A theoretical study on the conformational interconversions in 1,3-dithiane 1,1-dioxide (1,3-dithiane sulfone) has been carried out. Nineteen conformations have been considered. Four minima and five transition states have been identified. A description of the inversion-topomerization process of 1,3-dithiane sulfone is presented. Calculations show that two transition states are associated with inversion and three more with topomerization. IGLO calculations of the (1)J(C-H) one-bond coupling constants in 1,3-dithiane sulfone have also been carried out. These constants are compared with those obtained for 1,3-dithiane, thiane, and thiane sulfone and their magnitude is explained in terms of stereoelectronic interactions.
The deasphalting process is modeled using continuous thermodynamics for the residue−solvent equilibrium computation. The residue is considered to be a mixture of continuous components and the equilibrium as liquid−liquid using the perturbed hard chain theory equation of state (PHCT EOS). The PHCT EOS parameters were refitted from published literature data to accurately predict the residue and deasphalting products properties. Also, the perturbation term of the PHCT EOS was simplified, and the hard-sphere diameter calculation considers the correction of high temperatures. Deasphalted oil (DAO) yields for specific residues have been determined using butane, propane, and combinations of these solvents at various temperatures and solvent ratios. The model results indicated that the prediction of product yields, quality, and product distributions in the deasphalting process can be done with low error.
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