Anhydrous Phosphoric Acid Research Articles

Enhancement of the luminescent and optical properties of ceramic Ce:GAGG after surface treatment with phosphoric acid.

Surface modification of ceramic Ce-doped Gd3Al2Ga3O12 (Ce:GAGG) was performed by exposing small samples to anhydrous phosphoric acid (H3PO4) under different conditions (temperature and duration) to investigate the effects of chemical polishing treatment. When coupled to a photomultiplier tube (PMT) and used as a radiation detector, chemical treatment for 3 min at 190 °C improved the light (signal) output by 24.8% and energy resolution by 2.5% (percentage point), respectively. This can be attributed to a reduction in surface roughness that enhanced optical properties. Thus, chemical polishing could be a low-cost alternative to mechanical polishing especially for small or complex shaped ceramic scintillators.

Ab initio quantum chemical studies of isotopic fractionation during acid digestion reaction of dolomite for clumped isotope application.

In 'clumped isotope paleothermometry' carbonates are reacted with anhydrous phosphoric acid to extract CO2 that carries the isotopic signature of the reacting carbonates, and the amount of clumping in the product CO2 is measured. Previous theoretical models for determining clumped isotopic fractionation in product CO2 during acid digestion of carbonates are independent of the cations present in the carbonate lattice. Hence further study is required to understand the cationic effect. We studied the acid reaction mechanism based on the protonation of carbonates, calculated the acid fractionation factor for dolomite using the partition functions and vibrational frequencies obtained for the transition state structure, and determined the effect of cations on the acid fractionation factor. Experimentally, carbonates are reacted using the modified sealed vessel method and analyzed in the dual inlet of a ThermoFinnigan MAT 253 isotope ratio mass spectrometer. The oretically obtained acid fractionation factor can be expressed as Δ47 acid fractionation in dolomite = -0.28563 + 0.49508 * (105 /T2 ) - 0.08231 * (105 /T2 )2 for a temperature range between 278.15 and 383.15 K. The theoretical slope of the dolomite-acid digestion curve is lower than that of the calcite-acid digestion curve obtained using the identical reaction mechanism. Our theoretical slope is consistent with the result from the common acid bath experiments but higher than the slope obtained in our experimental study using the modified sealed vessel method and in a previous theoretical study using the H2 CO3 model. The transition state structure, obtained in our study, includes the cations present in the carbonate minerals and provides distinct acid fractionation factors for calcite and dolomite. The observed gentler slope of the theoretically calculated dolomite-acid digestion curve than of the calcite curve is expected considering the stronger Mg-O bond. Our experimental approach invokes post-digestion isotopic exchange and agrees with the previous theoretical estimates where post-digestion isotopic fractionation was considered.

Liquid–Liquid–Solid Equilibria in the Ternary System Water–Phosphoric Acid–Cyclohexane at 25 and 35 °C: Stability Domain of Hemihydrate and Anhydrous Phosphoric Acid

The water–phosphoric acid–cyclohexane ternary system was studied at 25 and 35 °C under atmospheric pressure, and the binodal curve was determined by the cloud-point method. In addition, the isoplethic section between 2H3PO4·H2O–cyclohexane was investigated using a Tammann diagram based on the thermal analysis of different samples with the determination of hemihydrate melting temperature. The concentration of phosphoric acid and cyclohexane was assayed by volumetric titration and gas chromatography, respectively; the amount of water was calculated by the material balance equation. The miscibility between phosphoric acid and cyclohexane was found to be very low with the appearance of a three-phase stability domain liquid–liquid–solid by the presence of phosphoric acid crystals: hemihydrate (2H3PO4·H2O) and anhydrous phosphoric acid (H3PO4).

Asymmetric Transfer Hydrogenation of 1‐Aryl‐3,4‐Dihydroisoquinolines Using a Cp*Ir(TsDPEN) Complex

We report herein a simple alternative method for the asymmetric transfer hydrogenation (ATH) of 1‐aryl‐3,4‐dihydroisoquinolines (1‐Ar‐DHIQs) that are known to be challenging substrates owing to their poor reactivity. The hydrogenation protocol employs the readily available Cp*Ir(TsDPEN) {where Cp* = pentamethylcyclopentadienyl and TsDPEN = (S,S)‐HNCHPhCHPhNTs2–} catalytic complex, 2‐propanol and HCOOH/triethylamine mixture as the solvent and hydrogen donor, and anhydrous phosphoric acid as an inexpensive additive. The series of examined substrates shows a favorable tolerance to various functional groups. Unlike 1‐alkyl‐DHIQs, where the enantiomeric excess (ee) starkly changes during the course of hydrogenation, 1‐Ar‐DHIQs exhibit a constant ee value, which makes the method practical and useful for the production of fine chemicals containing the 1,2,3,4‐tetrahydroisoquinoline motif.

Characterization of Type-II Acetylated Cellulose Nanocrystals with Various Degree of Substitution and Its Compatibility in PLA Films.

In order to decrease the self-agglomeration and improve the hydrophobic properties of type-II acetylated cellulose nanocrystals (ACNC II), various degree of substitution (DS) values of ACNCs were successfully prepared by a single-step method from microcrystalline cellulose with anhydrous phosphoric acid as the solvent, and acetic anhydride as the acetylation reagent, under different reaction temperatures (20–40 °C). To thoroughly investigate the DS values of ACNC II, analyses were performed using Fourier transform infrared spectroscopy (FT-IR), 13C cross polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR), and X-ray photoelectron spectroscopy (XPS). At a reaction temperature of 40°C, the highest DS value was successfully obtained. XRD proved that the crystal structure of ACNC II with various DS values was maintained after acetylation. TEM showed the threadlike shape for ACNC II with various DS values. The ACNC II with various DS values was introduced into a polylactic acid (PLA) matrix to produce PLA/ACNC composite films, which showed improved rheological and thermal properties. This improvement was primarily attributed to good dispersion of the ACNC II, and the interfacial compatibility between ACNC II and the PLA matrix. This study aims to analyze the compatibility of ACNC II with various DS values in the PLA matrix by microstructure, crystallization, and rheological and thermal tests.

Phosphorothioate analogs of P1,P3-di(nucleosid-5′-yl) triphosphates: Synthesis, assignment of the absolute configuration at P-atoms and P-stereodependent recognition by Fhit hydrolase

Di(nucleosid-5′-yl) polyphosphates (NPnN) are involved in various biological processes, and constitute signaling molecules in the intermolecular purinergic systems. They exert tumor suppression function and are substrates for specific hydrolases (e.g., HIT proteins). Their structural analogs may serve as molecular probes and potential therapeutic agents. Three P1,P3-bis-thio-analogs of symmetrical di(nucleosid-5′-yl) triphosphates (NP3N) bearing adenosine, guanosine or ribavirin residues (6, 7 and 8, respectively), were obtained by direct condensation of corresponding base-protected nucleoside-5′-O-(2-thio-1,3,2-oxathiaphospholane) with anhydrous phosphoric acid in the presence of DBU. Deprotected products 6 and 8 were separated into individual P-diastereoisomers, whereas 7 was partially separated to yield diastereomerically enriched fractions. The absolute configuration at P-stereogenic centers in the separated diastereoisomers was assigned by RP-HPLC analysis of the products of enzymatic digestion with snake venom phosphodiesterase. The Fhit-assisted hydrolysis rates for 6 and 7 are by 2–3 orders of magnitude lower than that for the reference AP3A, and depend on the configuration of the stereogenic phosphorus atoms, while 8 occurred to be resistant to this cleavage.

Lithium silicate–lithium phosphate (xLi4SiO4 −(1 − x)Li3PO4) coating on lithium nickel manganese oxide (LiNi0.7Mn0.3O2) with a layered structure

Solid solution of lithium silicate and lithium phosphate (xLi4SiO4−(1 − x)Li3PO4, LSP) is coated on LiNi0.7Mn0.3O2 using the reaction between the residual lithium compounds (Li2CO3 and LiOH) on the surface of LiNi0.7Mn0.3O2 particles and the sol prepared from tetraethyl orthosilicate (TEOS) and anhydrous phosphoric acid. The physical properties of the samples are analyzed by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Electrochemical analyses, such as cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) and galvanostatic cycling, are carried out for the samples. As a result, LSP-coating is found to be effective for improving the rate capability of LiNi0.7Mn0.3O2 as a cathode material for lithium-ion batteries. The specific capacity of the LSP-coated sample retains 58% at high current density of 7 C-rate (vs. 0.5 C-rate) while the bare sample shows only 44% capacity retention. Higher Li+-chemical diffusion coefficient and fast charge transfer process at the interface of the LSP-coated sample estimated by GITT and CV analyses are believed to be the reasons for the better rate capability.

Mannich Reaction as a New Route for the Synthesis of Tetrahydro Pyrimido Benzimidazolyl Coumarins

Condensation of coumarin‐4‐acetic acids (1) with ortho‐phenylenediamine (2) in anhydrous phosphoric acid afforded 4‐((1H‐benzo[d]imidazol‐2‐yl)methyl)‐2H‐chromen‐2‐ones (3). Attempted Mannich reaction of 3 with formalin and primary amines resulted in 4‐(2‐phenyl‐1,2,3,4‐tetrahydrobenzo[4,5]imidazo[1,2‐c]pyrimidin‐4‐yl)‐2H‐chromen‐2‐ones (6). The structures of synthesized compounds were elucidated by analyses including 2D HETCOR and DEPT experiments. Synthesized compounds have been subjected for anti‐inflammatory activity. Compound 6j exhibited promising anti‐inflammatory activity.

Characterization of Surface Acetylated Nanocrystalline Cellulose by Single-Step Method

Surface acetylated nanocrystalline cellulose (NCC) was prepared from cotton fiber by a single-step method under mild conditions using anhydrous phosphoric acid as the solvent. The absorbance peak of O-H was reduced, and the absorbance peaks of C=O and CH3 appeared in the Fourier transform infrared (FTIR) spectrum of the acetylated NCC with respect to that of the unmodified NCC. The roughly estimated degree of substitution was a little greater than 1.5 by FTIR analyses, implying that most of the free hydroxyl groups on the NCC surface were acetylated at 40 °C for 3 h. The carbons of the acetyl groups were clearly identified in the 13C cross polarization-magic angle spinning (CP-MAS) nuclear magnetic resonance (NMR) spectrum. The zeta potential was reduced from -32.12 mV to -20.57 mV after acetylation. Transmission electron microscope (TEM) and field-emission scanning electron microscope (FESEM) images showed that they were thread-like nano-crystals with a diameter less than 5 nm. Crystal structure analysis using X-ray diffraction (XRD) demonstrated that the acetylated NCC had the typical CelluloseⅡstructure. The PLA film reinforced with 3 wt% acetylated NCC content exhibited the highest tensile strength, which was increased by 117% compared to the control. SEM observation demonstrated good interfacial interaction between the acetylated NCC and the matrix.

Fabrication of nano-crystalline cellulose with phosphoric acid and its full application in a modified polyurethane foam

Nano-crystalline cellulose was fabricated in an anhydrous phosphoric acid system with medical absorbent cotton as its raw material. After ammonia neutralization, the whole system with produced phosphates and hydrolyzed saccharides was used as a modifier for preparing polyurethane foam (PUF). The NCC worked as a reinforce material, the phosphates served as flame-retardants, and the hydrolyzed saccharides partly replaced polyol. The addition of the modifier significantly improved mechanical property and flame-retardancy without an inferior thermal conductivity. When the dosage of modifier was 6% of the whole polyol, compressive strength increased 4.29 times, heat release rate dropped to 50.7%, and time to ignition extended to 2.6 times of those of the neat PUF. XRD and TEM analyses proved that the NCC in the modifier was rod-shape cellulose Ⅱ with diameter of 10 nm or so. FTIR analysis confirmed that the modifier well reacted with isocyanate, and SEM results revealed that the flame-retardant PUF had more uniform cells and more regular skeleton structure than the neat PUF.

HI extraction by H3PO4 in the Sulfur–Iodine thermochemical water splitting cycle: Composition optimization of the HI/H2O/H3PO4/I2 biphasic quaternary system

Abstract Iodine excess separation from hydriodic acid (HI) is one of the most challenging steps of the Sulfur–Iodine thermochemical water splitting cycle. One promising method is the extraction of HI by using phosphoric acid (H 3 PO 4 ), with the subsequent separation of gaseous hydriodic acid from water and H 3 PO 4 by a distillation step. The aim of the present work is to provide new experimental liquid–liquid equilibrium data for the biphasic HI/I 2 /H 2 O/H 3 PO 4 quaternary system, varying both temperature and solution composition in order to optimize the excess of anhydrous phosphoric acid to be added. Two temperature levels were tested, i.e. 100 °C and 120 °C, and the H 3 PO 4 amount was varied in the feed mixture from 7.7% wt to 38% wt while the [I 2 ]/[HI] and [H 2 O]/[HI] molar ratios were kept constant at, respectively, a value of 3.7 and 5.6. A temperature level of 120 °C, with an H 3 PO 4 initial concentration of about 29% wt leads to the lowest amount of water against HI, which minimizes energy costs in the phosphoric acid reconcentration step, the most energy consuming part in this separation process.

Silicophosphate/silicophosphite hybrid materials prepared by solventless ethanol condensation

We have developed organic-inorganic silicophosphate and silicophenylphosphite hybrid materials by means of alcohol condensation between organically modified alkoxysilane and anhydrous phosphoric or phosphonic acid under a solventless, catalyst-free, low-temperature, one-pot condition. The hybrid exhibits a low-melting property and is chemically more durable than that prepared by using a nonaqueous acid-base reaction between anhydrous phosphoric acid and organically modified chlorosilane. 29Si and 31P NMR analyses have shown that the alcohol condensation yield was around 80%. Quantum chemical calculations have also performed in order to clarify the chemical durability improvement of the hybrids.

Synthesis of New Substituted 5‐Methyl‐3,5‐diphenylimidazolidine‐2,4‐diones from Substituted 1‐(1‐Cyanoethyl‐1‐phenyl)‐3‐phenylureas.

The reaction of substituted phenyl isocyanates with 2-amino-2-phenylpropanenitrile and 2-amino-2-(4-nitrophenyl)propanenitrile has been used to prepare substituted 1-(1-cyanoethyl-1-phenyl)-3-phenylureas. In anhydrous phosphoric acid the first products to be formed from 1-(1-cyanoethyl-1-phenyl)-3-phenylureas are phosphates of 4-methyl-4-phenyl-2-phenylimino-5-imino-4,5-dihydro-1,3-oxazoles, which on subsequent hydrolysis give the respective ureidocarboxylic acids. On prolongation of the reaction time, the phosphates of 4-methyl-4-phenyl-2-phenylimino-5-imino-4,5-dihydro-1,3-oxazoles rearrange to give phosphates of 5-methyl-4-imino-3,5-diphenylimidazolidin-2-ones, and these are subsequently hydrolysed to the respective substituted 5-methyl-3,5-diphenylimidazolidin-2,4-diones. The ureidocarboxylic acids were also prepared by alkaline hydrolysis of 5-methyl-3,5-diphenylimidazolidin-2,4-diones. The 5-methyl-3,5-diphenylimidazolidin-2,4-diones and ureidocarboxylic acids were characterised by their 1H and 13C NMR spectra. Structure of the 5-methyl-5-(4-nitrophenyl)-3-phenylimidazolidine-2,4-dione was verified by X-ray diffraction. The alkaline hydrolysis of individual imidazolidine-2,4-diones was studies spectrophoto-metrically in sodium hydroxide solutions at 25 °C. The rate-limiting step of the base catalysed hydrolysis consists in decomposition of the tetrahedral intermediate. The reaction is faster if electron-acceptor sub-stituents are present in the 3-phenyl group of imidazolidine-2,4-dione cycle. The pKa values of individual 5-methyl-3,5-diphenylimidazolidine-2,4-diones have been determined kinetically.

Synthesis of new substituted 5‐methyl‐3,5‐diphenylimidazolidine‐2,4‐diones from substituted 1‐(1‐cyanoethyl‐1‐phenyl)‐3‐phenylureas

AbstractThe reaction of substituted phenyl isocyanates with 2‐amino‐2‐phenylpropanenitrile and 2‐amino‐2‐(4‐nitrophenyl)propanenitrile has been used to prepare substituted 1‐(1‐cyanoethyl‐1‐phenyl)‐3‐phenylureas. In anhydrous phosphoric acid the first products to be formed from 1‐(1‐cyanoethyl‐1‐phenyl)‐3‐phenylureas are phosphates of 4‐methyl‐4‐phenyl‐2‐phenylimino‐5‐imino‐4,5‐dihydro‐1,3‐oxazoles, which on subsequent hydrolysis give the respective ureidocarboxylic acids. On prolongation of the reaction time, the phosphates of 4‐methyl‐4‐phenyl‐2‐phenylimino‐5‐imino‐4,5‐dihydro‐1,3‐oxazoles rearrange to give phosphates of 5‐methyl‐4‐imino‐3,5‐diphenylimidazolidin‐2‐ones, and these are subsequently hydrolysed to the respective substituted 5‐methyl‐3,5‐diphenylimidazolidin‐2,4‐diones. The ureidocarboxylic acids were also prepared by alkaline hydrolysis of 5‐methyl‐3,5‐diphenylimidazolidin‐2,4‐diones. The 5‐methyl‐3,5‐diphenylimidazolidin‐2,4‐diones and ureidocarboxylic acids were characterised by their 1H and 13C NMR spectra. Structure of the 5‐methyl‐5‐(4‐nitrophenyl)‐3‐phenylimidazolidine‐2,4‐dione was verified by X‐ray diffraction. The alkaline hydrolysis of individual imidazolidine‐2,4‐diones was studies spectrophoto‐metrically in sodium hydroxide solutions at 25 °C. The rate‐limiting step of the base catalysed hydrolysis consists in decomposition of the tetrahedral intermediate. The reaction is faster if electron‐acceptor sub‐stituents are present in the 3‐phenyl group of imidazolidine‐2,4‐dione cycle. The pKa values of individual 5‐methyl‐3,5‐diphenylimidazolidine‐2,4‐diones have been determined kinetically.

31P and 51V MAS-NMR Characterisation of Mixed Vanadium and Titanium Phosphates Prepared from Molecular Precursors

Coprecipitation of mixed vanadium and titanium phosphates has been performed by reacting a mixed solution of vanadium alkoxide (VO(OPrn)3) and titanium alkoxide (Ti(OPrn)4) with anhydrous phosphoric acid (H3PO4). The goal is to obtain a mixture at a molecular level of phosphates with both acidic and redox properties. In protic solvents, such as propanol, the vanadium phosphate precipitation is slow, so, as indicated by the chemical analysis, the coprecipitation is not stoichiometric. The kinetics of precipitation of both vanadium and titanium phosphates are much faster in aprotic solvents such as tetrahydrofuran (THF) and result in homogeneous precipitates. 31P and 51V MAS-NMR experiments, have been used in order to characterise the homogeneity in these samples. Phase separation is observed upon heating at 700∘C.

General One-Step Synthesis of Free Hexofuranosyl 1-Phosphates Using Unprotected 1-Thioimidoyl Hexofuranosides

A general one-step strategy is developed for the synthesis of hexofuranosyl 1-phosphates starting from new unprotected glycofuranosyl donors. It required first the preparation of new 1-thiohexofuranosides bearing a thioimidoyl heterocycle as a leaving group. The presence of sulfur and/or nitrogen atom(s) on the aglycon allowed remote activation of these thioglycofuranosides by anhydrous phosphoric acid and led to the target phosphates 9, 27, 29, and 30 in good to excellent selectivities and, more importantly, with very limited or no ring expansion. Moreover, this one-step phosphorylation reaction could be significantly improved by avoiding any tedious protecting group manipulations on negatively charged compounds and by focusing on a simple but general procedure of purification. This approach was applied to the diastereocontrolled synthesis of d-galacto- and d-glucofuranosyl 1-phosphates and also to the preparation of rare epimer and/or deoxy counterparts, that is, d-manno- and d-fucofuranosyl derivatives.

Dual APD array readout of LSO crystals: optimization of crystal surface treatment

We are developing a compact positron emission tomography (PET) detector module with a depth of interaction capability (DOI) based on a lutetium oxyorthosilicate (LSO) scintillator array coupled at both ends by avalanche photodiode (APD) arrays. This leads to a detector with high sensitivity that can provide high and uniform image resolution. We report studies on improving the DOI resolution by optimizing the crystal surface treatment. Six 2/spl times/2/spl times/20 mm LSO crystals were treated with different surface finishes along their length: raw saw-cut, polished optical finish, and chemically etched by hot anhydrous phosphoric acid (H/sub 3/PO/sub 4/) with etching times varying from 1 to 5 min. The ratio of the signals from the two APD arrays was used to measure DOI, and the sum of the signals to measure the total light output. Crystals finished by chemical etching for 2-3 min gave the best overall detector performance, with DOI resolutions ranging from 3.1 to 3.9 mm for events above a 150-keV threshold and uniform light output for different DOI positions. The energy resolution ranged between 14% and 18%. This detector design appears promising for PET applications requiring very high resolution and high sensitivity, for example, in small animal imaging and human breast imaging.

Liquid crystalline solutions of cellulose acetate in phosphoric acid

The influence has been studied of both the acid strength of phosphoric acid and the degree of substitution of cellulose acetate on the formation of an anisotropic phase. The solvent composition is expressed as a P2O5 concentration. It was found that the clearing temperature increases strongly with decreasing amount of water in the solvent.The influence of the degree of substitution (DS) was studied on a series of samples with a DS ranging from 0.23 to 2.89. It was found that over the entire range good solubility occurred in anhydrous phosphoric acid. The DS hardly affected the clearing temperature in the process of dissolving a constant number density of polymer chains. However, the birefringence of the solution was strongly influenced by the DS, due to the intrinsic birefringence of the polymer chains.

Liquid crystalline solutions of cellulose in phosphoric acid

It was found that anhydrous phosphoric acid is an excellent direct solvent for cellulose. Dissolution is very fast, and liquid crystalline solutions are formed above a cellulose concentration of 7.5% (w/w) at room temperature; even solutions containing 38% (w/w) cellulose can be prepared. The composition of the solvent is expressed in a P2O5 concentration. Anhydrous conditions are obtained above a P2O5 concentration of 74% (w/w) (superphosphoric acid). The solutions were characterised by determining the clearing temperature, which was found to increase with decreasing water content in the phosphoric acid solvent and to level off under anhydrous conditions. Cellulose yarns with high moduli and high tenacities were wet spun from the anisotropic solutions. Superphosphoric acid is also capable of dissolving inter aliacellulose acetate, ethyl cellulose and chitin, with formation of anisotropic solutions.

Unveiling Novel Reaction Processes in Catalysis by Environmentalhrem (EHREM)

Abstract Dynamic interactions between gas molecule and solid surfaces are central to heterogeneous catalytic processes. Recently, we have developed a novel in-situ environmental high resolution electron microscopy (EHREM) method, capable of probing live gas-catalyst reactions at elevated temperatures directly (in-situ) on the atomic scale1. A Philips CM30 (S)TEM has been modified with an integrated environmental cell maintaining atomic resolution in controlled gas environments, upto ∼ 1000 °C. Using this method, we have studied important real-life catalysts, vanadyl pyrophosphates ((VO)2P2O7, hereafter referred to as VPO), used in n-butane oxidation to maleic anhydride (MA with end uses in furans. The catalyst samples were prepared using V2O5, anhydrous phosphoric acid in isobutyl alcohol and benzyl alcohol followed by calcination and activation. VPO is orthorhombic with a ∼ 16.59Å, b ∼ 7.76Å and c ∼ 9.58 Å. An EHREM lattice image of the fresh catalyst with electron diffraction (ED) and ‘rose’ morphology, is shown in Fig 1(a).