Paula C. Rodrigues Pinto

Recovery of Vanillin and Syringaldehyde from Lignin Oxidation: A Review of Separation and Purification Processes

Lignin is an underexploited side-stream of pulp and paper industry and biorefineries, being used for energy production at mill site or as low value material for dispersants or binding applications. However, an integrated process of reaction and separation can be implemented for the production of high added-value monomeric phenolic chemicals such as vanillin and syringaldehyde. In this review, the main research advances in the recovery of vanillin and syringaldehyde resulting from oxidation of lignin are addressed, covering various separation methodologies namely liquid-liquid extraction, supercritical fluid extraction, distillation, crystallization, membrane separation, and adsorption. Studies in this area started in the early years of the 20th century, but in the last decades several processes have been suggested, mainly for vanillin separation. Finding the ultimate industrially feasible process is still a necessary task and this review points out the most promising technologies and sequence of processes.

Lignin as Source of Fine Chemicals: Vanillin and Syringaldehyde

The sustainability of processes to integrate in biochemical and thermochemical platforms is a key factor for the success of lignocellulose-based biorefineries. Production and separation of high added-value compounds from renewable resources are emergent areas of science and technology with relevance to both scientific and industrial communities. Lignin is one of the raw materials with high potential due to its chemistry and proprieties. One of the routes is the production of aromatic aldehydes, vanillin, and syringaldehyde, toward environmental friendly processes as oxidation with O2, including separation of products by membrane and ion exchange processes. In this chapter, the types, availability, and characteristics of lignins are described, as well as the current trends of some industrial producers and processors. A concise yet comprehensive revision of the literature on lignin oxidation research focusing vanillin and syringaldehyde is provided. Separation processes for recovery of the aldehydes are included closing with a design of reaction and separation integrated process for aldehydes production from lignin.