Monolith structure loaded with metal promoted nanozeolites for enhanced propylene selectivity in methanol conversion
A catalyst system and a process for methanol to light olefin conversion with enhanced selectivity towards propylene. The catalyst system comprises a honeycomb monolith catalyst support coated with nanozeolite catalysts on the edges and inside the channels of the support structure. The nanozeolite catalysts have been pre-modified with metal. The catalyst system gives higher hydrothermal stability to the catalyst compared to randomly packed pellet catalyst and allows methanol to be converted to predominantly propylene at a low temperature, with decreased selectivity towards C 2 , higher olefins and paraffinic hydrocarbons.
1. A catalyst system for the conversion of methanol into light olefins comprising:
zeolite nanoparticles in the form of crystals having an average particle diameter of 10-50 nm modified with at least one promoter transition metal selected from the group consisting of iron, nickel, and chromium in the form of nanoparticles with an average particle diameter of 1-10 nm adsorbed onto a surface of the zeolite nanoparticles; and
a honeycomb monolith support with 400-1200 cells per square inch coated with the zeolite nanoparticles on the edges and inside the channels of the honeycomb monolith support;
wherein the catalyst system comprises 5-15 wt % of the promoter transition metal relative to the total weight of the catalyst system; and
wherein the catalyst is capable of converting methanol to propylene with a selectivity towards propylene of at least 40% relative to a total mass of light olefin products and a selectivity towards propylene that is greater than a selectivity towards ethylene relative to a total mass of light olefin products and that is greater than a selectivity towards butylene relative to a total mass of light olefin products.
2. The catalyst system of claim 1 , wherein the zeolite nanoparticles comprise metalloaluminosilicates and metallosilicalites of at least one transition metal selected from the group consisting of iron, nickel and chromium and wherein a ratio of metalloaluminosilicates to metallosilicalites is in a range from 1:1 to 2:1.
3. The catalyst system of claim 1 , wherein the zeolite nanoparticles are microporous molecular sieves having an MFI framework type, which have a BET surface area of 100-1000 m 2 g −1 and which have a pore size distribution of 0.6-1.0 nm.
4. The catalyst system of claim 1 , wherein the promoter transition metal is iron.
5. The catalyst system of claim 1 , further comprising a binder.
6. The catalyst system of claim 1 , wherein the zeolite nanoparticles further comprise alkaline earth metal ions.
7. The catalyst system of claim 1 , wherein the selectivity of the conversion towards propylene is 40-80% of the total mass of light olefin products.
8. A process of converting methanol into light olefins, comprising:
contacting the methanol in a reactor with the catalyst system of claim 1 .
9. The process of claim 8 , wherein the methanol is in vapor phase.
10. The process of claim 8 , wherein the process is carried out at a pressure of 0 psig to 50 psig.
11. The process of claim 8 , wherein the process is carried out in the presence of an inert gas.
12. The process of claim 8 , wherein the reactor is selected from the group consisting of a fixed-bed reactor and a moving-bed reactor.
13. The process of claim 8 , wherein the zeolite nanoparticles comprise metalloaluminosilicates and metallosilicalites of at least one transition metal selected from the group consisting of iron, nickel and chromium.
14. The process of claim 8 , wherein the zeolite nanoparticles are microporous molecular sieves having an WI framework type.
15. The process of claim 8 , wherein the promoter transition metal is iron.
16. The process of claim 8 , wherein the catalyst system further comprises a binder.
17. The process of claim 8 , wherein the zeolite nanoparticles further comprise alkaline earth metal ions.
18. The process of claim 8 , wherein the selectivity of the conversion towards propylene is 40-80% of the total mass of light olefin products.
19. A method of preparing the catalyst system of claim 1 , comprising:
(a) modifying zeolite nanoparticles with at least one promoter transition metal selected from the group consisting of iron, nickel and chromium;
(b) optionally mixing the metal-modified zeolite nanoparticles with a binder;
(c) coating the honeycomb monolith with the metal-modified zeolite nanoparticles, and optionally a binder, on the edges and inside the channels of the honeycomb monolith; and
(d) calcining the coated honeycomb monolith;
wherein the zeolite nanoparticles are microporous molecular sieves having an WI framework type.
20. The method of claim 19 , wherein the zeolite nanoparticles comprise metalloaluminosilicates, metallosilicalites of at least one transition metal selected from the group consisting of iron, nickel and chromium.