Catalysts for transesterification

Unactivated esters, typically alkyl esters, often show low reactivity toward lipase catalyst for transesterifications. In the case of the lipase-catalyzed polycondensation of dialkyl esters with glycols, the polymer of high molecular weight was not obtained. The molecular weight improved when vacuum conditions were used Mw reached more than 2 x 104 in the combination of diethyl sebacate and 1,4-butanediol catalyzed by lipase MM [30]. 

Transesterification or transamination are metal-directed reactions which are commonly encountered. We have discussed transamination processes in Section 5.5.2 and also in Chapter 3. The key step involves the attack of a co-ordinated alcohol or alkoxy group upon the carbonyl of a co-ordinated ester or amide. Many Lewis acidic metal ions have been shown to be effective catalysts for transesterification reactions for example, heating diethyl picolinate with copper(n) salts in methanol results in rapid and clean transesterification (Fig. 5-86). In the absence of the metal ion, the rate of reaction is vanishingly slow. 

Derrien, A., Renard, G. and Brunei, D. Guanidine linked to micelle-templated mesoporous silicates as base catalyst for transesterification. Stud. Surf. Sci. Catal., 1998,117, 445-452. 

As rationally designed multinuclear catalysts for transesterification of HPNPP, metal complexes such as 5 have been designed [42]. By random attachment of lauryl groups and Ni(n) complexes of terpyridine (TP) to PEI (6) we have synthesized a polymer that has much higher catalytic activity than 5 for the same reaction [43]. The contents of the pendant groups were varied in several combinations, and the best catalyst (]Ni(ii)TP]5Lau12PEI) contained 5 residue mol% Ni(n)TP and 12 residue mol% lauryl group. 

Tin(rv) bis(perfluorooctanesulfonyl)amide is a practical catalyst for transesterification and direct esterification using an equimolar ratio of the reactants in a fluorous biphase system (Equation (103)). The tin amide is completely recovered and reused in the immobilized fluorous phase without loss of its catalytic activity.269... 

Grasa GA, Kissling RM, Nolan SP (2002) A-Heterocyclic carbenes as versatile nucleophilic catalysts for transesterification/acylation reactions. Qrg Lett... 

Three patents have been issued in which two novel methods for forming sulfonic esters are described. A water-soluble derivative, sodium mono-0-(propylsulfonyl)rutin, was prepared by sequential treatment of rutin with sodium in ethanol, followed by propane sul-tone in N,N-dimethylformamide. The second method employed methyl p-toluenesulfonate in N,N-dimethylformamide, with potassium carbonate as a catalyst, for transesterification of the hemiacetal group of aldoses or ketoses. 

It has been disclosed that 1,3-disubstituted tetraalkyldistannoxanes are extremely effective catalysts for transesterifications of carboxylic esters in which secondary... 

H. Deleuze, X. Schultze, D. C. Sherrington, Synthesis of porous supports containing N-(p-hydroxyphenyl)- or N-(3-4-dihydroxybenzyl) maleimide-anchored titanates and application as catalysts for transesterification and epoxidation reactions, /. Polym. Sci. Pol. Chem. 38 (2000) 2879. 

Catalysts for transesterification of vinyl acetate as well as addition to triple bonds Thermometers and leveling bulbs Mercury vapor and fluorescent lamps Electrical switches... 

Complex reagent for transesterification. The aggregate prepared from NaH, f-BuONa, and Ni(OAc)2 is an effective catalyst for transesterification. 

Many metal complexes have been designed and synthesized as catalysts for transesterification of phosphate diesters to model mechanisms of RNases. Typical examples are monomeric Zn complexes (53) and (54) and dimetallic Zn complexes such as (55) (Scheme 35). For (53), the pseudo-first-order rate constant, k, for hydrolysis of BPP and for transesterification of... 

Uses Catalyst for transesterification and isomerization of fats and oils (food)... 

Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of Na20 Storage Hygroscopic moisture-sensitive keep tightly closed in a cool place protect from light handle and store under nitrogen Uses Catalyst for transesterification and... 

Alternative interesting applications for porous carbon materials have been recently reported. For example, porous carbons prepared from the large mesopore Fniim silica (KlT-5) demonstrated a superior ability to separate the tea components catechin and tannic add, compared to other p>orous materials, such as activated carbons and mesoporous silica [23]. Porous carbon nitride with a large surface area has been prepared using well-ordered mesoporous silica as a template for the polymerization between ethylenediamine and carbon tetrachloride [24]. In this case, the metal-free carbon nitride was able to function as an efficient basic catalyst for transesterification reactions. 

Poly(butylene succinate-co-butylene adipate) can be obtained from 1,4-butanediol and dimethyl esters of succinic and adipic acids through a two-step process of transesterification and polycondensation (31). A catalyst for transesterification is tetra-n-butyl-titanate used at a temperature of 200°C (30). The change of the molar mass with reaction time is shown in Figure 4.2. As can be seen from Fig-... 

Transesterification between hydroxyl-esters, carboxy-esters, or two ester groups is one of the most important polyesterification technique used for preparing various aliphatic, aliphatic-aromatic or aromatic polyesters (also known as arylates). Titanium alkoxides are very efficient catalysts for transesterification polymerizations, however in some cases it can cause undesirable discoloration to the resulting polymer [15]. A representative example is the synthesis of a polyester based on dimethyl terephthalate using titanium isopropoxide [16] (Fig. 2.3). 

Kouzu, M., T. Kasuno, M. Tajika, Y. Sugimoto, S. Yamanaka, and J. Hidaka. 2008. Calcium Oxide as a Solid Base Catalyst for Transesterification of Soybean Oil and Its Application to Biodiesel Production. Fuel 87 (12) 2798-2806. 

The monomers for transesterification reaction are dimethyl terephthalate and ethylene glycol (Scheme 4.2 (B)). An excess of ethylene glycol is used and the temperature should be 150-210 °C. When the reaction medium reaches the temperature, catalyst is added. Typical catalysts for transesterification reaction are derived-metal compounds based on Ti, Mn, Ge, Ca,... 

Homogeneous catalysts for transesterification reactions Precursor for Sn02 films on glass (Bu8n(0)0H) , Bu8n(OH)2Cl Bu8nCl3, MeSnCl3t... 

Zinc dichloride supported on silica gel has been used as an effective catalyst for transesterification of the phosphate insecticide, paraoxon (66) in... 

MgAl and MgCa oxides were found to be efficient catalyst for transesterification of ethyl butyrate and methanol and for methanolysis of sunflower oil. With 1 12 of oil and methanol and 2.5% of catalyst at a temperature of 60° C, 92% of yield of FAME was obtained. The best ratio of Mg Ca was foimd to be 3.8 and there was no leaching of catalyst into the reaction medium [37]. 

Nanocomposite mixed oxides of (strontium-titanium) Sr-Ti prepared by sol-gel method was used a heterogeneous catalyst for the transesterification of soybean oil to produce biodiesel. It was found that 1% of the catalyst afforded biodiesel in 98% yield within 15 min at a temperature of 60° C and oil to methanol ratio of 1 15. It was found that Sr/Ti molar ratio of 0.8 and the calcination temperature of 965° C was the most efficient catalyst for transesterification of soybean oil to biodiesel [40]. 

Alumina loaded with potassium as solid base catalyst was prepared and tested for the transesterification of soybean oil. Potassium nitrate (KNOj-SS wt%) on AljOj followed by calcinations at 773K for 5 h was found to be the active catalyst for transesterification at reflux temperature of methanol with oil to methanol ratio of 1 15, catalyst amount of 6.5% with 7 h of reaction time, which gave a conversion of 87% [42]. It was postulated that KNOj transformed to KjO or Al-O-K composites, which were proposed to be present in the active sites of the catalyst. In a similar type of study, KNO3 (35 wt%) loaded on Al Oj was used as catalyst for transesterification of jatiopha oil gave 84% conversion with oil to methanol ratio of 1 12 at 70° C and the authors showed that the catalyst can be used for three times [43]. 

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