Abstract:

Activated carbon (AC) has been demonstrated as a catalyst or catalyst support in catalytic pyrolysis of biomass and plastics due to its developed porosity and functional groups. However, the catalytic activity of AC catalyst is low, which needs to be improved by modification. The catalytic co-pyrolysis of corn straw and high-density polyethylene over boron doped activated carbon (BAC) catalyst was investigated in a fixed bed reactor. The effects of boron doping amount, catalyst to feedstock mass ratio and co-pyrolysis temperature on product yields and distributions were studied. The specific surface area, pore volume, surface functional groups and acidity of AC and BAC catalysts were measured by BET, FTIR and NH₃-TPD. XRD and XPS were used to characterize the crystal structure and presence morphology of boron in fresh and spent BAC catalysts. The results showed that the specific surface area and pore size of BAC catalyst decreased gradually with the increasing of boron doping, the surface functional groups did not change significantly, but the amount of strong and weak acids increased significantly. In the used BAC catalyst, boron mainly exists in the form of B-O bond, BC₃ diffraction peak disappears and B-C weak diffraction peak appears. With the increase of boron doping from 0.5%(mass) increased to 3.0%, the content of monocyclic aromatic hydrocarbons first increased and then decreased, while the content of polycyclic aromatic hydrocarbons exhibited an opposite trend with monocyclic aromatic hydrocarbons. With the boron doping amount of 1.0%, the co-pyrolysis temperature of 600℃ and the BAC catalyst to raw material mass ratio of 1.25, the content of monocyclic aromatic hydrocarbons reached the maximum value of 44.18%, and the content of polycyclic aromatic hydrocarbons was 19.75%. In addition, the presence of boron can effectively inhibit the deposition of coke and improve the lifetime of the BAC catalyst.

Key words: biomass, boron doping, activated carbon, catalyst, selectivity, aromatics

摘要：

活性炭（AC）由于其发达的孔隙结构和官能团，被用作生物质和塑料催化裂解的催化剂或催化剂载体。然而，AC催化剂的催化活性较低，需对其进行改性处理以提高催化性能。本文利用固定床反应器探究了掺硼活性炭（BAC）催化剂催化玉米秸秆和高密度聚乙烯共热解过程中硼掺杂量、催化剂/原料质量比、共热解温度对产物产率及分布的影响规律。采用BET、FT-IR、NH₃-TPD测试了AC与BAC催化剂的比表面积、孔容、表面官能团及酸性等性能，并采用XRD和XPS对BAC使用前后硼的晶体结构和存在形态进行了表征。结果表明，随着硼掺杂量的增加，BAC催化剂的比表面积和孔径逐渐降低，表面官能团无明显变化，而强弱酸量显著增加。使用后的BAC催化剂中硼主要以B—O键的形式存在，BC₃衍射峰消失，出现了B—C弱衍射峰。随着硼掺杂质量分数从0.5%增至3.0%，单环芳烃的含量先升高后降低，而多环芳烃的含量呈现出与单环芳烃相反的变化趋势。当硼掺杂量为1.0%、共热解温度为600℃和BAC催化剂/原料质量比为1.25时，单环芳烃含量达到最大值44.18%，此时多环芳烃的含量为19.75%。此外，硼的存在能有效抑制焦炭沉积，提高催化剂的寿命。

关键词: 生物质, 硼掺杂, 活性碳, 催化剂, 选择性, 芳烃