The b-oriented silicalite-1 membrane on the substrate α-Al2O3 pre-coated with a silica-zirconia intermediate layer was synthesized by using in-situ crystallization. The influence of chemical properties of the substrate surface on crystal growth and orientation was investigated. The result indicated that the surface modification by pre-coating a thin film of chitosan was conducive to the formation of b-oriented silicalite-1 membrane with good quality.
The influence of compression and decompression rates of carbon dioxide on the physiology of Absidia coerulea and Saccharomyces cerevisiae was investigated. Besides parameters such as pressure, temperature, exposure time, water content, and initial pH, the influence of either compression or decompression rate on the biological behavior of microorganisms was quite essential. For both microorganisms studied, an optimal rate for either compression or decompression process exists due to the integrated effect of pressure, exposure time as well as compression or decompression speed. The decompression rate has no significant effect on cell's viability after 180 min exposure in compressed CO2 because almost all the microorganisms were died before decompression.
A flux equation of diffusion for bi-disperse porous catalyst pellets was proposed by modifying the previously developed model equation over fractal trajectories. The proposed fractal model equation considered the same tortuous degree for both micro-and macro-pores. The experimental data of diffusion over a bi-disperse Ni/gamma-alumina pellet were obtained with a standard Wicke-Kallenbach diffusion cell for both carbon monoxide- ethylene and carbon dioxide-ethylene binary mixtures. The fitting between experimental results and the fractal model equation leads to a fractal dimension of 1.11. The prediction of diffusion flux over the bi-disperse Ni/gamma- alumina pellet by the proposed fractal model equation is much better than the traditional tortuosity-based model equation by comparison with the measured flux through the pellet.
Scanning electron microcopy （SEM） and differential scan calorimetry （DSC） were used to evaluate structure changes in Saccharomyces cerevisiae cells under the treatment of high-pressure CO2 over the fermentation broth. Compared with controlled fermentation, the ethanol concentration in the fermentation broth after 24 h greatly decreased under high-pressure CO2. DSC studies of whole cells showed that the ribosomes and DNA were not changed after high pressure CO 2 treatment although some components were denatured,leading to the lowering of the corresponding decomposition temperature. The fermentation under 1 and 8 MPa CO2 caused obvious changes on the wall surface of cells.Wrinkles were formed on the wall of cells and the cell wall coarseness increased at elevated pressure as observed with SEM observations.
The thermal stability, phase transformation, surface morphology, pore size distribution and permeation of the defect-free silica-zirconia membrane were investigated by using X-ray diffraction (XRD), atomic force microscopy (AFM), gas adsorption analyzer (BET), and gas permeation apparatus, respectively. Using silica as the stabilizing agent, the defect-free membrane was much more stable than pure zirconia. The crystal transformation of zirconia in the sil-ica-stabilized membrane could be prohibited by the interaction between silica and zirconia. ZrO2 crystals were kept tetragonal below 900℃, the size of which did not change with temperature between 700℃ and 900℃. It was further veri-fied by the AFM observation, pore size analysis and permeation study. This thermal stability makes the silica-zirconia membrane a good choice as the intermediate layer for zeolite and Pd-based membranes.
