Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide （TAHP）, for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phe...Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide （TAHP）, for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phene （DBT）, benzothiophene （BT） and 4, 6-dimethyl-dibenzothiophene （DMDBT）, which are the refractory sulfur compounds for hydrodesulfurization （HDS）, were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90℃ and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT 〉DBT 〉BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity （WHSV） from 40 h^-1 to 10 h^-1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide （TBHP）. The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500μg·g^-1. In the flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg·g^-1 to 7.2 μg·g^-1 at WHSV of 10 h^-1, and then reduced to 3.8 μg·g^-1 by adsorntion of Al2O3.展开更多
The activities of dimethyl carbonate and dimethyl sulfate as a methylation reagent were studied by density- functional theory （DFT）. B3LYP/6-31G（d, p） methods were used to optimize the structures of dirnethyl carb...The activities of dimethyl carbonate and dimethyl sulfate as a methylation reagent were studied by density- functional theory （DFT）. B3LYP/6-31G（d, p） methods were used to optimize the structures of dirnethyl carbonate and dimethyl sulfate and calculate theirs charge densities. Dimethyl sulfate is easier than dimethyl carbonate to react with a nucleophUic reagent. In dimethyl sulfate, the alkoxy carbons are the only reactive atomic nucleus because of steric hindrance. A nucleophilic reagent is more likely to react with carbonyl carbons than alkoxy carbons of dimethyl carbonate; in the presence of a Lewis acid, the phenyl nucleophilic reagent reacts with the Lewis acid first. Lewis acid increases the negative charge density of a nucleophUic reagent in polar solvent, and also incurs an accretion of steric hindrance. Polar solvent avails to ionize dimethyl carbonate and thus enables the reaction of methylation. The frequencies of transition state calculated by Gaussion 03 confirm the inferred reaction mechanism. The harvest rates of 4-methoxyphenol in the experiments of methylation reactions of hydroquinone with respectively dimethyl carbonate and dimethyl sulfate support the foregoing theortical conclusions.展开更多
Oxidative desulfurization was performed on Na2WO4 catalyst in the presence of hydrogen peroxide and acetic acid under mild reaction conditions （atmospheric pressure and temperature range of 293--343 K）. Different or...Oxidative desulfurization was performed on Na2WO4 catalyst in the presence of hydrogen peroxide and acetic acid under mild reaction conditions （atmospheric pressure and temperature range of 293--343 K）. Different organic compounds including benzothiophene （BT）, dibenzothiophene （DBT）, 4, 6-dimethyl dibenzothiophene （4, 6-DMDBT） were used to investigate the reactivity of this catalyst, and the effect of various parameters, such as temperature, solvents and the amount of oxidant reagent used in oxidative desulfurization reaction, was also examined. The results showed that the Na2WO4- H202 system was very effective for oxidative desulfurization, and the oxidation of BT, DBT and 4, 6-DMDBT was influenced by different parameters.展开更多
Both cubane-like clusters MoFe_3S_4 (Me_2dtc)_5·2CH_2Cl_2 (1) and MoFe_3S_4(C_4H_8dtc)_5·2EtCN (2) were used to study the temperature-dependent behavior of the molar magnetic susceptibility. A spin coupling ...Both cubane-like clusters MoFe_3S_4 (Me_2dtc)_5·2CH_2Cl_2 (1) and MoFe_3S_4(C_4H_8dtc)_5·2EtCN (2) were used to study the temperature-dependent behavior of the molar magnetic susceptibility. A spin coupling model was suggested and the fitting results agree with the model and structural and spectroscopic parameters.展开更多
基金Supported by Program for Changjiang Scholars and Innovative Research Team in University
文摘Homogeneous oxidation using an oil-soluble oxidant, tert-amyl hydroperoxide （TAHP）, for ultra-deep desulfurization was performed under mild conditions in the presence of molybdenum oxide catalysts. Dibenzothio- phene （DBT）, benzothiophene （BT） and 4, 6-dimethyl-dibenzothiophene （DMDBT）, which are the refractory sulfur compounds for hydrodesulfurization （HDS）, were employed as model substrates for a simulated diesel fuel. Activity of molybdenum oxide supported on a macroporous weak acidic resin was investigated. The mass conversion of DBT reached near 100% at 90℃ and a TAHP/DBT molar ratio of 3 with 1% of molybdenum oxide supported on Amberlite IRC-748 resin for 1 h. It was further found that the activities of the model substrates decreased in the or- der of DMDBT 〉DBT 〉BT. In the flow oxidation using TAHP as the oxidant, mass conversion of DBT increased remarkably from 61.3% to 98.5% when dropping the weight hourly space velocity （WHSV） from 40 h^-1 to 10 h^-1. A series of experiments dealt with selectivity of this oxidation using TAHP revealed that the model unsaturated compounds, i.e. 4, 6, 8-trimethyl-2-nonylene, and 2-methylnaphthalene did not affect the oxidation of DBT. Carbazole had nearly no effect on the conversion of DBT using TAHP, but had some influence on the one using tert-butyl hydroperoxide （TBHP）. The mass conversion of DBT decreased remarkably from 75.2% to 3.6% when the content of carbazole increased from 0 to 500μg·g^-1. In the flow oxidation using TAHP as the oxidant, the concentration of DBT in model fuels was reduced from 500 μg·g^-1 to 7.2 μg·g^-1 at WHSV of 10 h^-1, and then reduced to 3.8 μg·g^-1 by adsorntion of Al2O3.
文摘The activities of dimethyl carbonate and dimethyl sulfate as a methylation reagent were studied by density- functional theory （DFT）. B3LYP/6-31G（d, p） methods were used to optimize the structures of dirnethyl carbonate and dimethyl sulfate and calculate theirs charge densities. Dimethyl sulfate is easier than dimethyl carbonate to react with a nucleophUic reagent. In dimethyl sulfate, the alkoxy carbons are the only reactive atomic nucleus because of steric hindrance. A nucleophilic reagent is more likely to react with carbonyl carbons than alkoxy carbons of dimethyl carbonate; in the presence of a Lewis acid, the phenyl nucleophilic reagent reacts with the Lewis acid first. Lewis acid increases the negative charge density of a nucleophUic reagent in polar solvent, and also incurs an accretion of steric hindrance. Polar solvent avails to ionize dimethyl carbonate and thus enables the reaction of methylation. The frequencies of transition state calculated by Gaussion 03 confirm the inferred reaction mechanism. The harvest rates of 4-methoxyphenol in the experiments of methylation reactions of hydroquinone with respectively dimethyl carbonate and dimethyl sulfate support the foregoing theortical conclusions.
文摘Oxidative desulfurization was performed on Na2WO4 catalyst in the presence of hydrogen peroxide and acetic acid under mild reaction conditions （atmospheric pressure and temperature range of 293--343 K）. Different organic compounds including benzothiophene （BT）, dibenzothiophene （DBT）, 4, 6-dimethyl dibenzothiophene （4, 6-DMDBT） were used to investigate the reactivity of this catalyst, and the effect of various parameters, such as temperature, solvents and the amount of oxidant reagent used in oxidative desulfurization reaction, was also examined. The results showed that the Na2WO4- H202 system was very effective for oxidative desulfurization, and the oxidation of BT, DBT and 4, 6-DMDBT was influenced by different parameters.
文摘Both cubane-like clusters MoFe_3S_4 (Me_2dtc)_5·2CH_2Cl_2 (1) and MoFe_3S_4(C_4H_8dtc)_5·2EtCN (2) were used to study the temperature-dependent behavior of the molar magnetic susceptibility. A spin coupling model was suggested and the fitting results agree with the model and structural and spectroscopic parameters.
