The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent.Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate H_(2...The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent.Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O] during the leaching process,while calcium remained in the residue as calcium sulfate dihydrate(CaSO4·2H2O).About 99.2%of the tungsten was leached at 70℃,1.5 mol/L sulfuric acid,1 mol/L oxalic acid,a liquid/solid ratio of 25:1(mL/g),an oxalic acid to sulfuric acid molar ratio of 1:1,a stirring speed of 300 r/min and a leaching time of 2 h.H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O]was thermally decomposed into tungstic acid(H_(2)WO_(4)),and tungsten trioxide(WO_(3))was directly produced by calcining H_(2)WO_(4) at 700℃ for 2 h.The surface chemical reaction was determined to be the controlling step during tungsten leaching,and the apparent activation energy was calculated to be 51.43 kJ/mol.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
Charge-transfer salt (dbtf),HGeW12O40. 4H2O(C84H57O44S24GeW12)was synthesized by electrocrystallization and characterized by IR and electronic spectra.Its magnetic and conducting properties and crystal structure were ...Charge-transfer salt (dbtf),HGeW12O40. 4H2O(C84H57O44S24GeW12)was synthesized by electrocrystallization and characterized by IR and electronic spectra.Its magnetic and conducting properties and crystal structure were determined. The titlesalt crystallized in triclinic system with P1 space group. Its cell parameters are reflexions展开更多
基金financial supports from the National Natural Science Foundation of China (Nos.51564019, 51674125)Science and Technology Project of Jiangxi Provincial Education Department,China (No.GJJ181501).
文摘The extraction of tungsten from scheelite was carried out using a sulfuric acid solution with oxalic acid as the chelating agent.Tungsten was obtained in the form of highly soluble hydrogen aqua oxalato tungstate H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O] during the leaching process,while calcium remained in the residue as calcium sulfate dihydrate(CaSO4·2H2O).About 99.2%of the tungsten was leached at 70℃,1.5 mol/L sulfuric acid,1 mol/L oxalic acid,a liquid/solid ratio of 25:1(mL/g),an oxalic acid to sulfuric acid molar ratio of 1:1,a stirring speed of 300 r/min and a leaching time of 2 h.H_(2)[WO_(3)(C_(2)O_(4))·H_(2)O]was thermally decomposed into tungstic acid(H_(2)WO_(4)),and tungsten trioxide(WO_(3))was directly produced by calcining H_(2)WO_(4) at 700℃ for 2 h.The surface chemical reaction was determined to be the controlling step during tungsten leaching,and the apparent activation energy was calculated to be 51.43 kJ/mol.
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Charge-transfer salt (dbtf),HGeW12O40. 4H2O(C84H57O44S24GeW12)was synthesized by electrocrystallization and characterized by IR and electronic spectra.Its magnetic and conducting properties and crystal structure were determined. The titlesalt crystallized in triclinic system with P1 space group. Its cell parameters are reflexions
