Chemistry of inorganic compounds – Zeolite – Organic compound used to form zeolite
Reexamination Certificate
2001-08-30
2004-03-23
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
Organic compound used to form zeolite
C423S712000, C423S716000, C423S213200, C423S213500, C423S239200, C095S090000, C564S474000, C564S479000, C585S640000
Reexamination Certificate
active
06709644
ABSTRACT:
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to crystalline zeolite SSZ-62 that has the CHA crystal structure, a mole ratio greater than 10 of silicon oxide to aluminum oxide and has a crystallite size of 0.5 micron or less. The present invention also relates to a method for preparing SSZ-62 using specific sources of silicon and aluminum, and a N,N,N-trimethyl-1-adamantammonium cation templating agent, to processes employing SSZ-62 as a catalyst, and to processes using SSZ-62 to separate gasses.
SUMMARY OF THE INVENTION
The present invention is directed to a family of crystalline molecular sieves with unique properties, referred to herein as “zeolite SSZ-62” or simply “SSZ-62”. Preferably, SSZ-62 is obtained in its aluminosilicate form. As used herein, the term “aluminosilicate” refers to a zeolite containing both alumina and silica.
In accordance with this invention, there is provided a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of an oxide of a first tetravalent element to an oxide of a second tetravalent element which is different from said first tetravalent element, trivalent element, pentavalent element or mixture thereof and having a crystallite size of 0.5 micron or less.
In accordance with the present invention, there is also provided a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of silicon oxide to aluminum oxide, and having a crystallite size of 0.5 micron or less.
Also provided in accordance with the present invention is a method of preparing a aluminosilicate crystalline material having the CHA crystal structure and a crystallite size of 0.5 micron or less, said method comprising contacting under crystallization conditions an aluminum hydroxide gel dried to about 50 wt. % Al
2
O
3
with a slight alkalinity and the ability to absorb CO
2
and solubilize rapidly in water, precipitated silica with a water content of about 5-15 wt. %, and a templating agent comprising a N,N,N-trimethyl-1-adamantammonium cation.
This invention also provides a process for converting lower alcohols and other oxygenated hydrocarbons comprising contacting said lower alcohol or other oxygenated hydrocarbon under conditions to produce liquid products with a catalyst comprising a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of silicon oxide to aluminum oxide and having a crystallite size of about 0.5 micron or less.
Also provided by the present invention is an improved process for the reduction of oxides of nitrogen contained in a gas stream in the presence of oxygen wherein said process comprises contacting the gas stream with a zeolite, the improvement comprising using as the zeolite a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of silicon oxide to aluminum oxide and having a crystallite size of 0.5 micron or less. The zeolite may contain a metal or metal ions (such as cobalt, copper or mixtures thereof) capable of catalyzing the reduction of the oxides of nitrogen, and may be conducted in the presence of a stoichiometric excess of oxygen. In a preferred embodiment, the gas stream is the exhaust stream of an internal combustion engine.
The present invention further provides a process for producing dimethylamine comprising reacting methanol and/or dimethyl ether and ammonia in the gaseous phase in the presence of a catalyst comprising a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of silicon oxide to aluminum oxide and having a crystallite size of 0.5 micron or less.
Further provided by the present invention is an improved process for separating gasses using a membrane containing a zeolite, the improvement being the use in the membrane of a zeolite having the CHA crystal structure, a mole ratio greater than about 10 of silicon oxide to aluminum oxide and having a crystallite size of 0.5 micron or less.
DETAILED DESCRIPTION OF THE INVENTION
In preparing SSZ-62 zeolites, a N,N,N-trimethyl-1-adamantammonium cation is used as a crystallization template or structure directing agent (“SDA”). In general, SSZ-62 is prepared by contacting an aluminum hydroxide gel dried to about 50 wt. % Al
2
O
3
with a slight alkalinity and the ability to absorb CO
2
and solubilize rapidly in water, precipitated silica with a water content of about 5-15 wt. % with the SDA in an aqueous solution.
SSZ-62 is prepared from a reaction mixture having the composition shown in Table A below. Silicon- and aluminum-containing reactants are expressed as SiO
2
and Al
2
O
3
, respectively.
TABLE 1
Reaction Mixture
Typical
Preferred
SiO
2
/Al
2
O
3
20-50
25-40
OH—/SiO
2
0.15-0.40
0.25-0.40
Q/SiO
2
0.10-0.35
0.18-0.22
M
2
/SiO
2
0.05-0.20
0.12-0.18
H
2
O/SiO
2
10-25
12-20
where Q is the SDA, M is alkali metal or alkaline earth metal, and n is the valence of M.
In practice, SSZ-62 is prepared by a process comprising:
(a) preparing an aqueous solution containing an aluminum hydroxide gel dried to about 50 wt. % Al
2
O
3
with a slight alkalinity and the ability to absorb CO
2
and solubilize rapidly in water, precipitated silica with a water content of about 5-15 wt. % and a N,N,N-trimethyl-1-adamantammonium cation having an anionic counterion which is not detrimental to the formation of SSZ-62;
(b) maintaining the aqueous solution under conditions sufficient to form crystals of SSZ-62; and
(c) recovering the crystals of SSZ-62.
The source of silicon is precipitated silica with a water content of about 5-15 wt. %. An example of such a material is HiSil 233 available from PPG Industries, Inc.
The source of aluminum is an aluminum hydroxide gel dried to about 50 wt. % Al
2
O
3
. The gel has slight alkalinity and is able to absorb CO
2
. It is rapidly soluble in water. The aluminum hydroxide has a particle density of less than about 1.0 g/cm
3
, preferably less than about 0.9 g/cm
3
, more preferably less than about 0.8 g/cm
3
and most preferably in the range of about 0.1 g/cm
3
to about 0.8 g/cm
3
. An example of such a material is Reheis F-2000 available from Reheis Chemical Co.
The aluminum hydroxide, as added to the reaction mixture, further has an average particle size of less than about 40 microns, preferably less than about 25 microns, more preferably less than about 15 microns, still more preferably less than about 10 microns, and most preferably within the range of about 0.1 to 10 microns, with preferably less than about 25% of the particulates having a particle size outside the range of about 0.1 to 40 microns. In a more preferred embodiment, less than about 25%, even more preferably less than 10% of the particles have a particle size outside the range of about 0.1 to about 25 microns.
The aluminum hydroxide gel has a low alkali level before it is added to the reaction mixture. The gel contains less than about 0.12 wt. % and preferably less than 0.10 wt. % alkali. It is most preferred that the gel have an alkali content in the range of about 0.01 wt. % to about 0.10 wt. % where alkali may be one or more of the Group IA elements.
Typically, an alkali metal hydroxide and/or an alkaline earth metal hydroxide, such as the hydroxide of sodium, potassium, lithium, cesium, rubidium, calcium, and magnesium, is used in the reaction mixture; however, this component can be omitted so long as the equivalent basicity is maintained. The templating agent may be used to provide hydroxide ion. Thus, it may be beneficial to ion exchange, for example, the halide for hydroxide ion, thereby reducing or eliminating the alkali metal hydroxide quantity required. The alkali metal cation or alkaline earth cation may be part of the as-synthesized crystalline oxide material, in order to balance valence electron charges therein.
The SDA used to prepare SSZ-62 is a N,N,N-trimethyl-1-adamantammonium cation having the following structure:
The anion (X
−
) associated with the cation may be any anion which is not detrimental to the formation of the zeolite. Representative anions include halogen, e.g., fluoride, chloride, bromide and iodide, hydroxid
Miller Stephen J.
Yuen Lun-Teh
Zones Stacey I.
Chevron U.S.A. Inc.
Sample David
Sheridan Richard J.
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