Synthesis Of Zeolites From Attapulgite Clay And Its Applications

Zeolites, crystalline aluminosilicates built from TO4tetrahedra (T=Si and Al), are widely used in industrial processes such as catalysis, adsorption, and ion-exchange due to their large surface areas, uniform and intricate channels, high thermal and hydrothermal stabilities, and excellent shape-selectivity. Normally, aluminosilicate or siliceous zeolites are synthesized under hydrothermal conditions from using pure chemicals such as commercial silicas (e.g. fumed silica, colloidal silica, and water glass) and sodium aluminate in alkaline media at the temperatures of80-200℃. Concerning environmental and economic issues, natural clays such as kaolin have been used as starting raw materials for synthesizing zeolites. Therefore, the use of other natural minerals for synthesizing zeolites still has a challenge. ZSM-5zeolite is an important auxiliary in FCC catalyst. To increase the efficiency of ZSM-5in FCC catalysis process, tansition metals should be introduced into the framework of ZSM-5zeolite, which is costly in conventional industrial process. Therefore, simply and cheap methods are always sought to prepare metal ZSM-5zeolite.In this work, attapulgite is used as silica resource to prepare zeolites both high and low silica/aluminate ratio and Fe/Ti-ZSM-5zeolite in one step without additional iron and titanium resource.The first chapter of this thesis is the introduction of zeolites, including the conception of the zeolites, structure of zeolites, synthesis and mechanics of zeolites, together with a brief introduction of attapulgite.The second chapter of this thesis mainly studies the pretreatment of attapulgite, including different conditions of acid treatment, the morphology of attapulgite, the changes of crystal structure, the variety of chemical composition, and textural parameters before and after pretreatment.The third chapter of this thesis mainly studies the synthesis of high silica zeolites (e.g. ZSM-5, ZSM-22), and aluminum-rich zeolites (e.g. A, X) from attapulgite. The synthesis conditions of each zeolite, transfomation from attapulgite to zeolites, and the characters of the products are all researched in detail.The fourth chapter of this thesis mainly studies the synthesis of Fe/Ti-ZSM-5zeolite from the treated attapulgite mineral consisted of amorphous silica with Fe and Ti species in one step. Researchs focus on the formation of crystal and the characterizations of the products. More importantly, compared with conventional ZSM-5zeolite, Fe/Ti-ZSM-5exhibits good performance in catalytic cracking.