微反应器中甲醇自热重整

第23卷第6期催化学报2002年11月Vol. 23 No. 6Chinese Journal of CatalysisNovember 2002Article ll:0253-983x2002)60491Microchannel Reactor for Methanol Autothermal reformingChen Guangwen YUAN Quan LI ShulianDalian Institute of Chemical Physics, The Chinese Academy of Sciences Dalian 116023, Liaoning ChinaKey words: microchannel reactor methanol hydrogen proton exchange membrane fuel cell autothermal reformingCLC number: 0643/TQ03Document code: AAutomotive exhaust is currently one of the catalysts and reactor configurations. This papermajor pollution sources. As a pollution-free and en- mainly focuses on the performance of the methanolergy-saving power supply for electric vehicles the autothermal reforming( matr in microchannelfuel cell is the best candidate because of its high en- reactors. MATR, in principle is a combination ofergy conversion efficiency(50%70%)and zero partial oxidation and steam reforming on the sameor nearly zero emission. Hydrogen is the fuel for the catalyst particles the overall reaction rate is thusproton exchange membrane fuel cell PEMFC ) quite fast and the catalyst bed can be small. ThisThe on-board generation of hydrogen using liquid al- combination has a net reaction enthalpy change ofcohols and hydrocarbons is the most practical way zero, thus the reactor for this process does not refor PEMFC vehicles. Nowadays PEMFC technolo- quire any extra external heat transfer after havinggy has been well developed and is gradually in the reached the reaction temperature. The molar ratiostage of commercial application while the hydro- of H2 to MeOh, B, varies with the reaction tempergen-generating technology has become the bottle- atures. It can be seen in Table 1, that p increaseneck for the practical utilization of fuel cells. The with the reaction temperatures under stoichiometricminiaturization of the hydrogen source is prerequi- ratio and adiabatic conditionssite for its practical application. [1 23CH3OH+ (1-2P )H2O+ BO2->CO2+(3-2BHMicrochemical technology( mct)is a new diTable 1 Effect of reaction temperature on prection originating in the early 1990s. This technole/℃ogy focuses on the study of chemical engineering0.1230.1330.1370.140process properties and principles of micro devicesnd systems whose dimensions are less than hunfig 1 shows a chip of the microchannel reactodreds of microns. Owing to the small dimensionmade by a chemical etching method The chipthe specific area increases the surface effect is ermade of stainless steel. Table 2 shows its structurehanced and the entrance effect of transport process- parameterses( flow heat and mass transfer )leads to a remarkable increase of transfer rates, which exceed those ofconventional-sized devices by 2-3 orders of magnitude. The application of mCt can improve greatlythe efficiency of systems and diminish their volumeand weight. The integration of a microchannel reactor system and a heat exchanger system is the mainFig 1 Chip of microchannel reactortechnique of the MCT. Further study of it will pro-vide important theoretical directions for thmuas prepturization of a funel cell hydrogen source to accelerate lows中国煤化工 rates were cleaned balization[3-5]CNMHGany oily substancesAn on-board fuel processor will require novel then rinsed with distilled water and dried at 110 CReceived date: 2002-08-27. First author CHEN Guangwen male, born in 1967, doctor, associate professorCorresponding author: CHEN Guangwen, Tel: (0411 0379031 E-mail gwchen@ dicpac cnFoundationistfEupported by NNSF of China( 20176057 )and Innovative Fund of DICP, CAS( K2001E3)催化学报第23卷Table 2 Parameters of the structure of the chipIts rapid heat and mass transfer with Its sman1 12 V/mlmensions0.340.17300.50.545485H- Thickness of chip, h- Depth of channel, LFig 3 shows the composition of the dry productLength of channel, wc-Width of channelWallgas of MatR. H, has a high value of 43% and CHthickness between channels w- width of total chanis lower than 0.5%, while CO is higher than 15%nels, n1-Number of channel per chip 12- Number ofunder the reaction condition CO is the main poisonchip,V- Volume of microreactorThe unit of hh,,w,t and w is mmof the electrode catalyst( Pt )of the PEMFC so itmust be reduced to less than 1x10-5. To attainfor 2 h. Second, a wash-coat on the stainless steel that supplementary reactions, such as gas-waterwas made by a CeO2-ZrO solid solution 6 Finallyshift reaction and preferential oxidation, have to bthe main active component, Pt was added by ppplied. Meanwhile novel catalyst for MATR with(NH3)(OH) solution(0.1 g/ml )via dip-coat- high hydrogen selectivity should be developed toing, and dried at 120 C, then calcined at 400C reach this low co concentration levelfor 3 h, and reduced with 10%H2-90%N, at 400 Cfor 2 hThe molar ratios of h,o and O to meoh inthe feed were 1. 2 and 0. 3, respectively and airwas used as oxidant. Methanol and water were pre-e42.vaporized at 150 C then mixed with air and en-tered the microreactor which was placed in an ovenWater and methanol were removed from the exit gasby a cold trap while the dry gas entered a gC andsoap bubble flowmeter for composition analysis andflow-rate measurement respectively. The reactionwas carried out at450℃GHSV(MeOH)/IOCOO hFrom Fig 2, it is clear that the methanol conversion in the monolith reactor is rapidly reduced toFig 3 Product composition vs GHSV( MeOHlower than 80% at 20000 h-I, while it is stillin microchannel reactor(1)H2,(2)0O,(3)OO2,(4)CHhigher than 93 in the microchannel reactor evenat 186 000 h I, which is about 10 times higherthan that in the monolith reactor. The reason is thatIn conclusion owing to the small characteristicthe intrinsic rate of matr is very high so the ap dimensions of the microchannel reactor the effect ofparent reaction rate is heavily limited by mass and heat and mass transport is increased remarkablyheat transport. While the reaction rate increased re- The reaction rate increases and the methanol conmarkably and the conversion is still high even at version remains high at very high GHSV. Thehigh GHSV in the microchannel reactor owing to miniaturization of the hydrogen generation systemcan be achieved with a microchannel reactorReferences1 Choi Y, Stenger H G. Appl Catal B, 2002, 384): 2592 Tonkovich A Y, Zilka J L, LaMont M J, Wang Y,We-geng RS. Chem Eng Sci, 1999, 54(13/14): 29473 Service R F. Science, 1998, 28]5388): 400GHSV(MCOH)1000y分Lo中国煤化工10:2051CNMH Gchley D L.In:Ehrfeld WIternational conference otMicroreaction Technology. Frankfurt, 1999.1Fig 2 Meoh conversion vs GHSv Meoh )in different reactors( Chin Catal),2002,234):341(1) Microchannel reactor, (2 )Ceramic monolith reactor( Reactie而方数据:n(O2yn(MoH)=0.304,0=450℃)( Ed WGZh)