Acrylic acid Catalyst deactivation

The effects of added C02 on mass transfer properties and solubility were assessed in some detail for the catalytic asymmetric hydrogenation of 2-(6 -meth-oxy-2 -naphthyl) acrylic acid to (Sj-naproxen using Ru-(S)-BINAP-type catalysts in methanolic solution. The catalytic studies showed that a higher reaction rate was observed under a total C02/H2 pressure of ca. 100 bar (pH2 = 50bar) than under a pressure of 50 bar H2 alone. Upon further increase of the C02 pressure, the catalyst could be precipitated and solvent and product were removed, at least partly by supercritical extraction. Unfortunately, attempts to re-use the catalyst were hampered by its deactivation during the recycling process [11]. 

It is interesting to note that the addition of a small amount of oxygen into the feed serves to suppress the deactivation of catalyst in the reaction of HCHO with acetic acid. ° However, in the reaction of HCHO with propionic acid, the addition of oxygen is not effective. This may be ascribed to the difference in the reactivity between acrylic acid and methacrylic acid oxygen serves to reoxidize the reduced catalyst in the reaction with acetic acid, but oxygen is consumed in oxidizing methacrylic acid rather than in reoxidizing the reduced catalyst. ... 

Dimerization of methyl acrylate may open up a new way to production of adipic acid. The reaction was carried out in a continuous flow biphasic system where the catalyst (obtained from [Pd(acac)2] and the hemilabile (C4H9)2P-CH2-CH2-N(CHs)2 ligand) was dissolved in [bmim][BF4] together with some HBF4, and the substrate methyl acrylate was applied in toluene solution. At 80°C, no sign of catalyst deactivation was seen for 10 h, and the overall TON after 50 h was more than 4000, with a selectivity to A -dihydromuconate more than 90%... 

The condensation of 2-hydroxyacetophenone with benzaldehyde yielded exclusively 2 -hydroxy-chalcone, and the cyclization to flavanone was not observed. An investigation of the species adsorbed on the catalyst (289) suggested that CS condensation on the Ba(OH)2 surface occurs via a very rigid transition state, whereby the OH group of 2-hydroxyacetophenone is bonded to the catalyst surface and placed at great distance from the carbonyl carbon atom of the aldehyde, making the cyclization of 2 -hydroxy-chalcone to flavanone difficult. Deactivation of the catalyst was not observed in the presence of moderate amounts of organic acids, such as benzoic, acrylic, or trichloroacetic acid. 

Ti-host remarkably catalyzes the highly endo-selective (> 99%) acrolein-1,3-cyclohexadiene Diels-Alder reaction (Eq. 2) [80]. The half-lives of this reaction in the absence and presence (3 mol%) of a catalyst are r=500 h (no catalyst), 50 h (apohost 29 as an insoluble catalyst), 1 h (TiCl2(OCH(CH3)2)2 as a soluble catalyst) and 5 min (Ti-host as an insoluble catalyst). Thus, as a Lewis acid Ti-host shows a much higher activity than its soluble counterpart. As a solid catalyst, it allows easy product-catalyst separation, recovery of the catalyst without deactivation and hence its repeated use. In addition, Ti-host is also capable of catalyzing the Diels-Alder reaction between ethyl acrylate and 1,3-cyclohexadiene, which the apohost 29 fails to catalyze because of the lack of desorption of the product from the cavities. 

The performance of complex 10 bearing a quinolinylidene as a remote car-bene ligand (Figure 5.5) was compared to that of simple imidazol-2-ylidene and phosphine-containing palladium catalysts in the Heck coupling of activated and non-activated aryl bromides with butyl acrylate. " The remote carbene complex showed much higher activity in these reactions as well as in the Suzuki coupling of a deactivated aryl bromide with phenylboronic acid. Since the complexes tested were structurally very different, purely electronic comparisons... 

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