Chemistry of hydrocarbon compounds – Unsaturated compound synthesis – By dehydrogenation
Reexamination Certificate
2001-01-16
2003-04-29
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Unsaturated compound synthesis
By dehydrogenation
C585S660000, C585S662000, C585S663000
Reexamination Certificate
active
06555724
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process and catalyst for the dehydrogenation of hydrocarbons. More particularly, this invention relates to a catalyst and process for the dehydrogenation of paraffinic hydrocarbon utilizing a catalyst comprising a platinum group metal component, a zinc component and a magnesium component on a support component comprising ZSM or borosilicate, useful for the production of chemical industry feedstocks.
Propylene, also termed propene, is a commercially valuable feedstock employed in the manufacture of polypropylene, acrylonitrile, and propylene oxide. More than ninety-five percent of propylene is presently produced as a byproduct of olefins cracking and recovered. Propane dehydrogenation (hereinafter referred to as “PDH”) is an alternative route for producing propylene. However, previously known PDH processes have been hampered by relatively low chemical conversion of propane.
Processes for dehydrogenating paraffins in the presence of hydrogen and a catalyst comprising a platinum group metal on an amorphous alumina support have been disclosed in the art.
For example, U.S. Pat. Nos. 4,190,521, 4,374,046, and 4,458,098 to Antos disclose a catalyst comprising a platinum group component, nickel, and a zinc on a porous carrier material such as alumina for dehydrogenating paraffinic hydrocarbon.
U.S. Pat. No. 4,438,288 to Imai et al. discloses a dehydrogenation process using a catalyst comprising a platinum group component, an alkali or alkaline earth component, and optionally a Group IV component such as tin, on a porous support material such as alumina. The properties and characteristics of the catalyst generally necessitate periodic catalyst regeneration in the presence of a halogen.
Processes for dehydrogenating paraffins in the presence of hydrogen and a catalyst comprising a platinum group metal on an aluminosilicate or silicalite molecular sieve support have also been disclosed in the art.
For example, U.S. Pat. Nos. 4,665,267 and 4,795,732 to Barn and U.S. Pat. Nos. 5,208,201, and 5,126,502 to Barn et al. disclose processes for dehydrogenation of 2 to 30 paraffins using a catalyst comprising zinc and a platinum group metal on a support having the silicalite structure wherein the framework of the structure consists essentially of silicon and oxygen atoms or of silicon, zinc, and oxygen atoms. The catalyst is generally formed such that it is substantially free of all alkali or alkaline earth metals.
U.S. Pat. No. 4,727,216 to Miller discloses a process for dehydrogenating isobutane in the presence of a sulfur-containing gas and a dehydrogenation catalyst. The dehydrogenation catalyst comprises a sulfided L zeolite containing from 8-10% by weight barium, from 0.6-1.0% platinum, and tin at an atomic ratio with the platinum of about 1:1. The dehydrogenation catalyst further comprises an inorganic binder selected from the group consisting of silica, alumina, and aluminosilicates.
A process for dehydrogenating paraffins in the presence of hydrogen and a catalyst comprising a platinum group metal on a non-zeolitic borosilicate molecular sieve support has been disclosed in the art.
U.S. Pat. No. 4,433,190 to Sikkenga et. al. discloses a process for dehydrogenating and isomerizing a substantially linear alkane using a dehydrogenation catalyst comprising an AMS-1B crystalline borosilicate-based catalyst composition and containing a noble metal.
U.S. Pat. No. 6,103,103 to Alexander et. al. discloses a dehydrogenation process and catalyst comprising a platinum group metal and zinc on a support comprising borosilicate and an alkali metal which provides superior dehydrogenation performance in terms of paraffin conversion, olefin selectivity, and olefin yield which is superior to that of the prior art dehydrogenation catalysts and maintains such level of superior performance for an extended period of time.
Although previous researchers have recorded many important advances, as described above, a need still exists for an improved PDH catalyst and process. Chemical manufacturers would welcome an improved PDH catalyst and process which exhibits a relatively higher chemical conversion of propane and improved stability, as compared to previously known processes and catalysts.
For purposes of the present invention, paraffin conversion and olefin selectivity shall have the following meanings and shall be calculated by mole and in accordance with the following models:
Paraffin
Conversion
=
100
-
Mol
%
H
2
product
-
Mol
%
Paraffin
product
100
-
Mol
%
H
2
feed
×
100
Olefin
Selectivity
=
Mol
%
Olefin
product
100
-
Mol
%
H
2
product
-
Mol
%
Paraffin
product
×
100
It is therefore an object of the present invention to provide a dehydrogenation process and catalyst that effectively dehydrogenate paraffinic hydrocarbon.
It is another object of the present invention to provide a dehydrogenation catalyst that resists deactivation and prolongs catalyst cycle life under dehydrogenation conditions.
Other objects appear herein.
SUMMARY OF THE INVENTION
The above objects can be achieved by providing a dehydrogenation catalyst and a process employing such catalyst for dehydrogenating a hydrocarbon having from two to about 20 carbon atoms per molecule and producing an olefinic product, wherein the catalyst comprises from about 0.01 weight percent to about 2.0 weight percent of a platinum group metal-containing component, from about 0.01 weight percent to about 15.0 weight percent of a zinc-containing component, from about 0.01 weight percent to about 5.0 weight percent of a magnesium-containing component, and a support component comprising ZSM or borosilicate having a ZSM-type structure. The process comprises contacting the aforesaid hydrocarbon with the aforesaid catalyst under dehydrogenation conditions.
The dehydrogenation catalyst and process of the present invention provide superior overall dehydrogenation properties and particularly high levels of paraffin conversion that closely approach thermodynamic equilibrium, while resisting deactivation under dehydrogenation conditions, thereby extending catalyst life.
BRIEF DESCRIPTION OF THE INVENTION
In the process of the present invention, a chargestock containing hydrocarbon having from about two to about twenty carbon atoms per molecule, preferably from about two to about six carbon atoms per molecule, and most preferably about three carbon atoms per molecule, is exposed to a catalytic composition, as described below and at effective dehydrogenation conditions. The chargestock may additionally include hydrogen, steam, carbon dioxide, carbon monoxide, or nitrogen.
In one embodiment, the process of the present invention can be employed to dehydrogenate hydrocarbon as feed for commercial chemical manufacture. Feedstocks having from 2 to 4 carbon atoms can be dehydrogenated into olefinic feedstocks for the subsequent production of polyethylene, polypropylene, polybutene, or other chemical compositions that are commonly sold in solid or liquid forms.
In a second embodiment, the process of the present invention can be employed for dehydrogenating hydrocarbon for direct or eventual upgrade to ethers such as, but not limited to, MTBE, ETBE, and TAME. Feedstocks for use with the present invention and suitable for providing etherification feedstocks will generally comprise aliphatic or alicyclic hydrocarbon having from 3 to 7 carbon atoms. The preferred feedstocks generally comprise at least 5 weight percent paraffinic hydrocarbon and more preferably at least 10 weight percent paraffinic hydrocarbon to justify the capital and operating costs to perform dehydrogenation. Since most etherification processes convert branched olefins to ethers, the feedstock to such processes often must be isomerized prior to etherification. The
Alexander Bruce D.
Huff, Jr. George A.
BP Corporation North America Inc.
Dang Thuan D.
Henes James R.
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