焙烧高岭土水热合成高硅铝比小晶粒NaY分子筛

采用不同温度对高岭土进行焙烧活化,以焙烧高岭土为原料,在水热条件下直接法合成了高硅铝比小晶粒NaY分子筛.考察了晶种胶添加量、高土/偏土比例以及投料硅铝比对晶化过程和产物性质的影响.研究结果表明,在晶种胶添加量为14wt％、高土/偏土比例为1及投料硅铝比为15.0的条件下,以焙烧高岭土为原料合成的NaY样品的相对结晶度为77％,骨架硅铝比高达6.3,晶粒尺寸为300 ～ 600 nm.重油催化裂化性能评价结果表明,以高岭土合成NaY样品制备的催化剂DUT-E,具有优异的重油催化裂化活性(93.6％),高汽油收率(56.8％)及很低的焦炭产率(3.1％).     

高岭土的碱溶活化及合成高结晶度Y分子筛

以苏州高岭土为原料,经碱熔活化、补硅,在优化的合成条件下,可以原位水热合成NaY分子筛.详细考察焙烧温度对高岭土碱熔活化的影响,考察晶化时间、导向剂和合成体系中硅铝比和水钠比等因素对产物的影响.采用XRD结晶产物的晶态结构进行了表征.结果表明,以高岭土为原料可以合成出硅铝比较高、高结晶度、无杂晶的NaY分子筛.     

低Na_2O/Al_2O_3比凝胶一步晶化法合成高硅小晶粒NaY分子筛

NaY晶体的n(Na_2O)∶n(Al_2O_3)=1.0,但现有NaY合成工艺的起始凝胶的n(Na_2O)/n(Al_2O_3)均较高,导致大量原料中的Na_2O及相应量其他组分没有转化为产品,而是进入晶化母液被滤除,因此NaY生产企业期望采用更低n(Na_2O)∶n(Al_2O_3)的凝胶来提高NaY合成收率。对起始凝胶Na_2O与Al_2O_3物质的量比为3.84~4.64的水热合成NaY分子筛做了研究。结果表明,在100℃以下晶化时,n(Na_2O)∶n(Al_2O_3)=3.84的低碱度凝胶不能晶化出NaY分子筛;在100℃以上晶化时,n(Na_2O)∶n(Al_2O_3)=3.84的低碱度凝胶能够晶化出结晶度、硅铝比(Si O2与Al_2O_3物质的量比,下同)均较高且无杂晶的NaY。其最佳的晶化条件:晶化温度为110℃、晶化时间为30 h。并可重复制备出平均结晶度为95%、平均骨架硅铝比为5.93、典型粒径约为1μm的小晶粒NaY分子筛,原料平均转化率达68.2%。     

超细NaY分子筛的合成

在没有添加剂的条件下,研究了以工业级水玻璃为原料原位水热合成超细NaY分子筛,并采用XRD、TEM、BET等方法对所合成的分子筛进行了表征.考察了陈化时间、碱度、晶化时间、晶化温度对NaY分子筛结晶度和晶粒大小的影响.结果表明:在陈化时间64h、硅铝胶组成x为6.0、晶化时间4h、晶化温度100℃的优化条件下,合成了晶粒尺寸小于200 nm的NaY分子筛.     

小晶粒高硅铝比NaY分子筛低温合成研究

采用自制的偏铝酸钠为合成导向剂,在低温下水热晶化合成出了小晶粒高硅铝比的NaY分子筛。考察了合成导向剂的陈化温度、陈化时间、晶化碱度、晶化温度和晶化时间对产品的影响,得到了制备NaY分子筛最佳的工艺条件,并进行了放大制备。在此条件下,NaY分子筛结晶度(峰面积)≥90%,结晶度(峰高)≥85%,硅铝比≥5.5,晶粒尺寸均在(100～200) nm,不仅优于工业标样的指标要求,且易于放大。     

SAPO-34分子筛形貌和粒径的影响因素考察

以四乙基氢氧化铵为模板剂,水热合成法制备SAPO-34分子筛,采用XRD和SEM进行表征,考察硅铝比、晶化温度、晶化时间和陈化时间对分子筛形貌和粒径的影响。结果表明,在硅铝物质的量比为0.8、晶化温度200℃、晶化时间24 h和陈化时间4 h条件下,可合成晶粒均匀和晶体表面光滑的粒径仅为2μm的SAPO-34分子筛。     

高硅铝比小晶粒NaY分子筛/高岭土复合物的合成及其催化裂化性能

以两种不同粒径的高岭土为原料,采用水热法合成了高硅铝比小晶粒NaY分子筛/高岭土复合物,通过XRD、SEM、晶粒度分析和N₂物理吸附等表征手段对复合物进行了结构和形貌表征。结果表明,与商品NaY相比,高岭土合成样品的结构稳定性和水热稳定性显著提高,以细化高岭土为原料合成样品的晶粒尺寸达310 nm,比表面积达807 m²·g^-1。以改性NaY分子筛/高岭土复合物为活性组分制备了催化裂化催化剂,采用NH₃程序升温脱附(NH₃-TPD)技术对其酸性特征进行了分析,并在小型微反装置上对其重油催化裂化性能进行了评价。研究结果发现,随着骨架硅铝比增大,催化剂表面酸中心强度增加,而酸量下降。采用细化高岭土合成的NaY分子筛/高岭土复合物的分子筛晶粒更小,催化剂酸中心数量以及催化裂化性能均大幅度提升。随着高温焙烧高岭土/偏高岭土质量比的增加,合成产物中的高岭土基质含量增加,催化剂表面酸中心强度下降。以原料高温焙烧高岭土/偏高岭土质量比为0.5,骨架硅铝比为6.1(摩尔比)的样品制备的催化剂,去柴重油转化率高达85.4%,同时有高达64.2%的汽油收率,表现出优异的重油催化裂化性能。     

高岭土微球上晶种法原位合成ZSM-5分子筛的研究

以HZSM-5为晶种,水热条件下考察在高岭土微球上原位晶化合成ZSM-5分子筛的碱硅比、水硅比、晶化时间、晶化温度、晶种投入量和投料硅铝比等合成条件对晶化产物的影响,并对合成的ZSM-5进行了表征。结果表明,在晶化温度170 ℃、投料硅铝比90~150、晶种投入量10%、碱硅比0.15~0.2和水硅比20的条件下晶化一定时间,在高岭土微球上成功合成出粒径（1~2） μm、结晶度40%的ZSM-5分子筛晶体。     

动态晶化法合成N aP分子筛的研究

以硅酸钠和偏铝酸钠为原料,采用水热动态晶化法制备NaP分子筛,通过XRD,SEM,BET,PSD,FTIR表征手段对样品进行分析,考察了不同的硅铝比、晶化温度和动态转速对分子筛合成的影响,并对晶化过程进行了研究.结果表明在一定范围内提高初始原料的硅铝比、晶化温度、晶化时间和动态转速,有利于提高NaP分子筛的纯度.通过优化合成条件,在硅铝比为2.00,晶化温度为120℃,晶化时间为8 h,动态转速为70 r/min的条件下合成了粒径约为1.8μm的NaP分子筛.与静态晶化相比,动态晶化过程成核期较短,导致所需晶化时间显著降低,且合成产物具有较大的比表面积和孔径分布.     

模板剂法水热合成高硅铝比ZSM-5分子筛

以工业水玻璃和硫酸铝为主要原料,正丁胺为模板剂,利用水热法合成出了高硅铝比ZSM-5分子筛。考察了晶化时间、晶化温度、投料硅铝比、合成体系pH值以及模板剂用量等因素对晶化产物的影响。采用X射线衍射、傅里叶变换红外光谱、低温氮气吸脱附、核磁共振、扫描电子显微镜等手段对合成样品进行了表征。结果表明:合成ZSM-5分子筛最适宜的条件为:晶化时间36h,晶化温度170℃,投料硅铝比200,合成体系的pH=11.0,模板剂加入量为模硅比0.2。在最适宜条件下合成得到的ZSM-5分子筛产物具有高的相对结晶度,BET比表面积为335m2/g,晶粒尺寸约为5μm×15μm,骨架硅铝比大于100。     

预成型高岭土干胶转化合成NaY型分子筛

通过干胶转化法制备了整体式NaY分子筛,采用XRD、SEM及XRF分析表征原料及产物,系统考察了合成体系的n（SiO₂）/n（Al₂O₃）、n（Na₂O）/n（SiO₂）、水量、晶化温度和晶化时间对整体式NaY分子筛制备的影响。结果表明,合成体系n（SiO₂）/n（Al₂O₃）=7.5时,骨架硅铝比（二氧化硅与氧化铝物质的量比）最大为6.12;n（Na₂O）/n（SiO₂）逐渐增大,整体式NaY分子筛结晶度逐渐升高,当n（Na₂O）/n（SiO₂）增至0.35时,会导致P型分子筛的生成;晶化温度从90 ℃逐渐增至120 ℃时,整体式NaY分子筛结晶度也随之升高;在110 ℃下晶化20 h,产物的结晶度达到98%并趋于稳定。干胶转化制备整体式NaY分子筛必须有水的参与,n（H₂O）/n（SiO₂）为4.2左右对反应物的成型及整体式NaY分子筛的晶化较为适宜。     

ZrO2/SiO2- and La2O3/Al2O3-supported platinum catalysts for CH4/CO2 reforming

Surface-phase ZrO₂ on SiO₂ (SZrOs) and surface-phase La₂O₃ on Al₂O₃ (SLaOs) were prepared with various loadings of ZrO₂ and La₂O₃, characterized and used as supports for preparing Pt/SZrOs and Pt/SLaOs catalysts. CH₄/CO₂ reforming over the Pt/SZrOs and Pt/SLaOs catalysts was examined and compared with Pt/Al₂O₃ and Pt/SiO₂ catalysts. CO₂ or CH₄ pulse reaction/adsorption analysis was employed to elucidate the effects of these surface-phase oxides.

The zirconia can be homogeneously dispersed on SiO₂ to form a stable surface-phase oxide. The lanthana cannot be spread well on Al₂O₃, but it forms a stable amorphous oxide with Al₂O₃. The Pt/SZrOs and Pt/SLaOs catalysts showed higher steady activity than did Pt/SiO₂ and Pt/Al₂O₃ by a factor of three to four. The Pt/SZrOs and Pt/SLaOs catalysts were also much more stable than the Pt/SiO₂ and Pt/Al₂O₃ catalysts for long stream time and for reforming temperatures above 700 °C. These findings were attributed to the activation of CO₂ adsorbed on the basic sites of SZrOs and SLaOs.     

Ni/Al_2O_3催化剂的CO_2-TPD表征

Ni/Al_2O_3催化剂是甲烷二氧化碳重整反应制取合成气研究最多、最具应用潜力的一种催化剂。通过对催化剂进行CO_2-TPD研究,考察还原态Ni/Al_2O_3催化剂的CO_2脱附特性。结果表明,浸渍法制备的Ni/Al_2O_3催化剂CO_2脱附曲线呈现双峰,分别在(60~65)℃和(350~380)℃出现高低温两个活性位;高温CO_2吸附量为3.0 cm~3·g~(-1),低温CO_2吸附量为24.0 cm~3·g~(-1)。催化剂的CO_2吸附量与其Ni含量无关。考察选用不同载体的CO_2脱附行为,发现以Al_2O_3为载体的催化剂CO_2吸附量是MgO和SiO_2为载体催化剂的2~4倍,以TiO_2为载体的催化剂几乎不吸附CO_2。     

NiO/Al_2O_3基催化剂的TPR特性研究

NiO/Al_2O_3基催化剂用于替代贵金属催化剂,被广泛应用于石油和石化领域生产过程的加氢、脱硫和脱氮。采用TPR方法,研究不同Ni含量NiO/Al_2O_3及不同载体的催化剂还原特性。结果表明,NiO/Al_2O_3催化剂在10%H_2-Ar气氛下,还原温度范围较宽,为(300~800)℃,其中,(500~600)℃还原速率最大;随着NiO含量的增加,起始还原温度降低,还原耗氢量按比例增加;以MgO为载体的NiO催化剂还原呈现双峰特征,以SiO2和TiO2为载体的NiO催化剂的初始还原温度比NiO/Al_2O_3催化剂降低(100~200)℃。     

Lean NOx reduction with CO + H2 mixtures over Pt/Al2O3 and Pd/Al2O3 catalysts

The reduction of NO_x by hydrogen under lean burn conditions over Pt/Al₂O₃ is strongly poisoned by carbon monoxide. This is due to the strong adsorption and subsequent high coverage of CO, which significantly increases the temperature required to initiate the reaction. Even relatively small concentrations of CO dramatically reduce the maximum NO_x conversions achievable. In contrast, the presence of CO has a pronounced promoting influence in the case of Pd/Al₂O₃. In this case, although pure H₂ and pure CO are ineffective for NO_x reduction under lean burn conditions, H₂/CO mixtures are very effective. With a realistic (1:3) H₂:CO ratio, typical of actual exhaust gas, Pd/Al₂O₃ is significantly more active than Pt/Al₂O₃, delivering 45% NO_x conversion at 160 °C, compared to >15% for Pt/Al₂O₃ under identical conditions. The nature of the support is also critically important, with Pd/Al₂O₃ being much more active than Pd/SiO₂. Possible mechanisms for the improved performance of Pd/Al₂O₃ in the presence of H₂+CO are discussed.     

Effect of SiO2/Al2O3 ratio on the conversion of methanol to olefins over molecular sieve catalysts

A series of SAPO-34 molecular sieves with different SiO₂/Al₂O₃ ratios have been synthesized for the methanol-to-olefin (MTO) reaction. Their physico-chemical properties are characterized by various techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR) and N₂ adsorption-desorption. The results are compared with those of the commercial HZSM-5, which show that the crystallinity and particle diameter of SAPO-34 as well as HZSM-5 increase with SiO₂/Al₂O₃ ratio. The variation of BET surface area of SAPO-34 is different from that of HZSM-5 and the sample with SiO₂/Al₂O₃ ratio of 0.4 exhibits the highest BET surface area. FT-IR spectra indicate that HZSM-5 has both Br?nsted and Lewis acid sites and Br?nsted acid sites are stronger, whereas SAPO-34 samples are dominated only by Lewis acid sites. When the SiO₂/Al₂O₃ ratio increases, propylene and butylenes become the predominant product of the MTO reaction over HZSM-5. In contrast, the main products of this reaction catalyzed by SAPO-34 are ethylene and propylene. According to the product distribution, the reaction mechanism over HZSM-5 catalysts is proposed.     

Microstructure and flexure creep behaviour of SiC-particle reinforced Al2O3 matrix composites

The flexure creep behaviour of monolithic Al₂O₃ and 10 vol% SiC-particle reinforced Al₂O₃ matrix composites was investigated in air atmosphere at 1160 to 1400 °C and under a stress of 40 to 125 MPa. Two kinds of SiC particles with different particle sizes and oxygen contents were used in the composites, one having an average size of 0.6 μm with 1.7 vol% SiO₂ impurities and the other of average size 2.7 μm with 3.4 vol% SiO₂ impurities. Compared with the creep behaviour of monolithic Al₂O₃ the strain rate of the composites with 0.6 μm SiC particles did not decrease; however, the composites with 2.7 μm SiC particles exhibited excellent creep resistance. Microstructure analysis showed that the Al₂O₃ grains in the composites with 0.6 μm SiC particles were mainly equiaxed with most of the SiC particles lying at the grain boundaries or triplegrain junctions, whereas the grain features of the composites with 2.7 μm SiC particles were irregular and elongated and most of the SiC particles were entrapped into Al₂O₃ matrix grains. It was revealed that the entrapment of 2.7 μm SiC particles into Al₂O₃ matrix grains was related to the high SiO₂ impurity content on SiC particle surfaces, and the change of grain morphology and the good high-temperature oxidation resistance were responsible for the creep resistance increase of the composites with 2.7 μm SiC particles.     

超稳Y型分子筛的骨架硅铝比对甘油气相脱水反应的影响

以铵交换和高温水热处理法制备了不同硅铝比的超稳Y型分子筛（USY）,利用X射线衍射、扫描电镜、氮气吸附脱附和吡啶红外等技术对USY进行了表征。以USY为催化剂,考察了USY的骨架硅铝比对气相甘油脱水制丙烯醛的影响。X射线衍射和扫描电镜结果表明,铵交换和高温水热处理只是提高USY的硅铝比,相对结晶度略有降低,而对Y型分子筛的结构和形貌没有影响。氮气吸附-脱附和吡啶红外结果表明,随USY骨架SiO₂/Al₂O₃比提高,总酸量和B酸酸量逐渐降低,L酸酸量有所增多,介孔孔体积和平均孔径有所增大。气相甘油脱水反应结果表明,催化剂织构性质对甘油转化率和丙烯醛选择性的影响大于酸性的影响,因而SiO₂/Al₂O₃比为29的USY催化剂的反应性能最好,甘油转化率和丙烯醛收率分别达到了84.5%和51.8%。     

TiO2与SiO2掺杂对Al2O3相转变的研究

通过球磨混合法,制备TiO2、SiO2和TiO2+SiO2掺杂的Al2 O3粉体,经不同温度煅烧后进行X射线衍射(XRD)测试,比较研究这三种掺杂对Al2 O3粉体相转变温度的影响.研究结果表明,TiO2、SiO2掺杂对γ-Al2 O3向α-Al2 O3的相转变均有促进作用.在掺杂质量分数为0.5％的情况下,二者可分别...