Solvent Screening for the Supercritical Hydrogenation of Polyunsaturated Hydrocarbons Using VLE Calculations

Abstract

Preliminary knowledge of VLE behavior of multiphasic reaction mixtures is required for the operation and design of chemical reactors that work with supercritical fluid as solvents. In this case, the operating parameters of a continuous fixed-bed catalytic reactor are to be optimized for the selective hydrogenation of 1,5,9-cyclododecatriene (CDT) to form the second intermediate cyclododecene (CDE). Commercial simulators (Aspen, HYSYS, PRO-II), as well as a user-written program based on high-pressure flash calculations, are tested in predictions of the phase envelope of the reaction mixture. Important binary interaction parameters (Peng-Robinson) are determined by fitting experimental and calculated data for the solubilities of CDT and CDE in supercritical CO 2 . Data are calculated with the user-written program, whereas experimental solubility points are obtained in quasi-binary-equilibrium runs at very low fluid flow rates. It is observed that the commercial simulators poorly predict the near-critical region. Thus, to choose an adequate supercritical solvent, the program is used to compare the solubilities of solutes (CDT and hydrogen) under relatively moderate temperature and pressure conditions. Among CO 2 and the lower alkanes tested (ethane to butane), propane is found to satisfy these criteria, although its flammability is inconvenient.

Chemical Routes for the Transformation of Biomass into Chemicals

“…To avoid this limitation, a supercritical solvent that brings the substrate phase and the gas into a homogeneous single phase has been introduced. For soluble fatty acid derivatives, lower alkanes could be used, propane being the preferred one. − Consequently, in recent years, some studies have reported the hydrogenation of oleochemicals at supercritical single-phase conditions. Indeed, a large number of chemical reactions have been successfully conducted in supercritical fluids.…”

“…For soluble fatty acid derivatives, lower alkanes could be used, propane being the preferred one. [943][944][945] Consequently, in recent years, some studies have reported the hydrogenation of oleochemicals at supercritical single-phase conditions. Indeed, a large number of chemical reactions have been successfully conducted in supercritical fluids.…”

Neoteric solvents for asymmetric hydrogenation: supercritical fluids, ionic liquids, and expanded ionic liquidsThis work was presented at the Green Solvents for Catalysis Meeting held in Bruchsal, Germany, 13–16th October 2002.

“…Hydrogen and nitrogen are anti-solvents in CO 2 solution, 17,18 meaning that they decrease the solubility of other solutes. To illustrate the anti-solvent effect of H 2 , we used the Peng-Robinson equation of state to calculate the change in solubility of naphthalene in scCO 2 at 40 °C.…”

Phase equilibrium data on binary and ternary mixtures of methyl palmitate, hydrogen and propane

“…Furthermore, the methanol synthesis reaction is highly exothermic, posing a potential runaway hazard [15]. Therefore, investigations for substitutes of CO 2 , with emphasis on lower alkanes (ethane to hexane), are currently underway [16,17].…”