NaY母液回收与利用技术探讨

主要介绍了利用NaY（或NaX）母液和硫酸铝反应制备出硅铝胶，并用于合成NaY分子筛的原理及工业生产应用。考察分析了硅铝胶制备过程中的几个重要影响因素，重点研究了硅铝胶加入量及母液和硅铝胶的放置时间对NaY质量的影响。研究结果表明：硅铝胶反应pH值不同，凝胶速度不同，原料的利用率也不同；硅铝胶加入量在15％-45％之间时，对NaY质量影响不大，进一步提高硅铝胶的比例时，因硅铝胶中含有的铝已经超过了NaY成胶配方中所需的铝量，无法使用；母液放置时问较长时，由于形成其他晶型，回收利用后对NaY质量影响严重。     

L型沸石的离子交换与脱铝改性研究

为了改善L型沸石的催化性能,优化其在FCC中的应用,对L沸石进行离子交换和脱铝的改性研究。考察离子交换时间和离子交换方式对降低L沸石中氧化钾含量的影响及水热焙烧和化学脱铝对提高L沸石硅铝物质的量比的影响。结果表明,L型沸石离子交换时间不易过长,较适宜的时间为3 h。离子交换和水蒸汽处理相结合对降低L型沸石的钾含量更有效,离子交换和水蒸汽处理交替进行3次的样品氧化钾质量分数可降至0.82%。水热焙烧和化学脱铝能使L型沸石显著脱铝,其中,经过700 ℃水蒸汽处理1 h,再进行盐酸处理而制得改性L型沸石样品的硅铝物质的量比可达21.91,相对结晶度高于80％。     

高硅铝比NaY分子筛的合成

采用动态水热晶化法,利用工业原料不加模板剂直接合成高硅铝比的NaY分子筛,制备的NaY分子筛的硅铝物质的量比稳定在5.85~6.05,相对结晶度大于85%。考察了导向剂陈化时间及温度、体系碱度、预晶化温度及时间等对合成的NaY分子筛硅铝比和结晶度的影响,提出制备高硅NaY的最佳合成条件。     

低硅铝比EU-1沸石的合成与表征

对合成低硅铝比n(Si O2)/n(Al2O3)EU-1沸石过程中的硅源、晶化时间以及硅铝比进行了研究,研究结果表明:硅源选择硅溶胶最合适,硅铝比可以低到20,硅铝比为20的EU-1沸石的晶化时间为65 h即可,延长晶化时间对产品没有太大影响。以标准的EU-1沸石作为参考,对合成的硅铝比为20的EU-1沸石做了X-射线衍射(XRD)、红外光谱(FT-IR)、扫描电镜(SEM)和低温N2吸附-脱附等表征,结果表明:该法合成的硅铝比为20的EU-1沸石具有较好的结晶度,晶体形貌规整,具有适中的比表面积,孔结构发达,微孔和介孔分布比较均一。     

含铁沸石分子筛中硅铝比的测定

针对含铁沸石分子筛,提出用硅钼蓝光度法测硅,用EDTA和硝酸铅滴定法测铝铁合量,再用磺基水杨酸光度法测铁,根据测试结果计算硅、铝、铁的含量及求出硅铝物质的量比,并通过实验证明该方法简单可行。通过硅铝物质的量比的测定,能为分子筛产品的性能提供重要参考指标和理论依据,而且,根据实际需要,还可调整沸石的硅铝物质的量比,来满足所需性能。另外,本方法因为所需化学药剂常见,在一般实验室均可进行,所以在经济上和适用范围上都有较明显的优势,参考价值显著。     

丝光沸石酸脱铝及吸附性能研究

对丝光沸石直接酸脱铝进行了研究.考察了盐酸和草酸分别作用于丝光沸石的脱铝效果.通过N2吸附等温线的测定,考察了脱铝丝光沸石的吸附性能.实验结果表明,酸处理可以明显提高丝光沸石的Si/Al比,草酸的脱铝效果更好,但沸石的结晶度有所降低.     

连续滴定法测定甘氨酸铝锆中铝和锆的含量

采用连续滴定法测得甘氨酸铝锆中铝和锆的含量。采用EDTA络合滴定的实验方案,先将甘氨酸铝锆固体粉末配制成溶液,并将溶液的pH值调节在0.5～1之间,以二甲酚橙为指示剂,用EDTA滴定测得锆的含量;再将此溶液的pH值调节在5～6之间,然后加入过量的EDTA溶液,让铝离子与EDTA充分络合,最后过量的EDTA用硫酸锌标准溶液进行返滴定,从而测得铝离子的含量。实验证明,该法简便,结果准确。     

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。     

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％).     

沸石分子筛的高效绿色合成

通过不同方法,优化Sodalite沸石的晶化过程。采用加入过硫酸钠的方法,以及不同硅铝比配比的方法,测试不同时间Sodalite沸石的晶化效果。采用X-射线衍射(XRD)表征不同时间Sodalite沸石的晶化程度。结果表明,加入过硫酸钠后,Sodalite沸石的晶化速度明显加快,且以硅铝比为0.23的配比进行晶化,可以加快Sodalite沸石的晶化。此研究对高效合成沸石分子筛具有重大意义。     

Acid properties of mazzite zeolites studied by IR spectroscopy

The adsorption of ammonia, pyridine and benzene on non-dealuminated (Si/Al = 4.4) and dealuminated (Si/Al = 10 and 30) mazzite samples was followed by FT-IR spectroscopy. The dealumination of mazzites (by steaming and acid treatment) made all their narrow channels accessible to pyridine. Pyridine and ammonia adsorption and desorption showed that the broad OH band at approximately 3600 cm⁻¹ was composed of several submaxima corresponding to hydroxyl groups of various localizations and various acid strengths. With all the mazzite samples, the concentrations of Brönsted acid sites determined by ammonia adsorption were comparable with the values calculated from the chemical composition of zeolites (amounts of Al minus amount of Na) whereas those determined from pyridine adsorption were lower than these values. The greatest difference was found for the non-dealuminated MAZ-4.4, in which pyridine could not reach the sites of the narrow channels. The values of the extinction coefficients corresponding to the OH groups located in the large channels were higher than those corresponding to the OH groups of the narrow channels, thus showing the stronger acidity of the former OH groups. The acid strength of OH groups increased with the dealumination, as seen from the increase in the corresponding extinction coefficient and frequency shift Δν due to the hydrogen bonding of hydroxyl groups with benzene. Furthermore, the protonic acidity of the dealuminated mazzite of Si/Al = 30 was found to be stronger than that of mordenite and beta zeolite with comparable Si/Al.     

Dealumination of Zeolite Beta Catalyst Under Controlled Conditions for Enhancing its Activity in Acylation and Esterification

This work deals with the dealumination of zeolite beta under different conditions to optimize its catalytic performance. The dealumination was carried out either using oxalic or tartaric acid solution of different pH values or steaming up to 500 °C. The dealuminated zeolite samples were characterized using X-ray diffraction, N₂-physisorption, ICP, ²⁷Al NMR and NH₃-TPD. Their catalytic activities were studied for acylation reaction of 2-methoxy naphthalene or naphthalene with acetic anhydride and esterification of benzyl alcohol with hexanoic acid. Among the dealuminated samples examined, those treated with oxalic acid or tartaric acid at pH 2 showed high activity. The high activity can be correlated with the relative increase in the amount of strong acid sites and with the enhanced accessibility of the reactants to the active sites, which are caused by removal of extra-framework Al species on the acid treatments.     

Effects of steaming-made changes in physicochemical properties of Y-zeolite on cracking of bulky 1,3,5-triisopropylbenzene and coke formation

The effects of acidic properties and structural changes of Y zeolite, produced by steaming, on the zeolite cracking activity, coking tendency and distribution of various products during catalytic conversion of bulky 1,3,5-triisopropylbenzene (TIPB) are reported. NaY zeolite with framework Si/Al ratio of 2.4 was synthesized by a hydrothermal method and ammonium exchanged. The zeolite was dealuminated by a temperature-programmed steaming to form USY1 and USY2 zeolites with framework Si/Al ratio of 8.1 and 12.3 respectively. The catalysts were characterized by XRD, XRF, SEM, AAS, NH₃–TPD and N₂ adsorption–desorption techniques. The samples were in-situ activated at 748 K and evaluated by TIPB cracking at 623 K. The coke content of the catalyst beds was estimated by TPO using an FT-IR gas cell. The results of activity measurements reveal that the dealuminated zeolites lead to lower cracking activity initially; while, they exhibit higher activity at longer times. In addition, a slight modification of the window diameter of Y zeolite, as revealed by pore size distribution analyses, alters the diffusion limitation of the reactant and products through the pores of the zeolite and significantly affects the adsorbent–adsorbate interactions. TPO experiments show that compared to the precursor zeolite, lower amount of coke is formed on the dealuminated catalysts possessing lower density of acid sites. However, the coke formed on USY samples is heavier than that formed on its precursor Y zeolite. This may be attributed to the larger pores shaped in the dealuminated catalysts which in turn provide suitable places for coke formation and growth.     

介孔构建对CuY甲醇氧化羰基化反应活性的影响

采用H₄EDTA、H₂Na₂EDTA和NaOH溶液对原始NaY分子筛分别进行单独酸碱改性和酸碱连续改性,并采用液相离子交换法制备相应的CuY催化剂。结合N₂物理吸附、TEM、XRD、²⁹Si NMR、²⁷Al NMR、NH₃-TPD、Py-IR、ICP、XPS和CO-FTIR等对载体和催化剂的结构进行表征,研究了NaY分子筛介孔构建对CuY催化甲醇氧化羰基化反应活性的影响。结果表明,NaY分子筛经H₄EDTA单独处理后,部分骨架铝被脱除形成非骨架硅铝物种,得到的E-NaY并未形成明显的介孔;E-NaY经H₂Na₂EDTA酸洗处理后,非骨架铝和部分骨架铝被脱除,得到的EW-NaY具有明显的介孔结构;而E-NaY和EW-NaY经0.2 mol/L NaOH碱处理后,分子筛发生脱硅,同时伴随着非骨架铝重新插回分子筛骨架,得到的E0.2AT-NaY和EW0.2AT-NaY具有丰富的介孔结构。其中,EW0.2AT-NaY的介孔孔容（0.45 cm³/g）最大,且有丰富的Al缺陷结构,能够与反应物接触的Cu⁺交换位利用率最高。然而,由于EW0.2AT-NaY脱铝程度明显高于E0.2AT-NaY,导致能够与反应物接触的Cu⁺交换位数量（66 μmol/g）明显小于E0.2AT-NaY（176 μmol/g）,最终导致EW0.2AT-CuY催化剂中Cu⁺活性位数量及催化活性略低于E0.2AT-CuY,二者的催化活性约为原始CuY催化剂的2.2倍。     

Using ultrasound to improve the sequential post-synthesis modification method for making mesoporous Y zeolites

Mesoporous Y zeolites were prepared by the sequential chemical dealumination (using chelating agents such as ethylenediaminetetraacetic acid, H₄EDTA, and citric acid aqueous solutions) and alkaline desilication (using sodium hydroxide, NaOH, aqueous solutions) treatments. Specifically, the ultrasound-assisted alkaline treatment (i.e., ultrasonic treatment) was proposed as the alternative to conventional alkaline treatments which are performed under hydrothermal conditions. In comparison with the hydrothermal alkaline treatment, the ultrasonic treatment showed the comparatively enhanced efficiency (with the reduced treatment time, i.e., 5 min vs. 30 min, all with 0.2 mol·L⁻¹ NaOH at 65°C) in treating the dealuminated Y zeolites for creating mesoporosity. For example, after the treatment of a dealuminated zeolite Y (using 0.1 mol·L⁻¹ H₄EDTA at 100°C for 6 h), the ultrasonic treatment produced the mesoporous zeolite Y with the specific external surface area (S_external) of 160 m²·g⁻¹ and mesopore volume (V_meso) of 0.22 cm³·g⁻¹, being slightly higher than that by the conventional method (i.e., S_external = 128 m²·g⁻¹ and V_meso = 0.19 cm³·g⁻¹). The acidic property and catalytic activity (in catalytic cracking of n-octane) of mesoporous Y zeolites obtained by the two methods were comparable. The ultrasonic desilication treatment was found to be generic, also being effective to treat the dealuminated Y zeolites by citric acid. Additionally, the first step of chemical dealumination treatment was crucial to enable the effective creation of mesopores in the parent Y zeolite (with a silicon-to-aluminium ratio, Si/Al= 2.6) regardless of the subsequent alkaline desilication treatment (i.e., ultrasonic or hydrothermal). Therefore, appropriate selection of the condition of the chemical dealumination treatment based on the property of parent zeolites, such as Si/Al ratio and crystallinity, is important for making mesoporous zeolites effectively.     

Catalytic properties of dealuminated and cation-exchanged Y-type zeolites

Cumene dealkylation activity was determined for a series of dealuminated zeolites which were prepared by treatments with EDTA, SiCI₄, and steam al elevated temperatures. Upon dealumination the catalytic activity increased progressively up to 50% of framework aluminum removal. This is related to the increase of acid strength after aluminum removal and the extraction of weak acid site. However, beyond Si/Ai ratio close to 6, the acid strength of zeolite do not vary and the TOF based on framework aluminum is constant. Nonframework aluminum played a positive role in the enhanced catalytic activity. The variation of catalytic activity with cation was also examined. Catalytic activity is greatest for the small polyvalent cations. Comparison of the hydroxyl group with catalytic activity shows that the active sites are the acidic hydroxyl groups.     

The catalytic and acidic properties of an i‐Pr2NH‐templated SAPO‐11 and dealuminated derivatives

Crystalline silicoaluminophosphate (SAPO‐11) samples were synthesized with i‐Pr₂NH as a novel template, then dealuminated in H₄EDTA solution. These samples were characterized by catalytic skeletal isomerization of linear butylenes, IR analysis of adsorbed pyridine and ³¹P, ²⁹Si MAS‐NMR. Strong acid sites were concerned with Si domains, that were formed by either increasing the Si content of SAPO‐11 via a synthesis process or dealuminating treatment of as‐synthesized SAPO‐11. Acid sites of medium strength were located around isolated Si together with adjacent Al and the second nearest element P. Deep dealumination led to amorphous AlPO₄, and reduced crystallinity degree. The maximum yield of isobutylene in catalytic skeletal isomerization of linear butylenes were achieved around 763 K. It was confirmed that these reactions were mainly performed on Brønsted acid sites of medium strength.     

Hydrothermal stability of dealuminated mordenite type zeolite catalysts for the reduction of NO by C3H6 under lean-burn condition

Hydrothermal stability of mordenite type catalysts including synthetic (CuHM) and natural (CuNZA) zeolites has been examined under a simulated lean NO_x wet condition. When the catalysts were hydrothermally aged at 800°C with 10% H₂O for 6 h, the NO removal activity at the reaction temperature of 450°C was higher for natural zeolite than for synthetic one. It was mainly due to the Si/Al ratio of the catalyst. CuHM and CuNZA catalysts were dealuminated to investigate the effect of Si content of the zeolites on the hydrothermal stability. After the aging at 800°C for 24 h in the presence of 10% H₂O, NO removal activity of the dealuminated CuHM catalysts at the reaction temperature of 500°C was in the order of the Si/Al ratio of the catalysts. Such a significant improvement of the deNO_x performance was also observed for the dealuminated CuNZA catalysts. It reveals that the Si/Al ratio of zeolite catalysts is one of the crucial characteristics enhancing the water tolerance and hydrothermal stability of the catalysts for NO reduction under the lean NO_x wet condition. In addition, the loss of NO removal activity of the catalysts upon the hydrothermal aging is mainly attributed to the chemical alteration of Cu²⁺ ions on the catalyst surface through the structural collapse of the zeolite catalysts.     

Untersuchungen an dealuminierten Mordenit-Katalysatoren

Studies on dealuminated mordenite catalysts . Some basic aspects of zeolite structure and chemistry are introduced. Subsequently, an industrially important representative of these porous aluminosilicates, viz. mordenite, is treated in more detail. Particular attention is paid to its dealuminated modifications. The most important techniques of zeolite dealumination are presented in a general way. The effect of dealumination on chemical and physical properties of mordenite is discussed, in particular the influence on Brßonsted and Lewis acidity, adsorption, and diffusion, these being the fundamental phenomena in the context of catalysis on mordenites. Catalytic behaviour of dealuminated mordenites is reviewed with respect to a series of basic reactions including cracking, hydrocracking, and isomerisation of paraffins, dealkylation and disproportionation of alkylbenzenes, as well as coke formation. Correlations between activity and/or selectivity and both chemical and structural properties of dealuminated mordenites are demonstrated.     

纳米NaY分子筛复合材料的制备、表征及催化性能

在偏高岭土水热合成NaY分子筛的晶化过程中采用超声波陈化的方法,制备出了纳米NaY分子筛复合材料,采用XRD、SEM、TEM、HREM对其结构进行了表征,考察了其物化性质和催化性能,并和常规分子筛的催化性能作了比较。结果表明,用该方法合成的分子筛复合材料,颗粒大小为100nm左右,结晶度80.12%,硅铝摩尔比值5.12,比表面积762m2/g,中孔体积分数15.33%,结构崩塌温度901℃;用含该纳米分子筛的催化剂进行催化反应时,催化剂微分活性74%,汽油产率65.7%,焦炭产率2.3%。