Deep Cracking of Bulky Hydrocarbons into Light Products via Tandem Catalysis over Uniform Interconnected ZSM-5@AlSBA-15 Composites.

Deep cracking of bulky hydrocarbons on zeolite-containing catalysts into light products with high activity, desired selectivity, and long-term stability is demanded but challenging. Herein, the efficient deep cracking of 1,3,5-triisopropylbenzene (TIPB) on intimate ZSM-5@AlSBA-15 composites via tandem catalysis is demonstrated. The rapid aerosol-confined assembly enables the synthesis of the composites composed of a continuous AlSBA-15 matrix decorated with isolated ZSM-5 nanoparticles. The two components at various ZSM-5/AlSBA-15 mass ratios are uniformly mixed with chemically bonded pore walls, interconnected pores, and eliminated external surfaces of nanosized ZSM-5. The typical composite with a ZSM-5/AlSBA-15 mass ratio of 0.25 shows superior performance in TIPB cracking with outstanding activity (≈100% conversion) and deep cracking selectivity (mass of propylene + benzene > 60%) maintained for a long time (> 6 h) under a high TIPB flux (2 mL h-1), far better (several to tens of times higher) than the single-component and physically mixed catalysts and superior to literature results. The high performance is attributed to the cooperative tandem catalytic process, that is, selective and timely pre-cracking of TIPB to isopropylbenzene (IPB) in AlSBA-15 and subsequently timely diffusion and deep cracking of IPB in nanosized ZSM-5.

Fabrication of Uniform Melatonin Microparticles Potentially for Nasal Delivery: A Comparison of Spray Drying and Spray Freeze Drying.

PURPOSE: Insomnia is a major health concern, and melatonin (MLT) is key for initiating sleep. Delivering MLT nasally can enhance brain bioavailability by targeting the olfactory region. This study aimed to fabricate MLT embedded microparticles for nasal delivery. METHODS: MLT-cyclodextrin (CD) derivatives complex microparticles (MCCMPs) were fabricated by spray drying and spray freeze drying MLT and CD derivative solutions. Phase solubility and 1H-1H ROSEY NMR analysis assessed MLT-CD assembly. The effects of formulation compositions and process parameters on microparticle structural attributes were investigated. The in vitro nasal release and deposition performances were evaluated by a modified paddle-over-disk apparatus and 3D-printed nasal cavity cast, respectively. RESULTS: Sodium sulphobutylether-ß-cyclodextrin (SBE-ß-CD) exhibited the best complexation ability with MLT, with the indole structure of MLT included in its cavity. Spray dried MCCMPs showed dense structure with high density, while the spray freeze dried counterpart showed the brittle and porous structure with low density. Despite the porous structure may promote the release rate of spray freeze dried samples, the high hydrophilicity of the CD derivative overshadows this advantage. Samples prepared by spray drying not only exhibited rapid release rates but also could deposit more effectively in the olfactory region, as they avoid breakage due to their higher mechanical strength. The optimal sample showed ~ 86.70% of the MLT released at 20 min and ~ 10.57% of the deposition fraction in the olfactory region. CONCLUSIONS: This work compares MCCMPs fabricated by spray drying and spray freeze drying, providing the optimal formulation and process combinations.

Aerosol Spray Drying Guided Synthesis of Ultrasmall Alloyed Bimetallic Nanoparticles Supported on Silica for Catalytic Semihydrogenation.

Supported bimetallic nanoparticles (NPs) with ultrasmall sizes and homogeneous alloying are attractive for catalysis. However, facile synthesis of this type of material remains very challenging. Here, the aerosol drying impregnation method for rapid, scalable, and general synthesis of silica-supported bimetallic NPs is proposed. The method relies on aerosol spray drying to promote the mixing and dispersing of binary metal precursors on SiO2 . It is capable of controlling the composition and size of bimetallic NPs and avoids the use of expensive metal complex salts and complicated experiment procedures. Twelve permutations combining a noble metal (Pd, Ru, and Pt) and a base one (Fe, Co, Ni, and Cu) with ultrasmall sizes (1.4-2.2 nm in average size), uniform dispersion, and good alloying are synthesized. Interesting activity and selectivity trends in catalytic semihydrogenation of phenylacetylene over the supported Pd-based NPs can be observed. The silica-supported PdNi NPs deliver both high activity and styrene selectivity. Spectroscopic and density functional theory calculation results reveal the improved chemoselectivity originated from the suitably down-shifted d-band center of the PdNi NPs inducing an increased energy barrier for overhydrogenation and a weakened styrene adsorption.

Spray freeze dried niclosamide nanocrystals embedded dry powder for high dose pulmonary delivery.

Based on the drug repositioning strategy, niclosamide (NCL) has shown potential applications for treating COVID-19. However, the development of new formulations for effective NCL delivery is still challenging. Herein, NCL-embedded dry powder for inhalation (NeDPI) was fabricated by a novel spray freeze drying technology. The addition of Tween-80 together with 1,2-Distearoyl-sn-glycero-3-phosphocholine showed the synergistic effects on improving both the dispersibility of primary NCL nanocrystals suspended in the feed liquid and the spherical structure integrity of the spray freeze dried (SFD) microparticle. The SFD microparticle size, morphology, crystal properties, flowability and aerosol performance were systematically investigated by regulating the feed liquid composition and freezing temperature. The addition of leucine as the aerosol enhancer promoted the microparticle sphericity with greatly improved flowability. The optimal sample (SF- 80D-N20L2D2T1) showed the highest fine particle fraction of ∼47.83%, equivalently over 3.8 mg NCL that could reach the deep lung when inhaling 10 mg dry powders.

Micro-fluidic Spray Freeze Dried Ciprofloxacin Hydrochloride-Embedded Dry Powder for Inhalation.

Active pharmaceutical ingredient (API)-embedded dry powder for inhalation (AeDPI) is highly desirable for pulmonary delivery of high-dose drug. Herein, a series of spray freeze-dried (SFD) ciprofloxacin hydrochloride (CH)-embedded dry powders were fabricated via a self-designed micro-fluidic spray freeze tower (MFSFT) capable of tuning freezing temperature of cooling air as the refrigerant medium. The effects of total solid content (TSC), mass ratio of CH to L-leucine (Leu) as the aerosol dispersion enhancer, and the freezing temperature on particle morphology, size, density, moisture content, crystal properties, flowability, and aerodynamic performance were investigated. It was found that the Leu content and freezing temperature had considerable influence on the fine particle fraction (FPF) of the SFD microparticles. The optimal formulation (CH/Leu = 7:3, TSC = 2%w/w) prepared at - 40°C exhibited remarkable effective drug deposition (~ 33.38%), good aerodynamic performance (~ 47.69% FPF), and excellent storage stability with ultralow hygroscopicity (~ 1.93%). This work demonstrated the promising feasibility of using the MFSFT instead of conventional liquid nitrogen assisted method in the research and development of high-dose AeDPI.

A Bimetallic Fe-Mn Oxide-Activated Oxone for In Situ Chemical Oxidation (ISCO) of Trichloroethylene in Groundwater: Efficiency, Sustained Activity, and Mechanism Investigation.

Bimetallic Fe-Mn oxide (BFMO) has been regarded as a promising activator of peroxysulfate (PS), the sustained activity and durability of BFMO for long-term activation of PS in situ, however, is unclear for groundwater remediation. A BFMO (i.e., Mn1.5FeO6.35) was prepared and explored for PS-based in situ chemical oxidation (ISCO) of trichloroethylene (TCE) in sand columns with simulated/actual groundwater (SGW/AGW). The sustained activity of BFMO, oxidant utilization efficiency, and postreaction characterization were particularly investigated. Electron spin resonance (ESR) and radical scavenging tests implied that sulfate radicals (SO4•-) and hydroxyl radicals (HO•) played major roles in degrading TCE, whereas singlet oxygen (1O2) contributed less to TCE degradation by BFMO-activated Oxone. Fast degradation and almost complete dechlorination of TCE in AGW were obtained, with reaction stoichiometry efficiencies (RSE) of ΔTCE/ΔOxone at 3-5%, much higher than those reported RSE values in H2O2-based ISCO (≤0.28%). HCO3- did not show detrimental effect on TCE degradation, and effects of natural organic matters (NOM) were negligible at high Oxone dosage. Postreaction characterizations displayed that the BFMO was remarkably stable with sustained activity for Oxone activation after 115 days of continuous-flow test, which therefore can be promising catalyst for Oxone-based ISCO for TCE-contaminated groundwater remediation.

Conformal Coating of Co/N-Doped Carbon Layers into Mesoporous Silica for Highly Efficient Catalytic Dehydrogenation-Hydrogenation Tandem Reactions.

To maximize the utilizing efficiency of cobalt (Co) and optimize its catalytic activity and stability, engineering of size and interfacial chemical properties, as well as controllable support are of ultimate importance. Here, the concept of coating uniform thin Co/N-doped carbon layers into the mesopore surfaces of mesoporous silica is proposed for heterogeneous aqueous catalysis. To approach the target, a one-step solvent-free melting-assisted coating process, i.e., heating a mixture of a cobalt salt, an amino acid (AA), and a mesoporous silica, is developed for the synthesis of mesoporous composites with thin Co/N-doped carbon layers uniformly coated within mesoporous silica, high surface areas (250-630 m2 g-1 ), ordered mesopores (7.0-8.4 nm), and high water dispersibility. The strong silica/AA adhesive interactions and AA cohesive interactions direct the uniform coating process. The metal/N coordinating, carbon anchoring, and mesopore confining lead to the formation of tiny Co nanoclusters. The carbon intercalation and N coordination optimize the interfacial properties of Co for catalysis. The optimized catalyst exhibits excellent catalytic performance for tandem hydrogenation of nitrobenzene and dehydrogenation of NaBH4 with well-matched reaction kinetics, 100% conversion and selectivity, high turnover frequencies, up to ≈6.06 molnitrobenzene molCo-1 min-1 , the highest over transition-metal catalysts, and excellent stability and magnetic separability.

Dandelion inspired microparticles with highly efficient drug delivery to deep lung.

Active pharmaceutical ingredient (API) embedded dry powder for inhalation (AeDPI) shows higher drug loading and delivery dose for directly treating various lung infections. Inspired by the dandelion, we propose a novel kind of AeDPI microparticle structure fabricated by spray freeze drying technology, which would potentially enhance the alveoli deposition efficiency. When inhaling, such microparticles are expected to be easily broken-up into fragments containing API that acts as 'seed' and could be delivered to alveoli aided by the low density 'pappus' composed of excipient. Herein, itraconazole (ITZ), a first-line drug for treating pulmonary aspergillosis, was selected as model API. TPGS, an amphiphilic surfactant, was used to achieve stable primary ITZ nanocrystal (INc) suspensions for spray freeze drying. A series of microparticles were prepared, and the dandelion-like structure was successfully achieved. The effects of feed liquid compositions and freezing parameters on the microparticle size, morphology, surface energy, crystal properties and in vitro aerosol performance were systematically investigated. The optimal sample (SF(-50)D-INc7Leu3-2) in one-way experiment showed the highest fine particle fraction of ∼ 68.96 % and extra fine particle fraction of ∼ 36.87 %, equivalently ∼ 4.60 mg and ∼ 2.46 mg could reach the lung and alveoli, respectively, when inhaling 10 mg dry powders. The response surface methodology (RSM) analysis provided the optimized design space for fabricating microparticles with higher deep lung deposition performance. This study demonstrates the advantages of AeDPI microparticle with dandelion-like structure on promoting the delivery efficiency of high-dose drug to the deep lung.

A general "surface-locking" approach toward fast assembly and processing of large-sized, ordered, mesoporous carbon microspheres.

Drying to meet you: Using microfluidic jet spray drying technology in conjunction with the evaporation-induced self-assembly strategy gives fast assembly (2 s) of mesoporous carbon microspheres. The key feature of the drying is the formation of a rigid silica crust which locks the particle size and shape.

Spray dried hydroxyapatite-based supraparticles with uniform and controllable size and morphology.

This work aims to prepare uniform spray dried hydroxyapatite-based (SD HAP-based) supraparticles with controllable morphology via micro-fluidic spray drying. Sodium polyacrylate (PAAS) and sodium chloride (NaCl) were used to prepare the precursor suspensions by regulating the inter-particle repulsive forces and electrostatic shielding effect, respectively. The particle size (D50) and zeta potential of the suspension were highly associated with the mass ratio of HAP to PAAS (mH/mP) and the NaCl concentration (CNaCl), which further had significant effect on the permeability (k) of the droplet shell formed during spray drying and ultimately the supraparticle morphology. D50 ˂ 2 µm and absolute zeta potential ˃ 20 mV, obtained when mH/mP ˂ 100 under low CNaCl, rendered ultralow k and consequently deformed supraparticles; Whereas D50 ˃ 2 µm and absolute zeta potential ˂ 20 mV, achieved by decreasing PAAS amount, i.e. mH/mP ≥ 100 or improving CNaCl to efficiently screen surface net charge of HAP, high k and spherical supraparticles were thus preferentially formed.

Oxygen vacancies and interfacial iron sites in hierarchical BiOCl nanosheet microflowers cooperatively promoting photo-Fenton.

Controllable active site construction, crystal structure regulation and efficient charge separation are core issues in heterogeneous photo-Fenton. Herein, abundant oxygen vacancies and well-dispersed interfacial iron sites are simultaneously constructed in hierarchical nanosheet-assembled BiOCl microflowers. The composites exhibit superior performance in photo-Fenton oxidation of carbamazepine (10 mg L-1) with a low H2O2 concentration (1.3 mM). The high performance highly depends on the synergistic effects between oxygen vacancies and iron species. Rather than modulating the valence band, the involvements of oxygen vacancies and iron species could modify the conduction band of BiOCl. The presence of oxygen vacancies promotes the migration of photo-generated electrons and accelerates the redox cycling of ≡Fe(III)/≡Fe(II) to boost the activation of H2O2 to generate hydroxyl radicals, and oxygen vacancies can be well preserved after cyclic use. This work provides understanding on efficient utilization of oxygen vacancies and interfacial iron sites to assist photo-Fenton and the underlying electron transfer mechanism.

Spray Dried Levodopa-Doped Powder Potentially for Intranasal Delivery.

This work was aimed to develop levodopa (L-dopa) nasal powder to achieve controllable drug release and high nasal deposition efficiency. A series of uniform microparticles, composed of amorphous L-dopa and excipients of hydroxypropyl methyl cellulose (HPMC), polyvinylpyrrolidone (PVP), or hydroxypropyl-ß-cyclodextrin (CD), were fabricated by a self-designed micro-fluidic spray dryer. The effects of excipient type and drug/excipient mass ratio on the particle size, morphology, density, and crystal property, as well as the in vitro performance of drug release, mucoadhesion, and nasal deposition, were investigated. Increased amounts of added excipient, regardless of its type, could accelerate the L-dopa release to different extent. The addition of CD showed the most obvious effect, i.e., ~83% of L-dopa released in 60 min for SD-L1CD2, compared to 37% for raw L-dopa. HPMC could more apparently improve the particle mucoadhesion than PVP and CD, with respective adhesive forces of ~269, 111, and 26 nN for SD-L1H2, -L1P2, and -L1CD2. Nevertheless, the deposition fractions in the olfactory region for such samples were almost the same (~14%), probably ascribable to their quite similar particle aerodynamic diameter (~30 µm). This work demonstrates a feasible methodology for the development of nasal powder.

Facile spray-drying assembly of uniform microencapsulates with tunable core-shell structures and controlled release properties.

Microencapsulates with defined core-shell structures are of interest for applications, such as controlled release and encapsulation, because of the feasibility of fine-tuning individual functionalities of different parts. Here, we report a new approach for efficient and scalable production of such particles. Eudragit RS (a co-polymer of ethyl acrylate, methyl methacrylate, and a low content of methacrylic acid ester with quaternary ammonium groups) was used as the main shell component, with silica as the core component, formed upon a single-step spray-drying assembly. The method is capable of forming uniform core-shell particles from homogeneous precursors without the use of any organic solvents. Evaporation-induced self-assembly attained the phase separation among different components during drying, resulting in the core-shell spatial configuration, while precise control over particle uniformity was accomplished via a microfluidic jet spray dryer. Direct control over shell thickness can be achieved from the ratio of the core and shell ingredients in the precursors. A fluorescent compound, rhodamine B, is used as a highly water-soluble model component to investigate the controlled release properties of these microencapsulates, with the release behaviors shown to be significantly dependent upon their architectures.

Microdroplet confined assembly enabling the scalable synthesis of titania supported ultrasmall low-valent copper catalysts for efficient photocatalytic activation of peroxymonosulfate.

The synthesis of highly dispersed low-valent copper catalysts is very challenging because they are prone to oxidation and sintering. Herein, scalable synthesis of ultrafine Cu(0)/Cu(i) catalysts supported on mesoporous titania microspheres is enabled by a one-step microdroplet confined assembly method. The extremely fast solute assembly in the microdroplet induces excellent metal precursor dispersion, reduces sol-gel crosslinking, and creates wrinkled microspheres with surface crusts and hollow cavities. This structural architecture allows the generation of an inner reductive gas environment during calcination in air to reduce Cu(ii) and create oxygen vacancy (OV) sites in titania. The obtained catalysts exhibit excellent performance in the photocatalytic activation of peroxymonosulfate (PMS) for pollutant degradation. The Cu(0) species with a surface plasmon resonance effect and OV-rich anatase facilitate efficient solar light utilization and charge separation. The intimate interface between Cu(i)/Cu(0) and anatase enables fast electron transfer and timely copper redox cycling to promote the activation of PMS.

Study on the Stability, Evolution of Physicochemical Properties, and Postsynthesis of Metal-Organic Frameworks in Bubbled Aqueous Ozone Solution.

Metal-organic frameworks (MOFs) are highly promising in many areas. Their application and postsynthesis under strong oxidative environments are emerging. However, the stability, physicochemical property evolution, and possible postmodification and postsynthesis of MOFs in strong oxidative solutions are largely unknown. In this paper, the behaviors of a series of MOFs in bubbled aqueous ozone (O3) solutions are studied. The chosen MOFs are categorized into trimesic type including MIL-101(Fe) and MIL-96(Al); terephthalic type including MOF-74(Co), UiO-66(Zr), MIL-53(Al), and MIL-101(Cr); and imidazole type including ZIF-67(Co) and ZIF-8(Zn), based on the ligand structure. The intrinsic stability and evolution of the physicochemical properties of these MOFs during aqueous O3 treatment are elucidated using structural, morphological, textural, thermal, and spectroscopic analyses. Several stable, metastable, and instable MOFs are identified. The critical parameters that determine the stability and capability for postsynthesis of these MOFs in aqueous O3 solutions are discussed. The stability follows the general order of trimesic-type > terephthalic-type ≫ imidazole-type MOFs because of the distinct antioxidation capability of the ligands. The effects of the ligand, metal cation, and their coordination number on stability are discussed. MIL-100(Fe), MIL-96(Al), and MOF-74(Co) are stable in aqueous O3. UiO-66(Zr), MIL-53(Al), and MIL-101(Cr) are metastable that their porosity, particle size, and crystallinity can be postmodified. ZIF-67(Co) and ZIF-8(Zn) are instable and can be gradually and completely disassembled. Their particle size and morphology and surface groups can be tuned by controlling the treatment time. Postsynthesis of metal hydroxides from ZIF-67(Co) and gradual release of dissolved zinc ion from ZIF-8(Zn) are achievable. The stable MIL-96(Al) shows promising performance in catalytic ozonation for degrading 4-nitrophenol, and the α-Co(OH)2 derived from treating ZIF-67(Co) shows highly promising performance in the electrocatalytic oxygen evolution reaction (OER).

Scalable Synthesis of Uniform Mesoporous Aluminosilicate Microspheres with Controllable Size and Morphology and High Hydrothermal Stability for Efficient Acid Catalysis.

Mesoporous aluminosilicates are promising solid acid catalysts. They are also excellent supports for transition metal catalysts for various catalytic applications. Synthesis of mesoporous aluminosilicates with controllable particle size, morphology, and structure, as well as adjustable acidity and high hydrothermal stability, is very desirable. In this work, we demonstrate the scalable synthesis of Al-SBA-15 microspheres with controllable physicochemical properties by using the microfluidic jet-spray-drying technology. The productivity is up to ∼30 g of dried particles per nozzle per hour. The Al-SBA-15 microspheres possess uniform controllable micron sizes (27.5-70.2 µm), variable surface morphologies, excellent hydrothermal stability (in pure steam at 800 °C), high surface areas (385-464 m2/g), ordered mesopore sizes (5.4-5.8 nm), and desirable acid properties. The dependence of various properties, including particle size, morphology, porosity, pore size, acidity, and hydrothermal stability, of the obtained Al-SBA-15 microspheres on experimental parameters including precursor composition (Si/Al ratio and solid content) and processing conditions (drying and calcination temperatures) is established. A unique morphology transition from smooth to wrinkled microsphere triggered by control of the Si/Al ratio and solid content is observed. The particle formation and morphology-evolution mechanism are discussed. The Al-SBA-15 microspheres exhibit high acid catalytic performance for aldol-condensation reaction between benzaldehyde and ethyl alcohol with a high benzaldehyde conversion (∼56.3%), a fast pseudo-first-order reaction rate (∼0.1344 h-1), and a high cyclic stability, superior to the commercial zeolite acid (H-ZSM-5). Several influencing factors on the catalytic performance of the obtained Al-SBA-15 microspheres are also studied.

Chemical Crosslinking Assembly of ZSM-5 Nanozeolites into Uniform and Hierarchically Porous Microparticles for High-Performance Acid Catalysis.

Hierarchically porous zeolites combining the advantages of desirable mass transport of nanozeolites and easy separation and handling of micro-zeolites are ideal candidates in catalytic applications. Facile routes for the assembly of zeolite microparticles with hierarchical porosity and high mechanical strength are much expected. Herein, based on a microfluidic jet spray drying technology, we report a facile and scalable chemical crosslinking assembly strategy for the synthesis of hierarchical zeolite microparticles by directly using the conventional as-synthesized nanozeolite suspension as a precursor. This route not only avoids the energy-intensive centrifugal separation process of nanozeolites but also significantly increases the uniformity and mechanical strength of the microparticles. The soluble aluminosilicate species act as a stabilizer to improve the droplet stability during the drying process and then as a "cross-linker" to chemically bind and interconnect zeolite nanoparticles to form robust bodies after drying and calcination. Zeolite microparticles with variable morphologies (spherical, bowl-like, and dimpled) and uniform and controllable sizes (from 70 to 108 µm) can be obtained by adjusting the experimental parameters. The particle formation mechanism is discussed based on the zeolite microparticles obtained from the purified nanozeolite suspension as a control. The zeolite microparticles possess emerged uniform mesopores (∼6 nm) and a well-maintained high surface area, large pore volume, high microporosity, and strong acidity of the original nanozeolites. As a result, they exhibit excellent acid catalytic performances in acetolysis of epichlorohydrin and catalytic cracking of low-density polyethylene, far better than those of the commercial ZSM-5.

Spray-drying water-based assembly of hierarchical and ordered mesoporous silica microparticles with enhanced pore accessibility for efficient bio-adsorption.

The fast and scalable spray-drying-assisted evaporation-induced self-assembly (EISA) synthesis of hierarchically porous SBA-15-type silica microparticles from a water-based system is demonstrated. The SBA-15-type silica microparticles has bowl-like shapes, uniform micro-sizes (∼90 µm), large ordered mesopores (∼9.5 nm), hierarchical meso-/macropores (20-100 nm) and open surfaces. In the synthesis, soft- and hard-templating approaches are combined in a single rapid drying process with a non-ionic tri-block copolymer (F127) and a water-insoluble polymer colloid (Eudragit RS, 120 nm) as the co-templates. The RS polymer colloid plays three important roles. First, the RS nanoparticles can be partially dissolved by in-situ generated ethanol to form RS polymer chains. The RS chains swell and modulate the hydrophilic-hydrophobic balance of F127 micelles to allow the formation of an ordered mesostructure with large mesopore sizes. Without RS, only worm-like mesostructure with much smaller mesopore sizes can be formed. Second, part of the RS nanoparticles plays a role in templating the hierarchical pores distributed throughout the microparticles. Third, part of the RS polymer forms surface "skins" and "bumps", which can be removed by calcination to enable a more open surface structure to overcome the low pore accessibility issue of spray-dried porous microparticles. The obtained materials have high surface areas (315-510 m2 g-1) and large pore volumes (0.64-1.0 cm3 g-1), which are dependent on RS concentration, HCl concentration, silica precursor hydrolysis time and drying temperature. The representative materials are promising for the adsorption of lysozyme. The adsorption occurs at a >three-fold faster rate, in a five-fold larger capacity (an increase from 20 to 100 mg g-1) and without pore blockage compared with the adsorption of lysozyme onto spray-dried microparticles of similar physicochemical properties obtained without the use of RS.

Facile synthesis of alkaline-earth metal manganites for the efficient degradation of phenolic compounds via catalytic ozonation and evaluation of the reaction mechanism.

In this paper, we demonstrate the facile and general synthesis of alkaline-earth metal manganites, denoted as A(Mg, Ca, Ba)MnxOy, for efficient degradation of high-concentration phenolic compounds via catalytic ozonation. The representative CaMnxOy oxides show a hierarchical spherical structure constructed by crystalline nanorods and numerous macropores. They possess mixed Mn4+/Mn3+ chemical valences and abundant surface hydroxyl (OH) groups. The ozone (O3) decomposition rate on the CaMnxOy catalysts is greatly accelerated and follows the first-order law. These catalysts are promising for the degradation of phenolic compounds via catalytic ozonation, exhibiting rapid pseudofirst-order degradation kinetics, a high total organic carbon (TOC) removal efficiency and an excellent stability. Under optimized conditions (a low O3 dosage of 1.5 mg/min and a catalyst dosage of 7.5 g/L), for the treatment of concentrated phenol (50-240 mg/L), the CaMnxOy catalysts show 100% degradation and 50-70% mineralization within 1.0 h. The Ca2+ ions are essential to create redox Mn4+/Mn3+ couples and to significantly reduce manganese leaching. High surface ratios of Mn4+/Mn3+ and OH/lattice oxygen (Olat) are beneficial for enhancing the catalytic performance. Superoxide anion free radicals (O2-) and singlet oxygen (1O2) are the predominant reactive species for the oxidation degradation. The O2- reaction pathway is proposed. Specifically, the surface OH sites activate O3, displaying highly enhanced decomposition rates. The generated O2- and 1O2 play a role in oxidation. The redox Mn4+/Mn3+ and the Olat/oxygen vacancy (Olat/Ovac) couples play important roles in electron transfer. The proposed mechanism is supported by active site probing, radical scavenging, spectroscopic studies, and the results in the degradation of substituted phenols.

Solid-state nanocasting synthesis of ordered mesoporous CoNx-carbon catalysts for highly efficient hydrogenation of nitro compounds.

Selective catalytic hydrogenation of nitro compounds (NCs) is an attractive challenge with significant research being focused on the development of cobalt (Co)-based nanocatalysts. Herein, in order to achieve high activity and selectivity for the catalytic hydrogenation of NCs and identify the essential active Co-containing sites, a facile solid-state nanocasting approach is developed for the controllable synthesis of CoNx-doped ordered mesoporous carbon materials (denoted as CoNx-OMCs). Compared with the previous nanocasting synthesis of mesoporous catalysts, the current method requires no solvent and relies on melting and interfacial chemical interactions between silica and the precursors for loading and casting, and chemical coordination among the precursors for the formation and dispersion of the active sites. The resulting CoNx-OMCs possess high surface areas (∼941 m2 g-1), ordered mesopores (∼4.0 nm), high N content (∼6.8 wt%) and abundant CoNx sites and fine metallic Co nanoparticles. With molecular H2 as the reducing agent, the optimized catalyst delivers very attractive catalytic activities (100% conversions), selectivities (close to 100% selectivities) and stability (no obvious performance decay after cycling) in the hydrogenation of a series of NCs carrying diverse groups in aqueous solutions under mild conditions. A comparative study clearly reveals that the CoNx sites, not the metallic Co nanoparticles, are the key active sites for the hydrogenation of NCs. The CoNx sites are found to preferentially adsorb nitro groups, thus activating them and promoting their reduction. A detailed study reveals that the high catalytic performance relies on the synergistic cooperation of the catalyst composition and structure, which are tuneable by adjusting the synthetic conditions.