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Duan Y.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,Beijing Engineering Research Center for Biofuels | Shi Y.,Tsinghua University | And 3 more authors.
Catalysis Communications | Year: 2016

In this paper, SO4 2 -/Al2O3-SiO2 (SAS) was prepared and used for the esterification of octanoic acid with methanol. The effect of introduction of SiO2 was characterized by nitrogen sorption, ICP-AES, XRD, NH3-TPD, TG, FTIR and FTIR-pyridine adsorption. The results demonstrated that the doping of SiO2 resulted in the increase of BET surface areas and amount of surface sulfur species which led to an increase of acid sites especially Brönsted acid sites, which consequently boosted the catalytic esterification activity. In addition, the introduction of SiO2 can also increase the thermal stability of SO4 2 - and its interaction with Al2O3 support which resulted in the alleviation of catalyst deactivation. © 2016 Elsevier B.V. All rights reserved.

Zhang C.,Tsinghua University | Zhang C.,Beijing Engineering Research Center for Biofuels | Li J.,Tsinghua University | Li J.,Beijing Engineering Research Center for Biofuels | And 10 more authors.
Bioresource Technology | Year: 2013

The objective of this research was to propose and investigate the availability of digested banana stem (BS) to produce biogas. Squeezed BS with less moisture content was used for biogas production through a combination of NaOH pretreatment, solid-state fermentation, and codigestion technologies. NaOH doses were optimized according to biogas fermentation performance, and the best dose was 6% (by weight) based on the total solid (TS) of BS. Under this condition, the lignin, cellulose, and hemicellulose contents decreased from 18.36%, 32.36% and 14.6% to 17.10%, 30.07%, and 10.65%, respectively, after pretreatment. After biogas digestion, TS and volatile solid (VS) reductions of the codigestion were 48.5% and 70.4%, respectively, and the biogas and methane yields based on VS loading were 357.9 and 232.4. mL/g, which were 12.1% and 21.4%, respectively, higher than the control. Results indicated that the proposed process could be an effective method for using BS to produce biogas. © 2013 Elsevier Ltd.

Shi Y.,Tsinghua University | Cao Y.,Tsinghua University | Duan Y.,Tsinghua University | Chen H.,Tsinghua University | And 4 more authors.
Green Chemistry | Year: 2016

Bi-functional Mo/ZSM-22 catalysts were designed to upgrade palmitic acid and further to isomerize n-alkanes. Besides the effects on acidity, H+ cations might be beneficial for the distribution of MoOx particles, the higher surface Mo/Si ratio and the greater surface Mo4+ content of bi-functional Mo/ZSM-22 catalysts. In the upgrading of palmitic acid, strong acid sites of catalysts were proven to favor hydrodecarbonylation (HDC), isomerization and cracking. Mo6+ (or MoO3) preferred to support the HDC reaction, whereas Mo4+ (or MoO2) suitably improved the hydrodeoxygenation (HDO) reaction without carbon atom loss. That is, the Mo4+/Mo6+ ratio of Mo/ZSM-22 catalysts significantly influenced HDO/HDC selectivity. More importantly the improvement in HDO rather than HDC with the complete conversion of palmitic acid, could significantly decrease the negative effects of strong acid sites (such as HDC and cracking) to facilitate isomerization of n-alkanes to afford more branched alkanes with a higher iso-alkanes/n-alkanes ratio. © The Royal Society of Chemistry 2016.

Wu K.,Tsinghua University | Liu J.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,Beijing Engineering Research Center for Biofuels | And 4 more authors.
Bioresource Technology | Year: 2014

The differences in pyrolysis process of three species of aquatic biomass (microalgae, macroalgae and duckweed) were investigated by thermogravimetric analysis (TGA). Three stages were observed during the pyrolysis process and the main decomposition stage could be divided further into three zones. The pyrolysis characteristics of various biomasses were different at each zone, which could be attributed to the differences in their components. A stepwise procedure based on iso-conversional and master-plots methods was used for the kinetic and mechanism analysis of the main decomposition stage. The calculation results based on the kinetic model was in good agreement with the experimental data of weight loss, and each biomass had an increasing activation energy of 118.35-156.13. kJ/mol, 171.85-186.46. kJ/mol and 258.51-268.71. kJ/mol in zone 1, 2 and 3, respectively. This study compares the pyrolysis behavior of various aquatic biomasses and provides basis for further applications of the biomass thermochemical conversion. © 2014.

Yu M.,Tsinghua University | Li J.,Tsinghua University | Chang S.,Tsinghua University | Du R.,Tsinghua University | And 7 more authors.
Energies | Year: 2014

Ethanol production from NaOH-Pretreated solid state fermented sweet sorghum bagasse with an engineered strain of Z. mobilis TSH-ZM-01 was optimized. Results showed that: (1) residual solid removal during ethanol fermentation was unnecessary and 24 h fermentation duration was optimal for ethanol production; (2) ethanol yield of 179.20 g/kg of solid state fermented sweet sorghum bagasse achieved under the optimized process conditions of cellulase loading of 0.04 g/g-glucan, xylanase loading of 0.01 g/g-xylan, liquid to solid ratio of 9:1 and pre-hydrolysis duration for 72 h. © 2014 by the authors.

Ding R.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,Beijing Engineering Research Center for Biofuels | Chen Y.,Tsinghua University | And 4 more authors.
Catalysis Science and Technology | Year: 2016

Novel Co-doped MoO2/CNTs catalysts were prepared by a wet-impregnation method and employed in catalytic hydrodeoxygenation (HDO) of palmitic acid. The obtained catalysts were systematically characterized using various techniques, namely, XRD, BET surface area, XPS, FT-IR spectroscopy of adsorbed pyridine, Raman, H2-TPD, and H2-TPR. Characterization studies revealed the doping of Co ions into the lattice of MoO2, the interaction between metal species modified the electrical properties of the catalytic active sites, and the formation of new active sites and defects. The catalytic results showed that Co ions could significantly improve catalytic performance, and the best selectivity to hexadecane reached 89.3% at an extremely low temperature of 180°C. The increased presence of Mo2C particles, Lewis acidic sites and oxygen vacancies were all responsible for the noticeable catalytic performance of the Co doped catalyst. The mechanistic insights from this work confirmed the bifunctional role of Co-doped MoO2/CNTs catalysts for HDO of palmitic acid, which was catalyzed either solely by Mo2C or synergistically by Mo2C and MoO2. Insights into the nature of the active site would provide a useful knowledge for rational design of effective Mo-based HDO catalysts and assist future studies on more efficient catalytic conversion systems. © The Royal Society of Chemistry 2016.

Du R.,Tsinghua University | Yan J.,Tsinghua University | Feng Q.,Tsinghua University | Li P.,Tsinghua University | And 3 more authors.
PLoS ONE | Year: 2014

The rising demand for bioethanol, the most common alternative to petroleum-derived fuel used worldwide, has encouraged a feedstock shift to non-food crops to reduce the competition for resources between food and energy production. Sweet sorghum has become one of the most promising non-food energy crops because of its high output and strong adaptive ability. However, the means by which sweet sorghum stalks can be cost-effectively utilized for ethanol fermentation in large-scale industrial production and commercialization remains unclear. In this study, we identified a novel Saccharomyces cerevisiae strain, TSH1, from the soil in which sweet sorghum stalks were stored. This strain exhibited excellent ethanol fermentative capacity and ability to withstand stressful solid-state fermentation conditions. Furthermore, we gradually scaled up from a 500-mL flask to a 127-m3 rotary-drum fermenter and eventually constructed a 550-m3 rotarydrum fermentation system to establish an efficient industrial fermentation platform based on TSH1. The batch fermentations were completed in less than 20 hours, with up to 96 tons of crushed sweet sorghum stalks in the 550-m3 fermenter reaching 88% of relative theoretical ethanol yield (RTEY). These results collectively demonstrate that ethanol solid-state fermentation technology can be a highly efficient and low-cost solution for utilizing sweet sorghum, providing a feasible and economical means of developing non-food bioethanol. © 2014 DU et al.

Yu M.,Tsinghua University | Li J.,Tsinghua University | Li S.,Tsinghua University | Du R.,Tsinghua University | And 4 more authors.
Applied Energy | Year: 2014

A cost competitive integrated technology to convert solid state fermented sweet sorghum bagasse (SS) into cellulosic ethanol which combined ethanol distillation, NaOH pretreatment and simultaneous saccharification and co-fermentation (SSCF) was presented in this study. After solid-state fermentation, the SS was distilled with 10% (w/w dry material, DM) NaOH to separate sugar-based ethanol and pretreat lignocelluose simultaneously in one step and one distillation stripper, then the NaOH pretreated SS was subsequently converted into cellulosic ethanol by SSCF. Results showed that 69.49% ethanol theoretical yield was achieved under the optimal condition based on this novel integrated process. This integrated technology can significantly reduce the energy consumption and capital cost for cellulosic ethanol production, and ensure cellulosic ethanol produced from SS cost-effectively. © 2013.

Wu K.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,Beijing Engineering Research Center for Biofuels | Chen Y.,Tsinghua University | And 3 more authors.
ChemSusChem | Year: 2016

Different biobased chemicals are produced during the conversion of biomass into fuels through various feasible technologies (e.g., hydrolysis, hydrothermal liquefaction, and pyrolysis). The challenge of transforming these biobased chemicals with high hydrophilicity is ascribed to the high water content of the feedstock and the inevitable formation of water. Therefore, aqueous-phase processing is an interesting technology for the heterogeneous catalytic conversion of biobased chemicals. Different reactions, such as dehydration, isomerization, aldol condensation, ketonization, and hydrogenation, are applied for the conversion of sugars, furfural/hydroxymethylfurfural, acids, phenolics, and so on over heterogeneous catalysts. The activity, stability, and reusability of the heterogeneous catalysts in water are summarized, and deactivation processes and several strategies are introduced to improve the stability of heterogeneous catalysts in the aqueous phase. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Wu X.,Tsinghua University | Wu Y.,Tsinghua University | Wu Y.,Beijing Engineering Research Center for Biofuels | Wu K.,Tsinghua University | And 3 more authors.
Bioresource Technology | Year: 2015

In the current work, the co-pyrolysis kinetics of Dunaliella tertiolecta and PP were investigated via TGA, while TG-FTIR and TG-MS were used for the analysis of gas-phase components and volatiles transition. The TGA results show that PP with certain small particle size accelerates the pyrolysis process of the microalgae, while the existence of D. tertiolecta delayed that of PP. This significant interaction achieves maximum when mass ratio of PP and D. tertiolecta is 6:4. The activation energy estimated from FWO kinetic model also supports this interaction. The TG-FTIR and TG-MS results show that a significant decrease of CO2 occurs at PP and D. tertiolecta mass ratio of 6:4, indicating that small molecules (such as radicals) released by PP might react with CO2 produced by D. tertiolecta or carbonyl groups in the microalgae. © 2015 Elsevier Ltd.

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