A series of metal salt-modified carbon catalysts had been prepared to study the selective transformation of various carbohydrates into ethyl levulinate in an ethanol medium. The specific textural and chemical characte...A series of metal salt-modified carbon catalysts had been prepared to study the selective transformation of various carbohydrates into ethyl levulinate in an ethanol medium. The specific textural and chemical characteristics of prepared carbon samples were identified by Raman, XRD, XPS, NH;-TPD, FT-IR and nitrogen physisorption. Various parameters such as ethanol/water volume ratio, Na Cl addition, reaction temperature, and catalyst dosage played a great role in ethyl levulinate production. A desirable ethyl levulinate yield of 58.0 mol% with a highest ROF（rate of ethyl levulinate formation per gram of catalyst per hour） value of 2148.3 μmol/(g;·h) was achieved at 468 K over FeCl;modified carbon catalyst with respect to fructose conversion. The recycling experiments revealed that the sulfonated carbon catalysts exhibited relatively satisfied activity and stability.展开更多
Levulinate esters are versatile chemicals that have been used in various fields. Herein, the production of ethyl levulinate（EL） from corn stover was investigated under microwave irradiation. Several reaction paramet...Levulinate esters are versatile chemicals that have been used in various fields. Herein, the production of ethyl levulinate（EL） from corn stover was investigated under microwave irradiation. Several reaction parameters, including acid concentration, reaction temperature, reaction time, and liquid-to-solid mass ratio, were investigated to evaluate the reaction conditions. Response surface methodology（RSM） was employed to optimize the reaction conditions for the production of EL. A quadratic polynomial model was fitted to the data with an R2 value of 0.93. The model validation results reflected a good fit between the experimental and predicted values. A high conversion yield（58.1 mol%） was obtained at the optimum conditions of 190℃, 30.4 min, 2.84 wt% acid, and 15 g/g liquid-to-solid mass ratio. Compared with conventional heating, microwave irradiation facilitated the conversion of corn stover to EL by dramatically shortening the reaction time from several hours to ～30 min. Thus, microwave-assisted conversion of corn stover to EL is an efficient way of utilizing a renewable biomass resource.展开更多
Ultrasound-assisted pretreatment under mild operating conditions has been investigated for intensification of delignification to facilitate the obtaining of ethyl levulinate from biomass. The effect of pH (2 - 12), te...Ultrasound-assisted pretreatment under mild operating conditions has been investigated for intensification of delignification to facilitate the obtaining of ethyl levulinate from biomass. The effect of pH (2 - 12), temperature (30°C - 70°C) and pretreatment time (0 - 120 minutes) has been studied for different biomass samples. The most favorable conditions were basic pH, temperature of 70°C and pretreatment time of 2 h, obtaining values of delignification near 80 percent. The ethyl levulinate is obtained in microwave directly via from samples before and after delignification and analyzed for GC-MS. The results evidenced better yields for the delignified samples.展开更多
Ethyl levulinate(EL)is a key biomass-derived compounds due to its socio-economic benefits for the synthesis of commodity chemicals.Herein,we proposed an efficient one-step bamboo conversion to EL in ethanol,and a nove...Ethyl levulinate(EL)is a key biomass-derived compounds due to its socio-economic benefits for the synthesis of commodity chemicals.Herein,we proposed an efficient one-step bamboo conversion to EL in ethanol,and a novel stepwise fractionation to purify EL and lignocellulose degradation products.A proton acid,due to its high catalytic efficiency,yielded 26.65%EL in 120 min at 200℃.The productions of ethyl glucoside and 5-ethoxymethylfurfural were analyzed in terms of by-products formation.To the best of our knowledge,there is no single report on catalyst for one step synthesis of EL directly from bamboo,as well as a stepwise fractionation to purify EL.Due to similar physiochemical properties in each fraction,the platform molecules could broaden a new paradigm of bamboo biomass utilization for renewable energy and value-added biochemicals.In addition,glucose,ethyl glucoside,corn starch,and microcrystalline cellulose were also investigated as substrates,so that the reaction intermediates of this one-pot procedure were identified and a possible reaction mechanism was proposed.展开更多
The kinetics for production of ethyl levulinate from glucose in ethanol medium was investigated. The experiments were performed in various temperatures （433-473 K） and initial glucose concentrations （0.056-0.168 mo...The kinetics for production of ethyl levulinate from glucose in ethanol medium was investigated. The experiments were performed in various temperatures （433-473 K） and initial glucose concentrations （0.056-0.168 mol·L-1） with extremely low sulfuric acid as the catalyst. The results show that higher temperature can improve the conversion of glucose to ethyl levulinate, with higher yield of ethyl levulinate （44.79%, by mole） obtained at 473 K for 210 min. The kinetics follows a simplified first-order kinetic model. For the main and side reactions, the values of activation energy are 122.64 and 70.97 kJ·mo1-1, and the reaction orders are 0.985 and 0.998, respectively.展开更多
The molecular sieves supported TiO 2/SO 2- 4 catalyst was prepared by the liquid phase precipitation,then its preparation conditions were investigated in detail.The results indicated that the pH value of solution was ...The molecular sieves supported TiO 2/SO 2- 4 catalyst was prepared by the liquid phase precipitation,then its preparation conditions were investigated in detail.The results indicated that the pH value of solution was adjusted to 1.8,the mass ratio of TiO 2 to molecular sieves was 0.13∶100,the water in the system must be evaporated slowly at 90℃.And the best active temperature of catalyst was 50℃.The factors that had influence on the esterification of levulinic acid with alcohol were also discussed,the optimum reaction conditions were 5∶100(mass ratio) of catalyst to acid,5∶6(volume ratio) of alcohol to acid,oil bath temperature being kept at 110℃ and suitable reaction time being 1.5h.Under such conditions,the ester yield could be as high as 96.5%.展开更多
基金supported by the Natural Science Foundation of Guangdong Province, China (2014A030310386, 2016A030313173, 2015A030312007)the National Natural Science Foundation of China (21472189)+2 种基金the National Basic Research Program of China (973 Program, 2012CB215304)Science and Technology Planning Project of Guangdong Province, China (2015A010106010)Open fund of Key Laboratory of Renewable Energy, Chinese Academy of Sciences (y507ja1001)
文摘A series of metal salt-modified carbon catalysts had been prepared to study the selective transformation of various carbohydrates into ethyl levulinate in an ethanol medium. The specific textural and chemical characteristics of prepared carbon samples were identified by Raman, XRD, XPS, NH;-TPD, FT-IR and nitrogen physisorption. Various parameters such as ethanol/water volume ratio, Na Cl addition, reaction temperature, and catalyst dosage played a great role in ethyl levulinate production. A desirable ethyl levulinate yield of 58.0 mol% with a highest ROF（rate of ethyl levulinate formation per gram of catalyst per hour） value of 2148.3 μmol/(g;·h) was achieved at 468 K over FeCl;modified carbon catalyst with respect to fructose conversion. The recycling experiments revealed that the sulfonated carbon catalysts exhibited relatively satisfied activity and stability.
基金financially supported by the National Key R&D Program of China(no.2016YFE0112800)National Natural Science Foundation of China(no.31671572)
文摘Levulinate esters are versatile chemicals that have been used in various fields. Herein, the production of ethyl levulinate（EL） from corn stover was investigated under microwave irradiation. Several reaction parameters, including acid concentration, reaction temperature, reaction time, and liquid-to-solid mass ratio, were investigated to evaluate the reaction conditions. Response surface methodology（RSM） was employed to optimize the reaction conditions for the production of EL. A quadratic polynomial model was fitted to the data with an R2 value of 0.93. The model validation results reflected a good fit between the experimental and predicted values. A high conversion yield（58.1 mol%） was obtained at the optimum conditions of 190℃, 30.4 min, 2.84 wt% acid, and 15 g/g liquid-to-solid mass ratio. Compared with conventional heating, microwave irradiation facilitated the conversion of corn stover to EL by dramatically shortening the reaction time from several hours to ～30 min. Thus, microwave-assisted conversion of corn stover to EL is an efficient way of utilizing a renewable biomass resource.
文摘Ultrasound-assisted pretreatment under mild operating conditions has been investigated for intensification of delignification to facilitate the obtaining of ethyl levulinate from biomass. The effect of pH (2 - 12), temperature (30°C - 70°C) and pretreatment time (0 - 120 minutes) has been studied for different biomass samples. The most favorable conditions were basic pH, temperature of 70°C and pretreatment time of 2 h, obtaining values of delignification near 80 percent. The ethyl levulinate is obtained in microwave directly via from samples before and after delignification and analyzed for GC-MS. The results evidenced better yields for the delignified samples.
基金supported by National Science Foundation of China(No.32001274).
文摘Ethyl levulinate(EL)is a key biomass-derived compounds due to its socio-economic benefits for the synthesis of commodity chemicals.Herein,we proposed an efficient one-step bamboo conversion to EL in ethanol,and a novel stepwise fractionation to purify EL and lignocellulose degradation products.A proton acid,due to its high catalytic efficiency,yielded 26.65%EL in 120 min at 200℃.The productions of ethyl glucoside and 5-ethoxymethylfurfural were analyzed in terms of by-products formation.To the best of our knowledge,there is no single report on catalyst for one step synthesis of EL directly from bamboo,as well as a stepwise fractionation to purify EL.Due to similar physiochemical properties in each fraction,the platform molecules could broaden a new paradigm of bamboo biomass utilization for renewable energy and value-added biochemicals.In addition,glucose,ethyl glucoside,corn starch,and microcrystalline cellulose were also investigated as substrates,so that the reaction intermediates of this one-pot procedure were identified and a possible reaction mechanism was proposed.
基金Supported by the National Natural Science Foundation of China(21176227)the State Key Laboratory of Motor Vehicle Biofuel Technology(2013011)
文摘The kinetics for production of ethyl levulinate from glucose in ethanol medium was investigated. The experiments were performed in various temperatures （433-473 K） and initial glucose concentrations （0.056-0.168 mol·L-1） with extremely low sulfuric acid as the catalyst. The results show that higher temperature can improve the conversion of glucose to ethyl levulinate, with higher yield of ethyl levulinate （44.79%, by mole） obtained at 473 K for 210 min. The kinetics follows a simplified first-order kinetic model. For the main and side reactions, the values of activation energy are 122.64 and 70.97 kJ·mo1-1, and the reaction orders are 0.985 and 0.998, respectively.
文摘The molecular sieves supported TiO 2/SO 2- 4 catalyst was prepared by the liquid phase precipitation,then its preparation conditions were investigated in detail.The results indicated that the pH value of solution was adjusted to 1.8,the mass ratio of TiO 2 to molecular sieves was 0.13∶100,the water in the system must be evaporated slowly at 90℃.And the best active temperature of catalyst was 50℃.The factors that had influence on the esterification of levulinic acid with alcohol were also discussed,the optimum reaction conditions were 5∶100(mass ratio) of catalyst to acid,5∶6(volume ratio) of alcohol to acid,oil bath temperature being kept at 110℃ and suitable reaction time being 1.5h.Under such conditions,the ester yield could be as high as 96.5%.
