Biorefinery Makes Better Building Blocks

Novel technology transforms renewable natural oils into specialty chemicals

By Scott Baxter and Andy Shafer, Elevance Renewable Sciences

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Across a wide variety of global markets, leading manufacturers today are looking for high-performance specialty chemicals with improved sustainability profiles. Elevance Renewable Sciences is helping to address these market needs right now through its next-generation biorefinery technology that uses locally available renewable feedstocks to make specialty chemicals that can enable the manufacturers to offer products that exceed the performance of existing ones.

At its biorefinery, Elevance is producing novel products that function as chemical building blocks and deliver category-changing performance. These products are helping the industry move beyond petrochemicals to something that is better, a new generation of chemistry with a smaller environmental footprint.

Elevance uses a patented, Nobel-Prize-winning metathesis catalyst technology to transform renewable feedstocks such as palm oil into novel high-performing ester, olefin and triglyceride molecules and multi-functional polymers — a new category of products we call Renewicals — for use in a variety of markets. With catalytic metathesis, the synthesis routes are shorter, resulting in greater output as well as cleaner and more environmentally friendly production.

This unique process has allowed the company to scale up production easily at high yields and with commercially compelling economics.

Highly Efficient Catalysts

In olefin metathesis, the carbons attached with a double bond change places with other alkene carbons — enabling new chemical compounds and manufacturing processes previously impossible that offer compelling economics. The olefin metathesis catalyst technology used by Elevance is based on the work of Nobel Laureates Richard R. Schrock and Robert H. Grubbs.

Traditionally, metathesis only had been used with hydrocarbons in a high-pressure, high-temperature process. The real breakthrough came with the discovery of highly efficient metathesis catalysts that could handle complex plant oils as feedstocks to make new materials such as unsaturated methyl esters and olefins at industrial scale at low temperatures and pressures and, thus, with attractive economics.

A number of chemists made major contributions to the development of metathesis catalysts and their applications. However, Schrock and Grubbs and their coworkers have achieved crucial progress in this area.

Schrock’s first practicable catalysts. Schrock started research on new alkylidene complexes in the early 1970s. He gradually developed an understanding of which metals could be used in the catalysts and how they functioned. He identified molybdenum and tungsten as the most suitable metals, and produced some catalysts with those metals. However, there still was uncertainty as to what groups would bind to the metal to give stable, yet active, alkylidene complexes. A breakthrough came in 1990 when Schrock and coworkers reported the preparation of a group of very active well-defined molybdenum catalysts.

With this discovery, chemists began to realize that olefin metathesis could serve general purposes in organic synthesis. Metathesis gained increasing attention among researchers active in synthetic chemistry. It turned out that metathesis can replace a number of traditional synthesis methods. At the same time, it permits entirely new approaches to the synthesis of organic molecules. Molybdenum catalysts often are sensitive to oxygen and water, but with the right treatment, are very powerful tools in organic synthesis.

General catalysts developed by Grubbs. Yet another breakthrough in the development of metathesis catalysts came in 1992 when Grubbs and his coworkers published their discovery of a catalyst with the metal ruthenium. It was stable in air and demonstrated higher selectivity but lower reactivity than Schrock’s catalysts. The new catalyst also could initiate metathesis in the presence of alcohols, water and carboxyl acids. Grubbs continued to improve his catalysts. Figure 1 depicts the structure of one of his effective metathesis catalysts that are easy to synthesize.

Grubbs’ ruthenium catalysts have become the first well-defined ones for general metathesis applications and have given rise to uses in organic synthesis. Grubbs has continued developing ruthenium-based metathesis catalysts into even more powerful tools for synthesis, including that of polymers with special properties.

The Commercial Process

Elevance’s manufacturing platform (Figure 2) implements metathesis technology in novel combinations with established industrial processes (e.g., transesterification, hydrogenation and distillation) to create an integrated biorefinery capable of making both specialty chemicals and renewable, petroleum-based alternatives. Our biorefinery converts the triglycerides and fatty acids found in natural oils (such as plant, vegetable and algal oils) into multiple value-added chemical streams.

The heart of the process is proprietary olefin metathesis technology that operates at low temperature and pressure while being efficient, stable and predictable. The metathesis unit consists of three stages stacked in series — each having a continuously stirred tank reactor — designed by Elevance specifically for the equilibrium reaction and to operate in a temperature range of 55–65°C and a pressure range of 10–12 barg. The co-reactants along with the catalyst are fed into the lower portion of the first reactor and flow upward until exiting the top of the third and final reactor.

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