The rate of adsorption of pure CO 2 , O 2 , N 2 , and CH 4 on natural untreated clinoptilolite-rich volcanic tuff (Cp) from Tehuacan (Puebla, Mexico), and on cation-exchanged clinoptilolite samples (Ca-Cp, K-Cp, and Na-Cp) has been measured at 20 °C using a glass high-vacuum volumetric apparatus. The X-ray diffraction pattern of Cp showed that the main crystalline phases correspond to clinoptilolite-heulandite and minor amounts of mordenite, cristobalite, feldspar (albite), quartz, smectite, and opal. The adsorption rates of gases in the initial period (t < 180 s) were measured with a custom acquisition data card capable of registering pressure and time data five times per second, simultaneously. The influence of cation exchange on adsorption kinetics of the gases depended on the gas-adsorbent contact time (t). In the initial period, the adsorption rate of all gases on all samples decreased in the order Ca-Cp > K-Cp > Cp > Na-Cp, and the affinity decreased in the order CO 2 . N 2 > O 2 > CH 4 , whereas at equilibrium (t f ∞ s) the adsorption uptake decreased in the sequence CO 2 . CH 4 > N 2 > O 2 . The slow adsorption of methane in Na-Cp was probably due to diffusional difficulties as a result of channel blockage by Na + cations. By cation exchange of Cp an adsorbent can be tailored for the separation of N 2 /O 2 , N 2 /CH 4 , and CO 2 /CH 4 mixtures.

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ABSTRACT:The use of vegetable oils to replace fossil feedstock has become an area of opportunity and a priority for study in the fi eld of polymer science. Vegetable oils are considered as renewable resources with high potential, low cost and full availability. The aim of this study is the synthesis of biobased polyols from cottonseed oil (Gossypium barbadanse) and corn oil (Zea mays) as feedstock. Their synthesis was successfully performed, as can be concluded from the determination of their hydroxyl index as well as the structural and thermal characterization carried out in this work. Polyurethanes from biobased polyols were synthesized with two different isocyanates (HDI and MDI) and variable polyol/isocyanate ratio and they were further characterized by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and scanning electron microscopy, concluding that cottonseed and corn oils could be considered as valid alternatives for the synthesis of biobased polymeric materials.