Orange peel waste for biobased jet fuel synthesis: limonene hydrogenation using Raney-Nickel catalyst

The composition of conventional petroleum-based jet fuel consists of branched alkanes, cycloalkanes, and aromatic compounds. Due to the importance of the ecological transition, it is relevant to find bio-based alternatives. A representative example is pmenthane, a branched cycloalkane obtainable by hydrogenation of limonene [1]. The latter is a terpene which accounts up to 95% of essential oil extracted from orange peel. Considering that among citrus plantation, oranges constitute the 82% of them, and that peel made up to 50% of the fruit weight, the valorisation of the huge amount of orange peel waste produced worldwide is a great opportunity [2]. Typically, limonene hydrogenation (Fig.1) has been carried out using molecular hydrogen and Pt, Pd or Rh as catalysts [1, 3]. To verify the feasibility of the reaction using another source of hydrogen and less noble metal as catalyst, in this study the reaction was performed using Raney- Nickel as catalyst, sodium borohydride as hydrogen source and methanol as solvent. The experimental tests were carried out in autoclave, using limonene purchased from commercial sources. A Design of Experiment was set to statistically assess the impact of temperature (30 – 60 °C), catalyst amount (0.3 – 0.6 g), sodium borohydride amount (0.2 – 0.6 g), reaction time (6 – 24 h) and solvent amount (10 – 20 mL). Afterwords, limonene was extracted from orange peel waste by hydro distillation and tested as substrate for the synthesis of p-menthane at the optimized reaction conditions.