LiAlH4 Research Articles

A new zeolitic lithium aluminum imidazolate framework.

An aliovalent mixed-metal framework DUT-174 [LiAl(2-methylimidazolate)4]n, isostructural to ZIF-8, was synthesized from lithium aluminum hydride (LiAlH4) and 2-methylimidazole (2-mImH) through dehydrogenation. Lithium and aluminum cations acting as alternating framework nodes are coordinated tetrahedrally by (2-mIm)-. DUT-174 has a high specific surface area of 1149 m2 g-1 and CO2 uptake of 11.57 mmol g-1 at 195 K.

Electrolyte-Assisted Hydrogen Cycling in Lithium and Sodium Alanates at Low Pressures and Temperatures

An investigation of electrolyte-assisted hydrogen storage reactions in complex aluminum hydrides (LiAlH4 and NaAlH4) reveals significantly reduced reaction times for hydrogen desorption and uptake in the presence of an electrolyte. LiAlH4 evolves ~7.8 wt% H2 over ~3 h in the presence of a Li-KBH4 eutectic at 130 °C compared to ~25 h for the same material without the electrolyte. Similarly, NaAlH4 exhibits 4.8 wt% H2 evolution over ~4 h in the presence of a diglyme electrolyte at 150 °C compared to 4.4 wt% in ~15 h for the same material without the electrolyte. These reduced reaction times are composed of two effects, an increase in reaction rates and a change in the reaction kinetics. While typical solid state dehydrogenation reactions exhibit kinetics with rates that continuously decrease with the extent of reaction, we find that the addition of an electrolyte results in rates that are relatively constant over the full desorption window. Fitting the kinetics to an Avrami-Erofe’ev model supports these observations. The desorption rate coefficients increase in the presence of an electrolyte, suggesting an increase in the velocities of the reactant-product interfaces. In addition, including an electrolyte increases the growth parameters, primarily for the second desorption steps, resulting in the observed relatively constant reaction rates. Similar effects occur upon hydrogen uptake in NaH/Al where the presence of an electrolyte enables hydrogenation under more practical low temperature (75 °C) and pressure (50 bar H2) conditions.

Formaldehyde-free self-polymerization of lignin-derived monomers for synthesis of renewable phenolic resin

Most phenolic resins are synthesized with non-renewable petroleum-based phenol and formaldehyde, which have adverse effects on the environment and human health. To achieve green and sustainable production of phenolic resins, it is important to replace non-renewable toxic phenol and formaldehyde. Herein, a new strategy was proposed to completely replace phenol and formaldehyde, using lignin-derived monomers to synthesize renewable phenolic resins. Lithium aluminum hydride was utilized to reduce lignin-derived monomers, including vanillin, methyl vanillate, and syringaldehyde, to generate the corresponding vanillyl and syringic alcohol. With oxalic acid as the catalyst, vanillyl and syringic alcohol could be polymerized to phenolic resins without using formaldehyde. The structure of the phenolic resins based on lignin-derived monomers was analyzed by Fourier transform infrared spectroscopy and 13C and 31P nuclear magnetic resonance spectroscopy. Differential scanning calorimetry and thermogravimetric analysis were performed to characterize the thermal properties of the phenolic resins. The phenolic resins based on lignin-derived monomers exhibited excellent adhesion strength (6.14 MPa), glass transition temperature (Tg) (107–115 °C), and thermal stability, and its performance was similar to that of the commercial Novolak phenolic resin. This study presents a promising green and sustainable approach to synthesize renewable phenolic resins based on lignin-derived monomers without using formaldehyde.

Catalytic effect of SrTiO3 on the dehydrogenation properties of LiAlH4

Lithium alanate (LiAlH4) is regarded as one of the potential materials for on-board hydrogen storage applications because of its high hydrogen capacity. However, this advantage is restricted by several obstacles such as high decomposition temperature and slow desorption kinetics that deny its marketability. Hence, efforts such as decreasing the particle size by the mechanical milling technique and by adding dopants/catalysts have been investigated widely to overcome these drawbacks. In this work, the influences of strontium titanate (SrTiO3) on the dehydrogenation properties of LiAlH4 have been investigated for the first time. The onset decomposition temperature of the 10 wt% SrTiO3-doped LiAlH4 sample decreased from 145 °C to 80 °C in the first dehydrogenation step and from 178 °C to 120 °C in the second dehydrogenation step. For the desorption kinetic measurements at 90 °C, the 10 wt% SrTiO3-doped LiAlH4 sample could desorb about 3.0 wt% of H2 in 20 min compared to 0.2 wt% by the as-milled LiAlH4. The activation energies calculated by Kissinger analysis in the two-step dehydrogenation process of LiAlH4 were lowered after the addition of SrTiO3. From the X-ray diffraction analysis, we found that SrTiO3 did not react during the mechanical milling and heating (desorption) processes. SrTiO3 is believed to play a catalytic role by reducing the physical size of LiAlH4 during the mechanical milling process thereby improving the dehydrogenation storage properties of LiAlH4.

Гидроксипроизводные левоглюкозенона в реакциях энантиоселективного восстановления 1,3-дифенилпропан-1-она

The enantioselective reduction of prochiral ketones is an important method for the preparation of enanti-enriched secondary alcohols, which can serve as starting materials for optically active compounds. Chiral metal hydride reagents, such as lithium aluminum hydride (LiAlH4) and sodium borohydride (NaBH4), modified with chiral ligands, have been developed to effect enantioselective reduction. However, in most cases, derivatives are used to obtain chiral hydride reagents, which are rare and hardly available. Therefore, the search for more accessible and effective derivatives suitable for the modification of hydride reagents is an urgent task. Levoglucosenone is an optically pure enone of carbohydrate nature, readily available by pyrolysis of any cellulose-containing materials. Levoglucosenone is considered a promising bioplatform for both laboratory synthesis and industrial use. The prospect of the development of chemistry of levoglucosenone and its derivatives in industry makes it possible to pay attention to these compounds from the point of view of studying their possibilities as chiral inducers or auxiliaries. In this work, we studied the possibilities of chiral induction in the reduction reactions of 1,3-diphenylpropan-1-one with hydride reagents obtained by replacing hydrogens in LiAlH4 and NaBH4 with hydroxy derivatives of levoglucosenone. The reduction of 1,3-diphenylpropan-1-one with chiral aluminum hydride reagents proceeded with low enantioselectivity, mainly with a predominance of (S)-1,3-diphenylpropan-1-ol. It was found that the enantiomeric purity of the S-stereomer decreases with an increase in the substitution of hydrogen atoms in LiAlH4 by hydroxy derivatives of levoglucosenone. Reduction of 1,3-diphenylpropan-1-one with reagents obtained by partial neutralization of NaBH4 with hydroxy derivatives of levoglucosenone, on the contrary, predominantly leads to the formation of (R)-1,3-diphenylpropan-1-ol. The addition of AcOH and Bu4NCl to NaBH4 has a positive effect on the optical frequency of the R-alcohol. At the same time, enantioselectivity in the reactions was almost absent upon reduction of 1,3-diphenylpropan-1-one with reagents obtained by partial neutralization of BH3. The best results of enantioselective reduction were shown by unsaturated alcohols: (1S,4S,5R) -6,8-dioxabicyclo[3.2.1]oct-2-en-4-ol and (1S,4S,5R)-4-methyl-6,8-dioxabicyclo[3.2.1]oct-2-en-4-ol, of which (1S,4S,5R)-6,8-dioxabicyclo[3.2.1]oct-2-en-4-ol was the most effective. It is likely that an increase in the enantioselectivity of reactions carried out in the presence of hydroxy derivatives of levoglucosenone is possible by obtaining more bulky chiral ligands, provided that the double bond is retained.

Ballistic and thermomechanical characterisation of paraffin-based hybrid rocket fuels loaded with light metal hydrides

Rocket fuels are subjected to intense in-flight inertial, pressure and thermal loads that has drastic effect on its performance. In order to achieve optimal results, we require functionally-graded solid propellant (FGSPs), specifically designed for each flight condition. A novel series of FGSPs were developed using Paraffin Wax (as fuel) and Hydroxyl-terminated polybutadiene (as binder); treated with Dioctyl adipate (C22H42O4), Toluene diisocyante (C9H6N2O2) and Glycerol (C3H8O3). These FGSPs were further doped with light metal hydride nano-powders including Lithium aluminium hydride (LiAlH4) and Magnesium hydride (MgH2). The FGSPs were investigated for thermo-physical and ballistic performance using several characterisation techniques. The Magnesium hydride-doped FGSPs exhibited lower viscosity that fostered entrainment-aided combustion. FGSPs doped with Lithium aluminium hydride featured solid-like behaviour that makes them more stable in solid phase and less susceptible to in-flight loads. Thermal characterisation revealed that Lithium aluminium hydride makes FGSPs comparatively more resistant towards pyrolysis thereby producing greater char-yield. Eventually, combustion characteristics were evaluated by performing static ballistic firings of the developed FGSPs. The doped FGSPs exhibited significant enhancement in regression compared to the base fuel and conventional HTPB fuel. The MgH2-doped FGSP exhibited maximum enhancements of up to 224% and 353% as compared with the base fuel and HTPB, respectively.

Stereospecific Synthesis of (4E,10Z)- 4,10-Tetradecadienyl Acetate, the Major Sex Pheromone of Apple Leaf Miner Moth, Phyllonorycter ringoniella

: The main component of the sex pheromone of many lepidopteran pests, (4E,10Z)-4,10-tetradecadienyl acetate (1) has been synthesized stereoselectively by using a simple route with 4-pentynol as a starting material. The stereoselective formation of the 4E double bond is based on the stereospecific reduction of internal alkyne with lithium aluminium hydride (LAH) while Wittig reaction was used to achieve 10Z double bond in the target pheromone component. The GC purity of the final acetate was achieved 97.87% while isomeric purities are more than 99%. The green chemistry principle shows a new concept towards for the multistep pheromone synthesis via green metrics calculations.

Synthesis strategies towards amorphous porous carbons with selective oxygen functionalization for the application as reference material

Manipulation of carbon surface functionalization and especially of oxygen surface groups has been demonstrated to be key for obtaining high performance materials in a multitude of applications. Although control of carbon surface chemistry offers large potential in many technical relevant applications, qualitative and quantitative analysis of surface oxides for amorphous and porous carbons remains challenging. In this study, we attempt selective, organic chemistry-based functionalization of a polymer-derived porous model carbon featuring high oxygen loadings, with the aim to establish analytical standards for temperature programmed desorption (TPD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). In this context, quantitative chemical reduction of an oxidized carbon material with lithium aluminum hydride (LiAlH4) is utilized as the key for the synthesis of carbon materials with defined ensembles of oxygen surface groups (hydroxyl groups and ethers). Based on this reduction strategy, selective LiAlH4 reduction based on protection group chemistry leads to aldehydes, ketones and quinones as surface functional groups and chemical grafting is studied for the selective introduction of phenyl esters, methyl ethers and carboxylic acids. All materials are evaluated with respect to the applicability as analytical standard by DRIFT spectroscopy, TPD, X-ray photoelectron spectroscopy and titration methods.

Synthesis of spirocyclic tetrahydroisoquinolines (spiroTHIQs) via the Castagnoli-Cushman reaction

A new route to privileged spirocyclic tetrahydroisoquinolines (spiroTHIQs) has been developed. The key step in which the spirocyclic system is formed in generally good yields and diastereoselectivity is the three-component Castagnoli-Cushman reaction of homophthalic anhydride, cyclic ketones and ammonium acetate. Decarboxylation of the initial adduct yields THIQ lactams which are reduced by lithium aluminum hydride. The route is shorter, more convergent and operationally simpler than the previously reported syntheses of similar spirocyclic building blocks.

Synthetic modification of silica coated magnetite cored PAMAM dendrimer to enrich branched Amine groups and peripheral carboxyl groups for environmental remediation

Dendrimer with amine groups have several applications in gene delivery, drug delivery, metal encapsulation for catalysis and environmental remediation. Specifically, dendrimers having enriched amino groups with accessible void makes significant impact in the above fields. Besides, the carboxylic acid terminated amine dendrimers may enhance the efficacy as well. Therefore, herein we report the synthetic modification of poly(amidoamine) G3 dendrimer with magnetite core to enrich branched amine groups and peripheral carboxyl groups. To deliver this nanohybrid material, for the first-time silica coated magnetite cored poly(amidoamine) G3 dendrimer was synthesized by microwave assisted method. Subsequently amide groups present in the PAMAM have been reduced using lithium aluminum hydride to yield polyamine dendrimer namely poly (N-propylethane-1,2-diamine) G3. Further, peripheral amine groups were grafted with succinic anhydride to achieve carboxylic acid terminated dendrimer. The resulting nanomaterial was confirmed by FTIR, XRD, VSM, TGA, HRTEM and conductometry methods. In order to emphasize the structural efficacy of polyamine dendrimer, the metal ion uptake behavior has been discussed for the representative cations such as Pb2+, Cu 2+, Cr6+, Ca2+ and Ni2+ under the environmental concern. Magnetite cored polyamine dendrimer had evaluated for its recyclability test in the subsequent metal ion uptake studies and found to be satisfactory.

Axially chiral hemiaminals from nonracemic α-amino acid derivatives (thiohydantoins): Synthesis and isomer identification.

Stable, nonracemic axially chiral hemiaminals (O,N-hemiacetals) have been synthesized stereoselectively from lithium aluminum hydride (LiAlH4 ) reductions of nonracemic 5-methyl- and 5-isopropyl-3-(o-aryl)-2-thioydantoins in tetrahydrofuran (THF) at room temperature in 10 min. Predominantly S-configured hemiaminals at C-4 of the heterocyclic ring were produced from the S-configured thiohydantoins at C-5 (by 80% when the C5 substituent is methyl and by 97% when it is isopropyl). The configuration at C-5 was retained during the reduction reaction. The stereochemical outcome of the axially chiral hemiaminals resulted from their conformational preferences.

Textural analysis of aluminum hydride

The textural properties of aluminum hydride (alane, AlH3) prepared by wet synthesis from lithium aluminum hydride (LiAlH4) and aluminum chloride (AlCl3) were closely investigated with a focus on the effect of reactant ratios on crystal formation. XRD analysis showed that three crystals were almost similar, α-type AlH3, despite the different external morphology. TEM observations also demonstrated their similarity in chemical structures with an average lattice distance between atoms of 1.16Å. Slight differences in thermal decomposition and hydrogen content of each crystalline alane would be due to morphological difference and a little amount of impurities or by-products. When the ratio of reactants (LiAlH4 and AlCl3) was 3:1, a more evident cubic form which is desirable for the use of high energy propellants could be obtained, and the crystal size was 10–20μm.

Selective CO2 adsorption over functionalized Zr-based metal organic framework under atmospheric or lower pressure: Contribution of functional groups to adsorption

Selective capture of CO2 from offgas is important to mitigate the global warming; and metal organic frameworks (MOFs) have been attractive in the capture because of huge porosity, ready functionalization and so on. In this study, a stable Zr-based MOF, MOF-808, was modified with ethylenediaminetetraacetic acid (EDTA) and further reacted with ethylenediamine (ED); and finally reduced with lithium aluminum hydride (LAH) to introduce several functional groups (FGs) onto the MOF. Moreover, the MOFs were applied in CO2 adsorption under low pressure. The efficiency of MOF-808 in CO2 capture was improved with EDTA loading; however, interestingly, further reaction of MOF-808-EDTA with ED causes a very much decrease in the efficiency. Importantly, the reduction of MOF-808-EDTA-ED with LAH (for MOF-808-EDTA-ED-R) leads to a remarkable increase in the performance of the MOF, for high CO2 adsorption capacity, CO2/N2 selectivity and isosteric heat of adsorption. For example, MOF-808, MOF-808-EDTA, MOF-808-EDTA-ED and MOF-808-EDTA-ED-R showed CO2/N2 IAST selectivity (from CO2/N2 = 15/75) of 40, 48, 19 and 197, respectively, under 298 K and 1 atm. This unusual observation could be explained with the contribution of FGs and porosity. Or, amides in cyclic rings might be formed during reaction with ED; and the MOF with amides was poor in CO2 capture partly due to decreased porosity of the MOF; however, can be very effective in adsorption, after further reduction of amides to amines. This work shows the importance of modifications or FGs on MOFs in CO2 adsorption, or a simple reduction can increase the adsorption selectivity as much as 10 times, which might be helpful to mitigate the global warming.

Synthesis and characterization of high‐purity N,N‐dimethyltryptamine hemifumarate for human clinical trials

Since 2006, there has been a resurgent interest in the pharmacology and therapeutics of psychedelic drugs. Psilocybin, the 4-phosphoryl ester of N,N-dimethyltryptamine (DMT), has been studied most often, but DMT itself is also appealing because of its brief but profound psychological effects and its presence as an endogenous substance in mammalian brain. Although there have been a few studies of ayahuasca, a DMT-containing water infusion, only one human study with pure DMT has been reported since the early 2000s. Newly planned clinical trials to assess the safety and efficacy of DMT in humans with major depressive disorders require high-purity water-soluble DMT for intravenous administration. Accordingly, we synthesized and characterized DMT hemifumarate for these upcoming studies. The synthetic approach of Speeter and Anthony was slightly modified to gain some efficiency in time. In particular, this is the first known report to use aluminum hydride, generated in situ from lithium aluminum hydride, to reduce the intermediate 2-(1H-indol-3-yl)-N,N-dimethyl-2-oxoacetamide to DMT. A quench protocol was developed to produce a good yield of exceptionally pure free base DMT upon workup, which was then converted to the hemifumarate salt. Analysis of the final product included differential scanning calorimetry, thermogravimetric analysis, gas chromatography-mass spectrometry (GC-MS), 1 H and 13 C nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, residual solvent analysis by GC headspace sampling, X-ray powder diffraction analysis, and residual lithium analysis by inductively coupled plasma-mass spectrometry. The DMT hemifumarate was minimally 99.9% pure, with no significant impurities or residual solvents, thus meeting regulatory standards for administration to humans.

Formation of an Isomeric Mixture of Dienynes Instead of a Diallene

Attempts to convert 1,1,2,2,7,7,8,8-octaethoxyocta-3,5-diyne to a symmetric allene by reduction with lithium aluminum hydride failed. Instead reduction accompanied by isomerization occurred and afforded 1,1,2,7,8,8-hexaethoxyocta-2,6-dien-4-yne as a mixture of three isomers in 63% total isolated yield.

Effects of Defective Boron Nitride Additives on Lithium-Ion Conductivity and Hydrogen-Desorption Properties of LiAlH4

The lithium-ion conductivity and hydrogen-desorption properties of lithium alanate (LiAlH4)/boron nitride (BN) composites were investigated. The effects of boron nitrides with different structures (hexagonal (h-BN), turbostratic (t-BN), and cubic (c-BN)) on the properties were demonstrated. Compared with milled LiAlH4, the ion conductivity was improved in the h-BN and t-BN composites. Among the composites, the t-BN composite showed the highest conductivity and lowest activation energy (Ea) for ion conduction. In the 40 wt % t-BN composite, the conductivity at 80 °C reached as high as 1.1 × 10–3 S cm–1. Impedance plots that correspond to the interfacial conductivity were observed, which implies the appearance of LiAlH4/t-BN interfacial ion conduction. Ball-milling of LiAlH4 with BN caused the partial replacement of aluminum with boron to form LiBH4 phase, which would cause the Ea decrease. The LiAlH4 melting and hydrogen-desorption temperature decreased in the t-BN composite. In the c-BN composite, a large amount of stainless steel impurity during ball-milling caused desorption without melting. This study suggests that the addition of defective boron nitride like t-BN can be a useful strategy to improve the lithium-ion conductivity of complex hydrides. The t-BN additive effects on the hydrogen-desorption properties, which are different from transition metal catalysts, were also demonstrated.

Development of an AlCl3-Urea Ionic Liquid for the Electroless Deposition of Aluminum on Carbon Nanotubes.

Unlike the easy electroless deposition of other metals, the deposition of aluminum can be challenging. This is because the standard reduction potential of aluminum lies outside the electrochemical window (EW) of water. Ionic liquids such as AlCl3-1-ethyl-3-methylimidazolium chloride (EMIC) have been used because of their wide EW. Here, we introduce a novel ionic liquid for electroless deposition of aluminum by reacting AlCl3 and urea, with lithium aluminum hydride (LAH) as a reducing agent. Additionally, we report the first successful effort in coating carbon nanotubes (CNTs), as an example of nanostructures with high surface area to volume ratio, with aluminum using electroless deposition. The produced aluminum coating was found to be nanostructured, uniformly covering the CNTs and in close contact with their surfaces.

Hypergolic Ignition of Lithium–Aluminum–Hydride-Doped Paraffin Wax and Nitric Acid

Analytical reagent (AR)-grade nitric acid (69.3% by mass) and lithium–aluminum–hydride (LAH) as an additive to paraffin wax are evaluated as green propellant substitutes for state-of-the-art propellants currently used for in-space propulsion. The viabilities of hypergolic ignition and ignition delay (ID) times were measured for a range of conditions, including LAH loading in paraffin and ignition test chamber pressure. A strong inverse trend between ID and pressure was observed for the reaction of AR-grade nitric acid and pure LAH. A minimum of 50% mass loading of LAH in paraffin wax was required for reliable hypergolic ignition with AR-grade nitric acid at atmospheric pressure under a pure nitrogen environment.

Crystal structures and pressure-induced phase transformations of LiAlH4: A first-principles study

Given the fact that lithium aluminum hydride (LiAlH4) can exist in distinct crystalline structures under different conditions, in this study, we aim to theoretically investigate the structural properties and the pressure-induced phase transformations of its 13 closely related crystal structures by means of the density functional theory (DFT). The present study reveals that the phase transformation of LiAlH4 from the most stable form (α-phase) to the second most stable form (β-phase) occurs at approximately 3.3 GPa, corresponding to a volume collapse of ∼14% and a reduction of 22% in the crystal volume. Due to the relatively higher hydrogen weight content, β-LiAlH4 becomes a potentially attractive candidate for solid-state hydrogen storage at moderate pressures. The two most stable forms, i.e., the structures with the (i) P21/c (α-LiAlH4) and (ii) I41/a (β-LiAlH4) space groups, have been selected so that their structural and electronic properties can be discussed in greater detail. Our study also shows that the numerical results are greatly influenced by the choice of the DFT methods used, such as the exchange-correlation functionals and optimization schemes.

Preparation of multi-temperature responsive elastomers by generating ionic networks in 1,2-polybutadiene using an anionic melting method.

The development of reversible networks in elastomers provided unique inspiration for the design of advanced polymers with excellent properties. In this paper, we adopted an anionic melting method to introduce carboxylate groups into 1,2-polybutadiene (1,2-PB), using maleic anhydride as a modifier, and sodium hydride (NaH), calcium hydride (CaH2), and lithium aluminum hydride (LiAlH4) as metallization reagents. Na-Based, Ca-based, and Li/Al-based ionic bond networks were constructed in the covalently crosslinked 1,2-PB. The effects of the electronegativity and valence of the metal ions on the strength and reversible temperature of the ionic network were studied. Payne effect was shown by rheological tests, demonstrating the interactions between the ionic networks and rubber chains. The reforming temperature for these ionic networks was studied by stress-relaxation analysis, and shape memory experiments were performed based on these temperatures. This concept provides novel inspiration for the design of high-performance and temperature-adaptive elastomers.