铝硼复合氧化物负载Pt-Sn催化剂的丙烷脱氢性能研究

采用蒸发自组装法制备铝硼复合氧化物((AlB_x)_2O_3),真空配合浸渍法制备PtSn双金属催化剂,并应用于丙烷脱氢制丙烯.采用N_2物理吸附、 SEM、 TEM、 XRD、 H_2-TPR、 NH_3-TPD、 TG和ICP-OES对催化剂进行表征.掺入B可大幅增加载体的总酸量和酸中心密度,降低酸强度.当B掺入量为Al的10%时, Cat-AB_(0.1)的总酸量是Cat-AB_0总酸量的2.45倍,且只有弱酸中心.当B掺入量为Al的50%时, Cat-AB_(0.5)的酸中心密度是Cat-AB_0的4.3倍.以铝硼复合氧化物负载的催化剂均优于纯氧化铝负载的催化剂,催化剂的脱氢活性和稳定性与载体的硼铝摩尔比之间存在如下规律:AB_(0.1)AB_(0.3)AB_(0.5)AB_0.     

Ga2O3催化剂上CO2气氛中丙烷脱氢反应的研究

考察了Ga2O3对于丙烷脱氢和CO2气氛脱氢反应的催化性能.结果表明,Ga2O3具有较高的催化活性,其性能优于传统的Cr2O3脱氢催化剂.催化反应可能经过了一个丙烷异裂的过程,其中CO2是通过逆水煤气反应和Boudouard反应来促进催化剂性能的,在高于823K时该促进作用更为明显.催化剂的催化活性和其表面酸密度密切相关,在Ga2O3结构中,四配位Ga3+是其酸位的来源,并通过质子与氧化物的共同作用促进反应进行.催化剂的失活是由于表面的积碳和活性氧的消耗共同造成的.同时还对Ga2O3作为丙烷脱氢反应的催化剂的催化反应机理进行了初步探讨.     

镁铝水滑石的有机改性实验研究

采用共沉淀法合成了对甲基苯磺酸有机插层改性的镁铝水滑石,用XRD、FTIR、TG-DSC等技术表征产物特征.研究表明,合成的对甲基苯磺酸插层LDH物相纯净、结晶度高,层间无硝酸根,而且2:1型有更好的晶形;2:1型对甲基苯磺酸插层LDH在450-500℃层状结构逐渐被破坏,而3:1型在400-460℃0层状结构被破坏....     

丙烷在负载型催化剂上脱氢反应的研究——Ⅷ.丙烷在负载型金属催化剂上临氢脱氢

通过对丙烷在负载型金属催化剂上临氢脱氢反应性能的考察,发现除负载型Pt、Pd等具有脱氢活性外;负载型Cu也同样具有脱氢活性,并且随Cu载量增加而升高。对催化剂稳定性研究结果表明,载体与金属组分间相互作用是不容忽视的因素之一。催化剂选择性影响因素主要是加氢裂化或氢解反应。因此,对催化剂脱氢选择性的改善既可通过调变金属组分的脱氢加氢性能,也可通过改变载体酸性进行。     

铝硼复合氧化物负载Pt-Sn催化剂的丙烷脱氢性能研究

采用蒸发自组装法制备铝硼复合氧化物（(AlxBy)2O3）,真空络合浸渍法制备PtSn双金属催化剂,并应用于丙烷脱氢制丙烯。采用N2物理吸附、SEM、X射线粉末衍射、H2-TPR、NH3-TPD和TG对催化剂进行表征。掺入B可大幅增加载体的总酸量和酸中心密度,降低酸强度。当B掺入量为10%时,Cat-A0.9B0.1的总酸量是Cat-AB0总酸量的2.45倍,且只有弱酸中心。当B掺入量为50%时,Cat-A0.5B0.5的酸中心密度是Cat-AB0的4.3倍。以铝硼复合氧化物负载的催化剂均优于纯氧化铝负载的催化剂,催化剂的脱氢活性和稳定性与载体的硼铝摩尔比之间存在如下规律：A0.9B0.1＞A0.7B0.3＞A0.5B0.5＞AB0。 关键词：铝硼复合氧化物;PtSn/ (AlxBy)2O3催化剂;丙烷脱氢     

丙烷在负载型催化剂上脱氢反应的研究 Ⅶ.丙烷在负载型金属催化剂上临氢脱

通过对丙烷在负载型金属催化剂 上临氢脱氢反应性能的考察，发现除 负载 型Pt、Pd等具有脱氢活性外；负载型Cu 也同样具 有脱氢活性，并且随Cu载量增加而升高。对催化剂稳定性研究结果表明，载体与金属组分间相互作用是不容忽视的因素之一。催化剂选择性影响 因素主要是加氢裂化或氢解反应。因此，对催化剂脱氢选择性的改善既可通过调变金属组分的脱氢加氢性能，也可通过改变载体酸性进行。     

CrOx/SiO2催化剂上丙烷在CO2气氛中脱氢反应的研究

采用XRD、UV-vis DRS、ESR和微分吸附量热等技术,考察了铬担载量分别为2.5、5和10wt%的CrO_x/SiO₂催化剂的结构、表面性质和氧化还原性能。结果表明,催化剂表面上存在多种Cr的氧化态和聚集形式。随着Cr担载量从2.5wt%到10wt%的逐渐增大,催化剂表面占主导地位的Cr物种由CrO₃单体转为多聚CrO₃和Cr₂O₃晶相。在CO₂气氛中催化剂对丙烷转化率和丙烯选择性的大小顺序为2.5wt%CrO_x/SiO₂>5wt%CrO_x/SiO₂>10wt%CrO_x/SiO₂,反应过程中的原位ESR和UV-visDRS测定结果表明,催化剂表面的反应活性中心为Cr⁵⁺,Cr⁵⁺可由催化剂预处理过程中Cr³⁺的氧化及丙烷反应过程中CrO₃单体的还原产生,在反应中CO₂可使Cr³⁺重新氧化为Cr⁵⁺.     

以镁铝水滑石为前驱体制备复合氧化物催化丙酮气相缩合反应

采用共沉淀-恒温晶化法制备了系列镁铝水滑石(Mg-Al-LDH)样品,对镁铝水滑石在500 ℃焙烧得到镁铝复合氧化物(Mg-Al-LDO),采用IR、XRD、CO₂-TPD、SEM及N₂吸附-脱附等方法对Mg-Al-LDH和Mg-Al-LDO进行了表征。在温度250 ℃、液时空速1 h^-1条件下,采用固定床对镁铝复合氧化物催化剂对丙酮缩合反应的性能进行微反活性评价。研究结果表明,晶化时间与镁铝复合氧化物的弱碱性位和强碱性位的密度相关。丙酮缩聚反应的主要产物为异佛尔酮(IP)和异丙叉丙酮(MO),以及少量的异丙烯基丙酮、双丙酮醇,均三甲苯等。丙酮缩聚制备异佛尔酮的反应需要催化剂表面弱碱性位(S_w)与强碱性位(S_s)的协同作用,S_w与S_s需要匹配。晶化12 h得到的镁铝复合氧化物催化剂(LDO-12)的S_w/S_s=1.3,异佛尔酮(IP)选择性为65.3%,单程有效收率(IP+MO)为14.8%。     

阴离子插层镁铝水滑石结构及相互作用的理论研究

采用密度泛函理论(DFT)计算了MgAl-LDHs层板与无机阴离子(F^-、Cl^-、NO₃^-、CO₃^2-、SO₄^2-)和有机阴离子(水杨酸根离子([HO(C₆H₄)COO]^-)、苯甲酸根离子([(C₆H₅)COO]^-)、对二甲氨基苯甲酸根离子([p-(CH₃)₂N(C₆H₄)COO]^-)、十二烷基磺酸根离子[C₁₂H₂₅SO₃]^-、己烷基磺酸根离子[C₆H₁₃SO₃]^-、丙烷基磺酸根离子[C₃H₇SO₃]^-)间的相互作用,获得稳定超分子几何结构及相互作用能。层板主体与客体间存在较强的超分子作用,包括主客体间静电作用和氢键等。主、客体间相互作用能数值大小顺序为CO₃^2- > SO₄^2- > F^-> Cl^-> NO₃^-;[p-(CH₃)₂N(C₆H₄)COO]^-> [(C₆H₅)COO]^-> [HO(C₆H₄)COO]^-和[C₁₂H₂₅SO₃]^-> [C₆H₁₃SO₃]^- > [C₃H₇SO₃]^-。另外,还采用自然键轨道(NBO)计算和分析了LDHs 层板与阴离子间作用机理,从二阶微扰理论计算得到的稳定化能变化趋势与相互作用能数据基本吻合。     

The effect of C3S on the early hydration of C3A

Journal of Thermal Analysis and Calorimetry - The hydration of C3A, C3S and C3A+C3S mixtures was examined by thermogravimetry, differential thermogravimetry and calorimetry. The results showed the...     

Fe3O4/MAl水滑石(M=Zn、Co、Ni)复合物光催化降解亚甲基蓝的性能、动力学与机理

基于低成本、无毒害、光吸收性强的四氧化三铁（Fe₃O₄）和大比表面、高稳定性的水滑石（LDHs）,制备了Fe₃O₄@MAl-LDHs （M=Zn、Co、Ni）复合物并用于典型偶氮染料亚甲基蓝的光催化降解。通过X射线粉末衍射（XRD）、紫外可见（UV-Vis）吸收光谱、扫描电子显微镜（SEM）、透射电子显微镜（TEM）以及N₂吸附-脱附测试表征了复合材料的组成与结构。光催化实验表明,最佳反应条件为催化剂用量50 mg、光照强度500 W、pH=9、反应温度40℃,此时,Fe₃O₄@MAl-LDHs复合材料对亚甲基蓝的降解率从LDHs的23.2%大幅提升到87.0%。LDHs对亚甲基蓝的降解主要来自·OH,而Fe₃O₄@CoAl-LDHs光降解活性的贡献主要由·OH和空穴提供。此外,LDHs和Fe₃O₄@CoAl-LDHs的电化学性质也存在较大差异。     

Catalytic Activity of WO<Subscript>3</Subscript> and MoO<Subscript>3</Subscript> with Pt and Pd Additives in Oxidation of Hydrogen

We have shown that WO₃ and MoO₃ with Pt or Pd additives exhibit high catalytic activity in the reaction of H₂ oxidation. In the temperature range 313 K to 353 K, we have studied the kinetic behavior of the reaction on 0.1 mass % Pt(Pd)/WO₃ and Pt(Pd)/MoO₃ samples. We have established that the kinetics of H₂ oxidation on these catalysts correspond to an Eley - Rideal mechanism. __________ Translated from Teoreticheskaya i Eksperimental'naya Khimiya, Vol. 41, No. 5, pp. 313–316, September–October, 2005.     

The effect of experimental methods and measurement conditions on values of the kinetic parameters of [Co(NH3)6]2(C2O4)3·4H2O

Using the thermal decomposition of [Co(NH₃)₆]₂(C₂O₄)₃·4H₂O as a basis, the paper presents results which show how computed values of kinetic parameters are influenced by experimental conditions (ambient atmosphere, sample mass, linear heating rate) when using the non-isothermal methods and the Coats-Redfern (CR) modified equation. It also illustrates the influence of the experimental methods i.e. non-isothermal and isothermal (conventional) methods and also a quasiisothermal-isobaric one which can be recognised as equivalent to Constant Rate Thermal Analysis (CRTA). The results obtained have confirmed the significant influence of the experimental parameters as well as that of the experimental method used on the estimated values of kinetic parameters. The correlation between activation energy (E) and sample mass (m) or heating rate (β) is generally of a linear nature:E=a+bx     

Studies of the roles of Sn or Fe on γ-Al2O3-supported Pt catalysts by CO adsorption microcalorimetry and dehydrogenation reaction of C4 alkanes

CO adsorption microcalorimetry was employed in the study of γ-Al₂O₃-supported Pt, Pt-Sn and Pt-Fe catalysts. The results indicated that the initial differential heat of CO adsorption of the Pt/γ-Al₂O₃ catalyst was 125 kJ/mol. As CO coverage increased, the differential heat of adsorption decreased. At higher coverages, the differential heat of adsorption decreased significantly. 60% of the differential heat of CO adsorption on the Pt/γ-N₂O₃ catalyst was higher than 100 kJ/mol. No significant effect on the initial differential heat was found after adding Sn and Fe to the Pt/γ-Al₂O₃ catalyst. The amount of strong CO adsorption sites decreased, while the portion of CO adsorption sites with differential heat of 60–110 kJ/mol increased after increasing the Sn or Fe content. This indicates that the surface adsorption energy was changed by adding Sn or Fe to Pt/γ-N₂O₃. The distribution of differential heat of CO adsorption on the Pt-Sn(C)/γ-Al₂O₃ catalyst was broad and homogeneous. Comparison of the dehydrogenation performance of C₄ alkanes with the number of CO adsorption sites with differential heat of 60–110 kJ/mol showed a good correlation. These results indicate that the surface Pt centers with differential heats of 60–110 kJ/mol for CO adsorption possess superior activity for the dehydrogenation of alkanes. Project supported by FORD and the National Natural Science Foundation of China (Grant No. 09412302) and the Transcentury Training Program Foundation for the Talents by The State Education Commission of China.     

Extension of the Ye and Shreeve group contribution method for density estimation of ionic liquids in a wide range of temperatures and pressures

An extension of the Ye and Shreeve group contribution method [C. Ye, J.M. Shreeve, J. Phys. Chem. A 111 (2007) 1456–1461] for the estimation of densities of ionic liquids (ILs) is here proposed. The new version here presented allows the estimation of densities of ionic liquids in wide ranges of temperature and pressure using the previously proposed parameter table. Coefficients of new density correlation proposed were estimated using experimental densities of nine imidazolium-based ionic liquids. The new density correlation was tested against experimental densities available in literature for ionic liquids based on imidazolium, pyridinium, pyrrolidinium and phosphonium cations. Predicted densities are in good agreement with experimental literature data in a wide range of temperatures (273.15–393.15 K) and pressures (0.10–100 MPa). For imidazolium-based ILs, the mean percent deviation (MPD) is 0.45% and 1.49% for phosphonium-based ILs. A low MPD ranging from 0.41% to 1.57% was also observed for pyridinium and pyrrolidinium-based ILs.     

真空辅助法合成Fe_3(PO_4)_2·8H_2O及对LiFePO_4/C结构、形貌和电化学性能的影响(英文)

采用了一种真空辅助沉淀法制备Fe3(PO4)2·8H2O,并以此进一步合成粒径尺寸在400 nm左右LiFePO4颗粒.研究了Fe3(PO4)2·8H2O对于磷酸铁锂的形貌、结构、电化学性能的影响.X射线衍射(XRD)结果表明,真空辅助制备的Fe3(PO4)2·8H2O具有高纯度,以此制备的LiFePO4具有高结晶度和纯度.扫描电子显微镜(SEM)结果表明,真空辅助制备的Fe3(PO4)2·8H2O具有未完全发育的颗粒,以此制备的LiFePO4均匀无硬团聚.透射电子显微镜(TEM)结果显示真空辅助制备的LiFePO4包覆一层均匀的碳.真空制备的LiFePO4显示了优异的电化学性能,在1C、10C、20C倍率下的容量分别为140、113、100 mAh·g-1.真空制备的LiFePO4的循环伏安曲线显示了小的极化电压和尖锐的氧化峰.充放电平台曲线表明真空对LiFePO4高倍率性能起到重要作用.电化学阻抗谱(EIS)计算结果显示,真空和非真空制备的LiFePO4的锂离子扩散系数分别为1.42×10-13和4.22×10-14cm2·s-1,说明真空辅助能够提高LiFePO4的扩散系数.