Abstract:

In this study, wood chips and peanut shells were used as raw materials for biomass pyrolysis, and the distribution of organic products was studied. The catalyst was modified by two metal elements, Fe and Zn. The Fe-Zn modified ZSM-5 was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), infrared, and specific surface area test (BET). Biomass was pyrolyzed using a pyrolysis-mass spectrometer (PY-GC/MS) to investigate changes in product distribution of biomass catalytic pyrolysis. Under the action of the catalyst, the yield of the aromatic hydrocarbon product is greatly improved. In the pyrolysis process of wood chips, the Fe-supported molecular sieve catalyzed the highest yield of phenols, which was 18.30% higher than the catalytic pyrolysis yield of ZSM-5. The single-metal supported catalytic pyrolysis of Fe and Zn yielded the lowest yield of acid products, which was 50.66% lower than that of direct pyrolysis. The metal modified catalyst greatly increases the yield of aromatic products in the pyrolysis of peanut shells. The Zn modified catalyst has the highest yield of aromatic hydrocarbon products, and the Zn modified catalytic pyrolysis is 18.92% lower than that of direct pyrolysis. The lowest ketone yield was obtained by Zn modification, and the ketone yield was reduced by 19.74% compared with direct pyrolysis, showing a strong dehydroxylation effect. In addition, Zn modification catalysis and Fe-Zn bimetallic modification catalyzed the yield of acid products in the pyrolysis of peanut shells, and the acid yield decreased by 30.46% and 36.71% compared with direct pyrolysis. It was found that both Fe or Zn modified ZSM-5 molecular sieves have an inhibitory effect on the acid in the pyrolysis product and reduce the corrosivity of the product. The Fe modified (6%(mass)) ZSM-5 molecular sieve catalyst has a higher yield on the aromatic hydrocarbon product than Zn. The effect of equal mass content of Fe-Zn on the promotion of phenolic products is obvious. In addition, changes in pore volume and pore size distribution occurred on Fe-modified ZSM-5 catalysts, and this change was positively correlated with BTX yield in wood chips pyrolysis. The Fe loading forms a new mesoporous structure on the surface of the molecular sieve, which promotes the formation of aromatic hydrocarbons and phenolic compounds. Compared with the pyrolysis products of peanut shells, the 120—150 molecular weight of the wood chips pyrolysis products is more, which can be used as an intermediate product of cracking, and has a promoting effect on the formation of phenol and BTX. It indicates that different biomass materials, in direct pyrolysis, the molecular weight distribution of the product also affects the catalytic upgrading effect. Under the condition of single metal catalytic pyrolysis, compared with the catalytic effect of Zn-loaded ZSM-5 catalyst, the catalytic effect of Fe-modified catalyst on biomass pyrolysis products is significant.

Key words: biomass, catalyst, pyrolysis, molecular sieves, product characteristics

摘要：

选取木屑和花生壳作为原料进行生物质热解，研究有机产物分布，催化剂使用Fe、Zn两种金属元素进行改性。通过X射线衍射（XRD）、扫描电镜（SEM）、傅里叶红外（FT-IR）、比表面积测试（BET）对Fe-Zn改性的ZSM-5进行分析。使用闪速裂解-气质联用仪（PY-GC/MS）对原料进行热解，探究生物质催化热解的产物分布变化。催化剂的使用使得芳烃类产物产率获得较大提升，在木屑热解中，Fe负载的分子筛催化获得了酚类的最高产率，比ZSM-5催化热解产率提升18.30%。金属改性催化剂在花生壳热解中，大幅提升了芳烃类产物产率，其中Zn负载催化剂芳烃类产物产率最高，Zn负载催化热解比直接热解的酚类产率降低了18.92%。Zn负载催化获得了最低的酮类产率，与直接热解相比酮类产率降低19.74%，显示出较强的脱羟基效果。此外Zn负载催化和Fe-Zn双金属负载催化在花生壳热解中都大幅降低了酸类产物产率，与直接热解相比酸类产率分别降低了30.46%、36.71%。

关键词: 生物质, 催化剂, 热解, 分子筛, 产物特性