基于二维结构效应的高分散负载金属催化剂

负载型金属催化剂是煤化工、石油化工以及精细化工等领域应用最为广泛的催化剂.层状复合金属氢氧化物(LDHs)是一类具有典型层状结构的二维纳米材料,由于其组成的可调控性以及独特的二维结构效应,以LDHs材料作为前驱体和载体在制备活性位高分散的金属催化剂方面表现出显著的优势.本文重点综述了基于LDHs层板网阱限域效应和层间几何限域效应构筑高分散负载型金属催化剂的最新进展,探讨了LDHs基负载型金属催化剂在重要反应中的构效关系,并介绍了该类催化剂的工业实践情况.     

Ni-SiO2催化剂空间限域维度对CH4-CO2重整反应金属抗积碳能力的影响

制备了3种化学组成相同但金属活性位点空间结构不同的Ni-SiO₂催化剂(Ni/SiO₂负载型催化剂、 Ni/SBA-15介孔结构催化剂和Ni@SiO₂核壳结构催化剂), 考察了不同空间限域维度及结构对CH₄-CO₂重整反应活性金属抗积碳机制的影响规律. 结果表明, Ni/SiO₂催化剂无空间限域效应, 抗积碳能力最弱, 表现出最差的稳定性; Ni/SBA-15催化剂存在部分空间限域效应, 抗积碳能力明显提高, 表现出较好的稳定性但是仍有失活; Ni@SiO₂催化剂具有完全几何限域效应, 抗积碳能力最强, 表现出最优的稳定性.     

分子筛限域单原子金属催化剂的研究进展

分子筛由于具有规则的微孔孔道结构、 较大的表面积、 优异的(水)热稳定性, 被认为是限域合成超小尺寸金属物种的理想载体. 近年来, 分子筛限域单原子金属催化剂由于超高的金属分散度、 接近100%的金属利用率以及独特的电子结构, 被广泛地应用于重要的催化反应和气体吸附分离过程. 本文系统地总结了近年来分子筛限域不同类型单原子金属催化剂的合成策略, 以及其在多相催化和气体分离等领域的研究进展. 最后, 提出了分子筛限域单原子金属催化剂在合成与表征方面存在的挑战和未来的发展方向.     

二氧化碳电还原催化剂调控策略与结构效应（英文）

随着化石燃料的消耗,全球碳排放与日俱增,由此引发的温室效应对全球气候变化带来巨大的挑战,温室气体CO₂的减排与利用迫在眉睫.利用太阳能、风能等可再生资源生产的电能能够将CO₂还原为一系列有附加值的化学品如醇、酸等有机小分子,人为构造碳循环网络,实现碳中和.本文综述了电催化CO₂还原反应(CO₂RR)催化剂的调控策略和结构效应.从本征结构和外部结构的角度阐述了催化剂活性位点的调控策略.同时讨论了CO₂RR催化剂的结构效应,如串联催化、协同效应和限域催化.关于催化剂的调控策略,从催化剂的本征结构和外部结构两方面总结了近年CO₂RR催化剂的研究进展.特定的元素或化合物可以表现出不同的晶体结构,造成局部电子结构差异.而局部电子结构与催化剂的催化性能密切相关,调整晶体结构成为本征结构调控的核心问题,因此本文探讨了如何通过电化学方法和纳米晶体合成调节催化剂的本征结构.与本征结构不同,催化剂的外部结构与活性位点的微环境有关.催化剂的外部结构调节主要基于各种电子结构的协同...     

碳纳米管限域效应对肉桂醛选择加氢产物分布的影响

碳纳米管因其独特的电子结构和性能引起了研究者们广泛的兴趣,尤其是它有序的纳米级管腔结构,可以为催化剂和催化反应提供一种独特的一维限域环境.碳纳米管的限域效应主要由于其管腔几何和电子结构可以使反应物发生富集、对金属纳米颗粒的尺寸限制以及对电子结构的调变作用.一系列研究表明,碳纳米管的限域效应可以对催化剂的活性进行调变,但是对产物选择性的影响方面研究得较少,特别是管径小于4 nm的碳纳米管的限域体系.因此,本文以肉桂醛选择性加氢反应为探针,研究限域效应对产物选择性的影响规律.采用管径为1–3 nm的碳纳米管,基于气相填充的方法将Ru纳米团簇分散于碳纳米管的管腔中,得到碳纳米管限域的Ru催化剂(Ru@CNT);采用浸渍法制备了碳纳米管管外壁负载的催化剂(Ru/CNT)来进行对比.肉桂醛含有共轭的C=C和C=O键,由于C=C键能低于C=O,前者更易发生加氢反应.结果表明,分散在碳纳米管外壁的Ru催化剂可以催化肉桂醛中的C=C加氢,得到氢化肉桂醛(HCAL);而Ru@CNT催化剂不仅可以催化C=C加氢得到氢化肉桂醛HCAL,还可以催化C=O键加氢得到肉桂醇,以及氢化肉桂醇. 通过高分辨透射电镜、拉曼、程序升温还原、程序升温脱附对催化剂进行了表征.发现碳纳米管限域的纳米团簇金属颗粒的粒径大约为1–2 nm,与管外负载的金属颗粒相近,但是Ru@CNT催化剂上仍有部分金属纳米团簇分布在管外壁,这可能是Ru@CNT催化剂上有C=C键加氢产物的一个原因.碳纳米管独特的限域效应促进了Ru物种的还原,在H2气氛下管内Ru物种的还原温度比管外低20oC.金属与碳纳米管的内、外壁之间的电子相互作用,纳米管腔的空间限制作用及管腔富集作用可能是产物分布产生差异的原因.     

几种分子筛催化剂对丁烯-2齐聚反应的催化性能

采用连续固定床反应器,考察了几种具有不同酸性和孔道尺寸的分子筛催化剂上丁烯-2齐聚反应的性能,并与固体磷酸(SPA)催化剂进行了对比.结果表明,分子筛催化剂的酸性和孔道尺寸是影响丁烯-2齐聚反应活性和选择性的重要因素.具有八元环孔道的分子筛的扩散阻力大,反应活性很低;十二元环分子筛的孔道降低了扩散阻力,有利于提高催化剂的低温活性和C9= 选择性;十元环分子筛的孔道尺寸和强酸中心可以提高催化剂的活性,促进C9= 生成.SPA催化剂上C9= 选择性低于30%,而具有强酸中心的十元环ZSM-5和ZSM-22分子筛,以及十二元环β分子筛催化剂上可高达50%以上,这说明分子筛催化剂具有更好的齐聚催化性能.     

碳纳米管限域效应对肉桂醛选择加氢产物分布的影响（英文）

碳纳米管因其独特的电子结构和性能引起了研究者们广泛的兴趣,尤其是它有序的纳米级管腔结构,可以为催化剂和催化反应提供一种独特的一维限域环境.碳纳米管的限域效应主要由于其管腔几何和电子结构可以使反应物发生富集、对金属纳米颗粒的尺寸限制以及对电子结构的调变作用.一系列研究表明,碳纳米管的限域效应可以对催化剂的活性进行调变,但是对产物选择性的影响方面研究得较少,特别是管径小于4 nm的碳纳米管的限域体系.因此,本文以肉桂醛选择性加氢反应为探针,研究限域效应对产物选择性的影响规律.采用管径为1-3 nm的碳纳米管,基于气相填充的方法将Ru纳米团簇分散于碳纳米管的管腔中,得到碳纳米管限域的Ru催化剂(Ru@CNT);采用浸渍法制备了碳纳米管管外壁负载的催化剂(Ru/CNT)来进行对比.肉桂醛含有共轭的C=C和C=O键,由于C=C键能低于C=O,前者更易发生加氢反应.结果表明,分散在碳纳米管外壁的Ru催化剂可以催化肉桂醛中的C=C加氢,得到氢化肉桂醛(HCAL);而Ru@CNT催化剂不仅可以催化C=C加氢得到氢化肉桂醛HCAL,还可以催化C=O键加氢得到肉桂醇,以及氢化肉桂醇.通过高分辨透射电镜、拉曼、程序升温还原、程序升温脱附对催化剂进行了表征.发现碳纳米管限域的纳米团簇金属颗粒的粒径大约为1-2 nm,与管外负载的金属颗粒相近,但是Ru@CNT催化剂上仍有部分金属纳米团簇分布在管外壁,这可能是Ru@CNT催化剂上有C=C键加氢产物的一个原因.碳纳米管独特的限域效应促进了Ru物种的还原,在H_2气氛下管内Ru物种的还原温度比管外低20oC.金属与碳纳米管的内、外壁之间的电子相互作用,纳米管腔的空间限制作用及管腔富集作用可能是产物分布产生差异的原因.     

化学改性对催化裂化催化剂氢转移性能的影响

 研究了用草酸处理裂化催化剂的活性组分USY型分子筛以及在催化剂基质中添加磷改性的氧化铝等方法对裂化催化剂氢转移反应活性的影响. 实验结果表明,酸处理能脱除USY型分子筛孔道中的无定形氧化铝,疏通分子筛孔道,提高分子筛的氢转移反应活性,减少积碳; 对于含稀土的REUSY型分子筛,酸处理首先脱除的是稀土离子,降低了分子筛的裂化反应活性,但提高了氢转移反应活性. 在催化剂基质中添加磷改性的氧化铝能增加基质的弱酸性中心,增加裂化反应的活性中心,提高催化剂的裂化及氢转移反应活性,同时减少催化剂上的积碳.     

FTO反应Fe基催化剂载体的研究进展

在合成气一步法制备低碳烯烃(FTO)反应中铁基催化剂因成本低、易得、操作温度范围宽等诸多优点而备受关注。载体具有自身特定的结构性质、表面酸碱性、电子特性、缺陷位、孔道限域效应和表面物化可调节性,这些性质对FTO反应性能均有显著影响。双功能催化剂也是FTO反应突破Anderson-Schulz-Flory(ASF)分布的有效手段,但Fe基双功能催化剂设计时需要考虑反应原理。本文对近10年关于Fe基FTO反应催化剂的载体研究发展进行了综述,力求寻求这些研究中的规律性知识,以期对未来FTO反应铁基催化剂的制备和研究提供帮助。     

水对SBA-15负载的钴基费-托合成催化剂催化性能的影响

以SBA-15分子筛为载体,采用等体积浸渍法制备了负载量为20%的钴基催化剂,采用TEM、XRD、H2-TPR和N2物理吸附-脱附等方法对催化剂进行了表征,并在浆态床反应器中考察了水的加入对费-托合成反应性能的影响.结果表明,金属钴物种进入到SBA-15载体的孔道中;产物在孔道中的滞留以及水促进的金属钴物种的团聚,引起了催化剂活性的降低;水的加入有利于反应物和产物在孔道中的传输,增加CO的转化率;在SBA-15负载的钴基催化剂中,产物在孔道中的滞留对催化剂活性影响较大,引起的扩散限制是催化剂活性降低的重要原因.     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.