Many industries, from healthcare to aerospace and everything in between, have found ways to use 3D printing, but one area that’s still fairly new is using the technology to control chemical reactions – better known as catalysis. Catalysts are made from metals and ceramics, and can be formed to resemble objects such as gears, wheels, and honeycombs. 3D catalyst production consists of depositing chemically active agents onto structures that have been pre-printed, and according to specialty chemicals company Clariant, it’s not possible to 3D print catalysts in commercial quantities yet. But a recent development by the Ames Laboratory may bring us one step closer.
Ames is a US Department of Energy Office of Science national laboratory, and creates innovative energy solutions, materials, and technologies to solve global issues. It’s operated by Iowa State University, and has been focusing on its metal powder technology for the past year, but just developed a one-step 3D printing process to create chemically active catalytic objects.
The lab’s newly developed method takes just one step, and inexpensive, commercial SLA 3D printers, to combine the chemistry with the structure to form customizable catalysts. Researchers first design the structures in a computer, and then shine a laser through a bath full of customized resins to build them – the laser polymerizes the resins, which contain crosslinkers, monomers, and photoinitiators, and hardens them by layers.
“The monomers, or building blocks that we start with, are designed to be bifunctional,” explained J. Sebastián Manzano, a graduate student in the Department of Chemistry at Iowa State who conducted most of the experiments. “They react with light to harden into the three-dimensional structure, and still retain active sites for chemical reactions to occur.”
The product that’s built from this process comes with “catalytic properties already intrinsic to the object,” Ames states.
Manzano, Zachary B. Weinstein, Aaron D. Sadow, and Igor I. Slowing published a paper on their research, titled “Direct 3D Printing of Catalytically Active Structures,” in ACS Catalysis.
According to the abstract, “3D printing of materials with active functional groups can provide custom-designed structures that promote chemical conversions. Herein, catalytically active architectures were produced by photopolymerizing bifunctional molecules using a commercial stereolithographic 3D printer. Functionalities in the monomers included a polymerizable vinyl group to assemble the 3D structures and a secondary group to provide them with active sites. The 3D-printed architectures containing accessible carboxylic acid, amine, and copper carboxylate functionalities were catalytically active for the Mannich, aldol, and Huisgen cycloaddition reactions, respectively. The functional groups in the 3D-printed structures were also amenable to postprinting chemical modification. As proof of principle, chemically active cuvette adaptors were 3D printed and used to measure in situ the kinetics of a heterogeneously catalyzed Mannich reaction in a conventional solution spectrophotometer. In addition, 3D-printed millifluidic devices with catalytically active copper carboxylate complexes were used to promote azide–alkyne cycloaddition under flow conditions. The importance of controlling the 3D architecture of the millifluidic devices was evidenced by enhancing reaction conversion upon increasing the complexity of the 3D prints.”
The researchers used their innovative new method to build multiple catalysts, which were then tested and “demonstrated success” in a variety of chemical reactions that are often used in organic chemistry. In addition, by using post-processing, these catalysts were also able to adapt, which means that multi-step chemical reactions are a future possibility.
Slowing, a heterogeneous catalysis scientist at Ames Laboratory, said, “We can control the shape of the structure itself, what we call the macroscale features; and the design of the catalyst, the nanoscale features, at the same time. This opens up many possibilities to rapidly produce structures custom designed to perform a variety of chemical conversions.”
This research could help lead the way for scientists to develop even more efficient processes of producing catalysts for complex chemical reactions, which could then be used in a range of different industries.
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