共查询到18条相似文献,搜索用时 163 毫秒
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采用X射线粉末衍射(XRD)和扫描电镜(SEM)手段研究了合成条件对高岭土微球上原位晶化ZSM-5沸石的影响,并以含C5~C12烃的石脑油为原料,在固定流化床上评价了不同催化剂的催化裂解性能.结果发现,采用转动晶化方式,控制合适的原料组成与晶化时间,能得到结构完整的含纯相ZSM-5沸石的高岭土微球.对比催化剂水热老化前... 相似文献
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以硅酸钠试剂为硅源,铝酸钠试剂为铝源,反应体系各组分的物质的量之比为n(SiO2)∶n(Al2O3)∶n(Na2O)∶n(H2O)=2∶1∶1∶1∶50,采用水热合成法制备了4A分子筛,考察了晶化温度与晶化时间对该型分子筛结构和形貌的影响,并利用X射线衍射(XRD)、电镜扫描(SEM)及红外(IR)测试等手段对其进行了表征。结果表明,4A分子筛在晶化温度为100℃,晶化时间为14h的条件下具有良好的微孔结构及形貌。 相似文献
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以高岭土微球为全部硅铝原料,经焙烧、碱抽提、水热处理等工艺,直接原位晶化合成了Y分子筛。扫描电镜分析表明:在高岭土微球上均匀生成了晶型完整、粒度为1 μm左右的Y分子筛。结合X射线测试方法详细研究了体系硅铝比、碱度、碱抽提时间、导向剂构成及添加时间对Y分子筛合成的影响。研究表明:该水热反应体系的最佳配比为n(SiO2)/n(Al2O3)=10.0。反应适宜的碱度条件为:n(Na2O)/n(SiO2)=0.56,n(H2O)/n(Na2O)= 35,碱度过高或过低都易有P杂晶生成。碱抽提过程对合成Y分子筛十分关键,最佳的抽提时间控制在12 h。导向剂构成为透明高清状,加入时间控制在碱抽提结束时最优,此时合成的Y分子筛品质最好。 相似文献
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利用不同比例的高岭土和硅藻土为原料通过原位晶化方法合成出了结晶度较高的NaY分子筛,采用X射线衍射仪、扫描电子显微镜、N2吸附–脱附等测试手段对合成样品进行了表征。着重考察了m(高岭土):m(硅藻土)(质量比,下同)为6:4和2:8两种比例下,晶化合成体系中n(SiO2):n(Al2O3)(摩尔比,下同)、n(Na2O):n(SiO2)和n(H2O):n(Na2O)对原位晶化产物性能的影响。结果表明:在m(高岭土):m(硅藻土)为6:4的合成体系中,随n(SiO2):n(Al2O3)的增大,NaY分子筛的相对结晶度先增大后减小,增大体系的n(Na2O):n(SiO2)和减小n(H2O):n(Na2O)都有利于产品相对结晶度的提高;在m(高岭土):m(硅藻土)为2:8的合成体系中,增大n(SiO2):n(Al2O3),NaY分子筛的相对结晶度先增大后减小,但增大n(Na2O):n(SiO2)和减小n(H2O):n(Na2O),NaY分子筛的相对结晶度减小。 相似文献
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Investigation on the Synthesis of Zeolite NaX from Kerala Kaolin 总被引:1,自引:0,他引:1
The synthesis of zeolite NaX from a locally available kaolin has been studied. Two steps are involved in the reaction (1) thermal activation of the kaolin to get a dehydroxylated product called metakaolin (metakaolinisation) and (2) hydrothermal reaction (zeolitisation) of metakaolin in alkaline medium in presence of additional silica to crystallise the zeolite. The metakaolinisation temperature (400–1000°C) is found to have an important role in determining the type of zeolite formed during the hydrothermal reaction. Under specified conditions, the uncalcined kaolin is partially converted to hydroxy sodalite (HS), whereas the metakaolins prepared at 400, 500 and 600°C also change to HS but at a faster rate. Increasing the metakaolinisation temperature to 700°C, zeolite NaX is found to be the product (higher the temperature, faster the reaction). The quantity of additional silica which in turn determines the SiO2/Al2O3 ratio of the reaction mixture and the time given for zeolitisation were also found to influence the formation of zeolite NaX. When metakaolin alone was used in the reaction (SiO2/Al2O3 = 2), the product was X-ray amorphous. Higher ratios were obtained by the addition of sodium silicate. The ratios 3 and 5 gave phase pure NaX whereas 7 resulted in a mixture of NaA, NaP and HS zeolites. The optimum conditions to get phase pure zeolite NaX with good crystallinity from kaolin were found to be metakaolinisation of the clay at 900°C for 1 h, maintaining the mole ratios of SiO2/Al2O3 = 3; Na2O/SiO2 = 1.1 and H2O/Na2O = 40 in the reaction mixture, an ageing of the reactants at room temperature for 24 h and heating at 87 ± 2°C for 15 h under autogenous pressure. Seeding was not essential for the zeolite crystallisation. X-ray diffraction, electron microscopy, IR and solid state NMR spectral analysis, water adsorption and calcium/magnesium exchange or binding capacity measurements and chemical analysis of the selected products substantiated these findings. 相似文献
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研究了硫化温度和时间对胎面胶硫化特性、物理性能、耐磨性能和压缩温升的影响。结果表明,随着硫化温度降低和时间延长,F_(max)、F_(max)-F_L和定伸应力整体上呈增大趋势,拉伸强度和撕裂强度先增大到一个极值后减小;耐磨性能逐步提高;压缩温升从135℃开始逐步降低,生热性能提高。 相似文献
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《国际聚合物材料杂志》2012,61(9):878-890
The thermal behavior of poly-L-lactide (PLLA) isothermal crystallization upon cooling from the melt was investigated using differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD) and polarizing microscope (POM) by changing the crystallization temperature and time. It was indicated that 110°C should be a critical temperature for PLLA melting crystallization. The melting point of crystallized PLLA discontinuously changed with crystallization temperature, increased with temperature, but decreased at about 110°C, and thereafter again increased with higher crystallization temperatures. At 110°C a multiple endothermic peak was observed. PLLA crystals of higher perfection form when crystallized under higher temperature, which reflects the effects of high chain mobility in higher temperatures. During isothermal crystallization, PLLA crystallites become increasingly perfect, and thicken with prolonged time, leading to an increasing melting point. 相似文献
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为了增强碳化硅(SiC)的光致发光性能,设计了三层结构的多孔SiC薄膜,衬底是单晶硅,中间层是双通阳极氧化铝(AAO)模板,顶层是SiC薄膜。采用磁控溅射工艺在AAO模板上沉积SiC薄膜,沉积温度为100~500 ℃,溅射时间为1~30 min。研究了沉积温度和沉积时间对SiC的光致发光性能的影响。结果表明:SiC薄膜为非晶态,SiC主要沉积在AAO模板的上层骨架结构上;与未经过溅射的样品相比,当衬底温度为200 ℃,溅射时间为1 min时, SiC的荧光性能增强至14.23倍;多孔SiC薄膜的荧光主要来自2.3 eV的主峰和2.8 eV的次主峰,主峰可能来自Al2O3的O缺陷发光与SiC本征发光,次主峰可能来自SiO2的O缺陷发光。磁控溅射结合双通AAO模板法可应用于多孔荧光SiC薄膜的工业化快速制备。 相似文献
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研究了二段硫化条件(硫化温度和硫化时间)对均聚氯醚橡胶(CO)基本性能和压缩永久变形性能的影响。结果表明,二段硫化温度越高,硫化时间越长,胶料的拉伸强度和定伸应力越大,硬度越高;而撕裂强度、伸长率、拉断永久变形以及压缩永久变形越小,其中胶料的硬度、拉伸强度、伸长率、压缩永久变形在一定时间后基本上趋于平衡,较好的二段硫化条件为150℃~160℃×3~4h。 相似文献
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以提高间歇式微生物发酵的产品得率为目标 ,利用BP神经网络和本文提出的傅立叶神经网络 ,提出发酵过程的发酵时间模型和最优发酵温度模型 ;在此基础上 ,提出了针对不同生产批次采用不同的最优发酵温度的新方法 ,此方法使不同生产批次的发酵过程都可以在适合其自身的最优的发酵温度下进行发酵 ,从而提高发酵生产的得率。实践应用表明 ,采用此种生产方案 ,产品平均得率提高 5 %。 相似文献