Oxidative Dehydrogenation of Ethane and Propane using Ni-Loaded Catalysts

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Most important basic organic chemicals ethylene and propylene are commercially produced by energy consuming and less selective steam cracking of light hydrocarbons. In order to develop more energy saving and selective processes, catalytic oxidative dehydrogenation was investigated.As an active species of the catalyst, NiO was selected, and support material of NiO was exploited. MgO having high surface area was found to be an appropriate support and with 5 wt% loading of NiO on MgO, ethane conversion of 53% and ethylene selectivity of 62% were obtained at the reaction temperature of 600℃.Further studies on exploiting the support material of NiO, ZrO_2 was found to reduce the reaction temperature to 450℃. Additives of NiO-ZrO_2 catalyst were examined and SbOx and P_2O_5 were found to promote the catalytic activity and to increase selectivity to ethylene at 550℃ Ethane conversion of 35% and ethylene selectivity of 64% were obtained with the addition of 0.7 wt% SbOx.Addition of 0.52 wt% of P to Ni0-Zr02 catalyst, afforded ethane conversion of 33% and ethylene selectivity of 62% at 450℃, and an increase in the ratio of ethane/oxygen increased the ethane conversion to 41% with the selectivity to ethylene of 65%. The results are one of the highest selectivity to ethylene from ethane without dilution of the feed.Application of this catalyst system to the oxidative dehydrogenation to propane was not successful. Catalyst preparation was changed to the co-precipitation method using an aqueous solution of Ni(NO_3)_2 and ZrOCl_2 by adding aqueous ammonia. The catalyst exhibited moderate activity in the dehydrogenation of propane to propylene at 400℃.Transient response technique was developed to understand dehydrogenation mechanism using ethylbenzene as a substrate.