芳香卤代烃转化为芳腈新方法的研究（Ⅰ）

芳卤转化为芳腈是一个很重要的转化,在染料工业中有着广泛的应用。经典的方法是用氰化物与芳卤作用得到芳腈。近几年出现了一些新的方法。Greenall报道,芳卤与甲酰胺、乙酸酐在一定条件下能生成腈。但对反应的有关理论问题未作研究。我们采用不     

堆料机行走机构啃轨原因分析及解决措施

<正>我公司堆料机型号为DB1200/23.8,两条轨道轨距为5 m,在调试和使用中出现啃轨现象,对轨道和设备造成损害,增加了备品备件消耗。本文重点介绍堆料机行走机构啃轨的症状、原因及危害,并提出相应的解决措施,供同行参考。1啃轨的症状及危害1)磨损车轮和轨道行走机构啃轨是指车轮轴心线和轨道轴心线发生偏离,造成轮缘和轨道侧面强制性接触,致使轨道     

近年合成农药应用有机单元反应的统计分析

随着农药行业的发展,近几年在农药合成时所应用到的有机单元反应发生了一些变化,成环的、酰基化的、磺胺化的和甲氧基化等有机单元反应应用频率有所上升,而酯化和加成等反应则有所下降。经典和传统的合成农药方法与合成的新技术和新方法密切结合,将会优化农药的合成和生产,提高农药合成和生产的有效性和绿色环保性。     

用碘化钾直接滴定漂白粉的有效成分

漂白粉的有效成分是其中的Ca(OCl)_2。对漂白粉有效成分的分析,已有碘量法或亚砷酸盐滴定等经典而且可靠的方法。库里堡等会研究过用比色法进行测定。本文的主要目的是为车间分析提供节省碘化钾耗用量而且比较简便的方法。同时在理论上作了一些初步探讨。一、原理ClO~-是一个强氧化剂,能把碘离子氧化成游离的碘或IO~-、IO_3~-及IO_4~-等。决定的因素是反应时     

爆轰化学:非理想炸药中的扩散控制

炸药的性能既是爆轰波阵面附近所释放的峰值能量的函数,又是泰勒(Taylor)波期间释放的余能的函数。爆轰波阵面和膨胀之间能量的相对分配以及膨胀中能量释放的速率可能受化学动力学过程或扩散过程的支配。爆轰量热法已是研究这些过程所用的主要实验方法。对硝铵(AN)和梯恩梯(TNT)的一些配方,确定了总的能量释放;也确定了膨胀等熵线上一点或一个区域爆轰产物的定量分析。在这些配方中,组份和AN的颗粒大小都是变化的。为进一步洞察反应区中或其附近发生的反应,对选用的炸药也应用了同位素示踪法。在一种理想均质炸药中,做了类似的实验。     

爆轰化学:非理想炸药中的扩散控制

炸药的性能既是爆轰波阵面附近所释放的峰值能量的函数,又是泰勒(Taylor)波期间释放的余能的函数。爆轰波阵面和膨胀之间能量的相对分配以及膨胀中能量释放的速率可能受化学动力学过程或扩散过程的支配。爆轰量热法已是研究这些过程所用的主要实验方法。对硝铵(AN)和梯恩梯(TNT)的一些配方,确定了总的能量释放;也确定了膨胀等熵线上一点或一个区域爆轰产物的定量分析。在这些配方中,组份和AN的颗粒大小都是变化的。为进一步洞察反应区中或其附近发生的反应,对选用的炸药也应用了同位素示踪法。在一种理想均质炸药中,做了类似的实验。     

基于SBAS-InSAR升降轨融合的尾矿库地表形变监测

由于不同轨道的SAR数据成像几何不同，难以评定仅用单组SAR数据解得结果的准确性，为提高尾矿库地表形变监测结果的精度，以四川省攀枝花市米易县牛望田尾矿库为研究对象，基于2个轨道(65景升轨、56景降轨)的Sentinel-1A卫星影像，利用差分干涉测量短基线集时序分析技术(SBAS-InSAR)分别对升轨、降轨数据进行处理，然后融合升轨和降轨的数据处理结果，获得升轨、降轨和升降轨融合共3组形变数据，利用GNSS卫星监测结果对3组数据进行验证，结果表明：升降轨融合结果比单轨监测结果精度更高；2019年11月至2021年12月，尾矿库坝体发生了微小形变，坝体累计形变量为-22.77～10.48 mm,形成了一个面积约为111 361 m²的沉降区域和一个面积约为38 906 m²的抬升区域。后续研究可以通过引入外部数据或采用三轨InSAR数据，分别对尾矿库垂直、东西、南北3个维度的形变进行三维解算，以使监测结果更加准确。     

DMAP的制备和应用

在吡啶的存在下醇、胺与酸或酰卤反应是经典的酰化方法,但对于高位阻底物结果不理想。60年代末发现4—二甲胺基吡啶(4—Dimetylaminopyridin(?),DMAP)能使一些难酰化的反应顺利进行,之后人们对DMAP的制备方法和应用进行了广泛研究;发现DMAP在结构上有供电子的二甲胺基与母环的共振,从而能强烈地激活环上的氮原子进行亲核取代。一般来说,用DMAP代替吡啶可使酰化反应速     

铜催化剂在有机合成中的新应用发展

铜作为金属催化剂,在有机合成上有着广泛的应用。本文在大量查阅最近两年的文献资料基础上,归纳总结了金属催化剂铜,近两年在国内的新研究动向和新应用,综述了Cu在一些经典的催化反应中应用的研究进展,主要包括Cu催化偶联反应、Cu催化多组分反应和Cu金属配合物催化有机反应的应用;此外,还综述了铜催化剂在近两年内,在新的合成方法、新的合成工艺中的新应用。     

粗糙度对水汽在细颗粒表面异质核化影响的数值模拟

为研究水汽在细颗粒物粗糙表面上的异质核化特性,基于Fletcher经典核化理论、分子运动学理论等提出了一个考虑水汽分子表面扩散机制、线张力、粗糙度的异质核化模型,并将理论预测的临界过饱和度与已有的实验值进行对比,验证了模型的有效性。采用数值模拟的方法,研究了线粗糙度因子、表面粗糙度因子对临界成核自由能、成核速率、临界过饱和度的影响规律。研究结果表明：与表面光滑的细颗粒物相比,粗糙表面的细颗粒物与水汽间的微观接触角更小,细颗粒物的润湿性更好,更易于发生异质核化凝结;在线张力为负时,细颗粒物的表面越粗糙,其成核自由能和临界过饱和度越小,成核速率越大,有利于水汽分子在细颗粒物表面发生异质核化;表面粗糙度因子比线粗糙度因子对水汽在细颗粒物表面异质核化凝结的影响更大。     

聚乳酸固相缩聚模型

提出了聚乳酸固相缩聚的反应-扩散综合模型,该模型中考虑了可逆酯化反应和热降解反应.并由实验数据拟合得到了不同温度下各反应的速率常数以及水的扩散系数,进而得到它们的活化能;模拟了不同因素对固相缩聚过程的影响.研究表明在较低的温度下,热降解反应的影响较小,可以忽略;而在较高温度下,其影响显著.水的扩散速率对聚乳酸分子量的增长影响很大;小粒径颗粒有利于制备高分子量聚乳酸.     

A reactive molecular dynamics model of thermal decomposition in polymers. II. Polyisobutylene

An improved version of the reactive molecular dynamics method is presented. The method, which extends conventional (force-field-based) molecular dynamics to modeling chemical reactions, is used to simulate the thermal decomposition of polyisobutylene. The results of the simulations are generally consistent with experimental observations. A quantitative analysis of the results shows that the rate constant of the key initiation reaction, backbone scission, depends on the size of the molecular model of the polymer. This implies that the kinetics of some elementary reactions that take place in a polymer melt are affected by the macromolecular nature of the environment.     

Study on Lignin–Glyoxal Reaction by MALDI-TOF and CP-MAS 13C-NMR

Abstract

Matrix-Assisted Laser Desorption/Ionization Time-of-Flight (MALDI-TOF) mass spectrometry was used to elucidate lignin–glyoxal reactions. The reaction of glyoxal with a low molecular weight lignin involves a number of different reactions; in particular lignin depolymerization and recombination through condensation reactions with glyoxal to form glyoxalene bridges linking both lignin units and mainly fractions of lignin units derived from degradation during depolymerization. The reactive hydroxyglyoxalated lignin is the one species still available for co-reaction for use in wood adhesives. The reactions described increase the viscosity of the lignin as the reaction proceeds towards higher molecular mass species and the condensed species grow in relative proportions. NMR analysis confirmed the existence of functional groups pertaining to structures that are formed from glyoxalation of the lignin observed by some results obtained by MALDI-TOF. MALDI-TOF mass spectrometry appears to be a suitable method for examining lignin–glyoxal reactions.     

Synergetic coupling of photo and thermal energy for efficient hydrogen production by formic acid reforming

Most photocatalytic reactions are conducted near room temperature. In this work, we explored photothermal hydrogen production in a carefully designed photo reactor with external heating. Light sources of different wavelength bands were investigated. Formic acid was used as sacrificial regent to study the photothermal hydrogen production activity. Interestingly, the photothermal reaction is not the simple sum of the photo and thermal effects but their synergetic coupling and at 90°C it is 8.1 and 4.2 times of that under photo or thermal conditions alone. With thermal excitation, the bound electrons in Pt can be excited which can easily overcome the energy barrier between Pt and lowest unoccupied molecular orbital of the adsorbed reactants. Activation of the substrate itself by light is also found to be crucial to trigger such photothermal reaction. It is therefore different from traditional plasma resonance induced photothermal reaction where long wavelength IR light is more preferred. © 2017 American Institute of Chemical Engineers AIChE J, 63: 2916–2925, 2017     

Catalytic Production of Liquid Fuels from Biomass‐Derived Oxygenated Hydrocarbons: Catalytic Coupling at Multiple Length Scales

The catalytic processing of biomass‐derived feedstocks to liquid fuels and chemical intermediates is complex and expensive. Therefore, conversion processes involving a limited number of reaction, separation, and purification steps are necessary. Coupling of catalytic processes has the potential to lead to the development of new processes, thereby improving the overall economics of biomass conversion. Functional coupling at the molecular scale has the potential to produce novel catalytic materials to replace homogeneous catalysts. Active site coupling of different sites within the same reactor can help reduce operating costs by combining sequential reactions in a single reactor. Chemical reaction coupling of heterogeneous and homogeneous reactions may lead to improvements in overall catalytic performance for liquid phase processes by enhancing surface reactions with liquid phase reactions. Finally, phase coupling leads to improvements in overall yield by improving the equilibrium conversion or by suppressing undesired side reactions.     

Optimal design of solvents for extractive reaction processes

It is well known that solvents can have significant effects on rates and equilibrium compositions of chemical reactions. The computer‐aided molecular design (CAMD) of solvents for heterogeneous liquid phase reactions is challenging due to multiple solvent effects on reaction and phase equilibria. In this work, we propose a CAMD methodology based on a genetic algorithm (GA) for identifying optimal solvents for liquid phase reactions where the objective is to maximize the reaction equilibrium conversion. In particular, a novel molecular encoding method is introduced to facilitate the construction and evaluation of solvent molecules in a defined structure space. The reliability of the method for fast identification of optimal reaction solvents is demonstrated for a selected biphasic esterification reaction. The proposed approach opens up new perspectives for intensifying extractive reaction processes via the purposeful design of solvent molecules. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3238–3249, 2016     

Free radical chemistry of coal liquefaction: role of molecular hydrogen

Model compounds containing the types of carboncarbon bonds thought to be present in coal were pyrolyzed in the presence of tetralin and molecular hydrogen at 450 °C. The relative rates of conversion of the model structures are predictable from the bond dissociation energies of the compounds. Conversion of dibenzyl in the presence of both tetralin and molecular hydrogen or in the presence of hydrogen alone proceeds along two parallel reaction paths. Toluene is produced by a thermal cracking reaction in which the rate-controlling step is the thermal cleavage of the β-bond in dibenzyl. Benzene and ethylbenzene are produced by a hydrocracking reaction. The rate of the hydrocracking reaction is directly proportional to the hydrogen pressure. The strong bond in diphenyl is hydrocracked in a system containing both molecular hydrogen and a source of free radicals. These studies on model coal structures offer firm evidence that molecular hydrogen can participate directly in free radical reactions under coal liquefaction conditions. Under some conditions molecular hydrogen can compete with a good donor solvent to stabilize the thermally produced free radicals. Molecular hydrogen can also promote some hydrocracking reactions in coal liquefaction that do not occur to an appreciable extent in the presence of only donor.     

Nonisothermal suspension polymerization of vinyl chloride for enhanced productivity

In the present study, a mathematical model is developed to numerically predict nonisothermal batch suspension polymerization of vinyl chloride. Free volume theory was used to consider diffusion‐controlled reactions. Model predictions were validated against field data obtained in a pilot scale stirred tank reactor. Variable temperature trajectory was considered during the course of the reaction to improve productivity by reducing the polymerization time for a certain conversion. Variable temperature during the course of the polymerization was successfully implemented by considering the predefined K value. By using variable temperatures during the course of the reaction, the density of the short branches per 1,000 monomer units as a criterion for structure defect remained relatively unchanged. Maximum reduction in reaction time relative to the isothermal case with the same K value and final conversion was 44% for the best temperature trajectory. J. VINYL ADDIT. TECHNOL., 22:470–478, 2016. © 2015 Society of Plastics Engineers     

Review on the Reactivity of 1,1‐Diamino‐2,2‐dinitroethylene (FOX‐7)

1,1‐Diamino‐2,2‐dinitroethylene (FOX‐7) is a novel high‐energy insensitive material with good thermal stability and low sensitivity, and exhibits excellent application performance in the field of insensitive ammunitions and solid propellant. Although FOX‐7 is simple in molecular composition and structure, its chemical reactivity is abundant and surprising, including salification reaction, coordination reaction, nucleophilic substitution reaction, acetylate reaction, oxidizing reaction, reduction reaction, electrophilic addition reaction, among other reactions. These reactions are systemically summarized and some reaction mechanisms are analyzed in this review.     

Reactivity,Stored Energy,and Dislocations in Solid-Solid Reacting Systems

Strong neutron bombardment of graphite can displace many atoms from their lattice positions; many of the dislocated atoms do not anneal during the irradiation process and the net result is an increase of internal energy of the graphite. This increase is usually referred to as stored energy, or in the older literature this phenomenon is sometimes called the total Wigner energy. In addition to irradiation, mechanical milling, decomposition, precipitation, reduction of chemical compounds, and condensation of metal vapors can also produce stored energy in powders. The stored energy associated with defects in solids is an important aspect of the nature of the defects and the processes that produce them. It has been shown experimentally that stored energy results in a large increase of reactivity of the solid materials, and the spontaneous release of the energy in an inert atmosphere can lead to a large temperature rise. This short communication reports on several typical features of stored energy and illustrates the problem with a few experimental examples. Since stored energy substantially increases the reaction rate we can carry out many reactions at much lower temperatures. Consequently, in technical applications for specific reactions high-temperature furnaces can be replaced by high-performance mills operating at room temperatures or by cheap low-temperature furnaces.

Non-catalytic reactions, in spite of their importance, have not received as much attention as catalysis in the past. Major developments and working plants erected at the end of the last century without participation of the chemical engineering community, as, for example, cement manufacturing, steel production, and ore processing, did not encourage chemical engineers to study the governing phenomena in a systematic way. Consequently, modeling and experimental studies have been relatively few, and applied physics or metallurgy propelled development in the field.

Reactions, that take place in gaseous or liquid systems can usually be well reproduced if the external conditions of the experiment are identical and the experiment is carried out with precursors of identical concentration. The situation is rather different in systems where solid precursors participate in the reaction scheme. In this short note we will report on some phenomena, that are not well known in the realm of chemical reaction engineering and that might play a very important role in experimental investigation and optimization of a particular solid reaction system.