Y型分子筛催化剂的表面酸性及催化性能的研究

利用吡啶吸附红外光谱(Py-IR)和X-射线衍射法表征了磷钨酸(PW)、氢氧化铌改性分子筛的表面酸性和结构,用催化法脱除芳烃中微量烯烃的烷基化反应研究其酸催化性质。结果表明,催化剂的结构、表面酸含量和磷钨酸、氢氧化铌在催化剂中所占的比例,都显著地影响烷基化反应;Dawson结构的磷钨酸比Kiggen结构的磷钨酸具有较好的催化烷基化反应活性;随着磷钨酸含量的增加,催化剂B酸量先增加后减少,L酸量减少;随着氢氧化铌含量的增加,总B酸量和L酸量都减少,催化剂的活性随总B酸量与总L酸量比值的增加而提高;用磷酸或草酸处理氢氧化铌,总B酸量与总L酸量的比值增大,可进一步提高分子筛的活性和寿命。研究结果还表明,强B酸不利于脱烯烃反应。     

Y分子筛的改性及在加氢脱氮反应中的催化性能

采用水热法与草酸脱铝相结合法对Y分子筛进行改性,用孔体积饱和浸渍法制备了Ni-W/γ-Al2O3-USY加氢精制催化剂,考察了改性Y分子筛对催化剂的酸性及催化剂的HDN活性的影响,并对制备的催化剂进行了酸性表征。随着草酸加入量的增多,催化剂的总酸量减少;随着处理温度的增高,弱酸和强酸量分别有不同程度的增多。催化剂中适量的USY可以明显提高催化剂的总酸量,并提供对喹啉HDN的适中酸强度,明显提高催化剂的HDN活性。     

磷改性高岭土型流化催化裂化催化剂的表面酸性及裂化性能的研究

采用磷元素改性高岭土型流化床催化裂化(FCC)催化剂,热重-程序升温脱附(TG-TPD)和红外(IR)酸性测试结果表明,磷改性的催化剂,能够降低催化剂总酸量,弱酸量和强酸量,可增加中强酸的酸量,可以降低催化剂的B酸强度和L酸中心数。在微反活性和小型固定流化床装置上评价了磷改性催化剂的反应性能,经过磷改性的催化剂,可提高催化活性,增强重油转化能力,改善焦炭和汽油选择性。     

磷改性杂原子B - ZSM -5分子筛催化剂结构及其在液化气芳构化的应用

水热合成了杂原子硼ZSM -5分子筛,利用浸渍法制备了系列不同磷含量的HB - ZSM -5催化剂,并用于液化气的芳构化反应.考察了不同磷含量对芳构化反应性能的影响,并与吡啶吸附红外光谱(FT-IR)和固体核磁(NMR)相关联,研究了磷改性处理对催化剂表面酸性的影响.结果表明,磷改性HB - ZSM -5的芳构化活性得...     

氢氧化铌改性沸石分子筛的表面酸性及其催化活性

利用吡啶吸附红外光谱(Py-IR)表征了氢氧化铌改性分子筛的表面酸性,用催化法脱除芳烃中微量烯烃的反应研究其酸催化活性。结果表明,氢氧化铌的引入导致催化剂表面Brφnsted酸中心和Lewis酸中心重新分布,总Brφnsted酸量和Lewis酸量都随氢氧化铌含量的增加而减少;强B酸不利于脱烯烃反应;催化剂的活性随总Brφnsted酸量与总Lewis酸量比例的增加而提高,用磷酸或草酸处理氢氧化铌,总Brφnsted酸量与总Lewis酸量的比例增大,可进一步提高分子筛的活性和寿命。     

在改性的ZSM-5分子筛催化剂上重质烃类的裂化/芳构化性能

本文以重质烃类(沸程350～400℃)为原料,研究了Zn、Ni和S元素改性后的ZSM-5催化剂的催化裂化/芳构化性能。并探讨了Ni和S元素在改性中所起的作用。结果表明,锌改性的ZSM-S分子筛催化剂引入Ni和S元素后,反应产物中的芳烃含量明显增加,Ni和S元素具有抑制催化剂表面积炭的形成和保持催化剂的芳构化活性的作用。     

ZSM-5催化剂上FCC汽油加氢脱硫及芳构化性能的研究

采用四丙基氢氧化铵与氢氧化钠混合碱溶液对ZSM-5分子筛进行改性,运用X射线衍射、扫描电镜、N2物理吸附和NH3程序升温脱附等手段对样品进行表征。结果表明,改性后HZSM-5分子筛的介孔数量增多,比表面积、孔体积增大,强酸位酸量增多。在催化裂化汽油加氢脱硫及芳构化反应中,ZSM-5分子筛催化剂性能优异,呈现出良好的脱硫性能及烯烃芳构化活性。在压力为3 MPa,温度为300℃,氢油体积比为300∶1,空速为1.5 h-1的条件下,FCC汽油脱硫率达到94.2%,芳烃产率为20.7%     

FCC汽油馏分在水热处理Zn/HZSM-5催化剂上的芳构化反应

制备了300 ℃、350 ℃、400 ℃和500 ℃不同水热处理温度下的Zn/HZSM-5催化剂，并用于FCC汽油馏分的芳构化反应。考察了水热处理温度对芳构化反应性能的影响，并与吡啶吸附红外光谱(FT-IR)相关联，研究了水热处理温度对催化剂表面酸性的影响。结果表明，水热处理Zn/HZSM-5的芳构化活性稳定性得以改善, 与未经水热处理的催化剂相比，400 ℃水热处理的Zn(2%)/HZSM-5催化剂芳构化反应36 h时，芳烃质量分数仍高达74.25%。随着水热处理温度的升高， B酸酸中心数在300～400 ℃变化不大，500 ℃显著减少，L酸酸中心数升高，400 ℃达到最大值后呈降低趋势，烯烃转化率、烷烃转化率和产品芳烃含量升高，水热处理400 ℃时均达到最大值，分别为83.62%、95.44%和92.23%，表明此时B酸中心和L酸中心比例协调性最佳。     

Ga改性的HZSM-5分子筛甲醇芳构化催化反应性能

以浸渍法和水热合成法向ZSM-5分子筛中引入Ga助剂对其进行改性。采用XRD、XPS、NH₃-TPD和SEM等技术对改性前后的分子筛进行了表征。结果表明,采用两种不同引入方式引入Ga助剂对分子筛的晶体结构、孔径及形貌影响均很小,而对分子筛酸性的影响与Ga的引入方式有关。其中,浸渍法引入Ga对分子筛的酸性影响不明显,只是其中的强酸位略有减少。而水热合成法引入Ga会显著增加分子筛的弱酸及强酸的酸量。在固定床反应器上考察了Ga的引入对HZSM-5催化剂甲醇芳构化催化性能的影响。结果表明,水热合成法引入Ga较浸渍法引入Ga更能提高甲醇芳构化反应的活性和芳烃选择性。此外,Ga改性HZSM-5分子筛对其甲醇芳构化反应中积炭反应的抑制起到积极作用。     

改性对ZSM-5分子筛芳构化性能的影响

ZSM-5分子筛由于具有独特的择形性、良好的水热稳定性、耐酸和抗积碳性能,因而被广泛应用于芳构化过程。综述了国内外对ZSM-5分子筛芳构化催化剂的改性方法。Zn的加入不仅能促进低碳烃的芳构化反应,而且能增强催化剂的抗积碳性能。随着磷的引入,液体收率增加,芳烃含量增加。Ga离子交换改性的ZSM-5对低碳烃类的芳构化有明显的催化作用。P—Zn／HZSM-5催化剂不仅表现出较高的初活性,而且具有良好的稳定性。经水热处理的ZSM-5分子筛具有良好的芳构化稳定性。纳米HZSM-5沸石催化剂具有很强的烃类转化能力,烃类通过芳构化、异构化和烷基化等反应转化为高辛烷值的异构烷烃和芳烃。     

Hβ沸石催化降解聚烯烃的研究

将Hβ沸石进行水热处理和酸处理改性后,其比表面积、总孔容及平均直径均增大,二次孔孔容占总孔容的387%以上,说明改性后的沸石具有更通畅的孔道和较多的二次孔, 总酸量减少,酸强度分布降低。热重分析研究了处理前后的Hβ沸石作催化剂对聚苯乙烯及聚乙烯催化降解的作用。结果表明,Hβ沸石能显著降低聚乙烯的热降解温度,对聚苯乙烯的热降解温度影响不大。催化剂的酸量对聚乙烯降解温度、活化能及积炭生成有很大的影响。催化剂酸量增加,聚乙烯的降解温度和活化能均明显下降,但积炭量增加。催化剂对聚苯乙烯的热降解影响主要取决于孔结构。     

正己烷在Zn/HZSM-5上芳构化反应机理的探讨

比较了正己烷在HZSM-5、Al₂O₃和ZnO/Al₂O₃催化剂上的反应性能，探讨了锌含量和水热处理对Zn/HZSM-5芳构化性能的影响。发现B酸是芳构化反应不可缺少的活性中心，Zn-L因其氢解作用促进烃类的活化和脱氢，Al-L酸只是对正己烷有较弱的活化作用。提出了正己烷在Zn/HZSM-5上的芳构化反应机理。     

Effect of nickel incorporation on the acidity and stability of HZSM-5 zeolite in the MTO process

A study has been carried on the effect of Ni incorporation on the acidity (acid strength distribution and total acidity), on the hydrothermal stability of a HZSM-5 zeolite and on the kinetic performance of this catalyst in the MTO process at high temperature (up to 500 °C, in order to increase selectivity to olefins) and when there is a high water content in the feed (in order to minimise deactivation by coke). The incorporation of Ni in the HZSM-5 zeolite implies a decrease in the total acidity and in the acid strength of the zeolite and, consequently, the activity of the catalyst decreases. Nevertheless, the catalysts with Ni are hydrothermally more stable than the parent zeolite catalyst. A Ni content around 1 wt% is the optimum, as it allows for uninterrupted operation in reaction–regeneration cycles, with water contents higher than 50 wt% in the medium, without irreversible deactivation, whereas a higher Ni content produces an unnecessary loss of initial activity.     

甲烷芳构化反应催化剂Ｍｏ-Ｍ／ＨＺＳＭ-５表面性质的研究

对甲烷芳构化催化剂Ｍｏ-Ｍ／ＨＺＳＭ-５进行了异丙醇分解、ＮＨ３-ＴＰＤ-ＭＳ、积炭量测定表征,其结果均与芳构化性能有关。芳烃收率高,稳定性好,积炭量较少,而且具有相当量的酸量和一定量强酸量及较强的脱氢中心。     

Methane Aromatization over Cobalt and Gallium -Impregnated HZSM-5 Catalysts

The influence of the catalyst acidity, the ratio of cobalt in the catalyst on the conversion of methane and the stability were evaluated using a fixed-bed microreactor at atmospheric pressure and at a flow rate of 1500 mL/g h (GHSV 600 h^?1). The reaction was conducted at 973 K and 1023 K over gallium and cobalt -impregnated HZSM-5 catalysts. The 2%Ga–2% Co/HZSM-5 catalyst exhibited remarkable stability with no significant deactivation for 100 h on stream, and yielded a maximum conversion of methane to benzene equal to 9.9%. These catalysts were thoroughly characterized using XRD, N₂ adsorption measurements, TPD of NH₃ and FT-IR. The acidity changes severely affected aromatization, and resulted in drastic modifications in product distribution. From this work, we found that only a small fraction of tetrahedral framework aluminum, which corresponds to the Bronsted acid sites, is sufficient to accomplish the aromatization of the intermediates in methane aromatization reaction, while the superfluous strong Bronsted acid sites, which can be decreased by adding Ga and Co, are shown to be related with the aromatic carbonaceous deposits on the catalysts. After adding Ga and Co the strength of Lewis acid sites of the catalyst increased. But the total amount of the acidity on the catalyst decreased.     

Propane transformation over H-ZSM5 zeolite modified with germanium

The propane aromatization was studied over H-ZSM5 zeolite modified by Ge, Pt and Pt-Ge. The aromatization was performed in a micro-reactor at 773K and at atmospheric pressure. The addition of germanium on H-ZSM5 increases the activity for propane transformation but decreases the selectivity toward aromatic compounds. The transformation of propane on Pt/H-ZSM5 indicates a significant increase in the activity and a decrease in the selectivity toward aromatics, while on the bimetallic Pt-Ge/H-ZSM5 catalyst both the activity and the selectivity toward aromatics increase. The dehydrogenation of propane over GeO₂/SiO₂ at 773 K and the n-heptane transformation overH-ZSM5 and Ge/H-ZSM5 at 673 K were performed. Results confirm the dehydrogenation capacity of GeO₂ and show similar activity and selectivity for n-heptane conversion on H-ZSM5 and Ge/H-ZSM5. The acidic properties of the catalysts were determined by TPD/NH₃ and IR/Pyanalyses. Results show that both the total and strong acidity decrease with the addition of germanium. Therefore, it seems that germanium affects the activity of propane conversion due to the dehydrogenation capacity of GeO₂,while the selectivity toward aromatics decreases due to the lower capacity of cyclization, by decreasing the acidity and the number of strong acid sites. In contrast, the Pt-Ge/H-ZSM5 catalyst presents the highest selectivity toward aromatics (53.4%) which is attributed to the decrease in hydrogenolysis capacity of platinum. The TPR results of the Pt-Ge/H-ZSM5 catalyst indicate interaction of Pt-Ge, and from the hydrogen consumption it was seen that Ge⁴⁺ is partially reduced to Ge²⁺, which is attributed to the presence of metallic platinum. This revised version was published online in July 2006 with corrections to the Cover Date.     

柠檬酸改性原位晶化催化剂的性能及传质扩散行为研究

采用不同浓度的柠檬酸溶液对原位晶化催化剂进行了改性脱铝研究,利用XRD、荧光衍射、氮气吸附、吡啶红外吸附等表征手段对脱铝后的催化剂进行了分析表征,分析表征结果表明柠檬酸能显著调变催化剂孔结构,有效改变中强酸和总酸量。ACE的反应评价结果表明,采用柠檬酸改性后催化剂的裂化能力显著增强,转化率提高3.23%（质量分数）以上、油浆收率降低1.13%（质量分数）以上、液化气质量分数增加2.7%以上、柴油质量分数降低1.94%以上、焦炭选择性变好。说明柠檬酸改性可显著提高原位晶化催化剂酸性位可接近性,从而改善反应选择性,柠檬酸质量分数为0.5%时具有最佳的反应结果。以菲为探针分子测试的催化剂穿透曲线验证了这一点。     

Highly dispersed NiW/γ-Al2O3 catalyst prepared by hydrothermal deposition method

This article describes a novel hydrothermal deposition method for preparing highly dispersed NiW/γ-Al₂O₃ catalysts and demonstrates its advantages over the conventional impregnation method. Via the hydrothermal precipitation reactions between sodium tungstate and hydrochloric acid and between nickel nitrate and urea, respectively, the active species W and Ni were deposited on γ-Al₂O₃. In the hydrothermal deposition of WO₃, a surfactant hexadecyltrimethyl ammonium bromide (CTAB) was used to prevent the aggregation of WO₃. The characterization results obtained by means of X-ray photoelectron spectroscopy (XPS), N₂ adsorption and high-resolution transmission electron microscopy (HRTEM) measurements showed that compared with the catalyst prepared by the conventional impregnation method, the catalyst with the same metal contents prepared by the hydrothermal deposition had much higher W and Ni dispersion, higher specific surface area, larger pore volume, the significantly decreased slab length and slightly increased stacking degree of sulfided W species, leading to the significantly enhanced dibenzothiophene (DBT) hydrodesulfurization (HDS) activity. The DBT HDS assessment results also revealed that the catalyst containing 17.7 wt% WO₃ and 2.4 wt% NiO prepared by the hydrothermal deposition method had the similar DBT HDS activity as a commercial NiW/γ-Al₂O₃ catalyst containing 23 wt% WO₃ and 2.6 wt% NiO, resulting in the greatly decreased amount of active metals for achieving the same HDS activity.