Synthesis of cyclohexylphenol via phenol hydroalkylation using Co2P/zeolite catalysts

Cyclohexylphenol (CHP) is a high added-value chemical, extensively used for the preparation of dyes, resins and biocides. This molecule is currently synthetized by phenol alkylation with cyclohexene/cyclohexanol using highly polluting mineral Brønsted acids as catalysts. The present contribution reports the one-pot production of cyclohexylphenol via hydroalkylation, using phenol as the only organic reactant, over a number of bifunctional catalysts consisting of Co2P (5 wt% Co) supported over different zeolites (ferrierite, mordenite, beta and MCM-22). Phenol conversion increased in the order: Co2P/Mordenite (30%) < Co2P/Ferrierite (65%) < Co2P/Beta (77%) < Co2P/MCM-22 (90%), which reflects enhancing dispersion of cobalt phosphide phase and accessibility of acid centres with evolving external surface in nanocrystalline zeolite supports. On the other hand, remarkable differences were observed between the catalysts in terms of CHP formation. The highest values of CHP yield and selectivity (YCHP=43% and SCHP=56%) were attained over the Co2P/Beta catalyst, due to the combination of three-dimensional microporosity, large external surface area (as a consequence of its nanocrystalline nature) and highly dispersed Co2P nanoparticles. In addition, it is envisaged that the formation of CoAlPO phases might favour a balanced performance of metal and acid sites for the CHP production.