PNNL researchers design resilient zeolites to boost cellulosic production yiel

In Washington state, while popular catalysts called zeolites could help turn paper manufacturing waste and other biomass into fuel, the catalyst crumbles after just two days in hot water. And that’s a problem because hot water is nearly ubiquitous in biofuel production. At Pacific Northwest National Laboratory, a team discovered that fixing broken bonds deep inside the material stabilized the catalyst and let it thrive in hot water.

This study offers insights to help design resilient zeolites, increasing their efficiency at producing fuels and chemicals. Zeolites have a sponge-like network of pores, or internal cavities, where reactions are catalyzed. Unlike sponges, these pores are “highly regular”; they are the same size and evenly spread across the material. The reaction’s starting chemicals flow into the pores and the final products flow out. Zeolites can drive many different reactions such as transformations of single molecules or joining two molecules together.

This network of pores is made from silicon-oxygen-silicon and silicon-oxygen-aluminum bonds. These bonds form the material’s superstructure, much like the framing of a house. When these bonds are broken, it creates defects. Water molecules filling the pores exploit these defects and cause the zeolites to crumble.

Researchers wanted to prevent that damage from happening. Their first step was to synthesize zeolite samples riddled with defects, not on the surface, but inside the sample.

With the material synthesized, the team began to find ways to heal the defects inside the zeolite. They focused on the hydroxyl (-OH) groups at the defect sites and devised a way to rebuild the silicon-oxygen-silicon bonds.