Mesoporous Aluminophosphate Research Articles

Photocatalytic 4-Nitrophenol Reduction by Hydrothermally Synthesized Mesoporous Co- and/or Fe-Substituted Aluminophosphates

Mesoporous cobalt- and/or iron-substituted aluminophosphates were synthesized by a hydrothermal method, followed by pyrolysis and calcination. The substitution of the transition metal elements modified the electronic properties of the samples and the accompanying surface characteristics. The samples showed tunable catalytic activity through the substitution of Fe and/or Co. We have demonstrated that the light-induced photocatalytic 4-nitrophenol reduction reaction can be enhanced through the substitution of Fe and/or Co in aluminophosphates. The induction time associated with the three different types of samples, observed due to the influence of the substituents, allows us to understand the mechanism of the 4-nitrophenol reduction process in our samples. Our work solves the issue associated with the origin of induction time and the enhancement of the catalytic activity of mesoporous aluminophosphates in the 4-nitrophenol reduction reaction through a controlled modification of the electronic properties.

Cover Feature: Ionic liquid templated synthesis of cobalt‐substituted mesoporous aluminophosphates: A novel heterogeneous catalyst for selective oxidation of cyclohexane to cyclohexanol (ChemCatChem 8/2024)

Cover Feature: Ionic liquid templated synthesis of cobalt‐substituted mesoporous aluminophosphates: A novel heterogeneous catalyst for selective oxidation of cyclohexane to cyclohexanol (ChemCatChem 8/2024)

Ionic liquid templated synthesis of cobalt‐substituted mesoporous aluminophosphates: A novel heterogeneous catalyst for selective oxidation of cyclohexane to cyclohexanol

AbstractOrdered hexagonal mesoporous aluminophosphate and its cobalt‐substituted analogue were successfully synthesized using ionic liquid as a structure‐directing agent. The resulting materials were systematically characterized by various analytical, spectroscopic, and imaging methods, confirming the presence of divalent cobalt in the tetrahedral framework of the matrix. Further, the high surface area, pore volume, and thicker mesopore walls of these materials impart good thermal and hydrothermal stability. The mesoporous catalysts showed excellent activity towards the oxidation of cyclohexane reactions using hydrogen peroxide as an oxidant, with 98.5 % conversion and 90.4 % selectivity towards cyclohexanol.

Comparative Catalytic Performance Study of 12-Tungstophosphoric Heteropoly Acid Supported on Mesoporous Supports for Biodiesel Production from Unrefined Green Seed Canola Oil

In this study, three solid acid catalysts, namely mesoporous aluminophosphate-supported 12-tungstophosphoric heteropoly acid (HPW/MAP), mesoporous aluminosilicate-supported 12-tungstophosphoric heteropoly acid (HPW/MAS), and gamma alumina-supported 12-tungstophosphoric heteropoly acid (HPW/γ-Al2O3) were prepared and characterized. Mesoporous aluminophosphate (MAP) and mesoporous aluminosilicate (MAS) were synthesized via sol-gel and hydrothermal methods, respectively, and 25 wt.% of 12-tungstophosphoric heteropoly acid (HPW) was immobilized on the support materials using the wet impregnation method. The features of the fabricated catalysts were comprehensively investigated using various techniques such as BET, XRD, NH3-TPD, TGA, and TEM. The surface area of the supported catalysts decreased after HPW impregnation according to BET results, which indicates that HPW loaded on the supports and inside of their pores successfully. The density and strengths of the acid sites of the support materials and the catalysts before reaction and after regeneration were determined by the NH3-TPD technique. Accordingly, an increase in acidity was observed after HPW immobilization on all the support materials. The catalytic performance of the catalysts was studied through alcoholysis reaction using unrefined green seed canola oil as the feedstock. The maximum biodiesel yield of 82.3% was obtained using 3 wt.% of HPW/MAS, with a methanol to oil molar ratio of 20:1, at 200 °C and 4 MPa over 7 h. The reusability study of HPW/MAS showed that it can maintain 80% of its initial activity after five runs.

Ce and Ca/Nb doped Pd-mesocellular foam catalysts for gas-phase conversion of acetone to methyl isobutyl ketone

Herein, we report a study on the design of new palladium containing catalysts based on Ce- and Ca–Nb-mesocellular foam (MCF) supports for gas-phase conversion of acetone to methyl isobutyl ketone (MIBK). A comparison to other catalyst materials already described in the literature shows that the role of material structure (mesostructured cellular foams, hydroxyapatite or mesoporous aluminophosphate), acid-base character of the support, state of palladium species and the support metal dopants play important roles for the catalytic performance in the conversion of acetone to MIBK. Thus, the new catalytic system Pd/Ce-MCF with 11% of conversion and 94% of selectivity to MIBK (250 °C) is demonstrated to be more attractive in term of stability for the reaction over time than previously described in literature for Pd/hydroxyapatite. • Palladium was impregnated on cerium and calcium-niobium doped MCF support. • The oxidation state of palladium was influenced by the MCF support composition. • Both the state of palladium and sample basicity had impact on catalytic performance. • Pd/Ce-MCF demonstrated superior catalyst stability over prolonged reaction time.

Synthesis of high surface area aluminophosphate and -phosphonate xerogels by non-hydrolytic sol-gel reactions

We disclose the preparation of high-surface-area mesoporous aluminophosphates and aluminophosphonates by the non-hydrolytic sol-gel reactions (NHSG) of Al(NMe 2 ) 3 with trimethylsilylated phosphate OP(OSiMe 3 ) 3 , phosphonates RP(O)(OSiMe 3 ) 2 (R = Me, t Bu, Ph), and bis-phosphonates (Me 3 SiO) 2 (O)P–X–P(O)(OSiMe 3 ) 2 (X = C 6 H 4 , (C 6 H 4 ) 2 ) in dry toluene. The reactions proceed by silylamine elimination of Me 3 SiNMe 2 to provide organic-inorganic hybrid xerogels with properties influenced by organic substituents and the Al:P ratio of the precursors. Dried xerogels exhibit large surface areas (up to 1000 m 2 g −1 ) and matrices based on condensed Al–O–P networks. They stay stable under relatively harsh thermal conditions. 27 Al, 13 C, and 29 Si solid-state NMR spectroscopy was employed to characterize the aluminum coordination and the residual amido and trimethylsilyl groups. The catalytic performance of NHSG prepared material was examined in gas-phase dehydration of ethanol to ethylene exhibiting conversion and selectivity comparable to weak solid acid benchmark catalysts. The number of unreacted surface groups was determined by gravimetric measurements and by thermal analysis (TG-DSC). These residual groups have the potential to be used in post-synthetic grafting of catalytically active metal centers. • Aluminophosphates and aluminophosphonates are prepared by non-hydrolytic sol-gel synthesis. • Mesoporous xerogels with large surface areas (1030 m 2 g -1 ). • Gas-phase dehydration of ethanol to ethylene with good conversion and selectivity.

Amorphous magnesium substituted mesoporous aluminophosphate: An acid-base sites synergistic catalysis for transesterification of diethyl carbonate and dimethyl carbonate in fixed-bed reactor

Abstract Amorphous magnesium substituted mesoporous aluminophosphate (AlPO) were prepared, characterized and used as catalysts for the transesterification of diethyl carbonate and dimethyl carbonate in the fixed-bed reactor. The results of FT-IR and XPS confirm the substitution of Mg into the framework of AlPO. Magnesium substituted mesoporous aluminophosphate (MgAPO) have strong basic and weak acid sites according to the results of CO2-TPD and NH3-TPD. Compared with that of the AlPO catalyst, the pore diameters of the catalysts increased after the introduction of Mg. The activity and stability of the catalysts also improved with the introduction of Mg. The catalytic performance of these catalysts increases in the order of AlPO

Synthesis of aluminophosphate xerogels by non-hydrolytic sol–gel condensation of EtAlCl2 with trialkylphosphates

We have investigated the preparation of high-surface-area mesoporous aluminophosphates by non-hydrolytic sol–gel method based on reactions of EtAlCl2 with trialkylesters of phosphoric acid (OP(OR)3, R = Me, Et, iPr, nBu, in dry organic solvents. The condensations proceed by alkylchloride elimination. Various reaction and calcination conditions were examined. Porosity is obtained after calcination by removal of organic residual groups. This thermal processing at 300 °C of as-synthesized precursor gels leads to amorphous aluminophosphate xerogels with surface areas of 400–500 m2 g–1 provided by small mesopores (2–8 nm). Changes in the coordination environment of aluminium from six- to four-coordinate are evidenced by shift of 27Al MAS NMR resonances.

Removal and Recovery of Brilliant Green and Brilliant Yellow using Mesoporous Aluminophosphate Molecular Sieves from Aqueous Solution

Removal and Recovery of Brilliant Green and Brilliant Yellow using Mesoporous Aluminophosphate Molecular Sieves from Aqueous Solution

Phenolic Compounds Adsorption on Mesoporous Aluminophosphate Molecular Sieves from Aqueous Solution

Phenolic Compounds Adsorption on Mesoporous Aluminophosphate Molecular Sieves from Aqueous Solution

Mesoporous V-AlPO – New Partial Oxidation Catalyst

<p>Vanadium incorporated hexagonal mesoporous aluminophosphate characteristic of MCM-41 has been synthesized. Characterization of the catalyst has been done by using low angle XRD, N<sub>2</sub> adsorption, UVVIS DRS, thermal analysis, XPS and ESR spectroscopy. These techniques confirm the presence of vanadium in both +4 and +5 oxidation states in the calcined material. Liquid phase partial oxidation of toluene has been carried out on V-AlPO using 70% TBHP and 30% H<sub>2</sub>O<sub>2</sub> as oxidants. When 70% TBHP is used as an oxidant, it resulted in side chain oxidation giving rise to aldehyde/acid where as with 30% H<sub>2</sub>O<sub>2</sub>, side chain as well as ring oxidation takes place. Catalytic activity of V-AlPO has been compared with that of VMCM-48 and other vanadium containing catalytic systems. It has been observed that mesoporous V-AlPO shows higher conversion and is also selective towards side chain oxidation products. The higher conversion of V-AlPO over V-MCM-48 has been attributed to the stabilization of the active V<sup>+5/+4</sup> species in AlPO framework as compared to silicate analogue.</p>

A recoverable sandwich phosphorotungstate stabilized palladium (0) catalyst for aerobic oxidation of alcohols in water

The preparation, characterization and catalytic properties of tetra metal substituted sandwich phosphorotungstate [M4(H2O)2(PW9O34)2]10−(M4P2W18, M2+=Fe2+, Co2+, Mn2+, Cu2+, VO2+) stabilized Pd nanoparticles, which were in-situ encapsulated in mesoporous aluminum phosphate (mAPO) by a one-pot method, were demonstrated for aerobic oxidation of alcohol in water. The synthesized catalysts were characterized with N2 adsorption, XRD, TEM, FT-IR and UV–vis. TEM analysis revealed that Pd-M4P2W18/mAPO thus obtained has a mean palladium particle size of less than 5nm. The solid Pd-M4P2W18/mAPO catalysts exhibit excellent activity for aerobic oxidation of benzyl alcohols in water without any base additives. It was found the introduced M4P2W18 polyoxanions encapsulated palladium nanoparticles as both stabilizing agent and promoters, leading to enhanced activity and recyclability of palladium catalyst. The recycling test of representative Pd-(VO)4P2W18/mAPO for oxidation of benzyl alcohol suggested no significant decrease in activity and selectivity even after twelve times of successive reactions. This novel heterogeneous catalyst composed of polyoxometalates stabilized palladium nanocatalysts and mesoporous aluminophosphate can also be extended to the selective oxidation of various alcohols.

Modified mesoporous aluminophosphate as an efficient solid acid catalyst for the synthesis of novel O- and N-acetylated compounds: solvent free condition

Solid acids such as amorphous aluminophosphates (AlP) modified with different transition metals (Fe/Mo/W) were synthesized by either precipitation or co-precipitation methods. These solid acids were characterized by BET, NH3-TPD, PXRD and FT-IR techniques. The catalytic activity of these solid acids was evaluated in the synthesis of novel O- and N-acetylated compounds of various substituted alcohols, phenols, pyridine alcohols, furan alcohols, aryl alcohols and amines under solvent free conditions with acetic anhydride as an acetylating agent. The reaction conditions were optimized by varying the catalyst, molar ratio of the reactants, reaction temperature and amount of the solid acid catalyst. Among the solid acids, FeAlP consisting of 0.025 mol% Fe showed good catalytic activity in the acetylation reaction and produces high yield of acetylated products. In addition, the catalysts can also be reused in acetylation at least for 4 reaction cycles without significance loss of catalytic activity.

Effective acetylation of alcohols, phenols and amines over mesoporous aluminophosphate solid acids under solvent free conditions

Solid acids such as amorphous aluminophosphates (AlP) and iron aluminophosphates (FeAlP) were synthesized by either precipitation or co-precipitation methods. These solid acids were characterized by BET, NH3-TPD, PXRD, FT-IR and NMR techniques for their surface area, surface acidity, crystallinity and functionality. AlPs and FeAlPs were found to be mesoporous in nature. The catalytic activity of these solid acids was determined in acetylation of various alcohols, phenols and amines with acetic anhydride under solvent free conditions. The reaction conditions were optimized by varying the parameters such as molar ratio of the reactants, reaction temperature and amount of the solid acid catalyst. Among the solid acids, FeAlP consisting of 0.025 mol% Fe showed good catalytic activity in the acetylation reaction. These solid acid catalysts can also be reused for acetylation at least for five reaction cycles without any appreciable loss of catalytic activity.

Synthesis of mesoporous aluminophosphates-based materials using various copolymers as templates

The aim of this work was to study the effect that various copolymers and several synthesis conditions may have on the properties of mesoporous aluminophosphates obtained using AlCl3 and H3PO4 as aluminium and phosphorous precursors, respectively under non-aqueous conditions. Poly(styrene-co-allyl alcohol) and various triblock type copolymers were used as structure-directing agents in an acidic medium. The parameters investigated using the poly(styrene-co-allyl alcohol) included stirring time, Al/P mole ratio, synthesis time at 40°C, calcination temperature and the type and amount of polymer used. The resulting materials were characterized by nitrogen adsorption at −196°C, X-ray diffraction (XRD), temperature-programmed ammonia desorption (TPD-NH3) and transmission electron microscopy (TEM). Mesoporous aluminophosphates with surface areas up to 540m2/g were obtained.

A simple method for the synthesis of thermally stable large pore mesoporous aluminophosphate molecular sieves

Mesoporous aluminophosphate AlPO4 with high thermal stability has been simply synthesized from lauric and myristic triglycerides, as a novel templating agent. The ordered sample showed large pore size (153Å) and pore volume (0.37cm³/g), and also presenting a broad pore size distribution. The crystalline nature of the material was detail characterized by the powder X-ray diffraction method and supported by the observation using scanning electron microscope. The material has high thermal stability towards thermal treatment up to 1200°C. The catalyst shows very high activity for the esterification of n-butanol and acetic acid and also acts as a good adsorbent for the removal of organic dyes from aqueous solution.

Kinetic and Isotherm Studies of Removal of Metanil Yellow Dye on Mesoporous Aluminophosphate Molecular Sieves

The removal of metanil yellow dye was studied through adsorption on meosporous aluminophosphate molecular sieves at different experimental conditions like contact time, pH, dye concentration and adsorbent dosage. The experimental values were adopted to adsorption kinetic and adsorption isotherm equations for understanding the rate and mechanism of adsorption process. The adsorption process was well fitted with pseudo first second kinetics and Langmuir adsorption isotherm. The maximum adsorption capacity of metanil yellow on adsorbent was 75 mg/g. This study concludes that the mesoporous aluminophosphate material is a good material for removal of metanil yellow dye.

Cr-Substituted Mesoporous Aluminophosphate Molecular Sieve: Synthesis, Characterization, Crystallization Kinetics and Catalytic Activity

Cr-substituted mesoporous aluminophosphate molecular sieve (Cr-MAP) was synthesized and characterized. Crystallization kinetics curves measured as an index to the relative degree of crystallinity, according to the Arrhenius equation to calculate the apparent nucleation activation energy and crystal growth activation energy of Cr-MAP, which was 63.7 and 14.7 kJ• mol-1, respectively. Cr-MAP had highly catalytic activity for fabricating acetophenone by selectively oxizing ethylbenzene. Using tert-butylhydroperoxide as oxidant and chlorobenzene as solvent at 100 °C for 8 h, acetophenone selectivity, acetophenone yield and ethylbenzene conversion reaches 85.4, 62.2 and 72.8 %, respectively.

Hazardous dyes removal from aqueous solution over mesoporous aluminophosphate with textural porosity by adsorption

Dye pollution in aquatic nature produce serious environmental effects. In this investigation, mesoporous aluminophosphate molecular sieve synthesized and applied for the removal of hazardous dyes Malachite green (MG) and Methylene blue (MB). In the synthesis of mesoporous aluminophosphate (AlPO4) molecular sieve, the structure-directing agent, long-chain alkylbenzene has been used as a template. The template used for the synthesis of mesoporous material is environmentally biodegradable. The mesoporous AlPO4 was synthesized by the absence of an organic base, tetramethyl ammonium hydroxide (TMAOH) which is necessary to maintain the pH for the conventional AlPO4 synthesis methods. The synthesized mesoporous AlPO4 has high thermal stability up to 1173K and large porosity nature (40nm). It was confirmed by the characterization techniques such as low-angle XRD, FT-IR, TGA and BET surface area analysis. The morphology of the material was explained by using SEM and TEM. The hazardous dyes MG and MB removal studied under the various conditions like contact time, dye concentration, temperature, pH and adsorbent dosage to examine the adsorption characteristics of the newly synthesized mesoporous AlPO4 molecular sieves.

Biosynthesis of amorphous mesoporous aluminophosphates using yeast cells as templates

In this study aluminophosphates have been synthesized from aluminum isopropoxide and phosphoric acid solutions using yeast cells as template. The physicochemical characterization was carried out by thermogravimetric analysis; X-ray diffraction; Fourier transform infrared; N2 adsorption–desorption isotherms; scanning electron microscopy; transmission electron microscopy and potentiometric titration with N-butylamine for determination of: thermal stability; crystalline structure; textural properties; morphology and surface acidity, respectively. The calcined powders consisted of an intimate mixture of amorphous and crystallized AlPO particles with sizes between 23 and 30nm. The average pore size observed is 13–16nm and the specific surface area after calcinations (at 650°C) ranged between 176 and 214m2g−1.