Despite the great commercial relevance of zinc-promoted copper catalysts for methanol synthesis, the nature of the Cu–ZnO x synergy and the nature of the active Zn-based promoter species under industrially relevant conditions are still a topic of vivid debate. Detailed characterization of the chemical speciation of any promoter under high-pressure working conditions is challenging but specifically hampered by the large fraction of Zn spectator species bound to the oxidic catalyst support. We present the use of weakly interacting graphitic carbon supports as a tool to study the active speciation of the Zn promoter phase that is in close contact with the Cu nanoparticles using time-resolved X-ray absorption spectroscopy under working conditions. Without an oxidic support, much fewer Zn species need to be added for maximum catalyst activity. A 5–15 min exposure to 1 bar H 2 at 543 K only slightly reduces the Zn(II), but exposure for several hours to 20 bar H 2 /CO and/or H 2 /CO/CO 2 leads to an average Zn oxidation number of +(0.5–0.6), only slightly increasing to +0.8 in a 20 bar H 2 /CO 2 feed. This means that most of the added Zn is in a zerovalent oxidation state during methanol synthesis conditions. The Zn average coordination number is 8, showing that this phase is not at the surface but surrounded by other metal atoms (whether Zn or Cu), and indicating that the Zn diffuses into the Cu nanoparticles under reaction conditions. The time scale of this process corresponds to that of the generally observed activation period for these catalysts. These results reveal the speciation of the relevant Zn promoter species under methanol synthesis conditions and, more generally, present the use of weakly interacting graphitic supports as an important strategy to avoid excessive spectator species, thereby allowing us to study the nature of relevant promoter species.

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Here we report the synthesis and characterisation of high surface area MgO prepared via the thermal decomposition of various magnesium precursors (MgCO3, Mg(OH)2 and MgC2O4). Bimetallic gold-palladium nanoalloy particles were supported on these MgO materials and were tested as catalysts for the solvent-free selective aerobic oxidation of benzyl alcohol to benzaldehyde. All these catalysts were found to be active and very selective (>97%) to the desired product (benzaldehyde). However, MgO prepared via the thermal decomposition of magnesium oxalate displayed the highest activity among all the magnesium oxide supports tested. Attempts were made to unravel the reasons for the deactivation of these catalysts using different characterisation techniques namely in situ XRD, XPS, ICP-MS, TEM, and TGA-MS. From the data obtained, it is clear that MgO undergoes phase changes from MgO to Mg(OH)2 and MgCO3 during catalyst preparation as well as during the catalytic reaction. Besides phase changes, strong adsorption of reactants and products on the catalyst surface, during the reaction, were also observed and washing the catalyst with organic solvents did not completely remove them. The phase change and catalyst poisoning were reversed through high temperature heat treatments. However, these processes led to the sintering of the metal nanoparticles. Moreover, substantial leaching of the support material (MgO) was also observed during the reaction. These latter two processes led to the irreversible deactivation of AuPd nanoparticles supported on MgO catalyst during the solvent-free selective aerobic oxidation of alcohols. Among the three different MgO supports studied in this article, an inverse correlation between the catalytic activity and Mg leaching has been observed. This article reports a deeper understanding of the mode of deactivation observed in metal nanoparticles supported on MgO during liquid phase reactions.

For realization of a wearable artificial kidney based on regeneration of a small volume of dialysate, efficient urea removal from dialysate is a major challenge. Here a potentially suitable polymeric sorbent based on phenylglyoxaldehyde (PGA), able to covalently bind urea under physiological conditions, is described. Sorbent beads containing PGA groups were obtained by suspension polymerization of either styrene or vinylphenylethan-1-one (VPE), followed by modification of the aromatic groups of poly­(styrene) and poly­(VPE) into PGA. It was found that PGA-functionalized sorbent beads had maximum urea binding capacities of 1.4–2.2 mmol/g and removed ∼0.6 mmol urea/g in 8 h at 37 °C under static conditions from urea-enriched phosphate-buffered saline, conditions representative of dialysate regeneration. This means that the daily urea production of a dialysis patient can be removed with a few hundred grams of this sorbent which, is an important step forward in the development of a wearable artificial kidney.

In this work, we discuss the role of manganese oxide as a promoter in Cu catalysts supported on graphitic carbon during hydrogenation of CO2 and CO. MnOx is a selectivity modifier in an H2/CO2 feed and is a highly effective activity promoter in an H2/CO feed. Interestingly, the presence of MnOx suppresses the methanol formation from CO2 (TOF of 0.7 ⋅ 10−3 s−1 at 533 K and 40 bar) and enhances the low‐temperature reverse water‐gas shift reaction (TOF of 5.7 ⋅ 10−3 s−1) with a selectivity to CO of 87 %C. Using time‐resolved XAS at high temperatures and pressures, we find significant absorption of CO2 to the MnO, which is reversed if CO2 is removed from the feed. This work reveals fundamental differences in the promoting effect of MnOx and ZnOx and contributes to a better understanding of the role of reducible oxide promoters in Cu‐based hydrogenation catalysts.

The aim of this study is to develop polymeric chemisorbents with a high density of ninhydrin groups, able to covalently bind urea under physiological conditions and thus potentially suitable for use in a wearable artificial kidney. Macroporous beads are prepared by suspension polymerization of 5‐vinyl‐1‐indanone (vinylindanone) using a 90:10 (v/v) mixture of toluene and nitrobenzene as a porogen. The indanone groups are subsequently oxidized in a one‐step procedure into ninhydrin groups. Their urea absorption kinetics are evaluated under both static and dynamic conditions at 37 °C in simulated dialysate (urea in phosphate buffered saline). Under static conditions and at a 1:1 molar ratio of ninhydrin: urea the sorbent beads remove ≈0.6–0.7 mmol g−1 and under dynamic conditions and at a 2:1 molar excess of ninhydrin ≈0.6 mmol urea g−1 sorbent in 8 h at 37 °C, which is a step toward a wearable artificial kidney.

When someone has heard of a catalyst before, it has often been explained as a car part that cleans the exhaust gases. However, there are many more types of catalysts used in the industrial production of almost any chemical, ranging from enzymes (biocatalysis) for the production of medicines to solid catalysts for gasoline and plastics production. 1,2 A catalyst is in general a substance that is used to accelerate a chemical reaction from starting compound A to desired product B by lowering the activation barrier (figure 1.1A), while the substance itself is not consumed. 3 For example, inside the three-way catalytic converter in gasoline-type cars several catalyzed reactions simultaneously occur: hydrocarbons, carbon monoxide (CO), and nitrogen oxides (NOx) in the high exhaust stream are converted into the less harmful carbon dioxide (CO2), water (H2O), and nitrogen gas (N2). 4 Here, we focus on heterogeneous catalysts, which are solid catalysts used in liquid-or gas-phase reactions. The active compound in heterogeneous catalysts is often a metal (oxide or sulfide). Figure 1.1 (A) Energy diagram of a catalyzed and non-catalyzed chemical reaction with Eact representing the activation energy. (B) Transfer of electron density from the d-band of a metal to an anti-bonding orbital of a reactant (here σ* of an H2 molecule). Back-donation (as indicated by the arrow) induces bond breaking. Adapted from ref. [3]. (C) Different binding modes of a CO molecule on a metal surface. 493 60 2,000 b 12.4 50.7 42.6 6.3 [177] a N-C = ordered mesoporous nitrogen-doped carbon, KIT-6 = ordered mesoporous silica, last entry = physical mixture. b In mL gcat -1 h -1 . c C2+OH = higher alcohols, HC = hydrocarbons. d Without taking CO2 into account.

The role of Cu:Co composition in bi-metallic Cu-Co/ZnAl 2 O 4 catalysts on higher alcohol synthesis (HAS) was investigated at H 2 :CO = 4. The addition of Cu strongly facilitated Co reduction upon catalyst activation and suppressed coke deposition during HAS. Formation of predominantly hydrocarbons and higher alcohols was observed on the bi-metallic catalysts. Co/ZnAl 2 O 4 produced mainly CH 4 and Cu/ZnAl 2 O 4 mainly CH 3 OH, while at Cu:Co = 0.6 the best ethanol selectivity of 4.5 % was reached. The microstructure of the spent catalysts confirmed a close interaction of Cu and Co.