Catalyst – solid sorbent – or support therefor: product or process – Catalyst or precursor therefor – Metal – metal oxide or metal hydroxide
Reexamination Certificate
2002-04-18
2003-10-28
Parsa, J. (Department: 1621)
Catalyst, solid sorbent, or support therefor: product or process
Catalyst or precursor therefor
Metal, metal oxide or metal hydroxide
C502S306000, C502S314000, C502S318000, C502S079000, C502S080000, C502S208000, C502S214000
Reexamination Certificate
active
06638892
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst composition having as components zinc oxide, copper oxide and aluminum oxide in combination with Y zeolite and clay suitable for the conversion of syngas, a mixture of hydrogen and carbon monoxide, to dimethyl ether and to the process for converting synthesis gas (syngas) to dimethyl ether employing this catalyst. This invention also relates to two-step processes for converting syngas to light olefins by contacting the effluent from a conversion of syngas employing a catalyst composition having as components zinc oxide, copper oxide and aluminum oxide in combination with Y zeolite and clay with a second catalyst system having a SAPO component such as, in particular, SAPO-34 or modified SAPO-34. This invention is further related to catalyst systems useful in the conversion of syngas to light olefins in two step processes.
BACKGROUND OF THE INVENTION
Catalysts having zinc oxide, copper oxide and aluminum oxide as components are known to be effective as methanol synthesis catalysts. Catalysts having as components zinc oxide, copper oxide and aluminum oxide or chromium oxide in conjunction with a gamma aluminum oxide are known to effect the conversion of syngas to dimethyl ether. The present invention provides an improved conversion and selectivity to dimethyl ether by replacing gamma aluminum oxide with a combination of Y zeolite and clay in a catalyst system useful for the conversion of syngas.
Processes for converting methanol and its derivatives, including dimethyl ether, to light olefins employing a SAPO catalyst are also known. U.S. Pat. No. 4,499,327 discloses the preparation of light olefins from dimethyl ether or methanol employing a SAPO catalyst, but does not disclose the preparation of dimethyl ether using the process cited above.
There is a growing interest in alternative liquid fuels produced from natural gas. Dimethyl ether is a clean and efficient alternative diesel fuel which can be produced by the dehydration of methanol which can be synthesized from syngas. There is a significant economic advantage in integrating the process for producing dimethyl ether from syngas into a single process. There is also a continued expansion of the uses to which light olefins can be put and therefore a commercial reward for improving the methods by which light olefins can be produced. Syngas has proved to be an attractive source from which light olefins can be obtained. Accordingly, development of these improved processes for converting syngas to dimethyl ether or light olefins and development of the catalyst systems useful in these processes would be a significant contribution to the art.
SUMMARY OF THE INVENTION
It is an object of this invention to provide an improved method for converting syngas to dimethyl ether. It is another object of this invention to use this improved process in two step processes for the conversion of syngas to light olefins. Still another object of this invention is to employ SAPO in the second step of converting dimethyl ether to light olefins in these two step processes for converting syngas to light olefins. Another object of the invention is to provide methods for converting dimethyl ether to light olefins that show improved results employing modified SAPO-34 as compared to the use of SAPO-34 in a two step process. A yet further object of this invention is to provide the catalyst systems useful in the conversions set out above. Other objects and advantages will be apparent from the detailed description and the appended claims.
In accordance with an embodiment of this invention a method is provided for converting syngas by contacting syngas under conversion conditions with a catalyst comprising zinc oxide, copper oxide, aluminum oxide, Y zeolite and clay.
In accordance with another embodiment of this invention a method is provided for the conversion of syngas to dimethyl ether (DME) by contacting syngas under conversion conditions with a catalyst comprising zinc oxide, copper oxide, aluminum oxide, Y zeolite and clay.
In accordance with still another embodiment of this invention a method is provided for the conversion of syngas to light olefins by contacting syngas under conversion conditions with (A) a first catalyst comprising zinc oxide, copper oxide, aluminum oxide, Y zeolite and clay under conditions for the conversion of syngas to dimethyl ether and then contacting the effluent from contact with the first catalyst with (B) a second catalyst comprising SAPO under conditions for the conversion of dimethyl ether to light olefins.
In accordance with other embodiments of this invention methods are provided for the conversion of syngas to light olefins in which the second catalyst is SAPO-34 and (1) the temperature of the second step is increased as compared to the temperature of the first step or (2) the temperature of the second step is increased as compared to the temperature of the first step and the pressure of the effluent from the contact with the first catalyst is reduced before contact with the second catalyst.
In accordance with other embodiments of this invention methods are provided for the conversion of syngas to light olefins in which the second catalyst is a modified SAPO-34 such as SAPO-34 modified with lanthanum(III) nitrate hexahydrate; SAPO-34 modified with magnesium hydrate hexahydrate; SAPO-34 modified with tributyl borate or SAPO-34 modified with triethyl phosphate.
Other objects and advantages of the invention will become apparent from the detailed description and the appended claims.
DETAILED DESCRIPTION OF THE INVENTION
For the purposes of this disclosure the citing in the specification, claims or abstract of a component or components should be construed as including a restrictive phrase chosen from among the following: in the broadest sense as not excluding the presence of other components, i.e. “comprising”; in a more restricted sense as containing only the material cited as essential to the invention with no other material present in an amount to affect the invention, i.e. “consisting essentially of”, and in the most restricted sense as the presence of only the material cited, i.e. “consisting of”. The use of any of the quoted phrases limits the disclosed component or components in the sense defined above.
Synthesis gas (syngas) is a gaseous mixture of hydrogen and at least one carbon oxide, particularly carbon monoxide. Syngas is obtained using well known processes by the partial combustion or gasification of any organic material such as coal, other hydrocarbons, carbohydrates and the like. It is well known that Syngas can be subjected to a heterogeneous catalytic reaction using a copper-based catalyst such as copper oxide, zinc oxide and aluminum oxide to produce methanol. This is the same catalyst that is used in this invention along with Y zeolite and clay to produce dimethyl ether.
The Y zeolite useful in the production of dimethyl ether is well known and a typical synthetic zeolite usually prepared in the sodium form, that is, with a sodium cation in close proximity to each aluminum tetrahedron thereby balancing its charge. Type Y zeolite has a ratio of Al
2
O
3
to SiO
2
in the range of about Al
2
O
3
/3.0-6.0 SiO
2
and an effective pore size of approximately 7.4 Angstroms.
In the integrated process for producing dimethyl ether from syngas a commercial methanol catalyst, having copper oxide, zinc oxide and aluminum oxide as components is combined with Y zeolite, a clay component, preferably Bentonite, and sufficient water to form a paste which is then extruded, dried and then calcined to provide a catalyst mixture. The copper oxide is present in a range of about 20 percent by weight to about 40 percent by weight, preferably about 25 percent by weight to about 35 percent by weight. The zinc oxide is present in a range of about 5 percent by weight to about 25 percent by weight, preferably about 10 percent by weight to about 20 percent by weight. The aluminum oxide is present in a finite range of up to about 15 percent by weight, preferably up to about 10 pe
Drake Charles A.
Wu An-hsiang
Yao Jianhua
ConocoPhillips Company
Cross Ryan N.
Parsa J.
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