Chemistry of inorganic compounds – Zeolite
Reexamination Certificate
2000-07-27
2003-02-18
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
C423S713000, C423S714000, C423SDIG002, C502S085000
Reexamination Certificate
active
06521206
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to new crystalline molecular sieve CIT-6, a method for preparing CIT-6 using a tetraethylammonium cation templating agent, a method of using CIT-6 as a precursor for making other crystalline molecular sieves, and processes employing CIT-6 as a catalyst.
2. State of the Art
Because of their unique sieving characteristics, as well as their catalytic properties, crystalline molecular sieves are especially useful in applications such as hydrocarbon conversion, gas drying and separation. Although many different crystalline molecular sieves have been disclosed, there is a continuing need for new molecular sieves with desirable properties for gas separation and drying, hydrocarbon and chemical conversions, and other applications. New molecular sieves may contain novel internal pore architectures, providing enhanced selectivities in these processes.
SUMMARY OF THE INVENTION
The present invention is directed to a crystalline molecular sieve with unique properties, referred to herein as “molecular sieve CIT-6” or simply “CIT-6”. When the CIT-6 contains a metal (or non-silicon) oxide, such as aluminum oxide, boron oxide, titanium oxide or iron oxide, it is referred to as “catalytically active” CIT-6.
The CIT-6 can be made in two forms. The first contains silicon oxide, zinc oxide and optional metal (or non-silicon) oxides (such as aluminum oxide), wherein the zinc is in the crystal framework of the CIT-6. This form of CIT-6 is referred to herein as “Zn-CIT-6”.
Another form of CIT-6 is where the molecular sieve is composed only of silicon oxide. This form of CIT-6 is referred to herein as “all-Si CIT-6”.
Zn-CIT-6 and all-Si CIT-6 each have the topology of zeolite beta.
In accordance with this invention, there is provided a molecular sieve comprising an oxide of silicon and an oxide of zinc and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework.
The present invention further provides such a molecular sieve having the topology of zeolite beta, and having a composition, as synthesized and in the anhydrous state, in terms of mole ratios as follows:
SiO
2
/ZnO 10-100
M/SiO
2
0.01-0.1
Q/SiO
2
0.07-0.14
wherein M is lithium or a mixture of lithium and another alkali metal, and Q comprises a tetraethylammonium cation, wherein the molecular sieve contains zinc in its crystal framework.
Also in accordance with this invention there is provided a molecular sieve comprising silicon oxide, zinc oxide, and an oxide selected from aluminum oxide, boron oxide, gallium oxide, iron oxide, titanium oxide, vanadium oxide, zirconium oxide, tin-oxide or mixtures thereof and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework.
The present invention also provides such a molecular sieve having the topology of zeolite beta, and having a composition, as synthesized and in the anhydrous state, in terms of mole ratios as follows:
SiO
2
/ZnO 10-100
SiO
2
/W 30-250
M/SiO
2
0.01-0.1
Q/SiO
2
0.07-0.14
wherein W is an oxide of aluminum, boron, gallium, vanadium, iron, titanium or mixtures thereof M is lithium or a mixture of lithium and another alkali metal, and Q comprises a tetraethylammonium cation, wherein the molecular sieve contains zinc in its crystal framework.
Also provided in accordance with the present invention is a method of preparing a crystalline material comprising an oxide of silicon and an oxide of zinc and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework, said method comprising contacting in admixture under crystallization conditions sources of said oxides, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation.
The present invention also provides a method of preparing a crystalline material comprising an oxide of silicon, an oxide of zinc and an oxide selected from aluminum oxide, boron oxide, gallium oxide, vanadium oxide, iron oxide, titanium oxide or mixtures thereof and having the framework topology of zeolite beta, wherein the molecular sieve contains zinc in its crystal framework, said method comprising contacting in admixture under crystallization conditions sources of said oxides, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation.
Further provided by the present invention is a method of removing a tetraethylammonium organic template from the pores of a molecular sieve, said method comprising contacting the molecular sieve with acetic acid, or a mixture of acetic acid and pyridine at elevated temperature for a time sufficient to remove essentially all of the tetraethylammonium organic template from the molecular sieve. In a preferred embodiment, the molecular sieve has the topology of zeolite beta.
The present invention further provides a method of removing an organic template from the pores of a molecular sieve and at the same time removing zinc atoms from the framework of the molecular sieve, wherein the molecular sieve comprises an oxide of silicon, an oxide of zinc and, optionally an oxide selected from aluminum oxide, boron oxide, gallium oxide, vanadium oxide, iron oxide, titanium oxide or mixtures thereof, and has the framework topology of zeolite beta, said method comprising contacting the molecular sieve with acetic acid or a mixture of acetic acid and pyridine at elevated temperature for a time sufficient to remove essentially all of the organic template and zinc from the molecular sieve. The present invention also provides the product of this method.
Also provided by the present invention is a method of making a crystalline material comprising (1) contacting in admixture under crystallization conditions a source of silicon oxide, a source of zinc oxide, a source of lithium or a mixture of lithium and another alkali metal and a templating agent comprising a tetraethylammonium cation until a crystalline material comprised of oxides of silicon and zinc and having the topology of zeolite beta is formed, (2) contacting the crystals with acetic acid or a mixture of acetic acid and pyridine at an elevated temperature of about 60° C. or less for a time sufficient to remove essentially all of the organic template and zinc from the crystals, and (3) contacting the crystals with a solution containing a source of aluminum, boron, gallium, iron, vanadium, titanium, zirconium, tin or mixtures thereof. The present invention also provides the product of this method.
This invention also provides a crystalline molecular sieve having the topology of zeolite beta, a crystal size of less than one micron and a water adsorption capacity of less than 0.05 g/g of molecular sieve.
Further provided by the present invention is a crystalline silicate molecular sieve having the topology of zeolite beta, a crystal size of less than one micron and a water adsorption capacity of less than 0.05 g/g of molecular sieve.
In addition, the present invention provides a method of preparing a crystalline material having the topology of zeolite beta comprising impregnating a silica-containing mesoporous material with an aqueous solution comprising tetraethylammonium cation in an amount sufficient to form a crystalline product having the topology of zeolite beta, and wherein the water to mesoporous material molar ratio is from about 0.5 to about 2, and subjecting the impregnated mesoporous material to crystallizing conditions of heat and pressure for a time sufficient to form crystals of a material having the topology of zeolite beta.
The present invention additionally provides a process for converting hydrocarbons comprising contacting a hydrocarbonaceous feed at hydrocarbon converting conditions with a catalyst comprising a catalytically active molecular sieve comprising silicon oxide, zinc oxide, and an oxide selected from aluminum oxide, boron oxide, gallium oxide, iron oxide, zirconium oxide, tin
Davis Mark E.
Takewaki Takahiko
California Institute of Technology
Sample David
Sheridan Richard J.
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