Liquid-phase Reaction Research Articles

Cover Feature: Near Infrared Light‐to‐Heat Conversion for Liquid‐Phase Oxidation Reactions by Antimony‐Doped Tin Oxide Nanocrystals (ChemPhysChem 7/2023)

The Cover Feature represents the action of antimony-doped tin oxide support for catalysts as an effective near infrared light-to-heat converter significantly enhancing the catalytic activity and selectivity for liquid-phase catalytic reactions due to the local heating of the catalyst surface with the bulk solution temperature maintained at ambient temperature. Cover design by Shin-ichi Naya. More information can be found in the Concept by Hiroaki Tada and co-workers.

A Liquid-Phase reaction strategy to construct aqueous Sodium-Ion batteries anode with enhanced redox reversibility and cycling stability

NASICON-type NaTi2(PO4)3 compound is strongly considered to be a promising anode material for aqueous sodium-ion batteries, but suffering from low redox reversibility and poor cycling stability due to severe side reactions in aqueous electrolytes. Herein, a novel liquid-phase reaction strategy is reported for in-situ constructing carbon-coated NaTi2(PO4)3 nanocrystals (C-NTP) with enhanced redox reversibility and cycling stability. The construction mechanism, structural properties and electrochemical performance of the C-NTP material are carefully investigated. It is suggested that the material possesses a mesoporous carbon-coating structure and delivers outstanding performance with a high reversible capacity of 114.5 mAh·g−1 at 100 mA·g−1 and an impressive capacity retention of 82.1% after 1000 cycles at 1000 mA·g−1. The enhanced redox reversibility and cycling stability are attributed to the unique carbon-coating structure that improves the reaction kinetics and structural stability of the material owing to the high electronic conductivity and corrosion-resistant ability.

Heterogeneous characteristics and absorption enhancement of refractory black carbon in an urban city of China

In this study, field measurement was conducted using an integrated online monitoring system to characterize heterogeneous properties and light absorption of refractory black carbon (rBC). rBC particles are mainly from the incomplete combustion of carbonaceous fuels. With the data collected from a single particle soot photometer, thickly coated (BCkc) and thinly coated (BCnc) particles are characterized with their lag times. With different responses to the precipitation, a dramatical decline of 83 % in the number concentration of BCkc is shown after rainfall, while that of BCnc decreases by 39 %. There is a contrast in core size distribution that BCkc is always with larger particle sizes but has smaller core mass median diameters (MMD) than BCnc. The mean rBC-containing particle mass absorption cross-section (MAC) is 6.70 ± 1.52 m2 g−1, while the corresponding rBC core is 4.90 ± 1.02 m2 g−1. Interestingly, there are wide variations in the core MAC values which range by 57 % from 3.79 to 5.95 m2 g−1, which are also closely related to those of the whole rBC-containing particles with a Pearson correlation of 0.58 (p < 0.01). Errors would be made if we eliminate the discrepancies and set the core MAC as a constant when calculating absorption enhancement (Eabs). In this study, the mean Eabs is 1.37 ± 0.11 while the source apportionment shows that there are five contributors of Eabs including secondary aging (37 %), coal combustion (26 %), fugitive dust (15 %), biomass burning (13 %) and traffic-related emissions (9 %). Secondary aging is found to be the highest contributor due to the liquid phase reactions in formations of secondary inorganic aerosol. Our study characterizes property diversities and provides insights into the sources impacting the light absorption of rBC and will be helpful for controlling it in the future.

Influence of hot liquid flowing water on Zeolite Y stability

Zeolite Y is used in a wide field of catalysis because of its high surface area and strong acidity. Since flowing water is present in many catalytic liquid phase reactions, its impact was investigated. For that, the zeolite Y was treated with water at 200 °C and 42 bar in a flow reactor. The resulting characterization showed strong structural changes at high water flows. The typical zeolite structure was almost completely lost, but an amorphous phase similar to the faujasite framework was formed. Due to this, the characteristic micropores were destroyed (d = 0.7 nm, volume was reduced from 0.18 to 0.01 cm3/g) and small mesopores were created (d = 2–3 nm, volume was increased from 0.25 to 0.51 cm3/g). As a result, the specific surface area was not greatly reduced and was still at around 250 m2/g. In addition, the amount of octahedrally coordinated EFAl increased from 54 to 70% and a γ-Al2O3 as well as a kaolinite phase was observed. The formed tetrahedrally coordinated EFAl is responsible for EFAl-OH groups, which are strong Brønsted acid sites. In general, the total acid sites of the zeolite Y were not strongly reduced and the ratio of Lewis to Brønsted acid sites slightly increased from 70:30% to 80:20%. For all Al species, the oxygen coordination was strongly distorted. After water treatment, on Si a large number of coordinated OSi and OAl groups were substituted with OH groups. The ratio of Si to Al decreased from 1 to 0.7, because Si was dissolved out of the zeolite by the water. On the surface, it was vice versa, there the Si accumulated (the Si/Al ratio increased from 0.2 to 0.8), presumably as silica gel.

Effect of Mo-addition over a large enhancement of the hydrogen evolution reaction in WC/rGO nanocomposite

We report a large enhancement of the hydrogen evolution reaction in WxC/rGO nanocomposite by adding Mo to the composite. The mixed transition metal carbide (WxC-MoxC/rGO) nanocomposite was prepared by a liquid phase reaction followed by a high temperature (900 °C) annealing processes that led to the crystallization of WxC, MoxC and simultaneous reduction of graphene oxide to reduced graphene oxide (rGO). The WxC-MoxC/rGO (Mo = 0.25 g) catalyst achieved very good hydrogen evolution reaction with an overpotential of −170 mV at 10 mA and a Tafel slope of 76 mV dec−1 indicating the suitability of this composite for the hydrogen production.

Investigation of the mechanism of nickel hydroxide formation from nickel nitrate

Nickel hydroxides are widely used as electrochemically active substances in alkaline batteries and hybrid supercapacitors; they can be used for electrocatalysis, in electrochemical sensors, and as pigments. Knowledge of the formation mechanism of nickel hydroxides is necessary for developing and optimizing targeted synthesis methods. The thermal effects of processes in the formation of nickel hydroxide from nitrate were studied by the calorimetry method. The mechanism of precipitate formation was investigated by the method of simultaneous potentiometric (with a glass universal electrode) and conductometric titration. The nickel content in the samples obtained at the determined NaOH/Ni2+ ratios was investigated by the chemical method of trilonometry after preliminary dissolution. Calorimetric investigations showed that the reaction of nickel nitrate with NaOH was exothermic with ΔНreaction=‒28328.5 J/mol. The exothermic nature of the NaOH dilution process was revealed with ΔНdilution =‒2454 J/mol. According to the results of potentiometric titration, the formation of a basic salt of the NiOHNO3 type was not detected. Analysis of the results of conductometric titration revealed a two-stage chemical mechanism for the formation of nickel hydroxide from nitrate. At the first stage, which had a high rate, due to the liquid-phase reaction of the nickel cation with the hydroxyl anion, a primary precipitate of the composition Ni(OH)1.87(NO3)0.13 was formed. In the second stage, as a result of a slow topochemical reaction of the primary precipitate with hydroxyl anions, nitrate ions were displaced from the precipitate to form nickel hydroxide. These data are confirmed by the analysis of precipitate obtained at NaOH/Ni2+ ratios of 1.87 and 2.2: the Ni content was 52.95 % and 55.63 %, corresponding to the formulas Ni(OH)1.87(NO3)0.13∙0.68H2O and Ni(OH)2∙0.71H2O. This clearly indicated that the primary precipitate was nitrate-doped α-Ni(OH)2 and the final precipitate corresponded to the α-modification of nickel hydroxide

Liquid Phase Epoxidation of Propylene to Propylene Oxide with Hydrogen Peroxide on Titanium Silicalite-1: Spatially Resolved Measurements and Numerical Simulations

The spatial profile measurement technique was applied for the first time to a liquid phase reaction to study the selective oxidation of propylene to propylene oxide with hydrogen peroxide on titanium silicalite-1 catalyst, also known as the HPPO process. A spatial profiling reactor based on minimal invasive capillary sampling measurements was used to obtain the experimental data. The reactor is able to measure spatially resolved concentration and temperature profiles at industrially relevant conditions, that is, 40 °C and 20–35 bar pressure, with propylene in the liquid phase. The reaction was carried out at different contact times of LHSV 3.0, 6.0, and 12.0 h–1, respectively, achieving high conversion and selectivity. The experimental data show that the concentration profiles of the main epoxidation reaction follows a pseudo-zeroth-order behavior. In contrast, the side product concentration profiles exhibit a nonlinear trend. The primary side products of the reaction 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol were quantified. Furthermore, hydroxacetone and methoxyacetone from the consecutive reaction of 1-methoxy-2-propanol, 2-methoxy-1-propanol, and propylene glycol with hydrogen peroxide were detected as secondary side products. Formic acid, methylformate, dipropylene glycol methyl ether isomers, and dipropylene glycol isomers were detected in trace amounts. Quantitative data for the formation of hydroxyacetone is provided for the first time. The experimental concentration profiles were simulated using an axial 1D-pseudo-homogeneous dispersion model with two kinetic models reported in the literature. Additionally, a kinetic model based on the Eley–Rideal mechanism is proposed. Upon linearization, the derived model shows a correlation of R2 = 0.99 and R2 = 0.98 with the linearized form of the experimental differential rate. Statistical analysis of the models in this work shows that the derived Eley–Rideal mechanism has the highest correlation with the concentration gradients measured within the catalyst bed.

Lead-Free Halide Perovskite Cs2AgBiBr6/Bismuthene Composites for Improved CH4 Production in Photocatalytic CO2 Reduction.

CO2 photocatalytic conversion into value-added fuels through solar energy is a promising way of storing renewable energy while simultaneously reducing the concentration of CO2 in the atmosphere. Lead-based halide perovskites have recently shown great potential in various applications such as solar cells, optoelectronics, and photocatalysis. Even though they show high performance, the high toxicity of Pb2+ along with poor stability under ambient conditions restrains the application of these materials in photocatalysis. In this respect, we developed an in situ assembly strategy to fabricate the lead-free double perovskite Cs2AgBiBr6 on a 2D bismuthene nanosheet prepared by a ligand-assisted reprecipitation method for a liquid-phase CO2 photocatalytic reduction reaction. The composite improved the production and selectivity of the eight-electron CH4 pathway compared with the two-electron CO pathway, storing more of the light energy harvested by the photocatalyst. The Cs2AgBiBr6/bismuthene composite shows a photocatalytic activity of 1.49(±0.16) μmol g-1 h-1 CH4, 0.67(±0.14) μmol g-1 h-1 CO, and 0.75(±0.20) μmol g-1 h-1 H2, with a CH4 selectivity of 81(±1)% on an electron basis with 1 sun. The improved performance is attributed to the enhanced charge separation and suppressed electron-hole recombination due to good interfacial contact between the perovskite and bismuthene promoted by the synthesis method.

Role of hydroxyl on metal surface in hydrogenation reactions

The important role of surface hydroxyl in metal catalysis is attracting more attentions but rarely studied for liquid-phase hydrogenation reactions. Here we report such deliberate research with two model substrates, p-chloronitrobenzene and cinnamaldehyde. Graphene-supported iridium nanoparticles with hydroxyl on the metal surface were prepared by hydrothermal synthesis, and the surface hydroxyl can be removed by a mild pre-reduction. The catalyst with surface hydroxyl exhibited around three times higher rate for the hydrogenation of p-chloronitrobenzene than the catalyst without hydroxyl, and an opposite trend was found for the hydrogenation of cinnamaldehyde. Kinetic study revealed that although the surface hydroxyl halved the coverage of H on iridium, it increased the rate constant by a factor of eight through reducing the reaction barrier for the hydrogenation of p-chloronitrobenzene. Theoretical calculation confirmed that the surface hydroxyl can polarize the nitro group via a weak hydrogen-bond interaction and thus facilitate its hydrogenation.

Comparison of Direct Ink Writing and Binder Jetting for additive manufacturing of Pt/Al2O3 catalysts for the dehydrogenation of perhydro-dibenzyltoluene

Two additive manufacturing (AM) techniques, namely extrusion-based Direct Ink Writing (DIW) and powder-based Binder Jetting (BJ), were thoroughly compared to assess their respective advantages and drawbacks for catalyst shaping. The 3D printed monolithic Al2O3 supports were wet impregnated with H3Pt(SO3)2(OH) and tested for the dehydrogenation of perhydro-dibenzyltoluene (18H-DBT), a liquid organic hydrogen carrier (LOHC). The supports were analyzed regarding their specific surface area, compression strength, shrinkage behavior and pore size distribution with calcination temperatures ranging from 600 - 1200°C as well as 3D print specific characteristics. Benefiting the liquid phase reaction, pore diameters below 26nm were diminished above Tcalc = 1050°C, revealing a BET surface area of 26m2/g for BJ and 11m2/g for DIW printed supports. Furthermore, increasing the impregnation duration from 0.5h to 12h showed increased Pt loading, larger metal particles, and a deeper penetration into the support. Most notably, for BJ the Pt loading is generally higher due to higher meso- and macroporosity of the support. Catalytic 18H-DBT dehydrogenation with powder and monolithic catalysts showed equal dehydrogenation rates with both 3D printing methods, respectively. The achieved Pt productivity was about 4.3gH2gPt−1min−1 for powder tests and 2.7gH2gPt−1min−1 for monolithic pellets.

5,8-Di-tert-butyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione—A New Lipophilic N-oxyl Radical Precursor

N-hydroxyimides are widely known as organocatalysts for aerobic oxidation and oxidative coupling reactions, in which corresponding imide-N-oxyl radicals play the role of catalytically active hydrogen atom abstracting species. The drawbacks of many N-hydroxyimides are poor solubility in low polarity solvents and limited activity in the cleavage of unactivated C–H bonds. To overcome these shortcomings, we have synthesized a new lipophilic N-hydroxyimide, 5,8-di-tert-butyl-2-hydroxy-1H-benzo[de]isoquinoline-1,3(2H)-dione, with high solubility in low-polarity solvents such as DCM. According to the EPR study, the stability of the corresponding imide-N-oxyl radical is comparable to that of the non-tert-butylated analogue, naphthalimide-N-oxyl radical. DFT calculations showed that the NO–H bond dissociation enthalpy (BDE) in the synthesized tert-butylated-N-hydroxynaphthalimide is one of the highest in N-hydroxyimide series, which corresponds to high hydrogen atom abstracting reactivity and may be useful in catalysis of strong C–H bond oxidative cleavage. The synthesized compound can be considered as catalyst for liquid-phase free-radical oxidation and oxidative coupling reactions in non-polar media where solubility was previously the limiting factor.

Near Infrared Light-to-Heat Conversion for Liquid-Phase Oxidation Reactions by Antimony-Doped Tin Oxide Nanocrystals.

Effective utilization of the sunlight for chemical reactions is pivotal for dealing with the growing energy and environmental issues. So far, much effort has been focused on the development of semiconductor photocatalysts responsive to UV and visible light. However, the near infrared and infrared (NIR-IR) light occupying ∼50 % of the solar energy has usually been wasted because of the low photon energy insufficient for the band gap excitation. Antimony doping into SnO2 (ATO) induces strong absorption due to the conduction band electrons in the NIR region. The absorbed light energy is eventually converted to heat via the interaction between hot electrons and phonons. This Concept highlights the photothermal effect of ATO nanocrystals (NCs) on liquid-phase oxidation reactions through the NIR light-to-heat conversion. Under NIR illumination even at an intensity of ∼0.5 sun, the reaction field temperature on the catalyst surface is raised 20-30 K above the bulk solution temperature, while the latter is maintained near the ambient temperature. In some reactions, this photothermal local heating engenders the enhancement of not only the catalytic activity and selectivity but also the regeneration of catalytically active sites. Further, the photocatalytic activity of semiconductors can be promoted. Finally, the conclusions and possible subjects in the future are summarized.

Elucidating the Influence of Metal Surface Composition on Organic Adsorbate Binding Using Active Particle Dynamics

The adsorption strengths of organic compounds on metal surfaces are sensitive to the metal composition, and they play a central role in many catalytic reactions, helping to control the coverage of the reactant and altering the overall reaction rate. While adsorption energies are straightforward to measure and calculate in vacuum and gas-phase environments, adsorption energetics can be dramatically altered by the presence of solvent in liquid-phase reactions. However, the effects of metal composition on binding strengths in a liquid environment are less well understood, primarily due to the difficulty of accurate in situ measurements of organic binding on metal surfaces in the liquid phase. Here, we utilize the motion of active particles in water to probe the adsorption energies of an organic adsorbate (furfural) on a range of metal surfaces (pure Pd, pure Pt, and four PdAu alloy compositions) to elucidate the effect of metal composition. Janus particles with catalytic caps of particular metal compositions all exhibited active motion resulting from consumption of H2O2; adsorbate binding was inferred through the decrease in the velocity of active motion and was modeled by a Langmuir adsorption isotherm. The measured adsorption affinities were used to extract the adsorption enthalpy of furfural on the different metals. The Pd surface was found to bind furfural more strongly than the Pt surface by some 10 kJ/mol. Furthermore, the adsorption of furfural on the alloys was found to increase monotonically in magnitude with Pd content. The data reported herein aid the development of accurate understanding of organic adsorption in the presence of solvent and the role of the metal surface in tuning adsorption strengths to optimize catalytic processes in the liquid phase.

Cs0.33WO3/(t-m)-BiVO4 double Z-type heterojunction photothermal synergistic enhanced full-spectrum degradation of antibiotics

The Cs0.33WO3/(t-m)-BiVO4 double-Z heterojunction photocatalysts were prepared with photodeposition method and Cs0.33WO3 photothermal effect. After 180 min of reaction to Visible/NIR light, the dual Z-type heterojunction photocatalyst degraded 40 mg/L TC at the rates of 90.49 % and 91.94 %, respectively. The TOC removal rates were 73.41 % and 75.85 %, respectively. Moreover, the double Z-type heterojunction photocatalyst has good degradation stability and broad-spectrum degradability in the full spectral range. The presence of small polariton leap effects in Cs0.33WO3 crystals radiates energy in the form of phonons and raises the temperature of the liquid-phase reaction system, and the photothermal-photocatalytic synergy accelerates and enhances the degradation catalytic activity of the heterojunction. The synergistic contribution of photothermal effect-photocatalysis applied to environmental purification is presented in this study as a novel and practical research proposal.

Formic Acid Dehydrogenation over Ru- and Pd-Based Catalysts: Gas- vs. Liquid-Phase Reactions.

Formic acid has recently been revealed to be an excellent hydrogen carrier, and interest in the development of efficient and selective catalysts towards its dehydrogenation has grown. This reaction has been widely explored using homogeneous catalysts; however, from a practical and scalable point of view, heterogeneous catalysts are usually preferred in industry. In this work, formic acid dehydrogenation reactions in both liquid- and vapor-phase conditions have been investigated using heterogeneous catalysts based on mono- or bimetallic Pd/Ru. In all of the explored conditions, the catalysts showed good catalytic activity and selectivity towards the dehydrogenation reaction, avoiding the formation of undesired CO.

Metal–organic framework derived Co3S4 nanosheets grown on Ti mesh: an efficient electrocatalyst for electrochemical sensing of hydrazine

Co3S4 nanosheets on Ti mesh (Co3S4/TM) synthesized by a liquid phase reaction, subsequent anion exchange reaction and final hydrothermal vulcanization with Co-MOF as a precursor exhibit superior hydrazine sensing performance.

Synthesis of Schiff base stabilized AuNPs for enhanced catalytic degradation of pesticides, Cr(VI) detection, antioxidant, and antimicrobial activities

In this study, researchers synthesized ultra-small gold nanoparticles (AuNPs) using a Schiff-base and characterized them using several techniques. These Schiff-base stabilized AuNPs were then used for the catalytic reduction of organophosphate pesticides (malathion and parathion) in liquid phase reactions. The researchers achieved a high degradation efficiency of up to 95.06% and 99.1% with the addition of NaBH4 within a 50-min reaction time for malathion and parathion, respectively. Additionally, the synthesized AuNPs showed selectivity for sensing Cr(VI) metal ions at nanomolar concentrations (10–100 nM) using fluorometric detection.

NIOBIUM-DOPED PHOSPHOMOLYBDIC ACID CATALYST INCLUDED IN SILICA MATRIX: STUDY OF STABILITY AND REACTIVITY USING DIFFERENT LOADS

Heteropolyacids are used as catalysts in numerous reactions because they are inexpensive, nontoxic, have high acid strength and excellent redox properties. They have been used as acid catalyst in different ways, and numerous studies indicate that the incorporation of Nb into the structure of a solid generates an increase in the acidity of the sample, both at Lewis and Brönsted acid sites. Heteropolyacids have low surface area, which makes it necessary to include them in a support to increase the surface area and allow their use as heterogeneous catalysts in liquid phase reactions because they are very soluble in polar solvents. In this work, the synthesis of catalysts containing a niobium-doped heteropolyacid (PMoNb) included in silica at different concentrations is reported. The catalysts were characterized by ICP-MS, FT-IR, XRD, potentiometric titration, and their catalytic activity was tested in the selective oxidation of diphenyl sulfide to diphenyl sulfoxide, showing excellent results.

Platinum-based nanodendrites as glucose oxidase-mimicking surrogates.

Catalytic conversion of glucose represents an interesting field of research with multiple applications. From the biotechnology point of view, glucose conversion leads to the fabrication of different added-value by-products. In the field of nanocatalytic medicine, the reduction of glucose levels within the tumor microenvironment (TME) represents an appealing approach based on the starvation of cancer cells. Glucose typically achieves high conversion rates with the aid of glucose oxidase (GOx) enzymes or by fermentation. GOx is subjected to degradation, possesses poor recyclability and operates under very specific reaction conditions. Gold-based materials have been typically explored as inorganic catalytic alternatives to GOx in order to convert glucose into building block chemicals of interest. Still, the lack of sufficient selectivity towards certain products such as gluconolactone, the requirement of high fluxes of oxygen or the critical size dependency hinder their full potential, especially in liquid phase reactions. The present work describes the synthesis of platinum-based nanodendrites as novel enzyme-mimicking inorganic surrogates able to convert glucose into gluconolactone with outstanding selectivity values above 85%. We have also studied the enzymatic behavior of these Pt-based nanozymes using the Michaelis-Menten and Lineweaver-Burk models and used the main calculation approaches available in the literature to determine highly competitive glucose turnover rates for Pt or Pt-Au nanodendrites.

Formation mechanism of radial mesocrystals consisting of ZnO nanowires

Radial ZnO mesocrystals consisting of tapered ZnO nanowires (NWs) were synthesized by a liquid-phase reaction, which proceeds via the preferential zone-axis growth to ZnO NWs, and self-assembling of linear ZnO NW dimers.