Abstract Non-H2 and solvent-free catalytic conversion of waste lipids to liquid hydrocarbons is of great interest because of the associated low-cost, full-safety, and easy-operability. In this work, a solvent-free catalytic process for deoxygenating oleic acid was performed in H2 and non-H2 (N2, CH4, and CO2) media over nano-Ni/HZSM-5. 8-Heptadecene, a primary product obtained at 320 °C in four media, was derived from the straightforward decarboxylation of oleic acid. In non-H2 medium at 360 °C, the formation of C8–C15 alkanes was enhanced, with yields of ca. 65.05 mol%, 70.71 mol%, and 73.09 mol% for N2, CH4, and CO2, respectively. A low yield of 49.67 mol% C8–C15 alkanes in H2 medium suggested that the H2 medium reduced catalytic cracking. This was due to the preferential formation of stable heptadecane from 8-heptadecene in the presence of abundant H2. The absence of H2 favored the cracking of 8-heptadecene. These cracked products were further converted to C8–C15 alkanes, for which a mass supply of hydrogen was mandatory. Gas-phase reactions including methanation, Fisher-Tropsch (F-T) synthesis, and water-gas shift (WGS) reactions between deoxygenated gas products and reaction media provided significant pathways for the hydrogen required for the formation of alkanes. The CH4 medium also acted as a hydrogen source due to its decomposition, catalyzed by nano-Ni/HZSM-5. Coke was substantially formed in all the four media. It was highlighted that the medium of H2 favored the formation of aliphatic cokes, whereas the non-H2 media, particularly the CO2 medium, facilitated aromatic coke species on account of its weak oxidizability. Additionally, there was a severe loss of loaded Ni nanoparticles under H2 medium but a slight Ni loss in CO2 medium, which was proposed to the reason of aromatic cokes formation at the catalyst surface, acting as a trap for the loaded Ni nanoparticles.

中文翻译：

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通过纳米镍/HZSM-5 无溶剂催化油酸脱氧：反应介质和焦炭表征的影响

摘要 由于相关的低成本、完全安全和易操作性，非 H2 和无溶剂催化转化废脂质为液态碳氢化合物引起了极大的兴趣。在这项工作中，在 H2 和非 H2（N2、CH4 和 CO2）介质中，在纳米 Ni/HZSM-5 上进行了一种用于油酸脱氧的无溶剂催化过程。8-十七烯是一种在 320 °C 下在四种介质中获得的主要产物，源自油酸的直接脱羧。在 360 °C 的非 H2 介质中，C8-C15 烷烃的形成增强，产量约为 N2、CH4 和 CO2 分别为 65.05 mol%、70.71 mol% 和 73.09 mol%。H2 介质中 49.67 mol% C8-C15 烷烃的低产率表明 H2 介质减少了催化裂化。这是由于在大量 H2 存在下从 8-十七烯优先形成稳定的十七烷。没有 H2 有利于 8-十七烯的裂解。这些裂解产物进一步转化为 C8-C15 烷烃，为此必须大量供应氢气。气相反应包括甲烷化、费托 (FT) 合成和脱氧气体产物与反应介质之间的水煤气变换 (WGS) 反应，为形成烷烃所需的氢气提供了重要途径。由于 CH4 介质在纳米 Ni/HZSM-5 的催化下分解，它也用作氢源。在所有四种介质中基本上形成了焦炭。强调的是 H2 介质有利于脂肪族焦炭的形成，而非 H2 介质，尤其是 CO2 介质，由于其弱氧化性，促进了芳族焦物种。此外，在 H2 介质下负载的 Ni 纳米颗粒有严重的损失，而在 CO2 介质中镍的损失很小，这被认为是催化剂表面形成芳烃焦炭的原因，作为负载的 Ni 纳米颗粒的陷阱。