Yuhe Cao

Hydrodeoxygenation of prairie cordgrass bio-oil over Ni based activated carbon synergistic catalysts combined with different metals

Bio-oil can be upgraded through hydrodeoxygenation (HDO). Low-cost and effective catalysts are crucial for the HDO process. In this study, four inexpensive combinations of Ni based activated carbon synergistic catalysts including Ni/AC, Ni-Fe/AC, Ni-Mo/AC and Ni-Cu/AC were evaluated for HDO of prairie cordgrass (PCG) bio-oil. The tests were carried out in the autoclave under mild operating conditions with 500psig of H2 pressure and 350°C temperature. The catalysts were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and transmission electron microscope (TEM). The results show that all synergistic catalysts had significant improvements on the physicochemical properties (water content, pH, oxygen content, higher heating value and chemical compositions) of the upgraded PCG bio-oil. The higher heating value of the upgraded bio-oil (ranging from 29.65MJ/kg to 31.61MJ/kg) improved significantly in comparison with the raw bio-oil (11.33MJ/kg), while the oxygen content reduced to only 21.70-25.88% from 68.81% of the raw bio-oil. Compared to raw bio-oil (8.78% hydrocarbons and no alkyl-phenols), the Ni/AC catalysts produced the highest content of gasoline range hydrocarbons (C6-C12) at 32.63% in the upgraded bio-oil, while Ni-Mo/AC generated the upgraded bio-oil with the highest content of gasoline blending alkyl-phenols at 38.41%.

Catalytic cracking of inedible camelina oils to hydrocarbon fuels over bifunctional Zn/ZSM-5 catalysts

Catalytic cracking of camelina oils to hydrocarbon fuels over ZSM-5 and ZSM-5 impregnated with Zn2+ (named bifunctional catalyst) was individually carried out at 500 °C using a tubular fixed-bed reactor. Fresh and used catalysts were characterized by ammonia temperature-programmed desorption (NH3-TPD), X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and nitrogen isothermal adsorption/desorption micropore analyzer. The effect of catalysts on the yield rate and qualities of products was discussed. The loading of Zn2+ to ZSM-5 provided additional acid sites and increased the ratio of Lewis acid site to Brønsted acid site. BET results revealed that the surface area and pore volume of the catalyst decreased after ZSM-5 was impregnated with zinc, while the pore size increased. When using the bifunctional catalyst, the pH value and heating value of upgraded camelina oils increased, while the oxygen content and moisture content decreased. Additionally, the yield rate of hydrocarbon fuels increased, while the density and oxygen content decreased. Because of a high content of fatty acids, the distillation residues of cracking oils might be recycled to the process to improve the hydrocarbon fuel yield rate.

Nitrogen-modified biomass-derived cheese-like porous carbon for electric double layer capacitors

Lignin, an abundant biomass constituent in nature, was modified by pyrrole to produce nitrogen-doped porous carbon. The porous carbon was efficiently activated through simultaneous chemical and physical reactions using potassium hydroxide as an activation agent during the heat treatment. Surface area analysis showed that the activated carbon possessed mesopores (∼15 nm) and a large specific surface area of 2661 m2 g−1, with a cheese-like morphology. Electrochemical double layer capacitors fabricated using the activated carbon as an electrode material showed a specific capacitance of 248 F g−1 at a low current density of 0.1 A g−1 and 211 F g−1 at a high current density of 10 A g−1 in 6 M KOH solution. Charge and discharge for 1000 cycles at different current densities ranging from 0.1 to 10 A g−1 confirmed excellent specific capacitance retention and good cycling stability. This work demonstrates that the nitrogen-doped cheese-like porous activated carbon is a promising electrode material for electric double layer capacitors.

Adsorption of butanol vapor on active carbons with nitric acid hydrothermal modification

Butanol can be produced from biomass via fermentation and used in vehicles. Unfortunately, butanol is toxic to the microbes, and this can slow fermentation rates and reduce butanol yields. Butanol can be efficiently removed from fermentation broth by gas stripping, thereby preventing its inhibitory effects. Original active carbon (AC) and AC samples modified by nitric acid hydrothermal modification were assessed for their ability to adsorb butanol vapor. The specific surface area and oxygen-containing functional groups of AC were tested before and after modification. The adsorption capacity of unmodified AC samples was the highest. Hydrothermal oxidation of AC with HNO3 increased the surface oxygen content, Brunauer-Emmett-Teller (BET) surface area, micropore, mesopore and total pore volume of AC. Although the pore structure and specific surface area were greatly improved after hydrothermal oxidization with 4M HNO3, the increased oxygen on the surface of AC decreased the dynamic adsorption capacity.

Separation of glucosinolates from Camelina seed meal via membrane and acidic aluminum oxide column.

Glucosinolates are secondary metabolites, as well as representative bioactive therapeutic small molecules, which are found in Camelina seed meal. In this study, an ultrafiltration (UF) membrane was employed to remove protein after ethanol extraction of glucosinolates. After UF, preparative chromatography, based on acidic aluminum oxide, was used to further purify glucosinolates. The impact of different concentrations of NaCl elution buffer at 0.2, 0.5, and 1.0 mol/L on the recovery of glucosinolates was evaluated. The results indicated that elution with a 1.0 mol/L salt solution recovered 91.0% of glucosinolates from the UF permeate. The glucosinolate yield recovered from the seed meal was 9.52 µmol/g. High-performance liquid chromatography analysis showed that only the major glucosinolates peaks at retention times 13.0, 17.6, and 19.2 min appeared. This result indicated that most impurities of UF permeate were removed after anion exchange. Traditional protein removal methods for recovering glucosinolates, such as using heavy metal salt precipitate, are expensive and environmentally harmful. The glucosinolate separation process described herein can be used as a model process for purifying other natural bioactive chemicals from biofuel processing and other agricultural residues.