The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The lea...The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ~C, 6 h, 1.5 ml.g-1, 15 vol % H2SO4, and 5 % calcium fluoride （mass ratio of CaF2 to stone coal）. The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol.L-1 to the pH of 1.80 4- 0.05 by 200 g.L-1 lime milk, respectively. The solvent extraction experiments were carded out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81%, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate （Fe2Fs.7H20） and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KA1SO4 and FeA1Fs. In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.展开更多
An efficient copper-catalyzed regioselective acyloxy-trifluoromethylation of allenamides using Togni'sⅡreagent as the source of both the trifluoromethyl and acyloxy moieties was developed to create a workable rou...An efficient copper-catalyzed regioselective acyloxy-trifluoromethylation of allenamides using Togni'sⅡreagent as the source of both the trifluoromethyl and acyloxy moieties was developed to create a workable route to CF_(3)-substituted allylic esters.The reaction exhibited good functional group tolerance and high efficiency,affording the products in moderate to good yields.Mechanistic investigations indicated a radical process was likely involved in this transformation.展开更多
Benziodazole-triflate,as a novel heterocyclic hypervalent iodine(III)reagent,was prepared from the reaction of hypervalent chloroiodine(III)with silver triflate under mild conditions.The structure of this new reagent ...Benziodazole-triflate,as a novel heterocyclic hypervalent iodine(III)reagent,was prepared from the reaction of hypervalent chloroiodine(III)with silver triflate under mild conditions.The structure of this new reagent was elucidated by NMR spectroscopy and X-ray crystallography,and its reactions with diverseα-electron withdrawing group substituted carbonyl compounds were investigated.The results implied that benziodazole-triflate could be selectively used as both a 2-iodobenzamido-transfer reagent for the synthesis of oxazole compounds,and a triflate-transfer reagent for the triflation ofβ-keto-sulfones.Ionic mechanistic pathways,supported by density functional theory(DFT)calculations,were proposed to account for the divergent selectivities of the transformations.展开更多
The tert-butyl nitrite as a bifunctional reagent mediated radical alkene difunctionalization has emerged as a powerful strategy for synthesis of structurally diverse oxime-containing compounds.However,the phosphorus-c...The tert-butyl nitrite as a bifunctional reagent mediated radical alkene difunctionalization has emerged as a powerful strategy for synthesis of structurally diverse oxime-containing compounds.However,the phosphorus-centered radical initiated transformations remain largely elusive.Herein,a visible-lightinduced radical phosphinoyloximation of alkenes with secondary phosphine oxides and tert-butyl nitrite has been developed under photocatalyst-and metal-free conditions.This protocol features mild conditions,broad substrate scope,good functional tolerance,and operational simplicity,yielding a diverse array ofα-phosphinoyl oximes in moderate to good yields with high stereoselectivities.The photomediated homolytic cleavage of O–NO bond of tert-butyl nitrite generates the reactive tert-butoxyl radical and persistent NO radical to act as both HAT reagent and the source of oximes.展开更多
This study focuses on using a green reagent scheme of methanesulfonic acid (MSA) and citric acid (CA) to extract valuable metals from the cathodes, aiming to minimize environmental impact during the recycling process....This study focuses on using a green reagent scheme of methanesulfonic acid (MSA) and citric acid (CA) to extract valuable metals from the cathodes, aiming to minimize environmental impact during the recycling process. Leaching studies on LiCoO_(2) identified optimal conditions as follows: 2.4 mol/L MSA, 1.6 mol/L CA, S/L ratio of 80 g/L, leaching temperature of 90oC and leaching time of 6 h. The maximum Co and Li extraction achieved was 92% and 85%, respectively. LiCoO_(2) dissolution in MSA-CA leaching solution is highly impacted by temperature;Avrami equation showed a good fitting for the leaching data. The experimental activation energy of Co and Li was 50.98 kJ/mol and 50.55 kJ/mol, respectively, indicating that it is a chemical reaction-controlled process. Furthermore, cobalt was efficiently recovered from the leachate using oxalic acid, achieving a precipitation efficiency of 99.91% and a high-purity cobalt oxalate product (99.85 wt.%). In the MSA-CA leaching solution, MSA served as a lixiviant, while CA played a key role in reducing Co in LiCoO_(2). The overall organic acid leaching methodology presents an attractive option due to its reduced environmental impact.展开更多
Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reage...Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reagents that can replace cyanide. This paper intro-duces a method for synthesizing a gold leaching reagent. Sodium cyanate is used as the main raw material, with sodium hydroxide and so-dium ferrocyanide used as additives. The gold leaching reagent can be obtained under the conditions of a mass ratio of sodium cyanate,sodium hydroxide, and sodium ferrocyanide of 15:3:1, synthesis temperature of 600℃, and synthesis time of 1 h. This reagent has a goodrecovery effect on gold concentrate and gold-containing electronic waste. The gold leaching rate of roasted desulfurized gold concentratecan reach 87.56%. For the extraction experiments of three types of gold-containing electronic waste, the gold leaching rate can reach over90% after 2 h. Furthermore, the reagent exhibits good selectivity towards gold. Component analysis indicates that the effective compon-ent in the reagent could be sodium isocyanate.展开更多
The asymmetric conjugate additions of aryl Grignard reagents to trisubstituted enones by chiral P,N ligand L6 with low catalyst loading(0.25–1.0 mol%)are disclosed.Chiral 2-ester chromanone and its analogs bearing a ...The asymmetric conjugate additions of aryl Grignard reagents to trisubstituted enones by chiral P,N ligand L6 with low catalyst loading(0.25–1.0 mol%)are disclosed.Chiral 2-ester chromanone and its analogs bearing a quaternary stereogenic centers at C2 position were produced in high to excellent yields,enantioselectivities and high turnover number.The notable features of this reaction include its broad substrate scope,complete 1,4-addition regioselectivities,applicability to both batch and flow for large scale synthesis.This report develops an efficient strategy to apply aryl Grignard reagents in asymmetric 1,4-conjugation reactions and provides a direct method to incorporate quaternary chiral centers toward the synthesis of biologically relevant chromanone derivatives.展开更多
The radical difunctionalization of alkenes with sulfonyl bifunctional represents a powerful and straightforward approach to access functionalized alkane derivatives.However,both the mechanistic activation mode and the...The radical difunctionalization of alkenes with sulfonyl bifunctional represents a powerful and straightforward approach to access functionalized alkane derivatives.However,both the mechanistic activation mode and the substrate scopes of this type of radical difunctionalizations are still limited.We demonstrate herein a modular photoredox strategy for the difunctionalization of alkenes,employing arylsulfonyl acetate as the bifunctional reagent.This approach involves a radical addition/Smiles rearrangement cascade process,offering a robust alternative for the synthesis of valuableγ,γ-diaryl andγ-aryl esters.A complementary oxidative bifunctional reagents activation mode is identified to govern the radical cascade reactions,facilitating the simultaneous incorporation of aryl and carboxylate-bearing alkyl groups into the alkenes with excellent diastereoselectivity.Noteworthy features of this method include mild reaction conditions,organophotocatalysis,high atom-and step-economy,excellent functional group compatibility and great structural diversity.展开更多
The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significant...The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significantly changed by the reagent films. There were no evident rules between the average size of particles and sampling time interval, the placing angle and reagent concentration. The average particle size on the surface coated by composite reagent （2-3 μm） was smaller than that on the single reagent coated surface, while the largest particle size （4-5 μm） was observed on the surface coated with the Tween 60. The experiment also demonstrated that the best adhesive performance was obtained on the surface which was coated with 0.5% SDBS and 0.5% fluorocarbon composite reagents. The experiment results indicated that each reagent had a certain optimum adhesive range to the particle. The composite reagents with different proportion of single reagents exhibited some particular physical and chemical properties, which could effectively change the adhesive performance between the solid surface and the particles.展开更多
ZnO nanoparticles were synthesized via a direct precipitation method followed by a hetero- geneous azeotropic distillation and calcination processes, and then characterized by X-ray power diffraction, scanning electro...ZnO nanoparticles were synthesized via a direct precipitation method followed by a hetero- geneous azeotropic distillation and calcination processes, and then characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy, and ni- trogen adsorption-desorption measurement. The effects of Pt-loading amount, calcination temperature, and sacrificial reagents on the present ZnO suspension were investigated, photocatalytic H2 evolution efficiency from the The experimental results indicate that ZnO rianoparticles calcined at 400℃ exhibit the best photoactivity for the H2 production in comparison with the samples calcined at 300 and 500℃, and the photoeatalytie H2 production efficiency from a methanol solution is much higher than that from a triethanolamine solution. It can be ascribed to the oxidization of methanol also contributes to the H2 production during the photochemical reaction process. Moreover, the photocatalytic mechanism for the H2 production from the present ZnO suspension system containing methanol solution is also discussed in detail.展开更多
基金financially supported by the Key Science and Technology Support Program (No. 2011BAB05B01) from the Ministry of ScienceTechnology of China and the Special Science and Technology Program (No. 201009013) from the Ministry of Environmental Protection of China
文摘The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ~C, 6 h, 1.5 ml.g-1, 15 vol % H2SO4, and 5 % calcium fluoride （mass ratio of CaF2 to stone coal）. The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol.L-1 to the pH of 1.80 4- 0.05 by 200 g.L-1 lime milk, respectively. The solvent extraction experiments were carded out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81%, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate （Fe2Fs.7H20） and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KA1SO4 and FeA1Fs. In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.
文摘An efficient copper-catalyzed regioselective acyloxy-trifluoromethylation of allenamides using Togni'sⅡreagent as the source of both the trifluoromethyl and acyloxy moieties was developed to create a workable route to CF_(3)-substituted allylic esters.The reaction exhibited good functional group tolerance and high efficiency,affording the products in moderate to good yields.Mechanistic investigations indicated a radical process was likely involved in this transformation.
基金the National Natural Science Foundation of China(Nos.22071175,22071116)Tianjin Graduate Research and Innovation Project(No.2021YJSB196)and for financial supports。
文摘Benziodazole-triflate,as a novel heterocyclic hypervalent iodine(III)reagent,was prepared from the reaction of hypervalent chloroiodine(III)with silver triflate under mild conditions.The structure of this new reagent was elucidated by NMR spectroscopy and X-ray crystallography,and its reactions with diverseα-electron withdrawing group substituted carbonyl compounds were investigated.The results implied that benziodazole-triflate could be selectively used as both a 2-iodobenzamido-transfer reagent for the synthesis of oxazole compounds,and a triflate-transfer reagent for the triflation ofβ-keto-sulfones.Ionic mechanistic pathways,supported by density functional theory(DFT)calculations,were proposed to account for the divergent selectivities of the transformations.
基金the financial support from the National Natural Science Foundation of China(Nos.22201265,22201264)the China Postdoctoral Science Foundation(Nos.2022M710133,2022TQ0287)。
文摘The tert-butyl nitrite as a bifunctional reagent mediated radical alkene difunctionalization has emerged as a powerful strategy for synthesis of structurally diverse oxime-containing compounds.However,the phosphorus-centered radical initiated transformations remain largely elusive.Herein,a visible-lightinduced radical phosphinoyloximation of alkenes with secondary phosphine oxides and tert-butyl nitrite has been developed under photocatalyst-and metal-free conditions.This protocol features mild conditions,broad substrate scope,good functional tolerance,and operational simplicity,yielding a diverse array ofα-phosphinoyl oximes in moderate to good yields with high stereoselectivities.The photomediated homolytic cleavage of O–NO bond of tert-butyl nitrite generates the reactive tert-butoxyl radical and persistent NO radical to act as both HAT reagent and the source of oximes.
文摘This study focuses on using a green reagent scheme of methanesulfonic acid (MSA) and citric acid (CA) to extract valuable metals from the cathodes, aiming to minimize environmental impact during the recycling process. Leaching studies on LiCoO_(2) identified optimal conditions as follows: 2.4 mol/L MSA, 1.6 mol/L CA, S/L ratio of 80 g/L, leaching temperature of 90oC and leaching time of 6 h. The maximum Co and Li extraction achieved was 92% and 85%, respectively. LiCoO_(2) dissolution in MSA-CA leaching solution is highly impacted by temperature;Avrami equation showed a good fitting for the leaching data. The experimental activation energy of Co and Li was 50.98 kJ/mol and 50.55 kJ/mol, respectively, indicating that it is a chemical reaction-controlled process. Furthermore, cobalt was efficiently recovered from the leachate using oxalic acid, achieving a precipitation efficiency of 99.91% and a high-purity cobalt oxalate product (99.85 wt.%). In the MSA-CA leaching solution, MSA served as a lixiviant, while CA played a key role in reducing Co in LiCoO_(2). The overall organic acid leaching methodology presents an attractive option due to its reduced environmental impact.
基金financially supported by the National Natural Science Foundation of China (No.51974016)。
文摘Cyanide is the most widely used reagent in gold production processes. However, cyanide is highly toxic and poses safety haz-ards during transportation and use. Therefore, it is necessary to develop gold leaching reagents that can replace cyanide. This paper intro-duces a method for synthesizing a gold leaching reagent. Sodium cyanate is used as the main raw material, with sodium hydroxide and so-dium ferrocyanide used as additives. The gold leaching reagent can be obtained under the conditions of a mass ratio of sodium cyanate,sodium hydroxide, and sodium ferrocyanide of 15:3:1, synthesis temperature of 600℃, and synthesis time of 1 h. This reagent has a goodrecovery effect on gold concentrate and gold-containing electronic waste. The gold leaching rate of roasted desulfurized gold concentratecan reach 87.56%. For the extraction experiments of three types of gold-containing electronic waste, the gold leaching rate can reach over90% after 2 h. Furthermore, the reagent exhibits good selectivity towards gold. Component analysis indicates that the effective compon-ent in the reagent could be sodium isocyanate.
基金the financial support from the Sichuan Science and Technology Program(No.2022NSFSC0619)。
文摘The asymmetric conjugate additions of aryl Grignard reagents to trisubstituted enones by chiral P,N ligand L6 with low catalyst loading(0.25–1.0 mol%)are disclosed.Chiral 2-ester chromanone and its analogs bearing a quaternary stereogenic centers at C2 position were produced in high to excellent yields,enantioselectivities and high turnover number.The notable features of this reaction include its broad substrate scope,complete 1,4-addition regioselectivities,applicability to both batch and flow for large scale synthesis.This report develops an efficient strategy to apply aryl Grignard reagents in asymmetric 1,4-conjugation reactions and provides a direct method to incorporate quaternary chiral centers toward the synthesis of biologically relevant chromanone derivatives.
基金the National Natural Science Foundation of China(No.21901199)National Training Program of Innovation and Entrepreneurship for Undergraduates(No.S202310698011)Xi’an Jiaotong University(No.7121192002)for financial support.
文摘The radical difunctionalization of alkenes with sulfonyl bifunctional represents a powerful and straightforward approach to access functionalized alkane derivatives.However,both the mechanistic activation mode and the substrate scopes of this type of radical difunctionalizations are still limited.We demonstrate herein a modular photoredox strategy for the difunctionalization of alkenes,employing arylsulfonyl acetate as the bifunctional reagent.This approach involves a radical addition/Smiles rearrangement cascade process,offering a robust alternative for the synthesis of valuableγ,γ-diaryl andγ-aryl esters.A complementary oxidative bifunctional reagents activation mode is identified to govern the radical cascade reactions,facilitating the simultaneous incorporation of aryl and carboxylate-bearing alkyl groups into the alkenes with excellent diastereoselectivity.Noteworthy features of this method include mild reaction conditions,organophotocatalysis,high atom-and step-economy,excellent functional group compatibility and great structural diversity.
基金Project (50974132) supported by the National Natural Science Foundation of ChinaProject (2011QNZT094) supported by the Fundamental Research Funds for the Central Universities, China
文摘The experiments were conducted to investigate the behavior of airborne particles adhering to the glass slides which were coated by several reagent films. The results showed that the adhesion level could be significantly changed by the reagent films. There were no evident rules between the average size of particles and sampling time interval, the placing angle and reagent concentration. The average particle size on the surface coated by composite reagent （2-3 μm） was smaller than that on the single reagent coated surface, while the largest particle size （4-5 μm） was observed on the surface coated with the Tween 60. The experiment also demonstrated that the best adhesive performance was obtained on the surface which was coated with 0.5% SDBS and 0.5% fluorocarbon composite reagents. The experiment results indicated that each reagent had a certain optimum adhesive range to the particle. The composite reagents with different proportion of single reagents exhibited some particular physical and chemical properties, which could effectively change the adhesive performance between the solid surface and the particles.
基金This work was supported by the National Natural Science Foundation of China （No.20973128 and No.20871096）, the National High Tech Research and Development Program （No.2006AA03Z344）, and the Program for New Century Excellent Talents in University of China （No.NCET-07-0637）.
文摘ZnO nanoparticles were synthesized via a direct precipitation method followed by a hetero- geneous azeotropic distillation and calcination processes, and then characterized by X-ray power diffraction, scanning electron microscopy, transmission electron microscopy, and ni- trogen adsorption-desorption measurement. The effects of Pt-loading amount, calcination temperature, and sacrificial reagents on the present ZnO suspension were investigated, photocatalytic H2 evolution efficiency from the The experimental results indicate that ZnO rianoparticles calcined at 400℃ exhibit the best photoactivity for the H2 production in comparison with the samples calcined at 300 and 500℃, and the photoeatalytie H2 production efficiency from a methanol solution is much higher than that from a triethanolamine solution. It can be ascribed to the oxidization of methanol also contributes to the H2 production during the photochemical reaction process. Moreover, the photocatalytic mechanism for the H2 production from the present ZnO suspension system containing methanol solution is also discussed in detail.
