Upscaling Effects on Alkali Metal-Grafted Ultrastable Y Zeolite Extrudates for Modeled Catalytic Deoxygenation of Bio-oils

Abstract

Developing efficient solid catalysts is necessary when for example moving from batch chemistry to continuous flow systems. In this work, scale-up effects of zeolite-based catalyst materials have been tested in aldol condensation as a model reaction for bio-oil upgrading via deoxygenation. For this purpose, shaped catalyst bodies were obtained via extrusion of ultrastable Y zeolite (USY) using either attapulgite (Att.) or bentonite (Bent.) as clay binder, followed by post-alkali metal ion grafting of K+ after (rather than before) extrusion. This approach proved essential to preserve the catalysts’ crystallinity. The Att.-bound catalyst body was more active than its Bent.-counterpart, correlating well with the observed changes in physicochemical properties. The K-(USY/Att.) catalyst showed new basic oxygen and strong Lewis acidic sites resulting from clay incorporation, in addition to the Lewis acid (K+) and basic sites (K−OH) created upon grafting. For K-(USY/Bent.), the grafting proved less efficient, likely due to pore blockage caused by the binder. Bent. addition resulted in acid sites of moderate Brønsted and strong Lewis acidity, but hardly any of the basicity desired for the aldol condensation reaction. The poor potassium grafting yet led to some cation exchange with the binder (likely with the Na+ naturally present in the Bent. material). The results obtained demonstrate the critical importance of the choice of the binder material and the synthesis protocol adopted for upscaling solid base materials in the form of catalyst bodies.