The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous...The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N2 adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about i, 0.2 for benzene and 0.7 for H202.展开更多
A novel method based on the selective pressure of particle size （particle-size cultivation method, PSCM） was developed for the cultivation and operation of aerobic granular sludge in a continuous-flow reactor, and c...A novel method based on the selective pressure of particle size （particle-size cultivation method, PSCM） was developed for the cultivation and operation of aerobic granular sludge in a continuous-flow reactor, and compared with the conventional method based on the selective pressure of settling velocity （settling-velocity cultivation method, SVCM）. Results indicated that aerobic granules could be cultivated in continuous operation mode by this developed method within 14 days. Although in the granulation process, under particle-size selective pressure, mixed liquor suspended solids （MLSS） in the reactor fluctuated greatly and filamentous bacteria dominated the sludge system during the initial operation days, no obvious difference in profile was found between the aerobic granules cultivated by PSCM and SVCM. Moreover, aerobic granules cultivated by PSCM presented larger diameter, lower water content and higher specific rates of nitrification, denitrifieation and phosphorus removal, but lower settling velocity. Under long term operation of more than 30 days, aerobic granules in the continuous-flow reactor could remain stable and obtain good chemical oxygen demand （COD）, NH4^＋-N, total nitrogen （TN） and total phosphorus （TP） removal. The results indicate that PSCM was dependent on the cultivation and maintenance of the stability of aerobic granules in continuous-flow bioreactors.展开更多
To calculate ignition delay times,the governing equations about species and temperature,which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor,are deducted.The...To calculate ignition delay times,the governing equations about species and temperature,which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor,are deducted.The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium.When a species is assumed to be in the steady state,the corresponding differential equation can be replaced by an algebraic relation,which reduces the computational costs.The steady state solution of the reactor equations describes the three ignition temperature regimes and get“S-shaped curve”.The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations,which is solved.The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data.At last,two important parameters are discussed thoroughly and the temperature perturbation is given.It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.展开更多
Replacing fossil carbon sources with green bio-oils is a promising route to switch to a sustainable chemical industry,although their high oxygen contents are challenging.Catalytic hydrodeoxygenation is a favored route...Replacing fossil carbon sources with green bio-oils is a promising route to switch to a sustainable chemical industry,although their high oxygen contents are challenging.Catalytic hydrodeoxygenation is a favored route to upgrade bio-oils to renewable fuels and basic chemicals.In this work,we investigated Ni/SiO2 catalysts with differing metal dispersity in continuous mode conversion of guaiacol with a statistical experimental design for 250℃to 400℃,2 h up to 5 h time on stream(ToS)and subsequently different residence time besides other parameters.While low temperature(250℃)promotes cyclohexanol formation from guaiacol,high temperature(400℃)inhibits hydrogenation,leading to phenol and methane.For medium temperature(340℃),the selectivity for cyclohexanone increases.Cyclohexanol and cyclohexanone(KA-oil)are the industrial basis for polyamide 6.Furthermore,we clarified the role of 2-methoxycyclohexanol(2MC)in the reaction network towards KA-oil for continuous-mode operation.Statistical analysis was used to predict and optimize product selectivity and yield,leading to the best yield of cyclohexanone/-ol at 327.5℃,low ToS,medium residence time,high particle dispersity,and medium hydrogen pressure(15 bar(g)).展开更多
文摘The direct hydroxylation of benzene to phenol catalyzed by activated carbon-supported Fe （Fe/AC） in acetonitrile using H2O2 as the oxidant was studied in a continuous flow reactor. Results showed that the continuous operation could obtain high phenol yield of 28.1%, coupled with the turnover frequency of 3 h^-1, and high selectivity of 98% under mild condition. The catalyst was characterized by N2 adsorption/desorption, Boehm titration, X-ray photoelectron spectra, and Fourier transform infrared spectroscopy. It was observed that iron may interact with the carboxyl group forming iron-carboxylate like species, which act as the active phase. The apparent activation energy obtained by fitting an Arrhenius model to the experimental data was 13.4 kJ/mol. The reaction order was calculated to be about i, 0.2 for benzene and 0.7 for H202.
基金supported by the National Natural Science Foundation of China (No. 51208231)
文摘A novel method based on the selective pressure of particle size （particle-size cultivation method, PSCM） was developed for the cultivation and operation of aerobic granular sludge in a continuous-flow reactor, and compared with the conventional method based on the selective pressure of settling velocity （settling-velocity cultivation method, SVCM）. Results indicated that aerobic granules could be cultivated in continuous operation mode by this developed method within 14 days. Although in the granulation process, under particle-size selective pressure, mixed liquor suspended solids （MLSS） in the reactor fluctuated greatly and filamentous bacteria dominated the sludge system during the initial operation days, no obvious difference in profile was found between the aerobic granules cultivated by PSCM and SVCM. Moreover, aerobic granules cultivated by PSCM presented larger diameter, lower water content and higher specific rates of nitrification, denitrifieation and phosphorus removal, but lower settling velocity. Under long term operation of more than 30 days, aerobic granules in the continuous-flow reactor could remain stable and obtain good chemical oxygen demand （COD）, NH4^＋-N, total nitrogen （TN） and total phosphorus （TP） removal. The results indicate that PSCM was dependent on the cultivation and maintenance of the stability of aerobic granules in continuous-flow bioreactors.
文摘To calculate ignition delay times,the governing equations about species and temperature,which are in a closed volume based on the theory of thermal explosion and in a continuously stirred flow reactor,are deducted.The method referred to steady state assumptions is based on the observation that due to very fast chemical processes in combustion problems many chemical species and reactions are in a quasi-steady state or partial equilibrium.When a species is assumed to be in the steady state,the corresponding differential equation can be replaced by an algebraic relation,which reduces the computational costs.The steady state solution of the reactor equations describes the three ignition temperature regimes and get“S-shaped curve”.The reduced simplified 4-step mechanism for n-heptane from 1011 elementary reactions leads with the steady state assumptions to linear differential equations,which is solved.The simulation results of the 4-step reduced mechanism for n-heptane are fitted well with the experiment data.At last,two important parameters are discussed thoroughly and the temperature perturbation is given.It reduces the computational efforts considerably without losing too much accuracy and further supplies numerical methods for turbulent combustion in the diesel engine.
基金supported by the Chair of Inorganic Molecular Chemistry(TU Dresden)by Prof.Dr.Jan J.Weigand.Evonik AG provided the silica carrier material Aerosil380 for research purposesThe Federal State of Saxony(Germany)funded the first author’s work through the Saxon State Scholarship ProgramThe corresponding author thanks German Research Foundation(DFG)for funding of project SE 2450/2-1(Nbr.507997100).
文摘Replacing fossil carbon sources with green bio-oils is a promising route to switch to a sustainable chemical industry,although their high oxygen contents are challenging.Catalytic hydrodeoxygenation is a favored route to upgrade bio-oils to renewable fuels and basic chemicals.In this work,we investigated Ni/SiO2 catalysts with differing metal dispersity in continuous mode conversion of guaiacol with a statistical experimental design for 250℃to 400℃,2 h up to 5 h time on stream(ToS)and subsequently different residence time besides other parameters.While low temperature(250℃)promotes cyclohexanol formation from guaiacol,high temperature(400℃)inhibits hydrogenation,leading to phenol and methane.For medium temperature(340℃),the selectivity for cyclohexanone increases.Cyclohexanol and cyclohexanone(KA-oil)are the industrial basis for polyamide 6.Furthermore,we clarified the role of 2-methoxycyclohexanol(2MC)in the reaction network towards KA-oil for continuous-mode operation.Statistical analysis was used to predict and optimize product selectivity and yield,leading to the best yield of cyclohexanone/-ol at 327.5℃,low ToS,medium residence time,high particle dispersity,and medium hydrogen pressure(15 bar(g)).
