Investigations on MCM-41 as a fume catalytic incinerator: A heptane case study

This study shows that mesoporous MCM-41 compounds, that have hexagonal-close-packed channels, are good candidates as micro-reactors for fume catalytic incineration reactions. MCM-41 is synthesized and used as a catalyst to incinerate normal heptane (nC7) at different temperatures and equivalence ratios (φ). Destruction and removal efficiency (DRE, 99.99%) of heptane is achieved at 500 °C and φ=0.85 using MCM-41 as a catalyst compared to 73.45% under the same conditions without the catalyst. Even 99.9% DRE of heptane is achieved at 450 °C. The number and quantity of some analyzed products of incomplete combustion (PIC) are dramatically decreased when using MCM-41 material. No coke formation occurs. Under fuel-rich conditions, virtually complete consumption of oxygen molecules occurred at 450 °C when using MCM-41 compared to 75% in thermal incineration at the same conditions. While MCM-41 improves DRE at high temperature, e.g. 450 °C, it worsens it dramatically at lower ones, e.g. 300 °C. This inhibition of destruction effect depends also on the equivalence ratio of the mixture. It seems that diffusion properties and the chromatographic effect of MCM-41 channels become important at low temperatures. The enhanced DRE of heptane, upon using MCM-41, at relatively low temperatures, 450 °C, suggests that MCM-41 channels act as nano-vessels for free radical incineration reactions rather than a meter-scale incineration chamber as in the case in thermal incineration processes.