desired reaction temperature, preferably passing steam through water superheated through this catalyst. A mixture of water vapor and the olefinic reagent (for example, butylene, pentene, hexylene, isopentin or ethyl benzene) is then passed through the catalyst bed at a temperature of between 550 and 750 C,

     preferably between 575 and 700 C The usual method is to mix the gas containing the olefin with water vapor which has been superheated to 750 "C or higher (ie to a sufficient temperature. so that the resulting mixture is found

 <Desc / Clms Page number 20>

 at the desired reaction temperature) and passing this mixture through the catalyst bed. However, heat can be supplied by other methods, for example by forming the mixture of water vapor and hydrocarbon at a lower temperature and passing this mixture through a preheater to bring it to temperature. the desired temperature, or by external heating of the catalyst chamber itself.

   The yield of diolefin is usually highest when 5 to 15 volumes of water vapor per volume of the olefin-containing hydrocarbon are used, but water vapor can be used in high proportions. larger, if desired, for example 20 or more volumes.



  As previously mentioned, the rate of vapor circulation through the catalyst chamber can be varied widely, but in practice this circulation usually corresponds to 100-700 volumes of the olefin (expressed for 0 C and 760 mm pressure) per catalyst bed volume per hour.



   The vapors leaving the catalyst chamber are ordinarily sent to heat exchangers and other cooling devices to condense the water first and then the hydrocarbon products. The concentration of diolefin in the latter depends partially of the concentration of the olefinic reagent in the starting bunker material and it cannot be determined in a definite way. The diolefin product can be separated from the other hydrocarbons by any of the usual methods and the unreacted olefin can then be recycled to the process.



   During use in the process, the catalyst gradually accumulates a small amount of carbon or non-volatile organic material and loses some of its activity. Accordingly, the flow of the starting hydrocarbon material is periodically interrupted and air mixed with water vapor is blown through the catalyst bed, for example at temperatures between 450 and 700 ° C. preferably at a temperature close to the dehydrogenation temperature, to oxidize and separate the carbonaceous material and thereby reactivate the catalyst. Usually the ratio of the treatment time to the regeneration time is from 1/1 to about 5/1.

   At the end of the reactivation phase, we sweep at

 <Desc / Clms Page number 21>

 the catalyst chamber again to release it from the air by employing water vapor and the introduction of an olefin is recommenced at the same time as the water vapor. Usually, it is advisable to provide for reactivation of a catalyst after a period of 5 to 60 minutes of use in the dehydrogenation reaction. In practice, two or more catalyst chambers are used in a system provided with connections to pass the reaction mixture alternately through different catalyst beds. One catalyst bed is used in the dehydrogenation reaction, while another bed is being reactivated.

   By operating in this way, the dehydrogenation reaction can be carried out continuously.



  EXAMPLE 1
A concentrated acidic feed solution is prepared by mixing 34.4 kg of strontium nitrate, 15.7 kg of phosphoric acid (100%) 4.2 kg of nickel chloride and sufficient water to obtain the total 98.3 liters. This concentrate is diluted about 29 times with water to make 2840 liters. Analysis of the diluted solution gives the following 0.060 M / 1 (mole per liter) of Sr ++, 0.012M / 1 of Ni ++ and 0.058 M / 1 of PO4 = This solution is introduced at a rate of approximately 37.8 liters per hour in a stirred precipitation vessel with a capacity of 90.8 liters, which vessel contains water.



  At the same time, ammonia gas is introduced at a rate such that the contents of the vessel are maintained at a pH of about 6.5, and the temperature of the precipitation apparatus is adjusted to 25-27 C. Afterwards that the initial water has been displaced and the precipitation has reached a state of dynamic equilibrium, the overflow paste has a three minute deposit volume of 14-15 ml / 100 ml of paste and an alkalinity soluble (defined by the number of ml of HCl N / 10 required per 100 ml of supernatant liquid filtered to reach the modified methyl orange endpoint) from 5.6 to 6.1 ml. In this way, 5 successive batches were produced, each prepared as described above.

   Each batch is allowed to settle for 20 hours before decanting the clear supernatant liquid layer and filtering the dense paste. The filter cake is washed with water to separate soluble salts. This washed cake is then dried at 150 C for 4 hours

 <Desc / Clms Page number 22>

 and then at 180 C for 26 hours. Each batch is then checked to determine its catalytic activity for the dehydrogenation of n-butene. These five batches have practically all the same activity and are mixed together.

   The resulting material looks as follows on analysis:
 EMI22.1
 
<tb>% <SEP> Sr <SEP> 42.50
<tb>
<tb>% <SEP> Ni <SEP> = <SEP> 6.88
<tb>
<tb>
<tb>
<tb>% <SEP> P04 <SEP> = <SEP> 44.34
<tb>
<tb> Sr / Ni <SEP> = <SEP> 4.14
<tb>
<tb>
<tb>
<tb> Metal / PO4 <SEP> = <SEP> 1.29
<tb>
 
Before the roasting, this material shows, by X-ray diffraction analysis, 25% of strontium nickel acid phosphate, as defined in Table III, 15% of nickel strontium acid phosphate, as defined in Table II, and 60% nickel P-strontium phosphate.

   After roasting for 6 hours at 650 C in water vapor (3725 vol / vol / hour) and air (400 vol / vol / hour), the material is practically crystalline, as shown by its X-ray diffraction pattern indicating the presence of 5-10% strontium nickel pyrophosphate and 90-95% nickel ss-strontius phosphate.



  EXAMPLE 2
This example illustrates the possibility of employing the new catalyst for extended periods of cyclic operation at elevated temperature, without the catalytic activity being seriously affected. The results were obtained from a prolonged test in which the roasted catalyst of Example 1 was used. A 200 cm3 catalyst bed was placed in a 2.54 cm tube furnace, equipped with adjustment means. heating, butene and water vapor inlet conduits, a water condenser and devices for measuring and analyzing the product.

   The treatment conditions were as follows: Butene feed: 150 vol / vol / hour (all speeds are given at normal temperature and pressure) Volumetric water vapor / butene ratio. as indicated in table V Cycle: power supply; 15 minutes

 <Desc / Clms Page number 23>

 
Total: 30 minutes
Regeneration air-400 vol / vol / hour water vapor - 3000 vol / vol / hour
The proportion of the currents and the temperature were each modified during the test, the values being given in Table V.



   The analysis of the product stream, after condensation of the water vapor, was carried out by gas-liquid chromatography.



  The percent conversion is defined as "the number of moles of n-butene consumed times 100, divided by the number of moles of n-butene in the feed". Percent selectivity is "the number of moles of 1,3-butadiene produced times 100, divided by the number of moles of n-butene consumed". The vapor ratio is the vapor / butene feed volumetric ratio.



  Carbon deposition as carbon dioxide was determined by the weight gain, during the regeneration period, of a calibrated U-type tube containing 50% Ascarite and 50% aluminum. born. It has previously been found that substantially all of the carbon deposit is separated as carbon dioxide during the regeneration period. Table V gives the results obtained after various cycles of the test.



   During this time, the catalyst produced 0.68 to 0.77 kg of butadiene per 0.45 kg of catalyst per day.



   Table VI gives the results for carbonyl, in% by weight of carbon (based on the carbon of the feed) with various proportions of steam and at 640 C for cycles 58-128 and at 670 C for cycles. cycles 469-540. The other test results are the same as for the test described above. The results below (except for the case of 58 cycles and 496 cycles) are however given at times different from those provided in Table y and are therefore presented separately.



   TABLE VI Cycle Proportion of carbonyl vapor,% by weight of C (based on C in the feed)
 EMI23.1
 
<tb> 58 <SEP> 21.3 <SEP> 1.26
<tb>
<tb> 80 <SEP> 27.7 <SEP> 1.75
<tb>
<tb>
<tb> 128 <SEP> 17.5 <SEP> 1.08
<tb>
<tb>
<tb> 469 <SEP> 19.4 <SEP> 0.98
<tb>
<tb>
<tb> 480 <SEP> 15.5 <SEP> 0.84
<tb>
<tb>
<tb> 496 <SEP> 17.7 <SEP> 0.92
<tb>
<tb> 540 <SEP> -14.1 <SEP> 0.75
<tb>
 

 <Desc / Clms Page number 24>

 
These results show the effect of water vapor proportions and temperature on carbonyl formation, using the catalyst of the present invention. Operation at low proportions of water vapor and at higher temperatures will minimize carbonyl production.



  EXAMPLE 3 The catalyst of Example 1 was subjected to a 14 day test period as described in Example 2, with the cycle being set to the following sequences and times, proportions of
 EMI24.1
 
<tb> fear <SEP> of water <SEP> of <SEP> 10/1 <SEP>: <SEP>
<tb>
<tb> Power <SEP>: <SEP> 39 <SEP> minutes
<tb>
<tb>
<tb> Purge <SEP> to <SEP> the <SEP> steam <SEP> of water <SEP>: <SEP> 2 <SEP> minutes
<tb>
<tb>
<tb> Regeneration <SEP>: <SEP> 9 <SEP> minutes
<tb>
<tb>
<tb> Purge <SEP> to <SEP> the <SEP> steam <SEP> of water <SEP>: <SEP> 2 <SEP> minutes
<tb>
<tb>
<tb> Total <SEP>:

   <SEP> 52 <SEP> minutes
<tb>
 
This cycle allowed a "treat" period (defined as the period of time during which the hydrocarbon is fed to the reactor) of 75% of the total cycle. It also provides for a relatively long period of time. feeding time before regeneration.



   Under these conditions, the productivity was increased by 50% and the use of water vapor for regeneration (per weight of butadiene) was reduced by a factor of 3 compared to the productivity and use of corresponding water vapor in the usual "treatment" period, constituting 50% of the cycle time. The results given in Table VII illustrate, as in the case of Example II, the use of the catalyst at a high temperature and with a low proportion of water vapor, and show that the carbon build-up is practically zero, the percentage of carbonyls is very low, and the production of CO and CO2 during the "treatment" portion of the cycle is zero.

   Conversion to products other than butadiene is practically limited to methane, ethylene and propylene. The following results show the feed conversion on a carbon basis (wt%) for the period considered. The space velocity of the feed was 240 vol / vol / hour and the temperature was 685 C. The proportion of va-

 <Desc / Clms Page number 25>

 fear (water vapor versus hydrocarbon) for the given period was 10/1. During this period of cyclic operations, the productivity of the catalyst increased to 1.11 kg of butadiene per 0.45 kg of catalyst per day.



  EXAMPLE 4
The following example demonstrates that a precipitation temperature in the range of about 0 to 40 C has little or no effect on the activity of the catalyst.
Starting solutions of SrCl2 containing 2.40 M / L Sr ++, NiCl2 containing 3.13 M / L Ni ++, and H3PO4 containing 14.6 M / L PO4 = were used to prepare as follows. boasts a power solution of Sr-Ni-P04 ,. 5.67 liters of 0.545 liter SrCl2 solution are mixed together. of NiCl1 solution and 0.770 liter of H3PO4 solution and diluted to a volume of 24.65 liters.

   The resulting dilute acidic feed solution comprises: 0.552 M / L as Sr ++ 0.069 M / L as Ni ++, and 0.456 M / L as PO4 =
This gives an Sr / Ni ratio of 8/1 and a total metals to phosphate ratio of 1.36: 1. In each of the following four treatments 4.93 liters of this acidic feed is used.



   Each treatment is initiated with 2.72 liters of a solution containing 0.25 M / L NH4Cl. Dilute NH4OH (0.392M / L) is used to maintain the pH at 7.0. The acid feed is admitted to the precipitation apparatus at a constant rate (about 1.05 liters / hour) and the NH4OH solution is fed at a rate sufficient to maintain the pH.



   A precipitation apparatus with a capacity of 37.8 liters is used and provided with a jacket so that the temperature can be controlled by circulating water in this jacket. The resulting phosphate paste is allowed to settle overnight before recovery by the filtration and washing methods defined in Example 1. The wet cake is dried to a constant weight at 120 ° C. This dried cake is crushed so that it can pass through a 20 mesh sieve.

   Pellets are prepared using the resulting powder, mixing it with 3%.

 <Desc / Clms Page number 26>

 in weight of a lubricant formed by graphite, with then transformation of the material into pellets, then roasting of the latter in water vapor and air for 6 hours at 650 C. It is subjected to testing the toasted pellets resulting from each treatment, carrying out a dehydrogenation of but-ylene at 650 C using a butylene feed space speed of 300 vol / vol / hour and a water vapor / butylene volumetric ratio of 20/1.



   Table IX gives the precipitation temperature and percent conversion of the butylene feed, as well as the percent selectivity of conversion to butadiene.



   TABLE IX
 EMI26.1
 
<tb> Treatments
<tb>
<tb> A <SEP> B <SEP> C <SEP> D
<tb>
<tb> Precipitation <SEP> temperature <SEP>, <SEP> C <SEP> 8-10 <SEP> 16-18 <SEP> 25 <SEP> 30-33
<tb>
<tb>% <SEP> power <SEP> conversion <SEP> from
<tb> butylene <SEP> 28.3 <SEP> 26.1 <SEP> 27.6 <SEP> 28.0
<tb>
<tb>
<tb>% <SEP> selectivity <SEP> (in <SEP> butadiene) <SEP> 97.1 <SEP> 97.2 <SEP> 97.1 <SEP> 97,

  0
<tb>
<tb> Results <SEP> of <SEP> diffraction <SEP> at <SEP> rays <SEP> X
<tb>
<tb> Dry <SEP> powder
<tb>
<tb> Phase <SEP> of <SEP> table <SEP> II <SEP> 85% <SEP> 60% <SEP> 50% <SEP> 25%
<tb>
<tb> ss-Sr <SEP> Ni <SEP> PO4 <SEP> 15% <SEP> 40% <SEP> 50% <SEP> 75%
<tb>
<tb> Catalyst <SEP> burnt out
<tb>
<tb> ss-Sr <SEP> Ni <SEP> PO4 <SEP> 75% <SEP> 100% <SEP> 90% <SEP> 75%
<tb>
<tb> Sr <SEP> Ni <SEP> P2O7 <SEP> 25% <SEP> --- <SEP> 10% <SEP> 25%
<tb>
 EXAMPLE 5
The following example illustrates the use of the catalyst of the present invention in a process for the dehydrogenation of 3-methyl-1-butene to isoprene. The roasted catalyst of Example 1 is used.

   A 150 cc catalyst bed is placed in a 2.54 cm tubular furnace, equipped with heating control means, hydrocarbon and water vapor inlet conduits, condensers and devices. measurement and analysis. The test is carried out cyclically, providing 15 minutes of feed, 2 minutes of steam purge, 11 minutes of regeneration with water vapor and air, and 2 minutes of steam purge. water, for a total cycle time of 30 minutes. During the

 <Desc / Clms Page number 27>

 feed riodes, 3-methyl-1-butèns (purity of
99 mole%) in the reactor inlet line at a space velocity of 227 volumes (standard temperature and pressure) per volume of catalyst per hour.

   Water vapor is introduced at a rate of 3100 vol / vol / hour, to ensure a volumetric water vapor / hydrocarbon ratio of 13.7 / 1. During purging and regeneration, the water vapor rate is maintained at 3100 vol / vol / hour. Air is admitted during regeneration at a space velocity of 800 vol / vol / hour.



   During the feed period of three consecutive cycles, the treatment gas from the / reactor is sent to a condenser operating at about 0 C. The water vapor and the hydrocarbon products are condensed and separated in two. layers. The condenser cooperates with a cold collector, cooled to -78 ° C., which serves to separate by condensation the low boiling point hydrocarbon product. Non-condensable gases, eg H 2 CO, etc., are passed through a sampling system and finally removed by a measuring device.



   The aqueous layer is analyzed by gas-liquid chromatography to determine the percentage of carbonyls. The main portion of the hydrocarbon product is cooled to -78 ° C and mixed with the contents of the cold collector, followed by analysis of a liquid sample by gas-liquid chromatigraphy.



  Percent conversion is defined as "the number of moles of 3-methyl-1-butene consumed times 100, divided by the number of moles of 3-methyl-1-butene in the feed". Percent selectivity is defined as "the number of moles of isoprene (2-methyl-1, 3-butadiene) produced times 100, divided by the number of moles of 3-methyl-1-butene consumed". Non-condensable gases are continuously sampled and analyzed by gas-liquid chromatography. Carbon accumulation is determined by absorption of carbon dioxide in a calibrated U-type tube, containing 50% Ascarite and 50% alumina, with conversion to% by weight of carbon, relative to the carbon of the 'food.



   The various products are converted to a percentage of carbon relative to the weight of carbon in the feed.



   The analysis of the products resulting from cycles 91-93 during which the temperature was controlled at

 <Desc / Clms Page number 28>

 
 EMI28.1
 
<tb> 610 C.
<tb>
<tb>
<tb>
<tb>



  % <SEP> conversion <SEP> 39.08
<tb>
<tb>
<tb>
<tb>
<tb>% <SEP> of <SEP> selectivity <SEP> 76.03
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Balance <SEP> of <SEP> carbon <SEP>, <SEP>% <SEP> in <SEP> weight <SEP> of <SEP> C <SEP> (by <SEP> report <SEP> to < SEP> C <SEP> from <SEP> the power
<tb>
<tb>
<tb>
<tb> tation)
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Isorpene <SEP> 29.71
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Methyl <SEP> butene <SEP> 60.92
<tb>
<tb>
<tb>
<tb>
<tb> CO <SEP> 1.19
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> CO2 <SEP> 0.17
<tb>
<tb>
<tb>
<tb>
<tb> CH4 <SEP> 0.26
<tb>
<tb>
<tb>
<tb>
<tb> Ethylene <SEP> 0.77
<tb>
<tb>
<tb>
<tb>
<tb> Propylene <SEP> 0.81
<tb>
<tb>
<tb>
<tb>
<tb> Isobutene <SEP> 0.08
<tb>
<tb>
<tb>
<tb>
<tb> Butenes <SEP> and <SEP> butadiene <SEP> 2.66
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> n-pentanes <SEP> and <SEP> n-pertenes <SEP> 1,

  78
<tb>
<tb>
<tb>
<tb>
<tb> Pyperylene <SEP> (cis <SEP> and <SEP> trans) <SEP> 0.97
<tb>
<tb>
<tb>
<tb>
<tb> <SEP> deposit of <SEP> carbon <SEP> 0.14
<tb>
<tb>
<tb>
<tb>
<tb> Carbonyls <SEP> 0.48
<tb>
<tb>
<tb>
<tb>
<tb> Total <SEP> 99.94
<tb>
 20 EXAMPLE 6
An acidic feed solution is prepared using strontium nitrate, nickel chloride, phosphoric acid and water. The solution gives the following on analysis: 0.2521 moles of Sr ++ per liter, 0.0488 moles of Ni ++ per liter and 0.2448 moles of PO4 = per liter. This solution is introduced at a rate of 32.7 liters per hour into a stirred precipitation vessel of 90.8 liter capacity containing water.

   At the same time, ammonia gas is introduced at a rate such that the contents of the vessel are maintained at a pH of about 6.6, and the temperature of the apparatus is controlled at 25-28 °. vs. After the initial water has been displaced and the precipitation has reached a state of dynamic equilibrium the overflow paste has a settling volume in 3 minutes of 18-24 ml / 100 ml of paste and soluble alkalinity ( defined by the number of ml of HCl N / 10 necessary for 100 ml of filtered supernatant liquid in order to reach the endpoint modified with methyl orange) from 8.1 to 10,

  8 ml. The SrNi phosphate is allowed to settle before the clear supernatant liquid layer is decanted and the liquid is filtrated.

 <Desc / Clms Page number 29>

 dense paste.



   The filter cake is washed with water to separate the soluble salts. This washed cake was dried at 150 ° C. for 4 hours.



  The resulting material looks as follows on a @@ lysis:
 EMI29.1
 
<tb>% <SEP> Sr <SEP> = <SEP> 37.24
<tb>
<tb>% <SEP> Ni <SEP> = <SEP> 7.59 <SEP>
<tb>
<tb>% <SEP> P04 <SEP> = <SEP> 48.87
<tb>
<tb> Sr / Ni <SEP> = <SEP> 3.29 <SEP>
<tb>
<tb> Metral / PO4 <SEP> = <SEP> 1.11
<tb>
 
The X-ray diagram shows that the only crystal phase present is the acidic SrNi phosphate of unknown structure. After grilling for 6 hours at 650 C in water vapor (3725 vol / vol / hour) and air (400 vol / vol / hour). the material is nearly crystalline and consists of strontium nickel pyrophosphate, as shown by the x-ray diffraction pattern. When tested, the catalyst shows dehydrogenation activity for butene.



  EXAMPLE 7
4150 liters of an aqueous paste of 0.085 molar strontium hydroxide are prepared using 97.5 kg of Sr (OH) 2.8H2O (95%). A second 303 liter feed containing 24.2 kg of Ni (NO3) 2.6H2O 32.6 kg of H3PO4 and 5.80 kg of NH4OH was prepared with water as solvent. The second feed exhibits on analysis 0.029 mole of Ni ++, 0.057 mole of NH4 + and 0.115 mole of PO4 =.



   The strontium hydroxide paste was fed to a water-filled reactor, stirred at a rate of 35.9 liters per hour. The second feed is introduced at a rate of 23.4 liters per hour. Near its top, the reactor is provided with an overflow pipe through which a paste of strontium nickel phosphate is removed, this paste then being filtered.



   The pH of the mixture in the reactor is maintained at 7.9-8.0 and the temperature is maintained between 24 and 28 C.
During 78 hours, 8 harvests of strontium nickel phosphate are made. Each sample of catalyst is washed, dehydrated and dried at 140 ° C. The samples are then mixed and dried further to a constant weight at 175 ° C. The final product contains 44.66% by weight of Sr. 6.54% Ni and 41.48%

 <Desc / Clms Page number 30>

 phosphate. The Sr / Ni molar ratio is 4.78 and the metal / phosphate ratio is 1.47.



   A portion of the dried catalyst is mixed with 3% by weight of graphite and compressed into cylindrical pellets 0.48 cm long by 0.48 cm diameter.



   The pellets were roasted, as described in Example 1, and then tested for the dehydrogenation activity of n-butylene to butadiene in the test described previously. The results of the X-ray diffraction show that there is only p-strontium nickel phosphate as the crystalline phase.



   In the tenth cycle of this test, the conversion of butylene by passage at 650 ° C. is 38.5% and the selectivity to butadiene is 95.4%.



  EXAMPLE 8
This example illustrates the use of the catalyst in a continuous dehydrogenation process using steam, butene, air, and bromine as reactants. A Vycor glass tube with an internal diameter of 3.18 cm and a length of 61 cm is used as the reactor. Roasted catalyst pellets from Example 1 were placed in the tube over a 15.3 cm bed of crushed 4-8 mesh porcelain Raschig rings. A 150 ml sample forms a 20 cm bed. Ground Raschig rings are placed above the catalyst 22.9 cm. The temperature of the reactor is regulated by three external electric heating sections.



   The catalyst is used under continuous feed conditions for 336 hours over a temperature range of 595-620 ° C at butene space velocities nominally maintained at 150 vol / vol / hour. The hydrocarbon product is analyzed by gas-liquid chromatography and the results are expressed as mole% C4 free from hydrogen. The percent conversion is defined as the "number of moles of butera reacted per mole of butene of the feed. The percent selectivity is expressed as the number of moles of butadien produced per mole of butene reacted. * In the molar ratios of the reactants given in the results, the O2 / butene ratio is given although in reality air is used.

 <Desc / Clms Page number 31>

 



  The space velocities of the reactants were calculated based on the gas volumes corrected at normal temperature and pressure per volume of catalyst (150 ml) per hour. The reagents are introduced at the top of the reactor through a glass collector. Elemental bromine is dissolved in water to form a solution having the desired molar ratio. This solution is pumped in the form of a liquid into a preheater operating at 400 C. The mixed bromine and water vapor vapors are then introduced into the glass collector. A second inlet duct to this manifold, disposed downstream and discharging along the axis, admits air in the desired quantity.

   A third intake duct, located downstream of the first two and discharging downstream along the axis, admits butene-2.



   Various representative results are given in Table X under the conditions of temperature, butene space velocity and molar ratio of reactants cited therein.

 <Desc / Clms Page number 32>

 



    TABLE V Conditions used and analysis of the qaz products during the indicated cycle
 EMI32.1
 
<tb> Cycle <SEP> Temperature, <SEP> Report <SEP> steam / <SEP> conversion <SEP>% <SEP> election <SEP> Carbon <SEP> deposit, <SEP>% <SEP> in <SEP> weight
<tb>
 
 EMI32.2
 ### - ####### ## ËHSg ### ¯ ######## ¯¯ ##### ¯ (¯ based on C in power supply)
 EMI32.3
 
<tb> 58 <SEP> 640 <SEP> 21.3 <SEP> 46.02 <SEP> 94.65 <SEP> 0.19
<tb> 185 <SEP> 645 <SEP> 17.5 <SEP> 42.91 <SEP> 93.87 <SEP> 0.07
<tb> 249 <SEP> 655 <SEP> 17.0 <SEP> 44.02 <SEP> 92.78 <SEP> 0.001
<tb> 382 <SEP> 665 <SEP> 16.8 <SEP> 43.23 <SEP> 91.

   <SEP> 29 <SEP> 0.05
<tb> 496 <SEP> 670 <SEP> 17.7 <SEP> 44.30 <SEP> 90.32 <SEP> 0.08
<tb> 633 <SEP> 670 <SEP> 15.7 <SEP> 42.78 <SEP> 90.25 <SEP> 0.03
<tb> 701 <SEP> 675 <SEP> 17.7 <SEP> 42.92 <SEP> 89.66 <SEP> 0.01
<tb> 877 <SEP> 680 <SEP> 17.1 <SEP> 44.04 <SEP> 89.33 <SEP> 0.02
<tb> 1149 <SEP> 680 <SEP> 16.6 <SEP> 42.51 <SEP> 89.08 <SEP> 0.03
<tb>
 

 <Desc / Clms Page number 33>

   T A B L E A U VII
 EMI33.1
 
<tb> Bllan <SEP> of <SEP> carbon, <SEP> in <SEP> weight <SEP> aur <SEP> 'base <SEP> of <SEP> C <SEP> in <SEP> power supply)
<tb> cycle <SEP> production <SEP> of <SEP> Power supply, <SEP> CH4 <SEP> C2H4 <SEP> C3H6 <SEP> Butene <SEP> C4H6 <SEP> Deposit <SEP> Carbonyls <SEP> Acéty- <SEP> Co <SEP> and
<tb> steam <SEP> of water <SEP> v / v / hours <SEP> of <SEP> lene <SEP> Co2
<tb> 2535 <SEP> 10.2 <SEP> 251 <SEP> 0.87 <SEP> 0.42 <SEP> 2.64 <SEP> 72,

  30 <SEP> 23.31 <SEP> 0.03 <SEP> 0.26 <SEP> 0.17
<tb> 2593 <SEP> 10.7 <SEP> 243 <SEP> 0. <SEP> 92 <SEP> 0.39 <SEP> 2.63 <SEP> 71.78 <SEP> 23.82 <SEP> 0.03 <SEP> 0.26 <SEP> 0.18
<tb> 2679 <SEP> 10.9 <SEP> 246 <SEP> 0.87 <SEP> 0.30 <SEP> 2.65 <SEP> 71.75 <SEP> 23.00 <SEP> 0. <SEP> 01 <SEP> 0.27 <SEP> 0.16
<tb> 2757 <SEP> 10.4 <SEP> 243 <SEP> 0.95 <SEP> 0.47 <SEP> 2.64 <SEP> 72.11 <SEP> 23.28 <SEP> 0.03 <SEP> 0.37 <SEP> 0.16
<tb> 2817 <SEP> 9.7 <SEP> 254 <SEP> 0. <SEP> 90 <SEP> 0.37 <SEP> 2.49 <SEP> 73.18 <SEP> 23.64 <SEP> 0.02 <SEP> 0.29 <SEP> 0.11
<tb> 2911 <SEP> 10.2 <SEP> 244 <SEP> 0.72 <SEP> L, <SEP> 23 <SEP> 2.51 <SEP> 74.05 <SEP> 22.05 <SEP> 0.01 <SEP> 0.03 <SEP> 0.12
<tb>
 

 <Desc / Clms Page number 34>

   PAINTINGS
 EMI34.1
 
<tb> Temperature, <SEP> Butene <SEP> C.

   <SEP> Steam <SEP> Molar <SEP> proportions <SEP> Kg <SEP> of <SEP> butadiene / kg <SEP> of
<tb>
 
 EMI34.2
  c Vlir / hr '02 sz2% C% S catalyst / day
 EMI34.3
 
<tb> a. <SEP> 595 <SEP> 155 <SEP> 1 <SEP> 19.8 <SEP> 0.9 <SEP> 0.022 <SEP> 59.5 <SEP> 89, <SEP> 2 <SEP> 4.27
<tb> b. <SEP> 605 <SEP> 150 <SEP> 1 <SEP> 19.9 <SEP> 0.6 <SEP> 0.024 <SEP> 54.5 <SEP> 89.4 <SEP> 3.89
<tb> c. <SEP> 620 <SEP> 145 <SEP> 1 <SEP> 21.0 <SEP> 0.9 <SEP> 0.025 <SEP> 65.2 <SEP> 87.4 <SEP> 4.51
<tb> d. <SEP> 620 <SEP> 153 <SEP> 1 <SEP> 20.4 <SEP> 0.6 <SEP> 0.024 <SEP> 51.8 <SEP> 88.7 <SEP> 3.82
<tb> e. <SEP> 620 <SEP> 152 <SEP> 1 <SEP> 20.4 <SEP> 0.6 <SEP> 0.024 <SEP> 49.0 <SEP> 86.4 <SEP> 3.61
<tb> f. <SEP> 620 <SEP> 149 <SEP> 1 <SEP> 14.6 <SEP> 0.9 <SEP> 0.018 <SEP> 59.8 <SEP> 84.1 <SEP> 3.98
<tb> g.

   <SEP> 620 <SEP> 154 <SEP> 1 <SEP> la, 2 <SEP> 0.9 <SEP> 0.012 <SEP> 54.4 <SEP> 79.5 <SEP> 3.50
<tb>


 

Claims (1)

CLAIMS 1. A material formed by strontium nickel phosphate, comprising phosphate chemically combined with strontium and nickel in the relative proportions of 2 to 20 atoms of strontium per atom of nickel and of 1 to 2 atoms of the metals per atom. phosphorus atom, this strontium nickel phosphate containing ss-strontium nickel phosphate, strontium nickel pyrophosphate and mixtures thereof. 2. The material of claim 1, wherein the ss-stroontium nickel phosphate constitutes from 50 to 98% by weight, while the strontium nickel pyrophosphate constitutes from 2 to 50% by weight of the crystalline strontium nickel phosphates. forming this material. 3. The material of claim 1, wherein the nickel strontium phosphate is substantially the only nickel strontium phosphate in the composition. 4. The material of claim 1 wherein the ss-strontium nickel phosphate constitutes from 70 to 100% by weight of the constituents containing SR, Ni and PO4. 5. The material of claim 1 wherein the strontium nickel pyrophosphate is substantially the only strontium nickel phosphate in the composition. 6. The material of any one of claims 1 to 5, when pulverized and then compressed into pellets. 7. The material of claim 5, when mixed with an oxidizable lubricant prior to compression into tablets. 8. The material of any one of claims 1 to 6, when admixed with an amount of 0.5 to 10% by weight of chromic oxide before processing into pellets. 9. The material of any one of claims 1 to 8 which has been pulverized and then compressed into pellets. 10. The material of any one of claims 1 to 9 which has been mixed with an oxidizable lubricant prior to pelletizing. 11. Strontium nickel phosphate defined by the X-ray diffraction diagram, given in Table II. 12. Strontium nickel phosphate according to the claim <Desc / Clms Page number 36> cation 11, mixed with 15 to 75% by weight, based on the weight of the mixture, of 5-strontium nickel phosphate. 13. A process for the preparation of strontium nickel phosphates comprising mixing a water soluble salt of strontium or strontium hydroxide, a water soluble salt of nierai, and phosphoric acid, in an aqueous medium at a pH of 5.0 to 9.5, and the use of ammonia or a water-soluble amine, when a salt soluble in water is used as reagent. strontium water, to adjust the overall pH of the reaction medium. 14. The process for producing a dehydrogenation catalyst, which comprises mixing an aqueous solution of a soluble salt of strontium and a soluble salt of nickel, in proportions corresponding to 2-20 atoms. of strontium per atom of nickel, with an aqueous solution of a soluble ortho-phosphate, while maintaining the resulting mixture below a pH of 7.3, so that a material consisting of chemical phosphate radicals - only combined with strontium and nickel is formed and precipitated, and the separation and drying of the precipitate. 15. The process of claim 14, wherein the precipitation is effected by mixing the above solution with an aqueous solution of an alkaline reagent, the latter being present in an amount sufficient to give the resulting mixture a pH value. less than 7.3. 16. The process of claim 14 or 15, wherein the alkaline reagent is ammonium hydroxide. 17. The process of claim 14 or 15, wherein the alkaline reagent is ammonia. 18. A process for the production of a dehydrogenation catalyst consisting of strontium nickel phosphate, comprising mixing an aqueous solution of a nickel salt in orthophosphoric acid with a solution or paste of nickel. strontium hydroxide at an overall pH of 5.8 to 9.2 in a proportion of 2 to 20 atoms of strontium per atom of nickel and in a proportion of 1 to 2 atoms of the metals per phosphate group. 19. The process of claim 18, wherein a proportion of 2 to 6 atoms of stroncium per atom of nickel is used. <Desc / Clms Page number 37> 20. The process of claim 18 or 19, wherein the strontium hydroxide is in the form of an aqueous paste. 21. The process of claim 18 or 19, wherein the strontium hydroxide is in solution in water. 22. The process of claim 18 or 19, wherein the nickel chloride is dissolved in an aqueous solution of phosphoric acid. 23. The process of claim 18 or 19, wherein the nickel nitrate is dissolved in an aqueous solution of phosphoric acid. 24. The process of claim 18 or 19, wherein the metallic nickel or an oxide thereof is dissolved in an aqueous solution of phosphoric acid. 25. A process for the dehydrogenation of alkanes to alkenes and diolefins, alienates to diolefins, and alkyl aromatic hydrocarbons to ss-alkenyl aromatic hydrocarbons by passing the appropriate hydrocarbon through a heated zone present. steam and a dehydrogenation catalyst comprising using as a catalyst the strontium nickel phosphate material according to any one of claims 1 to 12. 26. A process for the dehydrogenation of alkanes to alkenes, alkenes to diolefins, and alkyl aromatics to ss-alkenyl aromatics, by passing the appropriate hydrocarbon through a zone heated in the presence of steam. water comprising the use of a strontium nickel phosphate material according to any one of claims 1 to 12, using a volumetric water vapor / hydrocarbon ratio at temperature. and normal pressure, 5/1 to 40/1, and a temperature of 450 to 750 C, at a space velocity of 100 to 700 volumes of hydrocarbon per volume of bed per hour. 27. A process for the dehydrogenation of hydrocarbons, comprising the continuous passage, through a reaction zone, of a reactive hydrocarbon at a space velocity of 50 to 500 volumes of hydrocarbon per volume of catalyst per hour, this catalyst consisting essentially of a dehydrogenation catalyst formed by a strontium nickel phosphate according to one <Desc / Clms Page number 38> any one of claims 1 to 12, simultaneously passing through this re-zone water vapor in an amount of 1 to 40 volumes per hydrocarbon, oxygen in an amount of. 0.25 to J me per mole of reactive hydrocarbon, and bromine in an amount 0.002 to 0.3 mole per mole of hydrocarbon, while maintaining the reaction zone at a temperature of 400 to 700 C 28. Phosphates of strontiun® @ @, their preparation and their use, as described above, in particular. in any of the examples given.