Molecular sieves sulfur removal with

A large use of molecular sieves ia the natural gas industry is LPG sweetening, in which H2S and other sulfur compounds are removed. Sweetening and dehydration are combined in one unit and the problem associated with the disposal of caustic wastes from Hquid treating systems is eliminated. The regeneration medium is typically natural gas. Commercial plants are processing from as Htde as ca 30 m /d (200 bbl/d) to over 8000 m /d (50,000 bbl/d). 

The color is adversely effected mainly by impurities in the LAB. In such cases LAB is refined before sulfonation with sulfuric acid. If the neutral oil content (paraffin hydrocarbons, sulfones, and/or unsulfonated LAB) is too high, the surfactant properties of the LAB are negatively affected. In such cases, for example, the paraffins are removed prior to sulfonation by treatment with molecular sieves [152]. 

B. Ethyl a-(bromomethyl)acry late. In a nitrogen-flushed, 1-L, round-bottomed flask equipped with a magnetic stirrer, Dean-Stark trap, and condenser are placed 42.0 g (0.25 mol) of a-(bromomethyl)acrylic acid and 300 mL of benzene. Approximately 50 mL of a binary azeotrope of benzene and water is distilled (Note 7). The Dean-Stark trap is removed and 100 mL of absolute ethanol (Note 8) and 1 mL of concentrated sulfuric acid are added slowly. The contents of the flask are boiled in a nitrogen atmosphere for 36 hr, the condensate being passed through 100 g of molecular sieves (Linde 3A) before being returned to the flask. About 125 mL of a mixture of benzene and ethanol is removed from the reaction... 

Purification. The commercial solvent, made by addition of SOj to butadiene and hydrogenation, contains various contaminants. One method of purification is by passage through a column of Linde molecular sieves and fractionation. Another is by repeated vacuum distillation from sodium hydroxide pellets until a mixture of 1 ml. with 1 ml. of 100% sulfuric acid developes no color in 5 min. the solvent is then distilled again from calcium hydride. Another involves treatment with permanganate and sulfuric acid to remove oxidizable impurities, addition of enough sodium pyrosulfite to give a clear solution, extraction with methylene chloride, treatment with P Os, decantation, and distillation. 

Derivation Benzene is alkylated with dodecene, to which it attaches itself in any secondary position the resulting dodecylbenzene is sulfonated with sulfuric acid and neutralized with caustic soda. For ABS (branched-chain alkyl) the dodecene is usually a propylene tetramer, made by catalytic polymerization of propylene. For LAS (straight-chain alkyl), the dodecene may be removed from kerosene or crudes by molecular sieve, may be formed by Ziegler polymerization of ethylene, or by cracking wax paraffins to a-olefins. 

The best arrangement, to remove these poisons as deeply as possible, includes a water wash with condensed or feed boiling water, followed by a water removal device. Currently a simple azeotropic and de-isobutanizer is recommended. The dry feed is then treated with the proper molecular sieves in order to remove both oxygenates and sulfur compoimds. It should be noticed that all these feedstock treatments are also recommended to minimize classical Dimersol catalyst consumption, but using Standalone Difasol leads to more severe treatments and therefore higher investment and chemical expense. Table 5 summarises the main acceptable poison contents in the Dimersol + Difasol arrangement and in the Standalone Difasol configuration. 

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