Pengmei Lv

The nanometer magnetic solid base catalyst for production of biodiesel

Nanometer magnetic solid base catalysts were prepared by loading CaO on Fe3O4 with Na2CO3 and NaOH as precipitator, respectively. The optimum conditions for preparation of this catalyst were investigated. The influence of the proportion of Ca2+ to Fe3O4 on the catalytic performance has been studied. The catalyst with highest catalytic activity has been obtained when the proportion of Ca2+ to Fe3O4 is 7:1; the catalytic activity of the catalyst calcined from Ca(OH)2 to Fe3O4 is better than that calcined from CaCO3 to Fe3O4; under the conditions of methanol/oil molar ratio of 15:1, catalyst dosage of 2wt% and temperature of 70°C, the biodiesel yield reaches to 95% in 80min, even to 99% finally. The catalytic activity and recovery rate of the nanometer magnetic solid base catalysts are much better than those of CaO. Calcination temperature was determined by differential thermogravimetric analysis. Ca2Fe2O5, a kind of new metal multiple oxide, was found in the catalyst through X-ray diffraction. At the end, these catalysts were characterized by scanning electronic microscope (SEM), transmission electron microscopy (TEM), and vibrating sample magnetometer (VSM).

Catalytic Hydrotreatment of Fatty Acid Methyl Esters to Diesel‐like Alkanes Over Hβ Zeolite‐supported Nickel Catalysts

A Ni/Hβ zeolite catalyst was prepared for the selective transformation of fatty acid methyl esters (FAMEs) into diesel‐like alkanes through hydrotreatment. Characterization of the physicochemical properties of a 10 wt % nickel‐loaded, Hβ zeolite support indicated that nickel(II) oxide aggregated into large particles approximately 23.9 nm in size, whereas nickel aggregated into particles 18.3 nm in size, significantly increasing the total acid sites of Hβ zeolite after hydrogen reduction. The reaction scheme of the whole FAME transformation was investigated by using a batch reactor. It was found that FAMEs were first hydrogenated mainly to saturated fatty acids, followed by hydrodeoxygenation without carbon loss, the main route toward alkanes. The hydrotreatment of FAMEs by decarboxylation or decarbonylation was favored at high temperatures and low hydrogen pressures on Hβ zeolite with higher nickel loadings. The metallic and acidic functionalities of nickel/Hβ zeolite catalysts exhibited a synergistic effect in hydrodeoxygenation without carbon loss, achieving high FAME conversion and yields of liquid C16 and C18 alkanes. Optimal catalytic performances were obtained with 10 wt % nickel loading over Hβ zeolite (Si/Al=25) at 270 °C with a pressure of 1.0 MPa H2 over 8 h. A maximum alkane product yield of 93.2 % was achieved for C15–C18 alkanes with complete FAME conversion. 80.3 % FAME conversion could was achieved after eight reaction cycles by using the nickel/Hβ zeolite catalyst with calcination after every use.

Core-shell Au-Pd nanoparticles as cathode catalysts for microbial fuel cell applications

Bimetallic nanoparticles with core-shell structures usually display enhanced catalytic properties due to the lattice strain created between the core and shell regions. In this study, we demonstrate the application of bimetallic Au-Pd nanoparticles with an Au core and a thin Pd shell as cathode catalysts in microbial fuel cells, which represent a promising technology for wastewater treatment, while directly generating electrical energy. In specific, in comparison with the hollow structured Pt nanoparticles, a benchmark for the electrocatalysis, the bimetallic core-shell Au-Pd nanoparticles are found to have superior activity and stability for oxygen reduction reaction in a neutral condition due to the strong electronic interaction and lattice strain effect between the Au core and the Pd shell domains. The maximum power density generated in a membraneless single-chamber microbial fuel cell running on wastewater with core-shell Au-Pd as cathode catalysts is ca. 16.0 W m−3 and remains stable over 150 days, clearly illustrating the potential of core-shell nanostructures in the applications of microbial fuel cells.

Combined use of GAP and AOX1 promoters and optimization of culture conditions to enhance expression of Rhizomucor miehei lipase

Rhizomucor miehei lipase (RML) is an industrially important enzyme, but its application is limited due to its high cost. In this study, a series of measures such as codon optimization, propeptide addition, combined use of GAP and AOX1 promoters, and optimization of culture conditions were employed to increase the expression of RML. Three transformants of the constitutive-inducible combined Pichia pastoris strains were generated by transforming the pGAPZαA-rml vector into the pPIC9K-rml/GS115 strain, which resulted in high-expression yields of RML. Using the shake flask method, highest enzyme activity corresponding to 140 U/mL was observed in the strain 3-17, which was about sixfold higher than that of pPIC9K-rml/GS115 or pGAPZαA-rml/GS115. After optimization of culture conditions by response surface methodology, the lipolytic activity of strain 3-17 reached 175 U/mL in shake flasks. An increase in the copy number simultaneously with the synergistic effect provided by two promoters led to enhanced degree of protein expression.

Insight into forced hydrogen re-arrangement and altered reaction pathways in a protocol for CO2 catalytic processing of oleic acid into C8–C15 alkanes

A new vision of using carbon dioxide (CO2) catalytic processing of oleic acid into C8–C15 alkanes over a nano-nickel/zeolite catalyst is reported in this paper. The inherent and essential reasons which make this achievable are clearly resolved by using totally new catalytic reaction pathways of oleic acid transformation in a CO2 atmosphere. The yield of C8–C15 ingredients reaches 73.10 mol% in a CO2 atmosphere, which is much higher than the 49.67 mol% yield obtained in a hydrogen (H2) atmosphere. In the absence of an external H2 source, products which are similar to aviation fuel are generated where aromatization of propene (C3H6) oxidative dehydrogenation (ODH) involving CO2 and propane (C3H8) and hydrogen transfer reactions are found to account for hydrogen liberation in oleic acid and achieve its re-arrangement in the final alkane products. The reaction pathway in the CO2 atmosphere is significantly different from that in the H2 atmosphere, as shown by the presence of 8-heptadecene, γ-stearolactone, and 3-heptadecene as reaction intermediates, as well as a CO formation pathway. Because of the highly dispersed Ni metal center on the zeolite support, H2 spillover is observed in the H2 atmosphere, which inhibits the production of short-chain alkanes and reveals the inherent disadvantage of using H2. The CO2 processing of oleic acid described in this paper will significantly contribute to future CO2 utilization chemistry and provide an economical and promising approach for the production of sustainable alkane products which are similar to aviation fuel.

Vertical distribution of microbial community and metabolic pathway in a methanogenic propionate degradation bioreactor

The methanogenic propionate degradation consortia were enriched in a propionate-fed semi-continuous bioreactor. The microbial community shift with depth, the microbial network and its correlation with metabolic pathway were also investigated. The results demonstrated that the maximum organic loading rate (OLR) of the reactor was 2.5g propionic acid (HPr) L-1d-1 with approximately 1.20LL-1d-1 of volumetric methane production (VMP). The organisms in the enrichment were spanning 36 bacterial phyla and 7 archaeal orders. Syntrophobacter, the main Hpr oxidizer in the digester, dominated bacteria with relative abundance changing from 63% to 37% with depth. The predominant methanogens shift from hydrogenotrophic Methanoculleus (∼60%) at the upper liquid layer to acetoclastic Methanothrix (∼51%) at the lower sediment layer in the bioreactor. These methanogens syntrophically support Syntrophobacter by degrading HPr catabolism by-products (H2 and acetate). Other bacteria could scavenge anabolic products (carbohydrate and protein) presumably derived from detrital biomass produced by the HPr-degrading community.

Hydrolysis dynamics for batch anaerobic digestion of elephant grass

Elephant grass might be a potential source of fine chemical precursors and bioenergy. In the present study, we investigated the dynamics of hydrolysis of elephant grass. Three models were used to fit the hydrolysis rate constants—flat, spherical, and cylindrical models. The hydrolysis rate constants obtained using the spherical model presented the best fit between the experimental and theoretical values. Furthermore, we determined the secondary reinforcement points and interventions that can be introduced to speed up the hydrolysis process. Our findings will provide information for studies on the hydrolysis of elephant grass and promote its application in the biogas industry as an alternative biofuel.

Novel Sanger’s Reagent-like Styrene Polymer for the Immobilization of Burkholderia cepacia Lipase

Sangers reaction, which was originally developed for amino acid detection, was utilized for enzyme immobilization. The newly synthesized polymer support, which was called polymer NO2-4-fluorostyrene-divinylbenzene (pNFD), was embedded with a Sangers reagent-like functional group for immobilizing enzymes covalently under mild reaction conditions. Using Burkholderia cepacia lipase (BCL) as the target enzyme, the immobilization efficiency and activity of pNFD-BCL reached as high as 1.2 mg·g-1 and 33.21 U·g-1 (a specific activity of 27 675 U·g-1), respectively, realizing 90% activity recovery. It also improved the optimal reaction temperature of BCL from 40 to 65 °C, under which its full activity could be retained for 4 h. The new carrier also widened the pH-adaptive range of BCL as 6.5-10.0, allowing the lipase to operate normally in weak acid environment. Reusability of pNFD-BCL was significantly improved as almost no activity and/or enantioselectivity loss was observed in 200 h of triglyceride hydrolysis reaction and 17 batches of ( R, S)-1-phenylethanol resolution reaction.

Study on the Rheological Properties of Organic Raw Materials for Seedling Pot

When the biodegradable seedling pot was prepared in the process of negative pressure adsorption, the rheological properties of materials had a great influence on the preparation of seedling pot. In this study, solution blended with NaOH and biogas slurry was used to pretreat the corn stalks, and then organic materials were prepared by beating. The viscosities of organic materials under different conditions were measured by digital rotary viscometer and the pretreatment time, TS, temperature, Alkali concentration and rotational speed on the rheological properties of organic materials were discussed. The results showed that the organic material had a rheological index of n < 1, which belonged to the pseudoplastic fluid; the apparent viscosity of the organic materials first decreased and then increased with the increase of the pretreatment time, and it increased in approximate S curve with the increase of TS, and decreased in approximate linear with the increase of temperature, and decreased linearly with the increase of alkali concentration. The viscosity decreased with the increase of rotation speed, and the higher the rotation speed, the slower the apparent viscosity decreased. The results of this study will provide the theoretical basis for the preparation of organic raw materials, pot molding and drying.

Promotional effect of transition metal doping on the properties of KF/CaO catalyst for biodiesel synthesis

ABSTRACT A series of heterogeneous KF/CaO catalysts modified with transition metals (lanthanum, cerium, and zirconium) were prepared via wet impregnation method and applied to the trsansesterification process of waste cooking oil (WCO) as feedstock with methanol to biodiesel production. The structure, performance of the solid catalysts was characterized by X-ray diffraction (XRD), temperature programmed desorption of CO2 (CO2-TPD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS). The effect of methanol/oil molar ratio, 1reaction time, reaction temperature, catalyst amount, and stability was investigated. The results showed that 10 wt% of lanthanum, cerium, and zirconium improved the catalytic activity of KF/CaO catalyst. The maximum catalytic activity using the lanthanum doping of 10wt% on KF/CaO catalyst was reached 98.7% under the optimal reaction condition of methanol/oil molar ratio of 12:1, reaction for 1 h at reaction temperature of 65°C, and 4% (wt/wt oil) catalyst amount. In addition, the FAME yield of KF/CaO/La catalyst remained higher than 95% after 10 cycles. The promotional effect of lanthanum doping could be attributed to the enhancement of the basicity strength of KF/CaO catalyst and block the leach of Ca2+ in the transesterification reaction.