Green diesel production from upgrading of cashew nut shell liquid

Highlights: • Green diesel was obtained via upgrading of the cashew nut shell liquid (CNSL). • Reactions of deoxygenation, hydrogenation and cracking occurred over Pd/C catalyst. • Different reactions parameters (temperature, pressure and time) were investigated. • 98% conversion was achieved at mild conditions: 300 °C, 40 bar H₂and 10 h. • The main product contains 89% of alkanes, 3% aromatic and 8% of oxygenated compounds. -- Abstract: In recent years, there has been a strong global interest in developing technologies for converting renewable and low-cost raw materials into green diesel and bio-jet fuel, which are made of hydrocarbons. In this work, cashew nut shell liquid (CNSL), which is an industrial waste, was used as a feedstock to produce green diesel. Different reaction conditions during the upgrading process (deoxygenation, hydrogenation and cracking) were evaluated using palladium over activated charcoal (Pd/C) as a catalyst. The catalyst was characterized by X-ray diffraction and specific surface area analysis. The influences of the reaction parameters, such as temperature (180, 250 and 300 °C), time (5 and 10 h) and pressure (10, 20, 30 and 40 bar), were investigated using 10% w/w Pd/C. The composition of the products was determined using gas chromatography coupled with mass spectrometry and infrared spectroscopy. Higher pressures and temperatures led to a higher degree of deoxygenation and hydrogenation. In contrast, lower pressures or temperatures resulted in higher degrees of cracking. From the optimization experiments, a 98% yield of hydrocarbons corresponding to the diesel range was obtained under a 40 bar H₂ atmosphere at 300 °C, 10 h, and 500 rpm (in a batch reactor). Of these hydrocarbons, 89% were saturated alkanes, 3% were aromatic compounds and 6% were oxygenated compounds. This new and sustainable route is promising because it involves the conversion of a low-value residue into green diesel using mild experimental conditions. Biofuel production from CNSL allows the total valorization of the residues in the cashew-nut agroindustrial chain and has potential industrial applications in many countries.