These homogeneous catalysts tend to generate large quantities of waste, including washwater streams, salts, and heavy metals. Often the catalyst is not reusable. Zeolites are being studied extensively as heterogeneous catalysts that can be recovered and recycled with greater ease and lower expense, leading to less waste and fewer byproducts. The use of zeolite catalysts provides such process advantages as improved selectivity, high activity, and reduced corrosion.
Some processes can gain efficiency and economy by using zeolites to combine several catalytic steps.
Even greater returns can be achieved by the use of continuous reactor processes. For example, the traditional synthesis routes in the production of many fragrances and flavors include strong acids, many steps, low yields, and much waste. Acidic zeolites have the potential to improve the process. The ability to form zeolites into different shapes has improved their compatibility with many reactor designs, such as the alpha-terpinyl alkyl ether reactor. This continuous reactor uses beta zeolites and has yielded excellent results with much less waste.