## 4 Applications of Zeolites in Catalysis, Bioprocesses, and Environmental Remediation
### Biomass Conversion  
Global concerns about new forms of production of useful products for society such as fuels and chemical compounds (platform molecules) have been in the focus of industry and research entities. In this scenario, processes involving biomass conversion have great importance, e.g., for biofuel production, which may replace a great quantity of fossil-derived fuels, allowing the generation of advanced biofuels, also called second- and third-generation biofuels, replacing the widely used ethanol (first-generation) [42] (p. 8). For zeolite utilization in biofuel production, hydrolysis, esterification-transesterification, isomerization, condensation, pyrolysis, and upgrading bio-oil can be performed [298]. The use of zeolites in biomass conversion to transportation fuels has been a great alternative use of catalysts with sustainability because some zeolites are formed from natural precursors or biomass wastes, e.g., coconut shell and lignocellulosic residues, and are the most abundant bioresource available composed of cellulose, hemicellulose, and lignin. Lignocellulosic biomass is used in pyrolysis oil to produce biomolecules, food aroma, pesticides, and biofuels. This process heats the material in the absence of oxygen, transforming it into an oil with fewer problems in processing. In this process, the zeolite bed converts the vapors of pyrolysis oil in hydrocarbons, H\({}_{2}\)O, CO\({}_{2}\) and coke [299]. Figure 16: Micrography of zeolite with a microorganism immobilized. Reproduced from [293]. Copyright 2007 Elsevier. In catalytic processes, for conversion of lignocellulosic matrices, the transport of heavy molecules through the zeolite pores is cumbersome and faces mass transport limitations. The interactions between biomass components and zeolites are different and not only based in carbocation-like active centers. One highlighted process involved the conversion of oxygen from biomass-derived products in hydrophobic molecules with good chemical and combustion properties. The hydrophilic substrates begin to present more of a hydrophobic nature, with changes in interactions with active centers along the course of the reaction. Reactions of dehydration and hydrogenolysis can form water in medium that can act as a poison for active sites. In addition, polymeric molecules react with external surface sites with continuation at the internal active sites [300]. One of the main goals in biomass conversion, including in triglyceride conversion (e.g., oils obtained from vegetables matrices), is the reduction of molecular mass; therefore, Bronsted acid sites might enable the cracking and upgrading of biomass components [301]. Oleic acid (cis-9-octadec acid) is a component of a large number of biomass matrices, being the main fatty acid in olive oil pressed from the ripe fruit of the olive (Olea europaea) [302]. This compound can undergo acid-catalyzed isomerization, forming a mono-branched-chain unsaturated fatty acid. In this reaction, the zeolites give considerable yields in comparison to clays. Their relatively small channels and pores are responsible for this. In the beginning of this process, coke formation with isomerization limited to the micropores occurs. The size and geometry of pores determine the type of compound formed that can be methyl mono-branched-chain unsaturated fatty acid or ethyl and propyl mono-branched-chain unsaturated fatty acid [301]. The effect of desilication of MOR zeolite on esterification of oleic acid as a model reaction has been investigated. The generation of mesoporous in the structure increased the conversion of biomass and maximized the life of the catalyst [303]. The types of zeolites used for biomass conversion include ZSM-5, beta zeolite, Y zeolite, mordenite, silicauliminophosphate and other porous materials. The shape selectivity of these materials is one of the factors in the behavior in formation of mono-branch-chain unsaturated fatty acid.