2-Naphtalenesulfonic Acid as Catalyst for Lignocellulosic Pretreatment: Study of Optimum Reaction Conditions by Response-Surface Methodology

Many processes leading to production of second generation biofuels, such as ethanol, include a fermentation step that requires sugars obtained from the polyglycoside fraction of lignocellulosic biomasses. Unfortunately, fermentable sugars are not so easy to obtain, because of the cellulose natural resistance to hydrolysis, due to its crystalline structure. A pretreatment step is necessary in order to reduce crystallinity, increase porosity and improve hydrolytic enzymes accessibility to the fibers. Among the pretreatment processes, those using mineral dilute acids are widely used, in particular with sulfuric acid. However, acid treatments need neutralization (generally by adding lime) with subsequent significant salts formation. In our work, we report the use of a water soluble organic acid, 2­naphthalenesulfonic acid, that shows a good activity as pretreatment catalyst. Moreover, it can be recovered by solvent extraction and recycled to the pre­hydrolysis step, avoiding neutralization and salt production.