Conversion Of Benzaldehyde Research Articles

Solid state – Green construction of starch- beaded Fe3O4@Ag nanocomposite as superior redox catalyst

In this present work, a novel approach which had been developed for the green synthesis of starch-decorated Fe3O4 @Ag nanocomposite by using one-step grinding method. The magnetic core shell nanocomposite was designed by magnetite (Fe3O4) surrounded by the starch (maize corn), a biopolymer which act as a matrix for argentum (Ag) nanoparticles. This leads to the core shell structure starch – Fe3O4 @Ag nanocomposite (NC). The morphological and physical properties of the prepared nanocomposite was characterized by FE-SEM, HR-TEM, XPS, VSM, XRD, FT-IR and UV-Vis spectroscopic studies. The average particle size of the nanocomposite was found to be 9–11 nm. In addition, the nanocomposite gains a retentivity magnetisation of 25.50 emu/g makes the NC saveable for reusability. The nanocomposite had a greater stability for more than a month was confirmed with the help of UV-DRS and XRD analysis. The main advantage of the catalyst is temperature independent; During the conversion of benzaldehyde to benzoic acid, the product yield was achieved higher at ambient condition. Furthermore, the NC exposes the outstanding catalytic performance for reductive degradation of various carcinogenic water pollutants such as Methylene Blue (MB) and Methyl Red (MR) within 14 min and 18 min respectively. Moreover, it is also capable for reduction of 4-nitrophenol in an efficient manner. Thus, the NC holds a greater activity towards oxidation and reductive degradation reaction.

Oxidation of aldehydes to carboxylic acids over geopolymer supported CuO

This article focuses on the synthesis of copper (II) oxide impregnated mesoporous geopolymer (CuO/Geo) catalyst and its catalytic activity for the oxidation of aldehydes to the corresponding carboxylic acids. CuO/Geo was synthesised by a two-step method. Mesoporous geopolymer was prepared which was used as a support for CuO through incipient wetness method. The synthesized catalyst was characterized using FE-SEM, FT-IR, BET surface area, XRD and XPS. For the oxidation reaction, water was used as the solvent and oxygen as the sole oxidant. On the basis of the experimental observations, CuO/Geo was found to be a good catalyst with 67% conversion of benzaldehyde to benzoic acid, observed in 10 h at 80 °C. It was established from XPS analysis that the oxidation reaction took place via Cu2+/Cu+/Cu2+ transformations. Density functional theory calculations provided insights into the adsorption energetics and the reaction mechanism. The mechanism for benzaldehyde oxidation was developed and the rate determining step was identified. The product formation step was observed to be the rate determining step with the free energy barrier of 59.6 kcal/mol.

Synthesis of biofuel precursors from benzaldehyde and cyclopentanone via aldehyde-ketone condensation in a deep eutectic solvent system.

Production of biofuel precursors from biomass-derived platform compounds (BDPC) has a profound influence on biofuel industries. Herein, an efficient catalytic system composed of the deep eutectic solvent (DES, i.e., ChCl/Fa) and SnCl4 (ChCl/Fa-SnCl4) was developed to produce biofuel precursors (C12 and C19) through aldehyde-ketone (A-K) condensation of benzaldehyde (BD) and cyclopentanone (CPO). ChCl/Fa-SnCl4 exhibited the prospective catalytic performance and given the high selectivity (SC12 = 49.20%, SC19 = 15.20%) and total yield (YC12+C19 = 64.37%) of C12 and C19, as well as 99.96% BD conversion under the optimized conditions (BD : CPO molar ratio of 1 : 6, ChCl : Fa molar ratio of 1 : 12, 4 mmol SnCl4, 80 °C for 120 min). Subsequently, the C12 and C19 precursors were successfully applied to generate cyclic alkanes (C12H14 and C19H18) by hydrodeoxygenation with selectivity of 37.61% and 24.10%, respectively. Finally, the potential catalytic mechanism was explored by density functional theory (DFT) calculations. The results unveiled that the formation of a stable structure for the ChCl/Fa-SnCl4 system was ascribed to the viable interactions among ChCl, Fa and SnCl4 by coordination bonds, electrostatic interactions and H-bonds, which decreased reaction energy barriers and drove the condensation of BD and CPO. In this case, the catalytic reactions between BD and CPO were enhanced to promote the synthesis of C12 and C19. This work provides a novel strategy for the applicability of different BDPC to synthesize fuel precursors for the development of liquid biofuels.

A Liquid-Liquid-Solid System to Manipulate the Cascade Reaction for Highly Selective Electrosynthesis of Aldehyde.

Electrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid-solid system. Herein, we report a novel liquid-liquid-solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200-fold from 0.4 % to 80.4 % compared with the liquid-solid system at a high current density of 136 mA cm-2 , which is the highest one up to date. In the tri-phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as-produced benzaldehyde can be in situ extracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions.

A Liquid‐Liquid‐Solid System to Manipulate the Cascade Reaction for Highly Selective Electrosynthesis of Aldehyde

AbstractElectrocatalytic synthesis of aldehydes from alcohols exhibits unique superiorities as a promising technology, in which cascade reactions are involved. However, the cascade reactions are severely limited by the low selectivity resulting from the peroxidation of aldehydes in a traditional liquid‐solid system. Herein, we report a novel liquid‐liquid‐solid system to regulate the selectivity of benzyl alcohol electrooxidation. The selectivity of benzaldehyde increases 200‐fold from 0.4 % to 80.4 % compared with the liquid‐solid system at a high current density of 136 mA cm−2, which is the highest one up to date. In the tri‐phase system, the benzaldehyde peroxidation is suppressed efficiently, with the conversion of benzaldehyde being decreased from 87.6 % to 3.8 %. The as‐produced benzaldehyde can bein situextracted to toluene phase and separated from the electrolyte to get purified benzaldehyde. This strategy provides an efficient way to efficiently enhance the selectivity of electrocatalytic cascade reactions.

Potassium-doped carbon nitride supported on SBA-15 for enhanced catalytic Knoevenagel condensation under mild conditions

Knoevenagel condensation reaction is an important reaction for the manufacture of α,β-unsaturated carbonyl compounds. Traditional base catalysts suffer from the disadvantage in catalystproduct separation. Herein, potassium-doped carbon nitride materials supported on SBA-15 (CN/SBA15-KCl) have been prepared through a one-pot calcination method. The characterization results of N2 adsorption–desorption, small-angle XRD, TEM, and SEM revealed that the ordered mesostructures of SBA-15 had been preserved after the loading of carbon nitride and KCl, and nitrogen and potassium species were dispersed on the surface of SBA-15 support. As solid bases, the CN/SBA15-KCl materials demonstrated high and steady catalytic performances in Knoevenagel condensation. Under 50 °C of reaction temperature, the optimized conversion of benzaldehyde was up to 74% at 4 h of reaction time, much higher than other carbon-nitride-based materials. The incorporation of potassium has been proved to enhance the basic strength of CN/SBA15, and therefore improved the catalytic activity.

Process Development for Benzyl Alcohol Production by Whole-Cell Biocatalysis in Stirred and Packed Bed Reactors.

The ocean is an excellent source for new biocatalysts due to the tremendous genetic diversity of marine microorganisms, and it may contribute to the development of sustainable industrial processes. A marine bacterium was isolated and selected for the conversion of benzaldehyde to benzyl alcohol, which is an important chemical employed as a precursor for producing esters for cosmetics and other industries. Enzymatic production routes are of interest for sustainable processes. To overcome benzaldehyde low water solubility, DMSO was used as a biocompatible cosolvent up to a concentration of 10% (v/v). A two-phase system with n-hexane, n-heptane, or n-hexadecane as organic phase allowed at least a 44% higher relative conversion of benzaldehyde than the aqueous system, and allowed higher initial substrate concentrations. Cell performance decreased with increasing product concentration but immobilization of cells in alginate improved four-fold the robustness of the biocatalyst: free and immobilized cells were inhibited at concentrations of benzyl alcohol of 5 and 20 mM, respectively. Scaling up to a 100 mL stirred reactor, using a fed-batch approach, enabled a 1.5-fold increase in benzyl alcohol productivity when compared with batch mode. However, product accumulation in the reactor hindered the conversion. The use of a continuous flow reactor packed with immobilized cells enabled a 9.5-fold increase in productivity when compared with the fed-batch stirred reactor system.

Macro-Meso-Microporous Metal-Organic Frameworks: Template-Assisted Spray Drying Synthesis and Enhanced Catalysis.

Hierarchically porous metal-organic frameworks (HP-MOFs) are promising in many applications. However, most previous studies focus on HP-MOFs with two kinds of pore structures. Herein, a strategy for efficient construction of HP-MOFs possessing macro-meso-micropores using template-assisted spray drying followed by etching process is proposed. Taking ZIF-8 as an example, using polystyrene (PS) templates, the complete HP-ZIF-8 with all the three categories of pores can be easily fabricated. The close arrangement of intrinsic microporous nanosized ZIF-8 (N-ZIF-8) in the spray drying process results in the creation of mesopores, while the macropores are further generated after the removal of PS templates. The structures of macropores and mesopores can be easily adjusted by altering the size and proportion of PS and the size of N-ZIF-8, respectively. Furthermore, this method is extended to the preparation of HP-HKUST-1. As a proof-of-concept, HP-ZIF-8 displays excellent catalytic properties in Knoevenagel reaction owing to its unique pore features. Compared with conventional microsized ZIF-8 (M-ZIF-8) with similar size, HP-ZIF-8 achieves the significantly increased conversion of benzaldehyde from 55% to 100% within 3 h, and shows better recycling performance than N-ZIF-8.

Liquid-Phase Hydrogenation of Benzaldehyde on Low-Percentage Pt-Containing Catalysts under Mild Conditions

The reaction of the liquid-phase hydrogenation of benzaldehyde is studied in two modes: at room temperature and atmospheric pressure, and at a temperature of 70°С and a pressure of 0.5 MPa on Pt/CeO2–ZrО2 catalysts with metal contents of 1 to 0.025 wt %. A 96% conversion of benzaldehyde is obtained on 1% Pt/CeO2–ZrО2 catalysts at room temperature, while a 97% conversion is obtained on 0.1% Pt/CeO2–ZrО2 catalysts at elevated temperatures. The selectivity of the formation of benzyl alcohol is in all cases 100%.

Three Si-substituted polyoxovanadates as efficient catalysts for Knoevenagel condensation and selective oxidation of styrene to benzaldehyde.

Three new Si-substituted polyoxovanadates (POVs), [Cd2(dien)2][Cd(dien)][Cd(Hdien)2][V15Si6O46(OH)2(H2O)]·7H2O (1), [Co(enMe)2]3[Co2(enMe)2(H2O)2][V16Si4O44(OH)2(H2O)]·6H2O (2), and [Co(teta)]4[V16Si4O42(OH)4(H2O)]·10H2O (3) (dien = diethylenetriamine; enMe = 1,2-diaminopropane; teta = triethylenetetramine) were synthesized by the hydrothermal method and characterized. Structural analysis sheds light on the fact that the {V15Si6O48}/{V16Si4O46} clusters of compounds 1-3 were formed by replacing {VO5} square pyramids in the classical {V18O42} cluster with {Si2O7} units. Compound 1 is a 2D bilayer structure formed by the [V15Si6O46(OH)2(H2O)]10- cluster and two types of bridging Cd complexes containing binuclear groups [Cd2(dien)2]4+. Compound 2 is a 3D framework constructed from the [V16Si4O44(OH)2(H2O)]10- cluster and two types of Co complex fragments including binuclear [Co2(enMe)2(H2O)2]4+. In compound 3, the [V16Si4O42(OH)4(H2O)]8- cluster is connected with bridging [Co(teta)]2+ to expand into a 2D network. Compounds 1 and 3 represent the first 2D assemblies based on a vanadosilicate cluster. 1-3 served as heterogeneous catalysts and exhibited highly efficient catalytic activities for the Knoevenagel condensation under mild ambient conditions with low catalyst loading, featuring the open Lewis base {V15Si6O48}/{V16Si4O46} sites and Lewis acid Cd2+/Co2+ sites. The conversion of benzaldehyde was up to 99.3% in 80 min at room temperature using 1 as a heterogeneous catalyst with only 0.37% catalyst loading. Moreover, compounds 1-3 as catalysts for selective oxidation of styrene to benzaldehyde exhibited excellent catalytic performance, high selectivity and could be readily recycled. Most strikingly, compound 1 showed excellent catalytic performance with 97.6% conversion of styrene and 100% selectivity of benzaldehyde in 15 min. In addition, the catalytic activity of catalyst 1 was well maintained after five cycling reactions.

Experimental and computational investigation of a green Knoevenagel condensation catalyzed by zeolitic imidazolate framework-8

ZIF-8 is a highly porous, stable, and abundant surface area material that can be used as an environmentally friendly catalyst for Knoevenagel condensations. The effects of the ratio of the reactants (benzaldehyde (BA):ethyl cyanoacetate (ECA)), reaction temperature, and catalyst concentration were systematically investigated using a ZIF-8 catalyst and water as the solvent. ZIF-8 (3–5 wt%) showed excellent catalytic performance with an almost complete conversion of BA in less than 6 h with a BA:ECA molar ratio of 1:2 at different temperatures. At 60 °C, the BA conversion rate and product selectivity of the reaction reached their highest values after 4 h with a BA:ECA molar ratio of 1:1. When employing 5.0 wt% ZIF-8, almost complete BA conversion was achieved after 3 h at room temperature. ZIF-8 also demonstrated good recyclability with almost no change in its catalytic activity over five cycles. The proposed reaction mechanism is based on the catalytic activity of the basic N sites on the surface of ZIF-8, and is supported by density functional theory calculations. The present approach provides a promising strategy for the construction of simple and environmentally friendly ZIF-8 catalysts.

Synthesis of Sitagliptin Intermediate by a Multi-Enzymatic Cascade System Using Lipase and Transaminase With Benzylamine as an Amino Donor.

Herein, we report the development of a multi-enzyme cascade using transaminase (TA), esterase, aldehyde reductase (AHR), and formate dehydrogenase (FDH), using benzylamine as an amino donor to synthesize the industrially important compound sitagliptin intermediate. A panel of 16 TAs was screened using ethyl 3-oxo-4-(2,4,5-trifluorophenyl) butanoate as a substrate (1). Amongst these enzymes, TA from Roseomonas deserti (TARO) was found to be the most suitable, showing the highest activity towards benzylamine (∼70%). The inhibitory effect of benzaldehyde was resolved by using AHR from Synechocystis sp. and FDH from Pseudomonas sp., which catalyzed the conversion of benzaldehyde to benzyl alcohol at the expense of NAD(P)H. Reaction parameters, such as pH, buffer system, and concentration of amino donor, were optimized. A single whole-cell system was developed for co-expressing TARO and esterase, and the promoter engineering strategy was adopted to control the expression level of each biocatalyst. The whole-cell reactions were performed with varying substrate concentrations (10–100 mM), resulting in excellent conversions (ranging from 72 to 91%) into the desired product. Finally, the applicability of this cascade was highlighted on Gram scale, indicating production of 70% of the sitagliptin intermediate with 61% isolated yield. The protocol reported herein may be considered an alternative to existing methods with respect to the use of cheaper amine donors as well as improved synthesis of (R) and (S) enantiomers with the use of non-chiral amino donors.

Application of polymer-bound Cu(II) complex of 2-phenylbenzimidazole towards oxidative bromination and oxidative esterification of organic substrates

Application of polymer immobilized Cu(II)(PS-Cu(II)PBMZL) complex of 2-phenylbenzimidazole in oxidative bromination and oxidative esterification of organic compounds is reported. The complex has been characterized by CHNS analysis, UV-Vis/DRS, FT-IR, ESR spectroscopic studies, magnetic moment measurements and TG analysis. A shift in νC=N in the polymer-bound complex compared with the ligand indicates its complexation to Cu(II) center. A distorted octahedral coordination of Cu(II) in PS-Cu(II)PBMZL is confirmed by the electronic spectral data and the efficient binding of PBMZL is ascertained by adecrease in the intensity of νCH2Cl peak in the PS-PBMZL compared to the polymer support. An array of experiments has been carried out to assess the influence of various reaction parameters on the performance of PS-Cu(II)PBMZL. The activity of the polymer-bound complex is higher than the unbound complex. In the case of oxidative bromination, PS-Cu(II)PBMZLH displayed a 65% phenol conversion with 61% 2-bromophenol selectivity. The % benzaldehyde conversion and methyl benzoate selectivity in the case of oxidative esterification has been found to be 79 and 82%. Compiling all these results along with the knowledge obtained regarding the most probable reactive species, tentative mechanisms have been proposed.

Simultaneous electrocatalytic hydrogenation of aldehydes and phenol over carbon-supported metals

Electrocatalytic hydrogenation of furfural, benzaldehyde, and phenol was studied on carbon-supported Rh, Ru, Pd, and Cu catalysts. All metals were active for hydrogenation of the carbonyl group in furfural and benzaldehyde, but only Rh/C was active for phenol hydrogenation. The intrinsic activities for furfural and benzaldehyde conversion were Pd/C < Ru/C ≤ Rh/C < Cu/C and Ru/C < Rh/C < Pd/C < Cu/C, respectively. While the trend in furfural hydrogenation remained the same in the presence of phenol, the trend in benzaldehyde hydrogenation in the presence of phenol changed to Rh/C < Ru/C < Pd/C < Cu/C. The Faradaic efficiencies for hydrogenation of both furfural (in the 10–40% range) and benzaldehyde (in the 45–100% range) followed the trend: Cu/C < Rh/C < Ru/C < Pd/C. When phenol and an aldehyde were present in the reactant solution, phenol hydrogenation was suppressed. In contrast, enhancements in the rates of carbonyl reduction were observed for both aldehydes in presence of phenol. Such enhancements depend on both the aldehyde and the metal catalyst. The enhancing factors for hydrogenation of furfural and benzaldehyde were in the 1.5–2 and 2–4 ranges, respectively. We conclude that intermolecular interactions between adsorbed phenol and the aldehydes is a general phenomenon that can potentially enhance the rates of carbonyl hydrogenation. This work highlights co-adsorption effects that pose both challenges and advantages for electrocatalytic reduction of organic compounds.

Vermiculites catalyze unusual benzaldehyde and dioxane reactivity

Transitioning towards green chemistry requires designing sustainable processes to produce both inexpensive and environmentally friendly materials capable of catalyzing complex chemical transformations in fine chemistry. In this context, natural silicate-based catalysts stand out as some of the most promising alternatives, yet vermiculites have been mostly overlooked so far, despite their high potential as clay catalysts with high negative layer charge, high number of exchangeable interlayer cations and high Lewis and Brønsted acidity. Thus, this work reports a previously undescribed and unusual reaction between benzaldehyde and dioxane in the presence of natural and ion-enriched (Al3+, Fe3+, Mg2+, Ni2+, Sn4+) vermiculite catalysts. The effects of different vermiculites on the reaction were assessed both at different activation/calcination temperatures (150 °C, 300 °C and 450 °C) and without activation. Regardless of temperature activation, all vermiculites catalyzed C-C bond cleavage, decarbonylation/ decarboxylation and radical oxidative coupling of benzaldehyde and dioxane, albeit in different yields. Non-activated, natural vermiculite provided the highest benzaldehyde conversion (92 %) and benzaldehyde-based selectivity to the coupling product, 1,4-dioxan-2-yl benzoate (11 %). High benzaldehyde conversion rates were observed also in reactions with aluminum-enriched vermiculite (Al-VMT) activated at 150 °C (84 %), providing 10% selectivity to the coupling product, and with iron (III)-enriched vermiculite (Fe-VMT) (38 % benzaldehyde conversion, 12% selectivity). Catalyst calcination prevented the formation of the 1,4-dioxan-2-yl benzoate while simultaneously enhancing benzaldehyde degradation to benzene. Ultimately, this study shows, for the first time, that vermiculites catalyze radical-oxidative coupling, yielding complex structures such as 1,4-dioxan-2-yl benzoate, which can be used as building blocks in fine chemistry.

Structural Regulation of Magnetic Polymer Microsphere@Ionic Liquids with an Intermediate Protective Layer and Application as Core-Shell-Shell Catalysts with High Stability and Activity.

A novel ionic liquid immobilized on a magnetic polymer microsphere catalyst is reported in this paper. The obtained core–shell–shell catalyst consisted of magnetic nanoparticles (MNPs) as the core, catalytic inert St-co-DVB as the intermediate protective layer, and cross-linked polyaryl imidazole ionic liquids as the active catalytic layer located at the outermost [Im[OH]/MNPs@P(St-DVB)@P(VBC-DVB)]. This catalyst exhibited a high ion-exchange rate (64.65%), high saturation magnetic strength, and excellent acid and alkali corrosion resistance. In the catalyzed Knoevenagel condensation of benzaldehyde and ethyl cyanoacetate, the conversion of benzaldehyde maintained at 92.1% during six times reuse. Optimizing the materials of the protective layer and regulating the thickness of the inert protective layer decreased the corrosion ratio of MNPs in acidic media from 44.82 to 0.44%. Adjusting the thickness of the catalytic layer realized excellent catalytic activity (97%) and high magnetic response performance. In summary, introducing an inert protective layer to the structure of ionic liquids immobilized on the magnetic polymer microsphere catalyst, regulating its thickness, and optimizing its structure achieved a catalyst with high activity, excellent stability, and easy magnetic separation.

Knoevenagel condensation reaction on a new highly-efficient La2O2CO3-TiO2 mixed oxide catalyst: Composition-effects on C[dbnd]C bond formation

The highly efficient catalytic abilities of some mixed oxides are due to cooperative interactions between acid and base functional groups present in their active sites. New La2O2CO3-TiO2 mixed oxide catalysts with different La/Ti molar ratios successfully synthesized through a facile solvothermal method were investigated for the Knoevenagel condensation reaction of various carbonyl compounds derivatives with malononitrile. The analytical determinations, including XRD, Raman, HRTEM, N2 adsorption/desorption and TPD of CO2 and NH3, witnessed the structural characteristics of the as-prepared La2O2CO3-TiO2 mixed oxide catalysts. La2O2CO3-TiO2 mixed oxide catalyst having molar ratio La/La + Ti = 0.09 composition (La2O2CO3(0.09)-TiO2) exhibited highest conversion of benzaldehyde for Knoevenagel reaction of benzaldehyde with malononitrile. More importantly, this catalyst could be successfully applicable to the Knoevenagel condensation of various carbonyl compounds derivatives with high yields above 85%. This acid-base bifunctional synergetic effect between La2O2CO3 and TiO2 contributes to improve the catalytic property of the catalyst.

Fabrication of new magnetite based sulfonic-phosphotungstic dual-acid catalyst for catalytic acetalization of benzaldehyde with ethylene glycol

A new sulfonic-phosphotungstic dual-acid hybrid catalyst based on silica coated magnetite nanoparticles (SCMNPs) containing two types of Bronsted acidic sites i.e. sulfonic acid (–SO3H) and phosphotungstic acid (HPW) groups, was prepared with chemical and electrostatic interactions of these acidic functional moieties with piperazine-grafted propylsilyl spacer groups. Physicochemical techniques including FT-IR spectroscopy, elemental analysis and inductively coupled plasma-optical emission spectroscopy (ICP-OES), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the prepared solid acid catalyst. Acetalization reaction between benzaldehyde and ethylene glycol was done to investigate the catalytic activity of prepared catalyst and 97% conversion toward acetal production was reached in short reaction time. The lower conversion was also achieved for the same catalyst without any HPW species, demonstrated the positive role of the second acidic sites on progression of this reaction. In addition, this easily separable solid acid catalyst reused for four runs with no observable loss in benzaldehyde conversion.

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.

Liquid phase oxidation of benzyl alcohol to benzaldehyde over chromium borophosphate catalyst synthesized by solution combustion method using different types of fuel

In this paper, chromium borophosphates have been prepared by the solution combustion method using different types of fuel and enhanced as a catalyst for liquid-phase oxidation of benzyl alcohol to benzaldehyde for the first time. Carbohydrazide, citric acid, hexamethylenetetramine, oxalyldihydrazide and urea used as an organic fuel and the obtained chromium borophosphates were systematically characterized by infrared spectroscopy, X-ray powder diffraction, thermogravimetry, scanning electron microscopy, and surface analysis techniques. They are structurally identical and thermally stable up to 1000 °C. According to fuel, their surface properties differ from each other and the long and short rod-like particles, which have a surface area between 7 and 19 m2 g−1, are formed. The effects of solvent type, reaction temperature, reaction time, peroxide amount and catalyst amount were also examined for catalytic studies, and the reaction conditions were optimized. As compared with the other fuels, hexamethylenetetramine-assisted synthesized chromium borophosphate catalyst provides high benzaldehyde conversion (52.09%) and selectivity (100%) under the optimized condition and has potential as a heterogeneous catalyst for oxidation reactions.