Sunhwan Hwang

The stability of a fluid layer heated uniformly from below

The onset of convective motion in a horizontal fluid layer under constant flux heating is analyzed by the modified frozen-time analysis confining temperature disturbances within a thermal penetration distance. For this purpose a new mathematical method is introduced in detail. It is found that the present stability analysis predicts the most reliable critical conditions based on the comparisons with the published experiments and theoretical models. At τc <0.01, the stability conditions lead to Rac = 14.1 τc-2 and ac = 0.248 Rac1/4 and the period required for the growth of disturbances to a detectable size is inversely proportional to Rac1/2.

Microporous and mesoporous ZSM-5 catalyst for catalytic cracking of C5 raffinate to light olefins.

ZSM5 catalysts (PAM(X)-ZSM5) with micropores and mesopores were prepared using polyacrylamide (PAM) as a soft template at different PAM content (X = 0, 0.12, 0.25, 0.53, 0.64, and 0.78 wt%), and they were applied to the production of light olefins (ethylene and propylene) through catalytic cracking of C5 raffinate. The effect of PAM content of PAM(X)-ZSM5 catalysts on the physicochemical properties and catalytic activities was investigated. N2 adsorption-desorption isotherms of PAM(X)-ZSM5 catalysts exhibited a broad hysteresis loop at high relative pressure, indicating the existence of mesopores in the catalysts. It was found that the catalytic performance of PAM(X)-ZSM5 catalysts was closely related to the mesoporosity of the catalysts. Conversion of C5 raffinate and yield for light olefins showed volcano-shaped trends with respect to mesopore/micropore volume ratio of the catalysts. Thus, an optimal PAM content was required to achieve maximum production of light olefins through catalytic cracking of C5 raffinate over microporous and mesoporous PAM(X)-ZSM5 catalysts.