Catalysts in esterification

It is used as a catalyst in esterification, dehydration, polymerization and alkylation reactions. Converted by e.g., ihionyl chloride, to melhanesulphonyl chloride (mesyl chloride) which is useful for characterizing alcohols, amines, etc. as melhanesulphonyl (mesyl) derivatives. 

Most compounds used as catalysts in esterifications contain elements belonging to groups III to VIII, mainly IV, VB, and VII A. 

The following experimental results are presented on the use of solid acid catalysts in esterification of dodecanoic acid with 2-ethylhexanol and methanol. In the next figures, conversion is defined as X [%] = 100-(1 - [Acid]fi ai / [Acid]Muai), and the amount of catalyst used is normahzed cat [%] - 100-A/cat / (A/acid + Milcohol)-Several alcohols were used to show the range of apphcability. The selectivity was assessed by testing the formation of side products in a suspension of catalyst in alcohol. Under the reaction conditions, no products were detected by GC analysis. 

The use of metal catalysts in esterifications and polyesterifications has been summarized by Fradet and Marechal [9], Tetrabutoxytitanium is a very efficient... 

Use Catalyst in esterification, alkylation, olefin polymerization, peroxidation reactions. 

Comparison data were presented, that demonstrate the use of the polysiloxane material as an advantageous substitute for organic cation exchange resins, sulfuric acid, p-toluene sulfonic acid and acidic zeolites. It is demonstrated, that materials like 1 and 2 are cost-efficient and reliable catalysts in esterification, alkylation, and condensation, whereas use of the bifunctional catalyst 3 gives excellent conversions in hydrogenolysis reactions in general. 

Only few reports are known describing zeolites as catalysts in esterification reactions. Corma et al. [1] published a relationship between the characteristics of HY zeolite and the catiilytic activity in the esterification of carboxylic acids. Yadov Ma et al. [2] have demonstrated that zeolites were able to do esterification reaction. The present investigation describes the use of zeolite HP in vapour phase esterification of acetic acid with C2-C4 alcohols and the activity of HP is compared with that of HY, DHY, HZSM-5 and Y-AI2O3,... 

Ion-exchange resins, especially the cation-exchange resins such as Dowex, Amberlyst series are manufactured mairJy by sulfonation of ethylbenzene first, followed by a cross-link with divinylbenzene (Liu Tan, 2001 Alexandratos, 2008 Tesser et al., 2010). Because of their selective adsorption of reactants, surface acid site features, and swelling nature, these resins not only catalyze the esterification reaction but also affect the equilibrium conversion. They also show excellent performance such as reusable, mechanical separation, continuous operation as a heterogeneous catalyst in esterification (Yang et al., 2007 JagadeeshBabu et al, 2011 Ju et al, 2011 Toor et al., 2011). 

Dowex, a common cation-exchange resin, is widely used as catalysts in esterification (Vahteristo et al., 2009). In 2005, Kulawska, et al. investigated the esterification of maleic anhydride with octyl, decyl or dodecyl alcohol over Dowex 50Wx8-100, and the kinetic data were measured in the tempjerature range of 403-433 K (Coalc/Coma =5 1). Based on the data, a first order reaction was foimd- first order with resp>ect to add and zero order with resp>ect to alcohol. The reaction rate can be described as follows. 

These preliminary catalytic results already show the potential of this solid acid catalyst in esterification reactions. In depth studies on the recyclabiUty of the catalyst and alternative sulphonation procedures are currently ongoing. 

The exchange resins 6nd application in (i) the purification of water (cation-exchange resin to remove salts, followed by anion-exchange resin to remove free mineral acids and carbonic acid), (ii) removal of inorganic impurities from organic substances, (iii) in the partial separation of amino acids, and (iv) as catalysts in organic reactions (e.g., esterification. Section 111,102, and cyanoethylation. Section VI,22). 

Acid—Base Chemistry. Acetic acid dissociates in water, pK = 4.76 at 25°C. It is a mild acid which can be used for analysis of bases too weak to detect in water (26). It readily neutralizes the ordinary hydroxides of the alkaU metals and the alkaline earths to form the corresponding acetates. When the cmde material pyroligneous acid is neutralized with limestone or magnesia the commercial acetate of lime or acetate of magnesia is obtained (7). Acetic acid accepts protons only from the strongest acids such as nitric acid and sulfuric acid. Other acids exhibit very powerful, superacid properties in acetic acid solutions and are thus useful catalysts for esterifications of olefins and alcohols (27). Nitrations conducted in acetic acid solvent are effected because of the formation of the nitronium ion, NO Hexamethylenetetramine [100-97-0] may be nitrated in acetic acid solvent to yield the explosive cycl o trim ethyl en etrin itram in e [121 -82-4] also known as cyclonit or RDX. 

If a waste sulfuric acid regeneration plant is not available, eg, as part of a joint acrylate—methacrylate manufacturing complex, the preferred catalyst for esterification is a sulfonic acid type ion-exchange resin. In this case the residue from the ester reactor bleed stripper can be disposed of by combustion to recover energy value as steam. 

Acidic Cation-Exchange Resins. Brmnsted acid catalytic activity is responsible for the successful use of acidic cation-exchange resins, which are also soHd acids. Cation-exchange catalysts are used in esterification, acetal synthesis, ester alcoholysis, acetal alcoholysis, alcohol dehydration, ester hydrolysis, and sucrose inversion. The soHd acid type permits simplified procedures when high boiling and viscous compounds are involved because the catalyst can be separated from the products by simple filtration. Unsaturated acids and alcohols that can polymerise in the presence of proton acids can thus be esterified directiy and without polymerisation. 

DiisononylPhthalate andDiisodeeylPhthalate. These primary plasticizers are produced by esterification of 0x0 alcohols of carbon chain length nine and ten. The 0x0 alcohols are produced through the carbonylation of alkenes (olefins). The carbonylation process (eq. 3) adds a carbon unit to an alkene chain by reaction with carbon monoxide and hydrogen with heat, pressure, and catalyst. In this way a Cg alkene is carbonylated to yield a alcohol a alkene is carbonylated to produce a C q alcohol. Due to the distribution of the C=C double bond ia the alkene and the varyiag effectiveness of certain catalysts, the position of the added carbon atom can vary and an isomer distribution is generally created ia such a reaction the nature of this distribution depends on the reaction conditions. Consequendy these alcohols are termed iso-alcohols and the subsequent phthalates iso-phthalates, an unfortunate designation ia view of possible confusion with esters of isophthaUc acid. 

Titanium alkoxides are used for the hardening and cross-linking of epoxy, siUcon, urea, melamine, and terephthalate resins in the manufacture of noncorrodable, high temperature lacquers in the sol-gel process as water repellents and adhesive agents (especially with foils) to improve glass surfaces as catalyst in olefin polymeri2ation, and for condensation and esterification. 

Esterification. Extensive commercial use is made of primary amyl acetate, a mixture of 1-pentyl acetate [28-63-7] and 2-metliylbutyl acetate [53496-15-4]. Esterifications with acetic acid are generally conducted in the Hquid phase in the presence of a strong acid catalyst such as sulfuric acid (34). Increased reaction rates are reported when esterifications are carried out in the presence of heteropoly acids supported on macroreticular cation-exchange resins (35) and 2eohte (36) catalysts in a heterogeneous process. Judging from the many patents issued in recent years, there appears to be considerable effort underway to find an appropriate soHd catalyst for a reactive distillation esterification process to avoid the product removal difficulties of the conventional process. 

Chemical Properties. MSA combines high acid strength with low molecular weight. Its pK (laser Raman spectroscopy) is —1.9, about twice the acid strength of HCl and half the strength of sulfuric acid. MSA finds use as catalyst for esterification, alkylation, and in the polymerisation and curing of coatings (402,404,405). The anhydrous acid is also usefijl as a solvent. 

Stannic chloride is also used widely as a catalyst in Eriedel-Crafts acylation, alkylation and cycHzation reactions, esterifications, halogenations, and curing and other polymerization reactions. Minor uses are as a stabilizer for colors in soap (19), as a mordant in the dyeing of silks, in the manufacture of blueprint and other sensitized paper, and as an antistatic agent for synthetic fibers (see Dyes, application and evaluation Antistatic agents). 

Stannous oxalate is used as an esterification and transesterification catalyst for the preparation of alkyds, esters, and polyesters (172,173). In esterification reactions, it limits the undeskable side reactions responsible for the degradation of esters at preparation temperatures. The U.S. Bureau of Mines conducted research on the use of stannous oxalate as a catalyst in the hydrogenation of coal (174) (see Coal). 

Acid—Base Catalysis. Inexpensive mineral acids, eg, H2SO4, and bases, eg, KOH, in aqueous solution are widely appHed as catalysts in industrial organic synthesis. Catalytic reactions include esterifications, hydrations, dehydrations, and condensations. Much of the technology is old and well estabhshed, and the chemistry is well understood. Reactions that are cataly2ed by acids are also typically cataly2ed by bases. In some instances, the kinetics of the reaction has a form such as the following (9) ... 

In recent years, the rate of information available on the use of ion-exchange resins as reaction catalysts has increased, and the practical application of ion-exchanger catalysis in the field of chemistry has been widely developed. Ion-exchangers are already used in more than twenty types of different chemical reactions. Some of the significant examples of the applications of ion-exchange catalysis are in hydration [1,2], dehydration [3,4], esterification [5,6], alkylation [7], condensation [8-11], and polymerization, and isomerization reactions [12-14]. Cationic resins in form, also used as catalysts in the hydrolysis reactions, and the literature on hydrolysis itself is quite extensive [15-28], Several types of ion exchange catalysts have been used in the hydrolysis of different compounds. Some of these are given in Table 1. 

Esters are usually prepared from carboxylic acids by the methods already discussed. Thus, carboxylic acids are converted directly into esters by SK2 reaction of a carboxyfate ion with a primary alkyl halide or by Fischer esterification of a carboxylic acid with an alcohol in the presence of a mineral acid catalyst. In addition, acid chlorides are converted into esters by treatment with an alcohol in the presence of base (Section 21.4). 

In this article we critically review most of the literature concerning non-catalyzed, proton-catalyzed and metal-catalyzed polyesterifications. Kinetic data relate both to model esterifications and polyeste-rificatiom. Using our own results we analyze the experimental studies, kinetic results and mechanisms which have been reported until now. In the case of Ti(OBu)f catalyzed reactions we show that most results were obtained under experimental conditions which modify the nature of the catalyst. In fact, the true nature of active sites in the case of metal catalysts remains largely unknown. 

Inventory of the Main Catalysts Used in Esterifications and Polyesterifications 65... 

Inventory of the main catalysts used in esterifications and polyesterifications, Chap. 4. 

The Ingold248 classification of esterification and hydrolysis reactions is reported in Table 4. Basic compounds are seldom used as catalysts for esterifications, at least in diluted media. Thus, in Table 4 all arrows are oriented right to left. However, some authors (Naudet193, Kutepov27 ) carried out base-catalyzed esterifications in concentrated media and proposed mechanisms. 

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