Production of levulinic acid from oil palm empty fruit bunch fiber using novel tin oxide catalysts

Levulinic acid (LA; 4-oxopentanoic acid, C 5 H 8 O 3 ) is a useful platform chemical for making diverse other commercial products. This work developed a novel catalytic system for efficient production of LA from oil palm empty fruit bunch (EFB), a widely available lignocellulosic waste. First, the EFB was pretreated with tetrahydrofuran to obtain a cellulose-rich solid substrate that was subsequently converted to LA in a stirred batch reactor using solid acid catalysts. The catalysts were sulfated tin oxide (SO 4 2- /SnO 2 ) and a newly developed iron-doped variant, sulfated iron–tin oxide (SO 4 2- /Fe–SnO 2 ). Iron doping significantly increased both the specific surface area (from 145.9 to 168.7 m 2 g –1 ) and the number of acid sites. The effects of reaction temperature (180–220 °C), reaction time (1–6 h), and the catalyst loading (0–4% w w -1 ) on the yield of LA and the other useful byproducts are reported. The sulfated iron-tin oxide catalyst was more active than the sulfated tin oxide under certain reaction conditions. Notably, it achieved a maximum LA yield of 31.2% w w −1 based on the pretreated EFB, or 39.9% w w −1 based on available cellulose, surpassing many metal oxide catalysts reported in the literature. The optimum reaction conditions were 200 °C, 1 h, and a SO 4 2− /Fe-SnO 2 catalyst loading of 2% w w −1 . The promising heterogeneous catalytic approach used here for upgrading lignocellulosic waste to higher value chemicals offers environmental and economic benefits. • Oil palm empty fruit bunch (EFB) cellulose was used to produce levulinic acid (LA). • Novel solid acid catalysts converted EFB cellulose to LA. • Iron doping enhanced the catalyst surface area and acidity. • LA yield was better than previously reported with many metal oxide catalysts. • New options for producing LA from renewable EFB for biorefinery applications.