Additive Manufacturing Plant-Derived Char Meshes for Point-Source CO2 Capture

The need for complex activated carbon geometry, which can only be achieved with additive manufacturing, is necessary when looking to lower vehicle emissions. Adding carbon capture materials to tailpipes of cars will allow for point-source carbon capture, which is far more effective and efficient than trying to capture CO2 from the air after it has been released. To prevent the negative side effects of clogging a tailpipe, meshes are necessary. The variability of tailpipe size and shape would also be very expensive for existing manufacturing techniques, meaning additive manufacturing would be required. Additive manufacturing with varied polymeric carbon precursor ratio also allows pore microstructure to be controlled. Certain size pores have more selectivity for chemicals like arsenic or heavy metals, that are common in these processes.

Currently, 3D printed monoliths are made through the solgel method in which polymers are extruded, then activated. Microporosity is obtained strictly from this activation process. From this method surface areas can reach >1050 m^2/g and mean pore diameter at 1.3-1.4 nm. By using 100% plant derived materials, lignin and cellulose, and without using an activation step, the process is much safer and thus easier to manufactor. Although the solgel method attains higher surface area than biochars, biochars are seen to be much more efficient at removing impurities than the activated carbon chars. The reason for this is that biochar has the functional groups to adsorb anions far better.

As a result, 3D printing aqueous inks loaded with polymeric carbon precursors to make biochars offers a cost- and time-efficient route to mass producing carbon-based prints with complex geometries and specific pore size distribution. From prior research, pore size distribution can change based from the ratio of the polymeric precursors, solids loading, and printing conditions. When the ratio of cellulose is high (>80%), pores tend to be in the 10-20 micron range because of interparticle spacing. When phenolic resin is the most prevalent (>80%) large pores (100-500) are formed from trapped gasses. In an optimal ratio, small pores (1-5 micron) with a large amount of nanopores are created as the phenolic resin fills in the interparticle spacing like glue. By analyzing pore structure with Mercury Porosimetry and Physisorption I will be able to quantify these trends and make an ink prediction roadmap to guide ink composition and printing conditions for various filter applications.