Vapor-phase dehydrogenation of ethanol to acetaldehyde was studied using Cu/SiO2 and ZnO/SiO2 catalysts prepared by the conventional impregnation method. Catalysts were characterized by XRD, nitrogen adsorption-desorption analysis, XPS, N2O-pulse method, CO2-TPD and C2H5OH-TPD. Use of copper ammonium complex for the preparation of Cu/SiO2 catalysts formed Cu particles on SiO2 too small for detection by XRD. The prepared Cu/SiO2 catalyst had high and selective dehydrogenation activity of ethanol to acetaldehyde. However, Cu/SiO2 catalyst was less stable at 350 °C due to sintering of Cu. Interestingly, a metal oxide catalyst, ZnO/SiO2, had fairly high and fully selective activity for dehydrogenation of ethanol to acetaldehyde. Furthermore, no changes in the activity and selectivity were observed for at least 6 h at 350 °C. The reaction pathways on the metal catalyst, Cu/SiO2, and the oxide catalyst, ZnO/SiO2, were studied by C2H5OH-TPD. Evolution of H2 was observed from ethanol contacted with Cu/SiO2 catalyst at 50 °C, suggesting dehydrogenation at this temperature. Desorption of acetaldehyde was observed above 200 °C. On the other hand, simultaneous desorption of H2 and acetaldehyde occurred on ZnO/SiO2 catalyst above 240 °C, suggesting that the rate determining step is the dissociative adsorption of ethanol at this temperature. Thus, the reaction pathways were very different for the metal catalyst and the oxide catalyst.
In this study, we focus on the use of tomato residue produced in the rural area of Kita-Hiroshima, Hiroshima, Japan as a feedstock for gas production via supercritical water gasification (SCWG). Calculation was made based on the amount of tomato residue produced in this area. The process was designed based on consideration of the energy recovery achieved with a heat exchanger network. The reactor temperature and pressure were set at 600 °C and 25 MPa, respectively. The process efficiency was calculated based on thermodynamics. The potential of tomato residue for gas production was evaluated from the perspective of energy, economics, and environmental impact. As a result, the net produced energy was calculated as 10.45 MJ/kg-feedstock from SCWG of tomato residues feedstock. In total, annual amount of tomato residues can produce energy to supply 76 MWh of electricity with a carbon dioxide reduction of 13.6 t.
Hydrophobic silica membranes prepared by the sol-gel method using phenyltrimethoxy-silane as the silica precursor were applied to separate toluene from toluene/H2 gaseous mixture. The hydrophobic silica membranes showed perm-selectivity for toluene due to the inhibition of H2 permeation by capillary condensation of toluene. Toluene flux increased and H2 flux decreased with time on stream. Silica membranes with different pore sizes were prepared using various concentrations of surfactant as a molecular template to form pores in the hydrophobic silica layer. The effect of pore size on the separation performance was investigated. The optimum molar ratio of surfactant to silica precursor was 0.12. The effects of feed rate, feed concentration of toluene and temperature on the separation performance were also investigated. Hydrophobic silica membrane showed high separation performance at low temperature and high concentration of toluene.
The deactivation factors of a Pd/Al2O3 catalyst in the selective hydrogenation process of cyclopentadiene (CPD) to cyclopentene (CPE) were investigated with using continuous flow system equipped with bench scale reactor (Mono-Tube Reactor) in order to develop effective manufacturing process of CPE. Catalytic activity was decreased with the passage of time on stream. To make clear the mechanisms of catalyst deactivation, some characterization and regeneration were performed on spent catalysts and the performances of regenerated catalysts were tested. Here, mechanism of catalyst deactivation was discussed on the basis of the results of the series of experiments.