Preparation, Properties And Applications Of Several Eco-materials Based On Montmorillonite Mineral

Focusing on the present problems that exist in bentonite resource development and utilization such as low-level technology, low resource utilization ratio, serious environmental pollution, short industry chain, poor product performance and high energy consumption; guided by the concept of ecological design, on the basis of the different characteristics of bentonite raw mineral; this thesis develop clean technology of bentonite deep processing with the advantages features including high utilization ratio of resources, less energy-consuming, environmental friendliness and excellent product property. The new montmorillonite ecomaterials obtained through the above technique were featured by excellent property, well environmental benignity and high additional value. Furthermore, the applications of ecomaterials performances in Fischer-Tropsch synthesis process were evaluated as well. This thesis mainly includes three parts:(1) deep processing technology of christobalite-free bentonite;(2) deep processing technology of cristobalite-rich bentonite;(3) application of orgnic modified montmorillonite in Fischer-Tropsch synthesis.The main work is as follow.(1) For christobalite-free bentonite, high purity montmorillonite was prepared by wet sodium modification process, which the purification and modification were carried out simultaneously. The optimal unit operation conditions were determined by researching the influence of wet modification process conditions on product quality and the relationship between them. Consequently, the final montmorillonite content of the resulting high purity sodium bentonite is as high as95.6%. Furthermore, the efficient dewatering of colloidal stable bentonite suspensions presents an intractable challenge for the wet purification process. On the basis of the consideration of the bentonite physical and chemical properties, five natural polymer flocculants, inchuding carboxymethylstach sodium, carboxyl chitosan, guar gum, hydroxypropyl guar gum and cationic hydroxypropyl guar gum, were choosed depending on the structure and property difference. The sodium bentonite slurry flocculation conditions of the five flocculants were studied by spectrophotometry. The bentonite flocculation mechanism of the five flocculants was explored based on their different flocculation properties. The sodium bentonite inorganic gel was prepared by bentonite wet purification slurry as raw material, and calcium oxide or calcium chloride as gel agent. The influences of gel agent type, gel agent dosage, dispersion time, dispersion speed and other reaction conditions on gel performance were compared. The mechanism of sodium bentonite inorganic gel was explored based on the difference gel performance. Finally, the bentonite Litter with advantages features including fast water uptake, more water uptake volume, high whiteness and high strength was prepared by the calcium bentonite..(2) For cristobalite-rich bentonite mineral resources, alkaline purification scheme was utilized economicly, efficiently and sustainably. Consequently, the montmorillonite content of the resulting high purity sodium bentonite through the alkaline purification process is as high as97%. In order to improve the utilization ratio of resources as far as possible and realize the recycl usage of the wastes, silica and nano SiO2were prepared by precipitated the extract wastes of cristobalite-rich bentonite alkaline purification. The effects of different precipitating agents were investigated. The influence of reaction temperature, pH, concentration and reaction time on the properties and yield of silica were compared. The effects of different surfactant on the resulting nano SiO2particle size were investigated as well. Then the optimal precipitation method and condition were determined. The alkaline purification process is not only to achieve the cristobalite-rich bentonite alkaline extraction liquid wastes recycl usage, but also to improve production efficiency, and do not pollute the environment. It reflects the thought of green technology.(3) Organic modified montmorillonite was used as a new carrier for Fischer-Tropsch synthesis. Due to the excellent thermal stability, special gas barrier and temperature switch behavior, the organic modifier as the protective coating of catalyst active components were used to in-situ isolate and protect the actual catalyst structure, consequently, to study the reaction involved in the cobalt-based Fischer-Tropsch synthesis in detail. Just like the original state of ancient organisms preserved well by amber, the polymer chains were in situ solidified to isolate and protect the actual catalyst structure, which ensured the ex situ analyzed catalyst state to fully represent the working state of the catalysts. Accordingly, some critical important issues which could not be studied clearly in past days, such as the phase transformation and sintering agglomeration of cobalt nanoparticles in reduction procedure, the identification and phase transformation of the active species during reaction, and the structure-property relationship of catalysts for the FTS, have been thoroughly revealed. By designing different organic modifiers, we can characterize nanostructure evolution of catalysts of various catalytic reactions under operation reaction conditions via ex situ characterization techniques. Therefore, a new way was opened for the future research of other catalytic systems.