Industrial waste derived CaO-based catalysts for upgrading volatiles during pyrolysis of Jatropha residues

- CaO-based catalysts derived from industrial waste were successfully synthesized.
- CaO-based catalysts had a potential for deoxygenation and denitrogenation.
- Biomass:catalyst ratio of 1:5 showed the optimum result for maximizing hydrocarbons.
- Ni/CaO showed the best catalyst for producing the highest hydrocarbon selectivity.

Lime mud, the industrial waste from pulp and paper mills, was used as a raw material for preparing calcium oxide (CaO)-based catalysts. Lime mud was heated at 1000 °C to transform it into active CaO and then modified by adding 5 wt% Fe or Ni (as nitrates) using the wet impregnation method and calcining to form the Fe/CaO and Ni/CaO catalysts. The fast pyrolysis of Jatropha residues to bio-oil with no catalyst and with the derived CaO, Fe/CaO and Ni/CaO catalysts was studied using an analytical pyrolysis-GC/MS at 500 °C at a biomass: catalyst ratio of 1:1 and 1:5. A Jatropha residue: catalyst ratio of 1:5 was more optimal for enhancing aliphatic hydrocarbon production and decreasing the amount of oxygenated and N-containing compounds. The presence of the CaO catalyst completely eliminated the undesirable acids and sugars in the bio-oil, significantly decreased N-containing compounds and considerably promoted the formation of aliphatic hydrocarbons up to 37.3%. The Fe/CaO and Ni/CaO catalysts further increased the selectivity for aliphatic hydrocarbons, and reduced aldehyde formation compared to with CaO, with Ni/CaO being the best catalyst for hydrocarbon selectivity (47.5%). Overall, these CaO-based catalysts derived from industrial lime mud waste can be used for catalytic fast pyrolysis applications.