The need to minimize anthropogenic CO2 emissions and our dependence on foreign fossil fuels has been a main driver for the discovery and development of renewable and sustainable production of fuels and chemicals from other sources. Toward this goal, non-edible lignocellulosic biomass (plant biomass composed of cellulose, hemicellulose, and lignin) is a promising renewable feedstock since it is abundant, does not directly compete with the food chain, can lead to nearly carbon-free processes with concomitant reduction in CO2 emissions, and contains the building block of chemicals and fuels, i.e., carbon.
It has been estimated that the annual crude oil demands in the US are of the same order of magnitude as the potentially available quantities of lignocellulosic materials and the throughput of chemicals is significantly lower, compared to fuels, and can easily be met. The recent boom in shale gas reduces our dependence on foreign petroleum, but also reduces the cracking of naphtha and thus, the production of C3-C6 chemicals from fossil fuels. One such example is BTX (Benzene, Toluene, Xylenes). Among BTX constituents, p-xylene (pX) is of great interest since it is the foundation for terephthalic acid (a polymer precursor for PET bottles used for the vast majority of food and liquid containers) and has an annual global demand of ~35 million metric tons/yr in 2010. The consumption of PET is expected to increase by 4-5%/yr over the next five years. pX has a similar number of carbon atoms to the building blocks of lignocellulose, and thus, its renewable production is an appealing target and forms the basis of the case study of the proposed work.
Penetration of biomass based chemicals into existing markets requires that their production is sustainable and cost competitive to that of the petrochemical counterparts. Economic analysis and life cycle analysis (LCA) are often conducted to evaluate new biomass-based processes. It is emphatically the case that such predictions (including our own work) are based on rudimentary information, e.g., overall yield, and as such, are very uncertain. Currently, catalysts, solvents, and separation schemes are by-and-large discovered by trial and error. This situation is reminiscent of the genesis of oil industry that was followed by a century of discovery to evolve to its current mature stage.
In order to realize renewable routes in the foreseeable future, a paradigm shift in philosophy and strategy is necessary that leverages recent scientific advances and core capabilities. It is the thesis of this research that a symbiotic program between systems analysis and fundamental science can lead to knowledge-based discovery and rapid commercialization while advancing scientific frontiers. This grand challenge-based vision defines the intellectual merit of the proposed program.
Intellectual Merit: To meet this grand challenge-based objective, a "hierarchical multiscale" program is planned, where systems analysis is informing the fundamental science of key processes and parameters, and the science team is performing experiments and simulations to collect this much needed knowledge to reduce systems uncertainty and render systems predictions reliable. In simple terms, the systems analysis focuses the space of scientific research and accelerates knowledge generation, where it makes sense to have, and the science in turn makes economic and life cycle analyses more reliable. The conversion of biomass-derived sugars to para-xylene has been selected as a representative case study.
Broader Impact: The proposed work will have impact on the specific domain of catalytic kinetics, separation technology, systems analysis, and the overall goal of establishing a sustainable manufacturing route of valuable chemicals from lignocellulose. The introduction of renewable chemicals can have a major impact on US economic development and sustainability. Similar to petro-based refineries, process synthesis will unavoidably play a vital role in sustainable and cost-effective biorefineries. The hierarchical multiscale program proposed herein can also pave the way of future research efforts between disciplines toward accelerated discovery and genesis of knowledge where is most impactful. The results will be disseminated broadly through publications, lectures, and integration of research findings within the graduate and undergraduate curricula of the two institutions involved. Graduate students will be trained in interdisciplinary science, including catalysis, reaction engineering, separation sciences, and process systems engineering, by establishing a new way of thinking in the development of a sustainable chemical process. In addition, the PIs will broaden participation of students from underrepresented groups and provide an enriching experience to K-12 students through a variety of educational activities.
