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1.
MgO助剂对甲烷部分氧化Ni/Al2O3催化剂结构和性能的影响   总被引:3,自引:1,他引:2  
采用分步浸渍法制备了MgO改性的Ni/Al2O3催化剂,采用BET、XRD、H2 TPR、TEM和活性评价等研究方法,考察了MgO助剂对Ni/Al2O3催化剂物化性质和甲烷部分氧化制合成气反应性能的影响。实验结果表明,MgO助剂提高了催化剂镍物种的均一性,抑制了NiAl2O4尖晶石的形成,并且增强了镍物种与载体的相互作用,这与MgO、NiO形成固溶体及与Al2O3形成MgAl2O4有关。同时,适量的MgO助剂可以提高Ni物种在催化剂中分散度,并提高其有效利用率,改性后的催化剂在甲烷部分氧化反应中显示出较好的反应性能。过量的MgO助剂对催化剂的反应性能产生负面影响,MgO的碱性可以促进逆水煤气变换反应,从而导致H2选择性降低和CO选择性提高。  相似文献   

2.
研究了γ-Al2O3负载的Co/γ-Al2O3催化剂上肉桂醛的选择加氢反应.反应结果表明,以CoCl2作为前驱物的Co/γ-Al2O3催化剂的选择性要高于以Co(NO3)2作为前驱物的Co/γ-Al2O3催化剂,而活性则正好相反.当钴的负载量小于9%时,随着钴负载量的增加,催化剂的活性和选择性随之增加,当钴的负载量大于9%时,随着钴负载量的增加,Co/γ-Al2O3催化剂的活性略有增加,而生成肉桂醇的选择性变化也很小,认为9%的钴负载量是催化剂反应活性和选择性的一个阈值.在所选定的范围内,反应温度和压力对肉桂醛加氢的选择性几乎没有影响.  相似文献   

3.
不同载体Ni基催化剂生物质热解气甲烷化反应性能   总被引:2,自引:0,他引:2  
采用浸渍法制备了Ni金属负载在不同载体(SiO2、ZrO2、CeO2、Al2O3和Al2O3-CeO2)表面形成的催化剂,研究了水蒸气和载体对生物质热解气甲烷化反应性能的影响。结果表明,随着水蒸气量的增加CO转化率逐渐增大,而甲烷选择性呈现先增加后降低的变化趋势,当nw ater/ngas比值为0.26时达到最大。载体Al2O3相比SiO2、ZrO2和CeO2具有更大的比表面积和Ni金属分散度,促进了生物质热解气甲烷化反应活性和选择性。相比于Ni-Al2O3催化剂,Al2O3-CeO2复合载体具有更多的镍金属负载量活性金属分散度,以及最好的低温甲烷化反应性能。在300℃的低温条件下,Ni-Al2O3-CeO2催化剂的CO转化率达到97%,CH4增长率达到110%。  相似文献   

4.
制备方法对La改性的Ni/γAl2O3催化甲烷部分氧化的研究   总被引:4,自引:3,他引:1  
采用共沉淀法和浸渍法制备La改性的Ni/γAl2O3催化剂,并用于催化甲烷部分氧化反应。共沉淀法制备的催化剂表现出较高的活性和稳定性。空速为80000h-1、800℃时甲烷的转化率接近100%,H2的选择性达99.8%,且在稳定性实验中保持15h活性变化不大。实验采用BET、TPR和XRD说明共沉淀法制备的镍基氧化铝催化剂中,La的加入提高了催化剂的比表面积,有效的抑制了大颗粒NiAl2O4的形成,降低了催化剂活性组分的还原温度,对POM显示出很高的催化活性。  相似文献   

5.
Ni/Al2O3是甲烷部分氧化制合成气反应常用的催化剂. 与Rh,Ru,Pt和Ir等贵金属负载型催化剂相比,其活性及选择性与Rh催化剂相近,且成本低,强度高,易于制备,是最具潜在应用前景的催化剂. 但是,在高温反应条件下,其活性组分Ni易烧结和流失,且催化剂表面易积炭而失活[1~3]. 此外,Ni与载体Al2O3在高温下相互作用生成难还原的NiAl2O4尖晶石,导致活性组分减少,造成催化剂活性下降. 人们通常都只注意到NiAl2O4的惰性,为了避免NiAl2O4晶相的生成,在消弱Ni与Al2O3之间的相互作用,提高催化剂的活性和稳定性等方面做了大量研究[4~7],但有关Ni与Al2O3之间的相互作用对稳定金属Ni的作用方面的报道却较少. Al-Ubaid等[8]发现Ni负载在NiAl2O4上显示出比其它载体更好的稳定性. Pena等[9]发现,NiAl2O4在乙炔加氢反应中有抑制积炭的作用. 范文浩等[10]在甲烷-二氧化碳重整制合成气催化剂的研究中,发现NiAl2O4的形成使催化剂的抗积炭性能大为改善,增强Ni-Al2O3相互作用,能有效地抑制碳丝生长. 本文在固定床流动反应装置上考察了Ni/Al2O3在甲烷部分氧化制合成气过程中的催化性能,并用XRD,XPS和TPR等手段考察了Ni负载量、焙烧温度和还原条件等对催化剂中Ni与Al2O3之间的相互作用及其对抗积炭性能的影响.  相似文献   

6.
甲烷部分氧化制合成气的La2O3助Ni/MgAl2O4催化剂   总被引:21,自引:2,他引:19  
 用MgO与载体Al2O3在高温下焙烧成MgAl2O4尖晶石,防止了Ni在反应过程中与载体形成NiAl2O4, 促进了Ni在载体表面的分散. 应用CODEX软件优化了La2O3在Ni/MgAl2O4催化剂中的加入量和活化温度. La2O3助Ni/MgAl2O4在本文实验条件下经100 h反应后活性和选择性均未发生变化. 程序升温烧碳结果表明,催化剂表面仅存在一种较高温度下才可除去的碳物种,它可能是石墨碳. XRD和BET结果证实,催化剂具有较高的结构稳定性. 荧光分析结果表明,在100 h的反应过程中活性组分未发生明显流失. 根据脉冲反应结果对以Niδ+-(La2O4-x)δ-作为氧的活性位和Ni0作为甲烷的活性位的直接氧化反应机理进行了初步探讨.  相似文献   

7.
甲烷在稀土助剂修饰的Ni/α-Al2O3催化剂上的解离   总被引:2,自引:0,他引:2  
采用脉冲-色谱法,考察了甲烷在La2O3、CeO2修饰的Ni/α-Al2O3催化剂上的解离,并用TPR、XRD等方法对催化剂进行了表征。结果表明,添加La2O3,能促进甲烷的解离,并可使解离产生的碳保持较高的活性;CeO2的添加对甲烷的解离积炭有一定的抑制作用;La2O3和CeO2均能抑制镍晶粒的聚集。甲烷在Ni基催化剂上的解离,具有一定的结构敏感性。  相似文献   

8.
钡改性的Ni/γ- Al2O3催化剂用于甲烷部分氧化的研究   总被引:10,自引:5,他引:5  
800 ℃、80 000 h-1、CH4/O2/N2=14/7/79下比较了质量分数20%的Ni/γ- Al2O3和Ba改性的Ni/γ- Al2O3催化剂,用于甲烷部分氧化反应的活性和选择性。结果表明,Ba的添加提高了镍基催化剂的活性和稳定性。BET和XRD表明,Ba的加入有利于高温焙烧下抑制大颗粒的Ni Al2O4的形成,保持了高比例的活性镍组分,提高了催化剂催化活性。常压下,xCH4接近100%,sCO、sH2达到92.2%和98.1%,催化剂15 h内活性稍微下降。Ba的加入使Al2O3的晶型转化温度由800 ℃提高到900 ℃,提高了载体的稳定性。  相似文献   

9.
氧化镍与载体相互作用对乙烷氧化脱氢的影响   总被引:5,自引:0,他引:5  
研究了担载型催化剂NiO/γ-Al2O3的乙烷氧化脱氧(ODHE)性能,发现在400-500℃的考察温区内,担载型NiO较纯NiO的乙烯选择性有较大提高,保持在80%~90%之间,其中含17%Ni的样品500℃时乙烷的转化率为31%,乙烯选择性达82%.XRD、H2-TPR及原位磁测量结果表明:催化剂的活性相是与载体相互作用较小的、处于表层的微晶态NiO,NiO中非化学计量氧仍为活性氧物种.催化剂焙烧温度的提高,一方面降低了活性相中非化学计量氧量,同时加剧了NiO与载体γ-Al2O3的相互作用,二者均使活性降低.O2-TPD研究表明:与纯NiO相比,在Nio/γ-Al2O3中,其非化学计量氧的脱附温度发生变化,其中,α氧脱附温度向低温移动约50℃,而对乙烯选择性有关的β氧的脱出则向高温区移动了约200℃,正好与反应温区对应,进一步证实非化学计量氧与ODHE反应之间存在对应关系,上述结果表明那些对氧化镍还原有一定的阻碍作用,尤其阻碍镍深度还原(Ni2 →Nio)的载体对促进反应的乙烯选择性是有利的.  相似文献   

10.
开发高活性的顺酐加氢制丁二酸酐和γ-丁内酯催化剂具有重要的工业意义.顺酐加氢多采用Cu基和Ni基催化剂,但一般Cu基和Ni基催化剂存在反应温度高(170–260℃)和稳定性差等缺点,很有必要开发高活性的顺酐加氢催化剂.我们以拟薄水铝石作为Al2O3载体的前驱体,采用浸渍法制备了一系列镍铝尖晶石型衍生的不同Ni含量的Ni/Al2O3催化剂,并研究了它们在顺酐加氢反应中的催化性能.还原前Ni/Al2O3催化剂的X射线衍射结果表明,催化剂含有NiAl2O4物种.氮吸附结果显示,不同Ni含量的催化剂均具有介孔结构.氢-程序升温还原研究发现,Ni/Al2O3催化剂经750℃还原2 h后,其表面上NiAl2O4物种能被高效还原.X射线粉末衍射结果表明,750℃还原的Ni/Al2O3催化剂中金属Ni颗粒尺寸随着Ni负载量升高而增大.利用一氧化碳-程序升温脱附对750℃还原的Ni/Al2O3催化剂进行研究,发现750℃还原的催化剂上金属Ni物种含量从高到低依次为:Ni(7.5%)/Al2O3>Ni(5%)/Al2O3>Ni(2.5%)/Al2O3.采用CO化学吸附获得的Ni(2.5%)/Al2O3,Ni(5%)/Al2O3和Ni(7.5%)/Al2O3催化剂上金属Ni颗粒尺度分别为8.0,12.8和15.7 nm.活性研究结果表明,750℃还原的Ni(5%)/Al2O3催化剂具有最高的催化活性,这可能是由于Ni(5%)/Al2O3催化剂具有较多的Ni活性位点和较合适的Ni颗粒粒度所致.进一步研究发现,在650–750℃还原温度下,Ni(5%)/Al2O3催化剂的还原度随着还原温度的升高而升高,Ni分散度随着还原温度的升高而降低.活性结果研究表明,700℃还原的Ni(5%)/Al2O3催化剂具有较多的Ni活性位点和较合适的Ni颗粒粒度,具有最高的加氢催化活性,其在120℃,H2压力为0.5 MPa和质量空速为2 h?1的反应条件下,能获得近100%的顺酐转化率和90%的丁二酸酐选择性,同时该催化剂具有优良的稳定性.以上结果表明,尖晶石型衍生的Ni/Al2O3催化剂是一个十分有应用前景的顺酐加氢催化剂.  相似文献   

11.
The spectral-polarization characteristics of absorption and phosphorescence of molecules of the initial form of nitro-substituted indolinospirobenzothiopyran were studied in oriented polyethylene films and in solutions with different polarity. An oscillator model of the electron transitions responsible for the formation of absorption and luminescence spectra was suggested. It was established that the principal differences in the spectral and photophysical properties of the compound studied and its oxygen-containing analog are associated with the fact that the electronegativity of the S atom is lower than that of the O atom. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1143–1146, June, 1997.  相似文献   

12.
非那雄胺能抑制5α-还原酶的活性,明显降低二氢睾酮水平,是一种治疗良性前列腺增生的有效药品。该合成工艺以甾烯酮酸为原料,将其与氯化亚砜反应,无须分离即与叔丁胺反应得17β-酰胺化合物,再氧化开环,环合,氢化,脱氢合成了非那雄胺。经元素分析、IR、1HNMR、13CNMR、MS分析表征了其结构。该法无须使用昂贵的2,2-二吡啶二硫化物和剧毒药品苯亚硒酸酐,且以乙酸铵代替氨气,降低了对设备的要求和腐蚀,更适用于工业生产。  相似文献   

13.
翟宗玺  刘树深  夏树屏 《化学学报》1990,48(10):946-950
用氧化镁氯化镁水溶液制备了8水合氯氧化镁[nMg(OH)2·MgCl2·8H2O], 并测定了其在盐酸中的溶解热, 实验结果表明, 氯氧化镁溶解热与n值呈线性关系, 根据溶解热求出5Mg(OH)2·MgCl2·8H2O和3Mg(OH)2·MgCl2·8H2O的生成热分别为-7727.1和5888.1kJ·mol^1^-。  相似文献   

14.
Two vanilloids, (5E)-8-(4-hydroxy-3-methoxyphenyl)oct-5-en-4-one (1) and 4-[3-hydroxydecyl]-2-methoxyphenol (2), isolated from the dried seeds of Grains of Paradise (Aframomum melegueta), were synthesized; the latter compound was made as the S-enantiomer and the material derived from the seeds was found to be a 1:1.7 mixture of the R and S isomers. The synthetic route used should allow the preparation of analogs having extended alkyl chains and consequently different lipophilicity, and 3, a homolog of 2, was also prepared.  相似文献   

15.

The heats of detonation of 20 simple high explosives and explosive mixtures were determined by means of an adiabatic detonation calorimeter designed by the authors. The results indicated that the performance of the instrument was reliable and the experimental data were very accurate. For explosive mixtures, there was a linear accumulative relationship between the heats of detonation of the explosive mixture and its components. Accordingly, the heats of detonation of explosive mixtures could be calculated directly from the heats of detonation of simple explosives and the characteristic heats of other components. The experiments showed that the gold or brass shell of the cylindrical charge could be substituted by a thick-walled porcelain shell, which had the advantage of cheapness.

  相似文献   

16.
Cotton cellulose was swollen in a sodium hydroxide solution and carboxymethylated by a two-bath method for different periods of time for each process. The kinetics of acid hydrolysis and the crystallinity of the swollen and carboxymethylated samples were measured. The proportion of broken bonds, rate constants for hydrolysis, and permeability of cellulose to hydrolyzing agents were calculated. The susceptibility of glycosidic linkages to acid hydrolysis was improved by carboxymethylation more than by swelling in alkali. The increased accessibility of carboxymethylcellulose to acid was regarded as a consequence of increased intra-and intercrystalline swelling and of the glycosidic bonds' weakness caused by the electron-attracting carboxymethyl group on the C-6 position.  相似文献   

17.
Main hydration products of two cement pastes, i.e. CSH-gel, portlandite (P) (and specific surface S) were studied by static heating, and by SEM, TEM and XRD, as a function of cement strength (C-33 and C-43) hydration time (th) and subsequent hydration in water vapour.Total change in mass on hydration and air drying, Mo, increased with strength of cement paste and with hydration time. Content of water escaping at 110 to 220°C, defined as water bound with low energy, mainly interlayer and hydrate water, was independent on cement strength but its content increased with (th). Content of chemically bound (zeolitic) water in CSH-gel, escaping at 220-400°C, was slightly dependent on strength and increased with (th). It was possibly derived from the dehydroxylation of CSH-gel and AFm phase. Portlandite water, escaping at 400-500°C, was independent on cement strength and was higher on longer hydration. Large P crystals were formed in the weaker cement paste C-33. Smaller crystals were formed in C-43 but they increased with (th). Carbonate formated on contact with air (calcite, vaterite and aragonite), decomposed in cement at 600-700oC. It was high in pastes C-33(1 month) and C-43(1 month), i.e. 5.7 and 3.3%, respectively; it was less than 1% after 6 hydration months (low sensitivity to carbonation) in agreement with the XRD study showing carbonates in the air dry paste (1month), and its absence on prolonged hydration (6 months) and on acetone treatment. Water vapour treatment of (6 months) pastes or wetting-drying increased this sensitivity.Nanosized P-crystals, detected by TEM, could contribute to the cement strength; carbonate was observed on the rims of gel clusters.This revised version was published online in November 2005 with corrections to the Cover Date.  相似文献   

18.
In this review, the research of the author in the field of colloidal systems is summarized. The factors influencing colloidal stability are systematized and analyzed. Examples are presented to illustrate the practical utilization of the theory of stability of colloids and thin films.This review was prepared on the basis of the works of the author, which were awarded the State Premium for 1991 in the field of science and technology, chemistry section.Institute of Physical Chemistry, Russian Academy of Sciences, 117915 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 8, pp. 1708–1717, August, 1992.  相似文献   

19.
20.
The aim of the presented work was the investigation of thermal oxidation of ilmenite in static air atmosphere. The investigations were carried out by use of a derivatograph (MOM, Hungary). The changes of crystallographic structure of investigated samples were identified by X-ray diffractometry on Philips PW-1710 diffractometer. In temperature above 500°C appears structure of hematite Fe2O3. On the basis of the thermogravimetric measurements, the contracting area and contracting volume models were found as the best fitting experimental data. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   

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