engleski

Production of Novel Ceramic Monolithic Catalysts for Catalytic Oxidation of BTEX Compounds using Stereolithography

In the field of chemical engineering, the term "monolith" refers to structures with clearly defined and invariable geometry. Monolithic structures typically serve as inert substrates or carriers of catalytically active components applied to such a structure by conventional methods for the preparation of heterogeneous catalysts. Increasing attention is being paid to the application of process intensification methodology, and, consequently, to the possibility of using additive manufacturing technologies (3D printing) to produce various catalysts from different materials, including ceramics [1, 2]. In this work, stereolithography (SLA) was used to fabricate ceramic monolithic catalyst carriers with different geometries for the production of novel monolithic catalysts for the catalytic oxidation of benzene/toluene/ethylbenzene/o-xylene (BTEX) gas mixture. For this purpose, a Form 2 3D printer (Formlabs) and commercially available ceramic resin (Formlabs) were used. 3D models of monolithic catalyst carriers of various geometries and surface areas (11, 15, 20, and 22 cm2) were created using Autodesk Fusion 360 and prepared for 3D printing using PreForm (Formlabs) slicer. The ceramic resin and heat-treated carriers were characterized in detail [3], while the catalysts used were previously characterized [4]. After heat treatment of the carriers, the precursors of the catalytically active components (Mn, Fe, Cu, and Ni) were applied in the form of 1 M aqueous solutions of nitrate salts using the impregnation technique. After application of the precursors, the carriers were calcined at 500 °C for 2 hours to form a stable layer of manganese mixed oxides, MnMOx (M = Fe, Cu, Ni). Adhesion tests were performed using ultrasound to test the mechanical stability of the catalyst layer. The test specimens were placed in a bottle containing petroleum ether and sonicated for 30 minutes. The test results showed excellent adhesion of the catalyst layer with mass losses below 2%. Catalytic oxidation of the gaseous BTEX mixture (Messer) was carried out in a reactor filled with a previously prepared monolithic ceramic catalyst. The gaseous BTEX mixture contained 50 ppm of benzene, toluene, ethylbenzene and o-xylene in nitrogen. Catalytic oxidation was carried out at atmospheric pressure, at various temperatures, and at constant total flow rate (92 ml/min) of the reaction mixture. As expected, the conversion of BTEX components increased with increasing temperature, and characteristic S-shaped curves were obtained. The carrier with a geometric surface area of 22 cm2 proved to be the most catalytically active. Regarding the chemical composition of the catalyst layer, the best results were obtained with MnFeOx, closely followed by MnCuOx, while MnNiOx showed the lowest catalytic activity under the operating conditions used. With the most active combination of 3D printed carrier (22 cm2) and mixed Mn oxides (MnFeOx), 90% conversion of benzene at 212 °C, toluene at 179 °C, ethylbenzene and o-xylene at 177 °C was achieved. Future work will focus on the development of catalyst carriers with more complex geometries, including the use of integrated static mixers, and a three-component catalyst (MnMOx, M=Fe, Cu) to further improve the BTEX conversions achieved.

Stereolithography ; Monolithic catalysts ; Catalytic oxidation ; BTEX ; Mixed manganese oxides

nije evidentirano