Optimization of Photocatalytic Conversion of Lignocellulosic Waste: A Green Route to Long-Chain Alcohols

Abstract

Tall oil fatty acid (TOFA) represents an important byproduct obtained from processing of lignocellulosic biomass, mainly in the pulp and paper industry. In this work, TOFA is first transformed into its soap form under optimized alkaline conditions. TOFA-based soap is then employed as feedstock for the production of long-chain alkenes through photocatalysis, using a photoreactor equipped with a ultraviolet a-light emitting diode source. The photocatalytic efficiency of TiO2 is improved by surface modification with NH4+ species. A response surface methodology (RSM) approach is applied to examine the influence of reaction duration (135, 180, and 225 min), photocatalyst loading (80, 110, and 140 mg), and the amount of TOFA-based soap (50, 100, and 150 mg). The maximum yield of Cn−1 long-chain alkenes (77.7 mg) is achieved at nearly 1:1 ratio of TOFA-based soap to NH4-TiO2 after 180 min irradiation at 365 nm. Under these optimized conditions, approximately 55% of the TOFA-based soap could be converted into long-chain alkenes. Hydration of these alkenes with sulfuric acid yields corresponding long-chain alcohols, which may act as precursors for bio-based extended surfactants and related applications. This study emphasizes the potential of TOFA, a byproduct of lignocellulosic waste streams, as a renewable feedstock for generating high-value chemicals.