The diolefins and alkenyl aromatics are very unstable components which can give gums by polymerization.In giving olefins and alky aromatics the hydrogenation improves the product quality.

二烯烃和烯基芳烃不稳定的组分，聚合产生凝胶。定烯烃和烷基芳烃，氢化以改善产品质量。