Abstract
Recently a new In-promoted Ni catalyst has been elaborated and published in our laboratory, that has beneficial properties in dry reforming of methane, including inhibited coking. In order to get deeper insights into the coke-free behavior of this SiO2-supported 3wt% Ni 2wt% In catalyst, we wished to monitor the interaction between CO and the catalyst. For this purpose DRIFTS studies under CO, CO2 or CO2+CH4 flow at different temperatures and CO pulse flow experiments at 600 oC followed by mass spectrometry were carried out. A linear carbonyl band at 2013 cm-1 in the DRIFT spectra of the In-promoted catalyst was attributed to CO bonded on Ni atoms surrounded by In neighbors. The lack of bridge and multi-coordinated carbonyls also proved the dilution of Ni surface with In. In the presence of a CH4:CO2=70:30 dry reforming mixture, stable Ni bonded CO species were found on NiIn/SiO2 suggesting that the metallic sites remained clean during the reaction (unlike on the reference Ni/SiO2). At the end of the refo...
Highlights
The unconventional natural gas resources such as shale gas or methane hydrates are sought to contribute to the future energy and material needs of mankind
= 1.8 where nm), probably n = 2−3).[16,17] in the form The band at of subcarbonyls (Ni(CO)n, 2051 cm−1 can be assigned to both chemisorbed monocarbonyls and physically adsorbed tetracarbonyls, while the band with a maximum at 1942 cm−1 and a broad shoulder around 1820 cm−1 can be determined as bridge or multibonded carbonlys on low index planes with different surface heterogeneities.[16,17]
In our case the small particle size is reflected in the dominancy of the subcarbonyl band; significant restructuring or nickel loss due to the formation and decomposition of tetracarbonyls seemed improbable, as the decrease of the 2051 cm−1 band stopped and the other bands practically did not change during CO chemisorption
Summary
The unconventional natural gas resources such as shale gas or methane hydrates are sought to contribute to the future energy and material needs of mankind. The experimental approach of this work was (i) to record infrared spectra under CO, CO2, or CO2 + CH4 flow at different temperatures because CO stretching frequency is highly sensitive to the electronic properties of the site to which it is bonded (possible answer to our first two questions above) and (ii) to quantify by mass spectrometry the gas phase and deduce the surface-kept species formed during CO pulses on pure Ni and In-promoted samples to investigate the contribution of the Boudouard reaction to the coke formation during dry reforming of methane (possible answer to our third and fourth questions above). The information obtained is to be correlated with the dry reforming behavior detailed in our earlier publication.[5]
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