Kinetics Study of the Hydrodeoxygenation of Xylitol over a ReOx-Pd/CeO2 Catalyst

In this study, we elucidate the reaction kinetics for the simultaneous hydrodeoxygenation of xylitol to 1,2-dideoxypentitol and 1,2,5-pentanetriol over a ReOx-Pd/CeO2 (2.0 weight% Re, 0.30 weight% Pd) catalyst. The reaction was determined to be a zero-order reaction with respect to xylitol. The activation energy was elucidated through an Arrhenius relationship as well as non-Arrhenius kinetics. The Arrhenius relationship was investigated at 150–170 °C and a constant H2 pressure of 10 bar resulting in an activation energy of 48.7 ± 10.5 kJ/mol. The investigation of non-Arrhenius kinetics was conducted at 120–170 °C and a sub-Arrhenius relation was elucidated with activation energy being dependent on temperature, and ranging from 10.2–51.8 kJ/mol in the temperature range investigated. Internal and external mass transfer were investigated through evaluating the Weisz–Prater criterion and the effect of varying stirring rate on the reaction rate, respectively. There were no internal or external mass transfer limitations present in the reaction.

Curing Kinetic Models of Resins for Microwave Assisted Pultrusion

Traditional description of the rate of the thermoset resin reaction by the Arrhenius relationship multiplied by a reaction function has been used in this study. The Kissinger method and ASTM E 698 procedure have been used for a determination of parameters of the Arrhenius relationship. N-th order, Prout-Tompkins and Kamal-Sourour models have been used and evaluated as the reaction functions to formulate the curing kinetic models of an epoxy resin.An engineering tool based on Microsoft Excel code has been developed by using the developed methodology. This tool has been successfully applied for a building of the curing kinetic model of vinyl ester resin with high microwave absorption properties to be used in the microwave assisted pultrusion processes.

Lifetime Prediction of EPU/Al Low Infrared Emissivity Coatings in Damp Heat

Stability of epoxy-polyurethane (EPU)/aluminum (Al) coatings (the change of coating emissivity during damp heat) was studied after exposure to the damp-heat test for varying lengths of time. We found that the emissivity increased with increasing heating temperature and time in damp heat. In addition, Arrhenius relationship was employed to calculate the lifetime of EPU/Al low infrared emissivity coatings in damp heat. Compared with observation data in damp heat, the calculated results validated the effectiveness of the model predictions, and showed that EPU/Al low infrared emissivity coatings exhibited good resistance to damp heat.

Removal of Thiophene from Binary Mixtures Using Polyether Block Amide (PEBAX) Film by Pervaporation

Reduction of organosulfurs in gasoline has become an urgent requirement in the world, especially in China. The goal of this work focuses on removal of thiophene from binary mixtures of thiophene and n-heptane by means of pervaporation. The PEBAX homogenous film was prepared by coating. The swelling experiments of film were studied for the affinity of PEBAX film to thiophene. The swelling degree of film increased with increasing thiophene content in the mixtures. The result indicates the PEBAX film had preferential sorption to thiophene rather than n-heptane. Pervaporation experiments were studied for investigating separation properties of the film. The effect of thiophene concentration in feed and operation temperature on separation properties of the film was researched. The results of pervaporation showed that both total and thiophene flux increased with increase of thiophene content in the feed and temperature, but the separation factor deceased with their increase. The activity energy was calculated according to the Arrhenius relationship. This work may offer useful visions into the possibility of the separation of sulfur compounds from gasoline via pervaporation.

Structure and Electric Property of BaTi2O5 Film by Laser Ablation

BaTi2O5 film was prepared on MgO (100) substrate by laser ablation, and the structure and electric property of the film were investigated. The film was b-axis oriented and epitaxially grown on the substrate along two in-plane directions with the a-axes ([100]-orientation) perpendicular to each other. The b-axis oriented BaTi2O5 film exhibited a sharp permittivity maximum (~ 2000) and had a high Curie temperature (750 K). The electrical conductivity increased with temperature and showed the Arrhenius relationship having an activation energy of 1.25 eV.

Intrinsic Gettering of Iron in Czochralski Silicon Crystals

ABSTRACTWe present a new experimental approach to studying the mechanism of intrinsic gettering of Fe in Czochralski silicon crystals. We present our experimental method and results for as-grown and intrinsic gettered wafers with high and low-level Fe surface contamination. We found that when annealing at the Fe supersaturation temperature, Fe concentration decreases faster in intrinsic gettered wafers than in as-grown wafers. Concentration saturated with annealing time for each sample and the saturated Fe concentration followed a simple Arrhenius relationship. Re-emission of Fe from the bulk defect region occurred above the gettering temperature. We conclude that in intrinsic gettering, Fe precipitates preferentially in the bulk defect region when the Fe impurities supersaturate as temperature drops.