Prozessanalysentechnologie und Reaktionstechnik im Bereich der Biomasseverwertung
- Process analytical technology and reaction engineering in the field of biomass-valorization
Eifert, Tobias; Liauw, Marcel (Thesis advisor); Leitner, Walter (Thesis advisor)
Dissertation / PhD Thesis
Dissertation, RWTH Aachen University, 2018
Process analytical technology (PAT) provides powerful tools to gather inline data of chemical processes; this data is most commonly used to optimize the processes in the process industry. PAT is not yet frequently used as a resource in R&D despite the significant advantages of early process optimization. Particularly in the field of biomass valorization, early development is required in order to successfully develop reaction systems which have to compete with heavily optimized processes from the petrochemical value chain. A methodology to evaluate kinetic parameters of biomass transformations employing PAT is presented. These kinetic parameters are then used to optimize a reaction by means of reaction engineering. Hereby, the transformation reactions represent the value chain of a biorefinery based on lignocellulose. The first step is the conversion of biomass to platform chemicals and the second step are further conversions to higher value products with desired properties. The dehydration of xylose to furfural was chosen as model systems for the first step and the hydrodeoxygenation of 5-hydroxymethylfurfural (5-HMF) to 2,5-dimethylfuran (2,5-DMF) represents the second step. The salient feature of the presented strategy involves the determination of reaction rates and activation energies for biomass conversions under process conditions without influence from occurring side reactions or fouling of optical probes. PAT was applied to the dehydration of the C5-sugar xylose to the platform chemical furfural. The reaction was comprehensively monitored in situ with ATR mid-IR and Raman spectroscopy at different reaction temperatures. The reaction kinetics for the dehydration of xylose to furfural and the side reaction of humin formation were simultaneously evaluated by chemometric and kinetic modeling of the inline data. This insight allowed for the proposal for an optimized reactor concept: a continuous reactor design to maximize the yields of furfural and minimize the production of humins. This continuous reactor was implemented and resulted in an improved selectivity towards furfural while using high reaction temperatures and short residence times. ATR UV/Vis, ATR mid-IR and Raman spectroscopy were used to monitor the hydrodeoxygenation of 5-HMF to 2,5-DMF under process conditions at different temperatures. The suitable PAT tools provided kinetic data and the data was evaluated by chemometric and kinetic modeling to show the activation energies of this reaction system. The kinetic modeling of the three in-process spectral data revealed the activation energy of 5-HMF consumption. The same methodology was used to investigate the pathways to 2,5-DMF via the intermediates. The gained knowledge allowed to determine the preferred pathway of this reaction system, which is first the hydrogenolysis towards 5-methylfurfural and subsequently the hydration to (5-methyl-2-furyl)methanol and then the hydrogenolysis towards 2,5-DMF.By using PAT tools in the field of research, especially in the field of biomass valorization, a system cannot only be optimized by in-process data, but this methodology also leads to a proven concept regarding the use of PAT for a subsequent production plant.