Process for direct oxidation of propylene to propylene oxide and large particle size titanium silicalite catalysts for use therein
View Patent ↗Large crystals of titanium silicalite or intergrowths of intergrown smaller crystals, having a mean particle size greater than 2 μm, have been found catalytically effective at commercially reasonable rates for the epoxidation of olefins in the presence of hydrogen peroxide. Crystals synthesized with a silica source having a low sodium content exhibit high levels of production and selectivity. The crystals have a low attrition rate and are easily filterable from a product stream.
1. A process for the preparation of a titanium silicalite catalyst comprising an intergrowth of titanium silicalite crystals having a mean particle size greater than 2 μm, said process comprising reacting a hydrolyzable titanium/silcon copolymer in the presence of a tetraalkylammonium hydroxide.
2. The process of claim 1 , wherein said tetraalkylammonium hydroxide comprises tetrapropylammonium hydroxide.
3. A process for the preparation of a titanium silicalite catalyst comprising an intergrowth of titanium silicalite crystals having a mean particle size greater than 2 μm, said process comprising reacting a hydrolyzable titanium/silcon copolymer in the presence of a tetraalkylammonium salt and a base.
4. The process of claim 3 , wherein said tetraalkylammonium salt is a tetrapropylammonium salt.
5. The process of claim 3 , wherein said salt is a halide.
6. The process of claim 3 , wherein said base comprises one or more of an organic amine, ammonia, or tetraalkylammonium hydroxide.
7. The process of claim 3 , wherein said hydrolyzable titanium/silicon copolymer comprises an alkyl silicate/titanate copolymer.
8. A process for the preparation of titanium silicalite olefin epoxidation catalysts of improved catalytic activity, said process comprising: a) preparing titanium silicalite crystals by crystal growth from a growth medium comprising a hydrolyzable titanium/silcon copolymer, an alkylammonium salt and a base to form a titanium silicalite product containing crystals or intergrowths thereof having a particle size greater than 2 μm; b) filtering the titanium silicalite product with a filter medium having a mean pore size greater than 0.5 μm; and c) recovering a filter cake of titanium silicalite crystals or intergrowths thereof relatively depleted of crystals or intergrowths having particle sizes less than 2 μm as compared with the amount of crystals or intergrowths with particle sizes less than 2 μm obtained in step a).
9. The process of claim 8 , wherein said base is an organic amine, ammonia, or a tetraalkylammonium hydroxide.
10. The process of claim 8 , wherein said alkylammonium salt is a tetrapropylammonium salt.
11. The process of claim 8 , wherein said filter medium has a mean pore size of from 1 μm to 8 μm.
12. The process of claim 8 , wherein said filter medium has a mean pore size of from 2 μm to 7 μm.
13. An olefin epoxidation catalyst suitable for epoxidation of olefins with an oxidant mixture comprising oxygen and hydrogen, prepared by a process comprising: treating a titanium silicalite catalyst produced by the process of claim 1 with a noble metal source to provide a titanium silicalite catalyst containing a noble metal such that hydrogen peroxide is generated in situ from hydrogen and oxygen.
14. The catalyst of claim 13 , wherein at least one noble metal is selected from the group consisting of palladium, gold, and platinum.
15. The catalyst of claim 13 , wherein said noble metal comprises palladium.
16. An olefin epoxidation catalyst suitable for epoxidation of olefins with an oxidant mixture comprising oxygen and hydrogen, prepared by a process comprising: treating a titanium silicalite catalyst catalyst produced by the process of claim 3 with a noble metal source to provide a titanium silicalite catalyst containing a noble metal such that hydrogen peroxide is generated in situ from hydrogen and oxygen.
17. The catalyst of claim 16 , wherein at least one noble metal is selected from the group consisting of palladium, gold, and platinum.
18. The catalyst of claim 16 , wherein said noble metal comprises palladium.
19. An olefin epoxidation catalyst suitable for epoxidation of olefins with an oxidant mixture comprising oxygen and hydrogen, prepared by a process comprising: treating a titanium silicalite catalyst prepared by the process of claim 8 with a noble metal source to provide a titanium silicalite catalyst containing a noble metal such that hydrogen peroxide is generated in situ from hydrogen and oxygen.