乙炔电催化氧化制备草酸的机理研究
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摘要
选择铂为电极电催化氧化乙炔合成草酸,通过紫外-可见分光光度法和红外光谱法对产品进行表征,利用第一性原理计算方法探讨乙炔在催化剂Pt(111)表面的吸附情况,采用循环伏安法(CV)研究铂电极在硫酸钠溶液中电催化氧化乙炔的电极过程,重点测定电极的稳态极化曲线并根据极化曲线推算塔菲尔斜率,结合表观传递系数及反应级数对拟定的乙炔电催化氧化制备草酸的反应机理进行验证.实验结果表明,乙炔分子在Pt(111)面上呈平行桥键构型时吸附最稳定;铂电极在含体积分数为2%丙酮的0.4 mol·L-1硫酸钠溶液中可将乙炔电催化氧化为草酸;反应的速率控制步骤为CH≡CH+2(OH·)ads→HOCH=CHOH.
A new method of electrocatalytic oxidation synthesis oxalic acid from acetylene was explored and the synthesized oxalic acid was characterized by Ultraviolet-visible spectrophotometry(UV-vis) and Infrared spectroscopy(IR). First-principles calculations were carried out to examine the adsorption of acetylene over the Pt(111) surface. The electrocatalytic oxidation behavior of acetylene has been investigated on a Pt electrode by cyclic voltammetry(CV) and steady-state polarization in Na2SO4 solution. The formation mechanism of oxalic acid in the Na2SO4 solution was proposed and the transfer coefficients of the reaction were calculated. The results show that acetylene molecule tends to adsorb through the threefold parallel-bridge configuration that is computed to be the most stable because of its lowest adsorption energy. is the rate-determining step in the electrolysis process. The rate of this step obtained from the assumed process agrees well with experiment.
A new method of electrocatalytic oxidation synthesis oxalic acid from acetylene was explored and the synthesized oxalic acid was characterized by Ultraviolet-visible spectrophotometry(UV-vis) and Infrared spectroscopy(IR). First-principles calculations were carried out to examine the adsorption of acetylene over the Pt(111) surface. The electrocatalytic oxidation behavior of acetylene has been investigated on a Pt electrode by cyclic voltammetry(CV) and steady-state polarization in Na2SO4 solution. The formation mechanism of oxalic acid in the Na2SO4 solution was proposed and the transfer coefficients of the reaction were calculated. The results show that acetylene molecule tends to adsorb through the threefold parallel-bridge configuration that is computed to be the most stable because of its lowest adsorption energy. is the rate-determining step in the electrolysis process. The rate of this step obtained from the assumed process agrees well with experiment.
引文
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[9]Liang Z H(梁镇海),Song X L(宋秀丽),Duan D H(段东红),et al.Method for double-electrode electrochemical synthesis of ethylene and oxalic acid from acetylene:China,CN201110226331.3[P].2011.
[10]Perdew J P,Chevary J A,Vosko S H,et al.Atoms,molecules,solids,and surfaces:Applications of the generalized gradient approximation for exchange and correlation[J].Physical Review B,1992,46(11):6671-6687.
[11]Wang Y,Perdew J P.Correlation hole of the spin-polarized electron gas,with exact small-wave-vector and highdensity scaling[J].Physical Review B,1991,44(24):13298-13307.
[12]Pack J D,Monkhorst H J,Freeman D L.Lithium crystal properties from high-quality Hartree-Fock wave functions[J].Solid State Communications,1979,29(10):723-725.
[13]Yu S L(于世林),Li Y W(李寅蔚),Xia X Q(夏心泉).Spectrum analysis[M].Chongqing:Chongqing University Press(重庆大学出版社),1994:42-69.
[14]Robert M M,Radhe K V,Michael P D,et al.Oxidative rearrangement of alkynes to carboxylic acid esters by[Hydroxy(tosyloxy)iodo]benzene in methanol[J].Tetrahedron Letters,1987,28(25):2845-2848.
[15]Gao P(高鹏),Zhu Y M(朱永明).Electrochemical based tutorial[M].Beijing:Chemical Industry Press(化学工业出版社),2013:108-109.
[16]Yu J G,Cao X J,Zhang H B,et al.Electrooxida tion of hydroxypivalaldehyde in an undivided cell[J].Chemical Research in Chinese Universities,2006,22(5):626-630.
[17]Gao P(高鹏),Zhu Y M(朱永明).Electrochemical based tutorial[M].Beijing:Chemical Industry Press(化学工业出版社),2013:86.