Abstract Two-step pyrolysis(TSP) of walnut shell(WS) coupled with acid washing pretreatment was carried out to investigate the coupling effects on improving the quality of bio-oil and selectivities of value-added chemicals by Pyrolysis-gas chromatography/mass spectrometry(Py-GC/MS). The first step temperature(T1) was set from 350 °C to 550 °C, and the second step temperature was set as 650 °C. Thermogravimetric analyzer coupled with FTIR spectrophotometer(TG-FTIR) was also used to analyze the pyrolysis characteristics of the sample. The results indicated that metallic species in walnut shell was obviously reduced after acid washing (5%HCl), hence the pyrolysis process was postponed and the bio-char yield decreased. TSP coupled with acid washing could reduce the contents of acids, ketones, alcohols, aldehydes, phenols and increased the contents of N-containg compounds, sugars and furans in the first step. The hydrocarbons content decreased and the sugars content further increased in the second step. Besides, some value-added chemicals were also enriched, such as furfural(6.19%), levoglucosan(34.29%) and 2-methoxy-4-methylphenol(6.03%), etc. It could be preliminarily concluded that T1 from 400 °C to 450 °C was suitable for achieving the high quality bio-oil and high selectivities of value-added chemicals.

中文翻译：

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核桃壳两步热解结合酸洗预处理的研究

摘要 以核桃壳（WS）两步热解（TSP）结合酸洗预处理为研究对象，采用热解-气相色谱/质谱法研究了提高生物油品质和高附加值化学品选择性的耦合效应。 (Py-GC/MS)。第一步温度（T1）设置为350°C至550°C，第二步温度设置为650°C。还采用热重分析仪与FTIR分光光度计(TG-FTIR)联用对样品的热解特性进行了分析。结果表明，酸洗（5%HCl）后核桃壳中的金属种类明显减少，因此热解过程推迟，生物炭产率降低。TSP结合酸洗可降低酸、酮、醇、醛、酚类，并在第一步中增加了含氮化合物、糖和呋喃的含量。在第二步中，烃含量降低，糖含量进一步增加。此外，还富集了一些高附加值化学品，如糠醛（6.19%）、左旋葡聚糖（34.29%）和 2-甲氧基-4-甲基苯酚（6.03%）等。 可以初步推断 T1 从 400 °C至 450 °C 适合实现高品质生物油和高附加值化学品的高选择性。