The influence of silicon on the catalytic properties of Cu/SAPO-34 for NOx reduction by ammonia-SCR

The effect of Si content in SAPO-34 on NO selective catalytic reduction over Cu/SAPO-34 catalyst was investigated. Three fresh catalysts with different Si contents, prepared by the same procedure, showed different NO conversions from 120 °C to 600 °C. These catalysts were characterized in detail by various techniques (ICP, XRD, SEM, NMR, NH3-TPD, H2-TPR and EPR). The NH3-TPD results indicate that the number of acid sites in Cu/SAPO-34 catalyst increases with increasing Si contents and the SCR activities of the samples correlate well with the number of acidic sites at low temperatures (200 °C). The EPR and H2-TPR results show that both the Si and the Al contents affect the number of isolated Cu2+ ions in Cu/SAPO-34 catalysts. The catalysts aged at 750 °C for 12 h showed higher SCR activities than those of the untreated samples, consistent with the higher numbers of the isolated Cu2+ ions.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Cu/SAPO-34 performs excellent SCR activity and good hydrothermal stability. ► The contents of Si can directly affect the structure of Cu/SAPO-34 catalysts. ► The Cu loading depends on both the Si contents and the Al contents of HSAPO-34. ► The density of the acidity of Cu/SAPO-34 is affected by the Si contents. ► The Si and Al contents affect the environment of Cu2+ species in Cu/SAPO-34.