Mechanical treatment of cellulose is an emerging concept for dramatically increasing the hydrolytic reactivity of cellulose. We report here the recent developments in the field of mix-milling and mechanocatalysis for cellulose pre-treatment. Mix-milling enhances the solid-solid contact between cellulose and carbon catalyst during hydrolysis reaction. Kinetic study shows that mix-milling specifically enhances the rate of cellulose to oligomer hydrolysis (13 fold), whereas the rate of oligomer to glucose hydrolysis is not influenced. Very high glucose yield of 88 % was obtained by mix-milling cellulose with K26 and using trace amount of HCl. Mix-milling was also applicable for single-pot hydrolytic hydrogenation of cellulose to sugar alcohols. Ru/AC catalyst was stable under mix-milling condition and 68 % of sugar alcohol was obtained using only 9 atm H2 pressure. Unlike mix-milling, mechanocatalysis takes advantage of presence of strong acid catalyst during milling to depolymerize cellulose. Completely soluble glucans were obtained after 7.5 h of milling in the presence of 0.25 mmol of acid g−1 cellulose. The glucans were highly reactive towards conventional and transfer hydrogenation reaction, affording ca. 90 % sugar alcohol yield in both cases after 1 h reaction. The transfer hydrogenation of cellulosic glucans was successfully upgraded to a lab-scale fixed-bed reactor.
The aim of this study was to improve the performance of alumina-based diesel oxidation catalysts by optimization of both the composition and pore structure of the support material. For this purpose, we prepared a series of alumina-based supports via sol-gel methodology and loaded these materials with the active catalytic components Pt and/or Pd. In terms of the composition, SiO2 showed promise as a secondary component at an optimum concentration of approximately 4 wt%. With regard to the pore structure, the catalytic activity for the oxidation of hydrocarbons and NO improved as the support mesopore size was increased up to approximately 10 nm. In addition, in the case of diesel fuel mist oxidation, it was shown that the presence of macropores above 1 μm was beneficial. On the basis of these results, we developed hybrid supports with both mesopores and macropores by the addition of a pore forming agent during the SiO2–Al2O3 preparation process, and confirmed a subsequent improvement in catalytic activity.
Metal phosphide has been widely investigated as a hydrotreating catalyst. The preparation and performance of noble metal phosphide catalyst was examined to develop new phosphide hydrotreating catalysts. The supports affect reducibility of phosphate as a P precursor. Since phosphate does not strongly interact with SiO2 and TiO2 supports, Rh2P was easily formed on these supports. Furthermore, formation of Rh2P enhanced the hydrodesulfurization (HDS) activity of supported Rh–P catalyst. The type of noble metal (NM) and P/NM ratio also strongly affect formation of noble metal phosphide and HDS activity. Excess P facilitates formation of noble metal phosphides at lower reduction temperature. In contrast, excess P causes the aggregation of noble metal phosphide and formation of phosphorus rich noble metal phosphide. Rh–1.5P/SiO2 catalyst had high and stable activity for HDS reaction. Furthermore, this catalyst showed significantly higher hydrodenitrogenation (HDN) activity than sulfided NiMoP/Al2O3 catalyst. Therefore, Rh2P has great potential as a new hydrotreating catalyst.
Novel hollow-fiber carbon membranes were successfully fabricated using poly(phenylene oxide) (PPO) and derivatives as a precursor polymer. These free-standing carbon membranes had permeation properties above the upper bound of conventional polymeric membranes including PPO precursor polymers. Metal-containing carbon membranes derived from sulfonated PPO (SPPO) were also prepared by the ion exchange method and the effect of metal cations on the gas transport properties was studied. Transition metal ions such as Ag+ significantly enhanced gas permeabilities without affecting the ideal selectivities. The development of flexible hollow-fiber carbon membranes was successfully achieved using SPPO as a precursor polymer. Superior flexibility combined with excellent gas separation performance were obtained by pyrolysis at 600 °C. The present findings indicate the potential for commercial application of carbon membranes. Some applications of carbon membranes were also investigated such as selective dehydration of olefin gases, alcohol dehydration by pervaporation and CO2/CH4 mixed gas separation.
Fluid catalytic cracking (FCC) commercial units require catalysts with high cracking activity to produce high octane number gasoline fraction to satisfy fuel oil demand and environmental regulations. Previously addition of rare earth metals obtained enhanced cracking activity, but the octane number was decreased by promotion of the hydrogen transfer reaction. This study investigated phosphorus material as a new component of FCC catalyst, to enhance the cracking activity and prevent octane number decrease. Mono aluminum phosphate (Al2O3 · 3P2O5 · 6H2O) induced increased cracking activity and higher octane number in FCC gasoline than rare earth metals.
Modified Ni/α-Al2O3 was investigated as a catalyst for partial oxidation of methane for syngas production at low temperature. Only Co-modified Ni/α-Al2O3 catalyst (Ni/Co/α-Al2O3) catalyzed the reaction below 673 K. 6.6 wt% Ni/3.6 wt% Co/α-Al2O3 catalyst showed the optimum balance of low reaction temperature and less carbon deposition. Structural analysis revealed close-contact or alloy structures between Ni and Co on Ni/Co/α-Al2O3 catalyst, which were crucial for low-temperature reaction. CH4/O2 pulse dosing test revealed that Co addition to Ni/α-Al2O3 catalyst improved CH4 combustion activity due to tolerance of oxidation.