Preparation of Amphiphilic Mesoporous Carbon-based Solid Acid from Kraft Lignin Activated by Phosphoric Acid and its Catalytic Performance for Hydration of α-Pinene

An amphiphilic mesoporous carbon-based solid acid (LCx-SO3H) with high specific surface area was prepared from kraft lignin that was carbonized using a phosphoric acid treatment. It was found that the specific surface area, pore structure, and amphiphilic nature of the catalyst was effectively controlled through adjusting the phosphoric acid dosage during lignin carbonization. Under optimum preparation conditions, the specific surface area, pore volume, and average pore size of the catalyst were 282.2 m(2)/g, 0.26 cm(3)/g, and 6.73 nm, respectively. The performance of this solid acid catalyst for the hydration of alpha-pinene was characterized via gas chromatography analysis. The conversion of alpha-pinene and the yield of aterpineol during hydration reaction were as high as 95.3% and 55.3%, respectively; these results were greater than the results from other hydration methods with sulfuric acid and commercially available solid acid catalysts (e.g., Amberlyst-15). After five recycles of the carbon-based solid acid without regeneration, conversion of alpha-pinene decreased from 95.3% to 92.6%, and the yield of alpha-terpineol decreased from 55.3% to 47.6%. These observations indicated that the solid acid catalyst derived from kraft lignin carbonization has high potential as a hydration agent for alpha-pinene.