A process for alkylation of an alkylatable aromatic compound to produce a monoalkylated aromatic compound, the process comprising: (a) passing a first feed stream comprising all fresh alkylatable aromatic compound and one or more feed impurities comprising reactive nitrogen compounds to a first reaction zone comprising a transalkylation catalyst; (b) passing a second feed stream comprising polyalkylated aromatic compounds to said first reaction zone; (c) contacting said first and second feed streams with said transalkylation catalyst in said first reaction zone under conditions to transalkylate said polyalkylated aromatic compounds with said alkylatable aromatic compound to produce said monoalkylated aromatic compound, and to remove at least part of said feed impurities; (d) removing from said first reaction zone a first effluent stream comprising unreacted alkylatable aromatic compound and said monoalkylated aromatic compound; (e) passing said first effluent stream to a fractionation system to separate said first effluent stream into a first light fraction comprising said unreacted alkylatable aromatic compound and a first heavy fraction comprising said monoalkylated aromatic compound; (f) recovering monoalkylated aromatic compound from said first heavy fraction; (g) passing said first light fraction comprising said alkylatable aromatic compound and a third feed stream comprising an alkylating agent to a second reaction zone comprising an alkylation catalyst; (h) contacting said first light fraction and third feed stream with said alkylation catalyst in said second reaction zone under conditions to alkylate said alkylatable aromatic compound with said alkylating agent and produce a second effluent stream comprising said monoalkylated aromatic compound, unreacted alkylatable aromatic compounds and polyalkylated aromatic compounds; and (i) recovering monoalkylated aromatic compound from said second effluent stream. (a) passing a first feed stream comprising all fresh alkylatable aromatic compound and one or more feed impurities comprising reactive nitrogen compounds to a first reaction zone comprising a transalkylation catalyst; (b) passing a second feed stream comprising polyalkylated aromatic compounds to said first reaction zone; (c) contacting said first and second feed streams with said transalkylation catalyst in said first reaction zone under conditions to transalkylate said polyalkylated aromatic compounds with said alkylatable aromatic compound to produce said monoalkylated aromatic compound, and to remove at least part of said feed impurities; (d) removing from said first reaction zone a first effluent stream comprising unreacted alkylatable aromatic compound and said monoalkylated aromatic compound; (e) passing said first effluent stream to a fractionation system to separate said first effluent stream into a first light fraction comprising said unreacted alkylatable aromatic compound and a first heavy fraction comprising said monoalkylated aromatic compound; (f) recovering monoalkylated aromatic compound from said first heavy fraction; (g) passing said first light fraction comprising said alkylatable aromatic compound and a third feed stream comprising an alkylating agent to a second reaction zone comprising an alkylation catalyst; (h) contacting said first light fraction and third feed stream with said alkylation catalyst in said second reaction zone under conditions to alkylate said alkylatable aromatic compound with said alkylating agent and produce a second effluent stream comprising said monoalkylated aromatic compound, unreacted alkylatable aromatic compounds and polyalkylated aromatic compounds; and (i) recovering monoalkylated aromatic compound from said second effluent stream.