Highly selective oxidation of styrene into benzaldehyde over nano CeWOx composite confined in N-doped carbon under solvent-free conditions

Abstract

Highly selective oxidation of styrene into benzaldehyde with molecular oxygen under solvent-free conditions still remains a great challenge. Herein, Ce-modified heteropolyacid-based poly(ionic liquid)s were prepared as precursors followed by carbonization to obtain nano CeWOx composite confined in N-doped carbon (CeWOx@NC). Then, the as-prepared catalysts were further characterized by FT-IR, TG, XRD, XPS, BET, SEM, TEM-EDS and H2-TPR to discuss the relationship between the structure and performance. The nano CeWOx composite with a mixed valence state of W4+ and W6+ was formed and well dispersed in the N-doped carbon. Moreover, the valence ratio of W4+ to W6+, redox capacity and oxygen vacancies could be tailored by carbonization temperature and incorporation of Ce, which was strongly correlated with the catalytic performance of CeWOx@NC catalysts. Benefited from that, the CeWOx@NC800 catalyst displays outstanding catalytic performance for solvent-free oxidation of styrene into benzaldehyde with styrene conversion of 45.1%, benzaldehyde selectivity of 89.2% and TOF of 310.1 h−1 at the optimum reaction conditions. Furthermore, the catalyst has shown robust stability and reusability.