NOVELTY - Producing (P1) synthesis product stream, where the stream contains higher molecular weight hydrocarbons and hydrogen halide, involves reacting gaseous alkanes and halogen to form halogenation product stream; separating the formed stream into gaseous stream and liquid alkyl halides stream; separating the liquid alkyl halides stream into monohalides stream and polyhalides stream, where the monohalides stream contains monohalogenated alkanes, and where the polyhalides stream contains polyhalogenated alkanes; and reacting a portion of the monohalogenated alkanes in the presence of a catalyst.    USE - For producing synthesis product stream which contains higher molecular weight hydrocarbons and hydrogen halide (claimed).    ADVANTAGE - The process is that separation of the methane from the brominated hydrocarbons should reduce the large recycle stream circulating through the entire process due to the large excess methane that may be used in the bromination step; and is that separation of the methane from the brominated hydrocarbons should reduce the feed rate to the synthesis reactor in the alkyl bromide conversation step. The size of the synthesis reactor can be reduced, which may result in considerable costs savings, especially if a fluidized bed reactor is employed. The process is that separation of polybrominated alkanes from the monobrominated alkanes prior to feeding the synthesis reactor should reduce coke formation.    DETAILED DESCRIPTION - Producing (P1) synthesis product stream, where the stream contains higher molecular weight hydrocarbons and hydrogen halide, involves reacting gaseous alkanes and halogen to produce halogenation product stream, where the halogenation product stream comprises alkyl halides, hydrogen halide, and unreacted alkanes; separating the halogenation product stream into gaseous stream and liquid alkyl halides stream, where the gaseous stream comprises hydrogen halide and unreacted alkanes, and where the liquid alkyl halides stream comprises alkyl halides; separating the liquid alkyl halides stream into monohalides stream and polyhalides stream, where the monohalides stream comprises monohalogenated alkanes, and where the polyhalides stream comprises polyhalogenated alkanes; and reacting a portion of the monohalogenated alkanes from the monohalides stream in the presence of a catalyst to produce the synthesis product stream. An INDEPENDENT CLAIM is included for system (S1) comprising a bromination reactor for reacting gaseous alkanes and bromine to produce bromination product stream, where the bromination product stream comprises alkyl bromides, hydrogen bromide, and unreacted alkanes; an alkyl bromides fractionation unit in fluid communication with the bromination reactor for separating the bromination product stream into gaseous alkane HBr stream and liquid alkyl bromides stream, where the gaseous alkane/HBr stream comprises hydrogen bromide and unreacted alkanes, and where the liquid alkyl bromides stream comprises alkyl bromides; polybromides fractionation unit in fluid communication with the alkyl bromides fractionation unit for separating the liquid alkyl bromides stream into polybromides stream and monobromides stream, where the polybromides stream comprises polybrominated alkanes, and where the monobromides stream comprises monohalogenated bromides; synthesis reactor in fluid communication with the polybromides fractionation unit for reacting a portion of the monobrominated alkanes from the monobromides stream in the presence of a catalyst to produce synthesis product stream, where the synthesis product stream comprises higher molecular weight hydrocarbons and hydrogen bromide; hydrogen bromide separator in fluid communication with the synthesis reactor for recovering a portion of the hydrogen bromide from the synthesis product stream; and second hydrogen bromide separator unit in fluid communication with the alkyl bromides fractionation unit for recovering a portion of the hydrogen bromide from the gaseous alkane/HBr stream.