Organic-free synthesis of small pore zeolite catalysts

Patent metadata

Field	Value
Publication number	US-2016101415-A1
Application number	US-201514882587-A
Country	US
Kind code	A1
Filing date	Oct 14, 2015
Priority date	Oct 14, 2014
Publication date	Apr 14, 2016
Grant date	—

Abstract

The present invention is directed to methods of enhancing the catalytic activities of 8-MR zeolites, the methods comprising treating a precursor 8-MR zeolite that has been prepared without the use of an organic structure directing agent and having an Si/Al ratio of less than 5, with high temperature steam for a period of time sufficient to extract at least a portion of the aluminum from the precursor zeolite framework to form a steam-treated zeolite having an Si/tetrahedral Al ratio of greater than 5, wherein the steam has a temperature in a range of from about 350° C. to about 850° C. The compositions produced by these methods and their use in catalytic reactions are also provided.

First claim

What is claimed:

1 . A method for improving the catalytic activity of a 8-MR zeolite, the method comprising treating the precursor 8-MR zeolite, prepared in the absence of any organic structure directing agent and having an Si/Al atom ratio of less than 5, with high temperature steam for a period of time sufficient to extract at least a portion of the aluminum from the precursor zeolite framework to form a steam-treated zeolite, wherein the steam has a temperature in a range of from about 350° C. to about 850° C.

2 . The method of claim 1 , wherein the ratio of the silicon to tetrahedral aluminum atoms in the steam-treated zeolite is greater than 5.

3 . The method of claim 1 , wherein the precursor 8-MR ring zeolite has a CHA, RHO, or KFI framework.

4 . The method of claim 1 , wherein the precursor 8-MR ring zeolite contains aluminum that is practically all tetrahedral, as measured by 27 Al NMR.

5 . The method of claim 1 , wherein the high temperature of the steam is in a range of from 350° C. to 400° C., from 400° C. to 450° C., from 450° C. to 500° C., from 500° C. to 550° C., from 550° C. to 600° C., from 600° C. to 650° C., from 650° C. to 700° C., from 700° C. to 750° C., from 750° C. to 800° C., from 800° C. to 850° C., or a sequential combination of two or more of these ranges for a period of from 4 hours to 12 hours.

6 . The method of claim 1 , wherein Si/Al atom ratio of the precursor zeolite is less than 2.5.

7 . The method of claim 1 , further comprising exchanging any alkali or alkaline earth metals in the precursor 8-MR zeolite with an acidifying agent prior to exposing the precursor 8-MR zeolite to the high temperature steam.

8 . The method of claim 1 , wherein at least a portion of the aluminum sites in the precursor 8-MR zeolite are acid in character.

9 . The method of claim 1 , wherein the aluminum extracted from the precursor zeolite framework is pentacoordinate, hexacoordinate aluminum, or both pentacoordinate and hexacoordinate aluminum, as characterized by 27 Al NMR.

10 . The method of claim 1 , wherein the atomic ratio of tetrahedral aluminum to total aluminum content in the steam-treated zeolite is in a range of from about 0.12 to about 0.6.

11 . The method of claim 1 , wherein the steam-treated zeolite has a measurably higher mesopore volume than does the precursor 8-MR zeolite.

12 . The method of claim 1 , wherein the steam-treated zeolite has a measurably smaller micropore volume than does the precursor 8-MR zeolite.

13 . The method of claim 1 , wherein the steam-treated zeolite has a micropore volume in a range of from 0.03 to 0.8 cc/gram of the steamed zeolite.

14 . The method of any one of claims 1 to 13 , wherein the steam-treated zeolite has a measurably smaller Brønsted acid site density than does the precursor 8-MR zeolite.

15 . The method of claim 1 , wherein the steam-treated zeolite has Brønsted acid site density in a range of from 0.6 to 1.2 mmol/gram of the steamed zeolite, as determined by ammonia temperature-programmed desorption.

16 . The method of claim 1 , further comprising washing the steam-treated zeolite with acid.

17 . The method of claim 16 , wherein the acid wash removes at least a portion of pentacoordinate, hexacoordinate aluminum, or both pentacoordinate and hexacoordinate aluminum formed in the steam-treated zeolite.

18 . A crystalline aluminosilicate composition prepared by the method of claim 1 .

19 . A crystalline aluminosilicate composition containing an 8-MR zeolite structure, the composition characterized by two or more of:
(a) an atomic ratio of the silicon to tetrahedral aluminum atoms greater than 5; (b) an atomic ratio of tetrahedral to total aluminum atoms in a range of from about 0.12 to about 0.6; (c) a microporous region and a mesoporous region, in which the microporous region comprises tetrahedral aluminum and the mesoporous region contains tetrahedral, pentacoordinate, and/or hexacoordinate aluminum; (d) a micropore volume comprising from 0.03 to 0.8 cc/gram of the composition; (e) a total Brønsted acid site density in a range of from 0.6 to 1.2, preferably 0.7 to 0.9 mmol/gram of the composition, as determined by ammonia temperature-programmed desorption; or (f) a mesoporous Brønsted acid site density in a range of from 0.1 to 4 mmol/gram of the composition, as determined by isopropylamine temperature-programmed desorption.

21 . A method comprising carbonylating DME with CO at low temperatures, reducing NOx with methane, cracking, dehydrogenating, MTO, oligomerizing alkenes, aminating lower alcohols (including methanol), separating and sorbing lower alkanes (e.g., C3-C6 alkanes, hydrocracking a hydrocarbon, dewaxing a hydrocarbon feedstock, isomerizing an olefin, producing a higher molecular weight hydrocarbon from lower molecular weight hydrocarbon, reforming a hydrocarbon, converting a lower alcohol or other oxygenated hydrocarbon to produce an olefin products, reducing the content of an oxide of nitrogen contained in a gas stream in the presence of oxygen, or separating nitrogen from a nitrogen-containing gas mixture by contacting the respective feedstock with the crystalline aluminosilicate composition of claim 19 under conditions sufficient to affect the named transformation.

22 . A method comprising contacting methanol with the crystalline aluminosilicate composition of claim 19 under conditions sufficient to convert the methanol to at least one type of olefin.

23 . The method of claim 21 , wherein the crystalline zeolite composition retains at least 80% of its catalytic activity to convert the methanol to at least one type of olefin for at least 2 g-methanol per gram zeolite composition, when reacted at a temperature in a range of 350° C. to 450° C.

Assignees

• California Inst Of Techn

Inventors

• Ji Yuewei
• Deimund Mark A
• Bhawe Yashodhan
• Davis Mark E

Classifications

• B01J2235/15

  X-ray diffraction · CPC title

• B01J35/70

  characterised by their crystalline properties, e.g. semi-crystalline (catalysts comprising carbon B01J21/18; molecular sieves B01J29/00) · CPC title

• B01J35/80

  characterised by their amorphous structures · CPC title

• C07C1/20 Primary

  starting from organic compounds containing only oxygen atoms as heteroatoms · CPC title

• B01J2235/05

  Nuclear magnetic resonance [NMR] · CPC title