Advanced Materials Research Vols. 805-806

Abstract: The electrochemical behavior of zinc electrode with bismuth addition in 35%KOH solutions has been investigated systematically by electrochemical methods including linear polarization, potentiostatic polarization, potential-time measurements at a constant current density, combining the observations of scanning electron microscopy (SEM). Linear polarization results showed that the open circuit potential shifted positively with increasing bismuth content, which is explained based on the gassing data and change in the exchange current of the zinc electrode. Addition of bismuth increased the exchange current of zinc reaction and caused an increase in the measured open circuit potential. Galvanostatic results showed that the addition of bismuth shortened the passivation time. Scanning electron microscopy images showed that the addition of bismuth aggravated the corrosion of zinc electrode which may be responsible for the increased tendency to passivation at high current densities. It has been found that at low current densities the reaction kinetics may be increased by addition of Bi, which is general agreement with the discharging test of actual alkaline batteries.

Abstract: The performance of a packed-bed reactor typically used in Gas-to-Liquid (GTL) or Biomass-to-Liquid (BTL) technologies in producing liquid fuels was affected by unfavorable high pressure drop, flow and temperature maldistributions which in turn could cause severe catalyst deactivation, and result in inefficient reaction etc. A certain types of fluid mixers such as Kenics^TM or Mixing & Stirring type static mixers had been suggested to improve the performance of this type of reactor. In order to design a proper modified reactor by mean of an installation of such mixing structures for the pilot plant in liquid fuel production via Fischer-Tropsch Synthesis (FTS) conducted at the RCC research center, this study had to characterize the hydrodynamics and heat transfers within a packed-bed modified by Kenics^TM and Mixing & Stirring type static mixers. During the FTS, the syngas i.e. CO and H₂ was fed through the bed of catalyst causing the temperature rise due to an exothermic enthalpy, and the flow and temperature distributions of mixed gas within the catalyst bed were influenced. The improved velocity and temperature distributions and heat transfers were exhibited by using such mixers e.g. rather uniform distributions and higher heat transfer coefficient. Thus, the better performance of the reactor could be expected.

Abstract: The production of syngas via carbon dioxide reforming or dry methane reforming (DMR) was studied in the present study. To reduce pressure drop and improve the performance, the reaction was carried out over a 10%Ni/Al₂O₃-MgO catalyst in a wall-coated monolith reactor at about 600 ^°C, atmospheric pressure. The monolith reactor comprised of 37 circular flow channels of 3-mm-diameter. The reactant gases i.e. CH₄ and CO₂ at stoichiometric molar ratio of 1:2 was fed into the reactor at the volumetric flow rate of 450, 600 and 750 mL/min corresponding to various gas space velocities (GSV) i.e. 0.57, 0.76, and 0.96 s^-1, respectively. Under 24-hr continuous operations, the stability of system could be sustained and the deactivation by carbon deposition was not observed. The experimental results did show that the conversion of methane depended upon the GSV i.e. the %CH₄ conversion were 50, 45 and 40% for the GSV of 0.57, 0.76, and 0.96 s^-1, respectively. In addition, the %H₂ yield, %H₂ selectivity, %CO yield, %CO selectivity also depended on the feeding rate and so affected the performance of the wall-coated monolith reactor as a reformer.

Abstract: LiFePO₄/C composites were synthesized by pyrolyzation of starch gel containing FeC₂O₄, Li₂CO₃ and NH₄H₂PO₄. The crystalline structures, micro-morphologies and electrochemical performances of LiFePO₄/C composites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and galvanostatic charge-discharge, respectively. The results indicated that the LiFePO₄ nanoparticles showed the homogeneous particle size distribution and were bound together by carbon network when carbon content was 3.9wt%. Moreover, this sample exhibited the highest initial discharge capacity of 154.8 mAh·g^-1 at 0.15 C rate, excellent cyclic ability and rate capability about 99.6 mAh·g^-1 applied 5 C rate in the 20th cycle at room temperature.

Abstract: By using heavy polycyclic aromatic hydrocarbon from a factory in Northwest China as raw material and 6% Ni/USY as catalyst, a study on hydrogenation process is carried out with a high-pressure hydrocracking assessment device, which mainly focuses on investigating the effect of LHSV, oil hydrogen ratio, temperature and pressure on heavy polycyclic aromatic hydrocarbon. Experimental results show that under the condition that the optimum LHSV is 3.0 h^-1 and the ratio of oil to hydrogen is 600, both conversion rate of heavy components and yield of one-membered ring increase at first and then decrease with reaction temperature, with the peak value of conversion rate at 320°C and yield peak at 340°C. Though fluctuates with the increase of pressure, but conversion rate of heavy components shows an overall upward trend. Yield of one-membered ring increases at first and then decreases with pressure, and eventually tends to stabilize. When the temperature is greater than 300°C, the yield slightly fluctuates with pressure and shows an overall increasing trend.

Abstract: Heat transfer characteristics of the CO₂-based foam fracturing fluid were investigated on the large-scale test loop of foam fracturing fluid. The relationship between thermal conductivity coefficient and shear rate was introduced into the expression of the convective heat transfer coefficient. Thus the expression of the convective heat transfer coefficient of power-law fluid was revised. The results show that the convective heat transfer coefficient of the fracturing fluid increases with the increase of the pressure, the foam quality and the shear rate. The convective heat transfer coefficient of the foam fracturing fluid calculated by the revised calculation formula is highly consistent with the experimental data at low pressure. The deviation is bigger at high pressure, but still within 20%.

Abstract: Natural gas can be a raw material to produce synthetic liquid fuels via Gas to Liquid process (GTL). The process is consist of 4 main parts which are cleaning unit, reforming unit, Fischer-Tropsch unit (FT) and product upgrading unit. To evaluate potential of having this kind of process for Nongtum A Reservoir, Thailand, technical feasibility of GTL process towards heat integration needed to be done. This work presented a process model, combined heat and power (gas generation) of Nongtum A Reservoir by using the total heat integration concept. Volume of natural gas at Nongtum A Reservoir is 56,634 m³/day at 10 bar, and 40 deg.C. ResuIts of the model simulation are the overall thermal efficiency of 10.32% to 14.88%, gasoline product of 435 to 575 bbl/day, and diesel product of 621 to 947 bbl/day depending upon a split ratio of natural gas to gas generation.

Abstract: The composite photocatalysts of Ni (OH)₂ modified Cd_1-xZn_xS (x=0, 0.2) nanorods were synthesized via a simple deposition-precipitation method using nanorods as support and Ni (NO₃)₂ as nickel hydroxide precursor. The structures, morphologies and optical properties of the catalysts were characterized by X-ray diffraction, scanning electron microscopy, high resolution transmission electron spectroscopy and UV-visible absorption spectroscopy. The photoactivities of the catalysts were examined toward hydrogen production by water splitting under simulated solar irradiation. Results show that the catalyst of Ni (OH)₂-Cd_0.8Zn_0.2S nanorods exhibits a significantly enhanced H₂-production activity in compared to the Ni (OH)₂-CdS nanorods. The reason for the different effects of Ni (OH)₂ modification on the photoactivities of the two catalysts was discussed, and the possible mechanism related to the photocatalytic process was proposed.

Abstract: The CeO₂/CuO catalysts were synthesized by the hydrothermal method. The study shows that the particle-like CeO₂ can self-assemble into the rod-like CeO₂ during the hydrothermal procedure and the rods of CeO₂ become shorter with the decrease of Ce/Cu molar ratio. The highly dispersed CuO is favorable for CO oxidation at lower temperature, and the bulk CuO can help CO oxidation at higher temperature due to the limitation of reduction.

Abstract: Aimed at the high water cut crude oil in Daqing Oilfield, polyether demulsifiers was synthesized indoor to investigate the dehydration effect of different initiator, catalyst, the mixture ratio of ethylene oxide and propylene oxide, block number of demulsifier on demulsifier. The results show that the polyether demulsifiers have high dehydration rate and out of the water of dehydration was clear. After using the polyether demulsifier, the crude oil demulsification temperature decreased from 55 °C to 40 °C and the average water cut of the crude oil is about 0.20%, it is reached the national crude oil external transport standard.