Production of Aromatics from Methane

Abstract

A catalyst for the conversion of methane to higher hydrocarbons including aromatic hydrocarbons comprises molybdenum or a compound thereof dispersed on an aluminosilicate zeolite, wherein the amount of aluminum present as aluminum molybdate in the catalyst is less than 2700 ppm by weight.

1 . A catalyst for the conversion of methane to higher hydrocarbons including aromatic hydrocarbons, the catalyst comprising molybdenum or a compound thereof dispersed on an aluminosilicate zeolite, wherein the amount of aluminum present as aluminum molybdate in said catalyst is less than 2700 ppm by weight; preferably less than 270 ppm by weight aluminum present as aluminum molybdate. 
     
     
         2 . The catalyst of  claim 1  wherein the amount of molybdenum or said compound thereof in the catalyst is between about 0.1 and about 20% by weight of the catalyst, based on elemental molybdenum, and wherein the aluminosilicate zeolite comprises ZSM-5 having a silica to alumina mole ratio between about 14 and about 500. 
     
     
         3 . The catalyst of  claim 1  wherein the catalyst exposure has been limited to not more than 100 wt ppm oxygen, preferably not more than 10 wt ppm oxygen, still more preferably not more than 1 wt ppm of oxygen in an oxygen-containing gas at a temperature not in excess of 650° C.; preferably not in excess of 550° C.; more preferably not in excess of 500° C. for a cumulative time not greater than 10 hours preferably for a cumulative time not greater than 1 hour. 
     
     
         4 . The catalyst of  claim 1  wherein the catalyst has been regenerated using an ozone-containing gas, wherein said ozone-containing gas optionally also comprises oxygen, at a temperature less than 500° C.; preferably less than 300° C.; more preferably less than 150° C.; most preferably less than 100° C. 
     
     
         5 . A catalyst for the conversion of methane to higher hydrocarbons including aromatic hydrocarbons, the catalyst comprising molybdenum or a compound thereof dispersed on an aluminosilicate zeolite, wherein the amount of hexavalent molybdenum in said catalyst is less than 1.4% by weight. 
     
     
         6 . The catalyst of  claim 5  wherein the amount of molybdenum or said compound thereof in the catalyst is between about 0.1 and about 20% by weight of the catalyst, based on elemental molybdenum, and wherein the aluminosilicate zeolite comprises ZSM-5 that has a silica to alumina mole ratio between about 14 and about 500. 
     
     
         7 . The catalyst of  claim 5 , wherein said catalyst exposure has been limited to not more than 100 wt ppm oxygen, preferably not more than 10 wt ppm oxygen, still more preferably not more than 1 wt ppm of oxygen in an oxygen-containing gas at a temperature not in excess of 650° C.; preferably not in excess of 550° C.; more preferably not in excess of 500° C. for a cumulative time not greater than 10 hours preferably for a cumulative time not greater than 1 hour. 
     
     
         8 . The catalyst of  claim 5  wherein the catalyst has been regenerated using an ozone-containing gas, said gas optionally further comprising oxygen, at a temperature less than 500° C.; preferably less than 300° C.; more preferably less than 150° C.; still more preferably less than 100° C. 
     
     
         9 . A process for converting methane to higher hydrocarbons including aromatic hydrocarbons, the process comprising contacting a feed comprising methane with a dehydrocyclization catalyst in a reaction zone under conditions effective to convert said methane to aromatic hydrocarbons, said dehydrocyclization catalyst comprising molybdenum or a compound thereof dispersed on an aluminosilicate zeolite and wherein the amount of aluminum present as aluminum molybdate in said catalyst is less than 2700 ppm by weight; more preferably less than 270 ppm by weight. 
     
     
         10 . The process of  claim 9  wherein the dehydrocyclization catalyst, as supplied to the reaction zone, contains less than 2700 ppm by weight aluminum present as aluminum molybdate; more preferably less than 270 ppm by weight aluminum present as aluminum molybdate. 
     
     
         11 . The process of  claim 9  wherein the process is operated so as to maintain the amount of aluminum present as aluminum molybdate in said catalyst at less than 2700 ppm by weight; more preferably less than 270 ppm by weight aluminum present as aluminum molybdate. 
     
     
         12 . The process of  claim 9 , wherein the amount of molybdenum or said compound thereof in the catalyst is between about 0.1 and about 20% by weight of the catalyst, based on elemental molybdenum, and wherein the aluminosilicate zeolite comprises ZSM-5 that has a silica to alumina mole ratio between about 14 and about 500. 
     
     
         13 . The process of  claim 9  wherein the catalyst exposure has been limited to not more than 100 wt ppm oxygen, preferably not more than 10 wt ppm oxygen, still more preferably not more than 1 wt ppm of oxygen in an oxygen-containing gas at a temperature not in excess of 650° C.; preferably not in excess of 550° C.; more preferably not in excess of 500° C. for a cumulative time not greater than 10 hours preferably for a cumulative time not greater than 1 hour. 
     
     
         14 . The catalyst of  claim 9  wherein the catalyst has been regenerated using an ozone-containing gas, said gas optionally further comprising oxygen, at a temperature less than 500° C.; preferably at a temperature less than 300° C.; more preferably at a temperature less than 150° C.; most preferably at a temperature less than 100° C. 
     
     
         15 . A process for reducing the coke selectivity of a molybdenum-containing aluminosilicate zeolite catalyst, the process comprising:
 (a) providing a catalyst comprising molybdenum or a compound thereof dispersed on an aluminosilicate zeolite, wherein the catalyst also comprises aluminum molybdate; and   (b) contacting said catalyst with an atmosphere containing steam at a temperature of about 200° C. to about 450° C. and a pressure of at least 1000 kPa to reduce the amount of aluminum molybdate in said catalyst;   preferably wherein the amount of molybdenum or said compound thereof in the catalyst is between about 0.1 and about 20% by weight of the catalyst based on elemental molybdenum; and wherein the aluminosilicate zeolite comprises ZSM-5 having a silica to alumina mole ratio between about 14 and about 500.