红外光谱研究Pt-Re/Al2O3重整催化剂的表面结构

CO和NO吸附或两者竞争吸附在Pt／Al2O3，Re／Al2O3和Pt－Re／Al2O3催化剂上的红外光谱可以给出Pt和Re的表面结构信息．本文研究的催化剂为低金属载量的Pt／Al2O3，Re／Al2O3和工业型Pt－Re／Al2O3，其中Pt含量0．22％，Re含量0．43％（质量分数）．实验结果表明，用NO与CO双分子竞争吸附的红外光谱实验方法可分别表征还原态Pt－Re／Al2O3重整催化剂上Pt表面和Re表面，并视需要可对Pt表面和Re表面进行半定量分析．在还原态工业型Pt－Re／Al2O3重整催化剂表面上，没有明显迹象表明有Pt－Re合金形成．     

Ni/MgAl(O) 催化剂上高温焦炉煤气中焦油组分的催化转化

 采用共沉淀-水热法合成了一系列 Ni/MgAl(O) 催化剂. 用甲苯和萘的混合物作为焦油模型化合物, 在固定床反应器上研究了该催化剂直接催化转化具有较低水蒸气/碳摩尔比的高温焦炉煤气中焦油为小分子气体的反应. 考察了催化剂组成、水蒸气/碳摩尔比和反应条件等对催化剂性能的影响. 结果表明, Mg/Al 摩尔比为 3 时 Ni/MgAl(O) 催化剂表现出最优的催化性能. 在 700~800 oC 和水蒸气/碳摩尔比为 0.68 的反应条件下, 15%Ni/Mg3Al(O) 催化剂能将甲苯和萘完全转化为 CO 和 CH4 等小分子气体. 在反应气中引入 0.05% H2S(摩尔分数) 气体的实验表明, 该催化剂在焦油催化转化反应中具有较好的抗硫能力. 另外, 在催化剂中加入少量 Pt 助剂能显著提高催化剂活性.     

甲烷部分氧化制合成气:载体及助剂对Ni系催化剂活性的影响

 采用浸渍法制备了Ni系催化剂,并用程序升温还原和X射线衍射技术对催化剂进行了表征,用固定床微反装置考察了催化剂的催化活性．活性考察结果表明,在Ni担载量为8％的Ni／γ－Al2O3,Ni／δ－Al2O3,Ni／θ－Al2O3和Ni／α－Al2O3四种催化剂上,甲烷部分氧化制合成气反应的活性及产物选择性存在着明显的差异．在770℃下,甲烷转化率及CO和H2的选择性按Ni／γ－Al2O3＜Ni／δ－Al2O3＜Ni／θ－Al2O3≈Ni／α－Al2O3顺序排列．在相同的条件下,加入适量的CeO2助剂后,Ni／γ－Al2O3和Ni／δ－Al2O3上的反应活性和选择性显著提高,而Ni／θ－Al2O3和Ni／α－Al2O3上的活性和选择性却变化不大．同时,表征结果显示,Ni易与γ－Al2O3形成镍铝尖晶石NiAl2O4,加入CeO2助剂能有效地抑制该组分的生成,而Ni／α－Al2O3样品中未发现NiAl2O4．因此,不同Ni／Al2O3催化剂体系上的反应活性及选择性的差异可归结为不同结构Al2O3载体的性质不同,及CeO2对抑制镍铝尖晶石生成的效果不同．     

贵金属对钴基催化剂上肉桂醛选择加氢反应的影响

 研究了贵金属改性的Co／γ－Al2O3催化剂上的肉桂醛选择加氢反应．结果表明，通过Pt，Pd和Ru贵金属改性，提高了催化剂的活性，但只有Pt改性的催化剂具有较高的选择性．w（Pt）＜0．5％时，催化剂的活性随着Pt含量的增加呈直线升高，当w（Pt）＝0．5％时，催化剂活性可提高近5倍，但催化剂的选择性变化很小．XRD结果表明，催化剂经还原后，γ－Al2O3上的钴主要为α－Co0．TPR结果表明，Pt的加入提高了Co3O4的还原性能，且Pt含量越高，Co3O4的还原温度越低．XPS结果表明，Pt改性的催化剂样品，其Co3O4大部分被还原为Co0．由于Pt与Co具有协同效应，故Pt改性的Co／γ－Al2O3催化剂既具有较高的活性，又具有很高的选择性．     

Pt／La-Al2O3＋Ce0.5Zr0.5O2催化燃烧脱除饮食油烟

采用浸渍法制备了低贵金属含量的Pt／La2O3，Pt／La—Al2O3＋Pt／OSM（2：1），Pt／La—Al2O3＋Pt／OSM（1：1），Pt／La—Al2O3＋Pt／OSM（1：2）4种整体式催化剂，在固定床反应器中对催化活性进行了评价。结果表明，稀土储氧材料（OSM）的添加有利于提高催化活性，降低油烟完全转化温度。La-Al2O3和OSM的质量比为1：1时催化活性最好，油烟完全转化温度为270℃，其空速适用范围是一至六万。该催化剂具有良好的应用前景。     

噻吩加氢脱硫和四氢萘催化加氢反应中的载体和助剂的影响

 为了更好地认识加氢脱硫和催化加氢反应中的载体影响和助剂效应，在同样的催化剂制备方法及反应条件下，研究了噻吩加氢脱硫（HDS）和四氢萘催化加氢（HYD）反应．结果表明，对于无助剂的Mo和W催化剂，载体对催化活性的影响顺序为TiO2－Al2O3＞ZrO2＞Al2O3．助剂的添加改变了催化剂活性顺序．Ni助剂催化剂的活性明显高于Co助剂催化剂．ZrO2担载的添加Ni的Mo和W催化剂分别获得了最佳的HDS和HYD活性．然而，添加Pt的Mo和W催化剂其HDS和HYD活性仅是Pt与Mo（W）二者的加和，Pt与Mo（W）之间没有协同效应．先将担载的Mo和W预硫化再将助剂引入体系的催化剂制备方法可以避免Ni和Co过早硫化形成类硫化镍（或硫化钴）物相，与采用螯合物分子方法制备的催化剂间有一定的相似性．     

加氢处理催化剂的制备和表征 Ⅰ.MoNiP/Al2O3催化剂的制备及助剂的作用

 采用专利方法制备出一种新型的γ－Al2O3,并以其为载体,制备出加氢处理催化剂MoNiP／Al2O3．用PAS－CA,XPS,DRS,TPR和微型反应色谱等技术对γ－Al2O3和催化剂进行了表征,考察了Ni和P两种助剂的作用．结果表明,γ－Al2O3具有较大的孔径,集中的孔分布和较高的机械强度;活性金属Mo在γ－Al2O3表面上的化学分散量（分散阈值）可达5．04～5．82μmol／m2．因而特别适合用作高活性加氢处理催化剂的载体．引入的Ni主要是同Mo／Al2O3催化剂表面上较稳定的金属－载体相互作用复合物反应,并生成类NiMoO4化合物;在MoNi／Al2O3催化剂中引入P,有利于抑制四面体配位结构的物种Mo［T］,增加八面体配位结构的物种Mo［O］,改善催化剂的还原性能,从而提高催化剂的加氢处理活性．助剂Ni和P的最佳含量分别为w（Ni）＝4．0％和w（P）＝2．6％．     

TPR in situ (57)~Fe MBS研究Fe/γ-Al_2O_3及Pt-Fe/γ-Al_2O_3催化剂

虽然γ－Al2O3。担载的Pt－Fe双组分催化剂与Pt－Sn双组分催化剂类似，对脱氢反应亦具有较好的催化活性[1]，但有关其表面结构的报道甚少．TPRinsituMBS技术研究含Fe催化剂可获得很多有用的信息[2，3]，本文以TPR及TPRinsitu57FeMBS技术研究了Pt－Fe／γ－Al2O3催化剂的表面组成及Pt、Fe与γ－A12O3相互作用情况．1实验部分催化剂采用分浸法制备“‘，所有含Fe样品”Fe含量均为wFc一0．1％．样品的TPR及TPRinsitu’7FeMBS的测量见文献［‘j．2结果和讨论2．ITPR研齐人AI，O，、PtFe／y－AI、0。的TPR港示于囹1．中…     

Pt，Pd助剂对Ni基催化剂中Ni的分散度及抗积碳性能的影响

研究了添加少量贵金属(Pt,Pd)的Ni/Al2O3催化剂对甲烷水蒸汽重整反应抗积碳能力和催化性能的影响.催化活性实验表明,添加少量Pt的样品显著提高了Ni/Al2O3催化剂的活性,稳定性,抗积碳和抗氧化能力,而添加Pd的样品对Ni/Al2O3催化剂的催化性能提高并不明显.利用氢气程序升温还原(H2-TPR),X射线晶体衍射(XRD),热重-差热分析(TG-DTA)等手段对反应前后的催化剂进行了表征,研究发现在Ni-Pt/Al2O3催化剂中Ni与Pt之间存在较强的相互作用力,在主要由Ni覆盖的表面形成了Ni-Pt双金属簇,提高了Ni的分散度,在催化剂的表面易于形成较小的Ni颗粒,抑制了Ni的烧结,改善了Ni基催化剂的抗积碳能力;贵金属Pt通过H2的溢流效应促进了Ni的还原,抑制了催化剂的氧化.而在Ni-Pd/Al2O3中,Ni和Pd存在着一定的偏析效应,不能有效的形成Ni-Pd双金属簇,在还原过程中分别被还原.     

稀土Ce对制合成气用Ce-Ni/Al2O3催化剂活性和稳定性的影响

 用浸渍法制备了Ni／Al2O3和Ce－Ni／Al2O3催化剂,并用BET,TGA－DTA和XPS技术对催化剂进行了表征,考察了稀土Ce对催化剂性能的影响,探讨了催化剂失活的原因．结果表明,在甲烷部分氧化和二氧化碳重整反应中,稀土Ce存在有部分还原变价过程（Ce4＋→Ce3＋）,不仅抑制了催化剂的积碳,而且改善了催化剂的水热稳定性和催化性能．经过较长时间反应的Ce－Ni／Al2O3催化剂,其比表面积下降,活性物种Ni和助剂Ce向体相迁移或部分流失,以及Ni晶粒的烧结聚集长大可能是造成催化剂逐渐失活的主要原因．     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.