CS270156B1 - SpSeob of catalytic dahydrogenation of alkane hydrocarbons - Google Patents

Abstract

The method of catalytic dehydrogenation of n-alkenes C6-C20 to β-alkanes with the same reaction length is described. This is a new process that allows the use of long dehydrogenation periods of up to 400 h and the increase in catalyst activity with relatively shorter reaction periods of an average of 2 to 4 h.

Description

The invention relates to a process for the preparation of alkenes Οθ - by catalytic dehydrogenation of alkanes of the same chain length using catalyst catalysts containing platinum or its compounds. The dehydrogenase process takes place continuously - cyclically in at least two reactors and at most. It consists of the dehydrogenation period and the oxidation-dehydrogenation period. After the dehydrogenation period, the C ₆ -C ₂₀ n-alkanes are fed in parallel to at least two reactors in the presence of hydrogen or an inert diluent other than N ₂ ; CO ₂ , CH ₄ ; H ₂ 0 - pens at a pressure of 0.1 MPa for 0.5 - 500 ha and a volume rate of 5 - 100 volumes of liquefied hydrocarbon per volume of catalyst per hour at a temperature of 400 - 650 ° C. During the oxidation-dehydrogenation period, the oxidation takes place in one or more reactors, the other or in other reactors, the oxidation being carried out with oxygen at a concentration of 0.1 20% by weight, diluted with N ₂ , CO ₂ ; H ₂ 0 in the form of steam for OJI - 10 h; at a temperature of 400 650 ° C. The dehydrogenation in this period takes place under conditions similar to those during the dehydrogenation period, preferably at a double volume flow rate of the feedstock starting from the dehydrogenation period.

In Czech. author's certificate 201 784 ea protects isothermal reactor equipment for catalyzed reactions and especially for dehydrogenation of n-alkenes, which consists of a vessel in which is placed multi-pass tube bundles which transfer heat for the dehydrogenation reaction and of a construction allowing radial or axial supply of reacted catalyst to the reactants. in the inter-tube space.

U.S. Pat. No. 3,742,078 discloses the process of producing olefins containing 4-30 carbon atoms in a molecule in the presence of a catalyst atom consisting of silicon oxides; from platinum group elements; Germany and Lithuania.

U.S. Pat. No. 3,310,599 protects the dehydrogenation of alkenes using catalysts containing noble metals, in particular platinum, as well as using lithium and aluminum, or their compounds, supported on aluminum alumina.

ČSSR AO 161 633 protected the dehydrogenation of alkenes on catalysts containing platinum in combination with antimony oxide, tin manganese, beryllium; alkali metals and mixed oxides of aluminum and magnesium.

ČSSR AO 206 291 opiates the dehydrogenation of elkanes enclosing 2-25 carbon atoms in the molecule of non-catalytic catalysts containing elements of the platinum group in combination with rare earth elements and elements of the scandium subgroup deposited on inorganic refractories.

In the Czechoslovak patent 179,765 ea describes an epoeob of a catalytic dehydrogenated alkane hydrocarbon or two catalyst beds and then ea, after superheating, mixes the diluent and hydrocarbons and brings the resulting mixture onto one or two catalysts.

The essence of the catalytic dehydrogenation of alkane hydrocarbons Οθ - C ₂₀ to alkenes according to the invention lies in the fact that the dehydrogenation takes place in at least two reactors and in the dehydrogenation period only dehydrogenation takes place, while in the oxidation dehydrogenation period at least in one species.

During the dehydrogenation period, there is a gradual clogging of catalysts (based on platinum) with carbonaceous substances and probably a decrease in the binding of some elements such as e.g. CeO ₂ , Šb0 ₂ ; None of which some catalysts contain.

Another factor influencing the conversion and selectivity of the dehydrogenate process is the reduction of catalyst activity due to long-term work, reduced bond strength in crystalline structures as well as the introduction of trace impurities Mo, SJ P, ’N into catalyst systems leading to reduced overall activity and reduced conversion! in dehydrogenation. Removal of carbonaceous substances as well as restoration of flood activity due to reduced binding of dehydrogenation catalysts and reduction of bond strength in rats

CS 270 156 Blast structures as well as the effect of trace impurities can be eliminated by the proposed dehydrogenation method.

Maximum dehydrogenation activity of catalyst systems is reached in the first hours of dehydrogenation periods · In the case of high catalyst activity where the reduction depends only on the amount of carbonaceous substances and bonds; it is therefore possible to choose dehydrogenation periods longer - up to a maximum of 500 hours; preferably a time of less than 40 100 h is selected, during which more difficult to regenerate graphite is formed from the catalyst system. The reduction in the intrinsic activity of the catalyst is compensated by the frequent regeneration of the catalyst systems. The system is mentioned (in which, during the length of the dehydrogenation period), the regeneration in one reactor in the oxidation-dehydrogenation period represents a maximum of 10% of the total dehydrogenation time, but β is preferably ea in the range of 1-3%. The regeneration takes place gradually in the individual reactors in such a way that the entire stream of hydrocarbon feedstock during the oxidative regeneration in one reactor is fed to the other reactor. 3e, however, it is possible to reduce this current and thus operate at the same conversion but reduced capacity of the plant during the oxidation-dehydrogenation period in the first reactor. Due to the substantially increased activity of the catalysts for dehydrogenation after oxidation, it is advantageous to continue in the initial phase and to draw the catalyst twice by volume, while in this way it is advantageous to reduce the formation of carbon deposits. Reduction of dehydrogenation activity / catalysts in addition to the simultaneous reduction of active centers and thus not only to lower dehydrogenation activity but also to a reduction in the formation of carbonaceous substances. This means that the total proportion of the oxidation period in the oxidation-dehydrogenation period remains in approximately the same percentage with respect to the dehydrogenation period.

Example 1 |

N-dodecane preheated to 460 ° C was metered in at a rate of 3.7 l / h together with hydrogen in a molar ratio of 1:10 into two isothermally operating reactors with a volume of '3' '·. ····' ''

100 cm containing AL ₂ 0g - Pt - Ce - Li catalysts in an amount of 50 cm in each reactor. The reactors are provided on the inlet and outlet side with shut-off valves through which the stream of hydrocarbon feedstock and hydrogen can be shut down and nitrogen and nitrogen * air * mixture fed to the reactor. The feedstock was passed parallel through the reactors for 120 hours. The conversion for n-dodecenes was 12-10% by weight, on average 11% by weight, with a salinity of 94% by weight. After 120 h and the dehydrogenation period, the setting of the fittings stemmed and the whole stream was fed to only one reactor / while in the second reactor after purging with nitrogen a nitrogen-air mixture was fed with oxygen concentration varying from 1 - 3%. 60 DEG C. higher in the first minutes than in the dehydrogenation, the temperature of the catalyst bed being reached after 60 minutes as in the dehydrogenation. After this time, the entire feed stream was transferred to the regenerated reactor by switching the valves to the regenerated reactor, the regeneration being carried out in the second reactor for 60 minutes. After this time, the stream of raw material and hydrogen was again divided into two reactors operating in parallel by connecting the reactor to the dehydrogenation period.

Claims (2)

Both the structure and the effect of trace impurities can be eliminated by the proposed dehydrogenation · The maximum hydrogenation activity of the catalyst systems is reached in the first hours of the dshydrogenation periods · In the case of high activity catalysts where its reduction is dependent only on the amount of carbonaceous substances and ties; therefore, it is possible to select the dehydration periods of up to 500 h, and preferably a shear period of 40-100 h is chosen, whereby the harder regenerable graphite does not form from the catalyst system. Reduction of the catalyst's own activity is compensated for by frequent regeneration catalyst systems. A system (in which, for a length of the dehydrogenation peri), the regeneration in one reactor in the oxidation-dehydrogenation period is at most 10% of the total dehydrogenation time, but preferably aa is in the range of 1-3%. The regeneration is carried out sequentially in the individual reactors by the whole hydrocarbon feed through the oxidation regeneration in one reactor next to the second reactor. However, it is possible to reduce this current and thereby operate at the same conversion, and in the reduced loading capacity during the oxidation-dehydrogenation period in the first reactor. In contrast to the substantial increased activity of the catalyst systems for dehydrogenation of pooxidation, it is advantageous to continue and double the volume of catalysts at an initial stage, it is possible to reduce the formation of carbonaceous deposits by this method. Reducing the dehydrogenation activity / catalysts in addition to simultaneously lowering the active centers and thus not only lowering the dehydrogenation activity but also reducing the formation of carbonaceous substances. Said circumstance means that the total period of oxidation period in the oxidation-dehydrogenation period is approximately equal to the percentage ratio relative to the dehydrogenation period. Example 1 {N-dodecane preheated to 460 ° C was dosed at 3/7 1 / h with a 1: 10 molar ratio to two isothermal 100 cm reactor containing AL20g - Pt - Ce catalysts at 50 cm in each re-actor. The reactors are provided with a closing armature on the inlet and outlet sides, and the hydrocarbon feed stream can be shut off with the hydrogen and nitrogen and nitrogen + air are introduced into the reactor. The feedstock passed through the reactor for 120 h in parallel. Conversion to n-dodecenes was 12-10% by weight. on average 11% by weight at a selectivity of 94% by weight. After 120 h, the dehydrogenation period was converted to matrix maturation, and the entire stream was fed to only one reactor (with the dueling mixture in the second reactor and flushed with nitrogen while the oxygen concentration was varied from 1-3%). the maximum temperature of 60 ° C is discharged in the first minutes as in the dehydrogenation process (after 60 minutes the same catalyst bed temperature as in the dehydrogenation is achieved). After this time, the flow of the valves allowed the entire feed stream to flow into the recovered reactor while the regeneration was carried out in the second reactor over a period of 60 ml. After this time the stream of raw material and hydrogen was re-divided into two parallel reactors by connecting the reactor to the dehydrogenation period. SUBJECT OF THE INVENTION 1. A method for the catalytic dehydrogenation of alkane hydrocarbons --θ - to alkenes of the same chain length using catalyst and platinum-containing catalysts, a compound thereof, and a labeled catalyst; that the dehydrogenation process proceeds not cyclically and consists of a dehydrogenation and oxidation-dehydrogenation period; wherein during the dehydrogenation period, n-alkanes Οθ - are introduced into the system of at least two and CS 270 156 B1 3 at maximum of five parallel working reactors without diluent or in presence of hydrogen, or other inert diluents such as due vapor; carbon dioxide, methane at a total pressure of 0.1 - 10 MPa for 0, 5 - 500 hours, at a temperature of 400 - 650 ° C, 8 preferably at a pressure of 0 - 2 MPa for 10 - 150 hours , at a volumetric velocity of 5 - 100 volumes of liquid hydrocarbon / catalyst volume, and at the beginning of the oxldane-dehydration period e, and the oxidation of the individual reactors in the dehydrogenation of at least 1 maximum in 5 reactors, the oxidation and the concentration of 0, 1 - 20 wt. Preferably, 1-5% by weight of the dilute diluent is hydrogen carbonate, water vapor, for 1.0-1.0 hours, preferably 0.2-3 hours at 400-660 ° C. 2. Spoeob according to claim 1, characterized in that the dehydrogenation is carried out in isothermal or adlabatic reactors, or in the combination of an isothermal and diabetic reactor.