The New Descriptors Effective on the Detonation Performance of Aluminized Explosives

The relationship between detonation velocity and the elemental composition of components of aluminized explosives are assessed through quantitative structure-property relationship (QSPR). Here, two new reliable, simple models are proposed for estimating aluminized explosives detonation heat and velocity based on molecular structure by applying QSPR. In this methodology it is assumed that these two detonation parameters can be presented as a function of elemental composition, density and several structural parameters. This new correlation of heat detonation has determination coefficient of 0.930, root mean square deviation (RMSD) of 324.4 and average absolute deviation (AAD) of 446kJ · kg^–1 for 36 aluminized explosives with different molecular structures as the training set. The predictive power of this new correlation is checked through a cross validation method. Statistical parameters reveal relatively good result for this correlation. Also, the determination coefficient of detonation velocity for the other new model is 0.960 and it has 151.1 (RMSD) and 107.9 m · s^–1 (AAD) for 42 aluminized explosives with different molecular structures as training set. Reliability and validity of new correlation investigated (Q²_Ext = 0.948, Q²_LOO = 0.938, and Q²_LMO = 0.937). The good ability of this new model for prediction detonation velocity of aluminized explosives are confirmed.     

Tetraglymes as Prochiral Host Reagents for Ammonia Borane

The molecular structure of the complex of ammonia borane (AB) with acyclic ether tetraglyme Me(OCH₂CH₂)₄OMe ( 1 ), 1· (AB)₂ was determined by single‐crystal X‐ray structure analysis for the first time. The crystal structure features two AB molecules, bonded by dihydrogen bonds, per one tetraglyme unit. The intermolecular BH ··· HN distances of 1.94 Å are shorter than those in the solid ammonia borane (2.02–2.32 Å). A comparison of the hydrogen and dihydrogen bonds in 1· (AB)₂ and in the complexes of AB with crown‐ethers (CE) was carried out. The complex formation with both the CE and the acyclic polyether 1 activates the B–H bond in AB via N–H ··· O hydrogen bonds and therefore increases the reducing activity of AB. Supposedly, the structure of 1· (AB)₂ is related to the initial steps of the AB activation in a polyether solution. The effect of the substituents on the complexation of the substituted derivatives of 1 comes down to a structural adjustment minimizing steric repulsion. Computations reveal that the complexation of diastereomeric disubstituted glymes with AB leads to the formation of diastereomeric complexes that differ noticeably in stability. This is a prerequisite for inducing stereoselectivity, which makes such complexes attractive for potential synthetic applications.     

催化氨硼烷水解制氢研究进展

当前,世界范围内的能源利用面临着巨大的挑战,开发绿色洁净能源十分重要。通过水解氨硼烷制备清洁可再生的氢气是解决能源问题的有效途径之一。选择合适的催化剂有效提高制氢效率是氨硼烷水解制氢的关键,开发高效安全的催化剂一直是该领域研究的重点和热点。本文从影响氨硼烷水解制氢反应中催化剂催化性能的因素出发,综述了活性金属组分和载体在催化剂制备过程中以及催化氨硼烷制氢反应中的作用。最后,对催化氨硼烷水解制氢过程所存在的问题以及今后的发展进行了总结和展望。     

快速合成廉价CuMo纳米粒子高效催化氨硼烷水解产氢

Noble-metal-free CuMo nanoparticles (NPs) without surfactant or support have been facilely prepared using NaBH₄ as a reducing agent. The as-prepared CuMo nanocatalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area measurements, and used as catalysts for the hydrolysis of ammonia borane (AB, NH₃BH₃) at room temperature. The as-synthesized Cu_0.9Mo_0.1 NPs exhibited a high activity towards the hydrolysis of AB with a turnover frequency (TOF) of 14.9 min^-1, a higher value than that reported for Cu catalysts. Our synthesis is not limited to CuMo NPs alone, but can easily be extended to CuW (3.6 min^-1), CuCr (2 min^-1), NiMo (55.6 min^-1), and CoMo (21.7 min^-1) NPs, providing a general approach to Cu-M (M = Mo, W, Cr) and TM-Mo (TM = Cu, Ni, Co) NPs as a series of novel catalysts for the hydrolysis of AB. The enhanced activity of bimetallic NPs may be attributed to the synergistic effects of the Cu-M NPs induced by the strain and ligand effects.     

Efficient Organocatalytic Dehydrogenation of Ammonia Borane

Dehydrogenation of ammonia borane by sterically encumbered pyridones as organocatalysts is reported. With 6‐tert‐butyl‐2‐thiopyridone as the catalyst, a turnover frequency (TOF) of 88 h^?1 was achieved. Experimental mechanistic investigations, substantiated by DLPNO‐CCSD(T) computations, indicate a mechanistic scenario that commences with the protonation of a B?H bond by the mercaptopyridine form of the catalyst. The reactive intermediate formed by this initial protonation was observed by NMR spectroscopy and the molecular structure of a surrogate determined by SCXRD. An intramolecular proton transfer in this intermediate from the NH₃ group to the pyridine ring with concomitant breaking of the S?B bond regenerates the thiopyridone and closes the catalytic cycle. This step can be described as an inorganic retro‐ene reaction.     

Synthesis of Ammonia Borane Nanoparticles and the Diammoniate of Diborane by Direct Combination of Diborane and Ammonia

Pure nanoparticle ammonia borane (NH₃BH₃, AB) was first prepared through a solvent‐free, ambient‐temperature gas‐phase combination of B₂H₆ with NH₃. The prepared AB nanoparticle exhibits improved dehydrogenation behavior giving 13.6 wt. % H₂ at the temperature range of 80–175 °C without severe foaming. Ammonia diborane (NH₃BH₂(μ‐H)BH₃, AaDB) is proposed as the intermediate in the reaction of B₂H₆ with NH₃ based on theoretical studies. This method can also be used to prepare pure diammoniate of diborane ([H₂B(NH₃)₂][BH₄], DADB) by adjusting the ratio and concentration of B₂H₆ to NH₃.     

氨硼烷释氢纳米金属催化剂的研究

化学储氢材料要求具有高的氢存储容量。氨硼烷（NH₃BH₃,AB）的氢含量高达19.6 wt%,是一种具有潜在应用前景的氢存储介质。AB的水解释氢容量高达7.8 wt %,热解释氢则可释放出19.6 wt %的氢,显示出其在化学储氢方面的巨大潜力。在AB释氢研究中,催化剂是研究的核心技术和重要方向。由于纳米催化剂在AB释氢中所表现出的优良催化性能,本文将对氨硼烷释氢纳米金属催化剂及其性能的研究进行全面的总结和展望。     

Contemplation on Detonation Pressures of Nitramines and ­Nitro Aromatics

A physical model and a mathematical theory for the detonation pressures of explosives materials were developed. The pressure values are expressed as function of the detonation velocity (D) and the average mass (m) of the gaseous products, and are applied for various nitramines and aromatic nitro compounds including nitro pyrimidines and nitro triazines. Some regression equations were obtained and discussed. The pressure values show poor linear dependence on the average mass of the products but good dependence on the detonation velocities alone or Dm. Moreover, for the same Dm value nitramines should produce more pressure than aromatic nitro compounds. This work deals with pressure developed by explosion products and interrelates it with detonation pressure within the constraints of certain assumptions and pays attention to so far unnoticed relationships at least under certain circumstances.     

Bimetallic RuM (M=Co,Ni) Alloy NPs Supported on MIL-110(Al): Synergetic Catalysis in Hydrolytic Dehydrogenation of Ammonia Borane

By adjusting various Ru/M (M=Co, Ni) molar ratios, a series of highly dispersed bimetallic RuM alloy nanoparticles (NPs) anchored on MIL-110(Al) have been successfully prepared via a conventional impregnation-reduction method. And they are first used as heterogeneous catalysts for the dehydrogenation reaction of AB at room temperature. The results reveal that the as-prepared Ru₁Co₁@MIL-110 and Ru₁Ni₁@MIL-110 exhibit the highest catalytic activities in different RuCo and RuNi molar ratios, respectively. It is worthy of note that the turnover frequency (TOF) values of Ru₁Co₁@MIL-110 and Ru₁Ni₁@MIL-110 catalysts reached 488.1 and 417.1 mol H₂ min^-1 (mol Ru)^-1 and the activation energies (E_a) are 31.7 and 36.0 kJ/mol, respectively. The superior catalytic performance is attributed to the bimetallic synergistic action between Ru and M, uniform distribution of metal NPs as well as bi-functional effect between RuM alloy NPs and MIL-110. Moreover, these catalysts exhibit favorable stability after 5 consecutive cycles for the hydrolysis of AB.     

氨硼烷催化水解制氢

氢气作为全球公认的清洁能源载体,备受关注。寻找安全高效的储氢材料以转型到氢能社会是当前氢能应用面临最大的挑战之一。氨硼烷(NH₃BH₃,AB)具有非常高的储氢质量分数(19.6 wt%)和体积储氢密度(0.145 kgH₂/L),因其在储氢和放氢性能方面的显著优势,被认为是一种颇具应用潜力的化学储氢材料。氨硼烷能够通过热解、醇解和水解放出氢气。其中,氨硼烷水解制氢可以通过催化剂进行可控放氢,且具有反应条件温和、不产生CO(易使催化剂中毒)等优点,被认为是一种安全高效和实用性强的制氢技术。本文简要介绍了氨硼烷的性质和合成,阐述了氨硼烷水解制氢的机理,综述了近年来氨硼烷水解制氢催化剂的研究进展,分析了碱对氨硼烷水解制氢的促进作用,并讨论了水解产物回收利用问题。     

氨基络合物制备氨硼烷及放氢性能研究

以NaBH₄为硼源、氨基络合物Ni(NH₃)₆Cl₂为氨源制备高储氢容量的氨硼烷(NH₃BH₃, Ammonia Borane, AB)及其放氢性能研究. 通过XRD, FTIR, ¹¹B NMR, ICP等手段分析表征了所制备产物的组成和纯度, 在此基础上探究了原料比例、反应温度、时间和溶剂等因素对产物的影响. 同时, 对不同原料比制得氨硼烷的热解放氢性能进行了研究. 实验结果表明: 当物质的量NaBH₄∶Ni(NH₃)₆Cl₂＝2∶1经过10 h的反应, 得到了纯度非常高的氨硼烷(纯度＞99%)|以NaBH₄∶Ni(NH₃)₆Cl₂＝3∶1得到的氨硼烷, 当以2 ℃/min进行升温时, 氢气释放主要集中在第一步, 并且没有硼烷和硼嗪等杂质气体的产生. 另外, 在产物中得到了金属Ni纳米颗粒, 经洗涤干燥后其粒径大小可控制在10 nm左右, 在催化氨硼烷等材料的水解放氢方面具有潜在的应用价值.     

核壳结构Cu@CoW的合成和对硼氨配合物水解的催化性能

分别以硼氨配合物和硼氢化钠为还原剂合成了核壳结构的Cu@CoW三元合金催化剂和非核壳结构的CuCoW三元合金催化剂,25℃下,Cu_0.4@Co_0.5W_0.1三元合金催化剂对于硼氨配合物水解反应的TOF（转换频率）值达到0.3690mol_H2·mol_cat^-1·s^-1,明显高于非核壳结构的Cu_0.4Co_0.5W_0.1催化剂,接近Pt、Pd等贵金属的催化活性,反应的活化能为49kJ·mol^-1。与非核壳结构的CuCoW合金相比,核壳结构的Cu@CoW三元合金催化剂的催化性能及稳定性均有明显提高。     

Catalytic Mechanisms of Transfer Hydrogenation of Azobenzene with Ammonia Borane by Pincer Bismuth Complex: Crucial Role of C=N Functional Group on the Pincer Ligand

Transfer hydrogenation of azobenzene with ammonia borane mediated by pincer bismuth complex 1 was systematically investigated through density functional theory calculations. An unusual metal-ligand cooperation mechanism was disclosed, in which the saturation/regeneration of the C=N functional group on the pincer ligand plays an essential role. The reaction is initiated by the hydrogenation of the C=N bond (saturation) with ammonia borane to afford 3^CN , which is the rate-determining step with Gibbs energy barrier (ΔG^≠) and Gibbs reaction energy (ΔG) of 25.6 and −7.3 kcal/mol, respectively. 3^CN is then converted to a Bi−H intermediate through a water-bridged pathway, which is followed up with the transfer hydrogenation of azobenzene to produce the final product N,N′-diphenylhydrazine and regenerate the catalyst. Finally, the catalyst could be improved by substituting the phenyl group for the tert-butyl group on the pincer ligand, where the ΔG^≠ value (rate-determining step) decreases to 24.0 kcal/mol.     

Renewed Insight into the Promoting Mechanism of Magnesium Hydride on Ammonia Borane

Our previous study found that mechanically milling with magnesium hydride (MgH₂) could dramatically improve the dehydrogenation property of ammonia borane (AB). Meanwhile, it appears that the MgH₂ additive maintains its phase stability in the milling and subsequent heating process. In an effort to further the mechanistic understanding of the AB/MgH₂ system, we reinvestigated the property and structure evolution in the hydrogen release process of the AB/0.5MgH₂ sample. Property examination using volumetric method and synchronous thermal analyses showed that the AB/0.5 MgH₂ sample releases ～13.8 wt % hydrogen after being heated at 300 °C. This hydrogen amount is in excess of that available from AB, indicative of the participation of a faction of MgH₂ in the dehydrogenation process of AB. Structural and chemical state analyses using Fourier transformation infrared spectroscopy and solid‐state ¹¹B nuclear magnetic resonance techniques further showed that part of MgH₂ participates in the dehydrogenation process of AB from the first step, resulting in the formation of Mg? B? N? H intermediate species. The incorporation of Mg in AB is believed to be a crucial event leading to dehydrogenation property improvements, particularly for the release of the last equivalent of H₂ in AB at relatively moderate temperature. These findings have provided renewed insight into the promoting mechanism of MgH₂ on the hydrogen release from AB.     

Production of Dihydrogen Using Ammonia Borane as Reagent and Pyrazole as Catalyst

Theoretical chemistry (DLPNO-CCSD(T)/def2-TZVP//M06-2x/aug-cc-pVDZ) was used to design a system based on ammonia boranes catalyzed by pyrazoles with the aim of producing dihydrogen, nowadays of high interest as clean fuel. The reactivity of ammonia borane and cyclotriborazane were investigated, including catalytic activation through 1H-pyrazole, 4-methoxy-1H-pyrazole, and 4-nitro-1H-pyrazole. The results point toward a catalytic cycle by which, at the same time, ammonia borane can initially store and then, through catalysis, produce dihydrogen and amino borane. Subsequently, amino borane can trimerize to form cyclotriborazane that, in presence of the same catalyst, can also produce dihydrogen. This study proposes therefore a consistent progress in using environmentally sustainable (metal free) catalysts to efficiently extract dihydrogen from small B−N bonded molecules.     

Catalytic Dehydrogenation of Ammonia Borane Mediated by a Pt(0)/Borane Frustrated Lewis Pair: Theoretical Design

A new efficient metal-based frustrated Lewis pair constructed by (P^tBu₃)₂Pt and B(C₆F₅)₃ was designed through density functional theory calculations for the catalytic dehydrogenation of ammonia borane (AB). The reaction was composed by the successive dehydrogenation of AB and H₂ liberation, which occurs through the cooperative functions of the Pt(0) center and the B(C₆F₅)₃ moiety. Two equivalents of H₂ were predicted to be liberated from each AB molecule. The generation of the second H2 is the rate-determining step, with a Gibbs energy barrier and reaction energy of 27.4 and 12.8 kcal/mol, respectively.     

核壳结构Cu@CoW的合成和对硼氨配合物水解的催化性能

分别以硼氨配合物和硼氢化钠为还原剂合成了核壳结构的Cu@CoW三元合金催化剂和非核壳结构的CuCoW三元合金催化剂,25℃下,Cu0.4@Co0.5W0.1三元合金催化剂对于硼氨配合物水解反应的TOF(转换频率)值达到0.369 0 molH2·molcat-1·s-1,明显高于非核壳结构的Cu0.4Co0.5W0.1催化剂,接近Pt、Pd等贵金属的催化活性,反应的活化能为49 kJ·mol-1。与非核壳结构的CuCoW合金相比,核壳结构的Cu@CoW三元合金催化剂的催化性能及稳定性均有明显提高。     

氨硼烷水解制氢的研究进展

介绍一种很有潜力的储氢材料——氨硼烷的合成及水解.重点讨论近几年氨硼烷水解的催化剂,并对催化剂的载体进行了介绍.     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3 mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3 mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。     

纳米晶态硼化钴的合成及其催化氨硼烷高效制氢

采用简单的煅烧工艺合成了纳米硼化钴(CoB)晶体,并首次研究了纳米CoB晶体在氨硼烷溶液水解制氢过程中的催化活性。研究发现,纳米CoB晶体具有较高的催化活性,在室温条件下其转换频率(TOF)为35.3mol_H2·mol_cat^-1·min^-1,优于同等条件下贵金属Pt催化剂(TOF=29.3mol_H2·mol_cat^-1·min^-1)。此外,循环测试8次后纳米硼化物晶体的催化制氢性能没有发生衰减。进一步研究发现CoB表面的Co⁰物种是催化制氢的活性位点,而表面的B物种位点能够有效辅助Co⁰位点实现协同催化氨硼烷制氢。