EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST IL REDUCIBILITY OF K-Fe-MnO/SILICALITE-2 CATALYST

K_2O and MnO are two kinds of necessary promoters to theselective production of light alkenes from CO hydrogenation over silicalite-2(Si-2) zeolite supported Fe catalyst. The addition of both K_2O and MnOpromoters into Fe/Si-2 catalyst leads to a remarkable increase in the COconversion and the selectivity to light oletins. Silicalite-2 zeolite as Fe-MnOcatalyst support can suppress the formation of α-Fe_2MnO_3 or/andα-Fe_(2-y)Mn_yO_3 as Well as α-Fe_2O_3 and/or α-Mn_2O_3, being favorable for(?)ncreasing the dispersion of active metal component. So MnO can promotethe reduction of Fe~(3-) and enhance the capacity of CO adsorption, which canimprove the activity of the activity of the catalyst for CO hydrogenation. While K_2Opromoter is unfavorable for reduction of Fe~(3-) to some degree with formation of Fe~(2-) as a new species after reduction. However, K_2O promoter can enhance the capacity and strength of CO adsorption greatly.So K_2O can alsoimprove the activity of catalyst for CO hydrogenation.     

EFFECTS OF K_2O AND MnO PROMOTERS ON THE PRODUCTION OF LIGHT ALKENES VIA SYNGAS OVER Fe/SILICALITE-2 CATALYST I.ACTIVITY OF K-Fe-MnO/SILICALIT-2 CATALYST

The activity and the selectivity to light alkenes of silicalite-2 (Si-2) zeolite supported F'e catalyst tor CO hydrogenation can he improved obviously with the addition of K2O and MnO promoters. The results of CO hydrogenation, CO-TPD, CO/H2-TPSR, C2H4/H2-TPSR and C2H4/H2 pulse reaction over K-Fe-MnO/Si-2 catalysts clearly show that the K2O additive into Fe-MnO/Si-2 catalyst leads to a remarkable increase in both the capacity and strength of the strong CO ad-species that will produce much more |Cad| via their disproportionation at higher temperatures. This results in an increase in the CO conversion and the selectivity to light olefins, and a decrease in CH4 formation. Moreover, K2O can suppress the disproportionate of C2H4 that occurs during the reaction as a side-reaction Meanwhile, the MnO promoter mainly prohibits the hydrogenation of C2H4 and C3H6, which is favorable to enhancing the selectivity to C2H4 and C3H6 and decreasing the formation of C2H6, and C3H8. It is also of interest that MnO has har     

FRACTAL ANALYSIS OF CATALYST NiO/α-Al_2O_3

We found that the Freundlich formula H=kC~(ln)can be used todescribe the isothermal adsorption curve of support α-Al_2O_3 with fractalstructures in nickel nitrate solutions.where n is relative to the surface fractaldimension D of α-Al_2O_3.     

SYNTHESIS OF HYDROCARBONS FROM CO_2 AND H_2 OVER Fe/C CATALYST

The production of hydrocarbons by hydrogenation of CO_2 is one ofthe most challenging aims in C_1 chemistry. In this work, we studiedCO_2 hydrogenation over iron catalyst supported on carbon under differentreaction conditions. The products of CO_2 hydrogenation on Fe/C catalyst weremainly hydrocarbons including more than 70% C_2~+ hydrocarbons. When thereaction temperature and pressure were elevated,the CO_2 conversion and theselectivity to hydrocarbon(HC) products increased. It was also found that theaddition of Cu onto Fe/C catalyst has an apperent effect on the activity andselectivity of Fe/C catalyst. It increased the CO_2 conversion and the selectivityto total HC Products to 62.8% and 100% respectively. The results obtainedfrom TPR and M(?)ssbauer spectroscopy proved that the iron was reduced mucheasier in Fe-Cu/C than in the Fe/C catalyst.     

ESR STUDY OF ZrO_2 CATALYST

ＥＳＲＳＴＵＤＹＯＦＺｒＯ＿２ＣＡＴＡＬＹＳＴ￥ＷｅｎＬＩ；ＬｉａｎｇＢｏＦＥＮＧ；ＹｕａｎＱｉＹＩＮ（ＬａｎｚｈｏｕＩｎｓｔｉｔｕｔｅｏｆＣｈｅｍｉｃａｌＰｈｙｓｉｃｓ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｌａｎｚｈｏｕ７３００００）...     

DEACTIVATION OF P_2O_5-MgO/RE_2O_3 CATALYST FOR OXIDATIVE COUPLING OF METHANE

Techniques including TPD,XPS,XRD and spectrophotometry have been applied to theinvestigation of the deactivation of a highly active P_2O_5-MgO/RE_2O_2 catalyst during a 100-h test.The results of the studies have shown that there is little difference in various properties between thefresh and the deactivated catalyst except for the surface acid-base property which is demonstrated to becontrolled by the presence of phosphorus on the catalyst surface.The deactivation of the catalyst ismainly due to the heavy loss of phosphorus on the surface that causes an increase of the surface basiccenters and a decrease of the surface acid centers,and the coordination between the acid and basiccenters is considerably weakened with a subsequence of the drop of the C_2 selectivity.     

STRUCTURAL AND ELECTRONIC EFFECTS OF TiO_2 IN CuO-ZnO/Al_2lO_3-TiO_2 CATALYST

The modification effects of TiO_2 towards Cu or CuO in supportedCuO-ZnO/Al_2O_3-TiO_2 catalyst were studied by XPS,TPD and test reaction.XPS showed that TiO_2 additive improved the dispersity of CuO or Cu in cata-lyst.TPR showed that the reduction temperature(Tr)of CuO in CuO-ZnO/Al_2O_3-TiO_2 increased with the content of TiO_2.XPS showed that the Eb valueof Cu in TiO_2 containing catalyst(Eb=993.7 eV) was larger than that inTiO_2 free catalyst(Eb=932.9 eV).These indicate that TiO_2 displayed elec-tronic effect on catalyst.Both structural effect improving the dispersity of Cuand electronic effect weakening the bond strength of Cu-S in catalyst caused theS-resistance of CuO-ZnO /Al_2O_3-TiO_2 catalyst greatly improved.     

OXIDATIVE COUPLING OF METHANE OVER Mn_2O_3-Na_2WO_4/SiO_2 CATALYST Ⅰ.CHARACTERIZATION OF ACTIVE SITES ON THE CATALYST

EPR and Raman spectroscopy have been used to characterize the catalyst. F-centers with EPR parameter of g=2. 0046 form when gas phase oxygen is admitted onto the catalyst reduced with methane at 800℃- Molecular oxygen plays an induced role in the electron transfer from W4 to the oxygen ion vacancy which is produced by methane reduction. Raman spectra give the further evidence for the production of lattice oxygen from molecular oxygen.     

PRODUCTION OF LIGHT ALKENES FROM CO AND/OR CO_2 HYDROGENATION OVER K-Fe-MnO/SILICALITE-2 CATALYST

High selectivity to light alkenes can be achieved from CO and CO_2hydrogenation over K-Fe-MnO/Si-2 catalyst.The alkene selectivity isinsensitive to reaction temperature for CO hydrogenation,while apparentlyincreases for CO_2 hydrogenation with raising reaction temperature.An increasein alkene selectivity is observed for both CO and CO_2 hydrogenation with GHSVrising,While a decrease with the elevation of reaction pressure for both CO/H_2and CO_2/H_2 reaction.A two-step mechanism is suggested forCO_2 hydrogenation to form hydrocarbons,by which the variations incontributions of CO and HC as products of CO_2/H_2 reaction with change ofreaction temperature,GHSV and pressure are explained.Moreover,thecatalyst is favorable for selective production of light olefins,which can alsoconcern the slightly secondary reactions of light olefins to some extent.     

EFFECT OF ThO_2 ON SrCO_3/BaSO_4 CATALYST IN OXIDATIVE COUPLING OF METHANE

IntroductionSincethepioneeringt"orkofKcllcrandBh.,i.IlI.theoxidativccoupl1ngofmethane(0CM)hasrcceivedx`orldt`.idcattcntion.Sofar-man}'kindsofcatal}'stsfor0CMhavcbecndeveIoped.0nthcbasisofextensivelitcrature,thccatal}'stsfor0CMboastssomccommonfcaturesasfolIo``sl2lf(l)thebasicityofcatalyst,(2)thestabilit}'ofcarbonateoncatal}'stsuffocc,(3)`"atcr-rcsistingpropcrt}',(4)conductionofox3'gcnions,(5)Psemiconductorundcrhightempcraturc.Thcscbricfl}'gcncralizcthccharactcristicsof0CMcataly'sts.butnot…     

INVESTIGATION OF THE ACTIVE PHASE OF Ag_xSb_yO_z/SiO_2 CATALYST FOR THE CONDENSATION OF ISOBUTENE AND FORMALDEHYDE INTO ISOPRENE

Chemical Composition,surface distribution of the elements and crystal structure offresh and deactivated Ag_xSb_yO_z/SiO_2 catalysts were investigated investigated by X-ray photoelectronspectroscopy(XPS),scanning Auger microprobc(SAM),electron microdiffraction(EMD)and atomic absorption spectroscopy(AAS).From the experimental results that in-clude the activity evaluation of model catalyst Sb_2O_4/SiO_2 Which Shows the inertness ofSb_2O_4 in Prins reaction,it is reasonable to infer that the active phase ofAg_xSb_yO_z/SiO_2 catalyst for Prins condensation reaction seems to be cubic AgSbO_3.Thereason of the deactivation of the catalyst was discussed.It is suggested that silver componentseems to be unstable in this catalyst.     

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.     

Li_2SO_4-Mn_xO_y/TiO_2 CATALYST FOR ETHYLENE SYNTHESIS BY CATALYTIC OXIDATION OF METHANE

The synthesis of ethylene by catalytic oxidation of methane over Li-2SO_4-Mn_xO_y/TiO_2 wascarried out in a conventional fixed bed flow reactor.A 246-h life test of the catalyst under the condi-tions of normal pressure,1073K,2g of catalyst,and flow rate(ml/min)CH_4:O_2:N_2=15:6:15showed that the C_2 yield and C_2 selectivity were 30.8％(C_2H_4 19.8％)and 82.5％ respectively.XRDpatterns of this multicomponent catalyst revealed that the support TiO_2 was mostly converted intofutile,MnTiO_3 was the main active component,LiMnO_2,Li_2TiO_3 and TiOSO_4 were the active andoxidation-controlling components.     

OXIDATIVE COUPLING OF METHANE OVER Mn_2O_3-Na_2WO_4/SiO_2 CATALYST IN THE ABSENCE OF DILUTE GAS

The oxidative coupling of methane over Mn2O3-Na2WO4/SiO2 catalyst has been investigated in the absence of dilute gas. 16.4% of C2 yield and 80.4% of the selectivity to C2 hydrocarbons were obtained at CH4/O2 = 8.5/1.5. The effect of flow rate on the selectivity to C2 hydrocarbons and CH4 conversion was different under the reaction condition of different ratio of CH4 to oxygen. The flow rate had a more remarkable effect on the selectivity at the lower ratio of methane to oxygen. The addition of steam into the reaction gas can increase C2 yield to some extent, but that of HC1 decrease the selectivity to C2 hydrocarbons.     

THE PREPARATION CHEMISTRY OF V/MgO CATALYST FOR OXIDATIVE DEHYDROGENATION OF ETHYLBENZENE

The structures and catalytic performances of V_2O_5, Mg_3V_2O_8 and V/MgO catalysts have been correlated by means of XRD, FTIR, TPR and flow micro-reactor tests. The postulation about active site has been made. Based on it, better catalysts have been first prepared via grafting and modification with Sb which are better than that via impregnation.     

METHANE OXIDATIVE COUPLING ON ThO_2/CaF_2CATALYST

The oxidative coupling of methane(OCM)over ThO_2/CaF_2 catalystwas investigated.The catalyst was found to be active and selective for OCMreaction.At 1153 K,the C_2~ yield was 19.9% with 61.7% C_2~ selectivityand 32.1% CH_4 conversion.XRD results indicated that F~-(?)O~(2-)exchangehappened between ThO_2 and CaF_2 phases.XPS and Raman results suggestedthat the active oxygen species were generated and suitable for OCM reactionover the catalyst.     

INFLUENCE OF VOCl_2-ADDITIVE IN Rh CATALYST ON CO HYDROGENATION

The influence of VOCl2 additive in the supported Rh catalysts derived from both Rh2 (CO )4 Cl2 and RhCl3 on CO hydrogenation was investigated. The VOCl2 additive as a promoter can effectively enhance the CO conversion and catalytic selectivity to ethanol. This effect is caused by the interaction of Rh with vanadium promoter. It is found that the Rh centers on which the gem- adsorbed CO could be formed are main active sites. The Rh2(CO)4Cl2 complex is better than the RhCl3 salt as the precursor of the Rh catalyst for the CO hydrogenation to ethanol.     

STUDY ON DEACTIVATION OF POTASSIUM-PROMOTED COBALT-MOLYBDENUM/ALUMINA WATER-GAS SHIFT CATALYST

The deactivation of a potassium-promoted CoMoK/Al_2O_3 Catalystwas investigated by means of XRD,XRF,XPS,ICP,FT-IR etc.The resultsshow that the reaction Pressure,deposition of Cl~- and the formation sulfateslead deactivation of the catalyst.The effect of impurities was studied systemati-cally with both qualitative and quantitative methods.The way to resolve thedeactivation of CoMoK/Al_2O_3 was discussed.     

TPR STUDY OF SOPPORT EFFECT ON NiO-La_2O_3 METHANATION CATALYST

lntroductionTio2islargelyemploycdincatalystprcparationductoitsreducibilityandStrongilltCodionwiththesupportcdcomponcntsl1].Hotvever,somedraWbacksofTiO2,suchaslowsurfacearea,poormechanicalstrengthandunstableanataSestruCtureathightettiperature,makeitsindustrialutiliZaionnearlyimpossible.Accordinly,thcY-AlO3-Tio2supportisdeveloPedformakinbeStuseoftheadvantagndbyPaSsbethedisadVantagsl2-].ThcreisnoncwcompoundformedbetWeeny-Al2O3andTiO2,Iinstedd,TiO2isuniformlydisperscdonthesurfaceofy-Al2…     

EFFECT OF ADDITIVES ON Li-La-TiO_2 CATALYST PROPERTIES IN METHANE OXIDATIVE COUPLING

For adjusting the surface properties of the catalysts some metroxides as the promoter were added into Li-La/TiO_2 system and enhanced theactivity and ethylene selectivity for the oxidative coupling of methane.Theeffect of the reactant composition,the gas hourly space velocity(GHSV)andthe reaction temperature on the performance of the catalysts were investigat-ed.It was found that the methane conversion,C_2 selectivity and Cyieid wereaffected by the promoters.The SUC series exhibited high activity,selectivityand stability.Over catalyst SUC-3,methane conersion was up to 41.5%,C_2 selectivity,61.7% and C_2 yield,25.6% at 770℃ and GHSV=14400h~(-1).SUC-2 has continuously been operated at 850C and GHSV=3428h~(-1)for 500 hours,the methane conversion,C_2 selectivity and C_2 yieldkept at the level of about 30,60 and 18% respectively.