Chemistry of hydrocarbon compounds – Adding hydrogen to unsaturated bond of hydrocarbon – i.e.,... – Hydrocarbon is contaminant in desired hydrocarbon
Patent
1997-08-26
2000-06-06
Yildirim, Bekir L.
Chemistry of hydrocarbon compounds
Adding hydrogen to unsaturated bond of hydrocarbon, i.e.,...
Hydrocarbon is contaminant in desired hydrocarbon
585261, 585264, 585275, 585277, 585841, 208144, C07C 7163, C07C 502
Patent
active
060720913
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This application is the national stage of PCT/FR96/02085, Dec. 27, 1996.
The invention concerns a process for the treatment of a feed partially constituted by hydrocarbons containing at least 3 carbon atoms per molecule, among them acetylenic and diolefinic hydrocarbons, also traces of arsine (AsH.sub.3), carbonyl sulphide (COS) and alkylthiols (mercaptans). The process consists of treating the feed in a distillation column comprising a stripping zone and a rectification zone associated with a hydrogenation reaction zone comprising at least one catalytic bed in which at least a portion of the acetylenic and diolefinic compounds contained in the feed for (or to) the hydrogenation zone is hydrogenated, the feed being drawn off from at least one draw-off level and representing at least a portion of the liquid flowing in the rectification zone, at least a portion of the effluent from the reaction zone being reintroduced into the rectification zone to ensure continuity of distillation so as to produce an effluent from the head of the distillation column which is highly depleted in acetylenic and diolefinic hydrocarbons containing at most 5 carbon atoms, and an effluent from the bottom of the distillation column which is also depleted in these compounds.
The process of the invention can also affect addition of light alkylthiols (methyl mercaptan and ethyl mercaptan) in the reaction zone to diolefinic hydrocarbons containing at most 5 carbon atoms, producing heavy thioethers containing at least 5 carbon atoms and boiling in the range of hydrocarbons containing at least 6 carbon atoms. The effluent from the reaction zone is reintroduced into the rectification zone so as to produce an effluent from the head of the rectification zone which is highly depleted in light alkylthiols and an effluent from the bottom of the distillation column which comprises thioethers containing at least 5 carbon atoms.
BACKGROUND OF THE INVENTION
Various processes used in the oil industry, such as thermal cracking, coking, visbreaking, catalytic cracking and steam cracking, produce large quantities of light olefinic hydrocarbon cuts which also contain acetylenic and diolefinic hydrocarbons.
The subsequent uses of these olefsins in the manufacture of polymers or fuel, for example, require selective elimination of the acetylenic and diolefinic hydrocarbons which is as complete as possible.
The usual technique for such purification is selective hydrogenation carried out in a stream of hydrogen in a reactor comprising a fixed bed of a catalyst constituted by a metal from group VIII. The feed, which arrives at ambient temperature, is generally pumped and reheated and reintroduced into the hydrogenation reactor. The hydrogen required is added in any suitable fashion. At the reactor outlet, the excess hydrogen and the gaseous hydrocarbons contained in the supply gas are removed from the liquid hydrocarbon-containing gas in any suitable fashion, generally in a separator drum followed, if necessary, by a topping column.
European patent application EP-A 1-0 556 025 recently described a process for selective hydrogenation of diolefins in a light olefinic hydrocarbon refinery cut. In this technology, hydrogenation of the diolefin is internal of the rectification zone of the distillation column, the catalyst itself acting as a distillation structure. This mode of operation economises on equipment. However in this type of technology, where the reaction and distillation proceed simultaneously in the same physical space, the liquid phase descends through the whole catalytic bed in the reaction zone in rivulets or streams of liquid. The gas phase containing the vaporised fraction of the feed and hydrogen rises through the catalytic bed in columns of gas. Since the hydrogen necessary for reaction is in the gas phase, hydrogenation occurs essentially in that phase on the portion of the catalyst in contact with the fraction of hydrocarbons which is in the gas phase.
In that technology, then, the lightest hydrocarbons are preferen
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Cosyns Jean
Didillon Blaise
Lebas Etienne
Montecot Francoise
Nocca Jean-Luc
Institut Francais du Pe'trole
Yildirim Bekir L.
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