ADSORPTION OF PROPANE ACID ON HIGH-SILICA ZSM-5 ZEOLITES OF NANOSTRUCTURE DIMENSIONS

Physical-chemical characteristics of zeolites, among other things, depend on the ratio of silicon and aluminum in their crystal structure. What makes zeolite particularly interesting is a great possibility of its modification, which results in new materials of desired characteristics. Due to their polyfunctional characteristics and a big spectrum of application in almost all industry branches, the interest in zeolites is constantly growing. This study examined adsorption of propane acid from the aqueous solution on high-silica zeolite samples produced by the modern nanotechnologies in the American company Zeolyst International (sign: CBV 28014). The adsorbents used were NH 4 ZSM-5 zeolite and its modified form-HZSM-5, with the ratio of SiO 2 /Al 2 O 3 equaling 280. Adsorption was examined in the temperature interval from 283 K to 303 K. The results proved that the growth of adsorption temperature resulted in the growth of the quantity of adsorbed propane acid both on the original and on the modified form of ZSM-5 zeolite, which indicated that in addition to physical adsorption the chemisorption also occurred, where the acid molecules were bonded to active centers by stronger chemical bonds. HZSM-5 zeolite, compared with NH 4 ZSM-5 zeolite, as expected, proved to be a better adsorbent for propane acid. obtained adsorption isotherms for the propane - 4 -ZSM-5 curve has propane The quantity of adsorbed by the number of acid is on plateau to Similar form and trend are also shown by the adsorption isotherms for the system propane - HZSM-5 at and temperatures the isotherm gets a typical Langmuir form. USA) was observed from the aqueous solution in the temperature interval from 283 K to 303 K. The specific surface of the original NH 4 -ZSM-5 zeolite is 400 m 2 /g, and specific surface of the modified form of HZSM-5 zeolite is 380 m 2 /g. The quantity of adsorbed acid, expressed by the number of acid molecules, is bigger on the second plateau by around 7 % to 17 %. The adsorption isotherms for the system of propane acid - HZSM-5 (at 283 and 288 K), have a similar form, while at the higher temperatures the curve gets the Langmuir form. A bigger affinity towards propane acid was shown by the modified zeolite, HZSM-5, probably because of a more distinct hydrophobic character of this zeolite compared to NH 4 -ZSM-5.

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