Oligomerization of 1-octene on micro-mesoporous zeolite catalysts

The oligomerization of 1-octene in the presence of micro- and micro-mesoporous catalysts based on zeolite Y (SiO₂/Al₂O₃ = 4.9) has been studied. The results of low-temperature nitrogen adsorption confirm the formation of mesopores with a diameter of 2–4 nm in the micro-mesoporous catalysts. An ammonia temperature-programmed desorption study of the acid properties of the synthesized zeolite catalysts has shown that the preparation of micro-mesoporous samples is accompanied by a decrease in the concentration and strength of acid sites. A comparison of the catalytic properties of the microporous and micro-mesoporous zeolites has revealed that the latter are the most active in 1-octene oligomerization and allow octene oligomers to be obtained with a selectivity of 65% at the 100% conversion of the monomer. The use of zeolite catalysts with the micro-mesoporous structure in the oligomerization of 1-octene affords oligomers with a broader molecular-mass distribution (degree of oligomerization n = 2–5) than on the microporous samples (n = 2 to 3).     

无导向剂快速合成小晶粒Y分子筛

考察了无有机模板剂、无导向剂条件下合成Y分子筛体系的n(Na₂O)/n(SiO₂)、n(SiO₂)/n(Al₂O₃)及硅源对Y分子筛结晶过程及其粒径的影响。结果表明,增加n(Na₂O)/n(SiO₂)有利于促进Y分子筛的形成,但同时也加速Y分子筛的转晶。Y分子筛的粒径随n(Na₂O)/n(SiO₂)的增加而减小,n(Na₂O)/n(SiO₂)=0.6和0.88的合成体系在100℃下反应3 h后,所得产物的平均粒径分别为0.4和0.3μm,n(Na₂O)/n(SiO₂)=1.04时形成的小晶粒Y分子筛易发生团聚而形成大颗粒。Y分子筛的n(SiO₂)/n(Al₂O₃)随n(SiO₂)/n(Al₂O₃)的增加而减小。n(SiO₂)/n(Al₂O₃)减少时,Y分子筛的粒径分布变宽(0.2～0.7μm)。以硅溶胶或固体纳米SiO₂为硅源合成所得Y分子筛的粒径分布较窄（0.3～0.5μm）,而以硅酸钠为硅源合成所得Y分子筛的粒径分布较宽(0.2～1.0 μm)。     

基于Y型沸石的解聚制备ZSM-5/Y沸石催化材料

以工业NaY沸石在碱性环境下解聚形成的硅、铝物种作为ZSM-5沸石生长的部分原料,通过补加适宜的硅物种和模板剂等,成功得到了具有核-壳结构的ZSM-5/Y沸石催化材料。采用XRD、FT-IR、NH3-TPD、SEM、EDS等对合成的材料进行表征,并以异丙苯和正庚烷的催化裂化反应评价了该复合材料作为裂解催化剂的催化活性,并与对应的机械混合物比较。结果表明,ZSM-5/Y沸石复合物的形成是一个由Y型沸石向ZSM-5沸石转变的过程,后合成的ZSM-5沸石包裹Y型沸石进行生长,形成以多晶Y型沸石为核,ZSM-5沸石为壳的复合物。ZSM-5/Y沸石复合物与对应的机械混合物的性质存在显著差异,并非两种沸石的简单加和。与对应的机械混合物相比,ZSM-5/Y沸石复合物催化正庚烷裂化反应的正庚烷转化率更高,低碳烃,特别是乙烯和丙烯的选择性更高;催化异丙苯裂化时,异丙苯转化率较低,壳层的孔道结构是其主要影响因素。     

Preparation of the Modified Y Zeolite for Removal of Organic Sulfur Compounds from FCC Gasoline

Abstract

Ce(IV)-loaded modified NaY (NH₄Y) zeolite was prepared for selective adsorptive desulfurization from fluid catalytic cracked (FCC) gasoline. Ce(β)Y was obtained from NH₄Y using a liquid-phase ion-exchange method. Ce(IV)Y was obtained from calcining Ce(β)Y at 550°C. The structures of the Ce(IV)Y and NaY samples, selective adsorption of organic sulfur compounds on Ce(IV)Y and NaY zeolite, sulfur content of FCC gasoline, and mechanism for adsorption of thiophene on Ce(IV)Y and NaY zeolite were investigated using X-ray diffraction (XRD), gas chromatography–sulfur chemiluminescence detection (GC-SCD), sulfur analysis, Fourier transform infrared (FTIR), frequency response (FR), and intelligent gravimetric analysis (IGA). The selective adsorption desulfurization from FCC gasoline containing organic sulfur compounds (S = 135 μg/g) was investigated with Ce(IV)Y adsorbent for removal.

The sulfur content was reduced to 20.14 μg/g. The thiophene adsorption mechanism showed that Ce(IV)Y can adsorb thiophene via π electronic interaction directly, and thiophene and Ce(IV) can form a stable sulfur–metal bond (S-M bond) that enhances the adsorption capacity of Ce(IV)Y for thiophene. This method for the modification of NaY zeolite provides a promising selective desulfurization process to prepare clean fuels.     

Acidic and catalytic properties of dealuminated zeolite Y treated with zirconyl nitrate solution

Structure, the constitution of a surface hydroxyl layer, and the acid properties and catalytic activity in n-hexane conversion were studied for dealuminated zeolites Y modified with zirconyl nitrate to have a zirconium loading of 0.2, 0.4, and 0.8 wt %. After dealumination with ammonium hexafluorosilicate solution and exchange for NH⁺ ₄, the initial zeolites were calcined at 500–550°C and washed with an acid or alkali solution. The investigation techniques used were X-ray diffraction, thermal analysis, IR spectroscopy, X-ray photoelectron spectroscopy, and temperature-programmed ammonia desorption. It was found that the introduction of zirconium increased the relative amount of strong acid sites, thus increasing the yield of n-hexane cracking products.     

An in situ study of dimethyl ether conversion over HZSM-5/Al2O3 zeolite catalysts by high-temperature diffuse reflectance infrared fourier transform spectroscopy

Isolated and associated OH groups have been in situ identified by high-temperature diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy of the surface of zeolites calcined until complete removal of water. It has been shown that the Brønsted acid sites (BASs) involved in dimethyl ether (DME) conversion on the zeolite surface exhibit two characteristic bands in the DRIFT spectra. It has been found that the composition of DME conversion products on HZSM-5 zeolite catalysts modified with Mg or Rh is temperature-dependent. Ethanol and a small amount of methanol were detected on an Rh-HZSM-5/Al₂O₃ zeolite catalyst at T = 270°C and were not observed on Mg-HZSM-5/Al₂O₃ under the same conditions. Spectral features of ketene were detected in the DRIFT spectra of the surface of Mg-HZSM-5/Al₂O₃ in a stream of DME. The spectrum of Rh-HZSM-5/Al₂O₃ calcined at 200°C exhibited spectral features of ethyl alcohol and bands characterizing a strong Lewis acid site (LAS) capable of hydrogenating ketene to ethyl alcohol. The spectra of the surface of all the zeolite catalysts tested in a DME stream at 320°C contain bands characterizing olefins and alkanes and do not exhibit the spectral features of alcohols and ketene.     

Effect of synthesis conditions on the properties of nanocrystalline faujasites

The effect of crystallization parameters on the properties of nanocrystalline zeolites Y has been studied to optimize the synthesis conditions. Zeolites Y are prepared by the three-stage hydrothermal crystallization with a gradual rise in synthesis temperature from room temperature to 60°C using the Na₂O/SiO₂ ratio in the reaction mixture and the number and duration of individual synthesis stages as variable synthesis parameters. It has been shown that an increase in the Na₂O/SiO₂ molar ratio in the reaction mixture above 9.6 leads to a change in the crystallization selectivity and causes formation of zeolite X with a crystal size of 200 nm as a crystalline product. An increase in the duration of the synthesis stage at 60°C is accompanied by increase in the crystal size and entails formation of an analcime impurity phase. A decrease in the duration of reaction mixture aging stages at 25 and 38°C leads to an increase in the zeolite Y nanocrystal sizes and a decrease in the crystalline product yield. It has been found that a pure zeolite Y phase with a nanocrystal size of 320–350 nm and a SiO₂/Al₂O₃ ratio of 3.6–4.2 is formed during the three-stage synthesis from a (7.2–9.6)Na₂O · Al₂O₃ · 14.4 SiO₂ · 290 H₂O reaction mixture with a yield of 0.60–0.88 g/g of reaction mixture.     

Influence of synthesis parameters on the crystallinity and Si/Al ratio of NaY zeolite synthesized from kaolin

Well-crystallized high-silica NaY zeolites (Si/Al>2.5) were prepared from a reaction mixture consisting of metakaolin, sodium silicate solution and seed solution via optimization of the mixture composition and reaction conditions. The transformation from kaolin to high-silica NaY zeolite was confirmed by XRD, SEM and IR techniques. Subsequently, the influence of synthesis parameters, i.e. initial SiO₂/Al₂O₃, initial Na₂O/SiO₂, initial H₂O/SiO₂, aging time of the seed solution, crystallization temperature and crystallization time, on the NaY growth was investigated in terms of crystallinity and Si/Al ratio. The results showed that the effects of initial SiO₂/Al₂O₃, initial Na₂O/SiO₂ and initial H₂O/SiO₂ on the crystallinity and Si/Al ratio of NaY zeolite are similar to those observed in the conventional syntheses of NaY zeolites only using sodium silicate solution as silicon source. However, due to the use of metakaolin as the main silicon and aluminum sources in the present study, a long crystallization induction period of 20 h was achieved, which can be attributed to the dissolution of metakaolin. In addition, different from the conventional syntheses of zeolite NaY, pure NaY zeolites (i.e. without NaP zeolite impurity) were still obtained even at 120 °C because of the use of a large quantity of seed solution (23 wt%) in the reaction mixture. As the aging time of the seed solution increased from 3.5 h to 22 h, the relative crystallinity of the NaY zeolite first increased sharply and then reached a plateau, while the Si/Al ratio first increased rapidly up to a maximum value of 2.75 corresponding to an aging time of 6.5 h, and then decreased sharply with the aging time.     

NaY分子筛的改性及对FCC汽油选择吸附脱硫的研究

利用草酸对NaY分子筛进行脱铝改性制备了NH4Y分子筛,NH4Y分子筛经过焙烧制得HY分子筛,再用实验制得的NH4Y分子筛进行液相离子交换和焙烧制得Ce（Ⅳ）Y分子筛。对分子筛进行静态吸附脱硫对比实验,并利用微库仑综合分析仪对静态和动态处理过的FCC汽油样品进行硫含量测定。结果表明,在静态条件下,Ce（Ⅳ）Y比HY分子筛的吸附脱硫效果略好,二者吸附脱硫率分别为79.0%和77.8% 。在动态条件下,Ce(Ⅳ)Y分子筛能够脱掉HY分子筛较难脱除的二甲基噻吩类硫化物。再生后的成型Ce(Ⅳ)Y分子筛的吸附能力可达到新鲜Ce（Ⅳ）Y分子筛的95.5%。     

Application of Zeolite Y-Based Ni–W Supported and In Situ Prepared Catalysts in the Process of Vacuum Gas Oil Hydrocracking

The activity of supported and in situ synthesized sulfide Ni–W catalysts based on a low-silicon zeolite Y (SiO₂/Al₂O₃ = 5.2) in the hydrocracking of vacuum gas oil is studied. It is shown that the temperature and time of reaction affect the fractional composition and the sulfur content in conversion products. It is found that the phase of tungsten sulfide as well as the mixed Ni?W?S phase active in hydrogenation are formed on the catalyst surface. It is proposed that an increase in activity for the in situ formed catalyst may be explained by a high content of sulfide phases on the catalyst surface and accessibility of the zeolite pore system.     

多级孔Y/ZrO2复合材料的制备

以NaY分子筛为晶种,利用固态反应原位水热晶化法合成了多级孔Y/ZrO2复合材料。采用X射线衍射、N2吸附 脱附、扫描电镜、拉曼光谱、固体核磁及吡啶红外等手段对所得材料的物理化学性质进行表征。结果表明,Y/ZrO2复合材料中Y型分子筛与ZrO2之间存在化学键合。ZrO2的引入不仅抑制Y型分子筛的生长,而且改变了Y型分子筛中骨架Si原子的配位环境。采用两段晶化法可以减弱ZrO2对Y型分子筛晶化的影响,使Y/ZrO2复合材料具有较高的相对结晶度。Y/ZrO2复合材料不仅具有Y型分子筛贡献的微孔结构,还拥有相对丰富的介孔结构。与Y型分子筛相比,Y/ZrO2复合材料的Brnsted酸与Lewis酸的含量较低。     

Effect of Modified Zeolite on One-Step Process of DME Synthesis

Abstract

HZSM-5 zeolites modified by MgO, CaO, and ZnO were prepared by impregnation and bifunctional catalysts were prepared by modified HZSM-5 zeolites and JC207 catalyst (a catalyst for methanol synthesis, which has been industrialized in China). Evaluation of catalytic activity was conducted in a fixed-bed reactor. Results show, with proper basic oxide-modified zeolite, a Br?nsted acid site (strong acid sites) shift to Lewis acid site (weak acid sites). Weak and less strong acid sites on HZSM-5 zeolite are activity centers for the formation of dimethyl ether (DME), whereas strong acid sites for by products such as hydrocarbons. Consequently, the selectivity of CO₂ and hydrocarbons decrease, especially with zeolite modified by CaO.     

改性Y型分子筛对石脑油脱硫效果的研究

NH4Y zeolite was prepared through ion-exchange of NaY zeolite with an ammonium salt. Then LaY zeolite was obtained through a secondary ion-exchange of NH4Y zeolite with a rare earth salt solution followed by calcination of the zeolite product. Dynamic adsorptive desulfurization of naphtha was conducted in the presence of the modified LaY zeolite, and the sulfur content of the treated naphtha samples was analyzed by microcoulometry. The test results showed that under dynamic conditions the LaY zeolite prepared through secondary ion-exchange of NH4Y zeolite, which was prepared using 1.0 mol/L ammonium salt, with the rare earth salt exhibited a better desulfurization efficiency. Furthermore, the LaY zeolite achieved a best desulfurization effect at an adsorption temperature of 45 ℃ and an adsorbent/oil ratio of 1:2.     

Nanosized Platinum-Loaded H-ZSM-5 Zeolite Catalysts for n-Hexane Hydroconversion

Abstract

A series of nanosized platinum-containing catalysts was successfully loaded on/in zeolite H-ZSM-5 via exchanging the zeolitic proton with platinum from Pt tetramine dichloride complex. Another series of Pt/H-ZSM-5 catalysts was prepared via wet impregnation of H₂PtCl₆ solution for comparison. The latter series was found to produce lower Pt dispersion. Pt dispersion was determined by H₂ chemisorption. Catalyst characterization via ammonia temperature-programmed desorption (TPD), temperature-programmed reduction (TPR), and transmission electron microscopy (TEM) was examined for all catalysts and showed large differences in particle sizes. The data on n-hexane reactions of the catalysts of both series confirmed the formation of Pt nanoparticles in the exchanged catalysts. The relatively lower density and strength of acid sites acquired by Pt-exchanged catalysts contributed to this difference; stronger acid sites in the impregnated catalysts are in favor of hydrocracking reactions, which inhibit isomerization selectivity.     

锌改性分子筛的噻吩硫转化功能研究

采用催化裂化微型反应评价装置，考察了不同稀土含量的Y型分子筛及其锌改性后对催化裂化汽油中噻吩硫转化能力的影响，并与分子筛酸性关联，提出噻吩反应的可能途径。结果表明：锌改性使分子筛的L酸量明显增加，噻吩的转化与分子筛的酸强度，酸密度以信催化剂的B酸，L酸均有密切关系，一定的酸强度和酸密度是噻吩裂解转化所需要的，而且噻吩转化是B酸，L酸协同作用的结果。     

Zinc-Modified ZSM-5 Nanozeolites Synthesized by the Seed-Induced Method: Interrelation of Their Textural,Acidic, and Catalytic Properties in DME Conversion to Hydrocarbons

The effect of the method of introduction of zinc cations and the zinc content in a nanocrystalline zeolite of the ZSM-5 type on the physicochemical and catalytic properties of the material in DME conversion to a mixture of liquid synthetic hydrocarbons has been studied. Zinc is introduced into the catalysts both during the zeolite synthesis and the ion exchange (Zn _n Al _m NZ5 and ZnNZ5, respectively). The use of nanocrystalline Zn _n Al _m NZ5 zeolites provides the formation of a mixture of liquid hydrocarbons with a high selectivity of no less than 90%; the liquid hydrocarbons contain more than 70% of isoparaffins and a small amount of aromatic compounds. An increase in the zinc loading of the Zn _n Al _m NZ5 zeolite from 0.9 to ~3% leads to an increase in the methanol content in the aqueous phase of the liquid product, an increase in the selectivity for liquid hydrocarbons, and a slight increase in the concentration of aromatic and unsaturated hydrocarbons in the mixture. In the presence of the ZnNZ5/Al₂O₃ catalyst with Zn introduced by ion exchange, the methanol content in the aqueous phase and the aromatics content in the liquid hydrocarbon mixture are significantly higher. The Zn _n Al _m NZ5 nanozeolites are characterized by a more developed external surface, a higher concentration of mesopores, and higher acidity.     

Product control in catalytic aromatization of C2+ hydrocarbons

Aromatization of light hydrocarbons (propane, butane, propane-propene mixture, and cat-cracker off-gases) on ZnO-zeolite and lanthanide-zeolite catalysts based on zeolite TsVM (SiO₂/Al₂O₃ = 62) and industrial catalyst SGK-1 was studied. It was shown that the modification of catalysts with lanthanides leads to an increase in both the total yield of xylenes and the p-xylene selectivity, a change that is explained by the formation of branched intermediates and steric specifics of their further conversion.     

Catalytic Cracking of <Emphasis Type="Italic">n</Emphasis>-Hexane and <Emphasis Type="Italic">n</Emphasis>-Heptane over ZSM-5 Zeolite: Influence of SiO<Subscript>2</Subscript>/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> Ratio

The performance of two types of ZSM-5 zeolite catalysts (MFI-type zeolite, SiO₂/Al₂O₃ = 50 and 300) was studied in the catalytic cracking of n-hexane and n-heptane as a model compound of light naphtha for production of light olefins at 500, 550, and 600°C. The physicochemical properties of ZSM-5 catalysts were characterized by means of XRD, BET, SEM and NH₃-TPD. The influence of SiO₂/Al₂O₃ molar ratio was investigated on conversion and product selectivity. ZSM-5 zeolite yielded higher conversion in the cracking of n-hexane compared to n-heptane and maximum conversion was achieved over ZSM-5(50) at 600°C. ZSM-5(50) showed higher alkane selectivity rather than olefins. It was found that ZSM-5(300) was more desirable in terms of having significant selectivity to light olefins as well as producing high propylene to ethylene ratio. The maximum propylene to ethylene ratio of 2.7 and 2.48 was observed over ZSM-5(300) at 500°C for n-hexane and n-heptane cracking, respectively.     

Conversion of higher <Emphasis Type="Italic">n</Emphasis>-alkanes under deep catalytic cracking conditions

The product distribution for the deep catalytic cracking of C₁₆-C₂₈ n-alkanes has been studied. Using the method of the temperature-programmed desorption of ammonia, the difference in the acid properties of HZSM-5 and ultrastable Y zeolites and the catalyst matrix components has been found. For the primary cracking of heavy hydrocarbon feedstock to occur, the catalyst matrix must have a high acidity. Bizeolite catalysts exhibit high selectivities for olefins with both normal and branched chains, which are due to a decrease in the contribution of the hydrogen redistribution reaction. For a bizeolite catalyst, the additivity of the selectivities for olefins and aromatic hydrocarbons, depending on the composition of the zeolite component, is observed.     

Preparation of a highly efficient Pt/USY catalyst for hydrogenation and selective ring-opening reaction of tetralin

Ultrastable Y zeolite(USY)-supported Pt catalyst was prepared by gas-bubbling-assisted membrane reduction. The influence of reaction conditions and the metal and acid sites of catalysts on the catalytic performance of catalyst in hydrogenation and selective ring opening of tetralin, 1,2,3,4-tetrahydronaphthalene(THN), was studied. It was found that the optimal reaction conditions were at a temperature of 280 °C, hydrogen pressure of 4 MPa, liquid hourly space velocity of 2 h~(-1) and H_2/THN ratio of 750. Under these optimal conditions, a high conversion of almost 100% was achieved on the 0.3 Pt/USY catalyst. XRD patterns and TEM images revealed that Pt particles were highly dispersed on the USY, favorable to the hydrogenation reaction of tetralin. Ammonia temperature-programmed desorption and Py-IR results indicated that the introduction of Pt can reduce the acid sites of USY, particularly the strong acid sites of USY. Thus, the hydrocracking reaction can be suppressed.