Conversion of methane to propanal at ambient pressure

A continuous process is described using three catalysts in sequence for the synthesis of the C3 oxygenate propanal, from methane and air, at 1 atm in 13.2% yield. The three catalytic reactions are the methane oxidative coupling to ethene, methane partial oxygenation to synthesis gas, and the hydroformylation of ethene. The combined process implies that a higher yield of propanal can be obtained than for the formation of ethene from the oxidative coupling reaction alone. We have examined the effect of reaction conditions on the yield of propanal. © 1993 American Chemical Society

Axial Changes of Catalyst Structure and Temperature in a Fixed-Bed Microreactor During Noble Metal Catalysed Partial Oxidation of Methane

The catalytic partial oxidation of methane (CPO) over flame-made 2.5%Rh–2.5%Pt/Al2O3 and 2.5%Rh/Al$_2$O$_3$ in 6%CH$_4$3%O$_2$/He shows the potential of in situ studies using miniaturized fixed-bed reactors, the importance of spatially resolved studies and its combination with infrared thermography and on-line mass spectrometry. This experimental strategy allowed collecting data on the structure of the noble metal (oxidation state) and the temperature along the catalyst bed. The reaction was investigated in a fixed-bed quartz microreactor (1–1.5 mm diameter) following the catalytic performance by on-line gas mass spectrometry (MS). Above the ignition temperature of the catalytic partial oxidation of methane (310–330 °C), a zone with oxidized noble metals was observed in the inlet region of the catalyst bed, accompanied by a characteristic hot spot (over-temperature up to 150 °C), while reduced noble metal species became dominant towards the outlet of the bed. The position of both the gradient in oxidation state and the hot spot were strongly dependent on the furnace temperature and the gas flow (residence time). Heating as well as a higher flow rate caused a migration of the transition zone of the oxidation state/maximum in temperature towards the inlet. At the same time the hydrogen concentration in the reactor effluent increased. In contrast, at low temperatures a movement of the transition zone towards the outlet was observed at increasing flux, except if the self-heating by the exothermic methane oxidation was too strong. The results indicate that in the oxidized zone mainly combustion of methane occurs, whereas in the reduced part direct partial oxidation and reforming reactions prevail. The results demonstrate how spatially resolved spectroscopy can help in understanding catalytic reactions involving different reaction zones and gradients even in micro scale fixed-bed reactors