High conductivity catalyst structures for applications in exothermic reactions

Highly exothermic catalytic reactions are problematic from a thermal management perspective and often dictate the type of reactor, heat exchanger, level of conversion/recycle and contacting scheme that are employed. To investigate the opportunity for enhanced heat transfer structures, 15 wt% Co/Al2O3 catalyst particles (149–177 μm dia.) were examined in both a packed bed configuration and after being entrapped within a 7.4 vol.% network of sintered Cu fibers (12 μm dia.). Fischer–Tropsch synthesis (FTS) at 225–255 °C, 20 bar, H2/CO of 2.0, was utilized as the probe reaction due to its exothermicity and temperature dependent selectivity. Both the hot spot and runaway state were prevented by utilizing metal microfibrous entrapped catalyst (MFEC) compared to the packed bed. In a 41 mm ID reactor, the maximum temperature deviation from the centerline to the reactor wall was only 6.4 °C for the copper MFEC. In contrast, the packed bed diluted to the same catalyst density and operated at an equivalent condition had a centerline temperature deviation of 460 °C indicating ignition. The more isothermal temperature profile through the catalyst bed of the copper MFEC led to a higher selectivity of heavy products than that of the packed bed. Also, it enabled a larger reactor diameter to be used with more precise and robust temperature control.

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► We determined the overall heat transfer coefficient for PB and MFEC.
► We examined the performances of these two catalyst structures in FTS.
► The enhanced heat transfer property of MFEC improved the thermal severity of FTS.
► Uniform temperature profile in MFEC resulted in slow catalyst deactivation.
► It also improved the heavy product selectivity.