Molecular Highway technology is a materials science platform for diffusion-limited catalytic and separations processes, such as those used to refine petroleum, produce chemicals and biofuels, and purify air and water. Zeolite catalysts and adsorbents powered by Molecular Highway technology perform better because of the presence of broad channels, or molecular highways, in the zeolite structure. Molecular highways improve diffusion into and out of the zeolite, enabling higher performance in diffusion-limited processes.
Zeolites are used extensively as catalysts and adsorbents (molecular sieves). Their crystalline structure, formed by a network of small pores (micropores, about 1nm in diameter) effectively crack or separate molecules, depending on the application. However, zeolite pores are very small, less than one nanometer in diameter, creating diffusion limits in the catalyst or adsorbent and limiting performance.
Molecular Highway technology enables the creation of a network of larger pores (mesopores, between 7-10nm in diameter) that act as broad channels within zeolite crystals. These broad channels – or molecular highways – dramatically improve the diffusion, significantly boosting performance over conventional zeolites.
The introduction of mesopores – molecular highways – can be clearly seen in transmission electron microscope (TEM) images, such as those shown below. The image is a TEM image of a conventional Y zeolite crystal showing its rows of lattice reflection lines resulting from the regular atomic structure within the crystal (a few are highlighted in red for clarity). The figure below also shows the crystal lattice lines, but in addition one can see the larger, lighter colored spots corresponding to the mesopores in the zeolite with Molecular Highway technology (a few of which are circled in red).
Rive has applied Molecular Highway technology to many different types of zeolites. The proprietary process can carefully control the size and concentration of mesopores, creating a zeolite structure that yields optimum performance for the intended application. Rive works closely with partners to develop and commercialize applications of Molecular Highway technology in a variety of markets.
While the photographs above are able to show static images of the mesopores, cutting edge imaging techniques can also provide an actual, three-dimensional look inside the crystal. A triad of complementary techniques, namely high-resolution gas adsorption coupled with hysteresis scanning and density functional theory, rotation electron diffraction, and electron tomography, has revealed the intracrystalline nature and connectivity of Rive’s size-tailored mesopores in zeolite Y:
Application in catalytic processes
Many processes utilize zeolite catalysts and additives. The performance of these materials is often constrained by their diffusion limits, which in turn govern reaction rates, yields, and ultimately, profitability. Molecular Highway technology – when applied to zeolite catalysts and additives in fluid catalytic cracking (FCC), hydrocracking, alkylation, isomerization, or dewaxing units – creates a network of broad channels in the zeolite that allows hydrocarbon feed molecules easy access to and exit from the active catalytic sites in the crystals. The enhanced access, or improved diffusion, leads to better product yields and product quality and opens up new routes to profitability, such as processing more barrels or running heavier feeds in oil refining.
Application in separations processes
Adsorptive separations is another area that benefits from the improved diffusional properties of Rive zeolite. Faster diffusion into the adsorbent means sharper adsorption wave-fronts and, consequently, greater time on stream before regeneration is necessary. Those, in turn, result in both lower energy usage and greater recovery efficiency for the desired product.
The separations performance of Rive zeolite was evaluated in a US Department of Energy sponsored study of the very challenging separation of propane and propylene. An adsorbent comprising Rive mesoporous zeolite X operated in a liquid phase separations process produced a 2-4X improvement in diffusion rate vs. conventional X zeolite, and the potential to reduce energy consumption by 70% vs. the distillation process used commercially today.
Rive co-founder Javier Garcia Martinez invented the core Molecular Highway technology while a post-doctoral researcher at MIT. Rive has an exclusive license to the patents owned by MIT, and has developed a broad IP portfolio that it owns outright.