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分解反应动力学可以深入分析氟碳铈矿分解反应过程,基于程序升温热重和质谱数据,采用Li Chung-Hsiung方法和Malek方法确定了氟碳铈矿分解反应过程的最概然机理函数、活化能和指前因子。热重实验结果表明,氟碳铈矿在空气和N2气氛围下400~600℃温度范围内分解,空气氛围更有利于氟碳铈矿分解反应的进行,分解过程可用A模型很好地描述,即氟碳铈矿分解反应的速率控制步骤包含产物成核、核增长和核吸收长大。空气氛围下,氟碳铈矿分解反应过程活化能和指前因子分别为17.657~24.885 kJ·mol-1和6.223~29.653 min-1;N2气氛围下,氟碳铈矿分解反应过程活化能和指前因子分别为25.532~30.236 kJ·mol-1和36.882~64.250 min-1,基于最概然机理函数、活化能和指前因子,建立了N2气和空气氛围下的稀土尾矿中氟碳铈矿的分解反应动力学模型。 相似文献
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固相热分解反应最可几机制的判断 总被引:1,自引:0,他引:1
固相热分解反应最可几机制的判断高永煜,邹文樵,冯仰婕(华东理工大学化学系上海200237)关键词热分解,动力学方程,反应机制固相热分解反应机制的判断,是热分析动力学中令人感兴趣的领域。常用的方法是从含机制函数的非等温积分动力学方程出发,分别用Sest... 相似文献
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针对氟碳铈矿高温焙烧产生含氟废气治理难度大,采用MgCl_2焙烧分解白云鄂博氟碳铈矿精矿。研究了焙烧温度、焙烧时间、盐矿比等工艺参数对稀土提取率的影响,得到最佳工艺条件:焙烧温度460℃,焙烧时间90 min,矿盐质量比1∶1.3,氟碳铈矿中的稀土提取率达到98.9%。通过热重分析(TGA-TG)、X射线衍射(XRD)、扫描电镜(SEM)和能谱分析(EDS)等方法,研究了MgCl_2分解氟碳铈矿氯化焙烧过程的反应机制:氟碳铈矿与MgCl_2分解产物反应生成氯氧化稀土,氯氧化稀土进一步分解得到氧化稀土,氟以MgF_2的形式存在。此工艺节能环保,有效解决了含氟废气问题。 相似文献
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非金属含氧酸盐的热分解反应严宣申(北京大学化学系100871)中学化学教材上介绍了KCIO3、CaCO5及硝酸盐的热分解反应,现以前两者为例讨论非金属含氧酸盐热分解反应的规律。就热分解产物而言,KClO3、CaCO2是两种不同类型的反应。如若CaCO... 相似文献
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为了探究萤石对氟碳铈矿浮选体系中颗粒分散和凝聚的影响。运用浊度测试、粒度分布测试、Zeta电位分析、DLVO理论计算等表征方法系统地研究了3种不同粒级(-74+47,-47+37,-37+33μm)萤石矿物颗粒在氟碳铈矿浮选溶液(质量比1∶1)中矿物颗粒分散与凝聚行为,研究结果表明:萤石加入后,混合矿样溶液浊度降低,粒度分布介于单矿物粒度分布之间;两矿物的表面电性相反,溶液DLVO理论计算值始终为负。萤石加入氟碳铈矿浮选体系后,颗粒间发生异相凝聚反应,且萤石粒度越小,颗粒间异相凝聚现象越明显。萤石覆盖在氟碳铈矿表面使其与捕收剂和气泡的黏附表面积减小,精矿回收率明显下降。 相似文献
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通过裂解/色谱-质谱联用(Py/GC-MS)与热失重-质谱联用(TGA—DTA/MS)对耐高温纤维间位、对位芳香族聚酰胺(PMIA,PPTA)在惰性气体下的热分解过程进行分析。Py/GC—MS迅速升温得到的裂解产物与TGA-DTA/MS连续升温得到的降解产物有较好的对应,3步降解的PMIA与1步降解的PPTA在过程上的差异反映在不同阶段降解与裂解产物的区别上。通过水解、均裂等反应机制对二者不同的热分解进行解释:在低分解温度时,运用水解机制解释了PMIA纤维3步的失重过程和低的耐热性;而随着温度升高,均裂机制增强,使得PPTA纤维在1000℃时失重较PMIA高。 相似文献
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氟碳铈矿提取稀土的绿色化学进展 总被引:15,自引:0,他引:15
氟碳铈矿是稀土工业的重要原材料,目前从氟碳铈矿提取稀土主要采用酸法工艺,该工艺虽然稀土回收高,但流程长,试剂消耗长,成本较高,同时酸法产生HF及废酸碱污染环境。因此寻找低成本,低污染的绿色化学处理工艺是近几十年中人们一直努力的方向。本文系统介绍了氟碳铈矿分解工艺的发展,并着重介绍邓氯化铵法提取氟碳铈矿稀土的的新工艺。该工艺采用盐类分解并氯化氟碳铈矿,直接用水浸取回收稀土,不引入酸和碱,提高了反应选择性,减轻了稀土在稀土杂质分负荷,降低了化工材料消耗,简化了工艺,提高了回收率,是符合绿色化学要求的工艺。 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
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Mohammed KajjoutChristian Rolando 《Tetrahedron》2011,67(25):4731-4741
Quercetin, the polyphenolic compound, which has the highest daily intake, is well known for its protective effects against aging diseases and has received a lot of attention for this reason. Both quercetin 3-O-β-d-glucuronide and quercetin 3′-O-β-d-glucuronide are human metabolites, which, together with their regioisomers, are required for biological as well as physical chemistry studies. We present here a novel synthetic route based on the sequential and selective protections of the hydroxyl functions of quercetin allowing selective glycosylation, followed by TEMPO-mediated oxidation to the glucuronide. This methodology enabled us to synthesize the five O-β-d-glucosides and four O-β-d-glucuronides of quercetin, including the major human metabolite, quercetin 3-O-β-d-glucuronide. 相似文献