Alkylene oxide catalyst and use thereof

Abstract

A supported silver catalyst and use thereof in a process for producing an alkylene oxide, such as ethylene oxide, by the direct oxidation of an alkylene with oxygen or an oxygen-containing gas, wherein the catalyst provides improved stability and improved resilience to reactor upsets and timely recovery to substantially pre-upset levels of catalyst activity and/or efficiency. In some embodiments, the catalyst also exhibits improved activity. A catalyst capable of producing ethylene oxide at a selectivity of at least 87 percent while achieving a work rate of at least 184 kg/h/m3 at a temperature of no greater than 235° C. when operated in a process where the inlet feed to a reactor containing the catalyst comprises ethylene, oxygen, and carbon dioxide, wherein the concentration of carbon dioxide in the inlet feed is greater than or equal to 2 mole percent.

What is claimed is: 
     
         1 . A continuous process for the production of alkylene oxide comprising:
 providing a supported silver catalyst prepared on an alumina-containing carrier, the carrier comprising greater than about 80 weight percent alpha-alumina and less than about 30 parts per million acid-leachable alkali metals by weight, the weight percent of the alumina and the concentration of the acid-leachable alkali metals being calculated on the weight of the carrier, wherein the acid-leachable alkali metals are selected from lithium, sodium, potassium, and mixtures thereof, the carrier having deposited thereon: (A) silver; (B) at least one first promoter selected from the group consisting of cesium, rubidium, and mixtures thereof; (C) at least one second promoter selected from the group consisting of sodium, lithium, and mixtures thereof; and (D) optionally, one or more additional solid promoters; wherein the deposited sodium, if employed, is present in a concentration from about 10 ppm to about 250 ppm, and wherein the deposited lithium, if employed, is present in a concentration from about 10 ppm to about 500 ppm by weight, the concentrations of the deposited sodium and lithium being calculated on the weight of the catalyst; and   contacting in a vapor phase an alkylene with oxygen or an oxygen-containing gas in the presence of the supported silver catalyst, the contacting being conducted under process conditions sufficient to produce the alkylene oxide.   
     
     
         2 . The process of  claim 2 , wherein the alkylene is ethylene, and the alkylene oxide is ethylene oxide. 
     
     
         3 . A process for producing ethylene oxide comprising:
 a) providing a reactor having an inlet and an outlet, the reactor containing a supported silver catalyst comprising deposited silver and one or more promoters;   b) providing to the reactor inlet a feed gas comprising ethylene, oxygen, and at least 2 mole % carbon dioxide;   c) withdrawing from the reactor outlet an outlet stream comprising ethylene oxide and carbon dioxide;   d) producing ethylene oxide at a reaction temperature less than 240° C.;   e) at a selectivity of at least 87 percent to ethylene oxide;   f) where the concentration of ethylene oxide in the outlet stream is at least 1.5 mole percent;   g) at a work rate of at least 176 kg of ethylene oxide per m 3  of catalyst per hour; and   h) recycling at least a portion of the reactor outlet stream to the reactor inlet feed.   
     
     
         4 . The process of  claim 3 , wherein at least a portion of the ethylene oxide or carbon dioxide in the outlet stream has been removed prior to recycling. 
     
     
         5 . A process for producing an ethylene glycol, an ethylene amine, or an ethylene glycol ether by converting the ethylene oxide produced by the process of  claim 2 . 
     
     
         6 . A continuous process for the production of alkylene oxide comprising:
 providing a supported silver catalyst prepared on an alumina-containing carrier, the carrier comprising greater than about 80 weight percent alpha-alumina and less than about 30 parts per million acid-leachable alkali metals by weight, the weight percent of the alumina and the concentration of the acid-leachable alkali metals being calculated on the weight of the carrier, wherein the acid-leachable alkali metals are selected from lithium, sodium, potassium, and mixtures thereof, the carrier having deposited thereon: (A) silver; (B) at least one first promoter selected from the group consisting of cesium, rubidium, and mixtures thereof; (C) at least one second promoter selected from the group consisting of sodium, lithium, and mixtures thereof; and (D) optionally, one or more additional solid promoters; wherein the deposited sodium, if employed, is present in a concentration from about 10 ppm to about 250 ppm, and wherein the deposited lithium, if employed, is present in a concentration from about ppm to about 500 ppm by weight, the concentrations of the deposited sodium and lithium being calculated on the weight of the catalyst; and contacting in a vapor phase an alkylene with oxygen or an oxygen-containing gas in a reactor containing the supported silver catalyst, wherein the reactor also contains an inlet feed and has withdrawn therefrom an outlet stream, the inlet stream comprises ethylene, oxygen, and carbon dioxide, the concentration of carbon dioxide in the inlet feed is greater or equal to 2 mole percent, at least a portion of the carbon dioxide is recycled from the outlet stream of the reactor to the inlet feed, and the supported silver catalyst is of producing ethylene oxide at a selectivity of at least 87 percent while achieving a work rate of at least 184 kg/h/m 3  of catalyst at a temperature of no greater than 240° C.   
     
     
         7 . The continuous process of  claim 6 , wherein the catalyst has already cumulatively produced at least 0.32 kT ethylene oxide per m 3  of catalyst. 
     
     
         8 . A process for producing an ethylene glycol, an ethylene amine, or an ethylene glycol ether by converting the ethylene oxide produced by the process of  claim 3 . 
     
     
         9 . The continuous process of  claim 1 , wherein the carrier comprises greater than about 95 weight percent alpha-alumina by weight, and the amount of silver deposited on the carrier is greater than about 25 percent by weight of the catalyst, the amount of cesium as the first promoter deposited on the carrier is from about 200 ppm to about 1200 ppm by weight of the catalyst, the amount of sodium deposited on the carrier is from about 10 ppm to about 150 ppm by weight of the catalyst, and the amount of lithium deposited on the carrier is from about 10 ppm to about 100 ppm by weight of the catalyst. 
     
     
         10 . The continuous process of  claim 1 , wherein the alpha-alumina carrier consists essentially of greater than about 98 weight percent alpha-alumina and less than about 30 ppm acid-leachable lithium, sodium, and potassium by weight; the weight percent of the alumina and the concentration of the acid-leachable alkali being calculated on the weight of the carrier; and the carrier further has deposited thereon manganese in an amount from about 20 ppm to about 200 ppm by weight; a promoting amount of sulfur compound and, optionally, rhenium, tungsten, molybdenum, or mixtures thereof, wherein the ratio of 2(moles sulfur plus moles tungsten plus moles molybdenum) plus moles rhenium divided by the total moles cesium and sodium [(2(S+W+Mo)+Re)/(Cs+Na)] ranges from greater than about 0.5/1 to about 1.5/1. 
     
     
         11 . The continuous process of  claim 1 , wherein the supported silver catalyst further comprises a promoting amount of sulfur compound and, optionally, rhenium, tungsten, molybdenum, or mixtures thereof, wherein the ratio of 2(moles sulfur plus moles tungsten plus moles molybdenum) plus moles rhenium divided by the total moles cesium and sodium [2(S+W+Mo)+Re)/(Cs+Na)] ranges from greater than about 0.5/1 to about 1.5/1. 
     
     
         12 . The continuous process of  claim 1 , wherein the catalyst comprises a synergistic combination of cesium, sodium, and lithium when used as a catalyst for the production of ethylene oxide. 
     
     
         12 . The continuous process of  claim 1 , wherein the silver supported catalyst further comprises a promoting amount of rhenium. 
     
     
         13 . The continuous process of  claim 1 , wherein the silver supported catalyst further comprises a promoting amount of manganese. 
     
     
         14 . The continuous process of  claim 1 , wherein the silver supported catalyst further comprises a promoter selected from compounds of sulfur, molybdenum, tungsten, and mixtures thereof. 
     
     
         15 . The continuous process of  claim 13 , wherein the promoting amount of manganese is at least about 1.5 micromoles per gram of catalyst. 
     
     
         16 . The continuous process of  claim 1 , wherein the alumina-containing support comprises particles of alpha-alumina each of which has at least one substantially flat major surface having a lamellate or platelet morphology which approximates the shape of a hexagonal plate, at least 50 percent of which (by number) have a major dimension of less than about 50 microns. 
     
     
         17 . The continuous process of  claim 10 , wherein catalyst is contained in a reactor having an inlet feed and having withdrawn therefrom an outlet stream, where the inlet feed comprises ethylene, oxygen, and carbon dioxide, the concentration of carbon dioxide in the inlet feed is greater than or equal to 2 mole percent, and ethylene oxide is produced at a selectivity of at least 87 percent, a work rate of at least 184 kg/h/m 3  of catalyst, and a reaction temperature of no greater than 235° C. 
     
     
         18 . The continuous process of  claim 10 , wherein the catalyst is contained in a reactor having an inlet feed hand having withdrawn therefrom an outlet stream, where the inlet feed comprises ethylene, oxygen, and carbon dioxide, the concentration of carbon dioxide in the inlet feed is greater than or equal to 2 mole percent, at least a portion of the carbon dioxide has been recycled from the outlet stream of the reactor, and ethylene oxide is produced at a selectivity of at least 87 percent, a work rate of at least 184 kg/h/m 3  of catalyst and a reaction temperature of no greater than 240° C.