Propane dry reforming over crystalline catalyst: Enhancement of synthesis gas production and its catalytic properties

Abstract

The light hydrocarbon (C1-C4 alkanes) dry reforming process has attracted considerable attention with increasing global gasoline price, for developing sustainable environmentallycompatible synthesis gas (H2/CO mixtures) production and utilization technologies. Dry reforming of propane (DRP) has been widely investigated, with most studies showing rapid deactivation due to carbon formation and sintering at high elevated temperature. DRP is highly endothermic reactions it acquires high energy. The metallic and bi-metallic catalyst has been showed high performance in DRP. Meanwhile, it has lost their catalytic ability due to sintering and coke formation. These propose demanding to improve catalysts that limit carbon formation and sintering while avoiding structural changes at the elevated temperatures typical of this reaction. The primary focus of this thesis is that the improving the carbon inhibition and antisintering by binary metal oxide in well defined structured such as spinel and perovskite catalyst and their systematic enhancement in the catalytic activity by a various combination of elements. In this work, we have investigated dry reforming of propane on two catalysts. First, the FeCe2O4 spinel catalyst was synthesized by the sol-gel method to evaluate the catalytic activity and carbon inhibition. A second, the SrNiO3 catalyst was synthesized by a sol-gel method in which rare earth substituted perovskite catalyst. All catalysts were performed DRP, and their physicochemical studies showed that the anti-sintering and minimal carbon formation. Catalysts characterization were measured via various techniques including BET surface area, pore volume, temperature programmed reduction, temperature programmed desorption of H2 and CO2. Morphological measurements such as X-ray diffraction, field emission – scanning electron microscopy, scanning electron microscopy-energy dispersive X-ray, Raman, and X-ray photoelectron spectroscopy were analyzed. XRD analysis confirmed the formation of crystallinity of metal oxide by various synthesis methods and EDS analysis verified the metal dispersion obtained from synthesis. The catalyst evaluation was performed in a fixed-bed reactor of the various temperature range at 550°C to 800°C under atmospheric pressure with stoichiometry ratio of carbon dioxide, and propane (CP) is 3. The catalysts showed the significant activity at elevated temperature. It was found that the conversion and syngas yield increased with increasing temperature. The catalysts exhibited the range of H2/CO ratio is (0.6 to 0.7), which shows the reaction proceeds through the thermodynamical reaction with different supports and hinders the carbon formation. The catalytic stability of all catalysts was also performed for 50 h time on stream (TOS) for the DRP at the high active reaction temperature. No significant deactivation was observed for the all catalysts at high temperature for a long time. The spent catalysts were characterized by XRD, FE-SEM, Raman, XPS and TPO analysis to understand the morphology of the catalyst and coke deposited on the catalyst. XRD patterns attributed that the carbon formed on each catalyst after 50 h TOS at elevated temperature, mainly low intense graphitic carbon (peak at 2θ = 26°) was observed in all catalyst and the crystallinity of catalyst sustain after DRP. The Raman results revealed the form of carbon on the catalyst after DRP, mainly the two peaks were attributed at 1300 ± 50 cm-1 and 1500 ± 50 cm-1 on all catalyst, which corresponds to the graphite and carbon nanotube respective with an intensity ratio of ID/IG. XPS analysis demonstrated the existence of mainly two peaks of carbon species, graphitic (-C-C-), and C-H. An oxidation process performed the quantitative measurement of carbon at 600°C; the deposited carbon reacts with O2 to CO2 at 600°C. The results were found that the minimal carbon formation of the catalyst compares with the conventional catalyst. The different lattice compounds showed the limiting of carbon formation and high sustainability due to the immense availability of lattice oxygen and surface oxygen in the crystalline form of catalyst.