The impact of the hydrodechlorination process on the physicochemical properties of bimetallic Ag-CuBeta zeolite catalysts

Beta zeolites with two Si/Al ratios of 17 and 1300 were used for synthesis of Ag 2.0 Cu 2.0 HAlBeta and Ag 2.0 Cu 2.0 SiBeta zeolites by conventional wet impregnation and two-step postsynthesis methods, respectively. The calcination of Ag 2.0 Cu 2.0 HAlBeta and Ag 2.0 Cu 2.0 SiBeta at 773 K for 3 h in air led to formation of C-Ag 2.0 Cu 2.0 HAlBeta and C-Ag 2.0 Cu 2.0 SiBeta. After reduction at 873 K for 3 h in flowing 10% H 2 /Ar, red-C- Ag 2.0 Cu 2.0 HAlBeta and red-C-Ag 2.0 Cu 2.0 SiBeta were obtained and investigated as the catalysts in gas phase hydrodechlorination of 1,2-dichloroethane at atmospheric pressure, at relatively low reaction temperature (523 K). The state of silver and copper in catalysts at different stages of their biography was characterized by low-temperature N 2 sorption, temperature – programmed reduction (TPR), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and temperature-programmed hydrogenation (TPH). We have shown that the state of silver and copper species change under HDC conditions. After catalytic run both agglomeration of metal particles and their re-dispersion took place. According to TPH, XRD and XPS measurements we postulate that the cause of this phenomenon is the formation of chlorine containing species in spent zeolite catalysts.