Study of Methanol Conversion over Fe-Zn-Zr Catalyst

Available online at www.sciencedirect.comScienceDirectJournal od Natural Gas ChemusinJournal of Natural Gas Chemistry 16(2007)326- -328SCIENCE PRESSCommunicationStudy of Methanol Conversion over Fe- Zn- Zr CatalystXiaoming Nil2，Yisheng Tan': Yizhuo Hanl*1. State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences,Taiyuan 030001, Shanxi, China; 2. Huaibei Coal Industry Teachers College, Huaibei 235000, Anhui, China[ Manuscript received January 24, 2007; revised May 22, 2007 ]Abstract:The methanol conversion over Fe-Zn-Zr catalyst was studied at 0.1 MPa and 280- -360 °C.The experimental results indicate that the main products of methanol conversion are methane and butane, .and that other hydrocarbons are scarcely produced. All results show that propylene is most probably theolefin formed first in methanol conversion rather than ethene over Fe-Zn- Zr catalyst. Methane is formedfrom methoxy group, and C4 is possibly yielded on the surface from propylene through binding with amethoxy group.Key words: methanol; conversion; Fe _Zn-Zr catalystRelative to petroleum, coal and natural gas areThe precipitate was aged for 2 h, and then filteredrelatively rich in the energy resource structure of ourand washed with distilled water 10 times. The gelscountry. The technique of converting these substanceswere dried at 120 °C for 12 h, and then calcined atinto methanol has already been developed. It is of400 °C for 4 h. The sodiun content in the cata-great significance to convert methanol further intolyst was confirmed to be less than 0.01wt% by atomsproducts with higher value for the rational utilizationscan spectroscopy (Atom Scan 16). The catalyst wasof energy resource in our country.pelletized and crushed into 60- -80 meshes. HY (JRC-The research on methanol conversion was doneZ-HY 4.8, Si/Al=4.8) was provided by the Referencein the early days, such as the study on the synthe-Catalyst of the Catalysis Society of Japan.sis ofpetroleum [1- -3]. In recent years, the study onThe reaction of methanol conversion was carriedmethanol conversion has again attracted the atten-out in a pressurized flow-type fixed-bed reactor. Thetion of researchers [4-7], and almost all research onreactor was made of a stainless-steel tube with an in-the hydrocarbon synthesis through methanol conver-ner diameter of 6 mm. The catalyst was first packedsion has been done on the zeolite catalyst [8-10].in the reactor, and then reduced in a stream of dilutedIn this article, we have attempted to study thehydrogen (5%H2 in N2) at 340 °C for 12 h. Aftermethanol conversion on a metal catalyst and have dis-the pre-reduction, the reactant gas (8% MeOH in N2)cussed the route of the hydrocarbon synthesis.was introduced into the reactor under 0.1 MPa. Af-The Fe-Zn-Zr catalyst was prepared by theter the reaction was completed under the prescribedcoprecipitation of the corresponding nitrates withconditions, all effluent gases were analyzed by on-linesodium hydroxide. The two solutions were concur-gas chromatograph using carbon molecular sieve col-rently added to a beaker and stirred continuously atumn中国煤化工de, and methane,60-65 °C. The pH value was maintained at about 7.0.andMHCNMHG_urbons, methanol,. Corresponding author. Tel: 0351-4044287; Fax: 0351-4044287; E-maFoundation item: this work was Financially supported by the National Natural Science Foundation of China (ProjectNo.29973056).Journal of Natural Gas Chermistry Vol. 16 No.32007327and dimethyl ether. The carbon dioxide concentra-tivity for CH4 with that for C4 with increasing tem-tion was analyzed by the Orsat analyzer.perature, an important phenomenon could be foundThe experiment of methanol conversion on the that the selectivity for C4 declined with the increaseFe-Zn-Zr catalyst was carried out at 0.1 MPa andof selectivity for CH4. It is evident that there is a280- 360 °C. The experimental results are shown in close relationship between the formation of C4 andTable 1 and Figure 1.CH4, and it is not dfficult for us to consider thatC4 and CH4 are probably formed during the reactionTable 1. Results of methanol conversionon Fe Zn-Zr catalystfrom a common intermediate.According to the experimental results and theConversionSelectivity (C-mol%)/C(%)DME co _CO2HCabove discussions, it is thought that the reaction may28088.9516.17 39.25 25.93 18.65take place as follows: methanol is first converted0092.6217.6941.0522.24 19.02into the methoxy binding on the catalyst surface, and32091.6220.86 42.53 18.20 18.41then methane is yielded from the reaction of methoxy89.0725.30 45.17 16.15 13.38group under the function of solid acid catalyst[11].36088.6022.29 49.46 15.12 13.13CH....CHI. -→ CH4 (Z : catalyst)P=0.1 MPa, SV=4500 m/(gcat h); HC: bhydrocarbons.C4 is probably formed directly from the same in-From the experimental results shown in Table 1,it was found that the conversion of methanol andtermediate (the binding of methoxy group on the cat-the hydrocarbon selectivity increased with increasingalyst surface). It may be yielded from the methoxytermperature to provide a peak at 300 °C, and thengroup with C3 through methanol to gasoline (MTG)decreased with increasing temperature. The selectiv-reaction [12]:ity for CO increased while that for CO2 decreasedC3 + CH30..Z-→C4 (Z :catalyst)monotonously with increasing temperature. The rea-son for this result is that the reverse water gas shiftThese reaction paths can reasonably account forreaction of CO and H2O produced during the reactionthe results presented in Figure 1. At the same time,of methanol dehydration is an endothermic reaction.it is indicated that the olefin formed first in methanolThe hydrocarbon distribution indicates that onlymethane and C4 are produced while other hydrocar-conversion over Fe Zn-Zr catalyst is more possibly thebons are scarcely obtained from the conversion ofC3Hs instead of the C2H4.Previously, some researchers regarded that themethanol on Fe-Zn-Zr catalyst (Figure 1). At theolefin formed first is C2H4 when they investigated thesame time, by comparing the changing trend of selec-hydrocarbon synthesis via methanol conversion over00 rzeolite catalysts [13- -14], but some others thoughtthat it should be C3H6 [15-16]. Over zeolite catalyst,various kinds of hydrocarbons are usually obtained8C340 cand it is difficult to explain which kind of alkene is8360Cthe olefin formed first by only relying on the hydro-carbon distribution. Based on whether C2H4 or C3H660is considered as the olefin formed first, the productdistribution may be explained equally reasonably.40-However, over Fe Zn-Zr catalyst, the bhydrocar-bon distribution of methanol conversion was obvi-ously dfferent from that over zeolite (Figure 2). Only20methane and C4 were produced and other bydrocar-bons were scarcely obtained.The marked difference between the hydrocarbondistri)n over FeZn-ZrFigure 1. Hydrocarbon distribution for methanol中国煤化cataly化工bat the reaction .conversion over Fe-Zn-Zr catalystReaction condition: 0.1 MPa, 8% CH3OH gas in N2, N2 flowrouteMHC N M H Ge-Zn-Zr catalystSV=4500 m/8cas+h)is different from that over zeolite. If the olefin formed328Xiaoming Ni et al,/ Journal of Natural Gas Chemistry Vol. 16 No. 32007CHgOH + CH3OCH3 -→C3Hs(3)80C3Hg + CH20-.Z→C4(470HYZOFe-Zn-ZrScheme 1. Proposed reaction path of hydrocar-60bons formation fronfrom methanol conver-sion over Fe-Zn-Zr catalyst40References30[1] Itoh H, Hidalgo C V, Hattori T, Niwa M, MurakamiY. J Catal, 1984, 85(2): 52120[2]ChangCD,KuoJCW,LangWH,JacobsM,.Wise J J, Silvestri A J. Ind Eng Chem Process DesDeu, 1978, 17(3): 255oL「3}] Liederman D, Jacob S M, VoltzS E, WiseJ J. IndCGC.Eng Chem Process Des Deu, 1978, 17(3): 340Figure 2. Hydrocarbon distribution of methanol[4] Sarkadi-Priboczki E, Kumar N, Salmi T, Murzin Dconversion over Fe -Zn-Zr catalyst and HYY, Kovacs Z. Catal Today, 2005, 100(3-4): 379zeoliteReaction condition: 0.1 MPa, 8% CH3OH gas in N2, N2 flow[5]QiGZ,XieZK,LiuHX,ZhongSQ,ZhangCSV=4500 m/(Seax:h)F, Chen Q L. Shiyou Huagong (Petrochem Technol),2006, 35(1): 29first during the reaction of methanol conversion was[6] Kito S, Satsuma A, Ishikura T, Niwa M, MurakamiC2H4, it will react with methanol and produce C3 asY, Hattori T. Catal Today, 2004, 97(1): 41follows:[7] Nishi K, Shimizu T, Yoshida H, Satsuma A, HattoriT. Appl Catal A, 1998, 166(2): 335C2H4 + CH0..Z- + C3[8] Popova M, Minchev C, Kanazirev V. Appl Catal A: .Gen, 1998, 169(2): 227However, as a matter of fact, the C3 was very9] Hutchings G J, Watson G W, Willock D J. Microp-little in the hydrocarbons whereas plenty of C4 wasorous Mesoporous Mater, 1999, 29(1-2): 67obtained. Hence, we consider that the C3H6 more[10] Wu X C, Abraha M G, Anthony R G. Appl Catal A:probably should be the olefin formed first rather thanGen, 2004, 260 (1): 63C2H4 during the hydrocarbons synthesis via methanol[11] WuEL, Kuhl G H, White T E Jr, Adv Chem Ser,conversion over Fe Zn-Zr catalyst. As for the forma-1971, 101: 490tion of C3H6, it may be formed from the complicated[12] Tan Y S, Fujiwara M, Ando H, Xu Q, Souma Y. StudSurf Sci Catal, 1998, 114: 435reaction of methanol and dimethyl ether.From the above discussion, the reaction path of[13] Chu CT W, Chang C D. J Catal, 1984, 8(2): 297hydrocarbons formation from methanol conversion[14] Haag W 0, Lago R M, Rodewald P G. J Mole Catal,1982, 17(2-3): 161 .over Fe Zn-Zr catalyst was proposed as follows:[15] Anderson J R, Mole T, Christov V. J Catal, 1980,61(2): 477CH3OH -→CH.....CHO(1) [16] Zhong B, LuoQ Y, Xiao Y K, Zhang W. RanicoHuarue Xuebao (J fuel Chem Technol), 1986, 14(1):CH....0CH. -→CH4 + HCHO (2)中国煤化工MYHCNMHG