Amines, selective adsorption

Most LB-forming amphiphiles have hydrophobic tails, leaving a very hydrophobic surface. In order to introduce polarity to the final surface, one needs to incorporate bipolar components that would not normally form LB films on their own. Berg and co-workers have partly surmounted this problem with two- and three-component mixtures of fatty acids, amines, and bipolar alcohols [175, 176]. Interestingly, the type of deposition depends on the contact angle of the substrate, and, thus, when relatively polar monolayers are formed, they are deposited as Z-type multilayers. Phase-separated LB films of hydrocarbon-fluorocarbon mixtures provide selective adsorption sites for macromolecules, due to the formation of a step site at the domain boundary [177]. 

Tsuchia, E., Nishide, H. Selective adsorption of metal ions to polymeric amines immobilized by template reaction, in Polymeric amines and ammonium salts (ed.) Goethals, E. J., p. 271, New York. Pergamon Press 1980... 

ABB Lummus Global Acetylene extraction C2S Selective adsorption of acetylene with dimethyl form amine (DMF) 4 1991... 

Fig. 4 Effects of ionic strength on selective adsorption of EPS from a BSA solution containing EPS by the various aminated cellulose adsorbents reported in Pig. 2. The selective adsorption of EPS was determined by a batchwise method with 0.2 g of the wet adsorbent and 2 mL of a sample solution [BSA 500 pg/mL, EPS E. coli 0111 B4) 100 ng/mL, pH 7.0, and ionic strength of p=0.05-0.8].

For these reasons, the effect of support on Ni based catalysts is better shown when comparing the MEA selectivity at low acetonitrile conversions (Table 2). The improvement of primary amine selectivity upon Mg addition could arise from a modification of the acido-basic properties of the support surface. To check any differences in these properties, the acid sites were probed by TPD of NH3 and adsorption of MEA followed by calorimetry. 

The main obstacle to wide employment of organic compositions for impregnation purposes lies in selective adsorption of certain components by the pores of the surface of the impregnated materials. If this happens, the components are separated, leading to disturbance of the system s stoichiometry and to lack of curing. For example, when concrete is impregnated with epoxy resin/amine hardener mixture, the upper part of the concrete becomes impregnated with epoxy resin only, and the deeper parts with hardener. 

Amine grafted silicas are promising sorbents for selective adsorption, especially for applications in enviromnental control and catalysis. For example, Lasperas et al. (1997) and Angeletti et al. (1988) used amine function-modified... 

For selective LPS removal, it is necessary not only to select the ligand of the adsorbent, but also to control the conditions of the buffer (pH and ionic strength). The effect of ionic strength on the selective adsorption of LPS from a BSA-containing solution by various aminated cellulose adsorbents 2x10 ) was examined (results are... 

As noted earlier, carbon dioxide is present in all the reactor effluents. Since CO2 is considered an impurity, it must typically be eliminated. In most designs, the CO2 is removed from the process gas by selective adsorption in a suitable solvent such as an amine solution. The CO2 is then stripped from the solvent as a separate stream. 

In the same spirit DFT studies on peroxo-complexes in titanosilicalite-1 catalyst were performed [3]. This topic was selected since Ti-containing porous silicates exhibited excellent catalytic activities in the oxidation of various organic compounds in the presence of hydrogen peroxide under mild conditions. Catalytic reactions include epoxidation of alkenes, oxidation of alkanes, alcohols, amines, hydroxylation of aromatics, and ammoximation of ketones. The studies comprised detailed analysis of the activated adsorption of hydrogen peroxide with... 

An alternative approach to increase the oxidation rate is the use of alkaline solutions, because bases enhance the reactivity of L-sorbose and weaken the adsorption strength of 2-KLG. Unfortunately, the rate enhancement at higher pH is accompanied by a drop in selectivity due to the poor stability of 2-KLG in alkaline solutions. To circumvent this problem, we have modified the platinum catalysts by adsorbed tertiary amines and carried out the oxidation in neutral aqueous solution [57], This allowed to enhance the rate without increasing the pH of the bulk liquid, which leads to detrimental product decomposition. Small quantities of amines (molar ratio of amine sorbose = 1 1700, and amine Pts = 0.1) are sufficient for modification. Using amines of pKa a 10 for modification, resulted in a considerable rate enhancement (up to a factor of 4.6) with only a moderate loss of selectivity to 2-KLG. The rate enhancement caused by the adsorbed amines is mainly determined by their basicity (pKa). In contrast, the selectivity of the oxidation was found to depend strongly on the structure of the amine. 

---