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Design of a continuous autohydrolysis pretreatment process of annual lignocellulose for industrial application
Citation Link: https://doi.org/10.15480/882.5105
Publikationstyp
Doctoral Thesis
Date Issued
2023
Sprache
English
Author(s)
Conrad, Marc-Julian
Advisor
Referee
Title Granting Institution
Technische Universität Hamburg
Place of Title Granting Institution
Hamburg
Examination Date
2023-01-20
Institut
TORE-DOI
Citation
Technische Universität Hamburg (2023)
In the last decade, several factories were put into operation that used the pretreatment of lignocellulose as a central refining stage, mainly to convert cellulose, sometimes also a fraction of hemicellulose, to lignocellulosic ethanol. The focus is on cheap lignocellulosic ethanol; thus, other parts of the non-edible biomass are turned to low-value applications due to low quality. The potential of hemicellulose and lignin remains vastly untapped. To shift the feedstock of the chemical industry to renewable resources, it is required for all compounds of lignocellulose to be refined in high quality so that they can be used for the production of chemicals.
Such full-fractionation processes are under development but fail to deconstruct the recalcitrant biomass efficiently. A critical challenge is the hydrolysis of hemicellulose. Before the conversion of the polymer is sufficiently high, the formed products (water-soluble pentose) decay to unwanted, harmful, and reactive degradation products like furfural. Reactors with in-situ product removal allow a full-fractionation under the conditions of excessive water and energy consumption, which is economically not feasible.
In this work, a two-step pretreatment is proposed and investigated experimentally. The hemicellulose conversion is stopped before the degradations take place to extract the desired product at its peak concentration. In the second step, the hemicellulose conversion is continued to the required level. The kinetic of this concept was investigated in Liquid Hot Water reactors and transferred to steam pretreatment reactors. A rigorous mass balance approves the high separation yields and avoidance of degradation products. The resulting (intermediate) products, oligomer xylan, glucose, and solid lignin, were tested in relevant applications to conclude the high quality of the products. Finally, critical steps are validated in continuous steam pretreatment reactors to allow the scaling of the process to an industrial scale.
Using a steam environment allows a fast and homogenous pretreatment while a minimal amount of liquid water and energy are required for the process. The resulting high concentration in the pretreated biomass is beneficial for the necessary extraction process. The pretreated biomass was used to develop an extraction process for this purpose. A new counter-current extraction process is designed and filed for a patent based on fast extraction in a stirred suspension with mild compressive dewatering for fast mass transport. Only a tiny amount of water can travel in the same direction as the solids to achieve a very low solvent (water) consumption, high extract concentrations, and a high extraction yield.
Such full-fractionation processes are under development but fail to deconstruct the recalcitrant biomass efficiently. A critical challenge is the hydrolysis of hemicellulose. Before the conversion of the polymer is sufficiently high, the formed products (water-soluble pentose) decay to unwanted, harmful, and reactive degradation products like furfural. Reactors with in-situ product removal allow a full-fractionation under the conditions of excessive water and energy consumption, which is economically not feasible.
In this work, a two-step pretreatment is proposed and investigated experimentally. The hemicellulose conversion is stopped before the degradations take place to extract the desired product at its peak concentration. In the second step, the hemicellulose conversion is continued to the required level. The kinetic of this concept was investigated in Liquid Hot Water reactors and transferred to steam pretreatment reactors. A rigorous mass balance approves the high separation yields and avoidance of degradation products. The resulting (intermediate) products, oligomer xylan, glucose, and solid lignin, were tested in relevant applications to conclude the high quality of the products. Finally, critical steps are validated in continuous steam pretreatment reactors to allow the scaling of the process to an industrial scale.
Using a steam environment allows a fast and homogenous pretreatment while a minimal amount of liquid water and energy are required for the process. The resulting high concentration in the pretreated biomass is beneficial for the necessary extraction process. The pretreated biomass was used to develop an extraction process for this purpose. A new counter-current extraction process is designed and filed for a patent based on fast extraction in a stirred suspension with mild compressive dewatering for fast mass transport. Only a tiny amount of water can travel in the same direction as the solids to achieve a very low solvent (water) consumption, high extract concentrations, and a high extraction yield.
Subjects
biorefinery, wheat straw, autohydrolysis, enzymatic hydrolysis, xylooligosaccharides
DDC Class
620: Ingenieurwissenschaften
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Name
Marc Conrad, Dissertation, 2023, Design of a continuous autohydrolysis pretreatment process of annual lignocellulose for industrial application.pdf
Size
4.79 MB
Format
Adobe PDF