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Bao-Xiang Peng Qing Shu Jin-Fu Wang Guang-Run Wang De-Zheng Wang Ming-Han Han 《Process Safety and Environmental Protection》2008,86(6):441-447
Biodiesel is a non-toxic and biodegradable substitute for petroleum-based diesel. However, it is impractical to use refined edible oils to produce biodiesel due to its high cost and priority for food products, especially in China, while waste oils with high free fatty acids (FFAs) can be considered as the raw materials. In the present work, a solid acid catalyst comprising SO42−/TiO2–SiO2 was prepared, characterized and studied for its activity for the production of biodiesel from several low cost feedstocks with high FFAs. The solid acid catalyst can be recycled, easily removed and can simultaneously catalyze esterification and transesterification. The influence of reaction parameters was studied, and the optimized reaction parameters are reaction temperature 200 °C, molar ratio of methanol to oil 9:1 and catalyst concentration 3 wt.%. The catalyst showed good stability. A continuous process for biodiesel production from cheap raw feedstocks was proposed, and a 10,000-tonnes/year biodiesel production demonstration plant has been built. 相似文献
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Biosorption properties of arsenate [As(V)] onto activated sludge were investigated in batch systems. The adsorption of As(V)
onto sludge increased from 23 to 266 μg/g dry weight through the methylation of the activated sludge. This increase resulted
from neutralization of carboxylic groups via the methylation process. The pH effect of As(V) uptake was also investigated
and As(V) adsorption by methylated sludge decreased significantly at high pH (pH > 11) due to competition between As(V) and
OH− ions for binding sites distributed on sludge surfaces. In contrast, low pH favored As(V) adsorption by methylated sludge
because of the elevated quantities of positively charged functional groups. The results suggest that methylated activated
sludge may provide promising applications for the simultaneous removal and separation of As(V) from aqueous effluents. 相似文献
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Xiaomin Zhang Wenjie Xiong Zengyu Yin Yongle Chen Youting Wu Xingbang Hu 《绿色能源与环境(英文)》2022,7(1):137-144
In this work, a series of novel proton-gradient-transfer acid complexes (PGTACs) were developed. Their physicochemical properties, including thermal stability, melting point, and Hammett acidity, were measured. The effects of catalyst loading, reaction temperature, and substrate expansion on the catalytic performance were systematically studied. It is found that the combination of bidentate N-heterocycle and H2SO4 (1:2 M ratio) could form simultaneously N–H covalent bond and N…H hydrogen bond, which makes the PGTACs excellent catalysts integrate the advantages of strong acids (high catalytic activity) and ionic liquids (phase separation) in the esterification reaction. Moreover, these PGTACs can be reused by convenient phase separation without obvious diminution of catalytic activity. It is concluded that these PGTACs are potential alternative candidates for esterification reaction in the process of industrial catalysis. 相似文献
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《Process Safety and Environmental Protection》2014,92(6):522-531
Acrylic acid (AA) is an important component for the production of acrylate polymer. In a typical acrylic manufacturing unit, waste water contains AA in a range of 4–15 wt.% contributes to the high values of chemical oxygen demand. Due to the toxicity of AA to the aquatic organism, this wastewater should be treated before it is discharged to the environment. The waste water could be evaporated before sending to the incineration which was neither economic feasible nor environmental friendly. Esterification of wastewater containing carboxylic acid with alcohol could be a promising method to recover the acid by converting it to ester while purifying the wastewater. In the present study, recovery of AA via esterification with 2-ethyl hexanol (2EH) was investigated. The model industrial wastewater with various concentration of AA (10–100% w/w) was reacted with 2EH to produce 2-ethyl hexyl acrylate (2EHA) in the setups with total reflux and continuously water removal. These Amberlyst-15 (ion exchange resin) catalyzed reactions were carried out under the mass transfer resistance free region. The performance of both systems was compared. The yield for the reactions of the AA solutions with the AA concentrations of 30–80% was enhanced significantly when the reactions were carried out using the second setup. The kinetic data of the esterification of dilute AA was well described by the Eley–Rideal (ER) kinetic model incorporated with a correction factor to consider the catalyst fouling effect and pseudo-homogeneous (PH) kinetic model for the AA polymerization. The findings have shown the potential of recovering AA from the waste water stream via esterification. The concentrated AA solutions or larger amount of inhibitor should be adopted to prevent the catalyst fouling by the deposition of poly-acrylic acid on the catalyst surface. 相似文献
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Esterification during the synthesis of tert-butyl peracetate (TBPA) is highly exothermic. Since peroxides (tert-butyl hydroperoxide TBHP and TBPA) are intrinsically thermosensitive, this synthesis process is potentially dangerous. In this work, the exothermic process and mechanism of TBPA synthesis using acetic anhydride (Ac2O) and TBHP under the catalysis of sulphuric acid (H2SO4) were clarified by calorimetry, infrared spectroscopy, and high-performance liquid chromatography. To substantially alleviate the thermal risk of the reaction, and to feasibly select appropriate synthesis conditions for ensuring the process safety of the synthesized products, several sets of isothermal and isoperibol experiments were performed using calorimetry. The intermediates formed and concentration changes during the reaction were monitored using in-situ Fourier-transform infrared spectroscopy. Differential scanning calorimetry and adiabatic calorimetry were used to assess the thermal hazard of the materials during the synthesis process. The reaction mechanism was verified using density functional theory calculations. The results revealed that a controlled increase in exothermicity could be achieved by adding aqueous TBHP to Ac2O in semi-batch experiments in isothermal mode, and accordingly, the highest yield was 95.71%. Experiments combined with theoretical calculations revealed that the primary exothermic event was the TBPA formation reaction, and the removal of a large amount of water from TBHP prior to this is favourable for the reaction. The criticality classes of this reaction were of Grade 2. 相似文献
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Reaction thermal runaway accidents occur frequently and occupy a high proportion in chemical accidents. Reducing accidents by controlling reaction temperature is of great implication to enhance the safety level of chemical processes. Phase change materials (PCMs) have a good energy storage potential, which can rapidly convert the reaction exotherm in the reaction process into its own phase change latent heat, urgently control the reaction temperature, and enhance the process thermal safety level. In this study, using n-octadecane as the core and melamine-formaldehyde (MF) resin as the shell, microencapsulated phase change materials (microPCMs) was made, which has a smooth spherical shape, good thermal stability, and a phase change enthalpy up to 162.87 J/g. The homogeneous esterification reaction of 2-butanol (2 B) and propionic anhydride (PA) was selected as the target reaction, and then the reaction was scaled up equivalently to investigate the effect of amplification to the reaction system. The results indicated that the temperature control of the esterification reaction system by microPCMs is the synergy between physical inhibition and chemical inhibition. The reaction temperature could be controlled by adding microPCMs, and the temperature control effect improved with the increase of microPCMs addition. In large scale reactors, microPCMs still has certain temperature control ability after being added. 相似文献
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《Journal of environmental science and health. Part. B》2013,48(4):627-640
Abstract Esterification of hemicelluloses of the xylan family was performed in order to produce hydrophobic films. Acylation reactions were carried out with lauroyl chloride in the N,N-dimethylacetamide/lithium chloride homogeneous system using 4-dimethylaminopyridine as activator and were induced by microwave irradiation. In the experimental conditions used, 108 and 172% mass ratios were obtained for the dodecyl-grafted xylan and heteroxylan, respectively. The degrees of substitution (DS) were 1.3 (maximum 2) for xylan and 1.2 (maximum 2.1) for heteroxylan. These products were further characterized by FT-IR spectroscopy. The mechanical and thermomechanical behavior of this new family of hydrophobic films were analyzed and compared to those obtained from cellulose with a similar DS by the means of tensile tests. Our results indicate that the dodecyl-grafted xylan film presents the best rigidity—resistance to traction ratio. 相似文献
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