Model compounds (glucose and glycerol) and real biomass (sugarcane bagasse and Chlorococcum littorale) were partially oxidized to hydrogen in high temperature high pressure water (120-300 °C at saturated pressure of water). Biomass conversion into gas directly by partial oxidation in a one-pot process was considered by use of a catalyst in a batch type reactor. The total gas yield and hydrogen selectivity from all the reactants were low. To improve the gasification efficiency, a two-step process was proposed: partial oxidation of the organic compound into hydrogen precursor (here formic acid) followed by selective decomposition of the intermediate into hydrogen. To clarify the possibility of the process, model compounds (glycerol and glucose) were used. The effects of operation parameters for each step (temperature, water to organic ratio, oxygen to organic ratio, catalyst) were investigated using a batch reactor. For glycerol oxidation at lower temperature (120-160 °C), kinetic analysis was performed to clarify the reaction mechanism and formic acid formation. For formic acid decomposition into hydrogen, several metal oxides were carried out to accelerate the reaction rate, and ZnO was found to be effective at 300 °C. The yield of hydrogen from the combination of formic acid formation from glucose and hydrogen formation from the oxidized material including formic acid was investigated using a flow apparatus. However, the yield of hydrogen was lower than expected and further improvement of the two-step reaction process is required.
Orthorhombic and trigonal Mo–V–oxides, which are the some of the most promising selective oxidation catalysts, were produced by the building blocks mechanism. Both oxides were produced by reaction of ammonium heptamolybdate and vanadyl sulfate under hydrothermal conditions. Structural characterization of the orthorhombic and trigonal Mo–V–oxides revealed that both oxides contained pentagonal (M)M5O21 units. The pentagonal (M)M5O21 units were also found in the reaction mixture before the hydrothermal reaction. Therefore, assembly of the pentagonal (M)M5O21 units can occur under hydrothermal conditions to form three-dimensional Mo–V-based metal oxide solids. Based on the building block mechanism, orthorhombic Mo–V–Sb–oxide single crystal large enough for single crystal X-ray analysis was formed, and the first single crystal X-ray structure analysis of the orthorhombic Mo–V-based oxides was obtained. The orthorhombic Mo–V–oxide has an interesting micropore channel, in which micropore volume is continuously and reversibly tunable by redox treatment.
Monod equation is often employed to express the increase in microbiology concentration. However, it is an empirical equation, and no statistical analysis on its validity has been reported. In this study, 1042 data points from 88 figures in 32 literatures are used to check the validity of Monod equation. Monod equation successfully reproduced the literature data with an average error less than 5 %. Maximum growth rate of Saccharomyces cerevisiae is compared between literatures, and it is found that the maximum growth rate largely depends on strain and medium. Temperature effect on the maximum growth rate can be expressed using the Arrhenius equation.
Demand for motor gasoline has been shrinking in developed countries, so the production of cracked distillates, used as gasoline blend stocks, requires other uses. Aromatics are widely used in the chemical industry and techniques to recover aromatics from the fractions must be developed. In this study, cracked kerosene was selected as an example of cracked distillates and liquid-liquid equilibria with aqueous solutions of sulfolane or methanol were measured. Firstly, the cracked kerosene was analyzed to identify the 23 major components. The distribution coefficients of aromatics were higher than those of alkanes, and the coefficients decreased with higher mass fraction of water in the aqueous phase. The separation selectivities of aromatics relative to nonane increased with the mass fraction of water in the aqueous phase, and with lower carbon number of the aromatics. The separation selectivities were slightly larger with the aqueous phase of sulfolane than with methanol. The distribution coefficients and separation selectivities of total aromatics relative to alkanes were higher with sulfolane aqueous solution than with aqueous solution of methanol. The addition of water could enhance the separation selectivity and the effects were greater for aqueous solution of methanol.
Catalytic hydrothermal saccharification of rice straw was carried out in the presence of sulfonated mesoporous silica (SBA-15) -based solid acid catalysts. Effects of reaction time, reaction temperature and weight ratio of solid acid catalyst to rice straw on the saccharification of rice straw were investigated. With increasing reaction time and reaction temperature, the yield of monosaccharide initially increased and then decreased, but the yield of byproducts increased. With increasing weight ratio of solid acid catalyst to rice straw up to 25 %, the yield of monosaccharide initially increased and then remained almost constant. The yield of monosaccharide was 38 % for the saccharification of rice straw carried out at 180 °C for 1 h with the weight ratio of rice straw/distilled water/solid acid catalyst equal to 3/30/0.5 (g/g/g). The composition of rice straw and crystallinity index of cellulose in rice straw before and after the saccharification were determined, respectively. Based on the composition analysis, most xylan and glucan derived from hemicellulose were decomposed, but glucan derived from cellulose was little decomposed via catalytic hydrolysis at 180 °C and below. On the other hand, xylan and glucan derived from hemicellulose were almost completely decomposed, and part of glucan derived from cellulose was also decomposed at 200 °C and above. At the same time, some ash and lignin in rice straw were removed in all the reactions.
The desulfurization behavior of oil sand bitumen in supercritical water (SCW) was examined to evaluate the possibility of desulfurization using SCW. Athabasca bitumen was treated with water, nitrogen, or toluene at 430-450 °C and 23-30 MPa using a batch autoclave. SCW showed the same trends in sulfur content, liquid and coke yields as high-pressure nitrogen. Furthermore, liquid products obtained using SCW had the same distributions of sulfur-containing compounds as high-pressure nitrogen and showed no specific results, whereas supercritical toluene was involved in desulfurization as a reactant. However, the reaction media influenced the sulfur distribution to coke with the variations of desulfurization ratio and sulfur conversion: that using SCW was higher than using toluene and lower than using nitrogen. SCW showed dispersion effect against the desulfurization reaction, whereas toluene showed radical scavenging and dispersion effects. The dispersion of reactant enhances intramolecular dehydrogenation and keeps the product toluene-soluble rather than coke. Because SCW retained heavy fraction as liquid product than high-pressure nitrogen, the desulfurization of bitumen using SCW was not evaluated to be practically promising.
Catalytic cracking of n-hexane over MFI-type zeolite catalysts was examined at a reaction temperature of 823 K under atmospheric pressure. Conversion of n-hexane depended on the Si/Al ratio of the MFI-type zeolite catalyst, so the relationships between the product yields and n-hexane conversion could be fitted as single, smooth curves. To investigate the effect of crystal size of MFI-type zeolite on the catalytic activity, light olefin yield and product composition, nano- and macro-sized MFI-type zeolites with crystal sizes of approximately 150-200 nm and 1.5 μm, respectively, were prepared. The nano-sized zeolite exhibited a high n-hexane conversion with stable activity for 18 h compared with the macro-sized zeolite. The high activity of the nano-sized MFI-type zeolite is considered to be due to rapid diffusion of the produced light olefins out of the intracrystalline pores of the nano-zeolite due to the low diffusion resistance. Accordingly, the nano-sized zeolite achieved high yield of light olefins (approximately 35 %) and long catalyst lifetime.