Guaiacol hydrotreating with in-situ generated hydrogen over ni/modified zeolite supports

Catalytic hydrotreating of guaiacol as a model compound was investigated using bifunctional catalysts constituted of Ni supported on chemically modified zeolites with increased mesoporosity. In the reaction conditions, the hydrogen required for the process was generated in situ by the Zn–H2O redox system, which represents a promising green alternative to the use of gaseous hydrogen. The guaiacol hydrotreating conversion using as support zeolites with increased mesoporosity, is largely higher than that obtained with the original ones. The introduction of mesopores through desilication treatment with NaOH and TBAOH significantly increased the mass transfer of guaiacol and improved the accessibility of the active sites, accordingly enhancing the catalytic performance. The alkaline treatment notably increased the mesopore volume of Ni/HZSM-5 and Ni/HBeta by 5.6 and 3.8 times, respectively. Ni supported on desilicated HBeta zeolite displayed high hydrodeoxygenation and hydrodearomatization efficiencies with values of 69.37% and 62.82%, respectively. The reusability of this catalyst was investigated, showing a decrease in the performance after three consecutive runs due to the oxidation of Ni active site, coking and zinc oxide contamination. The main of guaiacol conversion products are cyclohexane, cyclohexanone, cyclohexanol, benzene and phenol. A reaction pathway of guaiacol hydrotreating using Ni-zeolites catalysts is proposed.