Micro-explosion of liquid intermediates during the fast pyrolysis of sucrose and organosolv lignin

Abstract

A new methodology has been proposed to describe of the dynamics of bubble formation during pyrolysis of Organosolv lignin and sucrose (surrogates for biomass) using fast speed visualization (125fps) with mathematical modeling. The model uses a population balance to predict overall rates of bubble birth and death, bubble bursting, and aerosol ejection. The experimental studies were performed on a uniquely modified CDS Analytical Pyroprobe 5000 to visualize the formation of bubbles within the liquid intermediate phase at heating rates close 100 o C/s. Experimentally, we observed that bubbles follow a log-normal distribution versus bubble size within the liquid intermediate phase for both materials. This distribution function changes over time due to increased viscosity from solidification reactions that generate char and the changes in the rate of bubble formation. Micro-explosion intensity was used to estimate aerosol ejection intensity. The model predicts aerosol ejection yields of 21.18% w / w from Organosolv lignin and 17.40% w / w from sucrose during pyrolysis with an average droplet size of 10 m.

Identification of the fractions responsible for morphology conservation in lignocellulosic pyrolysis: Visualization studies of sugarcane bagasse and its pseudo-components

“…The materials were placed on sapphire discs which rested on the platinum wire resistor in a modified Pyroprobe 5000 (CDS Analytical) described [59]. Briefly, the reactor chamber is a glass tube (Pyrex 9825) open at both ends, screwed into a solid block of aluminum with a valve to regulate the continuous flow of nitrogen.…”

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

“…These works illustrated, through high speed photography and pyrolysis product analysis, that the liquid intermediate is made up of partially pyrolyzed oligomers which will either break down into monomers or turn into char at atmospheric pressure. Further studies with Montoya et al 207,267,268 demonstrated protocols to analyze and model ejection of aerosols from a thin film of pyrolyzing pseudo-biomass components.…”

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

“…Between 150 and 420 °C, lignin fragments primarily at the propyl chains, β‐O‐4, α‐O‐4, and C α C β bond bonds (Elder & Beste, ). These reactions form lignin oligomers, which go into the liquid intermediate phase and are thermally ejected, further split to monomers, or cross‐link into char (Montoya, Pecha, Chejne‐Janna, & Garcia‐Perez, ; B. Pecha et al, ; Smith, Pecha, Helms, Scudiero, & Garcia‐Perez, ). Above 380 °C, functional constituents of the aromatic ring detach and the lignin fragmentation product form clusters that combine into polyaromatic rings through a series of reactions that release CO, H 2 , CH 4 , and H 2 O (Huang, Wei, Qiu, Yin, & Wu, ; Smith et al, ).…”

“…While these atomistic and semi‐atomistic descriptions are useful for understanding fundamental reactions that occur during pyrolysis, their predictive capabilities are limited by an incomplete description of product speciation and coupling to physical processes that occur at larger length and time scales. For example, pyrolysis reactions are known to occur via a continuum wherein intermediates exist in a transitional liquid phase as oligomers and compounds undergo thermal decomposition which is not accounted for in most kinetic models and presents additional modeling challenges associated with capturing the physics of rapid phase transition (Lédé, ; Lédé, Ferrer, & Boutin, ; Montoya et al, ; Montoya, Pecha, Janna, & Garcia‐Perez, ; Pecha, Montoya, Chejne, & Garcia‐Perez, ; Teixeira et al, ).…”

“…ZSM‐5 deactivates rapidly because of coke accumulation on its exterior surface, which caps the micropores and prevents material from accessing the internal active sites (Mukarakate et al, ). This deactivation process is accelerated by the deposition oligomers found in aerosols that are formed during biomass pyrolysis (Chen, Du, Yang, & Wu, ; Garcia‐Perez et al, ; Montoya et al, ; Stankovikj, McDonald, Helms, & Garcia‐Perez, ; Teixeira et al, ; Zhou et al, ). In order to reduce the impact of rapid deactivation due to coking, ZSM‐5 catalysts are employed in riser reactors, which use large quantities of catalyst with relatively short residence times and employ in‐line catalyst regeneration.…”