Esterfication catalyst

Heterogeneous Transesterification and Esterf cation Catalysts 333 MeOH HaSOj... 

Homologation of methanol catalysed by 1 and 2 in presence of iodide promoter hydroiodic acid (entry Nos. 1 and 3), gave dimethyl ether selectively and while in the presence of water along with hydroiodic acid ( entry Nos. 2 and 4), both catalyst systems favoured the formation of acetic acid and dimethyl ether as the products. Catalyst 2 also gave methyl acetate a product of esterfication of acetic acid by methanol. Homogeneous catalyst 1 is at least two times more reactive than 2 in presence of water, however, catalyst 2 is more selective towards the formation of acetic acid (80%). 

For the sake of completeness, it may be added that sulfur dioxide has also been used as the catalyst in hydration (3 ) and dehydration (S3) reactions, in the curing of phenol-formaldehyde resins (34), in esterfication... 

As shown in Table 3.2, 5% BTCA in the presence of 10% SHP and 0.1% TiO (as a cocatalyst) was nsed, and the addition of TiO as a cocatalyst further increased WRA by 58.5%. This was becanse both TiO and SHP accelerated the catalytic reaction throngh the formation of ester bonds between the cyclic anhydride ring and the hydroxyl gronp of cellulose. The improvement of WRA by the addition of TiO in the BTCA treatment was probably dne to the nniqne photocatalytic properties of TiO, which is a kind of N-type semicondnctor. The hydroxyl radical (-OH) and snperoxide anion (-0 -) formed may have acted as catalysts to accelerate the formation of anhydrides from poly (carboxylic) acids. Fnrthermore, the effect of hydroxyl radical (-OH) and superoxide anion (-O -) on the increase of charge localization of the sohd cellulose medium in which esterfication and cross linking occur may also have been significant. Therefore, WRAs of cotton fiber treated with 5% BTCA, 10% SHP, and 0.2% TiO further increased to 61.3% compared with those of the untreated cotton fabric. The increment was proportional to the increase of TiOj from 0.1 to 0.2% in the BTCA treatment bath (Lam et al., 2011). 

Apart Ifom the aforementioned metal complexes there were entrapped in sol-gel matrices also several acids, bases and salts. Examples are the physically entrapped p-toluenesulfonic acid which has been used as an esterfication catalyst (Scheme 24-23) (Sarussi, 2000) the entrapped poly(vinylbenzyltrimetnyl)ammonium hydroxide which catalyzes aldol condensation (Scheme 24-24) (Gehnan, 2003a) and some entrapped sulfates and chlorides salts that promote dehydration of alcohols (Scheme 24-25) (Nishiguchi, 1989) and Friedel-Crafts alkylation (Scheme 24-26) (Miller, 1998), respectively. 

Hydrogenation followed by esterfication will eliminate most of the undesirable characteristics of bio-oils previously listed. Acetic acid is one of the most common carboxylic acids present in bio-oil and is a primary cause of the corrosiveness characteristic. Acetic acid can be reacted with methanol to form methyl acetate. When methyl acetate is hydrogenated using CuGCuCr O as the catalyst, methanol and ethanol are the products. These chemicals have value as fuel or can be introduced into another product stream. About 10-20% of the bio-oil being produced in the pyrolysis unit at MSU can be converted to esters. 

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