Abstract
Pine sawdust and wheat straw are abundant lignocellulosic wastes that have been recently converted into bioethanol under a biochemical platform scheme whose main waste is lignin. Lignin can be transformed into a wide variety of high added-value products, including its functionalization as a catalyst. A key step in the synthesis of a lignin-based catalyst is the sulfonation reaction, whose operating conditions, namely, H2SO4 to lignin ratio (mL/g), temperature and time, have been arbitrarily chosen. In this contribution, an optimization methodology (i.e., Box-Behnken) is applied in order to found the operating conditions during the sulfonation reaction that maximizes the total acid sites density of lignin-based catalysts from pine sawdust and wheat straw. The optimization results show that the time in sulfonation reactions can be significantly reduced, compared to those previously reported, without affecting the performance of both catalysts in esterification reactions. These results could be further considered for energy and costs reduction purposes during the conceptual design engineering of the sulfonation reaction.
Highlights
Pine sawdust and wheat straw are the main wastes from pine and wheat’s (Triticum spp.)industrial processing, respectively
This study aims to valorize the residual lignin from lignocellulosic wastes that have been processed in a biochemical platform scheme
The transformation of lignin from pine sawdust and processed wheat straw into a biocatalyst via a sulfonation reaction was optimized using a Box-Behnken experimental design whose factors were X1 : The ratio of concentrated H2 SO4 to lignin, X2 : Temperature (◦ C), and X3 : Time (h) affecting the Total Acid Sites (TAS), which was considered as a response variable in the design
Summary
Pine sawdust and wheat straw are the main wastes from pine and wheat’s (Triticum spp.)industrial processing, respectively. Pine sawdust has been considered as adsorbent for the disposal of olive mill wastewater [3] or as a fluoride remover [4], whereas wheat straw has been used for animal bedding [5] or as a cattle feed [6] These wastes have been considered as feedstock for (second generation) bioethanol production in a biochemical platform scheme [7,8], in which the hemicellulose and cellulose contained in such wastes are transformed into bioethanol, while the lignin content (i.e., residual lignin) is currently discarded or converted into electricity [9]. Hu et al [13] have synthesized a lignin based catalyst from activated
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