مهندسي اندازه حفره هاي نانو كريستال هاي زئوليت 5A سنتز شده از كائولن توسط روش ميكروامولسيون و بررسي جذب آن به وسيله پارافين هاي بلند زنجير

چكيده انگليسي :

Pore Size Engineering of 5A Zeolite Nanocrystal Synthesis Using Kaolin via Microemulsion Technique and Study of its Adsorption by Long Chain Paraffins Hamideh Aahi Hamideh ahi@gmail com Date of Submission 2011 3 7 Department of Chemical Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisor s Name and Email address K Shams K shams@cc iut ac ir Abstract Zeolites are microporous crystalline alumino silicates with cage like structures that have pores of uniform shape The pore size of zeolites is of dimensions in the range of 2 13 which is close to the molecular sizes of most of the chemical compounds Therefore these materials can be employed for selective separation of chemicals on the basis of their differences in molecular size and shape Zeolites have been successfully used as molecular sieves for many commercial applications such as drying of gases and solvents and separation of normal alkanes from isoalkanes cycloalkanes and aromatics Zeolites can be used at high temperatures and pressures and can stay intact in chemically aggressive environments That is why they can also be used in catalytic reactors The pore sizes of different zeolite types are discontinuous and the adsorption and sieving properties of zeolites depend largely on the pore size of the zeolite that is to be used As a result there exists much interest in the structural modification of the existing zeolites such that the pore size of the engineered zeolite is made suitable for a certain selective separation application Pore size engineering of zeolites can be carried by post synthesis procedures such as internal or external surface modification by chemical reactions preadsorption of polar molecules chemical vapor deposition or similar coating processes and thermal treatment or by ion exchange with appropriate ions or micrioemulsion technique during the synthesis of the zeolites Microemulsions usually consist of small droplets of water in oil or oil in water formed by the encapsulation of oil or water inside of a surfactant layer These microemulsions are generally comprised of a surfactant oil a co surfactant and water Because of the coexistence of oil and water in microemulsions there are two advantages in using microemulsions as a medium for zeolite growth during the synthesis process On one hand the microemulsion acts as a nanoreactor and on the other hand the surfactant will coordinate to the crystallographic faces of the growing crystals and affect the growth of the zeolite crystals In this research project 5A zeolite nanocrystals were synthesized using kaolin via microemulsion technique and the effects of the pertinent parameters such as composition of the reactants and intensity of the ultrasound on nanostructural modification were investigated In characterized X ray fluorescence XRF were used to identify ratio in kaolin and Powder X ray addition 4A zeolite was subjected to ion exchange by tin chloride and Sn A zeolite was synthesized and diffraction XRD Scanning Electron Microscopy SEM Energy dispersive X ray spectroscopy EDX were used to confirm zeolite crystallinity phase purity and morphology Then the best sample were subject to adsorption tests using a special cut of kerosene composed of paraffinic hydrocarbons and adsorption and sieving properties of the zeolite were studies by Gas Chromatography GC Results show that the microemulsion induces rapid growth as 4A zeolite formation begins within 2 h of the synthesis compared to 12 h for the samples that were not prepared by the microemulsion technique Also the results show that ultrasound play a great role in reducing the crystal size Microemulsion ultrasound method produces smaller more uniform and purer zeolite nanocrystals with larger pore size and greater ion exchange capacity than the conventional synthesis methods Key words 5A zeolite surfactant microemulsion ultrasound ion exchang

آهي، حميده

مهندسي اندازه حفره هاي نانو كريستال هاي زئوليت 5A سنتز شده از كائولن توسط روش ميكروامولسيون و بررسي جذب آن به وسيله پارافين هاي بلند زنجير

ماده فعال سطحي , امواج فراصوتي , تبادل يوني