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New insights into the chemical activation of lignins and tannins using K2CO3— a combined thermoanalytical and structural study KCI 등재
- 언어ENG
- URLhttps://db.koreascholar.com/Article/Detail/435062
Engineering of activated carbons (ACs) through chemical activation of organic precursors has been extensively studied for a wide variety of biopolymers, biomasses, wastes and other fossil-based precursors. Despite huge efforts to engineer evermore performant and sustainable ACs, “searching-for-the-best-recipe” type of studies are more the rule than the exception in the published literature. Emerging AC applications related to energy and gas storage require strict control of the AC properties and a better understanding of the fundamentals underlying their engineering. In this study, we provide new insights into the K2CO3 chemical activation of plant-based polyphenols—lignins and tannins—through careful thermoanalytical and structural analyses. We showed for the the first time that the reactivity of polyphenols during K2CO3 chemical activation depends remarkably on their purity and structural properties, such as their content of inorganics, OH functionalities and average molecular weight. We also found that the burn-off level is proportional to the K2CO3/ lignin impregnation ratio (IR), but only within a certain range—high impregnation ratios are not needed, unlike often reported in the literature. Furthermore, we showed for the first time that the K2CO3 chemical activation of different carbon surfaces from lignins and tannins can be modelled using simple global solid-state decomposition kinetics. The identified activation energies lay in the range of values reported for heterogenous gas-carbon surface gasification reactions ( O2-C, H2O- C, or CO2- C) in which the decomposition of C(O) surface complexes is the common rate-limiting step.
Abstract
1 Introduction
2 Materials and methods
2.1 Materials
2.2 Characterization of lignins and tannins
2.3 Simultaneous thermal analysis coupled to mass spectrometry (STA-MS)
2.3.1 Experimental protocol
3 Results and discussion
3.1 Direct carbonization of polyphenols
3.2 Effect of K2CO3 on the carbonization and activation of polyphenols
3.3 Polyphenol structure-thermal reactivity relationships
3.4 Effect of K2CO3lignin ratio on the carbonization and activation of lignins: case of SW-HL and SW-KL
3.5 Modeling the activation reaction kinetics
3.5.1 Phenomenology of carbon-K2CO3 activation reactions and model hypotheses
3.6 Is this the solid-state decomposition model applicable to all polyphenolic carbon surfaces?
4 Conclusions
References
