CS224608B2 - Method for producing a catalyst for methacryl acid production - Google Patents

Description

The present invention relates to a process for the production of a catalyst comprising molybdenum, phosphorus, vanadium, copper and oxygen having a heteropolyacid structure. This catalyst, used in the production of methacrylic acid by oxidation of methacrolein, has a very long life, is highly efficient and selective.

Although various catalyst systems have been proposed for the catalytic oxidation of methacrolein, they have not yet succeeded in industrial practice, unlike the oxidation of acrolein to acrylic acid. The reasons are that the yield of the end product is not as high as in the production of acrylic acid, the life of most catalysts is too short to maintain stable performance over extended periods of time and the like.

Most of these catalysts proposed for the catalytic gas-phase oxidation of methacrolein contain molybdenum-phosphorus as the main constituents and are structurally regarded as phosphomolybdens, for example mainly the ammonium or alkali salts of their heteropolyacids.

However, the greatest disadvantage of these catalysts is their short lifetime, when the heteropolyacid salt structure begins to decompose at the end of the reaction and X-ray diffraction analysis reveals the growth of MoO 2 crystals accompanied by a decrease in their catalytic activity. Accordingly, these catalysts do not have a sufficiently long service life for industrial use. In order to maintain catalytic efficiency in such a catalytic system for a longer period of time, it is inevitable to select very mild reaction conditions in these circumstances, which are contrary to economic requirements.

US Patents 3875220 and 4001316 disclose a catalyst for metacrolein oxidation. However, the yield of methacrylic acid obtained in the examples is not very high.

The use of a catalyst Mo-P-V-Al-Y-O (in which Y is an optional atom and means, for example, Cu and the like) having a heteropolyacid structure for the metacrolein oxidation has been disclosed in DOS 2739779. This catalyst is stable. The yield of methacrylic acid according to this publication is high, but not sufficient. Further, US patent application (Serial No. 948761) has been described relating to a catalyst Mo-PV-Cu-Z-O (wherein Z is an optional atom and means, for example, tin and the like) having a heteropolyacid structure and a method for producing methacrylic acid by oxidation. methacrolein from the presence of said catalyst. This catalyst has high efficiency and high selectivity, is very stable and has a very long life.

By further research, the above catalyst has been improved and the present invention relates to a process for the production of a catalyst which allows the production of methacrylic acid from methacrolein in high yield and in a stabilized state for a long time.

The present invention provides a process for the preparation of a catalyst of the general formula

Mo V _e P "Cu _and A _{S =} X-O" abcdefg where

Mo, V, P, Cu, As and O are molybdenum, vanadium, phosphorus, copper, arsenic and oxygen,

X 'means at least one of tin, olo, oer, cobalt, iron, zirconium, thorium, tungsten, germanium, nickel, rhenium, bismuth, antimony, ohr, boron, magnesium, silver, aluminum, zinc and titanium aa, b, c, d, e, f and g are atomic ratios of the elements wherein a has a value of 10b having a value of up to 3, with the exception of 0, preferably 0.5 to 2,

C has a value of 0.5 to 6, preferably 0.5 to 3, d has a value of up to 3, with the exception of 0, preferably 0.01 to 1.0, e has a value of up to 3, with the exception of 0, preferably 0.01 to 1.0, f has a value of 0 to 3, preferably 0 to 1.0, and g is dependent on the valence and atomic ratios of other elements having a heteropolyacid structure, characterized in that molybdenum oxide or heteromolybdic acid is reacted with the other substances containing the remaining catalyst elements mentioned above by mixing the components in water, and the resulting solution is evaporated to dryness.

Particularly preferred X components include tin, thorium, cerium, tungsten, germanium, rhenium, bismuth, antimony, boron and aluminum.

The catalyst prepared by the process of the invention comprises various elements and has a heteropolyacid structure, as evidenced by characteristic X-ray diffraction analysis peaks at 20 = 8.0 °, 8.9 °, 9.3 ° and the like. While the backbone structure of the catalyst is phosphovanadomolybdic acid, the other attached elements are believed to carry improvements in catalytic efficiency as well as selectivity and structure stability by partially replacing the backbone elements in phosphovaneomolybutyric acid to form a heteropolyacid.

The catalyst of the invention is water soluble because of my heteropolyacid structure as described above. It may additionally contain water-insoluble substances, such as oxides of the base elements, but these do not have a significant effect on the efficiency of the catalyst prepared by the process of the invention.

It is generally believed that the catalyst is also present in a reduced form resulting from its reduction by the metacrolein-containing feed gas under the reaction conditions of the initial stage. This reduced form can also be obtained by using reducible starting catalyst base elements by adding a reducing agent to prepare the catalyst or by applying a reducible gas to the catalyst.

The catalyst according to the invention is particularly advantageous for industrial use because of its high efficiency, high selectivity and also very long service life. Furthermore, the above reaction may be at high bulk velocity, since increasing the bulk velocity has no significant effect on the progress of the reaction using the catalyst of the invention.

The catalyst of the invention is water-soluble, which has the added advantage of being easier to apply to the support and also easier to recover by dissolving in water after deactivation for long use in the reaction.

The catalyst of the invention may be prepared by conventional methods for the preparation of conventional heteropolyacids, but the formation of the ammonium salt of the heteropolyacid in the final catalyst form should be avoided.

In accordance with the invention, the catalyst may be prepared by reacting the parent compound starting materials in water, converting the reaction product to the corresponding acid, if it is an ammonium salt and, if necessary, extracting the reaction product and evaporating to dryness. The reaction can also be carried out in an organic solvent. Conversion of the ammonium salt to the corresponding acid can be accomplished by conventional means, for example, by extraction with ether from an acidic aqueous solution, by means of ion exchangers, and the like. Extraction of the reaction product can be accomplished using a suitable organic solvent such as ether.

Particularly preferred preparation processes include processes using dispersed or dissolved starting materials, for example, oxides or phosphates of the catalyst component elements in water, their reaction with heating and optionally adding hydrogen peroxide, removing insoluble components if necessary and evaporating the solution to dryness, or in the reaction of phosphovanadmolybdic acid with oxides, phosphates, sulfates and other salts of the catalyst base elements.

Various compounds may be used as starting materials for the catalyst base elements, provided they are treated in a manner leading to the formation of a heteropolyacid catalyst, but not in the form of an ammonium salt.

Starting materials suitable for the molybdenum component include, for example, molybdenum oxide, molybdenic acid or a salt thereof, heteromolybdic acid or salts thereof, molybdenum metal and the like, preferably molybdenum oxide or heteromolybdic acid.

Starting materials suitable for the phosphorus component include orthophosphoric acid, phosphoric acid, phosphoric acid or salts thereof, phosphorous pentoxide and the like.

Starting materials suitable for the vanadium component include vanadium pentoxide, vanadium trisellate, vanadium sulphate, vanadic acid or salts thereof, vanadium metal and the like.

Starting materials suitable for the copper component include cuprous oxide, cuprous phosphate, cuprous sulfate, cuprous molybdenum, cuprous metal and the like.

Starting materials suitable for the arsenic component include arsenic oxide, orthoarsenic acid, metaarsenic acid, pyroarsenic acid or salts thereof, and the like.

Starting flights suitable for component X include the corresponding oxides of phosphates, nitrates, sulfates, carbonates, molybdates, the metallic form of the elements labeled X and the like.

The catalyst prepared by the process of the present invention exhibits high free-catalytic activity, but is expected to have a more beneficial effect in improving thermal stability, catalyst lifetime, and increased methacrylic acid yield when applied to a suitable support. Preferred carriers are silicon carbide, aluminum powder, diatomaceous earth, titanium dioxide, alpha-alumina and the like. Active carriers that react with a heteropolyacid are not suitable.

The annealing required in most cases is not required in the preparation of the catalyst according to the invention. Therefore, the catalyst can be prepared according to the invention more easily and its cost can be reduced.

The following examples do not provide oxygen data regarding catalyst composition. These are determined in accordance with the atomic ratios and valencies of the other elements.

He did

100 g of molybdenum trioxide, 6.3 g of vanadium oxide, 1.1 g of copper oxide, 8.0 g of orthophosphoric acid and 1.8 g of pyroarsenic acid are dispersed or dissolved in 100 ml of deionized water. The resulting mixture was refluxed for about 6 hours to give a clear, orange-red solution. The solution was evaporated to dryness in a hot bath. The dried product (ketalyst) thus obtained has the following composition: Μο, θν, Ρ, Ο ^ ₂ As _{0 2} . The heteropolyacid structure was confirmed by diffraction peaks at 20 = 8.0 °, 8.9 °, 9.3 ° etc. by X-ray diffraction analysis. The catalyst is adjusted by grinding to a particle size of 0.3-0.7 mm.

The catalyst prepared in this way is used in the preparation of methacrylic acid as follows. The catalyst, grinded to a particle size of 0.3-0.7 mm, is introduced into a tubular reactor made of Pyrex glass having an internal diameter of 8 mm and immersed in a fluid bath. Metecrolein: oxygen: oxygen: nitrogen: water plume = 1: 2.5: 14: 7 (in molar ratios) is passed through a tubular reactor at a flow rate of 1600 h ^-1 (relative to normal conditions) and continuous the oxidation reaction is carried out at 320 ° C for 120 days.

Catalyst X-ray diffraction analysis after a total reaction time (120 days) confirmed that no molybdenum oxide was formed during this time and that the catalyst structure had not changed.

In the manner described above, but using other reagents or ratios thereof, the following catalysts can be prepared, for example:

The structure of heteropolyacids was confirmed by X-ray diffraction analysis.

Continuous reactions were carried out with the above catalysts. After a total catalyst reaction time of 30 to 120 days, X-ray diffraction analysis confirmed that the catalyst structure had not changed.

Example 2

100 g of molybdenum trioxide, 6.3 g of vanadium oxide, 1.1 g of cuprous oxide, 8.0 g of orthophosphoric acid, 1.8 g of pyroarsenic acid and 2.1 g of tin oxide are used as starting materials for the preparation of a catalyst having the following composition: ^as 2 0 2 0.2 ^Bn in the same way as in Example 1. the dried product was confirmed by the structure of heteropolyacid diffraction peaks in X-ray diffraction 2Θ = 8.0 °, 8.9 · ^F, 9.3 ° etc.

2.1 g of tin oxide in the above process are successively replaced by 3.2 g of lead-lead oxide, 2.4 g of cerium oxide, 1.1 g of cobalt-cobalt oxide, 1.1 g of iron oxide, 1.7 g of oxide of zirconium, 3.7 g of thorium oxide, 3.2 g of tungsten oxide, 1.5 g of germanium oxide, 1.0 g of nickel oxide, 3.4 g of rhenium oxide, 3.2 g of bismuth oxide, 2.0 g of antimony trioxide 1.4 g of chromium trioxide, 0.9 g of boric acid, 0.6 g of magnesium oxide, 1.6 g of silver oxide, 0.7 g of zinc oxide, 1.1 g of titanium oxide and dried products of the following composition are obtained:

^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Sn 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Pb 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Ce 0.2 ^Mo 1 0 ^V 1 ^P 1 ^Cu 0.7 ^With 0.2 ^Co 0.2 Moi0 ^V 1 ^P 1 ^Cu 0 ₎ 2 ^As 0.2 ^Fe 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Zr 0.2 ^Li 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Th 0.2 ^Mo 1 0 ^V 1 ^P 1 ^Cu 0, 2 ^As 0.2 ^ 0.2 ^Mo 10 ^V 1 ^P 1 ^Gu 0.2 ^As 0.2 ^Ge 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Ni 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Re 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Bi 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Sb 0.2 ^Mo 1 0 ^V 1 ^P 0.2 ^As 1 ^Cu 0.2 ^Cr 0.2 ° 1O M ^V 1 ^P 0.2 ^As 1 ^Cu O, 0.2 ^Mo 2 ^B 1 0 ^P 1 ^V 1 ^Cu 0.2 0 ^As 2 ^Mg 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0, 2 ^ 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Al 0.2 ^Mo 10 ^V 1 ^P 1 ^Cu 0 , 2 ^As 0.2 ^Zn 0.2 ^Mo 1 0 ^V 1 ^P 1 ^Cu 0.2 ^As 0.2 ^Ti 02 '

The structure of the heteropolyl acids of these catalysts was confirmed by X-ray diffraction peaks at 2 = 8.0 °, 8.9 °, 9.3 ° etc.

Continuous reactions were carried out with the above catalysts under the same conditions as in Example 1.

After a reaction time of 30 days, X-ray diffraction analysis confirmed that the catalyst structure had not changed. ·

Claims (1)

THE INVENTION OF THE INVENTION A process for the preparation of a catalyst for the production of methacrylic acid of the general formula a Ho, V, P, Cu, As and 0X a, b, c, d, e, f, g are molybdenum, vanadium, phosphorus, copper, arsenic and oxygen, means at least one of tin, lead , cerium, cobalt, iron, zirconium, thorium, tungsten, germanium, nickel, ehenium, bismuth, antimony, chromium, boron, magnesium, silver, aluminum, zinc and titanium and represent the atomic ratio of the elements where and my value 10, b has a value of up to 3, with the exception of 0, preferably 0.5 to 2, c having a value of 0.5 to 6, preferably of 0.5 to 3, d of up to 3, with the exception of 0, preferably 0.01 to 1.0, e my value is up to 3, with the exception of 0, preferably 0.01 to 1.0, f has a value of 0 to 3, preferably 0, to 1.0 g and my value depends on the valences and atomic ratios of the other elements having a heteropolyacid structure characterized by by reacting molybdic oxide or heteromolybdic acid with other substances containing the above-mentioned basic catalyst elements by mixing The resulting solution was evaporated to dryness.