(GB2317618-A)      In a process for the liquid phase alkylation of a hydrocarbon substrate with an olefinic alkylating agent in the presence of an acid alkylation catalyst and a hydrocarbon having a lower boiling point than the substrate and with a large stoichiometric excess of the substrate over the alkylating agent, to form a liquid product mixture containing alkylation product, the lower boiling hydrocarbon and unreacted substrate, the improvement comprising: (a) generating from the liquid product mixture a vapour phase containing unreacted substrate and lower boiling hydrocarbon; (b) compressing and condensing the vapour phase to form a cooler liquid condensate depleted in the lower boiling hydrocarbon and a vapour phase enriched in the lower boiling hydrocarbon; (c) when total condensation takes place in step (b), and optionally if partial condensation takes place in step (b), flashing the liquid condensate to form a vapour phase enriched in the lower boiling hydrocarbon and a further cooled liquid phase depleted in the lower boiling hydrocarbon which is then recycled to the reactor; (d) recycling to the alkylation reactor the liquid phase formed from partial condensation in step (b) and/or from flashing in step (c); and (e) separating the lower boiling hydrocarbon from unreacted substrate (i) in at least a portion of the vapour phase formed from flashing in step (c) and/or from partial condensation in step (b), optionally after the vapour phase is compressed or after compression and partial condensation of the vapour phase and removal of the resulting liquid phase, or (ii) in at least a portion of the liquid phase formed by total condensation of the vapour phase.    USE -   Hydrocarbon substrates which can be alkylated include straight and/or branched chain 2-10C paraffins (e.g. butane and hexane, preferably 4-6C isoparaffins, e.g. isobutane, isopentane and isohexane). Volatile aromatic compounds (e.g. benzene, toluene and thiophene) can also be alkylated and the substrate may be obtained from refinery streams or gasoline blending stocks. The olefinic alkylation agents include 2-12C terminal and internal monoolefins (e.g. ethylene, propylene, isobutylene, butene-1, butene-2, trimethylethylene and the isomeric pentenes).    ADVANTAGE -   The process maximises the recycle to the alkylation reactor of unreacted hydrocarbon substrate; minimises the concentration of lower boiling hydrocarbons in the unreacted substrate recycled; and reduces the load on the tower used for removing the lower boiling hydrocarbon from the unreacted substrate. The efficiency of recycle of unreacted hydrocarbon substrate as a refrigerant in the alkylation reactor is improved.    (US5750818-A)      In a process for the liquid phase alkylation of a hydrocarbon substrate with an olefinic alkylating agent in the presence of an acid alkylation catalyst and a hydrocarbon having a lower boiling point than the substrate and with a large stoichiometric excess of the substrate over the alkylating agent, to form a liquid product mixture containing alkylation product, the lower boiling hydrocarbon and unreacted substrate, the improvement comprising: (a) generating from the liquid product mixture a vapour phase containing unreacted substrate and lower boiling hydrocarbon; (b) compressing and condensing the vapour phase to form a cooler liquid condensate depleted in the lower boiling hydrocarbon and a vapour phase enriched in the lower boiling hydrocarbon; (c) when total condensation takes place in step (b), and optionally if partial condensation takes place in step (b), flashing the liquid condensate to form a vapour phase enriched in the lower boiling hydrocarbon and a further cooled liquid phase depleted in the lower boiling hydrocarbon which is then recycled to the reactor; (d) recycling to the alkylation reactor the liquid phase formed from partial condensation in step (b) and/or from flashing in step (c); and (e) separating the lower boiling hydrocarbon from unreacted substrate (i) in at least a portion of the vapour phase formed from flashing in step (c) and/or from partial condensation in step (b), optionally after the vapour phase is compressed or after compression and partial condensation of the vapour phase and removal of the resulting liquid phase, or (ii) in at least a portion of the liquid phase formed by total condensation of the vapour phase.    USE -   Hydrocarbon substrates which can be alkylated include straight and/or branched chain 2-10C paraffins (e.g. butane and hexane, preferably 4-6C isoparaffins, e.g. isobutane, isopentane and isohexane). Volatile aromatic compounds (e.g. benzene, toluene and thiophene) can also be alkylated and the substrate may be obtained from refinery streams or gasoline blending stocks. The olefinic alkylation agents include 2-12C terminal and internal monoolefins (e.g. ethylene, propylene, isobutylene, butene-1, butene-2, trimethylethylene and the isomeric pentenes).    ADVANTAGE -   The process maximises the recycle to the alkylation reactor of unreacted hydrocarbon substrate; minimises the concentration of lower boiling hydrocarbons in the unreacted substrate recycled; and reduces the load on the tower used for removing the lower boiling hydrocarbon from the unreacted substrate. The efficiency of recycle of unreacted hydrocarbon substrate as a refrigerant in the alkylation reactor is improved.    (GB2317618-B)      In a process for the liquid phase alkylation of a hydrocarbon substrate with an olefinic alkylating agent in the presence of an acid alkylation catalyst and a hydrocarbon having a lower boiling point than the substrate and with a large stoichiometric excess of the substrate over the alkylating agent, to form a liquid product mixture containing alkylation product, the lower boiling hydrocarbon and unreacted substrate, the improvement comprising: (a) generating from the liquid product mixture a vapour phase containing unreacted substrate and lower boiling hydrocarbon; (b) compressing and condensing the vapour phase to form a cooler liquid condensate depleted in the lower boiling hydrocarbon and a vapour phase enriched in the lower boiling hydrocarbon; (c) when total condensation takes place in step (b), and optionally if partial condensation takes place in step (b), flashing the liquid condensate to form a vapour phase enriched in the lower boiling hydrocarbon and a further cooled liquid phase depleted in the lower boiling hydrocarbon which is then recycled to the reactor; (d) recycling to the alkylation reactor the liquid phase formed from partial condensation in step (b) and/or from flashing in step (c); and (e) separating the lower boiling hydrocarbon from unreacted substrate (i) in at least a portion of the vapour phase formed from flashing in step (c) and/or from partial condensation in step (b), optionally after the vapour phase is compressed or after compression and partial condensation of the vapour phase and removal of the resulting liquid phase, or (ii) in at least a portion of the liquid phase formed by total condensation of the vapour phase.    USE -   Hydrocarbon substrates which can be alkylated include straight and/or branched chain 2-10C paraffins (e.g. butane and hexane, preferably 4-6C isoparaffins, e.g. isobutane, isopentane and isohexane). Volatile aromatic compounds (e.g. benzene, toluene and thiophene) can also be alkylated and the substrate may be obtained from refinery streams or gasoline blending stocks. The olefinic alkylation agents include 2-12C terminal and internal monoolefins (e.g. ethylene, propylene, isobutylene, butene-1, butene-2, trimethylethylene and the isomeric pentenes).    ADVANTAGE -   The process maximises the recycle to the alkylation reactor of unreacted hydrocarbon substrate; minimises the concentration of lower boiling hydrocarbons in the unreacted substrate recycled; and reduces the load on the tower used for removing the lower boiling hydrocarbon from the unreacted substrate. The efficiency of recycle of unreacted hydrocarbon substrate as a refrigerant in the alkylation reactor is improved.    (JP11511762-W)      In a process for the liquid phase alkylation of a hydrocarbon substrate with an olefinic alkylating agent in the presence of an acid alkylation catalyst and a hydrocarbon having a lower boiling point than the substrate and with a large stoichiometric excess of the substrate over the alkylating agent, to form a liquid product mixture containing alkylation product, the lower boiling hydrocarbon and unreacted substrate, the improvement comprising: (a) generating from the liquid product mixture a vapour phase containing unreacted substrate and lower boiling hydrocarbon; (b) compressing and condensing the vapour phase to form a cooler liquid condensate depleted in the lower boiling hydrocarbon and a vapour phase enriched in the lower boiling hydrocarbon; (c) when total condensation takes place in step (b), and optionally if partial condensation takes place in step (b), flashing the liquid condensate to form a vapour phase enriched in the lower boiling hydrocarbon and a further cooled liquid phase depleted in the lower boiling hydrocarbon which is then recycled to the reactor; (d) recycling to the alkylation reactor the liquid phase formed from partial condensation in step (b) and/or from flashing in step (c); and (e) separating the lower boiling hydrocarbon from unreacted substrate (i) in at least a portion of the vapour phase formed from flashing in step (c) and/or from partial condensation in step (b), optionally after the vapour phase is compressed or after compression and partial condensation of the vapour phase and removal of the resulting liquid phase, or (ii) in at least a portion of the liquid phase formed by total condensation of the vapour phase.    USE -   Hydrocarbon substrates which can be alkylated include straight and/or branched chain 2-10C paraffins (e.g. butane and hexane, preferably 4-6C isoparaffins, e.g. isobutane, isopentane and isohexane). Volatile aromatic compounds (e.g. benzene, toluene and thiophene) can also be alkylated and the substrate may be obtained from refinery streams or gasoline blending stocks. The olefinic alkylation agents include 2-12C terminal and internal monoolefins (e.g. ethylene, propylene, isobutylene, butene-1, butene-2, trimethylethylene and the isomeric pentenes).    ADVANTAGE -   The process maximises the recycle to the alkylation reactor of unreacted hydrocarbon substrate; minimises the concentration of lower boiling hydrocarbons in the unreacted substrate recycled; and reduces the load on the tower used for removing the lower boiling hydrocarbon from the unreacted substrate. The efficiency of recycle of unreacted hydrocarbon substrate as a refrigerant in the alkylation reactor is improved.