Fractionation of P-2 Food-Grade Wax

Abstract— A procedure was developed for fractionating P-2 food-grade wax to obtain a close-cut component with increased content of С_20–24 n-alkanes. The wax fractionation was performed by centrifugation of its hexane solutions. An SL/8R programmable refrigerator centrifuge ensuring the relative centrifugal acceleration of 12 108g in the temperature interval from 40 to –10°C was used. At low temperatures, high-melting wax components were separated in the form of a precipitate in rotor test tubes. Low-melting components, including С_20–24 n-alkanes, were concentrated in hexane in the form of a solution. In the course of centrifugation, low-melting wax components became also enriched in isoparaffin and paraffin–naphthene hydrocarbons. The wax fractionation efficiency was evaluated by gas–liquid chromatography and by dielectric and IR spectroscopy. The optimum conditions of wax centrifugation from its hexane solutions were determined: relative centrifugal acceleration 12 108g and dilution of P-2 wax with the solvent in 2 : 1 to 4 : 1 weight ratio. The optimum centrifugation temperature is 5–9°С. Under these conditions, the content of С_20–24 n-alkanes in the low-melting fractions relative to the initial wax increases from 27.7 to 43.6–47.6 wt % at a yield of up to 45.5–66.0 wt %. The low-melting wax component, in contrast to the initial P-2 wax and high-melting wax component, does not contain a doublet in the IR spectrum at 728 cm^–1. A correlation equation relating the variation of the dielectric permittivity Δε of the waxes with temperature, Δε/Δt, in the region of their crystallization, Δt, to the hydrocarbon composition of P-2 wax and its fractions was obtained: Δε/Δt = 0.0009(C₁₁₊/∑(С_IP + С_PN) + 0.0065) (R² = 0.909). The values of Δ?/?t and hence the performance of paraffins in the low-temperature region of their active expansion is the higher, the higher is their total Cε/Δt and hence the performance of paraffins in the low-temperature region of their active expansion is the higher, the higher is their total C₁₁₊ n-alkane content and the lower is the content of crystallizing isoparaffin and paraffin–naphthene hydrocarbons ∑(С_IP + С_PN).