Kinetics and Chemorheological Analysis of Cross-Linking Reactions in Humins.

Sangregorio Sangregorio,Guigo Guigo,Sbirrazzuoli Sbirrazzuoli,Jong Jong

doi:10.3390/polym11111804

Abstract

Humins is a biomass-derived material, co-product of the acid-catalyzed conversion of cellulose and hemicellulose to platform chemicals. This work presents a thorough study concerning the crosslinking kinetics of humins by chemorheological analysis and model-free kinetics under isothermal and non-isothermal curing. Humins can auto-crosslink under the effect of temperature, and the reaction can be fastener when adding an acidic initiator. Thus, the effect of P-Toluenesulfonic acid monohydrate (pTSA) on the crosslinking kinetics was also studied. The dependencies of the effective activation energy (Eα-dependencies) were determined by an advanced isoconversional method and correlated with the variation of complex viscosity during curing. It is shown that humins curing involves multi-step complex reactions and that the use of an acidic initiator allows faster crosslinking at lower temperatures, involving lower Eα. The shift from chemical to diffusion control was also estimated.

Highlights

The necessity to focus on biorefinery technologies is exemplified by the growing concern on climate change and the exhaustion of fossil raw materials
The curing reaction was first studied by isothermal Differential Scanning Calorimetry (DSC)
Variation of the effectiveof activation energy with conversion was techniques havefor been used for these purposes

Summary

Introduction

The necessity to focus on biorefinery technologies is exemplified by the growing concern on climate change and the exhaustion of fossil raw materials. Humins is a biobased material, co-product of the acid-catalyzed conversions of cellulose and hemicellulose to platform chemicals. First studies concerning humins date almost one century [5], only in the last few years scientists took an interest in the formation and the characterization of this product [6,7,8,9,10,11]. Sumerkii et al [6] first postulated that humins formation occurs via 5-hydroxymethylfurfural (HMF). Aldol addition and condensation were proposed as key reactions in the acid-catalyzed growth of humins, adding

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