The preparation method of catalyst for the oxidation of propylene
The invention relates to a method for preparing a multi-component catalyst for the oxidation of propylene to acrolein. The method comprises mixing the components of a catalyst mass, drying, decomposition of metal salts, which are carried out in stages, with a gradual increase of temperature from 150 to 250aboutC for 10 hours, preferably from 150 to 180C for 3 hours, from 180 to S for 5 hours and from 210 to C within 2 hours, calcining the active components of the catalyst in two stages with an intermediate molding powder of the catalyst between them. The first stage of annealing the active catalyst components is carried out at 380-S, while the second 400-480P. The technical result of the invention is the achievement of the activity of the catalyst while maintaining its strength, which guarantees a long service life, 3 C.p. f-crystals, 1 table.
The invention relates to a method for preparing a multi-component catalyst for the oxidation of propylene to acrolein.
A known method of producing catalyst for the oxidation of propylene into acrolein by mixing solutions of ammonium salts of molybdenum, vanadium, tungsten with bismuth nitrate with further UPA is an SSSR, Sib. Department, 1964, page 211).
The disadvantage of this method is to obtain a catalyst with low activity.
There is a method of preparation of the catalyst, which consists in mixing an aqueous solution of heptamolybdate or ammonium tungstate with an aqueous solution of nitrates of cobalt, iron and bismuth followed by filtration, drying and calcination. (U.S. Pat. The USSR №1146916, Appl.24.04.81, publ.15.01.85 g 01 J 37/03).
The disadvantage of this method is that when filtering is a great loss of valuable components, which eventually become the catalyst of a given composition.
The closest in technical essence and the achieved result to the present invention is a method of preparation of the catalyst for oxidation of propylene to acrolein, which consists in mixing an aqueous solution of heptamolybdate ammonia with a solution of nitrate salts with further evaporation catalyst mass and vacuum heat treatment (ed. the certificate in No. 1659091, Appl. 20.06.89,, publ.30.06.91, 01 J 23/88.
The disadvantage of the above-mentioned catalyst is its poor durability. The low strength of the catalyst leads to its destruction during transportation, loading Rea the main catalyst for the oxidation of propylene, remain active for a long period of operation.
The technical result of the invention is the achievement of the activity of the catalyst while maintaining its strength, which guarantees a long life.
In the proposed method, the catalyst is prepared as follows. Mixed aqueous solutions of heptamolybdate ammonia with a solution of nitrate of iron, bismuth, cobalt, potassium and lithium. Obtained by co-precipitation of the catalyst suspension is stirred for 30 min until a homogeneous paste is obtained, then the last served on a spray dryer or evaporated with periodic stirring.
Catalyst powder decompose to the oxides at a temperature of 150-C for 10 hours with a gradual rise in temperature from 150 to 180C for 3 hours, from 180 to S for 5 hours and from 210 to C for 2 hours, then calcined for 6 hours at a temperature of 380-S, then molded by any known methods (extrusion or tableting). Granules of the catalyst calcined 4 hours at a temperature of 400-480P (preferably 420-S).
Features of the invention are new, as is not described in the known sources of information. The set of features of the image the second catalyst (strength of 3.0 MPa, conversion of 98%, the yield of the desired oxidation products 91%, the lifetime of more than 4 years).
The strength of the granules is determined on the device “Procomer 50”.
The limit of compressive strength of pellets in megapascal (MPa) calculated by the formula
where P is power in reading the display unit corresponding to the point of complete destruction of the granules, N.;
Sg- the cross-sectional area of the pellet, cm2.
In the examples below, the total degree of conversion of propylene (conversion) and the product yield of the reaction is determined as follows:
106,2 g heptamolybdate ammonium (NH4))6Mo7O24·4H2O are dissolved in 130 ml of distilled water at a temperature of 60C with stirring (solution No. 1).
Separately prepare a solution of nitrate salts (solution No. 2). In 25 ml of distilled water and 6 ml of nitric acid at a temperature of 50C dissolve to 58.2 g of cobalt nitrate Co (NO3)2·6N2Oh, here parts sprinkled with 19.4 g of bismuth nitrate Bi (NO3)3·5H2O, br15.15 g of iron nitrate Fe (NO3)3·N2O, 0.25 g of potassium nitrate (KPO3) and 0.32 g of lithium nitrate (LiN3·3H2O).
Solution No. 2 is poured PA in a drying Cabinet at a temperature of 110±10 ° C with periodic mixing, decompose to the oxides at a temperature of 150-C for 10 hours with a gradual rise in temperature from 150 to 180C for 3hours, from 180 to S for 5 hours and from 210 to S for 2hours, pulverized, calcined catalyst powder for 6 hours at a temperature of 380-S, then formed into granules laboratory syringe with the size of the nozzle 5 mm
Molded catalyst provalivajut on the air for 8-10 hours at room temperature, then finally dried in a drying Cabinet at a temperature of 110-120C and calcined 4 hours at a temperature of 420S. Get the catalyst composition of Co4Mo12Bi0,8Fe0,75K0,05Li0,06with the strength of granules 2.5 MPa.
In the flow reactor of stainless steel with a diameter of 25 mm load 40 ml of the catalyst granule size 5 mm Heating of the reactor is carried out by electric heaters. When passing through the catalyst gas mixture containing 8 vol.% propylene, 30% vol. water vapor and 62% vol. air at a temperature in the reaction zone S contact times of 3.0 with the conversion of propylene is 98%, the output of acrolein - 84%, acrylic acid - 6%.
7,1 kg of ammonium molybdate ((NH4)6Mo7O24·4H2Oh are dissolved in 11 l of the courtyard of the nitrate salts. 5.0 l of distilled water and 435 ml of nitric acid (density of 1.36 g/cm3) dissolved 2,35 kg of iron nitrate Fe (NO3)3·N2O, then here portions sprinkled 0.65 kg of bismuth nitrate Bi(NO3)3·5H2O 5,85 kg of cobalt nitrate Co (NO3)2·6N2Oh, 16.7 g of potassium nitrate (KPO3) and 17.4 g of lithium nitrate LiN3·3H2O.
Each subsequent salt added after complete dissolution of the previous one.
To a solution of ammonium molybdate in continuously operating mixer slowly poured the solution of nitrate salts. The resulting paste is stirred for 30 minutes to obtain a homogeneous mass, then paste the pump serves on the spray dryer. The temperature at the inlet of the dryer ~230S, output - 110S.
The resulting powder was decomposed to the oxides at a temperature of 150-C for 10 hours (with a gradual rise of temperature, as in example 1), and then calcined for 6 hours at a temperature of 400C and mold.
The obtained granules are calcined at a temperature of 420S 4 hours. Get the catalyst composition of Co6Mo12Bi0,41Fe1,75K0.05Li0,04with the strength of granules of 2.5-3.0 MPa.
6.5 liters of catalyst sarsala, the temperature of the melt is maintained automatically by electrical heating, the reaction zone the temperature control of the melt of the Solea.
Through the layer of catalyst is passed gas-vapor mixture, vol.%, propylene - 6, air - 54, water vapor - 40. The contact time of 2.5-3.0 s, the temperature of the melt 290±5C. Under these conditions, the conversion of propylene is 98%, the output of acrolein - 85%, of acrylic acid 5-6%. After 3000 hours of operation, the strength of the unloaded catalyst is slightly higher initial and amounted to 3.5 MPa while maintaining activity.
The catalyst prepare and test as in example 1, except the temperature of annealing. The temperature of calcination of the catalyst 480P.
On this catalyst, the conversion of propylene is 96%, the total yield of acrolein and acrylic acid 87%. The strength of the catalyst 3.5 MPa.
The results of the tests of the catalysts according to examples 1-4 are presented in the table.
Example 4 (comparative prototype)
Preparation of solutions of salts is conducted according to example No. 2 of the description of the present invention. Further, the preparation of the catalyst is carried out according to the prototype.
The coprecipitation of a catalyst mass produce PU is born 60C. After the co-precipitation of the resulting slurry is stirred for another 1.5-3.0 hours and evaporated at 100-110S. Received thtee (0,5-5,0 mm) pieces of the catalyst is subjected to vacuum heat treatment: at 150C (8-10 h); 180C (10 h); 230S (10 h) and 380-450S (8 h).
The catalyst corresponds to the empirical formula
During testing of the catalyst under the conditions of example 1, the conversion of propylene is 96%, the output of acrolein - 82%, acrylic acid - 6%. Loaded in the reactor pieces of the catalyst under the influence of the gas-vapor stream after 50 hours of operation begin to break down, therefore increasing the pressure in the system. To determine the strength of the catalyst is not possible.
1. The preparation method of catalyst for the oxidation of propylene, comprising mixing components of the catalyst mass, drying, decomposition of salts and annealing, characterized in that the decomposition of metal salts is carried out in stages, with a gradual increase of temperature from 150 to S for 10 h, and the annealing of the active catalyst components is carried out in two stages with an intermediate molding powder of the catalyst between them.
2. The method according to p. 1, is within 3 h, from 180 to C for 5 h and from 210 to C within 2 hours
3. The method according to p. 1, characterized in that the calcination of the powder of the active catalyst components is carried out at 380-C, and the annealing molded catalyst is carried out at 400-480P.