JPH0437008B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a process for producing hydrocyanic acid in high yield by reacting acetonitrile with oxygen and optionally ammonia in the gas phase in the presence of a cerium-based catalyst. When acrylonitrile is produced in the gas phase from propylene, ammonia, and oxygen or an oxygen-containing gas, hydrocyanic acid and acetonitrile are produced as byproducts. Hydrocyanic acid has wide uses as an industrial raw material, whereas acetonitrile has narrow uses and its industrial value is low. Therefore, converting acetonitrile into hydrocyanic acid is of great industrial significance. Conventionally, methods for producing hydrocyanic acid from acetonitrile include a method in which acetonitrile and ammonia are reacted at 1100 to 1400°C in the presence of a platinum group metal catalyst (Japanese Patent Publication No. 14560/1982), a method using a platinum alumina catalyst, or a method in the presence of a platinum catalyst. , a method in which acetonitrile, ammonia, and oxygen are reacted at a temperature of 800°C or higher (Industrial Chemistry Magazine Vol. 68, No. 2, pages 283-286) is known, but since it is a high-temperature reaction,
This cannot be said to be an industrially advantageous method in terms of energy balance. Also known is a method of producing hydrocyanic acid catalytically from acetonitrile, ammonia and oxygen or acetonitrile and oxygen in the presence of an oxide catalyst at a temperature of 400 to 500°C, optionally in the presence of water vapor. For example, a method using a catalyst containing iron-antimony as the main component (Japanese Patent Publication No. 49-33039), a method using a catalyst consisting of molybdenum-iron or molybdenum-iron-alkali metal (Japanese Patent Publication No. 71100-1989, Japanese Patent Publication No. 54-1988-1).
71800). Although these methods are attractive in that they can produce hydrocyanic acid at relatively low temperatures, they are still unsatisfactory in terms of yield. As a result of intensive research into catalysts that efficiently convert acetonitrile to hydrocyanic acid, the present inventors found that an oxide containing cerium and one or more elements selected from phosphorus, molybdenum, and tungsten, or vanadium as an additive, was used as a catalyst. It was discovered that hydrocyanic acid could be produced with high activity and high selectivity by using the same method, and the present invention was achieved based on this discovery. That is, an object of the present invention is to provide a method for efficiently producing hydrocyanic acid by reacting acetonitrile with oxygen and optionally ammonia in the gas phase. a catalyst consisting of at least one of cerium and oxygen;
This is achieved by using a catalyst consisting of at least one of phosphorus, tungsten and molybdenum, panadium, cerium and oxygen. The present invention will be explained in detail below. The catalyst used in the method of the present invention is a combination of cerium and oxygen, cerium and oxygen and at least one of phosphorus, tungsten and molybdenum, or at least one of phosphorus, tungsten and molybdenum and vanadium,
Specifically, the general formula CeMxVyOz (where M represents phosphorus, tungsten or molybdenum, and 0≦×10, 0≦y<2, more preferably 0≦×≦5, 0≦y≦1) (z represents the number of oxygen atoms necessary to satisfy the valences of other components). The above catalysts include small amounts of alkali metals, alkaline earth metals, thallium, silver, antimony, tellurium, copper, cobalt, nickel, chromium, manganese, lead, tin, rare earths other than cerium, thorium, uranium, niobium, and boron. It is also possible to contain elements such as , gallium, indium, arsenic, and bismuth. Examples of the cerium compound used for catalyst preparation include cerium salts such as cerium nitrate and cerium sulfate, and various oxides or hydroxides of cerium. As the phosphorus compound, various phosphoric acids and organic and inorganic phosphorus compounds are arbitrarily selected. As molybdenum compounds, molybdenum oxides such as molybdenum trioxide, molybdic acid or its salts, and phosphomolybdic acid or its salts are used, and as tungsten compounds, tungsten oxides such as tungsten trioxide, tungstic acid or its salts are used. , phosphotungstic acid or its salt, etc. are used. As the vanadium compound, compounds such as vanadium pentoxide and ammonium metavanadate are used. The catalyst composition of the present invention may be molded as it is without using a carrier, or a molded product can be obtained using a carrier such as silica, alumina, titania, silicon carbide, etc. The shape is not particularly limited and may be formed into any shape and size, such as a pellet shape or a spherical shape, depending on the usage conditions. To produce a catalyst using the above raw materials, the three-element compound of each component is dissolved or suspended in water, and if necessary, a carrier powder such as silica sol or alumina sol is suspended to form a uniform slurry or aqueous solution. After that, it may be formed by evaporation to dryness or spray drying, and then fired under air circulation. In producing a catalyst, when vanadium pentoxide or ammonium metavanadate is used as a vanadium compound, it is preferable to add a reducing agent such as oxalic acid to increase solubility in water. The calcination temperature and calcination time after catalyst formation are not particularly limited, but the calcination temperature is
The temperature is selected within the range of 400 to 800°C, preferably 500 to 700°C, and the firing is performed for 0.1 to 4 hours. The catalyst prepared in this way is packed into a fixed bed or fluidized bed reactor, and the reaction temperature is maintained at 300-500℃, and an oxygen-containing gas such as acetonitrile, oxygen or air, if necessary, contains ammonia and water vapor. Bring the mixed gas into contact. The raw material, acetonitrile, does not necessarily have to be of high purity; even if it is supplied as an aqueous solution, it will still produce propylene,
It may be supplied as a mixed gas such as ammonia or air. The molar ratio of oxygen to acetonitrile is usually in the range of 1 to 20 times. The reaction is usually carried out under normal pressure, but may be carried out under reduced pressure or increased pressure, if necessary. Further, the space velocity of the raw material gas can be appropriately selected from the range of 100 to 3000 hr ^-1 . EXAMPLES Next, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof. In addition, in the following examples, the reaction rate of acetonitrile, hydrocyanic acid selectivity, and hydrocyanic acid yield are defined by the following formula. Acetonitrile reaction rate (%) = Number of moles of acetonitrile consumed/Number of moles of supplied acetonitrile x 100 Hydrocyanic acid selectivity (%) = Number of moles of hydrocyanic acid produced/Number of moles of acetonitrile consumed x 100 Hydrocyanic acid yield (%) )=Number of moles of hydrocyanic acid produced/Number of moles of supplied acetonitrile x 100 Example 1 Under stirring, 0.712g of cerium nitrate [Ce( _NO3 ) _3.6H2O ] was dissolved in 250g of 20% by weight silica sol in 2ml _of water. A solution of 0.289 g of ammonium paramolybdate [(NH ₄ ) ₆ Mo ₇ O ₂₄ 4H ₂ O] dissolved in 2 ml of water was added, and a 10% by weight nitric acid aqueous solution was added to adjust the pH of the liquid. was adjusted to 2.2 and heated to dryness on a hot plate while stirring. The obtained solid material was formed into a tablet with a diameter of 6 mm and a thickness of 3 mm, and baked at 650° C. for 2 hours under air circulation. 1 ml of this catalyst was packed into a heat-resistant glass reactor with an inner diameter of 4 mm, and a mixed gas of 3.3% by volume of acetonitrile and air was fed as a feedstock into the reaction tube at a space velocity of 500 hr ^-1 to carry out the reaction at 440°C. The results are shown in Table 1. Example 2 A solution of 0.712 g of cerium nitrate dissolved in 2 ml of water and a solution of 0.289 g of ammonium paramolybdate dissolved in 2 ml of water were sequentially added to 272.9 g of 20% by weight silica sol under stirring. Next, add 0.462g of vanadium pentoxide (V ₂ O ₅ ) to water.
Weigh out 1/10 of the solution mixed with 10 ml and 0.972 g of oxalic acid [(COOH) _{2.2H 2} O], heated and dissolved, add to the above solution, and heat on a hot plate while stirring to dryness. I let it happen. The obtained solid was treated in the same manner as in Example 1 to obtain a granular catalyst. 1 ml of this catalyst was charged into the same reactor as in Example 1, and a mixed gas having the same composition as in Example 1 was fed into the reaction tube at the same space velocity to carry out the reaction. The results are also shown in Table 1. Example 3 The same experiment as Example 1 was repeated except that the amount of 20% by weight silica sol was 133.2 g and no ammonium paramolybdate was added. The results are also shown in Table 1. Example 4 The amount of 20% by weight silica sol was 321.4 g, and ammonium paratungstate [(NH ₄ ) ₁₀ W ₁₂ O ₄₁・5H ₂ O] was used instead of ammonium paramolybdate.
An experiment similar to Example 1 was repeated, except that 0.428 g was dissolved in 8.3 ml of water and the solution thus obtained was added. The results are shown in Table 2. Example 5 While stirring, a solution of 262.2 g of 20% by weight silica sol, 0.712 g of cerium nitrate dissolved in 2 ml of water, and 0.428 g of ammonium paratungstate in 8.3 ml of water
were added sequentially. Next, 0.447 g of vanadium pentoxide was mixed with 10 ml of water and 0.940 g of oxalic acid, and 1/2 of the solution was dissolved by heating.
Example 2 except that 10 amounts were measured and added.
The same experiment was repeated. The results are also shown in Table 2. Example 6 Example 1 except that the amount of 20 wt% silica sol was 162.2 g and 0.095 g of 85 wt% phosphoric acid (H ₃ PO ₄ ) was added instead of ammonium paramolybdate.
The same experiment was repeated. The results are shown in Table 3. Example 7 The same experiment as in Example 2 was repeated except that the amount of 20 wt% silica sol was 213.6 g and vanadium pentoxide was 0.462 g, and 0.189 g of 85 wt% phosphoric acid was added instead of ammonium molybdate. . The results are also shown in Table 3. Example 8 The catalysts shown in Table 3 were prepared in the same manner as in Example 7, and the same reactions as in Example 7 were carried out at the reaction temperatures shown in Table 3. The results are also shown in Table 3. Comparative Example 1 The same experiment as in Example 6 was repeated except that the amount of 20 wt % silica sol was 117.6 g and the 85 wt % phosphoric acid was 0.386 g and cerium nitrate was not added. Table 4 shows the catalyst composition, reaction temperature, and reaction results. Comparative Example 2 The same experiment as Experimental Example 1 was repeated except that the amount of 20% by weight silica sol was 116.9 g and cerium nitrate was not added. Table 4 shows the catalyst composition, reaction temperature, and reaction results. Comparative Example 3 The same experiment as in Example 4 was repeated except that the amount of 20% by weight silica sol was 186.0 g and ammonium paratungstate was 0.423 g, and cerium nitrate was not added. Table 4 shows the catalyst composition, reaction temperature, and reaction results.

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Claims (1)

[Claims] 1. A method for producing hydrocyanic acid by reacting acetonitrile with oxygen and optionally ammonia in the gas phase in the presence of a catalyst, comprising: a catalyst consisting of cerium and oxygen; at least one of phosphorus, tungsten and molybdenum; cerium; and a catalyst made of oxygen; a catalyst made of at least one of phosphorus, tungsten, and molybdenum; and a catalyst made of vanadium, cerium, and oxygen.