Second-generation bioethanol, which is produced from inedible lignocellulosic biomass resources, is an attractive green fuel for addressing climate change. The efficiency of fermentation processes for synthesizing bioethanol from lignocellulosic-biomass-derived sugars is drastically reduced by aromatic compounds such as 5-hydroxymethylfurfural and vanillin, which are undesirable contaminants released from lignocellulosic biomass into the fermentation broth, even at concentrations on the order of several millimolar. This review describes the selective removal of these aromatic toxins from aqueous mixtures containing sugar co-solute(s) using a variety of adsorbents involving aromatic domains as adsorption sites—metal-organic frameworks and surface-modified SiO2—without detectable adsorption of the latter compound(s). The design concept for adsorbents enabling such molecular recognition also is addressed; the surface area and shape of aromatic domains control the degree of interaction with guest molecules (i.e., sugars, furanics, and phenolics) and also are the key to achieving reversible adsorption/desorption processes.
The vapor-liquid equilibrium (VLE) and the saturated liquid density were measured for three binaries, propane + dimethyl ether (DME), DME + butane, and propane + butane, and the ternary, propane + DME + butane, at 313.15 ± 0.03 K. The apparatus was based on a recirculation method and incorporated an oscillation U-tube densimeter. Deviation of the saturated vapor pressure for pure propane, DME and butane were 0.556, 0.525, and 6.210 %, respectively, and that for the saturated liquid density for DME was 0.552 %, compared with the reported values. The experimental binary VLE data for propane + DME, DME + butane and propane + butane, agreed with reported values. The data were correlated with the prediction of the Benedict-Webb-Rubin (BWR) equation of state. The constants in the BWR equation for DME were determined in our previous research, and those for propane and butane were obtained from the literature. The correlation showed a good reproducibility. The averaged absolute deviations (AADs) for the mole fractions in the liquid and vapor phases were 2.156 % and 1.687 %, respectively, and for the saturated liquid density was than 1.490 %. The ternary VLE and the saturated liquid density was measured at 0.8830 MPa and 313.15 K. The VLE and the saturated liquid density were estimated by the BWR equation using only the binary parameters. The AADs for the mole fractions in the liquid and vapor phases were 2.905 % and 2.110 %, and that for the saturated liquid density was 1.432 %.
Kobe Steel, Ltd. and Chiyoda Corp. developed the KOBELCO Slurry Phase Hydrocracking (SPH) process for the ultimate heavy oil upgrading, both at upstream wells and refineries with a cracking rate higher than 90 %. Generally, with the heavy oil hydrocracking process, a higher cracking rate is associated with a greater sludge formation rate due to a radical reaction, large molecular condensation and polymerization induced by thermal cracking. This research objective is to apply optimized operation conditions, obtained through experimental results, to the new process system’s development for the pilot and commercial plants by achieving a more than 95 wt% VR cracking rate, more than 80 wt% of oil yield, and minimizing sludge generation. For this purpose, the reaction time, amount of limonite content, reaction pressure, and reaction temperature in the 1 L autoclave are tested to find the optimal reaction point. To scale up the SPH process to pilot plants and commercial plants, a new reaction model, for which reaction conditions are theorized, must be developed. This study proposes a new reaction model by simulating the autoclave tests, verifying its validity, and discussing future challenges and plans.
A two-step conversion of acetic acid to ethanol was discussed by ethyl esterification followed by catalytic hydrogenolysis for highly efficient bioethanol production from lignocellulose via acetic acid fermentation. Non-catalytic supercritical ethanol treatment was demonstrated for the esterification of acetic acid, and an appropriate condition was found to be 270 °C/20 MPa for ethyl acetate production. Because of the autocatalytic effect of acetic acid, a low ethanol ratio favored a fast reaction rate but diminished the ethyl acetate yield due to the reverse reaction. Therefore, it seems better to employ a water removal method during the esterification reaction for efficient conversion of acetic acid to ethyl acetate with minimal ethanol. For the hydrogenolysis of ethyl acetate, catalytic activities of several Cu-type catalysts were evaluated with a flow-type reactor. The Cu–Zn catalyst was more effective than other Cu–Cr-type ones in the temperature range of 210-270 °C, where only small amounts of methane and ethane (0.89 wt% at 270 °C upon the fed methyl acetate) were formed as by-products along with ethanol. These findings will help us to design an efficient bioethanol production process from acetic acid by the proposed two-step method.
Decarbonylation of biomass-derived furfural to furan is one of the attractive transformation reactions for valorization of biomass, since furan can be used as a feedstock chemical for the synthesis of solvent, fuel and polymer. Previous researches have manifested that Pd nanoparticles (NPs) act as an effective catalyst for this reaction; however, severe reaction conditions, such as high temperature and high pressure, have been required for accelerating reaction rate. In this study, we prepared small Pd NPs supported on several titania supports by a photo-assisted metal deposition (PAD) method utilizing their photo-responsive property. Transmission electron microscopy and X-ray absorption fine structure measurements disclosed that uniformly-dispersed Pd NPs with a smaller diameter could be obtained when Pd NPs were deposited on titania supports via PAD method compared with those prepared by the conventional wet impregnation method. In particular, Na+-type titanate nanotube (TNT) with tubular nanostructure and the associated high-surface-area served as an effective support to create highly-active Pd NPs, which exhibited superior catalytic performance in the liquid-phase decarbonylation of furfural compared with the conventional supported Pd catalysts. A clear relationship was observed between reaction rates and sizes of Pd NPs, and further detailed analysis suggested that coordinatively-unsaturated Pd atoms locating at the edge/corner sites of Pd0 NPs are the active species for this reaction.
Silylated ionic liquid (IL)-derived organosilica membrane was formed on porous Al2O3 substrate by the sol-gel method. The permeation and separation characteristics for a binary toluene/CH4 mixture were studied at various temperatures. The membrane showed selective permeation of toluene against CH4 at high temperature up to 170 °C, and stably separated toluene from CH4 at 150 °C for 3 h. The permselectivity was strongly controlled by the affinity of the permeate molecules toward the IL. The results showed that the silylated IL-derived organosilica membrane is promising for selective recovery of aromatic hydrocarbons from CH4. ATR-IR, N2 adsorption and nanopermporometry were performed to evaluate the microstructure and permeation mechanism of the organosilica membrane. These characterizations revealed that the membrane depended on two permeation pathways, “only the dense IL regions” and “organosilica network-derived micropores + dense IL regions.” The organosilica membrane contained about 1 nm-sized pores, and the contributions of two permeation pathways to gas permeation were successfully evaluated.
Lignin is a potentially useful source of aromatic monomers. Depolymerization of organosolv-lignin into aromatic monomers was investigated over charcoal-supported palladium, platinum, rhodium, or ruthenium catalyst (Pd/C, Pt/C, Rh/C, and Ru/C) in supercritical water (658-688 K) for reaction times of 0.5-3 h. Ru/C showed no catalytic activity for lignin depolymerization into aromatic monomers, but did catalyze conversion of lignin into gaseous products such as methane and carbon dioxide. In contrast, Pd/C, Pt/C, and Rh/C showed catalytic activity for lignin depolymerization into aromatic monomers. Yield of aromatic monomers decreased in the order Pd/C>Rh/C>Pt/C at 673 K and 1 h. Pd/C showed higher selectivity for phenolic aromatic monomers than Rh/C and Pt/C. Investigation of the activity of Pd/C at 673 K over time (0.5-3 h) found the highest yield of aromatic monomers (12.7 %) was obtained at 2 h.
This study investigated the effect of catalyst supports (SiO2, γ-Al2O3, ZrO2, CeO2, MgO) on the performance of transition metal (Fe, Co, Ni) catalysts for propane dehydrogenation (PDH) with co-feeding of hydrogen sulfide (H2S). Evaluation of the catalyst activity indicated that inert SiO2 is a suitable support for the PDH catalysts. The SiO2-supported Fe catalysts showed the highest activity and selectivity among the investigated catalysts. In order to clarify the effect of the support species on the structure and electronic state of the catalyst components, X-ray diffraction (XRD), X-ray absorption fine structure (XAFS), and X-ray photoelectron spectroscopy (XPS) were used to characterize the various Fe-loaded catalysts. From Fe K-edge X-ray absorption near edge structure (XANES) analysis, it is deduced that the catalysts in which Fe was in a higher oxidation state showed better performance for PDH with co-feeding of H2S. When SiO2 and Al2O3 were used as the supports, divalent and trivalent Fe cations were detected by XPS analysis. Such high-valence Fe species can accept an electron from an intermediate species, thereby enhancing the dehydrogenation performance.