Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,... – Hydrocarbon is contaminant in desired hydrocarbon
Reexamination Certificate
1999-07-22
2001-05-01
Griffin, Walter D. (Department: 1764)
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
Hydrocarbon is contaminant in desired hydrocarbon
C585S258000, C585S810000, C208S296000
Reexamination Certificate
active
06225515
ABSTRACT:
BACKGROUND OF THE INVENTION
The field of art to which this invention pertains is the purification of a diolefin hydrocarbon stream containing trace quantities of acetylene compounds. The production of diolefins is well known and widely practiced to produce a wide variety of products and precursor products utilizing a variety of diolefin production processes including naphtha cracking processes and by-products from fluid catalytic cracking processes. Most of these diolefin production processes produce undesirable trace quantities of acetylene. One technique which is used purify diolefin streams selectively hydrogenates the acetylene while minimizing the destruction or hydrogenation of the diolefin compounds.
The selective hydrogenation of the acetylene compounds is generally conducted in the presence of a selective hydrogenation catalyst and hydrogen and conducted at an elevated pressure and temperature. Such selective hydrogenation catalysts are well known in the art and include, for example, a catalyst containing copper metal associated with one or more activator metals impregnated on an alumina support. During the acetylene hydrogenation polymers are formed and deposited on the catalyst thereby reducing the activity of the catalyst. One known method of regenerating spent or partially spent catalyst is to perform a controlled carbon bum and subsequent metal reduction to remove catalyst contaminants which are formed as an undesirable by-product of the acetylene hydrogenation. The carbon bum regeneration techniques necessarily require that the reaction zone containing the spent catalyst be taken off-line and that ancillary regeneration equipment be provided.
INFORMATION DISCLOSURE
U.S. Pat. No. 3,634,536 (Frevel et al) discloses a process for selectively hydrogenating acetylenic impurities in an isopropene- or butadiene-containing stream whereby carbon monoxide is utilized during hydrogenation over a copper-based catalyst.
U.S. Pat. No. 4,440,956 (Couvillion) discloses a catalyst for the removal of acetylenes from liquid hydrocarbon streams with a minimum loss of diolefinic unsaturation present in the liquid composition.
Although a wide variety of process flow schemes, operating conditions and catalysts have been used in commercial activities, there is always a demand for new selective hydrotreating processes which provide lower costs, higher selectivity and longer on-stream operation.
The present invention is able to maintain the high activity of the selective hydrogenation catalyst by discontinuing the flow of diolefinic hydrocarbon feedstock to at least one off-line hydrogenation reaction zone and contacting the at least partially spent catalyst with hydrogen and a polymer solvent in order to recover at least a portion of the lost activity.
BRIEF SUMMARY OF THE INVENTION
The present invention is a selective acetylene hydrogenation process which is able to produce a high quality diolefin hydrocarbon having extremely low levels of acetylene over an extended period because of the ability to readily regenerate catalyst contained in an off-line reaction zone while continuing to operate an on-line selective hydrogenation reaction zone. The spent or partially spent catalyst is contacted with hydrogen and a polymer solvent in order to restore at least a portion of the fresh catalyst activity.
In accordance with one embodiment, the present invention relates to a process for the purification of a diolefin hydrocarbon stream containing trace quantities of acetylene compounds and the cyclic regeneration of an at least partially spent selective hydrogenation catalyst which process comprises: (a) introducing the diolefin hydrocarbon stream containing trace quantities of acetylene compounds and elemental hydrogen into a selective hydrogenation zone to selectively hydrogenate at least a portion of the acetylene compounds and to produce an at least partially spent selective hydrogenation catalyst; (b) passing the resulting effluent from the selective hydrogenation zone in step (a) to a fractionation zone to produce a diolefin hydrocarbon stream having a reduced concentration of acetylene compounds; (c) contacting the at least partially spent selective hydrogenation catalyst in the selective hydrogenation zone with a polymer solvent and hydrogen to reduce the polymer content of the selective hydrogenation catalyst to thereby increase hydrogenation activity; (d) passing the resulting effluent from the selective hydrogenation zone to the fractionation zone to produce a stream comprising polymer solvents and polymer compounds; (e) recycling at least a portion of the stream comprising polymer solvent and polymer compounds to provide at least a portion of the polymer solvent in step (c); (f) recovering at least another portion of the stream comprising polymer solvent and polymer compounds; (g) recovering the diolefinic hydrocarbon stream having a reduced concentration of acetylene compounds produced in step (b); and (h) introducing the diolefin hydrocarbon stream containing trace quantities of acetylene compounds and elemental hydrogen into the selective hydrogenation zone after contact with the polymer solvent and hydrogen.
In accordance with another embodiment, the present invention relates to a process for the purification of a butadiene hydrocarbon stream containing trace quantities of acetylene compounds and the cyclic regeneration of an at least partially spent selective hydrogenation catalyst which process comprises: (a) introducing the butadiene hydrocarbon stream containing trace quantities of acetylene compounds and elemental hydrogen into a selective hydrogenation zone to selectively hydrogenate at least a portion of the acetylene compounds and to produce an at least partially spent selective hydrogenation catalyst; (b) passing the resulting effluent from the first selective hydrogenation zone in step (a) to a fractionation zone to produce a butadiene hydrocarbon stream having a reduced concentration of acetylene compounds; (c) contacting the at least partially spent selective hydrogenation catalyst in the selective hydrogenation zone with a hexane solvent and hydrogen to reduce the polymer content of the selective hydrogenation catalyst to thereby increase hydrogenation activity; (d) passing the resulting effluent from the selective hydrogenation zone to the fractionation zone to produce a stream comprising hexane solvent and polymer compounds; (e) recycling at least a portion of the stream comprising hexane solvent and polymer compounds to provide at least a portion of the hexane solvent in step (c); (f) recovering at least another portion of the stream comprising hexane solvent and polymer compounds; (g) recovering the butadiene hydrocarbon stream having a reduced concentration of acetylene compounds produced in step (b); and (h) introducing the butadiene hydrocarbon stream containing trace quantities of acetylene compounds and elemental hydrogen into the selective hydrogenation zone after contact with the hexane solvent and hydrogen.
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patent: 4277313 (1981-07-01), Mehra et al.
patent: 4440956 (1984-04-01), Couvillion
patent: 4831200 (1989-05-01), Debras et al.
patent: 6040489 (2000-03-01), Imai
Cutts, Jr. John G.
Griffin Walter D.
Preisch Nadine
Tolomei John G.
UOP LLC
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