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A peptization mechanism of boehmitewas proposed in this work.The effects of peptization on the properties and performances of afluid catalytic cracking (FCC) catalyst were explored. A boehmitecolloid was prepared through peptization of boehmite with hydrochloricacid, and its particle size distribution was characterized duringpeptization. With an increase of the acid/alumina molar ratio from0 to 0.11, the particle size of the boehmite colloid decreased to3.5 nm. The particle size increased from 3.5 to 11 nm when the acid/aluminamolar ratio was further increased to 0.16 and remained at 10 nm thereafter.The smallest dispersed boehmite particles were obtained in an acid/aluminamolar ratio of 0.11. On the basis of many experiments, the dispersionand coalition mechanisms of boehmite during acid peptization wereproposed. Boehmite particles absorb protons on the surface hydroxylgroups and repel each other to form colloidal particles when the acid/aluminiaratio is low. With more hydrochloric acid added, large amounts ofchloride anions cause compression of the boehmite diffuse layer, thusresulting in boehmite coalition. A FCC catalyst was prepared by peptizingboehmite with an acid/alumina molar ratio of 0.11. The catalyst hasa larger external surface area, a higher mesoporous volume, and betteracidity distribution than the catalyst prepared with boehmite. Bothconversion of residue oil and yields of diesel and gasoline over apeptized catalyst are higher than those over the catalyst withoutbeing peptized. [ABSTRACT FROM AUTHOR]

Nanofibrousboehmite materials with controlled morphology weresynthesized without use of any surfactant by careful tuning of thepH value of the precursor, temperature, and time length of the hydrothermaltreatment, followed by a series of characterizations. When the pHvalue was controlled at 9.5 and hydrothermal treatment temperaturewas controlled at 90 °C for 12 h, the surface area and the porevolume of boehmite reached significantly large values of 367.9 m2/g and 1.01 cm3/g, respectively. The acquired fibrousmorphology can be well kept at 600 °C in the procedure of transformationinto γ-Al2O3. The heat treatment at highertemperatures will result in a morphology change accompanied by theformation of θ- Al2O3or α- Al2O3. The approach of the present study achievesprecise control of the size and morphology of the boehmite nanofibersat low temperatures. [ABSTRACT FROM AUTHOR]