In situ preparation of K2CO3 supported Kraft lignin activated carbon as solid base catalyst for biodiesel production

•A new method of in situ preparing carbon loading K2CO3 as solid catalyst is proposed.•Kraft lignin was used as precursor of solid catalyst for biodiesel production.•This solid catalyst is low-cost, efficient, environmentally friendly and reusable.•The solid catalysts were characterized to reveal the textures and catalytic performance. In this study, the catalysts K2CO3 supported Kraft lignin activated carbon (K2CO3/KLC) were prepared in situ by simply mixing K2CO3 with technical Kraft lignin (KL) and subsequently activating at 800°C for 2h under N2 flow. The precursor and catalysts were characterized by thermal gravity analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area. The catalytic performance of prepared catalysts was evaluated by transesterification of rapeseed oil with methanol. The effects of various parameters on biodiesel yield were investigated. The biodiesel yield of 99.6% was achieved by using the catalyst prepared by 0.6 of K2CO3/KL mass ratio and activation at 800°C, under the transesterification condition of 65°C, 2h, methanol to rapeseed oil molar ratio of 15:1 and 3.0wt.% catalyst (relative to the weight of rapeseed oil). The solid catalyst can be reused for 4 times and biodiesel yield remained over 82.1% for the fourth time.