Contributions of heterogeneous catalysis enabling resource efficiency and circular economy.

Our industry today is predominantly based on linear value chains. Raw materials are extracted from primary sources, processed into products, used, and disposed of at the end of their life cycle. This linear economy causes a wide range of negative environmental impacts owing to the resulting greenhouse gas emissions and pollution of marine and terrestrial ecosystems.

Metallic Impurities in Electrolysis: Catalytic Effect of Pb Traces in Reductive Amination and Acetone Reduction.

The electrochemical hydrogenation (e-hydrogenation) of unsaturated compounds like imines or carbonyls presents a benign reduction method. It enables direct use of electrons as reducing agent, water as proton source, while bypassing the need for elevated temperatures or pressures. In this contribution, we discuss the active species in electrocatalytic reductive amination with the transformation of acetone and methylamine as model reaction.

Origin of copper dissolution under electrocatalytic reduction conditions involving amines.

Cu dissolution has been identified as the dominant process that causes cathode degradation and losses even under cathodic conditions involving methylamine. Despite extensive experimental research, our fundamental and theoretical understanding of the atomic-scale mechanism for Cu dissolution under electrochemical conditions, eventually coupled with surface restructuring processes, is limited. Here, driven by the observation that the working Cu electrode is corroded using mixtures of acetone and methylamine even under reductive potential conditions (-0.

In situ adsorption of itaconic acid from fermentations of Ustilago cynodontis improves bioprocess efficiency.

Background: Reducing the costs of biorefinery processes is a crucial step in replacing petrochemical products by sustainable, biotechnological alternatives. Substrate costs and downstream processing present large potential for improvement of cost efficiency. The implementation of in situ adsorption as an energy-efficient product recovery method can reduce costs in both areas.

Copper Site Motion Promotes Catalytic NO Reduction under Zeolite Confinement.

Ammonia-mediated selective catalytic reduction (NH-SCR) is currently the key approach to abate nitrogen oxides (NO) emitted from heavy-duty lean-burn vehicles. The state-of-art NH-SCR catalysts, namely, copper ion-exchanged chabazite (Cu-CHA) zeolites, perform rather poorly at low temperatures (below 200 °C) and are thus incapable of eliminating effectively NO emissions under cold-start conditions. Here, we demonstrate a significant promotion of low-temperature NO reduction by reinforcing the dynamic motion of zeolite-confined Cu sites during NH-SCR.

Respiration-based investigation of adsorbent-bioprocess compatibility.

Background: The efficiency of downstream processes plays a crucial role in the transition from conventional petrochemical processes to sustainable biotechnological production routes. One promising candidate for product separation from fermentations with low energy demand and high selectivity is the adsorption of the target product on hydrophobic adsorbents. However, only limited knowledge exists about the interaction of these adsorbents and the bioprocess.

Innovative Electrochemical Strategies for Hydrogen Production: From Electricity Input to Electricity Output.

Renewable H production by water electrolysis has attracted much attention due to its numerous advantages. However, the energy consumption of conventional water electrolysis is high and mainly driven by the kinetically inert anodic oxygen evolution reaction. An alternative approach is the coupling of different half-cell reactions and the use of redox mediators.

Single-Atom Catalysts on Covalent Triazine Frameworks: at the Crossroad between Homogeneous and Heterogeneous Catalysis.

Heterogeneous single-site and single-atom catalysts potentially enable combining the high catalytic activity and selectivity of molecular catalysts with the easy continuous operation and recycling of solid catalysts. In recent years, covalent triazine frameworks (CTFs) found increasing attention as support materials for particulate and isolated metal species. Bearing a high fraction of nitrogen sites, they allow coordinating molecular metal species and stabilizing particulate metal species, respectively.

Finding the Sweet Spot of Photocatalysis─A Case Study Using Bipyridine-Based CTFs.

Covalent triazine frameworks (CTFs) are a class of porous organic polymers that continuously attract growing interest because of their outstanding chemical and physical properties. However, the control of extended porous organic framework structures at the molecular scale for a precise adjustment of their properties has hardly been achieved so far. Here, we present a series of bipyridine-based CTFs synthesized through polycondensation, in which the sequence of specific building blocks is well controlled.

Integrated Co-Electrolysis and Syngas Methanation for the Direct Production of Synthetic Natural Gas from CO and H O.

The concept of an integrated power-to-gas (P2G) process was demonstrated for renewable energy storage by converting renewable electrical energy to synthetic fuels. Such a dynamically integrated process enables direct production of synthetic natural gas (SNG) from CO and H O. The produced SNG can be stored or directly injected into the existing natural gas network.

Tailoring Activated Carbons for Efficient Downstream Processing: Selective Liquid-Phase Adsorption of Lysine.

The essential amino acid lysine is of great importance in the nutrition and pharmaceutical industries and is mainly produced in biorefineries by the fermentation of glucose. In biorefineries, downstream processing is often the most energy-consuming step. Adsorption on hydrophobic adsorbents represents an energy, resource, and cost-saving alternative.

Elucidating the mechanism of the CO methanation reaction over Ni-Fe hydrotalcite-derived catalysts via surface-sensitive in situ XPS and NEXAFS.

Hydrotalcite-derived Ni and Fe-promoted hydrotalcite-derived Ni catalysts were found to outperform industrial catalysts in the CO methanation reaction, however the origin of the improved activity and selectivity of these catalysts is not clear. Here, we report a study of these systems by means of in situ X-ray photoelectron spectroscopy and near-edge X-ray absorption spectroscopy elucidating the chemical nature of the catalysts surface under reaction conditions and revealing the mechanism by which Fe promotes activity and selectivity towards methane. We show that the increase of the conversion leads to hydroxylation of the Ni surface following the formation of water during the reaction.

Electronic parameters in cobalt-based perovskite-type oxides as descriptors for chemocatalytic reactions.

Perovskite-type transition metal (TM) oxides are effective catalysts in oxidation and decomposition reactions. Yet, the effect of compositional variation on catalytic efficacy is not well understood. The present analysis of electronic characteristics of B-site substituted LaCoO derivatives via in situ X-ray absorption spectroscopy (XAS) establishes correlations of electronic parameters with reaction rates: TM t and e orbital occupancy yield volcano-type or non-linear correlations with NO oxidation, CO oxidation and NO decomposition rates.

Molecular Porous Photosystems Tailored for Long-Term Photocatalytic CO Reduction.

The molecular-level structuration of two full photosystems into conjugated porous organic polymers is reported. The strategy of heterogenization gives rise to photosystems which are still fully active after 4 days of continuous illumination. Those materials catalyze the carbon dioxide photoreduction driven by visible light to produce up to three grams of formate per gram of catalyst.

Mg(OH) -Facilitated Liquid-Phase Conversion of Lactic Acid into 1,2-Propanediol over Cu: An Experimental and Theoretical Study.

Mg(OH) is found to exhibit superior performance in the liquid-phase conversion of lactic acid (LA) into 1,2-propanediol over Cu. A conversion of 90 % with a selectivity of 98 % is achieved at 513 K and 5 MPa H . Mg(LA) could be identified as a crucial intermediate in this reaction, as it undergoes faster conversion than the combination of LA and Mg(OH ) and regeneration of Mg(OH) through the conversion of Mg(LA) as a substrate.

Playing with covalent triazine framework tiles for improved CO adsorption properties and catalytic performance.

The rational design and synthesis of covalent triazine frameworks (CTFs) from defined dicyano-aryl building blocks or their binary mixtures is of fundamental importance for a judicious tuning of the chemico-physical and morphological properties of this class of porous organic polymers. In fact, their gas adsorption capacity and their performance in a variety of catalytic transformations can be modulated through an appropriate selection of the building blocks. In this contribution, a set of five CTFs (-) have been prepared under classical ionothermal conditions from single dicyano-aryl or heteroaryl systems.

Direct Synthesis of Methyl Formate from CO With Phosphine-Based Polymer-Bound Ru Catalysts.

Methyl formate was produced in one pot through the hydrogenation of CO to formic acid/formate followed by an esterification step. The route offers the possibility to integrate renewable energy into the fossil-based chemical value chain. In this work, a phosphine-polymer-anchored Ru complex was shown to be an efficient solid catalyst for the direct hydrogenation of CO to methyl formate.

Catalytic decomposition of NO over Cu-Al-O mixed metal oxides.

Cu-Al-O mixed metal oxides with intended molar ratios of Cu/Al = 85/15, 78/22, 75/25, 60/30, were prepared by thermal decomposition of precursors at 600 °C and tested for the decomposition of nitrous oxide (deNO). Techniques such as XRD, ICP-MS, N physisorption, O-TPD, H-TPR, FT-IR and XAFS were used to characterize the obtained materials. Physico-chemical characterization revealed the formation of mixed metal oxides characterized by different specific surface area and thus, different surface oxygen default sites.

Sulfonated covalent triazine-based frameworks as catalysts for the hydrolysis of cellobiose to glucose.

Covalent triazine-based frameworks (CTFs) were synthesized in large scale from various monomers. The materials were post-synthetically modified with acid functionalities gas-phase sulfonation. Acid capacities of up to 0.

Mechanistic Studies of the Cu(OH) -Catalyzed Isomerization of Glucose into Fructose in Water.

The isomerization of glucose to fructose is a crucial interim step in the processing of biomass to renewable fuels and chemicals. This study investigates the copper-catalyzed glucose-fructose isomerization in water, focusing on insights into the roles of the dissolved copper species. Depending on the pH, the thermodynamic equilibrium shifted towards one or a few copper species, namely Cu , Cu(OH) , and Cu(OH) .

Hydrogenation of CO to Formate over Ruthenium Immobilized on Solid Molecular Phosphines.

Formic acid is a promising hydrogen storage medium and can be produced by catalytic hydrogenation of CO . Molecular ruthenium complexes immobilized on phosphine polymers have been found to exhibit excellent productivity and selectivity in the catalytic hydrogenation of CO under mild conditions. The polymeric analog of 1,2-bis(diphenylphosphino)ethane exhibited the highest activity and turnover numbers up to 13 170 were obtained in a single run.

Efficient utilization of renewable feedstocks: the role of catalysis and process design.

Renewable carbon feedstocks such as biomass and CO present an important element of future circular economy. Especially biomass as highly functionalized feedstock provides manifold opportunities for the transformation into attractive platform chemicals. However, this change of the resources requires a paradigm shift in refinery design.

Supported Molybdenum Catalysts for the Deoxydehydration of 1,4-Anhydroerythritol into 2,5-Dihydrofuran.

Efficient deoxygenation strategies are crucial for the valorization of renewable feedstocks. Deoxydehydration (DODH) enables the direct transformation of two adjacent hydroxyl groups into a double bond. Supported molybdenum-based catalysts were utilized for the first time in DODH.

Synthesis of Butyl Levulinate Based on α-Angelica Lactone in the Presence of Easily Separable Heteropoly Acid Catalysts.

A series of choline (Ch)-exchanged heteropoly acids (HOCH CH N(CH ) ) H P W O [abbreviated as Ch H P W O , x=1-6] was synthesized and used as catalysts for the reaction of α-angelica lactone (alpha-AL) with n-butanol to form butyl levulinate (BL). The solubility of Ch H P W O in the reaction mixture was temperature dependent: The catalysts were soluble under the reaction conditions and precipitated upon cooling of the reaction mixture. This facilitated recovery of the catalysts from the liquid phase.

The Role of the Hydrogen Source on the Selective Production of γ-Valerolactone and 2-Methyltetrahydrofuran from Levulinic Acid.

A mechanistic study of the hydrogenation reaction of levulinic acid (LA) to 2-methyltetrahydrofuyran (MTHF) was performed using three different solvents under reactive H2 and inert N2 atmospheres. Under the applied reaction conditions, catalytic transfer hydrogenation and hydrogenation with molecular H2 were effective at producing high yields of γ-valerolactone. However, the conversion of this stable intermediate to MTHF required the combination of both hydrogen sources (the solvent and the H2 atmosphere) to achieve good yields.