CS230902B1 - Catalyst for preparation of nonsaturated carbonyl compounds by oxidation of olefin in gas phase and method of its preparation - Google Patents

Abstract

Catalysts according to the invention are intended for use oxidizing olefins to unsaturated carbonyl compounds, in particular for the oxidation of propylene to acrolein. They contain oxidic compounds elements VI. B groups in combination with oxidic IV. A, V. A and VIII. B groups of the periodic system. For catalysts This composition has been found suitable method of preparation leading to higher catalytic effects and benefits, eg mechanical strength.

Description

The preparation of unsaturated carbonyl compounds and unsaturated acids by gas-phase catalytic oxidation of unsaturated hydrocarbons is one of the subsidiary industrial processes of considerable economic importance. Wide application and further development of the process is conditional on mastering the production of highly active and selective catalysts. This requirement results from the complex mechanism of oxidation of unsaturated hydrocarbons, characterized by the simultaneous course of a series of sequential and parallel reactions. In the catalytic oxidation products of olefins, such as propylene, in addition to the desired valuable products, such as acrolein and acrylic acid, also saturated acids (formic, acetic, propionic), saturated aldehydes (formaldehyde, acetaldehyde), carbon dioxide and carbon monoxide, optionally unreacted propylene. Oxidation is accompanied by considerable heat release, which affects both the properties of the catalyst during long-term use under reaction conditions and the course of undesirable reactions.

In terms of suppressing the course of adverse reactions, certain qualitative requirements are placed on the properties of the catalyst. This is primarily due to the high olefin conversion and the high selectivity of olefin oxidation to valuable products. These requirements are given above all by economic considerations requiring maximum appreciation of the processed material. Equally important are the technological requirements which result from the fact that any unreacted olefin and unwanted products need to be separated from the valuable components in the subsequent processing nodes of the products leaving the oxidation reactor continuously.

A number of active and selective catalysts for the production process, such as acrolein and acrylic acid, are currently published and patented. For example, in DOS No. 2,125,032,

161 471 and 2 228 266 disclose a method of using catalysts containing Mo, W, Co, Fe, Bi, Si as oxides as main constituents. It is reported that an improvement in the catalytic properties is obtained when an element of the I.A or II.A group of the Periodic System, or thallium, is present in the catalyst. 5f DOS 2 202 733 discloses that improved catalytic properties are obtained if, in addition to Mo, Co, Fe and Bi, one of the elements Al, Ni,

W, Cr, In, Nb and always Sn. According to DOS 2,139,976 an active catalyst comprising Mo, Co, Ni, Fe, Bi, P, K can be prepared. These elements are applied in the form of solutions to the support by saturation.

It is clear from the cited sources that the desired catalytic effects are achieved by the simultaneous presence of more than four elements with different chemical properties. The actual chemical composition of catalysts of this type is unknown. However, the oxygen content of the finished catalyst varies according to the relative ratio of the catalyst components.

Water-soluble salts, such as nitrates, hydroxides, carbonates, salts of organic acids and the like, are usually used to prepare the catalysts. ammonium salts of complex acids.

Upon mixing of all catalyst components, a catalyst mass suspension of unknown composition is formed. Along with the desired products, a number of by-products have no catalytic effects. The exact composition of the by-products is not known since it varies according to the type of salts of the active components used to prepare the catalyst. It is contemplated that various ammonium salts of mineral acids are present, such as nitrate, carbonate, oxalate, acetate, formate, hydroxide, and optionally free mineral acids.

Various methods are used to prepare catalysts containing simultaneously more active components. The simplest methods include simply igniting a mixture of the starting compounds of the active components. The resulting annealing mass is formed into particles of the desired shape and size. Preferably, an inert material can also be added to the annealed mixture. This not only reduces the consumption of catalytically active components, but also provides catalysts with the desired mechanical and physicochemical properties. The catalytically active constituents can also be applied to the inert material or to the substances having the desired properties by saturation from the solutions or from the solution. by spraying a solution of the active components. The catalysts thus prepared are then further heat treated. A widespread method of preparing catalysts is by precipitation or co-precipitation of active components in solution, optionally in the presence of a carrier. Depending on the nature of the compounds used or the requirements for the formation of catalytically active substances with the desired additional properties, all important for industrial application, there are a number of different variants of this process. It is surprising at first glance that, despite the complicated chemical composition of the catalysts for the selective oxidation of unsaturated hydrocarbons, the published literature does not mention the preparation conditions ensuring the formation of catalysts with high activity and selectivity. It is even reported that the desired catalytic effects can be achieved by any of the generally known methods as outlined above.

This is interesting because many of the processes used consist of a series of steps evidently affecting the chemical and phase composition of the finished catalyst of a complex nature. Thus, the most commonly used process for the preparation of oxidation catalysts consists of the following operations: solution preparation, precipitation or co-precipitation, separation of solids from liquid (filtration, washing, drying), thermal treatment of catalyst mass drying, grinding, homogenization, shaping, thermal activation in gas stream aj.

In some cases, certain operations can be combined, eg shrinking or co-shrinking with shaping, drying with thermal activation, etc.

It has now been found that the improved catalytic effects of unsaturated hydrocarbon oxidation catalysts on unsaturated aldehydes and unsaturated acids, particularly propylene to acrolein and acrylic acid catalysts, are achieved not only by the simultaneous presence and correct ratio of one or more IV elements. A, V. A, VI. B with VIII. B groups of the periodic system as active components, but also by selecting the optimal technology for preparing the catalyst mass, which is the object of the present invention.

Catalyst for the preparation of unsaturated carboxylic compounds by gas-phase oxidation of olefins containing, in oxide form, in addition to molybdenum and optionally other VI elements. B of the Periodic System group by at least one of the elements of IV. A, V. A and VIII. The group B of the periodic system according to the invention has an atomic ratio of the elements in the range: Mo 12, or the sum of tungsten W and uranium U to 6, elements of group IV. A, i.e. silicon Si and tin Sn 0.5 to 10.0, elements of group V. A, ie phosphorus P, antimony Sb, bismuth Bi 0.1 to 10.0, and elements of group VIII. B, i.e. iron Fe, cobaltCo, nickel Ni 0.1 to 10.

The catalyst of this composition is prepared according to the invention by mixing solutions of water-soluble salts of the active catalyst components at temperatures up to 95 ° C, the resulting suspension is concentrated, dried and formed into tablets, after which the dried and formed catalyst mass is heat-treated temperatures of 105 to 300 ° C, with gradual start-up at a temperature of 30 to 100 ° C / ha and passing heat dissipating gas at a rate of 100 to 20,000 v / v. of the catalyst. h, and then further calcined at temperatures of 300 to 550 ° C for 2 to 24 h, preferably at 420 ° C for 6 hours.

Since catalyst tableting is a costly molding process, the more preferred method is to mix solutions of water-soluble salts of the active catalyst components at elevated temperatures up to 95 ° C, concentrate the resulting slurry and optionally dry and concentrate the catalyst slurry and / or the dried catalyst mass. knead with water, optionally with the addition of cellulose derivatives such as carboxymethylcellulose and / or urea and / or hexamethylmethyl tetramine or magnesium compounds such as magnesium oxide in a weight ratio to the dried catalyst mass of 0.1 to 5 to 1000. The resulting paste is then In a manner known per se, it is extruded into extrudates which, after drying, are heat-treated by annealing at 105 to 300 [deg.] C. and successively ramping to temperatures of 30 to 100 [deg.] C./h and passing heat dissipating gas at 100 to 20,000 vol. Vol. of the catalyst. h and then further calcined at 300 to 550 ° C for 2 to 24 hours, preferably at 420 ° C for 6 hours.

The catalyst thus prepared has advantageous mechanical properties, porosity and low bulk density, especially when compared to catalysts prepared from a dried and preheated catalyst suspension by tabletting.

The catalysts prepared according to the invention achieve high catalytic efficiency in comparison with the prior art catalysts of similar composition, at a substantially lower mass of catalyst charge in the oxidation reactor.

The annealed catalyst is preferably used in the oxidation of propylene at a reaction temperature of 250 to 420 ° C, in particular at 275 to 400 ° C. The composition of the incoming reaction mixture varies within wide limits of 1 to 15 74 mol. propylene, 5 to 60 mol. water vapor and 20 to 80 moles of air, some of the water vapor may be exchanged with another gas, such as nitrogen. The contact time of the reaction mixture (NTF) varies depending on the temperature and the composition of the reaction mixture in the interval of 0.5 to 20 s. Within certain limits, the yields of valuable products (acrolein, acid, acrylic) can be changed. of the examples. The oxidation of propylene can be carried out with a fixed bed or fluidized bed catalyst. When the oxidation is carried out with the catalyst in a fixed bed, preferably tubular reactors located in a circulating salt bath are used. In this case, the working pressure can be varied within a range of 0.1 to 1.0 MPa without deteriorating the catalytic properties of the catalyst. Catalyst efficiency is evaluated by parameters defined as follows:

Propylene conversion% = moles of propylene reacted _χ , qq moles of propylene feed

Selectivity to acrolein% (per acid = moles of acrolein (acrylic acid) x 100 acrylic) moles of reacted propylene

Acrolein (acrylic acid) yield% = conversion x selectivity

100 «

The following examples serve to further illustrate the invention.

Example 1

165 g of Co / NO2 / g · 6 HgO are dissolved with stirring in 330 ml of distilled water. Similarly, 404 g of Fe / NO3 / 9 · 9 HgO are dissolved separately ⁱⁿ 330 distilled water and 485 g of Bi / NO3.

. 5 HgO in 500 ml of distilled water, to which 100 ml of concentrated HNO4 had previously been added, dissolved in 3000 ml of distilled water, with 2,122 g / NH4 / gMo2O3. 4 HgO at 50 ° C. Warm solutions of cobalt, iron and bismuth nitrates are then added in portions with stirring to the molybdenum salt solution. Finally, 300 g of 30% stabilized silica sol are added. After stirring, the resulting suspension is dried at 120 ° C, formed into tablets and calcined in a flow of air at a rate of 2000 vol / vol. Cat./h at 450 ° C for 4 hours.

ml of crushed catalyst is charged into a 14 mm stainless steel U-reactor. The reactor is heated in a molten salt bath at 375 ° C while passing a gas mixture containing 3.25 mol%. propylene, 31% mol. nitrogen, 31 mol. % air and 34.75 mol%. water vapor. The contact time of the mixture is 3.6 seconds.

The conversion of propylene is 85.1 the yield of acrolein, acrylic acid and acetic acid are respectively 56.0%, 16.6%, 1.6%. The rest is CO and COg ·

Example 2

000 g of the dried catalyst mass prepared according to Example 1 was kneaded with the addition of 110 ml of distilled water into a paste which was processed into extrudates. These are first dried at 120 ° C, then at 250 ° C and finally calcined for 6 hours at 420 ° C.

ml of crushed catalyst is tested, as in case 1, at a contact time of 1.8 se5 kund. The conversion of propylene is 83.4 K, the yield of acrolein, acrylic acid and acetic acid is successively 68.7%, 7.8%, 0.3%. The remainder is CO and CO 3. . ,

Example 3

To 1000 g of the dried catalyst mass prepared according to Example 1, 110 ml of distilled water containing 1.4 g of carboxymethylcellulose are added while kneading. After kneading, the paste is extruded as in Example 2. The extrudates are dried at 130 ° C for 8 hours, at 160 ° C for 2 hours, and at 250 ° C for 1 hour, successively ramping to a preheating temperature of 60 ° C / h. speed v / v kat./h. Finally, they are annealed in a stream of air at 420 ° C for 6 hours.

The particulate strength of the catalyst, determined by detecting the amount of load on the piston of the measuring instrument leading to particle breakage, is expressed in relative units of 100%.

ml of crushed catalyst was tested at 350 ° C at a reaction time of 1.8 seconds with a composition similar to that of Example 1.

The conversion of propylene is 99.6%. The yields of acrolein, acrylic acid and acetic acid are respectively 87.9 T & 9.8% and 0.9% · The rest is CO and COg ·

He attaches

According to Example 3, 3 catalyst samples are prepared:

<sample A: without addition of carboxymethylcellulose sample B: with addition of 5.2 g urea sample C: with addition of 3.5 g magnesium oxide.

The catalyst samples are subjected to mechanical strength tests. According to the results, Catalyst B has the same strength as Catalyst A, but Catalyst C has a strength of 24% higher. The carboxymethylcellulose catalyst also has a strength of more than 25%. The bulk density of the catalyst with the above additions is 20% lower than the catalyst prepared by tableting according to Example 1.

Example 5

Along with the preparation of the solutions of Example 1, a solution of 125.5 g UOg / KO.sub.2 / g was further prepared. 6 HgO in 80 ml of distilled water. This solution is then metered into a molybdenum salt solution containing other solutions of the active catalyst components. The resulting suspension was treated as in Example 3 after stirring.

ml of crushed catalyst is tested at a reaction time of 1.8 seconds and a composition as in Example 1 at 35 ° C.

The propylene conversion is 95.1%. The yield of acrolein, acrylic acid and acetic acid are respectively 84.7%, 7.5% and 1.1 K> respectively. The rest are CO and COg.

Examples

According to Examples 1 and 3, a series of catalysts are prepared containing the elements of the invention in varying proportions.

All were evaluated by placing 5 rolls of crushed catalyst in a 14 mm diameter stainless steel U-reactor. The reactor is heated in a molten bath by passing a gas mixture containing 3.25 mol%. propylene, 31 mol%. of nitrogen 31 mol%. % air and 34.7 mol. water vapor. The contact time of the mixture is 1.8 seconds.

Catalyst Mo 12 : 1: Si 1: Bi 1: Fe 1: Co 1 Uo 12 : W 1: U 1: Si 0.5 : Bi 1 : Fe Uo 12: i W 1: Si 4: Bi 1: Fe 1: Ni 1 Uo 12: : Sn 0.5: Bi 1: Fe 1: Co 1 Mo 12: Si 2: Bi 0.5: P 1 : Fe 1 : Co Uo 12: : Si 1: Sb 1: Bi 1 : Fe 1 : Co

Example 7

Temperature ° C Propylene Conversion% Acrolein yield% 350 97.2 83.0 350 94.6 80.1 360 91.6 79.9 360 94.4 82.8 375 93.7 80.3 375 94.0 75.0

According to Example 1, but with 20 times the weight of the salts of the active components, a catalyst slurry is prepared, which after drying is heat treated as in Example 3. The preheated mass is formed into 5 mm particles.

550 ml of catalyst are tested in a 30 mm stainless steel reactor placed in a molten salt bath. The oxidation mixture contains 4.9 mol%. propylene, 21 mol% water vapor, mol%. air and the rest is nitrogen. At a temperature of 375 ° C and a contact time of 1,5 seconds at a pressure of 270 KPa, the following results shall be obtained after 3 100 operating hours:

propylene conversion 97%, yield of acrolein, acrylic acid and acetic acid successively 75%, 16%, 1.1%. The rest are CO and COg. The water condensate does not contain propionic acid or propionaldehyde in observable amounts.

Claims (3)

object of the invention Catalyst for the preparation of unsaturated carbonyl compounds by gas-phase oxidation of olefins containing, in an oxide form, in addition to molybdenum and optionally other VI elements. B of the Periodic System group by at least one of the elements of IV. A, V. A and VIII. B group of the periodic system, characterized in that the atomic ratio of the elements present is in the range: molybdenum 12, or the sum of tungsten W and uranium U to 6, elements of group IV. A, i.e. silicon Si and tin Sn 0.5 to 10.0, elements of Group V. A, ie phosphorus P, antimony Sb, bismuth Bi 0.1 to 10.0, and elements of Group VIII. B, ie iron Pe, cobalt Co, nickel Ni 0, <t to 10. 2. A process for the preparation of the catalyst according to claim 1, which comprises mixing, at a temperature of up to 95 DEG C., the water-soluble salts of the active components of the catalyst, concentrating the resulting suspension, drying and forming it into tablets. It is annealed at 105 to 300 ° C with gradual start-up at a temperature of 30 to 100 ° C / ha and passing heat dissipating gas at a rate of 100 to 20,000 v / v. of the catalyst. h, and then further calcined at 300 to 550 ° C for 2 to 24 h, preferably at 420 ° C for 6 hours. 3. A process for the preparation of the catalyst according to claim 1, which comprises mixing solutions of water-soluble salts of the active components of the catalyst at elevated temperatures of up to 95 [deg.] C., the resulting suspension is concentrated and optionally dried. knead with water, optionally with an aqueous solution of cellulose derivatives, preferably carboxymethylcellulose and / or urea and / or hexamethyltetramine and / or magnesium compounds, eg magnesium oxide in a weight ratio to the dried Severography, n. P., MOST Price 2.40 Kč with catalyst mass 0.1 to 5 to 1000, the resulting paste is then processed by extrusion into extrudates, which after drying are heat treated by annealing at temperatures of 105 to 300 ° C and gradual start-up at temperatures of 30 to 100 ° C / ha while passing the heat-dissipating gas at a rate of 100 to 20,000 vol / vol. of the catalyst. h and then further calcined at 300 to 550 ° C for 2 to 24 h, preferably at 420 ° C for 6 hours.