在改进的Ni-基催化剂上的甲烷部分氧化制合成气反应

第23卷第2期催化学报2002年3月Vol. 23 No. 2hinese Journal of catalysisMarch 2002Article Il:0253-983X2002)2-0103-02An Improved ni-Based Catalyst for Partial Oxidation ofMethane to SyngasCHU Wenling, YANG Weishen, LiN LiwuState Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, The Chinese Academy of SciencesDalian 116023, Liaoning, ChinaKey words: nickel hexaaluminate methane, partial oxidatioCLC number 0643Document code: AIn the partial oxidation of methane( pom) to gases, CH4, O2 and He in a molar ratio of 2: 1: 2syngas nickel-based catalysts can be quite practical were mixed and passed through 0. 5 g catalyst at abecause of their fast turnover rate high activity and flow rate 100 ml/ min. The reaction products werelow cost 1]. But previous investigations have shown analyzed using an HP 6890 gas chromatograph e-that nickel is more susceptible to coking and sinter- quipped with a tCd detectoring and loss of active species 31.We seek to develXRD results show that the crystal structure ofop new catalysts along the line of the concepts of the Ni-modified hexaaluminate BaNi, Al12, O19-8 isstrong metal-support interaction and have studied similar to that of BaAl12 019, implying that nickeldifferent supports to explore the advantages of the ions are incorporated into the BaAl12 O19 latticeinteraction. It has been pointed out that the interac- with Ni+ mainly in an octahedral environmenttion bet ween nickel and the support may play an im- Table 1 lists the results of activity and selectivity ofportant role in the activity and coking resistance of the hexaaluminate catalysts with various y values irthe catalysts. In our earlier studies 4, NiO/barium the POM reaction at 850 Chexaaluminate catalysts show high activity and selectivity and an excellent ability to suppressTable 1 Effect of y value in BaNi, Al12-- on thedeposition but the loss of nickel is serious. In thisactivity and selectivity at 850work we investigated the carbon deposition and theCH4 conversion( % CO selectivity( %0.155.20.3BaNi,A12-,O19-6a series of Ni-modified hexaaluminate cata0.9lysts,BaNi,Al12-,O19-y=0.1,0.3,0.6,0.990.7and 1.0), were prepared by the decomposition ofnitrates and calcination at high temperature. TheThe activity and selectivity are very low for a ystarting materials were Ba( NO3 h, Ni( NO3 2 value of 0.1, which indicates that the active species6H2O and AK NO3 ) 9H20 mixed aqueous solution is too few. But for values of y20.3, the catalystwith a molar ratio 1: y 12-y ) The mixture was show high activity and selectivity at 850C, withslowly added to hot 2-propanol containing polyethy- CH4 conversion of -92% and Co selectivity oflene glycol and the resulting solution was evaporated 95%, respectively. Moreover, there is no signifiat 80C to gradually remove water and 2-propanol. cant change in activity and selectivity with increas-The gel was then dried and calcined in air at 1 250 ing y Vaindicates t hat the catalyst can still℃for5hmaintal中国煤化工 HThe partial oxidation of methane was carriedCNMH Gamely the substiout in a fixed bed reactor with a continuous flow tution of Ni does not destroy the structure of thesystem under atmospheric pressure. The reaction catalysts at y <1.0Received date 2001-11-30. First author CHU Wenling female, born in 1970, doctor.Correspaaiogtfor: CHU Wenling. Tel: (0411 379301:E-mail : ewl@ dicp accn催化学报It was found from a 100 h life testing experment that the BaNi, Al2-019-y=0.3 )catalystkept CHa conversion of over 90 %o and CO selectivityof -94 % respectively which indicates that thecatalyst is stable under the POm reaction at 850Cfor 100 h. After reaction, the reactor was cooled toroom temperature in a He gas flow and then the catalyst was investigated by XPS( see Table 2Table 2 Comparison of the surface composition of differentysts analyzed by XPsSurface relative atomic ratioinding energy (ev)SamC0.372,010.0080.0371Used catalyst(100 h test)0.742.120.0080.0501.00The results of Xps indicate that the usedlyst suffered almost no loss of the nickel activespecies and demonstrate that the BaNi, Al12-,019-a(y=0.3 catalyst has excellent resistance to loss ofnickel during the high temperature reaction. The⊥surface relative atomic ratio of carbon increases from29527520.37 to 0.74 after the 100 h test, and the c 1sBinding energy (ev)eak at -283. 5 eV is contributed to carbon deposi-tion( Fig 1. From TG results, we found that carFig 1 XPS Spectra of C Is for fresh catalyst( a and usedbon deposition is only 0. 8% of the weight of catat( 100 h test )(b)lyst. This is much lower than that on NiO/barium(1)Surface COf", (2)Adventitious carlhexaaluminte4]and NiO/y-A1035, on which car(3)Carbon depositionbon deposition is 1. 54%( at 850 C for 100 h )and on the surface, which are relatively stable toward17.64%(at850℃for80h)sintering and carbon depositionFrom the results above, we can conclude thatReferencesBaNi,al2-voPOM reaction due to its high activity and especial1 Hickman D A, Schmidt L D. Science, 1993, 25] 5093)ly its excellent stability to suppress the carbon de2 Richardson JT, ParipatyaAppl Catal, 1990, 61position and loss of nickel which may be attributed(2):293to the strong interaction between Ni and its neigh3 Gadalla A M, Sommer M E. Chem Eng sci, 1989, 44boring atoms. A structural study of Lao.925 CO0. 75(12):282Al,Ou o of magnetoplumbite structure has shown 4 Chu W4 Chu W, Yang W, Lin L. Catal Lett, 2001, 74 3-4): 139that cobalt mainly enters the Al-O spinel blocks 63. 5 Zhang Y H. PhD Dissertation 1. Dalian Dalian Institute ofIt is therefore likely that nickel also occupies sites inChemical Physics, The Chinese Academy of Sciences. 2000the spinel blocks of the magnetoplumbite phase of 6 Gasperin M, Saine M C, Kahn A, Laville F, Lejus M.Jthe barium-modified catalysts and for this reason itSolid State Chem, 1984, 541: 61is more strongly bound. The strong interaction can(Ed LYX)result in the formation of mainly small Ni crystallites中国煤化工CNMHG