Catalysts propionic acid formation

The advent of a large international trade in methanol as a chemical feedstock has prompted additional purchase specifications, depending on the end user. Chlorides, which would be potential contaminants from seawater during ocean transport, are common downstream catalyst poisons likely to be excluded. Limitations on iron and sulfur can similarly be expected. Some users are sensitive to specific by-products for a variety of reasons. Eor example, alkaline compounds neutralize MTBE catalysts, and ethanol causes objectionable propionic acid formation in the carbonylation of methanol to acetic acid. Very high purity methanol is available from reagent vendors for small-scale electronic and pharmaceutical appHcations. 

The principal competing reactions to ruthenium-catalyzed acetic acid homologation appear to be water-gas shift to C02, hydrocarbon formation (primarily ethane and propane in this case) plus smaller amounts of esterification and the formation of ethyl acetate (see Experimental Section). Unreacted methyl iodide is rarely detected in these crude liquid products. The propionic acid plus higher acid product fractions may be isolated from the used ruthenium catalyst and unreacted acetic acid by distillation in vacuo. 

Aqueous phase reforming of glycerol in several studies by Dumesic and co-workers has been reported [270, 275, 277, 282, 289, 292, 294, 319]. The first catalysts that they reported were platinum-based materials which operate at relatively moderate temperatures (220-280 °C) and pressures that prevent steam formation. Catalyst performances are stable for a long period. The gas stream contains low levels of CO, while the major reaction intermediates detected in the liquid phase include ethanol, 1,2-pro-panediol, methanol, 1-propanol, propionic acid, acetone, propionaldehyde and lactic acid. Novel tin-promoted Raney nickel catalysts were subsequently developed. The catalytic performance of these non-precious metal catalysts is comparable to that of more costly platinum-based systems for the production of hydrogen from glycerol. 

The industrial catalytic Reppe process is usually applied in the production of acrylic acid. The catalyst is NiBr2 promoted by copper halides used under forcing conditions. The BASF process, for example, is operated at 225°C and 100 atm in tetrahydrofuran solvent.188 Careful control of reaction conditions is required to avoid the formation of propionic acid, the main byproduct, which is difficult to separate. Small amounts of acetaldehyde are also formed. Acrylates can be produced by the stoichiometric process [Eq. (7.20)], which is run under milder conditions (30-50°C, 1-7 atm). The byproduct NiCl2 is recycled ... 

Cellulose esters (e.g., cellulose triacetate, cellulose diacetate, cellulose propionate, and cellulose butyrate) are prepared by initially treating cellulose with glacial acetic acid (or propionic acid and butyric acid) followed by the corresponding acid anhydride with a trace of strong acid as a catalyst in chlorinated hydrocarbon. Complete esterification reactions result in the formation of a triester, which undergoes water hydrolysis to form a diester. Cellulose acetate alone or in combination with cellulose triacetate or cellulose butyrate is used as a semipermeable membrane for osmotic pumping tablets, primarily in controlled release systems. The permeability of the membrane can be further modulated by adding water-soluble excipients to the cellulose esters. 

Some insight into the mechanisms of the iodine-promoted carbonylation has been obtained by radioactive tracer techniques [17] and low-temperature NMR spectroscopy [18]. The mechanism involves the formation of HI, which in a series of reactions forms with rhodium a hydrido iodo complex which reacts with ethylene to give an ethyl complex. Carbonylation and reductive elimination yield propionic acid iodide. The acid itself is then obtained after hydrolysis. The rate of carboxylation was reported to be accelerated by the addition of minor amounts of iron, cobalt, or manganese iodide [19]. The rhodium catalyst can be stabilized by triphenyl phosphite [20]. However, it is doubtful whether the ligand itself would meet the requirements of an industrial-scale process. 

The high activity of a ruthenium-promoted iridium catalyst has improved productivity in plants that previously used rhodium catalysts [123], For example, a 75% increase in throughput was achieved at the Samsung-BP plant in Ulsan, South Korea. Another benefit of the iridium catalyst is higher selectivity, with smaller amounts of both gaseous and liquid by-products. The WGS reaction does occur, but at a lower rate than for rhodium, resulting in reduced formation of C02 and CH4. Since the process is less sensitive to CO partial pressure, the reactor can operate with a lower rate of bleed of recycle gas which, in combination with the secondary reactor, results in an increase in CO conversion from 85% (Rh) to >94% (Ir). Selectivity to acetic acid is >99% based on methanol with reduced propionic acid by-product formation relative to the process with the rhodium catalyst. This, along with the lower water... 

Dalapon is produced by the chlorination of propionic acid. Chlorination is carried out at high temperature in the presence of a catalyst, phosphorus trichloride or light, for example, to suppress the formation of 2,3-dichloropropionic acid. The technical acid is contamined by small quantities of 2-chloropropionic acid and... 

Nickel is a further transition metal of high importance in CO2 activation. Ethene and carbon dioxide react in the presence of nickel-(1,5,9-cyclododecatriene) and a chelating ligand such as dcpe or 2,2 bipyridyl (bipy) yielding an oxanickelacyclopentanone which can be decomposed to propionic acid, methyl propionate or - via succeeding reaction with carbon monoxide - to succinic anhydride [4,5]. Another catalyst leads to the formation of products with an ethene/ C02-ratio of 2 1 (Figure 4). By using nickelbis(cyclooctadiene) and... 

As pointed out earlier, ketene acetal involved in the Qaisen-Johnson rearrangements is obtained after alcohol exchange in the starting orthoester and elimination of the low-boihng-point alcohol. The whole process requires generally acid catalysis, propionic acid being the most common catalyst, and heating or even distillation to shift the equihbrium to the formation of the ketene acetal. Obviously, these reaction conditions are not always compatible with sensitive compounds. 

Carbonylation kinetics of ethanol to propionic acid using Rh/HI catalyst is O, 0.828 and 0.664 order with respect to dissolved [CO], [HI], [ethanol] and [Rh] respectively. A spectroscopic study of the RhCls/Mel/PPha catalysed carbonylation of NeOAc to acetic anhydride reveals initial formation of [Rh(CO)2l2) which enters an equilibrium with [Rhl(CO)(PPh3>2], both complexes can act as starting compounds in catalytic cycles . A catalytic procedure for the preparation of CO-labelled aroyl chlorides (Phl COCl, 2-C1C6H,13C0C1, S-OjNCjH 13COCI etc) employs... 

With propionic acid, propionanilide was obtained. The metal carbonyls Fe(CO)3 and Co2(CO)g were also used as catalysts. With 2-nitrobenzoic acid, no intra-molecular condensation was observed and only nitrobenzene was obtained by decarboxylation. The following mechanism has been proposed (note that the formation of a free nitrene is very unlikely) (Scheme 14) ... 

Formation of anhydride succeeds with Ni catalysts even at lower temperatures (230 to 250 °C) than the synthesis of propionic acid from ethylene. Thiolcarboxylic acid esters are obtained analogously by addition of thiols instead of carboxylic acids (2). Olefins, carbon monoxide and amines react to give saturated carboxylic acid amides (3) and acid chlorides are formed from hydrogen chloride and carbon monoxide in the presence of noble metal catalysts of the 8th group of the periodic table of the elements (4). 

The procedure can be extended to achieve selective a-bromination and iodination of carboxylic acids and the general mechanism of the a-halogenation is outlined in Chapter 5, p 170. The autocatalytic effects in the selective a-chlorination of propionic acid to the 2-chloro and 2,2-dichloro acids have been studied in a semibatch reaction at 90-130 °C. The reaction was performed in the presence of chlorosulfonic acid and dichloroacetic acid as catalysts and oxygen as the radical scavenger. Kinetic experiments indicated autocatalytic formation of both products and that the selectivity was independent of the chlorine concentration in the liquid phase. The results confirmed the validity of the proposed reaction scheme which involved formation of the reaction intermediate, propanoyl chloride from propionic acid and chlorosulfonic acid, the acid-catalysed enolization of the acid, and a hydroxyl-chlorine exchange reaction. The acid-catalysed enolization was the rate-determining step in the reaction sequence. ... 

Many drawbacks have arisen during the direct hydrogenation of lactic acid to PPG, for instance, catalyst deactivation due to the polymerization of lactic acid and the formation of undesirable propionic acid. In addition, hydrogenation is known to have a lower productivity. 

A one-pot solution polymerization was performed at room temperature using partially aromatic monomers, namely 4,4-bis(4 -hydroxyphenyl)valeric acid as AB2 and 3-(4-hydroxyphenyl)propionic acid as AB [118] (see Table 1, entry 5 for monomer combination), in the presence of 4-(A, A dimethylamino) pyridinium 4-tosylate (DPTS) as catalyst and dicyclohexylcarbodiimide (DCC). The dependencies of the DB and the thermal properties of the polymers on the AB AB2 monomer ratio were studied. Polyesters with statistical dendritic topology, controlled DB, and > 35,000 g/mol were obtained. The DB was found to decrease with an increase in the amount of AB monomers and increasing comonomer ratio in the polymer (rp = ratio of AB to AB2) as shown in Fig. 1. Interestingly, the DB for hb homopolyester and branched copolyester at rp = 0.46 was similar (see Fig. la), because of the fact that on adding the small-sized linear AB to the more voluminous AB2 monomers in the reaction mixture, the steric effects decreased, which promoted the formation of dendritic units formed by the AB2 monomer. The thermal... 

Industrial-scale production in the Cativa process (181-195°C, 22-32 bars) involves a primary reactor where methanol, catalyst, and the promoter are reacted with CO. The reactants are mixed by the jet mixing effect provided by the cooling loop in the primary reactor. The reactant mixture is passed into the second reactor to improve the formation of acetic acid, after which the catalyst is separated and recycled. The by-products in the Cativa process are propionic acid and acetaldehyde, which are separated from acetic acid by distillation. By oxidizing the latter, the yield can be improved. 

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