CA1135248A - Preparation and use of phosphorus-vanadium- oxygen catalysts in producing maleic anhydride - Google Patents
Preparation and use of phosphorus-vanadium- oxygen catalysts in producing maleic anhydrideInfo
- Publication number
- CA1135248A CA1135248A CA000363227A CA363227A CA1135248A CA 1135248 A CA1135248 A CA 1135248A CA 000363227 A CA000363227 A CA 000363227A CA 363227 A CA363227 A CA 363227A CA 1135248 A CA1135248 A CA 1135248A
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- Prior art keywords
- vanadium
- catalyst precursor
- phosphorus
- catalyst
- agglomerates
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Classifications
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/16—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation
- C07C51/21—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen
- C07C51/215—Preparation of carboxylic acids or their salts, halides or anhydrides by oxidation with molecular oxygen of saturated hydrocarbyl groups
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/002—Mixed oxides other than spinels, e.g. perovskite
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/14—Phosphorus; Compounds thereof
- B01J27/186—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J27/195—Phosphorus; Compounds thereof with arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium with vanadium, niobium or tantalum
- B01J27/198—Vanadium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/0009—Use of binding agents; Moulding; Pressing; Powdering; Granulating; Addition of materials ameliorating the mechanical properties of the product catalyst
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2523/00—Constitutive chemical elements of heterogeneous catalysts
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Catalysts (AREA)
- Furan Compounds (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
In the preparation of phosphorus-vanadium-oxygen catalyst, where vanadium and phosphorus are con-tacted under conditions to provide a catalyst precursor with vanadium in the tetravalent state, and the pre-cursor is formed into agglomerations and subsequently calcined at high temperatures, the improvement character-ized by wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhe-sion prior to calcining.
The catalyst is used in preparing maleic an-hydride with the enhanced surface adhesion reducing at-trition during preparation of the maleic anhydride.
In the preparation of phosphorus-vanadium-oxygen catalyst, where vanadium and phosphorus are con-tacted under conditions to provide a catalyst precursor with vanadium in the tetravalent state, and the pre-cursor is formed into agglomerations and subsequently calcined at high temperatures, the improvement character-ized by wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhe-sion prior to calcining.
The catalyst is used in preparing maleic an-hydride with the enhanced surface adhesion reducing at-trition during preparation of the maleic anhydride.
Description
- ~ f PREPARA'rION AND USE OF
PHOSPHORUS-VANA~IUM-OXYGEN CATALYSTS
IN PRODUCING MALEIC ANHY~RIDE
BACKGROUND OF THE INVENTION
A. Fiela oE the Invention The invention relates to a method for preparing catalysts and to a method for their use in the manufacture of maleic anhydride by the oxidation of aliphatic hydro-carbons, and more particularly to low attrition catalysts suitable for producing maleic anhydride from saturated hydrocarbons in high yields.
B. Description of the Prior Art Bergman et al., U.S. Patent 3,293,268 teaches a process of oxidizing saturated aliphatic hydrocarbons to produce maleic anhydride under controlled temperature conditions in the presence of a phosphorus-vanadium-oxygen catalyst.
Typical phosphorus-vanadium-oxygen catalysts for use_in tube-type reactors are formed as pills, pellets, slugs, tablets, or extrusions, collectively termed "agglomerates". Charging of such catalyst agglomerates to a reactor is a problem because the agglomerates are dusty, that is, have very low attrition resistance and the phosphorus-vanadium-oxygen dust is moderately toxic.
Catalyst structures are easily broken and such breakage can cause undesirable pressure drop difficulties during reactor operation. In attempts to alleviate such problems, high density forms have been employea using higher tabletting pressures.
These high density forms, with corresponding lower porosity, are less active than low density forms.
If the attrition of low density phosphorus-vanadium-oxygen catalysts could be significantly reduced without detriment to catalyst performance in the production of maleic anhydride, such reduction would constitute a significant advance ln the art and is an object of this invention.
3 ~ ~4 C-23-54-0~7 SUMMARY OF T~E I~ENTION
These and other advantages are achieved in a process for preparing phosphorus-vanadium-oxygen complex catalysts by contacting vanadium and phosphorus under con-ditions to provide a cataLyst precursor having greaterthan 50 atom % tetravalent vanadium, recovering the pre-cursor, forming the catalyst into agglomerates and cal-cining the catalyst precursors by the improvement compris-ing wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhesion prior to calcining and then drying the catalyst precursor. The wetting may take place before the formation of the cata-lyst precursor ir.to agglomerates, after the formation of the catalyst precursor into agglomerates, or both before and after The method for the preparation of maleic anhy-dride according to the lnvention comprises oxidizing a re-actant consisting essentially of the saturated aliphatic hydrocarbon having 4-10 carbon atoms in the presence of a phosphorus-vanadium-oxygen-co~ltaining complex catalyst pre-pared by the process comprising:
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor agglomerations at a temperature between about 300C and 600C , by the improvement comprising employing, as the catalyst, the product of the improved process wherein the catalyst precursor is wetted with an aqueous liquid in an amountsuficient to enhance surface adhesion and then dried prior to calcining whereby attrition of the catalyst dur-S2~
c-23-54-~070 , -2a-ingthe oxidizing of the reactant is substantially reduced The wetting may take place before the formation of the catalyst precursor into agglomerates, after the formation of the catalyst precursor into agglomerates, or both be-fore and after.
DEFINITIONS
As used herein the term "agglomeration" means the gathering together of particulates, particularly pow-dered materials which are brought together in a loose state of bonding to form larger particulates or structures.
Such "agglomerates" are usually redispersible.
The terms "granules" and "nodules" describe forms of agglomerates by reference to the end-condition of the product. "Granulation" and "granules" are used to des-cribe the formation of, and the resultant irregularlyshaped clusters, of particulates. "Nodulizing" and "nodules" are used to de cribe the formation of, and the resultant generally regularly shaped clusters, o parti~ulates, such as pills and pellets.
As used herein, ~he term "attrition" means degrading or deagglomerizing by wearing or grinding down through friction or breakage o~ the catalyst agglomerates or structures into dusts and/or fines.
By "aqueous liquid" is meant water or any liquid containing a substantial amoun~ of water. Any other constituents should, o~ course~ be relatively inert to the catalyst precurser. Such other constituents m~y include alcohols such as methanol and ketones such as acetone.
The term "percen~ (or %) attrition" means, according ~o the test described herein, the weight loss in gr~ms by friction and breakage of the catalyst structures (initial weight, grams - subsequent weight, grams) divided by the initial weight in grams of the catalyst structures, the quotient having been multiplied by 100.
The term "yield" means the ratio of the moles of maleic anhydride obtained of the moles to feed material introduced into the reactor.
The term "space velocity" means the hourly volume of gaseous feed expressed in cubic centimeters ~cc) at 15.5C. at standard atmosph~ric pressure, divided by the catalyst bulk volume, expressed in cubic centimeters, the term expressed as cc/cc/hour.
DETAILED DESCRIPTIO~ OF THE INVENTION
~ roadly described, the catalysts of this i~vention are prepared by contacting a phosphorus compound and a vanadium compound under conditions which will provide a catalyst precursor having a phosphorus to vanadium atom ratio between about 1:2 and about 2:1, and having greater .
.
-4- C-23-54-~7 than 50 atom percent of the vanadium in the tetravalent state. T~e catalyst precursors are recovered and formed into structures for use in a maleic anhydride reactor.
Thereafter, these catalyst precursors are calcined at a temperature between about 300C. and about 600C. to form the catalyst.
The vanadium compounds useful as a source of vanadium in the catalyst precursors are well known in the art. Suitable vanadium compounds include but are not limited to: vanadium oxides, such as vanadium pentoxide, vanadium tetroxide, vanadium trioxide, and the like, vanadium oxyhalides, such as vanadyl chloride, vanadyl dichloride, vanadyl trichloride, vanadyl bromide, vanadyl dibromide, vanadyl tribromide and the like; vanadium-L5 containing acids, such as metavanadic acid, pyrovanadic acid, and the like; vanadium salts, such as ammonium meta-vanadate, vanadium sulfate, vanadium phosphate, vanadyl formate, vanadyl oxylate, and the like. Of these, however, vanadium pentoxide is preferred.
The compounds useful as a source of phosphorus in the catalyst precursors are also well known to the art.
Suitable phosphorus compounds include: phosphoric acids, such as or~hophosphoric acid, metaphosphoric acid, and the like; phosphorus oxides, such as, phosphorus pentoxide and the like; phosphorus halides, such as phosphorus penta-chloride, phosphorus oxybromide, phosphorus oxychloride, and the like; trivalent phosphorus compounds, such as phosphorous acid, phosphorus trihalides (for example, phosphorus trichloride), organic phosphites (for example, trimethyl phosphite), sometimes known as phosphonates, and the Like. Of these, orthophosphoric acid and phosphorus pentoxide are preferred, with a mixture of orthophosph~ric acid and phosphorous acid being most preferred.
,
PHOSPHORUS-VANA~IUM-OXYGEN CATALYSTS
IN PRODUCING MALEIC ANHY~RIDE
BACKGROUND OF THE INVENTION
A. Fiela oE the Invention The invention relates to a method for preparing catalysts and to a method for their use in the manufacture of maleic anhydride by the oxidation of aliphatic hydro-carbons, and more particularly to low attrition catalysts suitable for producing maleic anhydride from saturated hydrocarbons in high yields.
B. Description of the Prior Art Bergman et al., U.S. Patent 3,293,268 teaches a process of oxidizing saturated aliphatic hydrocarbons to produce maleic anhydride under controlled temperature conditions in the presence of a phosphorus-vanadium-oxygen catalyst.
Typical phosphorus-vanadium-oxygen catalysts for use_in tube-type reactors are formed as pills, pellets, slugs, tablets, or extrusions, collectively termed "agglomerates". Charging of such catalyst agglomerates to a reactor is a problem because the agglomerates are dusty, that is, have very low attrition resistance and the phosphorus-vanadium-oxygen dust is moderately toxic.
Catalyst structures are easily broken and such breakage can cause undesirable pressure drop difficulties during reactor operation. In attempts to alleviate such problems, high density forms have been employea using higher tabletting pressures.
These high density forms, with corresponding lower porosity, are less active than low density forms.
If the attrition of low density phosphorus-vanadium-oxygen catalysts could be significantly reduced without detriment to catalyst performance in the production of maleic anhydride, such reduction would constitute a significant advance ln the art and is an object of this invention.
3 ~ ~4 C-23-54-0~7 SUMMARY OF T~E I~ENTION
These and other advantages are achieved in a process for preparing phosphorus-vanadium-oxygen complex catalysts by contacting vanadium and phosphorus under con-ditions to provide a cataLyst precursor having greaterthan 50 atom % tetravalent vanadium, recovering the pre-cursor, forming the catalyst into agglomerates and cal-cining the catalyst precursors by the improvement compris-ing wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhesion prior to calcining and then drying the catalyst precursor. The wetting may take place before the formation of the cata-lyst precursor ir.to agglomerates, after the formation of the catalyst precursor into agglomerates, or both before and after The method for the preparation of maleic anhy-dride according to the lnvention comprises oxidizing a re-actant consisting essentially of the saturated aliphatic hydrocarbon having 4-10 carbon atoms in the presence of a phosphorus-vanadium-oxygen-co~ltaining complex catalyst pre-pared by the process comprising:
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor agglomerations at a temperature between about 300C and 600C , by the improvement comprising employing, as the catalyst, the product of the improved process wherein the catalyst precursor is wetted with an aqueous liquid in an amountsuficient to enhance surface adhesion and then dried prior to calcining whereby attrition of the catalyst dur-S2~
c-23-54-~070 , -2a-ingthe oxidizing of the reactant is substantially reduced The wetting may take place before the formation of the catalyst precursor into agglomerates, after the formation of the catalyst precursor into agglomerates, or both be-fore and after.
DEFINITIONS
As used herein the term "agglomeration" means the gathering together of particulates, particularly pow-dered materials which are brought together in a loose state of bonding to form larger particulates or structures.
Such "agglomerates" are usually redispersible.
The terms "granules" and "nodules" describe forms of agglomerates by reference to the end-condition of the product. "Granulation" and "granules" are used to des-cribe the formation of, and the resultant irregularlyshaped clusters, of particulates. "Nodulizing" and "nodules" are used to de cribe the formation of, and the resultant generally regularly shaped clusters, o parti~ulates, such as pills and pellets.
As used herein, ~he term "attrition" means degrading or deagglomerizing by wearing or grinding down through friction or breakage o~ the catalyst agglomerates or structures into dusts and/or fines.
By "aqueous liquid" is meant water or any liquid containing a substantial amoun~ of water. Any other constituents should, o~ course~ be relatively inert to the catalyst precurser. Such other constituents m~y include alcohols such as methanol and ketones such as acetone.
The term "percen~ (or %) attrition" means, according ~o the test described herein, the weight loss in gr~ms by friction and breakage of the catalyst structures (initial weight, grams - subsequent weight, grams) divided by the initial weight in grams of the catalyst structures, the quotient having been multiplied by 100.
The term "yield" means the ratio of the moles of maleic anhydride obtained of the moles to feed material introduced into the reactor.
The term "space velocity" means the hourly volume of gaseous feed expressed in cubic centimeters ~cc) at 15.5C. at standard atmosph~ric pressure, divided by the catalyst bulk volume, expressed in cubic centimeters, the term expressed as cc/cc/hour.
DETAILED DESCRIPTIO~ OF THE INVENTION
~ roadly described, the catalysts of this i~vention are prepared by contacting a phosphorus compound and a vanadium compound under conditions which will provide a catalyst precursor having a phosphorus to vanadium atom ratio between about 1:2 and about 2:1, and having greater .
.
-4- C-23-54-~7 than 50 atom percent of the vanadium in the tetravalent state. T~e catalyst precursors are recovered and formed into structures for use in a maleic anhydride reactor.
Thereafter, these catalyst precursors are calcined at a temperature between about 300C. and about 600C. to form the catalyst.
The vanadium compounds useful as a source of vanadium in the catalyst precursors are well known in the art. Suitable vanadium compounds include but are not limited to: vanadium oxides, such as vanadium pentoxide, vanadium tetroxide, vanadium trioxide, and the like, vanadium oxyhalides, such as vanadyl chloride, vanadyl dichloride, vanadyl trichloride, vanadyl bromide, vanadyl dibromide, vanadyl tribromide and the like; vanadium-L5 containing acids, such as metavanadic acid, pyrovanadic acid, and the like; vanadium salts, such as ammonium meta-vanadate, vanadium sulfate, vanadium phosphate, vanadyl formate, vanadyl oxylate, and the like. Of these, however, vanadium pentoxide is preferred.
The compounds useful as a source of phosphorus in the catalyst precursors are also well known to the art.
Suitable phosphorus compounds include: phosphoric acids, such as or~hophosphoric acid, metaphosphoric acid, and the like; phosphorus oxides, such as, phosphorus pentoxide and the like; phosphorus halides, such as phosphorus penta-chloride, phosphorus oxybromide, phosphorus oxychloride, and the like; trivalent phosphorus compounds, such as phosphorous acid, phosphorus trihalides (for example, phosphorus trichloride), organic phosphites (for example, trimethyl phosphite), sometimes known as phosphonates, and the Like. Of these, orthophosphoric acid and phosphorus pentoxide are preferred, with a mixture of orthophosph~ric acid and phosphorous acid being most preferred.
,
2~ ~
-5- C-23-5~-~070 Preparation of Ca~alyst Precursors To prepare the catalyst precursors by the process of the present invention, a vanadium compound is brought together with a phosphorus compound in an acid solution and the mixture is heated to dissolve the starting materials.
A reducing agent is used to reduce pentavalent vanadium to tetravalent vanadium and to maintain the vanadium in the tetravalent state. As is well known to those skilled in the art, hydrogen halide acid or oxalic acid solutions, which are mild reducing agents, can serve not only as the acid but also as the reducing agent for the pentavalent vanadium.
Cn ~he other hand, a trivalent phosphorus compound can be used to provide tetravalent vanadium and also serve as a source of phosphorus to provide ~he catalyst precursor.
It is pre~erred to use phosphorous acid as the trivalent phosphorus compound which serves as an acid medium to provide the tetravalent vanadium in the precursor. The acid solution containing the phosphorus compound and the vanadium compound is heated until a blue solution is obtained, indicating that at least 50 atom percent of the vanadium is in the tetravalent state. The amount of time required to dissolve the phosphorus compound and the vanadium compound and to provide a substantial amount of the vanadium in the tetravalent state and to provide the catalyst precursors varies from batch to batch, depending upon the compounds used as starting materials and the temperature at which the compounds are heated. In general, however, heating the solution to at least 100C. or about 4 hours is sufficient.
- :
.
, 5; :4l~
~ he ~tom ratio of phosphorus to vanadiurn in the starting materials is important since i-t controls the phosphorus -to ~anadium a~om ratio in the final catalyst.
When phosphorus-vanadium-oxy~en precursors contain a phosphorus to vanadium atom ratio below about 0.5:1 or above about 2:1, the yield of maleic anhydride using the catalyst prepared from these precursors is so low that it is not of commercial signi~icance. It is preferred that phosphorus-vanadium-oxygen precursors have a phosphorus to vanadium 10atom ratio between about 1:1 and about 1.5:1. When the catalyst is used to convert a feed that is primarily butane to maleic anhydride, it is even more preferable that the precursor have a phosphorus to vanadium atom ratio between about 1:1 and about 1.2:1.
15If desired, although not actually required, a nonionic surfactant may be added to the mixture to control particle size and prevent agglomeration of the catalyst precursor during the preparation step. Nonionic surfactants may be broadly defined as compounds~ aliphatic or alkyl-aromatic in nature, which do not ionize in water solution.
For example, a well known class of nonionic surfactants is made available on the market under the trade mark of "Pluronic". These compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the con-densation of propylene oxide with propylene glycol. Thehydrophobic portion of the molecule which, of course, exhibits water insolubility, has a molecular weight of from about 1,500 to 1,800. The addition of polyoxyethylene radicals to this hydrophobic portion tends to increase the water solu-bility of the molecule as a whole and the liquid character ofthe product is retained up to the point where polyeyethylene content is about 50% of the total weight of the condensation product. Other suitable surfactants are described in U. S.
4,149,992~
- 7 - c- 23 - s4-~070 The amount of surfactant, when emplo~Jed, suita'Dle for use in the process of the present invention,can var~
- within wide lLmits. It has been found that the amount of surfactant should be at least about 0.01% by weight, based on the total weight of the mixture or dispersion, since at lower concentrations the effect o~ the surfactant is diminished considerably. On the other hand, there is no upper limit as to the amount of surfactant that can be used, although there does not seem to be any advantage in using more than about 1.0% by weigh~, and usually between about 0.05% and about 0.5% by weight, based on the total weight of the dispersion.
Recovery of the Catalyst Precursor After the ~anadium and phosphorus compounds are contacted and a substantial amount of the vanadium is in the tetravalent state, it is necessary to recover the phosphorus-vanadium-oxygen catalyst precursors. Techniques for recovexing the catalyst precursors are well known to those skilled in the art. For example, the catalyst pre-cursors can be deposited from aqueous solution on a carrier, such as alumina or titania, or alternatively, the catalyst precursors can be recovered by gentle heating to dryness to provide solid phosphorus-vanadium-oxygen catalyst precursors. This latter technique is preferred.
Forming Agglomerates After the phosphorus-vanadium-oxygen catalyst precursors have been recovered as dry powders, they are formed into agglomerates or structures, prior to subject-ing them to calcining conditions.
Techniques for forming appropriate agglomerates ~rom precursors for use in a fluidized bed reactor or in a fixed-tube heat-exchanger t~pe reactor are well known to those skilled in the art. For example, the precursor can be .
structured for use in a fluidized bed reactor by depositing the phosphorus-vanadium-oxygen precursor on a carrier.
Alternately, precursors can become comminuted for use in a fluidized bed reactor. They can be structured ~or use in fixed-tube heat exchanger/type reactors by e~truding a paste of the precursors through an orifice and then breaking or chopping into slugs or broken slugs. They can also be formed by pilling, tabletting, pelletizing or granulating the precursors by conventional means.
Wetting and Drying the Ca~alyst Precursor The wetting may take place before or after the forming of the agglomerates, or both before and after the forming of the agglomerates. The aqueous liquid is applied to 'che catalyst precursor by spray, fog, sprinkIe, or ~mmersion. Spraying is preferred. The amount of aqueous liquid applied is not critical, because any amount will to some extent enhance surface adhesion. It is not unknown to use liquids in the formation or the holdlng of agglomerates, the theory being that the liquid acts as a binder between particles, minute portions of the outer perimeters of which are dissolved and then solidified on drying, What is unique about ~his invention is that such liquid application can be applied to a phosphorus-vanadium- -oxygen catalyst precursor, without interferring in any way with subsequent catalyst activity, to achieve low attrition not only in handling of the catalyst, but in the use of the catalyst as well. After wetting and preferably before calcining the water should be removed in a con~entional drying step at temperatures of 70-250C. (100 150G.
pre~erred).
-5- C-23-5~-~070 Preparation of Ca~alyst Precursors To prepare the catalyst precursors by the process of the present invention, a vanadium compound is brought together with a phosphorus compound in an acid solution and the mixture is heated to dissolve the starting materials.
A reducing agent is used to reduce pentavalent vanadium to tetravalent vanadium and to maintain the vanadium in the tetravalent state. As is well known to those skilled in the art, hydrogen halide acid or oxalic acid solutions, which are mild reducing agents, can serve not only as the acid but also as the reducing agent for the pentavalent vanadium.
Cn ~he other hand, a trivalent phosphorus compound can be used to provide tetravalent vanadium and also serve as a source of phosphorus to provide ~he catalyst precursor.
It is pre~erred to use phosphorous acid as the trivalent phosphorus compound which serves as an acid medium to provide the tetravalent vanadium in the precursor. The acid solution containing the phosphorus compound and the vanadium compound is heated until a blue solution is obtained, indicating that at least 50 atom percent of the vanadium is in the tetravalent state. The amount of time required to dissolve the phosphorus compound and the vanadium compound and to provide a substantial amount of the vanadium in the tetravalent state and to provide the catalyst precursors varies from batch to batch, depending upon the compounds used as starting materials and the temperature at which the compounds are heated. In general, however, heating the solution to at least 100C. or about 4 hours is sufficient.
- :
.
, 5; :4l~
~ he ~tom ratio of phosphorus to vanadiurn in the starting materials is important since i-t controls the phosphorus -to ~anadium a~om ratio in the final catalyst.
When phosphorus-vanadium-oxy~en precursors contain a phosphorus to vanadium atom ratio below about 0.5:1 or above about 2:1, the yield of maleic anhydride using the catalyst prepared from these precursors is so low that it is not of commercial signi~icance. It is preferred that phosphorus-vanadium-oxygen precursors have a phosphorus to vanadium 10atom ratio between about 1:1 and about 1.5:1. When the catalyst is used to convert a feed that is primarily butane to maleic anhydride, it is even more preferable that the precursor have a phosphorus to vanadium atom ratio between about 1:1 and about 1.2:1.
15If desired, although not actually required, a nonionic surfactant may be added to the mixture to control particle size and prevent agglomeration of the catalyst precursor during the preparation step. Nonionic surfactants may be broadly defined as compounds~ aliphatic or alkyl-aromatic in nature, which do not ionize in water solution.
For example, a well known class of nonionic surfactants is made available on the market under the trade mark of "Pluronic". These compounds are formed by condensing ethylene oxide with a hydrophobic base formed by the con-densation of propylene oxide with propylene glycol. Thehydrophobic portion of the molecule which, of course, exhibits water insolubility, has a molecular weight of from about 1,500 to 1,800. The addition of polyoxyethylene radicals to this hydrophobic portion tends to increase the water solu-bility of the molecule as a whole and the liquid character ofthe product is retained up to the point where polyeyethylene content is about 50% of the total weight of the condensation product. Other suitable surfactants are described in U. S.
4,149,992~
- 7 - c- 23 - s4-~070 The amount of surfactant, when emplo~Jed, suita'Dle for use in the process of the present invention,can var~
- within wide lLmits. It has been found that the amount of surfactant should be at least about 0.01% by weight, based on the total weight of the mixture or dispersion, since at lower concentrations the effect o~ the surfactant is diminished considerably. On the other hand, there is no upper limit as to the amount of surfactant that can be used, although there does not seem to be any advantage in using more than about 1.0% by weigh~, and usually between about 0.05% and about 0.5% by weight, based on the total weight of the dispersion.
Recovery of the Catalyst Precursor After the ~anadium and phosphorus compounds are contacted and a substantial amount of the vanadium is in the tetravalent state, it is necessary to recover the phosphorus-vanadium-oxygen catalyst precursors. Techniques for recovexing the catalyst precursors are well known to those skilled in the art. For example, the catalyst pre-cursors can be deposited from aqueous solution on a carrier, such as alumina or titania, or alternatively, the catalyst precursors can be recovered by gentle heating to dryness to provide solid phosphorus-vanadium-oxygen catalyst precursors. This latter technique is preferred.
Forming Agglomerates After the phosphorus-vanadium-oxygen catalyst precursors have been recovered as dry powders, they are formed into agglomerates or structures, prior to subject-ing them to calcining conditions.
Techniques for forming appropriate agglomerates ~rom precursors for use in a fluidized bed reactor or in a fixed-tube heat-exchanger t~pe reactor are well known to those skilled in the art. For example, the precursor can be .
structured for use in a fluidized bed reactor by depositing the phosphorus-vanadium-oxygen precursor on a carrier.
Alternately, precursors can become comminuted for use in a fluidized bed reactor. They can be structured ~or use in fixed-tube heat exchanger/type reactors by e~truding a paste of the precursors through an orifice and then breaking or chopping into slugs or broken slugs. They can also be formed by pilling, tabletting, pelletizing or granulating the precursors by conventional means.
Wetting and Drying the Ca~alyst Precursor The wetting may take place before or after the forming of the agglomerates, or both before and after the forming of the agglomerates. The aqueous liquid is applied to 'che catalyst precursor by spray, fog, sprinkIe, or ~mmersion. Spraying is preferred. The amount of aqueous liquid applied is not critical, because any amount will to some extent enhance surface adhesion. It is not unknown to use liquids in the formation or the holdlng of agglomerates, the theory being that the liquid acts as a binder between particles, minute portions of the outer perimeters of which are dissolved and then solidified on drying, What is unique about ~his invention is that such liquid application can be applied to a phosphorus-vanadium- -oxygen catalyst precursor, without interferring in any way with subsequent catalyst activity, to achieve low attrition not only in handling of the catalyst, but in the use of the catalyst as well. After wetting and preferably before calcining the water should be removed in a con~entional drying step at temperatures of 70-250C. (100 150G.
pre~erred).
3~
The precursors are then calcined at ~emperatures between about 300 and about 600C. for at least ~o hours to provide the catalysts of the present invention. It is preferred to convert part of the tetravalent vanadium to pentavalent vanadium during the calcination step. The tetravalent vanadium can be converted to pentavalent vanadium by calcining the precursor in a free oxygen-containing gas, such as air, at temperatures of about 300 to about 600C. until about 20 to about 90 atom percent of the vanadium has been converted to pentavalent vanadium.
If more than about 90 atom percent of the vanadium is converted to pentavalent vanadium, usually caused by calcin-ing too long or at too high a temperature, the selectivity of the resultant catalyst, and consequently, the yield of maleic anhydride decrease. On the other hand, conversion of less than about 20 atom percent of the vanadium during air calcination does not seem to be beneficial. As wlll occur to those skilled in the art, the exact calcination conditions will depend on the method of preparing the precursor, equipment configurationsj or additives to the precursor;
however, it has been found that calcination at about 500C.
for about 4 hours is generally sufficient.
After calcining the catalyst precursor~ can be ~harged to a suitable reaetor without su~fering the attrition and dusting difficulties usually associated with prior art phosphorus vanadium-oxygen catalysts and can be used in accordance with prior art techniques to convert non-aromatic hydrocarbons to maleic anhydride.
Pr~paration of Maleic Anhydride The catalqsts of the present invention are useful ir~ a variety of reactors to convert non-aromatic hydrocarbons to maleic anhydride. Both fludizied bed reactors and fixed tube, heat exchanger type reactors are satisfactory, and the ~J
,.','~,'~
-lO- C-23-54-0070 details of the operation of such reactors are well '~no~m to those skilled in the art. The reaction to convert non-aromatic hydrocarbons to maleic anhydride requires only contacting ~he hydrocarbons admixed with a free-o~ygen containing gas, such as air or oxygen enriched air, with the catalysts at elevated temperatures. The hydrocarbon/-air mixture is contacted with the catalyst at a concentration of about l mole percent to about L0 mole percent hydrocarbon at a space velocity of about lO0 cc/cc/hour to about 3,000 cc/cc/hour at temperatures between about 300C. and about 600C. to provide excellent yields of maleic anhydride.
Maleic anhydride produced by using the conditioned catalysts of this invention can be recovered by any number of means ` well known to those skilled in the art. For example, maleic anhydride can be recovered by direct condensation or by absorprtion in suitable media with subsequent separation and purification of the anhydride.
A large number of non-aromatic hydrocarbons having from 4 to lO carbon atoms can be converted to maleic anhydride using the catalysts prepared according to the present process. It is only necessary that the hydrocarbon contain no~ less than 4 carbon atoms in a straight chain.
As an example, the saturated hydrocarbon n-butane is satisfactory, but isobutane (2-methylpropane) is not satisfactory for conversion to maleic anhydride although its presence is not harmful. In addition to n-butane, other suitable saturated hydrocarbons include the pentanes, the hexanes, the heptanes, the octanes, ~he nonanes, the decanes, and mixtures of any of these, with or wi~hout n-butane.
., ~ C-23-54-~070 Unsatura~ed hydrocarbons are also suit~ble ~or conversion to maleic anhydride using the agglomerated catalysts of this invention. Suitable unsaturated hydro-carbons include the butenes (l-butene and 2-butene), 1,3-butadiene, ~he pentenes, the hexenes, the heptenes, theoctenes, the nonenes, the decenes and mixtures of any of these, with or without the butenes.
Cycl~c compounds such as cyclopentane, cyclopen-tene, oxygenated compounds such as furan, dihydro~uran, or e~en tetrahydrofurfural alcohol are also satisfactory.
Of the a~orementioned feedstocks, n-butane is the preferred saturated hydrocarbon and the butenes are the preferred unsaturated hydrocarbons, with n-butane being most preferred of all feedstocks.
It will be noted that the aforementioned feed-stocks need not necessarily be pure substances, but can be technical grade hydrocarbons.
The principal product rom the oxidation of t:e above feed materials is maleic anhydride, although small amounts of citraconic anhydride (methylmaleic anhydride) may also be produced when the feedstock is a hydrocarbon containing more than 4 carbon atoms.
The following examples illustrate the in~ention, but should not be construed as delimiting.
~5 .
CATALYST PRECURSOR PREPARATION "A"
To a mixture of 340.0 grams (1.87 moles) of vana-dium pen~oxide, 1150 milliliters of water and 2.3 grams of nonionic surfactant were added 228.0 grams (1.98 moles) of 85% orthophosphoric acid and 173.0 grams (2.06 moles) of - 97.6% phosphorous -acid. The phosphorus to vanadium atom ratio was a~out 1.08:1, The aqueous mixture -12- C-23-54-007~
of vanadium and phosphorus compounds was charged to a 2-liter Parr autoclave, fitted with a thermowell, ~o 6-bladed stirrers, and a vent, and heated to about 100C.
and thereafter sealed. The mixture, while being stirred at 1,000 revolutions per minute (rpm), was heated to about 150C. in about 50 + 10 minutes and held at this temperature for about 4 hours. After the hold period, the autoclave was cooled to about 80C. in 50 + 10 minutes and opened.
The aqueous phosphorus-vanadium-oxygen catalyst precursor slurry was placed in an open dish casserole or tray and evaporated to dryness in an oven at about 120C. The resultant phosphorus-vanadium-oxygen catalyst precursor powder was ground to pass an 18 mesh sieve (U.S. Standard Sieve Size).
CATALYST PRECURSOR PREPARATION "B"
In a 3 ~ round flask with stirrer and reflux cooler, 595 g vanadium pentoxide, 285.6 g 96.8% phosphorous acid, 404.6 g 85% phosphoric acid and 2012.5 g deionized water are introduced. The atmomic ratio of phosphorus to vanadium was about 1.05:1, and the solution contained about 3% more phosphoric acid than stoichiometrically necessary ~or the reduction o~ the pentavalent vanadium. The mixture was heated under reflux conditions until the solution became blue. Then the heating was continued at a temperature of about 97 to 99C. After 24 hl a pale blue-greer deposit formed, and this formed a dispersion with the water and the dissolved phosphorus and vanadium compounds. It was heated for approximately 28 h more.
About 1985 g of the above material was brought together with about 250 ml deionized water in a 2 Q auto-clave, The autoclave was closed and heated for 4 h at about 150C, After the cooling, the autoclave was opened and the contents were placed in an open porcelain dish until dry in a forced ventilation oven heated to 120C. The dried powder was then triturated until it ran through an 18-mesh screen.
_ ~ ~ 3 ~
ATTRITION TEST
This procedure illustrates the attrition test used to determine percer.t attrition of the phosphorus-vanadium-oxygen catalyst precursors (or catalysts).
A 17.78 centimeter (7.0 inch) high x 9.525 centi-meter (3.75 inch) outside diameter 0.946 liter (1.0 quart) jar equipped with a screw-on cap and two 1.27 centimeter (0.5 inch) high x 8.89 centimeter (3.5 inch) long stain-less steel baffles cemented lengthwise to the inner sides at 180~ opposed angles was employed.
The catalyst samples were separately screened, using a 10 mesh sieve (U.S. Standard Sieve Size) to remove any dust and fines. Approxim~tely 50.00 grams of each of the screened samples were accurately weighed (initial weight in grams) and charged to the apparatus described above.
The baffled jar containing the catalyst precursor was placed on a roller mill and rolled at 1~0 + 5 revolutions per minute (rpm) for 15 minutes. The sample was then removed from the jar, screened, and weighed (subse~uent weight in grams) to determine the amount of attrited material which passed through the 10 mesh sieve. The percent attrition was calculated as follows:
7 Attrition = Initial weight, ~rams-Subse~uent weight, grams nitia weig t, grams x 100 The results are shown in Table 1 under the columns headed "~/0 Attritiont'.
, .J
- ~ 3 CRUSH STRENGTH TEST
This procedure illustrates the crush strength test used to determine the average crush strength (measured as longitudinal, side crush strength for tablets) of the phosphorus-vanadium-oxygen catalyst precursor structures.
A John Chatillon and Sons Universal Test Stand, Model LTCM (motorized, variable speed unit equipped with Chatillon Dial Push/Pull Gauges, either Model DPP-10 (10 pounds maximum) or Model DPP-50 (50 pounds maximum), de-pending on the anticipated range of crush strength, wasused as the test equipment.
The tablet was placed on its side under the center of the plunger and the instrument driven in the automatic mode at a setting of 2. The maximum force exerted during the test was taken as the crush strength for the tablet.
Generally 10 or more determinations were made from a given sample of tablets and the crush strength values a~eraged to give an average crush strength.(ACS). The r~sults are reported in Table 1.
Catalyst precursor powder like that made according to Preparation "A" ox "B" (as indicated) was formed into 0.48 centimeter (3/16 inc~.) diameter tablets using 1 weight percent graphite as a pelletizing lubricant. Alternatively, the powder was formed in~o larger tablets, called slugs, of about 1.27 centimeter (0.5 inch) diameter, follo~7ed by breaking up of the slugs and sizing with stainless steel screens to obtain irregular shapes, called broken slugs, in the size range of about 0.4 centimeter to about 0.8 centimeter.
The catalyst precursor tablets or broken slugs were placed in a tr~y and quantities of solvent atomized or misted over the structure while being gently rolled so that all sides of the structures would be exposed to the 3 S ~ ~
-15- C-23-~4-Q070 solvent. The solvent was removed by placing the structures in a forced draft oven at room temperature (23C.). The temperature of the oven was increased over a period of about one hour to about 125C. and maintained at about 125C. for 2-4 hours. Thereafter, the hardened structures were calcined at 400-500C. for about four hours to convert the catalyst precursor to active catalyst.
Samples of both uncalcined (after solvent removed) and calcined structures were subjected to the attrition test and the crush strength test to determine the effect of type and amount of solvent on the hardening or strengthening of the structures as a result o the treat~ent. The results are shown in Table 1.
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" ". . . .
E ~MPLES 18-22 Catalyst precursor powder, made according to "Preparation B", were tableted, hardened with water, and calcined as described in the previous examples. The amounts of water used to harden the tablets are shown at Table 2.
Performance is co~pared below with similar tablets not hardened with water.
The catalysts were tested by placing the tablets in a 2.54-cen~imeter (l-inch) inside diameter fixed tube reactors which give results comparable to those obtained in a production reactor. At a temperature of about 400C., using a feed stream containing 1.5 mole percent n-butane-in-air at a space velocity o~ about 1,470 cc/cc/hour, the n-butane was converted to maleic anhydride. The yield of maleic anhydride shown at Table 2 after the catalysts had been conditioned for at least 16 hours.
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The precursors are then calcined at ~emperatures between about 300 and about 600C. for at least ~o hours to provide the catalysts of the present invention. It is preferred to convert part of the tetravalent vanadium to pentavalent vanadium during the calcination step. The tetravalent vanadium can be converted to pentavalent vanadium by calcining the precursor in a free oxygen-containing gas, such as air, at temperatures of about 300 to about 600C. until about 20 to about 90 atom percent of the vanadium has been converted to pentavalent vanadium.
If more than about 90 atom percent of the vanadium is converted to pentavalent vanadium, usually caused by calcin-ing too long or at too high a temperature, the selectivity of the resultant catalyst, and consequently, the yield of maleic anhydride decrease. On the other hand, conversion of less than about 20 atom percent of the vanadium during air calcination does not seem to be beneficial. As wlll occur to those skilled in the art, the exact calcination conditions will depend on the method of preparing the precursor, equipment configurationsj or additives to the precursor;
however, it has been found that calcination at about 500C.
for about 4 hours is generally sufficient.
After calcining the catalyst precursor~ can be ~harged to a suitable reaetor without su~fering the attrition and dusting difficulties usually associated with prior art phosphorus vanadium-oxygen catalysts and can be used in accordance with prior art techniques to convert non-aromatic hydrocarbons to maleic anhydride.
Pr~paration of Maleic Anhydride The catalqsts of the present invention are useful ir~ a variety of reactors to convert non-aromatic hydrocarbons to maleic anhydride. Both fludizied bed reactors and fixed tube, heat exchanger type reactors are satisfactory, and the ~J
,.','~,'~
-lO- C-23-54-0070 details of the operation of such reactors are well '~no~m to those skilled in the art. The reaction to convert non-aromatic hydrocarbons to maleic anhydride requires only contacting ~he hydrocarbons admixed with a free-o~ygen containing gas, such as air or oxygen enriched air, with the catalysts at elevated temperatures. The hydrocarbon/-air mixture is contacted with the catalyst at a concentration of about l mole percent to about L0 mole percent hydrocarbon at a space velocity of about lO0 cc/cc/hour to about 3,000 cc/cc/hour at temperatures between about 300C. and about 600C. to provide excellent yields of maleic anhydride.
Maleic anhydride produced by using the conditioned catalysts of this invention can be recovered by any number of means ` well known to those skilled in the art. For example, maleic anhydride can be recovered by direct condensation or by absorprtion in suitable media with subsequent separation and purification of the anhydride.
A large number of non-aromatic hydrocarbons having from 4 to lO carbon atoms can be converted to maleic anhydride using the catalysts prepared according to the present process. It is only necessary that the hydrocarbon contain no~ less than 4 carbon atoms in a straight chain.
As an example, the saturated hydrocarbon n-butane is satisfactory, but isobutane (2-methylpropane) is not satisfactory for conversion to maleic anhydride although its presence is not harmful. In addition to n-butane, other suitable saturated hydrocarbons include the pentanes, the hexanes, the heptanes, the octanes, ~he nonanes, the decanes, and mixtures of any of these, with or wi~hout n-butane.
., ~ C-23-54-~070 Unsatura~ed hydrocarbons are also suit~ble ~or conversion to maleic anhydride using the agglomerated catalysts of this invention. Suitable unsaturated hydro-carbons include the butenes (l-butene and 2-butene), 1,3-butadiene, ~he pentenes, the hexenes, the heptenes, theoctenes, the nonenes, the decenes and mixtures of any of these, with or without the butenes.
Cycl~c compounds such as cyclopentane, cyclopen-tene, oxygenated compounds such as furan, dihydro~uran, or e~en tetrahydrofurfural alcohol are also satisfactory.
Of the a~orementioned feedstocks, n-butane is the preferred saturated hydrocarbon and the butenes are the preferred unsaturated hydrocarbons, with n-butane being most preferred of all feedstocks.
It will be noted that the aforementioned feed-stocks need not necessarily be pure substances, but can be technical grade hydrocarbons.
The principal product rom the oxidation of t:e above feed materials is maleic anhydride, although small amounts of citraconic anhydride (methylmaleic anhydride) may also be produced when the feedstock is a hydrocarbon containing more than 4 carbon atoms.
The following examples illustrate the in~ention, but should not be construed as delimiting.
~5 .
CATALYST PRECURSOR PREPARATION "A"
To a mixture of 340.0 grams (1.87 moles) of vana-dium pen~oxide, 1150 milliliters of water and 2.3 grams of nonionic surfactant were added 228.0 grams (1.98 moles) of 85% orthophosphoric acid and 173.0 grams (2.06 moles) of - 97.6% phosphorous -acid. The phosphorus to vanadium atom ratio was a~out 1.08:1, The aqueous mixture -12- C-23-54-007~
of vanadium and phosphorus compounds was charged to a 2-liter Parr autoclave, fitted with a thermowell, ~o 6-bladed stirrers, and a vent, and heated to about 100C.
and thereafter sealed. The mixture, while being stirred at 1,000 revolutions per minute (rpm), was heated to about 150C. in about 50 + 10 minutes and held at this temperature for about 4 hours. After the hold period, the autoclave was cooled to about 80C. in 50 + 10 minutes and opened.
The aqueous phosphorus-vanadium-oxygen catalyst precursor slurry was placed in an open dish casserole or tray and evaporated to dryness in an oven at about 120C. The resultant phosphorus-vanadium-oxygen catalyst precursor powder was ground to pass an 18 mesh sieve (U.S. Standard Sieve Size).
CATALYST PRECURSOR PREPARATION "B"
In a 3 ~ round flask with stirrer and reflux cooler, 595 g vanadium pentoxide, 285.6 g 96.8% phosphorous acid, 404.6 g 85% phosphoric acid and 2012.5 g deionized water are introduced. The atmomic ratio of phosphorus to vanadium was about 1.05:1, and the solution contained about 3% more phosphoric acid than stoichiometrically necessary ~or the reduction o~ the pentavalent vanadium. The mixture was heated under reflux conditions until the solution became blue. Then the heating was continued at a temperature of about 97 to 99C. After 24 hl a pale blue-greer deposit formed, and this formed a dispersion with the water and the dissolved phosphorus and vanadium compounds. It was heated for approximately 28 h more.
About 1985 g of the above material was brought together with about 250 ml deionized water in a 2 Q auto-clave, The autoclave was closed and heated for 4 h at about 150C, After the cooling, the autoclave was opened and the contents were placed in an open porcelain dish until dry in a forced ventilation oven heated to 120C. The dried powder was then triturated until it ran through an 18-mesh screen.
_ ~ ~ 3 ~
ATTRITION TEST
This procedure illustrates the attrition test used to determine percer.t attrition of the phosphorus-vanadium-oxygen catalyst precursors (or catalysts).
A 17.78 centimeter (7.0 inch) high x 9.525 centi-meter (3.75 inch) outside diameter 0.946 liter (1.0 quart) jar equipped with a screw-on cap and two 1.27 centimeter (0.5 inch) high x 8.89 centimeter (3.5 inch) long stain-less steel baffles cemented lengthwise to the inner sides at 180~ opposed angles was employed.
The catalyst samples were separately screened, using a 10 mesh sieve (U.S. Standard Sieve Size) to remove any dust and fines. Approxim~tely 50.00 grams of each of the screened samples were accurately weighed (initial weight in grams) and charged to the apparatus described above.
The baffled jar containing the catalyst precursor was placed on a roller mill and rolled at 1~0 + 5 revolutions per minute (rpm) for 15 minutes. The sample was then removed from the jar, screened, and weighed (subse~uent weight in grams) to determine the amount of attrited material which passed through the 10 mesh sieve. The percent attrition was calculated as follows:
7 Attrition = Initial weight, ~rams-Subse~uent weight, grams nitia weig t, grams x 100 The results are shown in Table 1 under the columns headed "~/0 Attritiont'.
, .J
- ~ 3 CRUSH STRENGTH TEST
This procedure illustrates the crush strength test used to determine the average crush strength (measured as longitudinal, side crush strength for tablets) of the phosphorus-vanadium-oxygen catalyst precursor structures.
A John Chatillon and Sons Universal Test Stand, Model LTCM (motorized, variable speed unit equipped with Chatillon Dial Push/Pull Gauges, either Model DPP-10 (10 pounds maximum) or Model DPP-50 (50 pounds maximum), de-pending on the anticipated range of crush strength, wasused as the test equipment.
The tablet was placed on its side under the center of the plunger and the instrument driven in the automatic mode at a setting of 2. The maximum force exerted during the test was taken as the crush strength for the tablet.
Generally 10 or more determinations were made from a given sample of tablets and the crush strength values a~eraged to give an average crush strength.(ACS). The r~sults are reported in Table 1.
Catalyst precursor powder like that made according to Preparation "A" ox "B" (as indicated) was formed into 0.48 centimeter (3/16 inc~.) diameter tablets using 1 weight percent graphite as a pelletizing lubricant. Alternatively, the powder was formed in~o larger tablets, called slugs, of about 1.27 centimeter (0.5 inch) diameter, follo~7ed by breaking up of the slugs and sizing with stainless steel screens to obtain irregular shapes, called broken slugs, in the size range of about 0.4 centimeter to about 0.8 centimeter.
The catalyst precursor tablets or broken slugs were placed in a tr~y and quantities of solvent atomized or misted over the structure while being gently rolled so that all sides of the structures would be exposed to the 3 S ~ ~
-15- C-23-~4-Q070 solvent. The solvent was removed by placing the structures in a forced draft oven at room temperature (23C.). The temperature of the oven was increased over a period of about one hour to about 125C. and maintained at about 125C. for 2-4 hours. Thereafter, the hardened structures were calcined at 400-500C. for about four hours to convert the catalyst precursor to active catalyst.
Samples of both uncalcined (after solvent removed) and calcined structures were subjected to the attrition test and the crush strength test to determine the effect of type and amount of solvent on the hardening or strengthening of the structures as a result o the treat~ent. The results are shown in Table 1.
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" ". . . .
E ~MPLES 18-22 Catalyst precursor powder, made according to "Preparation B", were tableted, hardened with water, and calcined as described in the previous examples. The amounts of water used to harden the tablets are shown at Table 2.
Performance is co~pared below with similar tablets not hardened with water.
The catalysts were tested by placing the tablets in a 2.54-cen~imeter (l-inch) inside diameter fixed tube reactors which give results comparable to those obtained in a production reactor. At a temperature of about 400C., using a feed stream containing 1.5 mole percent n-butane-in-air at a space velocity o~ about 1,470 cc/cc/hour, the n-butane was converted to maleic anhydride. The yield of maleic anhydride shown at Table 2 after the catalysts had been conditioned for at least 16 hours.
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Claims (10)
1. A process for preparing phosphorus-vanadium-oxygen complex catalysts having a phosphorus to vanadium atom ratio in the range of about 1:2 to about 2:1, the process comprising:
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor agglomerations at a temperature between about 300°C. and 600°C., characterized by wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhesion prior to calcining and then drying the catalyst precursor whereby attrition is substantially reduced.
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor agglomerations at a temperature between about 300°C. and 600°C., characterized by wetting the catalyst precursor with an aqueous liquid in an amount sufficient to enhance surface adhesion prior to calcining and then drying the catalyst precursor whereby attrition is substantially reduced.
2. The process improvement of Claim 1 character-ized in that the aqueous liquid comprises water, an alco-hol or a ketone.
3, The process improvement of Claim 1 charac-terized in that the catalyst precursor is wetted after being formed into agglomerations.
4. The process improvement of Claim 1 charac-terized in that the catalyst precursor is wetted before the catalyst precursor is formed into agglomerations.
5. The process improvement of Claim 1 charac-terized in that the catalyst precursor is wetted before and after being formed into agglomerates.
6. The process improvement of Claim 1 charac-terized in that the agglomerates are granules, broken slugs, nodules, tablets, or pills.
7. The process improvement of Claim 1 charac-terized in that a surfactant is employed in the prepara-tion of the catalyst precursor.
8. The process improvement of Claim 1 charac-terized in that drying is accomplished at a temperature of 70°-250°C.
9. A phosphorus-vanadium-oxygen catalyst char-acterized by being prepared by the improved process of Claim 1 and having a % attrition less than 2%,
10. A method for the preparation of maleic an-hydride by oxidizing a reactant consisting essentially of a saturated aliphatic hydrocarbon having 4-10 carbon atoms in the presence of a phosphorus-vanadium -oxygen-contain-ing complex catalyst prepared by the process comprising:
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor ag-glomerations at a temperature between about 300°C, and 600°C.
characterized by employing, as the catalyst, the product of the improved process wherein the catalyst precursor is wetted with an aqueous liquid in an amount sufficient to enhance surface adhesion and then dried prior to calcining whereby attrition of the catalyst during the oxidizing of the reactant is substantially reduced.
(a) contacting vanadium and phosphorus compounds under conditions which will provide a catalyst precursor wherein greater than 50 atom % of the vanadium is in the tetravalent state;
(b) recovering the catalyst precursor;
(c) forming the catalyst precursor into agglomerates; and (d) calcining the catalyst precursor ag-glomerations at a temperature between about 300°C, and 600°C.
characterized by employing, as the catalyst, the product of the improved process wherein the catalyst precursor is wetted with an aqueous liquid in an amount sufficient to enhance surface adhesion and then dried prior to calcining whereby attrition of the catalyst during the oxidizing of the reactant is substantially reduced.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US06/088,711 US4253988A (en) | 1979-10-26 | 1979-10-26 | Conditioning phosphorus-vanadium-oxygen catalyst |
| US088,711 | 1979-10-26 | ||
| US06/106,567 US4276222A (en) | 1979-12-26 | 1979-12-26 | Method of producing maleic anhydride |
| US106,567 | 1979-12-26 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1135248A true CA1135248A (en) | 1982-11-09 |
Family
ID=26778977
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000363227A Expired CA1135248A (en) | 1979-10-26 | 1980-10-24 | Preparation and use of phosphorus-vanadium- oxygen catalysts in producing maleic anhydride |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1135248A (en) |
| DE (1) | DE3040194A1 (en) |
| FR (1) | FR2468407B1 (en) |
| GB (1) | GB2061753B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4510258A (en) * | 1983-08-17 | 1985-04-09 | The Lummus Company | Catalysts containing mixed oxides of vanadium and phosphorus |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3293268A (en) * | 1964-03-23 | 1966-12-20 | Princeton Chemical Res Inc | Production of maleic anhydride by oxidation of n-butane |
| USB330354I5 (en) * | 1973-02-07 | 1975-01-28 | ||
| US4111963A (en) * | 1973-02-07 | 1978-09-05 | Monsanto Company | Method for preparing maleic anhydride |
| CH598863A5 (en) * | 1975-01-10 | 1978-05-12 | Lonza Ag | |
| US4151116A (en) * | 1977-08-05 | 1979-04-24 | Halcon Research And Development Corporation | Preparation of maleic anhydride |
-
1980
- 1980-10-24 CA CA000363227A patent/CA1135248A/en not_active Expired
- 1980-10-24 FR FR8022801A patent/FR2468407B1/en not_active Expired
- 1980-10-24 GB GB8034400A patent/GB2061753B/en not_active Expired
- 1980-10-24 DE DE19803040194 patent/DE3040194A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2468407A1 (en) | 1981-05-08 |
| FR2468407B1 (en) | 1986-06-27 |
| DE3040194A1 (en) | 1981-05-07 |
| DE3040194C2 (en) | 1989-07-20 |
| GB2061753B (en) | 1983-07-20 |
| GB2061753A (en) | 1981-05-20 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 19991109 |