STUDY ON DISPERSION SPEED AND MECHANISM OF MoO_3 AND CuCl ON THE SURFACE OF γ-Al_2O_3

It has been shown that many oxides and salts can disperse spontaneously onto supports with large surface area. A typical example studied widely is the disper-sion of MoO_3 on γ-Al_2O_3. However, the research work about the dispersion mecha-nism and kinetics is quite few.     

AN INVESTIGATION OF THE DISPERSION OF CuCl ON γ-Al_2O_3 SURFACE AND THE ADSORPTION OF ETHYLENE ON CuCl/γ-Al_2O_3 AND OTHER SUPPORTED TRANSITION METAL SALTS

In this work we investigate the dispersion of CuCl on γ-Al_2O_3 surface and the adsorptionof ethylene on CuCl/γ-Al_2O_3. X-ray diffraction experiments and u.v. diffuse reflectancespectra have shown that CuCl is highly dispersed on γ-Al_2O_3 surface, very likely as a mono-layer. The maximun amount of dispersion of CuCl on γ-Al_2O_3 surface determined by X-ray quantitative phase analysis is 0.095 g CuCl/100 M~2 on γ-Al_2O_3. The adsorption ofethylene on dispersed CuCl can be conveniently studied by the temperature programed de-sorption (TPD) method and shown to be achieved readily at ambient temperature and nor-mal pressure. The ability of adsorption for ethylene on CuCl/γ-Al_2O_3 is greater by threeorders of magnitude than that on undispersed CuCl particles of comparable size. The max-imum molecular ratio of ethylene adsorbed to dispersed CuCl is 0.19 C_2H_4/Cu~ . The cu-prous ions of dispersed CuCl can form surface complex with molecules such as C_2H_4 or C_3H_6so long as the stereochemical conditions are satisfied. These results may provide additionalscientific basis for separating unsaturated molecules from saturated ones by CuCl/γ-Al_2O_3.     

EFFECTIVE INFLUENCE OF THE SUPPORT SURFACE VACANT SITES ON THE DISPERSION STATE OF Fe_2O_3 SUPPORTED ON VARIOUS METAL OXIDES

ＥＦＦＥＣＴＩＶＥＩＮＦＬＵＥＮＣＥＯＦＴＨＥＳＵＰＰＯＲＴＳＵＲＦＡＣＥＶＡＣＡＮＴＳＩＴＥＳＯＮＴＨＥＤＩＳＰＥＲＳＩＯＮＳＴＡＴＥＯＦＦｅ２Ｏ３ＳＵＰＰＯＲＴＥＤＯＮＶＡＲＩＯＵＳＭＥＴＡＬＯＸＩＤＥＳＣｈｅｎＫａｉｄｏｎｇ，ＤｏｎｇＬｉｎ，Ｙ...     

INVESTIGATION ON SURFACE VALENCE STATE OF SUPPORTED CATALYST FOR ETHANOL CARBONYLATION BY XPS AND EDXA

One kind of NaZSM-5 zeolite-supported rhodium catalyst has beensythesized.It overcomes the shortcoming of the homogeneous catalyst andmaintains high activity,selectivity and high stability.Specimens of the zeolitecatalyst have been analysed by X-ray photoelectron spectroscopy(XPS)andenergy dispersion X-ray analysis(EDXA).The experimental results indicatethat the active component rhodium existing in the catalyst is trivalent,somesites of sodium in the catalyst are occupied by Rh~(+3)ions.     

DISPERSION STATE OF ZINC OXIDE ON SURFACE OF SILICA GEL AND SURFACE ACIDITY OF ZnO/SiO_2

The dispersion threshold level of zinc oxide on silica gel was determined by X-ray quantitative phase analysis. And the results of XPS experiments show that the surface of the sample is enriched with ZnO and there is a limit for the ZnO amount dispersed on the surface. The value of this limit is corresponding with the threshold level obtained by XRD. The measurements of surfaee acidity show that there are some stronger acid sites on the surface of ZnO/SiO_2, they have not been found on the ZnO or SiO_2 individually, and the total amount of acid increases remarkably. The acidity depends on the ZnO concentration in the surface phase and reaches the maximum at the threshold value.In this paper, we propose a new point of view for the origin of the acidity on surface of the ZnO/SiO_2 samples. ZnO is well dispersed on the surface of SiO_2 gel in a monolayer state. In this situation, some new surface structure units emerge as a result of interaction between dispersed ZnO and the carrier, which are responsible     

THE EFFECT OF ADDITIVE La_2O_3 ON THE DISPERSION AND THERMOSTABILITY OF NICKEL IN METHANATION CATALYST

It is showed that La_2O_3 and NiO could disperse on γ-Al_2O_3 as a monolayer and theirutmost monolayer capacities determined by quantitative XRD are 0.28g/100m~2 and 0.09g/100m~2respectively. In the methanation catalyst, Ni/La_2O_3/γ-Al_2O_3, the La_2O_3 is dispersed on thesurface of γ-Al_2O_3 as a monolayer and the metallic nickel crystallites are supported on thesurface with La_2O_3. It has been found by the XRD peak broadening that the average size ofnickel crystallites on the surface with La_2O_3 is much smaller than that without La_2O_3. Thismay be one of the main reasons for the increase of activity and thermostability of the La_2O_3containing methanation catalyst. This idea of modifying support surface by monolayercompound can also be applied to other catalysts.     

DECOMPOSITION OF KNO_3/γ-Al_2O_3 AND THE FORMATION OF SURFACE BASE SITES

ＤＥＣＯＭＰＯＳＩＴＩＯＮＯＦＫＮＯ３／γ┐Ａｌ２Ｏ３ＡＮＤＴＨＥＦＯＲＭＡＴＩＯＮＯＦＳＵＲＦＡＣＥＢＡＳＥＳＩＴＥＳ＊ＴｕＭａｉ，ＬｉＤａｔａｎｇ，ＺｈｕＪｉａｎｈｕａ，ＳｈｅｎＪｉａｎｙｉ＊＊（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｉｎｓ...     

XPS IN VESTIGATION OF γ-Al_2O_3 SUPPORTED Pt-CONTAINING DUAL-COMPONENT CATALYSTS

ＸＰＳＩＮＶＥＳＴＩＧＡＴＩＯＮＯＦγ┐Ａｌ２Ｏ３ＳＵＰＰＯＲＴＥＤＰｔ┐ＣＯＮＴＡＩＮＩＮＧＤＵＡＬ┐ＣＯＭＰＯＮＥＮＴＣＡＴＡＬＹＳＴＳ＊ＪｉａＪｉｆｅｉ１，ＫｏｕＹｕａｎ２，ＸｕＺｈｕｓｈｅｎｇ１，ＺｈａｎｇＴａｏ１，ＺｈａｎｇＢｉｎｇ２，Ｌｉ...     

EFFECT OF PREPARATION OF SUPPORTED Mo-CATALYST ON THE ADSORPTION AND SURFACE REACTION RATE COEFFICIENTS

The effects of preparative variables of the supported Mo catalyst on the properties of adsorp-tion and reaction were studied by the CRCT at 250-290°C under atmospheric pressure.The resultsshow that the Mo content and sulphurization temperature mainly affect the number of adsorption sitesof thiophene and the match of adsorbed thiophene and hydrogen.The calcination temperature influencesnot only the numbers and nature of adsorption sites of thiophene but also the turn-over frequency ofsurface reaction of adsorbed thiophene,which increases largely with calcination temperature,becausethe interaction of metal-support is stronger at higher calcination temperature.The results also show thatthe Mo content of monolayer capacity,sulphurization at 400°C and calcination at 500°C would lead toan optimum match of adsorbed thiophene and hydrogen,i.e.the highest reaction rate and the lowestactivation energy of reaction would be obtained under these treatment conditions.     

EFFECT OF La AND Zr ON THE CATALYTIC PERFORMANCE OF SUPPORTED COPPER CATALYST FOR DEHYDROGENATION OF METHANOL TO METHYL FORMATE

The catalytic dehydrogenation of methanol over supported Cu/SiO_2and Cu/Al_2O_3 prepared by impregnation and by ion-exchange (Cu/SiO_2(im),Cu/Al_2_3(im) and Cu/SiO_2(ex)), La_2O_3 and ZrO_2 promoted Cu/SiO_2 or Cu/Al_2O_3 catalyst has been studied in a fixed bed microreactor at 250℃ and atmo-spheric pressure. The Cu/SiO_2 (ex) catalyst was found to be very active and se-lective toward methyl formate (MF). However, Cu/SiO_2(im) catalyst wasless active and selective among the studied catalysts. The catalytic activity, MFselectivity and MF yield over Cu/SiO_2 And Cu/Al_2O_3 are greatly improved byLa and Zr. XPS and XRD results suggest that the crystallite size of copper wasreduced by coating La and Zr, the surface Cu/Si or Cu/Al atomic ratio in-creased. TPR results show when the support was coated with La and Zr thepeak temperatures of catalysts significantly decreased.     

INFLUENCE OF PREPARATION CONDITIONS ON THE DISPERSION AND DISTRIBUTION OF NICKEL SPECIES AND ON THE BEHAVIOR OF LOW MICKEL LOADING Ni/Al_2O_3 CATALYSTS

A series of low nickel loading catalysts were prepared by varying theimpregnation conditions before calcination,and characterized by CO methana-tion,XRD,surface area measurement and temperature programmed reductionmethds.It was found that the methanation activity decreased with increasingimpregnation time in excess of 24 h,but the pretreatment of the support byevacuation at room temperature enhanced the activity evidently,which was at-tributed to the formation of highly dispersed nickel species that could be reducedat relatively low temperature.Heating with or without evacuation also alteredthe activity due to the change in distribution of nickel species.     

MoO_3/γ-Al_2O_3,MoO_3/TiO_2和MoO_3/SiO_2的还原性质及表面状态研究

本文以XPS为检测手段研究了浸渍法制备的MoO_3/γ-Al_2O_3、MoO_3/TiO_2和MoO_3/SiO_2三个系列样品的还原性质。用XPS测定还原后与还原前强度比的比值,实验结果表明阈值后的样品还原后强度比急剧增大,说明晶相MoO_3从内孔向颗粒外表面大幅度迁移。而单层MoO_3的性质却各不相同,TiO_2上的单层MoO_3还原后部分凝聚,SiO_2上单层则部分迁移,而γ-Al_2O_3上的单层MoO_3既不迁移也不凝聚,亦即单层MoO_3的稳定性是Mo(Al)>Mo(Ti)>Mo(Si)。这也是MoO_3与这三个载体表面作用力强弱的顺序。用计算机对Mo3d谱峰解叠,结果表明,几乎所有样品还原后都只含有四价和五价钼。Mo(Al)和Mo(Si)体系还原后Mo~Ⅳ的百分数随负载量的增大而增大。我们认为反映了两种载体表面区域的不均匀性。Mo(Ti)体系还原后Mo~Ⅳ百分数在阈值附近出现转折点,阈值前各点还原性质相同,说明在应用还原为探测手段时,TiO_2表面表现为均匀的。以Mo~(Ⅳ)百分数衡量时,三个体系的还原性为Mo(Al)相似文献   

STUDIES ON THE STATE OF PALLADIUM AND HYDROGENATION ACTIVITY OF RESIN SUPPORTED PALLADIUM──TIN OXIDE CATALYSTS

ＳＴＵＤＩＥＳＯＮＴＨＥＳＴＡＴＥＯＦＰＡＬＬＡＤＩＵＭＡＮＤＨＹＤＲＯＧＥＮＡＴＩＯＮ　ＡＣＴＩＶＩＴＹＯＦＲＥＳＩＮＳＵＰＰＯＲＴＥＤＰＡＬＬＡＤＩＵＭ──ＴＩＮＯＸＩＤＥＣＡＴＡＬＹＳＴＳＨｕＷｅｉｂｉｎｇ（ＨｕｂｅｉＩｎｓｔｉｔｕｔｅｆｏｒＮ...     

THE PRECURSOR OF INSTABILITY FOR NONLINEAR SYSTEMS AND ITS APPLICATION TO EARTHQUAKE PREDICTION

By analysing the instability process of various nonlinear systems, we conclude that their instability precursors are the continual heightening of the response rate or response ratio.Applying this theory to earthquake prediction, we adopt the periodical change of the stress in crust caused by the tide-generating force as the loading and unloading. If we can measure the ratio of the response (such as crust deformation, gravity and seismicity) during the loading period to that during the unloading period, this parameter must contain some characteristic information about the seismogenic process.With nine earthquakes (M≥7) data that occurred in Chinese mainland during 1970-1988, we take the sum of square root o?energy of small earthquakes, which is called the released strain by Benioff, as the response to the tidal loading and unloading. We find that the response ratios of seven earthquakes increase obviously before the main earthquakes.     

STUDIES ON THE STATE OF PALLADIUM AND HYDROGENATION ACTIVITY OF RESIN SUPPORTED PALLADIUM—TIN OXIDE CATALYSTS

Sereral Pd-SnO2/D3520 and Pd-PbO/D3520 catalysts with Pd/D3520,SnO2/D3520 and PbO/D3520 catalysts as reference were studied by means of IR and XPS.Interaction between Pd and the second metal or between metal and support was observed.Results show that there is a strong interaction between Pd and the second metal,but there is not an obvious interaction between metal and support.The active constituent is Pd.Hydrogenation activity of the catalysts is altered because of the interaction between Pd and the second metal.The activity of the catalysis for hydrogenation has relation to outer layer valence electron density of Pd.     

应用XPS研究MoO_3在TiO_2,λ-Al_2O_3和SiO_2等载体表面上的分散量和表面状态

本文应用XPS法测定了MoO_3/TiO_2,MoO_3/γ-Al_2O_3和MoO_3/SiO_2等体系的I_(Mo3d)/I_(Ti2p),I_(Mo3d)/I_(Al2p),I_(Mo3d)/I_(Si2p)随MoO_3加入量(g/g载体)递变的关系。测定结果表明MoO_3在这几种载体上都有一分散阈值,阈值前MoO_3在载体上呈单层分散,阈值后剩余的MoO_3以晶粒形式分布在载体上。这些结果都与X射线相定量外推所得的结果吻合良好。说明这两种方法在研究氧化物负载型催化剂的分散量和表面状态上都是有效的。     

CHARACTERIZATION AND CATALYTIC PERFORMANCE OF PLATINUM SUPPORTED ON Sn-MgAl_2O_4

IntroductionSupportedPt-Sncatalystsareimpo~inthepdrileumandpthechendcalindustricsbecauseoftheirsuperiorcatalyticperformances.Forexample,Pt-Snsupportedonaneutralsupporthasbeenreportedtoexhibithighdehydrogenationselectivityanddebilitythansupportedplatinumca…     

APPLICATION OF THERMAL ANALYSIS TO THE QUICK DETERMINATION OF THE PROXIMATE ANALYSIS ITEMS AND CALORIC VALUE FOR COAL

A research on the application of a TG-DTA(thermal gravimetryaifferential thermal analysis)to the quick determination of moisture,organic volatilefixed carbon,ash and caloric value for coal is described.     

INVESTIGATION OF THE SURFACE CHARACTERISTICS AND CATALYTIC ACTIVITY OF Sb_xO_y/SiO_2CATALYSTS FOR VAPOR-PHASE SYNTHESIS OF ISOPRENE FROM ISOBUTYLENE AND FORMALDEHYDE

The surface characteristics and catalytic activity of Sb_xO_Y/ SiO_2 catalysts forvapor-phasc synthesis of isoprene from isobutylene and formaldehyde have been investi-gated by TPR, XRD, XPS, IR and catalytic activity evaluation. The results show that whenthe Sb loadings are less than about 5 wt%,Sb_xO_Y is compIctely dispersed on the surface ofsilica to form a surface compound with Sb(V)=O group and the catalysts have relativelyhigh catalytic activity; when the Sb loadings are more than 5 wt%, in addition to this surfacccompound, the crystalline α-Sb_2O_4 is formed on the support surface and causes rapid de-crease of catalytic activity. It is suggcsted that the catalytic activity of Sb_xO_Y /siO_2 catalystsresults from synetgistic catalysis of the surface compound Sb(V)=O as the basic sites andthe surface silanol Si-OH as the acidie sites. The mechanism of this synergistic catalysis forisoprene production is discussed.     

EFFECT OF Y_2O_3 ON THE PROPERTY OF NiO/Al_2O_3 CATALYST FOR PARTIAL OXIDATION OF METHANE

The effects of Y_2O_3 on the property of NiO/Al_2O_3 catalyst forcatalytic partial oxidation of methane were investigated in a continuous flowfixed bed reactor(20 mm i.d.,860 mm long).The catalysts werecharacterized by XRD and pore measurement.For comparison,similar studieswere carried out for the catalysts loaded with Zr or W oxide.The results showthat different additives and impregnating methods could greatly affect thedispersion of component Ni.The catalytic activity,the selectivity to CO andthe stability are improved because of the less facile interation between thesupport and nickel oxide,greater surface area and better dispersion of metalNi for NiO/Al_2O_3 catalyst modified by Y_2O_3.