Novel Micro-Mesoporous Composite ZSM-5 Catalyst for Aromatics Production by Catalytic Fast Pyrolysis of Lignin Residues

Wenbo Wang,Simin Li,Shuang Xue,Haoran Sun,Zhongyang Luo

doi:10.3390/catal10040378

Abstract

The industrial utilization of lignocellulosic biomass is often accompanied by lots of lignin residues. Catalytic fast pyrolysis (CFP) is a high-throughput method to convert lignin to aromatics and phenolics. In order to optimize catalytic performance, conventional zeolite catalysts often need to have mesostructural modification. Here, based on hierarchical zeolite (HZ), a novel micro-mesoporous composite zeolite was obtained by redeposition under mild conditions. The conversion of two industrial lignin residues, Kraft Lignin (KL) and Pyrolytic Lignin (PL), was investigated. Interestingly, the hierarchical sample was more suitable for the case of higher concentration of primary pyrolysis products such as CFP of PL, with aromatics yield of 12.7 wt % and a monocyclic aromatic hydrocarbons (MAHs) to polycyclic aromatic hydrocarbons (PAHs) mass ratio of 4.86. The mesoporous composite zeolite possessed a better PAHs suppression capability as M/P reached 6.06, and was suitable for low reactants’ concentration and high oxygen content, such as KL CFP, with a higher aromatics yield of 3.3 wt % and M/P of 5.12. These results were compared with poplar sawdust as actual biomass, and mesoporous samples were both highly efficient catalysts with MAHs yield over 10 wt % and M/P around 5.

Highlights

In the current transformation of the energy sector, biomass as a renewable energy resource can provide a greener way to obtain chemicals and fuels [1,2]
Through in-situ Catalytic fast pyrolysis (CFP), the zeolite catalyst is physically mixed with raw materials, and the lignin residues or lignocellulosic biomass can be converted into aromatic hydrocarbons in one step [10,11,12]
The samples obtained by various preparation methods appear significantly different under transmission electron microscopy (TEM)

Summary

Introduction

In the current transformation of the energy sector, biomass as a renewable energy resource can provide a greener way to obtain chemicals and fuels [1,2]. Biomass utilization has a long history, such as in the paper industry, as well as for biodiesel production, fermentation to produce ethanol, biogas production, etc. Fast pyrolysis has been used to directly produce bio-oil [3]. When lignocellulosic biomass is used as a raw material, its lignin content is very problematic, bringing many problems—which include difficulties obtaining efficient conversion, affecting the yield of other components and increasing costs and potential pollution [4,5]. Through in-situ CFP, the zeolite catalyst is physically mixed with raw materials, and the lignin residues or lignocellulosic biomass can be converted into aromatic hydrocarbons in one step [10,11,12]. Aromatics can be used as raw materials for chemical industry and medicine, and as additives for aviation fuel. Except for the economic advantages of CFP, there are accompanying problems, such as rapid deactivation of conventional catalysts, Catalysts 2020, 10, 378; doi:10.3390/catal10040378 www.mdpi.com/journal/catalysts

Methods

Results

Conclusion