Combined steam and CO2 reforming of CH4 using coke oven gas on nickel-based catalyst: Effects of organic acids to nickel dispersion and activity

Enhanced Stability of Spatially Confined Copper Nanoparticles in an Ordered Mesoporous Alumina for Dimethyl Ether Synthesis from Syngas

“…The amounts of acid sites on the solid acid Al 2 O 3 were found to be 0.11, 0.29, and 0.24 mmol of NH 3 /g on the commercial Al 2 O 3 , mesoAl, and mesoAl­(HT), respectively. In general, large acid sites of the supporting materials are responsible for a high dispersion of the supported metals through the selective adsorption of metal ions. ,− Interestingly, total acid sites on the fresh Cu/Al 2 O 3 catalysts were significantly increased to 0.13, 0.45, and 0.42 on the Cu/Al, Cu/mesoAl, and Cu/mesoAl­(HT), respectively, as summarized in Table . These increases seem to be due to a newly formed copper aluminate species, especially on the Cu/mesoAl and Cu/mesoAl­(HT).…”

Synergy Effects of Cobalt Oxides on Ni/Co-Embedded Al2O3 for Hydrogen-Rich Syngas Production by Steam Reforming of Propane

“…The spectra of X-ray absorption near-edge structures (XANES) and their phase compositions are summarized in Table 3 phases was significantly increased up to 0.57 and 0.60 on the reduced and used NCA(4). In addition, the observed larger compositions of the NiO and NiAl 2 O 4 phases on the used NCA catalysts compared to that of the reduced ones can be attributed to a high temperature SRP reaction condition with excess oxidative water vapor [33]. The relative composition of Co species also clearly showed the oxidation states as well as their distributions on the NCA catalysts according to Al/Co ratios.…”

“…However, the specific rates, defined as [converted mols of C 3 H 8 divided by the moles of Ni and Co metals per hour], revealed the lower rate of 0.96 on the NCA(0.5) (largest metal content) with larger metal aggregates with smaller active sites [20] and higher rate of 1.37 on the NCA(2) even though the metal particles on the NCA(2) were aggregated during the SRP reaction. This suggests that the Ni and Co metals have some additional synergy effects through the proper distributions of the active metallic Co nanoparticles on the NCA surfaces as well as optimal formations of the thermally stable spinel CoAl 2 O 4 and NiAl 2 O 3 phases on the bulk CA(2) support [12,32,33,37], as explained in the following section. In addition, the highly reduced NCA(0.5) and NCA(1) revealed a slightly lower H 2 selectivity of 70.1-71.2% and higher CH 4 selectivity of 4.4-5.2% compared to the less reduced NCA(2) with those values of 73.2% and 2.0%, which can be possibly attributed to the more preferential methanation activity as well as coke depositions by possibly inducing the smaller contributions of SRM activity on the metallic Co and Ni surfaces [4][5][6][7][8]33].…”

“…It is worth noting that NCA(3) and NCA(4) had the smallest crystallite sizes of 6.3-6.5 nm (dispersion of 3.0-3.6%) among the reduced NCA catalysts. In addition, the characteristic diffraction peaks assigned to the spinel-type [12,33]. Interestingly, the peaks of the main diffraction at 44.2 • -44.5 • were shifted to the higher two theta values and broadened with a decrease of cobalt contents, especially on the NCA(3) and NCA(4), due to the smaller crystallite formations corresponding to larger surface areas.…”

“…There were insignificant amounts of soft coke precursors formed on the NCA catalysts, which can be hydrogenated to CH 4 at low temperature of~300 • C, however, hard coke precursors detected at the temperature regions of 550-800 • C [38] were mainly observed on all the used NCA catalysts. The hydrogenation peak positions at~600 • C shifted to higher temperatures with an increase of the Al/Co ratio, which was possibly attributed to the formations of much stronger interacting, harder cokes on the Al 2 O 3 -rich surfaces [32,33]. In addition, the relative amounts of those hard coke precursors were found to be decreased with an increase of Al/Co ratios, being especially smaller on the NCA(2) and NCA(3), owing to the smaller crystallites, which can be responsible for less formation of cokes since the larger metallic Ni and Co nanoparticles act as active sites for coke depositions [39].…”