Rh complex encapsulated hexagonal mesoporous silica as an efficient heterogeneous catalyst for the selective hydroformylation of styrene

A rhodium complex encapsulated into the mesopores of hexagonal mesoporous silica [HRh(CO)(PPh3)(3)-HMS] was investigated for the heterogeneous catalytic hydroformylation of styrene. The catalyst system efficiently catalyzed the hydroformylation of styrene with 100 % conversion, yielding the desired iso-aldehyde selectively. The investigations were performed in detail to study the effects of the amount of catalyst, weight ratio of complex HRh(CO)(PPh3)(3)-tetraethylorthosilicate, concentration of styrene, pCO, pH(2) and temperature on the hydroformylation of styrene. The kinetic performance of the catalyst was favored on increasing the amount of the catalyst, styrene concentration, pH(2) and temperature. The rates were decreased on increasing pCO. The determined activation energy (E-a = 32.50 +/- A 0.8 kJ mol(-1)) indicated that E-a associated with heterogeneous catalysis is lower than that of the homogeneous catalysis. Under the employed reaction conditions, the iso-aldehyde could be achieved up to 88.90 % with 100 % styrene conversion. The heterogeneous catalyst, HRh(CO)(PPh3)(3)-HMS was separated and reused effectively up to seven catalytic cycles.