Au/MBFCN多组分复合型催化剂用于低温催化氧化丙烯制丙烯醛

钼铋系催化剂在丙烯氧化制丙烯醛反应中具有独特优势,但对反应温度、水汽配比的要求均较高。金催化剂的低温催化性能优异且对产物选择性高,我们结合二者的优势,通过调变载体制备过程中沉淀终止时的pH得到了一系列多组分复合氧化物担载金催化剂（Au/MBFCN）。反应结果显示,pH=4、载金量为0.5wt%时得到的催化剂Au/MBFCN-4性能较优,在水汽配比5vol%、反应温度300 ℃下,丙烯转化率可达22.9%,丙烯醛选择性为91.2%。用HRTEM、XRD、Raman和XPS等对催化剂进行表征,发现pH较低时得到的催化剂中MoO3、Bi2Mo3O12、Fe2(MoO4)3等活性晶相的含量较多,是Au/MBFCN-4低温催化性能优异的主要原因。     

钼酸铁超微粒子的制备及其选择性氧化正丁醇的研究

以Fe(NO3)3·9H2O和(NH4)6Mo7O24·4H2O为原料,采用溶胶-凝胶法于不同条件下制备Fe2(MoO4)3超微粒子催化剂,并研究了这些催化剂对正丁醇选择性氧化制备正丁醛的催化性能,从而找出Fe2(MoO4)3超微粒子催化剂选择性氧化正丁醇的最佳实验条件。结果表明,制备Fe2(MoO4)3超微粒子的适宜条件为:溶液初始pH=1.0,以EDTA为螯合剂,EDTA/(铁+钼)摩尔比为0.4时制得的催化剂对正丁醇的选择性氧化性能最好,此时正丁醛的产率可达39.3%。     

Mo-HMS的制备及其催化丙烯液相环氧化反应性能

采用一步水热法合成了Mo-HMS催化剂,并用X射线衍射、N2吸附-脱附、透射电镜、激光拉曼光谱和紫外-可见光谱对催化剂的结构及表面钼物种进行了表征.结果表明,一步水热法可将Mo物种引入HMS载体中,而不破坏分子筛孔道结构,Mo物种在载体表面呈多种分布状态,包括单核的钼物种、聚集状态的多聚钼酸根离子(如Mo7O246)和晶相MoO3.与浸渍法制备的MoO3/HMS及溶胶-凝胶法制备的MoO3/SiO2相比,一步法可以使催化剂中MoO3晶相的含量分别下降39%和61%,在丙烯与异丙苯过氧化氢的环氧化反应中,Mo-HMS表现出最佳的催化性能.这可归结于Mo-HMS中Mo物种较高的分散度.     

过氧化叔丁醇在钼催化剂下对咔唑的催化氧化研究

以油溶性过氧化叔丁醇(TBHP)为氧化剂,采用钼(Ⅵ)类催化剂,对油品中性质稳定的氮化物-咔唑进行了催化氧化研究。考察了钼催化剂及其载体对咔唑氧化的影响。结果表明,在无负载条件下,乙酰丙酮钼(MoO2(acac)2)的催化活性略高于三氧化钼(MoO3);经弱酸性树脂(D113)负载后,MoO3催化活性显著提高;三种载体(Al2O3、树脂D113和树脂D751)均能提高钼催化剂的活性,使咔唑转化率达到65%以上,其中MoO3/Al2O3催化活性最高。杂金属Ni和Co的加入导致MoO3/Al2O3催化活性降低。其次,进行了氧化反应选择性研究,实验发现在反应液中含有二苯并噻吩时,TBHP/MoO3/D113能优先氧化咔唑;而TBHP/MoO3/D751对咔唑和二苯并噻吩具有近似的氧化活性。最后根据光谱数据对咔唑系列产物的结构进行了初步推测。     

V2O5／C催化乙二醛氧化为乙醛酸的研究

选用V2O5作为催化剂,活性炭为载体,偏钒酸铵的草酸溶液为浸溃前驱体,采用等体积浸渍法制备了V2O5/C催化剂,将其应用于乙二醛的液相氧化．并对反应液用液相色谱进行了定性,在确定了催化体系中氧化产物的基础上,考察了V2O5含量和焙烧温度对催化剂催化性能的影响,利用XRD和TEM等手段对催化剂进行了表征．结果显示,V2O5含量较低时（w（V2O5）〈3％）,催化剂的活性组分分散度较高,乙二醛转化率和乙醛酸的选择性都随着V2O5的含量提高而逐渐增加;当负载量为3％时,催化效果最佳,乙二醛转化率和乙醛酸的选择性分别达到16．16％和76．75％;     

V-Mo-O催化剂的制备及催化甲苯合成苯甲醛的研究

甲苯低温液相催化氧化制备苯甲醛是最具有竞争力的苯甲醛绿色合成路线.我们研究了溶胶凝胶法制备的V-Mo-O催化剂在液相低温条件下选择性氧化甲苯制备苯甲醛的性能.结果显示,钒钼摩尔比和焙烧温度是影响催化剂的主要因素,当钒钼的摩尔比为6∶7,焙烧温度为500℃时,催化剂表现出最佳性能.物性表征显示,该条件下合成催化剂V-Mo-O晶体呈棒状结构,直径约700 nm,长度约6μm.体相主要以Mo6V9O40和MoO3相态存在.X光电子能谱表征显示,MoO3物种分散于结晶体外表面,这种不同氧化态钼物种的分层组装可能有助于氧物种的传递,有利于提高其催化性能.催化剂在80℃温度下,以双氧水为氧化剂,冰乙酸为溶剂,反应30 min,甲苯的转化率达到38.9%,苯甲醛的选择性为69.7%.     

负载型纳米Au/Cr_2O_3催化甘油氧化合成甘油酸

制备了一系列负载型纳米Au/Cr_2O_3催化剂,采用ICP、FTIR、XRD和N2吸附脱附对所制备的催化剂进行了表征.以3%的H_2O_2为氧化剂,考察其对甘油选择性氧化反应的催化性能.结果表明,该类催化剂在甘油选择性氧化反应中表现出了较好的催化性能,其中Au/Cr_2O_3(0.95%)的催化性能最好,甘油转化率可达81.5%,甘油酸选择性为67.0%,且该非均相催化剂重复使用10次后仍保持较高的催化活性.     

Na-W-Mn/SiO2催化剂体系中W和Mn对甲烷氧化偶联反应的作用

制备了一系列不同W,Mn含量的Na-W-Mn/SiO2催化剂,并进行了其催化甲烷氧化偶联反应性能评价和XPS,XRD表征.研究结果表明,W和Mn的含量分别为2.2%≤W≤8.9%和0.5%≤Mn≤3%时,催化剂具有较好的甲烷氧化偶联反应性能.Mn的表面浓度与甲烷的转化率和乙烯的选择性有较好的对应关系,W的表面浓度与乙烷的选择性有一定的关联,据此提出Na-O-Mn和Na-O-W都是甲烷氧化偶联反应的活性中心.反应的活性相是Na2WO4,Na2W2O7和Mn2O3.     

MoO3/SiO2催化剂的异丁烷选择氧化反应性能

分别采用浸渍法和溶胶－凝胶法制备了MoO3/SiO2催化剂，用XRD，TPR，IR，TPD和活性评价等手段对催化剂的影响，晶格氧活泼性，化学吸附性能和异丁烷选择氧化反应性能进行了研究。结果表明，催化剂表面由Lewis碱位Mo=M,Mo-O-Mo中的晶格氧和Lewis酸位Mo^6 构成，在MoO3/SiO2催化剂上，异丁烷主要通过甲基的H双位吸附在表面的Lewis碱位Mo=O上；在常压条件下，异丁烷选择氧化产物主要为异丁烷，甲基丙烯醛和甲基丙烯酸，其中深度氧化产物CO2主要由吸附的异丁烯继续反应生成；采用溶胶－凝胶法制备的MoO3/SiO2催化剂，可得到较高的异丁烷转化率和含氧有机物选择性。     

气态环己烷催化氧化制丁二酸酐的研究--纳米催化剂活性组分对目标反应的影响

本文以气态环己烷催化氧化制丁二酸酐为目标反应,对TiO2-Al2O3纳米复合载体上的添加组分进行了研究与探索.结果表明,实验条件下,活性最好的催化剂添加物组成为:V2O5负载量为载体质量的5.0%,P与V原子个数比为1.5,催化剂中Mo、Sb、K的质量百分含量分别为1.25%、0.6%、4.0%.     

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.     

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.     

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.     

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.     

Copper catalyzed/mediated synthetic methodology for ebselen and related isoselenazolones

Scope of the copper catalyzed/mediated selenium-nitrogen coupling reaction has been studied for the synthesis of isoselenazolones. It is noticed that the 2-chloro, 2-bromo-, and 2-iodo-aryl amides substrates can be exploited in the selenium-nitrogen coupling reaction by employing 25-100 mol % of CuI/1,10-phenanthroline (L) and potassium carbonate as a base in DMF. Furthermore, electron rich 2-chloro-arylamides also underwent selenium-nitrogen coupling reaction to give biologically important selenium-nitrogen heterocycles. Also, copper-catalyzed selenium-nitrogen coupling reaction has been meticulously applied for the synthesis of diaryl diselenides having methoxy, amine, and amide functionality from respective aryl iodides in the presence of stoichiometric amount of succinimide as an external Se-N coupling partner.