In this work, we report a novel means, named liquid phase in-situ hydrodeoxygenation of bio-derived phenol to cyclohexene and cyclohexane over Raney Ni and Nafion/SiO 2 . In this method, producing hydrogen , hydrogenation and dehydration are merged and coupled owing to the close reaction conditions. The overall specific reaction pathway was studied and influences of Nafion loading, temperature, H 2 O/MeOH ratio and the quantity of catalysts on the reaction were also researched. In terms of 3 g phenol, the suitable operating conditions are drawn as follows: the Nafion loading 13 wt%, the reaction temperature 200 °C, H 2 O/MeOH ratio 20 mL:15 mL, Raney Ni 1 g, Nafion/SiO 2 0.3 g. The conversion rate of phenol and the total yield of cyclohexene and cyclohexane can reach respectively 100% and 87%. The whole reaction system is performed in the liquid phase using in situ hydrogen produced from methanol aqueous-phase reforming, not requiring an external source of hydrogen. The operating conditions are gentle, and the cost is considerably reduced.
Jianchun Niu,Shuomeng Zhang,Yunqi Li,Xiaoyu Li,Jialin Zhang,Shanfu Lu,Qinggang He
The operating temperature of modified Nafion membranes remains too low to satisfy the requirements for high-temperature proton exchange membrane fuel cells (HT-PEMFCs) because most can only operate well below 120 °C. In this article, we prepare a series of Nafion/SiO 2 composite membranes with different contents of doped silica nanoparticles by in situ growth of SiO 2 nanoparticles near the –SO 3 H group. The water dynamic change process and the functional properties of Nafion/SiO 2 composite membranes are studied and found to correlate well with structural parameters, such as crystallinity and average chain spacing. Also, microstructure information including the phase separation structure changes, structural complexity, and ion cluster fraction of Nafion/SiO 2 composite membranes at different temperatures are investigated using synchrotron-based in situ small angle X-ray scattering (SAXS). Differing from expectations, the amount of water in the Nafion/SiO 2 composite membranes may not be the decisive factor to maintain proton conductivity at relatively high temperatures. Instead, the complexity or connectivity of the proton transport channel may play a more important role in the effective proton transfer inside the composite membranes, which also provides valuable guidance and insight for the development of novel HT-PEM materials with well-designed ion transport pathways in the future.
Using Nafion212 membrane and TEOS solution as raw materials, Nafion212/SiO2 composite membranes were prepared. In the in situ sol-gel reaction process, a series of Nafion/SiO2 composite membranes were prepared by varying the reaction temperature and reaction time. The effects of different modification schemes on Nafion/SiO2 composite membranes were studied using SEM, EDS, TEM, TGA, XRD, and mechanical tensile experiments, among other methods. The results show that Nafion/SiO2 composite membranes prepared at 3°C exhibit a well-separated phase structure and excellent water retention properties, with a water uptake of 29.23% and a swelling ratio of 24.25%. These membranes also demonstrate outstanding physical and chemical performance, with a maximum tensile stress of 13.6 MPa and an elongation at a break of 270%. At 110°C, the proton conductivity of the Nafion/SiO2 composite membrane reaches 0.172 S/cm, meeting the requirements for high-temperature proton exchange membrane fuel cells.
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