Chromium Oxide Supported on Silicalite-1 Zeolite as a Novel Efficient Catalyst for Dehydrogenation of Isobutane Assisted by CO2

The chromium oxide catalysts supported on silicalite-1 zeolite (Cr/S-1) with a Cr content between 0.5% and 7% were synthesized via an incipient wetness method. The catalysts were characterized by XRD, N2 adsorption, TEM-EDX, UV-vis, DRIFTS, 29Si MAS NMR, XPS, H2-TPR, and NH3-TPD. The optimum 3%Cr/S-1 catalyst with 3%Cr is more active and stable than SBA-15-supported one with the same Cr content, which is a consequence of a higher content of Cr6+ in the fresh 3%Cr/S-1 catalyst and a higher content of Cr6+ retained on the former catalyst during the reaction. The 3%Cr/S-1 catalyst affords an isobutane conversion of 36.5% with 71.2% isobutene selectivity. The catalytic activity is well correlated with the content of Cr6+ in the fresh catalysts. Carbon dioxide displays a promoting effect on the dehydrogenation reaction.

The Ammonia Leaching Method of Recycling the Spent Copper-Chromium Oxide Catalysts

The spent copper chromium oxide catalyst of furfural hydrogenation was recycled.by ammonia leaching method. This method not only has the characteristics of simple process, low cost, quick effect, but also avoids the use of various oxidants increasing the security of the experimental operation and the generation of carcinogen hexavalent chromium.The experimental results show that the optimum process conditions of ammonia leaching is: the concentration of ammonia 15mol / L, the leaching temperature is at 180 °C, leaching time for 4h, the optimal dosage of (NH4)2SO40.6g/10g. The copper leaching rate can reach more than 80% of the maximum.