Abstract
Lipase-catalyzed synthesis of esters has been widely investigated due to numerous advantages in comparison with the conventional chemical process catalyzed with concentrated acids since use of chemical catalysts leads to several problems. The most important disadvantages are corrosion of equipment, hazards of handling of the corrosive acids that are not reused, loss of conversion, yield and selectivity. The activity of water in reaction mixture seems to be one of the crucial factors affecting yield of enzymatic synthesis, since the excess of water promotes hydrolysis of the ester. Therefore, a significant part of related studies was focused on attempts to increase the yield of esters by efficient control of water activity. In our experimental work an attempt was made to regulate the activity of water by addition of water adsorbents in reaction mixture for synthesis of amyl isobutyrate. Two adsorbents were used: silica gel and molecular sieves (zeolites). The use of water adsorbents was optimized with respect to timing of adsorbent addition and pretreatment of adsorbent. The pretreatment of adsorbent with substrate did not increase the yield of ester. It was found that the timing of adsorbent addition is crucial factor. The addition in early phases of reaction leads to the decrease in ester yield compared to reaction without adsorbents. On the other hand, when the adsorbent was added in the late stage of reaction it exhibited beneficial influence on the yield of ester. The increase of yield was higher with silica gel (10%) than with molecular sieves (3.5%). These discrepancies can be ascribed to higher water adsorbing capacity of silica gel in systems with higher water content. Superior behavior of silica gel in ester synthesis in conjunction with simple process of regeneration recommends the use of this adsorbent for increasing the yield of lipase-catalyzed ester synthesis.
Highlights
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Summary
(Q]LPVNL SRVWXSFL VLQWH]H HVWDUD NRML VH SULPHQMXMX X SUHKUDPEHQRM IDUPD FHXWVNRM L NR]PHWL NRM LQGXVWULML LPDMX VYH YHþL ]QD DM MHU VH VYUVWDYDMX X ]H OHQH SRVWXSNH L GRELMHQL SURL]YRGL PRJX GD GRELMX HWLNHWX SULURGQRJ SURL]YRGD 5D]OL LWL DGVRUEHQWL YRGH SULPHQMXMX VH X RYRM UHDNFLML MHU GRYRGH GR VPDQMHQMD EU]LQH SRYUDWQH UHDNFLMH KLGUROL]H HVWUD L SRYHþDQMD SULQRVD çHOMHQRJ SURL]YRGD 8 RYRP UDGX MH RSWLPL]RYDQR YUHPH GRGDYDQMD DGVRU EHQWD X UHDNFLRQX VPHåX 8VWDQRYOMHQR MH GD DGVRUEHQWL SR]LWLYQR XWL X QD SULQRV DPLO2L]REXWLUDWD VDPR XNROLNR VH GRGDMX SUL NUDMX UHDNFLMH GRN GR GDWDN DGVRUEHQWD QD SR HWNX UHDNFLMH GRYRGL GR VPDQMHQMD SULQRVD HVWUD 6L OLND JHO MH SRND]DR YHþL HIHNDW QD SULQRV HVWUD SRYHþDQMH RG RG PROHNXOVNLK VLWD ]HROLWD
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