JPH0299B2 - - Google Patents

Description

[Detailed description of the invention]

The field of the invention is the production of maleic anhydride from n-butane and catalysts therefor. Maleic anhydride is of great commercial interest throughout the world and is widely used in the production of alkyd resins. It is also a versatilely used intermediate in chemical synthesis. As a result, large quantities of maleic anhydride are produced each year to meet this demand. The production of maleic anhydride by catalytic oxidation of benzene and butene is well known, and the main method currently used for the production of maleic anhydride is by air oxidation of benzene in the presence of certain heavy metal oxide catalysts. However, the inherent toxicity of benzene fumes tends to preclude the use of benzene as a feedstock, and new plants tend to utilize butane oxidation methods. Catalysts proposed for the oxidation of butane to maleic anhydride have generally been based on vanadium and phosphorus. US Pat. No. 3,293,268 discloses that the oxidation of butane to maleic anhydride can be carried out in the presence of a phosphorus-vanadium-oxygen containing complex catalyst. Although this catalyst can oxidize butane, it does not give sufficiently high yields. The yield of maleic anhydride is reported to be only 30-50% by weight. To improve the yield of maleic anhydride,
Various activators, stabilizers and promoters are disclosed in the prior art. Documents include U.S. Patent Nos. 3867411, 3832359, 3888886, 4002650,
Same No. 4147661, Same No. 4149992, Same No. 4151116,
4152338, 4152339 and UK Patent Application No. 2019839A. Although the prior art described above has helped bring about some improvements in the performance of phosphorus-vanadium catalysts, there remains much room for improvement in terms of high conversion, yield and catalyst life. The object of the present invention is to produce phosphorus produced in an organic medium.
The purpose of the present invention is to provide a vanadium-zinc oxide catalyst which, prior to use in the production of maleic anhydride from a butane feedstock, has a characteristic powder X-ray diffraction pattern using steel K-alpha radiation.
This catalyst is in a phase containing more than % of is 700−850〓( When used in the production of maleic anhydride from butane at temperatures between 371 DEG and 454 DEG C., K-Alpha radiation is used to convert the steel into a second phase with a characteristic powder diffraction pattern as follows. Line position d angstrom 2.θ degree Intensity 6.3 14.2 10 4.8 18.5 7 3.9 23.0 100 3.1 28.5 58 3.0 30.0 29 2.7 33.8 7 Another objective is to
The object of the present invention is to provide a method for producing maleic anhydride from butane at a temperature of 650-850°C (343-454°C). The new catalyst consists of a zinc-promoted phosphorus-vanadium oxide catalyst. A suitable atomic ratio of vanadium to phosphorus is in the range of 0.5:1.0-1.25:1.0.
A range of 0.6:1.0-1.0:1.0 is preferred. A good total atomic ratio of zinc to vanadium is in the range of 0.005:1 to 0.4:1. The total atomic ratio of zinc to vanadium is
Preferably, the range is 0.01:1-0.25:1.
The atomic ratio of phosphorus to vanadium is 0.8:1-2:1
A range of 1:1 to 1.7:1 is preferred. The catalyst prepared according to the invention can be prepared from an organic solvent system in which vanadium pentoxide is reduced in the presence of zinc together with hydrogen chloride gas. The vanadium-zinc oxide is then reacted with crystalline orthophosphoric acid, and the water of reaction is removed by azeotropic distillation to produce a precipitate of crystalline vanadium-phosphorous-zinc mixed oxide, which is preferably filtered and dried from the mother liquor. , which can then be used as an oxidation catalyst for the production of maleic anhydride from butane feedstock. Suitable organic solvents are alcohols or mixtures of alcohols and aromatic hydrocarbons such as benzene and ortho-xylene. Aliphatic alcohols are usually used in this process, with isobutanol being the preferred alcohol. Precipitation of the phosphorus-vanadium-zinc complex is accomplished by using a cosolvent to reduce the solubility of this complex in solution. Precipitation can also be carried out by lowering the temperature and removing the solvent. The use of co-solvents such as benzene or ortho-xylene also serves to facilitate the removal of excess water through azeotropic distillation. Precipitation of the phosphorus-vanadium-zinc mixed oxide can be suitably achieved by azeotropic distillation of the organic solvent and reaction water followed by evaporation of the organic solvent. Zinc can be added as a compound with vanadium or separately in solution. Suitable zinc compounds include zinc metal, zinc chloride, zinc oxide and most soluble zinc salts. If it is desired to improve the physical properties of the catalyst, it is treated with an inert support such as alumina, titania, silicon carbide, silica, pumice or preferably a suspension of silicon. The catalyst can be reinforced with such materials at any stage of its manufacture. According to the invention, the average valence of vanadium is
It is in the range of 4.0−4.4. The various phosphoric anhydrides that can be used in the preparation of the present catalysts include ortho- or pyrophosphoric acid, triphosphoric acid or metaphosphoric acid. Vanadium compounds include vanadium pentoxide, vanadium tetrachloride, vanadium trichloride, vanadium oxydichloride, vanadium oxytrichloride,
Vanadium tetroxide, and the most soluble vanadium complex. Suitable vanadium compounds include vanadium oxides such as vanadium pentoxide, vanadium trioxide, etc.; vanadyl chloride, vanadyl dichloride,
Vanadium oxyhalides such as vanadyl trichloride, vanadyl bromide, vanadyl dibromide, vanadyl tribromide, etc.; Vanadium-containing acids such as metavanadate, pyrovanadic acid, etc.; ammonium metavanadate, vanadium sulfate, vanadium phosphate, vanadyl formate, Vanadium salts such as vanadyl oxalate and the like are included. However, vanadium pentoxide is preferred. X-ray diffraction pattern as shown below: Line position d Angstrom 2.θ degrees Intensity 5.7 15.6 100 4.5 19.7 41 3.7 24.3 25 3.3 27.1 32 3.1 28.8 14 2.9 30.5 40 2.8 32.2 9 2.7 33.7 2 A characteristic phase showing 0 The catalyst with one is about 650-
It has been discovered that when used in the production of maleic anhydride from butane raw material at a temperature of 850°C (343-454°C), it has a second phase with the following X-ray pattern: Line position d angstrom 2.θ degrees Intensity 6.3 14.2 10 4.8 18.5 7 3.9 23.5 100 3.13 28.5 58 2.98 30.0 29 2.65 33.8 7 The X-ray shape described above is formed by encompassing at least 80% of the catalyst. This catalyst shows excellent selectivity and yield in the production of maleic anhydride from butane. The catalyst also has a long life and is directly regenerated, making it useful for commercial production of maleic anhydride. In a preferred embodiment, a solution of the vanadium compound in a hydrocarbon solvent is prepared by reducing vanadium pentoxide with gaseous hydrogen chloride. A zinc compound, preferably metallic zinc, is added to the solution prior to the reduction step. The temperature at which vanadium oxide is reduced is 70-230〓 (21-110℃), preferably
It is in the range of 90−160〓(32~71℃). After reduction,
Phosphorus is conveniently added as orthophosphoric acid, preferably 100% orthophosphoric acid. After precipitation of the mixed oxide and appropriate soaking, it is filtered from the mother liquor and dried in a vacuum oven at about 200-250°C with a thorough nitrogen purge. The dried mixed oxide is converted into n-
It is activated by heating in the presence of a hydrocarbon such as butane. A catalyst for the production of maleic anhydride by the oxidation of butane, consisting of a phosphorus-vanadium mixed oxide containing zinc as a promoter, the atomic ratio of vanadium to phosphorus being in the range 0.5:1-1.25:1. , the total atomic ratio of zinc to vanadium is 0.01:1
-0.25:1, the catalyst is in the initial phase K
Using alpha radiation, it has a characteristic initial powder X-ray diffraction pattern as shown below, line position d angstrom 2.θ degrees intensity 5.7 15.6 100 4.5 19.7 41 3.7 24.3 25 3.3 27.1 32 3.1 28.8 14 2.9 30.5 40 2.8 32.2 9 2.7 33.7 20 The catalyst was heated to a temperature of about 600°C-800° (316-427°C) under the conditions of the oxidation reaction of butane to maleic anhydride using copper K-alpha radiation. It is characterized by a change to a phase with the following characteristic powder X-ray diagram: Line position d angstrom 2.θ degree Intensity 6.3 14.2 10 4.8 18.5 7 3.9 23.0 100 3.1 28.5 58 3.0 30.0 29 2.7 33.8 7 do. The invention is also characterized in that it includes a method for oxidizing butane to maleic anhydride by contacting the butane with the novel catalyst in the presence of oxygen. Oxidation of butane to maleic anhydride is carried out by contacting a low concentration of n-butane with the catalyst described above in oxygen. Although air is perfectly satisfactory as a source of oxygen, diluent gases such as synthetically produced oxygen and nitrogen can also be used. Air rich in oxygen can be used. The gaseous charge fluid to the oxidation reactor typically contains nitrogen and about 0.2-1.7 mole percent n-butane. about
0.8-1.5 mole percent n-butane is sufficient to obtain the optimum yield of maleic anhydride of the process of the invention. Higher concentrations can be used but pose an explosion hazard.
Of course, low concentrations of butane, below about 1%, reduce the overall yield obtained at equal flow rates and are therefore usually not used economically. Although the flow rate of the gaseous fluid through the reactor can be varied within fairly wide limits, a preferred operating range is a rate of about 100-4000 c.c. of feed per cc of catalyst per hour, and more preferably a rate of about 100-4000 c.c. of feed per cc of catalyst per hour.
It is 1000−2400c.c. The residence time of the gaseous fluid is usually less than about 4 seconds, more preferably less than about 1 second, and effective operation cannot be achieved at a velocity less than this. Flow rate and residence time are calculated under standard conditions of 760 mm of mercury and 25°C. Many reactors are useful, and shell-and-tube heat exchanger type reactors are quite satisfactory. The top of such a reactor can vary in diameter from about 1/4 inch to about 3 inches and in length from about 3 inches to about 10 inches or more. The oxidation reaction is exothermic and therefore relatively close control of the reaction temperature must be maintained.
It is desirable to maintain the surfaces of the reactor at a relatively constant temperature, and a solvent that conducts heat from the reactor is necessary to aid in temperature control. Such media include wood metals, molten sulfur, mercury, molten lead, etc., but a eutectic salt bath is perfectly suitable. One such salt bath is sodium nitrate, sodium nitrite.
Potassium nitrate is a eutectic isothermal mixture. A further method of temperature regulation is to use a metal block reactor in which the metal surrounding the tube acts as a temperature regulator. As will be recognized by those skilled in the art, the heat exchange medium is maintained at the appropriate temperature, such as by a heat exchanger.
reactor or iron, stainless steel, carbon steel,
Glass tubes such as Nickel and Vycor. Carbon steel and nickel tubes have excellent long life under the reaction conditions described herein. Usually the reactor is about 1/2-1/1 of the catalyst volume present.
0 1/4 inch Alundum pellets, inert ceramic balls,
Includes main heating zone using nickel balls or chips. The reaction temperature can be varied within certain limits, but normally the reaction must be carried out at a temperature within a fairly critical range. The oxidation reaction is an exothermic reaction, and once the reaction has begun, the primary purpose of the salt bath or other medium is to remove heat from the reaction ball and regulate the temperature. Even better performance is obtained when the reaction temperature normally used is no more than 20-50° higher than the salt bath temperature. Of course, the reactor temperature will also depend to some extent on the reactor size and butane concentration. The reaction can be carried out at atmospheric pressure, superatmospheric pressure, or subatmospheric pressure. The outlet pressure is at least slightly higher than ambient pressure to ensure positive flow from the reaction. The pressure of the inert gas must be high enough to overcome the pressure drop through the reactor. Maleic anhydride can be recovered by a number of methods known to those skilled in the art. For example, this recovery is carried out by direct condensation or absorption in a specific medium with specific manipulation and purification of the maleic anhydride. Although the following examples are provided for a thorough understanding of the invention,
These examples are given for illustrative purposes only and are not intended to limit the invention in any way. In the examples, the terms "conversion,""selectivity," and "yield" are defined as follows. % conversion = moles of hydrocarbons reacted / moles of hydrocarbons in feedstock x 100 % selectivity = moles of maleic acid produced / moles of feedstock hydrocarbons consumed x 100 Yield weight % = (conversion) x (selectivity) x 1.69 Example 1 750 ml of methanol and vanadium pentoxide are placed in a 4-neck flask that can be heated with an electric mantle equipped with a mechanical stirrer, reflux condenser, thermometer, barrett trap, and a gas inlet tube.
91g (0.5gfw) and 20 mesh 6.5g zinc
(0.1gaw) was charged. Gaseous hydrogen chloride was introduced at the condenser outlet at an undetectable rate. The solution is warmed to reflux. The reaction proceeds smoothly and the solution becomes a uniform reddish-brown color without any solid suspension. HCl was added for an additional 30 minutes to ensure reaction. After the reaction, 125 g (1.28 gfw) of crystalline orthophosphoric acid was added into an additional 100 ml of methanol and the mixture was refluxed. Benzene (250ml) is added and the solution is refluxed overnight. The solvent is removed and a solid precipitates out. Filter the solid (blue) and wash with methanol.
It was dried in a 20 lbs vacuum pot with 225 ml of N ₂ flowing through it. A sample of this mixed oxide was analyzed by X-ray with the following results. Line position d angstrom 2.θ degrees Intensity 5.7 15.6 100 4.5 19.7 41 3.7 24.3 25 3.3 27.1 32 3.1 28.8 14 2.9 30.5 40 2.8 32.2 9 2.7 33.7 20 Example 2 Same as Example 1 using experimental equipment and conditions of contains 91 g (0.5 gfw) of vanadium pentoxide, 19.6 g (0.3 gaw) of 20 mesh zinc and methanol.
750ml was used to produce mixed oxide (2). Example 3 The mixed oxide prepared in Examples 1 and 2 was 5%
sterotex and formed into 1/8" pills for analytical evaluation. A 4 g load of the mixed oxide was added into a small reactor containing 1.5% butane-synthetic air mixed air mixture. , 250-300㎓ for 2 hours to remove the stereotex. The mixed oxide was then raised to the desired temperature for an additional 4 hours and analysis of maleic anhydride was carried out by gas-liquid partition chromatography. The results are shown in the table and table.The catalyst sample was subjected to X-ray analysis and the following results were obtained: Line position d angstrom 2.θ degrees Intensity 6.3 14.2 10 4.8 18.5 7 3.9 23.0 100 3.1 28.5 58 3.0 30.0 29 2.7 33.8 7

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Claims (1)

[Claims] 1. A catalyst for the production of maleic anhydride by the oxidation of butane consisting essentially of a phosphorous-vanadium mixed oxide, containing zinc as a promoter, the catalyst comprising: reduction, followed by reaction of the vanadium-zinc oxide solution with phosphoric acid such that the atomic ratio of vanadium to phosphorus is 0.5:1-
1.25:1 and the total atomic ratio of zinc to vanadium is 0.01:1-0.25:1, and the catalyst in the first phase is prepared using copper K alpha radiation to form a characteristic initial powder as follows: It has an X-ray diffraction pattern, line position d angstrom 2.θ degrees intensity 5.7 15.6 100 4.5 19.7 41 3.7 24.3 25 3.3 27.1 32 3.1 28.8 14 2.9 30.5 40 2.8 32.2 9 2.7 33.7 20 Oxidation of butane to maleic anhydride When heated to a temperature of about 600-800㎓ under the reaction conditions of copper K, the following characteristic powder X-ray diffraction pattern is obtained using alpha radiation: Line position d 2.θ degrees Intensity 6.3 14.2 10 4.8 18.5 7 3.9 23.0 100 3.1 28.5 58 3.0 30.0 29 2.7 33.8 7 A catalyst that converts into a phase having 2 Phosphorus atom is 0.81 for each vanadium atom:
1-2:1 catalyst according to claim 1. 3 Zinc atom is 0.01 for each vanadium atom
-0.25 of the catalyst according to claim 1.