Nanocatalysis is the process of applying catalytic metal nanoparticles for the conversion of a number of chemicals. This is because metal nanoparticles can enhance catalytic efficiency through their large surface-are-to-volume ratios as well as special electronic features. In the recent past, Nanocatalysis under continuous flow has been considered as a perfect system for effective chemical manufacturing. Continuous flow Nanocatalysis comes with benefits over the typical batch systems, which include safety, high reaction efficiency, and reproducibility. Above all, these benefits are in keeping with the recent regulation on green sustainable chemistry.
Metal nanoparticles incorporated in the flow reactors function as an excellent platform for continuous flow Nanocatalysis because there exists no contamination by catalysts in the products. Unfortunately, the design of porous structure for the flow reactors appears to be a major challenge in developing effective chemical manufacturing processes. A porous structure inside a flow reactor can act as a flow channel and tune the access of reactants to catalysts set in the reactors, which will determine reaction efficiency. Therefore, there is a growing interest for the development of flow reactors with tailored porous channels.
There is also the need for efficient continuous flow Nanocatalysis with superior recycling system for green sustainable chemistry. In order to realize this, paper, which has been applied traditionally, will offer a great potential for implementation as an effective recyclable flow reactor. This is reference to its highly porous structure, high stability in most solvents, high absorption capacity, it’s recyclable, and is both hydrophilic and hydrophobic in nature.
Hirotaka Koga and colleagues from Osaka University in Japan developed an efficient, recyclable, and renewable paper reactor for continuous flow Nanocatalysis. They constructed the paper reactor by assembling wood pulp with tailored nanoscale pores in its walls. They then derived hierarchically interconnected micro and nano-scale pores from the pulp and cellulose nanofiber networks, respectively. Their research work is published in peer-reviewed journal, ChemSusChem.
The wood-derived as well as designed porous structures in the paper reactor provided efficient access of reactants to embedded metal nanoparticle catalysts. When fabricating the paper reactor, the authors anchored the gold nanoparticles catalysts in the wood pulp, and tailored the cellulose nanofiber network-derived nanoscale pores in the walls of the wood pulp. The gold nanoparticles were prepared in situ within wood pulp by using the polyethylenimine, which was pre-attached to the surfaces of the pulp, as both adsorbent and reductant for the gold precursor ions. Tailoring of the nanoscale pores in the wall of the pulp was achieved by a simple t-butyl alcohol treatment. Afterwards, the gold nanoparticle-anchored wood pulp with the nanoscale pores in its wall was fabricated into the paper reactor by a papermaking process.
The paper reactor contained hierarchical micro and nanoscale flow-through pores derived from wood pulp and cellulose nanofiber networks, respectively. This boosted the reaction efficiency and reduced the use of the gold nanoparticles. The authors successfully demonstrated the recycling, reuse, and renewal of gold nanoparticle-anchored paper reactor. Therefore, the gold nanoparticle-anchored paper reactor provided better opportunities for supporting green processing by reducing catalyst wastage, recycling, reuse, and renewal, while at the same time achieving efficient production of useful chemicals.
The paper reactor could be synthesized from ubiquitous as well as several wood resources via large area mass production such as the well-established papermaking process. This method can be extended to other nanoparticle catalysts as well as corresponding chemical reactions. This will allow for facile, highly effective, and sustainable chemical manufacturing using paper.
Hirotaka Koga, Naoko Namba, Tsukasa Takahashi, Masaya Nogi, and Yuta Nishina. Renewable Wood Pulp Paper Reactor with Hierarchical Micro/Nanopores for Continuous-Flow Nanocatalysis. ChemSusChem 2017, 10, 2560 – 2565.
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