Effect of Aging Time on the Phase Composition and Surface Properties of Co-precipitated CuO/ZnO/Al۲O۳ Catalysts Used for the Vapor Phase Hydrogenation of Aldehydes

Co-precipitated CuO/ZnO/Al۲O۳ catalysts have recently become the materials of choice for Vapor Phase Hydrogenation (VPH) processes. Their effective utilization requires finetuning the synthesis parameters that affect the properties of the final catalyst. Aging time is often considered a telling parameter that imparts significant effects on the properties of the catalyst. This paper investigates how properties such as phase composition, porosity, and surface area are affected by the duration of the aging step. For this purpose, a series of CuO/ZnO/Al۲O۳ catalysts were synthesized using a constant pH co-precipitation method. Three different aging times—zero, two, and four hours—were employed with sodium carbonate as the precipitant. The co-precipitated catalyst precursors were calcined for three hours at ۶۲۳ K to yield the unreduced catalysts. The samples were characterized by X Ray diffraction (XRD) analysis, atomic absorption spectroscopy (AAS), and Brunauer-Emmett-Teller (BET) surface area and porosity analysis. It has been observed that although all samples contain malachite, rosasite, and hydrotalcite phases, the compositions and quantities of the crystalized phases are dependent on the aging time. The results also show a correlation between aging time and the surface area of the catalyst—with a maximum surface area of ۸۶ m۲/g corresponding to the optimum aging time of two hours.

کلیدواژه ها:

Co precipitation ، Aging ، Vapor Phase Hydrogenation ، CuO/ZnO/Al۲O۳ Catalysts