Abstract:

Multihole hollow carbon spheres (MHCS) were prepared by using a hard template method. The effects of heat treatment temperature, metal loading, and etching on the electromagnetic parameters of MHCS were systematically studied. Among the prepared carbon spheres, MHCS-800 with high dielectric loss (ε″ = 213) was selected as the support for catalysts, while SCS-800 (ε″ = 50) and SCS (ε″ = 0.08) served as control groups. These carbons after sulfonation were used to catalyze the hydrolysis of fructose. Based on the reaction kinetics under microwave (MW) and conventional heating conditions, the influence of dielectric loss on the MW-assisted catalytic effect was investigated. The results showed that the conversion rate can reach 97.7% within 5 min using MHCS-800-SO₃H as catalysts under 80 W MW power irradiation. Besides, the reaction rate constant (k) under MW is 0.76 min^-1, which is 8.97 times of that under conventional heating (k=0.0847 min^-1). The MW enhancement effect occurred in MHCS-800-SO₃H is much more significant compared with SCS-800-SO₃H and SCS-SO₃H (where k values were increased by 164.9% and 11.9%, respectively). The above results can be attributed to the combination of the hollow porous structure and the high graphitization degree of MHCS-800, which is conducive to the formation of “hotspots” on the surface of catalyst particles, thereby accelerating catalytic reactions.

Key words: microwave irradiation, fructose dehydration, multiphase reaction, kinetics, dielectric loss, catalysis

摘要：

利用硬模板法制备了中空多孔碳球（MHCS），系统研究了热处理温度、金属负载量、刻蚀前后对MHCS电磁参数的影响。从中选取高介电损耗值（ε″）的MHCS-800（ε″ = 213）作为催化剂载体，并以SCS-800（ε″ = 50）和SCS（ε″ = 0.08）作为对比样品，经磺化后用于催化果糖水解制5-羟甲基糠醛，根据在微波加热和常规油浴条件下的反应动力学探究了ε″对微波催化效果的影响。结果表明，在80 W微波功率辐照下使用MHCS-800-SO₃H作为催化剂，5 min转化率即可达97.7%；反应速率常数（k）为0.76 min^-1，是常规加热（k = 0.0847 min^-1）的8.97倍，该催化剂相较于SCS-800-SO₃H和SCS-SO₃H的微波催化效果（k比常规分别提升了164.9%、11.9%）更加显著。以上研究结果源于中空多孔结构和高的石墨化程度相耦合更有利于在催化剂颗粒表面形成“热点”，从而加速催化反应。

关键词: 微波辐照, 果糖水解, 多相反应, 动力学, 介电损耗, 催化