A study of the redox properties of MoOx/SiO2

A sample of MoOx/SiO2, in which all of the Mo cations are present as isolated mono-oxo molybdate moieties, was prepared and investigated to understand the redox chemistry of such molybdate species and their ability to exchange oxygen with O2 and H2O. Raman spectroscopy was used to monitor the exchange of 18O for 16O in the Mo=O bond of isolated molybdate species, whereas mass spectrometry was used to follow the isotopic composition of the gaseous species, i.e., O2 and H2O. Reduction in H2 at 920 K results in the loss of one O atom per Mo atom, and consistent with this, all of the Mo(VI) cations are reduced to Mo(IV) cations. Raman spectroscopy shows that virtually all Mo=O bonds of the original molybdate species are lost upon reduction. While reoxidation of Mo(IV) cations by O2 is quantitative, studies using 18O2 reveal that only a small part of the newly formed Mo=O bonds are 18O labeled, and that the balance are 16O labeled, indicating that O-atom exchange between the support, SiO2, and the supported MoOx species occurs during reoxidation. Rapid exchange of O atoms was observed upon exposure of both bare SiO2 and MoOx/SiO2 to H2(18)O at 920 K, and the presence of MoOx species was found to enhance the rate of exchange. By contrast, very slow exchange of O atoms was observed when the oxidized catalyst was exposed to 18O2 at 920 K. In situ observations of the catalyst during exposure to a mixture of H2 and 18O2 at 920 K showed that all of the Mo cations remained in the VI oxidation state and that O atom exchange occurred at a rate comparable to that observed upon exposure to H2(18)O. The results of this investigation suggest that reoxidation of Mo(IV) cations following H2 reduction involves the formation of a Mo-peroxide species and subsequent O atom migration from such a species to the SiO2 support. It is proposed that the steady-state oxidation of H2 also involves the formation of Mo-peroxide species by interaction of O2 with a small number of Mo(IV) centers. The Mo-peroxide species are then rapidly reduced by H2 to form H2O and a Mo=O bond. The rapid exchange of O atoms between the gas phase and the catalyst observed during steady-state oxidation of H2 is attributed to interactions of the product H2O with the catalyst, rather than to O atom migration originating from the Mo-peroxide species formed on the catalyst surface.     

改良铜钴催化剂体系上由合成气制混合醇的研究

在铜钴基催化剂体系上，由合成气制备混合醇的反应在６．０ＭＰａ的条件下进行．双活性组分体系中铜和钴是以强相互作用状态而共存的，分子探针实验表明，铜和钴的并存对于确保醇的碳链增长是重要的，助剂ＭｏＯ_ｘ的加入显著提高了Ｌａ_２Ｚｒ_２Ｏ_７担载的铜钴基催化剂Ｃｏ／ＣｕＬＺ的活性和选择性，其作用主要表现为通过氢的可逆溢流效应而改善了体系的氢化性能，和增大了ＣＯ的插入反应能力。在改良催化剂体系上，获得了５３％的醇选择性和１４７ｇ／Ｋｇｃａｔ／ｈ的混合醇产率，内含３３％的高级醇。     

Preparation and Catalytic Property of MoOx with Meso-porosity

A partially reduced molybdenum oxide (MoOx) with meso-porosity was prepared for the first time and its catalytic performance in n-heptane isomerization carried out in a fixed bed flow reactor has been studied. And the evolvement of MoOx formation has been characterized by X-ray diffraction and catalytic performance in n-heptane isomerization. The MoOx catalyst obtained from H2 reduction for 12 h, possessing a maximum pore volume at diameter ca. 4.1 nm, exhibited high activity in n-heptane isomerization. The composition of this catalyst is of the predominant MoOx phases, MoO2 phase and trace amount of metal Mo phase.     

SiO2骨架支撑MoOx催化剂用于正庚烷异构化反应

 采用SEM，XRD，EDS及N2吸附－脱附方法研究了骨架型MoOx－SiO2催化剂和负载型MoOx／SiO2催化剂的物理化学结构，并在常压固定床流动反应器上考察了两种催化剂对正庚烷异构化反应的催化性能．结果表明，在MoOx－SiO2催化剂中，44．6％的SiO2即可起到很好的骨架支撑作用；MoOx晶相以足够大的空间区域聚集包裹在SiO2骨架中，形成类似MoOx催化剂的独特的中孔结构．与MoOx催化剂相比，MoOx－SiO2催化剂显著提高了机械强度，并维持了MoOx催化剂较高的活性和选择性．由于钼物种和载体之间的相互作用，负载型MoOx／SiO2催化剂表现出较低的比活性．脉冲注入H2S实验结果表明，MoOx－SiO2催化剂具有较好的抗硫性能．     

NiO-MoO3/SiO2光催化剂的结构与光吸收性能

采用表面改性法制备了负载型复合半导体NiO-MoO3/SiO2, 用程序升温还原、 X射线衍射、 拉曼光谱、 透射电镜、 比表面积测定和紫外-可见光漫反射光谱技术对固体材料的组成结构和光吸收性能进行了表征. 结果表明, NiO-MoO3/SiO2的平均粒径约为10 nm, 在载体表面存在xNiO·MoO3复合氧化物的微晶, NiO和MoO3在固体材料表面产生相互修饰作用. NiO的加入有助于提高MoO3在载体SiO2表面的分散程度, 抑制MoOx的聚合, 减小微晶尺寸, 而且可以增强固体材料的光吸收性能, 提高复合半导体对光能的利用率.     

ZrO_2晶相对MoO_x/ZrO_2催化剂结构及其甲醇选择氧化性能的影响

以纯的单斜氧化锆(m-ZrO2)和四方氧化锆(t-ZrO2)为载体,采用浸渍法分别合成了具有不同MoOx表面密度的MoOx/m-ZrO2和MoOx/t-ZrO2催化剂,并结合粉末X射线衍射,Raman光谱和H2程序升温还原等技术表征了不同ZrO2晶相对MoOx分散状态、结构以及甲醇氧化反应性能的影响.在低于锆表面MoOx的单层分散阈值(～5nm-2)时,m-ZrO2比t-ZrO2能够更有效地分散MoOx,形成高分散的孤立或二维结构的MoOx物种,避免了晶相MoO3的出现.当Mo表面密度超过单层分散阈值后,经过600℃焙烧,MoOx与ZrO2载体发生固相反应生成晶相ZrMo2O8,m-ZrO2比t-ZrO2更有利于ZrMo2O8的生成.提高Mo表面密度,催化剂表面的酸性随之增强,说明晶相ZrMo2O8比分散的MoOx物种具有更强的酸性.t-ZrO2与MoOx作用形成的强酸中心更有利于催化甲醇脱水生成二甲醚,但m-ZrO2使得MoOx具有更高的氧化还原能力和催化甲醇选择氧化反应的活性.ZrO2晶相对MoOx/ZrO2催化剂影响的研究结果将有助于研究VOx等其它金属氧化物催化剂以及发展酸性和氧化还原性双功能催化剂体系.     

新型水溶性配体-负载金属氢甲酰化催化剂:TPPTS-Rh/SiO2

考察了几种硅胶负载贵金属催化剂和HRhCO(TPP)3催化剂的1-己烯氢甲酰化反应,对Rh/SiO2、 HRhCO(TPPTS)3/SiO2 和TPPTS-Rh/SiO2上的1-己烯氢甲酰化结果进行了比较.结果表明, TPPTS-Rh/SiO2催化剂的醛的选择性和醛的正异比n/b接近HRhCO(TPPTS)3/SiO2 的相应的催化性能,而远高于Rh/SiO2的相应的催化性能, 7.0 MPa高压下TPPTS-Rh/SiO2催化剂的活性大幅度增加,达到0.0692 S-1.实验排除了其他可能,认为是含有孤对电子的TPPTS 和Rh/SiO2中高度分散的Rh粒子产生了化学键的作用,形成了具有匀相性能的支撑水膜多相催化剂: TPPTS-Rh/SiO2.     

(二苯甲酰甲烷基)(环戊二烯基)二氯化钛/MgCl2-SiO2/MAO中各组分对乙烯聚合的影响

研究开发了一种新型非茂负载乙烯聚合催化剂 CpTi(dbm)Cl2 MgCl2 SiO2 MAO ,并考察了该催化剂中各组分对乙烯聚合活性的影响 .结果表明 ,SiO2 不仅可以改善催化剂的流动性和分散性 ,还有益于提高催化活性 .MgCl2 对活性中心有一定化学改性作用 ;MgCl2 、SiO2 和CpTi(dbm)Cl2 的比例的变化对载体型催化剂的催化活性有一定影响作用 ;采用适量的MAO对复合载体MgCl2 SiO2 活化 ,能提高催化活性 .用ZnCl2 MAO对SiO2处理制成的复合载体催化剂CpTi(dbm)Cl2 MgCl2 ZnCl2 SiO2 MAO ,可以提高催化活性 ,“锌调”作用明显 ,随着锌化合物含量的增加 ,聚合物相对分子质量下降 ,相对分子质量分布加宽 ,并且其催化活性也增加 .     

Studies on the structure and catalytic performance of S and P promoted Na-W-Mn-Zr/SiO2 catalyst for oxidative coupling of methane

A series of Na-W-Mn-Zr/SiO2 catalysts promoted by different contents of S or/and P were prepared and their catalytic performance for oxidative coupling of methane was investigated to clarify the effect of S and P on the Na-W-Mn-Zr/SiO2 catalyst. The catalysts were characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). From the characterization results, it is found that the addition of S and P to the Na-W-Mn-Zr/SiO2 catalyst helps the formation of active phases, such as α-cristo...     

SARS冠状病毒E蛋白的结构研究及功能预测

结合生物信息学方法及分子模拟手段,选择较高准确度的方法,预测了SARSE蛋白的分子结构并探讨其潜在的生物学活性和功能.研究结果表明,SARSE蛋白跨膜区25个疏水的氨基酸形成α-螺旋结构,包埋于病毒外壳磷脂双分子层中;N端10个氨基酸残基位于膜外;C端41个残基则附着于磷脂双分子膜内侧.同时发现,C端由9个氨基酸组成的劈裂是一个可能的活性部位.对分子进行进一步静电势分析证实,E蛋白C端可能的活性部位具有较大的静电势,可能的活性残基具有最大电荷密度,故有较强的结合受体或与其它蛋白相互作用的能力.     

Selective Oxidation of Methane to Methanol Using Molecular Oxygen on MoOx／（LaCoO3＋Co3O4） Catalysts

Comparatively high CH3OH selectivity (60.0%) and yield (6.7%) were obtained on MoOx/(LaCoO3 Co3O4) catalysts in selective oxidation of methane to methanol using molecular oxygen as oxidant. The interaction between MoOx and La-Co-oxide modified the molecular structure of molybdenum oxide and the ratio of O^-/O^2- on the catalyst surface, which controlled the catalytic performance of MoOx/(LaCoO3 Co3O4) catalysts.     

Quantum Chemical Studies on the Mechanism of Producing Oxygenates in Fischer-Tropsch Synthesis on M/SiO2(M = Ni,Ru,Rh,Pd)

EHMO calculations and orbital analyses of fragment;;have been performed for the formation of oxygenates in Fischer-Tropsch synthesis on the butterfly model for four different metal (Ni,Ru,Rh,Pd) catalysts supported on SiO2.Calculations were made for the four processes,i.e.,CO-dissociation;Coupling of CO and H to produce CHO;Insertion of CO to M-CH3;insertion of CH2 to M-CH3 On the basis of comparing the degree of CO bonds activation and the energy barriers of the foregoing processes for these four catalysts,it is concluded that Ni/SiO2 can be used as the methanation catalyst.On Ru/SiO2 and Rh/SiO2 C2-oxygenated compound can be produced (acetaldehyde),especially Rh/SiO2 is the even better catalyst,and Pd/SiO2 is a methanol synthesis catalyst.     

结构助剂SiO2、Al2O3对铁基催化剂浆态床F-T合成性能的影响

采用连续共沉淀与喷雾干燥成型技术相结合的方法制备了微球状Fe/Cu/K/SiO2和Fe/Cu/K/Al2O3催化剂，研究SiO2和Al2O3作为结构助剂对铁基催化剂吸附行为、炭化行为及F-T合成反应性能的影响。表征结果表明,与Al2O3相比较，SiO2抑制了H2的吸附，但促进了CO的吸附，有利于催化剂的炭化。催化剂在260℃、1.5MPa、H2/CO=0.67和2000h-1下的浆态床F-T合成反应评价表明，Fe/Cu/K/SiO2催化剂具有较高的F-T合成活性、高的水煤气变换反应（WGS）活性，且其烃产物选择性明显向高炭数方向偏移，而Fe/Cu/K/Al2O3催化剂则表现出较低的F-T合成活性、低的水煤气变换反应（WGS）活性和高的轻质烃选择性。但Fe/Cu/K/Al2O3催化剂比Fe/Cu/K/SiO2催化剂具有更好的运行稳定性。     

Synthesis of Methyl Glycolate by Hydrogenation of Dimethyl Oxalate over Cu-Ag/SiO2 Catalyst

Methyl glycolate is a good solvent and can be used as feedstock for the synthesis of some important organic chemicals. Catalytic hydrogenation of dimethyl oxalate (DMO) over copper-silver catalyst supported on silica was studied. The Cu-Ag/SiO2 catalyst supported on silica sol was prepared by homogeneous deposition-precipitation of the mixture of aqueous cuprammonia complex and silica sol. The proper active temperature of Cu-Ag/SiO2 catalyst for hydrogenation of DMO was 523—623 K. The most preferable reaction conditions for methyl glycolate (MG) were optimized: temperature at 468—478 K, 40—60 mesh catalyst diameter, H2/DMO ratio 40, and 1.0 h-1 of LHSV.     

官能化硅胶负载Pd—Cu催化剂的制备及催化芳香氯化物水相脱氯作用

将聚乙烯吡烷酮（PVP）与双金属Pd^2 、Cu^2 配位后,再负载于用平均分子量为600的聚乙二醇（PEG）官能化的硅胶上（SiO2-PEG600),制成一种新型双负载双金属催化剂PVP-PdCl2-CuCl2/SiO2-PEG600,将其用于催化难溶于水的芳香卤化物水相脱卤,在无需加入任何有机溶剂的情况下,对芳香氯化物呈现出高的脱氯活性和选择性,并具有良好的重复使用性能。通过IR、TEM、比表面积测定等手段,探讨了催化剂各组分在催化脱卤中的作用及可能的催化脱卤机理。     

固体催化剂活性表面的化学不均匀性

固体催化剂活性表面的化学不均匀性朱建军林西平＊（江苏石油化工学院化学工程系常州２１３０１６）关键词固体催化剂，活性表面，分形维，化学不均匀性１９９６－１０－２８收稿，１９９７－０３－１０修回中国石化总公司和回国留学服务中心资助项目本院九五届毕业生于晓...     

钡修饰Ir/SiO2催化剂对氨分解促进作用的研究

研究了浸渍法制备的Ba修饰S iO2担载型铱(Ir)基催化剂(Ba-Ir/S iO2)在氨催化分解模型反应的作用。结果表明Ba的添加显著提高了催化剂的活性和稳定性。采用H2-TPR和H2-TPD对Ba-Ir/SiO2进行分析和研究,结果显示助催化剂Ba和活性催化组分Ir之间发生了强相互作用。Ba-Ir/SiO2在氨催化分解模型反应中的主要活性物种是零价态的Ir。     

反应条件对固相合成负载羰基铑原子簇催化剂及其性能的影响

本文报告了由金属盐直接固相合成负载铑络合物或原子簇催化剂的新方法及IR谱表征。CO容易使表面吸附有水分子的RhCl_3/SiO_2还原并生成表面羰基物Rh~+-(CO)_2/SiO_2;CO、CO/H_2和CO/2H_2等不同还原气对表面络合物的生成没有影响。采用H_2还原只能得到金属Rh催化剂。水是重要影响因素,如果RhCl_3/SiO_2先抽空脱水,再用含水的CO还原,就会使Rh~+(CO)_2/SiO_2转化为Rh_6(CO)_(16)/SiO_2。此外,还考察了负载原子簇的CO加氢和热分解反应性能。采用CO还原RhCl_3/SiO_2制备的催化剂同负载原子簇催化剂的反应行为非常相近,而且比传统催化剂具有更高的反应活性。     

CO和NO在Rh2-V/SiO2催化剂上共吸附的红外光谱

应用CO和NO吸附态原位红外光谱方法研究了还原态Rh2／SiO2，Rh2－V／SiO2催化剂上的活性中心铑的状态和助剂钒的作用. Rh2催化剂用Rh2（CO）4Cl2化合物制备. 在还原Rh2／SiO2催化剂上，CO吸附出现四个红外吸收峰：2085，2028cm－1（孪生态吸附RhⅠ（CO）2），2060cm－1（线式吸附RhⅡCO），1867cm－1（桥式吸附RhⅢ2CO）．在还原Rh2－V／SiO2催化剂上，CO在RhⅡ和RhⅢ中心上的吸附峰大大减弱，可以解释为Rh°向钒离子转移电子生成了带正电荷的铑中心（Rhδ＋）；同时RhⅠ（CO）2键能增加，降低了孪生CO被NO置换的程度。     

CuCl/SiO2-TiO2 催化剂的结构及其催化甲醇氧化羰基化反应性能

 在微波辐射条件下, 将 CuCl 快速分散到载体表面制得 CuCl/SiO2-TiO2 催化剂, 利用 X 射线衍射、透射电镜、N2 吸附-脱附、热重、H2 程序升温还原和 CO 程序升温脱附对催化剂进行了表征. 结果表明, 微波辐射制备的催化剂中 CuCl 和载体发生了强相互作用, 比传统加热制备的催化剂中形成更多的易还原铜物种, 吸附 CO 的能力更强. 在甲醇液相氧化羰基化反应中, 微波辐射制备的催化剂上甲醇转化率为 11.7%, 碳酸二甲酯选择性达 96.5%, 高于相同条件下传统加热制备催化剂的活性.