基于3D打印技术的甲烷水蒸气重整研究

Study of Methane Steam Reforming Based on 3D-Printing Technology

天然气(主要成分为甲烷)重整是天然气高效清洁利用的重要途径,重整获得富含氢气的重整气,可供固体氧化物燃料电池进行高效发电。甲烷水蒸气重整需要反应器以及负载其上的重整催化剂,基于3D打印技术的多孔结构具有良好的耐高温、抗氧化和结构稳定性等特点,负载Ni基催化剂用于甲烷催化重整可有效提升反应器稳定性,但相关研究较少。采用浸渍法将Ni-CeO_(2)/γ-Al_(2)O_(3)催化剂负载于3D打印制备的多孔结构和金属泡沫反应器,通过催化剂形貌、分布规律、相结构以及热稳定性的表征,研究了重整反应温度、浆料配比、反应器结构等因素对甲烷水蒸气重整效果的影响。结果显示,催化剂的最佳配比是PVA含量为3.5%(若无特殊说明,均为质量分数),Ni含量为19%,CeO_(2)和γ-Al_(2)O_(3)的含量分别为16%和2.5%。重整测试结果表明,负载催化剂前,重整反应温度低于700℃时,Inconel625和泡沫Ni多孔反应器重整得到的氢气浓度均低于13%(体积分数),而重整反应温度高于800℃时,Inconel625和泡沫Fe多孔反应器重整效果接近,但Inconel625稳定性优于泡沫Fe;负载催化剂后,NCA-I(Inconel625)样品始终表现出低于NCA-N(泡沫Ni)和NCA-F(泡沫Fe)的重整性能,这主要是因为NCA-I含有较多的Cr元素,高温下Cr氧化生成Cr2O3氧化膜,阻碍了反应气和Ni的接触,但测试后NCA-I样品表现出优异的稳定性,无明显脆化和断裂现象,可有效提升重整反应器的稳定性。

Natural gas(the main composition of natural gas is methane)reforming is one of the most efficient and cleanest utilization of natural gas.The obtained reformed gas,mainly consisting of H_(2),can be supplied as fuels to solid oxide fuel cells for efficiently power generating.Reactor loaded with catalysts is necessary for methane steam reforming.The 3D-printed porous structure exhibits outstanding stability at elevated tempe-rature and excellent resistance to the highly oxidizing condition,which can obviously improve the stability of the methane reforming reactor.In this work,Ni-CeO_(2)/γ-Al_(2)O_(3) catalysts were loaded onto the 3D-printed porous structure and metallic foams via impregnation.The catalyst morphology,element distribution,phase structure and thermal stability were obtained through characterization methods such as SEM,XRD and TG.Accordingly,the effects of temperature,slurry ratio and the reactor structure on methane steam reforming were studied.Resultantly,an optimized catalyst recipe was obtained as 3.5wt% PVA,19wt%Ni,16wt%CeO_(2) and 2.5wt% γ-Al_(2)O_(3).The reforming tests showed that without catalysts,the hydrogen concentration of 3D-printed Inconel625 porous reactor and Ni foam was as low as 13vol% at a temperature below 700℃;while above 800℃,the 3D-printed Inconel625 porous reactor and Fe foam presented similar reforming performance,but the 3D-printed reactor showed a better repeatability.Moreover,with catalyst loading,the NCA-I(3D-printed Inconel625 porous reactor)samples always showed a lowered reforming performance than NCA-N(Ni foam)and NCA-F(Fe foam),which is mainly due to the existence of Cr that brings Cr_(2)O_(3) film to the exposed surface during the reforming process and thus hinders the contact between the reaction gas and the active surface.However,the NCA-I samples showed excellent stability that no obvious embrittlement and fracture were observed after reforming test,which shows the potential to effectively improve the stability of reforming reactors.