Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

OP-IV-3conventional flow reactor, the same bulk catalyst was selected as for microreactor preparation(which was prepared with the use of all intermediate procedures for Cu/CeO 2-x washcoatinginto microreactor channels). It was founded that in all cases the CO output concentrationinitially decreased and then increased with temperature over both packed bed reactor andmicroreactor with copper-cerium oxide catalyst (Fig. 1). The minimum value of COconcentration in the microreactor was as low as 10 ppm from 180 to 220 °C. The minimumvalue of CO concentration in the packed bed flow reactor was 800 ppm at 210 °C. Almost100% selectivity was observed in the microreactor at T = 150 °C. A further increase in thetemperature resulted in a dramatic decrease in selectivity to 33%. The same trend wasobserved for the packed bed reactor, but selectivity was no more than 80% at 180 °C andfurther increase in the temperature resulted in a dramatic decrease in selectivity to 33%.[CO], ppm100001000100Packed bed reactor,10 wt. % Cu/CeO 2-xSelectivity, %10080604010Microreactor10 wt. % Cu/CeO 2-x110 140 170 200 230 260Temperature, o C200110 140 170 200 230 260Temperature, o CFigure 1.Effect of temperature on the outlet CO concentration and selectivityInlet gas composition: 60 vol. % H 2 , 1 vol. % CO, 1.5 vol.% O 2 , 20 vol. % CO 2 ,10 vol. % H 2 O, He (N 2 ) – balance. P = 1 atm; WHSV = 45000 cm 3 /g·h.The better performance of the microreactor as compared to the packed bed reactor can beexplained by the following consideration. At high flow rates, the reaction releases significantamount of heat. In microreactor, the released heat dissipates quite readily over metallicplatelet that facilitates the reaching of isothermic state (temperature difference at themicroreactor inlet, center and outlet was no more than 1-2 °C). In the packed bed reactor, thecatalyst bed was not isothermic at high CO conversion rates (the temperature difference at thereactor inlet, center and outlet was 10-15 °C). In the case of hindered heat removal from thecatalyst surface, side reactions tend to proceed. Reverse water gas shift seems to be one ofthese reactions. Due to RWGS, the outlet CO concentration in the packed bed reactorincreases. In the microreactor, no hot spots appear due to prompt dissipation of the releasedheat that facilitates more efficient CO removal.The work is supported partially by grants BRHE Y4-С-08-12, INTAS № 06-1000014-5774, «Global Energy» Foundation.145