Catalyst development for different petrochemical applications is of great importance to the industry due to, in general, the high cost of the catalysts. In modern catalysis, the particle size of the active phase, usually a precious metal, has been changed from macro to nano scale. The metal nanoparticles are usually coated by monolayers of oxide nanoparticle; forming what is called core-shell catalysts which are active at lower temperatures and stable at higher temperatures. Therefore, the control of the composition and morphology of the catalyst has a strong influence on catalyst performance.
Methane OxidationWe have demonstrated that core-shell catalysts, with metal nano-particles surrounded by a thin oxide shell, can be synthesized in solution and then deposited onto various oxide supports. In the cases of Pd@ceria/alumina and Pd@titania/alumina, the materials have shown very high CH4 oxidation activities at relatively low temperatures and considerable stabilities at high temperatures (Fig. 1). Currently, we are investigating the effects of H2O, CO2 and SO2 on the oxidation rates. Catalysts surfaces will be characterized by state-of-the-arts surface sensitive techniques.
Fig.1. Heating and cooling cycles were obtained with heating and cooling rates @ 200C/min (at space velocity of around 1,70,00 ml/g.h with O2/CH4 = 2).
We are investigating the stability and effectiveness of Ni nano particles compared to classical Ni catalysts. Our investigation aims to reduce the reaction temperature, maximize H2 and CO production and minimize cock formation.
Fig.2. Comparison of stability of Ni/Alumina and Ni.NPs/Alumina @ a space velocity of 13,00 ml/g.h at 750 0C.
We will be using Cu based catalysts to reduce CO2 by H2 into methanol. The reaction rate will be investigated in a high pressure fixed-bed reactor at various pressures and temperatures.
CO2 capturing on solid sorbents is currently studied under lower temperature. The lower temperature sorbent is polyethylenime (PEI) immobilized on mesoporous silica foam. The high temperature sorbent is CaO nano particles doped with different alkaline earth metals.
Fig. 3: adsorption/desorption of CO2 on PEI/MPS
Fig. 4 Adsorption/desorption of CO2 on CaO nanoparticles at 650 0C