共查询到20条相似文献,搜索用时 15 毫秒
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The structural change of Pd induced by acid sites of zeolite was studied by using EXAFS. The anchoring of dispersed PdO on the acid sites of ZSM-5 was evidenced from the reversible structural change of Pd upon the reduction and oxidation treatments. The novel method to regulate the dispersion of metal Pd and PdO through changing the acid concentration of zeolite was proposed. 相似文献
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本文以工业水玻璃为原料,对合成超细NaY分子筛进行了研究.考察了添加吐温-20、乙酸及二者混合物对合成NaY分子筛的影响,采用XRD、SEM、TEM等技术对所合成的分子筛进行了表征.结果表明,加入吐温20、乙酸及二者混合物均能降低分子筛的粒径,且添加二者混合物对于降低分子筛的晶粒尺寸和提高分散度均具有明显的促进作用,当二者混合物组成为吐温20含量为合成体系Al2O3含量的0.1%,乙酸含量是合成体系Al2 O3含量的150%时,可以得到粒径分布较窄、晶粒大小为180 nm左右及分散度较好的NaY分子筛. 相似文献
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ZSM-5分子筛催化合成乙撑胺 总被引:15,自引:1,他引:15
研究了从单乙醇胺 (MEA)和氨合成乙撑胺。所用的催化剂为 ZSM- 5分子筛。反应条件为 :t=2 80~ 3 6 0°C,p=2 .0~ 8.0 MPa,NH3/MEA=5~ 5 0 (摩尔比 )。反应对 EDA、PIP、TEDA的选择性较高 ,MEA的转化率可达到 85 %。 相似文献
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以三乙醇胺为模板剂, 采用静态晶化水热法合成出一种特殊结构的沸石分子筛 (称作SAO-25) , 合成过程中不易发生混晶和转晶, 重复性良好。对SAO-25 沸石进行了物相分析和红外光谱研究, 考察了它的吸附性能和酸性。在SAO-25 沸石分子筛上进行正构烷烃 (n2-C6) 裂解反应测试, 显示出较高的催化活性; 在重油裂解反应测试中, 显示出很高的C=3、C=4 轻烯烃选择性。 相似文献
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Fe-modified ZSM-5 zeolites (Si/Al = 25) were prepared by adopting the liquid ion-exchange method with nitrate and oxalate of iron as Fe precursors and their catalytic performance was studied in the N2O decomposition reaction. The results of FT-IR and H2-TPR investigations indicated that (i) part of the iron ions could replace Brönsted acid protons at the straight channel wall (α sites), intersection of straight and sinusoidal channels (β sites), and sinusoidal channel wall (γ sites) within the ZSM-5 zeolite; and (ii) different Fe precursors gave rise to various distributions of α, β, and γ sites. We observed that the Fe-ZSM-5 catalyst prepared with iron oxalate as Fe precursor outperformed the ones prepared with iron nitrate as Fe precursor in the direct decomposition of N2O. Furthermore, the catalytic activity of iron ions located at the α sites was higher than those of iron ions located at the β and γ sites. 相似文献
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Dolores Esquivel Aurora J. Cruz-Cabeza César Jiménez-Sanchidrián Francisco J. Romero-Salguero 《Catalysis Letters》2012,142(1):112-117
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A beta zeolite modified by treatment with aluminium ions has been characterized by different techniques, such as XRD, XPS, N2 adsorption, and TPD of pyridine and acetonitrile. Compared to the parent zeolite, it has shown some differences concerning the local environment of the aluminium atoms and the distribution of the acid sites. The modified zeolite has been tested as catalyst in a model reaction, i.e. the conversion of methanol to hydrocarbons, where it has exhibited higher activity than the parent zeolite. 相似文献16.
采用水热合成法制备了无模板剂ZSM-5分子筛,考察了制备工艺对无模板剂ZSM-5分子筛结构的影响,并用X-射线衍射(XRD)、扫描电子显微镜(SEM)、NH3程序升温脱附(NH3-TPD)、傅立叶变换-红外光谱(FT-IR)和N2低温吸附(BET)等方法对合成产物的物相、形貌和酸性等进行了表征。结果表明,在140℃晶化24 h,可制得性能较好的无模板剂ZSM-5分子筛,其相对结晶度为151%,具有较大的比表面积、适中的酸强度和较高的热稳定性,在催化甲醇制丙烯(MTP)单程反应中,甲醇转化率为100%,丙烯选择性为39.5%。 相似文献
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Co-ZSM-5分子筛催化剂是一种具有较强催化活性的醛氨缩合催化剂,其主要特点是反应条件温和、择形选择性高、副产物较少等优点.醛氨缩合反应是制备烷基吡啶最具代表性的反应路线之一,作者研究了在Co-ZSM-5分子筛催化剂上的醛氨缩合反应,详细考察了反应温度、催化剂用量、原料配比(甲醛/乙醛摩尔比)、n(氨/原料摩尔比)值、反应时间以及催化剂使用次数等因素对醛氨缩合反应的影响,系统地研究了醛氨缩合反应的规律,并优化了反应条件.研究发现Co-ZSM-5分子筛催化剂的失活过程经历4个阶段高水平活性稳定期、活性衰退期、低水平活性稳定期和二次活性衰退期4个阶段.升高温度、增大催化剂用量、一定的原料配比和n值、延长反应时间均对提高醛氨缩合反应性能有积极的影响.研究显示,反应条件在反应温度450℃、常压、原料配比为2/3、n值为2、反应时间1~2 h内,反应对烷基吡啶的选择性较高,烷基吡啶的产率可达85%以上. 相似文献
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With benzaldehyde as a model compound, the hydrogenation of aromatic aldehydes to aromatic hydrocarbons was investigated. Cu-HZSM-5 exhibited excellent catalytic performance for the reaction. The obtained catalysts were characterized by N2 adsorption/desorption, N2O chemisorptions, X-ray diffraction, NH3-temperature programmed desorption and X-ray photoelectron spectroscopy. It was found that Cu0 active species exhibited poor activity for the hydrogenation of benzene ring, while the strong acidity of HZSM-5 accelerated the hydrogenation reaction via hydrogen spillover phenomenon and the C–O activation effect. In addition, the catalyst was proved to be effective for the hydrogenation of a series of aromatic aldehydes to corresponding aromatic hydrocarbons. 相似文献