Submitted to: American Chemical Society National Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 8/31/2005
Publication Date: 8/31/2005
Citation: Eller, F.J., Taylor, S.L. 2005. Use of critical carbon dioxide to optimize an enzyme catalyzed reaction (abstract). American Chemical Society National Meeting. Abstract Book (Fall 2005). 52.
Technical Abstract: It was hypothesized that the equilibrium point of an enzyme-catalyzed reaction could be shifted to the right if the product could be partitioned into an immiscible carbon dioxide (CO2) phase. The molar ratios of starting material to product in CO2 were compared over a range of temperatures and pressures to determine if a given combination may be useful in driving the equilibrium of the reaction. The experimental set up included a 300 mL stirred reactor, a supercritical fluid chromatograph (SFC) for analyzing samples in the CO2 phase within the reactor, two syringe pumps to maintain the pressure during sampling, and a third syringe pump to introduce CO2. A circulating water bath was used to control the temperature of the system. SFC samples could be taken without removing a significant amount of material and changing the component concentrations in the process. Similarly, the temperature and pressure could be changed without disturbing the original component ratios. The initial molar ratio of starting material to product was 1:1, representing the theoretical equilibrium point of the reaction. After adding 150 mL of this mixture, the vessel was sealed, pressurized and allowed to reach the desired temperature. All possible combinations of six temperatures (i.e., 20, 30, 40, 50, 60, & 70°C) with four pressures (i.e., 6.9, 8.3, 10.3, & 13.8 MPa) were tested. Although the solubilities of all components were proportional to the density of the CO2 over the ranges tested in this experiment (i.e., proportional to pressure and inversely proportional to the temperature) the changes with temperature and pressure were not equal for the components. Some combinations resulted in a much higher ratio of product to starting material in the CO2, suggesting that the equilibrium could indeed be shifted to the right. Other combinations resulted in a higher ratio of starting material to product.