Influence of binder concentration in zeolitic ZSM-5/bentonite 3D-printed monoliths manufactured through robocasting for catalytic applications

Abstract

In this work, a 3D printing method, robocasting was utilized to manufacture zeolite ZSM-5-based woodpile monolith catalysts of approximately 10-mm diameter, using bentonite clay as binding matrix. The effect of three different binder concentrations, in the 40–60 wt.% range, on the rheological, physicochemical, and mechanical properties was examined. The rheometer measurements showed that the printing pastes have identical shear thinning behavior and demonstrate sufficient storage modulus, irrespective of the binder concentration. The printed monoliths had high BET surface areas and porosity. The results showed that the ZSM-5 crystals retained their porous structure, textural characteristics, and crystalline structure during the additive manufacturing process. Pyridine FTIR measurements demonstrated reduced total acidity and number of Brønsted acid sites in the final specimens due to the dilution with the bentonite powder. However, the acidity reduction was roughly proportional to the binder concentration, signifying that the ZSM-5 crystallites also retain their acidity during the robocasting printing. Finally, the mechanical reliability of the thermally treated monoliths was determined by calculating the Weibull modulus values through linear regression of the Weibull equation. The increase in the binder concentration increased the compression strength by a factor of 4.5 and achieved superior mechanical reliability.Graphical abstract