Carrier for ethylene oxide catalysts
An improved carrier for an ethylene epoxidation catalyst is provided. The carrier includes an alumina component containing a first portion of alumina particles having a particle size of, or greater than, 3 μm and up to 6 μm, and a second portion of alumina particles having a particle size of, or less than, 2 μm. An improved catalyst containing the above-described carrier, as well as an improved process for the epoxidation of ethylene using the catalyst are also provided.
1. A carrier for an ethylene epoxidation catalyst, the carrier comprising alumina containing a first portion of alumina particles having a particle size of, or greater than, 3 μm and up to 6 μm, and a second portion of alumina particles having a particle size less than 1 μm, wherein at least 20 wt% but less than 100 wt% of the alumina particles have said particle size less than 1 μm, wherein said wt% is relative to the weight of alumina in the carrier.
2. The carrier according to claim 1 , wherein the first portion of alumina particles has a particle size of, or greater than, 3 μm and up to 5 μm.
3. The carrier according to claim 1 , wherein at least 20 wt% but less than 100 wt% of the alumina particles have a particle size of, or less than, 2μm, wherein said wt% is relative to the weight of alumina in the carrier.
4. The carrier according to claim 1 , wherein the alumina is a-alumina.
5. The carrier according to claim 1 , further comprising a stability-enhancing amount of mullite.
6. The carrier according to claim 5 , wherein the stability-enhancing amount of mullite is about 0.5-20 wt% mullite by total weight of the carrier.
7. The carrier according to claim 5 , wherein the stability-enhancing amount of mullite is about 1-15% mullite by total weight of the carrier.
8. The carrier according to claim 5 , wherein the stability-enhancing amount of mullite is about 3-12% mullite by total weight of the carrier.
9. The carrier according to claim 1 , further comprising a promoting amount of rhenium.
10. The carrier according to claim 1 , further comprising a promoting amount of an alkali or alkaline earth metal.
11. The carrier according to claim 1 , further comprising a promoting amount of cesium.
12. The carrier according to claim 1 , wherein the carrier possesses a pore size distribution having a peak pore size of, or less than, 2 μm.
13. The carrier according to claim 1 , wherein no more than 40% of the pores have a pore size of or less than 1 μm.
14. An ethylene epoxidation catalyst comprising:
a) a carrier comprising alumina containing a first portion of alumina particles having a particle size of, or greater than, 3 μm and up to 6 μm, and a second portion of alumina particles having a particle size less than 1 μm, wherein at least 20 wt% but less than 100 wt% of the alumina particles have said particle size less than 1 μm, wherein said wt% is relative to the weight of alumina in the carrier;
b) a catalytic amount of silver deposited on and/or in said carrier; and
c) a promoting amount of rhenium deposited on and/or in said carrier.
15. The catalyst according to claim 14 , wherein the first portion of alumina particles has a particle size of, or greater than, 3 μm and up to 5 μm.
16. The catalyst according to claim 14 , wherein at least 20 wt% but less than 100 wt% of the alumina particles have a particle size of, or less than, 2 μm, wherein said wt% is relative to the weight of alumina in the carrier.
17. The catalyst according to claim 14 , wherein the carrier possesses a pore size distribution having a peak pore size of, or less than, 2 μm.
18. The catalyst according to claim 14 , wherein no more than 40% of the pores have a pore size of or less than 1 μm.
19. A method for the vapor phase conversion of ethylene to ethylene oxide in the presence of oxygen, the method comprising reacting a reaction mixture comprising ethylene and oxygen in the presence of a catalyst comprising:
a) a carrier comprising alumina containing a first portion of alumina particles having a particle size of, or greater than, 3 μm and up to 6 μm, and a second portion of alumina particles having a particle size less than 1 μm, wherein at least 20 wt% but less than 100 wt% of the alumina particles have said particle size less than 1 μm, wherein said wt% is relative to the weight of alumina in the carrier;
b) a catalytic amount of silver deposited on and/or in said carrier; and
c) a promoting amount of rhenium deposited on and/or in said carrier.
20. The method according to claim 19 , wherein the first portion of alumina particles has a particle size of, or greater than, 3 μm and up to 5 μm.
21. The method according to claim 19 , wherein at least 20 wt% but less than 100 wt% of the alumina particles have a particle size of, or less than, 2 μm, wherein said wt% is relative to the weight of alumina in the carrier.
22. The method according to claim 19 , wherein the carrier Possesses a pore size distribution having a peck pore size of, or less than, 2 μm.
23. The method according to claim 19 , wherein no more than 40% of the pores have a pore size of or less than 1 μm.