Direct, Selective Production of Aromatic Alcohols from Ethanol Using a Tailored Bifunctional Cobalt–Hydroxyapatite Catalyst

Enabling direct oxidation of ethane to acetaldehyde with oxygen using supported PdO nanoparticles

Industrial-scale production of acetaldehyde relies heavily on homogeneous catalysts. Here, we used ethane as the feedstock and developed ZSM-5-supported PdO nanoparticles for the direct oxidation of ethane to acetaldehyde by utilizing O2 and CO. PdO nanoparticles clearly demonstrate effective activity and prevent the further deep oxidation of acetaldehyde.

Multicomponent synthesis via acceptorless alcohol dehydrogenation: an easy access to tri-substituted pyridines

Herein, we report palladium supported on a hydroxyapatite catalyst for synthesizing tri-substituted pyridines using ammonium acetate as the nitrogen source via acceptorless alcohol dehydrogenation strategy. The strategy offers a broad substrate scope using inexpensive and readily available alcohols as the starting material. The catalyst was prepared using a simple method and analyzed by several techniques, including FE-SEM, EDS, HR-TEM, BET, XRD, FT-IR, UV-visible spectroscopy, and XPS, demonstrating the anchoring of Pd nanoparticles on hydroxyapatite in the zero oxidation state. Moreover, several controlled experiments were carried out to understand the reaction pathway and a suitable mechanism has been proposed.

Enabling direct-growth route for highly efficient ethanol upgrading to long-chain alcohols in aqueous phase

Upgrading ethanol to long-chain alcohols (LAS, C6+OH) offers an attractive and sustainable approach to carbon neutrality. Yet it remains a grand challenge to achieve efficient carbon chain propagation, particularly with noble metal-free catalysts in aqueous phase, toward LAS production. Here we report an unconventional but effective strategy for designing highly efficient catalysts for ethanol upgrading to LAS, in which Ni catalytic sites are controllably exposed on surface through sulfur modification. The optimal catalyst exhibits the performance well exceeding previous reports, achieving ultrahigh LAS selectivity (15.2% C6OH and 59.0% C8+OH) at nearly complete ethanol conversion (99.1%). Our in situ characterizations, together with theoretical simulation, reveal that the selectively exposed Ni sites which offer strong adsorption for aldehydes but are inert for side reactions can effectively stabilize and enrich aldehyde intermediates, dramatically improving direct-growth probability toward LAS production. This work opens a new paradigm for designing high-performance non-noble metal catalysts for upgrading aqueous EtOH to LAS.

Design Strategies for Hydroxyapatite-Based Materials to Enhance Their Catalytic Performance and Applicability

Hydroxyapatite (HAP) is a green catalyst that has a wide range of applications in catalysis due to its high flexibility and multifunctionality. These properties allow HAP to accommodate a large number of catalyst modifications that can selectively improve the catalytic performance in target reactions. To date, many studies have been conducted to elucidate the effect of HAP modification on the catalytic activities for various reactions. However, systematic design strategies for HAP catalysts are not established yet due to an incomplete understanding of underlying structure-activity relationships. In this review, tuning methods of HAP for improving the catalytic performance are discussed: 1) ionic composition change, 2) morphology control, 3) incorporation of other metal species, and 4) catalytic support engineering. Detailed mechanisms and effects of structural modulations on the catalytic performances for attaining the design insights of HAP catalysts are investigated. In addition, computational studies to understand catalytic reactions on HAP materials are also introduced. Finally, important areas for future research are highlighted.

Highly dispersed Co anchored on Ce-doped hydroxyapatite as a dual-functional catalyst for selective hydrogenolysis of 5-hydroxymethylfurfural

Hydrodeoxygenation (HDO) is an indispensable approach to produce renewable biofuels and value-added chemicals using natural biomass and its derivatives. 2,5-Dimethylfuran (DMF) is considered to be a very promising liquid biofuel, and it can be fabricated by HDO of the biomass derivative 5-hydroxymethylfurfural (HMF). Herein, a highly efficient bifunctional catalyst, Co/HAP(Ce), was fabricated by anchoring highly dispersed Co on Ce-doped hydroxyapatite (HAP(Ce)). Co/HAP(Ce) displayed excellent HDO catalytic activity to convert HMF to DMF, and 99% HMF conversion and 96% DMF selectivity can be obtained under 150 °C, 2 MPa H2 conditions for 5 h. Density functional theory calculations revealed that H2 can be more easily activated by Co/HAP(Ce). Systematic studies confirmed that the high activity of Co/HAP(Ce) can be ascribed to the desired acid-alkali properties, highly dispersed cobalt species and strong metal-support interactions. This research provides a cost effective approach for designing efficient catalysts for HDO of biomass and its derivatives.

Chitosan derived efficient and stable Pd nano-catalyst for high efficiency hydrogenation

The design and development of green and efficient supported catalysts is the frontier direction in the field of green synthesis, which conforms to the strategic concept of green sustainable chemistry and "carbon neutrality". Herein, we used a renewable resource chitosan (CS) derived from seafood wastes of chitin as carriers to design two different chitosan-supported palladium (Pd) nano-catalysts through different activation methods. The Pd particles were firmly and uniformly dispersed on the chitosan microspheres due to the interconnected nanoporous structure and functional groups of chitosan, proved by diverse characterizations. The chitosan supported catalysts (Pd@CS) was applied to hydrogenation of 4-nitrophenol, which showed competitive catalytic activity compared to commercial Pd/C, un-supported nano-Pd and Pd(OAc)₂ catalysts, as well as excellent catalytic activity, good reusability, long-life and broad applicability in selective hydrogenation of aromatic aldehydes, suggesting potential of applications in green industrial catalysis.

Effects of Various Ripening Media on the Mesoporous Structure and Morphology of Hydroxyapatite Powders

Mesoporous hydroxyapatite (HA) materials demonstrate advantages as catalysts and as support systems for catalysis, as adsorbent materials for removing contamination from soil and water, and as nanocarriers of functional agents for bone-related therapies. The present research demonstrates the possibility of the enlargement of the Brunauer-Emmett-Teller specific surface area (SSA), pore volume, and average pore diameter via changing the synthesis medium and ripening the material in the mother solution after the precipitation processes have been completed. HA powders were investigated via chemical analysis, X-ray diffraction analysis, Fourier-transform IR spectroscopy, transmission electron microscopy (TEM), and scanning (SEM) electron microscopy. Their SSA, pore volume, and pore-size distributions were determined via low-temperature nitrogen adsorption measurements, the zeta potential was established, and electron paramagnetic resonance (EPR) spectroscopy was performed. When the materials were synthesized in water-ethanol and water-acetone media, the SSA and total pore volume were 52.1 m²g^-1 and 116.4 m²g^-1, and 0.231 and 0.286 cm³g^-1, respectively. After ripening for 21 days, the particle morphology changed, the length/width aspect ratio decreased, and looser and smaller powder agglomerates were obtained. These changes in their characteristics led to an increase in SSA for the water and water-ethanol samples, while pore volume demonstrated a multiplied increase for all samples, reaching 0.593 cm³g^-1 for the water-acetone sample.

Process schemes of ethanol coupling to C4 olefins based on a genetic algorithm for back propagation neural network optimization

C4 olefin is an important feedstock for the chemical industry. Designing an effective and stable industrial process for preparing C4 olefin from renewable ethanol is crucial for further sustainable chemical production. In this study, a comprehensive evaluation system of an experimental scheme was constructed based on the Analytic Hierarchy Process/Entropy Weight Method-Technique for Order Preference by Similarity to Ideal Solution (AHP/EWM-TOPSIS) and Chemical production indicators. Using this evaluation system, a Back Propagation Neural Network (BPNN) based on a Genetic Algorithm (GA) was constructed after simulating C4 olefin production conditions using the Improved Mixed Congruential method. Subsequently, the production scheme with the highest evaluation score was determined when the temperature was not limited and when the temperature was lower than 350°C through a series of mathematical models. Overall, our mathematical models provide guidance for the commercial production of ethanol to butene and effectively reduce the risk of scaling up the chemical process to pilot or industrial scale.

Drug Molecular Immobilization and Photofunctionalization of Calcium Phosphates for Exploring Theranostic Functions

Theranostics (bifunction of therapeutics and diagnostics) has attracted increasing attention due to its efficiency that can reduce the physical and financial burden on patients. One of the promising materials for theranostics is calcium phosphate (CP) and it is biocompatible and can be functionalized not only with drug molecules but also with rare earth ions to show photoluminescence that is necessary for the diagnostic purpose. Such the CP-based hybrids are formed in vivo by interacting between functional groups of organic molecules and inorganic ions. It is of great importance to elucidate the interaction of CP with the photofunctional species and the drug molecules to clarify the relationship between the existing state and function. Well-designed photofunctional CPs will contribute to biomedical fields as highly-functional ormultifunctional theranostic materials at the nanoscales. In this review, we describe the hybridization between CPs and heterogeneous species, mainly focusing on europium(III) ion and methylene blue molecule as the representative photofunctional species for theranostics applications.

Insight and Activation Energy Surface of the Dehydrogenation of C2HxO Species in Ethanol Oxidation Reaction on Ir(100)

Dehydrogenation of an organic compound is the first and the most fundamental elementary reaction in many organic reactions. In ethanol oxidation reaction (EOR) to form CO 2 , there are a total of 46 pathways in C 2 H x O (x=1-6) species leading to the removal of all six hydrogen atoms in five C-H bonds and one O-H bond. To investigate the degree of dehydrogenation in EOR under operando conditions, we performed density function theory (DFT) calculations to study 28 dehydrogenation steps of C 2 H x O on Ir(100). An activation energy surface was then constructed and compared with that of the C-C bond cleavages to understand the importance of the degree of dehydrogenation in EOR. The results show that there are likely 28 dehydrogenations in EOR under fuel cell temperatures and the last two hydrogens in C 2 H 2 O are less likely cleaved. On the other hand, deep dehydrogenation including 45 dehydrogenations can occur under ethanol steam reforming conditions.

Highly dispersed silver nanoparticles supported on hydroxyapatite catalyst with different morphology for CO oxidation

Supported nano-silver (nano-Ag) catalysts have been widely used in heterogeneous catalysis. However, because of their poor thermal stability, it restricts the practical application. In order to solve this issue, we...

Direct synthesis of p-methyl benzaldehyde from acetaldehyde via an organic amine-catalyzed dehydrogenation mechanism

p-Methyl benzaldehyde (p-MBA) is a class of key chemical intermediates of pharmaceuticals. Conventional industrial processes for p-MBA production involve the consecutive photochlorination, amination, and acid hydrolysis of petroleum-derived p-xylene, while producing vast pollutants and waste water. Herein, we report a direct, green route for selective synthesis of p-MBA from acetaldehyde using a diphenyl prolinol trimethylsilyl ether catalyst. The optimized p-MBA selectivity is up to 90% at an acetaldehyde conversion as high as 99.8%. Intermediate structure and ¹⁸O-isotope data revealed that the conversion of acetaldehyde to p-methylcyclohexadienal intermediates proceeds in an enamine-iminium intermediate mechanism. Then, controlled experiments and D-isotope results indicated that the dehydrogenation of p-methylcyclohexadienal to p-MBA and H₂ is catalyzed by the same amines through an iminium intermediate. This is an example that metal-free amines catalyze the dehydrogenation (releasing H₂), rather than using metals or stoichiometric oxidants.

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A direct route to produce p-methyl benzaldehyde from biomass-derived acetaldehyde

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Revealing the reaction kinetics and mechanism under reaction conditions

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An example of an organic amine-catalyzed dehydrogenation-aromatization reaction

Customized Cellulose Fiber Paper Enabled by an In Situ Growth of Ultralong Hydroxyapatite Nanowires

Cellulose fiber (CF) paper is a low-cost, sustainable, and flexible substrate, which has gained increasing interest recently. Before practical usage, the functionalization of the pristine CF paper is indispensable to meet requirements of specific applications. Different from conventional surface modification or physical mixing methods, we report in situ growth of ultralong hydroxyapatite nanowires (HAPNWs) with lengths larger than 10 μm on the CF paper. HAPNWs are radially aligned on the surface of CFs, creating a micro/nanoscale hierarchical structure. By means of the excellent ion exchange ability of HAP and the hierarchical structure, the functions of the CF paper can be easily customized. As a proof-of-concept, we demonstrate two kinds of functional CF paper: (1) the photoluminescent CF paper by doping Eu³⁺ and Tb³⁺ ions into the crystal lattice of HAPNWs and (2) the superhydrophobic CF paper by coating poly(dimethylsiloxane) on the HAPNW hierarchical structure, which can be applied for self-cleaning and oil/water separation. It is expected that an in situ growth of ultralong HAPNWs will provide an instructive guideline for designing a CF paper with specific functions.

Polyethylene upcycling to long-chain alkylaromatics by tandem hydrogenolysis/aromatization

The current scale of plastics production and the accompanying waste disposal problems represent a largely untapped opportunity for chemical upcycling. Tandem catalytic conversion by platinum supported on γ-alumina converts various polyethylene grades in high yields (up to 80 weight percent) to low-molecular-weight liquid/wax products, in the absence of added solvent or molecular hydrogen, with little production of light gases. The major components are valuable long-chain alkylaromatics and alkylnaphthenes (average ~C30, dispersity Ð = 1.1). Coupling exothermic hydrogenolysis with endothermic aromatization renders the overall transformation thermodynamically accessible despite the moderate reaction temperature of 280°C. This approach demonstrates how waste polyolefins can be a viable feedstock for the generation of molecular hydrocarbon products.

Identifying the roles of acid–base sites in formation pathways of tolualdehydes from acetaldehyde over MgO-based catalysts

Basic (M–O)-type centers convert C₄ intermediates to renewable xylene analogs and proximal acid sites tune isomeric selectivity.

Hydroxyapatite nanowires rich in [Ca-O-P] sites for ethanol direct coupling showing high C6-12 alcohol yield

Herein, we have shown that the [Ca-O-P] sites exposed on hydroxyapatite are clearly responsible for C-C formation in ethanol direct-coupling, and their high density accelerates the C-C coupling rate and boosts C6-12 alcohol production. Notably, nanowire-like hydroxyapatite exhibited 30.4% selectivity to n-butanol and 63.9% selectivity to C6-12OH at a conversion of 45.7% at 325 °C, and thereby close to 30% yield of C6-12OH, which is greatly higher than that using the state-of-the-art catalysts (6%).