Abstract: An olefin isomerization process useful in recovering isobutylene from mixed butylene feed streams is disclosed. Preferably, the feed stream is passed through a first reaction zone to convert some butene-1 to butene-2 and then fed to the lower part of a two-part fractionation system. The butene-2-rich bottoms is withdrawn and the overhead vapor is passed through a second reaction zone in admixture with hydrogen before entering the second or upper part of the fractionation system. The bottoms liquid of the upper part of the fractionation system flows into the lower part of the fractionation system. Isobutylene and recycle hydrogen are recovered from the overhead vapor of the upper part of the fractionation system.

Abstract: A process for the catalytic dehydrogenation of C.sub.2 + normally gaseous paraffinic hydrocarbons to produce the corresponding monoolefinic hydrocarbons is disclosed. The energy-efficient process is particularly directed to the separation of recycle hydrogen from the olefinic hydrocarbon products and unreacted paraffinic hydrocarbons.

Abstract: A process for the isomerization of acyclic hydrocarbons and alkylaromatic hydrocarbons is disclosed. The mixed-phase feed stream is heated and the liquid-phase portion of the feed stream is simultaneously vaporized by indirect heat exchange against the effluent of the reaction zone. Prior to this exchange, the effluent of the isomerization zone is heated in a fired heater to a temperature above that employed in the reaction zone. The inventive concept eliminates the need to pass mixed-phase feed streams through fired multi-pass heaters.

Abstract: Problems associated with heating the mixed-phase feed stream of a hydrocarbon conversion process are reduced by a method of operation which includes heating the feed stream to a sufficient temperature for passage into a reaction zone by indirect heat exchange. The effluent stream of the reaction zone is then further heated in a fired heater and is passed through the indirect heat exchange zone in which the feed stream was heated.

Abstract: A hydrocarbon stream comprising C.sub.2 to C.sub.8 hydrocarbons is stripped at a high temperature to allow passage of the stripper bottoms stream into a reaction zone without further heating, and the effluent of the reaction zone is then heat exchanged against the feed stream to the stripper column to recover heat. Operation of the reaction zone at the desired temperature is achieved by adjusting the amount of the stripper bottoms stream which is split off for cooling by heat exchange against the feed to the stripper column. The cooled split-off portion is then admixed with the remaining high temperature portion. Adjusting the flow rate of the portion of hot reaction zone effluent which is heat exchanged against the stripper feed stream is performed to control either the temperature of the stripper feed stream or the temperature of the reaction zone effluent as it is passed to a downstream operation.

Abstract: A process for the production of alkylaromatic hydrocarbons by the alkylation of benzene wherein the alkylation zone effluent is fractionated to form a bottoms stream comprising benzene, the alkylaromatic hydrocarbon and a light paraffin. The light paraffin is then removed from the bottoms stream in a first recycle column which produces a recycled overhead stream comprising the paraffin and benzene. The bottoms stream of the first recycle column is separated in a second recycle column, which is operated at about the same bottom temperature but a lower pressure than the first recycle column. The benzene-rich overhead stream of the second recycle column is preferably recycled to the alkylation zone.

Abstract: An improved method of simultaneously removing high-boiling materials and a volatile dissolved substance, such as carbon dioxide or hydrogen sulfide, from a hydrocarbon stream as is performed in feed preparation columns. About 25 to 75 percent of the feed stream is vaporized in a flash zone, and the vapor stream from the flash zone is combined with the overhead vapor stream of a fractionation column. The liquid remaining after the flash operation is passed into a lower intermediate point of the fractionation column. The high-boiling materials are removed at the bottom of the column, and the product stream is removed from the fractionation column at a higher intermediate point.

Abstract: A hydrocarbon stream comprising benzene is stripped at a high temperature to allow passage of the stripper bottoms stream into a clay treating zone without further heating, and the effluent of the clay treating zone is then exchanged against the feed stream to the stripper column to recover heat. Operation at the optimum clay treating temperature is achieved by adjusting the amount of the stripper bottoms stream which is split off for cooling by heat exchange against the feed to the stripper column. The cooled split-off portion is then admixed with the remaining high temperature portion. Adjusting the flow rate of the portion of hot clay treater effluent which is heat exchanged against the stripper feed stream is performed to control the temperature of either the stripper feed stream or the temperature of the clay treater effluent as it is passed into a downstream fractionator.

Abstract: A process for the production of paraxylene by the catalytic isomerization of xylenes wherein the reaction zone effluent is fractionated in three columns in series with the overhead product of the second column in the series being sent to a paraxylene separation zone, C.sub.9 hydrocarbons being rejected as the bottoms product of the third column, and the overhead product of the third column being combined with the raffinate stream of the paraxylene separation zone and recycled to the isomerization zone.

Abstract: A hydrocarbon stream comprising benzene is stripped at a high temperature to allow passage of the stripper bottoms stream into a clay treating zone without further heating, and the effluent of the clay treating zone is then exchanged against the feed stream to the stripper column to recover heat. Operation at the optimum clay treating temperature is achieved by adjusting the amount of the stripper bottoms stream which is split off for cooling by heat exchange against the feed to the stripper column. The cooled split-off portion is then admixed with the remaining high temperature portion.

Abstract: An improved method of simultaneously removing high-boiling materials and a volatile dissolved substance, such as oxygen, from a hydrocarbon stream as is performed in feed preparation columns. About 25 to 75 percent of the feed stream is vaporized in a flash zone, and the vapor stream from the flash zone is combined with the overhead vapor stream of a fractionation column. The liquid remaining after the flash operation is passed into a lower intermediate point of the fractionation column. The high-boiling materials are removed at the bottom of the column, and the product stream is removed from the fractionation column at a higher intermediate point.