Catalyst – solid sorbent – or support therefor: product or process – Zeolite or clay – including gallium analogs – And additional al or si containing component
Reexamination Certificate
1999-01-15
2001-05-29
Dunn, Tom (Department: 1754)
Catalyst, solid sorbent, or support therefor: product or process
Zeolite or clay, including gallium analogs
And additional al or si containing component
C502S064000, C502S071000, C502S074000
Reexamination Certificate
active
06239057
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a catalyst for producing higher carbon number hydrocarbons from low carbon number hydrocarbons, such as methane. The catalyst comprises a porous support having dispersed thereon rhenium and a metal selected from the group consisting of iron, cobalt, vanadium, manganese, molybdenum, tungsten and mixtures thereof. An example of the porous support is zeolite ZSM-5. This invention also relates to a process for preparing the catalyst and a process for producing higher carbon number hydrocarbons using the catalyst. The process for preparing higher carbon number hydrocarbons comprises contacting low carbon number aliphatic hydrocarbons with a catalyst in the presence of CO or CO
2
at conversion conditions to produce the higher carbon number hydrocarbons.
BACKGROUND OF THE INVENTION
It is well known to produce aromatic compounds such as benzene, toluene and xylenes from petroleum naphtha streams. Attempts have also been made to produce useful aromatic compounds from low molecular weight aliphatic compounds by, for example, the pyrolysis of natural gas, acetylene and other gases. However, this technique produces benzene and other useful aromatic compounds in very low yields while producing large amounts of tar, insoluble carbon residue and high molecular weight aromatic compounds, all of which are of little commercial use. Specifically, in the pyrolysis of methane and acetylene, the reaction is carried out at a temperature of about 1,000° C. or higher with a conversion rate of only a few percent and a selectivity to naphthalenes of less than 1%. Consequently, this method has little practical application.
There are reports in the art of processes for converting natural gas into aromatic compounds. For example, U.S. Pat. No. 5,288,935 discloses a process for producing liquid hydrocarbons from natural gas, in which natural gas is first separated into a methane rich fraction and a C
2
+ fraction, the methane is then selectively oxidized with oxygen, the effluent from the selective oxidation is then mixed with a part of the C
2
+ fraction and pyrolyzing the resulting mixture to obtain an aromatic product. The final step is carried out at a temperature of about 300° C. to about 750° C. in the presence of an aromatizing catalyst consisting essentially of a zeolite, gallium, at least one metal from the Group VIII metals and rhenium and at least one additional metal selected from the group consisting of: tin, germanium, lead, indium, thallium, copper, gold, nickel, iron, chromium, molybdenum and tungsten; an alkaline metal or alkaline earth metal and an aluminum matrix.
It is also known that the dehydrocondensation of methane with CO or CO
2
to form benzene and naphthalene can be carried out using a molybdenum/HZSM-5 or iron/cobalt modified Mo/HZSM-5. S. Liu, Q. Dong, R. Ohonishi and M. Ichikawa,
Chem. Commun
. (1998), p. 1217-1218, and S. Liu, L. Wang, Q. Dong, R. Ohonishi, and M. Ichikawa,
Stud. Surf. Sci. Catal
., Vol. 119, p. 241-246. In contrast to this art, applicants have developed a novel catalyst which comprises rhenium on a porous support such as a zeolite and which optionally can contain other metals such as iron, cobalt, platinum and molybdenum. It has been found that the catalysts of the present invention have higher activities for converting methane to benzene and also have a higher selectivity for the higher carbon number hydrocarbon products such as benzene, toluene and xylene and ethane and ethylene.
SUMMARY OF THE INVENTION
As stated, the present invention relates to a catalyst for converting low carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons, a process for preparing the catalyst, and a process for converting low carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons. Accordingly, one embodiment of the invention is a catalyst for converting low carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons comprising a porous support having dispersed thereon rhenium and a promoter metal selected from the group consisting of iron, cobalt, vanadium, gallium, zinc, chromium, manganese, molybdenum, tungsten and mixtures thereof. Another embodiment of the invention is a process for preparing the catalyst described above, the process comprising impregnating the support with a rhenium compound and a promoter metal compound, calcining the impregnated support at calcination conditions to give a calcined product and treating the calcined product with hydrogen and methane at treatment conditions to give the catalyst.
Yet another embodiment of the invention is a process for converting low carbon number aliphatic hydrocarbons to higher carbon number hydrocarbons comprising contacting the low carbon number aliphatic hydrocarbons at conditions to give the higher carbon number hydrocarbons. These and other objects and embodiments will become more apparent after a detailed description of the invention.
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Ichikawa Masaru
Ohnishi Ryuichiro
Wang Linsheng
Dunn Tom
Molinaro Frank S.
Tolomei John G.
UOP LLC
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