ROLE OF MoO_3 AND La_2O_3 PROMOTERS IN Ni-CATALYZED METHANATION REACTIONS OF CO

A series of catalysts containing nickel were prepared by impregna-tion.The activity,heat resistance and sulfur resistance of catalysts were inves-tigated using catalytic microreactor.The experimental results show that the Ni/γ-Al_2O_3 catalysts containing molybdenum or lanthanum possess higher activity,better heat resistance and sulfur resistance than Ni/γ-Al_2O_3 catalyst.The sur-face behaviour of catalysts and the role of molybdenum or lanthanum in Ni-Mo-La/γ-Al_2O_3 system have been studied by XRD,TEM,XPS and TPY.It hasbeen shown that the addition of molybdenum or lanthanum can increase theconcentration of nickel atoms on the surface of catalysts,make the crystallinegranule of nickel smaller,increase the number of active centers of nickel andaffect the electronic structure of nickel.All these avtions will improve thecatalytic activity and surface behaviour of catalllysts.     

SYNTHESES OF POLYMERIC LIGAND-BOUND RHODIUM COMPLEXES AND THEIR CATALYTIC APPLICATION FOR THE HYDROFORMYLATION OF DIISOBUTYLENE

Ten polymeric ligand bound rhodium complexes were synthesized by the reaction ofRh_2(CO)_4Cl_2 and functional cross-linked poly-styrene consisting of amine, aminophosphine andphosphite groups. These polymeric catalysts were used for hydroformylation of diisobuty-lene at a temperature of 110℃, under pressures of 100, 80, 60 kg/cm~2 and H_2/CO = 1: 1 for 6h, benzene being used as the solvent. Most of the catalysts prepared showed good catalyticproperties. IR spectral analysis indicates that the polymeric amine bound rhodium catalystspossess a polydentatc structure. The rhodium elution of the catalysts was examined. Therelationship between the structure of ligands, the rhodium elution and catalytic activity wasdiscussed. A curve of rhodium elution v.s. the number of catalytic application cycles wasinvestigated. The influence of reaction conditions and additives on the loss of rhodium wasalso studied. The possible mechanism of rhodium elution of the polymeric catalysts wassuggested.     

PROPERTIES OF POLYMER SUPPORTED Ni-Cu BIMETALLIC CATALYSTS PREPARED BY SOLVATED METAL ATOM IMPREGNATION

D-72 resin supported nickel-copper catalysts prepared by solvated metal atom impreg-nation (SMAI) were studied by magnetic measurements and X-ray photoelectron spectro-scopy (XPS). The Ni particles on the catalysts are very highly dispersed and displaysuperparamagnetic behaviour. Ni-Cu alloy clusters were found to be formed. The sur-face compositions are different from the bulk concentrations. In contrast with the surfaceenrichment in copper generally observed on conventional Ni-Cu catalysts, the surfaces ofthese catalysts are enriched in nickel. The nickel is in both zero and valent states, whilecopper is mainly in metallic state. Catalytic data show that the formation of Ni-Cu alloyclusters has a profound effect on the catalytic activities of the catalysts in the hydrogena-tion of furfural. The activity of the Ni:Cu ratio of one bimetallic catalysts is much higherthan that of the Ni or Cu monometallic catalyst.     

CATALYTIC BEHAVIOR OF PQLYMER-BOUND PALLADIUM COMPLEXES FOR DECARBONYL-ARYLATION

The activities and stabilities of the polymer-bound palladium complexes fordecarbonyl-arylation were investigated in this paper.It was found that the activities ofpolymer-bound complexes are comparable to those of their homogeneous counterparts.Among the catalysts examined,the sulfur-containing polymer-bound palladium complexeshave high activity and better stability than the phosphine-,amine-and nitrile-containingpolymerie palladium catalysts.Experimental work was undertaken to evaluate the possibleside reactions.The factors which caused the catalyst deactivation were discussed and the in-flucnce of experimental parameters on the reaction was studied as well.     

THE XPS STUDY OF Cu-Co BASED CATALYSTS FOR SYNGAS CONVERSION TO ALCOHOLS

The copper-cobalt based catalysts were effective for higher alcohol synthesis, the surface state of the catalysts and the nature of the active sites were investigated by using XPS and XAES spectra, and some strong interactions were also observed, in each of the three cases, (after calcination, after reduction, and during the syngas reaction).     

PROPERTIES OF HIGHLY DISPERSED PALLADIUM CATALYSTS ON POLY N-VINYL-2-PYRROLIDONE

Four kinds of palladium catalysts dispersed on poly-N-vinyl-2-pyrrolidone were prepared by using CH3OH-NaOH, NaBH4, H2O or CH3OH-H2O as the reducing agent in the process of catalyst preparation. The catalysts were characterized by XPS, TEM, XRD and used for the hydrogenation of methyl acrylate. It was found that the valence state of palladium and distribution of palladium particles as well as the hydrogenation rate were greatly affected by the reducing agent. The best evenly dispersed palladium catalyst showing high hydrogenation activity was prepared using CH3OH-NaOH as the reducing agent.     

ACTIVATION OF O_2 AND CATALYTIC PROPERTIES OF CeO_2/CaF_2 CATALYSTS FOR METHANE OXIDATIVE COUPLING

The investigation of the catalytic properties of the CaF_2 modifiedCeO_2 catalysts for the methane oxidative coupling (MOC) to prepare C_2 hydro-carbons indicated that most of the CaF_2 modified CeO_2 catalysts were efficientfor the MOC reaction. Addition of CaF_2 to CeO_2 can make the C_2 selectivity in-crease from 2. 2％ (over CeO_2) to 46-63％, and the CH_4 conversion increasefrom 26％ to 28-30％. When the CeO_2 content was decreased within a defi-nite region, the activity and C_2 selectivity of the catalysts increased remark-ably. The XRD characterization revealed that F~-—O~(2-)exchange happened be-tween CaF_2 and CeO_2 phases. TPD, XPS, Raman and ESR experiments indicat-ed that O~-, O_2~(2-) and O_2~-species were formed over CeO_2/CaF_2 catalysts. Withthe increase of CaF_2 content in the catalysts, the kinds and the surface concen-trations of the above mentioned oxygen species decreased, while the C_2 selectivi-ty increased.     

STUDY ON HIGHLY ACTIVE ZIEGLERNATTA CATALYSTS FOR POLYMERIZATION OF OLEFINS

In this paper, highly active Ziegler-Natta catalysts of MgCl_2 supported TiCl_4 for synthesis ofpolyolefins, using di-n-butyl phthalate (DNBP) as internal donor and diphenyl dimethoxyl silane(DPDMS) as external donor, have been prepared. The conditions controlling the treatment ofsupport were studied. The interactions of various components present in the catalysts and theirinfluences on catalytic performance were investigated. It is found that by using DNBP and DPDMSas internal and external donors together the polymer products with higher isotactic index can beobtained. Plausible structure model and mechanism were proposed.     

PROMOTING EFFECTS OF Cs ON Fe/AlPO_4-5 CATALYST FOR CO HYDROGENATION

The positive effects of Cs added to Fe/AIPO_4-5 catalysts in CO hy-drogenation were studied.Cs-modified Fe/AIPO_4-5 catalysts prepared by im-pregnating method using non-aqueous acetone solution of iron nitrate werefound to be active and selective for CO conversion and light olefins formation.The characterizations of catalysts by TPR,TPD,XPS and Mssbauer techniquesindicated that the Cs addition promoted the reduction of the catalyst and adsorp-tion of CO on the surface of the reduced catalysts.A strong interaction betweeniron and AlPO_4-5 support was revealed.The results show that the AlPO_4-5molecular sieves not only can be used as the support of catalyst but also cancontrol the growth of carbon chain of the products and maintain the activity ofthe catalyst for CO hydrogenation.     

CATALYSTS FOR OXIDATIVE DIMERIZATION OF METHANE(ODM)—ROLE OF SURFACE LITHIUM IN Li-Mn-Mg OXIDES

A series of Lithium-doped Mn-MgO catalysts were characterized byXPS,XRD and AAS.It was found that lithium was of considerable significance in improving catalytic properties for ODM.Lithium ion may enter intothe lattice of MgO.When Li/Mn>1,new phases of lithium oxide and lithiumcarbonate appeared.The lithium content on surface was detected for catalystsA_(15),A_(30)and A_(50).The percentages of adsorbed oxygen species and carbonspecies(CO_3~(2-)) were increased with the increase of lithium content.Whenlithium was present on the surface of the catalysts,C_2-yield and C_2-selectivitywere greatly increased.     

硅花园法合成硅酸铝质子酸

A series of aluminasilicate Br?nsted acid catalysts were synthesized with the “silica garden” method, and characterized with XRD, XPS and NH₃-TPD technique. Acid center concentration was measured using ionic ex-change method. The catalytic activities for cumene cracking of the silica garden Br?nsted acid catalysts were ob-served and compared to that of zeolite HY and traditional acidic aluminasilicate catalysts. It was found that the 6-coordinate and 4-coordinate aluminum atoms were in silica garden Br?nsted acid catalysts. There were two kinds of acid centers and a little of crystal in silica garden Br?nsted acid catalysts. And it was also found that the crystal increased the acidities of the catalysts. The catalytic activity and strong acid center concentration of the silica garden Br?nsted acid catalysts were between that of zeolite HY and traditional acidic aluminasilicate catalysts.     

OXIDATIVE DEHYDROGENATION OF PROPANE OVER CHLORIDE-PROMOTED V-Mg-O CATALYSTS

Propane oxidative dehydrogenation (OXD) over V-Mg-O and MCl_n(M=Cu~+, Li~+, Ag~+, Cd~(2+))-promoted V-Mg-O catalysts was studied. XRDresult showed that the V-Mg-O catalysts were composed of MgO andMg_3(VO_4)_2. The promtion effects of CuCl and LiCl were significant, but ofAgCl and CdCl_2 were not efficient. XPS results indicated that on the catalystthere existed two kinds of oxygen species, lattice oxygen O~(2-) and adsorptiveoxygen (O_2~-). They affected the catalytic activity and selectivity in the OXDof propene.     

掺杂Cr助剂的Pt/USY催化剂上正庚烷异构化反应研究

The Pt-supported USY zeolite catalysts doped with Cr, Al or Zn were prepared by impregnation, and characterized by XRD, low temperature nitrogen physisorption, H2-chemisorption and IR spectroscopy of the pyridine adsorption. Catalytic activities were evaluated via the hydroisomerization of n-heptane with an atmospheric fixed-bed reactor. The Pt dispersion and acidity of the Pt-supported USY catalyst were influenced by the addition of the promoters. The Pt-supported catalysts promoted by Cr, Al or Zn, especially by Cr, were catalytically much more stable and exhibited much higher catalytic activity and selectivity for isomerization of n-heptane than the catalysts without the dopant. Both the conversion and selectivity are discussed in relation with the physicochemical properties of catalysts.     

TPD STUDY OF STEAM ADSORPTION ON Ni-RE CATALSTS

Adsorbability to steam of nickel catalysts unpromoted and promot-ed with rare earth for hydrocarbon steam reforming has been comparativelyinvestigated using TPD technique.The results showed that the adsorptive ca-pacity for steam of promoted Ni catalyst was mainly attributed to the rareearth additive and the amounts of adsorbed steam on reduction state catalystswere 1—1.4 times more than those on oxidation state catalysts.The adsorp-tive capacity for steam depended on not only the impregnation mode but alsothe contents of rare earth.At high contents of rare earth,there were threedifferent adsorption sites on the surface of catalysts.But when less than1.3%,the effect on adsorbability to steam became negnigible.The promotedNi-catalyst exhibited good coking-resistance and sulfur-tolerance.This mightbe attributed to its great capacity of adsorption to steam.     

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.     

AROMATIZATION OF C_6 PARAFFIN OVER Pt/ML(M=K,Rb)AND Pt/AlPO_4-5 CATALYSTS AT DIFFERENT TEMPERATURE

The reaction product distributions from the reactions of n-C6 and MCP over different Pt-catalysts at different temperatures were studied. It is shown that the product distributions depended on the reaction temperatures The influences of the zeolite channel functioned only at high temperature. The activity and selectivity of aromatization of n-C6 over Pt/AIPO4-5 were lower than those over Pt/L zeolite catalysts. A1PO4-5 is a non-basic support and its product distribution and reaction mechanism were different from that of basic-support catalysts such as Pt/KL and Pt/RbL.     

EFFECTS OF CONFORMATION OF POLYMER LIGANDS IN COPPER(Ⅱ) COMPLEXES ON CATALYLIC ACTIVITIES AND MECHANISM OF OXIDATIVE COUPLING OF β-NAPHTHOL

Copper(Ⅱ) complexes of sericin, chitosan, 6-and 2-aminodeoxystarch were used as catalysts in oxidative coupling of β-naphthol, the effects of conformation of the polymer ligands in these complexes on activities of the catalysts and mechanisms of the reaction were studied. It was found that if the catalysts react with the substrate by mechanism similar to the enzymic catalysis they must be composed of polymer ligands with highly coiled, especially with densely helicoidal, conformations. While catalysts composed of loosely coiled or helicoidal hgands react with the substrate through molecular collision and have relatively lower activities only. Under nitrogen, catalysts from sericin and chitosam reacting with β-naphthol give optically active β-binaphthol, rotating polarized light to right, but the stereoselectivities are rather low.     

HYDROFORMYLATION CATALYSIS USING POLYMER-SUPPORTED MULTINUCLEAR RHODIUM CARBONYL CLUSTER CATALYSTS

A series of polymer-supported tetranuclear rhodium carbonyl cluster catalysts were prepared b the reaction of Rh_4(CO)_(12) with several kinds of polymer supports such as crosslinked poly (N-vinylpyrrolidone) (PNVP) and crosslinked poly ( styrene-co-maleic anhydride) (PMAn), and subsequently were used to catalyze the hydroformylation of olefins. The catalysts were characterized by IR, SEM and XPS. The influence of the supports structure and crosslinking, metal's content and particle size of the supports on the catalysts hydroformylation properties was studied. The factors which affect the catalytic conversion were also examined. The experimental results show that the polymer-supported Rh cluster catalysts possess very high catalytic activity and aldehyde selectivity as well as good reproducibility.     

CATALYSIS OF POLYSTYRENE N-HYDROXYL SULFONAMIDE FOR ESTERIFICATION OF BUTANOL WITH ACETIC ANHYDRIDE

1. INTRODUCTION The development of efficient polymer-supported catalysts has attracted much attention [1]. For obtaining polymeric catalysts, catalytically active groups were introduced onto polymers mostly by copolymerization of the appropriate monomers bearing the desired catalyticfunctionalities (e.g. imidazole, OH, and COOH) or by modification of preformed polymers.Another possibility involves the attachment of side chains, containing the desired arrangement of functional groups, o…     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al_2O_3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.