Synthesis and Characterization of Ag/Al2O3 Catalysts for the Hydrogenation of 1-Octyne and the Preferential Hydrogenation of 1-Octyne vs 1-Octene.

ABSTRACT

Catalysts featuring 2, 5, and 10 wt % silver supported on alumina were prepared by the deposition precipitation method and activated under hydrogen. All catalysts were characterized by Brunauer-Emmett-Teller (BET) measurements, inductively coupled plasma-optical emission spectrometry (ICP-OES), backscattered electron scanning electron microscopy (BSE-SEM), high-resolution transmission electron microscopy (HR-TEM), hydrogen-temperature-programmed reduction (H2-TPR), H2-chemisorption, thermogravimetric analysis (TGA), infrared (IR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and isopropylamine (IPA) TPD and evaluated in a continuous plug flow fixed-bed reactor. Metal nanoparticles with average sizes of 4.5, 11.5, and 21.1 nm were identified by HR-TEM for the 2, 5, and 10 wt % Ag/Al2O3 catalysts, respectively. A conversion of 99% was observed for 1-octyne over particles between 10 and 15 nm in size, with stable operation up to 24 h (decreasing thereafter) at a temperature of 140 °C and a pressure of 30 bar in the competitive hydrogenation reaction. No conversion of 1-octene was noted in competitive reactions (mixed 1-octyne and 1-octene feed) but rather a gain of 1-octene throughout the 72 h time-on-stream. The performance of all catalysts was influenced by both the metal and support, where the latter impacted the overall acidity of the catalysts, thus affecting their long-term stability.