Thermal stability of nano-KH particles and their chemical reactivities

The variation of specific surface area and chemical reactivity of nano-KH particles treated at different temperatures has been studied, The BET surface area of nano-KH decreases with the increase of heat treatment temperature, while the chemical reactivity per unit surface increases steadily. These results indicate that the state of KH surface is changed after heat treatment. Large specific surface area of nano-KH is a major factor for its high chemical reactivity, nevertheless, the surface in an activated state with high surface energy is also an important factor for its high chemical reactivity. Nano-KH alone can polymerize styrene rapidly with the formation of polystyrene.

The study of Ti doped ZSM-5 particles and cavities inside them

The TEM study of titanium-containing ZSM-5 zeolite before and after hydrothermal treatment was performed. The use of different TEM techniques, such as conventional TEM, HRTEM and EDX-line scans provides important information about the microscopic structure of the zeolite catalyst consisting from several phases. The hydrothermal treatment of zeolite powder leads to strong changes in the morphology of the constituting particles. They are characterized by a homogeneous structure before hydrothermal treatment while the occurrence of holes after thermal treatment was observed, These changes lead to the enrichment of zeolite with titanium which obviously enhance its catalytic activity. Some of the titanium surplus precipitates as TiO2 anatase nanoparticles within the holes. (C) 2001 Elsevier Science B.V. All rights reserved.

Large-pore mesoporous SBA-15 silica particles with submicrometer size as stationary phases for high-speed CEC separation

A new mesoporous sphere-like SBA-15 silica was synthesized and evaluated in terms of its suitability as stationary phases for CEC. The unique and attractive properties of the silica particle are its submicrometer particle size of 400 nm and highly ordered cylindrical mesopores with uniform pore size of 12 nm running along the same direction. The bare silica particles with submicrometer size have been successfully employed for the normal-phase electrochromatographic separation of polar compounds with high efficiency (e.g., 210 000 for thiourea), which is matched well with its submicrometer particle size. The Van Deemeter plot showed the hindrance to mass transfer because of the existence of pore structure. The lowest plate height of 2.0 mu m was obtained at the linear velocity of 1.1 mm/s. On the other hand, because of the relatively high linear velocity (e.g., 4.0 mm/s) can be generated, high-speed separation of neutral compounds, anilines, and basic pharmaceuticals in CEC with C-18-modified SBA-15 silica as stationary phases was achieved within 36, 60, and 34 s, respectively.