LiAlH4 Research Articles

Synthesis of Tris[2‐(dimethylamino)ethyl]amine with Regiospecific Deuterium Labels

AbstractSimple synthetic routes to regioselectively deuterated tris[2‐(dimethylamino)ethyl]amine (Me6TREN) variants are described. Imine formation with formaldehyde‐d2 from tris(2‐aminoethyl)amine (TREN) and subsequent reductions with NaBD4 afforded N[CH2CH2N(CD3)2]3 or d18‐Me6TREN in 79 % yield. A trisubstitution protocol from 2‐bromo‐N,N‐dimethylacetamide and ammonium carbonate and subsequent reduction of the N(CH2CONMe2)3 intermediate by lithium aluminum deuteride has afforded N[CH2CD2N(CH3)2]3 or (d6‐arm)‐Me6TREN in three steps and 52 % overall yield. A similar protocol from 2‐bromo‐N,N‐dimethyl‐d2‐acetamide, obtained in two steps from d4‐acetic acid, with reduction of the N(CD2CONMe2)3 intermediate by lithium aluminum hydride has afforded N[CD2CH2N(CH3)2]3 or (d6‐cap)‐Me6TREN in four steps and 13 % overall yield from CD3COOD.

Reinforce the dehydrogenation process of LiAlH4 by accumulating porous activated carbon

Herein, it is reported that activated carbon (AC) alters the hydrogen storage behavior of lithium alanate (LiAlH4) prepared by the ball milling technique. Notable improvements in onset decomposition temperature and desorption kinetics are attained for LiAlH4 added 10 wt.% of AC composite compared to as-received and as-milled LiAlH4. The onset decomposition temperature of LiAlH4-10 wt.% AC dropped to 100 °C and 160 °C for the first and second steps. The composite also released 3.4 wt.% of hydrogen after 90 min compared to as-received and as-milled which is less than 0.2 wt.% of hydrogen within the same period. The XRD result discovered an additional peak of the Li3AlH6 and Al compounds appeared after the milling process, concluding that LiAlH4 becomes unstable after the addition of AC. FTIR measurement has verified the presence of the Li3AlH6 and carbon bonding in the LiAlH4-10 wt.% AC composite. The composite's activation energy (Ea) for the first and second steps is 70 kJ/mol and 85 kJ/mol, respectively. These values decrease from as-milled LiAlH4 for both steps, demonstrating the catalytic effect of AC in this system. FESEM images illustrate that after ball milling, the particle size of LiAlH4-10 wt.% AC composite decreases. The considerable improvement in the hydrogen storage characteristic of the LiAlH4-10 wt.% AC composite is thought to be the collaborative role of amorphous carbon.

Synthesis of (±)‐Physovenine through Electrochemical C−O Bond Formation

AbstractWe investigated an electrochemical C−O bond formation approach to (±)‐physovenine. The reaction conditions are mild compared to canonical routes, which typically utilize strong hydride reagents such as lithium aluminum hydride. This enabled extension of the electrochemical cyclization to a substrate bearing the fully functionalized phenyl ring of the natural product. The electrochemical cyclization is diastereoselective and starting from enantiopure substrate would provide a single enantiomer of physovenine. In the course of an initial formal synthesis, we identified conditions to afford modest enantioselective substrate synthesis that demonstrate the feasibility of an enantioselective synthesis. Among the substrates investigated, acetyl‐, tosyl‐ or Boc‐nitrogen substitution led to an alternative electrochemical C−O bond formation pathway where the hydroxyl nucleophile cyclized onto the aromatic ring vs. the 2‐position of the indoline. This work expands the utility of electrochemical C−O bond formation and provides a foundation for further applications to functionalized cyclic ether construction.

Post-polymerization modification of poly(ethyl sorbate) leading to various alternating copolymers

Eight novel alternating copolymers that are not accessible with general methodologies have been synthesized by the post-polymerization modification of poly(propylene-alt-allyl alcohol)100 (PPAA100). PPAA100 is obtained from a group transfer polymerization (GTP) made poly(ethyl sorbate)100 (PES100) by first hydrogenating its backbone double bonds followed by reducing its pendent esters to hydroxyl groups using lithium aluminum hydride. The post-polymerization modification of PPAA100 includes its condensation reactions with three reactive electrophiles, and its Mitsunobu reactions with five nucleophiles. The chemical transformations of the hydroxyl group to other functionalities have resulted in the eight unique head-to-head alternating copolymers which possess a fixed propylene structural unit and an allyl alcohol derived monomeric unit, such as allyl ester, sulfonate, phosphate, ether, halide, and imide. The chemical structures of the obtained polymers are verified by 1H and 13C NMR and FT-IR spectroscopies. Finally, the thermal properties of the resulting polymers with different side groups are studied.

Improved Dehydrogenation Properties of LiAlH4 by Addition of Nanosized CoTiO3.

Despite the application of lithium aluminium hydride (LiAlH4) being hindered by its sluggish desorption kinetics and unfavourable reversibility, LiAlH4 has received special attention as a promising solid-state hydrogen storage material due to its hydrogen storage capacity (10.5 wt.%). In this work, investigated for the first time was the effect of the nanosized cobalt titanate (CoTiO3) which was synthesised via a solid-state method on the desorption behaviour of LiAlH4. Superior desorption behaviour of LiAlH4 was attained with the presence of a CoTiO3 additive. By means of the addition of 5, 10, 15 and 20 wt.% of CoTiO3, the initial desorption temperature of LiAlH4 for the first stage was reduced to around 115-120 °C and the second desorption stage was reduced to around 144-150 °C, much lower than for undoped LiAlH4. The LiAlH4-CoTiO3 sample also presents outstanding desorption kinetics behaviour, desorbing hydrogen 30-35 times faster than undoped LiAlH4. The LiAlH4-CoTiO3 sample could desorb 3.0-3.5 wt.% H2 in 30 min, while the commercial and milled LiAlH4 desorbs <0.1 wt.% H2. The apparent activation energy of the LiAlH4-CoTiO3 sample based on the Kissinger analysis was decreased to 75.2 and 91.8 kJ/mol for the first and second desorption stage, respectively, lower by 28.0 and 24.9 kJ/mol than undoped LiAlH4. The LiAlH4-CoTiO3 sample presents uniform and smaller particle size distribution compared to undoped LiAlH4, which is irregular in shape with some agglomerations. The experimental results suggest that the CoTiO3 additive promoted notable advancements in the desorption performance of LiAlH4 through the in situ-formed AlTi and amorphous Co or Co-containing active species that were generated during the desorption process.

Limonin Derivatives via Hydrogenation: Structural Identification and Anti-Inflammatory Activity Evaluation

Limonin is a natural compound which is rich in the fruit of various plants of the Rutaceae family and demonstrated to have a wide range of biological activities. In this work, seven limonin derivatives were successfully synthesized by hydrogenation of limonin, using different reducing agents (sodium cyanoborohydride, lithium aluminum hydride, and sodium borohydride). The chemical structure of the seven derivatives was characterized and identified by a series of techniques, including HR-ESI-MS, 1H-NMR, 13C-NMR, 2D-NMR, and IR. Among the seven limonin derivatives, six limonin derivatives were found to be new compounds which have not been previously reported. Then, the anti-inflammatory activities of the seven synthesized limonin derivatives, as well as the anti-inflammatory activities of eight known natural limonins, were evaluated and compared. Natural limonins, 30-O-Acetylhainangranatumin E and Xylogranatin A, presented significantly better anti-inflammatory activity. Xylogranatin A could inhibit LPS-induced RAW264.7 cell inflammatory factors, with a 90.0% inhibition ratio of TNF-α and 63.77% inhibition ratio of NO release in LPS-induced BV2 cells at 10 μM. Other natural limonins showed poor anti-inflammatory activity. In comparison, all the synthetic limonin derivatives showed decent anti-inflammatory activities, with the highest inhibition ratio of TNF-α of 37.8% and inhibition ratio of NO release of 12.5% in LPS-induced BV2 cells at 10 μM.

Improved hydrogen storage properties and mechanisms of LiAlH4 doped with Ni/C nanoparticles anchored on large-size Ti3C2Tx

Lithium aluminum hydride (LiAlH4) with a high hydrogen capacity of 10.5 wt% has become one of the most promising solid-state hydrogen storage materials for onboard hydrogen fuel cell systems. However, neither dehydrogenation kinetics nor cycling behaviors of LiAlH4 can fulfill the requirements of practical application. Here, we prepared the Ni/C nanoparticles anchored on large-size Ti3C2Tx nanosheets, firstly introduced into LiAlH4 to investigate its catalytic effect. Dehydrogenation experiments demonstrate that LiAlH4 doped with 7 wt% Ni/C@Ti3C2 starts to release hydrogen at 56.9 °C. Also, it can release about 4.3 wt% hydrogen within 50 min at 120 °C. The activation energies of LiAlH4 doped with 7 wt% Ni/C@Ti3C2 for the first and second steps are 34.5% and 53.2% lower than the as-received LiAlH4, respectively. Under 300 °C and 40 bar hydrogen, it can absorb 0.58 wt% hydrogen. It is found that in situ formed intermetallic Al2Ti during ball milling can weaken the Al-H bonds in LiAlH4 through interfacial charge transfer and the dehybridization, benefitting for the breaking of the Al-H bond in LiAlH4. In addition, Al2Ti can promote the adsorption and splitting of H2, contributing to the rehydrogenation of LiAlH4.

Effect and mechanism of lithium aluminium hydride on the pyrolysis process of RDX

Searching for efficient additives for explosives and propellants is always desirable but challenging. To understand the contribution of lithium aluminium hydride (LiAlH4) to the decomposition process of cyclotrimethylenetrinitramine (RDX), the thermal decomposition behaviours of RDX with various ratios of LiAlH4 addition were investigated by thermogravimetric-differential scanning calorimetry (TG-DSC). The main pyrolysis gas products of RDX, RDX/LiAlH4 (4:1) and RDX/LiAlH4 (1:1) were compared by combining thermogravimetric-Fourier infrared spectroscopy (TG-FTIR) and thermogravimetric-photoionization mass spectrometry (TG-MS) techniques, and the influence of LiAlH4 on the main RDX pyrolysis pathways was analysed. The results show a strong interaction between LiAlH4 and RDX during thermal decomposition, and the decomposition peak temperature of RDX decreases from 239.8 °C to about 166.4 °C coupled with explosive decomposition. In the presence of LiAlH4, the active hydrogen of the melted LiAlH4 interacts with the nitro-oxygen of RDX, significantly decreasing the decomposition temperature of RDX and changing the decomposition pattern. This study contributes to further insight into the pyrolysis properties and decomposition mechanism of nitramine energetic materials in the presence of metal hydrides.

Synthesis and characterization of d5 -barbarin for use in barbarin-related research.

Based on structural similarities and equine administration experiments, Barbarin, 5-phenyl-2-oxazolidinethione from Brassicaceae plants, is a possible source of equine urinary identifications of aminorex, (R,S)-5-phenyl-4,5-dihydro-1,3-oxazol-2-amine, an amphetamine-related US Drug Enforcement Administration (DEA) controlled substance considered illegal in sport horses. We now report the synthesis and certification of d5 -barbarin to facilitate research on the relationship between plant barbarin and such aminorex identifications. D5 -barbarin synthesis commenced with production of d5 -2-oxo-2-phenylacetaldehyde oxime (d5 -oxime) from d5 -acetophenone via butylnitrite in an ethoxide/ethanol solution. This d5 -oxime was then reduced with lithium aluminum hydride (LiAlH4 ) to produce the corresponding d5 -2-amino-1-phenylethan-1-ol (d5 -phenylethanolamine). Final ring closure of the d5 -phenylethanolamine was performed by the addition of carbon disulfide (CS2 ) with pyridine. The reaction product was purified by recrystallization and presented as a stable white crystalline powder. Proton NMR spectroscopy revealed a triplet at 5.88 ppm for one proton, a double doublet at 3.71 ppm for one proton, and double doublet at 4.11 ppm for one proton, confirming d5 -barbarin as the product. Further characterization by high resolution mass spectrometry supports the successful synthesis of d5 -barbarin. Purity of the recrystallized product was ascertained by High Performance Liquid Chromatography (HPLC) to be greater than 98%. Together, we have developed the synthesis and full characterization of d5 -barbarin for use as an internal standard in barbarin-related and equine forensic research.

Nanoconfinement of lithium alanate for hydrogen storage

LiAlH4 is considered as a promising material for solid state hydrogen storage. However, the lack of reversibility along with sluggish kinetics hinders its practical application. In this paper, hollow carbon nanospheres (HCNs) were used as a porous scaffold to confine LiAlH4 via solvent impregnation method. Nanoconfined LiAlH4 (LiAlH4@HCNs) exhibited significant improvements in hydrogen sorption compared to its bulk counterpart. LiAlH4@HCNs releases hydrogen sharply at 146 °C with full conversion to LiH within 1.5 h. The desorbed material can also be regenerated back to some extent into LiAlH4 under 8 MPa H2 at 150 °C. Measurement of the pressure-composition isotherm suggests an alteration in the equilibrium state upon confinement of LiAlH4 in voids of a few nanometres and thus altered hydrogen thermodynamic paths.

Enantioselective Synthesis of α-Alkenylated γ-Lactam Enabled by Ni-Catalyzed 1,4-Arylcarbamoylation of 1,3-Dienes

Enantioselective Synthesis of α-Alkenylated γ-Lactam Enabled by Ni-Catalyzed 1,4-Arylcarbamoylation of 1,3-Dienes

Alcoholysis features of lithium aluminum hydrides for its hydrolysis reaction at low-temperature

Lithium aluminum hydrides are promising hydrogen storage materials due to their high hydrogen storage density. Hydrolysis of LiAlH4 is an ideal path to reach the operating temperature (−40/60 °C) target released by department of energy without extra heating processes. Ethylene glycol is a common antifreeze agent ingredient for low temperature reactions. However, the reaction features of ethylene glycol with LiAlH4 are still unknown. Here, the reaction behaviors of ethylene glycol with LiAlH4 have been studied. The reaction of LiAlH4 powder with ethylene glycol has been found to be hindered by the thin layer alcoholysis products on the surface. The alcoholysis products have been found to be easily react with water to yield Li–Al layered double hydroxides. The alcoholysis products have been demonstrated to be Li–Al double layered alcoholates, which is analogous to Li–Al layered double hydroxides. The ethylene glycol groups in the alcoholysis products are easily substituted by –OH in the presence of water. Thus, only water is consumed from the antifreeze agents for low temperature hydrogen release.

Lessons Learned─Lithium Aluminum Hydride Fires

Lithium aluminum hydride (LiAlH4) is well-known and widely used as a highly reactive reagent that reduces a wide variety of substances. Given its high reactivity profile, it has also been involved in numerous incidents causing fires small and large. Several research laboratory fires initiated by pulverizing LiAlH4 pellets have brought attention to friction-induced ignition, deficiencies in vendor-supplied Safety Data Sheets, and challenges to researcher training that involve known─but specific─conditions that are incompatible with reactive reagents.

Enhancing the dehydrogenation properties of LiAlH4 using K2NiF6 as additive

Lithium alanate (LiAlH4) is a material that can be potentially used for solid-state hydrogen storage due to its high hydrogen content (10.5 wt%). Nevertheless, a high desorption temperature, slow desorption kinetic, and irreversibility have restricted the application of LiAlH4 as a solid-state hydrogen storage material. Hence, to lower the decomposition temperature and to boost the dehydrogenation kinetic, in this study, we applied K2NiF6 as an additive to LiAlH4. The addition of K2NiF6 showed an excellent improvement of the LiAlH4 dehydrogenation properties. After adding 10 wt% K2NiF6, the initial decomposition temperature of LiAlH4 within the first two dehydrogenation steps was lowered to 90 °C and 156 °C, respectively, that is 50 °C and 27 °C lower than that of the аs-milled LiAlH4. In terms of dehydrogenation kinetics, the dehydrogenation rate of K2NiF6-doped LiAlH4 sample was significantly higher as compared to аs-milled LiAlH4. The K2NiF6-doped LiAlH4 sample can release 3.07 wt% hydrogen within 90 min, while the milled LiAlH4 merely release 0.19 wt% hydrogen during the same period. According to the Arrhenius plot, the apparent activation energies for the desorption process of K2NiF6-doped LiAlH4 are 75.0 kJ/mol for the first stage and 88.0 kJ/mol for the second stage. These activation energies are lower compared to the undoped LiAlH4. The morphology study showed that the LiAlH4 particles become smaller and less agglomerated when K2NiF6 is added. The in situ formation of new phases of AlNi and LiF during the dehydrogenation process, as well as a reduction in particle size, is believed to be essential contributors in improving the LiAlH4 dehydrogenation characteristics.

Catalytical enhancement on hydrogen production from LiAlH4 by Fe–Fe2O3 addition

Hydrogen storage technology plays an important role on the development of hydrogen fuel cell and lithium aluminum hydride is a powerful candidate for solid-state hydrogen storage materials. However, the high stability and slow dehydrogenation kinetics of LiAlH4 hinder its application. In this paper, the two-step thermal decomposition properties of LiAlH4 with and without Fe–Fe2O3 catalysts are investigated. According to the master plots, the model of mample power law (Pn) and nucleation and growth (An) are the optimal mechanism functions for the two-step decomposition of LiAlH4, respectively. After doping catalysts, the activation energies decrease significantly. The theoretical and optimized kinetic method are consistent with each other on activation energy. And the latter can also yield other kinetic parameters for a more comprehensive kinetic modelling of LiAlH4 decomposition. Furthermore, Fe–Al2O3 and Fe–Al intermetallics generated during dehydrogenation might significantly improve the hydrogen release properties of LiAlH4.

Recent Advances on Mg–Li–Al Systems for Solid-State Hydrogen Storage: A Review

The problem of providing compact and safe storage solutions for hydrogen in solid-state materials is demanding and challenging. The storage solutions for hydrogen required high-capacity storage technologies, which preferably operate at low pressures and have good performances in the kinetics of absorption/desorption. Metal hydrides such as magnesium hydride (MgH2) are promising candidates for such storage solutions, but several drawbacks including high onset desorption temperature (>400°C) and slow sorption kinetics need to be overcome. In this study, we reviewed the recent developments in the hydrogen storage performance development of MgH2 and found that the destabilization concept has been extensively explored. Lithium alanate or LiAlH4 has been used as a destabilizing agent in MgH2–LiAlH4 (Mg–Li–Al) due to its high capacity of hydrogen, which is 10.5 wt.%, and low onset desorption temperature (∼150°C). In this article, a review of the recent advances in the Mg–Li–Al system for the solid-state hydrogen storage material is studied. We discussed the effect of the ratio of MgH2 and LiAlH4, milling time, and additives in the Mg–Li–Al system. After the destabilization concept was introduced, the onset of the desorption temperature and activation energy of MgH2 were reduced, and the sorption properties improved. Further study showed that the intermetallic alloys of Li0.92Mg4.08 and Mg17Al12 that were formed in situ during the dehydrogenation process provide synergetic thermodynamic and kinetic destabilization in the Mg-Li-Al composite system.De/rehydrogenation measurements indicate that the intermetallic alloys of Li0.92Mg4.08 and Mg17Al12 were fully reversibly absorbed and desorbed hydrogen. Next, the remaining challenges and a possible development strategy of the Mg–Li–Al system are analyzed. This review is the first systematic study that focuses on the recent advances in the Mg–Li–Al system for storage solutions for hydrogen in solid-state materials.

Catalytic effect of Al2TiO5 on the dehydrogenation properties of LiAlH4

Lithium alanate (LiAlH4) is considered as a promising material for storing hydrogen (H2) in solid-state form for onboard applications due to its advantage of high gravimetric H2 capacity. LiAlH4 could release H2 ∼7.9 wt.% when heated up to ∼250 °C. Nevertheless, the high desorption temperature, sluggish desorption kinetics, and irreversibility hamper the application of LiAlH4 for solid-state H2 storage materials. Therefore, in this study, we have used aluminum titanate (Al2TiO5) as an additive to diminish the desorption temperature and enhance the desorption kinetics of LiAlH4. The addition of a small amount of Al2TiO5 (5 wt.%) into LiAlH4 significantly decreased the decomposition temperature and enhanced the desorption kinetics, in which Al2TiO5-doped LiAlH4 started to release H2 at ∼90 °C and was able to desorb H2 as much as ∼3.5 wt.% at 90 °C within 1 h. Without the catalyst, pure LiAlH4 starts to release H2 at ∼145 °C and only desorbs H2 as low as 0.3 wt.% at 90 °C within 1 h. The activation energies for H2 release in the two-step desorption process of LiAlH4 were reduced after catalysis with Al2TiO5. The activation energies of as-milled LiAlH4 were 80 kJ/mol and 91 kJ/mol, respectively, as calculated by the Arrhenius plot. The activation energies were lowered to 68 kJ/mol and 79 kJ/mol after milling with Al2TiO5. The scanning electron microscopy images revealed that the LiAlH4 particles became smaller and less agglomerated when Al2TiO5 was added. It is believed that the in-situ formation of active species during the desorption process and reduction in particles size play a vital role in improving the dehydrogenation properties of the Al2TiO5-doped LiAlH4 system.

Synthesized and Characterization TiO2-AlLiH4 Nanostructure for Photocatalytic Activity Application for Removal the Residue of Hydrocarbons in Environment

The novel approach includes The sol-gel technique was used to make titanium dioxide nanoparticles and then for photodegradation Benz[a]anthracene a crystalline, aromatic hydrocarbon, as a trial sample of the residue of hydrocarbons in environments close to oil refining facilities and oil fields, methods, the bandgap was modified by solid-state reaction with Lithium aluminium hydride (AlLiH4) reductive compounds. The optical properties were measured using a UV-visible spectrophotometer (Absorbance (A), energy bandgap (Eg), and absorption coefficient (α). TiO2 and TiO2- solid-state reaction showed a clear blue shift of the absorption bandgap which were (2.8ev, 2.7ev, 2.25ev, 2.0ev) to) TiO2, calcination TiO2-AlLiH4 (500C°) then TiO2 -AlLiH4 (750 C°)) respectively. The structure of prepared TiO2 Nanopowders was identified using XRD, Distribution of particle size varied significantly compared to the Sheerer formulation predicted crystallite size (D). which was in a good accordant compared with ASTM results, the particle size and their distribution were characterized using (AFM). To the surface forms and compositions diameters of nanoparticles) SEM) was implemented. The microanalysis of energy scattering X-ray (EDX) was used to examine the chemical makeup of the entire samples. Using UV-Vis spectrophotometry, the photocatalytic response was examined. The photocatalyst impact on the benz[a]anthracene decomposition rate by using catalyst TiO2- and solid-state (TiO2-NaBH4 (550,750)) and (TiO2-AlLiH4 (500,750 C°). A photocatalytic effect is the catalyst's influence on the catalyst. Using the constant weight of the catalyst and benz[a]anthracene The most effective weight was found (1*10-4 M).

Effect of micro- and nano-CuO on the thermal decomposition kinetics of high-performance aluminized composite solid propellants containing complex metal hydrides

In the present work, an attempt has been made to unveil the effect of micro- and nano-particles of copper oxide (µCuO and nCuO) on the thermal decomposition of composite solid propellants (CSPs) based on ammonium perchlorate, hydroxyl terminated polybutadiene and binary fuel mixture of aluminum and lithium tetrahydridoaluminate (AP/HTPB/Al+LiAlH4). The prepared CSPs were analyzed by different analytical techniques. The second part of the study was devoted to the kinetic modeling of the thermal decomposition process of the fabricated CSPs samples. In the light of the obtained results, it was concluded that the use of µCuO and nCuO accelerated the decomposition of CSPs. Moreover, the incorporation of nCuO to the LiAlH4-based propellant increased substantially the heat release and decreased the average activation energy compared to the baseline samples. Moreover, the decomposition reaction mechanisms of the investigated propellant samples have clearly changed through the incorporation of nano- and micro-CuO.

Inverse Electron-Demand Aza-Diels-Alder Reaction of α,β-Unsaturated Thioesters with In Situ-Generated 1,2-Diaza-1,3-dienes for the Synthesis of 1,3,4-Thiadiazines.

A highly regioselective inverse electron-demand aza-Diels-Alder reaction of α,β-unsaturated thioesters with 1,2-diaza-1,3-dienes generated in situ from α-halogeno hydrazones was developed. With α,β-unsaturated thioesters as C═S dienophiles, the developed protocol enables the formation of diverse 3,6-dihydro-2H-1,3,4-thiadiazine derivatives in excellent yields. In the presence of lithium aluminum hydride, 3,6-dihydro-2H-1,3,4-thiadiazine derivatives could be further transformed into 5,6-dihydro-4H-1,3,4-thiadiazines in good yields.