Ethanol conversion using copper or iron impregnated titanium-pillared bentonite catalysts

Abstract

Ti-pillared bentonite (Ti-PB) was synthesized starting from raw bentonite, which was obtained from the Hançılı area in the Middle Anatolia region. This material was subsequently impregnated with either iron or copper from solution. XRD analysis confirmed that the TiO₂ anatase phase was present in all synthesized samples. The Ti-PB support exhibited a specific BET surface area of 346 m²g^-1 and a micropore volume of 0.092 cm³g^-1, with a corresponding basal spacing of 4.40 nm at 500 °C. The introduction of iron or copper led to only minor variations in these surface areas. XPS analysis identified Cu 2p_3/2 and 2p₁ peaks corresponding to CuO (Cu²⁺), as well as Fe 2p₃ and 2p₁ peaks attributed to Fe₃O₄ (Fe²⁺/Fe³⁺) in the copper or iron incorporated Ti-PB catalysts. The mass loss for the metal-containing Ti-PBs was 13% lower than that of the support up to 700 °C. The Ti-PB material was found to possess both Lewis and Brønsted acid sites, the incorporation of copper significantly enhanced the Lewis acidity. These acidic centers acted as active sites, significantly impacting the reaction pathways for ethanol conversion and the formation of ethylene. Homogeneous distribution of copper or iron oxide structures across the surfaces of both the natural bentonite layers and the titanium pillars was observed. At 400 °C, Cu@Ti-PB reached 80% ethanol conversion with 75% ethylene selectivity, 60% ethylene yield and 7% acetaldehyde selectivity, 6% acetaldehyde yield, while Fe@Ti-PB achieved 65% conversion with 40% ethylene selectivity, 26% ethylene yield and 31% acetaldehyde selectivity, 20% acetaldehyde yield.