Kinetic and catalytic aspects of dimethylterephtalate transesterification also through the use of model molecules

Heterogeneous Catalysts for Biodiesel Production

“…After the Lewis complex formation (stage 1), the alcohol nucleophilic bonding (stage 2), and the new ester formation (stage 3), the new ester desorbs from the Lewis site (stage 4) and the cycle is repeated. If the strength of acidic sites is too high, the desorption of the product is not favored, determining a slow reaction rate ,– . This mechanism was confirmed for both homogeneous ,, and heterogeneous catalysts by the observation that an optimal range of strength for Lewis acidic sites exists and that very strong Lewis acidic catalysts are less active in transesterification reactions ,– .…”

“…Zn acetate is a good catalyst for transesterification reactions, , and recently, Di Serio et al found that it can be used to catalyze the esterification and transesterification of oils with high FFA concentrations. One of the first reported attempts to heterogenize the zinc catalyst for oil transesterification is contained in the English patent GB795573 which describes the use of a zinc silicate as catalyst in the transesterification of coconut oil at 250−280 °C.…”

Polyesters

“…282 The results indicate that very strong or very weak carbonyl-metal interactions are unfavorable factors with regard to catalytic activity. 282,283 The absence of interactions obviously results in poor catalytic activity. On the other hand, very strong carbonyl-metal interactions would result in the formation of stable complexes, slowing the ligand exchanges responsible for the catalytic effect.…”

Development of catalyst complexes for upgrading biomass into ester-based biolubricants for automotive applications: a review

“…The study reveals that the catalysts activity depends on the metal acidity and the structures of ester and alcohols; hence, every ester–alcohol couple will have a specific metal choice that will give the maximum activity. 75 Besides, these catalysts are more efficient in the presence of high free fatty acid concentrations with a 5 × 10 −3 : 1 weight ratio of catalyst to oil at 200–250 °C when 2.0 g (0.2% w/w of FFA) of soybean oil and 0.88 g of methanol is used ( Table 18 ). The results show that the Cd(OAc) 2 catalyst successfully achieved a maximum of 89% conversion contrary to that of Ba(OAc) 2 , which generated a lower conversion under the same reaction conditions.…”