Cellulase-Producing Bacteria from Thai Higher Termites, <Emphasis Type="Italic">Microcerotermes</Emphasis> sp.: Enzymatic Activities and Ionic Liquid Tolerance

The three highest hydrolysis-capacity-value isolates of Bacillus subtilis (A 002, M 015, and F 018) obtained from Thai higher termites, Microcerotermes sp., under different isolation conditions (aerobic, anaerobic, and anaerobic/aerobic) were tested for cellulase activities—FPase, endoglucanase, and β-glucosidase—at 37 °C and pH 7.2 for 24 h. Their tolerance to an ionic liquid, 1-butyl-3-methylimidazolium chloride ([BMIM]Cl), was also investigated. The results showed that the isolate M 015 provided the highest endoglucanase activity whereas the highest FPase and β-glucosidase activities were observed for the isolate F 018. The isolate F 018 also showed the highest tolerance to [BMIM]Cl in the range of 0.1–1.0 vol.%. In contrast, the isolate A 002 exhibited growth retardation in the presence of 0.5–1.0 vol.% [BMIM]Cl.     

A reality check on using NaAlH4 as a hydrogen storage material

Sodium aluminum hydride or sodium alanate (NaAlH₄) has been considered as a potential material for hydrogen storage. Although its theoretical hydrogen storage capacity is 5.5 wt.% at 250 °C, the material still has its drawback in the regeneration issue. With the use of certain catalysts, the regeneration problem can somewhat be alleviated with added benefits in the decrease in the hydrogen decomposition temperature and the increase in the decomposition rate. This work summarizes what we have learned from the decomposition of NaAlH₄ with/without catalysts and co-dopants. The decomposition was carried out using a thermovolumetric apparatus. For the tested catalysts—HfCl₄, VCl₃, TiO₂, TiCl₃, and Ti—the decomposition temperature of the hydride decreases; however, they affect the temperature in the subsequent cycles differently and TiO₂ appears to have the most positive effect on the temperature. Sample segregation and the morphological change are postulated to hinder the reversibility of the hydride. To prevent the problems, co-dopants—activated carbon, graphite, and MCM-41—were loaded. Results show that the hydrogen reabsorption capacity of HfCl₄- and TiO₂-doped NaAlH₄ added with the co-dopants increases 10–50% compared with that without a co-dopant, and graphite is the best co-dopant in terms of reabsorption capacity. In addition, the decomposition temperature in the subsequent cycles of the co-dopant doped samples decreases about 10–15 °C as compared to the sample without a co-dopant. Porosity and large surface area of the co-dopant may decrease the segregation of bulk aluminum after the desorption and improve hydrogen diffusion in/out bulk of desorbed/reabsorbed samples.     

Study on the adsorption of 1,5-, 1,6- and 2,6-dimethylnaphthalene on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites

Adsorption of the equilibrium mixture of 1,5-, 1,6- and 2,6-dimethylnaphthalene (DMN) was investigated on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites using pulse test and breakthrough techniques. It was found that the adsorption of the DMNs would proceed through a complex mechanism governing by at least molecular diffusion, acid-base interaction, preferential interaction with cation and molecular displacement. All ion-exchanged faujasite zeolites only provided rejective systems for 2,6-DMN and some of them were potential adsorbents for the 2,6-DMN purification.