1, 3-丁二烯热裂解的动力学计算与模型研究

1, 3-丁二烯是碳氢燃料燃烧和裂解过程中生成的一种重要产物,也是形成多环芳烃(PAHs)的一种重要前驱体。目前,关于1, 3-丁二烯燃烧实验以及机理的研究较多,但是其热裂解机理的研究较少。本文在B3LYP/CBSB7水平下对1, 3-丁二烯裂解过程中相关反应的反应物、产物以及过渡态进行了几何结构优化和频率计算,并通过组合方法CBS-QB3计算得到了单点能和热力学参数。对于紧致过渡态的反应和无能垒反应,分别采用过渡态理论(TST)和可变反应坐标过渡态理论(VRC-TST)计算其高压极限条件下的反应速率常数。计算得到的反应速率常数与已有文献报导的结果吻合较好。通过量子化学计算,对Hidaka等人提出1, 3-丁二烯的热裂解机理模型进行了更新和改进:更新后的机理模型包含45个物种和224步反应,并对更新后的机理模型进行了模拟验证。结果表明,更新的机理模型能更好地预测1, 3-丁二烯激波管裂解实验过程中C₂H₂、1-丁烯-3-炔(C₄H₄)以及苯(C₆H₆)主要产物的浓度分布,为进一步完善核心机理(C₀-C₄)模型提供了可靠的热、动力学参数。     

Au/ZrO2催化剂中ZrO2的尺寸效应:1,3-丁二烯加氢反应

在不同温度(673～1073K)下,于流动N2气中焙烧ZrO(OH)2醇(乙醇)凝胶,制备了不同尺寸的ZrO2-AN纳米晶(6～30nm).采用沉积-沉淀方法制备了相应的质量分数为0.7%的Au/ZrO2-AN催化剂.用XRD,XRF,TEM/HRTEM,EDS,N2吸附和1,3-丁二烯加氢反应对ZrO2-AN和Au/ZrO2-AN催化剂进行了表征.结果表明,在所有的Au/ZrO2-AN样品中,Au粒子的平均尺寸为4～5nm,ZrO2-AN的颗粒大小没有因为负载Au粒子而发生改变.1,3-丁二烯在Au/ZrO2-AN催化剂催化下能以100%的选择性进行加氢反应生成单烯烃.随着Au/ZrO2-AN催化剂中ZrO2-AN纳米晶尺寸的增加或“载体”焙烧温度的升高,1,3-丁二烯的转化率明显降低;1-丁烯的选择性先增加后减小,2-丁烯中反/顺异构体的摩尔比在0.5～1.0的范围内逐渐增大,TEM/HRTEM表征结果清楚地表明,Au/ZrO2-AN催化剂中Au粒子与ZrO2-AN颗粒接触界面/周边随ZrO2-AN颗粒尺寸的减小而明显增加,这很可能是含有更小尺寸ZrO2-AN纳米粒子的Au/ZrO2-AN催化剂具有更高的催化活性的重要原因.     

月桂酸碱金属离子盐/芳基杂环磷酸铝盐复配体诱导等规聚丙烯结晶成核作用

以芳基杂环磷酸铝盐(AHP-Al OH)作为成核主体,分别含有Li+、Na+、K+3种碱金属离子的月桂酸盐(alkali metal salt of lauric acid,AMSLA)为配体,研究了该类复配体系协效诱导等规聚丙烯(i PP)成核作用规律.通过偏光显微观察、示差扫描量热分析、力学性能测试、光学性能测试以及耐热性能表征等手段,研究不同碱金属离子对复合材料结晶结构、结晶行为以及力学性能、光学性能、耐热性的影响.结果表明,Li L、Na L和KL对i PP的成核作用较差,对球晶尺寸的细化不明显,平均尺寸为161μm,与纯i PP在球晶尺度在同一数量级,结晶温度提高小于6.5℃,成核有效性低于20%,对复合材料力学性能、光学性能及耐热性的改善非常有限;APH-Al OH对i PP的成核作用达到中等水平,晶体尺寸比纯i PP减小了1个数量级,达到16μm,结晶温度提高13.7℃,成核有效性提高到45.4%,力学性能,光学性能及耐热性同样达到中等水平;Li L、Na L和KL与APH-Al OH复配后对i PP的球晶尺度迅速减小至5μm以下,比纯i PP球晶尺寸小2个数量级,结晶峰值温度可提高20℃以上,成核有效性高达60%以上,拉伸强度、弯曲强度、弯曲模量平均分别提高15.0%、44.2%、64.0%.雾度值平均下降72.8%,透光率平均增加13.9%,热变形温度平均升高53.8%.AMSLA和APH-Al OH之间表现出极强的协效成核作用,AMSLA中碱金属阳离子对复配体之间的协效成核作用影响对不同性能之间有不同表现,其对结晶峰值温度,力学性能、耐热性能方面的影响表现为Na+K~+Li~+,而对光学性能方面表现为Li~+Na~+K~+.     

Eu3＋、Si4＋共掺杂TiO2光催化剂的协同效应

采用溶胶-凝胶-浸渍法制备了Eu/Ti/Si纳米光催化剂, 并通过XRD、FT-IR、EPR等进行了表征.结果表明,掺入Eu3＋和Si4＋, 阻止了TiO2从锐钛矿晶型向金红石晶型的转变, 使TiO2的粒径减小, 且Eu3＋能够促进Si4＋进入TiO2的晶格中.以甲基橙为光催化反应模型化合物, 考察了光催化剂的活性.测定了甲基橙在不同光催化剂上的吸附常数,探讨了催化剂对甲基橙的吸附机理. Eu3＋和Si4＋的最佳掺入量分别为wEu=0.03％、wSiO2=39.06％,且Eu3＋和Si4＋同时掺入TiO2光催化剂产生协同效应.讨论了光催化活性与催化剂性质的关系.     

Eu~(3 )、Si~(4 )共掺杂TiO_2光催化剂的协同效应

采用溶胶-凝胶-浸渍法制备了Eu/Ti/Si纳米光催化剂,并通过XRD、FT-IR、EPR等进行了表征.结果表明,掺入Eu3 和Si4 ,阻止了TiO2从锐钛矿晶型向金红石晶型的转变,使TiO2的粒径减小,且Eu3 能够促进Si4 进入TiO2的晶格中.以甲基橙为光催化反应模型化合物,考察了光催化剂的活性.测定了甲基橙在不同光催化剂上的吸附常数,探讨了催化剂对甲基橙的吸附机理.Eu3 和Si4 的最佳掺入量分别为wEu=0.03%、wSiO2=39.06%,且Eu3 和Si4 同时掺入TiO2光催化剂产生协同效应.讨论了光催化活性与催化剂性质的关系.     

Enhanced Electrochemical Reduction of CO2 to CO on Ag/SnO2 by a Synergistic Effect of Morphology and Structural Defects

Silver (Ag)-based materials are considered to be promising materials for electrochemical reduction of CO₂ to produce CO, but the selectivity and efficiency of traditional polycrystalline Ag materials are insufficient; there still exists a great challenge to explore novel modified Ag based materials. Herein, a nanocomposite of Ag and SnO₂ (Ag/SnO₂) for efficient reduction of CO₂ to CO is reported. HRTEM and XRD patterns clearly demonstrated the lattice destruction of Ag and the amorphous SnO₂ in the Ag/SnO₂ nanocomposite. Electrochemical tests indicated the nanocomposite containing 15% SnO₂ possesses highest catalytic selectivity featured by a CO faradaic efficiency (FE) of 99.2% at −0.9 V versus reversible hydrogen electrode (vs RHE) and FE>90% for the CO product at a wide potential range from −0.8 V to −1.4 V vs RHE. Experimental characterization and analysis showed that the high catalytic performance is attributed to not only the branched morphology of Ag/SnO₂ nanocomposites (NCs), which endows the maximum exposure of active sites, but also the special adsorption capacity of abundant defect sites in the crystal for *COOH (the key intermediate of CO formation), which improves the intrinsic activity of the catalyst. But equally important, the existed SnO₂ also plays an important role in inhibiting hydrogen evolution reaction (HER) and anchoring defect sites. This work demonstrates the use of crystal defect engineering and synergy in composite to improve the efficiency of electrocatalytic CO₂ reduction reaction (CO₂RR).     

Adsorption and Corrosion Inhibition Effect of 1,1′-Thiocarbonyldiimidazole on Mild Steel in H2SO4 Solution and Synergistic Effect of Iodide Ion

The inhibition effect of 1,1′-thiocarbonyldiimidazole (TCDI) on the corrosion behaviors of mild steel (MS) in 0.5 mol·L⁻¹ H₂SO₄ solution was studied with the help of potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and linear polarization resistance (LPR) techniques. The effect of immersion time on the inhibition effect of TCDI was also investigated over 72 h. For the long-term tests, hydrogen evolution with immersion time (V_H2-t) was measured in addition to the three techniques already mentioned. The thermodynamic parameters, such as adsorption equilibrium constant (K_ads) and adsorption free energy (ΔG_ads) values, were calculated and discussed. To clarify inhibition mechanism, the synergistic effect of iodide ion was also investigated. The potential of zero charge (PZC) of the MS was studied by electrochemical impedance spectroscopy method, and a mechanism of adsorption process was proposed. It was demonstrated that inhibition efficiency increased with the increase in TCDI concentration and synergistically increased in the presence of KI. The inhibition efficiency was discussed in terms of adsorption of inhibitor molecules on the metal surface and protective film formation.