流化床反應器中甲烷部分氧化制合成氣

第21卷第2期催化學(xué)報2000年3Vol. 21 NoChinese Journal of CatalyMarch 2000Article ID:0253-9832000)2009702Partial Oxidation of methane to Syngas in Fluidized Bed reactorJI Yaying, LI Wenzhao, XU Hengyong, YU ChunyingDalian Institute of Chemical Physics, The Chinese Academy of Sciences, Dalian 116023, ChinaKey words fluidized bed reactne, partial oxidation syngas, hot spotCLC number: 0643/TQ54ocument code: AMost previous studies on the partial oxidation of of the reactor an expanded section($50 mm x 20methane( POM have used either fixed beds or cm )was used to disengage catalystmonolith catalysts 1. The presence of hot spots andTable 1 Performance of pom in differentcarbon formation in a fixed bed reactor affects thereactors at800℃lifetime of Ni-based catalysts. The fluidized bed re-△0XCH4)SC0)SH2)actor is in principle a suitable device to handle theseFixed bed53037097.098.51oblems. The use of the solid catalysts as internalFluidized bed 7001092.393.497.4heat carriers in the bed will provide a more homogeEquilibrium92,397,2neous reactor temperature. In addition, the move6— -Ignition temperature,△- Temperature risement of particles within the fluidized bed can help toTable 1 shows the comparison of performancelimit the amount of carbon formation by recircula- of poM in the reactors with 8% NV/ALO catalysttion of carbon-deposited catalysts to oxygen-rich (150 mg, 20-40 mesh for fixed bed and 5g, 160zones of the bed. Bharadwa et at reported that -200 mesh for fluidized bed), with CH4-0,(Vthe selectivity for CO and H2 higher than 95% and (cHAy v(0,)=2.0) feed flows of ca 500 ml/minCHA conversion higher than 90% could be obtained for fixed bed and 600 ml/ min( for fluidized bedover Rh and Ni catalysts in a fluidized bed reactor. It is shown that the catalyst could light off automatSantos et al 3]reported that an al most flat tempera- ically in the CHa-0, feedstocks at 530C owing toture profile was achieved within the bubbling zone, the reduction of nio to ni o in the fixed bed reactowith CHA conversion and selectivity for Co and H2 and the bed temperature rapidly increased to 900 Cclose to the equilibrium values. In this paper, we within a few seconds after ignition. The bed tempresent the results on the PoM to syngas in a static perature rise was 370C which approached the calfluidized bed of Ni/y-Al2O3 catalystculated adiabatic temperature rise of 384 C underThe Ni-based catalyst was prepared by impreg- the same conditions. In the fluidized bed reactor, itnation.The used support was y-Al2O3 with 160was difficult for the catalyst to ignite because the200 mesh. A long quartz reactor( 922 mm X 350 catalyst circulated continuously between 0-containmm) with a sintered quartz distributor plate and a ing and O,-free zone. Only after the catalyst was requartz thermowell(o d 3 mm) placed vertically in duced in H, or CHa at 700 did pOM take placethe bubbling zone was used. In addition a movable中國煤化工 The bed temperaturequartz probe(o d 4 mm ) was inserted to monitorgICNMHG800℃( as shown inthe concentration gradient along the bed. At the top Fig 1) On increasing ow rate to 0.9 L/ minReceived date: 1999-10-13. First author: JI Y aying, female, born in 1966, PhD studeng. Tel: (0411 M671991-747; E-mail hy Xu@ ms dicpaccnFoundatio毀費" ported by the key project of The Chinese Academy of Sciences(y908催化學(xué)報第21卷the bed temperature gradient at 800C gradually highest values at 2 cm from the distributor anddecreased to 2C. This indicates that the tempera- subsequently showed a slight decrease in the bubture distribution in the fluidized bed was much im- bling zone indicating that the gas back-mixing wasproved owing to the better catalyst mixing. Table 1 insignificant. In spite of important variations in theshows also that the CHa conversion in the fixed bed temperature profiles( see Fig 1), no decrease in thereactor seemed to exceed equilibrium value, but this performance was found when d >5 cm( see Fig 2)is due to the presence of the hot spots in the catalyst However, some small catalyst particles were enbed. In the fluidized bed reactor the experimental trained in the freeboard region as the gas flow rateresults approached the calculated equilibrium results exceeded a certain value, and the catalyst therevery wellcould catalyze the back reactions owing to the lowertemperature, the decreases in CHA conversion androduct selectivity occurred see Table 2)aTable 2 Effect of flow rate on performance of POM influidized bed reactor at 800 CS/%94.297.02.060.690.994.897.62.061.291,994.798.22.07perature profiles along the fluidized be0.991.393.798.42.10reactor at different retemperature(1)600,(2)700,(3)8000.389,194.097.12.06( d-Distance from the distributor0.694.5970.92.10591.795,72,09carbon deposit was found in the first 5 h and only5. 6 of carbon was detected after run for 100 hmentioned conditions. The carbformed in a given region(e. g. the oxy gen-deficientdifferent region (e. g. the oxygen-rich bed enFig 2 Performance of POM along the fluidizedtrance ) and oxidized because the catalyst was conbed reactor at800℃tinuously recirculated(1)X(CH4)、(2)S(C0),(3)S(H2)The gas concentrations were axially measured1中國煤化工CNMHGO,199,13x1):267In the reactor over the catalyst under the conditions 2 BhanauWay557selmut L, U., Catal, 1994,146(1):Ilqv=0. 6 L/min, V( CH4(O2)=2.0 and 0=800 3 Santos a, Menendez m, santamariCatal TodayC. The results are given in Fig 2. Oxygen was 1994,21(2/3):481completely consumed over the distributor, CH4 conversion are亮教據 vity for CO and H2 achieved theEd WGZh)