GB1566314A

GB1566314A - Catalyst with mo, v, nb and process for preparing unsaturated acids

Info

Publication number: GB1566314A
Application number: GB4188776A
Authority: GB
Original assignee: Union Carbide Corp
Current assignee: Union Carbide Corp
Priority date: 1975-10-09
Filing date: 1976-10-08
Publication date: 1980-04-30
Also published as: FR2327218B2; NL7514221A; DE2601699C3; IT1050757B; DE2601699B2; BE846952R; IT1050390B; FR2327218A2; NL7514709A; FR2327219B2; FR2327219A2; DE2601699A1; BE846951R

Description

(54) CATALYST WITH Mo, V, Nb AND PROCESS FOR PREPARING UNSATURATED ACIDS (71) We, UNION CARBIDE CORPORATION, a corporation organised and existing under the laws of the State of New York, United States of America, of 270 Park Avenue, New York, State of New York 10017, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to catalysts, their preparation and use in the vapor phase catalytic oxidation of a, ss unsaturated aliphatic aldehydes to the corresponding unsaturated aliphatic carboxylic acid.

The use of molybdenum and vanadium containing catalyst systems for the gas phase oxidation of alpha-beta unsaturated aliphatic aldehydes, such as acrolein, to the correspond ing alpha-beta-unsaturated carboxylic acids, such as acrylic acid, has been known.

In these reactions a gaseous reaction mixture which usually contains the aldehyde, molecu lar oxygen and water, as steam, is brought into contact with the catalyst, by continuously passing a stream of the reaction mixture through a bed of the catalyst. Such known catalyst systems would include those disclosed in the following United States patents: 3,087,964; 3,358,020; 3,408,392; 3,435,069; 3,439,028; 3,530,175; 3,567,722; 3,567,773; 3,574,729; 3,644,509; 3,655,749; 3,670,017 and 3,703,548 and in Belgian Patent 821,325. Not all of these catalyst systems, however, are currently useful for commercial purposes. Some of these catalyst systems, for example, do not provide the relatively high levels of % conversion, productivity and % selectivity, which are all required, presently, of a commercially useful catalyst system.

The terms % conversion, productivity, and % selectivity which are employed herein with respect to the present invention are defined as follows: I conversion = 100X A moles of aldehyde in the reaction mixture which is fed to the catalyst bed la wherein A = the molar aldehyde.equivalent sum (carbon basis) of all carbon containing products, excluding the aldehyde in the effluent II productivity = pounds of alpha-beta unsaturated aliphatic carboxylic acid product produced per cubic foot of catalyst (in the catalyst bed) per hour of reaction time moles of alpha-beta-unsaturated aliphatic carboxylic acid produced Ill % selectivity = l00 X A (or efficiency) wherein A is defined above in equation Ia.

According to the present invention alpha-beta-unsaturated aliphatic carboxylic acids are produced with a relatively high % conversion, productivity and % selectivity by oxidizing the corresponding alpha-beta-unsaturated aldehyde in the vapor phase by contacting the aldehyde, in the presence of molecular oxygen and steam, with certain catalyst compositions containing molybdenum, vanadium and niobium.

According to the present invention there is provided a catalyst comprising the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio MOa Vb Tc Xd wherein T is Nb or Nb plus Ti and /or Ta where less than 50% by weight of T is Ti and/or Ta wherein X is at least one of Co, Cr, Cu, In, Mn and Y, a is 12, b is 0.1 to 20, and preferably 1 to 14, and most preferably 2 to 8, c is 0.1 to 12, and preferably 0.5 to 2, and d is 0 to 3.0, and preferably 0.01 to 1.0 The numerical values of a, b, c and d represent the relative gram-atom ratios of the elements Mo, V, T, and X, respectively, which are present in the catalyst composition.

The elements Mo, V, T, and X are present in the catalyst composition with oxygen in the form, it is believed, of various metal oxides, as such, and possibly as chemical combinations of oxides such as spinels and perovskites.

The catalyst is preferably prepared from a solution of soluble salts and/or complexes and/or compounds of each of the metals Mo, V, T and X. The solution is preferably an aqueous system having a pH of 1-12, and preferably 5 + 3, at a temperature of about 20 to 100"C. The solution of the metal containing compounds is prepared by dissolving sufficient quantities of soluble compounds of each of the metals, so as to Provide the desired a:b:c:d atom-mole ratios of the elements Mo, V, T and X, respectively. The selected salts, complexes or compounds of the metals Mo, V, and T should be mutually soluble. If the selected salts, complexes or compounds of the metal X are not mutually soluble with the other metal compounds, they can be added last to the solution system. The catalyst composition is then prepared by removing the water or other solvent from the mixture of the metal compounds in the solution system. Any portion, and preferably i.e. about < 50 weight So, of the niobium may be replaced by titanium and/or tantalum in the catalyst composition.

The water or other solvent can be removed from the mixture of the dissolved metal compounds by evaporation.

Where the catalyst is to be used on a support, the metal compounds are deposited on a porous support usually having a surface area of about 0.01 to 500, and preferably 0.1 to 2, square meters per gram. The support has an apparent porosity of 30-60 %; at least 90isof the pores have a pore diameter in the range of 20-1500 microns. The support is usually used in the form of particles or pellets which are about 1/8 to 5/16 inch in diameter. The deposition is accomplished by immersing the support in the solution and then evaporating off the major portion of the solvent, and then drying the system at about 80 to 1400C. for 2 to 60 hours. The dried catalyst is then calcined by being heated at 200 to 550"C., and preferably 325-425"C., for 2 to 24 hours in air to produce the desired MOa Vb Tc Xd composition.

When used on the support, the supported oxides usually comprise about 10 to 50 weight % of the total catalyst composition, with the remainder being the support.

The molybdenum is preferably introduced into solution in the form of ammonium salts thereof such as ammonium paramolybdate, and organic acid salts of molybdenum such as acetates, oxalates, mandelates and glycolates. Other water soluble molybdenum compounds which may be used are partially water soluble molybdenum oxides, molybdic acid, and the nitrates and chlorides of molybdenum.

The vanadium is preferably introduced into solution in the form of ammonium salts thereof such as ammonium meta-vanadate and ammonium decavanadate, and organic acid salts of vanadium such as acetates, oxalates and tartrates. Other water soluble vanadium compounds which may be used are partially water soluble vanadium oxides, and the sulfates and nitrates of vanadium.

The niobium is preferably introduced into solution in the form of oxalates. Other sources of soluble niobium which may be used are niobium compounds in which the niobium is coordinated, bonded, or complexed to a beta-diketonate, a carboxylic acid, an amine, an alcohol or an alkanolamine.

Where titanium is used for a portion of the niobium, the titanium is preferably introduced into solution in the form of a water soluble chelate co-ordinated with ammonium lactate.

Other soluble titanium compounds which may be used are those in which titanium is coordinated, bonded, or complexed to a beta-diketonate, a carboxylic acid, an amine, an alcohol or an alkanolamine.

Where tantalum is used for a portion of the niobium, the tantalum is preferably introduced into solution in the form of oxalates. Other sources of soluble tantalum which may be used are tantalum compounds in which the tantalum is coordinated, bonded, or complexed to a beta-diketonate, a carboxylic acid, an amine, an alcohol or an alkanolamine.

The cobalt, chromium, copper, indium, manganese and yttrium are preferably introduced into solution in the form of nitrates. Other water soluble compounds of these elements which may be used are the water soluble chlorides and organic acid salts such as the acetates, oxalates, tartrates, lactates, salicylates, formates and carbonates of such metals.

It is believed that, for the catalysts to be most effective, the Mo, V, T, X metal components should be slightly reduced below their highest possible oxidation states. This may be accomplished during the thermal treatment of the catalyst in the presence of reducing agents such as NH3 or organic reducing agents, such as the organic complexing agents, which are introduced into the solution systems from which the catalysts are prepared. The catalyst may also be reduced in the reactors in which the oxidation reaction is to be conducted by the passage of hydrogen or hydrocarbon reducing agents such as ethane, ethylene or propylene through the catalyst bed.

The alpha-beta-unsaturated aldehydes which are oxidized in the process of the present invention have the structure

wherein R1 is H or a C1 - C6 alkyl radicals and R2 and R3 are the same or different and are H or CH3.

These aldehydes thus include acrolein and methacrolein. Where acrolein and/or methacrolein are oxidized, the corresponding alpha-beta-unsaturated carboxylic acid would be acrylic acid and/or methacrylic acid, respectively.

The aldehydes may be oxidized individually or in combinations thereof.

The components of the reaction mixtures which are employed in the process of the present invention, and the relatives ratios of the components in such mixtures, are the following 1 mole of aldehyde, 0.2 to 5 moles of molecular oxygen (as pure oxygen or in the form of air), 1 to 25 moles of water (in the form of steam), and optionally, 0.1 to 5 moles of alpha-beta-unsaturated olefin having the same number of carbon atoms as the aldehyde being oxidized. Propylene, for example, can be used in the reaction mixture when acrolein is being oxidized to acrylic acid.

The water, or steam, can be used as a reaction diluent and as a heat moderator for the reaction. Other diluents which may be used are inert gases such as nitrogen, CO2 and gaseous saturated hydrocarbons.

The olefin may be present due to the fact that the aldehyde feed may be emanating as the effluent from an olefinoaldehyde oxidation reaction process, and such effluent usually contains unreacted olefin.

The components of the reaction mixutre are uniformly admixed prior to being introduced into the reaction zone. The components are preheated, individually or after being admixed, prior to their being introduced into the reaction zone, to a temperature of about 200 to 300"C.

The preheated reaction mixture is brought into contact with the catalyst composition, in the reaction zone, under the following conditions: pressure of about 1 to 10, and preferably of about 1 to 3 atmospheres, temperature of about 200 to 400"C., and preferably of about 250 to 3500C., contact time (reaction mixture on catalyst) of about 0.1 to 10, and preferably of about 1 to 3, seconds, and a space velocity of about 1000 to 6000 h-1, preferably 4000 to 5000 h-'.

The contact time may also be defined as the ratio between the apparent volume of the catalyst bed and the volume of the gaseous reaction mixture fed to the catalyst bed under the given reaction conditions in a unit of time.

The reaction pressure is initially provided by the feed of gaseous reactants and diluents, and after the reaction is commenced, the pressure is maintained, preferably, by the use of suitable back-pressure controllers placed on the gaseous effluent side of the catalyst bed.

The reaction temperature is preferably provided by placing the catalyst bed within a tubular converter whose walls are immersed in a suitable heat transfer medium, such as tetralin, molten salt mixtures, or other suitable heat transfer agent, which is heated to the desired reaction temperature.

The following examples are merely illustrative of the present invention and are not intended as a limitation upon the scope thereof.

The examples provided below disclose the preparation of various catalyst compositions, and the use of such compositions in the oxidation of acrolein to acrylic acid.

The activity of each experimental catalyst was determined in a jacketed one-inch stainless steel reactor or converter tube 78 inches long. The jacket contained tetralin which served as a heat transfer medium.

The center portion (55 inches) of the reactor tube was charged with 800 ml of catalyst with a one-eighth inch movable thermocouple in the catalyst bed.

The catalysts were tested at 30 psig, with a space velocity of 4600 hr - or contact time of 1.2 seconds, and an inlet feed composed of 3 mole % acrolein, 6 mole % oxygen, 15 mole % steam, and 75 mole % nitrogen.

The activity of the catalysts was tested by adjusting the temperature of the reactor tube jacket to produce a maximum temperature (hot spot) of 304-306"C. in the catalyst bed, while the oxidation reaction was occurring.

Space velocity is calculated by determining the total reactor outlet gas equivalents (liters) of the total effluent evolved over a period of one hour. This room temperature volume is converted to the volume at 0 C at 760 mm Hg.

IV Space Velocity = liters of outlet gas equivalents/hour liters of catalyst in reactor = 1 =h-1 hours at OOC. and atmospheric pressure Examples 1 to 19 and 23 are comparative examples and Examples 20 to 22, 24 and 25 are examples in accordance with the present invention.

Example I Mo2.4V0 6NbO 3Cu0 ls or Mol2V3Nbl 5Cu0 7^ Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80"C. in a stainless steel beaker.

To the resulting solution were added 475 grams of niobium oxalate solution (containing 0.3 gram atoms Nb) and 36 grams of copper nitrate [Cu(NO3)2.3H2O] (0.15 gram atoms Cu) dissolved in 100-ml water.

The resulting mixture was heated while stirring and approximately 60 per cent of the water was evaporated off.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. SA-5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200C. for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400"C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.5 weight per cent. Catalytic test results for this material are given in Table I.

Example 2 Mo2 4V0 6Nb0 3Fe0 l5 or Mo,2V3Nbl 5Fe0 ,5 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of amonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80"C. in a stainless steel beaker.

To the resulting solution were added 474 grams of niobium oxalate solution (95.3 gms Nb2Os/1) (0.3 gram atoms Nb) and 60 grams of ferric nitrate [Fe(NO3)3.9H2O] (0.15 gram atoms Fe) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (SA-5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200C. for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 24.4 weight per cent. Catalytic test results for this material are given in Table I.

Example 3 Mo2.4 V0.6Nb#.3Mn0.15 or Mo12V3Nb1.5Mn0.75 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80"C. in a stainless steel beaker.

To the resulting solution were added 475 grams of niobium oxalate solution (95.3 gms.

Nb2O5/1)(0.3 gram atoms Nb) and 54 grams of 50.3% manganous nitrate aqueous solution (0.15 gram atoms Mn).

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.6 weight %. Catalytic test results of this material are given in Table I.

Example 4 Mo2.4 V0.6Fe0.15 or Mo12V3Fe0.75 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800C. in a stainless steel beaker.

To the resulting solution were added 60 grams ferric nitrate [Fe(NO3)3.9H2O] (0.15 gram atoms Fe) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. SA-5218) 1/4" spheres were ended. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200C. for a period of 16 hours.

Example 5 Mo2 4V0 6Fe0 l5 (made with 0.75 (mole) parts (NH4)2 oxalate) or Mol2V3FeO-75 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80"C. in a stainless steel beaker.

To the resulting solution were added 107 grams of ammonium oxalate [(NH4)2C204.H2O] (0.75 gram moles (NH4)2C204) and 60 grams of ferric nitrate [Fe(NO3)3.9H2O] (0.15 gram atoms Fe) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (&num;SA-5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200C. for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400"C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 26.3 weight per cent. Catalytic test results for this material are given in Table I.

Example 6 Mo2 8V0, or Mo12V3 Eighty-two grams of ammonium meta-vanadate (0.7 gram atoms of V and 256 grams of oxalic acid (2.1 moles) were dissolved in two liters of water while stirring at 60-80"C. in a stainless steel beaker.

To the resulting solution were added 495 grams of ammonium paramolybdate (2.8 gram atoms Mo) dissolved in 1 1. water.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 26.5 weight %. Catalytic test results for this material are given in Table I.

Example 7 M02.4V0.6CU0.15 or Mo12V3Cu075 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 C. in a stainless steel beaker.

To the resulting solution were added 90 grams of ammonium lactate solution (containing 0.6 gram mole NH4 lactate) and 36 grams of copper nitrate [Cu(NO3)2.3H20] (0.15 gram atoms Cu) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. SA-5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200. for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined with a muffle furnace for 5 hours at 400"C. in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 26.0 weight %. Catalytic test results for this material are given in Table I below.

Example 8 Mo2 8V0 ,NbO 35 or Mol2V3Nbl 5 Eighty-two grams of ammonium meta-vanadate (0.7) gram atoms of V) and 494 grams of ammonium paramolybdate (2.8 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 550 grams of niobium oxalate solution (containing 0.35 gram atoms Nb) and 28 grams of ammonium nitrate (0.35 gram moles NH4NO3) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. 5218)1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.7spa Catalytic test results for this material are given in Table II below.

Example 9 Mo2 4VO 6NbO 3 or Mol2V3Nbl 5 Seventy grams of a mmonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution there was added a slurry of 40 grams of niobium pentoxide (containing 0.3 gram atoms of Nb) in 300 ml of a solution containing 0.6 moles of ammonium lactate and 0.3 moles of ammonium nitrate. The ammonium lactate was formed from 55 grams of lactic acid (in 100 ml of H2O) and 37 grams of NH40H (29 weight %NH4OH in 100 ml H2O). The ammonium nitrate (29 grams in 100 ml of H2O) was added to equalize the nitrate content of this system, prior to drying, with the nitrate content of catalyst systems containing the X element(s). The Nb2O5 did not dissolve.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.6%. Catalytic test results for this material are given in Table II below.

Example 10 Mo2 4V0 6Nb0 3Cr0 ls or Mol2V3Nbl 5Cr0 ,5 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 280 grams of niobium oxalate solution (containing 0.3 gram atoms Nb) and 60 grams of chromium nitrate enneahydrate (0.15 gram atoms Cr) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. 5218)1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 23.1 %. Catalytic test results for this material are given in Table II below.

Example 11 Mo2 4V0 6Nb0 3CoO l5 or M012V3Nb1.5C00.75 Seventy grams of ammonium meta-vanadate (0.6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 475 grams of niobium oxalate solution (containing 0.3 gram atoms Nb) and 44 grams of cobalt nitrate hexahydrate (0.15 gram atoms Co dissolved in 100-ml w

Mo2,4P0 6Nb0 3CuO l5 or Moi2P3Nb1 '5Cu075 Sixty eight grams of 86.1 % phosphoric acid in 200 ml H2O (0.6 gram atoms of P) and 35.2 grams of ammonium hydroxide in 100 ml H2O (0.6 gram atoms of N) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 273 grams of niobium oxalate solution (containing 0.3 gram atoms Nb) dissolved in 300 ml of H20 and 36 grams of cupric nitrate (0.15 gram atoms Cu) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. 5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400" in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 20.9%. The catalytic results for this material are given in Table III below.

The support used in Examples 1-13 was essentially an (N86/ 14) Al203/SiO2 material having an apparent porosity of 36-42% and a surface area of < 1 m2/gram. About 100% of the pores in the support had a pore diameter of about 20-180 microns.

The pH of the solutions used in each of Examples 1-13 for the preparation of the catalysts was in the range of 5 + 3.

The results of Examples 4 to 7 reported below in Tables I and II demonstrate that not all compositions containing the elements Mo, V and X, as defined above, provide catalysts which can be used in the oxidation of alpha-beta unsaturated aldehydes such as acrolein to produce the corresponding alpha-beta unsaturated acid at relatively high levels of % conversion, productivity and % selectivity.

The results of Example 9 demonstrates the desirability of providing the elements in the form of soluble compounds and complexes. The niobium was used in the form of waterinsoluble Nb2O5 and the resulting catalyst provided poor results.

The results of Examples 12 and 13, as reported in Table III below, in comparison to the results of Examples 8 and 1, respectively, demonstrate that the use of phosphorous, in lieu of vanadium in the catalysts, does not produce acceptable results.

TABLE I Example Catalyst Description Metal* Hot Spot Conversion AA/Ft Cat. Efficiency Atomic Ratios Oxides in C % /hr.Lbs. % Catalyst % 1 Mo2.4V0.6Nb0.3Cu0.15 27.5 301 91.8 24.40 92.9 2 Mo2.4V0.6Nb0.3Fe0.15 24.4 306 87.3 22.50 93.6 3 Mo2.4V0.6Nb0.3Mn0.15 27.5 295 94.5 23.80 92.4 4 Mo2.4V0.6Fe0.15 27.5 305 13.4 2.20 58.0 5 Mo2.4V0.6Fe0.15 (a) 26.3 318 20.3 3.10 50.9 6 Mo2.8V0.7 (b) 26.5 305 7.7 1.40 62.9 7 Mo2.4V0.6Cu0.15 (c) 26.0 305 30.4 7.40 83.9 AA = acrylic acid (a) Used 0.75 (mole) parts ammonium oxalate.

(b) Used 2.1 (mole) parts oxalic acid.

(c) Used 0.60 (mole) parts ammonium lactate.

* oxides of the metals Mo, V, Nb, and/or X.

TABLE II Example Catalyst Description Metal* Hot Spot Conversion AA/Ft Cat. Efficiency Atomic Ratios Oxides in C % /hr. Lbs. % 4 Mo2.4V0.6Fe0.15 27.5 305 13.4 2.20 58.0 5 Mo2.4V0.6Fe0.15 (a) 26.3 318 20.3 3.10 50.9 6 Mo2.8V0.7 (b) 26.5 305 7.7 1.40 62.9 7 Mo2.4V0.6Cu0.15 (c) 26.0 305 30.4 7.40 83.9 8 Mo2.8V0.7Nb0.35 (d) 27.7 295 96.0 24.5 91.5 9 Mo2.4V0.6Nb0.3 (e) 27.6 305 29.4 6.3 78.0 10 Mo2.4V0.6Nb0.3Cr0.15 23.1 304 86.2 21.6 93.0 11 Mo2.4V0.6Nb0.3Co0.15 27.5 305 96.9 23.9 90.0 AA = acrylic acid (a) Used 0.75 (mole) parts ammonium oxalate. (d) Used 0.35 (mole) parts ammonium nitrate.

(b) Used 2.1 (mole) parts oxalic acid. (e) Used 0.3 gram atoms Nb2O5 and 0.6 moles ammonium lactate.

(c) Used 0.60 (mole) parts ammonium lactate.

* oxides of the metals Mo, V, Nb, and or X.

TABLE III Example Catalyst Description Metal** Hot Spot Conversion AA/Ft Cat Efficiency Atomic Ratios Oxides in C % /hr., lbs. % Catalyst, % 8 Mo2.8V0.7Nb0.35 (d) 27.5 295 96.0 24.5 91.5 1 Mo2.4V0.6Nb0.3Cu0.15 27.5 301 91.8 24.40 92.9 12 Mo2.4P0.6Nb0.3 17.5 305 28.65 5.6 72.50 13 Mo2.4P0.6Nb0.3Cu0.15 20.9 304 5.85 1.1 67.23 AA = acrylic acid ** Oxides of the metals Mo, B, Nb, P and/or X.

(d) Used 0.35 (mole) parts ammonium nitrate.

Examples 14-25 Catalysts 14-25 were prepared as disclosed below, and evaluated in the experimental catalyst test procedure described above. Each of the catalysts of Examples 14-25 contain the elements Mo, V and Nb in various ratios, and, in addition, the catalysts of Examples 14, 16, 23, 24 and 25 also contain at least one of the X elements. The composition of each of these catalysts is given at the heading of the respective examples, and the test results are reported in Table IV below.

The supports used in Examples 24-25 was the same as that used in Examples 1-13. The support used in Examples 14, 15, and 17-23 was an (~86/14) Al203/SiO2 material having an apparent porosity of ~52%and a surface area of < 1m2/gram. About 90% of the pores in this support had a pore diameter of about 50-400 microns.

The support used in Example 16 was predominantly alumina. It contained only 0.35% Si.

This support had an apparent porosity of about 62% and a surface area of < 1 m2/gram.

About 90% of the pores in this support had a pore diameter of about 2-100 microns.

The pH of the solutions used in each of Examples 14-25 for the preparation of the catalysts was in the range of 5 + 3.

The results of Examples 14-25 demonstrate the relatively high levels of % conversion, % efficiency and productivity that can be obtained with the catalysts of the present invention for the oxidation of alpha-beta unsaturated aliphatic aldehydes such as acrolein to the corresponding alpha-beta unsaturated carboxylic acid.

Example 14 Mo12V3Nb15Cu075 or M01.08V0'27Nb0 135CU0.0675 32 Grams of ammonium meta-vanadate (0.27 gram atoms of V) and 191 grams of ammonium paramolybdate (1.08 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 124 grams of niobium oxalate solution containing 0.135 gram atoms Nb plus 17 grams of copper nitrate [Cu(NO3.3H2O] (0.0675 gram atoms Cu) dissolved in 100-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 770 grams (1000 ml) Norton silica-alumina (No. SA-5205) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 20.3%.

Example 15 Mo12V1.5Nb0.75 or Mo2.64V0.33Nb0.165 38.6 Grams of ammonium meta-vanadate (0.33 gram atoms of V) and 466 grams of ammonium paramolybdate (2.64 gram atoms of MO) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 260 grams of niobium oxalate solution containing 0.165 gram atoms Nb.

The resulting mixture was heated while stirring and approximately 60 percent of the water was evaporated off.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.8%.

Example 16 Mol2V3Nbl 5CuO ,s or Mol 32VO 33NbO l66CuO og2s 39.0 Grams of ammonium meta-vanadate (0.33 gram atoms of V) and 233 grams of ammonium paramolybdate (1.32 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 260 grams of niobium oxalate solution containing 0.166 gram atoms Nb plus 20 grams of copper nitrate [Cu(NO3)2.3H2O] containing 0.75 gram atoms Cu dissolved in 100 ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 687 grams (10 ml) Norton alumina (No.5513)5/16" rings were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 17.4%.

Example 17 Mo12V6Nb3 or Mo1.32V0.66Nb0.33 77 Grams of ammonium meta-vanadate (0.66 grams atoms of V) and 233 grams of ammonium paramolybdate (1.32 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 519 grams of niobium oxalate solution containing 0.33 gram atoms Nb.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 770 grams (1000 ml) Norton silica-alumina (No. 5205) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 4.4%.

Example 18 Mo12V6Nb1.5 or Mo1.2V0.6Nb0.15 70 Grams of ammonium meta-vanadate (0.6 gram atoms of V) and 212 grams of ammonium paramolybdate (1.2 gram atoms of Mo were dissolved in two liters of water while stirring at 60-800, in a stainless steel beaker.

To the resulting solution were added 236 grams of niobium oxalate solution containing 0.15 gram atoms Nb.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 770 grams(100 ml) Norton silica-alumina (No. SA-5205) 1/4" spheres were a ded. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air.

The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 20.5%.

Example 19 Mo12V12Nb1.5 or Mo1.1V1.1Nb0.138 129 Grams of ammonium meta-vanadate (1.1 gram atoms of V) and 194 grams of ammonium paramolybdate (1.1 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 216 grams of niobium oxalate solution containing 0.138 gram atoms Nb.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 770 grams (1000 ml) Norton silica-alumina (No. SA-5205) 1/4" spheres were a ded. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 20.4%.

Example 20 Mol2V0 75Nbl 5 or Mol 6V0 lNb0 2 Twelve grams of ammonium meta-vanadate (0.1 gram atoms of V) and 283 grams of ammonium paramolybdate (1.6 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 315 grams of niobium oxalate solution containing 0.2 gram atoms Nb.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 41)09 in an ambient atmosphere of air.

The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 17.3%.

Example 21 Mo12V0.375Nb1.5 or Mo 1.7V0.053Nb0.213 6.23 Grams of ammonium meta-vanadate (0.053 gram atoms of V) and 300 grams of ammonium paramolybdate (1.7 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 335 grams of niobium oxalate solution containing 0.213 gram atoms Nb.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400" in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 15.2%.

Example 22 Mo12V18NB1.5 or Mo0.9V1.35Nb0.113 158 Grams of ammonium meta-vanadate (1.35 gram atoms of V) and 159 grams of ammonium paramolybdate (0.9 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 177 grams of niobium oxalate solution containing 0.113 gram atoms Nb.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400" in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 22.1%.

Example 23 M o 2 . 4 V 0 . 6 N b 0 . 3 F e 0 . 0 3 C u 0 . 0 3 C o 0 . 0 3 C r 0 . 0 3 M n 0 . 0 3 or Mo12V3Nb1.5Fe0.15Cu0.15Co0.15Cr0.15Mn0.15 70 Grams of ammonium meta-vanadate (0,6 gram atoms of V) and 424 grams of ammonium paramolybdate (2.4 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution was added 472 grams of niobium oxalate solution containing 0.3 gram atoms Nb plus 12.12 grams of Fe(NO3)3.9H2O (0.03 gram - atoms Fe plus 7.25 grams Cu(NO3)2.3H2O (0.03 gram-atoms Cu) plus 8.73 grams Co(NO3)2,6H20 0.03 gram atoms Co) plus 12.0 grams Cr(NO3)3.9H2O (0.03 gram atoms Cr) plus 10.67 grams of 50.3% Mn(NO3)2 solution (0.03 gram atoms Mn) dissolved in 129 ml water.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400" in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 27.2%.

Example 24 Mo12V3Nb1 5Y075 or Mol 92VO 48Nb0 24Yo l2 56 Grams of ammonium meta-vanadate (0.48 gram atoms of V) and 339 grams of ammonium paramolybdate (1.92 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 218 grains of niobium oxalate solution containing (0.24 gram atoms Nb) plus 44 grams of yttrium nitrate [Y(NO3)3.5H2O] (0.12 gram atoms Y) dissolved in 80-ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. SA-5219) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 400" in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained in 13.0%.

Example 25 Mo12V3Nb1.5In0.75 or Mo1.92V0.48Nb0.24In0.12 56 Grams of ammonium meta-vanadate (0.48 gram atoms of V) and 339 grams of ammonium paramolybdate (1.92 gram atoms of Mo) were dissolved in two liters of water while stirring at 60-80 , in a stainless steel beaker.

To the resulting solution were added 218 grams of niobium oxalate solution containing (0.24 gram atoms Nb) plus 47 grams of indium nitrate [In(NO3)3.5H20] (0.12 gram atoms In) dissolved in 80 ml water.

The resulting concentrated slurry was transferred to a stainless steel evaporating dish and 1040 grams (1000 ml) Norton silica-alumina (No. SA-5218) 1/4" spheres were added. This was followed by drying by evaporation with stirring on a steam bath. Further drying was carried out at a temperature of 1200 for a period of 16 hours.

The dried material was then transferred to a tray fabricated from 10-mesh stainless steel wire screen and calcined in a muffle furnace for 5 hours at 4000 in an ambient atmosphere of air. The amount of catalyst deposited on the support calculated from the weight increase of the catalyst obtained is 12.2%.

TABLE IV Example Catalyst Description Metal* Hot Spot Conversion AA/Cu.Ft. of Efficiency No. Atomic Ratios Oxides in % % Catalyst % Catalyst % /hr., lbs.

14 Mo1.08V0.27Nb0.135Cu0.0675 20.3 304 98.3 25.0 94.5 15 Mo2.64V0.33Nb0.165 27.8 305 96.8 24.3 90.9 16 Mo1.32V0.33Nb0.166Cu0.083 17.4 305 75.4 20.8 94.6 17 Mo1.32V0.66Nb0.33 4.4 305 57.7 15.0 92.3 18 Mo1.2V0.6Nb0.15 20.5 303 91.6 24.8 91.0 19 Mo1.1V1.1Nb0.138 20.4 304 96.2 21.9 88.4 20 Mo1.6V0.1Nb0.2 17.3 304 95.0 24.8 92.7 21 Mo1.7V0.053Nb0.213 15.2 305 86.6 21.7 90.9 22 Mo0.9V1.35Nb0.113 22.1 304 87.2 18.0 76.8 23 Mo2.4V0.6Nb0.3Fe0.03Cu0.03 27.2 30.5 97.6 24.8 92.6 Co0.03Cr0.03Mn0.03 24 Mo1.92V0.48Nb0.24Y0.12 13.0 305 78.3 19.0 93.9 25 Mo1.92V0.48Nb0.24In0.12 12.2 305 78.4 19.9 94.6 * Oxides of the metals Mo, V, Nb and X We are aware of British Patent Specification No. 1,488,044 which claims: 1. A calcined oxidation catalyst containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio MOaVbTcXd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50%by weight of T is Ti and/or Ta, wherein X is selected from the group consisting of Cu, Co, Cr and/or Mn a is 12, b is 1 to 14, c is 0.1 to 12, and d is O to 3.0 2. A process for preparing a calcined catalyst composition containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio MOa Vb Tc Xd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50% by weight of T is Ti and/or Ta, Wherein X is selected from the group consisting of Cu, Cr, Co and Mn and a is 12, b is 1 to 14, c is 0.1 to 12 and d is 0 to 3.0 which comprises dissolving soluble compounds of each of the elements Mo, V, T and, if required X, in a solvent to form a solution thereof having a pH of 1 to 12, said compounds bemg used in such quantities as to provide the desired a:b: c:d ratios, removing the solvent from said solution, and calcining by heat the resulting mixture of said compounds in air for 2 to 24 hours at 2500 to 450"C.

Claims

3. A process for the production of an a , B-unsaturated aliphatic carboxylic acid by vapor phase catalytic oxidation of the corresponding unsaturated aliphatic aldehyde with molecular oxygen in the presence of steam which comprises contacting the reaction mixture with a calcined oxidation catalyst containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio MOa Vb Tc Xd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50% of T is Ti and/or Ta, wherein X is selected from the group consisting of Cu, Co, Cr and/or Mn. a is 12, b is 1 to 14, c is 0.1 to 12, and d is 0 to 3.0 However, we make no claim herein to the catalyst, process for preparing the catalyst, or process for the production of unsaturated aliphatic carboxylic acid as claimed in our British Patent Specification No. 1,488,044. No claim is herein made to a calcined oxidation catalyst containing iron or to the preparation or use of such a catalyst. Further, no claim is herein made to a calcined oxidation catalyst containing catalytically active forms of silicon or to the production or use of such a catalyst. The term "catalytically active forms of silicon" is not intended to include inert support materials containing silicon. Subject to the forgoing disclaimers WHAT WE CLAIM IS:

1. A calcined oxidation catalyst containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio MOa Vb Tc Xd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50% by weight of is Ti and/or Ta, Wherein X is at least one of Co, Cr, Cu, In, Mn and Y, a is 12, b is 0.1 to 20, c is 0.1 to 12, and d is 0 to 3.0.

2. A catalyst as claimed in claim 1 in which b is 1 to 14.

3. A catalyst as claimed in claim 2 in which b is 2 to 8.

4. A catalyst as claimed in any one of claims 1 to 3 in which c is 0.5 to 2.

5. A catalyst as claimed in any one of claims 1 to 4 in which d is 0.01 to 1.0.

6. A catalyst as claimed in any one of claims 1 to 5 in which X comprises Co.

7. A catalyst as claimed in any one of claims 1 to 5 in which X comprises Cr.

8. A catalyst as claimed in any one of claims 1 to 5 in which X comprises Cu.

9. A catalyst as claimed in any one of claims 1 to 5 in which X comprises In.

10. A catalyst as claimed in any one of claims 1 to 5 in which X comprises Mn.

11. A catalyst as claimed in any one of claims 1 to 5 in which X comprises Y.

12. A catalyst as claimed in any one of claims 1 to 11 which is supported on an inert support.

13. A catalyst as claimed in claim 12 in which said support is silica, alumina, or silicaalumina.

14. A catalyst as claimed in claim 12 or claim 13 which comprises 10 to 50%by weight catalyst and 50 to 90% by weight support.

15. A catalyst as claimed in any one of claims 1 to 14 in which T is Nb.

16. A catalyst as claimed in claim 1 substantially as hereinbefore described with reference to any one of Examples 20 to 22, 24 or 25.

17. A process for preparing a catalyst composition containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio Moa Vb Tc Xd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50% by weight of T is Ti and/or Ta, Wherein X is at least one of Co, Cr, Cu, In, Mn and Y, a is 12 b is 0.1 to 20, c is 0.1 to 12, and d is O to 3.0 which comprises dissolving soluble compounds of each of the elements Mo, V, T and, if required X, in a solvent to form a solution thereof having a pH of 1 to 12, said compounds being used in such quantities as to provide the desired a:b:cd ratios, removing the solvent from said solution, and heating the resulting mixture of said compounds in air for 2 to 24 hours at 200 to 5000C.

18. A process as claimed in claim 17 in which the temperature of said heating is 325 to 425"C.

19. A process as claimed in claim 17 or claim 18 in which said pH is 5 + 3.

20. A process as claimed in any one of claims 17 to 19 in which the soluble compound of Mo is an ammonium salt of Mo.

21. A process as claimed in any one of claims 17 to 20 in which the soluble compound of Nb is on oxalate.

22. A process as claimed in any one of claims 17 to 21 in which the soluble compound of V is an ammonium salt of V.

23. A process as claimed in any one of claims 17 to 22 in which when Ta and/or Ti are present the soluble compound of Ta is an oxalate and the soluble compound of Ti is a water soluble Ti chelate coordinated with ammonium lactate.

24. A process as claimed in any one of claims 17 to 23 in which the soluble compound of X is a nitrate.

25. A process as claimed in any one of claims 17 to 24 in which b is 1 to 14.

26. A process as claimed in claim 25 in which b is 2 to 8.

27. A process as claimed in any one of claims 17 to 26 in which c is 0.5 to 2.

28. A process as claimed in any one of claims 17 to 27 in which d is 0.01 to 1.0.

29. A process as claimed in any one of claims 17 to 28 in which X comprises Co.

30. A process as claimed in any one of claims 17 to 28 in which X comprises Cr.

31. A process as claimed in any one of claims 17 to 28 in which X comprises Cu.

32. A process as claimed in any one of claims 17 to 28 in which X comprises In.

33. A process as claimed in any one of claims 17 to 28 in which X comprises Mn.

34. A process as claimed in any one of claims 17 to 28 in which X comprises Y.

35. A process as claimed in any one of claims 17 to 34 in which said catalyst is supported on an inert support.

36. A process as claimed in claim 35 wherein said support is silica, alumina or silicaalumina.

37. A process as claimed in claim 35 or claime 36 in which said catalyst comprises 10 to 50% by weight catalyst and 50 to 90% by weight support.

38. A process as claimed in any one of claims 17 to 37 in which T is Nb.

39. A process as claimed in claim 17 substantially as hereinbefore described with reference to any one of Examples 20 to 22, 24 or 25.

40. A catalyst whenever produced by a process as claimed in any one of claims 17 to 39.

41. A process for the production of an a, p-unsaturated aliphatic carboxylic acid by vapor phase catalytic oxidation of the corresponding unsaturated aliphatic aldehyde with molecular oxygen in the presence of steam which comprises contacting the reaction mixture with a calcined oxidation catalyst containing the elements Mo, V, T and, optionally X, in combination with oxygen in the atomic ratio.

MOa Vb Tc Xd wherein T is Nb or Nb plus Ti and/or Ta wherein less than 50% of T is Ti and/or Ta, wherein X is at least one of Co, Cr, Cu, In, Mn and Y, a is 12, b is 0.1 to 20, c is 0.1 to 12, and d is O to 3.0.

42. A process as claimed in claim 41 in which b is 1 to 14.

43. A process as claimed in claim 42 in which b is 2 to 8.

44. A process as claimed in any one of claims 41 to 43 in which c is 0.5 to 2.

45. A process as claimed in any one of claims 41 to 44 in which d is 0.01 to 1.0.

46. A process as claimed in any one of claims 41 to 45 in which X comprises Co.

47 A process as claimed in any one of claims 41 to 45 in which X comprises Cr.

48. A process as claimed in any one of claims 41 to 45 in which X comprises Cu.

49. A process as claimed in any one of claims 41 to 45 in which X comprises In.

50. A process as claimed in any one of claims 41 to 45 in which X comprises Mn.

51. A process as claimed in any one of claims 41 to 45 in which X comprises Y.

52. A process as claimed in any one of claims 41 to 51 in which said oxidation catalyst is supported on an inert support.

53. A process as claimed 52 in which said support is silica, alumina or silica-alumina.

54. A process as claimed in claim 52 or 53 in which said catalyst comprises 10 to 50% by weight catalyst and 50 to 90% by weight support.

55. A process as claimed in any one of claims 41 to 54 in which said alpha-beta unsaturated aliphatic aldehyde has tfie structure

wherein R1 is H or a C1 to C6 alkyl radical and R2 and R3 is independantly selected from H and -CH3.

56. A process as claimed in claim 55 in which said unsaturated aliphatic carboxylic acid is acrylic acid and said unsaturated aliphatic aldehyde is acrolein.

57. A process as claimed in any one of claims 41 to 56 in which said reaction mixture comprises, per mole of aldehyde, 0.2 to 5 moles of molecular oxygen and 1 to 25 moles of steam.

58. A process as claimed in any one of claims 41 to 57 in which said reaction mixture includes, per mole of aldehyde, 0.1 to 5 moles of alpha-beta-unsaturated olefin having the same number of carbon atoms as said aldehyde.

59. A process as claimed in any one of claims 41 to 58 in which said contacting is conducted at a pressure of 1 to 10 atmospheres.

60. A process as claimed in claim 59 in which said contacting is conducted at a pressure 1 to 3 atmospheres.

61. A process as claimed in any one of claims 41 to 60 in which said contacting is conducted at a temperature of 200 to 400"C.

62. A process as claimed in claim 61 in which said contacting is conducted at a temperature of 250 to 350"C.

63. A process as claimed in any one of claims 41 to 62 in which the contact time of said contacting is 0.1 to 10 seconds at a space velocity of 1000 to 6000 h-'.

64. A process as claimed in claim 63 in which the contact time of said contacting is 1 to 3 seconds.

65. A process as claimed in claim 63 or claim 64 in which the space velocity is 4000 to 5000 h-l.

66. A process as claimed in any one of claims 41 to 65 wherein T is Nb.

67. A process as claimed in claim 41 substantially as hereinbefore described with reference to any one of Examples 20 to 22, 24 or 25.

68. Unsaturated aliphatic carboxylic acid whenever produced by a process as claimed in any one of claims 41 to 67.