Selective catalytic synthesis of 2-ethyl phenol over Cu1-xCoxFe2O4-kinetics, catalysis and XPS aspects

A systematic study of catalytic ethylation of phenol is carried out with ethanol as a function of feed composition, time on stream (TOS), temperature, and catalyst composition over Cu1-xCoxFe2O4 (x = 0.0 - 1.0) ferrospinel system. Phenol ethylation gives 2-ethyl phenol as a major product under the reaction conditions employed, while its selectivity decreases as temperature and Co-content increases. Compositions containing both Cu and Co ( 0 < x < 1) are found to be more efficient for better catalytic performance than the end compositions ( x = 0 and 1); x = 0.5 shows the highest catalytic performance. TOS studies clearly exhibit the stable activity for x less than or equal to 0.75 for at least 50 h. X-ray photoemission spectra (XPS) and X-ray induced Auger electron spectroscopy analysis revealed the partial reduction of metal ions during reaction. Valence band studies clearly show an increase in overlap of metal-ion 3d bands from fresh to spent catalysts by a large decrease in energy gap between them. Cu-rich compositions display a large amount of Cu species on the surface and highlight its importance in the ethylation. High catalytic activity displayed by 0 < x < 1 emphasizing the importance of both Cu and Co for better catalytic performance.