Temperature dependence of heterogeneous uptake of hydrogen peroxide on silicon dioxide and calcium carbonate.
Temperature dependence of heterogeneous uptake of hydrogen peroxide on silicon dioxide and calcium carbonate.
复制标题
DOI：
10.1021/jp304446y
复制
发表时间：
2012-07
期刊：
影响因子：
--
通讯作者：
Li Zhou;Weigang Wang;M. Ge
中科院分区：
文献类型：
--
作者：
Li Zhou;Weigang Wang;M. Ge
用Knudsen电池反应器研究了二氧化硅(SiO_2)和碳酸钙(CaCO_3)在253~313K温度范围内过氧化氢的非均相动力学过程，得到了温度的函数关系。动力学研究表明，初始吸收系数随温度的降低而明显增大。它们可以通过公式γBet(SiO_2)=[EXP(934.5/T-12.7)]/[1+EXP(934.5/T-12.7)]和γBet(CaCO_3)=[EXP(1193.0/T-11.9)]/[1+EXP(1193.0/T-11.9)]来计算。根据吸收系数对温度的依赖关系，确定了SiO_2和CaCO_3的吸收过程的焓(ΔHOBS)和熵(ΔSOBS)分别为-(7.77±1.55)KJ(-1)和-(105.8±21.2)JK(-1)，CaCO_3为-(9.92±1.98)KJ(-1)和-(98.6±19.7)JK(-1)。H_2O_2在CaCO_3和SiO_2上的脱附活化能分别为(5.9±0.9)kJ·m o l(-1)和(9.15±1.1)kJ·m o l(-1)。结果表明，在此温度范围内，过氧化氢主要可逆地吸附在二氧化硅和碳酸钙上，并且在这些矿物气溶胶上的快速吸附，特别是在低温下，为进一步的复杂反应提供了一个活性表面。
The heterogeneous kinetic processes of hydrogen peroxide on silicon dioxide (SiO2) and calcium carbonate (CaCO3) have been studied over the temperature range from 253 to 313 K using a Knudsen cell reactor, and the functions of temperature were obtained. The kinetic study indicates that the initial uptake coefficients increase evidently with a temperature decrease. They can be calculated by the equations γBET(SiO2) = [exp(934.5/T - 12.7)]/[1 + exp(934.5/T - 12.7)] and γBET(CaCO3) = [exp(1193.0/T - 11.9)]/[1 + exp(1193.0/T - 11.9)]. On the basis of the temperature dependence of uptake coefficients, the enthalpy (ΔHobs) and entropy (ΔSobs) of uptake progresses were determined to be -(7.77 ± 1.55) KJ mol(-1) and -(105.8 ± 21.2) J K mol(-1) for SiO2 and -(9.92 ± 1.98) KJ mol(-1) and -(98.6 ± 19.7) J K mol(-1) for CaCO3. The activation energies for desorption (Edes) of H2O2 on CaCO3 and SiO2 were calculated to be (5.9 ± 0.9) KJ mol(-1) and (9.15 ± 1.1) KJ mol(-1). The results suggest that hydrogen peroxide could mainly be adsorbed on SiO2 and CaCO3 reversibly in this temperature region, and the quick uptake on these mineral aerosols, especially at low temperature, provides an active surface for further complex reactions.