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Phenol hydroxylation with TS-1 was studied in a chromatographic reactor. TS-1 not only acts as the catalyst for the reaction but also the adsorbent for the separation. The reaction/separation was carried out at 60°C with water and 0.2 wt% of aqueous H2O2 as the desorbent. Separation of hydroquinone(HQ) can be achieved in all cases. With water as the desorbent, separation of catechol(CT) depends on the phenol feed concentration, which has been confirmed from both reaction/separation in the chromatographic reactor and equilibrium competitive adsorption experiment. Some unknown by-products not commonly reported in batch experiments have been observed here. TS-1 can also be regenerated using just water. With the aqueous mixture of H2O2 as the desorbent, separation of HQ and CT is possible. Reactive separation schemes based on the simulated counter-current technology have been proposed according to the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: The concept of fabricating hollow fibers with double-layer mixed-matrix materials using the same polymeric matrix has been demonstrated for gas separation. Polyethersulfone (PES)–beta zeolite/PES–Al2O3 dual-layer mixed-matrix hollow fiber membranes with enhanced separation performance have been fabricated. This study presents an innovative approach of utilizing low cost PES and Al2O3 to replace expensive polyimides as the supporting medium for dual-layer mixed-matrix hollow fibers and eliminating interlayer de-lamination problems. The incorporations of 20wt% beta zeolite in the outer selective layer and 60wt% Al2O3 in the inner layer coupled with spinning at high elongational draw ratios yield membranes with an O2/N2 selectivity of 6.89. The presence of Al2O3 particles enables the membrane to retain its porous substructure morphology in the course of annealing above the glass transition temperature of PES. Moreover, spinning at high elongational draw ratios results in the re-distribution of Al2O3 particles towards both edges of the inner layer. Not only do the permeance and selectivity of the fibers increase, but also greater mechanical properties and lower degree of shrinkages are obtained. Therefore, the combination of PES–beta zeolite and PES–Al2O3 nanoparticles with a reasonable draw ratio may be another promising approach to produce hollow fibers with double-layer mixed-matrix materials. [Copyright &y& Elsevier]

Abstract: In this study, an alternative non-energy intensive system for the production of 2,6-DMN (catalytic isomerization in a solvent media and adsorptive purification) was investigated using the pulse test technique. The integrations of the isomerization to the adsorption were accomplished in two different approaches; subsequent adsorption after the isomerization and the reactive adsorption based technique. By subsequently connecting the adsorption unit after the isomerization with the selected adsorbent, catalyst and desorbent, the system shows a potential for producing high purity 2,6-DMN. Moreover, the results also suggest a possibility to enhance the overall productivity of 2,6-DMN by separating the chemical from the product stream during the isomerization. However, the results from the reactive adsorption study indicate only a narrow possible operating window for the high purity 2,6-DMN production. Carrying out the system at the temperatures that the isomerization can reach its equilibrium entails the reduction in either the 2,6-DMN separation due to the very fast in the reaction kinetics or the 2,6-DMN yield by the backward isomerization from 2,6- to 1,6- and 1,5-DMN. On the other hand, operating the system below the equilibrium of the isomerization at appropriate temperatures is only a possible approach to produce high purity 2,6-DMN using the reactive adsorption technique. [Copyright &y& Elsevier]

Abstract: The segregation of bulk Al after the hydrogen desorption may be one of many reasons why there is the incomplete hydrogen re-absorption and the need for higher desorption temperature in subsequent desorption of HfCl4- and TiO2-doped NaAlH4. In this work, we attempted to improve hydrogen storage capacity of 4mol% HfCl4- and 4mol% TiO2-doped NaAlH4 by adding a co-dopant (graphite, activated carbon, and MCM-41) using ball milling technique. It was found that the co-dopants significantly affect the hydrogen desorption/re-absorption of the hydride. Results show that the hydrogen re-absorption capacity of HfCl4- and TiO2-doped NaAlH4 added with the co-dopants increases 10–50% as compared with that without a co-dopant, and graphite seems to be the best co-dopant. Moreover, the hydrogen desorption temperature in the subsequent cycle of co-dopant doped samples decreases about 10–15°C compared to the sample without a co-dopant. It could be explained that high porosity and large surface area of the co-dopants would decrease the segregation of bulk Al after the desorption and improve hydrogen diffusion in/out bulk of desorbed/re-absorbed samples. [Copyright &y& Elsevier]