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1.
以Beta分子筛为载体,采用等体积浸渍法制备Fe-Mn/Beta催化剂,并对其在富氧条件下丙烯选择性催化还原NO性能进行了研究。通过N2吸附-脱附、X射线衍射(XRD)、X射线光电子能谱(XPS)、透射电子显微镜(TEM)、程序升温还原(H2-TPR)和原位漫反射傅里叶变换红外光谱(in-situ DRIFTS)等研究手段对催化剂进行表征,考察Mn组分对催化剂的物理化学性质、C3H6-SCR反应活性和反应中间产物的影响。结果表明,引入Mn物种可以显著提高Fe-Mn/Beta催化剂的低温催化活性,1.5Fe1.0Mn/Beta催化剂NO还原效率350℃最高可达99.4%,在250-400℃反应温度下显示出很高的反应活性和N2选择性。原位红外光谱研究表明,分子筛离子交换位上孤立的铁离子是丙烯选择性氧化的主要活性位,分散良好的MnO2物种不能提高催化剂对丙烯的活化能力,但有助于促进形成NO2吸附物种,从而提升了Fe-Mn/Beta催化剂的低温C3H6-SCR性能。经高温水热老化处理后,Fe-Mn/Beta催化剂脱硝活性明显下降,这与孤立的Fe3+离子迁移形成FexOy团聚物种有关。  相似文献   

2.
采用蒸氨法制备了镧(La)改性的负载型铜硅(Cu/SiO2)催化剂,并对其乙酸甲酯(MeOAc)气相加氢制乙醇(EtOH)的催化性能进行了研究。采用N2吸附-脱附(N2 adsorption-desorption)、X射线粉末衍射(XRD)、电感耦合等离子体发射光谱(ICP-OES)、氢气程序升温还原(H2-TPR)、傅里叶红外光谱(FT-IR)、高分辨透射电镜(HRTEM)、光电子能谱(XPS)和原子发射光谱仪(AES)等手段对催化剂进行了的表征,发现La物种的加入产生了较多的层状硅酸铜,增强了Cu和La物种之间的相互作用。La物种的加入在结构方面提高了催化剂的比表面积,降低了铜物种的粒径,提高了铜物种的分散度;在电子还原调控方面提高了Cu+的含量,增强了催化剂吸附酰基和甲氧基的能力。与未改性的Cu/SiO2催化剂相比,镧改性后Cu/SiO2催化剂的乙酸甲酯加氢性能得到大幅提升;其中La掺杂量0.5%的Cu/SiO2  相似文献   

3.
纳米催化材料的性能主要由粒子尺寸、形貌和界面决定,即活性位点的电子及几何结构.尺寸、形貌可控的纳米催化材料的合成及其反应性能的研究,即催化剂的构效关系,一直是催化领域的研究热点.氧化物负载的金属催化剂广泛应用于多相催化反应过程.基于氧化铈优异的氧化还原性能, Cu/CeO2催化剂在CO氧化、N2O消除、水气变换、甲醇合成等反应中表现出优异性能.其中,通过铜物种与氧化铈表面化学键合形成的金属-载体界面通常被认为是催化活性中心.铜物种和氧化铈的相互作用主要体现在氧化铈固定铜物种,而铜物种促进氧化铈的氧化还原能力,涉及Cu2+/Cu+/Cu0和Ce3+/Ce4+之间电子的传输和转移.Cu/CeO2催化剂活性位的原子结构与金属-载体相互作用程度密切相关.氧化铈形貌和铜负载量是决定界面电子和几何结构的重要因素.常见的纳米氧化铈形貌包括纳米粒子(多面体)、纳米棒和纳米立方体,可分别选择性暴露(111)、(110)和(100)...  相似文献   

4.
采用铜胺配合物(Cu2+-四乙烯五胺,Cu-TEPA)作为结构导向剂,通过一步水热法合成不同铜铝比(nCu/nAl)和硅铝比(nSi/nAl)的Cu-SSZ-13分子筛催化剂,研究其在贫燃条件下丙烯选择性催化还原NO(C3H6-SCR)的性能。当nCu/nAl=2、nSi/nAl=6时2.0Cu-SSZ-13(6)催化剂具有最好的低温脱硝活性,200℃时NO转化率超过80%,在250~300℃可实现100%脱硝效率和~100%N2选择性,同时具有较强的抗水、抗硫性能。为研究不同nCu/nAl和nSi/nAl对催化剂物理化学特性的影响,通过X射线衍射(XRD)、扫描电子显微镜(SEM)、N2吸附-脱附测试、H2程序升温还原(H2-TPR)、氨气程序升温脱附(NH3-TPD)、紫外可见光谱(UV-Vis)等手段对样品进行表征。结果表明,2.0Cu-SSZ-13(6)具有最佳的脱硝性能,这是因为其具有最大的比表面积、最强的表面酸性和分布最多的孤立态Cu2+离子。Cu-SSZ-13上丰富的酸性位可以有效促进C3H6和NO的吸附和活化,SSZ-13分子筛八元环中孤立的Cu2+离子具有良好的氧化还原性能,是C3H6-SCR反应的主要活性位。随着nCu/nAl的增加,孤立的Cu2+离子会在分子筛表面迁移、集聚形成CuO物种,从而导致C3H6-SCR活性下降。  相似文献   

5.
以Ti3AlC2和CuCl2·2H2O为前驱体,成功制备了Cu0纳米颗粒修饰和Cu2+自插层的手风琴状二维催化剂Cu0/Cu2+-Ti3C2Tx,用于电催化还原CO2。对材料的电化学性能进行了测试,结果表明,在CO2饱和的0.5 mol/L KHCO3电解液中,与原始的Ti3AlC2相比,Cu2+/Cu0-Ti3C2Tx催化剂电催化CO2转化为乙烯(C2H4)的起始电位从-0.65 V(vsRHE)降至-0.01 V(vs RHE),最大电流密度从0.19 mA/cm2增至2.50 mA/cm2  相似文献   

6.
采用共沉淀法制备Cu/Zn/Al前驱体,经甲酸处理后N2气氛焙烧得到Cu-ZnO-Al2O3催化剂(CZA)用于CO2加氢制甲醇反应。使用XRD、BET、TG-DSC、SEM、H2-TPR、N2O滴定、XPS-AES、CO2-TPD表征技术对催化剂的物相组成、结构性质以及Cu物种的比表面积、分散度以及价态分布进行分析和讨论。结果表明,甲酸处理调节了催化剂中Cu+与Cu0的比例,同时增加催化剂的中强碱性,并提高甲醇选择性。在W/F(H2/CO2=70/23)=10 g·h/mol、t=200℃、p=3 MPa反应条件下,使用HCOOH/Cu(物质的量比)=0.8甲酸处理获得的催化剂,CO2转化率6.7%,甲醇选择性达76.3%。  相似文献   

7.
355 nm光照下利用瞬态吸收光谱技术进行了有氧、无氧条件下二苯醚与亚硝酸体系的反应机理研究, 考察了其中瞬态物种的衰减行为, 并对其光解产物进行了GC-MS分析. 研究表明, HNO2在355 nm紫外光的照射下产生的OH自由基和二苯醚反应生成C12H10O-OH 加合物, N2条件下C12H10O-OH衰减的速率常数为(1.86±0.14)×105 s-1, 在有氧条件下, C12H10O-OH可转化为C12H10O-OHO2, 衰减的速率常数为(6.6±0.4)×106 s-1. N2条件下最终产物为苯酚、2-羟基二苯醚、4-羟基二苯醚、4-硝基二苯醚.  相似文献   

8.
以NH4Y分子筛为载体、 乙酰丙酮铜为铜源, 采用固相反应法制备了无氯CuY催化剂, 并用于催化甲醇氧化羰基化合成碳酸二甲酯(DMC). 结合不同反应时间催化剂的X射线衍射(XRD)、 N2吸附-脱附、 热重(TG)、 程序升温脱附/还原(NH3-TPD/H2-TPR)、 透射电子显微镜(TEM)和X射线光电子能谱(XPS)等表征结果, 分析了反应过程中Cu物种演变对其催化活性的影响. 结果表明, 新鲜催化剂中铜物种主要以Cu+形式存在, 占铜物种的48%; 随着反应的进行, 活性中心Cu+逐渐被氧化为Cu2+, 进而生成CuO物种, 部分CuO逐渐迁移至催化剂外表面. 在反应100 h内, Cu+含量逐渐减小至36.7%, CuO含量增加, 导致DMC的时空收率及选择性不断下降, 副产物二甲氧基甲烷(DMM)和甲酸甲酯(MF)的选择性逐渐提高. 当反应时间延长至190 h时, Cu+含量为33.6%, 略有下降, DMC的时空收率和选择性趋于平稳. 继续延长反应时间至300 h, 催化剂中铜物种状态基本不变, 催化剂催化性能保持稳定.  相似文献   

9.
铜基铈钴镧复合氧化物催化剂制备及其选择催化还原NO   总被引:1,自引:0,他引:1  
采用改进的共沉淀法制备铈钴镧复合氧化物(Ce-Co-La-O)载体,等体积浸渍负载活性组分Cu,制得铜基铈钴镧复合氧化物(Cu/Ce-Co-La-O)催化剂。考察该催化剂在富氧条件下对C3H6选择性还原NO反应(C3H6-SCR)的催化性能,并且利用BET、XRD、H2-TPR、Py-IR、TG和SEM等方法,研究催化剂结构与性能的关系。实验结果表明,Co能显著增加B(Brφnsted)酸的酸量并有效提高还原能力;La能进一步增加B酸的酸量并明显提高热稳定性;Ce-Co-La-O能够形成固溶体结构,发生良好的相互协同作用。因此,Cu/Ce-Co-La-O催化剂具有良好的低温催化活性和热稳定性,最佳催化活性温度为250 ℃,NO转化率高达81.6%,600 ℃时NO转化率仍可达52.5%。  相似文献   

10.
张俊峰  甘欣  傅文甫 《化学学报》2007,65(11):1071-1075
通过亲核取代反应, 在2,2'-联苯二酚氧基环氯磷腈母体N3P3(O2C12H8)2Cl2 (1)和N3P3(O2C12H8)Cl4 (2)上引入2-醛基吡啶与对胺基苯酚形成的席夫碱侧基, 合成了两种新型环磷腈化合物N3P3(O2C12H8)2(p-O-Ph-N=C-Py)2 (3)和N3P3(O2C12H8)(p-O-Ph-N=C-Py)4 (4), 这些化合物是一类能形成配合物的多齿配体. 通过元素分析, IR, 1H NMR, 31P NMR和TOFMS确定其结构, 研究了它们的吸收光谱和荧光光谱. H和Cu离子对其光谱性质的影响研究表明两种化合物的吸收和荧光光谱对H和Cu离子异常敏感, 因而在作为这些阳离子的荧光探针方面具有应用前景.  相似文献   

11.
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%.  相似文献   

12.
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.  相似文献   

13.
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.  相似文献   

14.
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.  相似文献   

15.
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.  相似文献   

16.
KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.  相似文献   

17.
The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.  相似文献   

18.
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.  相似文献   

19.
Zhanhui Yang  Shiyi Yang  Jiaxi Xu 《Tetrahedron》2017,73(23):3240-3248
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.  相似文献   

20.
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.  相似文献   

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