Study On Catalytic Materials Used For Simultaneous Removal Of NO_X, SO_X, CO From FCC Fuel Gas And On Related Mechanism

The Fluid Catalytic Cracking (FCC) is the major gasoline-producing process in refinery. Considerable amounts of harmful gases (SOx, NOx, CO) are generated with the FCC operations. In the United States, FCC operations are estimated to emit 6%-7% of the total SOx emissions and 10% of the NOx emissions. Because of the special physico-chemical atmosphere in the FCC regenerator, the catalysts which can be used for effectively removing these gases simultaneously from the flue gas have not been developed up to now.In our research, we have developed a kind of new rare-earth-promoted mult-component catalysts (CuCeMgAl(O)) using coprecipitation method which exhibit excellent performance for simultaneous removal of NOx, SOx, CO from the NO + SO2 + CO + 02 + H20 reaction system. This kind of catalysts have following properties: high activity for NO + CO reaction with the excellent resistance to 502 poisoning; excellent hydrothermal and thermal stability; high catalytic activity for the reaction of SO2 and 02 and effective capturing capacity for SOx under regenerator conditions. Many analyzing techniques including TPD, TPR, TPSR, in-situ JR and XPS were employed to characterize the catalysts and to elucidate the reaction mechanism. The results are summarized as follows:1.Mg2 in the hydrotalcite can be substituted partially by Cu2 in the course of coprecipitation, and Ce4~ ions exist in the form of CeO2, it can not enter into the structure of hydrotalcite. With the increase of activation temperature, the structure of hydrotalcite is destroyed gradually and CuO, MgO or spinel phase can be detected by XRD. The addition of cerium can inhibit the formation of spinel phase and make the CuO disperse well. The reduction temperature of copper ion in the CuCeMgA1(O) is lower than that in the CuMgAJ(O), which indicates the synergic effect between copper ion and cerium ion.2.XPS analysis shows that most of copper ions in the CuMgAl(O) arewhereas considerable amounts of Cu~ and oxygen vacancies exist in the CuCeMgAl(0) which are produced by the partial substitution of Ce4~ in the CeO2 by Cut.3.For the reduction of NO by CO. the activity of CuCeMgAl(0) is higher than that of CuMgAJ(O) and CeMgAl(O); the presence of a small amount of oxygen and I~20 rnthe reaction system increases the activity of CuCeMgAJ(0); the reactions of NQ+C0, CO+02 on CuCeMgAl(O) are not affected by the presence of 502 while the activity for CO+H20 reaction decreases slightly; the CuMgA1(O) is deactivated for NO+C0, CO+H20 reactions in the presence of SO2, whereas the activities of CeMgAl(O) for all these three reactions (NO+CO, CO+02, CO+H20) were inhibited by addition of SO2 into reaction system.4.In the reaction system of NO(0.06%) + C0(l.4%) + 02(0.5%) + H20(l.0%) +S02(0.05%), one part of 502 is reduced to 5, one part is adsorbed on the catalysts in theform of sulfate, and the rest is emitted; the SO2 removal ratio on the CuCeMgA1(O) IS Ca.88%; in the oxidizing atmosphere (502±02), the SOx adsorption capacity onCuCeMgAl(0) is much higher than that of the industrialized DeSOx catalyst SOXGT.5.Among the three catalysts of CuCeMgA1(O), CuMgAl(O) and CeMgAJ(O), CuCeMgA1(O) has the highest NO adsorption capacity at room temperature. There are three kind of adsorption cites in the surface of CuCeMgAl(0); in the NO+CO+02 system, the reaction of CO+02 occurs before CO+NO reaction, meanwhile, CuCeMgAI(O) has high activity for the reaction of CO and SO2.6.In-situ FT-JR study reveals that CO is selectively adsorbed on the Cu4 sites and2+NO is selectively adsorbed on the Cu sites when Cu4 and Cu24 coexists on the surface;with the increase of adsorption temperature, CO-Cu4 bands shift to lower frequencies; NO can be adsorbed on the oxygen vacancies in the surface of CeO2, but no JR characterizations take on; when NO and CO are coadsorbed on the CuCeMgA.l(O). the intensities of Cu'-CO bands and Cu2~-NO bands are both decreased considerably; with the increase of temperature, NO...