Advancing catalytic fast pyrolysis through integrated multiscale modeling and experimentation: Challenges, progress, and perspectives

Abstract

Catalytic fast pyrolysis (CFP) is a conversion process that integrates rapid thermochemical depolymerization of solid feedstocks with catalytic transformation to yield small molecules for fuel and chemical products. This process is well-suited for the conversion of nonfossil feedstocks such as biomass and waste plastics, and thereby holds great potential for the production of renewable commodities. In spite of many technological developments in various aspects of CFP achieved over decades of research, this technology has yet to attain commercial success for the production of fuels and chemicals from renewable feedstocks. Effective CFP processes require careful coordination of chemical and physical phenomena that span very large length and time scales. A broad spectrum of scientific progress in both pyrolysis and catalytic upgrading has provided the foundation for successful deployment of CFP, although additional progress in process-scale integration is yet required for commercial realization. Modeling and simulation tools provide an important framework wherein the CFP technologies by be better understood and evaluated from a holistic perspective. Here we provide a detailed description of the multiscale phenomena underlying CFP, describe challenges and associated technical progress, and suggest strategies for an integrated approach to advance this technology toward commercialization.

Effects of Moisture on Diffusion in Unmodified Wood Cell Walls: A Phenomenological Polymer Science Approach

“…This multiscale structure leads to difficulties associated with obtaining experimental data that de-couple intra-cell wall and inter-cell wall transport processes. Many studies that model bulk transport through woody materials employ approximations for transport in porous media that couple transport through cell wall material and void regions [21]. Eitelberger and Hofstetter developed an insightful multiscale homogenization approach that considers wood structure at multiple length scales [22], but the approach was lacking experimental validation of assumptions made at each scale.…”

Progress in understanding the four dominant intra-particle phenomena of lignocellulose pyrolysis: chemical reactions, heat transfer, mass transfer, and phase change

“…See Table 5 for more detailed information about these models. Further discussion on coupling atomic scale models, single particle models, and reactor scale models can be seen in Ciesielski et al 26 and a focus on reactor scale modelling in Xiong et al 288,289 Conclusions From this review, the following conclusions and recommendations can be drawn:…”

“…It has been argued that one reason for failure to scale up is a lack of understanding of the fundamental phenomena of biomass pyrolysis. 26 The purpose of this review is to describe the four principal intra-particle phenomena of biomass pyrolysis: chemical reactions, heat transfer, mass transfer, and phase change. The authors believe that too little attention has been given to phase change, particularly with regards to the liquid intermediate stage between native biopolymer and vaporized organic compounds.…”

“…Left) A visual reconstruction of the softwood fiber structure of pine based on X-ray tomography data26 illustrates that heat and mass both move more readily in the direction of cell axes than in radial direction and (right) heat flux resistance pathways for wood, depending on the direction of the flux 212. Left image reprinted (adapted) with permission from Ciesielski et al26 Copyright (2018) Wiley.…”

Novel Micro-Mesoporous Composite ZSM-5 Catalyst for Aromatics Production by Catalytic Fast Pyrolysis of Lignin Residues

“…Combined with the structural characteristics of the catalyst, the major factor in KL conversion was the catalyst's exterior structure, and the internal pore structure had a great effect on PL conversion. In contrast to the configurational diffusion in micropore channels, the diffusion mechanism in mesopores needed to consider the joint contribution of configurational diffusion and Knudsen diffusion [30]. The hierarchical sample had funnel-shaped openings on the surface, with pore size as large as 20 nm or more.…”