ABSTRACT

The tin (Sn)-modified HZSM-5 was employed to upgrade biomass pyrolysis volatiles to prepare bio-oil, and the deterioration of bio-oil and catalyst was focused. A new parameter indicating the physicochemical properties was defined as the comprehensive fuel-grade index (CFI). The catalyst initially demonstrated the better performance to transform oxygen-containing organics to hydrocarbons; consequently, the bio-oil had a higher CFI value. The fresh catalyst produced 33.43% of bio-oil with the higher hydrocarbon content of 41.60%, and the proportions of monocyclic aromatic hydrocarbons (MAHs) and light aliphatic hydrocarbons (LAHs) reached 74.59% and 20.02%, respectively. However, with the extension of catalyst using-time, the obvious decrease of hydrocarbons caused the significant decrease of CFI. Furthermore, the cracking and reforming diffusion performance supported by the acid and textural properties of the catalyst deteriorated severely, which contributed to the proportion increase of polycyclic aromatic hydrocarbons (PAHs). The decrease of the acid and textural properties were attributed to the coke generated and deposited into the pores and on the surface of the catalyst. The deposited cokes could be divided into two types including semihydrogenated coke and carbonaceous coke, and the former was the main one. The carbonaceous coke was formed in the initial stage of catalytic reaction, gradually inducing more precursors to cover active sites and block pores, and then generated more semihydrogenated coke, eventually causing the catalyst performance deterioration. This study provided an insight for improving sustainability in terms of understanding process deterioration.

摘要

用锡（Sn）改性的HZSM-5来提高生物质热解挥发物的含量，以制备生物油，并着重研究了生物油和催化剂的劣化。指示理化性质的新参数定义为综合燃料等级指数（CFI）。最初，该催化剂表现出将含氧有机物转化为碳氢化合物的更好性能。因此，生物油的CFI值较高。新鲜催化剂产生了33.43％的生物油，其中烃含量更高，为41.60％，单环芳烃（MAHs）和轻质脂肪烃（LAHs）的比例分别达到74.59％和20.02％。然而，随着催化剂使用时间的延长，碳氢化合物的明显减少导致CFI的显着下降。此外，催化剂的酸和质构性质支持的裂解和重整扩散性能严重恶化，这导致多环芳烃（PAHs）的比例增加。酸和质构性质的降低归因于产生的焦炭并沉积到孔中和催化剂表面上。沉积的焦炭可分为半氢化焦炭和碳质焦炭两种，其中前者为主要。碳质焦炭是在催化反应的初始阶段形成的，逐渐诱导出更多的前体覆盖活性位点并堵塞孔，然后生成更多的半氢化焦炭，最终导致催化剂性能下降。