Hydrogenation of α-Methylstyrene in a Piston-Oscillating Monolith Reactor

Abstract

The hydrogenation of R-methylstyrene (AMS) to cumene was investigated in a novel piston-oscillating monolith reactor (POMR). Low-frequency (0-17.5 Hz) and -amplitude (2.5 mm) mechanical oscillations were applied to the three-phase system at 46 °C and 0.44 MPa of H 2 . For comparison purposes, the reaction was also carried out in a stirred tank at identical temperatures and pressures and at similar power input per volume. Results show activity improvements of up to 84% for 17.5 Hz, 2.5 mm piston oscillations over low-frequency gas flow pulsing conditions, and significantly greater improvements when compared to trickle beds or conventional monolith reactors. The POMR also gives as good or better selectivity toward cumene than a stirred tank at identical conditions. While the effects of catalyst pretreatment and its impact on the Pd crystallite size also have an important role in determining the catalyst activity and long-term stability in AMS hydrogenation, these results suggest that the impact of low-frequency and -amplitude oscillations, applied to structured reactors, is considerable.

Partial Hydrogenation of Soybean Oil in a Piston Oscillating Monolith Reactor

“…Previously it has been also reported that oscillations cause pressure fluctuations in such a reactor. 25 The standard deviations of the reactor pressure at various frequencies are listed in Table 1; it is seen that for a reaction that is first (12) order in H 2 , the observed enhancements in k cannot be explained by the variation in pressure. For comparison purposes, soy oil hydrogenation was also carried out in a stirred vessel using the same type of monolithic catalyst as in the POMR and under identical temperature and pressure conditions.…”

“…A more detailed discussion of these mass transfer calculations can also be obtained from our previous work. 25 By combining these three steps the overall volumetric mass transfer coefficient (k ov a) can be determined as 41 Using these equations, the values of the individual volumetric mass transfer coefficients were computed at the conditions of this study. The gas superficial velocity was fixed for all experiments based on the gas recycle rate.…”

“…25 It has also been shown that this arrangement allows for a more homogeneous gas distribution and higher interfacial areas due to enhanced bubble breakage. The reactor is operated in semibatch mode as H 2 is allowed to enter the reactor to replace the H 2 consumed.…”

“…25 These improvements result from low frequency/amplitude oscillations that enhance external gas mass transfer to the surface, while also altering the surface wetting behavior. The liquid films are apparently reduced in thickness for at least part of the cycle.…”

Effect of method of preparation on activity of Pd/Al2O3 monolith catalysts

“…The catalyst adhesion properties were improved by using pseudo-boehmite as a binder. Bussard et al (2008) obtained well-adhered Pd/Al 2 O 3 monolith catalyst for hydrogenation of -methyl styrene (AMS) using palladium deposited -alumina powder without any binder. Usually investigators have prepared monolith catalysts by a two-step process.…”