US 5,871,650 A · Supported zeolite membranes with controlled crystal width and preferred orientation grown on a growth enhancing layer

Abstract

The present invention is directed toward a new zeolite membrane which exhibits a columnar cross-sectional morphology and preferred crystallographic orientation comprising a porous substrate having coated thereon a mesoporous growth enhancing layer and a layer of columnar zeolite crystals on said mesoporous growth enhancing layer, and wherein said mesoporous growth enhancing layer comprises nanocrystalline or colloidal sized zeolites, nanocrystalline or colloidal zeolite and metal oxide, or nanocrystalline or colloidal zeolite and colloidal metal, or nanocrystalline or colloidal zeolite, colloidal metal and metal oxide, and wherein said mesoporous growth enhancing layer has interstices of about 20 to about 2000 .ANG., and wherein said columnar zeolite layer is a polycrystalline layer wherein 99.9% of said columnar zeolite crystals have at least one point between adjacent crystals that is .ltoreq.20 .ANG.. The invention is further directed to a process of producing a zeolite membrane exhibiting a columnar crystallographic orientation.

Claims26

Dependent claims

A zeolite membrane which exhibits a columnar cross-sectional morphology and preferred crystallographic orientation comprising a substrate having coated thereon a mesoporous growth enhancing layer and a dense layer of columnar zeolite crystals on said mesoporous growth enhancing layer, and wherein said mesoporous growth enhancing layer comprises zeolites;

zeolite and metal oxide;
zeolite and colloidal sized metal;
or zeolite, colloidal sized metal and metal oxide, and wherein said zeolites are selected from the group consisting of nanocrystaline zeolites and colloidal sized zeolites, and wherein said substrate is selected from the group consisting of porous and nonporous substrates, and wherein said mesoporous growth enhancing layer has interstices of about 20 to about 2000 .ANG., and wherein said columnar zeolite layer is a polycrystalline layer, wherein 99% of said columnar zeolite crystals have at least one point between adjacent crystals that is .ltoreq.20 .ANG..

A process for preparing a zeolite membrane exhibiting a columnar cross-sectional morphology and preferred crystallographic orientation comprising the steps of:

(a) coating a substrate with a growth enhancing layer wherein said growth enhancing is prepared by utilizing a solution comprising distilled water with zeolite, zeolite and metal oxide, zeolite and colloidal metal, or zeolite, colloidal metal and metal oxide wherein said zeolite is selected from the group consisting of nanocrystalline zeolite and colloidal zeolite, and wherein said metal oxide is colloidal metal or metal oxide prepared from sol-gel processing, followed by calcination at a temperature of about 200.degree. to about 1000.degree. C. for about at least about 2 hours,
said solution for preparing said growth enhancing layer being a solution having a concentration of 0.1 to 10 wt. % solids, provided that
said coating step (a) is performed by dipping said substrate when said substrate is a tubular or honeycomb substrate and spin coating said substrate when said substrate is a disk or plate substrate;
(b) immersing said substrate having said growth enhancing layer coated thereon in a zeolite synthesis mixture wherein said substrate is oriented such that said growth enhancing layer is oriented from 90.degree. to 270.degree. C. in said synthesis mixture and wherein in said 180.degree. orientation said growth enhancing layer is horizontal and facing downward, and wherein said growth enhancing layer is at least about 5 mm from the bottom of said alkaline synthesis mixture;
(c) autoclaving said substrate containing zeolite synthesis mixture for a time and at a temperature sufficient to form a columnar zeolite layer on said growth enhancing layer and wherein settling of particles from said zeolite synthesis mixture during autoclaving onto said columnar zeolite layer is prevented;
(d) washing said substrate having said growth enhancing layer and columnar zeolite layer thereon with a solution comprising water for a time and at a temperature sufficient to remove unreacted zeolite synthesis mixture to form a membrane, provided that when said zeolite synthesis mixture contains an organic template said membrane is calcined at a temperature ranging from about 400.degree. C. to about 600.degree. C. for at least about one hour.

3 more elements

Dependencies are inferred from the claim text.

Supported zeolite membranes with controlled crystal width and preferred orientation grown on a growth enhancing layer

Life of this patent

Supported zeolite membranes with controlled crystal width and preferred orientation grown on a growth enhancing layer

Life of this patent

Abstract

Claims26