Chinese Journal of Catalysis ›› 2025, Vol. 71: 25-53.DOI: 10.1016/S1872-2067(24)60248-2

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Advances in humins formation mechanism, inhibition strategies, and value-added applications

Yitong Wanga,1, Chaofeng Zhangb,1, Cheng Caia,*(), Caoxing Huangb, Xiaojun Shenc, Hongming Loud, Changwei Hue, Xuejun Panf, Feng Wangg,*(), Jun Xiea,*()   

  1. aKey Laboratory of Energy Plants Resource and Utilization, Guangdong Engineering Technology Research Center for Agricultural and Forestry Biomass, Institute of Biomass Engineering, South China Agricultural University, Guangzhou 510642, Guangdong, China
    bJiangsu Co-Innovation Center of Efficient Processing and Utilization of Forest Resources, College of Light Industry and Food Engineering, Nanjing Forestry University, Nanjing 210037, Jiangsu, China
    cState Key Laboratory of Efficient Production of Forest Resources, Beijing Forestry University, Beijing 100083, China
    dSchool of Chemistry and Chemical Engineering, Guangdong Provincial Key Lab of Green Chemical Product Technology, South China University of Technology, Guangzhou 510641, Guangdong, China
    eKey Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610065, Sichuan, China
    fDepartment of Biological Systems Engineering, University of Wisconsin-Madison, 460 Henry Mall, Madison, WI, 53706, USA
    gState Key Laboratory of Catalysis, Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China
  • Received:2024-12-18 Accepted:2025-02-08 Online:2025-04-18 Published:2025-04-13
  • Contact: * E-mail: wangfeng@dicp.ac.cn (F. Wang), chengcai@scau.edu.cn (C. Cai),xiejun@scau.edu.cn (J. Xie).
  • About author:Cheng Cai graduated from the School of Chemistry and Chemical Engineering, South China University of Technology in 2020, and carried out postdoctoral work at the Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, China in 2021. Now he is working in the Institute of Biomass Engineering, South China Agricultural University. His main interests include chemical catalytic conversion of lignocellulose, immobilization of enzyme, preparation and application of lignin and cellulosic materials.
    Feng Wang received his PhD degree from the Dalian Institute of Chemical Physics, Chinese Academy of Sciences in 2005, and went to the University of California, Berkeley, USA for postdoctoral work in the same year. He is currently the Deputy Director of Dalian Institute of Chemical Physics, Chinese Academy of Sciences. His research interests include multiphase catalytic reactions, catalytic conversion of biomass, photocatalytic conversion, life cycle assessment and economic and technology assessment.
    Jun Xie graduated from the College of Life Sciences of Sichuan University in 2001 with a Doctor of Science degree, and joined South China Agricultural University (SCAU) in August 2003 as a professor and supervisor of doctoral students. He is currently the Director of the Institute of Biomass Engineering, South China Agricultural University. His main research areas are catalytic conversion of biomass energy, efficient energy and medicinal plant resources and utilization, and preparation and application of small molecule collagen peptides.

    1Contributed to this work equally.

  • Supported by:
    National Key Research and Development Program of China(2021YFC2101602);National Natural Science Foundation of China(22378150);National Natural Science Foundation of China(32471809);Young Talent Support Project of Guangzhou Association for Science and Technology(QT2024-009);Research Fund for High-level Talents Introduction of Nanjing Forestry University(163105164);Natural Science Foundation of Jiangsu Province(BK20220106)

Abstract:

Humins, as a group of by-products formed through the condensation and coupling of fragment intermediates during lignocellulosic biomass refining, can cause numerous negative effects such as the wastage of carbon resources, clogging of reactor piping, deactivation of catalyst, and barriers to product separation. Elucidating the generation mechanism of humins, developing efficient inhibitors, and even utilizing them as a resource, both from the perspective of atom economy and safe production, constitutes a research endeavor replete with challenges and opportunities. Orbiting the critical issue of humins structure and its generation mechanism from cellulose and hemicellulose resources, the random condensation between intermediates such as 5-hydroxymethylfurfural, furfural, 2,5-dioxo-6-hydroxyhexanal, and 1,2,4-benzenetriol etc. were systematically summarized. Additionally, the presence of lignin in real biorefining processes further promotes the formation of a special type of humins known as "pseudo-lignin". The influences of various factors, including raw materials, reaction temperature and time, acid-base environment, as well as solvent systems and catalysts, on the formation of humins were comprehensively analyzed. To minimize the formation of humins, the design of efficient solvent systems and catalysts is crucial. Furthermore, this review investigates the approaches to value-added applications of humins. The corresponding summary could provide guidance for the development of the humins chemistry.

Key words: Humins, Lignocellulosic, Biomass refining, Biomass conversion, Pseudo-lignin