Fe—Zn—M／HZSM—5复合催化剂上CO2加氢性能的研究

研究了380℃、5.0MPa条件下,在Fe-Zn-M/HZSM-5(M=Cr、Al）复合催化剂上进行的CO2催化加氢的反应,考察了Fe-Zn-M中Fe含量、分子筛的硅铝比及Fe-Zn-M/HZSM-5的比率对CO2转化率和产物选择性的影响。结果表明,随着Fe含量的增加,复合催化剂的活性增强、目的产物选择性降低;Fe-Zn-M与HZSM－5间有适宜的配比;分子筛的硅铝比影响到复合催化剂的活性和选择性,随着分子筛硅铝比的降低,复合催化剂的活性增强,目的产物选择性提高。     

Ni晶粒粒径对Ni/SiO_2催化月桂酸甲酯脱氧制烃性能的影响

采用等体积浸渍-干燥-还原法及等体积浸渍-干燥-焙烧-还原法制备了3种具有不同Ni晶粒粒径的Ni/SiO2催化剂,利用H2-TPR、XRD、TEM、H2-TPR、NH3-TPD及TGA技术对其及前驱体进行了表征,并在固定床反应器上评价了其催化月桂酸甲酯脱氧制十一烷(C11)和十二烷(C12)的性能,分析了Ni晶粒粒径对其脱氧性能的影响。结果表明,采用等体积浸渍-干燥-还原法制备的催化剂中Ni晶粒粒径较小,提高还原温度可以促进Ni晶粒长大。随Ni晶粒粒径增大,月桂酸甲酯的转换频率提高,而C11和C12总选择性、C11/C12物质的量比及裂解产物选择性降低,Ni/SiO2催化剂上月桂酸甲酯脱氧为结构敏感反应。此外,还考察了重时空速对Ni/SiO2催化剂脱氧性能的影响,随重时空速提高,月桂酸甲酯转化率、C11和C12总选择性、C11/C12物质的量比及裂化产物选择性降低。月桂酸甲酯通过脱羰/脱羧反应路径生成的CO/CO2几乎全部加氢转化为CH4,表明Ni/SiO2催化剂具有很高的甲烷化活性。研究还发现,较小Ni晶粒烧结、有机物种吸附及积炭会导致催化剂失活。     

多级孔Fe-HBeta分子筛的合成及其催化性能探究

采用软模板法一步合成了一系列铁同晶取代的多级孔Beta分子筛(nFe-HBeta,n=Fe/Al),并通过等体积浸渍法制备出系列Ni基催化剂(10Ni/nFe-HBeta)。结果表明,系列nFe-HBeta均为结晶度高、孔道结构丰富的片状结构。异质铁原子的引入在降低介孔相有序度的同时,促使沸石颗粒粒径下降,中强酸性位点数量显著减少。对于10Ni/nFe-HBeta催化剂而言,骨架铁与NiO之间存在协同作用,可增强活性组分Ni与载体间的作用力,提高活性金属Ni的分散度,降低NiO颗粒粒径。在乙醇水蒸气重整催化反应中,铁元素的引入可规避酸性位以抑制乙醇脱水反应,同时加强CO和CH_4的水蒸气重整反应,有效提高H_2选择性。其中,10Ni/0.15Fe-HBeta催化剂在500℃时,H_2选择性高达72.15%,C_2H_5OH转化率为99.6%,反应12 h后的积炭量仅为4.3%。     

担载Ru-Co原子簇催化剂在乙烯甲酰化中的催化行为

众所周知，催化活性和选择性与活性组分的粒度、结构有很大的关系，而通过金属有机原子簇化合物载于无机载体上可以获得金属高分散度和金属组分组成均匀的催化剂，在一系列反应中显示了较高的活性和选择性[1-3]．在前面的研究中，肖丰收等报导了担载的Ru－CO双金属原子簇催化剂在CO＋H2反应中对含氧化合物的形成显示了很高的活性和选择性[4-5]．在本文中，作者利用红外光谱等技术研究了在SiO2担载的Ru－Co双金属原子簇催化剂上乙烯甲酸化反应，并对含氧化合物的形成机理进行了讨论．1实验部分在催化剂的制备过程中所有的操作都是在高纯…     

钐改性Ni/Al_2O_3催化剂及其用于甲醇水蒸气重整制氢反应研究

采用浸渍法制备Sm改性Ni/Al_2O_3催化剂并将其用于甲醇水蒸气重整制氢,考察了不同负载量Sm对Ni/Al_2O_3催化剂性能的影响。结果表明:Ni/Al_2O_3催化剂中添加Sm有利于NiO的形成,使还原后的催化剂得到更多的活性组分Ni,从而提高H_2的选择性和CH_3OH的转化率,降低CO的选择性。此外, Sm的最佳负载量为10%,此时H_2选择性为95.8%,甲醇转化率为92.6%, CO的选择性降至4.9%。当Sm负载量高于10%时,催化剂中NiO粒径过大,催化剂性能降低。     

N,O共修饰的Ni纳米颗粒/氮掺杂介孔碳CO2高效电还原催化剂

利用可再生电力能源将CO2电还原(CO2RR)为高附加值燃料和化学品(CO、甲酸盐和碳氢化合物等)是一种高效、绿色的CO2资源化利用新技术.然而,由于CO2分子中双键难以活化,且存在析氢竞争反应,即使对于CO2电还原为CO这一简单反应,除少数贵金属(Au、Ag和Pd及其合金)外,当前大多数电催化剂对产物CO的选择性和活性仍较低.因此,开发高效、稳定且廉价的CO2RR催化剂具有重要意义.过渡金属Ni储量高、成本低,是潜在的CO2RR催化剂.然而,受限于Ni对*H及*CO等中间物种相对强的吸附能力,Ni基催化剂催化生成产物CO的活性和选择性较低.近年来研究表明,通过对Ni基材料进行表面修饰,可以调控Ni表面与中间物种的吸附强度,从而有效提升Ni基催化剂对CO2RR反应的活性和选择性.鉴于此,本文通过N,O共调控的策略对负载于N掺杂介孔碳上的Ni纳米颗粒进行表面修饰,制得的N,O-Ni/CMK3催化剂能够高效、高选择性地将CO2电还原为CO.X射线衍射、高角度环形暗场扫描透射电子显微镜和X射线光电子能谱等表征结果表明,N,O-Ni/CMK3中的Ni纳米颗粒由金属Ni核和N掺杂的NiO壳组成,即Ni纳米颗粒表面被N,O共调控,这种独特的表面使其表现出与金属Ni不同的CO2RR催化性能.电化学测试结果表明,在0.5 M KHCO3电解液中,N,O-Ni/CMK3催化剂表现出较好的选择性(生成CO法拉第效率达97％)、活性(CO分电流密度为13.01 mA cm?1)和转换频率(4.25 s?1).表征结果表明,N,O共同调控的Ni是该催化反应的活性中心.此外,得益于N,O共调控的Ni表面,N,O-Ni/CMK3催化剂比O调控的Ni催化剂具有更好的电化学稳定性.本文通过调节Ni催化剂的表面化学环境来调控催化剂与反应中间物种的吸附强度,显著提高了Ni基催化剂对CO2RR反应的催化活性和CO选择性,为开发高活性、高选择性的过渡金属催化剂提供了新思路.     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响

在Y分子筛上浸渍0.1 wt% Pd和0.1–0.5 wt% Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni2+离子交换.采用程序升温还原表征了HY分子筛负载的Pd, Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450 oC和1 atm条件下进行.结果发现,当0.1 wt% Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理. Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

Fe-Zn-M/HZSM-5复合催化剂上CO_2加氢性能的研究

研究了 380℃、 5 .0 MPa条件下 ,在 Fe- Zn- M/ HZSM- 5 (M=Cr、 Al)复合催化剂上进行的 CO2 催化加氢的反应 .考察了 Fe- Zn- M中 Fe含量、分子筛的硅铝比及 Fe- Zn- M/ HZSM- 5的比率对 CO2 转化率和产物选择性的影响 .结果表明 ,随着 Fe含量的增加 ,复合催化剂的活性增强、目的产物选择性降低 ;Fe- Zn- M与 HZSM- 5间有适宜的配比 ;分子筛的硅铝比影响到复合催化剂的活性和选择性 ,随着分子筛硅铝比的降低 ,复合催化剂的活性增强 ,目的产物选择性提高     

CO在Ni/Ti2O3体系上吸附的DV-Xα研究

用DV-X_α方法计算了Ni_3Ti_2O_3,CO-Ni_3Ti_2O_3,CO-Ni_4和CO-Ni_3Ti各原子簇的电子结构。这些原子簇分别模拟担载在Ti_2O_3上的金属Ni,CO在Ti_2O_3担载的Ni表面的化学吸附,CO在纯Ni及Ni_3Ti表面上的化学吸附。比较计算的结果表明,Ti~(3+)离子和金属Ni之间形成强共价键;成键过程中电子由Ni向Ti~(3+)转移,Ni原子带0.07个正电子电荷。计算的Ni-CO键和C—O键的Mulliken重叠集居指出,Ti~(3+)-Ni之间的强成键及电子转移没有导致Ni吸附CO的活性降低及吸附的CO的活化程度的提高。这就表明,电子因素,即Ti~(3+)-Ni之间的强成键及电子转移似乎不是导致所谓的金属载体强相互作用(SMSI)的主要原因。     

金属含量对Ni-Pd/H-Y上正癸烷加氢异构化反应活性和产物选择性的影响（英文）

在Y分子筛上浸渍0.1 wt%Pd和0.1–0.5 wt%Ni,用X射线衍射表征了该催化剂的结晶度,用透射电镜测得平均金属粒径.催化剂中Pd和Ni的化学态用X射线光电子能谱测定,其酸性则用氨-程序升温脱附进行了表征,发现一些酸位被Ni~(2+)离子交换.采用程序升温还原表征了HY分子筛负载的Pd,Ni和Pd-Ni催化剂的还原性能.正癸烷加氢异构化反应在200–450℃和1 atm条件下进行.结果发现,当0.1 wt%Pd/HY中Ni添加量增至0.3 wt%时,正癸烷转化率和异构化选择性增加.单支链和双支链异构体选择性的增加表明该反应遵循质子化环丙烷中间体机理.Ni添加量超过阈值导致活性和异构化选择性急剧下降.综上可见,双金属催化剂更有利于选择性生成双支链异构体,其辛烷值更高.     

CO hydrogenation over small Pt, Ir and Pt?Ir bimetallic clusters entrapped in the supercage of NaY zeolite

In CO hydrogenation, small (ca. 1 nm) Pt–Ir bimetallic clusters encapsulated in the supercage of NaY zeolite showed significant non-linear Schulz-Flory distributions, especially high selectivity for C₄ hydrocarbons, which is different from those of Pt or Ir clusters entrapped inside the supercage of NaY.     

FTIR studies of zeolite matrix effects on the properties of palladium clusters confined in the supercages of NaX and NaY

Palladium clusters have been synthesized by the "ship-in-a-bottle" approach in the supercages of NaX and NaY faujasite zeolites. In comparison with CO adsorbed on a bulk Pd electrode, the same molecule adsorbed on the Pd clusters electrodes evoked an enhanced IR absorption (EIRA). The enhancement factors have been determined to be about 38 and 51 in NaX and NaY, respectively. IR band centers of linear-bonded CO, bridge-bonded CO, and multi-bonded CO in NaX are measured, respectively, 12, 14, and 11 cm(-1) lower than those of the corresponding adsorption modes in NaY. The adsorption of CO and the oxidation of adsorbed CO in NaX matrix are faster than that in NaY matrix. These results suggest that part of the Pd2+ ions in NaX are located in sites III and III' that are near the 12-ring window of the supercage of zeolite, which lead to the formation of small Pd clusters. The present study is of significant importance in exploring the dependence of catalyst properties on structures, as well as in understanding and predicting the locations and properties of metal clusters in zeolites.     

Highly active Pd containing EMT zeolite catalyst for indirect oxidative carbonylation of methanol to dimethyl carbonate

Palladium containing EMT zeolite catalyst(Pd/EMT) was prepared and used for the indirect oxidative carbonylation of methanol to dimethyl carbonate(DMC).The EMT zeolite was employed as a new catalyst support and compared with the conventional Pd containing FAU zeolite catalyst(Pd/FAU).The Pd/EMT in contrast to the Pd/FAU catalyst exhibited high intrinsic activity with the turnover frequency of 0.25 s^-1 vs.0.11 s^-1.The Pd/EMT catalyst showed high CO conversion of 82% and DMC selectivity of 79%,that maintained for at least 130 h,while the activity of the Pd/FAU catalyst rapidly deteriorated within 12 h.The enhanced interactions between Pd and EMT zeolite inhibited the sintering of palladium clusters and maintained the Pd2+ active sites in the Pd/EMT catalyst.The stabilization of the mono-dispersed Pd clusters within the EMT zeolite is paramount to the excellent performance of the catalyst for the indirect oxidative carbonylation of methanol to DMC.     

嵌入Y型分子筛中钯簇合成与结构的研究

Pd clusters encaged in Y-zeolite (Pd0Y) have been prepared by means of exchanging zeolite HY with [Pd(NH3)4]2+ under microwave radiation. The product formed was deaminized by heating, washed sufficiently with de-ionized water and reduced with hydrogen. The crystal phase diffraction of Pd was not found in the XRD spectrogram of Pd0y. According to polycrystal X-ray diffraction data. Radial Electron Distribution Function (REDF) of Pd0Y was calculated to elucidate the structure of Pd cluster. The results show that the Pd clusters are of the Al type closely packed arrangement. The dimension of them is about 12 Å. They are encaged in the supercage of zeolite Y. Their occupancy on the supercage is as small as 0.06 so that the framework structure of zeolite Y is unchanged. Therefore, the high dispersing Pd cluster aggregating in supercage exhibit strong catalytic effect. The CO-conversion of Pd0Y with Pd 0.72% and 6.13% (in mass fraction) is 67 % and 100 % (in volume fraction) respectively. Evaluation conditions:
mixed gas containing 0.02% CO and air,
space velocity 3000 h-1,
reaction temperature 0 ℃.     

An appropriate one-pot synthesis of dihydropyrimidinones catalyzed by heteropoly acid supported on zeolite: An efficient and reusable catalyst for the Biginelli reaction

A mild and efficient catalytic method has been developed for the synthesis of 3,4-dihydropyrimidin-2 (1H)-ones (DHPM) by a one-pot three-component cyclocondensation reaction using molybdophosphoric acid (MPA) supported on Y zeolite in high to excellent yields. The reaction investigated in the presence of molybdophosphoric acid encapsulated in the supercage of zeolite for comparison. In the second method, no appreciable progress was observed due to large size of dihydropyrimidinone compounds towards the supercage dimension of Y zeolite. In addition, the catalyst was recovered and reused for several times without efficient loss in catalytic activity.     

高活性甲醇氧化羰基化CuY催化剂的结构及催化活性中心

采用硝酸铜溶液和NaY分子筛溶液离子交换制备了CuY催化剂,通过加入氨水提高交换溶液的pH值以及高温焙烧活化,显著提高了甲醇氧化羰基化合成碳酸二甲酯的催化活性,与固相离子交换、沉积和浸渍法制备的催化剂相比,虽负载的铜量较低,但催化活性较高. 通过元素分析、XRD、H2-TPR、XPS和AES等对CuY催化剂微观结构的表征表明,在Cu(NO3)2离子交换溶液中加入氨水,促进了Cu2+离子交换的进行,提高了CuY催化剂的Cu交换量,并且交换的Cu2+主要落位于分子筛的超笼中. 在惰性气氛中焙烧活化CuY催化剂,Cu2+自还原为Cu+,氨促进了自还原过程的进行,显著提高了催化剂的活性. 焙烧活化温度越高,越有利于超笼中Cu2+→Cu+的自还原过程,使超笼中Cu+的含量增加, CuY催化活性增加. 进一步研究表明Y分子筛超笼中的Cu+是主要的催化活性中心.     

Boosting Size‐Selective Hydrogen Combustion in the Presence of Propene Using Controllable Metal Clusters Encapsulated in Zeolite

A strategy is presented for making metal clusters encapsulated inside microporous solids selectively accessible to reactant molecules by manipulating molecular sieve size and affinity for adsorbed molecules. This expands the catalytic capabilities of these materials to reactions demanding high selectivity and stability. Selective hydrogen combustion was achieved over Pt clusters encapsulated in LTA zeolite (KA, NaA, CaA) in a propene‐rich mixture obtained from propane dehydrogenation, showing pore‐size dependent selectivity and coking rate. Propene tended to adsorb at channels or external surfaces of zeolite, interfering the diffusion of hydrogen and oxygen. Tailoring the surface of LTA zeolite with additional alkali or alkaline earth oxides contributed to narrowing zeolite pore size and their affinity for propene. The thus‐modified Pt@KA catalyst displayed excellent hydrogen combustion selectivity (98.5 %) with high activity and superior anti‐coking and anti‐sintering properties.     

Generation of active site confined inside supercage of NaY zeolite on a nano-scale and its ethylene polymerization

To generate an active site that consisted of one Cp₂ZrCl₂ molecule and 1-2 MAO molecules inside supercage of NaY zeolite, two preparation ways for supported catalyst were estimated. First, higher concentration of MAO and Cp₂ZrCl₂, and long reaction time were introduced during the preparation of supported catalyst. It showed activity in ethylene polymerization without any additional MAO. It indicates that Cp₂ZrCl₂ coordinated with only 1-2 MAO molecules could be an active site due to the fact that supercage has nano-scaled diameter of supercage, 1.2 nm, and it could contain only 1-2 MAO molecules inside it theoretically. In situ generation of active site between NaY/MAO and homogeneous Cp₂ZrCl₂ also showed experimental evidence that an active site was generated inside the supercage of NaY zeolite. It showed low activity with long activation time, suggesting the presence of a diffusion effect of Cp₂ZrCl₂ in the pore of NaY. However, NaY/Cp₂ZrCl₂ and homogeneous MAO system showed the characteristic PE polymerization with homogeneous catalyst, indicating that active site was not generated inside the supercage of NaY.     

自放热条件下甲烷部分氧化制合成气

天然气组成的９０％以上是甲烷．目前由天然气制合成气的主要方法是水蒸汽重整法,这种方法投资大、设备复杂、能耗高、生产的合成气不适于直接用来合成甲醇和烃类等．甲烷部分氧化可直接制得Ｈ２与ＣＯ摩尔比为２的合成气,这是一个温和的放热过程、具有大空速和低温等优...     

Importance of Size and Distribution of Ni Nanoparticles for the Hydrodeoxygenation of Microalgae Oil

Improved synthetic approaches for preparing small‐sized Ni nanoparticles (d=3 nm) supported on HBEA zeolite have been explored and compared with the traditional impregnation method. The formation of surface nickel silicate/aluminate involved in the two precipitation processes are inferred to lead to the stronger interaction between the metal and the support. The lower Brønsted acid concentrations of these two Ni/HBEA catalysts compared with the parent zeolite caused by the partial exchange of Brønsted acid sites by Ni²⁺ cations do not influence the hydrodeoxygenation rates, but alter the product selectivity. Higher initial rates and higher stability have been achieved with these optimized catalysts for the hydrodeoxygenation of stearic acid and microalgae oil. Small metal particles facilitate high initial catalytic activity in the fresh sample and size uniformity ensures high catalyst stability.