A process for alkylation of an alkylatable aromatic compound to produce a
monoalkylated aromatic compound, comprising the steps of (a) contacting
at least one the alkylatable aromatic compound and at least one the
alkylating agent with at least one molecular sieve catalyst under
suitable alkylation or transalkylation conditions in at least one
reaction zone, to produce at least one effluent which comprises the
monoalkylated aromatic compound, wherein the suitable alkylation or
transalkylation conditions comprise a water content being in a range from
about 1 wppm to about 10 wt. % based on the combined weight of the
alkylatable aromatic compound and the alkylating agent; and (b)
maintaining the water content in the reaction zone; wherein the cycle
length of the molecular sieve catalyst operated inside the range of the
water content is greater than the cycle length of the molecular sieve
catalyst operated outside the range of the water content.