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Efforts to selectively convert polypropylene (≈30 % of all plastic waste) have not been particularly successful. Typical distributions span from gas to solid products, highlighting a challenging cleavage control. Here, carbon‐supported platinum nanoparticles were designed for complete hydrocracking into liquid hydrocarbons (C5–C45). The metal and carrier phases operated synergistically. The cleavage activity depended on platinum and its rate rose with decreasing particle size. The carbon carrier controlled selectivity via hydrocarbon binding strength, which depended on the chain length and on the surface oxygen concentration. An optimal binding provided by carbons with high oxygen content promoted both adsorption of long chains and desorption of short products. This strategy achieved an unprecedented 80 % selectivity toward motor oil (C21–C45). Carbons exhibiting too strong binding (low oxygen content) hindered product desorption, while non‐binding materials (e. g., silica or alumina) did not promote plastic–Pt contact, leading in both cases to low performance. This work pioneers design guidelines in a key process towards a sustainable plastic economy. [ABSTRACT FROM AUTHOR]

The impact of carbon monoxide on CO2‐to‐methanol catalysts has been scarcely investigated, although CO will comprise up to half of the carbon feedstock, depending on the origin of CO2 and process configuration. In this study, copper‐based systems and ZnO−ZrO2 are assessed in cycling experiments with hybrid CO2−CO feeds and their CO sensitivity is compared to In2O3‐based materials. All catalysts are found to be promoted upon CO addition. Copper‐based systems are intrinsically more active in CO hydrogenation and profit from exploiting this carbon source for methanol production, whereas CO induces surplus formation of oxygen vacancies (i. e. the catalytic sites) on ZnO−ZrO2, as in In2O3‐based systems. Mild‐to‐moderate deactivation occurs upon re‐exposure to CO2‐rich streams, owing to water‐induced sintering for all catalysts except ZnO−ZrO2, which responds reversibly to feed variations, likely owing to its more hydrophobic nature and the atomic mixing of its metal components. Catalytic systems are categorized for operation in hybrid CO2−CO feeds, emphasizing the significance of catalyst and process design to foster advances in CO2 utilization technologies. [ABSTRACT FROM AUTHOR]

Metal promotion in heterogeneous catalysis requires nanoscale-precision architectures to attain maximized and durable benefits. Herein, we unravel the complex interplay between nanostructure and product selectivity of nickel-promoted In2O3 in CO2 hydrogenation to methanol through in-depth characterization, theoretical simulations, and kinetic analyses. Up to 10 wt.% nickel, InNi3 patches are formed on the oxide surface, which cannot activate CO2 but boost methanol production supplying neutral hydrogen species. Since protons and hydrides generated on In2O3 drive methanol synthesis rather than the reverse water-gas shift but radicals foster both reactions, nickel-lean catalysts featuring nanometric alloy layers provide a favorable balance between charged and neutral hydrogen species. For nickel contents >10 wt.%, extended InNi3 structures favor CO production and metallic nickel additionally present produces some methane. This study marks a step ahead towards green methanol synthesis and uncovers chemistry aspects of nickel that shall spark inspiration for other catalytic applications. Palladium-promoted indium oxide is a catalyst with potential to realize the large-scale conversion of CO2 into the commodity methanol. This work focuses on the low-cost nickel as an alternative appealing promoter, revealing the atomic-level catalyst design unlocking maximal selectivity and activity. [ABSTRACT FROM AUTHOR]

Identification and quantification of redox‐active centers at relevant conditions for catalysis is pivotal to understand reaction mechanisms and requires development of advanced operando methods. Herein, we demonstrate operando EPR spectroscopy as an important technique to quantify the oxidation state of representative CrPO4 and EuOCl catalysts during propane oxychlorination, an attractive route for propylene production. In particular, we show that the space‐time‐yield of C3H6 correlates with the amount of Cr2+ and Eu2+ ions generated over the catalysts during reaction. These results provide a powerful strategy to gather quantitative understanding of selective alkane oxidation, which could potentially be extrapolated to other functionalization approaches and operating conditions. [ABSTRACT FROM AUTHOR]

Decarbonizing the chemical industry will eventually entail using CO2 as a feedstock for chemical synthesis. However, many chemical syntheses involve CO2 reduction using inputs such as renewable hydrogen. In this review, chemical processes are discussed that use CO2 as an oxidant for upgrading hydrocarbon feedstocks. The captured CO2 is inherently reduced by the hydrocarbon co‐reactants without consuming molecular hydrogen or renewable electricity. This CO2 utilization approach can be potentially applied to synthesize eight emission‐intensive molecules, including olefins and epoxides. Catalytic systems and reactor concepts are discussed that can overcome practical challenges, such as thermodynamic limitations, over‐oxidation, coking, and heat management. Under the best‐case scenario, these hydrogen‐free CO2 reduction processes have a combined CO2 abatement potential of approximately 1 gigatons per year and avoid the consumption of 1.24 PWh renewable electricity, based on current market demand and supply. [ABSTRACT FROM AUTHOR]

Methanol is an attractive energy vector in a closed loop including its synthesis from CO2 and H2 and on‐demand reforming to the starting feedstocks. Catalytic materials for the two reactions were mostly studied separately, with very few works assessing the feasibility of the same system for both. Here, key kinetic drivers of methanol synthesis (MS) and methanol steam reforming (MSR) were identified for the main catalyst families, with special focus on Cu−ZnO−Al2O3, In2O3, and Pd/ZrO2. It was shown that the relative activity level was preserved in either direction, whereas the distinctly favored (reverse) water‐gas shift modulated selectivity differently. Low selectivity in kinetically controlled MS could be overcome in MSR by exploiting thermodynamics as the driving force, with many catalysts unfit for MS still comprising appealing candidates for MSR and only few being suited for MS as well as MSR. Overall, readily identifiable properties describing catalyst behavior in the forward and backward reactions were highlighted, effectively linking research in the two fields and setting a stronger basis for developing a methanol‐based hydrogen storage unit with a single reactor. [ABSTRACT FROM AUTHOR]

Chemical modifiers enhance the efficiency of metal catalysts in numerous applications, but their introduction often involves toxic or expensive precursors and complicates the synthesis. Here, we show that a porous boron nitride carrier can directly modify supported palladium nanoparticles, originating unparalleled performance in the continuous semi‐hydrogenation of alkynes. Analysis of the impact of various structural parameters reveals that using a defective high surface area boron nitride and ensuring a palladium particle size of 4–5 nm is critical for maximizing the specific rate. The combined experimental and theoretical analyses point towards boron incorporation from defects in the support to the palladium subsurface, creating the desired isolated ensembles determining the selectivity. This practical approach highlights the unexplored potential of using tailored carriers for catalyst design. [ABSTRACT FROM AUTHOR]

Catalytic alkane oxychlorination has recently been demonstrated as attractive for the selective conversion of natural gas into olefins, which are pivotal commodities of the chemical industry. Herein, the oxychlorination of ethane, propane, and butane over metal phosphates (Fe, Mn, and V), europium oxychloride, titanium oxide, and cerium oxide is investigated to assess the role of the carbon number on the reactivity and product distribution. Three categories of catalysts are distinguished: systems showing the highest activity in the oxychlorination of ethane CeO2, (VO)2P2O7, propane (EuOCl, FePO4, TiO2), or butane (Mn3(PO4)2). All catalysts achieve high (70–95%) selectivity toward ethylene in ethane oxychlorination, whereas they favor combustion and cracking pathways in the case of propane and particularly of butane. Furthermore, the catalytic oxidation of alkane and of HCl and alkyl chloride dehydrochlorination is assessed to rationalize the catalytic performance, revealing a linear correlation between the reactivity of the catalysts and the ability of the material to evolve chlorine, which weakens with increasing carbon number. In addition, the olefin selectivity in alkane oxychlorination is found to be driven by the rate of alkyl chloride dehydrochlorination and the propensity toward alkane cracking and combustion over the catalysts, both increasing from ethane to butane. [ABSTRACT FROM AUTHOR]

Controlling the structure sensitivity of catalyzed reactions over metals is central to developing atom‐efficient chemical processes. Approaching the minimum ensemble size, the properties enter a non‐scalable regime in which each atom counts. Almost all trends in this ultra‐small frontier derive from surface science approaches using model systems, because of both synthetic and analytical challenges. Exploiting the unique coordination chemistry of carbon nitride, we discriminate through experiments and simulations the interplay between the geometry, electronic structure, and reactivity of palladium atoms, dimers, and trimers. Catalytic tests evidence application‐dependent requirements of the active ensemble. In the semi‐hydrogenation of alkynes, the nuclearity primarily impacts activity, whereas the selectivity and stability are affected in Suzuki coupling. This powerful approach will provide practical insights into the design of heterogeneous catalysts comprising well‐defined numbers of atoms. [ABSTRACT FROM AUTHOR]

The need for more sustainable products and processes has led to the use of new methodologies with low carbon footprints. In this work, an efficient tandem process is demonstrated for the liquid‐phase catalytic upgrading of lignocellulosic biomass‐derived γ‐valerolactone (GVL) with trioxane (Tx) to α‐methylene‐γ‐valerolactone (MeGVL) in flow system using Cs‐loaded hierarchical beta zeolites. The introduction of mesopores along with the presence of basic sites of mild strength leads to MeGVL productivity 20 times higher than with the bulk beta zeolite, reaching 0.325 mmol min−1 gcat−1 for the best‐performing catalyst, the highest value reported so far. This catalyst proves stable upon reuse in consecutive cycles, which is ascribed to the partial depletion of the basic sites. The obtained MeGVL is subjected to visible‐light‐induced polymerization, resulting in a final material with similar properties to the widely used poly(methyl) methacrylate. [ABSTRACT FROM AUTHOR]

Single‐atom heterogeneous catalysts (SACs) attached to carefully chosen hosts are attracting considerable interest; principally because they offer maximum utilization per metal atom and are usually readily recyclable. However, diminution of the atomic population of nanoparticles or nanoclusters to single atoms can significantly alter reactivity because of the consequent changes in the active‐site structure. By examining various diverse applications, we ascertain whether the performance of SACs is enhanced or suppressed. We also note that SACs generally display unique kinds of catalytic cycles. The choice of host is crucial since it influences both the electronic and steric environment of the metal center. Moreover, it may function as a cocatalyst. All these aspects impact upon the design of new SACs, which exhibit similarities to hetero‐ and homogeneous predecessors. Additionally, SACs offer a viable replacement of soluble metal complexes in processes that remain difficult to heterogenize. Breaking with tradition: The performance of single‐atom heterogeneous catalysts (SACs) is reviewed and discussed in detail. Key factors that influence performance are described and compared to heterogeneous and homogeneous analogues comprising supported nanoparticles/clusters or metal complexes. SACs follow distinct catalytic cycles in many of the examples described. [ABSTRACT FROM AUTHOR]

Ethylene and propylene are the key building blocks of the chemical industry, but current processes are unable to close the growing gap between demand and manufacture. Reported herein is an exceptional europium oxychloride (EuOCl) catalyst for the selective (≥95 %) production of light olefins from ethane and propane by oxychlorination chemistry, thus achieving yields of ethylene (90 %) and propylene (40 %) unparalleled by any existing olefin production technology. Moreover, EuOCl is able to process mixtures of methane, ethane, and propane to produce the olefins, thereby reducing separation costs of the alkanes in natural gas. Finally, the EuOCl catalyst was supported on suitable carriers and evaluated in extrudate form, and preserves performance for >150 h under realistic process conditions. [ABSTRACT FROM AUTHOR]

Sugar alcohols are applied in the food, pharmaceutical, polymer, and fuel industries and are commonly obtained by reduction of the corresponding saccharides. In view of the rarity of some sugar substrates, epimerization of a readily available monosaccharide has been proposed as a solution, but an efficient catalytic system has not yet been identified. Herein, a molybdenum heteropolyacid-based catalyst is developed to transform glucose, arabinose, and xylose into less-abundant mannose, ribose, and lyxose, respectively. Adsorption of molybdic acid onto activated carbon followed by ion exchange to the cesium form limits leaching of the active phase, which greatly improves the catalyst stability over 24 h on stream. The hydrogenation of mixtures of epimers is studied over ruthenium catalysts, and it is found that the precursor to the desired polyol is advantageously converted with faster kinetics. This is explained by density functional theory on the basis of its more favorable adsorption on the metal surface and the lower energy barrier for the addition of a hydrogen atom to the primary carbon atom. Finally, different designs for a continuous process for the conversion of glucose into mannitol are studied, and it is uncovered that two reactors in series with one containing the epimerization catalyst and the other containing a mixture of the epimerization and hydrogenation catalysts increases the mannitol/sorbitol ratio to 1.5 from 1 for a single mixed-bed reactor. This opens a prospective route to the efficient valorization of renewables to added-value chemicals. [ABSTRACT FROM AUTHOR]

A catalytic process is demonstrated for the selective conversion of methane into carbon monoxide via oxychlorination chemistry. The process involves addition of HCl to a CH4-O2 feed to facilitate C−H bond activation under mild conditions, leading to the formation of chloromethanes, CH3Cl and CH2Cl2. The latter are oxidized in situ over the same catalyst, yielding CO and recycling HCl. A material exhibiting chlorine evolution by HCl oxidation, high activity to oxidize chloromethanes into CO, and no ability to oxidize CO, is therefore essential to accomplish this target. Following these design criteria, vanadyl pyrophosphate (VPO) was identified as an outstanding catalyst, exhibiting a CO yield up to approximately 35 % at 96 % selectivity and stable behavior. These findings constitute a basis for the development of a process enabling the on-site valorization of stranded natural-gas reserves using CO as a highly versatile platform molecule. [ABSTRACT FROM AUTHOR]

Optimal amounts of CO2 are added to syngas to boost the methanol synthesis rate on Cu-ZnO-Al2O3 in the industrial process. The reason for CO2 promotion is not sufficiently understood at the particle level due to the catalyst complexity and the high demands of characterization under true reaction conditions. Herein, we applied operando synchrotron X-ray powder diffraction and modulated-excitation infrared spectroscopy on a commercial catalyst to gain insights into its morphology and surface chemistry. These studies unveiled that Cu and ZnO agglomerate and ZnO particles flatten under CO/H2 and/or CO2/H2. Under the optimal CO/CO2/H2 mixture, sintering is prevented and ZnO crystals adopt an elongated shape due to the minimal presence of the H2O byproduct, enhancing the water-gas shift activity and thus the methanol production. Our results provide a rationale to the CO2 promotion emphasizing the importance of advanced analytical methods to establish structure-performance relations in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

Ceria catalyzes the one-step production of the vinyl chloride monomer (VCM) from ethylene with a high yield because of its bifunctional character: redox centers oxychlorinate ethylene to ethylene dichloride (EDC), which is subsequently dehydrochlorinated to VCM over strong acid sites generated in situ. Nanocrystalline CeO2 and CeO2-ZrO2 lead to a VCM yield of 25 % in a single pass, outperforming the best reported systems and reaching industrially attractive levels. The use of CeO2 intensifies the current two-step process within PVC production encompassing CuCl2-catalyzed oxychlorination and thermal cracking. In addition, ceria-based materials offer stability advantages with respect to the archetypical CuCl2-based catalysts. [ABSTRACT FROM AUTHOR]

Selective hydrogenations lay at the heart of many industrial processes. The archetypal catalysts for this class of reactions are generally prepared by 'metal poisoning' strategies: the active metal is protected and selectively deactivated with various compounds. This approach has been applied for decades, with limited understanding. Low product selectivity and presence of toxic elements in the catalyst pose severe constraints in the utilization of these materials in the future. Thus, to develop more sustainable catalysts, this field has recently gained momentum. This Review analyzes the concepts and frontiers that have been developed in the last decade: from nanostructuring less conventional metals in order to improve their ability to activate H2, to the use of oxides as active phases, from alloying, to the ensemble control in hybrid materials, and site isolation approaches in single-site heterogeneous catalysts. Particular attention is given to the hydrogenation of alkynes and nitroarenes, two reactions at the core of the chemical industry, importantly applied in the manufacture of polymers, pharmaceuticals, nutraceuticals, and agrochemicals. The strategies here identified can be transposed to other relevant hydrogenations and can guide in the design of more advanced materials. [ABSTRACT FROM AUTHOR]

Porous MnO2 microspheres distributed around magnetic carbon-coated cobalt nanoparticles were developed. The performance of these nanoparticles rivals that of Pd-based catalysts for the selective oxidation of alcohols. Excellent recyclability was conveniently achieved by magnetic decantation and is demonstrated in ten consecutive cycles with no apparent material or performance losses. [ABSTRACT FROM AUTHOR]

Without techniques sensitive to complex pore architectures, synthetic efforts to enhance molecular transport in zeolite and other porous materials through hierarchical structuring lack descriptors for their rational design. The power of positron annihilation lifetime spectroscopy (PALS) to characterize the pore connectivity in hierarchical MFI zeolites is demonstrated, establishing a direct link with the enhanced catalyst lifetime in the conversion of methanol to valuable hydrocarbons. The unique ability to capture subtleties of the hierarchical structure originates from the dynamic nature of the ortho-positronium response to the pore network. The findings reveal the strong dependence on the way in which the hierarchical zeolites are manufactured, having direct implications for the practical realization of these advanced catalysts. [ABSTRACT FROM AUTHOR]

Rutile TiO2 is a heavily investigated oxide with, to date, scarce applications in industrial catalysis. The inactivity of this material in oxidations has been related to its inability to dissociate molecular oxygen. Herein we show how rutile catalyzes the oxidation of HBr to Br2 through defect states that are introduced during the reaction. The identification of active, stable, and abundant materials for bromine production is key to the future implementation of Br2-mediated alkane functionalization processes. The catalytic properties of TiO2 are discussed in comparison to expensive rutile-type oxides, such as RuO2 and IrO2, on the basis of surface characterization and molecular modeling. [ABSTRACT FROM AUTHOR]

Making a quick recovery: The widespread implementation of bromination reactions to manufacture value‐added products is contingent upon the development of sustainable and cost‐effective means to recycle copious amounts of HBr byproduct. We report families of heterogeneous catalysts for the full recovery of Br2 through HBr oxidation that display unprecedented low‐temperature activity and stability. [ABSTRACT FROM AUTHOR]

The article discusses a study which shows the stability of copper chromium oxide (CuCrO2), a copper-based catalyst with high hydrogen chloride (HCl), under oxidizing and chlorinating environments. It says that a novel CuCrO2-CeO2 composite for HCl oxidation has been developed. It concludes that the first copper-based CuCrO2 delafossite that has unique bulk chlorination resistance and allows stable chlorine production has been developed.

Wax on, wax off: Bifunctional cobalt‐based catalysts on zeolite supports are applied for the valorization of biosyngas through Fischer‐Tropsch chemistry. By using these catalysts, waxes can be hydrocracked to shorter‐chain hydrocarbons, increasing the selectivity towards the C5–C11 (gasoline) fraction. The zeolite topology and the amount and strength of acid sites are key parameters to maximize the performance of these bifunctional catalysts, steering Fischer‐Tropsch product selectivity towards liquid hydrocarbons. [ABSTRACT FROM AUTHOR]

Carbon-supported Pt catalysts enable this outcome, for which activity and selectivity are tunable via Pt particle size and surface oxygen content of carbon, respectively. Cover Feature: Direct Conversion of Polypropylene into Liquid Hydrocarbons on Carbon-Supported Platinum Catalysts (ChemSusChem 23/2021) Keywords: cracking; heterogeneous catalysis; plastic waste; polypropylene; recycling EN cracking heterogeneous catalysis plastic waste polypropylene recycling 5076 5076 1 12/08/21 20211206 NES 211206 B The Cover Feature b shows a landscape reflecting the pressing problem of plastic waste generation where a resolute humanoid emerges, symbolizing the potential of chemical recycling. [Extracted from the article]

Last site standing: A new gENeration of hierarchical Pt/H ‐ ZSM ‐ 22 zeolites is designed for the efficiENt processing of upcoming rENewable feedstocks. The ENhanced accessibility of the active sites is vital for the superior activity and exceptional selectivity in the hydroisomerization of model molecules such as nonadecane and pristane. [ABSTRACT FROM AUTHOR]

In heterogeneous catalysis, rates with Arrhenius-like temperature dependence are ubiquitous. Compensation phenomena, which arise from the linear correlation between the apparent activation energy and the logarithm of the apparent pre-exponential factor, are also common. Here, we study the origin of compensation and find a similar dependence on the rate-limiting surface coverage term for each Arrhenius parameter. This result is derived from an experimental determination of the surface coverage of oxygen and chlorine species using temporal analysis of products and prompt gamma activation analysis during HCl oxidation to Cl2 on a RuO2 catalyst. It is also substantiated by theory. We find that compensation phenomena appear when the effect on the apparent activation energy caused by changes in surface coverage is balanced out by the entropic configuration contributions of the surface. This result sets a new paradigm in understanding the interplay of compensation effects with the kinetics of heterogeneously catalysed processes. [ABSTRACT FROM AUTHOR]

Abstract: Selectivity control in heterogeneously catalyzed hydrogenation of conjugated hydrocarbons (ene-yne and diene compounds) is a challenging task. Available studies on the topic mainly encircle 1,3-butadiene as the substrate and palladium as the catalyst, while more elaborated playground molecules and other metals remain largely unexplored. This study investigates the gas-phase hydrogenation of valylene (2-methyl-1-butene-3-yne) and isoprene (2-methyl-1,3-butadiene) over Pd, Pb-poisoned Pd, CO-modified Pd, Cu, Ni, and bimetallic Custs. Chemoselectivity, regioselectivity, full hydrogenation, and Crmation/scission footprints of the catalytic systems at different inlet hydrogen-to-hydrocarbon ratios and conversion degrees have been rationalized. Complementary studies of 3-methylbutyne and 1-penten-4-yne hydrogenation were carried out in order to analyze (i) the impact of isomerization on the observed mono-olefin distribution in valylene/isoprene hydrogenation and (ii) the conjugation issue in partial ene-yne hydrogenation. Our results lead to an improved understanding of hydrogenation of polyunsaturated hydrocarbons and open doors to design more selective heterogeneous catalysts and related processes for this practically important class of reactions. [Copyright &y& Elsevier]

The gas-phase hydrogenation of propyne to propene was investigated over a series of heterogeneous catalysts based on Pd (in the absence and the presence of CO), Ni, Au, Cu, and Cu–Ni. Catalytic tests in a continuous flow micro-reactor at ambient pressure and density functional theory (DFT) calculations were combined to understand complex structure–selectivity–activity relationships and their dependence on key experimental variables such as H2/alkyne and CO/H2ratios. The wide scope of our work enables the identification of similarities and differences between these systems and paves the way to design more selective catalysts. [ABSTRACT FROM AUTHOR]

Abstract: This manuscript concisely reviews the significance of the temporal analysis of products (TAP) technique in catalysis research from its introduction to the scientific community in the late 1980s. Evolutionary aspects of this time-resolved transient pulse method are presented, highlighting its relevance for elucidation of mechanistic and kinetic aspects of adsorption, diffusion, and reaction in gas–solid systems. The high-temperature ammonia oxidation over noble metal catalysts is used to underline key advantages of the TAP reactor in mechanistic studies, narrowing the often-encountered pressure and materials gaps between techniques operating at ambient pressure and in ultra-high vacuum. Perspectives to further enhance the capabilities of this technique are briefly put forward. [Copyright &y& Elsevier]

Innentitelbild: Quantification of Redox Sites during Catalytic Propane Oxychlorination by Operando EPR Spectroscopy (Angew. Keywords: alkane activation; heterogeneous catalysis; operando EPR spectroscopy; propane oxychlorination; reaction mechanism EN alkane activation heterogeneous catalysis operando EPR spectroscopy propane oxychlorination reaction mechanism 3354 3354 1 02/10/21 20210215 NES 210215 B Operando-EPR wird heiß b Im Forschungsartikel auf S. 3640 demonstrieren Guido Zichittella, Yevhen Polyhach, Javier Pérez-Ramírez et al. die Operando-EPR-Spektroskopie als zentrale Technik zur Bestimmung des Oxidationszustands von CrPO SB 4 sb - und EuOCl-Katalysatoren während der katalytischen Hochtemperatur-Oxychlorierung von Propan. Alkane activation, heterogeneous catalysis, operando EPR spectroscopy, propane oxychlorination, reaction mechanism. [Extracted from the article]

Cover Feature: Synthesizing High-Volume Chemicals from CO2 without Direct H2 Input (ChemSusChem 23/2020) Keywords: carbon capture and utilization; C-C coupling; dry reforming; heterogeneous catalysis; oxidative dehydrogenation EN carbon capture and utilization C-C coupling dry reforming heterogeneous catalysis oxidative dehydrogenation 6049 6049 1 12/09/20 20201207 NES 201207 B The Cover Feature b shows a decoupling of CO SB 2 sb utilization from the H SB 2 sb economy. Carbon capture and utilization, C-C coupling, dry reforming, heterogeneous catalysis, oxidative dehydrogenation. [Extracted from the article]

Highlights from the article: Cover Feature: Sustainable Continuous Flow Valorization of -Valerolactone with Trioxane to -Methylene- -Valerolactone over Basic Beta Zeolites (ChemSusChem 12/2019) B The Front Cover b shows a sustainable continuous-flow process for upgrading lignocellulosic-biomass-derived -valerolactone to -methylene- -valerolactone by utilizing a tailored Cs-loaded hierarchical beta catalyst. Heterogeneous catalysis, sustainable chemistry, biomass, zeolites, flow chemistry.

Turning myth into reality. Pérez‐Ramírez et al. show in their Communication on page 13670 ff. the outstanding performance of EuOCl for the production of light olefins from ethane and propane by oxychlorination chemistry. The high activity, selectivity, and stability of the system are illustrated by the mythological princess Europa, who was carried from Asia to the Hellenic world by Zeus, who was disguised as a white bull. Both the continent of Europe and the element europium later took her name. [ABSTRACT FROM AUTHOR]

The Cover picture shows a samba singer and dancer shouting “Azúcar!” (Spanish for sugar) and was inspired by the two‐step conversion of common carbohydrates into rare sugar alcohols. The scene symbolizes the core message of the manuscript; the importance of studying the transformation at both catalyst and process levels. The development of suitable epimerization and hydrogenation catalysts, embodied by the maracas, proved insufficient to ensure high efficiency, in the same way as musical instruments offer limited entertainment alone. A process is needed, depicted by the performer, the design and operating conditions of which are tuned to maximize selectivity to the desired products. More details can be found in the Full Paper by Lari et al. on page 3407 in Issue 24, 2016 (DOI: 10.1002/cssc.201600755). [ABSTRACT FROM AUTHOR]

The inside back cover page of the journal "Angewandte Chemie International Edition" is presented.

Abstract: Alkyne hydrogenation, a widely used process in industry to purify olefin streams, comprises a prototype reaction to understand selectivity in heterogeneously catalyzed reactions. The selectivity of the reaction on palladium catalysts to the alkene, alkane, or oligomers strongly depends on the state of the (sub)surface; i.e., the occurrence of complex carbide/hydride phases. In practice, hydrogenation reactors in C2 and C3 cuts of steam crackers require continuous CO feeding in order to enhance the alkene selectivity of palladium-supported catalysts. In the present work, we have studied the impact of carbon monoxide on the formation of carbide and hydride phases as a standpoint to derive structure–performance relationships under realistic process conditions. For this purpose, catalytic tests on a standard 1wt.% Pd/Al2O3 and Density Functional Theory on Pd(111) were combined. The influence of: (i) the alkyne (ethyne and propyne), (ii) the hydrogen:alkyne ratio (1–10), (iii) the carbon monoxide:hydrogen ratio (0–0.2), and (iv) the catalyst pretreatment on the product distribution was assessed in a continuous flow fixed-bed reactor at ambient pressure. In absence of CO, subtle changes in the hydrogen:alkyne ratio generate undesired products. Carbon monoxide enables the external control of the catalyst state by suppressing the formation of subsurface hydride and carbide phases, thereby stabilizing a high alkene yield in a broad range of feed hydrogen:alkyne ratios. This scenario contrasts with the more fragile regime of the hydride–carbide phases under CO-free conditions. DFT calculations obtained a single Brønsted–Evans–Polanyi relationship independently of the state of the catalyst (carbide, hydride, CO-covered) and the alkyne–alkene–alkane set (C2, C3). [Copyright &y& Elsevier]

Identification and quantification of redox‐active centers at relevant conditions for catalysis is pivotal to understand reaction mechanisms and requires development of advanced operando methods. Herein, we demonstrate operando EPR spectroscopy as an important technique to quantify the oxidation state of representative CrPO4 and EuOCl catalysts during propane oxychlorination, an attractive route for propylene production. In particular, we show that the space‐time‐yield of C3H6 correlates with the amount of Cr2+ and Eu2+ ions generated over the catalysts during reaction. These results provide a powerful strategy to gather quantitative understanding of selective alkane oxidation, which could potentially be extrapolated to other functionalization approaches and operating conditions. [ABSTRACT FROM AUTHOR]

The recent development of amorphous silica-alumina catalysts for the heterogeneously-catalyzed production of methylenedianiline (MDA) has resulted in an economically and environmentally attractive alternative to the industrially employed HCl catalyst. However, the quantitative kinetic description of the complex reaction network, a key prerequisite for reactor choice and process assessment, is unfeasible when using classical power-law based models due to the wealth of components and interactions involved. Based on high throughput batch experiments coupled with a detailed product analysis, we herein reveal that all possible reactions in an MDA mixture can be represented in terms of interactions between a small number of reoccurring functional groups. A corresponding categorization of all mixture components enables the description of the reaction network using population balance equations, an approach previously applied to polymerization, aggregation, and cell-growth processes. Thereby, every possible binary interaction between two molecules in the system can be accounted for, resulting in an unprecedented resolution regarding oligomeric species and improved predictive capabilities based on a small number of parameters. The translation of the deepened mechanistic understanding into advanced kinetic models enables to circumvent previous limitations, and is expected to accelerate the industrial realization of the sustainable process. [ABSTRACT FROM AUTHOR]

Uranium oxide finely dispersed on ZrO2 crystals represents an effective and robust catalyst for the industrially relevant oxidation of HCl to chlorine. Remarkably, the catalytic performance increases significantly during the first 80 h on stream and remains stable thereafter. According to XRD results, this self-activation of the catalyst is accompanied by the disappearance of the starting α-U3O8 phase. The uranium distribution on the ZrO2 crystals at different stages of the reaction was visualized by aberration-corrected HAADF-STEM. The mostly mono-atomic uranium oxide layers present in the fresh catalyst broaden during reaction and often form a homogeneous coating over the support crystals comprising small uranium oxide species mostly comprising a single uranium atom. These species are found to be often located on top of columns of ZrO7 polyhedra, pointing to a strong fixation on the carrier. This observation likely explains the unique stability of the zirconia-supported uranium oxide catalyst in the Deacon reaction. [ABSTRACT FROM AUTHOR]

Abstract: As-synthesised and reconstructed NH4-Al-dawsonite and NH4-Ga-dawsonite, and the materials obtained by thermal treatment in the range 373–873K, were studied as heterogeneous catalysts for the epoxidation of cyclooctene with hydrogen peroxide at 353K and ambient pressure by means of High-Throughput Experimentation. The structural, morphological, and textural properties of the materials were investigated by elemental analysis, ICP-OES, XRD, FTIR, TEM, N2 adsorption, and TGA. The temperature at which the dawsonite precursors were treated proved to be crucial in determining the activity of the catalysts. The best catalyst identified in this work was obtained by calcination at 573K of reconstructed Ga-dawsonite. This material provides an epoxide yield of 51% and 99% selectivity after 4h at 353K. Remarkably, many of the catalysts derived from Al-dawsonite displayed an enhanced epoxidation activity upon recycling, reaching up to 30% epoxide yield with 98% selectivity over Al-dawsonite treated at 473K. [Copyright &y& Elsevier]