Distribution in strength of the acid centers in sulfonic cation in the form of exchanger granules and fibers was studied by the novel modification of the thermal desorption method.Previously [133], we studied the activity of sulfonic cation exchanger granules and fibers in the synthesis of methyl tert-alkyl ethers and found that FIBAN K-1 surpasses in the activity KU2-8 (gel structure) in the synthesis of methyl tert-butyl ether (MTBE) and Dowex msm 31 (macroporous structure) in the synthesis of methyl tert-amyl ether (MTAE).The main advantage of fibrous sulfonic cation exchanger FIBAN K-1 is that the fiber diameter is by approximately an order of magnitude smaller than the diameter of KU-2-8 and Dowex msm 31 granules. This decreases intradiffusion inhibition and intensifies mass exchange.The diameter of the Carbopon fiber can be estimated as 5310 mm, which is substantially smaller than FIBAN K-1 fiber diameter. Hence, sulfonic cation exchanger supported on Carbopon, when used as a catalyst of acid3base reactions, can provide more intense mass exchange than FIBAN K-1.The performance of sulfonic cation exchanger substantially depends on its acidity, i.e., concentration and strength of acid centers. The literature survey [4 3 6] shows that the most adequate method of its determination is ammonia thermal desorption. However, for organic ion exchangers with a low thermal stability, ammonia is acceptable only for determination of weak acid centers. To determine strong acid centers, another thermal desorption method is required.In this work, we studied sorption and acid properties and catalytic activity (by an example of MTAE synthesis) of two samples of sulfonic cation exchanger supported on Carbopon (sample I with gel structure and sample II with macroporous structure) in comparison with their structural analogs, fibrous (FIBAN K-1) and granular (Dowex msm 31) sulfonic cation exchangers.
EXPERIMENTALThe sorption of various liquids with the initial Carbopon, synthesized samples of the supported sulfonic cation exchanger, FIBAN K-1 fibrous sulfonic cation exchanger with gel structure, and Dowex msm 31 granular sulfonic cation exchanger with macroporous structure was evaluated gravimetrically. A cation exchanger sample (~0.5 g) dried to the constant weight at 90oC was introduced into a test tube, 10 ml of a liquid was added, and the mixture was stored for 3 h. The sample was centrifuged (4000 rpm) for 15 min, weighed, and dried to the constant weight at 90oC. The sorption value, G l (g l g 31 ), was calculated as the ratio of the liquid weight to the weight of dry sample:where m 1 is the sample weight after centrifuging and m 2 , sample weight after drying at 90oC.The average value of three parallel experiments was used in calculations. Along with G l , the volume sorption V l (cm l 3 g 31 ) was also calculated.As seen from Table 1, sorption of water with Carbopon is 0.64 g l g 31 , which is substantially larger than sorption of methanol and the other components of the reaction mixture of the MTAE synthesis, and of n-oc...
