Impact of Bentonite Clay on In Situ Pyrolysis vs. Hydrothermal Carbonization of Avocado Pit Biomass
Impact of Bentonite Clay on In Situ Pyrolysis vs. Hydrothermal Carbonization of Avocado Pit Biomass
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DOI：
10.3390/catal12060655
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发表时间：
2022-06
期刊：
影响因子：
3.9
通讯作者：
Madeline Karod;Zoe A. Pollard;M. T. Ahmad;Guolan Dou;Lihui Gao;Jillian L. Goldfarb
中科院分区：
文献类型：
--
作者：
Madeline Karod;Zoe A. Pollard;M. T. Ahmad;Guolan Dou;Lihui Gao;Jillian L. Goldfarb
通过废弃生物质的热化学转化生产的生物燃料可以成为化石燃料的可持续替代品，但目前需要昂贵的下游升级才能用于现有基础设施。在这项工作中，我们探讨了如何低成本，丰富的粘土矿物，膨润土，可以作为原位多相催化剂两个不同的热化学转化过程：热解和水热碳化（HTC）。将鳄梨核与20重量%膨润土粘土组合，并在600 °C下热解，并在250 °C下水热分解，这是文献中常用的条件。在热解过程中，膨润土促进了Diels-Alder反应，将呋喃转化为芳香族化合物，从而降低了生物油的氧含量，并产生了更适合现有基础设施的燃料。不含粘土催化剂的HTC生物油含有100%呋喃，主要是5-甲基糠醛，但在粘土存在下，约25%的生物油转化为2-甲基-2-环戊烯酮，从而添加两个氢原子并除去一个氧原子。在这两个过程中使用粘土降低了生物油的相对氧含量。对所得焦的近似分析表明，随着粘土夹杂物的存在，固定碳（FC）增加，挥发性物质（VM）减少。通过含有更多的FC，对于环境应用而言，HTC衍生的炭可以比热解衍生的炭更稳定。向两种方法中添加膨润土粘土没有产生显著不同的生物油产率，使得通过添加粘土催化剂，在不减少回收的生物油的量的情况下产生更有价值的生物油。
Biofuels produced via thermochemical conversions of waste biomass could be sustainable alternatives to fossil fuels but currently require costly downstream upgrading to be used in existing infrastructure. In this work, we explore how a low-cost, abundant clay mineral, bentonite, could serve as an in situ heterogeneous catalyst for two different thermochemical conversion processes: pyrolysis and hydrothermal carbonization (HTC). Avocado pits were combined with 20 wt% bentonite clay and were pyrolyzed at 600 °C and hydrothermally carbonized at 250 °C, commonly used conditions across the literature. During pyrolysis, bentonite clay promoted Diels–Alder reactions that transformed furans to aromatic compounds, which decreased the bio-oil oxygen content and produced a fuel closer to being suitable for existing infrastructure. The HTC bio-oil without the clay catalyst contained 100% furans, mainly 5-methylfurfural, but in the presence of the clay, approximately 25% of the bio-oil was transformed to 2-methyl-2-cyclopentenone, thereby adding two hydrogen atoms and removing one oxygen. The use of clay in both processes decreased the relative oxygen content of the bio-oils. Proximate analysis of the resulting chars showed an increase in fixed carbon (FC) and a decrease in volatile matter (VM) with clay inclusion. By containing more FC, the HTC-derived char may be more stable than pyrolysis-derived char for environmental applications. The addition of bentonite clay to both processes did not produce significantly different bio-oil yields, such that by adding a clay catalyst, a more valuable bio-oil was produced without reducing the amount of bio-oil recovered.