Comparison of jet loop and trickle-bed reactor performance in large-scale exploitation of glucose reductive aminolysis
Graphical abstract
Introduction
Glucose reductive aminolysis is a complex but environmentally benign route for the production of short chain alkanolamines and diamines, e.g., N,N-dimethylaminoethanol (DMAE) and N,N,N’,N’-tetramethylethylenediamine (TMEDA) when using dimethylamine (DMA) as the aminating agent [1]. Apart from being a green production route, it is also inherently safe as it does not involve any toxic or hazardous intermediates such as ethylene oxide and 1,2-dichloroethane [2,3]. In our previous work we have unraveled the complex kinetics of the reductive aminolysis of glucose with DMA, particularly shedding a light on the interplay between homogeneous and heterogeneously catalyzed reactions in the production of DMAE and TMEDA [4].
In the present work we aim at exploiting this interplay to optimize the glucose reductive aminolysis product yields in two very different reactor types, i.e., a jet-loop and trickle bed reactor [[5], [6], [7]]. The former reactor type has a low catalyst-to-liquid ratio while the trickle bed reactor has a high catalyst-to-liquid ratio. Furthermore, in the jet-loop reactor the contents are well-mixed and small catalyst particles (10−100 μm scale) flow along with the liquid phase while in the trickle bed reactor the gas and liquid flow exhibit a concurrent plug flow pattern over a bed of larger catalyst pellets (>1 mm scale). As a result, the homogeneous reaction steps are expected to exhibit a more pronounced impact on the overall jet-loop reactor behavior while the heterogeneously catalyzed reaction steps are deemed to contribute more significantly during trickle bed operation. An analysis based on a generic, less complex, but similar reaction scheme and neglecting heat transfer effects indicated indeed that the product requiring the higher number of homogeneous reaction steps is predominantly produced in a jet-loop reactor while the trickle bed reactor operating conditions could be tuned to optimize the product spectrum in either direction [8]. The reductive aminolysis chemistry is, however, more complex than the generic one. More specifically, the number of homogeneous reactions steps prior to the heterogeneously catalyzed hydrogenation is higher and undesired hydrogenated products can be formed along the course of the reaction. Moreover, there is a significantly higher chance for highly temperature dependent degradation in this more complex reaction network.
Within this group of chemical reactions the reductive amination has been, and is still being, performed in both types of reactors considered [[9], [10], [11]]. The more efficient removal of the heat generated by these exothermic reactions and mixing of hydrogen into the liquid phase are arguments in favor of the jet loop reactor compared to the trickle bed reactor. The advantage of the trickle bed reactor is, next to the easy option for continuous production, the high catalyst-to-liquid ratio, thus favoring heterogeneously catalyzed reactions as long as the supply of all reactants, c.q. hydrogen, to the active sites is sufficiently fast. The reductive amination results cannot be just extrapolated to the reductive aminolysis of glucose. In contrast to the reductive amination smaller carbohydrate chains are being formed by retro-aldol cleavages in the reductive aminolysis and a keto-enol tautomerism opens the reaction path to the main product. Furthermore, the components involved in this work are prone to irreversible and very temperature-dependent homogeneous degradation reactions and these critical aspects will be discussed in this work. Maximizing the gas-liquid interphase mass transfer is critical to maintain low concentrations of these degradation components.
Here, the main aspects discussed above such as the interplay of homogeneous and heterogeneously catalyzed reactions, the removal of generated heat and unavoidable degradation reactions as they occur in the reductive aminolysis of glucose with DMA are addressed by performing large scale 1D reactor simulations for a jet-loop and a trickle bed reactor. A lab scale experimental assessment was performed to verify the simulated product yields in both reactors.
Section snippets
Experimental
The trickle bed experiment was performed in a large lab scale fixed bed reactor with a length of 1.17 m and a diameter of 0.015 m. 200 g of Ni KL6504K-P (60 % Ni/SiO2) catalyst, acquired from CRI catalyst company, particles were crushed to a diameter of 1.4·10−3 m and placed in the reactor. This resulted in a bulk density of 1000 kgcat mr -3. DMA, as provided by Eastman Chemical Company, was present in a separate vessel as a liquid under its own vapor pressure. For feeding it is pressurized
Simulation results
The effect of varying the operating conditions such as the initial DMA to glucose ratio nDMA/nglucose° and the inlet/initial temperature T on the product spectrum of the reductive aminolysis of glucose has been examined. In addition, the total feed flow rate of glucose syrup Fglucose° and the initial hydrogen to glucose ratio nH2/nglucose° were varied in the trickle bed reactor simulations while the catalyst mass Wcat was varied for the jet loop reactor. In all cases the amount of hydrogen fed
Conclusions
Commercial-scale reactor simulations for the reductive aminolysis of glucose have shown that, irrespective of whether a trickle bed reactor or a jet loop reactor was considered, the optimization of the product spectrum primarily translates to TMEDA yield maximization. In the jet loop reactor a TMEDA yield of 57 % can be obtained. In addition, a DMAE yield of 12 % is obtained. This is mainly achieved by working at a high ratio of DMA to glucose amounting to 40 mol mol−1. This corresponds to the
CRediT authorship contribution statement
Jeroen Poissonnier: Conceptualization, Methodology, Investigation, Writing - original draft. Annelies Callewaert: Conceptualization, Methodology. Kristof Moonen: Conceptualization, Writing - review & editing. Guy B. Marin: Supervision, Writing - review & editing. Joris W. Thybaut: Supervision, Writing - review & editing.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This work was supported by Flanders Innovation & Entrepreneurship VLAIO (IWT)via the intermediary of FISCH/CATALISTI, contract 145020 – Carboleum.
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