ADSORPTION OF AROMATIC-HYDROCARBONS AND ORGANIC SULFUR-COMPOUNDS BY NAX ZEOLITE

The development and extensive commercial use of liquid-phase processors for the recovery of pure n-paraffins by means of synthetic zeolites is closely related to the problem of improving the feedstock quality, mainly its hydrocarbon composition. The aromatic hydrocarbons that are present in the feedstock create an energy barrier close to the entrances to the void spaces in the zeolite crystals, blocking the channels in type CaA zeolite. This blockage, which promotes an additional specific interaction of the aromatic hydrocarbon molecules with the zeolite crystal surface, hinders the n-alkane molecules from passing into the adsorbed phase and creates problems in the production of pure straight-chain paraffins. The n-alkanes that are obtained in some cases must be subjected to dearomatization, where it is also desirable to use zeolites. In the reported experiemnts, the authors have investigated the adsorption of aromatic hydrocarbons by zeolite in the liquid phase at 20 and 70 degree C. As model compounds they used prepurified aromatic hydrocarbons and synthesized sulfur compounds (Table 1), and also an alkylbenzene fraction consisting of monoalkylbenzenes with an average of 12 carbon atoms in an unbranched side chain. Isooctane was used as a solvent for the aromatic hydrocarbons in liquid-phase adsorption. Data are tabulated, plotted, and evaluated in terms of practical recommendations for industrial operations.