4,4′-Dimethylbiphenyl (DMBP) can be easily transformed into diamines, diols and diacids, making it a major precursor in different organic chemicals, especially in the polymer industry. For instance, 4,4′-biphenyldicarboxylic acid, the diacid form of DMBP, is important in producing polymer products with high molecular weight without intermediate solidification. As such, it has been identified as a potential precursor in the production of engineering plastics, liquid crystal polymers and polyester fibers with excellent heat resistance and high tensile strength.
Although coupling reactions of arenediazonium salts or aryl chlorides are proven routes for synthesizing 4,4′-DMBP, they are not very selective, require costly substrates and produce waste in large amounts. Producing 4,4′-DMBP from benzene or toluene has recently emerged as an alternative and more effective route. It involves the production of (methylcyclohexyl)toluene (MCHT) via hydroalkylation of toluene and dehydrogenation of the intermediates to DMBP. However, the main challenge of this route is the difficulty in separating the mixture of several isomers (such as the 3,4′-, 3,3′-, etc.). Alternative routes involving benzene follow a similar pathway.
With the projected growth in the global polyester fiber market, developing more effective and robust routes for sustainable synthesizing 4,4′-DMBP is imperative. Producing polyesters using DMBP derived from renewable sources could reduce its overall lifecycle greenhouse gas emissions. In particular, it has already been shown that replacing oil-based toluene with biomass-derived furfural for 4,4′-DMBP manufacturing is a promising strategy for green production of polyester.
Herein, the University of Delaware researchers: PhD candidates Yuqing Luo, Mi Jen Kuo, Mingchun Ye, Professor Raul Lobo and Professor Marianthi Ierapetritou conducted a lifecycle assessment and technoeconomic analysis to compare the environmental and economic performances of two conceptual design for 4,4′-DMBP production. The first toluene-based design involved alkylation of toluene to MCHT, MCHT dehydration to DMBP and isomerization of lower-valued 3,3′-DMBP. The second renewable furfural-based design considered a three-step process: hydrogenation of furfural to 2-methylfuran (MF), oxidative coupling of MF to 5,5′-DMBF (dimethylbifuran) and tandem Diels-Alder dehydration of 5,5′-DMBF to 4,4′-DMBP. Their work is currently published in the research journal, Industrial and Engineering Chemistry Research.
The research team established that the proposed biomass-based DMBP production route is a sustainable, environmentally friendly and profitable technology. By optimizing the reaction conditions, using more robust catalysts, and shortening the reaction times, the commercial viability of this production process was improved, and the cost breakdown provided insights into the path toward profitability. Such process innovations are essential in improving further the operational and financial feasibility of biomass-based production routes. Furthermore, through sensitivity analysis, feedstock and 3,4′-DMBP isomer prices were identified as the most critical parameters for economic evaluation.
The toluene-based process benefits from inexpensive toluene feedstock and small equipment sizes, thus showing a lower 4,4′-DMBP minimum selling price ($2,488/t) than that of furfural-based process ($3,044/t) at a scale of 83 kmol/h feedstock. Nevertheless, when other factors were considered, the toluene-based process was less appealing economically. For instance, the furfural-based process was more carbon-efficient, producing significantly less greenhouse gas emission (5.00 kg CO2 equiv/kg DMBP) than toluene-based method (8.28 kg CO2 equiv/kg DMBP). Other advantages of furfural-based process included smaller plant size requirement, lower sensitivity to fluctuations in the market price of isomers and better controllability of the product quality.
In summary, this is the first study to perform process simulation and evaluate the environmental and economic feasibility of sustainable DMBP production. Optimizing the reaction conditions could further improve conversion and prevent unwanted side reactions. In a statement to Advances in Engineering, the authors explained that their new proposed biomass-based DMBP production path provides a promising alternative route for the sustainable production of high-quality, cost-effective and environmentally friendly polyesters.

Mi Jen Kuo obtained her bachelor’s degree from National Tsing Hua University in Hsinchu, Taiwan in 2019. Currently, she is a fourth-year graduate student in Professor Lobo’s group in the Department of Chemical and Biomolecular Engineering at University of Delaware. Her research mainly focuses on catalytic conversion of biomass-derived furans into commodity aromatic molecules. Her target molecule is called 4,4’- dimethylbiphenyl (DMBP), which can be prepared from furfural, a molecule derived from non-edible lignocellulosic biomass. The uniqueness and importance of her research is that there are many isomers of DMBP while 4,4’-DMBP is one of the most valuable, and her synthesis route yields the 4,4’- isomer with nearly 100% regioselectivity. This can avoid the recrystallization separation steps caused by the production of the isomers. The diacid made from DMBP can be incorporated into the PET plastics, one of the most important commercial polyesters, to enhance both mechanical and optical properties.

Marianthi Ierapetritou is the Bob and Jane Gore Centennial Chair Professor in the Department of Chemical and Biomolecular Engineering at University of Delaware. Prior to that she has been a Distinguished Professor in the Department of Chemical and Biochemical Engineering at Rutgers University. During the last year at Rutgers University, she led the efforts of the university advancing the careers in STEM for women at Rutgers as an Associate Vice President of the University.
Dr. Ierapetritou’s research focuses on the following areas: 1) process operations; (2) design and synthesis of flexible production systems with emphasis on pharmaceutical manufacturing; 3) energy and sustainability process modeling and operations; and 4) modeling of biopharmaceutical production. Her research is supported by several federal (FDA, NIH, NSF, ONR, NASA, DOE) and industrial (BMS, J&J, GSK, PSE, Bosch, Eli Lilly) grants.
Among her accomplishments are the appointment as the Gore Centennial Professor in 2019, the promotion to distinguished professor at Rutgers University in 2017, the 2016 Computing and Systems Technology (CAST) division Award in Computing in Chemical Engineering which is the highest distinction in the Systems area of the American Institute of hemical Engineers (AIChE), the Award of Division of Particulate Preparations and Design (PPD) of The Society of Powder Technology, Japan; the Outstanding Faculty Award at Rutgers; the Rutgers Board of Trustees Research Award for Scholarly Excellence; and the prestigious NSF CAREER award. She has served as a Consultant to the FDA under the Advisory Committee for Pharmaceutical Science and Clinical Pharmacology, elected as a fellow of AICHE and as a Director in the board of AIChE. She has more than 290 publications and has been an invited speaker to numerous national and international conferences.
Dr. Ierapetritou obtained her BS from The National Technical University in Athens, Greece, her PhD from Imperial College (London, UK) in 1995 and subsequently completed her post-doctoral research at Princeton University (Princeton, NJ).

Raul F. Lobo is the Claire D. LeClaire professor and Associate Chair of the Department of Chemical and Biomolecular Engineering at the University of Delaware. His research interests span the development of novel porous materials for catalysis and separations, the chemistry of zeolites, catalysis for energy and the environment, and the scientific aspects of catalyst synthesis. He has published over two hundred refereed reports and he is co-inventor in nine US patents. He obtained his undergraduate degree in Chemical Engineering at the University of Costa Rica in 1989 and later moved to California to pursue graduate studies in Chemical Engineering at Caltech. He worked for one year at Los Alamos National Laboratory, New Mexico as a postdoctoral fellow and started his academic career at the University of Delaware in 1995.

Yuqing Luo is a doctoral student at the University of Delaware (in the group of Professor Marianthi Ierapetritou, from Dec 2019). He worked as a research intern at the University of Pennsylvania on living radical polymerization kinetics in 2018. He received his bachelor’s degree in Macromolecule Science (Applied Chemistry) from Shanghai Jiao Tong University in 2019. His current research interests include sustainable process design and simulation, techno-economic analysis, life-cycle assessment, as well as flexible process and supply chain optimization under uncertainties.
Reference
Luo, Y., Kuo, M. J., Ye, M., Lobo, R., & Ierapetritou, M. (2022). Comparison of 4,4′-dimethylbiphenyl from biomass-derived furfural and oil-based resource: Technoeconomic Analysis and lifecycle assessment. Industrial & Engineering Chemistry Research, 61(25), 8963–8972.