费-托合成Fe-Mo/SiO2双金属催化剂的性能

用原位穆斯堡尔谱和微型固定床反应器考察了Fe-Mo/SiO_2催化剂在还原、碳化和反应中的物相及费-托合成(F-T)反应性。富钼的Fe-Mo/SiO_2催化剂在550℃H_2中还原生成Fe-Mo合金,该合金在300℃合成气中碳化转化为Fe-Mo碳化物,是F-T反应中的主要物相。该催化剂的活性较高,其选择性体现了铁和钼的平均性质。富铁的Fe-Mo/SiO_2催化剂在550℃H_2中还原主要生成Fe~(2+),还有Fe-Mo合金和α-Fe,碳化时大部分转化为Fe~(3+),在F-T反应中的主要物相为Fe~(2+)及碳化铁,该催化剂的活性很低,其选择性类似于Fe-Mo/SiO_2。     

非担载铁—钼催化剂在氢还原过程中的物相研究

本文利用原位穆斯堡尔谱和XRD研究了10%Fe/MoO_3催化剂在氢还原过程中铁和钼的物相及其变化.结果表明.在铁和钼还原的同时,它们之间的相互作用增强,使得在350℃—500℃的温度范围内.升高还原温度,催化剂的还原度反而下降.在350℃铁可部分地还原为零价,这时钼仅还原为MoO_2在500℃,钼开始还原到零价.这时还原生成的Fe~0形成Fe-Mo合金,在550℃铁和钼全部还原为零价,铁以Fe-Mo合金存在,其穆斯堡尔谱显示精细结构.     

高分散费-托合成铁/活性炭催化剂的研究——Ⅰ.铁/活性炭催化剂的恒温还原及其穆斯堡尔谱

使用原位穆斯堡尔谱研究了非担载铁氧化物和不同担载量的铁/活性炭催化剂在不同温度下的还原,详细分析了活性炭载体上高分散超顺磁铁物类的穆斯堡尔谱。还原前铁/活性炭催化剂中的铁物类为结构松散的α-Fe_2O_3和没有充分脱水的氧化铁,铁的担载量不很小时可经Fe_3O_4还原到金属态,但活性炭载体可稳定Fe~(3+)使之难以还原,在500℃氢气中大部分铁才还原为金属。铁的担载量很小时,其还原以Fe~(2+)为中间产物,0.2%Fe/AC氢气化剂在500℃氢气还原18小时生成磁分裂金属铁和超顺磁金属铁(δ=0.37mm/s,△=0,H=0),其正的同质异能移表示了铁-活性炭间的电荷转移。     

高分散费-托合成/铁活性炭催化剂的研究——Ⅱ.铁-锰催化剂的恒温还原及其穆斯堡尔谱

使用原位穆斯堡尔谱考察了非担载铁-锰氧化物和铁-锰/活性炭(Fe-Mn/AC)催化剂在不同温度下的还原。还原前Fe-Mn/AC催化剂中存在的为超顺磁α-(Fe_1-_xMn_x)_2O_3和没有充分脱水的铁-锰氧化物。铁的还原同时受铁-锰和铁-活性炭相互作用的影响,载体活性炭使F~(3+)相对稳定而难以还原,锰则促进铁还原到Fe~(2+)并形成相对稳定的FeO-MnO固溶体而难以还原到Fe~0。对4%Mn-8%Fe/AC催化剂,即使在500℃氢气中处理,仍有相当数量的Fe~(3+)和Fe~(2+)不能还原。     

铁/活性炭催化剂的氮化及其碳化行为

用原位穆斯堡尔谱考察了不同担载量的Ｆｅ／ＡＣ催化剂的氮化以及随后的碳化行为。Ｆｅ／ＡＣ催化剂经５００℃Ｈ预还原后，于３５０℃流动态氨气中氮化５小时可生成ε－氮化铁，其穆斯堡尔谱呈双峰（δ～０．４２ｍｍ／ｓ，△～０．３２ｍｍ／ｓ）。再在合成气（２Ｈ２／ＣＯ）中进行碳化处理，ε－氮化铁中的氮原子可逐渐被碳原子取代而转化为氮碳化铁和碳化铁，但铁的担载量越高，这种取代越困难。８％Ｆｅ／ＡＣ催化剂在２５０℃     

高分散费-托合成铁/活性炭催化剂的研究Ⅲ.碳化性质

使用原位穆斯堡尔谱考察了具有不同担载量的Fe/AC以及Fe-K/AC和Fe-Mn/AC催化剂在300℃合成气(H_2/CO=2)中的碳化行为。发现在活性炭载体上铁的担载量(或分散度)制约着碳化时生成的碳化铁的种类。铁的粒径很小(～30A)时生成ε’-Fe_(2·2)C碳化铁,铁的粒径在70A左右可生成ε-Fe_2C碳化铁,而大粒子铁(>200A)和体相铁则生成x-Fe_5C_2碳化铁,Fe-K/AC和Fe-Mn/AC催化剂在碳化时生成的碳化铁种类仍受铁的粒径制约,助剂K和Mn不影响生成的碳化铁的种类,但Mn可延缓铁的碳化。     

K2O-Fe2O3系催化剂的穆斯堡尔谱研究

利用穆斯堡尔谱在K2O-Fe2O3催化剂中检出了α-Fe2O3(大晶粒及微晶)、KFeO2、K1+XFe11O17、α-Fe2O3和γ-FeOOH等物相,它们的相对含量取决于催化剂的含钾量及煅烧温度,相对含量的改变导致样品的穆斯堡尔谱图出现了复杂的变化.与XRD相比,穆斯堡尔谱可对钾与氧化铁的相互作用进行更有效的表征,穆斯堡尔谱和TPR研究都表明钾可延缓催化剂中Fe(III)的被还原.     

铬铁矿中四面体上亚铁和八面体上三价铁的次近邻效应

本文使用穆斯堡尔谱学研究了四个天然铬铁矿。在所研究的四个铬铁矿中,其中三个铬铁矿的谱被拟合成四面体A位置上三个或四个Fe~(2+)双峰和四面体A和八面体B位置上一个或二个Fe~(3+)双峰。第四个铬铁矿的谱拟合成四面体A位置上一个Fe~(3+)双峰和八面体B位置上二个Fe~(3+)双峰。所得到的四面体A位置上Fe~(2+)离子的同质异能位移为～0.9mm/s,八面体B位置上Fe~(3+)离子的同质异能位移为～0.3mm/s,以及在A位置和B位置上逐渐变化的四极分裂。本文计算出B位置上的二项式分布,并且使用次近邻效应解释了铬铁矿Ⅰ,Ⅱ和Ⅲ中A位置上Fe~(2+)离子和铬铁矿Ⅳ中B位置上Fe~(3+)离子在穆斯堡尔谱中所形成的多重四极双峰。     

K2O-Fe2O3系催化剂的穆斯堡尔谱研究

利用穆斯堡尔谱在K2 O Fe2 O3催化剂中检出了α Fe2 O3(大晶粒及微晶 )、KFeO2 、K1 XFe11O17、α FeOOH和γ FeOOH等物相 ,它们的相对含量取决于催化剂的含钾量及煅烧温度 ,相对含量的改变导致样品的穆斯堡尔谱图出现了复杂的变化 .与XRD相比 ,穆斯堡尔谱可对钾与氧化铁的相互作用进行更有效的表征 ,穆斯堡尔谱和TPR研究都表明钾可延缓催化剂中Fe(III)的被还原 .     

SO2-4对铁基催化剂上费托合成反应的影响

以FeCuK/SiO2为母体催化剂,用不同浓度的NH4HSO4水溶液进行等体积浸渍,制备了不同SO2-4含量的费托合成(FTS)铁基催化剂.采用原子发射光谱、低温N2吸附、 X射线光电子能谱、程序升温还原和穆斯堡尔谱等技术对催化剂进行了表征,并在H2/CO摩尔比0.67,WHSV=2 000 h-1,压力1.5 MPa和温度250 ℃条件下进行了浆态床FTS反应.结果表明,少量SO2-4能促进催化剂在H2中的还原;在合成气还原过程中,少量SO2-4对催化剂的碳化程度影响不大,但大量SO2-4严重抑制催化剂的碳化.在约500 h的运行实验中,各催化剂样品表现出的催化活性有所差异,但均呈现较好的稳定性.SO2-4可抑制水煤气变换反应活性,且随着SO2-4含量的增加,抑制作用愈加明显;同时,催化剂上浸渍少量SO2-4可有效抑制CH4的生成,提高低碳烯烃的选择性.     

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.