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1.
在Zn-Cr催化剂上超临界相合成低碳醇的链增长机理   总被引:1,自引:0,他引:1  
在固定床反应器中,用化学富集法研究了在Zn-Cr催化剂上超临界相合成低碳醇的链增长机理,得到超临界流体中低碳醇形成的链增长模式和产物分布方程,分析了超临界流体对低碳形成链增长的影响,结果表明,低碳醇的形成是以碳链增长的方式进行的,COH→CCOH→CCCOH→CC(CH3)COH为低碳醇形成的机理。在链增长各步骤中,α-加成速度慢,是低碳醇形成的控制步骤,β-加成速度快,为链的增长步骤,超临界流体  相似文献   

2.
Zr-Mn-K催化剂超临界相合成甲醇与异丁醇的研究   总被引:1,自引:0,他引:1  
用共沉淀法和超临界流体干燥法,分别制备了Zr-Mn-K沉淀型催化剂和超细催化剂.以正十一~十三烷的混合物为超临界介质,在反应温度360~410℃、合成气压力7.5MPa、GHSV1700h-1及介质压力2.08MPa的实验条件下,分别考察了超细催化剂和沉淀催化剂的气相和超临界相催化合成气制甲醇、异丁醇的性能.气相和超临界相反应的研究均表明,超细催化剂催化合成异丁醇的活性高于沉淀催化剂;在超临界条件下反应,超细催化剂上产物的异丁醇含量较高(为23%~32%),甲醇含量为22%~33%,其它醇均在10%左右.气相与超临界相反应结果的对比显示,超临界流体促进产物的脱附与传递,提高了CO的转化率.但超临界流体对甲烷的萃取作用强于对醇的萃取,醇选择性低于气相反应.在超临界条件下合成甲醇、异丁醇仍遵循异丁醇形成的链增长机理,超临界流体改变了链增长各步骤的相对速度,致使超临界相反应的产物分布不同于气相反应的产物分布.  相似文献   

3.
分别以清洁及氧悠Cu(100)表面作为金属态铜和部分氧化态铜的表面模拟,用键级守恒-Mores势法研究了两种表面上CO2加氢制甲醇反应的能量学,计算结果表明,在两种表面上,CO2加氢制甲醇反应的优势反应途径均为“CO2,s→HCOOs→H2COs→CH3Os→CH3OHs”与清洁铜表面上的相应基元步骤相比,在Cu(100)-p(2×2)O表面上甲醇合成反应各基元步骤具有更低的活化能;HCOOs是含  相似文献   

4.
本文在563K、6MPa及H_2/CO=2的条件下,考察了Cu/Co比不同的几个RaneyCu-Co催化剂的反应性能。结果表明:RaneyCu-Co催化剂上CO加氢产物主要为C_1-C_6正构醇及C_1-C_8正构烃。烃和醇产品的分布均符合Schulz-Flory方程。但醇产品的链增长几率(0.3-0.55)均小于烃产品的值(0.6-0.75)。Cu/Co比不同的催化剂在进入活性稳定区之前,均经过了一个不尽相同的活性波动区,活性趋于稳定所需时间随Cu/Co比增大而缩短。Cu/Co=0.3-1.5(原子比)时,就醇收率而言,RaneyCu-Co催化剂明显高于共沉淀Cu-Co催化剂,Cu/Co=0.8(原子比)时,稳定醇收率达0.57g·g ̄(-1)·h ̄(-1)。  相似文献   

5.
本文采用H2-TPD,CO-TPD及CO/H2TPSR技术对三种方法(SMAD、浸渍、共沉淀)制备的Cu-Co催化剂进行了表征,并与低碳醇合成选择性进行了关联.Cu-Co催化剂上H2-TPD谱中共有四个脱附峰(A,B,C,D),其中C峰对应于低配位Co中心上的活化吸附氢,其面积百分数随不同催化剂的变化规律与醇选择性的变化规律一致.与CO-TPD谱对比,Co及Cu-Co催化剂上CO/H2TPSR谱中都出现一个新的甲烷析出峰(473~573K),归属为活化吸附氢与表面活泼碳物种之间的反应,其面积百分数随不同催化剂的变化规律与醇选择性的变化一致。基于上述结果,就CO插入中心问题进行了讨论.  相似文献   

6.
Ni-Cu和MgO-SiO_2间的相互作用及其对催化性能的影响   总被引:2,自引:0,他引:2  
本文用TPR,IR,TPD和TPSR等技术研究了以表面改性法制备的MgO-SiO2(MSO)表面复合物担载的Ni-CU合金间的相互作用及其对CO加氢反应催化性能的影响.结果表明,NiO-CuO与MSO间的相互作用导致部分MO与MSO形成表面物种从而使金属组分氧化物还原温度明显升高;还原后的Ni-Cu/MSO表面上存在着两类活性中心,即合金相中的Ni与载体相中的Mg2+(或Mg2+-O);在两类活性中心的协同作用下,CO吸附除有孪生、线式和桥式吸附态物种外,还有一种新的卧式吸附态(Ni...C=O→Mg2+).这种吸附态的活化程度较高,易在表面上发生裂解形成Ni-C和Mg2+-O,其中Ni-C是加氢反应的碳源;H2在催化剂表面上发生解离吸附形成Ni-H和Mg2+-OH,前者比较活泼,是加氢反应的氢原.CO加氢生成烃类的反应在Ni中心上按"表面碳"机理进行,其生成CZH4的选择性高于80%;H2O的生成反应按2(Mg2+-OH)-→Mg2++(Mg2+-O)+H2O方式进行.  相似文献   

7.
Cu—Co催化剂催化CO2合成醇的原位红外表征及其反应机理   总被引:2,自引:0,他引:2  
黄伟  刘崇微 《分子催化》1995,9(1):37-43
本文采用“原位”红外光谱结合XPS和XRD比较了CuCrk、CoCrK和CuCoCrK三种催化剂在2.5MPa,270℃条件下,CO2+H2合成醇的中间体及其演变过程;初步探讨了Cu-Co催化剂中活性金属的作用、氧化物的作用、以及甲醇合成机理和碳链增长机理。研究结果表明,Cu是最主要的合成甲醇活性组分,Co能够导致CO2离解吸附,而碳链增长则需要二者的协同作用。吸附在金属表面的甲酸盐是甲醇合成的中  相似文献   

8.
本文采用"原位"红外光谱结合XPS和XRD比较了CuCrK、CoCrK和CuCoCrK三种催化剂在2.5MPa,270℃条件下,CO_2+H_2合成醇的中间体及其演变过程;初步探讨了Cu-Co催化剂中活性金属的作用、氧化物的作用、以及甲醇合成机理和碳链增长机理。研究结果表明,Cu是最主要的合成甲醇活性组分,Co能够导致CO_2离解吸附,而碳链增长则需要二者的协同作用。吸附在金属表面的甲酸盐是甲醇合成的中间体,CO插入表面其它基团是碳链增长的关键步骤,一定量的氧化物的存在对Cu基催化剂合成甲醇活性是必不可少的,能够起到稳定表面甲酸盐的作用。  相似文献   

9.
超临界相CO加氢合成甲醇,异丁醇的研究   总被引:16,自引:1,他引:15  
以正十一~十三烷的混合物为超临界介质,在反应温度360~410℃、合成气压力75MPa、进气空速1700h-1、介质压力178MPa、总压93MPa的实验条件下,研究了固定床反应器中Zn-Cr、Cu-Zn-Cr催化剂在超临界相和气相条件下合成甲醇、异丁醇的性能。结果表明,超临界相反应的CO转化率高于气相反应。在超临界条件下反应,醇类选择性随着温度升高下降较慢,而气相反应醇类选择性随着温度升高下降较快。气相反应产物以甲醇、异丁醇为主,含少量乙醇和正丙醇,超临界相反应的产物分布与气相反应的明显不同,甲醇含量减少,乙醇、正丙醇和异丁醇都有不同程度增加。超临界流体的存在对合成醇链增长有影响,在不同催化剂上的产物分布有较大差异  相似文献   

10.
超细Mo-Co-K催化剂合成低碳醇性能的研究   总被引:4,自引:4,他引:0  
张业  钟炳 《燃料化学学报》2000,28(2):111-115
采用类凝胶法和超临界干燥技术制得超细Mo-Co-K催化剂。研究了还原态催化剂上CO加氢合成低碳醇的反应性能,考察了不同钼钴比、钾盐助剂呈和反应条件对合成低碳醇性能的影响,在300℃、6.0MPa,10000h^-1的反应条件下,超细Mo-Co-K(Mo/Co=7:1,K含量为1%)催化剂上低碳醇的时空产率达到624.4g/kg-cat.h,醇选择性与48.5%,OH/C1OH=1.08。  相似文献   

11.
Abstract

2-(Thiocyanatoacetyl)thiophene 2 and its selenium analog 3 couple with diazotized anilines and yield 3-aryl-2-imino-5-(2-thenoyl)-2,3-dihydro-1,3,4-thiadiazoles 6 and 3-aryl-2-imino-5-(2-thenoyl)-2,3-dihydro-1,3,4-selenadiazoles 7 respectively. The reactions of both 6 and 7 with nitrous acid, acetic anhydride and benzoyl chloride are described. Azo coupling of 2-amino-4-(2-thienyl)thiazole 17 and its selenazole analog 18 with diazotized anilines yielded the arylazo derivatives 19 and 20 respectively. Reaction of the hydrazidoyl bromide 16 with potassium thiocyanate, potassium selenocyanate, thiourea and selenourea yields 6, 7, 19, and 20 respectively.  相似文献   

12.
13.
PHOTOLYSIS AND RADIOLYSIS OF NITROMETHANE AND NITROETHANE   总被引:1,自引:0,他引:1  
Abstract— Prolonged photolysis of nitromethane and nitroethane in liquid and vapour phases, with simultaneous photolysis of the nitrogen dioxide formed, was studied in the absence and presence of cupric oxide. A high-pressure quartz immersion lamp providing the full range of visible and u.v. spectrum, with a high output of radiation at 366 and 313 mμ, was employed as source of light. The products of photolysis were detected by microanalytical methods, infrared-absorption spectrum analysis and gas chromatography. Photolysis of liquid nitro-alkanes resulted in formation of many compounds; saturated hydrocarbons, and in the case of nitroethane, ethylene, were submitted to detailed examination. Photolysis in the vapour phase was carried out in a specially designed glass apparatus. The main products were nitrogen dioxide, aldehydes and polyaldehydes; hydrocarbons were not estimated.
Liquid nitromethane and nitroethane were also irradiated with γ-rays from a 60Co source. The radiolysis products were similiar to those obtained on photolysis. The mechanism of photolytic decomposition of nitroalkanes is proposed and discussed.  相似文献   

14.
9-氨基壬酸系从癸二酸经单酯化、氨化和Hofmann重排制得。该单体以10克规模在玻璃管中和以4公斤量在15升聚合釜中,于260℃聚合成聚壬酰胺。聚合物在288℃纺丝,120℃牵伸,得到尼龙-9纤维。测定了聚合物和纤维的结构和多种性能。  相似文献   

15.
用顺丁烯二酸酐 (MAH)对具有分子包结能力的 β 环糊精 (β CD)进行化学改性 ,合成出了丁烯二酸单酯化 β CD单体 (MAH β CD) .通过氧化还原自由基引发MAH β CD与N 异丙基丙烯酰胺 (NIPA)聚合 ,合成出含 β CD结构单元的新型水凝胶 .用核磁共振、红外光谱及元素分析对MAH β CD单体及共聚物的结构和组成进行了表征 .溶胀研究结果表明 ,该水凝胶具有较好的pH、温度及离子强度敏感性 ;并且水凝胶在较高羧基(—COOH)含量和弱碱环境中 ,仍能表现出明显的温敏性  相似文献   

16.
The attractive Interactions between typically hydrophobic molecules such as hexane or CCl4, and the repulsive Interactions between extremely hydrophilic molecules such as poly(ethylene oxide) (PEO), when immersed in water, as well as the interactions between these molecules and water, have been examined from a surface thermodynamic viewpoint, taking the changes in surface free energy into account, as a function of temperature. It was found that attractive hydrophobic Interactions are not, as vas generally believed up to now, invariably entropic. Hydrophobic Interactions can be mainly enthalpic or mainly entropic, or more or less equal mixtures of both, depending on each individual case; however, all hydrophobic interactions are polar (in the sense of Lewis acid-base) in nature. Repulsive hydrophilic interactions are enthalpic, and also polar in nature. The interaction between hydrophobic solutes and water is mainly enthalpic, and is apolar in nature.  相似文献   

17.
生物质热解、加氢热解及其与煤共热解的热重研究   总被引:39,自引:3,他引:36  
在加压热天平上用非等温热重法进行生物质(锯末、稻壳)在N2气氛下的热解和加氢热解研究。考察了升温速率(5~25℃/min)和压力(0.1~7MPa)的影响,求取了热解动力学参数,并研究了生物质与煤在常压N2气下的共热解过程。研究结果表明:生物质在400℃左右即完成热解反应,总失重率大于70%(W%,daf.),热解时仅一个峰位于300℃左右;与煤热解行为相同,随升温速率及压力的升高,转化率下降,DTG峰移向高温,但由于热解反应在较低温度下进行,氧气的存在对生物质热解TG和DTG的影响远小于煤热解。证明生物质热解以其内部氢对自由基的饱和及分子重排反应为主。生物质热解可用一级反应动力学处理,主要热解阶段及表现活化能分别为:锯末,267~314℃,69.66kJ/mol;稻壳,283~310℃,53.45kJ/mol;生物质由于与煤的热分解温度相差很大,因而在其共热解过程中无协同作用。  相似文献   

18.
Abstract— The spectra of absorption, fluorescence and excitation of monolayers and thin films containing chlorophyll a together with a carotenoid (cis-β-carotene, trans-β-carotene, fucoxanthin, or zeaxanthin), were measured at — 196°C. The concentration ratios used, (Chl)/(Car), were 6:1, 4:1, 3:1, 2:1, 1:1 and 1:3, and the area densities, 3·70, 2·55, 1·76, 0·71, 0·37 and 0·17 nm2/pigment molecule. In dilute monolayers, (3·70 nm2/molecule), with a constant concentration ratio (Chl)/(Car) = 3:1, evidence of three β-carotene forms, with absorption bands at 460, 500 and 520 nm (C460, C500 and C520), and of a chlorophyll a form with an absorption band at 669–672 (Chl669–672) was found. On increasing the density to 0·2–0·3 nm2/molecule, a conversion of C460 and C520 into C500, was observed, and several more additional (probably more strongly aggregated) chlorophyll a forms appeared, with absorption bands at 672–733 nm. With excess carotene [(Chi)/(Car) = 1:3] the forms C460, C500, C520 and Chl669–672 were present even in the most dense films (0·2–0·3 nm2/molecule). The same was found with other carotenoids: if one of the pigments was in excess, aggregated forms of the other tended to disappear. In the transfer of energy from carotenoids to chlorophyll a, C500 was found to be the main donor. In layers with a concentration ratio (Chl)/(Car) = 3:1, the efficiency of transfer was less than 10 per cent at the lowest density used (3·70 nm2/molecule); it increased to 50 per cent, as the density was increased to 0·20 nm2/molecule. When the relative concentration of the carotenoid was increased to (Chl)/(Car) = 1:1, the efficiency of energy transfer dropped to 25 per cent even at 0·20 nm2/molecule. It seems that the efficiency of energy transfer between carotene molecules (prior to its transfer to chlorophyll a) is low, and effective transfer occurs only between β-carotene and immediately adjacent chlorophyll a molecules.  相似文献   

19.
制备了不同含量的纯聚乙烯醇(PVA)水凝胶和不同表面活性剂含量的多孔PVA水凝胶,采用数字散斑测量其泊松比,并使用电镜和显微镜观察其微观结构,探讨了纯PVA水凝胶与多孔PVA水凝胶组成、微观结构、泊松比、压缩模量和体积模量的变化及相互关系.研究发现,采用表面活性剂成孔,反复冷冻成型制备的闭孔结构水凝胶,其泊松比随应力应变增加而减小;随PVA含量增加而泊松比值减小;随表面活性剂含量增加,孔径变大,泊松比值减小.PVA水凝胶泊松比值与压缩模量和体积模量的比值成正比.  相似文献   

20.
气体分离膜是近年发展起来的应用前途广阔的一个领域。近年来由于非对称膜技术的开发,美国和日本已开始用硅橡胶涂复在多孔聚砜上制成PDMS-PS复合膜。PDMS是透气量最高而稳定的膜材料,但氧氮分离系数仅为2。 乙基纤维素(EC)具有机械强度高、抗热、耐寒和稳定性好等优点,是一种具有潜力的优秀膜材料。其中取代基的位置和含量对膜的性能有较大的影响。日、美等国科学家利用EC对氧氮的良好分离系数制成了中孔纤维材料富氧器、EC涂复在聚二甲基硅氧  相似文献   

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