Acetic acid catalyst composition

A pure perovskite phase with the composition SrBi2Ta209 and a crystal size <50 nm was formed at 1073 K from a xerogel precursor, obtained by gelation from Ta(EtO)5 and Sr-acetate and BiO-nitrate solution in methoxyethanol using an acetic acid catalyst [70]. Acetate ions act as bidentate ligands in this solution, equalizing the hydrolysis/condensation rates of Ta and other ions. 

However, the gels in this study must be treated under the temperature at which wood is not thermally degraded. Therefore, in a reaction medium of the metal alkoxide/alcohol (solvent)/acetic acid (catalyst), the moisture-conditioned wood or water-saturated wood is soaked at ambient temperature under reduced pressure or atmospheric pressure. The water present within the wood cells initiates the reaction of the hydrolysis and polycondensation of metal alkoxide. The soaked wood is subsequently treated at a temperature between 50 and 60 C for 24h, and at 105°C for another 24h to prepare wood-inorganic composites (Saka, 1992 Ogjso, 1993). 

Continuous esterification of acetic acid in an excess of -butyl alcohol with sulfuric acid catalyst using a four-plate single bubblecap column with reboiler has been studied (55). The rate constant and the theoretical extent of reaction were calculated for each plate, based on plate composition and on the total incoming material to the plate. Good agreement with the analytical data was obtained. 

Although catalytic wet oxidation of acetic acid, phenol, and p-coumaric acid has been reported for Co-Bi composites and CoOx-based mixed metal oxides [3-5], we could find no studies of the wet oxidation of CHCs over supported CoO catalysts. Therefore, this study was conducted to see if such catalysts are available for wet oxidation of trichloroethylene (TCE) as a model CHC in a continuous flow fixal-bed reactor that requires no subsequent separation process. The supported CoOx catalysts were characterized to explain unsteady-state behavior in activity for a certain hour on stream. 

This mixture is fed into bubble columns and contacted with chlorine gas at 3.5 bar and 115-145 °C [57]. A typical reaction mixture has a composition of 38.5% acetic acid, 11.5% acetic anhydride and 50% chlorine gas. The crude product is first purified by distillation. Thereafter, either crystallization or hydrogen reduction at a Pd catalyst is conducted to separate the monochlorinated from the dichlorinated product. 

Effect of Catalyst Composition. Where acetic is the typical acid substrate, effective ruthenium catalyst precursors include ruthenium(IV) oxide, hydrate, ruthenium(III) acetyl-acetonate, triruthenium dodecacarbonyl, as well as ruthenium hydrocarbonyls, in combination with iodide-containing promoters like HI and alkyl iodides. Highest yields of these higher MW acids are achieved with the Ru02-Mel combination,... 

The reaction is reversible and therefore the products should be removed from the reaction zone to improve conversion. The process was catalyzed by a commercially available poly(styrene-divinyl benzene) support, which played the dual role of catalyst and selective sorbent. The affinity of this resin was the highest for water, followed by ethanol, acetic acid, and finally ethyl acetate. The mathematical analysis was based on an equilibrium dispersive model where mass transfer resistances were neglected. Although many experiments were performed at different fed compositions, we will focus here on the one exhibiting the most complex behavior see Fig. 5. 

In a more detailed examination of the ruthenium-cobalt-iodide "melt" catalyst system, we have followed the generation of acetic acid and its acetate esters as a function of catalyst composition and certain operating parameters, and examined the spectral properties of these reaction products, particularly with regard to the presence of identifiable metal carbonyl species. 

It is clear that ruthenium-cobalt-iodide catalyst dispersed in low-melting tetrabutylphosphonium bromide provides a unique means of selectively converting synthesis gas in one step to acetic acid. Modest changes in catalyst formulation can, however, have profound effects upon liquid product composition. 

The Ru/Rh/Cs/HOAc Catalyst Composition. Table I illustrates the effect, on product distribution and catalytic activity, of the incremental addition of cesium ions to a catalyst precursor composition containing ruthenium and rhodium, in the molar ratio of 10 1, dissolved in glacial acetic acid. The results of control experiments, in which no cesium is present, are also included. 

Figure 1 Product distribution as a function of added triethylamine in the Ru/Rh/EtgN/HOAc catalyst composition. Reaction conditions Ru (2.0 mmol), Rh (0.2 mmol), glacial acetic acid (50 ml), 1000 atm CO/H2 (1 1), 230oC.

Before bismuth-promotion the Pt-on-alumina catalyst was pre-reduced in water with hydrogen. The pH was decreased to 3 with acetic acid and the appropriate amount of bismuth nitrate dissolved in water (10 - lO " M) was added into the mixed slurry in 15-20 min, in a hydrogen atmosphere. Promotion of unsupported Pt was carried out similarly. The metal composition of the bimetallic catalysts was determined by atomic absorption spectroscopy. 

Our initial work on the TEMPO / Mg(N03)2 / NBS system was inspired by the work reported by Yamaguchi and Mizuno (20) on the aerobic oxidation of the alcohols over aluminum supported ruthenium catalyst and by our own work on a highly efficient TEMP0-[Fe(N03)2/ bipyridine] / KBr system, reported earlier (22). On the basis of these two systems, we reasoned that a supported ruthenium catalyst combined with either TEMPO alone or promoted by some less elaborate nitrate and bromide source would produce a more powerful and partially recyclable catalyst composition. The initial screening was done using hexan-l-ol as a model substrate with MeO-TEMPO as a catalyst (T.lmol %) and 5%Ru/C as a co-catalyst (0.3 mol% Ru) in acetic acid solvent. As shown in Table 1, the binary composition under the standard test conditions did not show any activity (entry 1). When either N-bromosuccinimide (NBS) or Mg(N03)2 (MNT) was added, a moderate increase in the rate of oxidation was seen especially with the addition of MNT (entries 2 and 3). 

The catalyst claimed by Saudi Basic is in large part amorphous, but shows a few diffraction lines relative to a crystalline compound characterized by d values at 4.03 (100% I), 3.57, 2.01 and 1.86 A. Doping the compound with P improves the yield to acetic acid this was attributed to an enhancement of surface acidity, which facilitates the ethylene adsorption and the acetic acid desorption. A detailed investigation of catalyst composition confirmed that the former model originally proposed by Merzouki et al. [4a, b] was the most likely [4c]. Therefore, the excellent properties... 

Table 9.1 summarizes catalyst compositions and corresponding performances. The oxidation of ethane to acetic acid is now commercial an industrial plant is installed, with the technology developed by Saudi Basic. Elements that have contributed to the successful development of the process are (1) the discovery of a catalytically active compound, the multifunctional properties of which can be modified and tuned to be adapted to reaction conditions through incorporation of various elements (2) the stability of the main products, ethylene and acetic acid, which do not undergo extensive consecutive degradation reactions (3) the possibility of recycling the unconverted reactant and the major by-product, ethylene (4) the use of reaction conditions that minimize the formation of CO and (5) an acceptable overall process yield. 

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