Influence of Axial Temperature Profiles on Fe/SiO₂ Catalyzed Non‐oxidative Coupling of Methane

Abstract

The effect of the axial temperature profile upstream and downstream of catalyst bed on the performance of non‐oxidative‐coupling‐of‐methane (NOCM) over Fe/SiO2 was determined. A three‐zone oven was used with independent temperature control of the catalyst‐zone as well as the zones upstream and downstream. It was found that catalytic initiation followed by residence time at 1000 °C downstream the catalyst bed increases CH4 conversion by a factor of 8, while decreasing carbonaceous deposit selectivity from 40 to 12 C%. Residence time at 1000 °C upstream of the catalyst bed causes deposit formation on the catalyst without significantly influencing methane conversion. A shallow catalyst bed followed by significant residence time at high temperature maximizes methane conversion and minimizes coking. This work shows that axial temperature profile and residence time upstream and downstream of the catalyst bed strongly influence the performance in catalytic NOCM.

Effect of ethane and ethylene on catalytic non oxidative coupling of methane

“…The catalyst is synthesized according to the method described in 19 and details concerning the catalyst synthesis as well as characterization can be found in 22 . In short, inhouse synthesized Fe 2 SiO 4 is mixed with quartz and ball-milled in N 2 atmosphere overnight using a zirconia milling jar.…”

“…Product gasses are analyzed using a three-channel Varian CP-3800 inline gas chromatograph, the tubing between the reactor and the GC is heated to 200 °C to minimize hydrocarbon condensation. Further details concerning the reactor setup are presented in 22 .…”

“…Measurements were carried out at temperatures in excess of 950°C. Follow-up research showed that methane conversion can be increased by in-situ hydrogen removal 20 , by using a catalytic wall reactor 21 and by increasing the residence time in the reactor at high temperature downstream the catalyst bed (post-catalytic volume) 22,23 . However, all these studies reported coke formation and lower catalytic activity [19][20][21][22][23][24][25] compared to the original work of Guo et al 19 .…”

“…Follow-up research showed that methane conversion can be increased by in-situ hydrogen removal 20 , by using a catalytic wall reactor 21 and by increasing the residence time in the reactor at high temperature downstream the catalyst bed (post-catalytic volume) 22,23 . However, all these studies reported coke formation and lower catalytic activity [19][20][21][22][23][24][25] compared to the original work of Guo et al 19 . It is generally accepted that the catalyst initiates methane conversion, through formation of methyl radical, followed by free radical chain reactions and coupling reactions in gas phase, determining the product distribution 19,22,25 .…”

“…However, all these studies reported coke formation and lower catalytic activity [19][20][21][22][23][24][25] compared to the original work of Guo et al 19 . It is generally accepted that the catalyst initiates methane conversion, through formation of methyl radical, followed by free radical chain reactions and coupling reactions in gas phase, determining the product distribution 19,22,25 . The publications concerning the Fe/SiO 2 catalyst have focused on a pure methane feed, even though natural gas contains a significant fraction of C 2 hydrocarbons 1 .…”