A process for producing an alkylated aromatic compound stream from at least partially untreated alkylatable aromatic compound stream having catalyst poisons and an alkylating agent stream, wherein said untreated alkylatable aromatic compound stream is treated to reduce catalyst poisons, the process comprising the steps of: (a) contacting said alkylatable aromatic compound stream having said catalyst poisons and an alkylating agent stream with a treatment composition in a treatment zone separate from an alkylation reaction zone under treatment conditions to remove at least a portion of said catalyst poisons and to alkylate at least a portion of said alkylatable aromatic compound to form a treated effluent stream which comprises treated alkylatable aromatic compound, an alkylated aromatic compound and a reduced amount of catalyst poisons, wherein said alkylatable aromatic compound stream having said catalyst poisons and said alkylating agent stream are in partially or completely liquid phase, wherein said treatment composition comprises a porous crystalline molecular sieve that has the structure of *BEA or FAU, and wherein said treatment composition has a surface area/surface volume ratio of greater than 30 in -1 (12 cm -1), the surface area/surface volume ratio of the treatment composition being obtained by dividing the surface area of the formulated particle by the geometric surface volume of the formulated particle, said treatment conditions include a temperature of from 30°C to 300°C and a pressure from 101 kPa to 4601 kPa, and a molar ratio of untreated alkylatable aromatic compound to alkylating agent of greater than or equal to 25:1; and (b) contacting said treated alkylatable aromatic compound in said effluent stream and additional said alkylating agent stream with a catalyst composition in said alkylation reaction zone separate from said treatment zone under at least partial liquid phase catalytic conversion conditions to form an alkylated effluent stream which comprises additional alkylated aromatic compound, wherein said catalyst composition comprises a porous crystalline material having a framework structure type selected from the group consisting of FAU, *BEA, MOR, MWW and mixtures thereof, wherein said at least partial liquid phase catalytic conversion conditions include a temperature of from 100°C to 300°C, a pressure from 689 kPa to 4601 kPa, a molar ratio of treated alkylatable aromatic compound to alkylating agent of from 0.01:1 to 25:1, and a feed weight hourly space velocity (WHSV) based on alkylating agent of from 0.1 to 500 hr -1. (a) contacting said alkylatable aromatic compound stream having said catalyst poisons and an alkylating agent stream with a treatment composition in a treatment zone separate from an alkylation reaction zone under treatment conditions to remove at least a portion of said catalyst poisons and to alkylate at least a portion of said alkylatable aromatic compound to form a treated effluent stream which comprises treated alkylatable aromatic compound, an alkylated aromatic compound and a reduced amount of catalyst poisons, wherein said alkylatable aromatic compound stream having said catalyst poisons and said alkylating agent stream are in partially or completely liquid phase, wherein said treatment composition comprises a porous crystalline molecular sieve that has the structure of *BEA or FAU, and wherein said treatment composition has a surface area/surface volume ratio of greater than 30 in -1 (12 cm -1), the surface area/surface volume ratio of the treatment composition being obtained by dividing the surface area of the formulated particle by the geometric surface volume of the formulated particle, said treatment conditions include a temperature of from 30°C to 300°C and a pressure from 101 kPa to 4601 kPa, and a molar ratio of untreated alkylatable aromatic compound to alkylating agent of greater than or equal to 25:1; and (b) contacting said treated alkylatable aromatic compound in said effluent stream and additional said alkylating agent stream with a catalyst composition in said alkylation reaction zone separate from said treatment zone under at least partial liquid phase catalytic conversion conditions to form an alkylated effluent stream which comprises additional alkylated aromatic compound, wherein said catalyst composition comprises a porous crystalline material having a framework structure type selected from the group consisting of FAU, *BEA, MOR, MWW and mixtures thereof, wherein said at least partial liquid phase catalytic conversion conditions include a temperature of from 100°C to 300°C, a pressure from 689 kPa to 4601 kPa, a molar ratio of treated alkylatable aromatic compound to alkylating agent of from 0.01:1 to 25:1, and a feed weight hourly space velocity (WHSV) based on alkylating agent of from 0.1 to 500 hr -1.