碳酸盐缓冲体系中HS-电化学氧化机理及动力学性质
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摘要
采用电化学方法,考察HS~-在铂片电极上的循环伏安特性,并以循环伏安法、计时电量法、计时电流法测定其电极过程的动力学参数。结果表明:在Na2_CO_3-Na HCO_3缓冲溶液中,HS~-的循环伏安曲线在-0.05V电位值处有一个氧化峰,无还原峰;其氧化峰电流值I_p与扫描速率的开方(v~(1/2))呈线性关系(R=0.989),表明HS~-在电极上的氧化反应为受扩散控制的不可逆过程;初步推断其电极反应得失电子数为1、质子不参与反应,电极反应产物为S_2~(2-),S_2~(2-)可能进一步氧化产生S_4~(2-)。在20～60℃范围内,其HS~-的扩散系数D值随温度升高由1.33×10~(-6)cm~2/s增大至7.20×10~(-6)cm~2/s,HS~-的反应速率常数kf值由6.99×10~(-3)s~(-1)增大至1.70×10~(-2)s~(-1),当脱硫工艺温度为40℃时,其相应D值为3.07×10~(-6)cm~2/s、k_f值为1.09×10~(-2)s~(-1),反应级数为0.257;HS~-在电极上电化学氧化的平均活化能E_η=17.3kJ/mol。
Electrochemical method was used to investigate the cyclic voltammetric behavior of HS~-on platinum electrode. And the kinetic parameters of the electrode process were measured by cyclic voltammetry, chronoamperometry and chronoamperometry.The results show that in the Na_2 CO_3-NaHCO_3 buffer solution, the cyclic voltammogram of HS~-has an oxidation peak at the potential of -0.05 V and no reduction peak, and the oxidation peak current value Ipis linear with the square root of the scan rate(v~(1/2))(R=0.989), which indicates that the oxidation of HS~-on the electrode is an irreversible process controlled by diffusion. It is preliminarily inferred that the number of transferred electrons in the electrode reaction is 1, protons do not participate in the reaction, and the electrode reaction product is S2~(2-), which may be further oxidized to produce S4~(2-). In the range of 20 to 60℃, the diffusion coefficient D value of HS~-increases from 1.33 ×10~(-6) cm~2/s to 7.20 ×10~(-6) cm~2/swith increasing temperature,and the reaction rate constant kfof HSincreases from 6.99×10~(-3) s~(-1) to 1.70×10~(-2) s~(-1) with increasing temperature.When the temperature of desulfurization process is 40℃, the values of D,kfand reaction order are 3.07 ×10~(-6) cm~2/s, 1.09 ×10~(-2) s~(-1) and 0.257, respectively.The average activation energy of the electrochemical oxidation of HS~-on the electrode(E_η) is 17.3 kJ/mol.
Electrochemical method was used to investigate the cyclic voltammetric behavior of HS~-on platinum electrode. And the kinetic parameters of the electrode process were measured by cyclic voltammetry, chronoamperometry and chronoamperometry.The results show that in the Na_2 CO_3-NaHCO_3 buffer solution, the cyclic voltammogram of HS~-has an oxidation peak at the potential of -0.05 V and no reduction peak, and the oxidation peak current value Ipis linear with the square root of the scan rate(v~(1/2))(R=0.989), which indicates that the oxidation of HS~-on the electrode is an irreversible process controlled by diffusion. It is preliminarily inferred that the number of transferred electrons in the electrode reaction is 1, protons do not participate in the reaction, and the electrode reaction product is S2~(2-), which may be further oxidized to produce S4~(2-). In the range of 20 to 60℃, the diffusion coefficient D value of HS~-increases from 1.33 ×10~(-6) cm~2/s to 7.20 ×10~(-6) cm~2/swith increasing temperature,and the reaction rate constant kfof HSincreases from 6.99×10~(-3) s~(-1) to 1.70×10~(-2) s~(-1) with increasing temperature.When the temperature of desulfurization process is 40℃, the values of D,kfand reaction order are 3.07 ×10~(-6) cm~2/s, 1.09 ×10~(-2) s~(-1) and 0.257, respectively.The average activation energy of the electrochemical oxidation of HS~-on the electrode(E_η) is 17.3 kJ/mol.
引文
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[2]广西化工研究所,等.栲胶法脱硫工业生产试验报告[J].广西化工技术,1978,(3):17-36.
[3]黄子衎.栲胶法在焦炉气脱硫中的应用[J].煤化工,2004,32(2):52-55.
[4]化肥司栲胶脱硫调查组.部份中型氮肥厂栲胶脱硫情况调查[J].中氮肥,1989,(2):16-21.
[5]梁锋,徐丙根,施小红,等.湿式氧化法脱硫的技术进展[J].现代化工,2003,23(5):21-24.
[6]梅安华.小合成氨厂工艺技术与设计手册(上册)[M].北京:化学工业出版社,1994:372.
[7]牛艳霞.栲胶脱硫工艺副产物生成机理及影响因素的研究[D].太原:太原理工大学,2010.
[8]凌开成,牛艳霞.栲胶脱硫技术[M].北京:化学工业出版社,2016:10.
[9]张卫帅,董跃,凌开成,等.栲胶脱硫过程中单质硫生成机理[J].洁净煤技术,2011,17(2):60-63.
[10]董跃.在二元催化氧化脱硫反应体系中多硫离子作用的研究[D].太原:太原理工大学,2012.
[11]Zheng D,Zhang X,Wang J,et al.Reduction mechanism of sulfur in lithium-sulfur battery:From elemental sulfur to polysulfide[J].J Power Sources,2016,301:312-316.
[12]薛敏华,付泽剑,莫友彬,等.栲胶法脱硫过程硫化物测定的电位分析法评估[J].天然气化工-C1化学与化工,2016,41(2):78-82.
[13]易清风.铂电极上硫化钠溶液的电化学氧化研究[J].稀有金属,2002,26(6):448-451.
[14]刘秀玲.硫化物电化学氧化过程研究[J].材料保护,2001,34(3):1-3.
[15]阿伦.J.巴德,拉里.R.福克纳.电化学方法原理和应用[M].第二版.北京:化学工业出版社,2005:145-171.
[16]吕桂琴,马淑贤.计时电量法测定4,5-二氮芴-9-酮的扩散系数和反应速率常数[J].北京理工大学学报,2014,34(6):650-654.
[17]吴浩青,李永舫.电化学动力学[M].北京:高等教育出版社,1998:96.
[18]高作宁,姚慧琴,韩晓霞,等.生理介质中苦参碱和槐定碱的电化学动力学性质研究[J].中国中药杂志,2005,30(23):1836-1839.
[19]吴辉煌.电化学[M].北京:化学工业出版社,2004:84.
[20]舒佘德,陈白珍.冶金电化学研究方法[M].长沙:中南工业大学出版社,1990:90.
[21]易清风.石墨电极上硫化钠的阳极氧化机理探索[J].物理化学学报,2000,16(3):263-268.