Research For Hydroformylation Of Ethylene In FCC Off-gas To Propanal Over PPh₃-Rh/SiO₂ Catalysts

Propanal is an important chemical material which is mainly used to produce chemical intermediates such as propanal, propanoic acid. In China, few factories produce it and the domestic demand gradually increased. At present, the yields of propanal mainly used homogeneous low-pressure hydroformylation method with the Rhodium and phosphine compound homogeneous catalysts, which used pure ethylene material. But this route faced some problems including difficult separation of catalysts with the products and high cost of the catalysts recover.FCC off-gas is the exhaust gas, which cann't be liquid in the refinery, and its components are very complex. Usually, it is bumed as fuel or exhaust gas, however it contained much value chemical materials such as ethylene and hydrogen. If the very cheep ethylene in FCC Off-gas is used as starting material to make a product of high market value propanal, it not only increases use routes of FCC off-gas and the profits of refinery, but also resolves our country's domestic demand gap for propanal and its ramifications.In this article, we prepared a kind of PPh3-Rh/SiO2 heterogeneous catalyst that used organic phosphine ligands (PPh3) directly modified the Rh/SiO2 catalyst with an idea of organic-inorganic hybrid catalysis, which led to the originality of a hybrid of heterogeneous and homogeneous catalysts. And we studied the hydroformylation of ethylene in FCC off-gas in column reactor through varying the reaction factors including reaction temperature, pressure, space velocity, n(P)/n(Rh) and the calcinations temperature. An ethylene hydroformylation TOF of 900 h-1 can be achieved under conditions: n(P)/n(Rh)=15, 383K, 1.0MPa, GHSV=5000h-1. The rhodium in this catalyst is not easy to be leached as homogeneous one and the separation between products and catalyst is very convenient.By using of TG, 31PMAS NMR, XPS, TPD and FTIR techniques thePPh3-Rh/SiO2 catalysts were characterized. The coordination bond between phosphine ligands and Rh atom and the valence state of the surface Rh is made clear before and after the CO/H2 adsorbed on the PPh3-Rh/SiO2. The adsorption state of CO, H2 and C2H4 on PPh3-Rh/SiO2 was observed. It is found that linearly CO bonded on Rh coordinated PPh3 ligands is the catalytic active site of PPh3-Rh/SiO2 catalyst for ethylene hydroformylation under gas-solid phase conditions.