Corrosive solid, acidic, organic

Friedel-Crafts alkylations are among the most important reactions in organic synthesis. Solid acid catalysts have advantages in ease of product recovery, reduced waste streams, and reduction in corrosion and toxicity. In the past, people have used (pillared) clays (18), heteropolyacids (19) and zeohtes (20) for Friedel-Craft alkylations, with mixed success. Problems included poor catalyst stabihty and low activity. Benzylation of benzene using benzyl chloride is interesting for the preparation of substitutes of polychlorobenzene in the apphcation of dielectrics. The performance of Si-TUD-1 with different heteroatoms (Fe, Ga, Sn and Ti) was evaluated, and different levels of Fe inside Si-TUD-1 (denoted Fei, Fe2, Fes and Feio) were evaluated (21). The synthesis procedure of these materials was described in detail elsewhere (22). 

Deoxygenation reactions are catalyzed by acids and the most studied are solid acids such as zeolites and days. Atutxa et al. [61] used a conical spouted bed reactor containing HZSM-5 and Lapas et al. [62] used ZSM-5 and USY zeolites in a circulating fluid bed to study catalytic pyrolysis (400-500 °C). They both observed excessive coke formation on the catalyst, and, compared with non-catalytic pyrolysis, a substantial increase in gaseous products (mainly C02 and CO) and water and a corresponding decrease in the organic liquid and char yield. The obtained liquid product was less corrosive and more stable than pyrolysis oil. 

Contact with water. This is commonly the case with the corrosive solids, such as the inorganic base potassium hydroxide and the organic crotonic acid. As solids, these do not have any available hydrogen or hydroxyl ions but easily form solutions in contact with water or moisture fi om the air or from skin, eyes, lung tissues, etc. 

The disadvantages of using mineral acids such as concentrated HCl or H2SO4 to hydrolyse biomass is that they are toxic, corrosive, hazardous and difficult to recycle. The use of heterogeneous solid acids can ease product separation and provide better catalyst recyclability. For example, mesoporous transition metal oxides have been used in biomass transformations. " Polymer-based acids have been employed for the hydrolysis of various organic substrates. " In particular, carbon-based solid acids made by sulfonation of carbonized polymers, such as the solid acid shown in Figure 7.7, have shown promise. Sulfonated bio-char has been similarly used. ... 

Important applications for titanium have been developed in processes involving acetic acid, malic acid, amines, urea, terephthalic acid, vinyl acetate, and ethylene dichloride. Some of these represent large scale use of the material in the form of pipework, heat exchangers, pumps, valves, and vessels of solid, loose lined, or explosion clad construction. In many of these the requirement for titanium is because of corrosion problems arising from the organic chemicals in the process, the use of seawater or polluted cooling waters, or from complex aggressive catalysts in the reaction. 

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