The potential of Ru/CeO2 catalysts to catalyze the synthesis of ammonia from renewable hydrogen was explored under ambient and high-pressure conditions. Different types of Ru precursors, CeO2, and their combinations strongly influenced NH3 synthesis activity. The catalytic activities of Ru(acac)3 and Ru(NO)(NO3)3 were relatively high at ambient pressure. The activity of 1 wt% Ru/CeO2 with Ru(NO)(NO3)3 as a Ru precursor was studied at high pressure. The dependence of NH3 synthesis activities on temperature, pressure, space velocity, and H2/N2 ratio were investigated. The parameter dependences differed somewhat between different types of CeO2. Use of CeO2 with high surface area resulted in relatively high NH3 synthesis rates and good low-pressure activity. Demonstration of NH3 synthesis using the optimized Ru/CeO2 catalyst was performed with a bench-scale plant with the recirculation of unreacted gases. NH3 synthesis activity was measured using more than 130 combinations of temperature, pressure, space velocity, and H2/N2 ratio. NH3 concentrations in the product gases were close to equilibrium value for the reaction conditions around 400 °C. The effects of operation load on the response of NH3 production was acceptable. Ru/CeO2 catalysts are good candidates for industrial NH3 synthesis from renewable hydrogen.
A new swirling liquid flow type fine bubble organic reactor was developed to introduce gaseous reactants as fine bubbles for gas-liquid organic reactions. Promotion of gas-liquid organic reaction by O2 fine bubbles was verified using oxidation of benzaldehyde as a model reaction. The remarkable promotion effects of O2 fine bubbles were confirmed. Promotion of the reaction was dominated by improvement of the conversion rather than the selectivity. Reaction using O2 fine bubbles required about 1/5 of the reaction time for 90 % conversion compared to the aeration method with the same O2 flow rate. The unique properties of fine bubbles compared to normal-sized bubbles, such as large surface area per volume, low floating speed, and maintenance of supersaturation of gas in the solvent, were considered to have greatly affected the conversion rate improvement.
Mesoporous carbon materials have been employed as supports of iron–carbon complex catalysts for slurry phase Fischer-Tropsch (FT) synthesis. The mesoporous carbon-supported iron catalysts were prepared through the co-precipitation from aqueous solutions of ferrous and copper sulfates in the presence of mesoporous carbon materials synthesized through the soft-template and hard-template methods. The iron catalyst supported by the soft-templated mesoporous carbon exhibited a sharp product distribution at C5-C9 fractions (62 % in hydrocarbons) in FT synthesis at 260 °C under 2 MPa-G. On the other hand, the catalyst supported by the hard-templated mesoporous carbon having far larger mesopore openings showed a high selectivity to higher hydrocarbons (69 % of C10+ in hydrocarbons) with a high hydrocarbon productivity (0.74 g/g-Fe h). This catalyst also showed high catalytic activity and long lifetime up to 30 h even at lower reaction pressure of 1 MPa-G. The very large inner space of mesopores that are not easily blocked through the wax formation would be responsible for such high catalytic activity.
The presence of semiclathrate hydrate former salts such as tetra n-butylammonium chloride (TBAC) mild the thermodynamic conditions of hydrate formation, considerably. As opposed to the abundant studies undertaken on the thermodynamics of hydrate forming in the presence of these salts, their kinetics needs further investigation. In this research, the kinetics of methane-TBAC semiclathrate hydrate forming has been focused on. The effects of the polysorbate 80, various weight fractions of TBAC, and beginning pressure of the cell on the moles of gas encaged in hydrate cavities and storage capacity of formed hydrates are investigated. The tests were carried out in the isothermal condition of 276.65 K. The results revealed that by raising the weight fraction of TBAC from 5 to 15 wt%, the moles of gas encaged in hydrate cavities and storage capacity of formed hydrate decreases. Utilization of polysorbate with a concentration of 15 ppm along with TBAC, promotes the kinetics of semiclathrate hydrate forming process (HFP) and raises the storage capacity, compared to TBAC aqueous solution. Finally, the influence of the beginning pressure of the cell on the kinetics of TBAC-methane hydrate forming is studied. Results indicate that by raising the beginning pressure of the cell, the moles of gas encaged in hydrate cavities and storage capacity raises.
Methanol production from methane in a batch reactor using whole cells of Methylosinus trichosporium OB3b grown in medium containing 50 μmol L–1 copper was examined. Methanol productivity of the biocatalyst was 9.56 mmol g-dry cell–1 h–1, about 3-fold higher than that of the bacteria grown in medium containing 1.25 μmol L–1 copper, indicating that methanol productivity of the methane bioconversion is improved by higher copper concentration in the growth medium. Methanol production almost ceased after 60-h reaction due to product inhibition. Therefore, repeated batch reaction was performed, in which the bacterial cells were collected after 24-h reaction and re-used in the next cycle. In the fourth cycle, 83 % of the methanol productivity was retained. About 856 mmol g-dry cell–1 of methanol was obtained after 4 cycles, which was 3.7-fold higher than the methanol obtained in a single batch reaction for 96 h.