The Chemical Engineering Journal and the Biochemical Engineering Journal最新文献

From experimental results obtained in a wide range of operating conditions (temperature and contact time) in an isothermal fixed bed integral reactor, the validity both of the kinetic models proposed in the literature as well as their modifications, for the methanol-to-gasoline (MTG) process at zero time on-stream, has been studied. The kinetic parameters for the various models have been calculated by solving the equation of mass conservation in the reactor for the lumps of the kinetic models. The usefulness of the model of Schipper and Krambeck for simulating the operation in the isothermal fixed bed integral reactor has been proven in the 573–648 K range.

An efficient method based on tendency modelling is presented to design operating conditions aiming at optimization of end-use properties of a terpolymer used as a viscosity index improver. In order to implement this strategy, a copolymerization model and relationships between the terpolymer structure and the properties are set up according to a sequential procedure. Six preliminary runs were required to start the process. Further runs were performed according to the predictions of an adaptive tendency model in order to minimize a performance index related to reaction time and end-use properties of the terpolymer. It was found that quasi-optimal conditions were reached after only four runs calculated according to this method.

Naphthalene dissolved in n-hexadecane was used as a model compound to simulate the aromatics in diesel fuels for hydrogenation activity tests. The aluminium borate (ABx) supports were prepared by the coprecipitation method. The aromatic hydrogenation activity of Pt/aluminium borate catalyst (Pt—ABx) is higher than that of Pt—γ-Al₂O₃ catalyst, but its cis-decalin selectivity is lower than that of Pt—γ-Al₂O₃ catalyst owing to the higher acidity of ABx than γ-Al₂O₃ support. When the Al:B atomic ratio decreases, the hydrogenation and hydrogenolysis activities of Pt—ABx catalyst increase but the cis-decalin selectivity decreases.

When boron is added to the Pt—γ-Al₂O₃ catalyst to give Pt—Bx—Al₂O₃ catalyst, it improves the catalyst hydrogenation activity but reduces the cis-decalin selectivity since the acidity of the support increases. However, the hydrogenation activity of Pt—Bx—Al₂O₃ catalyst deceases when the Al:B ratio is smaller than 8. The Pt—Bx—Al₂O₃ is a better aromatic hydrogenation catalyst than Pt—AB_x catalyst since its hydrogenolysis activity is lower.

The applicability of wedge meters and segmental orifice meters to monitor the flow rate of oil-in-water emulsions was investigated. A flow loop consisting of wedge meters and segmental orifice meters of various shapes and sizes was designed and developed. The discharge coefficients were determined for various differently concentrated oil-in-water emulsions. The oil concentration was varied from 0% to 75.18% by volume. The results indicate that wedge meters and segmental orifice meters are feasible flow-measuring devices for emulsions. The single-phase calibration curves (discharge coefficient vs. Reynolds number) are applicable to two-phase oil-in-water emulsions. The size and shape of the wedge element have a significant effect on the discharge coefficient.

The effect of solid particles on the flow characteristics of axisymmetric turbulent coaxial jets has been studied. A laser Doppler anemometer was used to measure the mean and fluctuating velocities of the two phases. Both 50 and 200 μm silica particles were used. Experimental results are presented which indicate a significant influence of the solid particles on the flow characteristics.

The concentration of anti-native insulin antibodies was measured by liposome immune lysis assay (LILA) using liposomes coupled with a peptide which corresponds to residues 19–30 of the B-chain of porcine insulin. Although native insulin was slightly soluble in the reaction solution used in binding the antigens to the liposomes, this peptide was readily soluble in the solution. Thus liposomes coupled with a sufficient amount of the antigen could be easily obtained. Antibodies against native insulin from several species bound to the peptide on the surface of the liposomes, and the antigen-antibody complexes activated the complement system. By using the peptide-coupled liposomes, the concentrations of antibodies against insulin from several species were measured by the LILA method without the limitation of the solubility of the antigens.

The macroscopic effects of mechanical mixing on the biological activities of Saccharomyces cerevisiae cells employed in batch fermentations of dilute starch hydrolysate solutions are studied. The rotational speed strongly affects the overall product yield over 300 min⁻¹. Also the fermentation kinetics is markedly influenced by agitation intensity, in that the process appears to be limited by substrate diffusion from the bulk to the cell inside up to 450 min⁻¹, whereas cell metabolism becomes of greater significance over this threshold. A new model is also presented to describe the decrease in specific productivity with the increase in either the mixing intensity or the exposure time to shear stress. The present results suggest the existence of different types of simultaneous mechanisms for metabolic activity inhibition and/or death linked to mechanical mixing.