Study On Oxidative Dehydrogenation Of Ethane Over Na-W-Mn-S-P-Zr/SiO₂ Catalysts

It is well known that ethylene is the essential organic chemicals and play a decisive role in the national petrochemical industry. Its technology level of development has become a measure standard of the country development level. The demand for ethylene is growing with the development of the world economy. Because of the lack of oil resources and the huge market gap of ethylene, the subject of using natural gas to produce ethylene has got great attention of many scientists from all over the world. Ethane is one of the principal components of natural gas and liquefied petroleum gas. It has great theoretic and practical meaning to study on the progress of oxidative dehydrogenation of ethane to ethylene.We used Na-W-Mn-S-P-Zr/SiO₂ catalyst which was developed by our team in the oxidative dehydrogenation of ethane to ethylene. The catalytic performance of several catalysts in oxidative dehydrogenation of ethane with O₂ or CO₂ was investigated, and the effects of different components,different prepare methods and different addition sequence to the activities of catalysts were discussed,and the structure and redox capability of the catalysts were characterized by XRD and TPR. The activities rules of oxidative dehydrogenation of ethane with O₂ or CO₂ on different catalysts were similar. The catalyst prepared by mixture slurry method shows the best catalytic performance. The additions of S or/and P to the Na-W-Mn-Zr/SiO₂ catalyst can improve the activity of catalyst. Crystalline cristobalite,Na₂SO₄,Na₂WO₄,ZrO₂ and Mn₂O₃ species are the effective phases for oxidative dehydrogenation of ethane, and ZrSiO₄ species may be an effective phase too. The catalysts with high redox capability show good catalysis activities for oxidative dehydrogenation of ethane.The effects of reaction conditions to oxidative dehydrogenation of ethane with O₂ or CO₂ were discussed. We found that T=660℃, C₂H₆/O₂=1.5, GHSV=4800h^-1 is an optimum reaction condition for oxidative dehydrogenation of ethane on the Na-W-Mn-Zr-S-P/SiO₂ catalyst. And when the reaction condition is T=750℃, C₂H₆/CO₂=1/2, GHSV=2400h^-1, the highest activity of catalysts for oxidative dehydrogenation of ethane with CO₂ was obtained over the six-component catalyst, on which the ethylene yield was 48.46%, respectively. This suggested that it is possible for using CO₂ instead of O₂ in oxidative dehydrogenation of ethane.