Fine particles Silicoaluminophosphate-34 were synthesized by hydrothermal sol-gel method. The effect of crystallization time, as one of the important synthesis factors on particle size and crystallinity, kinetic and equilibrium adsorption, and selectivity of CO2 / CH4 has been studied in this work. The adsorption isotherms are obtained at moderate gauge pressures (100 - 3000 kPa) and temperatures (278, 288 and 298 K), and the equilibrium adsorption parameters as well as heat of adsorption are determined for the synthesized SAPO-34. The observed adsorption selectivity of CO2 to CH4 was determined to be around eight for that sample with higher degree of crystallinity. The crystallinity, isotherm parameters, adsorption selectivity and heat of adsorption confirm that the synthesized fine particle of SAPO-34 could be a good candidate for separation of CO2 from CH4.

Zeolites due to their structures can be used as molecular sieves for purification of materials and solutions. Zeolites with PHI and SOD structure are so common and applicable for this purpose. Hydroxy sodalite and phillipsite are the more abundant members of zeolites which display good selectivity for very small molecules and some ions such as Sr, Pb, Zn, Cu and Rb. There is not any pure natural deposit of these zeolites and purify methods are not cost-effective. Therefore, introducing an effective method to prepare these zeolites is necessary. In this study, hydroxy sodalite and phillipsite have been synthesized respectively from clinoptilolite and volcanic ash at hydrothermal conditions in the presence of alkaline solutions. Mineralogical studies show that K, Na and Cl ions are necessary in SOD and PHI structure. The effect of K+ concentrations and temperature in the presence of constant value of Na+ and Cl- are being considered as the variable parameters in the present experiment. NaCl used as source of Na+ and Cl- ions. Alkaline solutions were prepared by using 2 to 12 grams KOH powder and synthesize mixture were heated at temperatures of 100 and 150oC. Results of this study show that phillipsite is synthesized at 100 and 150oC in all runs. Hydroxy sodalite is appeared just in 150oC by using clinoptilolite as initial material. Analcime formed as by-product of volcanic ash phase transition at 150oC.

Separation of nitrogen from a gaseous mixture is required for many industrial processes. In this study, the adsorption of nitrogen on zeolite 4A was investigated in terms of different adsorption isotherm models and kinetics. An increase in the initial pressure from 1 to 9 bar increases the amount of adsorbed nitrogen from 6. 730 to 376. 030 mg/(g adsorbent). The amount of adsorbed nitrogen increased from 7. 321 to 40. 594 mg/(g adsorbent) by raising the temperature from 298 to 333 K at a pressure equal to one bar; however, it then dropped to 15. 767 mg/(g adsorbent) when temperature decreased to 353 K. Increasing the amount of the adsorbent from 1 to 4 g decreased the specific adsorption from 67. 565 to 21. 008 mg/(g adsorbent) at a temperature of 298 K and a pressure of 3 bar. Furthermore, it was found that the nitrogen adsorption experimental equilibrium data are consistent with Sips and Langmuir-Freundlich models. The highest overlap was achieved through second order and Ritchie’ s models.

In this study, Kaolin, Bentonite, and Feldspar were used as a low-cost source of Si and Al to synthesize the molecular sieve 13X. The synthesized Zeolites were characterized by XRD, FTIR, SEM, TGA, and BET analysis and used as a suitable adsorbent for CH4 adsorption. The surface areas were 591, 505, 472, and 588 m2/g for natural kaolin (13X-K), bentonite (13X-B), feldspar (13X-F) and commercial molecular sieve 13X (13X–C), respectively. The 13X-K had the highest thermal stability than 13X-B and 13X-F. The adsorption capacities (pressure >20bar) of 13X (kaolin), 13X (bentonite), and 13X(feldspar) were 3.6, 2.4, and 1.95 mmol/g, respectively. The adsorption data were fitted to some isotherms including Langmuir, Freundlich, Sips, BET, and Toth. It was found that the Sips model showed better fitting in comparison to other models. The thermodynamic of adsorption was also investigated; the positive value of ∆S_ads^0 revealed the increased randomness at the solid-solution interface during the gas adsorption. The thermodynamic study also indicated that the adsorption process was exothermic and spontaneous. The adsorption capacities of synthesized 13X samples were compared to other adsorbents; it was found that 13X–K showed considerable performance and can be introduced as a suitable adsorbent for applications on a large scale.