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The direct synthesis of dimethyl carbonate from methanol and CO2 is particularly attractive as it provides a green alternative to other routes while allowing CO2 conversion. Although the evaluation of catalyst formulations figures prominently in the literature, one can hardly identify which formulations are the most active. One of the reasons is that there is no standard testing protocol. Initial water content in the reactive mixture is critical as it can drag down thermodynamic equilibrium. This study aims to rank catalyst activities and to identify the most active catalysts using a systematic protocol for the measurement of the true catalytic activity. Based on an assessment of critical parameters, a protocol for the measurement of the activity in the liquid phase, taking care to the limitation induced by thermodynamic equilibrium, was developed. Special attention was paid to the quantitative assessment of critical experimental parameters. Following the protocol, a screening of various pure and mixed oxides of about 60 different solids was carried out. Finally, an optimization study was carried out on Zr–Ce mixed oxides produced by different synthesis methods, leading to the discovery of the catalyst which, to the best of our knowledge, is the most active reported so far. [ABSTRACT FROM AUTHOR]

The synthesis of 19 carefully selected Pt/γ‐Al2O3−Cl formulations was followed by high‐throughput catalytic testing in order to unravel the effect of an active phase formulation change on n‐heptane reforming performances. Pt/γ‐Al2O3−Cl catalysts were prepared with different Pt (0.3–1 %wt) and Cl (0.1–1.4 %wt) contents and using two γ‐Al2O3 supports so that both sites concentrations and sites locations at the crystallite surface vary among the catalyst pool. Catalytic tests were conducted in mild conditions for a comparison of catalysts in kinetic regime. Results show that Pt and Cl concentrations control the competition between hydroisomerisation, hydrogenolysis and hydrocracking pathways. Aromatisation, on the contrary, is poorly affected by formulation changes. Non‐monotonous trends linking Pt/Cl ratio to isomerisation selectivity are found for both γ‐Al2O3 supports. This study provides new insights for the description of bi‐functional transformations in catalytic naphtha reforming. [ABSTRACT FROM AUTHOR]

Pt/NaY zeolites with bulk and hollow morphologies have been used as model catalysts in the hydrogenation of cyclohexene as model reaction. In contrast to most hierarchical zeolites, the presence of a single internal cavity modifies only the mean diffusion length, without changing the external surface area and the crystal size. Differences in catalytic activities have been attributed to a shorter diffusion length in hollow crystals. The volume fraction of zeolite used in bulk crystals (ca. 0.63–0.70) matches well with the shell thickness in hollow crystals, leading to an efficiency factor value for the latter close to 1. No core needed! Why keep unused parts of catalysts? Removing the poorly accessible core of NaY crystals supporting Pt enabled the increase in the effectiveness factor of cyclohexene hydrogenation from 0.63 to 0.97, thus limiting the need of rare and expensive noble metals. [ABSTRACT FROM AUTHOR]

The issues of heterogeneous catalyst optimization are presented in the framework of high throughput iterative screening. To be efficient, the optimization procedures should consider the limitations of the facilities in terms of screening capacities, experimentation costs, and experimental noise. The issues of algorithm reliability are also addressed. Based on the simulation results, this work highlights the most important features of the evolutionary strategies (ES) that lead to successful optimizations. We show that the monitoring of the population diversity during the optimization is a key parameter. Finally, we provide some best practice recommendations for experimentalists who are not experts in metaheuristic methods and who are willing to apply ES for material library designs. [ABSTRACT FROM AUTHOR]

This study reports a detailed investigation of catalyst library design by genetic algorithm (GA). A methodology for assessing GA configurations is described. Operators, which promote the optimization speed while being robust to noise and outliers, are revealed through statistical studies. The genetic algorithms were implemented in GA platform software called OptiCat, which enables the construction of custom-made workflows using a tool box of operators. Two separate studies were carried out (i) on a virtual benchmark and (ii) on real surface response which is derived from HT screening. Additionally, we report a methodology to model a complex surface response by binning the search space in small zones that are then independently modeled by linear regression. In contrast to artificial neural networks, this approach allows one to obtain an explicit model in an analogical form that can be further used in Excel or entered in OptiCat to perform simulations. While speeding the implementation of a hybrid algorithm combining a GA with a knowledge-based extraction engine is described, while speeding up the optimization process by means of virtual prescreening the hybrid GA enables one to open the “black-box” by providing knowledge as a set of association rules. [ABSTRACT FROM AUTHOR]

A simple kinetic model based on the zeolite acid strength, the number of Brønsted acid sites, and the catalyst efficiency was developed for the cracking of n-hexane. A series of HY zeolites with a mesopore volume from 0.04 to 0.32 cm3/g was synthesized and characterized by various physical-chemical methods and tested for n-hexane cracking. The generation of mesoporosity influenced several other important parameters, such as acidity and extra-framework aluminum. Zero-length column diffusion measurements for mesitylene showed a large decrease in the characteristic diffusion time upon the introduction of mesoporosity, which changed only slightly with a further increase in mesoporosity. Similar n-hexane physisorption enthalpies were measured for all samples. The highest initial activity for n-hexane cracking per catalyst volume was observed for the sample with an intermediate mesopore volume of 0.15 cm3/g. The three mesoporous H-USY zeolites showed the same value of the intrinsic rate constant and the same activation energy. The difference in initial activity of the mesoporous zeolites was caused by the difference in the number of Brønsted acid sites. The increase in initial activity for the mesoporous zeolites compared to a microporous zeolite was caused by an increase in the acid strength. [ABSTRACT FROM AUTHOR]

Metal phthalocyanine complexes encapsulated in MIL-101, and used as “ship-in-a-bottle” catalysts, show outstanding TONs in the aerobic oxidation of tetralin. [ABSTRACT FROM AUTHOR]

Review: 155 refs. [ABSTRACT FROM AUTHOR]

Abstract: This paper emphasises the electrochemical and catalytic properties of a Ni–10% GDC (10% gadolinium-doped ceria) cermet anode of a single-chamber solid oxide fuel cell (SC-SOFC). Innovative coupling of electrochemical impedance spectroscopy with gas chromatography measurements was carried out to characterise the anode material using an operando approach. The experiments were conducted in a symmetric anode/electrolyte/anode cell prepared by slurry coating resulting in 100μm-thick anode layers. The electrochemical performance was assessed using a two-electrode arrangement between 400°C and 650°C, in a methane-rich atmosphere containing CH4, O2 and H2O in a 14:2:6 volumetric ratio. The insertion of a Pt–CeO2 based catalyst with high specific surface area inside the cermet layer was found to promote hydrogen production from the Water Gas Shift reaction and consequently to improve the electrochemical performances. Indeed, a promising polarisation resistance value of 12Ωcm2 was achieved at 600°C with a catalytic loading of only 15wt.%. [ABSTRACT FROM AUTHOR]

[Display omitted] • 3,3′-dimethyl-1-butene isomerization activity is correlated to the concentration of moderate Brønsted acid sites. • 2,6-di-tert-butylpyridine is are very sensitive IR probe for moderate Brønsted acid sites such as alumina supported catalysts. • A correlation between catalytic performance and acidity characterization is demonstrated for reforming catalysts. The characterization of surface acid sites is a major issue for the mechanistic understanding and activity prediction of a solid catalyst, especially for applications that require the use of bi-functional materials. The concentration of Brønsted acid sites is measured by two main methods: adsorption of a probe molecule, and catalytic activity in a model reaction. In a previous study, we reported that the adsorption of 2,6-di- tert -butylpyridine on the surface of alumina-supported reforming catalysts (PtSn/Al 2 O 3 –Cl) was very effective in determining the density of Brønsted acid sites. In this work, the acidity of reforming catalysts was studied through their activity in the model reaction of 3,3-dimethyl-1-butene isomerization. We have demonstrated that the activity of reforming catalysts is clearly correlated with the surface chlorine density and more extensively with the density of Brønsted acid sites as measured by the adsorption of 2,6-di- tert -butylpyridine. As a result, this study highlights the relevance of using 2,6-di- tert -butylpyridine adsorption in the characterization of the Brønsted acidity of an alumina with no metal phase interference. [ABSTRACT FROM AUTHOR]

Despite the development of selective catalyst formulations for oxidative coupling of methane (OCM), kinetic and reactor design studies have been hampered by a lack of data for truly isothermal reaction conditions. Because of the high exothermicity, the temperature of a fixed-bed reactor filled with Mn-Na 2 WO 4 /SiO 2 catalysts will show hot-spots with a loss of selectivity. The objective of this study is to measure catalyst activity under relevant reaction conditions of pressure (3 bar), biogas composition (no dilution) and contact time, while keeping the process isothermal. To this aim, we have synthesized and shaped a trilobed Mn-Na 2 WO 4 /α-Al 2 O 3 catalyst, which may be used as is at industrial scale, and measured its performance in a single-pellet reactor. We found that the presence of CO 2 did not degrade the catalyst performance, even on the long run, which should enable the use of a CO 2 -rich stream such as biogas. Actually, higher methane conversions have been obtained in the presence of CO 2 , likely due to a possible contribution of methane dry reforming reaction. We also noticed a slow catalyst activation over the first 100 h, while selectivity was kept constant. [Display omitted] • Oxidative methane coupling in the presence of carbon dioxide was studied. • A single pellet reactor was used to avoid temperature gradients. • Carbon dioxide does not impact the catalyst performance. • Opens the pathway for biogas applications. [ABSTRACT FROM AUTHOR]

Pt nanoparticles supported on ZSM-5 nanoshells have been prepared by a mild desilication method. The zeolite support is a ZSM-5 crystal with extremely thin walls (ca. 15 nm) that contain meso/microporous defects. The 2–3 nm diameter Pt nanoparticles are entrapped and highly dispersed in these ZSM-5 nanoshells. The particles are stable up to 750 °C in H 2 owing to this immobilization. Catalytic activities for toluene hydrogenation were compared with those of reference Pt-based catalysts. The reaction rates obtained on the novel Pt-ZSM-5 nanoshells catalyst were about 100 times higher than those measured over conventional Pt-ZSM-5 catalysts. The highly defective zeolite nanoshell allowed even bulky molecules such as mesitylene to access all the Pt particles. This was in contrast to Pt nanoparticles encapsulated in ZSM-5 hollow single crystals, which were totally inactive due to molecular sieving. This novel Pt-ZSM-5 nanoshell catalyst shows outstanding sintering-resistance and mass transfer properties owing to its hierarchical design. [ABSTRACT FROM AUTHOR]

Abstract: In this work, we report a quantitative structure-activity relationship of functionalized ZIF-type materials (SIM, Substituted Imidazolate Material). Keeping the catalytic center unmodified, post-synthetic modification allows an efficient control of the hydrophilic–hydrophobic balance which drives the competitive adsorption of reactants and products. Hence, we attribute the increase in the reaction rate of Knoevenagel condensation (up to seven times) to the modification of the environment of catalytic sites through the creation of hydrophobic environment surrounding the catalytic sites. Surface tension properties are monitored by measuring the contact angle with a water droplet on a SIM thin film grown on a flat support. We show that the contact angle is directly correlated to the catalytic activity of Knoevenagel condensation. Hence, we propose that the contact angle of a catalyst thin layer with water can be a quantitative descriptor of direct relevance for catalytic processes which produces water and/or for catalysts that are poisoned with water. Finally, we measured the intrinsic reaction rate free of external and internal diffusion limitations by controlling the thickness of the SIM shell on SIM/alumina beads. Insights on the localization of the active sites (surface vs. bulk) are provided. [Copyright &y& Elsevier]

Abstract: Following the development of a high-throughput (HT) methodology for the evaluation of diesel soot oxidation catalysts in a 16 parallel channels reactor, a library of over 60 catalysts was tested under optimized conditions. The catalyst compositions were chosen to include solids which specific properties like oxygen storage capacity, oxygen mobility and ionic conductivity. The key parameters for high activity appear related to the presence of active and mobile surface oxygen species, and to an appropriate catalyst particle size in order to favour the number of contacts with the soot. In contrast, high oxygen storage capacity and bulk oxygen ion mobility do not appear as relevant properties for high catalytic activity. Nine new formulations were found to perform better than the reference catalyst “high surface area (HSA) ceria” (Rhodia). [Copyright &y& Elsevier]