Highly selective BTX from catalytic fast pyrolysis of lignin over supported mesoporous silica

Abstract

The post synthesis of Al(3+) or Zr(4+) substituted MCM-48 framework with controlled acidity is challenging because the functional groups exhibiting acidity often jeopardize the framework integrity. Herein, we report the post-synthesis of two hierarchically porous MCM-48 composed of either aluminum (Al(3+)) or zirconium (Zr(4+)) clusters with high throughput. All prepared catalysts have been characterized by HR-TEM, XRD, IR, N2-adsorption, NH3-TPD, TGA and MAS NMR. They exhibit BET surface areas of 597 and 1112m(2)g(-1) for 8.4% Al/MCM-48 and 2.9% Zr/MCM-48, respectively. XRD analysis reveals that the hierarchical porosity of parental MCM-48 is reserved even after incorporation of Al(3+)or Zr(4+). Zr/MCM-48 catalysts are demonstrate a superior performance versus that of Al/MCM-48 and MCM-48 because of the mild (ZrO2) or nil (SiO2) Lewis acidity contributed from Zr-μ2-O group as well as smaller pore sizes suitable for the restriction of unwanted side reactions. The reaction conditions which were affecting the catalytic pyrolysis and final products were gas flow rate, pyrolysis temperature, and catalyst to lignin ratio. A total of 49% of BTX product were obtained over 2.9% Zr/MCM-48 at 600°C. The Lewis acid character was the governing factor which helps in pyrolysis and directly affects the BTX formation.

Keywords: BTX; Fast pyrolysis; Lignin; MCM-48.