TY - JOUR
T1 - Rh/ZrO2@C(MIL) catalytic activity and TEM images. CO2 conversion performance and structural systematic evaluation of novel catalysts derived from Zr-MOF metallated with Ru, Rh, Pd or In
AU - Alqarni, Dalal S.
AU - Marshall, Marc
AU - Gengenbach, Thomas R.
AU - Lippi, Renata
AU - Chaffee, Alan L.
N1 - Funding Information:
There are several reports that Ru-doped oxides are more active and stable catalysts for CO2 methanation than the usual Ni-based catalysts [20,21]. These advantages may outweigh the extra cost of the noble metal. Recently, Ru embedded in ZrO2 derived from a MOF was compared as a catalyst for CO2 methanation with Ru supported in other ways. Lippi et al. [42] found that even under high gas flow rates, Ru/ZrO2 made by heating Ru/UiO-66 under CO2/H2 converted 98% of CO2, with about 99% selectivity for CH4, and was stable for at least 160 h [42]. The excellent activity and stability of Ru/thermally treated MOFs is not restricted to UiO-66. We previously demonstrated that Ru/ZrO2@C(MIL) prepared by heating Ru/MIL-140C-10 under CO2/H2 was similar in activity and stability to Ru/ZrO2 from Ru/UiO-66, despite the presence of C and differences in the ZrO2 phase proportions [43].In the used, as in the activated [33] In/ZrO2@C(MIL), the In was uniformly dispersed in the 10?20 nm ZrO2 particles (Fig. 7 and Fig. S7), with no indication of distinct In particles. The In, like the Zr, might therefore also be associated with the O, so that the EDX did not indicate the chemical state of the In. The uniform dispersion of the In might be due to the diffusion of low-melting In (156.6 ?C [64]) or relatively low-melting chlorides during activation. The morphology was broadly similar to that of the material prepared by heating the MOF under activation conditions (fresh activated catalyst), though the micrographs of the catalyst after heating under activation conditions did not show the filaments so clearly [33]. The EDX In/Zr peak area ratios (Fig. 7h and Fig. S7(h)) and the analysis of the catalyst after heating under activation conditions suggested that the In concentration in the used catalyst was about 2.9 ? 1.0 wt%, similar to the surface In concentration of 2.4 wt% calculated from the atomic concentrations in Table 2. This was much less than that expected from the analysis of the starting MOF, supporting the earlier suggestion that much of the In was volatilized during activation [33]. TEM images for the used ZrO2@C(MIL) suggested similar morphology to the activated catalyst and the metal-loaded catalysts, with small ZrO2 particles in a carbonaceous matrix (Fig. S8).The authors acknowledge use of the facilities, and the assistance of Dr. Tim Williams, at the Monash Centre for Electron Microscopy. D. Alqarni acknowledges the support of a Saudi Arabian Government scholarship. The authors also acknowledge the Emissions Testbed of the CSIRO Active Integrated Matter Future Science Platform (AIM FSP) for supporting the high-throughput catalyst testing studies and subsequent data processing.
Funding Information:
The authors acknowledge use of the facilities, and the assistance of Dr. Tim Williams, at the Monash Centre for Electron Microscopy. D. Alqarni acknowledges the support of a Saudi Arabian Government scholarship. The authors also acknowledge the Emissions Testbed of the CSIRO Active Integrated Matter Future Science Platform ( AIM FSP) for supporting the high-throughput catalyst testing studies and subsequent data processing.
Publisher Copyright:
© 2022 Elsevier Inc.
PY - 2022/5
Y1 - 2022/5
N2 - A set of novel materials, denoted M/ZrO2@C(MIL) (M = Ru, Rh, Pd & In), were prepared by thermal transformation of MIL-140C containing 10% bipyridine linkers (MIL-140C-10), to provide sites for metal coordination within the framework. These materials were transformed into active catalysts for CO2 hydrogenation when heated in a gas mixture of H2 and CO2 (3:1), at 500 °C. The thermal treatment provided high surface area catalysts with high stability and high Ru or Rh metal dispersion which were very effective for the hydrogenation of CO2 to CH4, giving a CH4 production of 3.0–3.7 mol/g Ru/h or 4.2–4.3 mol/g Rh/h (at 400 °C, 33 bar and WHSV 23 L/h/g cat.). PXRD, XPS and TEM indicated that the effective catalysts consisted of nanoparticles of Ru0 (2–5 nm) or Rh0 (6 nm) associated with larger ZrO2 nanoparticles (10–20 nm), which were dispersed upon carbonaceous ribbons. Interestingly, at 250-350 °C, Pd/ZrO2@C(MIL) yielded mainly CO rather than CH4, with some CH3OH. The CH4 and CO production were not stable at 400 °C. TEM results for this catalyst indicated Pd0 and ZrO2 nanoparticles (initially 20 nm and 10–20 nm diameter, respectively). The lower, unstable activity compared to Ru and Rh could have been due to the initially larger Pd particles and their tendency to grow in size with reaction time. In/ZrO2 has mainly been used to catalyse CH3OH production, but In/ZrO2@C(MIL) gave less CH3OH than In/monoclinic ZrO2 and was less selective. At 400 °C In/ZrO2@C(MIL) was a stable, reverse-water-gas-shift catalyst (producing 0.9 mol CO/g In/h at WHSV 20 L/g cat/h). The In was well dispersed in the ZrO2–C and of small particle size. The poor selectivity for methanol may have been due to the tetragonal phase of the ZrO2 and the low surface In concentration.
AB - A set of novel materials, denoted M/ZrO2@C(MIL) (M = Ru, Rh, Pd & In), were prepared by thermal transformation of MIL-140C containing 10% bipyridine linkers (MIL-140C-10), to provide sites for metal coordination within the framework. These materials were transformed into active catalysts for CO2 hydrogenation when heated in a gas mixture of H2 and CO2 (3:1), at 500 °C. The thermal treatment provided high surface area catalysts with high stability and high Ru or Rh metal dispersion which were very effective for the hydrogenation of CO2 to CH4, giving a CH4 production of 3.0–3.7 mol/g Ru/h or 4.2–4.3 mol/g Rh/h (at 400 °C, 33 bar and WHSV 23 L/h/g cat.). PXRD, XPS and TEM indicated that the effective catalysts consisted of nanoparticles of Ru0 (2–5 nm) or Rh0 (6 nm) associated with larger ZrO2 nanoparticles (10–20 nm), which were dispersed upon carbonaceous ribbons. Interestingly, at 250-350 °C, Pd/ZrO2@C(MIL) yielded mainly CO rather than CH4, with some CH3OH. The CH4 and CO production were not stable at 400 °C. TEM results for this catalyst indicated Pd0 and ZrO2 nanoparticles (initially 20 nm and 10–20 nm diameter, respectively). The lower, unstable activity compared to Ru and Rh could have been due to the initially larger Pd particles and their tendency to grow in size with reaction time. In/ZrO2 has mainly been used to catalyse CH3OH production, but In/ZrO2@C(MIL) gave less CH3OH than In/monoclinic ZrO2 and was less selective. At 400 °C In/ZrO2@C(MIL) was a stable, reverse-water-gas-shift catalyst (producing 0.9 mol CO/g In/h at WHSV 20 L/g cat/h). The In was well dispersed in the ZrO2–C and of small particle size. The poor selectivity for methanol may have been due to the tetragonal phase of the ZrO2 and the low surface In concentration.
KW - CO methanation temperature dependence
KW - In in ZrO–C
KW - Metal particle size/dispersion
KW - Pd
KW - Reverse-water-gas shift
KW - Rh
KW - Ru
KW - Tetragonal ZrO
UR - https://www.scopus.com/pages/publications/85127769986
U2 - 10.1016/j.micromeso.2022.111855
DO - 10.1016/j.micromeso.2022.111855
M3 - Article
AN - SCOPUS:85127769986
SN - 1387-1811
VL - 336
JO - Microporous and Mesoporous Materials
JF - Microporous and Mesoporous Materials
M1 - 111855
ER -