Investigation of the melting temperature of 3-chloromandelic acid in a high-pressure mixture of carbon-dioxide and organic solvents
The high-pressure fluid-induced melting point depression is exploited in several fields of science. For example, in case of polymers, lower melting (or glass transition) temperature is beneficial concerning machinability, and the micronization process ‘particles from gas saturated solutions’ (PGSS) is also based on this phenomenon. The melting temperature measurements were conducted in mixtures of carbon dioxide (CO2) and organic solvents in a high-pressure view cell. In connection with the previous work of the group I chose 3-chloromandelic acid as the model compound. First, I used a mixture of cyclohexane and isopropyl acetate as co-solvent and carbon dioxide with a constant molar fraction (x(CO2 )=0.966) at 16 MPa pressure. I illustrated my results in a chiral melting phase diagram, which did not differ from the measurements of 3-chloromandelic acid in pure carbon dioxide , but it was different from the measurements, which were done in the mixture of carbon dioxide and acetonitrile as co-solvent. From these results, I concluded that the quality and quantity of the organic solvent may affect the melting temperature, so I measured the melting temperature of 3-chloromandelic acid first at constant (16 MPa) pressure and molar fraction (x(CO2)=0.983) in the mixture of carbon dioxide and different organic co-solvents, then with different molar fraction of methanol. I observed that the melting temperature significantly depends on the co-solvent and its molar fraction. Only 0.02 molar fraction of methanol reduced the melting temperature from 107 °C, which was measured in pure carbon dioxide to 82 °C. In this narrow range (between x(MeOH)=0 and x(MeOH)=0.02) the melting temperature depends almost linearly on the molar fraction of the co-solvent. Finally, I tried to find some correlation between the Hansen solubility parameters of the high-pressure mixture of organic solvents and carbon dioxide and the melting temperature.
author
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Arany Dóra
Biomérnöki alapképzési szak, nappali BSC
alapképzés (BA/BSc)
consultatns
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Mihalovits Máté
doktoráns , Kémiai és Környezeti Folyamatmérnöki Tanszék
