PRODUCTION OF LIGHT OLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅳ. PERFORMANCE OF THE K-Fe-Mno/Si-2 CATALYST

IntroductionInordertodevelopanewcatalystwithbCttercarelyticedivityforseleCtiveproductionoflightolefinsfromCOZhydrogenation,asilicalite-2(St-2)zeolitesupportedFecatalystpromotedbyalkalimetalandMnOadditiveshasbeenacquiredwithmorethan68%oflightolefinselectiv…     

EFFECTS OF BINDERS ON THE PRODUCTION OF LIGHT ALKENES FROM SYNGAS OVER K-Fe-MnO/SILICALITE-2 CATALYST I. EFFECT OF VARIOUS BINDERS ON CO HYDROGENATION

The performance of the K-Fe-MnO/Si-2 catalyst for the production of light olefins via Co hydrogenation changes obviously with the addition of binders. The results of CO hydrogenation. TPR, Mossbauer spectra CI0TPF, CO/H2-TPSR and C2H4/H2-TPSR are employed to investigate the effects of various binders on the physical-chemical states and catalytic behaviors of K-Fe-MnO/Si-2 catalyst to produce light olefins via syngas, TiO2 can promote the reduction of Fe and strengthen the adsorption of CO resulting in raising olefin selectivity. Other binders such as Al2O3, SiO2, MgO, once added into the catalyst, may cause formation of inorganic salts between FeO and Binders leading to a decrease of Fe reduction and a loss of olefin selectivity for CO hydrogenation. Especially, For K-Fe-MnO/Si-2 catalyst with Al2O3 binder directly, the strong secondary reactions of ethylene during CO hydrogenation cause a very poor light olefin selectivity, which will be improved greatly by modifying Al2O3.     

EFFECTS OF BINDERS ON THE PRODUCTION OF LIGHT ALKENES FROM SYNGAS OVER K-Fe-MnO/SILICALITE-2 CATALYST Ⅱ. MODIFICATION EFFECT OF Al_2O_3 BINDER ON CO HYDROGENATION

lntroductionInordcrtoselcctivcl}'produccIightoIcfinsfroms}'ngas.thcbinderusedforimprovingthecatal}'ststrcngthshouldbcfavorabIcforprimary'formingofligl1tolcfinsfroms}ngasandforprohibitingsidereactionsoflightoIcfi.sIll.lthasbccnshownthattheundesirablcstrengthofsilicalitc-2zcolitccanbcimprovcdb}addingbindcrs.Hot`ycver.thcadditionofthcbinder`"illcauscsomcchangcsinthcph}'sical-chcmicalstatcofthecatal}ticactivemetalas``cllasitscatal}ticbcha.io,ll'2I.InourprcviouspaperTiO2wasprovedtobcadcsirablcbi…     

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     

PRODUCTION OF LIGHT OLEFINS FROM CO2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST. I.CATALYTIC REACTIVI-FY AND REACTION MECHANISM

K-Fe-MnO/Silicalite-2 is a desirable catalyst for the production of light olefins from CO2 hydrogenation The activity can be improved greatly with increasing the Fe loading, and the selectivities to hydrocarbons rise with Fe loading increase However, an ambiguous effect of Fe loading on the selectivity of light olefin in hydrocarbon products is observed. The CO2 hydrogenation containing a two-step mechanism CO2+H2=CO+H2O, a reversible water gas shift reaction, and CO+(m/2n+1)H2 =1/nCnHm+H2O2, a Frscher-Tropsch reaction, is suggested by the results of CO2-TPD and CO2/H2-TPSR as well as CO/H2-TPSR characterizations.     

EFFECTS OF BINDERS ON THE PRODUCTION OF LIGHT ALKENES FROM SYNGAS OVER K-Fe-MnO/SILICALITE-2 CATALYST Ⅰ. EFFECT OF VARIOUS BINDERS ON CO HYDROGENATION

Intr0ductionRcccntl}.n1uchprogrcsshasbcc11n1adcinthcscIcctivcCOh\'drogcnationproducingliglltolcfinsvIas}'ngasb}'dct'clopingasilicalitc-2zcolitcsupp0rtcdFccatal\'st.Ithasbccllshox\llthatasilicaIitc-2zcoIitcsupportcdFccatal\'stpromotcdb}'aIkalin1ctalandMnOdispla}sadcsirabIcolcfil1sclccti\'it}(asl1ighas7()%)andadcsirablcCOcont'crsion(muchhighcrthan7O%)\\ithabett.,rcactionlifconst,ca.I1~31.Ho\\cvcr-thcundcsirablcstrcl1gthofSi-2zcolitcisunsuitabIcforitsapplicatiOninindustry-\\hichsIlouldbci…     

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.     

PRODUCTION OF LIGHT OLEFINS FROM CO2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST III. PROMOTION EFFECT OF K2O PROMOTER

K2O is a vital promoter to the Fe-MnO/silicalite-2 catalyst for light olefin formation from CO2 hydrogenation. With addition of it into the Fe-MnO/Si-2 catalyst the selectivity to light olefins increases greatly, while CH4 formation is inhibited evidently. Meanwhile, an obvious increment in CO2 conversion is also observed with the addition of K2O promoter. And it has been manifested that adding K2O to the Fe-MnO/Si-2 catalyst leads to remarkable increases in both the capacity and strength of the strong CO2 and CO adspecies. These produce much more[Cad] via their disproportionation at higher temperatures. This results in increase in the CO2 conversion and the selectivity to light olefins, and a decrease in CH4 formation.     

Fe—Silicalite—2催化剂表面CO2加氢反应性能的研究

研究了Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２加氢低碳烯烃反应性能，利用ＣＯ２－ＴＰＤ，ＣＯ２／Ｈ２－ＴＰＳＲ和ＣＯ／Ｈ２－ＴＰＳＲ表征手段，考察了铁含量及ＭｎＯ助剂对Ｆｅ／Ｓｉｌｉｃａｌｉｔｅ－２催化剂ＣＯ２吸附脱附及加氢反应性能的影响，表明随铁含量增加可提高催化剂对ＣＯ２的吸附能力，有利于提高ＣＯ２加氢反应的转化率。     

PRODUCTION OF LIGHTOLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅱ. PROMOTION EFFECT OF MnO PROMOTER

IntroductionItilasbeenshot'-nthattileadditionofMnOpromotertoFocatal}stcanresultinaremarkableimprovementinthesclectivit}'to11ghtalkenesforCOh}!drogenationll'l.Ho-c'cvcr.thecadetofMnOonCH4formationandCOconversionisvery'ambigUouslltolMoreover.MnOpromotergrca…     

PRODUCTION OF LIGHT OLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYSTⅢ. PROMOTION EFFECT OF K_2O PROMOTER

ThisprojectissllpportedbytheNationalNaturalScienceFotmdationofChina.IntroductionRecentstUdyonCOZhydrogenationfortheformationofhydrocarbonshascausedagreatinterest,especiallyintheproductionoflightalkenes.msreactionwillprovideanalternativeroutetoproducebasic…     

K_2O和MnO助剂对Fe／Silicalite－2催化剂CO加氢制低碳烯烃性能的影响

在Ｓｉｌｉｃａｌｉｔｅ－２分子筛担载的铁催化剂中添加ＭｎＯ和Ｋ２Ｏ助剂，可显著提高其ＣＯ加氢制低碳烯烃的选择性及催化活性．ＭｎＯ助剂主要抑制乙烯和丙烯的加氢反应而提高烯／烷比值；Ｋ２Ｏ助剂则增加催化剂对ＣＯ的吸附能力，同时抑制乙烯在催化剂表面的二次反应（主要是乙烯的歧化反应），从而有利于提高低碳烯烃的选择性及催化剂活性．     

合成气制低碳烯烃K－Fe－MnO／MgO催化剂的研究Ⅰ．MnO助剂的作用

采用ＣＯ加氢反应、ＣＯ－ＴＰＤ、ＣＯ／Ｈ＿２－ＴＰＳＲ及Ｃ＿２Ｈ＿４／Ｈ＿２－ＴＰＳＲ等手段，研究合成气制低碳烯烃反应Ｋ－Ｆｅ－ＭｎＯ／ＭｇＯ催化剂中ＭｎＯ的助剂作用。结果表明ＭｎＯ能大幅度提高低碳烯烃的选择性，尤其是乙烯的选择性；ＭｎＯ能抑制催化剂表面的乙烯加氢，因而有利于提高低碳烯烃的选择性及烯／烷的比值。     

PRODUCTION OF LIGHT OLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅰ.CATALYTIC REACTIVI-FY AND REACTION MECHANISM

IntroductionRcccntl}'.researchinterestinhctcrogcllcotlscatal\'ticCOZh\'drogcnationhasfocusedontileproductionofh}'drocarbonsl1~-if.Asfortheformationoflightolefins.afo\'papershat'cbccllptlblishcdlit>l.Ho\\c\cr.tileprodllctionoflightolcfillsf'ronlCOZh}'droge…     

Ni/ZrO2催化剂上甲烷水蒸气重整反应的研究

研究了Ni/ZrO2催化剂对甲烷水蒸气重整制合成气的反应性能。考察了催化剂的还原温度、载体焙烧温度以及反应温度、原料配比和空速等对催化剂性能的影响。利用XRD、TEM、XPS等手段对催化剂的织构形貌进行了表征。研究表明，Ni/ZrO2催化剂用于甲烷水蒸气重整制合成气不仅具有较高的活性，也具有较好的稳定性。水蒸气比增加，CH4转化率增大、CO选择性下降。CH4转化率及CO选择性均随空速增大而下降。使用10%Ni/ZrO2催化剂，在650 ℃、空速1.984×104 h－1、原料气配比H2O∶CH4∶N2=2∶1∶2.67的条件下，获得CH4转化率85%、CO选择性70%的结果。     

Ni-Mo/Al_2O_3催化剂上硫转移反应的研究

制备了以γ-Al2O3为载体的Ni-Mo催化剂,并用于FCC汽油的加氢硫转移反应。对Ni-Mo/Al2O3催化剂上的硫转移反应机理进行了研究,考察了不同反应条件对硫转移反应的影响。实验结果表明,硫醇与烯烃的反应在催化剂表面的加氢活性位上进行,小分子的硫醇发生加氢脱硫,生成吸附态H2S,吸附态的H2S与烯烃反应,生成大分子硫醇和硫醚;另外小分子硫醇还可直接与烯烃发生反应,生成硫醚。提高反应温度、压力、氢油比或降低空速,均可提高催化剂的硫转移反应活性,轻质硫转化率得到明显提高,且单烯选择性还能维持在98%左右。     

Co/TiO2催化剂上肉桂醛的选择加氢

研究了超细TiO2负载的Co/TiO2催化剂上肉桂醛的选择加氢反应,讨论了Co负载量对肉桂醛加氢反应活性和选择性的影响.结果表明,随着Co负载量的增加,催化剂的活性和选择性提高.以CoCl2为前驱物的Co/TiO2催化剂的选择性要高于以Co(NO3)2为前驱物的Co/TiO2催化剂,而催化剂的活性正好相反.以CoCl2为前驱物的Co/TiO2催化剂上,Co负载量为10%和20%时,两者的选择性没有差别,只是前者的活性略低.TPR结果表明,两种前驱物的Co/TiO2催化剂在还原性能方面没有差别.XRD结果表明,TiO2表面上的Co均以Co3O4状态存在.两种不同前驱物的Co/TiO2催化剂在活性和选择性方面存在的差别是由于KCl的存在.     

CO和CO2在Cu／ZnO／Al2O3催化剂上加氢反应机理的原位红外研究

ＣｕＺｎＯＡｌ2Ｏ3催化剂用于合成甲醇的反应机理已经进行了大量的研究[1～3]。近年来,利用原位红外技术在研究合成甲醇的催化反应机理方面取得了不少研究成果[4～7]。但大多数实验是采用低铜含量催化剂[4,5]。本文采用高温加压式原位红外池,在513Ｋ和20ＭＰａ的条件下,...     

水热法Fe-Mn催化剂制备及其合成气制低碳烯烃催化活性

以水热合成法制备了K原位改性的Fe-Mn催化剂,考察了其CO加氢合成低碳烯烃催化活性。采用SEM、TEM、XRD、H₂-TPR和FT-IR等手段对催化剂进行了表征。结果表明,制备的催化剂前驱体呈50~70 nm的球形颗粒,表面富含羰基和羟基,物相组成以Fe₃O₄为主,用于反应后有Fe₅C₂和MnCO₃相生成。与共沉淀法制备催化剂相比,在设定的反应条件下,不同K含量改性的催化剂均具有较高的活性,以原料配比Fe:Mn:C₆:K=3:1:5:0.10的催化剂性能最佳,CO转化率达95.02%,总低碳烯烃收率为62.86 g/m³(H₂+CO),CH₄和CO₂选择性分别为13.88%和13.98%。     

A kinetic study on the conversion of cis-2-butene with deuterium on a Pd/Fe3O4 model catalyst

The conversion of cis-2-butene with deuterium over a well-defined Pd/Fe(3)O(4) model catalyst was studied by isothermal pulsed molecular beam (MB) experiments under ultra high vacuum conditions. This study focuses on the processes related to dissociative hydrogen adsorption and diffusion into the subsurface of Pd nanoparticles and their influence on the activity and selectivity toward competing cis-trans isomerization and hydrogenation pathways. The reactivity was studied both under steady state conditions and in the transient regime, in which the reaction takes place on a D-saturated catalyst, over a large range of reactant pressures and reaction temperatures. We show that large olefin coverages negatively affect the abundance of D species, as indicated by a reduction of both reaction rates under steady state conditions as compared to the transient reactivity on the catalyst pre-saturated with D(2). Limitations in D availability during the steady state lead to a very weak dependence of both reaction rates on the olefin pressure. In contrast, when the surface is initially saturated with D, the transient reaction rates of both pathways exhibit positive kinetic orders on the butene pressure. Cis-trans isomerization and hydrogenation show kinetic orders of +0.7 and +1.0 on the D(2) pressure, respectively. Increasing availability of D noticeably shifts the selectivity toward hydrogenation. These observations together with the analysis of the transient reaction behavior suggest that the activity and selectivity of the catalyst is strongly controlled by its ability to build up and maintain a sufficiently high concentration of D species under reaction conditions. The temperature dependence of the reaction rates indicates that higher activation energies are required for the hydrogenation pathway than for the cis-trans isomerization pathway, implying that different rate limiting steps are involved in the competing reactions.