Dispersed Pd Research Articles

Synergistic interplay of CuOx and Pd nanodots on TiO2 for efficient and highly selective photocatalytic oxidation of CH4 to oxygenates with O2

Direct photocatalytic methane oxidation to produce liquid oxygenates offers a promising approach for the upgrading of abundant methane under mild conditions, yet it remains a formidable challenge in achieving high reaction rates while maintaining high selectivity. Herein, we report the highly dispersed CuOx and Pd nanodots decorated TiO2 for photocatalytic oxidation of CH4 with O2 at room temperature, which exhibits a remarkable C1 oxygenates production rate of 39.5 mmol·g−1·h−1 with a nearly 100 % selectivity, outperforming most of the state-of-the-art photocatalysts. Both experimental and theoretical studies suggest that the impressive photocatalytic performance is attributed to the synergy of Cu+ species and Pd nanodots. Cu+ species not only promote the interfacial electrons transfer from TiO2 to Pd, but also mediate CH4 oxidation reaction to avoid overoxidation of oxygenates to CO2, while the resulting electron-rich Pd sites boost the production of primary products (CH3OOH and CH3OH) by lowering the reaction energy. This work provides a new pathway for developing highly efficient photocatalysts for the selective conversion of methane to value-added chemicals by designing bimetallic cocatalysts.

Electrodeposition Decoration of Pd0 on F‐Co(OH)2 Nanoarrays with Intentionally Introduced Pd2+ Species for Efficient Electrocatalytic Hydrodechlorination of 2,4‐Dichlorophenol

AbstractDeveloping a Pd‐based catalyst possessing high efficiency and low mass loading remains a big obstacle for the large‐scale application of electrocatalytic hydrodechlorination (EHDC) of chlorophenols (CPs). Herein, high dispersion Pd nanoparticles imbedded in Pd2+ hydroxide species are decorated on the surface of F−Co(OH)2 nanowire arrays with a newly developed electrodeposition and hydrolysis coupled process. EHDC of 2,4‐dichlorophenol (2,4‐DCP) with the as‐obtained Pd/F−Co(OH)2/NF‐a exhibits superior performance than other control samples in this work and literature reports. A 100 % removal of 2,4‐DCP is accomplished within 120 min, featuring fast reaction kinetics (kobs=5.0×10−2 min−1) and mass activity (MA=22.2 min−1 g−1Pd). Mechanism investigation shows that the intentionally introduced Pd2+ sites play a pivotal role in the adsorption of 2,4‐DCP, while high dispersion of Pd facilitates the generation of active H*, thus promoting the catalytic performance. This work presents a valuable example for designing high‐performance Pd‐based EHDC catalysts by composition tuning.

Masked second-shell sulfur coordinating atomically dispersed Pd on tin oxide boosts the direct synthesis of hydrogen peroxide

The coordination environments of isolated metals significantly influence the catalytic properties of materials. However, challenges persist in the precise modulation of these microenvironments. In this study, we achieved atomically dispersed Pd on sulfur-doped tin dioxide (SnO2) through the controlled oxidation of SnS2 nanosheets pre-loaded with single-atom Pd (Pd/SnS2). Our findings reveal that the synthesized catalyst features a central single-atom Pd, which coordinates with oxygen and tin in the first coordination shell and sulfur binding tin in the second shell. The coordination of isolated Pd with sulfur in the out-of-plane second shell layer enhances oxygen adsorption while inhibiting OO dissociation, thus directing hydrogen peroxide selectivity. This results in a higher productivity and durability of hydrogen peroxide compared to pristine Pd/SnS2 and traditional samples. This work presents an effective strategy to tailor and preserves the coordination micro-environment of central single-atom metals during catalytic reactions.

Structure-Driven Performance Enhancement in Palladium-Graphene Oxide Catalysts for Electrochemical Hydrogen Evolution.

Graphene oxide (GO) has recently gained significant attention in electrocatalysis as a promising electrode material owing to its unique physiochemical properties such as enhanced electron transfers due to a conjugated π-electron system, high surface area, and stable support for loading electroactive species, including metal nanoparticles. However, only a few studies have been directed toward the structural characteristics of GO, elaborating on the roles of oxygen-containing functional groups, the presence of defects, interlayer spacing between the layered structure, and nonuniformity in the carbon skeleton along with their influence on electrochemical performance. In this work, we aim to understand these properties in various GO materials derived from different graphitic sources. Both physiochemical and electrochemical characterization were employed to correlate the above-mentioned features and explore the effect of the location of the palladium nanoparticles (Pd NPs) on various GO supports for the hydrogen evolution reaction (HER). The interaction of the functional groups has a crucial role in the Pd dispersion and its electrochemical performance. Among the different GO samples, Pd supported on GO derived from graphene nanoplate (GNP), Pd/GO-GNP, exhibits superior HER performance; this could be attributed to the optimal balance among particle size, defect density, less in-plane functionalities, and higher electrochemical surface area. This study, thus, helps to identify the optimal conditions that lead to the best performance of Pd-loaded GO, contributing to the design of more effective HER electrocatalysts.

Rice Straw Biochar as an Effective Support for Pd Nanoparticles for Ethanol Electro‐Oxidation Reaction in Alkaline Condition

AbstractHerein, we report the utilization of biochar derived from rice straw (RSB) as an effective support matrix for Pd nanoparticles and its application as an electrocatalyst for ethanol electro‐oxidation (EEO) in an alkaline medium. Rice straw, a common agricultural byproduct, was pyrolyzed at 600 °C, 700 °C, and 800 °C under N2 atmosphere. Pd was loaded onto the RSB via borohydride reduction of Pd2+, with a nominal loading of 20 % Pd. Spectroscopic and morphological characterization revealed the formation of dispersed Pd nanoparticles on the RSB surface. Pyrolysis temperature was observed to influence both the porosity of the resulting RSB and the dispersion and degree of exposure of Pd nanoparticles deposited on the surface. Electrochemical characterization revealed that Pd/RSB could be a potential EEO electrocatalyst for direct ethanol fuel cell applications. Pd/RSB‐700 exhibited better performance in terms of EEO forward mass activity (jf) and forward and backward mass activity (jf/jb) ratio relative to Pd/RSB‐600 and Pd/RSB‐800. Moreover, Pd/RSB was shown to be superior to commercial Pd on carbon black in terms of electrochemical stability. This study opens the potential of rice straw biochar as a sustainable and environmentally friendly carbon‐based support matrix for Pd‐based EEO electrocatalysts.

High-Temperature Behavior of Pd/MgO Catalysts Prepared via Various Sol-Gel Approaches.

A series of Pd/MgO catalysts based on nanocrystalline MgO were prepared via different sol-gel approaches. In the first two cases, palladium was introduced during the gel preparation, followed by drying it in supercritical or ambient conditions. In the third case, aerogel-prepared MgO was impregnated with an ethanol solution of Pd(NO3)2. The prepared catalysts differ in particle size and oxidation state of palladium. The catalytic performance and thermal stability of the samples were examined in a model reaction of CO oxidation at prompt thermal aging conditions. The as-prepared and aged materials were characterized by low-temperature nitrogen adsorption, UV-vis spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, and ethane hydrogenolysis testing reaction. The highest initial activity (T50 = 103 °C) was demonstrated by the impregnated sample, containing Pd0 particles of 3 nm in size. The lowest T50 value (215 °C) after aging at 1000 °C was demonstrated by the impregnated Pd/MgO-WI sample. The high-temperature behavior of the catalysts was found to be affected by the initial oxidation state and dispersion of Pd. Two deactivation mechanisms, such as the agglomeration of Pd particles and migration of small Pd species into the bulk of the MgO support with the formation of Pd-MgO solid solutions, were discussed.

Selective hydrogenation of 5‐hydroxymethylfurfural to 5‐hydroxymethyltetrahydrofurfural over heterogeneous Pd catalyst under mild conditions

5‐Hydroxymethylfurfural (5‐HMF) derived from lignocellulose represents an important platform molecule that could be employed in the selective hydrogenation of the furan ring to prepare 5‑hydroxymethyltetrahydrofurfural (HMTHF). However, the reported catalytic systems for the synthesis of HMTHF using 5‐HMF still require additional hydrogen pressure. In this study, the Pd/ZrO2 catalyst with uniformly dispersed Pd nanoparticles was prepared via a simple impregnation reduction process. This catalyst exhibited excellent catalytic activity and selectivity for the hydrogenation of 5‐HMF to HMTHF. High HMTHF yield up to 92.3% was produced under mild reaction conditions of ambient hydrogen pressure and room temperature in methanol solvent. This result was superior to the most catalytic systems that had been reported so far. The mechanism study revealed that the active hydrogen species on the surface of the Pd nanoparticles and the reaction solvent in this study were the pivotal factors influencing the hydrogenation of furan rings in 5‐HMF.

Highly Dispersed Pd@ZIF‐8 for Photo‐Assisted Cross‐Couplings and CO2 to Methanol: Activity and Selectivity Insights

AbstractOur study unveils a pioneering methodology that effectively distributes Pd species within a zeolitic imidazolate framework‐8 (ZIF‐8). We demonstrate that Pd can be encapsulated within ZIF‐8 as atomically dispersed Pd species that function as an excited‐state transition metal catalyst for promoting carbon–carbon (C−C) cross‐couplings at room temperature using visible light as the driving force. Furthermore, the same material can be reduced at 250 °C, forming Pd metal nanoparticles encapsulated in ZIF‐8. This catalyst shows high rates and selectivity for carbon dioxide hydrogenation to methanol under industrially relevant conditions (250 °C, 50 bar): 7.46 molmethanol molmetal−1 h−1 and >99 %. Our results demonstrate the correlations of the catalyst structure with the performances at experimental and theoretical levels.

Enhanced carbon monoxide poisoning resistance of Pd/BEA by integrating with CeO2 for low temperature NO adsorption: The role of CeO2 on oxidizing carbon monoxide to CO32−

Passive NOx adsorption (PNA) represents a promising technology for controlling NOx emissions during cold starts. However, Pd/zeolite catalysts, the latest generation of PNA materials, suffer from serious deactivation under CO concentrations, owing to the CO induced aggregation of highly dispersed Pd sites to PdO particles. In this work, we found that the resistance to CO poisoning of Pd/BEA can be enhanced by integrating with CeO2 through physical mixing. The resulting CeO2 + Pd/BEA composite catalyst demonstrated a notably higher NOx storage capacity (with a NOx/Pd ratio of 1.3) compared to Pd/BEA (0.8). This improvement can be attributed to the interaction between CeO2 and the BEA support, which promoted the formation of nitrates on CeO2 during NO adsorption at 80 °C. More importantly, CeO2 effectively shielded Pd2+ ions from reduction by CO, with 88 % of Pd2+ ions remaining after CO exposure, significantly outperforming Pd/BEA, which retained only 66 %. Spectra characterization and DFT results indicate that the defects in CeO2 strongly trapped CO (−0.973 eV), and the oxidation of trapped CO to CO32− by adsorbed oxygen (Oads) was exothermic (−1.35 eV), which reduced the exposure of Pd2+ ions to CO and inhibited the reduction and agglomeration of Pd2+ ions. While the composite sample still exhibited a slight reduction in NOx storage capacity after CO poisoning, with the NOx/Pd ratio decreasing from 1.3 to 0.9. The DFT simulation results indicate that the Ce-Oads bonds in CeO2 are weakened during the decomposition of the CO32− intermediate. This weakening could potentially facilitate the release of Oads, thereby reducing the Oads content as evidenced by spectral evidence. The decrease of Oads diminished nitrate formation on the CeO2 component in composite sample, resulting in the decline of NOx storage capacity after CO poisoning.

Atomically Dispersed Palladium Catalyst for Chemoselective Hydrogenation of Quinolines.

Chemoselective hydrogenation of quinoline and its derivatives is a significant strategy to achieve the corresponding 1,2,3,4-tetrahydroquinolines (py-THQ) for various potential applications. Here, we precisely constructed a titanium carbide supported atomically dispersed Pd catalyst (PdSA+NC/TiC) for quinoline hydrogenation, delivering above 99% py-THQ selectivity at complete conversion with an outstanding turnover frequency (TOF) of 463 h-1. AC-HAADF-STEM and XAFS demonstrate that the atomic dispersion of Pd includes Pd-Ti2C2 single atoms and Pd clusters with atomic-layer thickness. Theoretical calculation and experimental results revealed that H2 dissociation and subsequent hydrogenation rates were greatly promoted over Pd clusters. Although the adsorption of quinolines and intermediates are easier on Pd clusters than on Pd single atoms, the desorption of py-THQ is more favored over Pd single atoms than over Pd clusters. The desorption step may be the main reason for 5,6,7,8-tetrahydroquinoline (bz-THQ) and decahydroquinoline (DHQ) formation. Thus, a low reaction activity and py-THQ selectivity were received over PdSA/TiC and PdNP/TiC, respectively.

Low-pressure CO2 hydrogenation coupled with toluene methylation to para-xylene using atomic Pd-doped ZnZrOx–HZSM-5

Selective methylation of aromatics using CO2/H2 presents a promising avenue for producing high-value-added chemicals with high selectivity. Herein, we introduced atomically dispersed Pd species into ZnZrOx solid solution and combined with HZSM-5 to create a bifunctional catalyst, applying to selectively synthesize para-xylene through toluene methylation using CO2/H2 at low pressure. Remarkably, 0.1 wt% Pd in PdZnZrOx–HZSM-5 afforded the selectivity of xylene in CO-free products and para-xylene in xylene to 90.0% and 85.6% at 0.5 MPa, respectively. Spectroscopic characterizations revealed that atomically dispersed Pd species enhance the dissociation of adsorbed hydrogen and facilitate the creation of oxygen vacancies, benefiting the CO2 hydrogenation to CHxO intermediates. Density functional theory calculations suggested that Pd-doped ZnZrOx reduces the energy barrier for hydrogenating H2COOH* to H2CO*, aiding to form CH3O* intermediate for toluene methylation. This work provides insights into the design of catalysts for the selective methylation of aromatics using CO2/H2 at low pressure.

Three-dimensional gel network structure of agarose interlayer dispersed Pd nanoparticles in copper foam electrode for electrocatalytic degradation of doxycycline hydrochloride

In this study, we successfully prepared palladium/agarose/copper foam (Pd/AG/CF) composite electrodes by utilizing the three-dimensional network structure agarose (AG), a green material derived from biomass, and homogeneously immobilizing palladium (Pd) atoms on a copper foam (CF) substrate through a facile route. The electrode showed excellent performance in the electrocatalytic degradation of doxycycline (DOX), with a high DOX degradation rate of 92.19 % in 60 min. In-depth studies revealed that palladium can form metal-metal interactions with the CF substrates, which enhances the electron transfer on the catalyst surface. In addition, the introduction of agarose effectively prevented the agglomeration of palladium nanoparticles. In addition, the hydroxyl functional groups in the molecular structure of agarose facilitate interactions between water molecules and the electrode interface through the formation of hydrogen bonds, thereby further enhancing the efficiency of the electrocatalytic reaction. In addition to good stability and reusability. Microbial toxicity test results show that the degraded wastewater has minimal impact on the environment. Also, possible degradation pathways of DOX were explored in this study. Finally, a novel continuous flow reactor was designed, featuring a unique design that ensures full contact between wastewater and the composite electrodes, thereby achieving continuous and efficient treatment of antibiotic wastewater.

Are adolescents with premenstrual disorder at risk for cardiac arrhythmias?

One of the most commonly experienced symptoms of premenstrual disorder (PMD) is anxiety, and there is a notable rise in sympathomimetic activity in this patient group. Studies have linked fluctuations in systemic autonomic tone to electrocardiography (ECG) changes. This study aims to investigate the relationship between anxiety, a common symptom of PMD, and alterations in QT dispersion (QTd) and P-wave dispersion (Pd) in adolescent females. This cross-sectional study included female adolescents aged 12-18 with regular menstruation for at least 3 months. Participants completed the premenstrual syndrome scale (PMSS) and were divided into two groups, PMD and control, according to the PMSS score. A standard 12-lead body surface ECG was performed and QTd and Pd values were determined in each participant. Of the 43 participants, 27 were categorized into the PMD group, with a mean age of 15.15 ± 1.43 years. Age at menarche and menstrual cycle patterns were comparable between the PMD and control groups. Statistical analysis revealed significantly higher Pmin (p = 0.010) and Pd values (p < 0.001) in the PMD group compared to controls. A positive correlation between PMSS scores and Pd (p = 0.049) was also observed. Changes in atrial conduction and ventricular repolarization due to the pathophysiology of PMD may increase the risk of developing atrial and ventricular tachyarrhythmias over time. Screening patients with PMD using an ECG may be useful in identifying potentially at-risk adolescents.

Photocatalytic Methanol Dehydrogenation Promoted Synergistically by Atomically Dispersed Pd and Clustered Pd.

Supported metal in the form of single atoms, clusters, and particles can individually or jointly affect the activity of supported heterogeneous catalysts. While the individual contribution of the supported metal to the overall activity of supported photocatalysts has been identified, the joint activity of mixed metal species is overlooked because of their different photoelectric properties. Here, atomically dispersed Pd (Pd1) and Pd clusters are loaded onto CdS, serving as oxidation and reduction sites for methanol dehydrogenation. The Pd1 substitutes Cd2+, forming hole-trapping states for methanol oxidation and assisting the dispersion of photodeposited Pd clusters. Therefore, methanol dehydrogenation on CdS with supported Pd1 and Pd clusters exhibits the highest turnover frequency of 1.14 s-1 based on the Pd content and affords H2 and HCHO with a similar apparent quantum yield of 87 ± 1% at 452 nm under optimized reaction conditions. This work highlights the synergistic catalysis of supported metal for improved photocatalytic activity.

P133 ALTERED P-WAVE DISPERSION IN NEWLY DIAGNOSED YOUNG HYPERTENSIVES

Background and objective: P wave dispersion (Pd) is a useful electrocardiographic marker for predicting the onset of atrial fibrillation. It has been little studied in recent hypertension. The aim was to determine the behavior of maximum P wave duration (Pmax) and Pd in young hypertensive patients with recent onset and its relationship with other variables. Methods: A cross-sectional, prospective, comparative study was performed in 60 young men (30 hypertensive and 30 non-hypertensive). P wave measurements were obtained with 12-lead electrocardiogram. Statistical analysis included applications of simple linear correlation, sample means were compared by Student's t-test. Results: There were no significant differences in the baseline characteristics of both groups. Pmax (78.67 ± 5.71 ms) and Pd (42.33 ± 6.26ms) were found to be significantly prolonged (p&lt;0.001) in the hypertensive group compared to normotensive subjects (Pmax 61.00 ± 7.69 ms; Pd 25.00 ± 8.61 ms). Pd correlated significantly (r = 0.716; p&lt;0.001) with systolic and diastolic blood pressure (r = 0.696; p&lt;0.001). Conclusions: Pmax and Pd are found to be increased in young patients with recent-onset hypertension, and these values increase in direct proportion to blood pressure figures.

Hydrogen spillover enhances the selective hydrogenation of α,β-unsaturated aldehydes on the Cu–O–Ce interface

The industrially important selective hydrogenation of α,β-unsaturated aldehydes to allyl alcohol is still challenging to realize using heterogenous hydrogenation catalysts. Supported Cu catalysts have shown moderate selectivity, yet low activity for the reaction, due to the electronic structure of Cu. By anchoring atomically dispersed Pd atoms onto the exposed Cu surface of Cu@CeO2, we report in this work that hydrogen spillover activates the inert metal-oxide interfaces of Cu@CeO2 into highly effective and selective catalytic sites for hydrogenation under mild reaction conditions. The as-prepared catalysts exhibit much higher catalytic activity in the selective hydrogenation of acrolein than Cu@CeO2. Comprehensive studies reveal that atomically dispersed Pd species are critical for the activation and homolytic splitting of H2. The activated H atoms easily spill to the Cu–O–Ce interfaces as Cu–Hδ– and interfacial Ce–O–Hδ+ species, making them the active sites for hydrogenation of polar C=O bonds. Moreover, the weak adsorption of allyl alcohol on the Pd and Cu–O–Ce interfacial sites prevents deep hydrogenation, leading to selective hydrogenation of several α,β-unsaturated aldehydes. Overall, we demonstrate here a synergic effect between single atom alloy and the support for activation of an inert metal-oxide interface into selective catalytic sites.

Constructing highly dispersed Pd on Ca-Al layered double hydroxide for efficiently selective oxidation of cumene

The selective oxidation of cumene to produce cumene hydroperoxide (CHP) with high yield continues to be a challenge when using traditional catalysts, despite the importance of CHP as a key intermediate in phenol industry. Herein, Ca-Al layered double hydroxide (CaAl-LDH) supported Pd was prepared by one-step co-precipitation approach, wherein the Pd species on the CaAl-LDH support were highly dispersed and evidenced by TEM and CO-DRIFTS characterization. The synthetic Pd/CaAl-LDH exhibited the remarkably high catalytic performance, and the selectivity of CHP could reach a very high level (92.1 %) on the high cumene conversion of 52.0 %. The high loading of Pd (4 wt.%) leads to the obvious aggregation of Pd on the edge and surface of CaAl-LDH, Pd nanoparticles could accelerate the decomposition of target product CHP, and thus resulting the decrease of CHP in selectivity. The reaction mechanism was studied by simple radical scavenging experiments, and it was suggested that the activation of oxygen molecules was the main pathway for Pd/CaAl-LDH to promote the oxidation reaction of cumene.

Is the development of arrhythmia predictable in rheumatoid arthritis?

This study aimed to determine whether there is a difference in the electrocardiography (ECG) measurements of healthy controls and rheumatoid arthritis (RA) patients and to predict whether they can be used to determine the risk of arrhythmia in patients. The prospective study included 50 cardiac asymptomatic RA patients (38 males, 12 females; mean age: 46.8±9.1 years; range, 18 to 60 years) who met the 2010 American College of Rheumatology/European Alliance of Associations for Rheumatology RA criteria and 50 healthy volunteers (34 males, 16 females; mean age: 43.4±10.4 years; range, 18 to 60 years) as a control group between June 1, 2022, and August 31, 2022. Disease activity of the patients was calculated with the Disase Activity Score (DAS28). Heart rate, minimum and maximum QT intervals, QT dispersion, minimum and maximum P waves, P wave dispersion (Pd), minimum and maximum Tp-e intervals, Tp-e dispersion, minimum and maximum corrected QT (QTc) intervals, QTc dispersion, and the Tp-e/QTc ratio in ECGs were calculated. The mean disease duration of the RA group was 9.09±5.74 years. The mean C-reactive protein level was 9.83±8.29, the mean erythrocyte sedimentation rate was 26.12±16.28 mm/h, and the mean DAS28 was 3.03±0.37. There was a statistically significant increase in the maximum P wave, Pd, maximum QT, QT dispersion, maximum QTc, QTc dispersion, maximum Tp-e, Tp-e dispersion, and Tp-e/QTc dispersion parameters in the RA group compared to the control group, while there was a significant decrease in the minimum P wave, minimum QT, and minimum QTc parameters. In our study, the Pd, QTc dispersion, Tp-e dispersion, and Tp-e/QTc dispersion values of our patients, which indicate the risk of atrial and ventricular arrhythmia, were found to be significantly higher. This finding suggests that our patients had an increased risk of cardiac morbidity and mortality. Arrhythmias are the likely source of the increase in sudden cardiac death in RA, and these new indicators measured on ECG can be used as standardized cardiovascular morbidity and mortality indicators in the future.

Hocheffizienter Niedrigbeladener PdOx/AlSiOx‐Katalysator für die Ethylen‐Dimerisierung

AbstractDie Ethylen‐Dimerisierung ist ein industrieller Prozess, der derzeit mit homogenen Katalysatoren durchgeführt wird. Hier stellen wir einen hochaktiven heterogenen Katalysator vor, der winzige Mengen von atomar dispergiertem Pd enthält. Er erfordert keine Cokatalysatoren oder Aktivatoren und übertrifft die Leistung früherer Katalysatoren, die unter ähnlichen Reaktionsbedingungen getestet wurden. Die Selektivität für C4‐ und C6‐Kohlenwasserstoffe betrug bei 200 °C etwa 80 % bzw. 10 % bei 42 % C2H4‐Umsatz unter Verwendung eines industriell relevanten Reaktionsgemisches mit 50 Vol.‐% Ethylen. Unsere Experimente zur Kinetik und Katalysatorcharakterisierung, ergänzt durch Dichtefunktionaltheorie‐Berechnungen, liefern molekulare Einblicke in die lokale Umgebung isolierter Pd(II)Ox‐Spezies und ihre Rolle bei der Erzielung einer hohen Aktivität in der Zielreaktion. Als der entwickelte Katalysator rationell mit einem Mo‐haltigen Olefinmetathesekatalysator im gleichen Reaktor integriert wurde, reagierten die gebildeten Butene mit Ethylen zu Propylen mit einer Selektivität von 98 % bei etwa 24 % C2H4‐Umsatz.

Highly Efficient Low-loaded PdOx/AlSiOx Catalyst for Ethylene Dimerization.

Ethylene dimerization is an industrial process that is currently carried out using homogeneous catalysts. Here we present a highly active heterogeneous catalyst containing minute amounts of atomically dispersed Pd. It requires no co-catalyst(s) or activator(s) and significantly outperforms previously reported catalysts tested under similar reaction conditions. The selectivity to C4- and C6-hydrocarbons was about 80 % and 10 % at 42 % ethylene conversion at 200 °C using an industrially relevant feed containing 50 vol % ethylene, respectively. Our kinetic and catalyst characterization experiments complemented by density functional theory calculations provide molecular insights into the local environment of isolated Pd(II)Ox species and their role in achieving high activity in the target reaction. When the developed catalyst was rationally integrated with a Mo-containing olefin metathesis catalyst in the same reactor, the formed butenes reacted with ethylene to propylene with a selectivity of 98 % at about 24 % ethylene conversion.