## 4 Applications of Zeolites in Catalysis, Bioprocesses, and Environmental Remediation
### Zeolites in Environmental Remediation  
The global changes in environment is an actual concern of many international institutions working with the screening of factors that turn ecosystems in hard conditions, such as the increase in deposition of heavy metals in water bodies, accumulation of organic compounds that offers deleterious effect for many organisms e.g., the herbicides and general pesticides disposed on soil and water and the gas evolution that gives undesirable effects for the global temperature and for the life quality of people from many cities. Zeolite production on an industrial scale is the beginning of the discussion on the role of these products in environmental protection. Industrial interest for zeolite production began in 1954, and year by year the amount of produced material increases by hundreds of thousands of tons. The production process in scaling up is the first contribution of the material for environmental protection, because there is a necessity for aluminosilicate hydrogels or clay minerals, i.e., sources found in many natural environments requiring less use of hazardous chemicals as precursor. The temperature employed contributes to energy efficiency because low temperatures are used, another relevant contribution of zeolites for direct development of ecofriendly industrial processes. Indirectly, its production is useful for the production of fine chemicals and is part of clean technological steps used in industry, converting raw materials in more than 70,000 everyday products and as a product protagonist for biomass conversion, fuel cell development, thermal energy storage, carbon dioxide adsorption and wastewater treatment [347; 348; 349]. The amount of biomass generated in different sectors of human activity is around 100 billion tons annually, comprising energy in form of organic chemical compounds derived from the photosynthesis process in plants, although there is biomass from animals, but in less quantity. The zeolite assumes its role as catalyst when the biomass might be transformed in other types of products where the main aggregate value is the generation of energy as biofuels or compounds from fine chemistry sector, produced from a renewable source and reducing the accumulation of biomass in environment. Therefore, in this regard, zeolites are one of the main agents to promote biomass valorization, accelerating the reactions involved and promoting less energy use in production. Biomass conversion in fuels needs two characteristics of zeolites as catalysts--acid/base catalyst or a single multifunctional catalyst--allowing the structure to convert oxygenate compounds that can generate biofuel additives and intermediates of biofuel additives as well. It is important to highlight the development of hierarchical zeolites, i.e., structures with auxiliary mesoporous and macroporosity, increasing the performance in reactions involved [350]. In research, there are tools to make a systematic study of a particular zeolitic structure for biomass valorization as biofuel, such as the use of oleic acid as a molecule for esterification study [351]. In this scenario, computational simulations are helpful to verify the relevant structural aspects, allowing the use of the lab scale for a previous study of the viable use of a determined structure. The microalgal biomass is a promising source of hydrocarbons useful for production of biofuels and has been applied in the aviation sector. Not a complex method to cultivate, rapid growth and facile harvest with the zeolite H-ZSM-5 is used as catalyst for cracking of molecules found in this source [352]. The development of fuel cells, namely, hydrogen fuel cells, is a modern development that shows how zeolites can act in eco-friendly processes, since zeolites are used to construct fuel cells. A fuel cell can be highlighted as one of the most important products of modern era. These devices use molecules of hydrogen gas for an oxidizing process with molecular oxygen, producing water in vapor form.