富氧条件下Ir催化NO反应

用浸渍法制备了系列Ir催化剂, 研究了富氧条件下Ir催化NO的反应, 考察了催化剂的催化反应性能及负载量和载体对催化活性的影响. 结果表明, 在Ir催化剂上不仅发生了NO氧化反应, 同时也发生了NO还原反应; Ir催化剂对NO反应有催化作用, 催化活性随Ir负载量的增加而增强. 载体对催化剂活性有一定的影响, 负载量低于0.1%(w)时, 催化NO氧化的活性顺序为Ir/ZSM-5>Ir/γ-Al2O3>Ir/SiO2, 这主要受载体自身性质的影响; 负载量高于0.1%时, 催化NO氧化的活性顺序为Ir/ZSM-5>Ir/SiO2>Ir/γ的活性顺序为Ir/γ-Al2O3>Ir/SiO2>Ir/ZSM-5, 这主要由于载体吸附作用促进了NO2在Ir催化剂上吸附分解. 与Pt催化剂相比, Ir催化剂更有利于促进NO还原.     

CO2气氛下负载型Cr2O3催化剂上乙苯脱氢制苯乙烯反应

 采用浸渍法制备了负载型Cr2O3/Al2O3和Cr2O3/SiO2催化剂,并考察了催化剂在CO2气氛下催化乙苯脱氢制苯乙烯反应的活性. 结果表明,Cr2O3/Al2O3的催化活性高于Cr2O3/SiO2. 这可能是由于Cr2O3在Al2O3载体表面的分散度大大高于在SiO2表面的分散度. 催化剂的催化活性与Cr2O3的负载量有关,在w(Cr2O3)=25%时,Cr2O3/Al2O3的催化活性最高. CO2气氛对乙苯脱氢反应有明显的促进作用; 在CO2气氛下,Cr6+物种可能是催化乙苯脱氢反应活性位的前驱体.     

钡修饰Ir/SiO2催化剂对氨分解促进作用的研究

研究了浸渍法制备的Ba修饰S iO2担载型铱(Ir)基催化剂(Ba-Ir/S iO2)在氨催化分解模型反应的作用。结果表明Ba的添加显著提高了催化剂的活性和稳定性。采用H2-TPR和H2-TPD对Ba-Ir/SiO2进行分析和研究,结果显示助催化剂Ba和活性催化组分Ir之间发生了强相互作用。Ba-Ir/SiO2在氨催化分解模型反应中的主要活性物种是零价态的Ir。     

金红石型氧化钛负载的铱在催化分解N_2O推进剂反应中的应用（英文）

氧化亚氮(N_2O)是一种性能独特优越的新型绿色推进剂,分解后可以生成高温富氧燃气,实现自增压式多种模式推进,是小卫星推进系统理想的推进剂选择,因而具有广阔的应用前景.在标准状态下,N_2O热分解反应活化能为250 k J/mol,致使其非催化热分解温度高达600 ℃,显然小卫星的能源系统无法满足,必须采取催化分解的手段,改变反应路径、降低反应活化能,使N_2O能够在较低的温度下分解.有关N_2O分解催化剂的报道很多,如纯相或复合氧化物、金属交换分子筛和负载贵金属等,但是这些催化剂仍然存在活性较低等问题,难以满足N_2O推进系统的应用需求.氧化钛是光催化和金催化常用的催化剂,经还原后能够形成氧缺陷,可以为涉氧反应提供电子,而N_2O分解会产生大量氧,氧脱附是其速率控制步骤,因而以氧化钛为载体,有望促进氧脱附及N_2O分解.与此同时,氧化铱具有较高的N_2O分解活性,而且与金红石型氧化钛晶格相似,相似的晶格参数可能会促进其在氧化钛表面的分散,进一步提高N_2O分解性能.基于此,本文以金红石氧化钛(r-TiO_2)为载体,采用匀相沉积沉淀法制备了不同载量的金红石氧化钛负载铱催化剂(Ir/r-TiO_2),并制备了锐钛矿型氧化钛、混合晶相P25和γ-Al_2O_3负载铱催化剂作为对比.通过活性测试我们发现,Ir/r-TiO_2催化剂显示了非常优异的N_2O分解活性,N_2O转化率明显高于参比催化剂,在250℃就能够开始分解,在300 ℃可以分解完全,而且当Ir含量降低到0.1%时,催化剂仍然保持与2 wt%Ir/γ-Al_2O_3相当的催化活性.随后我们采取多种表征手段对Ir/r-TiO_2的活性本质和N_2O分解机理进行了探究.首先利用BET、HAADF-STEM和XRD对催化剂的基本物性进行了测试,发现Ir/r-TiO_2具有较低的比表面积,但金属铱在金红石氧化钛表面表现出较高的分散度,平均粒径仅为1.25 nm.采用H-2-TPR和O 1s XPS考察了催化剂的电子特性和还原特性,发现Ir/r-TiO_2催化剂上高分散的Ir与氧的结合能较弱,易于还原,有助于N_2O的分解和生成氧的脱附.进一步采用原位N_2O-DRIFT对N_2O分解过程进行了研究,发现了桥式过氧物种,并据此提出了N_2O在Ir/r-TiO_2催化剂上的分解机理.     

共沉淀法制备氧化铝负载Co-Mo双金属氮化物催化剂

采用硝酸铝和硝酸钴的乙醇溶液与钼酸铵的碳酸铵水溶液共沉淀制备了Al2O3负载Co-Mo双金属氧化物前驱体,结合氨程序升温还原法制得了氮化物催化剂Co-Mo-N/Al2O3.利用X射线衍射和N2物理吸附方法表征了制备的前驱体和钝化态Co-Mo-N/Al2O3催化剂的晶相和孔结构,用程序升温脱附、程序升温表面反应及扫描电子显微镜考察了共沉淀法和浸渍法制备的催化剂的晶格稳定性、活性中心和表面形貌,用氨分解反应表征了Co-Mo-N/Al2O3催化剂的活性.结果表明,焙烧温度对催化剂比表面积有较大影响,低温焙烧的样品中活性组分散性较好,673K焙烧制得催化剂的氨分解活性最高.与浸渍法制备的Co-Mo-N/Al2O3催化剂相比,共沉淀法制备的催化剂具有更高的晶格稳定性、更均匀的活性组分分布和更高的氨分解活性.     

富氧条件下Ag/Al2O3和Cu/Al2O3组合催化剂催化C3H6选择性还原Nox的性能

 在全自动催化剂活性评价装置上,考察了富氧条件下Ag/Al2O3和Cu/Al2O3两种催化剂上催化丙烯还原NOx的活性. 在实验温度范围(200～650 ℃)内,Ag/Al2O3具有 优异的催化丙烯选择性还原NOx的活性,但同时有大量副产物CO形成. Cu/Al2O3选择性催化丙烯还原NOx的活性不高,却能有效促进CO的氧化. 在无水条件,Ag/Al2O3-Cu/Al2O3组合体系具有与Ag/Al2O3相似的脱除NOx活性,同时使CO在300 ℃以后几乎完全转化. 在10%水蒸气存在的情况下,Ag/Al2O3-Cu/Al2O3组合催化剂脱除NOx的活性下降,但水蒸气对CO转化率的影响不大.     

CuCl／SiO2-Al2O3催化剂的表面结构及甲醇氧化羰基化催化性能

通过掺杂Al对无定形层析硅胶进行表面改性,采用固体离子交换法制备了CuCl/SiO2-Al2O3催化剂,并考察了它在甲醇液相氧化羰基化合成碳酸二甲酯反应中的催化性能.结果表明,掺杂Al制备的SiO2-Al2O3载体仍保持了硅胶的无定形结构,比表面积降为200m2/g,但表面酸性明显增强,具有B酸中心.CuCl不仅分散于SiO2-Al2O3载体表面,而且与载体表面的B酸发生离子交换作用形成了表面Cu 物种,使催化剂比表面积降为148m2/g,且两种Cu 物种共同构成了催化活性中心.当CuCl/SiO2-Al2O3催化剂的Si/Al比为5,在500℃焙烧时,催化剂上甲醇氧化羰基化反应的碳酸二甲酯的选择性和时空收率分别达到74%和1.27g/(g.h).     

贵金属铱对氨分解用镍基催化剂的促进作用研究

用湿式浸渍法制备了不同贵金属质量分数的镍-铱双金属催化剂,以氨分解为模型反应对其催化性能进行考察.结果表明,贵金属铱的添加提高了10%Ni/γ-Al2O3的低温活性.在铱的质量分数不高于1%时,氨分解反应活性随铱质量分数的增加出现最大值(相应的Ir质量分数为0.7%),对应的10%Ni-0.7%Ir/γ-Al2O3催化剂在400 ℃时,氨分解率为43.55%,较单组分的Ni催化剂高40.0%.用H2-TPR、H2-TPD 、BET和XRD表征方法对催化剂进行了表征.结果表明,Ir与活性组分Ni之间存在协同作用.铱的添加促进了活性组分的分散、减小了镍的晶粒尺寸,且增加了催化剂活性位的数量,从而提高了催化剂的氨分解性能.     

纳米CeO2基固溶体催化柴油机碳颗粒物燃烧性能

采用柠檬酸溶胶鄄凝胶法制备CeO2基固溶体催化剂(Ce0.7Zr0.3O2-δ、Ce0.7Pr0.3O2-δ和Ce0.7Gd0.3O2-δ), 并考察了固溶体和三种常用载体(TiO2、SiO2和Al2O3)及其负载KNO3后的催化碳黑燃烧活性. 结果表明, CeO2基固溶体催化剂具有很高的催化燃烧活性, 其活性接近TiO2、SiO2和Al2O3负载30%KNO3催化剂的活性. 因为纳米CeO2基固溶体的形成, 提高了催化剂的抗烧结能力, 使氧更活泼, 从而提高氧化还原性能, 有利于碳颗粒燃烧. 由于CeO2基固溶体本身的高活性, 因此KNO3的添加不能明显提高CeO2基固溶体催化剂(尤其是Ce0.7Zr0.3O2-δ和Ce0.7Pr0.3O2-δ)的催化燃烧活性, 但KNO3能显著提高TiO2, SiO2和Al2O3的催化燃烧活性.     

稀土-铁催化剂催化还原烟气中SO2制硫磺

以煤气为还原气,以Fe为主活性金属,稀土为助剂催化还原冶炼烟气中SO2制取硫磺,研究了不同稀土、不同稀土含量及不同催化剂制备方式对稀土-过渡金属催化剂催化还原SO2制硫磺活性的影响,并考察了其反应机制.结果表明:不同稀土对Fe/Al2O3催化剂有不同的改性作用,Sm和Dy的加人大大提高了催化剂的活性,在360 ℃时,smFe/Al2O3的硫产率增大到86.62%,比同温度下Fe/Al2O3的提高了40.5%;在400℃时,DyFe/Al2O3的硫产率增大到91.62%.比同温度下Fe/Al2O3的提高了26.4%;REFe/Al2O3催化剂的活性与稀土含量有一定的关系,对SmFe/Al2O3催化剂,稀土Sm的最佳含量为1.0%;不同方式制备的稀土催化剂活性不同,对硫产率来说其大小顺序为:钐铁溶液混浸>先浸钐后浸铁>先浸铁后浸钐;煤气还原SO2的反应机制为中间产物机制.     

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%.     

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.     

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.     

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.     

Knoevenagel condensation catalyzed by novel Nmm-based ionic liquids in water

A series of novel N-methyl morpholine (Nmm) based ionic liquids with 1,2-propanediol group were synthesized and used as catalysts for Knoevenagel condensation at room temperature in water. Under the effect of the catalyst, various aldehydes or aliphatic ketones could react with a wide range of activated methylene compounds well, including malononitrile, alkyl cyanoacetate, cyanoacetamide, β-diketone, barbituric acid, 2-arylacetonitrile and thiazolidinedione. Furthermore, most of the products could be separated just by filtrating and washing with water. Additionally, the catalyst is recyclable and applicable for the large-scale synthesis.     

Construction of polyheterocyclic spirotetrahydrothiophene derivatives via sulfa-Michael/aldol cascade reaction

A series of polyheterocyclic spirotetrahydrothiophene derivatives were obtained in moderate to excellent yields via a catalyst-free sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 under mild conditions. We also present the first asymmetric sulfa-Michael/aldol cascade reaction of chalcones 1 and commercially available 1,4-dithiane-2,5-diol 2 with moderate to good enantioselectivities catalyzed by readily available chiral phase-transfer catalysts (PTCs).     

Suzuki-Miyaura reactions of the soluble guanylate cyclase inhibitor NS2028: a non-product specific route to C-8 substituted analogues

Both soluble guanylate cyclase (sGC) inhibitors ODQ 1 and NS2028 2 are synthesized via improved protocols. In the former case treating 3,4-dihydroquinoxalin-2(1H)-one oxime 8, which can be prepared in two steps from 1,2-benzenediamine, with 1,1′-carbonyldiimidazole (CDI) gives the dihydro-ODQ 10 that in the presence of KMnO₄ oxidises to give ODQ 1 in an overall yield of 46% starting from 1,2-benzenediamine. In the latter case, the synthesis affords NS2028 2 from 2-amino-4-bromophenol 3 in three steps with an overall yield of 85% and avoids the need for chromatography. Furthermore, Suzuki-Miyaura reaction conditions are described that enable the preparation of 8-aryl and 8-heteroaryl derivatives of NS2028 directly from NS2028 2. Finally, demethylation of the 8-(methoxyphenyl) substituted analogues afforded the 8-(hydroxyphenyl) derivatives 40-42. All new products are fully characterised.