负载型钴锰复合氧化物臭氧辅助催化降解低浓度甲醛的性能研究

制备了负载型钴锰复合氧化物Co-MnOx/ZSM-5催化剂,采用浸渍法将催化剂负载到堇青石蜂窝陶瓷上,在密封舱内进行催化降解甲醛研究,考察了室温下臭氧辅助催化降解室内低浓度甲醛的特性.同时,也探讨了催化剂制备工艺对催化剂活性的影响.实验结果表明:在500℃煅烧温度条件下制备的10%Co-MnOx/ZSM-5催化剂具有最高的催化活性.通过XRD、BET、TEM、XPS和TG-DSC等手段的表征结果表明,其高活性可能是主要来自于形成的CoMnO3晶相和Mn4+与Mn3+价态共存.     

负载型钴锰复合氧化物臭氧辅助催化降解低浓度甲醛的性能研究

制备了负载型钴锰复合氧化物Co-MnOx/ZSM-5催化剂,采用浸渍法将催化剂负载到堇青石蜂窝陶瓷上,在密封舱内进行催化降解甲醛研究,考察了室温下臭氧辅助催化降解室内低浓度甲醛的特性。同时,也探讨了催化剂制备工艺对催化剂活性的影响。实验结果表明：在500oC煅烧温度条件下制备的10% Co-MnOx/ZSM-5催化剂具有最高的催化活性。通过XRD、BET、TEM、XPS和TG-DSC等手段的表征结果表明,其高活性可能是主要来自于形成的CoMnO3晶相和Mn4 与Mn3 价态共存。     

LaMO3(M=Co,Mn)钙钛矿型催化剂上VOCs催化燃烧的研究

研究了LaMO3(M=Co,Mn)钙钛矿型催化剂对VOCs的催化燃烧性能,该类催化剂对单一VOC和混合VOCs均有很好的催化活性,而LaMnO3的催化活性要比LaCoO3的催化活性更好,氧化还原滴定实验表明,LaMnO3催化剂中锰以Mn4 (大约35%)和Mn3 价态存在,而在LaCoO3催化剂中发现钴均以Co3 价态存在;在混合VOCs催化燃烧的试验中,3种有机物的易氧化性依次为正丙醇＞甲苯＞环己烷,达到99%的转化率时,环己烷的反应温度则比甲苯的反应温度要约低40℃.     

LaMO3(M=Co,Mn)钙钛矿型催化剂上VOCs催化燃烧的研究

研究了LaMO3(M=Co,Mn)钙钛矿型催化剂对VOCs的催化燃烧性能,该类催化剂对单一VOC和混合VOCs均有很好的催化活性,而LaMnO3的催化活性要比LaCoO3的催化活性更好,氧化还原滴定实验表明,LaMnO3催化剂中锰以Mn4+(大约35%)和Mn3+价态存在,而在LaCoO3催化剂中发现钴均以Co3+价态存在;在混合VOCs催化燃烧的试验中,3种有机物的易氧化性依次为正丙醇＞甲苯＞环己烷,达到99%的转化率时,环己烷的反应温度则比甲苯的反应温度要约低40℃.     

臭氧催化氧化脱除低浓度甲醛的新方法

甲醛作为一种典型的室内挥发性有机污染物,对人体健康危害很大.目前,在可用于室内甲醛脱除的诸多方法之中,臭氧催化氧化法因可于室温下使用廉价的金属氧化物催化剂实现对甲醛的高效脱除,从而受到了科研工作者的广泛关注.然而,考虑到室内甲醛的浓度极低,且存在着长期缓慢释放的特点,传统的臭氧催化氧化法应用于实际的室内甲醛脱除不仅会造成能量的浪费,而且还易因未完全分解臭氧的连续释放带来二次污染问题.为了提高臭氧催化氧化脱除甲醛过程的臭氧利用率,降低能耗,并有效缓解未分解臭氧引起的二次污染,本文将一种循环的甲醛存储-臭氧催化氧化新方法应用于室内低浓度甲醛的脱除.该新方法包含甲醛存储与臭氧催化氧化两个过程,在存储阶段低浓度甲醛吸附存储于催化剂表面,而在臭氧催化氧化阶段臭氧将存储的甲醛氧化为CO2与H2O,并重新释放催化剂表面的吸附位.因负载型氧化锰具有优良的臭氧分解能力,本研究以Al2O3负载的MnOx为催化剂,通过研究前驱体及担载量对甲醛脱除反应的影响,筛选出了最优的MnOx/Al2O3催化剂,并对相对湿度的影响规律进行了考察,最后通过低浓度甲醛存储-臭氧催化氧化循环实验验证了该甲醛臭氧催化氧化新过程的可靠性.我们采用传统的等体积浸渍法,基于不同的前驱体制备MnOx/Al2O3催化剂.XRD表征结果表明,乙酸锰为前驱体制得的MA/Al2O3催化剂中MnOx相主要为Mn3O4(粒径约为6.0 nm);而硝酸锰前驱体所得MN/Al2O3催化剂中则含有MnO2与Mn2O3相,且其MnOx颗粒粒径较大,约为9.5 nm.XPS测试结果表明,MA/Al2O3催化剂含有Mn2+,Mn3+及Mn4+,其中Mn3+与Mn4+的含量分别为75%与12%;而MN/Al2O3催化剂则仅含有Mn3+与Mn4+,含量分别为35%与65%.上述XRD与XPS结果相一致,说明以乙酸锰为前驱体所得催化剂的分散度较高且易形成低氧化态的Mn.甲醛存储-臭氧催化氧化实验结果表明,与Al2O3及MN/Al2O3相比,MA/Al2O3催化剂具有更高的甲醛存储与催化氧化脱除性能.基于MA/Al2O3催化剂,不同Mn负载量下的甲醛存储与臭氧催化氧化实验结果表明,Mn负载量为10 wt%时MA/Al2O3的性能最佳.因而,进一步的实验中我们均选用最优的10 wt%MA/Al2O3为催化剂,其在50%相对湿度下的甲醛存储量为26.9μmol/mL,臭氧催化氧化阶段碳平衡为92%,CO2选择性为100%.相对湿度的影响结果(23℃)则表明,由于水分子与甲醛分子间存在着竞争吸附作用,甲醛存储容量随相对湿度的增加而降低;但因相对湿度增加可建立利于甲醛氧化的新途径,故臭氧催化氧化性能随相对湿度增加而增强.综合考虑,10 wt%MA/Al2O3上甲醛存储-臭氧催化氧化的最优相对湿度为50%.为验证所提出新方法的实用性,我们基于10 wt%MA/Al2O3开展了甲醛存储-臭氧催化氧化的4次循环实验.4次循环实验中的甲醛存储以及臭氧催化氧化处理的规律可基本保持一致.50%相对湿度下,低浓度甲醛(15×10-6)在空速为27000 h-1时的穿透时间为110 min,而在臭氧催化氧化阶段(150×10-6臭氧,空速15000 h-1)仅需约50 min即可实现对存储甲醛的氧化脱除(碳平衡大于92%,CO2选择性100%),表明该新方法较传统的臭氧催化氧化方法臭氧用量可节省60%.     

无模板法合成介孔棒状钴酸锰及其苯乙烯环氧化反应性能

通过简单的无模板水热法及煅烧处理成功合成了介孔棒状钴酸锰。采用X射线衍射(XRD)、场发射扫描电镜(FE-SEM)、透射电镜(TEM)、氮气吸附-脱附和X射线光电子能谱(XPS)等手段对材料的晶体结构、表面形貌、孔结构和表面化学组成进行了表征。结果表明,目标产物钴酸锰样品介孔结构形成良好,孔径分布在6 nm。此外,钴酸锰的棒状形貌直径为100～200 nm,长度为2～3μm。相比于其他Co基、Mn基催化剂,钴酸锰被首次应用在苯乙烯环氧化反应中,表现出了极高的催化活性,苯乙烯的转化率达到95.8%,对氧化苯乙烯的选择性为58.2%。而且,在5次循环试验后,催化活性并没有发生明显的改变,进一步证明了催化剂的稳定性。同时,系统研究了主要反应参数(反应时间、反应温度、苯乙烯/叔丁基过氧化氢(TBHP)的物质的量比值)对介孔棒状钴酸锰催化活性的影响。     

四羰基钴/咪唑离子液体在羰基化合成丙二酸二甲酯反应中的催化性能

采用原位法合成了不同类型的四羰基钴/咪唑离子液体催化剂, 并考察了其在氯乙酸甲酯羰基化反应中的催化性能. 研究了咪唑环上不同支链对催化活性的影响. 结果表明, 1-丁基-3-甲基咪唑羰基钴离子液体[Bmim][Co(Co)₄]不仅催化活性高, 选择性好, 而且对空气和水有较好的稳定性能. 在p_CO=2.0 MPa, 85 ℃, 反应3 h的条件下, [Bmim][Co(Co)₄]催化剂循环使用4次, 氯乙酸甲酯的平均转化率为94.3%, 丙二酸二甲酯的平均选择性和平均产率分别为98.5%和92.9%. 与传统的Na[Co(Co)₄]催化剂相比, [Bmim][Co(Co)₄]催化剂在保证高活性的条件下可以实现羰基钴催化剂的直接循环使用.     

锰氧八面体分子筛室温同时去除甲醛和臭氧的性能研究

通过回流法、无溶剂法及水热法合成了3种锰氧八面体分子筛催化剂（OMS-2）,并对其室温同时去除甲醛和臭氧的反应活性进行了研究.结果表明无溶剂法制备的锰氧八面体分子筛（OMS-2-S）具有最高的甲醛转化率,且水气的加入对3种OMS-2催化剂的二氧化碳产率均具有明显的促进作用.并通过XRD、SEM和XPS等技术对催化剂进行表征,考察了催化剂物理化学性质对其催化活性的影响.从表征结果可得,较强的吸附能力、丰富的氧空位及较强的氧物种移动性是OMS-2-S催化剂活性较高的原因.     

负载型过渡金属氧化物催化剂催化分解臭氧性能研究

通过浸渍法制备了γ-Al_2O_3负载镍、锰、钴等不同金属氧化物催化剂,在25℃、200000 mL/(gcat·h)的空速条件下,研究了其臭氧催化分解性能。结果表明,10%NiO/γ-Al_2O_3催化剂催化活性最佳,20 h内臭氧转化率高于96%。借助XRD、XPS、TEM、SEM-EDS、H2-TPR等表征手段,揭示出在NiO/γ-Al_2O_3催化剂表面形成的镍铝尖晶石结构可能是其优良臭氧分解性能的内在原因。此外,揭示出在不同过渡金属氧化物负载型催化剂上臭氧分解机理不同,相关研究为镍、锰等过渡金属氧化物催化剂催化分解臭氧的反应机理提供了新思路,并为开发高效的臭氧分解催化剂提供了指导。     

La助剂添加方式对甲烷催化燃烧用Mn/Al2O3催化剂的影响

采用等体积浸渍法制备了La改性的Mn/Al2O3催化剂.以甲烷燃烧反应为探针反应,考察了La2O3的引入方法对其催化活性的影响.催化剂的物化性质经TPR,XRD和XPS表征.研究结果表明,La的添加顺序对催化剂的物化性质和催化活性有显著影响.在以共浸渍方式制备的催化剂A中,载体与锰物种之间的相互作用大受削弱,锰晶粒变小,分散度增加,催化剂的活性显著提高,甲烷转化率为50%,对应的反应温度比未加L丑时降低了90℃.在先浸LB后浸Mn制备的催化剂C中,La的存在也使催化剂的催化活性大大改善,效果与催化剂A相当.当以先浸Mn后浸La的方式加入助剂时,催化剂B的比表面积降低,催化活性下降.     

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.