3D Printing of Activated Carbon and Exemplary Application as Adsorbent in the Electric Swing Adsorption

Abstract

Due to its tunable porosity and chemical versatility, activated carbon is one of the most widespread porous materials in industry used in applications such as adsorption and catalysis. Nevertheless, commercially available activated carbons suffer from low thermal and electric conductivity in the bulk, abrasion, and undefined bed porosity, since they are provided in the form of powders, pellets, or spherical particles. These obstacles could be overcome through the free design offered by 3D printing. However, present methods for the 3D printing of carbon either lack design freedom of the printed object or fail to introduce microporosity. In this work, a novel method for the 3D printing of carbon was developed. The method is based on lithographic 3D printing of a porous polymer, which is then transformed into activated carbon by a thermal treatment. Through the implementation of porogen templating into the printing process, meso- and macropores were introduced in the polymer precursor. In an optimized oxidation and pyrolysis procedure, the macrostructure and templated pores were retained and an additional fraction of micropores was introduced. Using CO2 activation the pore size was tailored and the specific surface area and pore volume increased to 2213 m²/g and 1.68 ml/g (QSDFT), respectively. These values are similar to those presented for activated carbons. Mechanical stability was maintained throughout the process. Through upscaling, activated carbon open-cellular monolithic structures of 40 mm in length and 20 mm in diameter were created. In an electric swing adsorption process, they exhibited a much better thermal and electric conductivity than a carbon pellet bed. Although the pelletized carbons showed a higher adsorption capacity because of a more densely packed bed, the monoliths could be regenerated much faster, due to their continuous macrostructure. The unique design flexibility of 3D printed carbons in combination with their top-notch porous properties will contribute to the optimization of industrial processes that rely on the use of activated carbons in the fields of adsorption, catalysis and energy application.