Methanol Steam Reforming Reactions on CuZn(Zr)AlO Catalyst

雪Jourmeal NaturlGas Che hletryJournal of Natural Gas Chemnistry 13(2004)49 -52SCIENCE PRESSMethanol Steam Reforming Reactions on CuZn(Zr)AlO CatalystYongfeng Li*，Xinfa Dong,Weiming LinSouth China University of Technology, Guangzhou 510640, China[Manuscript received December 02, 2003; revised December 15, 2003)Abstract; The catalytic performances of methanol steam reformning reactions on CuZn(Zr)AIO catalystswere studied. When the ZrOz promoter was added to a CuZnAIO catalyst, its methanol conversion,H2 production and H2 sletity improved greatly. By using the #COPZr-2 catalyst as an example,which exhibited the best catalytic performance, the optimized reaction conditions were established to be:250 °C, 0.1 MPa, H2O/MeOH=1.3, WHSV=3.56 h-', and without carrier gas. A 150 h stability test ofthe #COPZr-2 catalyst showed that the catalyst had good stability, as the methanol conversion and H2production could be kept at 88% and 83% respectively. Moreover, outlet H2 and CO contents were >63%and 0.20%-0.31%, respectively.Key words: ZrO2, methanol, steam reforming, CuZnAIO1. IntroductionCu-containing catalysts in onboard H2 generators. Inthis study, a series of CuZn(Zr)AlO catalysts wereScientifc evidence strongly suggests that theprepared by the coprecipitation method, which dis-rapid building up of greenhouse gases in the atmo-played good activities and stabilities in SRM.sphere is the cause of the earth's temperature-raising,which changes the earth's climate, and has many po-2. Experimentaltential consequences. Eforts are currently underwayto reduce the emissions of greenhouse gases such as2.1. Catalyst preparationCO2 from the transportation sector by the use of hy-drogen (H2) fueled fuel cells such as polymer elec-The CuZn(Zr)AIO catalysts were prepared by thetrolyte membrane fuel cell (PEMFC) for powering ve-coprecipitation method. An aqueous solution con-hicles. There are several routes for hydrogen produc-taining Cu, Zn, Zr, and Al nitrate was used for thetion from primary fuels. One of the promising routescoprecipitation at 343 K and pH=8.0 -9.0, with 1 Mis the steam reforming of methanol (SRM). The equi-Na2CO3 as the precipitating agent. After being agedlibrium conversion of SRM can reach around 100% atat 333 K for 3 h, the precipitate was filtered, washed423 K at atmospheric pressure [1]. Cu-containing cat-with distilled water, dried at 383 K for 12 h, and fi-alysts show particularly high activities and selectivi-nally calcined at 723 K for 6 h.ties for SRM at low temperatures (503- 573 K), andthey are regarded as the main catalysts for onboard2.2. Catalytic reactionH2 generators. However, the Clu-containing catalystshave the problem of low catalytic stability [2 4]. How中国煤化工wsing a fxc-bdto solve this problem is still the key for applying the fAow:MYHC N M H Gatmospheric pres-●Corresponding author.Tel; 086-020-87057751; Fax: 086-020-87057789; E-mail address: liyf@ms.giec.ac.cnThis work is supported by the National Science Foundation of Guangdong Province (000435), Research Foundation for theDoctoral Program of Higher Education of China (20010561003), Science and Technology Program of Guangzhou(2001J1-C0211).5(Yongfeng Li et al./ Journal of Natural Gas Chemistry Vol. 13 No. 1 2004sure. A 0.2 g sample of the catalyst, diluted withS(H2)=n(H2, out)/3x 100%quartz sand (both in 20-40 mesh), was packed in an(MeOH, conversion)7 mm i.d. stainless steel tubular reactor. After re-Y(H2) = X(MeOH) x S(H2) x 100%duction in 10 vol% flowing H2 at 573 K for 5 h, pre-n(CO2, out)mixed water and methanol with a given H2O/MeOHS(CO2)=n(CO2, out) + n(CO, out)x100%molar ratio was fed into the pre-heater by means ofa micro-eeder. The reaction products first passed acold trap, then the gaseous products such as H2, CO,3. Results and discussionCO2, CH4 were detected on-line by an HP4890 GCequipped with thermal conductivity detectors and a3.1. Efect of ZrO2-promoter on the catalyticTDX-01 column. The liquid products such as waterperformanceand methanol were detected by a Shang Fen 102G GCThe performance of the CuZn(Zr)AIO catalyst isshown in Table 1. From the comparison of the perfor-401 organic supporter column. Unless otherwise men-mance between the catalysts #COP-1 and #COPZr-tioned, the catalytic activity was evaluated from the1, it can be seen that the adding of the ZrO2 promoterdata collected between 5 h and 6 h of on-stream op-could improve the overall catalytic performance of theeration for methanol conversion (X(MeOH)), H2 se-CuZnAlO catalyst, and the methanol conversion, H2lectivity (S(H2)), CO2 seletivity (S(CO2)) and H2selectivity and H2 production increased by 17%, 10%production (Y(H2)), and they are given as follows:and 20% respectively. Furthermore, by comparing theperformances among the #COPZr-1, #COPZr-2 andX(MeOH) =! x 100%#COPZr-3, it can also be seen the #COPZr-2 withn(MeOH, input)10%Zr showed the best catalytic performance.Table 1. Performance of CuZn(Zr)AIO catalyst in SRMOutlet content (%)DesignationCatalystX(CH3OH)/% S(H2)/% Y(H2)/% S(CO2)/%MeOH H2O H2 CO2 CO N2COP-1Cue0Zn3oAl039.286.033.799.421.8 30.3 36.3~ 10.9 0.065 0.562COPZr-1 CueoZn3oZrsAls56.195.453.599.314.0 18.3 51.2 15.8 0.118 0.577COPZr-2CueoZn2sZr1oAls90.055.099.61.9 21.5 50.4 15.70.067 0.525COPZr-3_ CueoZn2oZr15Als54.448.199.6 .14.5 25.1 45.8 14.1 0.060 0.476Reaction conditions: 250 °C, 0.1 MPa, H2O/MeOH=1.3:1, WHSV=11.35 h-', and without carrier gas.3.2. Establishing of optimized reaction condi- best catalytic performance in SRM, it was used as antionsexample to evaluate the effects of pseudo contact time,reaction temperature and H2O/MeOH molar ratio onSince the #COPZr-2 catalyst has exhibited thethe catalytic performance(see Figures 1-3).10. Methol Iiversion)- H2 yield0.580 E0.4日o.3 EoE0t0 E/30上中国煤化工节811011(W/F)/(g* h/mol)HCNMHG/mo)Figure 1. Efect of pseudo contact time (W/F) on the catalytic performance over #COPZr-2 in SRMReaction conditions were: 250 °C, 0.1 MPa, H2O/MeOH=1.3:1, and without carrier gasJournal of Natural Gas Chemistry Vol. 13 No.1 20045100 r).5 r◆Methanol conversion-0- H yield0.4F80 t80.350-言40 t0.1 F20 L210 220 23( )240250 260 270210 22023024250 26070Reaction temperature (C)Figure 2. Effect of reaction temperature on the catalytic performance over #COPZr-2 in SRMReaction conditions: 0.1 MPa, H2O/MeOH= 1.3:1, WHSV=4.45 h~l , and without carrier gas0F- o- H2 yield70 F0L-0.1..3.60.73n(H,0)1 n(MeOH)m(H20)1 n(MeOH)Figure 3. Efect of H2O/MeOH molar ratio on the catalytic performance over #COPZr-2 in SRMReaction conditions: 250 °C, 0.1 MPa, WHSV=2.97 h~1 , and without carrier gasIn order to achieve the desired goal of#COPZr-2 catalyst under the optimized reaction con-higher methanol conversion， higher H2 produc-ditions. It can be seen that the #COPZr-2 catalysttion and lower outlet CO content, it was estab-had good initial activity, and the catalytic perfor-lished that the optimized reaction conditions were:mance decreased a little at first, and then remained250 °C, H2O/MeOH=1.0- 1.3:1, W/F=6.74 (g:h)/molstable after 9 h. At this point, the methanol conver-(namely WHSV=3.56 h-1).sion an中国煤化工t about 88% and3%, rE H,content was3.3. Stability test of the catalyst>63%，YHC N M H Gvas 0.20%-0.31%.These results can well meet the demands of onboardFigure 4 depicts the 150 h stability test of theH2 generators.52Yongfeng Li et al./ Journal of Natural Gas Chemistry Vol. 13 No.1 200410- + Methanol conversion)0-0- H2 yield1.20F宫1.后0.0.661100 120 140 16020) 100 1240 160Time on stream (h)Figure 4. Time course of SRM over the #COPZr-2 catalystReaction conditions: 250 °C, 0.1 MPa, H2O/MeOH= 1.3, WHSV=3.56 h-1, and without carrier gas4. ConclusionsReferencesThe adding of the ZrO2 promoter can improve the[1] Amphlett J C, Creber K A M, DavisJ M et al. Int Joverall catalytic performance of the CuZnAlO cata-Hydrogen Energ, 1994, 19(2): 131lysts. Using the #COPZr-2 catalyst as an example,[2] Yongtaek C, Harvey G s. Appl Catal B, 2002, 38: 259which exhibited the best catalytic performance, the[3)| Alejo L, Lago R, Pena M A et al. Appl Catal A, 1997,optimized reaction conditions were established. The162: 281150 h stability test of the #COPZr-2 catalyst showed[4] Yanyong L, Takashi H, Kunio s et al. Appl Catal A,that the catalyst has good stability.2002, 223: 137中国煤化工MYHCNMHG