Brine purification filtration

The soluble ions of iron and aluminium are usually reduced to a minimum by adjusting the electrolyte pH. For the removal of solid iron hydroxide and aluminium hydroxide Bayer decided to use a new pre-coat-free brine purification technology -back-pulse filtration using GORE-TEX membrane filter cloths. 

The first step in brine purification is chemical treatment to remove certain impurities. The elements of hardness (calcium and magnesium) must be removed, along with iron and heavy metals. This is done by precipitation, adding a source of carbonate ion to remove calcium and a source of hydroxide ion to remove the other metals. Sulfate ion also can be removed by precipitation, using either calcium or barium ion. Precipitation processes cannot usefully be considered in isolation. The nature of the solids formed in this way determines how they will behave in the later processes that are designed for their physical removal. The subsections that follow therefore describe in a general way the flow behavior and settling rates of precipitated particles. Later sections of the chapter cover the details of sedimentation and filtration of the solids. 

To a solution of thioglycoside (1.0 equiv), 1-benzenesulfinyl piperidine (1.0 equiv), TTBP (2.0 equiv), and freshly activated 3 A powdered molecular sieves in dichloromethane (25.0 ml mmol-1) was added trifluoromethanesulfonic anhydride (1.1 equiv) at —60 °C under an argon atmosphere. The reaction mixture was stirred for 5 min, after that a solution of the glycosyl acceptor (1.5 equiv) in dichloromethane (4.0 ml mmol-1) was added. The reaction mixture was stirred at — 60 °C for 2 min, after that it was slowly warmed to room temperature and quenched by the addition of saturated aqueous NaHC03. The organic layer was washed with brine, dried (MgS04), filtered and the filtrate was concentrated to dryness. Purification of the crude product by column chromatography over silica gel afforded the product. 

The mixture was filtered and the enzyme washed with MTBE until the filtrate turned colorless. The filtrate was then successively washed with 1 M aqueous HCl, saturated NaHCOa and brine and then concentrated and deprotected directly without further purification (typical yield 80 %). 

A 1-L, oven-dried, round-bottomed flask equipped with a magnetic stirrer is charged with 9.92 g (27.9 mmol) of methyl R)-3-(tert-butyldiphenylsilyloxy)-2-methylpropionate and 200 mL of dry hexanes (Note 15). The solution is cooled to -78°C, and 31.5 mL (31.5 mmol) of 1 M diisobutylaluminum hydride (in hexane) (DIBAL-H) (Note 16) is added dropwise over 15 min via a syringe pump. After the addition is complete, the resultant solution is stirred at -78°C for 2 hr. The reaction is quenched by pouring the cold solution info 250 mL of saturated aqueous Rochelle s salt. Ether (300 mL) and HjO (75 mL) are added and the biphasic mixture is stirred vigorously for 1 hr (Note 17). The layers are separated and the ether layer is washed with brine. The aqueous layer is extracted with ether (2 x 50 mL) and the combined extracts are dried over Na2S04. Filtration of the solution and concentration of the filtrate under reduced pressure followed by purification of the crude product by flash chromatography (Note 18) yields 7.85 g (86%) of (R)-3-(tert-bUtyldiphenylsilyloxy)-2-methylpropanal as a white solid (Note 19). 

To a suspension of AgC104 (95 mg, 0.46 mmol), SnCl2 (87 mg, 0.46 mmol), and crushed 4-A molecular sieves (200 mg, dried) in ether (3.5 mL) at —15°C was added alcohol 11 (224 mg, 0.25 mmol) in ether (3.5 mL). After 2 min, tetrasaccharide fluoride 13 (454 mg, 0.25 mmol) in ether (3.5 mL) was added in one portion, and the reaction mixture was allowed to stir at - 15°C for 2 h and at room temperature for 10 h. The reaction mixture was diluted with ether (50 mL) and filtered through Celite. The filtrate was washed with saturated aqueous NaHCOj solution (2 mL) and brine (2 mL), dried (MgS04), and evaporated to give a yellow syrup. Purification by flash chromatography (silica, ether-petroleum ether) afforded hexasaccharide 14 (442 mg, 66%) [a]D +66.50° (c 1.9, CH2C12). 

To a solution of copper chloride (2.4 mg, 0.024 mmol) in DMF (1.5 ml) was added l-chloro-2-phenylacetylene (50 mg, 0.37 mmol) at r.t. To the mixture was added trimethyl(4-methoxyphenylethynyl)silane (50 mg, 0.25 mmol). The reaction mixture was stirred for 48 h at 80 °C, quenched with 3 M HCl, and extracted with diethyl ether (25 ml x 2). The combined ethereal layer was washed with aqueous NaHCOj solution, then with brine and dried over MgS04. Filtration and evaporation provided a brown oil. Purification by column chromatography (Si02, hexane dichloromethane = 10 1) gave l-(4-methoxyphenyl)-4-phenyl-1,3-butadiyne (36 mg, 65% yield) as a colorless solid. 

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