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1.
季东  汪毅  刘涛  苏怡  李萍  高雄厚 《分子催化》2007,21(3):193-199
采用廉价的硅溶胶作为硅源,吡咯烷为模板剂,静态水热晶化法合成出不同硅铝比的ZSM-23分子筛.采用XRD,SEM,吡啶吸附红外光谱等技术,对合成的ZSM-23分子筛的结构、形貌、表面酸性质进行了表征.并进行了所制样品对C4烷烃催化裂解制乙烯丙烯反应催化性能的研究.本文详细考察了硅铝比、反应温度、反应空速以及催化剂稳定性等各种因素对催化性能的影响.结果表明,ZSM-23分子筛的乙烯丙烯收率达到56.0%,丁烷转化率达到88.9%.  相似文献   

2.
以低硅铝比(n(SiO2)/n(Al2O3)=20-45)的ZSM-5分子筛为催化剂, 研究了混合C4烃的催化裂解反应, 并对不同硅铝比的ZSM-5分子筛进行了酸性表征. 混合C4烃的催化裂解反应结果表明, 低硅铝比的ZSM-5分子筛具有较高的低温催化活性, 高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂, 低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂. 在反应温度为625 ℃时, 硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%. 酸性表征结果表明, 硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量, 这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.  相似文献   

3.
低硅铝比ZSM-5分子筛上C4烃的催化裂解反应   总被引:1,自引:0,他引:1  
以低硅铝比(n(SiO2)/n(Al2O2)=20-45)的ZSM-5分子筛为催化剂,研究了混合C4烃的催化裂解反应,并对不同硅铝比的ZSM-5分子筛进行了酸性表征.混合C4烃的催化裂解反应结果表明,低硅铝比的ZSM-5分子筛具有较高的低温催化活性,高硅铝比ZSM-5分子筛催化剂上乙烯和丙烯的收率高于低硅铝比ZSM-5分子筛催化剂,低硅铝比ZSM-5分子筛上苯和甲苯的收率高于高硅铝比ZSM-5分子筛催化剂.在反应温度为625℃时,硅铝比为20的ZSM-5分子筛催化剂上乙烯、丙烯、苯和甲苯的总收率可达79.42%.酸性表征结果表明,硅铝比低的ZSM-5分子筛具有更多的Bronsted(B)酸酸量、Lewis(L)酸酸量及总酸酸量,这是低硅铝比ZSM-5分子筛具有低温高活性及高的苯和甲苯收率的原因.  相似文献   

4.
中孔分子筛SO42-/Zr-MCM-41催化裂解聚丙烯反应研究   总被引:1,自引:0,他引:1       下载免费PDF全文
采用水热合成法制备了不同硅锆比的中孔分子筛Zr-MCM-41,用强酸性基团SO42-对其进行修饰,制得SO42-/Zr-MCM-41中孔分子筛.采用XRD、FT-IR、NH3-TPD及氮气吸附脱附等技术对其结构和酸强度进行表征.通过改变硅锆比、负载不同的酸性基团对Zr-MCM-41的酸性进行调变,并将其用于催化聚丙烯(PP)的裂解反应,结果表明S i/Zr=40的SO42-/Zr-MCM-41具有较好的催化裂解活性.另外,与热裂解以及HZSM-5和Zr-MCM-41为催化剂时PP的裂解反应结果进行了比较,结果证明SO42-/Zr-MCM-41不仅具有较高的裂解转化率,而且具有较高的液体产物收率,适宜于空间位阻较大的PP的催化裂解反应.  相似文献   

5.
以十六烷基三甲基溴化铵(CTAB)为模板剂,正硅酸乙酯(TEOS)为硅源,乙二胺为碱性介质,水热法合成了硅铝、硅镧及硅(铝 镧)摩尔比为30的Al-MCM-41、La-MCM-41和Al-La-MCM-41介孔分子筛,通过XRD、IR、NH3-TPD吸附脱附、BET、热分析及CCl4吸附等方法对分子筛的晶体结构和表面物性进行了研究,XRD及BET研究结果表明,所合成的分子筛具有典型的六方介孔结构特征及较大的比表面积.NH3-TPD结果表明所合成的介孔分子筛均达到中强酸酸度.将Al-MCM-41、La-MCM-41和Al-La-MCM-41分别用于催化乙氧基化反应,研究结果表明Al-La-MCM-41具有更高的催化活性,Al-La-MCM-41为正辛醇质量的5%,反应温度为120℃,反应压力0.2MPa,n(醇)∶n(环氧乙烷)=1∶3时,正辛醇聚氧乙烯醚产品的收率达92%.  相似文献   

6.
采用阳离子表面活性剂十六烷基三甲基溴化铵为模板剂,以正硅酸乙酯为硅源,以硫酸铝为铝源,水热合成了以催化油浆窄馏分为添加剂的高比表面积Al-MCM-41介孔分子筛,并利用XRD,HREM,TG-DTA及N2吸附-脱附等测试手段对合成样品进行了表征.合成的Al-MCM-41分子筛的比表面积和孔体积分别达到1295m^2/g和1.5cm^3/g,其平均孔径为4.3nm.重点研究了Al-MCM-41分子筛结晶度、晶胞参数、比表面积、孔体积及平均孔径等结构性质随催化油浆窄馏分添加量及其组成的变化规律,并从合成机理上进行了解释.  相似文献   

7.
 考察了原位合成的不同硅铝比的Cu-ZSM-5/堇青石整体式催化剂上的NO分解反应.结果表明,在573~773K的温度范围内,硅铝比分别为60,55和40的催化剂在723K下NO的转化率最高,而硅铝比小于25的催化剂上的NO转化率很低.低温有利于N2O的生成.整体式催化剂上的NO转化率低于单纯的分子筛催化剂Cu-ZSM-5,但其催化转换频率高于后者.  相似文献   

8.
采用静态水热法合成了含有不同锌含量的锌铝磷酸盐分子筛(ZnAPO-5),利用XRD、SEM、N2-吸附、MAS-NMR及ICP-AES等方法对合成的ZnAPO-5分子筛进行了表征。研究结果表明在选定的合成条件下,可以合成出AFI结构类型的ZnAPO-5分子筛,合成的ZnAPO-5分子筛结晶度较高,具有规整的六方棱柱晶体外形,杂原子同晶取代为锌取代骨架元素铝。ZnAPO-5分子筛上的正己烷催化裂解反应活性评价结果显示在反应温度为723 K~823 K时正己烷的催化裂解呈中等反应活性,正己烷的转化率随反应温度和接触时间的增加而增加,正己烷的浓度项反应级数为1,裂解反应表观速率常数随反应温度的升高而增大,且遵从Arrhenius公式;由裂解产物分布可知,在选定的实验条件下该反应以单分子反应为主。  相似文献   

9.
以六亚甲基亚胺为模板剂,采用动态水热晶化法合成了不同硅/铝比的HMCM-22分子筛,并以其为甲醇脱水活性组分与铜基甲醇合成活性组分(Cu-ZnO-Al2O3)组成双功能催化剂,在连续流动加压固定床微型反应器上考察了其对合成气直接制二甲醚反应的催化性能. 结果表明,随着HMCM-22分子筛硅/铝比的增大, CO转化率变化不大,但CO2和烃类副产物的生成量逐渐减少,从而导致目的产物二甲醚的选择性和收率均逐渐升高. 氨程序升温脱附和吡啶吸附红外光谱表征结果表明,随着分子筛硅/铝比的增大, HMCM-22分子筛的酸中心的数量逐渐减少.  相似文献   

10.
单学蕾 《催化学报》2001,22(3):242-244
考察了原位合成的不同硅铝比的Cu-ZSM-5/堇青石械催化剂上的NO分解反应。结果表明,在573-773K的温度范围内,铝硅比分别为60,55和40的催化剂在723K下NO的转化率最高,而硅铝比小于25的催化剂上的NO转化率很低。低温有利于N2O的生成。整体式催化剂上的NO转化率低于单纯的分子筛催化剂Cu-ZSM-5,但其催化转换频率高于后者。  相似文献   

11.
Al-MCM-48 molecular sieves (Si/Al molar ratios = 25, 50, 75, and 100) were synthesized hydrothermally using cetyltrimethyl-ammonium bromide as the structure directing template. The orderly arrangement of mesopores was evident from the low angle X-ray diffraction patterns and transmission electron microscopy images. The catalytic performance of the materials was evaluated in the vapor phase isopropylation of phenol with isopropyl acetate. Phenol conversion decreased with the increase in the Si/Al ratio of the catalysts. The major reaction product was 4-isopropyl phenol with 78% selectivity. The delocalization of phenolic oxygen electron pair over the aromatic ring promoted para-selective alkylation. Such delocalization could be aided by the hydrophilic surface of the molecular sieves. Although an ester was used as the alkylating agent, phenyl isopropyl ether was not formed in the reaction.  相似文献   

12.
The reaction of benzaldehyde with aliphatic glycols was performed over Al-MCM-41 with various Si/Al ratios. The effects of various parameters like temperature, mole ratio, reaction time and catalyst amount on the formation of acetals were optimized. The mesoporous Al-MCM-41 (Si/Al ratio 36, 57, 81 and 108) were synthesized by hydrothermal method. The synthesized catalysts were characterized by X-ray diffraction (XRD), nitrogen adsorption–desorption isotherm (BET), thermo gravimetric-differential thermal analysis (TGA-DTA) and TEM techniques. The acidity of the catalysts was measured by pyridine adsorption followed by FT-IR analysis. TEM analysis showed that the honeycomb-like regular arrangement of hexagonal pores on the molecular sieves. The highly hydrophobic Al-MCM-41 (108) showed higher activity than the other Si/Al ratios. The activity of the catalysts showed the following order Al-MCM-41 (108) > Al-MCM-41 (81) > Al-MCM-41 (57) > Al-MCM-41 (36). The hydrophobicity and nucleophilicity of the glycols highly influences the conversion of benzaldehyde, it followed the order; hexylene glycol (HG) > propylene glycol (PG) > ethylene glycol (EG). The results showed that mole ratio of 1:3 (aldehyde:glycol) gave higher yield than the other mole ratios.  相似文献   

13.
以硅酸钠为硅源、硫酸铝为铝源、CTAB为模板剂,采用水热法合成了负载型固体酸Al-MCM-41中孔分子筛催化剂,并通过X射线衍射(XRD)、热重差热分析(TG-DTA)、扫描电镜(SEM)和红外(IR)方法对其进行了表征,同时研究了该催化剂在二芳基乙烷合成反应中的催化性能。考察了各种反应因素的影响,确定其最佳合成条件为:原料苯乙烯与二甲苯质量之比为1∶7.5,催化剂用量为1 %(总投料质量百分比),反应时间为3 h,反应温度为140 ℃,产率可达87.1 %,比传统催化剂浓硫酸提高了17 %。研究结果表明,该催化剂是替代液体酸合成二芳基乙烷的理想固体酸催化剂。  相似文献   

14.
Abstract

Al-MCM-41 samples with various Si/Al ratios were prepared and then used to disproportionate methyltrichlorosilane (MTS) to produce dichlorodimethylsilane (DMCS). The catalysts were characterized by FT-IR, X-ray powder diffraction (XRD), 27Al magic angle spinning nuclear magnetic resonance (27Al MAS NMR), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and N2 absorption–desorption. It reveals that all samples show the hexagonal structure of MCM-41 and exhibit large BET surface areas (over 842 m2·g?1). FT-IR spectra of pyridine adsorption demonstrates that Al-MCM-41 samples have Lewis (L) and Brønsted (B) acidic sites, and the B acidic sites are stable in the temperature ranging from 423 to 623 K. The effects of aluminum content and temperature on the disproportionation reaction were also investigated. The results show that the Al-MCM-41 with the Si/Al ratio of 15:1 exhibits an excellent activity with 100% conversion of MTS and 47% selectivity of DMCS at 623 K under atmospheric pressure.  相似文献   

15.
以硅酸钠为硅源、硫酸铝为铝源、CTAB为模板剂,采用水热法合成了骨架负载型固体酸Al-MCM-41介孔分子筛催化剂,并通过X射线衍射(XRD)、扫描电子显微镜(SEM)和红外(IR)方法对其进行了表征,同时研究了该催化剂在二芳基乙烷合成反应中的催化性能. 考察了各种反应因素的影响,确定其最佳合成条件为:原料m(苯乙烯)∶m(二甲苯)=1∶7.5,催化剂用量为1%(总投料质量分数),反应时间为3 h,反应温度为140 ℃,产率可达87.1%,比传统催化剂浓硫酸提高了17%. 研究结果表明,该催化剂是替代液体酸合成二芳基乙烷的理想固体酸催化剂.  相似文献   

16.
AlMCM-48介孔分子筛对萘异丙基化反应的活性   总被引:1,自引:1,他引:0  
2-烷基萘和2,6-二烷基萘是很有价值的化学品,2-烷基萘可用于染料,药物,香料等精细化学品的生产,2,6-二烷基萘是生产新型聚合材料的重要原料,以煤焦油中萘 原料经傅-克反应可获得烷基萘,工业上传统的液相反应用H2SO4,H4PO4,AlCl3等作催化剂[1],由于存在腐蚀性强,产物分离难,污染重等弊病,人们极力探求性能优良,环境友好的新型催化剂,各种沸石分子筛如ZSM-5,HY,HM,β-沸石等对萘 烷基化反应的催化性能都有探讨^[2-6],据报道,用H-ZSM-5催化萘的甲基反应显示较高的选择性^[2],n(2-甲基萘)/n(1-甲基萘)达到8;(2,6-二甲基萘+2,7-二甲基萘)在二取代产物中达到80.8%,但萘的转化率较低,约10%,由于H-ZSM-5的孔径较小,它对萘的异丙基化反应几乎无活性[6],HY,Hβ对萘的异丙基化反应活性较高,但选择性差,n(2,6-二甲基萘/2,7-二甲基萘)=1,HM对萘的异丙基化反应选择性较高,而萘的转化率不高,约30%^[3-6],掺要Ce的丝光沸石选择性和活性都有所提高[7],本文研究了用后处理方法固载铝的AlMCM-48介孔分子筛对萘的异丙基化反应的催化作用,考察了Si/Al对反应的影响。β  相似文献   

17.
万颖  马建新  王正  周伟 《化学学报》2004,62(19):1877-1882
利用程序升温反应技术考察了cu交换度对Cu-Al-MCM-41上NO选择性还原反应性能的影响,同时结合XRD,N2吸附等温线,NMR,ICP-AES,TPD和TPR等技术对催化剂的结构特征和化学吸附性能进行了表征.结果表明,经Cu离子交换的Al-MCM-41并未改变载体的结构特征,仍保持长程有序的中孔结构.影响Cu-Al-MCM-41催化剂选择性还原活性的主要因素是Cu交换度,而不是Cu含量,前者决定了活性中心(主要是Cu^2 )的浓度.当Cu交换度低于100%时,随着Cu交换度的增加,NO最大转化率增加.当交换度超过100%后,催化剂的还原活性下降,此时出现的CuO起完全氧化的催化作用而非选择性还原的催化作用.在n(Si)/n(Al)=10,Cu交换度接近100%的Cu-Al-MCM-41上360℃时可获得79%的NO最大转化率.  相似文献   

18.
通过微波加热的方法,分别合成了硅/铝比(30、40、50、55、60)不同的含磷铝结构单元的AlMCM-41复合分子筛,并以此为载体采用共浸渍和程序升温高纯氢气还原的方法制备了负载量为30%(以WO3计)的磷化钨催化剂。采用X射线衍射(XRD)、BET比表面积测定、扫描电镜(SEM)及X光电子能谱(XPS)等手段对催化剂进行了表征。通过高压微反装置对催化剂的二苯并噻吩(DBT)加氢脱硫(HDS)性能进行了评价。结果表明,在催化剂表面检测到活性组分WP和以类似-Al-O-W-P结构形式存在的具有一定活性的物种。WP是主要的活性相,硅/铝比对WP活性相在催化剂表面所占的比例有一定影响。不同硅/铝比的催化剂表现出不同的选择性加氢性能,但直接加氢脱硫是催化剂DBT HDS的主要路径。其中,硅铝比为55的催化剂具有相对最高的DBT HDS的转化率(93.1%),且其直接加氢脱硫产物(联苯)的选择性相对最高(82.7%),这对减少氢耗,保护环境有利。  相似文献   

19.
Catalytic steam reforming of acetic acid and hydroxyacetone (acetol) as model compounds of the aqueous fraction of bio-oil (biomass derived pyrolysis liquids) was studied in fluidized bed reactor over Ni/Al catalysts modified with calcium or magnesium. Attrition tests showed that the use of small quantities of these promoters improved the mechanical strength of the reforming catalyst. An optimum Ca/Al molar ratio of 0.12 and a Mg/Al molar ratio of 0.26 leaded to attrition rates of 0.22 and 0.27 wt%/h, respectively. Steam reforming experiments were performed at 650 °C and a steam to carbon molar ratio (S/C) of 5.58. The promoted catalysts showed different acetic acid steam reforming activities depending on the Ca/Al or Mg/Al molar ratios. Magnesium modified catalysts with a Mg/Al molar ratios of 0.26 and 0.50 showed good performances with almost no activity loss with time in contrast to the calcium modified catalysts that showed higher CO and CH4 yields. The addition of calcium generated a NiO phase with less interaction with the support. The highest H2 yield and carbon conversion in acetic steam reforming were obtained by a magnesium promoted catalyst with a Mg/Al ratio of 0.26, while the nonpromoted Ni/Al catalyst showed the best performance in acetol steam reforming. Then, the nature of the organic compound influenced the performance of the different catalysts.  相似文献   

20.
The Mobil Composition of Matter No. 41 (MCM-41) containing Cu and Al with Si/Al ratios varying from 100 to 10 and 1 to 6 wt.% of Cu was synthesized under hydrothermal and impregnation conditions, respectively. The samples were characterized by nitrogen adsorption–desorption measurements, X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), UV–Vis diffuse reflectance spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), temperature-programmed desorption (TPD), and 29Si and 27Al magic-angle spinning–nuclear magnetic resonance (MAS–NMR) spectra. X-ray diffraction patterns indicate that the modified materials retain the standard MCM-41 structure. TPR patterns show the two-step reduction of Cu species. TPD study shows that Cu-impregnated Al-MCM-41 samples are more acidic than Al-MCM-41. From the MAS–NMR it was confirmed that most of the Al atoms are present tetrahedrally within the framework and some are present octahedrally in extraframework position. Impregnation of Cu shifted Al to the extraframework position. The catalytic activity of the samples toward hydroxylation of phenol in aqueous medium was evaluated using H2O2 as the oxidant at 80 °C. The effects of reaction parameters such as temperature, catalyst amount, amount of H2O2, and solvent were also investigated. Sample containing 4 wt.% copper-loaded Al-MCM-41-100 showed high phenol conversion (78%) with 68% catechol and 32% hydroquinone selectivity.  相似文献   

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