Process for the simultaneous production of maleic anhydride and its hydrogenated derivatives

Abstract

A process is described for the co-production of maleic anhydride and at least one C 4 compound selected from butane-1,4-diol, γ-butyrolactone, and tetrahydrofuran in which maleic anhydride is produced by partial oxidation of a hydrocarbon feedstock selected from C 4 hydrocarbons and benzene to yield a vaporous reaction effluent stream comprising maleic anhydride, water, unconverted hydrocarbon feedstock, and carbon oxides. A part of the maleic anhydride present in the vaporous reaction effluent stream is condensed to form a crude maleic anhydride stream and leave a residual vaporous stream containing residual amounts of maleic anhydride. Further maleic anhydride is absorbed from the residual vaporous stream by absorption in an organic solvent, water or an aqueous solution. Maleic anhydride is then recovered from the loaded liquid absorptions medium. Said at least one C 4 compound is produced by hydrogenation of a C 4+ hydrogenation feedstock selected from maleic anhydride, maleic acid, dialkyl maleates, and mixtures of two or more thereof. The process is characterised in that material of the crude maleic anhydride stream is used as the C 4+ hydrogenation feedstock or is used to prepare the C 4+ hydrogenation feedstock.

1. A process for the co-production of maleic anhydride and at least one C 4  compound selected from the group consisting of butane-1,4-diol, γ-butyrolactone and tetrahydrofuran wherein:
 maleic anhydride is produced by steps comprising: 
 supplying a source of gaseous oxygen and a hydrocarbon feedstock selected from C 4  hydrocarbons and benzene to a catalytic partial oxidation zone which contains a charge of a partial oxidation catalyst capable of effecting the partial oxidation of the hydrocarbon feedstock to form maleic anhydride and which is maintained under catalytic partial oxidation conditions;  
 (ii) recovering from the partial oxidation zone a vaporous reaction effluent stream comprising maleic anhydride, water, unconverted hydrocarbon feedstock, and carbon oxides;  
 (iii) condensing a part of the maleic anhydride present in the vaporous reaction effluent stream in a condensation zone to form a crude maleic anhydride stream;  
 (iv) recovering from the condensation step (iii) a residual vaporous stream containing residual amounts of maleic anhydride;  
 (v) absorbing further maleic anhydride from the residual vaporous stream of step (iv) by absorption in a liquid absorption medium selected from an organic solvent, water, and an aqueous solution;  
 (vi) recovering from the absorption step (v) a loaded liquid absorption medium; and  
 (vii) recovering maleic anhydride from the loaded liquid absorption medium;  
 
 
       and wherein:
 said at least one C 4  compound selected from the group consisting of butane-1,4-diol, γ-butyrolactone and tetrahydrofuran is produced by steps comprising: 
 (viii) providing a C 4+  hydrogenation feedstock selected from maleic anhydride, maleic acid, dialkyl maleates, monoalkyl maleates and mixtures of two or more thereof;  
 (ix) supplying said C 4+  hydrogenation feedstock and hydrogen to a hydrogenation zone which contains a charge of a hydrogenation catalyst effective for catalytic hydrogenation of the C 4+  hydrogenation feedstock to yield said at least one C 4  product and which is maintained under catalytic hydrogenation conditions; and  
 (x) recovering from the hydrogenation zone a hydrogenation product stream containing said at least one C 4  product;  
 
 
       wherein crude maleic anhydride condensate of the crude maleic anhydride stream of  condensation of maleic anhydride is effected in step (iii) in the presence of a liquid condensation medium consisting of a liquid selected from the group consisting of maleic anhydride, monoesters of maleic acid, diesters of maleic acid, and mixtures of two or more thereof, wherein the crude maleic anhydride stream of step ( iii ) is used as the C 4+  hydrogenation feedstock of step (viii) or is used to prepare the C 4+  hydrogenation feedstock of step (viii). 
     
     
       2. A process according to  claim 1 , wherein all of the crude maleic anhydride stream of step (iii) is used as the C 4+  hydrogenation feedstock of step (viii) or is used to prepare the C 4+  hydrogenation feedstock of step (viii). 
     
     
       3. A process according to  claim 1 , wherein at least some of the maleic anhydride recovered in step (vii) is used as or  to prepare further C 4+  hydrogenation feedstock for use in step (viii). 
     
     
       4. A process according to  claim 1 , wherein the liquid absorption medium used in step (v) is selected from water and an aqueous solution so that the loaded absorption solution contains maleic acid and that at least some of the maleic acid present in the loaded absorption medium is used as or  to prepare further C 4+  hydrogenation feedstock for use in step (viii). 
     
     
       5. A process according to  claim 4 , wherein at least some of said resulting maleic acid is first concentrated by removal of excess water prior to use in step (viii). 
     
     
       6. A process according to  claim 4 , wherein maleic acid present in the loaded absorption medium is mixed with crude maleic anhydride of step (iii) for use as or to prepare the C 4+  hydrogenation feedstock of step (viii). 
     
     
       7. A process according to  claim 1 , wherein step (v) comprises absorbing vaporous maleic anhydride from the effluent stream in an organic solvent. 
     
     
       8. A process according to  claim 7 , wherein the organic solvent is a dialkyl phthalate or a dialkyl hexahydrophthalate. 
     
     
       9. A process according to  claim 1 , wherein in step (iii) condensation of maleic anhydride is effected by indirect cooling against a cooling medium selected from water and a process fluid. 
     
     
       10. A process according to  claim 1 , wherein in step (iii) condensation of maleic anhydride  said liquid condensation medium is effected in the presence of a liquid condensation medium selected from maleic anhydride, monoesters of maleic acid, and diesters of maleic acid, said liquid condensation medium being  sprayed into the vaporous reactant effluent stream so as to form a mixture of crude maleic anhydride and said liquid condensation medium which is used as, or to prepare, the C 4+  hydrogenation feedstock of step (viii). 
     
     
       11. A process according to  claim 1 , wherein the C 4+  hydrogenation feedstock is a dialkyl maleate which is prepared by reaction of maleic anhydride with an alkyl alcohol to form a monoalkyl maleate which is then esterified with further alkyl alcohol to form a dialkyl maleate. 
     
     
       12. A process according to  claim 11 , wherein the alkyl alcohol is methanol and the dialkyl maleate is dimethyl maleate. 
     
     
       13. A process according to  claim 11 , wherein the hydrogenation catalyst of step (ix) is selected from copper chromite and promoted copper catalysts. 
     
     
       14. A process according to  claim 1 , wherein the C 4+  hydrogenation feedstock is maleic anhydride. 
     
     
       15. A process according to  claim 1 , wherein the source of gaseous oxygen is air or a mixture of oxygen and recycle off gas. 
     
     
       16. A process according to  claim 1 , wherein the hydrocarbon feedstock is a butane feedstock. 
     
     
       17. A process according to  claim 16 , wherein the partial oxidation catalyst comprises vanadium-phosphorus oxide. 
     
     
       18. A process according to  claim 17 , wherein the vaporous reaction effluent stream is cooled prior to step (iii) and that a guard bed of a phosphorus-absorbing material is placed in the path of the cooled vaporous reaction effluent stream prior to step (iii) thereby to remove phosphorus-containing materials therefrom. 
     
     
       19. A process according to  claim 18 , wherein the phosphorus-absorbing material comprises a charge of spent vanadium-containing partial oxidation catalyst. 
     
     
       20. A process according to  claim 1 , wherein the catalytic partial oxidation zone comprises a fixed bed reactor, a tubular reactor, a fluidised bed reactor, or a moving bed reactor. 
     
     
       21. A process according to  claim 1 , wherein an alkyl alcohol is used as wash liquor to wash condensation surfaces of the condensation zone to remove deposits of maleic acid and fumaric acid thereon and that the resulting solution is combined with the C 4+  hydrogenation feedstock. 
     
     
       22. A process according to  claim 7 , wherein the organic solvent is selected from the group consisting of dimethyl phthalate, dibutyl phthalate, dimethyl hexahydrophthalate, and dibutyl hexahydrophthalate. 
     
     
       23. A process for the co- production of maleic anhydride and at least one C   4+    compound selected from the group consisting of butane -   1 , 4   - diol, γ - butyrolactone and tetrahydrofuran wherein:      maleic anhydride is produced by steps comprising:    ( i )  supplying a source of gaseous oxygen and a C   4    hydrocarbon feedstock to a catalytic partial oxidation zone which contains a charge of a phosphorous - containing partial oxidation catalyst capable of effecting the partial oxidation of the C   4    hydrocarbon feedstock to form maleic anhydride and which is maintained under catalytic partial oxidation conditions;      ( ii )  recovering from the partial oxidation zone a vaporous reaction effluent stream comprising maleic anhydride, water, unconverted hydrocarbon feedstock, and carbon oxides;      ( iii )  condensing a part of the maleic anhydride present in the vaporous reaction effluent stream in a condensation zone to form a crude maleic anhydride stream;      ( iv )  recovering from the condensation step  ( iii )  a residual vaporous stream containing residual amounts of maleic anhydride;      ( v )  absorbing further maleic anhydride from the residual vaporous stream of step  ( iv )  by absorption in a liquid absorption medium selected from an organic solvent, water, and an aqueous solution;      ( vi )  recovering from the absorption step  ( v )  a loaded liquid absorption medium; and      ( vii )  recovering maleic anhydride from the loaded liquid absorption medium;        
       
         and wherein:  
           said at least one C   4    compound selected from the group consisting of butane -   1 , 4   - diol, γ - butyrolactone and tetrahydrofuran is produced by steps comprising:    ( viii )  providing a C   4+    hydrogenation feedstock selected from maleic anhydride, maleic acid, monoalkyl maleates, dialkyl maleates, and mixtures of two or more thereof;      ( ix )  supplying said C   4+    hydrogenation feedstock and hydrogen to a hydrogenation zone which contains a charge of a hydrogenation catalyst effective for catalytic hydrogenation of the C   4+    hydrogenation feedstock to yield said at least one C   4+    product and which is maintained under catalytic hydrogenation conditions; and      ( x )  recovering from the hydrogenation zone a hydrogenation product stream containing said at least one C   4+    product; wherein      
           the vaporous reaction of effluent stream is cooled prior to step  ( iii ) , that a guard bed of a phosphorous - absorbing material is placed in the path of the cooled vaporous reaction effluent stream prior to step  ( iii )  thereby to remove phosphorous - containing materials therefrom, and that material of the crude maleic anhydride stream of step  ( iii )  is used as the C   4+    hydrogenation feedstock of step  ( viii )  or is used to prepare the C   4+    hydrogenation feedstock of step  ( viii ). 
       
     
     
       24. A process according to  claim 23 , wherein all of the crude maleic anhydride stream of step ( iii )  is used as the C   4+    hydrogenation feedstock of step  ( viii )  or is used to prepare the C   4+    hydrogenation feedstock of step  ( viii ). 
     
     
       25. A process according to  claim 23 , wherein at least some of the maleic anhydride recovered in step ( vii )  is used as or to prepare further C   4+    hydrogenation feedstock for use in step  ( viii ). 
     
     
       26. A process according to  claim 23 , wherein the liquid absorption medium used in step ( v )  is selected from water and an aqueous solution so that the loaded absorption solution contains maleic acid and that at least some of the maleic acid present in the loaded absorption medium is used as or to prepare further C   4+    hydrogenation feedstock for use in step  ( viii ). 
     
     
       27. A process according to  claim 26 , wherein at least some of said resulting maleic acid is first concentrated by removal of excess water prior to use in step ( viii ). 
     
     
       28. A process according to  claim 26 , wherein maleic acid present in the loaded absorption medium is mixed with crude maleic anhydride of step ( iii )  for use as or to prepare the C   4+    hydrogenation feedstock of step  ( viii ). 
     
     
       29. A process according to  claim 23 , wherein step ( v )  comprises absorbing vaporous maleic anhydride from the effluent stream in an organic solvent.   
     
     
       30. A process according to  claim 29 , wherein the organic solvent is a dialkyl phthalate or a dialkyl hexahydrophthalate. 
     
     
       31. A process according to  claim 29 , wherein the solvent is selected from the group consisting of dimethyl phthalate, dibutyl phthalate, dimethyl hexahydrophthalate, and dibutyl hexahydrophthalate. 
     
     
       32. A process according to  claim 23 , wherein in step ( iii )  condensation of maleic anhydride is effected by indirect cooling against a cooling medium selected from the group consisting of water and a process fluid.   
     
     
       33. A process according to  claim 23 , wherein in step ( iii )  condensation of maleic anhydride effected in the presence of a liquid condensation medium selected from the group consisting of maleic anhydride, monoesters of maleic acid, and diesters of maleic acid, said liquid condensation medium being sprayed into the vaporous reactant effluent stream so as to form a mixture of crude maleic anhydride and said liquid condensation medium which is used as or to prepare the C   4+    hydrogenation feedstock of step  ( viii ). 
     
     
       34. A process according to  claim 23 , wherein C 4+    hydrogenation feedstock is a dialkyl maleate which is prepared by reaction of maleic anhydride with an alkyl alcohol to form a monoalkyl maleate which is then esterified with further alkyl alcohol to form a dialkyl maleate.   
     
     
       35. A process according to  claim 34 , wherein said alkyl alcohol is methanol and said dialkyl maleate is dimethyl maleate. 
     
     
       36. A process according to  claim 34 , wherein the hydrogenation catalyst of step ( ix )  is selected from the group consisting of copper chromite and promoted copper catalysts.   
     
     
       37. A process according to  claim 23 , wherein the C 4+    hydrogenation feedstock is maleic anhydride.   
     
     
       38. A process according to  claim 23 , wherein the source of gaseous oxygen is air or a mixture of oxygen and recycle off gas. 
     
     
       39. A process according to  claim 23 , wherein the hydrocarbon feedstock is a butane feedstock. 
     
     
       40. A process according to  claim 38 , wherein the partial oxidation catalyst comprises vanadium- phosphorous oxide.   
     
     
       41. A process according to  claim 23 , wherein the phosphorus- absorbing material comprises a charge of spent vanadium - containing partial oxidation catalyst.   
     
     
       42. A process according to  claim 23 , wherein the catalytic partial oxidation zone comprises a fixed bed reactor, a tubular reactor, a fluidised bed reactor, or a moving bed reactor. 
     
     
       43. A process according to  claim 23 , wherein an alkyl alcohol is used as wash liquor to wash condensation surfaces of the condensation zone to remove deposits of maleic acid and fumaric acid thereon and that the resulting solution is combined with the C 4+    hydrogenation feedstock.