Acidic cation-exchange

Dowex 50W-X2 0.6 0.70 Strongly acidic cation exchanger with S-DVB matrix for separation of peptides, nucleotides, and cations. Molecular weight exclusion <2700. 

Weakly acidic cation exchangers—gel type—carboxylic acid functionality... 

Bio-Rex 70 2.4 0.70 Weakly acidic cation exchanger with car-boxylate groups on a macroreticular acrylic matrix for separation and fractionation of proteins, peptides, enzymes, and amines, particularly high molecular weight solutes. Does not denature proteins as do styrene-based resins. 

Acidic Cation-Exchange Resins. Brmnsted acid catalytic activity is responsible for the successful use of acidic cation-exchange resins, which are also soHd acids. Cation-exchange catalysts are used in esterification, acetal synthesis, ester alcoholysis, acetal alcoholysis, alcohol dehydration, ester hydrolysis, and sucrose inversion. The soHd acid type permits simplified procedures when high boiling and viscous compounds are involved because the catalyst can be separated from the products by simple filtration. Unsaturated acids and alcohols that can polymerise in the presence of proton acids can thus be esterified directiy and without polymerisation. 

In many industrial appHcations, strong acid cation-exchange resins are used in the hydrogen form to process Hquids containing low concentrations of salts. 

Weak acid cation exchangers have essentially no abiUty to spHt neutral salts such as sodium chloride [7647-14-5]. On the other hand, an exchange is favorable when the electrolyte is a salt of a strong base and a weak acid. 

The acryHc weak base resias are syathesized from copolymers similar to those used for the manufacture of weak acid cation-exchange resias. For example, uader appropriate temperature and pressure conditions, a weak acid resia reacts with a polyfuactioaal amine, such as dimethylaminopropylamine [109-55-7] (7) to give a weak base resia with a tertiary amine fuactioaaHty. 

Examples of pressure drop variation for new resin as a function of flow rate and water temperature are shown in Eigure 5 for a standard styrenic strong acid cation exchanger. The lower pressure drop at the higher temperature is a reflection of water viscosity. 

Eig. 5. Pressure drop as affected by resin type, flow rate, and temperature, where A, B, and C, correspond respectively to acryUc strong base anion exchanger (Amberlite IRA-458), styrenic strong base anion exchanger (Amberlite IRA-402), and styrenic strong acid cation exchanger (Amberlite IR-120), all at 4°C. D represents styrenic strong acid cation resin (Amberlite IR-120) at 50°C (14). To convert kg/(cm -m) to lb/(in. -ft), multiply by 4.33 to convert... 

When strong acid cation exchangers are used in the Na" form and strong base anion exchangers are used in the CL form, they are regenerated with a 10% sodium chloride [7647-14-5], NaCl, solution. Other concentrations may be used, perhaps with some adjustment in flow rate. 

Another alternative involves the use of a weak acid cation exchanger in the hydrogen form. This resin is not capable of removing aH cations. It removes only the amount equivalent to the bicarbonate in the influent water. The acidity in the effluent stream is carbonic acid [463-79-6] which can be eliminated by installing a degasifter. 

Sucrose is inverted, or converted, to an approximate 50—50 mix of fmctose and glucose by hydrochloric acid or a strong acid cation exchanger in the hydrogen form. 

Methyl Isopropenyl Ketone. Methyl isopropenyl ketone [814-78-8] (3-methyl-3-buten-2-one) is a colorless, lachrymatory Hquid, which like methyl vinyl ketone readily polymerizes on exposure to heat and light. Methyl isopropenyl ketone is produced by the condensation of methyl ethyl ketone and formaldehyde over an acid cation-exchange resin at 130°C and 1.5 MPa (218 psi) (274). Other methods are possible (275—280). Methyl isopropenyl ketone can be used as a comonomer which promotes photochemical degradation in polymeric materials. It is commercially available in North America (281). 

The choice of catalyst is based primarily on economic effects and product purity requirements. More recentiy, the handling of waste associated with the choice of catalyst has become an important factor in the economic evaluation. Catalysts that produce less waste and more easily handled waste by-products are strongly preferred by alkylphenol producers. Some commonly used catalysts are sulfuric acid, boron trifluoride, aluminum phenoxide, methanesulfonic acid, toluene—xylene sulfonic acid, cationic-exchange resin, acidic clays, and modified zeoHtes. 

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