Process for production of formaldehyde from dimethyl ether

Abstract

Dimethyl ether is converted to formaldehyde using a supported catalyst comprising molybdenum and/or vanadium oxides. The surface density of the oxide(s) ranges from greater than that for the isolated monomeric oxides upwards, so long as there is a substantial absence of bulk crystalline molybdenum and/or vanadium oxide(s). Conversion and selectivity to formaldehyde are improved as compared to data reported for known catalysts. Also disclosed is a catalyst comprising molybdenum and/or vanadium oxides supported on a layer of stannic oxide that is disposed on the surface of a particulate alumina or zirconia support.

What is claimed is:  
     
         1 . A process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides, wherein the support is selected from catalyst supports that allow the formation of monolayers of molybdenum and/or vanadium oxide on the surface of the support but that do not substantially react with the molybdenum and/or vanadium oxide to form unreducible mixed oxides, wherein the molybdenum oxide, vanadium oxide, or mixture of such oxides is dispersed on the surface of the support, the surface density of the oxide or oxides on the support being greater than the surface density of the respective isolated monomeric oxide or oxides, and wherein the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.  
     
     
         2 . A process according to  claim 1  in which the surface density of the oxide or oxides on the support is from about 50% of the surface density of a monolayer of the oxide or oxides to about 300% of the surface density of a monolayer of the oxide or oxides.  
     
     
         3 . A process according to  claim 1  in which the surface density of the oxide or oxides on the support is approximately that of a monolayer of said oxide or oxides.  
     
     
         4 . A process according to  claim 1  in which the support is selected from alumina, zirconia, stannic oxide, titania, silica, and mixtures thereof.  
     
     
         5 . A process according to  claim 1  in which the oxide comprises molybdenum oxide.  
     
     
         6 . A process according to  claim 5  in which the support comprises alumina.  
     
     
         7 . A process according to  claim 5  in which the support comprises zirconia.  
     
     
         8 . A process according to  claim 5  in which the support comprises stannic oxide.  
     
     
         9 . A process according to  claim 8  in which the support comprises a layer of stannic oxide disposed on a particulate alumina or zirconia.  
     
     
         10 . A process according to  claim 5  in which the surface density of the molybdenum oxide is from about 1.5 to about 20 Mo/nm 2 .  
     
     
         11 . A process according to  claim 6  in which the surface density of the molybdenum oxide is from about 50% of the surface density of a molybdenum oxide monolayer on the alumina support to about 300% of the surface density of a molybdenum oxide monolayer on the support.  
     
     
         12 . A process according to  claim 7  in which the surface density of the molybdenum oxide is from about 1.5 to about 50 Mo/nm 2 .  
     
     
         13 . A process according to  claim 7  in which the surface density of the molybdenum oxide is from about 50% of the surface density of a molybdenum oxide monolayer on the zirconia support to about 400% of the surface density of a molybdenum oxide monolayer on the support.  
     
     
         14 . A process according to  claim 5  in which the surface density of the molybdenum oxide is approximately that of a monolayer of molybdenum oxide on the support.  
     
     
         15 . A process according to  claim 1  in which the oxide is vanadium oxide.  
     
     
         16 . A process according to  claim 15  in which the support comprises alumina.  
     
     
         17 . A process according to  claim 15  in which the support comprises zirconia.  
     
     
         18 . A process according to  claim 15  in which the support comprises stannic oxide.  
     
     
         19 . A process according to  claim 18  in which the support comprises a layer of stannic oxide disposed on particulate alumina or zirconia.  
     
     
         20 . A process according to  claim 15  in which the surface density of the vanadium oxide on the support is from about 50% of the surface density of a monolayer of vanadium oxide to about 300% of the surface density of a monolayer of vanadium oxide.  
     
     
         21 . A process according to  claim 1  in which methyl formate is a co-product with the formaldehyde.  
     
     
         22 . A process according to  claim 1  in which selectivity to formaldehyde is 50% or greater.  
     
     
         23 . A process for the production of formaldehyde by oxidation of dimethyl ether in the presence of a supported catalyst comprising molybdenum oxide, vanadium oxide or a mixture of molybdenum and vanadium oxides, wherein the support is selected from alumina, zirconia, stannic oxide, titania and silica, and mixtures thereof, wherein the surface density of the oxide or oxides on the support is from about 50% of the surface density of a monolayer of the oxide or oxides to about 300% of the surface density of a monolayer of the oxide or oxides, and wherein the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.  
     
     
         24 . A process according to  claim 23  in which the surface density of the molybdenum or vanadium oxide or mixture of said oxides on the support is approximately that of a monolayer of said oxide or oxides on the support.  
     
     
         25 . A process according to  claim 23  in which the oxide is molybdenum oxide.  
     
     
         26 . A process according to  claim 25  in which the support comprises alumina.  
     
     
         27 . A process according to  claim 25  in which the support comprises zirconia.  
     
     
         28 . A process according to  claim 25  in which the catalyst comprises a layer of zirconia disposed on particulate alumina.  
     
     
         29 . A process according to  claim 25  in which the support comprises stannic oxide.  
     
     
         30 . A process according to  claim 29  in which the support comprises a layer of stannic oxide disposed on particulate alumina or zirconia.  
     
     
         31 . A process according to  claim 26  in which the surface density of the molybdenum oxide is from about 1.5 to about 20 Mo/nm 2 .  
     
     
         32 . A process according to  claim 26  in which the surface density of the molybdenum oxide is from about 50% of the surface density of a molybdenum oxide monolayer to about 300% of the surface density of a molybdenum oxide monolayer.  
     
     
         33 . A process according to  claim 27  in which the surface density of the molybdenum oxide is from about 1.5 to about 50 Mo/nm 2 .  
     
     
         34 . A process according to  claim 27  in which the surface density of the molybdenum oxide is from about 50% of the surface density of a molybdenum oxide.  
     
     
         35 . A process according to  claim 25  in which the surface density of the molybdenum oxide is approximately that of a monolayer of molybdenum oxide.  
     
     
         36 . A process according to  claim 23  in which the oxide is vanadium oxide.  
     
     
         37 . A process according to  claim 36  in which the support comprises alumina.  
     
     
         38 . A process according to  claim 36  in which the support comprises zirconia.  
     
     
         39 . A process according to  claim 36  in which the support comprises stannic oxide.  
     
     
         40 . A process according to  claim 39  in which the support comprises a layer of stannic oxide disposed on a particulate alumina or zirconia.  
     
     
         41 . A process according to  claim 36  in which the surface density of the vanadium oxide on the support is from about 50% of the surface density of a monolayer of vanadium oxide to about 300% of the surface density of a monolayer of vanadium oxide.  
     
     
         42 . A process according to  claim 23  in which methyl formate is a co-product with the formaldehyde.  
     
     
         43 . A process according to  claim 22  in which selectivity to formaldehyde is 50% or greater.  
     
     
         44 . A catalyst comprising molybdenum oxide, vanadium oxide, or a mixture of molybdenum oxide and vanadium oxide supported on a layer of stannic oxide, the stannic oxide layer being disposed on a particulate alumina or zirconia support, in which the surface density of the molybdenum and/or vanadium oxide or oxides on the support is greater than that for the respective monomeric isolated oxide or oxides, and the catalyst is characterized by a substantial absence of bulk crystalline molybdenum and/or vanadium oxides.  
     
     
         45 . A catalyst according to  claim 44  in which the surface density of the oxide or oxides on the support is from about 50% of the surface density of a monolayer of the oxide or oxides to about 300% of the surface density of a monolayer of the oxide or oxides.  
     
     
         46 . A catalyst according to  claim 44  in which the surface density of the molybdenum and/or vanadium oxide or oxides on the support is approximately that of a monolayer of the oxide or oxides at the surface of the support.  
     
     
         47 . A catalyst according to  claim 44  comprising molybdenum oxide supported on a layer of stannic oxide that is disposed on a particulate alumina support, and in which the surface density of the molybdenum oxide is from about 1.5 to about 20 Mo/nm2.  
     
     
         48 . A catalyst according to  claim 44  comprising molybdenum oxide supported on a layer of stannic oxide that is disposed on a particulate alumina support, and in which the surface density of the molybdenum oxide is approximately that of a monolayer of the oxide or oxides at the surface of the support.