Amarjeet M. Rajput

Beneficial effects of cobalt addition to Ni-catalysts for oxidative conversion of methane to syngas

Abstract Addition of cobalt to NiO Yb 2 O 3 , NiO ZrO 2 and NiO ThO 2 catalysts causes a drastic reduction in the rate of carbon formation and also results in a large decrease in the reaction start (or the catalyst activation) temperature in the oxidative conversion of methane to syngas.

Oxidative conversion of methane to CO and H2 over Pt or Pd containing alkaline and rare earth oxide catalysts

A number of Pt (1.0 wt%) and Pd (1.0 wt%) containing alkaline earth oxide (namely, MgO and CaO) and rare earth oxide (namely, La2O3, Pr6O11, Nd2O3, Sm2O3, Gd2O3, Dy2O3 and Er2O3) catalysts have been compared for their performance in the oxidative conversion of methane to CO and H2 at 700 and 800°C and at very low contact time [GHSV = 5.0 (±0.2) × 105 cm3.g−1.h−1]. The catalysts are characterized by their specific surface area and H2 chemisorption at 40°C. Among the Pt- and Pd-containing catalysts, the best performance is shown by Pt/Gd2O3 and Pd/Sm2O3, respectively. These catalysts show high selectivity for CO but low selectivity for hydrogen due to reverse water gas shift reaction. Since alkaline and rare earth oxides are basic in nature, they act not only as a support for dispersing noble metals but also play a significant role in deciding the activity/selectivity of the Pt- or Pd-containing catalysts.

Oscillations in homogeneous oxidative dehydrogenation of ethane to ethene

The non-catalytic homogeneous dehydrogenation of ethane to ethene under unsteady-state conditions, showing sustained oscillations in the reaction temperature and product composition, has been investigated in a flow reaction system under different process conditions. The oscillations are observed only over a narrow range of reactor temperature (610–650 °C) and only for a C2H6/O2 ratio of <8.0. Their period and amplitude are strongly influenced by the temperature, space velocity, C2H6/O2 ratio and feed dilution by N2 or water vapour. The oscillations are found to be dependent on heat transfer and hence are thermokinetic in origin. The unsteady/steady reaction behaviour is most probably a result of the competing free radical reactions involved in both the exothermic oxidative conversion of ethane (which is pronounced at lower temperatures) and the endothermic thermal cracking of ethane, particularly unimolecular cracking of ethyl radicals (which is pronounced at higher temperatures), accompanied by different rates of heat transfer, under different reaction conditions.