林晓娜, 雷寒武, 易维明, 蔡红珍, 陈晓云, 郭亚东. 活性炭催化生物质与低密度聚乙烯共热解[J]. 农业工程学报, 2021, 37(15): 189-196. DOI: 10.11975/j.issn.1002-6819.2021.15.023
    引用本文: 林晓娜, 雷寒武, 易维明, 蔡红珍, 陈晓云, 郭亚东. 活性炭催化生物质与低密度聚乙烯共热解[J]. 农业工程学报, 2021, 37(15): 189-196. DOI: 10.11975/j.issn.1002-6819.2021.15.023
    Lin Xiaona, Lei Hanwu, Yi Weiming, Cai Hongzhen, Chen Xiaoyun, Guo Yadong. Catalytic co-pyrolysis of biomass and low-density polyethylene over activated carbon catalyst[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(15): 189-196. DOI: 10.11975/j.issn.1002-6819.2021.15.023
    Citation: Lin Xiaona, Lei Hanwu, Yi Weiming, Cai Hongzhen, Chen Xiaoyun, Guo Yadong. Catalytic co-pyrolysis of biomass and low-density polyethylene over activated carbon catalyst[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(15): 189-196. DOI: 10.11975/j.issn.1002-6819.2021.15.023

    活性炭催化生物质与低密度聚乙烯共热解

    Catalytic co-pyrolysis of biomass and low-density polyethylene over activated carbon catalyst

    • 摘要: 为探究生物质主要组分与聚烯烃塑料在活性炭共催化热解过程的相互作用机理,该研究采用磷酸活化法制备了活性炭催化剂,利用固定床反应器对纤维素、木聚糖、木质素、花旗松单独催化热解及其与低密度聚乙烯共催化热解产物的产率及组成进行了分析。结果表明,活性炭催化纤维素和木聚糖单独热解的主要产物为呋喃类物质,其质量分数分别为78.6%和83.2%;而活性炭催化木质素热解的主要产物为简单酚类物质(86.6%)。与理论计算值相比,四种混合物共催化热解所得液体产率降低了8.7%~11.4%,气体产率提高了22.6%~64.0%;液体产物中芳烃和轻质脂肪烃(C9~C16)的质量分数增加而氧化物的质量分数降低;气体产物中H2的体积分数有所增加而CO和CO2的体积分数明显降低。活性炭催化剂作用下,生物质三组分与低密度聚乙烯之间相互作用的影响程度有所不同。

       

      Abstract: This study aims to explore the interaction of biomass components and plastics in the catalytic co-pyrolysis over the Activated Carbon (AC) catalyst. A fixed bed reactor was used to conduct the catalytic pyrolysis of cellulose, xylan, lignin, Douglas Fir (DF) alone, and the catalytic co-pyrolysis of their mixture with Low-Density Polyethylene (LDPE) over AC catalyst. AC catalyst was prepared via phosphoric acid activation followed by microwave carbonization. The obtained AC catalyst was characterized by a Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), temperature-programmed desorption of ammonia (NH3-TPD), and scanning electron microscopy (SEM). The main surface functional groups of AC were -OH (3 400 cm-1), -C-H (2 950 cm-1), -C=O (1 700 cm-1), -C=C (1 550 cm-1, 880 cm-1), and -CH-Ar (750 cm-1). Notably, the functional groups of -C-O-P (1 150 cm-1) and -P-O (1 050 cm-1) were successfully introduced in the catalyst, providing effectively active sites for the cracking and aromatization reactions to form aromatics. The BET surface area of AC was 1 440.0 m2/g, with a much higher external surface area of 1 412.8 m2/g and a lower micropore surface area of 27.2 m2/g. The total pore volume of AC was 0.86 cm3/g with low micropore volume. The peak at 100-200 ℃ was the weak acid site, which attributed to the weakly absorbed NH3 on the external surface of AC catalyst, whereas, the peak at 200~300 oC corresponded to the medium strength acid sites. The surface morphology of AC catalyst exhibited an irregular pore structure, due mainly to the chemical activation by phosphoric acid created the porosity in biomass matrix via the release of volatiles, shrinkage, fusion, and cracking reactions. Furthermore, the liquid yield was obtained from the catalytic pyrolysis of different feedstocks in the catalysis of AC catalyst. The order was ranked: Cellulose (55.0%) >xylan (36.0%) > DF (32.0%) > lignin (22.5%). The highest yield of char was obtained from the lignin pyrolysis, whereas, the pyrolysis of DF produced the maximum yield of gas. The catalytic pyrolysis of cellulose and xylan produced mainly furans, accounting for 78.6% and 83.2%, respectively. The main products of lignin pyrolysis were sample phenols. CO and CO2 were the main gas components during catalytic pyrolysis of cellulose, indicating that carbonylation and decarboxylation reactions were dominant at the active sites of the AC catalyst. The gas composition of lignin was H2 and CO2, which were from the dehydrogenation and decarboxylation reactions of side chains of lignin structural units. The results were attributed to the different structures and compositions of biomass feedstocks. The catalytic pyrolysis of LDPE produced aromatics and C9-C16 hydrocarbons as the main liquid product and H2 as the main gas products. The experimental liquid yield of four mixtures was reduced by 8.7%-11.4%, while the gas yield increased by 22.6%-64.0%, compared with the simulated. The content of aromatics and light aliphatic hydrocarbons (C9-C16) increased in liquid products, whereas, the content of oxygenates decreased significantly. The H2 content increased, whereas, the contents of CO and CO2 decreased in gas products, indicating that there were interactions between biomass components and LDPE during catalytic co-pyrolysis. The interactions of cellulose /LDPE and hemicellulose /LDPE were mainly Diels-Alder reactions between furans and olefins, while the interaction of lignin and LDPE was mainly hydrogen transfer reaction, which promoted the dehydroxylation and demethoxylation reactions of phenols. These interactions greatly contributed to the formation of aromatic hydrocarbons and light aliphatic hydrocarbons (C9-C16), meanwhile, a large amount of hydrogen (80.6%-91.9%) was released.

       

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