Researchers from the Skolkovo Institute of Science and Technology, Zelinsky Institute of Organic Chemistry of RAS, Platov South-Russian State Polytechnic University, and elsewhere have created a palladium-on-carbon catalyst for drug, pesticide, and plastic production that is very sparing in terms of precious metal use. In the new catalyst, palladium is carried on carbon particles manufactured from biomass processing waste. That form of recycled carbon has almost no pores for the active metal to get lost in, so as little as one-hundredth the usual amount of palladium in industrial catalysts proves sufficient. The study was recently published in ChemSusChem.

Catalysts are indispensable for the production of fuels, polymers, and drugs. Many catalysts are made by depositing precious metals — platinum, palladium, rhodium, etc. — on a carrier material, such as activated carbon. Recent research, however, has revealed that up to 98% of the precious metal in such catalysts can become trapped in the micropores of the carbon carrier, rendering the metal inaccessible to the reactants and virtually useless for catalysis.

So how can we make catalytic particles more effective and get rid of all the “dead” metal in them? The solution is to use alternative carbon materials as carriers that would have no micropores and yet would possess a large surface area and the capacity to hold precious metal atoms and nanoparticles in place. Such carbon materials are expensive and hard to make, though.

Skoltech researchers and their colleagues have come up with a new material composed of carbon and nitrogen, which has very few micropores harboring “dead” metal. By virtue of its high nitrogen content, the novel material is good at retaining the active metal atoms and nanoparticles on its surface. A palladium catalyst the team made based on the new carbon carrier proved very low in “dead” metal and exceedingly active in the industrially significant cross-coupling and hydrogenation reactions, essential for the production of drugs, pesticides, and monomers — key components for making plastics.

The introduction of the new catalyst would have an advantage beyond cutting the cost of synthesis for many industrial products. By virtue of its drastically lower overall palladium content, the catalyst will cause far less palladium contamination, which is particularly important for pharmaceutics, since that metal is toxic.

Intriguingly, the feedstock for making the unique carbon-based carrier material, which underlies the new catalyst, is organic waste matter called humins. This is a byproduct of plant biomass processing in the chemical industry, which has all the right properties and a sufficiently high content of carbon, enabling the researchers to develop a simple way for synthesizing their nitrogen-enriched carrier material. The resulting catalyst outperformed most previously known palladium-on-carbon catalysts manufactured from biomass processing waste in the reactions considered by the researchers.

The study was authored by researchers from Skoltech, Platov South-Russian State Polytechnic University, MISIS University, Zelinsky Institute of Organic Chemistry of RAS, and Boreskov Institute of Catalysis of UB RAS.