Study of Different Pore Structure of SBA-15 Supported NiCu Catalysts toward Catalytic Ethanol Steam Reforming Reaction

• Main Authors: Yan-Tzuo Liu, 劉彥佐
• Other Authors: Bing-joe Hwang
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/11617101107227418194

碩士 === 國立臺灣科技大學 === 化學工程系 === 98 === In this study, a simple sol-gel method is employed for synthesizing Ni-Cu nanoparticles inside the confined space of SBA-15 support. The nanoparticles are small and uniform rather than that made by conventional method. In addition, the nanoparticles are well-dispersed along the channels without blockage. The unique properties can be maintained even higher nanoparticle loading. The average grain size of nanoparticles only increases slightly from ~ 3 nm (10 wt%) to 3.5 nm (20 wt%). The synthesized NiCu/SBA-15 catalysts show good performance for hydrogen production via the steam reforming of ethanol reaction (SRE). For 0.05 g of NiCu55/SBA-15 (Ni: 5 wt%, Cu: 5 wt%) with the feeding molar ratio of H2O/EtOH = 6 and WHSV = 1.66 h-1, the ethanol conversion reaches 100% at 600 oC. Meanwhile, H2 selectivity of 70.4 %, CO2 selectivity of 22.4 %, CO selectivity of 6.4%, CH4 selectivity of 0.8% are shown in the product steam, indicating the excellent hydrogen production performance. In order to discuss the effect of various pore structures to the catalyst stability during SRE reactions, SBA-15 of short channels (platelet-like SBA-15), and of large pore sizes are prepared for comparison. The results indicate the stability of the catalysts can be effectively improved with proper pore structure. In term of coking issue, SBA-15 of shorter channels and larger pore sizes can inhibit the pore blockages caused by coking formation, therefore the catalyst life is improved. Considering the degradation time of ethanol conversion efficiency, the traditional SBA-15 is 5 hrs, while obvious improvement is done for the large-pore-size SBA-15 (18 hrs) and the platelet-like SBA-15 (30 hrs). Considering the surface property effect of the support, the acidic SBA-15 support leads to dehydration of ethanol to water and ethane, and subsequently coking of the catalysts makes themselves inactive. To tackle this drawback, MgO and CaO alkali materials are added to modify the surface acidity. However, MgO shows strong interaction with Ni after calcination, where MgO trends to cover on the Ni surface and is not suitable for nickel-based catalyst system. In contrast, CaO exhibits positive effect to SRE. In case of NiCu55/LS (large pore size SBA-15), the stability is able to extend (around 14 hrs) after adding 20 wt% CaO to SBA-15.