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

Abstract

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 twostep 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, temperatureprogrammed 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 redispersion 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.

Promoting Light Hydrocarbons Yield by Catalytic Hydrodechlorination of Residual Chloromethanes Using Palladium Supported on Zeolite Catalysts

“…As the NPs are isolated from others NPs due to their encapsulation on the zeolite cages and different channels, the catalytic activity can be improved, as well as the stability [20]. Due to this, zeolites are commonly used in liquid phase hydrodechlorination reactions [13,21,22], however, fewer studies have been applied to gas phase HDC [23][24][25][26]. In those gas-phase studies, conversion usually decreased after a few hours on stream, high selectivities to methane were obtained, and/or very low reactant inlet concentrations (below 100 ppm) were used [23,27,28].…”

Selectivity to Olefins in the Hydrodechlorination of Chloroform with Activated Carbon-Supported Palladium Catalysts

“…Other studies presented good results on the dechlorination of monochloromethane to olefins using molecular sieves like ZSM-5, HZSM-5, SAPO-34, and HSAPO-34 as catalysts, − but they suffered a rapid deactivation, which is a limiting factor for the application of this technology. The catalysts most commonly used in gas-phase HDC are composed of a metallic active phase (such as, Pt, Pd, and Rh) supported on different porous materials, such as activated carbons, zeolites, or zirconia, − among others. We recently studied the behavior of Pd, Pt, Rh, and Ru catalysts in the hydrodechlorination of chloromethanes to yield ethane and ethylene.…”