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Presidential Green Chemistry Challenge: 2016 Academic Award

Professor Paul J. Chirik of Princeton University

 

Catalysis with Earth Abundant Transition Metals

  • Discovered catalysts that don't use hard-to-obtain platinum to make silicones that are used in:
    • silicone rubber;
    • tires;
    • shampoos;
    • furniture fibers;
    • paper coatings; and
    • other consumer goods.
  • This new class of catalysts could reduce the mining of many tons of ore which reduces costs and:
    • energy usage by 85 billion BTUs per year;
    • waste generation by 8.5 million kilograms per year; and
    • carbon generation by 21.7 million kilograms per year.
 

Summary of Technology:

Metal-catalyzed chemical reactions have enabled many of the technological innovations of modern society with applications ranging from the synthesis of advanced materials to new medicines. For decades, catalyst technology has relied on some of the least abundant elements in the Earth’s crust – palladium, platinum, rhodium, and iridium. In addition to their high cost, price volatility, and toxicity, extraction of these elements has significant environmental consequences. Obtaining one ounce of a precious metal, for example, often requires mining approximately 10 tons of ore which creates a CO2 footprint that is estimated to be 6,000 times that of abundant metals such as iron.

Alkene hydrosilylation is an example of a metal-catalyzed chemical reaction that is used on an industrial scale in the manufacture of silicones from alkenes and silanes. Silicones are found in a range of consumer products including adhesives, household utensils, medical devices, health care products, and low rolling resistance tires. The platinum catalyst used in alkene hydrosilylation reactions is often not recovered, however, which results in a significant environmental footprint for this commercially important process.

Professor Chirik and his research group, in collaboration with Momentive Performance Materials, discovered a new class of hydrosilylation catalysts based on earth-abundant transition metals such as iron and cobalt that have superior performance to existing platinum catalysts. This base metal catalyst technology offers the opportunity to enable new chemical processes that provide the desired product exclusively, eliminate distillation steps, and avoid generation of byproducts and unnecessary waste. This technology is based upon “metal-ligand cooperativity,” a broad catalysis concept pioneered by the Chirik group, where electron changes occur concomitantly between the metal and the supporting ligand.

Hydrosilylations to produce various commercial silicone products have been conducted on multi-gram scales using this new technology. The discovery of these air-stable, readily-synthesized iron and cobalt catalysts with unprecedented activity and selectivity may ultimately transform the industrial approach to commercial silicone products.


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