Studies on octane boosting of industrial feedstocks on Pt/H-BEA zeolite

Structural properties of H-Beta (BEA) zeolite were optimized by steam dealumination followed by acid leaching. At mild dealumination, the zeolite (BZ-2) exhibited higher values of surface area pore volume and improved acid properties. On BZ-2, 0.3 wt% of Pt was loaded by incipient wetness impregnation method (Pt/BZ-2) and used for production of branched paraffins from two industrial feedstocks. The feedstock containing heavier hydrocarbons (feed 1) could yield as high as 26 U increase in Research Octane Number (RON), against 11-13 U increase in RON observed for lighter feedstock (feed 2). The study indicated that isomerization and cracking followed by dimerization (alkylation) reactions are responsible for the production of branched paraffins. The catalyst exhibited more octane gain when tested in the presence of N₂, but the corresponding catalyst exhibited comparatively lower TOS yields and inferior intensity of XRD bands after the reaction.     

Shape-selective methylation of 2-methylnaphthalene with methanol over hydrothermal treated HZSM-5 zeolite catalysts

Shape-selective methylation of 2-methylnaphthalene (2-MN) was carried out over hydrothermally treated HZSM-5 (SiO₂/Al₂O₃=83) zeolite catalysts under a fixed-bed down-flow reactor, methanol and 1,3,5-trimethylbenzene (TMB) were used as methylating agent and solvent, respectively. The results show that hydrothermal treatment improves the selectivity to 2,6-dimethylnaphthalene (2,6-DMN) and the stability. HZSM-5 catalyst hydrothermally treated at 550 °C followed by acid leaching exhibits 7.1% of 2,6-DMN yield after 5 h time on stream (TOS), and 13.4% of 2-MN conversion with the 2,6-/2,7-DMN ratio of 1.8 after 8 h of TOS.     

Effect of temperature and time in the hydrothermal treatment of HY zeolite

Zeolite HY was steamed at 1 bar water pressure in steps of 100 K from 473 K to 1073 K in dependence of the time (0.5–20 h). Three routes of hydrothermal reactions can be outlined: At low temperature (473 K), a partly framework dissolution occurs accompanied by the formation of X-ray amorphous material. At intermediate temperatures (773–873 K), framework dealumination takes place with the occurrence of different non-framework species. Thereby, with increasing steaming time, saturation of the Si/Al ratio occurs on low levels (Si/Al ratios of about 4 and 5, respectively). At 973 K, a crossover from a low level saturation in Si/Al (6) towards higher values (11) is observed, which is accompanied by a partial amorphization of the zeolite with formation of aluminium oxide and silica gel and a significant decrease in crystal size as well. At high temperatures (1073 K), a fast thermal decomposition occurs. The IR spectra directly reveal an aluminosilicate phase as decomposition product of the framework. At 573 K, the zeolite framework remains unchanged.     

Influence of steaming and acid-leaching treatments on the hydrophobicity of HBEA zeolite determined under static conditions

A series of HBEA dealuminated samples was prepared by treatment with HCl or steaming of a parent sample. Samples were characterized by XRD, elemental analysis, nitrogen adsorption and pyridine adsorption–desorption followed by IR spectroscopy. The hydrophobicity coefficient, determined by separated static adsorption of water and toluene was used as a quantitative measurement of the hydrophobic properties. It is shown that dealumination causes drastic increase of the hydrophobicity of the different samples. The increase of the hydrophobic character is rather higher for steamed samples than for the acid-leached ones. For the same number of Brønsted sites, the water uptake on the steamed samples corresponds to 11 molecules by unit cell whereas it is 17 for the acid-leached samples. The low hydrophobic character of acid-leached samples is attributed to the creation of hydroxyl nests during acid treatment.     

Structural characteristics of modified natural zeolite

Natural zeolite of Slovak provenience has been modified with magnetic nanoparticles at selected temperatures of 20, 50 and 85 °C with the aim to enhance its sorption properties. The pore, surface and structural properties of zeolite/iron oxide composite were characterized using nitrogen adsorption measurements, electron probe microanalysis and powder X-ray diffraction. The crystallinity of the host zeolite was strongly influenced by the temperature of iron oxide particles precipitation, but it was still retained. It followed from the nitrogen adsorption measurements that the surface area and the pore volume of zeolite composites have increased in relation to the precipitation temperature, the best sorption properties were revealed at the composite prepared at 85 °C. As followed also from the SEM images, the iron oxide nanoparticles being of size 30 nm are forming mesoporous aggregates adsorbed on the zeolite surface. Fractal analysis used to describe the modified geometry of zeolite composites has given the values of surface fractal dimension between 2.36 and 2.51.     

Activity and stability of alumina zeolite nickel catalysts

The catalytic properties of nickel catalysts (50 wt.% of alumina and 50 wt.% of Ni,H-ZSM-5) were investigated and related to the amount of NiO (0–8 wt.%) and the method of nickel incorporation (8 wt.% NiO). Consideration was also given to the method by which zeolite and alumina were combined. The cracking properties of the catalysts increased when the amount of NiO was raised up to 4 wt.%. To decrease the content of aromatic hydrocarbons in the products it is necessary to raise the amount of NiO to a higher level than 4 wt.%. The catalyst prepared by peptisation of the mixture of zeolite and aluminium hydrogel (with ageing process) displayed reduced activity and stability because of the low susceptibility of NiO to reduction.     

Investigation of hydrothermal synthesis parameters on characteristics of T type zeolite crystal structure

Hydrothermal synthesis of zeolite T in aqueous alkaline solutions without using templates was investigated. Zeolite T crystals were prepared via hydrothermal synthesis using milk-like aluminosilicate gel with a composition of aSiO₂:bAl₂O₃:cNa₂O:dK₂O:xH₂O. The effects of molar compositions including silicon module (n_RM = a/b) and relative alkalinity (α = OH/SiO₂), and crystallization conditions including crystallization temperature (T) and time (t) on the yield of T-type crystals were investigated. This research work examines changes in the yield of crystalline zeolite phases by varying the gel composition parameters (n_RM = 20-25, and α = 0.71-0.82) and crystallization process temperature and time (T = 100°−140 °C, t = 120-216 h), while keeping constant the parameters [OH] = 2.77 m, U_RM(Na/Na + K) = 0.75, stirring time = 24 h , stirring temperature = 30 °C, and drying temperature = 100 °C. The crystal species of zeolite T were characterized by XRD (X-ray diffraction) and SEM (Scanning Electron Microscope).     

Studies on the effect of 4A zeolite on the properties of intumescent flame-retardant agent filled natural rubber composites

This investigation focused on the research of 4A zeolite on the properties of intumescent flame retardant (IFR) agent filled natural rubber (NR) systems. The first part focused on the evaluation of such characteristics as cure characteristics, tensile property, abrasion loss, and cross-linking density of NR composites. Experimental results demonstrated that the addition of 4A zeolite could increase the cross-linking density of the NR systems. The incorporation of 0.3 phr of 4A zeolite with 50 phr of IF Ragent could improve the elongation value from 480 to 610%, probably 27% increase. Also, the abrasion loss was decreased from 0.95 to 0.70 cm³, nearly 26%. The second part focused on the study of flame-retardant (FR) properties of 4A zeolite filled NR systems. The properties and structure of these composites were characterized by limited oxygen index (LOI), thermogravimetric analysis (TGA), and cone calorimeter. It was proved that the addition of 0.3 phr of 4A zeolite into the IFR filled NR systems could lead to an increase of LOI value and thermal stability, together with a decrease of mass loss ration, rate of heat release (RHR), carbon monoxide (CO) evolution and carbon dioxide (CO₂) evolution, and so on, in a word, an improvement of FR properties.     

TMCS修饰MFI分子筛膜的制备及乙醇/水分离稳定性的研究

采用三甲基氯硅烷（TMCS）作为修饰源对MFI分子筛膜进行表面改性,系统考察了TMCS浓度以及修饰时间对于MFI分子筛膜在分离乙醇/水混合物时的性能影响。SEM、XRD、²⁹Si NMR、FT-IR、接触角实验及分离实验结果表明,TMCS可以与硅羟基反应,嫁接分子筛膜表面,在消除膜表面硅缺陷的同时提高膜的疏水性及膜分离性能的稳定性。随着TMCS浓度以及反应时间的增加,修饰后MFI分子筛膜的通量及分离因子略有下降,但稳定性增强。在TMCS的浓度为0.4%（质量）,修饰时间为2 h时,所得到的膜具有最佳渗透汽化分离性能,并可在60℃下分离5%（质量）乙醇/水混合物时保持良好的稳定性。在连续90 h渗透汽化分离过程中,其渗透通量稳定在1.61 kg·m^-2·h^-1 左右,分离因子保持在20以上。     

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.     

Palladium-exchanged MFI-type zeolites in the catalytic reduction of nitrogen monoxide by methane. Influence of the Si/Al ratio on the activity and the hydrothermal stability

Pd-exchanged MFI-type zeolites containing 3.7 and 0.7 framework aluminium atoms per unit cell (corresponding to Si/Al ratios of 25 and 131) were found active in the selective reduction of nitrogen monoxide in the presence of excess oxygen. Upon steaming at 800°C, both catalysts exhibited the total loss of their catalytic activity in the reduction of NO. Such a behaviour was ascribed to the complete aggregation of Pd ions into large metal particles on the external surface of the zeolite crystals. Both supports, although maintaining their crystallinity, are shown to experience extended dealumination upon steaming. Although the loss of Pd exchange capacity could partially explain the Pd migration and sintering, a mechanism involving the formation of mobile Pd hydroxyl entities condensing into PdO particles outside the zeolite crystallites is preferred.     

含磷的骨架富硅超稳Y分子筛(PSRY)的研究

通过对骨架富硅超稳Y分子筛进行磷改性研究,表明磷的引入使分子筛在水热处理过程中晶胞更易收缩,水热稳定性提高,且分子筛酸性发生变化,强酸中心向中强酸中心转移。以该分子筛为活性组元制备的催化剂工业应用结果表明,催化剂具有好的焦炭选择性和高的中间油馏份收率。     

Hydrothermal stability of HZSM-5 catalysts modified with Ni for the transformation of bioethanol into hydrocarbons

The hydrothermal stability of catalysts prepared from HZSM-5 zeolites doped with Ni (by impregnation) has been studied in the transformation of bioethanol into hydrocarbons, in order to remove the main barrier for the use of HZSM-5 zeolite catalysts in this process, which is the irreversible deactivation by dealumination of the zeolite above 400 °C with water in the reaction medium. The main effect of doping is the attenuation of the zeolite acid strength from 135 to 125 kJ (mol of NH₃)⁻¹ for a Ni content of 1 wt.%. The catalysts maintain a high level of activity and a high selectivity of propene and butenes, and Ni doping significantly attenuates irreversible deactivation of the catalyst by dealumination of the zeolite. The zeolite catalyst doped with 1 wt.% of Ni maintains its kinetic behaviour in reaction-regeneration cycles when the reaction step is carried out at 500 °C and with 5 wt.% of water in the feed. This catalyst allows operating at 400 °C without irreversible deactivation with bioethanol containing 75 wt.% of water.     

改性天然沸石对橡胶复合材料性能的影响

为了提高沸石在橡胶中的分散，增强沸石与橡胶的界面相互作用，本文采用硝酸（H）和双-（γ-三乙氧基硅基丙基）四硫化物（S）对天然沸石（NZ）进行复合改性（S-HNZ），然后将改性沸石与天然橡胶（NR）混炼制备沸石/天然橡胶复合材料，研究不同改性沸石对天然橡胶性能的影响。采用FTIR、XRD、SEM等测试手段对改性前后NZ的结构进行表征，研究了橡胶复合材料的硫化性能，动态热机械性能（DMA）及力学等性能。结果表明：经酸处理后天然沸石（HNZ）骨架脱铝呈疏水性，且硅烷成功接枝到天然沸石表面。添加S-HNZ的橡胶复合材料焦烧时间和正硫化时间均缩短，硫化反应速率加快；另外，与NR相比，NR/S-HNZ的300%定伸应力和抗拉强度分别提高了46.7%和10.8%；DMA结果显示，NR/S-HNZ储能模量（E''）和玻璃化转变温度（Tg）均高于NR，表明经复合改性后，复合材料的交联密度增加，形成较强的交联网络，极大提高了沸石与橡胶大分子链之间的界面结合力。     

红辉沸石两步水热法合成A型分子筛机理研究

以红辉沸石为原料,采用两步水热法将其转化为A型分子筛,系统地探讨A型分子筛的转化机理。对不同晶化时间的样品进行系统表征,深入解析天然红辉沸石转化A型分子筛的成核机制、生长控制、晶型稳定转化等结构基础问题。研究表明,A型分子筛的生长可分为3个阶段：在成核诱导期（晶化时间≤0.5 h）,凝胶中的β笼通过双四元环构筑成α笼,生成较多晶核及少量1μm小晶体;此后为快速生长期（晶化时间1～4 h）,大量晶核通过聚集生长形成2μm大晶体;在生长稳定期（晶化时间5～8 h）,通过二次成核凝胶将会转化为更多的分子筛晶体。A型分子筛的形成遵循：铝硅酸盐凝胶→四元环、六元环→双四元环、β笼→α笼的晶化过程,因而其转化过程符合液相转化机理。     

多维NaY分子筛的水热稳定性研究

引入功能梯度化设计概念,合成了表面多维化的NaY分子筛,采用X射线衍射仪、X射线荧光光谱仪、比表面积、微反活性和小型流化床催化剂评价装置(ACE)等表征分子筛及其催化剂老化前后的性能。结果表明,由多维NaY分子筛制备的稀土Y型分子筛REY-D, 其水热稳定性低于常规NaY分子筛所制得的REY-C分子筛。当分子筛与基质结合后,结果相反,多维NaY分子筛催化剂的老化活性高于常规NaY分子筛所制得的催化剂,且随着老化时间的延长,效果更明显。ACE选择性测试结果表明,采用多维NaY分子筛所制得的催化剂汽油收率高,而重油和柴油收率低,且汽油产品中烯烃含量低,液化气中的低碳烯烃含量高。     

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.     

沸石改性及其吸附性能研究

对沸石进行降低硅铝比改性，改性沸石对H2O，H2S，NH3的饱和吸附量分别为16.8％，18．2mg/g，71．1mg/g，而只进行过焙烧的沸石为9．3％，11．7mg/g,38.4mg/g，表明沸石经降低硅铝比改性后，对H2O，H2S，NH3的吸附量大大提高。     

Evaluation of natural zeolite as a viscosity-modifying agent for cement-based grouts

The effects of natural zeolite on the rheological and workability properties of the grout mixtures were studied. Setting times of grouts were also determined as part of the experimental study. For comparison, grout mixtures were also prepared with a commercially available viscosity modifying admixture (VMA). The experimental results show that addition of natural zeolite modifies both the rheological and workability properties of grouts. For a constant superplasticizer (SP) content, an increase in the zeolite amount significantly increases the yield stress, the apparent and plastic viscosity, and reduces the fluidity and deformability. Moreover, an increase in the amount of SP causes a significant reduction in both the yield stress and plastic viscosity of the grouts. It was also observed that, grouts prepared with natural zeolite addition have a pseudo-plastic behavior, and shear-thinning behavior increases with an increase in the zeolite amount. Therefore, it has been shown that using natural zeolite as a VMA it is possible to obtain grouts that have satisfactory rheological properties, especially if natural zeolite is used in combination with a superplasticizer.     

Preparation and characterization of zeolite catalysts for etherification reaction

Catalytic etherification of 2-naphthol with ethanol has been carried out over a series of solid-acid catalysts such as H-Beta, H-MOR and H-ZSM-5 using a flow-type reactor. H-Beta zeolite shows higher conversion and catalytic stability than other catalysts for the production of 2-naphthyl ethyl ether, which may be correlated to the amount and strength of acid sites. H-Beta zeolites with different Si/Al ratios show that conversion decreases with increasing Si/Al ratios. The NH₃-TPD profiles indicate that the weak acidity decreases more sharply with increase in Si/Al ratios, compared with the strong acidity. The influences of ethanol/2-naphthol molar ratios, reaction temperature, and space velocity with respect to catalytic activities are investigated for H-Beta zeolite in the present work.