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We report the significantly enhanced CO oxidation activity of Pd nanoparticles covered with [Zr6O4(OH)4(BDC)6] (UiO-66, BDC = 1,4-benzenedicarboxylate). The catalytic activity was much higher than those of Pd and Ru nanoparticles on ZrO2. The origin of the enhancement was suggested to be a change in the CO adsorption properties on Pd nanoparticles. [ABSTRACT FROM AUTHOR]

Ru is an important catalyst in many types of reactions. Specifically, Ru is well known as the best monometallic catalyst for oxidation of carbon monoxide (CO) and has been practically used in residential fuel cell systems. However, Ru is a minor metal, and the supply risk often causes violent fluctuations in the price of Ru. Performance‐improved and cost‐reduced solid‐solution alloy nanoparticles of the Cu‐Ru system for CO oxidation are now presented. Over the whole composition range, all of the CuxRu1−x nanoparticles exhibit significantly enhanced CO oxidation activities, even at 70 at % of inexpensive Cu, compared to Ru nanoparticles. Only 5 at % replacement of Ru with Cu provided much better CO oxidation activity, and the maximum activity was achieved by 20 at % replacement of Ru by Cu. The origin of the high catalytic performance was found as CO site change by Cu substitution, which was investigated using in situ Fourier transform infrared spectra and theoretical calculations. Copper helps out: The weakening of the CO adsorption energy on Ru atoms by alloying with Cu atoms plays an important role in the enhancement of the CO oxidation activity of CuxRu1−x nanoparticles. The weakening of the CO adsorption energy on Ru atoms originating from the CO adsorption site change was confirmed by experimental and theoretical investigations. [ABSTRACT FROM AUTHOR]

The activity of Pt catalysts supported on AlO modified with various acid-base additives has been investigated for oxidation of NO to NO. Although Pt dispersion was changed by the additives, there was no clear effect of Pt dispersion on the catalytic activity. The measurement of solid acid-base properties of the modified Pt/AlO indicated that the NO oxidation activity increased by the increase of surface density of strong acid sites and decreased by the increase of basic sites. It was suggested that platinum on the acidic supports keeps its highly active metallic state for NO oxidation, while the formation of nitrate/nitrite on the basic supports inhibits the reaction on the Pt surface. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines the effect of the addition of Y2O3 in ZrO2 support, on the support basicity, the Pt dispersion and the catalytic activity for the oxidation of n-C4H10. The ZrO2 supports, with and without 2mol% of Y2O3, and the supported-Pt catalysts calcined at 600 and 900°C have been studied. The basicity and acidity of ZrO2 determined by CO2-TPD and NH3-TPD was improved by Y2O3 dopant. Catalyst characterizations such as XRD, CO chemisorption and CO adsorption followed by IR spectroscopy demonstrated the positive effect of Y2O3 dopant to increase the stability of Pt particles even at high calcination temperatures, and so to increase the catalytic activity. [Copyright &y& Elsevier]

The catalytic performance of Pt/AlO for the total oxidation of a hydrocarbon mixture of n-decane and 1-methylnaphthalene was investigated by using in situ FT-IR spectroscopy. Although carbonate and/or carboxylate species were mainly detected under steady-state conditions, the formation of an acrylate species during the initial stage of the reaction was observed under transient conditions. Based on a comparison of the reaction and formation behavior of the acrylate species and CO as a gaseous product, it was proposed that the total oxidation of the hydrocarbon mixture proceeds via the formation of an acrylate species as a reaction intermediate. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Abstract: The addition of Nb2O5 was found to promote considerably the catalytic activity of Ir/SiO2 for the selective reduction of NO with CO under excess O2- and SO2-free conditions. Improvement of durability against oxidation of Ir metal by Nb2O5 addition is the main reason for the activity enhancement. Adding Nb2O5 to Ir/SiO2 (Nb2O5/Ir/SiO2) was more effective than using Nb2O5/SiO2 support for Ir (Ir/Nb2O5/SiO2). The excellent activity of Nb2O5/Ir/SiO2 can be attributed to the strong interaction of Ir with Nb2O5 as well as high Ir dispersion. [Copyright &y& Elsevier]

Abstract: The effect of metal additives on the catalytic performance of Ir/SiO2 catalyst for the selective reduction of NO with CO in the presence of O2 and SO2 was investigated. Among the 19 additives tested here, the addition of barium was the most effective to enhance the activity of Ir/SiO2 at low temperature and low SO2 concentration. Catalyst characterization suggested that barium prevents catalyst deactivation as an oxidation-retardant for the active Ir metal supported on SiO2. [Copyright &y& Elsevier]

Abstract: The effect of metal additives on the catalytic performance of Rh/SiO2 for the selective reduction of NO with H2 in the presence of O2 and SO2 was investigated. The addition of Zn was effective to enhance the catalytic activity of Rh/SiO2 for NO reduction at low temperatures and high O2 concentrations. The structural characterizations of Zn/Rh/SiO2 samples and in situ FT-IR measurements revealed that Zn additive plays two important roles in enhancing the catalytic activity of Rh/SiO2: (i) prevention of catalyst deactivation as an oxidation–retardant for the active Rh metal species supported on SiO2 and (ii) promotion of a reaction step, which generates NH x species as a key reaction intermediate for NO reduction by H2 in the presence of O2 and SO2. [Copyright &y& Elsevier]

Heterogeneous Catalysis. In their Communication on page 2230 ff., H. Kitagawa et al. show that decreasing the CO adsorption energy on Ru atoms by alloying with Cu atoms enhances the CO oxidation activity of CuxRu1−x nanoparticles. [ABSTRACT FROM AUTHOR]

The catalytic activity of Ir/WO3/SiO2 for the selective reduction of NO with CO (CO-SCR) in the presence of excess O2 was significantly increased by the presence of coexisting H2O, whereas NO reduction hardly occurred in the absence of H2O. Coexisting H2O plays an important role preventing catalyst deactivation caused by oxidation of the catalytically active Ir sites at high temperatures. [ABSTRACT FROM AUTHOR]

Abstract: This paper provides novel knowledge about the positive effect of ZrO2 sol addition on CeO2–ZrO2 mixed oxides (CZ) catalyst for the total oxidation activity of toluene. The composite catalysts of CZ powders with 6–23wt.% ZrO2 prefer to make better microstructure for catalytic oxidation activity than CZ itself. Possible mechanism on improvement of conversion of toluene to CO2 was proposed due to the modification of surface basicity by ZrO2 addition. It was discussed that the stronger adsorption site of CO2 on dispersed ZrO2 would accelerate to remove reactant CO2 from active CZ surface onto dispersed ZrO2 in the oxidation reaction of toluene. [Copyright &y& Elsevier]

Abstract: Copper-exchanged in to zeolites containing large, medium and small pores were studied for selective catalytic reduction (SCR) of NO with NH3 in the presence and absence of decane. Cu/ZSM-5 and Cu/ERI exhibited higher NO x conversion compared to Cu/FER and Cu/MOR. On the other hand NO x conversion over Cu/FER was more stable in the presence of decane compared to Cu/MOR and Cu/ZSM-5 catalysts. Fresh and used Cu/zeolite catalysts were analyzed by H2-TPR, NH3-TPD, ESR and TGA. Copper species with different reducibility and isolated Cu2+ ions in different coordinations were identified by H2-TPR and the ESR techniques respectively. The initial NO x conversion activity of Cu/zeolites seems to depend on the number of isolated Cu2+ species, which were affected by the zeolite structure. Whereas, the catalysts resistance to hydrocarbon poisoning depended on the pore geometry of the zeolites. During NH3-SCR, the presence of large pores and cages in the zeolite lead to hydrocarbon deposit and retention by the zeolites which blocks the active sites and also decreases the active intermediates needed for NO x conversion. Cu/ZSM-5 with higher number of isolated Cu2+ species showed higher initial NO x conversion compared to other Cu/zeolite catalysts. Cu/FER on the other hand with small pore and cage diameter with one-dimensional channel structure showed higher hydrocarbon poisoning resistance. [Copyright &y& Elsevier]