OXYDEHYDROGENATION OF ETHANE OVER ZSM-5 ZEOLITE CATALYSTS - EFFECT OF STEAM

The oxydehydrogenation of ethane over zeolite based catalysts (H+-, Na+-, Ni2+-, Pt2+-, Ga3+-, and [V]-ZSM-5) was studied in the temperature range 450-600-degrees-C. Selectivity to ethylene and higher hydrocarbons close to 80% was achieved at 550-degrees-C. Basic (Na-ZSM-5) and neutral ([V]-ZSM-5) zeolite catalysts were shown to be more active and selective for the oxydehydrogenation of ethane than ZSM-5 in acid form. In addition to the oxydehydrogenation product, a significant amount of higher hydrocarbons (C3+) was produced when using zeolites containing Ga3+-, Pt2+, or Ni2+- cations. Na+-, V5+, and H+-exchanged ZSM-5 catalyst are less effective in facilitating the production of higher hydrocarbons (C3+). Steam often has a profound effect on the performance of zeolite based catalysts. The addition of steam can enhance their selectivity to hydrocarbon products and reduce their tendency to form methane. Relatively high conversion (ca. 43%) and high selectivity (ca. 78%) to hydrocarbons were achieved at temperatures around 550-degrees-C. Higher reaction temperature results in significant increase of the formation of methane while lower reaction temperature leads to lower selectivity to hydrocarbon products.