RU2200060C1 - Catalyst preparation method - Google Patents

Abstract

FIELD: multi-purpose catalysts. SUBSTANCE: invention provides preparation of vanadium catalyst suitable for use in sulfuric acid production, for CO removal from process gases and neutralization of nitrogen oxides in vehicle exhaust gases, in organic synthesis, etc. Colloidal silicate gel mass containing 5 to 20% silicon dioxide (60-98% of the weight of catalyst in sum) is saturated at 5-40 C with ammonium metavanadate in the form of saturated solution (2-40% of the weight of catalyst) in presence of aqueous ammonia solution added to pH 3-5. Resulting gel-like mass is granulated in presence of plasticizer to give catalytic product, which is dried at 130-220 C. EFFECT: increased catalyst activity due to elevated formation of active sites. 3 ex

Description

The invention relates to the field of heterogeneous catalysis and can be used in the production of sulfuric acid, for the purification of process gases from CO, also for the neutralization of NO _x contained in the exhaust gases of vehicles, in organic synthesis, etc.

 A known method of producing a platinum catalyst by impregnating solid silica gel with a solution of platinum chloride, followed by its reduction with hydrogen at a temperature of 770K (see J. Andersen. The structure of metal catalysts. - M .: Mir. - 1978. - S. 171-202).

 The disadvantage of this method is the high cost of the catalyst, the use of scarce platinum and the need for synthesis of the catalyst in an explosive atmosphere of hydrogen.

 The closest in technical essence is a method of producing a vanadium catalyst, including obtaining a colloidal silicate gel mass, separating the resulting mass from the liquid phase by filtration and saturating it with a metavanadate compound followed by granulation and drying of the catalytic product (see A.G. Amelin. Sulfuric acid technology. - M .: Chemistry. - 1971. - S. 193-199 - prototype).

The specified vanadium catalyst (BAS) used in the sulfuric acid technology is obtained by mixing in the reactor an alkaline solution of potassium vanadate with liquid potassium glass with continuous stirring and a temperature of up to 70 ^o С, after which hydrochloric acid AlCl ₃ solution and aqueous are added to the mixture with stirring BaCl ₂ solution. The resulting gel mass is filtered off on a filter press and squeezed on a hydraulic press. The precipitate with a moisture content of 40-45% is molded in the form of granules, tablets or rings, and then dried for ~ 30 hours at a temperature in the range of 60-105 ^o C.

 The disadvantages of this method are the presence of chlorine in the composition of the catalyst, multi-stage, duration and complexity of the production method of biologically active substances.

 The problem to be solved is to create a method for producing a catalyst having high efficiency and reactivity and increasing the technological parameters of catalytic processes.

The essence of the proposed method for producing a catalyst is as follows. The known method includes obtaining a colloidal silicate gel mass, separating the resulting mass from the liquid phase by filtration and saturating it with a metavanadate compound, followed by granulation and drying of the catalytic product. The difference between the claimed invention and the known one is that the filtered colloidal silicate gel mass containing 5-20 wt.% Silicon dioxide (SiO ₂ ) is saturated with ammonium metavanadate (NH ₄ VO ₃ ) in the presence of aqueous ammonia at pH 3-5 at the following ratio of components, wt.%:
Colloidal silicate gel mass - 60 - 98
Saturated ammonium metavanadate solution - 2 - 40
after which the gel mass is subjected to granulation and drying, moreover, the colloidal silicate gel mass is saturated with ammonium metavanadate at a temperature of 5-40 ^{° C.} , the gel mass saturated with ammonium metavanadate is granulated in the presence of a plasticizer, and the catalytic product is dried at a temperature of 130-220 ^° C.

 The solution to this problem is achieved by obtaining a colloidal silicate gel mass containing 5-20 wt.% Silicon dioxide and 80-95 wt.% Water, which is then saturated with ammonium metavanadate in the presence of aqueous ammonia to pH 3-5.

Obtaining a gel silicate mass with a SiO ₂ content _of less than 5% is not technologically advanced, because the mass with such silica content is very weak and difficult to separate from the filter cloth, which leads to large losses of silicate mass.

Obtaining from the primary aluminosilicate solutions a gel silicate mass containing more than 20% SiO ₂ is also not technologically advanced, because a mass containing less than 80% water is inactive and a significant part of it becomes ballast when interacting with ammonium metavanadate. That is why for the task, the composition of the gel silicate mass containing 5-20 wt.% SiO ₂ and 80-95 wt.% Water is optimal. The gel mass of this composition can be easily separated from the filter cloth and used for subsequent technological operations.

The gel silicate mass is pulped in a saturated aqueous solution of ammonium metavanadate. Moreover, depending on how much V ₂ O ₅ should be contained in the final product, the volume of a saturated solution of ammonium metavanadate is precisely dosed. The weight ratio between SiO ₂ and V ₂ O ₅ when pulping (based on dry matter) is 90-99 wt.% For SiO ₂ and 1-10 wt.% For V ₂ O ₅ .

For this, the colloidal silicate gel mass should be at least 60 wt.%, Because at a lower content, a catalyst is obtained with a V ₂ O ₅ content of more than 10% and not more than 98 wt.%, because at its higher content, a catalyst is obtained with a V ₂ O ₅ content below 1%, and a saturated solution of ammonium metavanadate should be no more than 40 wt.% and at least 2 wt.%, respectively.

The range of contents of V ₂ O ₅ (1-10%) in the proposed catalyst is a requirement of the sulfuric acid industry to the quality of this kind of product. For example, in the vanadium contact mass of biologically active substances, the content of V ₂ O ₅ is 8%, and in the vanadium contact mass of BDS the content of V ₂ O _{5 is} ~ 7.2%. When the content of V ₂ O _{5 is} less than 1%, the catalyst becomes inactive and it is impractical to obtain it.

In order to create optimal contact conditions between SiO ₂ and ammonium metavanadate, the pulping operation is carried out in the presence of NH ₄ OH, the solution of which is introduced to maintain the pH of the solution within 3-5.

At pH 3-5, optimal conditions are created for the coprecipitation of the SiO ₂ gel and ammonium metavanadate. Maintaining a pH within 3-5 is determined by the solubility of SiO ₂ and the deposition conditions of ammonium metavanadate. At pH <3, SiO ₂ in the form of orthosilicic acid passes into a water-soluble form and gelation does not occur. At pH> 5, other forms of silicic acid appear, which greatly slow down the gelation process and sharply reduce the performance of the process.

In the pH range 3-5, the gelation time of the silicate mass is minimal, and ammonium metavanadate uniformly impregnates the pores in SiO ₂ and subsequently crystallizes on its surface, which is necessary to obtain the final product.

The pulping operation is carried out in the range of 5-40 ^° C. At a temperature of less than 5 ^{° C., the} content of NH ₄ VO ₃ in the saturated solution of ammonium metavanadate does not exceed 0.5 wt.% And the rate of chemical reactions of the interaction of vanadate with the surface of the silicate is very low, and at a temperature above 40 ^o With begins dehydration of the gel, which reduces the quality of the product.

The gel mass obtained as a result of mixing the components is first subjected to granulation to obtain granules 5-8 mm in size, and then dried at a temperature of 130-220 ^o C for 30-35 hours. To increase the strength of the structure of the obtained product, granulation is carried out in the presence of a plasticizer, for example, a 0.5% solution of OP-7.

At a drying temperature of 130-220 ^o C for 30-35 hours, the granules of the silicate mass of the catalyst are dehydrated, and the vanadium pentoxide crystallizes on a silica gel base. The drying interval of 130-220 ^o C is determined by the fact that ammonium metavanadate begins to decompose with the removal of ammonia and water at a temperature of 130 ^o C, and at a temperature of 220 ^o C the process of its decomposition is completely completed and only vanadium pentoxide remains on the surface of the silica gel. In this case, the residual water content in the product obtained in this way does not exceed 5-7%.

 The proposed method for producing a vanadium catalyst is as follows.

The filtered silicate gel mass containing 5-20% SiO ₂ is treated in the reactor with a 2-4.8% solution of ammonium metavanadate at a pH of 3-5 and a temperature of 5-40 ^o With a ratio, wt.%: Colloidal silicate gel mass 60-98, ammonium metavanadate 2-40. Then the gel mass is granulated on a plate granulator in the presence of a plasticizer, and drying is carried out in a drying drum at 130-220 ^o C.

 Examples of specific performance of the method.

Example 1 of a specific implementation of the method of producing a vanadium catalyst with a content of 9.5% V ₂ O ₅ .

1 kg of filtered colloidal silicate gel mass containing 20% silicon dioxide (200 g of SiO ₂ and 800 g of water) is mixed with 0.6 dm ^{3 of a} saturated solution of ammonium metavanadate containing 28.8 g of NH ₄ VO ₃ with the addition of an aqueous solution ammonia to a pH of 3.5 and a temperature of 8 ^o C for 60 minutes The gel mass is granulated with 0.5% OP-7 plasticizer and dried at 135 ^{° C.} for 30 hours. A granular product is obtained containing 200 g of SiO ₂ , 22.4 g of V ₂ O ₅ and 14.5 g of H ₂ O. In the resulting product, the content of the components is, wt.%: Vanadium pentoxide 9.5; silica 84.4; water 6.1.

Example 2 of the method for producing a vanadium catalyst with a content of 5.7% V ₂ O ₅ .

1 kg of colloidal silicate gel mass containing 12% silicon dioxide (120 g of SiO ₂ and 880 g of H ₂ O) is mixed with 0.2 dm ^{3 of a} saturated solution of ammonium metavanadate containing 9.6 g of NH ₄ VO ₃ , with the addition of aqueous ammonia solution to a pH of 4.7 and a temperature of 38 ^o C for 60 minutes The gel mass is granulated with 0.5% OP-7 plasticizer and dried at 215 ^{° C.} for 30 hours. A granular product is obtained containing 120 g of silica, 7.5 g of vanadium pentoxide and 4.8 g of water. In the obtained granular product, the content of the components is, wt.%: Vanadium pentoxide 5.7; silicon dioxide 90.7; water 3.6.

Example 3 of the method for producing a vanadium catalyst with a V ₂ O ₅ content of 1.65%.

1 kg of colloidal silicate gel mass containing 6% silicon dioxide (60 g of SiO ₂ and 940 g of H ₂ O) is mixed with 0.03 dm ^{3 of a} saturated solution of ammonium metavanadate containing 1.44 g of NH ₄ VO ₃ , with the addition of aqueous ammonia solution to a pH of 4.1 and a temperature of 30 ^o C for 60 minutes The gel-like mass is granulated with a 0.5% solution of OP-7 plasticizer and dried at a temperature of 175 ^o C for 30 hours. A granular product is obtained containing 60 g of silica, 1.12 g of vanadium pentoxide and 3 g of water. In the obtained granular product, the content of the components is, wt.%: Vanadium pentoxide 1.75; silicon dioxide 92.5; water 5.75.

The use of colloidal silicate gel mass is necessary to create optimal conditions for uniform distribution of a given amount of V ₂ O ₅ over a highly developed surface of silica gel. In the catalyst obtained in this way, the active substance is not only vanadium pentoxide, but also the surface of silica gel, whose role is not only to create a highly developed surface, but also to ensure the multifunctional nature of catalysis.

 Compared with the known method for producing such products, the proposed method allows to obtain a more active catalyst due to the formation of a larger number of active sites in the finished product on a silica gel basis.

Claims (1)

A method of producing a catalyst, including obtaining a colloidal silicate gel mass, separating the obtained mass from the liquid phase by filtration and saturating it with ammonium metavanadate, followed by granulation and drying of the catalytic product, characterized in that the colloidal silicate gel mass containing 5-20 wt. % silicon dioxide, saturated with ammonium metavanadate when adding an aqueous solution of ammonia to pH 3-5 in the following ratio, wt. %:
Colloidal silicate gel mass - 60 - 98
Saturated ammonium metavanadate solution - 2 - 40
after which the gel mass is subjected to granulation and drying, moreover, the colloidal silicate gel mass is saturated with ammonium metavanadate at a temperature of 5-40 ^° C, granulation of the saturated ammonium metavanadate gel mass is carried out in the presence of a plasticizer, and the catalytic product is dried at a temperature of 130-220 ^o C.