2D Carbon-Supported Platinum Catalysts for Hydrosilylation Reactions

Russian Journal of General Chemistry - 2D carbon structures were prepared by carbonization of biopolymers (starch) via self-propagating high-temperature synthesis process. Electron microscopic,...     

Carbon-Supported Silver Catalysts for CO Selective Oxidation in Excess Hydrogen

Carbon materials were used as supports for Ag catalysts that are prepared using the conventional wet impregnation method, and their catalytic properties for CO selective oxidation in excess hydrogen at temperatures below 483 K were tested. A variety of techniques, e.g. N2 adsorption, XPS, TPD, UV-Vis DRS, TEM and SEM, were used to determine the influence of physical and chemical properties of the carbon on the properties of Ag catalyst. It was found that defects on the carbon surface served as nucleation sites for silver ions, while functional groups on carbon surface induced their reduction to the metallic form. The formation of silver particles on carbon was governed by homogeneous and/or heterogeneous nucleation during the impregnation and subsequent activation processes. The best catalytic performance was obtained with a Ag/carbon black catalyst with a uniform size distribution of silver nanoparticles (about 12 nm), moderate BET surface area (with a mesoporous structure), and a limited amount of carbon-oxygen groups. The research indicates that carbon materials are potentially good supports for silver catalysts for preferential oxidation of CO in excess hydrogen.     

Methanol-to-Olefin Conversion over Zeolite Catalysts: Active Intermediates and Deactivation

Methanol-to-olefin (MTO) conversion over various zeolites with different topologies, Si/Al molar ratios, and crystallite sizes were investigated to verify the effects of pore shape and size, acidity, and external surface area on the catalytic activity, product selectivity, and deactivation. The IR and electron spin resonance (ESR) study of zeolite catalysts used in MTO also proceeded to deduce the active intermediates formed in their cages or pores. The zeolites with 8 membered-ring (MR) pore entrances such as CHA, ERI, LTA, and UFI commonly exhibited high selectivity to lower olefins due to their small entrances, but the CHA catalyst with the smallest cage maintained its activity longer than other 8MR zeolites. The slow condensation of polymethylbenzene (PolyMB) to polyaromatic hydrocarbons (PAH) on MOR zeolite with a high Si/Al molar ratio due to its low concentration of strong acid sites resulted in a slow deactivation. The extremely small crystallites of H-SAPO-34 and H-ZSM-5 less than 100 nm showed an adverse effect in MTO; while the large crystallites above 1,000 nm also exhibited poor catalytic performance because of their small external surface. The study of IR regarding the adsorbed and occluded materials on zeolites demonstrated the effect of pore shape and size on the active intermediates: the zeolites with larger pores and cages allowed the formation of alkylbenzenes with long alkyl groups which preferred to be condensated to PAH. The well-resolved hyperfine splitting of ESR spectra observed on H-SAPO-34 used in MTO clearly illustrated the presence of hexamethylbenzenium radical cations. The small intersections of phosphorous-modified H-ZSM-5 allowed the formation of tetramethylbenzenium radical cations in MTO. The formation of PolyMB radical cations, their role as active intermediates and the effect of topology, acidity, and crystallite size of zeolites on their deactivation were discussed.     

活性炭担载的Rh-M0-K合成醇催化剂

采用XRD、EXAFS等技术研究微量贵金属Rh对活性炭担载的Rh-Mo-K合成醇催化剂结构的影响,并关联其催化性能.氧化态Rh-Mo-K/AC样品中Rh与Mo有着较强的相互作用,使得K2Mo2O7向MoO2转化.硫化还原后,Mo主要以MoS2微晶形式存在,其有序结构尺度随Rh含量的增加而减小.经Rh助剂修饰后,催化剂的合成醇催化性能有明显的提高.     

PtRuMo/C催化剂的制备及其对甲醇的电催化氧化作用

阳极甲醇氧化;电催化剂;PtRuMo/C催化剂的制备及其对甲醇的电催化氧化作用     

活性炭负载钌基氨合成催化剂的制备和催化活性

A series of active carbon supported ruthenium based catalysts, promoted by alkali and alkaline earth nitrate, are prepared by impregnation method and with RuCl 3·3H 2O as precursor. Effects of support, promoter and preparation conditions on catalytic activity are discussed. The catalytic activity is evaluated with a fixed bed micro reactor at lower pressure. The results show that the impregnation sequence affects the catalytic activity obviously. Ba Ru K/C is the preferred impregnation sequence. And effects of nature, producing area and pre treatment of the support on catalytic activity are also examined. Catalytic activity increases with the amount of Ru deposited on the support, it attains maximum when Ru loading is 8%. Optimal molar ratio of promoter to Ru is 10.     

NO在氧化铝负载的Pd催化剂上吸附的TPD-MS研究

消除汽车尾气中的氮氧化物(NOx)对保护大气环境有着重要意义.为了除去NOx,已经进行了许多卓有成效的研究,例如NOx在分子筛上的直接分解和催化还原,在贵金属三效催化剂上的还原等.     

Pre-reduced Activated Carbon-Supported Molybdenum-Based Catalysts for the Production of Mixed Alcohols from Synthesis Gas

Unsupported or supported Mo-based catalysts have been widely employed in petroleum industry, for hydrotreating^[1],and for the production of hydrocarbons^[2] and alcohols_[3] by hydrogenation of CO (or CO₂). Oxides, such as alumina, silica, silica-alumina, are commonly used as the supports for these purposes. Carbon-supported materials have been claimed to have potential advantages over oxide-supported ones, such as lower tendency of carbon deposition^[4], less dehydration and thus less secondary reactions. Here we present results on mixed alcohol synthesis over H₂-prereduced C-supported Mo-based catalysts.     

助剂对合成碳酸二甲酯用活性炭负载Wacker催化剂结构和性能的影响

 以碱金属或碱土金属的盐或氢氧化物为助剂修饰活性炭(AC)负载的Wacker催化剂PdCl2-CuCl2. 甲醇气相氧化羰基化合成碳酸二甲酯(DMC)的反应活性评价结果表明,以乙酸钾(KOAc)为助剂的效果最好. 在KOAc/CuCl2摩尔比为1.0的条件下制备的催化剂用于该合成反应时,DMC的时空产率提高了5倍. XRD,SEM及EPR表征结果显示,在催化剂中加入适量的KOAc,有利于Cu2Cl(OH)3物相在载体表面的形成和分散,从而加快了催化剂活性物种Cu和Pd的氧化还原循环速度.     

Ho改性OMS-2催化CO选择性还原NO的研究

采用水热法一步合成了Ho改性的OMS-2催化剂(Hox-OMS-2),并对其CO选择性催化还原NO(CO-SCR)性能进行了研究。研究结果表明,当Ho/Mn摩尔比为0.05时,Ho0.05-OMS-2催化剂在225 ℃表现出非常有吸引力的CO-SCR活性,可实现接近100%的NO转化率和N2选择性。Ho的掺杂过量时会导致催化剂团聚。此外,Ho0.05-OMS-2催化剂具有较好的抗SO2性能。通过XRD、BET、XPS、H2-TPR对催化剂进行表征,探究Ho物种的掺杂对OMS-2催化剂的物理化学性质的影响。结果表明,Hox-OMS-2催化剂低温活性的增强可归因于晶格膨胀、较低的结晶度、高比表面积、较高的Mn4 含量和更多的表面氧空位。     

活性炭负载钴基催化剂上合成气制混合醇

在两种分别来自椰壳炭和杏核炭的活性炭AC1和AC2上,采用真空浸渍法制备了Co基催化剂15%Co/AC1和15Co%/AC2,并考察了其在CO氢化反应中的催化性能.结果表明,AC1和AC2的孔结构基本相同,但表面含氧官能团的数量和种类不同.含氧官能团影响了催化剂Co物种的形态,从而使催化剂在反应中表现出不同的性能.助剂K和zr的添加改变了15%Co/AC1催化剂的活性和选择性.在3.0 Mpa,495 K,H2/CO(体积比)=2和GHSV=500 h-1反应条件下,15%Co/AC1和15%Co/AC2上C1～C18醇的选择性分别为20.6%和9.6%.在其它条件不变,GHSV=1500 h.反应条件下,15%Co-0.01%K-2%Zr/AC1催化剂上CO转化率和醇选择性分别为28.0%和34.3%,液相产物中醇占60.9%,其中C6～C18高碳醇占液相产物的20.6%.     

Study on Highly Active Catalysts and a Once—Through Process for Methanol Synthesis from Syngas

Highly active CNT-promoted co-precipitated Cu-ZnO-Al2O3 catalysts, symbolized as CuiZnj;Alfc-a;%CNTs, were prepared, and their catalytic activity for once-through methanol synthesis from syngas was investigated. The results illustrated that, under the reaction conditions (at 493 K, 5.0 MPa, the volume ratio of H2/CO/CO2/N2= 62/30/5/3, GHSV= 4000 h-1), the observed single-pass CO-conversion and methanol-STY over a Cu6Zn3Al1-12.5%CNTs catalyst reached 64% and 1210 mg/(h-g), which was about 68% and 66% higher than those (38% and 730 mg/(h-g)) over the corresponding CNT-free catalyst, Cu6Zn3Al1, respectively. The characteristic studies of the catalysts revealed that appropriate incorporation of a minor amount of the CNTs into the CuiZnjAlk brought about little change in the apparent activation energy of the methanol synthesis reaction, however, led to a considerable increase in the catalyst's active Cu surface area and pronouncedly enhanced the stationary-state concentration of active hydrogen-adspecies on     

Comparative Study of NO and CO Oxidation Reactions on Single-Atom Catalysts Anchored Graphene-like Monolayer

Noble metal single-atom catalysts (NM-SACs) anchored at novel graphene-like supports has attracted enormous interests. Gas sensitivity, catalytic activity, and d-band centers of single NM (Pt and Pd) atoms at graphenylene (graphenylene-NM) are investigated using first-principle calculations. The adsorption geometries of gas reactants on graphenylene-NM sheets are analyzed. It is found that the adsorption energies of reactant species on graphenylene-Pt are larger than those on graphenylene-Pd, because the d-band center of the Pt atom is closeser to the Fermi level. The NO and CO oxidation reactions on graphenylene-NM are investigated via four catalytic mechanisms, including Langmuir-Hinshelwood (LH), Eley-Rideal (ER), New ER (NER), and termolecular ER (TER). The results show that the NO and CO oxidations via LH and TER mechanisms can occur owing to the relatively small energy barriers. Moreover, the interaction of 2NO+2CO via ER mechanism is the energetically more favorable reaction. Although the NO oxidation via the NER mechanism has rather low energy barriers, the reaction is unlikely to occur due to the low adsorption energy of O₂ compared with CO and NO. This research may provide guidance for exploring the catalytic performance of SACs on graphene-like materials to remove toxic gas molecules.     

贵金属铂对镍基催化剂上萘转化性能的影响

 在常压连续流动固定床反应器上，以萘作为生物质气化气中焦油的模型化合物，研究了Pt对Ni／Al2O3催化剂上萘的转化率、CO和H2的选择性及收率的影响，比较了Ni－Pt／Al2O3和Ni／Al2O3两种催化剂上萘的水蒸气转化所产生的积碳量和副产物的种类，并初步考察了Ni－Pt／Al2O3催化剂上萘的水蒸气转化反应的动力学．     

油脂碳碳双键加氢高活性镍催化剂的研究

采用沉淀法和化学混合法,制备了用于椰子油加氢改性的Ｎｉ／硅藻土和Ｎｉ／ＳｉＯ２催化剂,用原子吸收,碘价分析,活性和ＢＥＴ比表面积测定及ＸＲＤ,ＴＧ－ＤＴＡ,ＩＲ等手段,对催化剂的产物进行了物理和化学表征。结果表明,控制合适的制备条件,用上述两种方法都可以制得活性很好的单元镍催化剂,且加氢后除熔点升高外,未改变油脂的其它物理性质。沉淀法（Ｎｉ／硅藻土）的制备条件对催化剂的实际镍含量与加氢活性有较大影     

单位点催化剂的简便构筑方法、原理及性能研究

<正>单位点催化剂(文献中也时常称为单原子催化剂)是负载型催化剂的极限,因其最大的原子利用率、独特的催化性能、均一的配位环境等特点成为近年来科学研究的前沿热点~1。金属单原子表面能高,容易团聚,其制备过程通常较为复杂,因此,方便地构建稳定性高的单位点催化剂对于开展相     

Hydrocarbon Effects on the Promotion of Non-Thermal Plasma NO–NO2 Conversion

Kinetic modeling of non-thermal plasma chemistry is conducted to investigate hydrocarbon (CH₄, C₂H₄, C₃H₆, and C₃H₈) effects on the promotion of NO–NO₂ conversion. A reduced plasma chemistry model, in which radical reactions are selectively involved, is validated with experimental data. The higher reactivity of hydrocarbon additive with O radicals, which produces initial radicals, is requisite to initiate hydrocarbon decomposition, thus providing NO–NO₂ conversion. Initial radicals by plasma discharge induce continual hydrocarbon decomposition and this self-preserved reaction mechanism greatly contributes to the promotion of energy efficient NO–NO₂ conversion. Increase in the conversion extent by ethylene and propylene additives is substantial because of their stronger affinity with O radical. The primary routes of NO–NO₂ conversion process differed by hydrocarbon additives are presented and discussed with the assistance of sensitivity analysis.     

Novel Catalysts for Gasification of Biomass with High Conversion Efficiency

We have developed catalysts for the gasification of biomass with much higher energy efficiency than the conventional methods (noncatalyst, dolomite, and commercial steam reforming Ni catalyst). In our investigation, the Rh/CeO₂ gave high yields of syngas for cellulose gasification using a fluidized-bed reactor with batch feeding of cellulose. However, the catalyst was deactivated because of sintering of CeO₂ during the reaction. To prevent the CeO₂ sintering, we have further improved the catalyst and found that Rh/CeO₂/SiO₂ was quite stable for the gasification of cellulose. It was demonstrated that Rh/CeO₂/SiO₂ gave almost complete gasification of real biomass (wood powder) at 873 K. These results indicate that the combination of this kind of catalyst and fluidized-bed reactor can realize the energy-efficient biomass gasification.