Influence of the catalyst loading on the activity and the CO selectivity of supported Ru catalysts in the selective methanation of CO in CO2 containing feed gases

Abstract

We have investigated the methanation of CO and CO 2 over Ru/zeolite catalysts with different Ru loading in semi-realistic reformate gases by in situ X-ray absorption spectroscopy (XAS), in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and kinetic measurements. Increasing the Ru loading causes an increase of the mean particle size from 0.9 nm (2.2 wt.% Ru) to 1.9 nm (5.6 wt.% Ru). At the same time, also the activity for CO methanation increases, while the selectivity for CO methanation, which is constant at 100% for reformate gases with 0.6% CO, decreases at low CO contents. The latter findings are interpreted in terms of a change in the physical effects governing the selectivity for CO methanation with increasing Ru particle size, from an inherently low activity for CO 2 dissociation and subsequent CO ad methanation on very small Ru nanoparticles to a site blocking mechanism on larger Ru nanoparticles. In the latter mechanism, CO 2 methanation is hindered by a reaction inhibiting adlayer of CO at higher CO ad coverages, i.e., at not too low CO concentrations, but facile in the absence of a CO adlayer, at lower CO concentrations in the reaction gas mixture.

Improved Performance of Ru/γ‐Al2O3 Catalysts in the Selective Methanation of CO in CO2‐Rich Reformate Gases upon Transient Exposure to Water‐Containing Reaction Gas

“…On the other hand, it is well known that CO adsorption is weaker on smaller Ru particles than that on larger ones. [18] In total,t his results in al ower CO ad coverage for Ru/Al 2 O 3 with smaller Ru particles under otherwise identical, dry reaction conditions.…”

Coke oven gas: Availability, properties, purification, and utilization in China

“…Ni is the most studied and considered the most suitable catalyst for methanation of carbon oxides because of its high selectivity for CH 4 and its relatively low price [91][92][93][94]. Different support materials have been used for the dispersion of Ni and other active metals, including SiO 2 , Al 2 O 3 , TiO 2 , ZrO 2 , CeO 2 , and zeolite [95][96][97][98][99]. The activity and selectivity of the supported metal catalysts are strongly affected by the amount of metal loading, the size of the dispersed metal particles, the interactions between the support and the active species, and the composition of the support material [100].…”

The Effect of the Ruthenium Crystallite Size on the Activity of Ru/Carbon Systems in CO Methanation

“…Okuhara et al [27] reported an increase of TOF of CO methanation as the dispersion of Ru decreased in Ru/Al 2 O 3 systems. Eckle et al [29] discovered that increasing the Ru mean particle size from 0.9 to 1.9 nm causes an increase of activity for CO methanation over Ru/zeolite catalysts. Extended studies performed by Panagiotopoulou et al [13] demonstrated that TOF of CO/CO 2 hydrogenation over Ru catalysts depends on the metal crystallite size.…”