Lignin from Hardwood and Softwood Biomass as a Lubricating Additive to Ethylene Glycol.

Liwen Mu,Minjiao Chen,Jiahua Zhu,Alireza Vahidi,Yijun Shi,Paul Christakopoulos,Mattias Grahn,Ulrika Rova,Leonidas Matsakas,Jian Wu

doi:10.3390/molecules23030537

Liwen Mu, Minjiao Chen + Show 8 more

Open Access

https://doi.org/10.3390/molecules23030537

Copy DOI

Abstract

Ethylene glycol (EG)-based lubricant was prepared with dissolved organosolv lignin from birch wood (BL) and softwood (SL) biomass. The effects of different lignin types on the rheological, thermal, and tribological properties of the lignin/EG lubricants were comprehensively investigated by various characterization techniques. Dissolving organosolv lignin in EG results in outstanding lubricating properties. Specifically, the wear volume of the disc by EG-44BL is only 8.9% of that lubricated by pure EG. The enhanced anti-wear property of the EG/lignin system could be attributed to the formation of a robust lubrication film and the strong adhesion of the lubricant on the contacting metal surface due to the presence of a dense hydrogen bonding (H-bonding) network. The lubricating performance of EG-BL outperforms EG-SL, which could be attributed to the denser H-bonding sites in BL and its broader molecular weight distribution. The disc wear loss of EG-44BL is only 45.7% of that lubricated by EG-44SL. Overall, H-bonding is the major contributor to the different tribological properties of BL and SL in EG-based lubricants.

Highlights

Lignin, a cross-linked polymer with phenylpropanoic monomers, is the second most abundant biopolymer in nature [1]
It is observed that the viscosity of ethylene glycol (EG)-BL is larger than that of EG-SL at a lower lignin loading of less than 38%; this trend reverses at 44 and 50%
Organosolv lignin dissolution was dissolved in EG up to 50 wt%

Summary

Introduction

A cross-linked polymer with phenylpropanoic monomers, is the second most abundant biopolymer in nature [1]. The carbohydrate portion fromleaving lignocellulosic leaving ligninwith as ana high insoluble residue with a These two methods produce a large amount of wastewater during the isolation process and cause high lignin yield [11,12]. The organosolv isolation process and cause irreversible reactions that severely change the structure of the isolated processIn uses organicthe solvents to extract ligninuses fromorganic a biomass feedstock under lignin mild conditions, which lignin. Lignin was demonstrated as an effective lubricant additive in ionic liquids [20], base. The H-bonding strength between lignin and the lubricant base could be modulated by the by the versatile molecular structures of lignin extracted from different plant species. Organosolv lignins isolated from of our knowledge, the effect of lignin type on its efficiency as a lubricant additive has never been studied. The H-bonding between different lignin and EG and the effect of lignin molecular weight distribution on the lubricating performance of these new lubricants are investigated

Results and Discussion

IRIRspectra ethylene glycol

Materials

Preparation of Lubricants

Characterization

Conclusions