Molecular sieves water removal

By-product water formed in the methanation reactions is condensed by either refrigeration or compression and cooling. The remaining product gas, principally methane, is compressed to desired pipeline pressures of 3.4—6.9 MPa (500—1000 psi). Einal traces of water are absorbed on siHca gel or molecular sieves, or removed by a drying agent such as sulfuric acid, H2SO4. Other desiccants maybe used, such as activated alumina, diethylene glycol, or concentrated solutions of calcium chloride (see Desiccants). 

Molecular sieve 2eohtes are an example of a Class 4 drying agent (see Molecular Sieves). Water is removed by physical adsorption, but at no time does the adsorbent change phase or dissolve. 

The 4 A Molecular Sieves System. The initial procedure for the Sharpless reaction required a stoichiometric amount of the tartrate Ti complex promoter. In the presence of 4 A molecular sieves, the asymmetric reaction can be achieved with a catalytic amount of titanium tetraisopropoxide and DET (Table 4-2).15 This can be explained by the fact that the molecular sieves may remove the co-existing water in the reaction system and thus avoid catalyst deactivation. Similar results may be observed in kinetic resolution (Table 4-3).15... 

In summary, when we compare the properties of the low and intermediate zeolites with those of the high silica zeolites and silica molecular sieves, we find that their resulting properties allow the low and intermediate zeolites to remove water from organics and to carry out separations and catalysis on dry streams. In contrast, the hydrophobic high silica zeolites and silica molecular sieves can remove and recover organics from water streams and carry out separations and catalysis in the presence of water. 

Both sulfonyl chloride and isothiocyanate will hydrolyze in aqueous conditions therefore, the solutions should be made freshly for each labeling reaction. Absolute ethanol or dimethyl formamide (best grade available, stored in the presence of molecular sieve to remove water) should be used to dissolve the reagent. The hydrolysis reaction is more pronounced in dilute protein solution and can be minimized by using a more concentrated protein solution. Caution DMSO should not be used with sulfonyl chlorides, because it reacts with them. 

Gases For nitrogen end argon passage through purification trass such os Mg(CIOt)i ond molecular sieve to remove water, CO. ond hydrocarbons then deexygenate in c furnace ot 623 K w th copper turnings... 

The hexasolvated compound was being prepared from a mixture of the hydrated salt, methanol and dimethyl sulfoxide but inexplicably mercury(I) oxide came out of solution. This was redissolved by addition of perchloric acid and the solution was refrigerated for 60 h. After addition of molecular sieve to remove the water present, the solution was filtered and the sieve treatment repeated four more times. During the final filtration, a violent explosion occurred in the funnel. The most likely cause was formation of methyl perchlorate promoted by the dehydrating action of the sieve, but dimethyl sulfoxide also forms an unstable salt with perchloric acid, so this also may have been involved [1], During preparation of... 

If the makeup gas to the ammonia synthesis loop is absolutely free of catalyst poisons, such as H2O and C02, it can flow directly to the ammonia synthesis converter. This leads to the most favorable arrangement from a minimum energy point of view. This can be accomplished by allowing the gas that leaves the methanation step to pass through beds of molecular sieves to remove water and traces of C02 74... 

The hydrotreated base naphtha contained less than 0.5 ppm sulfur. The naphthas were dried over molecular sieve and stored under an inert gas (Ar) prior to use in the pilot unit. Using Karl-Fischer analysis the water content of the dried naphthas was measured to be 5-8 wt ppm. In order to compensate for the effect of the remaining water on the chloride content of the catalyst, 0.8 wt ppm chloride as 1,1,2-trichloroethane was added to the naphthas. Hj (99.995%, Norsk Hydro), supplied from gas cylinders, was passed over a deoxo catalyst (BASF R3-11) at 70°C and a 4A molecular sieve to remove traces of oxygen and water, respectively. The deoxo catalyst as well as the molecular sieve were regenerated between each test run. 

For precision cleaning applications, the lines from the carbon dioxide supply systems should be filtered using both molecular sieves to remove water vapor... 

Aqueous solubility of solvents is related to polarity and dipole moment. Many solvents are hygroscopic and need drying agents, such as molecular sieves to remove moisture from them. Solubility of solvents in water and vice versa are listed in Table 6. It is observed that the solvents with -OH, -C(0)Me, -COOH, -NH2, and -CN groups have high degree of miscibility with water, whereas hydrocarbons, esters, and chlorinated compounds have a low solubility in water. 

Tartaric acid is the least expensive chiral starting material with twofold symmetry available from natural sources. The Sharpless Ti tartrate asymmetric epoxidation catalyst consists of titanium(IV) tetraisopropoxide (Ti(OiPr)4) in combination with a chiral tartrate diester to induce asymmetry in the reaction of allylic alcohols. It is used with an alkyl hydroperoxide such as TBHP in the presence of 3A or 4A molecular sieves (to remove water) for the epoxidation of allylic alcohols [75]. It was the first effective asymmetric epoxidation catalyst reported. 

The //-benzoquinone was used as a catalytic oxidant and electron-transfer mediator with good conversion and selectivity at room temperature. It was also found that the choice of the solvent was critical, the oxidation of hydroquinone to benzoquinone catalyzed by Co(salophen)(PPh3) being more than ten times faster in methylene chloride than in benzene. A significant improvement was obtained by the use of RuClfOAcXPPhs) and molecular sieves to remove the water formed. A further improvement can be expected from the encapsulation of Co(salophen) catalyst. 

In the case of the heterogenized catalyst it was not necessary to neither use an extra axial ligand such as triphenylphosphine nor molecular sieves to remove the water. 

Unlike the work by Li and co-workers, Guo found that the reaction works best in the absence of solvent and slight improvement in yield of 17 was found when using molecular sieves to remove the presence of water. Acetic acid was found to be an... 

The Matheson Company Inc. provided VF monomer, which was passed through a column packed with silica gel and molecular sieves (for removal of inhibitor and water), and distilled under vacuum. Urea (Fischer, certified ACS) was recrystallized three times from anhydrous ethanol, and 250 mmol was placed in a bulb attached to a vacuum manifold. Then 160 mmol of purified VF was added to the bulb, followed by a trace of methanol (0.2 ml) to initiate complex... 

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