preparation, characterization and catalytic testing over bimetallic pt-pd/hzsm-5 catalysts in no reduction by propylene

Bi-functional and bi-metallic zsm-5 catalysts with different noble metal mass ratios were prepared using the deposition-precipitation method and ionic exchange with nh4+. systemic xrd, bet/bjh, stem, and xps spectroscopy investigations of the structural and electronic properties of these catalysts showed that 2⁓3-nm pt and pd metallic nanoparticles were highly dispersed over the zsm-5 support, with strong interactions between platinum and palladium, and a good distribution of the acid sites on the surface of the catalysts which have been observed using the ftir method by adsorption of pyridine. considering optimized values of no/c3h6 ratio=1 and ghsv= 22000 h^-1, some parameters, acidity, temperature, surface morphology, and catalytic activity performance of pd-pt/hzsm-5 zeolites were investigated in the selective catalytic reduction of no by c3h6, pd-pt/hzsm-5 bi-functional catalysts exhibited improved catalytic properties relative to their monometallic counterparts. the results show that the active components are uniformly dispersed and distribute well in the micro-porous support. for the pt0.6pd0.4/hzsm-5 catalyst, the maximum conversion of no to n2 approached 63% at 450 ºc with 100% n2 selectivity. by contrast, for the 1%pt/hzsm-5 catalyst, the maximum no conversion to n2 reached 52% at 450 ºc and only 42% for 1%pt/hzsm-5. the pt0.6pd0.4/zsm-5 catalyst also exhibited high durability and catalytic activity at high reaction temperatures.