Integrated process for producing an alkenylsubstitutes aromatic compound

An integrated process of preparing a C2-5 alkenyl-substituted aromatic compound using a C6-12 aromatic compound and a C2-5 alkane as raw materials. The process involves feeding a C2-5 alkane, for example ethane, and a C2-5 alkyl-substituted aromatic compound, for example ethylbenzene, to a dehydrogenation reactor for concurrent dehydrogenation to a C2-5 alkene, for example ethylene, and a C2-5 alkenyl-substituted aromatic compound, for example stryrene; separating the dehydrogenation effluent to recover a gaseous stream containing alkene, hydrogen, and alkane, and to recover the aromatics with high efficiency; feeding the gas stream and a C6-12 aromatic compound to an alkylation reactor to obtain the corresponding C2-5 alkyl-substituted aromatic compound, which is recycled to the dehydrogenation reactor; subjecting the alkylation unit vent stream containing alkane and hydrogen to a separation step to recover alkane, which is recycled to the dehydrogenation unit; hydrogen, which is recovered at 99% chemical grade purity and energy.