SU740276A1 - Method of preparing vanadium-molybdenum catalyst for acrolein oxidation - Google Patents

Description

(54) VANADIUM-MOLYBDENE CATALYST PREPARATION METHOD FOR ACROLEIN OXIDATION The invention relates to methods for preparing catalysts for oxidation, in particular for the oxidation of acrolein to acrylic acid. A known method for preparing a vanadium-molybdenum catalyst by mixing a carrier with salts of vanadium and mulibdenum. Organic substances, such as glycerol 11, are added to the solution of the katashieator in a solution of the salts of the starting components. Molybdenum catalyst scrub & l mixing media silica gel, aluminum oxide and others - a solution containing salts of vanadium and molybdenum, such as vanadate and h-ammonium molybdate "Received nnuyu suspension is evaporated with stirring and then dissolved calcining in flowing air at temperatures that povy11enii from 300 to 50 for 2 h. The disadvantages of this method include the fact that high values of activity and selectivity of Tschizator are achieved as a result of catalyst activation by the reaction mixture at elevated temperature. The aim of the invention is to obtain a catalyst with increased aq. activity and selectivity that do not require activation. This goal is achieved by describing the Е® "method of preparing the V. anadium-g" of an elibdenum catalyst, which consists in smoothing a solution of the compounds of vanadium and molybdenum with a C-silica-gel carrier, followed by drying and calcination, the calcination being carried out in a flow of reducing gas. The catalyst was prepared as follows. Prepare a solution of vanadium and molybdenum compounds. Silica gel carrier is added to the resulting solution. The suspension is evaporated, dried and calcined at 250-350 ° C in a stream of reducing gas. Hydrogen, hydrogen-nitrogen, hydrogen-water vapor, propylene nitrogen, carbon monoxide, etc. can be used as a reducing gas. Calcination can be carried out in two ways: either the catalyst is heated in a stream of reducing gas to a predetermined temperature and kept for 0.4 hours predominantly, 0.5 hours, or the catalyst is introduced into a heated furnace and the pressure in the stream of reducing gas is 0.25-4. 0.25-1 hours. The specific calcination conditions are determined by the nature of the reducing gas. After keeping the catalyst at a given temperature, it is cooled in a stream of reducing gas to room temperature and discharged. After storage - at room temperature, the catalyst does not require activation. Example, (Comparative). 4.4 g of vanadate and 30.8 g of ammonium molybdate vapor are dissolved by heating in distilled water. While stirring, 57 g of silica gel in the form of A-175 aerosil is introduced into the resulting solution. The orange-colored suspension evaporated to dryness. The resulting product was dried in an oven at 2 hours, at -18 hours. The dried catalyst was crushed and a fraction of 1-2 mm was collected. A fraction of the catalyst in the amount of 20 cm is loaded into a molybdenum glass reactor, which is placed in a tube furnace. The piercing is carried out in a dry air current. The air velocity in the flow meter set 10 l / h and include. heating stove. The rate of temperature rise. The calcination is carried out at 4 hours and cooled to about 150 ° C. Discharge catalyst is yellow-green. Example 2. The catalyst is prepared as described in Example 1, but the heat treatment is carried out in a stream of hydrogen, purified from oxygen and moisture. For this, dried catalysis in an amount of 20 cm (fraction 1-2) is loaded into a tube furnace. The reactor is flushed with hydrogen at a rate of 30 l / h for 0.5 h, then the furnace is turned on. The rate of temperature rise. The calcination is carried out at 2 for 4 hours. After calcination, the catalyst is cooled in a stream of hydrogen and unloaded. The calcined catalyst is colored blue-green. Example 3. The catalyst is prepared according to Example 2. When the temperature reaches 2, the heating system is turned off and the catalysts are cooled in a stream of hydrogen. The finished catalyst is painted in blue-green color. EXAMPLE 4 The catalyst was prepared according to example 2, but the catalyst was introduced into a heated reactor and held in a stream of hydrogen at a temperature of 0.25 hours. Example 5. The catalyst was prepared according to example 1, but calcination was carried out in azo-propylene mixture containing 9% propylene. A dried catalyst in an amount of 10 cm is loaded into the reactor and the gas mixture is purged for 0.5 h. After that, the heating is turned on and the temperature is raised to 280 ° C for 2 hours. The flow rate of the gas mixture is 2 l / h. Calcination at the temperature is carried out for 4 hours. After calcination, the catalyst is colored blue. Example 4H 2 O 5 -36 g of ammonium p-molybdate is dissolved by heating in 500 ml of a 2% solution of oxalic acid. 66.6 g of aerosil are added to the resulting solution with stirring. Further processing of the obtained suspension is carried out analogously to Example 2. The catalytic properties of the obtained samples were determined in the reaction of acrolein oxide – acryne acid in a flow-circulation installation with and the composition of the acrolein-Oj (vapor) 4: 7: 20 mixture (about ,%), the rest is nitrogen. The catalytic properties of the obtained samples are given in the table, from which it can be seen that the catalysts calcined in a reducing medium (examples 2-6) do not require activation of the reaction mixture. As can be seen from the table, according to the proposed method, it is possible to prepare a catalyst with high activity and selectivity in the process of oxidizing acrolein to acrylic acid, without its additional activation.

1.38

15

11 3 1.5

81

1.44 72

5 3 1.43 78

4.5

1.46

68

1.43

81

85 93

0.1

1.3 2.8

five

90

1.8 92

2.5

1.7

1.4

90

92

2.9

Claims (2)

1.Patent Frangshi number 2040546, cl. C 07 S 51/00, published 1971. 2.US Patent No. 3,439,028, cl. 260-530, publ. 1969 (prototype).