Fast Pyrolysis of Lignin Pretreated with Magnesium Formate and Magnesium Hydroxide

Mayank Patel,William J Desisto,Nick Hill,Sampath Gunukula,Charles A Mullen

doi:10.3390/en13194995

Mayank Patel, William J Desisto + Show 3 more

Open Access

https://doi.org/10.3390/en13194995

Copy DOI

Journal: Energies	Publication Date: Sep 23, 2020
Citations: 3	License type: CC BY 4.0

Affiliation: University of Maine, Eastern Regional Research Center

Abstract

Kraft lignin (Indulin AT) pretreated with magnesium formate and magnesium hydroxide was fast-pyrolyzed in a continuously fed, bench-scale system. To avoid fouling issues typically associated with lignin pyrolysis, a simple laboratory test was used to determine suitable ranges of magnesium hydroxide and formic acid to lignin for feeding without plugging problems. Various feedstock formulations of lignin pretreated with magnesium hydroxide and formic acid were pyrolyzed. For comparison, calcium formate pretreated lignin was also tested. The organic oil yield ranged from 9% to 17% wt % on a lignin basis. Carbon yields in the oil ranged from 10% to 18% wt % on a lignin basis. Magnesium formate pretreatment increased oil yield and carbon yield in the oil up to 35% relative to the higher 1:1 g magnesium hydroxide/g lignin pretreatment. However, a lower magnesium hydroxide pretreatment (0.5:1 g magnesium hydroxide/g lignin) resulted in oil yields and carbon yields in the oils similar to the magnesium formate pretreatments. Magnesium formate pretreatment produced more oil but with a higher oxygen content than calcium formate under the same conditions. The GC-MS analysis of product oils indicated that phenols and aromatics were more prevalent in pyrolyzed magnesium-formate-pretreated lignin.

Highlights

Fast pyrolysis has been examined as a method to depolymerize lignin for possible uses as a liquid fuel and source of phenolics and biopolymers [1,2,3]
The fast pyrolysis of lignin is challenged by reactor feeding problems associated with the physical and chemical properties of lignin
The fast pyrolysis of lignin is challenged by reactor feeding problems associated with the physical lignin with alkaline earth salts prior to fast pyrolysis can improve reactor feeding and pyrolysis and chemical properties of lignin

Summary

Introduction

Fast pyrolysis has been examined as a method to depolymerize lignin for possible uses as a liquid fuel and source of phenolics and biopolymers [1,2,3]. Challenges to lignin pyrolysis scale-up because of lignin melting and char foaming/agglomeration was reported in an international collaborative study [4]. Two strategies have been used to mitigate this challenge in lignin pyrolysis: reactor design and feed additives. To overcome this challenge via reactor design, the lignin feed can be injected in slugs [6], diluted with an inert material like clay [7], or fed to a reactor that breaks up foaming char [8,9]. A recent study looked at eleven different additives and their influence on lignin agglomeration and pyrolysis and found that both magnesium hydroxide and calcium hydroxide were effective in inhibiting lignin agglomeration [15]

Methods

Results

Discussion

Conclusion