Chemistry of hydrocarbon compounds – Purification – separation – or recovery – By plural serial diverse separations
Reexamination Certificate
2000-05-08
2002-05-14
Dang, Thuan D. (Department: 1764)
Chemistry of hydrocarbon compounds
Purification, separation, or recovery
By plural serial diverse separations
C585S254000, C585S260000, C585S261000, C585S262000
Reexamination Certificate
active
06388162
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to a process of removing dienes from an olefin feedstock. A preferred olefin feedstock is for the production of primary alcohol compositions by skeletal isomerization of the olefins followed by hydroformylation. The olefin feedstock may be purified before and/or after skeletal isomerization. The olefins in the feedstock preferably have a carbon chain length of about 8 to about 36 carbon atoms, preferably about 10 to about 20 carbon atoms, most preferably about 12 to about 18 carbon atoms.
BACKGROUND OF THE INVENTION
Alcohols of long chain olefins having about 10 to 28 carbon atoms have considerable commercial importance in a variety of applications, including detergents, soaps, surfactants, and freeze point depressants in lubricating oils. These alcohols are produced by a number of commercial processes, such as by oxo or hydroformylation of long chain olefins. Typical commercially available long chain alcohols are the NEODOL® alcohols available from Shell Chemical Company, the EXXAL® alcohols available from Exxon Chemical Company, and the LIAL® alcohols available from Enichem.
In the manufacture of the NEODOL® alcohols, a redominantly linear olefin feed is subjected to hydroformylation by reacting carbon monoxide and hydrogen onto the olefin in the presence of an oxo catalyst to form an alcohol. Over 80% of the alcohol molecules in the resulting alcohol are linear primary alcohols. Of the branched primary alcohols in the composition, most, if not all of the branching is on the C2 carbon atom relative to the hydroxyl bearing carbon atom. These alcohols subsequently can be converted to anionic or nonionic detergents or general surfactants by sulfonation or ethoxylation of the alcohol, or by conversion of the alcohol to an alcohol-ethoxysulfate.
The NEODOL® alcohols are commercially successful intermediates to the production of detergents. One reason for this success undoubtedly is that the NEODOL® alcohols are economically produced with high yields of linear alcohols. The sulfonates of linear alcohols are more biodegradable than the sulfonates of branched long chain alcohols. Since detergents and soaps used by consumers for washing ultimately are released into the environment, the need for surfactants or detergents with maximal biodegradability is well recognized.
The highly linear NEODOL® alcohols have the advantage of a high level of biodegradability; however, the high degree of linearity of these alcohols also increases their hydrophobicity, thereby decreasing their cold water solubility/detergency. Government regulations call for both increased biodegradability and increased solubility.
Alcohols that have been found to meet both the biodegradability and the solubility government standards are branched primary alcohols (and their sulfate derivatives): having about 8 to about 36 carbon atoms; having an average number of branches per molecular chain of at least 0.7 (defined below); having less than 0.5 atom % of quaternary carbon atoms; and, having at least methyl and ethyl branching. These alcohols, as well as a method for preparing them, are described in U.S. Pat. No. 5,849,960, incorporated herein by reference. The method basically involves contacting a feed comprising linear olefins having 7 to 35 carbon atoms with a skeletal isomerization catalyst, and converting the resulting skeletally isomerized olefin to a saturated branched primary alcohol, preferably by hydroformylation.
Unfortunately, olefin feedstreams have been found to contain at least some level of dienes. Dienes can lower the catalytic performance of many commonly used catalysts, such as those used for skeletal isomerization of olefins and those used for hydroformylation.
SUMMARY OF THE INVENTION
The present invention provides a method for purifying an olefin stream comprising: providing an olefin feedstock wherein the olefins have an average molecular chain length of from about 8 to about 32 carbon atoms, the olefin feedstock comprising a first quantity of dienes; and, contacting the olefin feedstock with a hydrogenation catalyst and a gas feed comprising hydrogen at a feedstock flow rate and under conditions effective to reduce the first quantity of dienes to a second quantity of dienes without substantially increasing final paraffin content in the olefin feedstock.
DETAILED DESCRIPTION OF THE INVENTION
Typical olefin feedstocks comprise from about 100 to about 2000 ppm dienes. The invention pertains to a method for removing these dienes or, more specifically, for selectively converting these dienes to olefins with minimal production of paraffins.
Olefin feedstocks from substantially any source may be treated according to the invention to remove dienes. The invention is not limited to the treatment of olefin feedstocks which are to be subjected to skeletal isomerization and/or to hydroformylation. However, preferred feedstocks are olefin feedstocks which are to be subjected to skeletal isomerization and/or to hydroformylation to produce branched primary alcohols such as those produced in U.S. Pat. No. 5,849,960, incorporated herein by reference. With respect to the process described in that patent, the olefin feedstock may be treated to remove or convert dienes either before or after skeletal isomerization. The method preferably converts about 60 wt. % or more of the dienes to olefins without producing more than about 1 wt. % paraffins.
In order to accomplish the required selective conversion of dienes to olefins, one of the unsaturated carbon-carbon bonds in the dienes is selectively hydrogenated, leaving a monoolefin. The invention accomplishes this selective hydrogenation by feeding the olefin feedstock at a relatively slow (trickle flow) rate to a known, selective hydrogenation catalyst in the presence of a reduced hydrogen content reaction gas.
Any suitable low activity/high selectivity (or “mild”) hydrogenation catalyst may be used. Suitable catalysts typically comprise, on a suitable support, a metal selected from Groups 9, 10, or 11 of the Periodic Table of the Elements, F. Cotton et al.
Advanced Inorganic Chemistry
(Fifth Ed. 1998). Preferred metals for use as a catalytic agent in the present process are Co, Ni, Pd, and Pt, most preferably palladium, either alone or alloyed with Ag, Cu, Co, and combinations thereof. The reactivity of the catalyst may be reduced to achieve selectivity by using less of a more active metal on the support or by using a less reactive metal. Where palladium is used as the catalytic agent, the concentration of palladium on a support is from about 0.05 to about 0.5 wt. %, preferably about 0.05 to about 0.2 wt. %.
Examples of suitable supports for the catalytic metal include, but are not necessarily limited to aluminas, silicas, molecular sieves, activated carbon, aluminosilicate clays, and amorphous silicoaluminas, preferably alumna, silica and carbon. Most preferred support materials are alumina and silica. Preferred supports have up to about 15 m
2
/g surface area, and preferably have from about 2 to about 5 m
2
/g surface area. A most preferred catalyst for use in the present invention comprises palladium on an alumina support.
The catalyst may or may not be modified using a suitable promotor, such as chromium, barium, or lanthanium. A preferred promoter is chromium at a preferred concentration of from about 0.05 to about 0.2 wt. %, preferably about 0.05 wt. %. Where chromium is used as a promoter, other suitable additives which may be used at from about 0.05 to 0.25 wt %, preferably about 0.05 wt %, include, but are not necessarily limited to Ba, La, Dy, Ce, Nb, or Sm, preferably Ba or La. A preferred commercially available catalyst is K-8327, a palladium on aluminum catalyst available from W.C. Heraeus GmbH, Catalyst Department PKT, Heraeusstrasse 12-1, D-63450 Hanau, Germany.
Surprisingly, the catalysts preferably are used in a fixed bed trickle flow reaction mode at low feed flow. Persons of ordinary skill in the art would expect that a relatively long exposure time between the feedstock and the catalyst in a trickle fl
Bolinger Cornelius Mark
Himelfarb Paul B.
Dang Thuan D.
Shell Oil Company
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