Real-time investigation of the photodissociation dynamics of p-chlorotoluene and p-dichlorobenzene

De-excited dynamics of p-chlorotoluene and p-dichlorobenzene have been investigated by the femtosecond pump-probe method in a supersonic molecular beam. The yields of the parent ion and daughter ion are examined as a function of the delay time between the pump and probe laser pulses. The lifetime constants of excited p-chlorotoluene and p-dichlorobenzene are determined. Possible de-excitation mechanisms are suggested that the initially excited S-1 state is predissociative via the repulsive triplet state. The substituent effects of additional chlorine atom and methyl group are discussed. Moreover, for the first time, we observe a novel quantum beat oscillation in p-dichlorobenzene. (c) 2005 Elsevier B.V. All rights reserved.

Ligand modified real heterogeneous catalysts for fixed-bed hydroformylation of propylene

A novel ligand modified heterogeneous catalyst has been developed for hydroformylation of propylene, which showed excellent activity, selectivity and stability and need not be separated from the product after reaction in a fixed-bed reactor. The coordination bonds between triphenyl phosphine (PPh3) and Rh/SiO2 were confirmed by means of thermogravimetric (TG), solid-state P-31 NMR, XPS and FT-IR. Two types of active species for hydroformylation were formed, which were proved by in situ FT-IR techniques. The problem of metal leaching was greatly reduced by directly fastening Rh particles on the support, and the active Rh species that was responsible for the outstanding performance of propylene hydroformylation was tightly bound by the very strong metal-metal bonds. No sign of deactivation was observed over a period of more than 1000 h on the condition that PPh3 was added at 300-350 h of time on stream. (c) 2005 Elsevier B.V. All rights reserved.