Amorphous Aluminophosphate Research Articles

Microwave synthesis of fuel additive over modified amorphous aluminophosphate: Kinetics

The afford work is deliberated to scrutinize a simple solid acid catalytic system for the synthesis of solketal used as a fuel additive under microwave irradiation. The solid acids such as amorphous aluminophosphate (AlPOS) and metal‐aluminophosphates (m-AlPOS) were prepared and characterized by PXRD, FT-IR, BET, SEM, TEM, EDAX, NH 3 -TPD/n-butylamine back titration and ICP-OES techniques. FeAlPOS solid acid showed highest glycerol conversion in a shorter time with comparable catalytic activity of p-TSA Bronsted acid. The impact of reaction parameters like temperature, time, amount of catalyst, molar ratio, speed of agitation and reusability are discussed. The particle size of the m-AlPO samples were reckoned by deploying Debye-Scherrer equation. Reactant pre-adsorption experiments and kinetic study were also taken up. FeAlPOS catalyst is an efficient solid acid catalyst for acetalization of glycerol with acetone and its catalytic activity comparable with p-TSA (homogeneous acid catalyst) under microwave irradiation. .

Contrasting structure-property relationships in amorphous, hierarchical and microporous aluminophosphate catalysts for Claisen-Schmidt condensation reactions

Amorphous aluminophosphates are industrial catalysts that are active in aldol-type condensations, dehydration and alkylation. The intrinsic nature of the active sites present in these materials is poorly understood. Herein we report a comparative investigation of the catalytic active sites in amorphous and crystalline aluminophosphates (AFI topology) and their corresponding iron-containing analogues, employing Claisen-Schmidt condensation of acetophenone and benzaldehyde as the test reaction. Secondary porosity generated via the soft-templating approach in hierarchically-porous HP FeAlPO-5, and the presence of large mesopores in amorphous Am FeAlPO resulted in improved mass-transport and high conversion of carbonyls. The nature and concentration of the active acidic sites within these materials were characterized by pyridine-DRIFTS and propylamine-TPD studies and was shown to play a crucial role in the activation of carbonyl groups and better catalytic performance. Am FeAlPO(5) nearly outperformed HP FeAlPO-5, thus providing a promising alternative for expanding scope in industrial and pharmaceutical applications.

Investigation of active sites using solid state 27Al and 31P MAS NMR in ceramic amorphous aluminophosphate materials prepared from different potassium salts of phosphate for the synthesis of diphenyl urea derivatives

Ceramic amorphous aluminophosphate (CAmAlP) catalysts were prepared by precipitation method using different phosphate salts of potassium such as KH2PO4, K4P2O7 and K2HPO4 as well as H3PO4. The prepared materials were characterized by PXRD, FT-IR, XPS, SEM, BET Surface area, NH3-TPD, 27Al NMR and 31P NMR analytical methods. The catalytic activity of the materials was checked in the synthesis of diphenyl urea (DPU) from aniline and diethyl carbonate, under refluxing conditions. Further, the general application of the catalysts was tested using various substituted anilines. The recyclability of the catalysts was also studied. Uncertainties in percentage yields were calculated to check the reproducible surface properties. The P-XRD, BET Surface area and NH3-TPD results indicated that the materials were amorphous with mesoporous texture, surface areas and acidities in the range 200–260 m2/g and 0.4–0.7 mmol/g respectively. 27Al NMR studies revealed that Al is present in three different coordination states such as tetrahedral, pentagonal and octahedral. The relative percentages of these Al sites depends on the type of the potassium precursor phosphate salt used. Both tetrahedral and pentagonal Al sites in conjunction with each other represented catalytically active sites. An increase in the pentagonal sites contributed to additional increments to the catalytic activity of CAmAlP. The catalyst prepared from KH2PO4 was found to be the best and demonstrated 96% DPU yield.

Understanding the setting and hardening process of wollastonite-based brushite cement. Part 2: Influence of the boron and aluminum concentrations in the mixing solution

The mixing solution of wollastonite-based brushite cement is a phosphoric acid solution containing metallic cations and borax. This work complements a previous study devoted to the influence of the H3PO4 concentration, Ca/P and liquid-to-solid (l/s) ratios on the setting and hardening process of the binder by providing new insight into the role of aluminum and boron.Boron retards the setting and decreases the heat released during the process. It also contributes to reduce the macroporosity of the hardened material but yields to poor compressive strength. With aluminum in the mixing solution, the mechanical properties are greatly improved thanks to the precipitation of an amorphous aluminophosphate which increases the density of the cement matrix. But aluminum alone leads to fast setting. A joint addition of boron and aluminum to the mixing solution makes it possible to get a material with optimized properties both in fresh and hardened states.

Interaction between phosphorus and zeolite/binder: A realumination study on beta zeolites

Abstract Zeolite/binder (beta/Al2O3) was treated with different concentrations of phosphoric acid, and the samples pre- and post-treatment were characterized by several methods. It was found that the content of tetrahedral framework Al species in the beta zeolite increased after the sample was impregnated with phosphoric acid, and the generated aluminophosphate reduced the external surface area of the catalyst but had no effects on the catalytic ability of the beta zeolite. The realumination behavior of beta zeolite is proposed in this work. Polyphosphate reacted with hexa-coordinated aluminum, resulting in the formation of amorphous aluminophosphate species, which were then transferred to the silicon hydroxyl structure cavity on the zeolite to complete realumination. The influence of the sample before and after phosphoric acid modification on the activity of synthesized polyoxymethylene dimethyl ethers was discussed. When the phosphoric acid concentration was 0.5 M, the time to reach the same conversion of trioxane (about 94%) was shortened by 60 min compared to the parent sample.

Selective Crystallization of AlPO4-41 Molecular Sieve in the Presence of Diethylamine

A promising method providing the practical implementation of synthesis of AlPO4-41 alumophosphate molecular sieve with high phase purity using boehmite, phosphoric acid, and diethylamine as the template has been proposed. It has been shown that the mixing of the precursors at room temperature leads to the formation of a gel consisting of diethylamine phosphate, an amorphous aluminophosphate, and undissolved boehmite. It has been found that the introduction of the stage of gel aging at 90°C leads to the dominant formation of an amorphous aluminophosphate, the subsequent crystallization of which ensures the formation of high phase purity AlPO4-41 having cubic morphology of crystals with a size of 0.5–1 μm, a BET specific surface area S of 210 m2/g, and a micropore volume of 0.08 cm3/g.

Investigation on the nature of catalytically active sites in non-crystalline aluminophosphates from 27Al and 31P MAS-NMR studies

Amorphous aluminophosphate (AmAlPO4) materials were synthesized by conventional precipitation technique from different phosphate precursors (Na4P2O7, NaH2PO4, Na2HPO4, (NH4)H2PO4, (NH4)2HPO4 and H3PO4) without using any structure directing agents. All the prepared materials were analyzed by 27Al and 31P MAS-NMR, PXRD, FT-IR, XPS, BET, NH3- TPD and SEM-EDS. The catalytic activity of the materials was checked for synthesis of diphenyl urea (DPU). Phosphoric acid (H3PO4) as a precursor was found to be more active catalyst (which yielded 90% of DPU) than the salt forms. 27Al and 31P MAS-NMR studies showed the presence of variable percentages of tetra and penta coordinated Al species, which are attributed to the catalytic activity of AlPO4. AmAlPO4 materials prepared were amorphous having intrinsic mesoporosity, moderate surface area and moderately strong acidic sites. A synergetic combination of all these surface properties play a subtle role in determining the activity of the differently coordinated Al species in the catalysts.

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.

Selective Crystallization of Aluminophosphate Molecular Sieves with an AEL Structure

The effect of the temperature and exposure time of the starting aluminophosphate gels on their chemical and phase composition was studied. When the source of aluminum is its hydrated oxide (boehmite), gels with different contents of ammonium phosphate, undissolved boehmite, and amorphous aluminophosphate can be formed. The formation of a gel with dominant amorphous aluminophosphate allows selective crystallization of AlPO4-11 of high phase purity and ~100% crystallinity. The developed procedure for the preparation of highly dispersed aluminophosphate AlPO4-11 molecular sieves with these properties allows a transition to crystallization of silicoaluminophosphates SAPO-11—promising domestic catalysts for industrial hydroisomerization of n-paraffins in the production of Arctic diesel fuels and group III oils and isomerization of butenes.

Selective Crystallization of Aluminophosphate Molecular Sieve with AEL Structure

The influence of temperature and ageing of initial aluminophosphate gels on their chemical and phase composition was studied. The hydrated oxide (boehmite) was used as the source of aluminum to prepare gels containing ammonium phosphate, undissolved pseudoboehmite and amorphous aluminophosphate in different proportions. The gel with predominant amorphous aluminophosphate was shown to provide selective crystallization of high phase purity AlPO4-11 with the crystallinity degree close to 100 %. The developed method for preparation of these disperse molecular aluminophosphate sieves AlPO4-11 is a step to crystallization of silicoaluminophosphates SAPO-11 that are promising Russian catalysts for industrial processes of hydroisomerization of n-paraffins used for manufacturing of Arctic diesel fuel, III group oils and isomerization of butenes.

Thermally induced structural transformations of linear coordination polymers based on aluminum tris(diorganophosphates).

The thermal transitions of inorganic-organic hybrid polymers composed of linear aluminum tris(diorganophosphate) chains with a general formula of catena-Al[O2P(OR)2]3 (where R = C1-C8 alkyl group or phenyl moiety) have been studied by means of DSC, powder XRD, TGA and TG-QMS, as well as optical spectroscopy. DSC and XRD reveal that most of them undergo reversible structural transformations in the solid state between -100 and 200 °C caused by the changes in conformation of their organic substituents; however, a translational displacement of the rigid polymeric chains occurs only in the case of the derivative bearing long 2-ethylhexyl groups, which becomes liquid at about 140 °C. The thermal decomposition of the studied polymers begins between 200 and 265 °C depending on the type of organic substituent R decorating their aluminophospate core. TGA combined with mass spectrometry of the evolved gaseous products shows that the pyrolytic decomposition of Al[O2P(OR)2]3 proceeds either through β-elimination of olefin (for compounds with C2-C8 aliphatic ligands), or a homolytic cleavage of the P-OR bond (for methyl and phenyl derivatives); both processes are accompanied by condensation of the newly formed POH groups and liberation of water. Powder XRD, FTIR and SEM analyses of the solid residues indicate that thermolysis of Al[O2P(OR)2]3 accompanied by olefin elimination leads to the formation of condensed aluminum phosphates, mainly aluminum cyclohexaphosphate, exhibiting porous morphology. On the other hand, thermal degradation of methyl or phenyl derivatives results in amorphous aluminophosphate residues, and the latter contains conducting carbonaceous phases.

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.

Investigation of water assisted phase transformation process from AlPO4-5 to AlPO4-tridymite

Water assisted phase transformation process from crystalized AlPO4-5 to AlPO4-tridymite was studied by the combination of X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and in situ multinuclear MAS NMR. It is found that water first activates the residue amorphous aluminophosphate in crystalized AlPO4-5 sample through hydrolysis and condensation reactions. Then the activated aluminophosphate species reassemble into AlPO4-tridymite crystalline. Meanwhile, AlPO4-5 transforms into orthorhombic phase during heating process. With further crystallization of AlPO4-tridymite, the amorphous phase is gradually consumed, and mass transportation between AlPO4-5 and AlPO4-tridymite is established through gradually amorphization of AlPO4-5. Finally, most of the AlPO4-5 transforms into the thermodynamically stable dense phase AlPO4-tridymite.

Amorphous metal-aluminophosphate catalysts for aldol condensation of n-heptanal and benzaldehyde to jasminaldehyde

Amorphous aluminophosphate (AlP) and metal-aluminophosphates (MAlPs, where M = 2.5 mol% Cu, Zn, Cr, Fe, Ce, or Zr) were prepared by coprecipitation method. Their surface properties and catalytic activity for the synthesis of jasminaldehyde through the aldol condensation of n-heptanal and benzaldehyde were investigated. The nitrogen adsorption-desorption isotherms showed that the microporosity exhibited by the aluminophosphate was changed to a mesoporous and macroporous structure which depended on the metal incorporated, with a concomitant change in the surface area. Temperature-programmed desorption of NH3 and CO2 revealed that the materials possessed both acidic and basic sites. The acidic strength of the material was either increased or decreased depending on the nature of the metal. The basicity was increased compared to AlP. All the materials were X-ray amorphous and powder X-ray diffraction studies indicated the absence of metal oxide phases. The Fourier transform infrared analysis confirmed the presence of phosphate groups and also the absence of any M-O moieties in the materials. The selected organic reaction occurred only in the presence of the AlP and MAlPs. The selectivity for the jasminaldehyde product was up to 75% with a yield of 65%. The best conversion of n-heptanal with a high selectivity to jasminaldehyde was obtained with FeAlP as the catalyst, and this material was characterized to have less weak acid sites and more basic sites.

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 orderly nanoporous aluminophosphate and zirconium phosphate materials and their catalytic applications.

Amorphous alumino phosphate (AP) and zirconium phosphate (ZP) materials possessing an ordered nanoporosity have been successfully synthesized by a hydrothermal method using a P123 block co-polymer as the structure directing agent. The materials exhibited excellent catalytic activity towards selective alkylation of phenol with cyclohexanol, where AP showed as high as 100% selectivity to produce the industrially important O-alkylation product, while the corresponding ZP selectively produced a C-alkylation product (93% selectivity).

Multinuclear Solid-State NMR Studies on the Formation Mechanism of Aluminophosphate Molecular Sieves in Ionic Liquids

In the present work, multinuclear solid-state NMR techniques together with power X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to monitor the crystallization process of aluminophosphate AlPO4-11 molecular sieves in 1-ethyl-3-methylimidazolium bromide ([emim]Br) ionic liquids (ILs). The local environments of the selected solid samples were probed by one-dimensional 27Al, 31P, and 19F MAS NMR experiments, and more information was obtained from two-dimensional 27Al→31P heteronuclear correlation (HETCOR) and 27Al triple-quantum MAS (3Q MAS) experiments. It is found that a large amount of amorphous aluminophosphates was formed with the F–Aloct–O–Ppar and Altet–O–Ppar structures in the initial stage of aging. With increasing crystallization time, the partially condensed framework phosphorus species disappeared gradually and became fully condensed. Meanwhile, the octahedral Al was transformed into the pentahedral and tetrahedral Al species with the structures of F–Alpenta–O–Pful and Altet–O–Pful in the AlPO4-11 frameworks. During the crystallization process, [emim] cations acting as the structure-directing agents were occluded into the channels, and F– anions were connected with pentahedral Al in the final AlPO4–11 phase. All of these findings can allow proposing a possible formation mechanism for the synthesis of AlPO4-11 in ionic liquids.

비정질 인산알루미늄 철의 표면 성질 및 촉매 특성: 함유된 철의 양에 의한 효과

ABSTRACT. Iron aluminophosphates (FeAlP) with different percentage of iron were synthesized and characterized for their surfaceand bulk properties. The catalytic activity was determined in the transesterification of diethyl malonate with benzyl alcohol. Benzyl ethylmalonate and dibenzyl malonate were obtained as the only products. FeAlP with 0.025 mole % of iron was found to be distinc tly different in its textural and catalytic properties. Formation of diester was found to be favored by the acid sites of intermedi ate strength.The presence of hydrated alumina and the polycondensed phosphates in the materials reduced the catalytic activity of iron alumino-phosphates in transesterification reaction. Keywords: Amorphous aluminophosphates, Transesterification, Benzyl malonates, Iron loading 비정질 인산알루미늄 철의 표면 성질 및 촉매 특성 : 함유된 철의 양에 의한 효과 A. V. Vijayasankar, C. U. Aniz † , and N. Nagaraju * Department of Chemistry, Catalysis Research Laboratory, St. Joseph’s College Research Centre, 36. Lalbagh Road, Shanthi Nagar, Bangalore 560027, India

Novel aluminophosphate (AlPO) bound ZSM-5 extrudates with improved catalytic properties for methanol to propylene (MTP) reaction

Novel aluminophosphate (AlPO) binders consisting of dense phases of alpha-cristobalite and tridymite were prepared by the treatment of pseudo-boehmite (AlO(OH)) with phosphoric acid. The ZSM-5 extrudates prepared by using AlPO binders have been characterized by XRD, N 2 sorption, NH 3-TPD, 27Al and 31P NMR techniques to elucidate the changes that occurred in the textural properties of the catalyst and their implications on the catalytic activity of the resultant ZSM-5-based extrudates towards methanol to propylene (MTP) reaction. XRD indicated the chemical interaction of P with the alumina binder to form a highly dense crystalline phase of aluminophosphate, alpha-cristobalite. N 2 adsorption, while NH 3-TPD studies revealed the changes in pore morphology of AlO(OH) binder and acidity of ZSM-5 in phosphorus containing extrudates. The drastic decrease in mesoporosity of the AlO(OH) observed after phosphorus addition indeed envisions the disappearance of inter-crystalline voids in the AlO(OH), probably due to a change in its morphology from the crystalline phase to amorphous AlPO phase. 27Al and 31P NMR studies further confirmed the formation of AlPO in these samples. The resultant ZSM-5-based extrudates exhibited enhanced properties of hydrothermal stability, mechanical strength, propylene yield and coke resistance in methanol to propylene (MTP) reaction. The positive aspect of P addition was continuously increased with P amount; at optimum P/Al (binder) ratio of ∼0.8, the catalyst exhibited about 80% yield to C 2–C 4 olefins with the major component being propylene (∼50%) at near 100% methanol conversion. The catalyst also exhibited the stable performance in the studied period of 150 h.

Mesoporous Aluminophosphate Thin Films with Cubic Pore Arrangement

Mesoporous aluminophosphate thin films with 3D cubic (Im3m) pore arrangement were synthesized for the first time. Thin films were templated with block copolymer nonionic templates Pluronic F127 and F108 and deposited on a glass substrate by dip-coating. In situ SAXS investigations show the formation of a highly ordered mesostructure upon the dip-coating process, which remains stable up to at least 670 K. A cubic mesostructure was observed also by TEM. Template removal process was monitored by TG and FT-IR. A transition from an amorphous aluminophosphate gel to a well-defined aluminophosphate framework was observed by MAS NMR.