This paper presents a robust kinetic model for the dehydration of xylose in concentrated sulfuric acid (i.e., 0.1– 2 M) at 120–160 °C, i.e., conditions that were not yet explored in the literature and hold promise in terms of process intensification. The model is built on an extensive set of batch experiments and an integral analysis method of the kinetic data. Direct condensation of furfural and xylose is not a major degradation route, but the former reacts with other dehydrated intermediates. The kinetic constants of xylose dehydration and furfural degradation show a non-linear dependency with respect to the hydronium concentration at higher acid concentrations (>1 M). This trend could be attributed to a simultaneous attack of two hydronium ions on the formyl group of the C1 atom and on the hydroxyl group of the C3 atom occurring under high acid concentrations (>1 M). Unlike previously reported models, the developed kinetic model is able to predict the experimental results (xylose conversion and furfural yield) within a 95% confidence interval under a wide range of temperatures and sulfuric acid concentrations. Even more, this model is also able to predict the experimental results reported in the literature obtained with sulfuric acid with high accuracy.

In this paper, we describe the continuous production of furfural coupled with in situ stripping using hydrogen gas. With respect to the conventional semibatch process, which requires excessive steam as stripping agent and results in highly diluted furfural, this new process configuration reduces the net energy input, increases the efficiency of the downstream hydrogenation of furfural, and proposes a shift toward a continuous operation. Based on well-established thermodynamic data and previously reported kinetics, we have developed a first-principle reactor model that successfully describes the experimental observations without the use of any fitting parameters. This robust predictive model is used to further optimize the continuous production of furfural via this route.

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