Impact of thermal ethylene degradation in zeolite-templated carbon synthesis

Abstract

Which is the best temperature for the synthesis of Zeolite-Templated Carbons (ZTCs)? This is the question which will be foregrounded in the present article. ZTCs were achieved using ethylene on protonic beta zeolite at different synthesis temperatures comprised between 490 and 890 °C. By comparing the results achieved from TGA, nitrogen physisorption at 77 K, XRD and XPS, an optimal ZTC synthesis temperature could be determined. For low temperature synthesis (i.e. 490 °C), textural defects arise in the carbon network, possibly related to the low reactivity of ethylene. At temperatures above 700 °C thermally induced ethylene transformation was evidenced, leading to the development of carbon species on the external surface of the zeolite and hence to the generation of composite materials. Below 700 °C, ZTC formation exclusively proceeds through a zeolite acid-site catalyzed mechanism, whilst with increasing temperature the thermally induced ethylene transformation path gains impact. We further prove that ZTC/turbostratic carbon composites can be achieved through a purely thermally induced ethylene transformation path by using an all-silica beta zeolite as template.