Two stage process for the production of unsaturated carboxylic acids by oxidation of lower unsaturated hydrocarbons

Abstract

A process for the production of alpha-beta unsaturated carboxylic acid with high yield at low temperature and atmospheric pressure, includes two stages for catalytic vapor-phase oxidation of olefins with molecular oxygen. In a first stage, olefins are oxidized using catalyst A having a composition according to the formula Mo a Pd b Bi c Fe d X 1 e X 2 f X 3 g O z , wherein X 1 =one or more of Co, Ni, V, Pt, Rh; X 2 =one or more of Al, Ga, Ge, Mn, Nb, Zn, Ag, P, Si, W; X 3 =at least one or more of K, Mg, Rb, Ca, Sr, Ba, Na; and O=oxygen; to produce a first stage product containing alpha-beta unsaturated aldehydes In a second stage, alpha-beta unsaturated aldehydes in the first stage product are oxidized using catalyst B having a composition according to the formula Mo a V b Al c X d Y e O z wherein X=W or Mn or both; Y=at least one or more of Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, K; and O is oxygen which satisfies the valences of the other elements; to produce mainly alpha-beta unsaturated carboxylic acid. A portion of the oxygen is introduced into the reaction stream between the first and second stages or in multistages. More particularly, the invention relates to a two stage process for catalytic oxidation of propylene or iso-butylene to yield acrylic acid or methacrylic acid.

What is claimed is:  
     
         1 . A process for production of carboxylic acid using a two-stage catalytic vapor-phase oxidation of olefins comprises 
 introducing into a first stage reactor, a feedstream comprising olefins, oxygen, steam and inert gas;    contacting the feedstream in the first stage reactor with a catalyst composition comprising a catalyst having the formula   Mo a Pd b Bi c Fe d X 1   e X 2   f X 3   g O z      wherein 
 X 1 =at least one or more of Co, Ni, V, Pt, Rh  
 X 2 =at least one or more of Al, Ga, Ge, Mn, Nb, Zn, Ag, P, Si, W  
 X 3 =at least one or more of K, Mg, Rb, Ca, Sr, Ba, Na  
 O=oxygen  
 a is 1,  
 b is 0< to 0.3,  
 c is 0< to 0.9,  
 d is 0< to 0.9,  
 e is 0< to 0.9,  
 f is 0< to 0.9,  
 g is 0< to 0.3,  
 z is a number which satisfies the valences of the other elements in the formula,  
    said contacting in the first stage reactor under reaction conditions sufficient to produce a first stage product comprising aldehyde;    introducing the first stage product into a second stage reactor;    contacting the first stage product in the second stage reactor with a catalyst composition comprising a catalyst having the formula   Mo a V b Al c X d Y e O z      wherein 
 X=W or Mn or both  
 Y=at least one or more of Pd, Sb, Ca, P, Ga, Ge, Si, Mg, Nb, K  
 O is the valence oxygen, and  
 a is 1,  
 b is 0.01 to 0.9,  
 c is 0< to 0.2,  
 d is 0< to 0.5,  
 e is 0< to 0.5,  
 z is a number which satisfies the valences of the other elements in the formula;  
    said contacting in the second stage reactor under conditions sufficient to produce a second stage product comprising carboxylic acid.    
     
     
         2 . The process of  claim 1  further comprising introducing oxygen into the product stream intermediate between the first and second stages or at multistages.  
     
     
         3 . The process according to  claim 1 , wherein the olefins are propylene or isobutylene and carboxylic acids are acrylic acid or methacrylic acid.  
     
     
         4 . The process according to  claim 1 , wherein the feedstream comprises olefins in an amount of about 2% to about 50% by volume, oxygen in an amount of about 3% to about 40% by volume, steam in an amount of about 3% to about 50% by volume, and inert gas in an amount of about 3% to about 80% by volume.  
     
     
         5 . The process according to  claim 4  wherein the feedstream comprises olefins in an amount of about 5% to about 30% by volume, oxygen in an amount of about 5% to about 30% by volume, steam in an amount of about 5% to about 40% by volume, and inert gas in an amount of about 5% to about 75% by volume.  
     
     
         6 . The process according to  claim 4  wherein the inert gas comprises nitrogen, propane, argon, carbon dioxide or mixtures thereof.  
     
     
         7 . The process according to  claim 1 , wherein the conditions in the first stage comprise a temperature in the range of about 250° C. to about 450° C. and a pressure of 1 atm to 30 atm, and the conditions in the second stage comprise a temperature in the range of about 180° C. to about 350° C. and a pressure of 1 atm to 30 atm.  
     
     
         8 . The process according to  claim 1 , wherein the oxygen is in the form of molecular oxygen, air or mixture thereof.  
     
     
         9 . The process according to  claim 1 , wherein part of the amount of oxygen is introduced between the first and second stages or at multistages.  
     
     
         10 . The process according to  claim 9  wherein the part of the amount of oxygen is about 2% to 15% by volume.  
     
     
         11 . The process according to  claim 1 , wherein conversion of olefins in the first-stage reaction is at least 90% and conversion of aldehydes in second-stage reaction is at least 95%.  
     
     
         12 . The process according to  claim 1 , wherein the olefin comprises propylene, the carboxylic acid product comprises acrylic acid, and conversion of propylene in a once through process produces at least 88% acrylic acid product yield.  
     
     
         13 . The process according to  claim 1 , wherein oxygen is supplied as a molecular oxygen-containing gas having purity of at least 90% by volume.  
     
     
         14 . The process according to  claim 1 , wherein the olefins comprise ethylene, propylene, iso-butylene, or n-butylene; the aldehydes comprise acetaldehyde, acrolein or methacrolein; and carboxylic acids corresponding to the aldehydes are produced in the process.  
     
     
         15 . The process according to  claim 1 , wherein the second stage product further comprises off-gas, and the process further comprises separating the off-gas from the carboxylic acid product of the second stage, and recycling the off-gas to the first-stage.  
     
     
         16 . The process according to  claim 15 , wherein the separated off-gas contains steam which is recycled to the first stage.  
     
     
         17 . A catalyst for oxidation of unsaturated hydrocarbons, said catalyst having the formula 
       Mo a Pd b Bi c Fe d X 1   e X 2   f X 3   g O z   
       wherein 
 X 1 =at least one or more of Co, Ni, V, Pt, Rh  
 X 2 =at least one or more of Al, Ga, Ge, Mn, Nb, Zn, Ag, P, Si, W  
 X 3 =at least one or more of K, Mg, Rb,Ca, Sr, Ba, Na  
 O=oxygen  
 a is 1,  
 b is 0< to 0.3,  
 c is 0< to 0.9,  
 d is 0< to 0.9,  
 e is 0< to 0.9,  
 f is 0< to 0.9,  
 g is 0< to 0.3,  
 z is a number which satisfies the valences of the other elements in the formula.  
 
     
     
         18 . The catalyst of  claim 17  further comprising a support.  
     
     
         19 . The catalyst of  claim 18  wherein said support is selected from the group consisting of alumina, silica, titania, zirconia, zeolites, heteropoly acids, silicon carbide, molecular sieves, microporous or nonporous materials, and mixtures thereof.  
     
     
         20 . The catalyst of  claim 19  wherein said supported catalyst is in fluidizable form or another physical shape.