Start-up of thermally-integrated microchannel reformers with a noble metal reforming catalyst

The wash coating process produces a porous layer on all surfaces of the foam, which layer forms a base for the catalyst coating. The interstices as well as the outside surfaces of the open cell foam monolith are wash coated and are also catalyzed. Since the catalyst beds are of minimal size and weight they are especially suited to vehicular applications where size and weight are critically important, and because vehicle applications require rapid start-up capability that is closely dependent on the size and weight of the components. Small, light-weight catalyst and reactant beds can be rapidly heated with a minimum energy input. Heat is generated internally in the reformer catalyst bed due to the addition of air to the process gas stream, which is a fuel-steam mixture. Thus, there is no need to spread the reforming catalyst along large heat transfer surfaces as is required with a conventional steam reformer. The use of an open cell foam monolith as the catalyst support bed can increase the catalyzed surface area of the support bed by a factor of at least three, depending on the pore size of the foam catalyst support bed. Use of the foam support bed can also reduce the volume of the bed by a factor of at least three, and can reduce the weight of the bed by an even greater factor, as compared to a pelletized catalyst bed. The increased open volume results in a much lower pressure drop across the catalyst bed than can be achieved with a pelletized bed. Start-up of the thermally-integrated microchannel reformer can be achieved by either pre-heating the bed with a hot gas, such as steam, or by fabricating either the entire monolith or just the inlet section with a conductive resistance monolith element. The resistance element can be connected to an electrical source such as a car battery which will enable the monolith to reach operating temperatures within less than twenty seconds. The inlet portion of the catalyst bed is operable to bum oxygen and a minor amount of the fuel gas so as to raise the temperature of the inlet portion of the catalyst bed. This raises the temperature of the gas stream to temperatures which provide enhanced conversion of the fuel stream to a high hydrogen-content gas. Minimal oxygen requirements serve to inhibit carbon formation in the catalyst bed. Other carbon formation-suppressing catalyst bed components such as calcium oxide, lanthanum oxide, and cerium oxide, for example, could also be used. For a methanol fuel, the subsequent reforming section of the catalyst bed is provided with a conventional copper, copper-zinc or noble metal reforming catalyst, or a combination of a copper or copper-zinc reforming catalyst, and a noble metal reforming catalyst.

wash涂层（wash coating）工艺会在泡沫的所有表面生成多孔层，该多孔层可作为催化剂涂层（catalyst coating）的基底。开孔泡沫整体式载体（open cell foam monolith）的孔隙间隙与外表面均经过wash涂层处理，同时也负载了催化剂。由于催化剂床层（catalyst beds）的尺寸与重量均极小，其尤其适用于对尺寸和重量要求严苛的车载应用（vehicular applications）；且车载应用对快速启动性能（rapid start-up capability）有较高要求，而该性能与部件的尺寸和重量密切相关。小型轻量化的催化剂与反应物床层（reactant beds）仅需极低的能量输入即可实现快速加热。重整器催化剂床层（reformer catalyst bed）内部会因向燃料-蒸汽混合物（fuel-steam mixture）工艺气流中通入空气而产生热量，因此无需像传统蒸汽重整器（conventional steam reformer）那样，将重整催化剂铺设在大面积换热表面上。以开孔泡沫整体式载体作为催化剂载体床层（catalyst support bed），根据泡沫催化剂载体床层的孔径（pore size）不同，可将载体床层的催化表面积提升至少三倍。与粒状催化剂床层（pelletized catalyst bed）相比，采用泡沫载体床层还可将床层体积至少缩减三倍，床层重量的缩减幅度则更大。由于床层的开孔体积更大，催化剂床层的压力降（pressure drop）远低于粒状床层。热集成微通道重整器（thermally-integrated microchannel reformer）可通过两种方式实现启动：一是采用蒸汽等热气体对床层进行预热；二是将整体式载体（或仅将入口段）与导电电阻整体式元件（conductive resistance monolith element）集成。该电阻元件可连接至汽车电池等电源（electrical source），使整体式载体可在20秒内达到工作温度。催化剂床层的入口段可通过燃烧氧气与少量燃料气来提升自身温度，进而将气流加热至适宜温度，以增强燃料气流向高氢气含量气体的转化效率。极低的氧气用量可抑制催化剂床层内的积碳（carbon formation）。也可采用氧化钙（calcium oxide）、氧化镧（lanthanum oxide）、氧化铈（cerium oxide）等其他抑制积碳的催化剂床层组分。对于甲醇燃料（methanol fuel），催化剂床层的后续重整段可采用常规的铜、铜锌（copper-zinc）或贵金属（noble metal）重整催化剂，或铜/铜锌重整催化剂与贵金属重整催化剂的组合。