Tungsten Carbide Beats Platinum in Plastic Recycling Efficiency

Researchers at the University of Rochester have created a new version of tungsten carbide that works as well as platinum in chemical reactions and does much better at breaking down plastic waste. The material beats platinum by more than ten times in turning old plastics into new products. This work came out this week and points to cheaper ways to handle plastic trash and make fuels from carbon dioxide.

Background

Platinum plays a big role in making everyday items like plastics and cleaning products. Factories use it as a catalyst to speed up chemical reactions. But platinum costs a lot and supplies are limited. Scientists have looked for years for replacements that are cheaper and more common.

Tungsten carbide fits that bill. It is abundant and already used in tools and machinery. The problem has been getting it to work right in chemical reactions. Its atoms can arrange in different ways, called phases. Some phases are stable but not great at speeding reactions. Others work better but hard to make and keep.

Marc Porosoff, an associate professor in chemical engineering at the University of Rochester, led a team to fix this. They focused on controlling how tungsten carbide forms at high heat. By adjusting temperatures and particle sizes, they locked in a useful phase. This phase, beta-W2C, handles reactions that turn carbon dioxide and hydrogen into carbon monoxide and water. Carbon monoxide serves as a building block for fuels and chemicals.

The same approach applies to plastics. Most plastic waste comes from tough polymers like polypropylene in water bottles. Breaking these down needs strong catalysts. Platinum works but deactivates fast and costs too much. Tungsten carbide offers metallic and acidic traits that cut through long chains without those issues.

Key Details

Porosoff's group made the beta-W2C phase using a method called temperature-programmed carburization. They kept particles small, at nanoscale, to trap the phase before it changes to a less active form. Tests showed it matches platinum in the reverse water-gas shift reaction, which makes carbon monoxide from CO2.

For plastics, a related study used tungsten carbide in hydrocracking. This process chops big plastic molecules into smaller ones for new products. Linxiao Chen from the University of North Texas led that work, with help from Porosoff and Siddharth Deshpande, another Rochester professor. They tested it on polypropylene.

How It Breaks Down Plastics

Hydrocracking splits polymer chains under heat and pressure with hydrogen. Platinum catalysts sit in tiny pores that block long plastic chains. Tungsten carbide has open surfaces that let chains in easily. Its mix of metal and acid properties snaps the bonds.

Results showed tungsten carbide over ten times more efficient than platinum. It handled contaminants better and stayed active longer. The process turns waste into short chains for fuels or new plastics.

"Tungsten carbide, when made with the correct phase, has metallic and acidic properties that are good for breaking down the carbon chains in these polymers," says Porosoff. "These big bulky polymer chains can interact with the tungsten carbide much easier."

The team also noted stable phases form naturally, but active ones need precise control. High temperatures during making push it to beta-W2C if done right.

What This Means

This catalyst cuts reliance on rare metals. Industries spend billions on platinum yearly. Tungsten carbide costs less and comes from common sources. For CO2 conversion, it could help make fuels without digging up more platinum.

Plastic recycling stands to gain most. Over 400 million tons of plastic made each year, much ends in landfills or oceans. Current recycling rates hover below 10 percent. Efficient upcycling like this turns waste into valuable olefins for new plastics or fuels. Markets for those olefins top 40 billion dollars.

Companies could scale this for real plants. Fine-tuning might boost yields further. It supports circular economy goals, where waste feeds back into production. Less plastic in environment means fewer pollution issues.

Challenges remain. Catalysts lose steam over repeated use from carbon buildup or sintering. Researchers suggest tweaks like doping or core-shell designs to last longer. Testing on mixed plastics, not just pure types, comes next. Sorting tech with AI could help feed cleaner waste to reactors.

Porosoff's phase control method applies beyond plastics and CO2. It works for petrochemicals too, like making detergents. Other teams praise it as a step forward in metal carbide use.

"This work solves a long-standing challenge in transition-metal carbide catalysis," says Linxiao Chen, a chemical engineer at the University of North Texas. "With this development, catalysis scientists will be able to tune these materials leading to performance that eventually reaches the level of platinum."

Wider adoption depends on industry tests. Lower costs could speed chemical plants to green methods. Plastic makers might rethink waste streams. Governments pushing recycling targets will watch closely.

The findings appear in journals like the Journal of the American Chemical Society. Teams from Rochester and North Texas collaborated. More work builds on this base for everyday use.