CS198242B2 - Method of preparation of the catalyser on the base of the vanadium and molybdenum - Google Patents

Abstract

based catalyst is prepd. by first impregnating an inert, porous, support with an aq. soln. of V and Mo salts, at Mo33:V2O5 ratio 0.3-1.2, which also contains organic reducing agents (I) such a acids or their NH4 salts. The impregnated catalyst is then heated to remove volatiles a and calcined. (I) is 0.4-1.2 moles per mole V2O5 and the soln.also contains activators, esp. PMNa and 1 of Ni, Fe, Co, Ag, Cu, Cr, Cd, U, W, K, Te and Ta. Specified (I) are oxalic, citric, ascorbic, formic and maleic acids or their NH4 salts. The catalysts are simply and inexpensively prepd. (dissolution of the metal salts in conc. HCl is avoided), gives good yields and have long active lifetimes.

Description

SUMMARY OF THE INVENTION The present invention provides a process for the production of catalysts based on vanadium and molybdenum, which are used to produce acid anhydride. by maleic oxidation of benzene in. gaseous state. Catalysts are generally used in this manufacturing process. containing vanadium trioxide and molybdenum trioxide, in which the molar ratio of molybdenum trioxide to vanadium trioxide is usually in the range 0,3 to 1,2.

The active substance based on vanadium and molybdenum most often contains the above-mentioned oxides of promoters, which are the oxides of elements. such as lithium, sodium, potassium, cobalt, nickel, iron, chromium, copper, silver, tungsten, uranium, phosphorus, tellurium, tantalum etc.

For the catalytic properties of catalysts based on. vanadium and molybdenum are decisive for their chemical and phase composition, the carrier used and its structure, the type - and - concentration of promoters and, moreover, used. a process which has a significant influence on the quality of the catalysts.

These. Catalysts are most often produced by appropriately applying the active material to a support o. low surface area. Electro-corundum, carborundum and sintered α-alumina corundum are generally suitable as supports.

In the case of supported catalysts, the active mass is deposited on the support, i.e. the support is impregnated with a solution prepared especially for this purpose. This impregnating solution contains the corresponding. salts dissolved in aqueous mites of mineral or organic acids. . Sometimes deposition is active. carrier materials. is carried out by a sintering process using a mixture of the respective salts; or. oxides. Catalysts obtained by impregnating the support with aqueous solutions. is dried after the impregnation is complete. and then calculate,. most often at a temperature in the range of 320 to 450 ° C.

All types of fixed catalysts,. used in the partial oxidation of benzene in vapors must be characterized by considerable mechanical strength, such as. i. thermal stability, since under industrial conditions they operate continuously for 2 to 3 years in catalyst beds. o. thickness about 3. m at a temperature of up to about 400 ° C, which may even be in the reaction zone. even higher.

Vanadium and molybdenum catalysts, which are prepared by impregnation, are often used to produce maleic anhydride. . carriers with a solution prepared. by dissolving hot vanadium oxide and molybdenum oxide. in concentrated hydrochloric acid. Hereby. in this way high catalysts are obtained. efficiency and high stability, and this is achieved. equal. distribution - of the active mass - on the grains of the catalyst, as well as the adhesion of this active mass. During the dissolution of vanadium pentoxide in concentrated hydrochloric acid, atomic chlorine is released, which is known to be very active chemically, so that the chemical equipment used has to be subject to very high requirements in terms of its chemical resistance. high cost of equipment. In addition, concentrated hydrochloric acid and chlorine released during the process always present a potential hazard to the operator working in the production of the catalyst and also contaminate the environment. For these reasons, taking into account safety and hygiene conditions and also to reduce the production cost of the catalysts, it would be desirable not to use hydrochloric acid in the production of the catalyst. The process for preparing catalysts by impregnating the carrier with solutions which are prepared by dissolving the respective salts of vanadium and - molybdenum as well as the corresponding promoters - provides. . Catalysts which, in the oxidation of benzene - to - maleic anhydride, give a low yield and thus do not meet the requirements of the prior art. Therefore, the catalysts thus produced are not used on an industrial scale.

Better, more active catalysts can be prepared when aqueous, highly concentrated solutions of some organic acids, including oxalic acid, are used as solvents instead of water. In the case of this acid, 3 to 6 moles of oxalic acid are used per mol of vanadium pentoxide introduced. By selecting such a concentration of the acid - oxalic acid or other organic acid - in the solution, good solubility of the introduced salts is achieved, but in the last impregnation stage the catalyst grains are bonded or even the whole of the catalyst mass produced is sintered. In addition, in this process, low adhesion is achieved between the active material and the support, which not only makes the production of catalysts more difficult, but also has a negative effect on the industrial application of the stationary catalyst bed. .

The purpose of the invention. is the elaboration - simple and - what - - - the cheapest -. process - producing catalysts based on. vanadu -. and molybdenum. By using these - catalysts - in the gas phase oxidation of benzene, maleic anhydride is to be obtained in high yields. These catalysts - when used on an industrial scale - also have a long service life

Surprisingly, it has now been found that the process for producing catalysts based on vanadium and molybdenum can be - considerably simplified if the prior art - dissolution of the active catalyst mass components in concentrated mineral acids or in a large amount of organic acids is replaced by dissolution of these - components in the water.

It is therefore an object of the present invention to provide a process for producing a catalyst. based on vanadium and molybdenum for gas-phase oxidation of benzene to maleic anhydride by impregnating an inert porous carrier with an aqueous solution containing dissolved vanadium and molybdenum salts - with a molar ratio of molybdenum to molybdenum oxide in the range of 0.3 to 1 , 2 promoters such as phosphorus, potassium, - sodium, nickel, cobalt, iron, silver, copper and tantalum, as well as organic acids, and subsequent evaporation of the volatile components, - which process is carried out by - preparing an aqueous - a solution containing vanadium and molybdenum salts as well as promoters, organic carboxylic acids having reducing properties, or their ammonium salts, in an amount of 0.4 to 1.2 moles of acid or its salt per liter are added to this solution mole of vanadium oxide '

This solution - is -. impregnates an inert porous carrier on a low specific surface.

The carrier impregnation solution is prepared as follows: ammonium, a vanadic acid salt or vanadium pentoxide, is dissolved in hot water, and then molybdic acid, its anhydride, or its ammonium salt is dissolved in the solution, the molar ratio of molybdenum oxide to oxide being dissolved. The vanadium is in the range of 0.3 to 1.2. However, it is particularly preferred to use a catalyst in which the molar ratio of said oxides is in the range of 0.3 to 0.6. Promoters such as phosphorus and sodium as well as at least one of the metallic elements such as nickel, cobalt, iron, silver, copper and tantalum are then introduced into the solution. These promoters are - in the form of - well-soluble salts - in which the second component - is volatile under the conditions of the catalyst calcination running in the temperature range of 200 to 400 degrees Celsius. In this case, the salts of said metals turn into oxides. The reducing agent is then re-introduced into the finished solution in the form of a water-soluble organic substance, such as, for example, the corresponding organic acids or their ammonium salts. Ammonium oxalate, an acid, is used as reducing agent. oxal, - lemon, ascorbic, maleic, ant. or the ammonium salts of these acids, which are introduced into the solution in an amount of 0.4 to 1.2 mol, preferably 0.6 to 1.0 mol, per mole. mole of vanadium pentoxide which is in solution in the form of an appropriate soluble salt. an inert, porous carrier having a low specific surface area in the range of 0.01 to 1.0 m 2 / g is impregnated with the prepared solution. The carrier, heated in a rotating vessel, is poured over the impregnating solution at a temperature of 60 to 200 ° C. After all of the impregnating solution has been consumed, the catalyst obtained is dried and calcined at a temperature in the range of 200 to 400 ° C.

The process according to the invention, for the production of a catalyst based on vanadium and molybdenum, has a number of advantages over the processes used hitherto, namely: it allows the use of concentrated hydrochloric acid as well as other solvents whose use is difficult, harmful and expensive. In contrast, the catalyst components of the invention are dissolved in hot water and then small, well-defined amounts of organic substances with reducing properties such as oxalic acid or its ammonium salt, citric acid, maleic acid, ascorbic acid or its ammonium salts are added to the solution. .

Also, it is not necessary to work in a costly acid-resistant device, which makes the process of the invention very cheaper and is much simpler compared to the known processes for producing vanadium and molybdenum catalysts of this type. The catalysts produced by the process according to the invention are characterized by good mechanical strength, good adhesion of the active material to the support, as well as a long service life under operating conditions. The use of these catalysts ensures that a considerable degree of conversion of benzene to maleic anhydride is achieved.

The following examples further illustrate the invention and describe a process for the preparation of vanadium oxide and molybdenum oxide catalysts, which catalysts are used to produce maleic anhydrides in the gas phase.

Example 1

250 g of ammonium vanadate, 104 g of molybdic monohydrate, 12 g of nickel nitrate hexahydrate, 13.3 g of sodium chloride, 3.9 g of phosphorus pentoxide and 91 g of oxalic acid are dissolved in 6 liters of water. 2 g of tantalum chloride dissolved in 200 ml of anhydrous ethanol are then added to this solution. The sintered corundum support contained in the rotating fused quartz vessel is slowly sprinkled with the solution thus prepared and slowly heated by the flame of the gas burner so as to maintain the temperature of the support at 80-100 ° C. When all of the prepared impregnation solution has been consumed, i.e., after the carrier has been consumed, the temperature of the rotating fused silica vessel is slowly raised to 300-380 ° C, thereby calcining the catalyst contained therein for 2-3 hours. Thereafter, the heating is stopped and after about 15 minutes the vessel is rotated. After cooling, the catalyst is sieved to remove dust particles and any lumps formed by sintering the individual catalyst grains.

This catalyst is charged to a 3 m long reactor which is heated by a melt bath. A mixture of benzene vapor and air of 42 g benzene per m ^{3 of} air is passed through the reactor, with a benzene throughput of 120 g per liter of catalyst per hour.

The operating temperature is 300 ° C. At a total benzene conversion of 97 mol. The yield of maleic anhydride was 75 mol%. θ / ο.

Example 2

Similarly to Example 1, the active ingredient components are dissolved in 6 liters of water, but 103 g of ammonium oxalate are used instead of oxalic acid. The solution thus prepared, which contains the same amount of the other components as in Example 1, is impregnated with the carrier. The catalyst obtained is then dried and calcined as described in Example 1. Using this catalyst, the total benzene conversion is 97 mol. %, the yield of maleic anhydride reached 74 mol. %.

Example 1 a d 3

As in Example 1, the individual components of the impregnation solution were dissolved in 6 liters of water, but 71 g of maleic anhydride was used instead of oxalic acid. In the same manner as in Example 1, the prepared impregnating solution is impregnated with a carrier and the catalyst obtained is dried and calcined as described in Example 1. Using this catalyst, benzene vapors are oxidized to maleic anhydride with 86 mol. % yield for a total benzene conversion of 91 mol. ^! %.

Example 4

Using the procedure of Example 1, the same active ingredient components are dissolved in 6 liters of water, except that 22 g of silver nitrate is used instead of nickel nitrate. This solution, which contains the same amounts of the other components as the solution in Example 1, is impregnated with the carrier. The catalyst obtained is dried and calcined as. as described in Example 1. The use of the catalyst thus prepared in the oxidation of benzene vapor at 300 DEG C. yields maleic anhydrides of 73 mol. θ / ο at a total benzene conversion of 97 mol. percent.

Example 1 a d 5

The individual components of the impregnation solution were dissolved in 6 liters of water in succession as in Example 1, but the nickel nitrate was replaced with 22 g of silver nitrate and no tantalum pentoxide was added. The solution thus prepared, which contains the same amount of other ingredients as the solution in Example 1, is impregnated with the carrier. The catalyst obtained is dried and calcined as described in Example 1. With the catalyst thus produced, a yield of maleic anhydride of 66 mol is obtained at the oxidation of benzene vapor at 420 ° C. % with a total benzene conversion of 94 mol. θ / ο.

Example 6

The individual components of the impregnation solution were dissolved in 6 liters of water in succession, as in Example 1, except that the nickel nitrate was replaced by 22 g of silver nitrate and the oxalic acid was replaced by 103 g of ammonium oxalate. The solution thus prepared, which contains the same amount of the other components as the solution in Example 1, is impregnated with the carrier. The catalyst obtained is dried and calcined as described in Example 1.

Using the catalyst thus prepared, maleic anhydride is obtained in a yield of 73 mol. % with a total benzene conversion of 97 mol. %. ·

Example 7

The individual components of the impregnation solution were dissolved in 6 liters of water in succession, as in Example 1. To this solution was added 4 g of potassium nitrate. However, the solution does not contain tantalum pentoxide.

The solution thus prepared, which contains the same amount of the other components as the solution in Example 1, is impregnated with the carrier. The obtained catalyst was dried and calcined as described in Example 1.

By using this catalyst, a yield of 73 moles of maleic anhydride is obtained in the benzene vapor oxidation at 400 ° C. % with a total benzene conversion of 96 mol. ° / o.

Example 8

The individual components of the impregnating solution were dissolved in 6 liters of water as described in Example 1, but tantalum pentoxide was not added to the solution, and nickel nitrate was replaced with 17 g of copper nitrate.

This solution, which contains the same amount of other components as the solution in Example 1, is impregnated with the carrier. The catalyst obtained is dried and calcined as in Example 1.

The catalyst thus produced achieves a yield of 68 moles of maleic anhydride in the oxidation of benzene vapors at 430 ° C. % at a total benzene conversion of 93 mol. -%.

Example 9

The components of the impregnation solution were dissolved in 6 liters of water in the order and procedure described in Example 1, but using, instead of nickel nitrate, 16.7 g of iron (II) nitrate, nonahydrate, of formula Fe: (NO3) 2. 9 HZO - and instead - oxalic acid. 103 g - ammonium oxalate. The resulting solution, which contains the other components in the same amount as described in Example 1, is impregnated with a carrier. The catalyst is dried and calcined in the same manner as in Example 1. The catalyst thus prepared is used to produce maleic anhydride at a temperature of

380 ° C. The yield of anhydride is 74 mol. % in total conversion of 97 mol. %.

Example 10

In 6 liters of water, the solution of the impregnating solution was dissolved in the order a according to Example 1. However, instead of nickel nitrate, 14.8 g of cobalt chloride hexahydrate of the formula CoCl2 were used. 6HaO and 103 grams of ammonium oxalate instead of oxalic acid. The carrier is impregnated with a solution containing the same amount of the other components as described in Example 1. The catalyst is dried and calcined with the same catalyst. - as shown in the example. The catalyst thus prepared is used for the production of maleic anhydride at a temperature of 380 ° C. The yield of anhydride is 74 mol. % with a total conversion of 96 mol. -%.

Example 11

The impregnating solution is prepared as described in Example 1, but instead of -91 g of oxalic acid, -73 g of ammonium oxalate is added. Using a catalyst prepared as described in Example 1, the yield of maleic anhydride is 72 mol. % at a total conversion of 96 mol. %. .

Example 1 a d 1 2

The impregnation solution was prepared as described in Example 1, but 152 g of ammonium oxalate was added in place of 91 g oxalic acid. Using a catalyst prepared as described in Example 1, the yield of maleic anhydride is 70 mol. percent at a total conversion of 96 mol. %.

Example 1.3

The impregnation solution was prepared as described in Example 1, but instead of 91 g oxalic acid, only 27 g was used. Using the catalyst prepared. as described in Example 1, the yield of maleic anhydride is 40 mol. % - - at a total conversion of 62 mol. %.

Example 1 a d 1 - 4

The impregnation solution was prepared as described in Example 1, but instead of 91 g of oxalic acid, 336 g of this acid was used. Using the catalyst prepared as described in Example 1, the yield of maleic anhydride was 30 mol. % with a total conversion of 45 mol. %.

Table

Effect of Reducer Amount on Catalyst Efficiency Catalyst Prepared According to Example No. Molar Ratio Reducer Amount Amount To Vanadium Oxide Mole / Mole Maleic anhydride yields mole% total benzene conversion mole% note

1 0.68 75 97 11 0.48 72 96 12 1.00 70 96 13 0.20 40 62 at temperature 420 ° C is 50% anhydride yield 14 2.50 30 45 at temperature

420 ° C is 40% anhydride yield

SUBJECT

Claims (2)

SUBJECT A process for the preparation of a vanadium and molybdenum catalyst for the gas phase oxidation of benzene to maleic anhydride by impregnating an inert porous support with an aqueous solution comprising dissolved vanadium and molybdenum salts having a molar ratio of molybdenum to vanadium oxide in the range of 0.3 to 1.2, promoters such as phosphorus, sodium, potassium, nickel, cobalt, iron, silver, copper and tantalum, as well as organic acids, and subsequent evaporation of volatile components, characterized by INVENTION by preparing an aqueous solution containing salts of vanadium and molybdenum as well as promoters, and to this solution are added organic carboxylic acids having reducing properties, or their ammonium salts, in an amount of 0.4 to 1.2 moles of acid or its salt per mole of vanadium oxide. Process according to claim 1, characterized in that oxalic, citric, ascorbic, formic or maleic acids are used as the carboxylic acids having reducing properties. Sevirografia, n. P., Lávod 7, Most