K-MoO3/γ-Al2O3催化剂表面物种状态、组成和性能

应用XPS、XRD、ESR 和TPR技术分析了KCl助剂含量变化对MoO_3/γ-Al_2O_3催化剂表面物种状态、组成及其硫化还原性能的影响. K/Mo比小于0.8时, 钾离子完全和钼作用, 形成钾钼作用物种, 催化剂硫化后发生K~+表面富集, Cl~-游离并流失; K/Mo比0.8时, 钾钼作用达到饱和; K/Mo比大于0.8时, 多余的K~+和Cl~-结合以体相KCl形式存在. 钾钼作用减弱了Mo(Ⅵ)和载体之间的作用, 部分抑制了Mo(Ⅵ)的硫化还原. 钾钼作用物种硫化后可能产生CO合成醇的活性中心.     

碳纳米管促进的Co-Mo-K硫化物基催化剂用于合成气制低碳混合醇

 以自行制备的多壁碳纳米管(CNT)作为添加剂,制备共沉淀型CNT促进的Co-Mo-K硫化物基催化剂. 实验发现,与未添加CNT的催化剂相比,添加少量CNT可显著提高CO的加氢转化活性和生成低碳醇的选择性. 在5.0 MPa, 623 K, V(CO)∶V(H2)∶V(N2)=45∶45∶10, GHSV=3600 ml/(g·h)的反应条件下, Co1Mo1K0.3-10%CNT催化剂上CO的转化率达21.6%, 相应的总醇(C1～4醇)时空产率为241.5 mg/(g·h), 产物中C2+醇/C1醇=1.39 (C基选择性比). 添加少量CNT并不会导致Co1Mo1K0.3硫化物基催化剂上CO加氢反应表观活化能发生明显变化,但却导致工作态催化剂表面催化活性Mo物种(Mo4+)的摩尔百分率有所提高; 另一方面, CNT促进的催化剂对H2有更强的吸附活化能力,并能在相当大程度上抑制水煤气变换副反应的发生. 这些因素有利于提高催化剂的活性和选择性.     

TRANSESTERIFICATION OF METHANOL WITH ETHYL ACETATE AND ETHANOL WITH METHYL FORMATE CATALYZED BY DBN

采用三步合成了１，５二氮杂环双环［４，３，０］壬烯５（ＤＢＮ）并考察了其在酯交换反应中的催化活性。结果表明，在没有环氧丙烷（ＰＯ）助剂存在时，ＤＢＮ的催化活性很低；但在有ＰＯ助催化剂存在时，ＤＢＮ对酯交换反应的催化活性极高，其催化活性随ＤＢＮ和ＰＯ浓度的增加而增大。考察了反应温度对ＤＢＮ催化剂的酯交换活性的影响，提出了酯交换反应的催化机理。     

碱金属助剂对MnOx／ZrO2催化合成

 研究了MnOx／ZrO2催化剂中添加的碱金属助剂对以合成气合成甲醇及异丁醇反应的影响，并采用BET，XRD和NH3－TPD等表征技术，考察了碱金属助剂的添加对催化剂结构和表面性质的影响．结果表明，碱金属助剂对MnOx／ZrO2催化剂的催化性能有明显影响．在实验条件下，添加1．0％K（K2CO3作为前驱物）的催化剂，其催化性能最好，醇的选择性高达74．8％，异丁醇选择性达16．3％．添加碱金属助剂也使MnOx／ZrO2催化剂的表面性质发生了很大变化，从而影响催化剂的催化性能．     

助剂对甲烷部分氧化制合成气镍基催化剂性能的影响

考察了添加助剂铈、镧和钙对镍基催化剂反应性能的影响，发现助剂对以α-Al2O3为载体的镍基催化剂的调变作用比以γ-Al2O3为载体的镍基催化剂好，且助剂铈对催化剂的性能改善最好。在此基础上，研究了不同载量的铈对催化剂性能的影响。结果表明，铈的质量分数为1%时对催化剂的性能改善最好。同时采用XRD、XPS、TG等技术，研究了助剂铈对10％Ni/γ-Al2O3催化剂的改性作用。XRD分析表明，铈负载量较低时，催化剂中的CeO2高度分散在催化剂表面，铈负载量较高时，CeO2形成微晶颗粒，降低了催化活性。     

添加钠对低镍甲烷化催化剂结构性能的影响

用活性测试、XRD和EXAFS方法研究了一系列含Ni 6wt％、添加不同量Na助剂的γ-Al_2O_3担载Ni甲烷化催化剂的结构性能。结果表明:Ni与Al_2O_3有较强的相互作用。添加不同量的Na助剂能增强或削弱这种作用,从而影响催化剂宏观性能,Na在Al_2O_3上是高度分散的。它的影响是通过改变载体表面性能从而改变Ni的状态及其分布,Ni的分散度和Ni-Al_2O_3相互作用而完成的。适量Na可提高Ni的分散度,优化Ni-Al_2O_3相互作用,从而提高催化剂活性。过量Na则会加强Ni-Al_2O_3相互作用,或者造成NiO自身聚集形成NiO晶相,从而降低Ni利用率,使催化剂活性降低。     

Ni助剂FeMnK/SiO2费托合成催化剂的结构性质及还原碳化行为研究

研究了Ni助剂对共沉淀型FeMnK/SiO2催化剂的结构性质和还原炭化行为的影响。结果表明，添加少量Ni助剂提高了催化剂的比表面积，降低了平均孔径，促进了催化剂中铁氧化物的分散。在H2-TPR中，Ni助剂降低了催化剂的还原温度；在CO-TPR中，Ni助剂使催化剂的还原和炭化峰前移，提高了氧的移除速率，增加了碳的引入量；在合成气等温还原中，Ni助剂提高了催化剂的活化速率，在相同的还原时间内可获得更高的F-T合成反应活性。     

Promotional Effect of Bismuth as Dopant in Bi-Doped Vanadyl Pyrophosphate Catalysts for Selective Oxidation of n-Butane to Maleic Anhydride

Bismuth-promoted (1% and 3%) vanadyl pyrophosphate catalysts were prepared by refluxing Bi(NO3)3·5H2O and VOPO4·2H2O in isobutanol. The incorporation of Bi into the catalysts lattice increased the surface area and lowered the overall V oxidation state. Profiles of temperature programmed reduction (TPR) in H2 show a significant shift of the maxima of major reduction peaks to lower temperatures for the Bi-promoted catalysts. A new peak was also observed at the low temperature region for the catalyst with 3% of Bi dopant. The addition of Bi also increased the total amount of oxygen removed from the catalysts. The reduction pattern and reactivity information provide fundamental insight into the catalytic properties of the catalysts. Bi-promoted catalysts were found to be highly active (71% and 81% conversion for 1% and 3% Bi promoted catalysts, respectively, at 703 K), as compared to the unpromoted material (47% conversion). The higher activity of the Bi-promoted catalysts is due to that these catalysts possess highly active and labile lattice oxygen. The better catalytic performance can also be attributed to the larger surface area.     

Recent Technological Developments in Cobalt Catalysts for Fischer-Tropsch Synthesis

Co-based catalysts are often utilized due to their high Fischer-Tropsch synthesis (FT) activity,C+5 hydrocarbon selectivity, low water-gas shift reaction (WGS) activity and relatively low cost. Selective control of C5+ hydrocarbons and the catalyst longevity are critical in the design of cobalt catalysts.Thus, various methods to improve the performance of Co catalysts have been suggested. The progress in cobalt catalysts reviewed in the last few decades, mainly involved the support, promoter, preparation and deactivation of Co-based catalysts.     

过渡金属对Pd/γ-Al2O3催化剂活性的影响

 利用分步等体积浸渍的方法，从蒽醌法生产双氧水的角度，制备\r\n了系列氢化催化剂．同时，利用TPR，XRD和TEM等技术，考察了第4周期\r\n过渡金属对Pd／γ－Al2O3催化剂活性的影响．结果表明，铁系元素和\r\n锌助剂有利于钯在载体上的分散，提高了Pd的催化活性，使氢化效率提\r\n高5％～16％，抗失活能力增强．