Continuous Photocatalytic Steam Reforming of Methanol in the Gas Phase Over Pt/Srtio3

Mechanistic understanding of the thermal-assisted photocatalytic oxidation of methanol-to-formaldehyde with water vapor over Pt/SrTiO3

“…1) which revealed severe changes in catalyst activity, stability and selectivity at temperatures Z120 1C, a mismatch in temperature of about 20 1C was obtained, likely caused by the indirect temperature measurements in DRIFTS studies. 9 Still in general, the low methoxy surface coverage at high temperatures agrees well with the high methanol conversion. The change in selectivity to CO at the expense of formaldehyde and methyl formate formation is in line with the more intense CO band observed in the DRIFTS measurements, and the intensity increase of bands associated to formate suggest its contribution to deactivation of 0.1Pt/STO at higher reaction temperatures.…”

“…5). 9 In the absence of illumination, the amount of physisorbed water decreased as expected indicated by the lower intensity of the characteristic broad band at 3506 cm À1 , but otherwise no significant changes were observed with increasing temperature. Thus, even at 200 1C, no change of the bands from hydroxyl groups (3659 cm À1 and 3691 cm À1 ) or of methoxy groups (2928 cm À1 , 2825 cm À1 , 1152 cm À1 ) were observed indicating a high stability or their fast regeneration from gas-phase water and methanol.…”

“…In STO, paramagnetic OV (V 1+ O ) are only predominant in a relatively narrow window of the Fermi energy around 2.5 eV, while diamagnetic states (V 0 O and V 2+ O ) are predominant over most of the Fermi energy region. 9 The absence of a clearly observable OV-EPR signal in STO and Pt/STO before and after MeOH oxidation studied herein, could therefore either be due to a very low OV abundance or due to OVs in diamagnetic states.…”

“…illumination, while an immediate increase in formaldehyde and methyl formate is detected once the photocatalyst is illuminated. 4,9 CH 3 OH + H 2 O -3H 2 + CO 2…”

“…7,8 Using anaerobic reaction conditions with water as oxidant, photocatalytic conversion of methanol in the gas phase over Pt/SrTiO 3 (Pt/STO) leads to the formation of valuable chemicals like formaldehyde or methyl formate in a distinctive temperature window o120 1C. 9 Operation at temperatures above 120 1C resulted in a higher selectivity to CO at the expense of formaldehyde and methyl formate selectivity, and the photocatalyst was shown to suffer from severe deactivation with time on stream. 9 Moreover, methanol conversion was found to be dependent on the Pt loading and 0.1 wt% of Pt deposited by reductive photodeposition resulted in the highest conversion of methanol.…”