Zeolites octanoic acid

Beers, A. E. W., van Bokhoven, J. A., de Lathouder, K. M., Kapteijn, F. and Moulijn, J. A. Optimization of zeolite Beta by steaming and acid leaching for the acylation of anisole with octanoic acid a structure-activity relation, J. Catal., 2003, 218, 239-248. 

In a series of valuable studies, the activity of various cation-exchanged Y zeolites in the acylation of toluene and xylenes with aliphatic carboxylic acids was investigated In a model reaction between toluene and octanoic acid, the activity of rare earth-, transition metal-, and alkaline earth-cation-exchanged Y zeolites was considered. CeY zeolite exhibits the highest activity (3 yield = 75%) in the para-acylation (Scheme 4.3) in agreement with the results published in an early study qj., contrary, unmodified Y zeolite shows a lower activity (3 yield < 40%), and transition metal and alkaline-earth-exchanged Y are nearly inactive. 

Figure 4.2 Dependence of the degree of sodium ion exchanged by cerium ion on the activity of Y zeolite in the acylation of toluene by octanoic acid at 200°C.

Anisole can be acylated with carboxylic acids over ZSM-5 catalyst. The reaction is carried out in a batch reactor under reflux for 2 d. Table 4.12 shows fhe resulfs obfained utilizing carboxylic acids with different chain length. Prom propanoic acid to stearic acid, the conversion decreases from 92% to 1%, showing a trend opposite to that observed with REY zeolites. This behavior can be ascribed to the small micropore size of ZSM-5, in which the formation of large molecules is difficulf (for penfanoic to octanoic acid) or impossible (for longer-chain carboxylic acids). The poor conversion of AAC can be affribufable to the low reflux temperature. 

Gauthier et al. (1989) studied the activity of various cation-exchanged Y-type zeolites in the acylation of toluene with octanoic acid, obtaining selectivities to the para isomer of 94% at 75% yield of acylated product. The most efficient catalysts were rare-earth-exchanged zeolites (70% exchange), the following order of activity being observed Cr3+, Zr4+ < M2+, Cu2+, Co2+ <11 < Pr3+, La3+, Gd3+, Yb3+, Ce3+. 

Acylation of anisole with carboxylic acids, in particular with octanoic acid, is described to be carried out over variously activated HBEA zeolites [51, 52]. Activation of the zeolite by treatment with oxalic acid after steaming results in a significant decrease of the surface area (from 670 to 500mVg) and an increase of the bulk SAR (from 13 to 51). This provides an increase in activity and selectivity in fact, HBEA itself exhibits an activity, defined as the initial apparent first-order constant k, of 0.031/g j h and a selectivity toward compound 17 (R = C. Hjj) of 80% at 50% conversion, whereas a great activity increase ( =0.121/g -h) and a selectivity improvement... 

Jacobs et al. employed an acidic zeolite catalyst for the racemization of sec-alcohols, which occurs through the formation of carbocations [44] (Figure 4.19). The KR is catalyzed by CALB in the presence of vinyl octanoate as acyl donor. DKR takes place successfully in a biphasic system (octane/H2O, 1 1) at 60 °C. 

Vinyl octanoate was obtained from TCI (Tokyo, Japan). All other chemicals with the exception of the zeolite beta are available from Sigma Aldrich. The synthesis of a particularly active modification of low-alumina zeolite beta has been described by us. Commercial material, available as samples from, for example, Zeolyst or Siidchemie can be used, but because of excessive acidity may result in up to 15 % of styrene formation. 

Acid zeolites have also been tested for the racemisation of alcohols under biphasic conditions. Their scope was found, however, to be limited to benzylic alcohols, since electron-rich benzylic alcohols were not suitable substrates because of the formation of dimers. Under optimised conditions, based on the use of H-Beta zeolite, CAL-B lipase and an excess of vinyl octanoate at 60°C, enantiopure (i )-l-phenylethyl octanoate (>99% ee) was obtained in... 

Acid zeolites have also been tested for the racemisation of alcohols under biphasic conditions.Their scope was found, however, to be limited to benzylic alcohols, since electron-rich benzylic alcohols were not suitable substrates because of the formation of dimers. Under optimised conditions, based on the use of H-Beta zeolite, CALB lipase, and an excess of vinyl octanoate at 60 °C, enantiopure (R)-l-phenylethyl octanoate (>99% ee) was obtained in 90% yield from 1-phenylethanol. In addition, Lozano et al. have recently performed the DKR of this alcohol in the presence of acidic zeolite catalysts (CBV400) in an ionic liquid-supercritical carbon dioxide system with a continuous reaction system. Therefore, when Novozym 435 was employed at 50 °C and 100 bars in the presence of vinylpropanoate as the acyl donor, the expected (R)-phenylethylpropionate was produced in excellent yield of 98% with enantioselectivity of 97% ee and without any activity loss during 14 days of operation. 

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