Feed pretreating

A process for alkylation of an aromatic hydrocarbon stream having impurities, said process comprising the steps of:

• (a) contacting the hydrocarbon feedstock with a first molecular sieve comprising 13× molecular sieve and having a Si/Al molar ratio less of than 5 to remove at least a portion of said impurities and to produce a partially treated aromatic hydrocarbon stream;
• and then
• (b) contacting said partially treated hydrocarbon stream with a second molecular sieve comprising a zeolite US-Y and having a Si/Al molar ratio of greater than 5 to remove substantially all of the remaining portion of said impurities, to produce a fully treated hydrocarbon feedstock having a reduced amount of impurities and wherein said second molecular sieve being different from the first molecular sieve;
• (c) contacting the fully treated aromatic hydrocarbon stream with an alkylating agent in the presence of an alkylation catalyst having a cycle length and under alkylation conditions, to produce an alkylated aromatic hydrocarbon stream;
• wherein said cycle length of said alkylation catalyst is greater than said cycle length using said first molecular sieve alone or said second molecular sieve alone.