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.     

Ethylene Epoxidation over Alumina-Supported Silver Catalysts in Low-Temperature AC Corona Discharge

In this paper, the epoxidation of ethylene over different catalysts—namely Ag/(low-surface-area, LSA)α-Al₂O₃, Ag/(high-surface-area, HSA)γ-Al₂O₃, and Au–Ag/(HSA)γ-Al₂O₃—in a low-temperature corona discharge system was investigated. In a comparison among the studied catalysts, the Ag/(LSA)α-Al₂O₃ catalyst was found to offer the highest selectivity for ethylene oxide, as well as the lowest selectivity for carbon dioxide and carbon monoxide. The selectivity for ethylene oxide increased with increasing applied voltage, while the selectivity for ethylene oxide remained unchanged when the frequency was varied in the range of 300–500 Hz. Nevertheless, the selectivity for ethylene oxide decreased with increasing frequency beyond 500 Hz. The optimum Ag loading on (LSA)α-Al₂O₃ was found to be 12.5 wt.%, at which a maximum ethylene oxide selectivity of 12.9% was obtained at the optimum applied voltage and input frequency of 15 kV and 500 Hz, respectively. Under these optimum conditions, the power consumption was found to be 12.6 × 10^?16 W s/molecule of ethylene oxide produced. In addition, a low oxygen-to-ethylene molar ratio and a low feed flow rate were also experimentally found to be beneficial for the ethylene epoxidation.     

Production of Hydrogen-Rich Syngas from Biogas Reforming with Partial Oxidation Using a Multi-Stage AC Gliding Arc System

The aim of this research work was to evaluate the possibility of upgrading the simulated biogas (70?% CH₄ and 30?% CO₂) for hydrogen-rich syngas production using a multi-stage AC gliding arc system. The results showed that increasing stage number of plasma reactors, applied voltage and electrode gap distance enhanced both CH₄ and CO₂ conversions, in contrast with the increases in feed flow rate and input frequency. The gaseous products were mainly H₂ and CO, with small amounts of C₂H₂, C₂H₄ and C₂H₆. The optimum conditions for hydrogen-rich syngas production using the four-stage AC gliding arc system were a feed flow rate of 150?cm³/min, an input frequency of 300?Hz, an applied voltage of 17?kV and an electrode gap distance of 6?mm. At the minimum power consumption (3.3?×?10^?18?W?s/molecule of biogas converted and 2.8?×?10^?18?W?s/molecule of syngas produced), CH₄ and CO₂ conversions were 21.5 and 5.7?%, respectively, H₂ and CO selectivities were 57.1 and 14.9?%, respectively, and H₂/CO (hydrogen-rich syngas) was 6.9. The combination of the plasma reforming and partial oxidation provided remarkable improvements to the overall process performance, especially in terms of reducing both the power consumption and the carbon formation on the electrode surface but the produced syngas had a much lower H₂/CO ratio, depending on the oxygen/methane feed molar ratio. The best feed molar ratio of O₂-to-CH₄ ratio was found to be 0.3/1, providing the CH₄ conversion of 81.4?%, CO₂ conversion of 49.3?%, O₂ conversion of 92.4?%, H₂ selectivity of 49.5?%, CO selectivity of 49.96?%, and H₂/CO of 1.6.     

Reforming of CO<Subscript>2</Subscript>-Containing Natural Gas Using an AC Gliding Arc System: Effect of Gas Components in Natural Gas

The objective of the present work was to study the reforming of simulated natural gas via the nonthermal plasma process with the focus on the production of hydrogen and higher hydrocarbons. The reforming of simulated natural gas was conducted in an alternating current (AC) gliding arc reactor under ambient conditions. The feed composition of the simulated natural gas contained a CH₄:C₂H₆:C₃H₈:CO₂ molar ratio of 70:5:5:20. To investigate the effects of all gaseous hydrocarbons and CO₂ present in the natural gas, the plasma reactor was operated with different feed compositions: pure CH₄, CH₄/He, CH₄/C₂H₆/He, CH₄/C₂H₆/C₃H₈/He and CH₄/C₂H₆/C₃H₈/CO₂. The results showed that the addition of gas components to the feed strongly influenced the reaction performance and the plasma stability. In comparisons among all the studied feed systems, both hydrogen and C₂ hydrocarbon yields were found to depend on the feed gas composition in the following order: CH₄/C₂H₆/C₃H₈/CO₂ > CH₄/C₂H₆/C₃H₈/He > CH₄/C₂H₆/He > CH₄/He > CH₄. The maximum yields of hydrogen and C₂ products of approximately 35% and 42%, respectively, were achieved in the CH₄/C₂H₆/C₃H₈/CO₂ feed system. In terms of energy consumption for producing hydrogen, the feed system of the CH₄/C₂H₆/C₃H₈/CO₂ mixture required the lowest input energy, in the range of 3.58 × 10⁻¹⁸–4.14 × 10⁻¹⁸ W s (22.35–25.82 eV) per molecule of produced hydrogen.     

Reforming of CO<Subscript>2</Subscript>-Containing Natural Gas Using an AC Gliding Arc System: Effects of Operational Parameters and Oxygen Addition in Feed

In this research, the reforming of simulated natural gas containing a high CO₂ content under AC non-thermal gliding arc discharge with partial oxidation was conducted at ambient temperature and atmospheric pressure, with specific regards to the concept of the direct utilization of natural gas. This work aimed at investigating the effects of applied voltage and input frequency, as well as the effect of adding oxygen on the reaction performance and discharge stability in the reforming of the simulated natural gas having a CH₄:C₂H₆:C₃H₈:CO₂ molar ratio of 70:5:5:20. The results showed marked increases in both CH₄ conversion and product yield with increasing applied voltage and decreasing input frequency. The selectivities for H₂, C₂H₆, C₂H₄, C₄H₁₀, and CO were observed to be enhanced at a higher applied voltage and at a lower frequency, whereas the selectivity for C₂H₂ showed an opposite trend. The use of oxygen was found to provide a great enhancement of the plasma reforming of the simulated natural gas. For the combined plasma and partial oxidation in the reforming of CO₂-containing natural gas, air was found to be superior to pure oxygen in terms of reactant conversions, product selectivities, and specific energy consumption. The optimum conditions were found to be a hydrocarbons-to-oxygen feed molar ratio of 2/1 using air as an oxygen source, an applied voltage of 17.5 kV, and a frequency of 300 Hz, in providing the highest CH₄ conversion and synthesis gas selectivity, as well as extremely low specific energy consumption. The energy consumption was as low as 2.73 × 10⁻¹⁸ W s (17.02 eV) per molecule of converted reactant and 2.49 × 10⁻¹⁸ W s (16.60 eV) per molecule of produced hydrogen.     

Ethylene Epoxidation in AC Dielectric Barrier Discharge Over Silver-Based Catalysts with Different Second Metals

Plasma Chemistry and Plasma Processing - This work was to investigate the effects of Ag-based catalysts and the addition of a second metal (Sn or Cu) loaded on an 0.1% wt% Ag catalyst on the...     

Synthesis Gas Production from CO2-Containing Natural Gas by Combined Steam Reforming and Partial Oxidation in an AC Gliding Arc Discharge

In this study, a technique of combining steam reforming with partial oxidation of CO₂-containing natural gas in a gliding arc discharge plasma was investigated. The effects of several operating parameters including: hydrocarbons (HCs)/O₂ feed molar ratio; input voltage; input frequency; and electrode gap distance; on reactant conversions, product selectivities and yields, and power consumptions were examined. The results showed an increase in either methane (CH₄) conversion or synthesis gas yield with increasing input voltage and electrode gap distance, whereas the opposite trends were observed with increasing HCs/O₂ feed molar ratio and input frequency. The optimum conditions were found at a HCs/O₂ feed molar ratio of 2/1, an input voltage of 14.5?kV, an input frequency of 300?Hz, and an electrode gap distance of 6?mm, providing high CH₄ and O₂ conversions with high synthesis gas selectivity and relatively low power consumptions, as compared with the other processes (sole natural gas reforming, natural gas reforming with steam, and combined natural gas reforming with partial oxidation).     

Combined Reforming and Partial Oxidation of CO<Subscript>2</Subscript>-Containing Natural Gas Using an AC Multistage Gliding Arc Discharge System: Effect of Stage Number of Plasma Reactors

The effect of stage number of multistage AC gliding arc discharge reactors on the process performance of the combined reforming and partial oxidation of simulated CO₂-containing natural gas having a CH₄:C₂H₆:C₃H₈:CO₂ molar ratio of 70:5:5:20 was investigated. For the experiments with partial oxidation, either pure oxygen or air was used as the oxygen source with a fixed hydrocarbon-to-oxygen molar ratio of 2/1. Without partial oxidation at a constant feed flow rate, all conversions of hydrocarbons, except CO₂, greatly increased with increasing number of stages from 1 to 3; but beyond 3 stages, the reactant conversions remained almost unchanged. However, for a constant residence time, only C₃H₈ conversion gradually increased, whereas the conversions of the other reactants remained almost unchanged. The addition of oxygen was found to significantly enhance the process performance of natural gas reforming. The utilization of air as an oxygen source showed a superior process performance to pure oxygen in terms of reactant conversion and desired product selectivity. The optimum energy consumption of 12.05 × 10²⁴ eV per mole of reactants converted and 9.65 × 10²⁴ eV per mole of hydrogen produced was obtained using air as an oxygen source and 3 stages of plasma reactors at a constant residence time of 4.38 s.     

Study of Ca-ATMP precipitation in the presence of magnesium ion

ATMP (aminotri(methylenephosphonic acid)), a phosphonate scale inhibitor used in the petroleum industry, was used as a model scale inhibitor in this study. One of the goals of this work was to determine the range of conditions under which Mg ions, which are formed in reservoir formations containing dolomite, modulate the formation of Ca-ATMP precipitate as a scale inhibitor. The results revealed that the amount of ATMP precipitated decreased with addition of Mg ions in solution at all values of the solution pH. Furthermore, an increase in both the solution pH and the concentration of the divalent cations in solution resulted in a change of the molar ratio of (Ca + Mg) to ATMP in the precipitates. At a low solution pH (pH 1.5), Mg ions had little effect on the composition of the Ca-ATMP precipitate. However, at higher values of the solution pH (pH 4 and 7), the Ca to ATMP molar ratio in the precipitates decreased with increasing concentration of the Mg. Here it was found that Mg ions replaced Ca ions on available reactive sites of ATMP molecules. These results determined the limits of the Mg ion concentration, which affects the precipitation of Ca-ATMP, Mg-ATMP, and (Ca + Mg)-ATMP. The dissolution of the scale inhibitors was studied using a rotating disk reactor. These experiments showed that the total divalent cation molar ratio (Ca + Mg) to ATMP in the precipitates is the primary factor that controls the rate of dissolution (release) of the phosphonate precipitates. The phosphonate precipitate dissolution rates decreased as the molar ratio of divalent cations to ATMP in the precipitates increased.     

Removal of solvent-based ink from printed surface of HDPE bottles by alkyltrimethylammonium bromides: effects of surfactant concentration and alkyl chain length

Three alkyltrimethylammonium bromides (i.e., dodecyl-, tetradecyl-, and hexadecyltrimethylammonium bromide or DTAB, TTAB, and CTAB, respectively) were used to remove a blue solvent-based ink from a printed surface of high-density polyethylene bottles. Either an increase in the alkyl chain length or the surfactant concentration was found to increase the deinking efficiency. Complete deinking was achieved at concentrations about 3, 8, and 24 times of the critical micelle concentration (CMC) of CTAB, TTAB, and DTAB, respectively. For CTAB, ink removal started at a concentration close to or less than its CMC and increased appreciably at concentrations greater than its CMC, while for TTAB and DTAB, significant deinking was only achieved at concentrations much greater than their CMCs. Corresponding to the deinking efficiency of CTAB in the CMC region, the zeta potential of ink particles was found to increase with increasing alkyl chain length and concentration of the surfactants, which later leveled off at some higher concentrations. Wettability of the surfactants on an ink surface increased with increasing alkyl chain length and concentration of the surfactants. Lastly, solubilization of ink binder in the surfactant micelles was found to increase with increasing alkyl chain length and surfactant concentration. We conclude that adsorption of surfactant on the ink pigment is crucial to deinking due to modification of wettability, zeta potential, pigment/water interfacial tension, and dispersion stability. Solubilization of binder (epoxy) into micelles is necessary for good deinking because the dissolution of the binder is required before the pigment particles can be released from the polymer surface.