在CeO2-ZrO2中加入La2O3对改善单Pd三效催化剂性能的作用

浸渍法制备了CeO₂-ZrO₂-La₂O₃复合氧化物，用XRD、热分析（TG-DTA，DSC）、BET表面积、H₂-TPR等对合成样品进行表征，研究了La₂O₃的加入对CeO₂-ZrO₂和单钯Pd/CeO₂-ZrO₂/γ-Al₂O₃/蜂窝陶瓷催化剂性能和热稳定性的影响。结果表明，在CeO₂-ZrO₂-La₂O₃中，La的存在能促进CeO₂-ZrO₂固溶体的还原，提高贮氧能力；在Pd/CeO₂-ZrO₂/γ-Al₂O₃中加入La有利于提高催化剂的耐热稳定性，阻止γ-Al₂O₃在高温下的晶相转变，进一步稳定Al₂O₃的结构，保持其高的表面积。在贵金属Pd的负载量为1 g·L^-1的条件下，测定了Pd/CeO₂-ZrO₂-La₂O₃/γ-Al₂O₃/蜂窝陶瓷催化剂对CO、C₃H₈和NOx的三效催化净化活性。结果表明，在Pd/CeO₂-ZrO₂/Al₂O₃/蜂窝陶瓷催化剂中加入La₂O₃后，能明显地改善催化剂的低温活性和三效催化性能，经1 000 ℃老化10 h后，CO、C₃H₈和NO_x净化的起燃温度（T₅₀）分别为330 ℃、350 ℃和380 ℃。     

固相浸渍法和湿浸渍法制备CuO/CeO2催化剂及其CO氧化性能的对比研究

采用固相浸渍法和常规湿浸渍法制备了一系列CuO/CeO₂催化剂,并结合X射线衍射（XRD）、氢气-程序升温还原（H₂-TPR）、激光拉曼光谱（LRS）、原位漫反射红外光谱（in situ DRIFTS）、X射线光电子能谱（XPS）等手段考察了制备方法对催化剂结构性质及其在CO氧化反应中性能的影响. XPS和H₂-TPR结果表明,固相浸渍法更有利于得到高分散的铜物种,并促进CuO物种的还原. LRS结果表明,相比于湿浸渍法,固相浸渍法能产生更多氧空位,而这些氧空位可以活化参与反应的O₂. CO氧化活性测试结果表明,当铜负载量相同时,固相浸渍法制备的催化剂相比于湿浸渍法表现出更好的催化性能. 结合多种表征结果发现,催化剂CO氧化性能与其表面氧空位和Cu⁺-CO浓度紧密相关,提出了CuO/CeO₂催化剂在CO氧化反应中可能的协同作用机制.     

载体材料对单Pd三效催化剂性能及催化活性的影响

采用共沉淀法制备了耐高温高比表面的La₂O₃-Al₂O₃(LA)以及铈含量分别为15%、33%和47%的储氧材料CeO₂-ZrO₂-La₂O₃-Al₂O₃(CZLA)、CeO₂-ZrO₂-La₂O₃+La₂O₃-Al₂O₃(CZL+LA)和CeO₂-ZrO₂-La₂O₃(CZL)₄类载体材料,并用浸渍法制备了整体式Pd/LA、Pd/CZLA、Pd/CZL+LA和Pd/CZL汽油车尾气净化三效催化剂,考察了载体材料对单Pd三效催化剂的影响。采用低温N₂吸附-脱附、H₂-程序升温还原(H₂-TPR)以及X射线光电子能谱(XPS)对载体材料及催化剂进行了表征,并考察了催化剂的空燃比性能和三效催化性能。结果表明,CZLA有效地结合了铈基和铝基载体材料的优点,表现出了优异的织构性能、热稳定性及还原性能。老化前后,其负载的单Pd三效催化剂在低温还原率、表面元素含量及Pd的电子结合能等性能方面表现出了最小的差异。催化剂活性测试结果表明,Pd/CZLA的三效窗口明显较宽,且拥有最低的起燃温度,尤其经1000℃老化处理后,其催化活性最高,C₃H₈、NO_x和CO的起燃温度分别为370、257和223℃。可见,相较于其他3种载体材料,CZLA更适合于负载单Pd三效催化剂,从而满足更高标准的三效催化剂的性能要求。     

碱土金属对ZrO2-Al2O3及其负载Pd-Rh密偶催化剂的影响

采用胶溶法制备了一系列碱土金属改性的ZrO₂-Al₂O₃, 并以其为载体采用等体积浸渍法制备了Pd-Rh密偶催化剂. 采用低温N₂吸附-脱附、X射线衍射(XRD)、氨气程序升温脱附(NH3-TPD)对载体样品进行了表征. 结果表明, 碱土金属的添加增大了ZrO₂-Al₂O₃的比表面积, Sr-Zr-Al样品经1000 °C焙烧5 h后具有最大的比表面积, 为164 m²·g^-1. 对催化剂进行了H₂程序升温还原(H₂-TPR)、X射线光电子能谱(XPS)和活性表征, 考察了催化剂对C₃H₈的转化活性. 测试结果表明, 添加碱土金属能有效提高催化剂上丙烷的转化活性.     

(CeO2)x-(La-Al2O3)1-x复合氧化物对柴油车尾气中可溶性有机成分的催化氧化

采用共沉淀法制备了一系列(CeO₂)_x-(La-Al₂O₃)_1-x复合氧化物(其中x为质量分数, x=0.00, 0.25, 0.50, 0.75, 1.00), 以其为催化剂. 采用热重-差热分析(TG-DTA)法模拟测试该系列催化剂对柴油车尾气中可溶性有机成分(SOF)的催化氧化性能. 结果表明, 当x=0.75时, 催化剂活性最高, 可使SOF在125℃起燃, 355℃完全转化. 并用低温N₂吸附-脱附, 储氧量(OSC)测试, X射线衍射(XRD), X射线光电子能谱(XPS)和H₂程序升温还原(H₂-TPR)等手段对催化剂进行了表征. 研究结果表明, 适量La 和Al 共掺杂增大了氧化铈的比表面积和催化剂中Ce³⁺所占的比例, 从而提高了催化剂对SOF的低温吸附能力和催化剂的储释放氧能力, 因而提高了催化剂对SOF的氧化活性. 所制备的(CeO₂)_0.75-(La-Al₂O₃)_0.25复合氧化物适合应用到柴油车尾气净化催化剂中.     

助剂对Ni/γ-Al2O3催化剂上多环烃JP-10重整制氢反应性能的影响

采用等体积浸渍法制备了碱金属Na、碱土金属Mg以及稀土金属Ce改性的15% Ni-5% M/γ-Al₂O₃镍基负载型催化剂(标记为NMA,M=Na、Mg、Ce)。通过XRD (X射线衍射)、N2吸附-脱附、H₂-TPR (H₂-程序升温还原)、TEM (透射电镜)、NH₃-TPD (NH₃-程序升温脱附)、TG (热重)和拉曼光谱技术对催化剂的物相、织构、表面性质等进行了表征分析,并在微通道反应器内研究了多环烃挂式四氢双环戊二烯(JP-10)催化重整制氢性能。结果表明,不同助剂的加入均在一定程度上提高了Ni/γ-Al₂O₃(NA)催化剂的活性和抗积碳性能。其中,NNaA催化剂的表面活性镍物种的浓度最高,颗粒尺寸最小,且其表面总酸量较低,在高温重整反应中对活性组分镍的抑制聚集作用最为明显,从而使其获得最佳的改性效果。在常压、750℃、水碳比(S/C)为2.4、重时空速(WHSV)为472 h^-1条件下,NNaA催化剂上JP-10的转化率和H₂选择性分别可达82.9%和73.3%,而积碳量仅为0.53 mg·g_feed^-1。反应后该催化剂的积碳多为丝状碳,而其他催化剂的积碳多为无定形碳。     

沉淀剂和Ag含量变化对甲醛降解性能的影响

采用不同沉淀剂制备CeO₂-Co₃O₄复合金属氧化物载体,通过浸渍负载不同含量Ag获得Ag/CeO₂-Co₃O₄催化剂.借助氮气物理吸附、XRD、Raman和H₂-TPR等手段研究了催化剂的物理化学性质.结果表明：当WHSV=30 000 mL·g^-1·h^-1时,催化剂能表现出良好的催化氧化甲醛性能,在≤ 90℃时实现甲醛的完全转化.草酸沉淀能有效降低Ce-Co氧化物的结晶度,使得Co²⁺含量增加,提供更多的氧空位,促进了氧分子的活化与迁移,从而提高了催化活性.随着Ag含量增加,使得由草酸沉淀制备的Ag/CeO₂-Co₃O₄催化剂的活性增强,且金属与载体间的相互作用也增强,当Ag负载量为1%（重量百分比）时活性最佳.     

焙烧温度对MnOx-CeO2-WO3-ZrO2催化剂上NH3选择性还原NO的影响

采用共沉淀法制备了MnO_x-CeO₂-WO₃-ZrO₂催化剂,考察了催化剂焙烧温度对O₂和H₂O存在下NH₃选择性催化还原（NH₃-SCR） NO的影响,并利用低温N₂吸附、X射线衍射（XRD）、透射电镜（TEM）、X射线光电子能谱（XPS）、NH₃程序升温脱附（NH₃-TPD）和CO脉冲反应对催化剂进行了表征. 结果表明在NH₃-SCR反应中,催化剂的低温活性随焙烧温度的提高而降低,这是由于催化剂表面化学吸附氧和酸性位减少引起的;催化剂的高温活性随焙烧温度的提高先增加后减小,这与催化剂表面最易释放氧数量的变化趋势相反. 700 ℃焙烧的催化剂具有良好的低温活性和最宽的反应温度窗口,在空速为90000 h^-1的条件下,该催化剂的起燃温度（50% NO转化率）为189 ℃,且反应温度在218-431 ℃范围内,NO转化率可达到80%-100%.     

一个新的满足未来排放标准的摩托车尾气净化催化剂

采用共沉淀法制备CeO₂-ZrO₂-La₂O₃-PrO₂-Al₂O₃复合氧化物载体材料,以浸渍法制备了Pd-Rh,Pt-Rh和Pt-Pd-Rh型整体式催化剂. 用N₂吸附-脱附、程序升温还原、储氧量和X射线衍射对其进行了表征,并考察了老化前后催化剂的空燃比特性、空速特性和温度特性. 结果表明,在三种催化剂中,Pt-Pd-Rh型催化剂表现出更优异的性能. 在40000 h^-1空速下,新鲜Pt-Pd-Rh型催化剂对C₃H₈,CO和NO的起燃温度T₅₀分别为239,187和191 ℃,ΔT （T₉₀ - T₅₀）分别为21,3和3 ℃. 老化后,C₃H₈,CO和NO的T₅₀分别为298,203和223 ℃,ΔT分别为22,5和13 ℃,且老化前后空燃比窗口较宽,适合于未来排放标准的摩托车尾气净化.     

铈铬比例对CeO2-CrOx复合氧化物催化剂上1,2-二氯乙烷催化氧化性能的影响

采用共沉淀法制备了不同铈铬比例的CeO₂-CrO_x复合氧化物(Ce/Cr 摩尔比分别为9/1、4/1、2/1、1/1、1/2、1/4、1/8)以及单纯的CeO₂和Cr₂O₃, 并研究了各催化剂对1,2-二氯乙烷(DCE)的催化氧化性能. 结果表明,相较于单纯的CeO₂, 不同铈铬比例的复合氧化物催化剂对DCE的催化氧化活性有明显提高, 其中Ce/Cr 摩尔比为2/1的CeO₂-CrO_x复合氧化物上DCE的氧化活性最好, 且只有极微量的含氯等副产物产生; 随着Ce/Cr 摩尔比减小, 对HCl的选择性有下降的趋势. 通过X射线衍射(XRD)、N₂吸附/脱附(BET)、紫外拉曼(UV-Raman)光谱、H₂程序升温还原(H₂-TPR)、NH₃程序升温脱附(NH₃-TPD)等实验技术, 研究了铈铬比例对铈铬复合氧化物的物理化学性质的影响. 结果表明, 适当比例Ce-Cr的复合, 形成了结构较稳定的Ce-Cr-O固溶体, 提高了催化剂活性氧物种的流动性, 催化剂表面酸量及强弱酸比例, 从而有利于DCE的吸附活化, 进一步脱氯降解以及深度氧化.     

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.