负载型P-Mo-V/SBA-15催化剂上的甲烷选择氧化反应

以磷钼钒杂多酸(H₅PMo₁₀V₂O₄₀)为前驱体、介孔SBA-15为载体, 采用浸渍法制备不同负载量的P-Mo-V氧化物催化剂. 在甲烷选择氧化反应中, 考察了负载量、反应温度、空速等对甲烷转化率和产物选择性的影响. 结果表明, 催化剂对甲烷选择氧化制甲醛具有较高活性, 甲烷转化率随负载量的增大和反应温度的升高而提高, 甲醛的选择性随负载量的增大先升后降. 反应温度为640 ℃、空速为48300 L•kg^－1•h^－1、氧化物负载量w＝2.89%时, 甲醛的时空产率最高(295 g•kg_cat^－1•h^－1). 多种表征表明, 氧化物负载量w≤2.89%时, P-Mo-V氧化物在载体介孔孔道内以高分散形式存在. 催化剂的酸性和氧化还原性质与负载量相关, NH₃-TPD和H₂-TPR的测试结果表明, 较弱的酸性位和较低还原温度的活性组分有利于甲烷选择氧化制甲醛.     

不同载体负载的Cr基催化剂催化CO2氧化异丁烷脱氢制异丁烯

制备了介孔分子筛MSU-1,γ-A12O3,AC(活性炭)和MgO负载的CrOx催化剂,并考察了其催化CO2氧化异丁烷脱氢制异丁烯反应性能.结果表明,各催化剂活性的顺序为:CrOx/MSU-1 ＞CrOx/A12O3＞ CrOx/AC＞ CrOJMgO.其中在CrOx/MSU-1催化剂上,异丁烷的转化率和异丁烯的收率分...     

一步催化合成二苯甲烷二氨基甲酸甲酯

研究了以H4SiW12O40-ZrO2/SiO2为催化剂,碳酸二甲酯(DMC)、苯胺和甲醛溶液为原料,一步催化合成二苯甲烷二氨基甲酸甲酯(MDC)的反应,考察了反应时间、反应温度和H4SiW12O40负载量等反应条件对催化性能的影响.适宜的反应条件是:DMC/苯胺/甲醛摩尔比为20/1/0.05,H4SiW12O40负载量为10%,443 K下反应7 h后降温到373 K下反应4.5 h.在此优化条件下,MDC的收率为24.9%.     

Li-Nd-Mg氧化物上甲烷氧化偶联

自从1982年Keller首先报导了甲烷氧化偶联制乙烯、乙烷的催化反应以来,引起国内外广泛的重视,若甲烷的转化率C达35%,C_2的选择性S(C_2)达88%,乙烯/乙烷较大时,则甲烷氧化偶联催化过程可以工业化.当前国内外的工作重点是寻求甲烷转化率高,C_2选择性好的催化剂.Li和烯土复合氧化物催化剂引起人们注意,C_2的收率Y(C_2)可达24.6%,本文采用高温灼烧而成的Li-Nd-Mg复合氧化物,Y(C_2)可达31.3%. 实验部分Li-Nd-Mg复合氧化物由高温灼烧而成,实验采用小型固定床石英反应器,反应器的直     

La_2O_3/γ-Al_2O_3催化剂用于二甲醚二氧化碳重整制氢

采用等体积浸渍法制备了不同负载量的La2O3/γ-Al2O3催化剂,并考察了负载量和反应温度对催化剂用于二甲醚二氧化碳重整制氢反应的性能影响。结果表明,反应温度为550℃、La2O3负载量为15%时,催化剂表现出最好的性能:二甲醚的转化率为100%,二氧化碳的转化率达到85.4%,产物氢气的选择性高达93.3%,一氧化碳的选择性为76.04%,副产物甲烷的选择性仅为6.3%。550℃时其平均积炭速率为1.387 5 mg/(g·h)。研究还利用XRD、BET、TEM、TG等方法对催化剂进行了表征。     

La2O3助剂对Co/AC催化剂上费-托合成反应性能的影响

 通过改变稀土助剂La2O3的负载量,考察了La2O3助剂对活性炭负载Co基催化剂(Co/AC)上费-托合成性能的影响,并通过XRD, SEM, TPR和CO-TPD对催化剂进行了表征. 结果表明, La2O3的加入可提高催化剂的活性,降低产物中甲烷的选择性. 对于15%Co/AC催化剂,加入少量的La2O3(w(La)=0.7%～1.7%)可使CO转化率从27%升高到56%, 甲烷选择性从16.5%下降到7.8%,C5+选择性从55.4%升高到74.7%; 但加入过多的La2O3(w(La)=8.1%～12.4%)时,甲烷选择性反而升高. XRD和SEM结果表明, La2O3的加入提高了催化剂中Co的分散度. TPR和CO-TPD结果表明, La2O3与Co之间存在着相互作用,并使催化剂的还原度下降,尤其是La2O3负载量高的催化剂还原度下降更加明显,导致Co/AC催化剂上CO的高温吸附量的增加.     

CO_2催化加氢甲烷化负载型铁催化剂性能的研究

用浸渍法制备了一系列无机氧化物负载的金属铁催化剂 ,在 CO2 加氢甲烷化反应中考察了催化活性 .结果表明 ,载体对铁催化剂的活性影响显著 :其顺序为 Ti O2 >Zr O2 >海泡石 >Al2 O3>Si O2 .CO2 转化率及甲烷选择性均与金属负载量、空速和原料气配比有关 ;制备过程中的氨处理有利于催化剂活性的提高 ;第二组分 族及非 族金属的添加对催化活性具有较大影响 .     

VPO催化剂制备条件对其催化甲苯氨氧化反应性能的影响

 用浸渍法制备了负载型钒磷氧(VPO)催化剂,并以甲苯氨氧化合成苯甲腈为探针反应,考察了载体、还原剂、P/V比和V2O5负载量对催化剂性能的影响. 结果表明,大比表面积SiO2负载的VPO催化剂性能稳定,在高温下也具有较好的选择性. 采用不同还原剂制备的催化剂在反应一段时间后活性趋于一致,表明催化剂活性中心是在反应气氛下形成的. P/V比对催化剂活性和结构影响较大,P的加入破坏了V2O5的晶型结构,使磷酸盐物种从催化剂体相向表面聚集,减少了催化剂表面存在的过度氧化物种O-和O-2的数量,选择性氧化物种晶格氧(O2-)起主要氧化作用,提高了催化剂的选择性. V2O5负载量增大,催化剂活性提高,但生成苯甲腈的选择性降低. 表面单分子层覆盖的VOx可能是反应的活性位和选择性位.     

甲烷部分氧化制合成气Ni/MgO和Ni-MgO/MgO催化剂的研究

甲烷氧化偶联制乙烷、乙烯以及甲烷选择氧化制甲醇、甲醛等反应 ,因其转化率和收率低 ,故短期内无法实现工业化 .目前 ,工业上应用甲烷蒸汽转化制合成气 ,进而合成氨等化工产品 .甲烷蒸汽转化制的合成气 ,其 H2 /CO≥ 3,不适用于甲醇合成和 F- T合成 .而甲烷部分氧化制的合成气 ,其H2 /CO≤ 2 ,因而最适合用于甲醇合成和 F- T合成 ,故近 1 0年来倍受科学家的关注[1 ,2 ] .在 CH4部分氧化制合成气中 ,钌、铑、钯、铂等贵金属催化剂的活性高、选择性好、稳定性好[1 ] ,但价格昂贵 (负载量以 1 2 %～ 4 0 %为佳 ) ,因而难以实现商品化 .N…     

发烟硫酸中Pd／C催化甲烷选择氧化制甲醇

以PdCl2为前驱体,采用浸渍法制备了Pd/C催化剂,并在发烟硫酸中考察了其催化甲烷选择氧化反应的性能,采用X射线粉末衍射、X射线光电子能谱、高分辨透射电镜和CO吸附等方法对催化剂进行了表征. 甲烷选择氧化反应得到的主产物硫酸单甲酯经水解后得到甲醇,在5%Pd/C催化剂、Pd用量30 μmol、反应温度180 ℃、反应压力4.0 MPa、反应时间 4 h 和发烟硫酸中SO3含量为50%的优化工艺条件下,甲烷转化率为23.6%, 甲醇的选择性和收率分别为69.5%和16.4%, 在一定程度上可实现催化剂的多次重复使用. Pd/C催化剂上的甲烷选择氧化反应可能遵循亲电取代机理,催化性能与Pd负载量、Pd粒子尺寸和分散度等有关.     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

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.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.