ABSTRACT
Global concerns about the impact of waste on the environment are growing, and the production of products with a higher value than waste is of great attention. To increase efficiency, catalysts play a key role in increasing the quality and speed of the reaction. The selection of catalysts is an important step in improving the performance and efficiency of reaction products. Catalysts are homogeneous or heterogeneous; acidic or alkaline; or biocatalysts. At short reaction times, medium heat, and atmospheric pressure, homogeneous catalysts show high performance. On the other hand, high energy consumption, emulsion formation and production of excess water, and removal of the catalyst from the mixture are the main disadvantages of the homogeneous catalyst. To solve this problem, heterogeneous catalysts are used. The advantages of using heterogeneous catalysts include providing a large surface area, easier separation from the product, and resistance to mass transfer. Calcium oxide, magnesium oxide, enzymes, and proteins are used to make heterogeneous catalysts, but they are more expensive than homogeneous catalysts. In this chapter, current technologies which can convert the waste plastics to gasoline, syngas, and carbon nanotubes through catalysis–pyrolysis are briefly investigated. In the following, other methods of water and keratin recycling using catalysts are explained, and in the last part, biocatalysts are briefly summarized.
