对2-甲基嘧啶-4,6-二酮(MPO)制备1,1-二氨基-2,2-二硝基乙烯(FOX-7)过程中的副产物二硝基甲烷进行了回收,经氢氧化钾水溶液中和制得了性质稳定的长针状晶体二硝基甲烷钾盐(KDNM),用KDNM、甲醛、叔丁胺作原料通过Mannich缩合反应制得了1...对2-甲基嘧啶-4,6-二酮(MPO)制备1,1-二氨基-2,2-二硝基乙烯(FOX-7)过程中的副产物二硝基甲烷进行了回收,经氢氧化钾水溶液中和制得了性质稳定的长针状晶体二硝基甲烷钾盐(KDNM),用KDNM、甲醛、叔丁胺作原料通过Mannich缩合反应制得了1,3-二叔丁基-5,5-二硝基六氢嘧啶,通过浓硫酸与浓硝酸的混酸体系硝解1,3-二叔丁基-5,5-二硝基六氢嘧啶制得了1,3,5,5-四硝基六氢嘧啶(DNNC),总产率达到78.9%(以二硝基甲烷钾盐计)。采用1H NMR、红外、质谱对DNNC和中间物的结构进行了表征。研究了p H值、溶剂、温度对Mannich缩合反应的影响以及硝化体系的选择对硝解反应的影响。确立了Mannich缩合反应的最佳工艺条件为:二硝基甲烷钾盐∶甲醛∶叔丁胺的摩尔比为1.0∶3.5∶2.0;10%甲醇水溶液为溶剂,室温下用盐酸调节p H值至8,随后升温至50℃,反应3 h,产率达到85.3%。硝解反应中采用20 m L 98%H_2SO_4与10 m L HNO_3的混酸体系作为硝解体系,产率达到92.5%。展开更多
Pickering emulsions stabilized by salicylic acid and arginine modified titanium dioxide （TiO2-SA-Arg） nanopar- tides were prepared in this study for photocatalytic degradation of nitrobenzene in a rotating annular r...Pickering emulsions stabilized by salicylic acid and arginine modified titanium dioxide （TiO2-SA-Arg） nanopar- tides were prepared in this study for photocatalytic degradation of nitrobenzene in a rotating annular reactor, and the effects of various design parameters of the rotating annular reactor, initial nitrobenzene concentration, catalyst amount, and solution pH on the degradation rate of nitrobenzene were investigated. Meanwhile, the degradation mechanism of nitrobenzene was proposed. The results show that increasing the aeration rate, the rotational speed, and light intensity results in a higher photocatalytic degradation rate of nitrobenzene owing to the effective clearance of electrons and a high quantity of oxidative free radicals. The degradation of nitroben- zene in the rotating annular reactor follows the pseudo first-order kinetics, but it is not well described by the Langmuir-Hinshdwood equation. Aeration has a significant effect on the photocatalytic degradation pathway of nitrobenzene. Because nitrobenzene can undergo reduction reaction as electron acceptors and oxidative deg- radation initiated by hydroxyl free radicals, the photocatalytic degradation of nitrobenzene follows the reduction mechanism under no aeration, but the oxidation mechanism under aeration.展开更多
Dissociation of methyl nitrite is the first step during CO catalytic coupling to dimethyl oxalate followed by hydrogenation to ethyl glycol in a typical coal to liquid process. In this work, the first-principle calcul...Dissociation of methyl nitrite is the first step during CO catalytic coupling to dimethyl oxalate followed by hydrogenation to ethyl glycol in a typical coal to liquid process. In this work, the first-principle calculations based on density functional theory were performed to explore the reaction mechanism for the non-catalytic dissociation of methyl nitrite in the gas phase and the catalytic dissociation of methyl nitrite on Pd(111) surface since palladium supported on alpha-alumina is the most effective catalyst for the coupling. For the non-catalytic case, the calculated results show that the CH_3O–NO bond will break with a bond energy of 1.91 eV, and the produced CH_3O radicals easily decompose to formaldehyde, while the further dissociation of formaldehyde in the gas phase is difficult due to the strong C–H bond. On the other hand, the catalytic dissociation of methyl nitrite on Pd(111) to the adsorbed CH_3O and NO takes place with a small energy barrier of 0.03 eV. The calculated activation energies along the proposed reaction pathways indicate that(i) at low coverage, a successive dehydrogenation of the adsorbed CH_3O to CO and H is favored while(ii) at high coverage, hydrogenation of CH_3O to methanol and carbonylation of CH_3O to methyl formate are more preferred. On the basis of the proposed reaction mechanism,two meaningful ways are proposed to suppress the dissociation of methyl nitrate during the CO catalytic coupling to dimethyl oxalate.展开更多
In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of ele...In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of electrochemical reactions associated with palladium were recognized,indicating that Pd(II)undergoes a single step two-electrons irreversible process.Electroreduction reaction of Pd(II)and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid,respectively.Stirring could facilitate the reduction of Pd(II)in relatively low nitric acid concentration(3 mol/L).The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K.The diffusion coefficient of Pd(II)increased from 1.89×10 8cm2/s at 288 K to 4.23×10 8cm2/s at 318 K,and the activation energy was calculated to be 21.5 kJ/mol.In electrowinning experiments,SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases,which is uniform all over the entire surface of Pt electrode.The recovery ratios of Pd at different nitric acid concentrations are high,and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration.When stirring was introduced during electrolysis,the electrodeposition rate of Pd increased substantially.展开更多
文摘对2-甲基嘧啶-4,6-二酮(MPO)制备1,1-二氨基-2,2-二硝基乙烯(FOX-7)过程中的副产物二硝基甲烷进行了回收,经氢氧化钾水溶液中和制得了性质稳定的长针状晶体二硝基甲烷钾盐(KDNM),用KDNM、甲醛、叔丁胺作原料通过Mannich缩合反应制得了1,3-二叔丁基-5,5-二硝基六氢嘧啶,通过浓硫酸与浓硝酸的混酸体系硝解1,3-二叔丁基-5,5-二硝基六氢嘧啶制得了1,3,5,5-四硝基六氢嘧啶(DNNC),总产率达到78.9%(以二硝基甲烷钾盐计)。采用1H NMR、红外、质谱对DNNC和中间物的结构进行了表征。研究了p H值、溶剂、温度对Mannich缩合反应的影响以及硝化体系的选择对硝解反应的影响。确立了Mannich缩合反应的最佳工艺条件为:二硝基甲烷钾盐∶甲醛∶叔丁胺的摩尔比为1.0∶3.5∶2.0;10%甲醇水溶液为溶剂,室温下用盐酸调节p H值至8,随后升温至50℃,反应3 h,产率达到85.3%。硝解反应中采用20 m L 98%H_2SO_4与10 m L HNO_3的混酸体系作为硝解体系,产率达到92.5%。
文摘Pickering emulsions stabilized by salicylic acid and arginine modified titanium dioxide （TiO2-SA-Arg） nanopar- tides were prepared in this study for photocatalytic degradation of nitrobenzene in a rotating annular reactor, and the effects of various design parameters of the rotating annular reactor, initial nitrobenzene concentration, catalyst amount, and solution pH on the degradation rate of nitrobenzene were investigated. Meanwhile, the degradation mechanism of nitrobenzene was proposed. The results show that increasing the aeration rate, the rotational speed, and light intensity results in a higher photocatalytic degradation rate of nitrobenzene owing to the effective clearance of electrons and a high quantity of oxidative free radicals. The degradation of nitroben- zene in the rotating annular reactor follows the pseudo first-order kinetics, but it is not well described by the Langmuir-Hinshdwood equation. Aeration has a significant effect on the photocatalytic degradation pathway of nitrobenzene. Because nitrobenzene can undergo reduction reaction as electron acceptors and oxidative deg- radation initiated by hydroxyl free radicals, the photocatalytic degradation of nitrobenzene follows the reduction mechanism under no aeration, but the oxidation mechanism under aeration.
基金Supported by the National Natural Science Foundation of China(21303102)China Postdoctoral Science Foundation funded project(2012M520900 and 2013T60449)
文摘Dissociation of methyl nitrite is the first step during CO catalytic coupling to dimethyl oxalate followed by hydrogenation to ethyl glycol in a typical coal to liquid process. In this work, the first-principle calculations based on density functional theory were performed to explore the reaction mechanism for the non-catalytic dissociation of methyl nitrite in the gas phase and the catalytic dissociation of methyl nitrite on Pd(111) surface since palladium supported on alpha-alumina is the most effective catalyst for the coupling. For the non-catalytic case, the calculated results show that the CH_3O–NO bond will break with a bond energy of 1.91 eV, and the produced CH_3O radicals easily decompose to formaldehyde, while the further dissociation of formaldehyde in the gas phase is difficult due to the strong C–H bond. On the other hand, the catalytic dissociation of methyl nitrite on Pd(111) to the adsorbed CH_3O and NO takes place with a small energy barrier of 0.03 eV. The calculated activation energies along the proposed reaction pathways indicate that(i) at low coverage, a successive dehydrogenation of the adsorbed CH_3O to CO and H is favored while(ii) at high coverage, hydrogenation of CH_3O to methanol and carbonylation of CH_3O to methyl formate are more preferred. On the basis of the proposed reaction mechanism,two meaningful ways are proposed to suppress the dissociation of methyl nitrate during the CO catalytic coupling to dimethyl oxalate.
基金supported by the National Natural Science Foundation of China(91026019,91126006)
文摘In this study,the electrochemical behavior of Pd(II)in nitric acid media was investigated using various electrochemical techniques.By analyzing the cyclic voltammogram of Pd(II)recorded at Pt electrode,a series of electrochemical reactions associated with palladium were recognized,indicating that Pd(II)undergoes a single step two-electrons irreversible process.Electroreduction reaction of Pd(II)and auto-catalytic reactions of nitrous acid are supposed to play a leading role in low and high concentrations of nitric acid,respectively.Stirring could facilitate the reduction of Pd(II)in relatively low nitric acid concentration(3 mol/L).The value of charge transfer coefficient was determined to be 0.18 for the measurements at 298 K.The diffusion coefficient of Pd(II)increased from 1.89×10 8cm2/s at 288 K to 4.23×10 8cm2/s at 318 K,and the activation energy was calculated to be 21.5 kJ/mol.In electrowinning experiments,SEM images of palladium obtained by electrolysis reveal the dendrite growth in all cases,which is uniform all over the entire surface of Pt electrode.The recovery ratios of Pd at different nitric acid concentrations are high,and the faradic efficiency of electrolysis decreases with increasing the nitric acid concentration.When stirring was introduced during electrolysis,the electrodeposition rate of Pd increased substantially.
