Abstract Supported silver catalysts active for conversion of ethylene to ethylene oxide are prepared by coating the surface of catalyst support with an overlayer of a silver salt/polyacrylonitrile complex and then heating to about 200*-600*C to pyrolyze the polyacrylonitrile and convert the silver ions into discrete less than 150nm (nanometers) particles of silver. The silver salt/polyacrylonitrile complex overlayer is preferably prepared in situ by polymerization of a silver salt complexed acrylonitrile monomer on the surface of the support. Supported silver catalysts prepared by this process, when activated by treatment with a flowing stream containing a mixture of ethylene and oxygen in combination with an inert gas or by treatment with a flowing stream of air under conditions of time and temperature which facilitate removal of the excess carbon residue but avoid sintering of the catalyst particles, are highly active and selective in the conversion of ethylene to ethylene oxide.
A PROCESS OF PREPARING A SUPPORTED SILVER CATAYLST ACTIVE IN THE CONVERSATION OF ETHYLENE TO ETHYLENE OXIDE CONTAINING FROM ABOUT 2 TO 20% BY WEIGHT METALLIC SILVER DEPOSITED EVENLY ON THE SURFACE OF A CATALYST SUPPORT AS DISCRETE PARTICLES HAVING AN AVERAGE DIAMETER OF LESS THAN ABOUT 150MM WHICH COMPRISES: A. COATING THE SURFACES OF ACATALYST SUPPORT WITH AN OVERLAYER OF POLYACRYLONITRILE COMPLEXED WITH SILVER SALT AND B. HEATING THE COATED SUPORT AT A TEMPERATURE OF FROM ABOUT 200* TO ABOUT 600*C FOR A PERIOD OF TIME SUFFICIENT TO PYROLZE THE POLYACRYLONITRILE AND CONVERT THE SILVER IONS OF THE COMPLEXED SILVER SALT INTO DISCRETE PARTICLES OF SILVER.
Claim 2
Dependent Claim
107 words
A PROCESS OF PREPARING A SUPPORTED SILVER CATAYLST ACTIVE IN THE CONVERSATION OF ETHYLENE TO ETHYLENE OXIDE CONTAINING FROM ABOUT 2 TO 20% BY WEIGHT METALLIC SILVER DEPOSITED EVENLY ON THE SURFACE OF A CATALYST SUPPORT AS DISCRETE PARTICLES HAVING AN AVERAGE DIAMETER OF LESS THAN ABOUT 150MM WHICH COMPRISES: A. COATING THE SURFACES OF ACATALYST SUPPORT WITH AN OVERLAYER OF POLYACRYLONITRILE COMPLEXED WITH SILVER SALT AND B. HEATING THE COATED SUPORT AT A TEMPERATURE OF FROM ABOUT 200* TO ABOUT 600*C FOR A PERIOD OF TIME SUFFICIENT TO PYROLZE THE POLYACRYLONITRILE AND CONVERT THE SILVER IONS OF THE COMPLEXED SILVER SALT INTO DISCRETE PARTICLES OF SILVER.
Claim 3
Dependent Claim
40 words
The process in accordance with claim 1, wherein the catalyst product of the polyacrylonitrile pyrolysis step (b) is activated by removal or burn off of the excess carbonaceous residue under conditions which avoid or minimize sintering of the catalyst particles.
Claim 4
Dependent Claim
42 words
The process in accordance with claim 2, wherein the catalyst activation is accomplished by treatment with a flowing stream of a gaseous mixture of ethylene and oxygen in combination with an inert gas or a flowing stream of air at elevated temperatures.
Claim 5
Dependent Claim
56 words
The process in accordance with claim 3, wherein the catalyst activation is accomplished by treatment with a flowing stream of a gaseous mixture of ethylene and oxygen in combination with an inert gas at treatment temperatures in the range of about 190* to about 230* C for a time period of not less than 40 hours.
Claim 6
Dependent Claim
33 words
The process in accordance with claim 4, wherein the concentrations of ethylene and oxygen are 20-40 molar and 5-10 molar, respectively, in the treatment stream with the balance of the stream being nitrogen.
Claim 7
Dependent Claim
39 words
The process in accordance with claim 1, wherein the overlayer of polyacrylonitrile complexed with a silver salt is deposited on the support surface by polymerization of acrylonitrile complexed with a silver salt in the presence of the uncoated support.