A process for separating organic nitrogen compounds from a hydrocarbon stream said process comprising: taking a contaminated hydrocarbon stream (68,8) including water and organic nitrogen compounds including nitriles; contacting said hydrocarbon stream with an acidic, molecular sieve at a temperature of at least 120°C in a nitrogen adsorption zone (72,162); and recovering a decontaminated hydrocarbon stream (10,23) including a smaller concentration of nitriles than in said contaminated hydrocarbon stream, said contaminated hydrocarbon stream includes at least 20 wppm water and further characterized in that said decontaminated hydrocarbon stream includes a hydrocarbon alkylation substrate and further including: passing a first alkylation substrate feed stream (12,12') comprising an alkylation substrate and impurities to an impurity adsorption zone (46,114) containing a purifying adsorbent comprising clay or resin selective for the adsorption of impurities and recovering from the impurity adsorption zone a purified alkylation substrate feed stream (48,48') comprising the alkylation substrate and having a concentration of impurities that is less than the concentration of impurities in the first alkylation substrate feed stream; and passing an alkylation agent and at least a portion of the purified alkylation substrate feed stream and at least a portion of the decontaminated hydrocarbon stream (10,23) comprising the hydrocarbon alkylation substrate to an alkylation reaction zone (20,30) containing an alkylation catalyst, said impurity adsorption zone and said nitrogen adsorption zone being spaced from said alkylation reaction zone, alkylating the alkylation substrate with the alkylation agent to produce alkylate, and recovering from the alkylation reaction zone a reaction effluent stream (18, 332) comprising the alkylate. taking a contaminated hydrocarbon stream (68,8) including water and organic nitrogen compounds including nitriles; contacting said hydrocarbon stream with an acidic, molecular sieve at a temperature of at least 120°C in a nitrogen adsorption zone (72,162); and recovering a decontaminated hydrocarbon stream (10,23) including a smaller concentration of nitriles than in said contaminated hydrocarbon stream, said contaminated hydrocarbon stream includes at least 20 wppm water and further characterized in that said decontaminated hydrocarbon stream includes a hydrocarbon alkylation substrate and further including: passing a first alkylation substrate feed stream (12,12') comprising an alkylation substrate and impurities to an impurity adsorption zone (46,114) containing a purifying adsorbent comprising clay or resin selective for the adsorption of impurities and recovering from the impurity adsorption zone a purified alkylation substrate feed stream (48,48') comprising the alkylation substrate and having a concentration of impurities that is less than the concentration of impurities in the first alkylation substrate feed stream; and passing an alkylation agent and at least a portion of the purified alkylation substrate feed stream and at least a portion of the decontaminated hydrocarbon stream (10,23) comprising the hydrocarbon alkylation substrate to an alkylation reaction zone (20,30) containing an alkylation catalyst, said impurity adsorption zone and said nitrogen adsorption zone being spaced from said alkylation reaction zone, alkylating the alkylation substrate with the alkylation agent to produce alkylate, and recovering from the alkylation reaction zone a reaction effluent stream (18, 332) comprising the alkylate.