KR960003796B1 - Regeneration of heteropolyacid waste catalysts - Google Patents

Abstract

This relates to regeneration of waste heteropolyacid catalyst. The method comprises :1)removing hydrocarbon deposited on the nonactivated catalyst by treating it with mixture stream of oxygen and nitrogen, and reoxidation; 2)making the catalyst slurry adding the purified water; 3)adding 0.5-4mol phosphoric acid and refluxing it with oxygen stream for 2-100hrs; 4)adding oxalic acid, its salt or mixture of heterocyclic compd, and refluxing for 2-50hrs; 5)stirring the slurry at room temp for 1-10hrs, filtering and washing; and 6)drying and molding.

Description

New Regeneration Method of Heteropoly Acid-Based Waste Catalyst

The present invention is a new regeneration of a heteropolyacid-based waste catalyst that has been deactivated for a long time, such as gas phase oxidation reaction of methacrolein, gas phase oxidation dehydrogenation reaction of isobutylaldehyde and isobutyl acid, oxidation reaction of isobutane, etc. to prepare methacrylic acid. It is about a method.

Heteropolyacid catalysts based on phosphorus and molybdenum show high catalytic activity in gas phase oxidation of methacrolein, oxidative dehydrogenation of isobutyl aldehyde, isobutyl acid, and oxidation of isobutane due to their strong acid properties and oxidative capacity. .

However, phosphomolybdic acid itself is susceptible to deterioration due to poor thermal stability, and is easily reduced due to strong oxidation ability, while crystallization is strong at low temperatures in solution, while crystal water is released and the cohesion between particles is extremely low. There is a disadvantage in that moldability is extremely bad because it is weak and easily broken.

Therefore, techniques for combining various metals and attempting to improve the performance of the catalyst by adjusting the physical and chemical properties of the catalyst are proposed in the following patent documents. (E.g., U.S. Patent 4,042,625,4,272,408, Japanese Patent Application Laid-Open No. 82- 32734, 82-12830, 83-74142, 83-166938, 84-66349, 86-5043, 86-76436, 88-167152, 89-119942, 92-16242, Korean Patent 36019, 36020, European Patent 0043100 and the like).

Generalized expression of the catalyst specified in the patent is represented by the formula (1).

(X _a Cu _b Y _c ) (P _{1 + d} As _e ) (Mo ₁₂ V _f W _g ) O _h .

Wherein Cu, P, As, Mo, V, W, O represent copper, phosphorus, arsenic, molybdenum, vanadium, tungsten, oxygen, and X is at least one element selected from cesium, rubidium, potassium, thallium , Y represents an element selected from bismuth, antimony, tin, chromium, silver, palladium, lead, calcium, barium, magnesium, tellurium, selenium, strontium, cobalt, zirconium, germanium, ammonium and pyridinium ion.

The parentheses in the formula (1) are shown to systematically indicate the properties of the 12-heteropolyacid catalyst system, the first parenthesis means that the proton, the relative cation of the 12-phosphomolybdate anion, is partially substituted with other metals. The second parenthesis indicates some substitution of phosphorus by the central element phosphorus and arsenic, and the third parenthesis indicates some substitution of molybdenum by the condensation elements molybdenum, vanadium and tungsten.

In the above formula (1), a, b, c, d, e, f, g and h represent the atomic ratios of each element. When molybdenum composition is 12, a is 0.5 to 2, b is 0.05 to 1, c Has a value from 0 to 2 and a + b + c has a value less than or equal to 3 + f. d is from 0 to 2, e is from 0 to 1, f and g have values from 0 to 3, and h has the necessary values to match valences.

Catalysts having improved properties of heteropolyacids represented by the general formula (1) show relatively good activity in the oxidation reaction of methacrolein and the oxidative dehydrogenation reaction of isobutylaldehyde and isobutyl acid, but the activity gradually decreases as the reaction time passes. And ultimately remain as spent catalyst that is no longer valuable as a catalyst.

This is ultimately due to the physical and chemical properties of the heteropolyacid itself. The deactivation is caused by the deposition of hydrocarbons in the catalyst particles and the degradation of the catalyst resulting in the decomposition of phosphomolybdic acid and its salts into molybdenum trioxide and phosphorus oxide, It is known that the basic particles of the catalyst are sintered and the specific surface area is greatly reduced, and that the component separation is performed by the surface movement of some components.

As a method of regenerating an inactivated waste catalyst, a method of regenerating a catalyst while the catalyst is charged in a known technique is performed by adding air or oxygen including steam to a catalyst maintained at 200-500 ° C. in European Patent 384,755. In the Japanese Patent Application Laid-Open No. 81-91,846, nitrogen oxide is used as an oxidizing agent for regeneration.

As a known method for regenerating the waste catalyst recovered from the reactor, Korean Patent Publication No. 88-5965 is a method of treating with an aqueous solution containing ammonia water, nitrogen heterocyclic compounds and / or amines and / or ammonium carbonate, drying and calcining, In British Patent No. 2,029,719, a method of treating hydrogen peroxide and / or ozone with ammonia water followed by adding ammonium nitrate, and in Japanese Patent Laid-Open No. 81-163,755, refluxing for a long time while adding air to the catalyst aqueous solution, and then evaporating and drying the same. The catalyst is being regenerated.

Among the known methods, the regeneration by heating the catalyst while flowing the gas such as air, oxygen, nitrogen oxide, etc. while the catalyst is charged in the reactor is only a temporary increase in the activity of the catalyst, and complete regeneration of the catalyst. It doesn't work. This is because the deactivation of the catalyst is more likely to be caused by changes in physical and chemical properties that are not renewable in that state than due to the reduction of the catalyst component and the deposition of hydrocarbons in the particles.

Thus, a patented technique known as this method for recovering and regenerating a waste catalyst with severely reduced activity from the reactor is summarized as a technique for the treatment of molybdenum oxide resulting from the decarbonization of the deposited hydrocarbons and the reoxidation of the reduced components and thermal decomposition. do.

Among the above techniques, decarbonization and reoxidation are essential processes, but a known technique for treating molybdenum oxide is to dissolve and remove molybdenum trioxide in the form of ammonium of molybdate by using ammonia water, or to make ammonium salt of phosphomolybdate, Although a common method for the preparation of phosphomolybdic acid and / or salt catalysts from molybdenum oxide or molybdic acid and salts thereof, the excess ammonia used to dissolve small amounts of molybdenum trioxide provides catalyst selectivity by forming ammonium salts of phosphomolybdic acid. Limit the increase.

This is known to many patents (European Patent 0043100, Japanese Patent Application Laid-Open No. 82-12830, 84-66349, 89-119942, 92-16242, Korean Patent 36019, 36020). It is important to use organic small heterocyclic compounds such as pyridine, piperazine, piperidine, pyrimidine, etc. as a precipitant to induce a secondary structure having an active structure. When the ammonium salt of heteropoly acid is produced first, the nitrogen heterocyclic compound is used. Since over cation exchange does not occur, it cannot be led to an optimal active structure.

Ammonium salt is preferentially generated even when treated with an aqueous solution containing ammonia and nitrogen heterocyclic compounds as in Korean Patent Publication No. 88-5965.

In addition, when treated with ammonia, it is difficult to make a catalyst having a uniform distribution of components during evaporation and drying because alkali-soluble components, including copper added as an essential component to increase the reoxidation power of the catalyst, are dissolved in an aqueous solution. There are also many limitations in the formation of the catalyst. For example, in order to obtain a powder having a desired composition from the slurry obtained in the regeneration process, the concentrated cake may be dried or spray dried as it is, and at this time, the water-soluble components may not be transported to the particle surface.

The same phenomenon occurs when molding a catalyst using a penis or extruder, making it difficult to produce a molded catalyst having a uniform composition.

Localization of these components lowers the selectivity of the catalyst, acts as a hot spot in the reaction, and accelerates the deactivation and recrystallization of the catalyst components, thereby promoting deactivation of the catalyst. It can shorten the life. Furthermore, since phosphomolybdic acid itself decomposes in an alkaline state, treatment with ammonia can make the regeneration process more difficult and degrade the catalytic performance.

In addition, the regeneration of the spent catalyst cannot achieve its intended purpose by treatment of any part of the cause of deactivation as described above, but there are disadvantages in that the known patent technology does not become a comprehensive treatment technology.

Accordingly, an object of the present invention is to provide a comprehensive system for the use of inert heteropolyacid-based waste catalysts for a long time in the gas phase oxidation reaction of methacrolein and the oxidative dehydrogenation reaction of isobutyl acid, and the like to achieve almost the same performance as the original catalyst. The present invention provides a regeneration method, wherein the present invention treats a waste catalyst with phosphoric acid and an oxidizing agent to heteropolyoxidize pyrolysis product molybdenum trioxide, reoxidize a reduced component, oxalic acid and / or its salt and nitrogen heterocyclic compound. By mixing all the active ingredients to make the active ingredient insoluble state, make a slurry liquid with a uniform component distribution, filter and wash it, remove excess phosphoric acid and unnecessary components, and dry and shape.

The regeneration method according to the present invention will be described in more detail as follows.

The waste catalyst which has lost activity is treated with a mixed gas of oxygen and nitrogen steam in the reaction state to remove hydrocarbons deposited in the catalyst particles and at the same time sufficiently reoxidize the reduced catalyst component and recover it in the reactor.

The above process is to facilitate the post-treatment process in the waste catalyst treatment. When distilled water is added to the spent catalyst particles, the formed catalyst particles are easily slurried. The slurry liquid can be filtered or recycled as is, depending on the size of the carrier (or dispersant) used in the preparation of the catalyst.

Usually, 5-50% by weight of silica or alumina treated at high temperature is used to control the reactivity and improve the thermal properties in forming the heteropolyacid catalyst. When the size of the silica or alumina particles used is 50 mesh or less, When regeneration is carried out and larger particles are used, it is preferable that the carrier (or dispersant) be separated and then treated.

To the slurry liquid is added phosphoric acid corresponding to 0.05-20 mol, preferably 0.1-10 mol, or simply 0.5-4 mol, preferably 0.5-2 mol, based on molybdenum trioxide produced by pyrolysis, and air or oxygen The mixture is refluxed for 2-100 hours, preferably 10-30 hours, while bubbling and flowing.

At this time, the reduced catalyst component may be oxidized by adding an oxidizing agent such as hydrogen peroxide or ozone, nitric acid, bromine or phosphomolybdic acid.

The amount of phosphomolybdic acid used is quantitatively measured by measuring the amount of phosphomolybdic acid sublimed during the reaction, or the amount of phosphomolybdenum trioxide resulting from thermal decomposition and sublimation from the catalyst. To this is added a mixture of oxalic acid or a salt thereof and a nitrogen heterocyclic compound and refluxed for 2-50 hours, preferably 4-20 hours.

Oxalic acid or its salt is preferably 0.1-3 mol, preferably 0.3-1 mol, and nitrogen heterocyclic compound 1-10 mol, preferably 3-6 mol, relative to phosphomolybdic acid. The slurry solution is then stirred at room temperature for 1-10 hours, preferably 2-6 hours, filtered and washed with deionized water. The washed cake may be dried and then molded between 50-200 ° C. or blown out with appropriate moisture and molded by extrusion.

Molding may be carried out using any method such as extrusion, tableting, coating, or globular method, and the shape of the molded body may be in any form such as spherical, tablet or hollow. The shaped catalyst is first dried at 80-200 ° C. for 2-6 hours, and activated by calcination.

The firing conditions were first baked at 380-450 ° C. for 2-10 hours under nitrogen atmosphere and secondly baked at 280-420 ° C. for 2-10 hours.

The regeneration catalyst, which has undergone regeneration, shaping and activation, is charged to a stainless steel tube reactor and reacted with a fixed bed.

The catalytic activity test results are defined as follows.

* Reactant: Methacrolein, isobutyl acid

** Product: Methacrylic Acid

Comparative Example 1

The composition is Cs ₁ . ₃ Cu ₀ . ₂ Tl0. ₁ P ₁ . _A catalyst of ₁ Mo ₁₂ V _1.0 O _x + SiO ₂ (30 wt%) was used for the oxidation of methacrolein for 8,000 hours.

During the reaction, the supply of methacrolein was stopped and reactivation was performed for 24 hours while gradually increasing the oxygen ratio under the condition that the molar ratio of oxygen: nitrogen: steam was (2-8): 73: 15, and 350 ° C.

The reaction temperature was lowered to 320 ° C. and the reaction was carried out under the condition that the molar ratio of methacrolein: oxygen: nitrogen: steam was 3.5: 8: 73.5: 15 and GHSV was 1,200hr ^-1 .

The reaction test results are shown in Table 1.

Example 1

The deactivated catalyst was detected by molybdenum trioxide, which is the result of pyrolysis of heteropolyacid by XRD and FT-IR analysis, and the sintering of the catalyst was observed by SEM and BET. 200 g of the deactivated catalyst, 200 ml of deionized water, 8 g of 85% phosphoric acid, 10 g of 12-phosphomolybdic acid, and 10 ml of 35% hydrogen peroxide were added to a circular flask equipped with a condenser, and then heated to reflux for 24 hours. To this slurry was added 6.4 g of oxalic acid and 33 g of pyridine mixture, refluxed for 12 hours, lowered to room temperature and stirred for 3 hours. This slurry liquid is filtered and washed with deionized water.

The moisture of the cake-like material is blown off moderately and molded into a cylinder in the extruder. After drying at 110 ° C., primary firing was performed at 430 ° C. for 3 hours under nitrogen atmosphere, and secondary firing was carried out for 3 hours under an air atmosphere of 380 ° C.

The calcined catalyst undergoes oxidation of methacrolein under the same conditions as in Comparative Example 1.

The reaction test results are shown in Table 1.

Comparative Example 2

The composition is Cs ₁ . ₄₅ Cu ₀ . ₂₇ Bi ₀ . ₁ P ₁ . ₁ Mo ₁₂ V ₁ . A ₀ O _x catalyst of iso-butyric acid: oxygen: steam: the molar ratio of nitrogen 3.1: 2.8: 6.2: 87.9, and a space velocity were the oxidative dehydrogenation of iso-butyric acid for 6,000 hours at the conditions 2,800hr ^-1.

A portion of the catalyst was taken (100 g) and 500 ml of deionized water and 20 ml of 25% ammonia water were added and refluxed for 5 hours. Concentrated hydrochloric acid is added to make the pH below 1, refluxed for 12 hours, evaporated and dried. The dried product is dispersed in water, 20 g of pyridine is added, and evaporated and dried again. The dried product is dispersed in water, 20 g of pyridine is added, and evaporated and dried again. After molding and firing, an isobutyl acid dehydrogenation reaction is carried out under the above conditions.

The reaction test results are shown in Table 1.

Example 2

To 100 g of the catalyst of Comparative Example 2, 100 g of deionized water, 4 g of 85% phosphoric acid, 5 g of 12-phosphomolybdate, and 5 ml of concentrated solution were added, and the mixture was heated to reflux for 24 hours while being bubbled with air. 3.2 g of oxalic acid and 16 g of pyridine mixture were added to the slurry solution and refluxed for 12 hours, after which the catalyst was regenerated in the same manner as in Example 1.

The regenerated catalyst was subjected to an oxidative dehydrogenation reaction of isobutyl acid under the same conditions as in Comparative Example 2.

The reaction test results are shown in Table 1.

TABLE 1

Claims (4)

A mixed gas of oxygen, nitrogen and water vapor is used as a heteropolyacid-based waste catalyst that has been inactivated for a long time in the (gas) oxidation reaction of methacrolein, the gas phase oxidation dehydrogenation reaction of isobutylaldehyde and isobutyl acid, and / or the oxidation reaction of isobutane. After removing the hydrocarbons deposited with and prior to reoxidation or dissolving in water, slurrying them in water, and then treating them with acids and oxidants for heteropolyoxidation, the active ingredients are made insoluble. A new regeneration method of a heteropolyacid crab spent catalyst represented by the following formula (1), wherein a mixed precipitate of oxalic acid and / or a salt thereof and a nitrogen heterocyclic compound is used to make a slurry liquid with a uniform distribution. (X _a Cu _b Y _c ) (P _{1 + d} As _e ) (Mo ₁₂ V _f W _g ) O _h ... … … … … … … … … … … … … (One) In Formula (1), Cu, P, As, Mo, V, W, and O represent copper, phosphorus, arsenic, molybdenum, vanadium, tungsten, and oxygen, and X represents at least one selected from cesium, rubidium, potassium, and thallium. Y is an element selected from bismuth, antimony, tin, chromium, silver, palladium, lead, calcium, barium, magnesium, tellurium, selenium, strontium, cobalt, zirconium, germanium, ammonium, and pyridinium ions. a, b, c, d, e, f, g and h each represent an atomic ratio, and when molybdenum composition is 12, a is 0.5-2, b is 0.05-1, c is 0-2 and a + b + c has a value of 3 + f or less. d is 0-2, e is 0-1, f and g are 0-3, and h is the value needed to meet valence. In the catalyst regeneration method according to claim 1, in the step of treating with an acid and an oxidizing agent, excess phosphoric acid is used as the acid, and further 12-phosphomolybdic acid is added, followed by heat treatment to sublimate molybdenum or phosph during the reaction. A method of regenerating a spent catalyst comprising replenishing form molybdate or inducing molybdenum or vanadium oxide into a heteropolyacid structure. The catalyst regeneration method according to claim 1 or 2, wherein a mixed precipitate of a nitrogen heterocyclic compound and an oxalic acid and / or salt thereof is used to induce the catalyst sintered during the reaction into the active structure and maintain the uniformity of the composition. Recycling method of the spent catalyst, characterized in that. The catalyst regeneration method according to any one of claims 1 to 3, wherein the catalyst slurry is filtered and washed to remove chemical species unnecessary for the catalytically active component.