Coal is of utmost importance for the energy and chemical engineering fields of China,as it contributes to 56.8%of primary energy supply in 2020 in the country.‘‘On the one hand,coal is the major source of energy and resources for its rich endowment in China;However,on the other hand,it is the major source of environmental pollution due to the implementation of outdated technologies.Therefore,according to Professor Kechang Xie in 2004,‘‘The only way out is to develop and promote the clean and efficient coal utilization technologies”.In the past 40 years,China has made a significant progress in research and development related to modern coal chemical engineering,including lab-scale fundamental research and industrial-scale construction of many giant chemical plants.

Globally,the laboratory led by Professor Xie has been one of the most active and influential teams working on clean coal technologies.Professor Xie was elected as an academician of the Chinese Academy of Engineering in 2003 and a foreign associate of the National Academy of Engineering(USA)in 2013 for understanding the molecular structure and reactivity of coal,and for leadership in the modern clean coal conversion industry.He graduated from Tianjin University with Bachelor’s degree in 1968,and gained his Master’s degree at Taiyuan Institute of Technology in 1981.From 1983 to 1985,he continued his study as a visiting scholar at University of South Carolina in the United States.In 1999,he finished his doctoral dissertation in the field of energy at Shinshu University in Japan.Professor Xie has been the recipient of many honors and recognitions,including the Meritorious Figure of Energy 70 Years Award(2019),the Meritorious Figure of Coal Technologies Award by China Coal Society(2019),the Ho Leung Ho Lee Foundation Science and Technology Award (2008),the National Distinguished Professional Talents (2002),andetc.Notably,he and his team members won the second prize of the State Natural Science Award of China (2008) for investigating the structure–reactivity relationship of coal,and the second prize of the State Science and Technology Advancement Award for their contribution in developing novel desulfurization technologies and materials for the cleanup of coal gasification gas (2001).

Beyond his academic achievements,Professor Xie has held and continues to hold many leadership positions in many organizations.Between 1995 and 2010,he served as the President of the Taiyuan University of Technology.He was the Vice President of the Chinese Academy of Engineering (2010–2014).He is the Vice President of the Chinese Institute of Engineering Development Strategies,member of the Expert Committee for Beijing-Tianjin-Hebei Integrated Development,member of the National Expert Committee on Climate Change,and member of the Consulting committee of the China Energy Investment Corporation.In these positions,he keeps initiating and promoting the implementation of clean coal technologies,the revolution of energy production and consumption,and the concept of low-carbon utilization of high-carbon resources.

At Taiyuan University of Technology,Professor Xie has advised over 100 graduate students,postdoctoral researchers and young colleagues,who are globally the leading scientists and engineers in the field of Energy Chemical Engineering.He established the Key Laboratory of Coal Science and Technology in 1985.This laboratory was approved as the Key Laboratory of the Shanxi Province and the Ministry of Education of the People’s Republic of China in 1997 and 2003,respectively.In 2021,the laboratory was approved as the State Key Laboratory of Clean and Efficient Coal Utilization.Over the years,Professor Xie and his team members have been focusing on research related to coal science and technology,including coal structure and reactivity,coal conversion into fuels and chemicals,energy saving and emission reduction during coal utilization,and strategic planning of clean and efficient coal utilization.The team assumed the leadership of the National Basic Research Program of China(also known as 973 program)twice,finished more than 20 Key Projects of the National Science Foundation of China,and involved in several Key Consulting Projects of the Chinese Academy of Engineering.The dedication of the whole laboratory has led to the research outcome in the form of more than 100 refereed papers and more than 20 authorized patents every year,and the industrial applications of several technologies and products.

The current special issue honors Professor Xie and his team for their outstanding contributions to the development of clean coal technologies with impacts on the fields of energy and environment.It is a compilation of articles from researchers working on coal-related topics by invitation.All submissions have been subjected to the usual rigorous peer review process.Upon the completion of the whole editorial process,a total of 26 papers have been accepted for publication.The contributions cover a number of topics,including reviews of the clean coal conversion technologies in China,utilization of high-sulfur coal and coal gasification slag,and research articles of lignite pyrolysis,coal tar upgrading,and syngas conversion to fuels and chemicals.

We would like to express our sincere gratitude to all the authors contributing to this issue and the reviewers for their constructive comments and suggestions for the submissions.In particular,we thank Editor-in-Chief Prof.Weiyang Fei,Executive Editor-in-Chief Prof.Guangsheng Luo,and the editorial office staff of Chinese Journal of Chemical Engineering for their contributions and support.