Selectivity Reversal in Oxidative Dehydrogenation of Ethane with CO2 on CaO–NiO/Al2O3 Catalysts

• Published in: Catalysis letters 2017, Vol.147 (1), p.82-89
• Main Authors: Sagar, T. V., Surendar, M., Padmakar, D., Parameswaram, G., Lingaiah, N., Rao, K. S. Rama, Reddy, I. A. K., Sumana, C., Prasad, P. S. Sai
• Format: Article
• Language: English
• Subjects: Aluminum oxide; Basicity; Calcium oxide; Carbon dioxide; Catalysis; Catalysts; Chemisorption; Chemistry; Chemistry and Materials Science; Coke; Composition; Dehydrogenation; Ethane; Ethene; Fourier transforms; Hydrocracking; Impregnation; Industrial Chemistry/Chemical Engineering; Infrared analysis; Infrared spectroscopy; Nickel aluminides; Nickel base alloys; Nickel compounds; Nickel oxides; Organometallic Chemistry; Physical Chemistry; Selectivity; Shift reaction; Water gas
• ISSN: 1011-372X; 1572-879X
• DOI: 10.1007/s10562-016-1899-y

CaO–NiO/Al 2 O 3 catalysts were prepared by wet impregnation method, keeping the NiO composition constant at 25 wt.% and varying the CaO composition in the range 6–12 wt.%. The catalysts were evaluated for oxidative dehydrogenation (ODH) of ethane with CO 2 at atmospheric pressure and in the temperature range of 600–700 °C. The physicochemical characterization of the catalysts was carried out using X-ray diffraction (XRD), BET surface area, Temperature programmed reduction (TPR), Temperature programmed desorption of CO 2 (CO 2 -TPD), H 2 chemisorption, Carbon analysis and Fourier transform infrared (FT-IR) spectroscopy. NiO/Al 2 O 3 showed higher ethane and carbon dioxide conversions, but with lower ethene selectivity. The addition of CaO in NiO/Al 2 O 3 reversed the course of reaction leading to high selectivity to ethene, although at reduced conversions. 9 wt.% CaO containing NiO/Al 2 O 3 emerged as the most promising catalyst giving the highest yield of ethene. CaO addition increased the basicity and the coke resistance. The shift in selectivity with CaO addition is explained in terms of more probability for reverse water gas shift reaction on a basic site rather than the hydrocracking reaction on the acidic sites of Ni/Al 2 O 3 . The 9 wt.% CaO-25% NiO/Al 2 O 3 catalysts were also prepared by changing the sequence of impregnation and by adopting simultaneous deposition of the two oxides on Al 2 O 3 . The activity of these catalysts was compared to identify the best method of catalyst preparation. Graphical Abstract Ca promotion of NiAl modifies the surface basic property increasing ethene/methane selectivity ratio from 1 to 4, and enhances coke resistance.