Supercritical water gasification is expected to be an effective gasification process for wet biomass, but its reaction kinetics has not been elucidated for actual biomass feedstocks. In this study, seven biomass species are gasified in a supercritical water gasification reactor with and without use of a suspended activated carbon catalyst, and the overall gasification rates are determined. The feedstocks can be classified into three groups depending on the gasification characteristics. Representative gasification-rate parameters are presented. The homogeneous reaction had a pre-exponential factor of 50.0 s−1 and an activation energy of 67.9 kJ/mol. The heterogeneous reaction for feedstocks with high cellulose content had a pre-exponential factor of 4.87 × 109 s−1 and an activation energy of 161 kJ/mol, while, feedstocks with low cellulose content had a pre-exponential factor of 1.91 × 104 s−1 and an activation energy of 84.2 kJ/mol.
Direct conversion of methane to other valuable products such as ethylene, methanol, benzene, carbon, hydrogen, and syngas has been widely investigated. Such conversion requires high temperatures because of the strong C–H bond in CH4, and such high-temperature reactions present various problems: sequential reaction to decrease the selectivity to target products, need for multiple heat exchangers to use or recover high-temperature waste heat, materials that are stable at high temperatures, etc. To solve these problems, several trials have been undertaken to lower reaction temperatures using plasma, Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA), and electric fields. This review describes recent trends in methane conversion, and describes our methods to lower the reaction temperature.
TON type zeolites with different SiO2/Al2O3 ratios (57, 81, 112, and 140) were synthesized using 1,6-diaminohexane, n-butyl alcohol, and 1-ethylpyridinium bromide as structure-directing agents, and the catalytic performance of protonated forms for conversion of ethanol into light olefins such as ethylene, propylene, and butenes was investigated. Although the yields of light olefins were dependent on the SiO2/Al2O3 ratios of the HTON type zeolites and the reaction conditions such as temperature and contact time, the relatively high propylene yield of ca. 25 C-% was obtained. HTONs with higher SiO2/Al2O3 ratios exhibited longer catalyst life. These results strongly indicate that TON type zeolite with 10-membered rings (0.46 nm × 0.57 nm) and only straight channels has high potential for the production of propylene from ethanol. The catalytic performance of HTON type zeolite was slightly improved by strontium modification.
To investigate the effect of fuel composition on mixture formation in the intake port-injection gasoline engine, engine tests with in-cylinder gas sampling were conducted using 10 types of model gasoline consisting of 13 hydrocarbon components, and the hydrocarbon components in the cylinder gas sampled before ignition were analyzed by gas chromatography. Hydrocarbon components with higher boiling point tended to have lower evaporated fractions under all test conditions, and m-xylene with boiling point of 139 °C and components with higher boiling point may influence the total amount of vaporized fuel under the low temperature engine oil/water conditions found during cold starting. Comparison of the quantities of evaporated components from experiments found very good agreement with values from numerical calculations based on equations derived from the saturated vapor pressures of components. In conclusion, the vaporization characteristics of hydrocarbon components of fuels in an engine may be determined by the saturated vapor pressures.
Thermal cracking of paraffinic atmospheric residue (AR) was performed in a continuous-flow reactor under the reaction conditions of 440-520 °C and N2 0.2-0.8 MPa, and the effects of the reaction temperature and pressure on the product distribution were examined. The vacuum residue fraction gradually decreased up to 480 °C and almost disappeared at higher temperatures. Accordingly, the yields of total distillate and coke increased and became nearly constant over 480 °C. As the heavy distillate yield increased over 480 °C, the yield of lighter distillates was the highest at 480 °C and decreased at higher temperature. When the reaction pressure was increased, the heavy distillate yield decreased with increasing yields of lighter distillates and coke. Two paraffinic and two Middle East ARs were thermally cracked under the conditions of 480 °C, N2 0.4 MPa and 0.5 h, and the product composition and properties were compared. The yield of distillates (C4-500 °C) was around 90 % for paraffinic ARs, and 70-80 % for Middle East ARs. The sulfur contents of the distillate products from paraffinic ARs were much lower than those of Middle East ARs, but the difference in the nitrogen contents was not significant. Pyrolyzed middle and heavy distillates were hydrotreated to investigate their hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) reactivities. The HDS rates of the distillates obtained from paraffinic ARs were 4-6 times higher than those of Middle East ARs. The HDN rates were comparable for the middle distillates, but the HDN rates of the heavy distillates from paraffinic ARs were lower than those from Middle East ARs.
Ultrasonic preparation of two-phase water-in-oil (W/O) emulsion fuel was carried out using an ultrasonic apparatus with a rod horn. The effect of the position of the horn tip emitting ultrasound into the sample mixture on emulsion stability was investigated for water (10 vol%)/diesel fuel/surfactant (2 vol%) mixtures. In addition, the effects of ultrasonication time and vegetable oil addition on viscosity, water droplet size and combustion characteristics of the emulsion fuels prepared by ultrasonic treatment were studied for water (5 vol%)/diesel fuel/surfactant (2 vol%) and water (5 vol%)/diesel fuel/vegetable oil (5 vol%)/surfactant (2 vol%) mixtures. The stability of the emulsion fuel significantly depended on the tip position of the ultrasonic horn immersed in the mixture. Both the stability and viscosity of the emulsion increased with sonication time for the first 10 min and then remained constant. The water droplets in the emulsions of water/diesel fuel/surfactant and water/diesel fuel/vegetable oil/surfactant were extremely fine and median diameter of the droplets was about 0.3 μm. The water content in the W/O emulsion fuels was significant in the reduction in soot, NO and NOx during combustion.
Asphaltene dispersed in toluene at 10-500 mg/L was analyzed using small-angle X-ray scattering (SAXS) with synchrotron radiation. The degree of fluctuation in the solutions showed a discontinuous maximum at 50 mg/L. Distance distribution function (DDF) analysis of the SAXS profiles suggested that the asphaltene formed a complex aggregated structure at 50 mg/L, whereas rodlike structures formed at 100 and 500 mg/L. The results indicate that 50 mg/L is a specific concentration on asphaltene aggregation state in toluene.