Adsorptive desulfurization on a heteroatoms Y zeolite prepared by secondary synthesis

Gallium atoms have been introduced into the framework of Y zeolite by treating the zeolite with an aqueous solution of ammonium hexafluoro gallate.Desulfurization of various model fuels containing about 500 μg/g sulfur has been studied over the synthesized Y zeolite(GaAlY).The sulfur adsorption capacity is 7.0,17.4,14.5,16.9,6.9 and 5.8 mg(S)/g adsorbent for thiophene,tetrahydrothiophene(THT),4,6-dimethyldibenzothiophene(4,6-DMDBT),dibenzophiophene(DBT),benzothiophene(BT) and 4-methyldibenzothiophene(4-MDBT...     

常温常压下β沸石改性吸附剂脱除噻吩类硫的研究

在合成不同硅铝比Naβ沸石的基础上,采用固相离子交换方法制备了Cu(I)、Ag(I)离子改性的β沸石系列吸附剂。样品的结晶度和BET比表面积有所降低,XRD表征结果表明,所制备的样品保持了结构的完整性,随着硅铝比的增加,Naβ样品的BET比表面积增加。Cu(I)、Ag(I)离子的引入使样品的红外骨架振动峰向低波数移动,与相同硅铝比的Naβ沸石相比,吸附剂的BET比表面积有所降低。对模型油的静态吸附结果表明,硅铝摩尔比为25时Cu(I)β吸附性能最好,模型油中硫的质量分数降到10×10－6以下,脱除率达到95％,Ag(I)β次之,脱除率达到87％。常温常压下固定床动态吸附穿透实验得到Cu(I)β、Ag(I)β的穿透硫容分别为0.144mmol/g和0.132mmol/g。     

Adsorptive desulfurization by copper species within confined space

Copper species were incorporated into SBA-15 by solid-state grinding precursor with as-prepared mesoporous silica (SPA). The obtained materials (CuAS) were well-characterized by XRD, TEM, N(2) adsorption, H(2)-TPR, IR, and TG and compared with the material derived from calcined SBA-15 (CuCS). Surprisingly, CuO up to 6.7 mmol·g(-1) can be highly dispersed on SBA-15 by use of SPA strategy. Such CuO forms a smooth layer coated on the internal walls of SBA-15, which contributes to the spatial order and results in less-blocked mesopores. However, the aggregation of CuO takes place in CuCS material containing 6.7 mmol·g(-1) copper, which generates large CuO particles of 21.4 nm outside the mesopores. We reveal that the high dispersion extent of CuO is ascribed to the abundant silanols, as well as the confined space between template and silica walls provided by as-prepared SBA-15. The SPA strategy allows template removal and precursor conversion in one step, avoids the repeated calcination in conventional modification process, and saves time and energy. We also demonstrate that the CuAS material after autoreduction exhibits much better adsorptive desulfurization capacity than CuCS. Moreover, the adsorption capacity of regenerated adsorbent can be recovered completely.     

One-step synthesis of hierarchical zeolite beta via network formation of uniform nanocrystals

A hierarchical mesoporous network of zeolite beta with very high micropore as well as mesopore volume was synthesized without the need of a porogen at near 100% yield in the form of easily retrievable micrometer-sized particles. This was achieved by a dense-gel synthesis utilizing steam-assisted conversion (SAC) to induce a burst of nucleation. During the first phase of the synthesis, individual, evenly sized zeolite beta nanoparticles are formed that subsequently condense into a porous network displaying uniform mesopores. The final product consists of hierarchical self-sustaining macroscopic zeolite aggregates assembled from 20 nm crystalline domains of zeolite beta. The small size of the zeolite crystals in the resulting materials gives rise to mesopores with dominant pore sizes of about 13 nm. Large surface areas between 630 and 750 m(2)/g and total pore volumes up to 0.9 mL/g were obtained without sacrificing the microporosity (usually larger than 0.20 mL/g). Crystallization conditions were optimized for different Si/Al ratios between 10 and 33. A complete conversion into hierarchical zeolite beta was achieved in only a few hours at 170-180 °C if the amount of water present during the steam-assisted conversion was adequately adjusted. This dense gel steam conversion process proves to be a highly efficient strategy for fabricating hierarchical zeolite beta networks in a single step.     

Adsorptive desulfurization of propylene derived from bio-ethanol

We studied adsorption characteristics of a series of LTA zeolite as an adsorbent for desulfurization of propylene, that was produced from bioethanol by ethanol-to-olefin (ETO) conversion. A breakthrough curve (BTC) for adsorption of methanethiol, as one of the sulfur impurities of propylene produced from bioethanol, in the presence of propylene was measured using a fixed-bed column packed with the LTA zeolite. The BTC revealed that the effect of the competitive adsorption of propylene on the LTA zeolite strongly depended on a cation species exchanged in the micropores of the zeolite. Among the cation species examined in this study, bivalent cation of zinc (Zn²⁺) was proved to be the most effective one to increase the amount of methanethiol adsorbed on the LTA zeolite under the presence of propylene. The specific interaction of methanethiol with the LTA zeolite exchanged with Zn²⁺ was confirmed by the measurement of a temperature-programmed desorption (TPD) spectrum of methanethiol.     

Adsorptive desulfurization of diesel with mesoporous aluminosilicates

Mesoporous aluminosilicates (MAS) bearing microporous zeolite units and mesoporous structures were synthesized by the hydrothermal method. Adsorptive desulfurization ability of model oil and hydrotreated diesel was studied. The effects of template concentration, crystalization time and calcination time were investigated. The desulfurization ability of adsorbents was improved by transitional metal ion-exchanging. The adsorptive desulfurization of diesel was carried out on a fixed-bed system. The results show that the adsorptive capacity is MAS>MCM-41>NaY. The improvement of desulfurization ability of MAS by Cu⁺ is more significant than that of Ag⁺. Supported by National Basic Research Program of China (Grant No. 2006CB202507), National High-tech R&D Program (Grant No. 2006AA02Z209), and the National Natural Science Foundation of China (Grant No. 20806086)     

Oxidative dehydrogenation of propane by nitrous oxide and/or oxygen over Co beta zeolite

The oxidative dehydrogenation of propane has been studied with nitrous oxide (or mixture of nitrous oxide and oxygen) as oxidant. Nitrous oxide is a more selective but less active oxidant as compared with molecular oxygen. Upon increasing the concentration of N2O in the reaction mixture of propane and oxygen results in a substantial increase of propane conversion, while the selectivity to propene remains constant. The synergistic effect of O₂ and N₂O leads to a threefold higher yield of propene relative to than that of oxygen or nitrous alone. This revised version was published online in June 2006 with corrections to the Cover Date.     

磺酸型树脂酰胺化修饰及修饰产物的吸附脱硫研究

吸附技术以其低成本、低损耗和非破坏性等特征,在化工的清洁化方面受到广泛关注,对于汽油、柴油等烃类燃料的深度脱硫而言,吸附工艺正逐步显示出良好的应用前景[1～3].吸附剂是吸附技术的核心,已经使用或正在研制的烃类脱硫用吸附剂主要是一些无机材料,如经过不同修饰的分子筛和金属氧化物等[4～6].有机高分子吸附剂的开发研究还处于起步阶段,但已经发现有些聚合物材料可以通过化学修饰或负载,起到对烃体系中硫化物的吸附脱除作用[7～9].     

碱液后处理对纳米ZSM-5沸石孔道和酸度的影响

采用XRD、N2物理吸附、NH3-TPD以及TEM、IR和NMR手段,系统研究了NaOH碱液后处理对低硅铝比纳米ZSM-5沸石(Si/Al摩尔比为14.5、晶粒度为20～50 nm)孔道和酸度的影响.结果表明,在碱液中,低硅铝比纳米ZSM-5沸石主要发生限域脱硅,而且低硅铝比纳米ZSM-5沸石的碱液脱硅难度大于高硅铝比沸石.但在适当的碱液处理条件下(碱硅比为0.19～0.35,温度为60～80℃,处理时间为2～5 h)可以在其晶体内产生大量介孔,增加比表面积和孔容;同时增加弱酸和中强酸的浓度,并提高L酸比例.L酸的大量增加主要是由于产生了裸露的骨架铝(≡Alδ+),这与文献的观点有所不同.     

Amino acid adsorption on zeolite beta

A thermodynamic equilibrium model has been developed to describe amino acid adsorption on microporous materials. The model addresses electrostatic, hydrophobic and steric interactions. A procedure for fitting the model's parameters is presented and should be applicable to the majority of the common 20 amino acids. The approach is demonstrated using experimental measurements of L-phenylalanine and L-arginine on zeolite beta. Between the adsorption mechanisms of ion exchange and physisorption, the first can contribute as much as two-thirds of the phenylalanine adsorbed at saturation. For the materials tested, ion exchange is maximized when the zeolite's silicon-to-aluminum ratio is 12. When this atom ratio is raised to 100, ion exchange no longer plays a significant role, but the amount physisorbed increases by 30%.     

二次合成Y型杂原子分子筛的吸附脱硫研究

采用液-固相同晶取代反应制备骨架含Ga的Y型分子筛(AlY),研究其吸附脱除硫质量分数为500×10^-6模拟燃料中的硫化物。AlY处理含噻吩、四氢噻吩(THT)、4,6-二甲基二苯并噻吩(4,6-DMDBT)、二苯并噻吩(DBT)、苯并噻吩(BT)和4-甲基二苯并噻吩(4-MDBT)的模拟燃料时的吸附容量分别为7.0、17.4、14.5、16.9、6.9 和5.8mg(S)/g吸附剂。采用密度泛函理论(DFT)中的广义梯度近似方法(GGA)计算各分子中硫原子上的电荷数,噻吩、四氢噻吩、4,6-二甲基二苯并噻吩(4,6-DMDBT)、二苯并噻吩(DBT)、苯并噻吩(BT)和4-甲基二苯并噻吩(4-MDBT)中硫原子上电荷数分别为-0.159、-0.298、-0.214、-0.211、-0.193、-0.188。四氢噻吩和4,6-DMDBT中硫原子上的电子密度大于噻吩中硫原子上的电子密度,这就使得四氢噻吩和4,6-DMDBT中的硫原子与吸附位间的作用会明显大于噻吩中的硫原子与吸附位间的作用。采用AlY处理催化裂化汽油时的脱硫率可达68%。     

稀土金属氧化物对Y分子筛吸附脱硫性能的影响

以Y分子筛为母体,采用浸渍法制备了Y₂O₃/Y、CeO₂/Y和La₂O₃/Y三种吸附剂.以脱除正辛烷中的苯并噻吩为探针反应,考察了稀土金属氧化物负载量、吸附温度、吸附时间和剂油比对吸附剂脱硫性能的影响.结果表明,稀土金属氧化物最佳负载量为5%(质量分数),所得吸附剂在50 ℃、1 h、剂油比1∶30条件下,脱硫率均达到60%以上.甲苯的存在明显降低了吸附剂的脱硫性能.稀土金属氧化物在吸附过程中发生流失,在相同的条件下,三种稀土金属氧化物中,Y₂O₃的流失量最小,而CeO₂的流失量最大,CeO₂的流失量是Y₂O₃的10倍.     

Direct observation of growth defects in zeolite beta

High-resolution transmission electron microscopy reveals linear, "double pore" defects in the important zeolite beta. Structural interpretation of these defects gives evidence for the mechanism by which the zeolite crystallizes.     

纳米富铝β沸石的合成与表征

以低硅铝比焙烧后的硅铝胶固体为初始原料,在含F-近中性与低含水量体系下晶化合成出相对高结晶度的纳米富铝β沸石。实验考察了合成条件、硅铝胶焙烧对晶化产物的影响和晶化过程中Al配位状况变化,并采用XRD、XRF、SEM/TEM2、7AlMAS NMR物化方法对晶化产物进行表征。结果表明,含F-离子、H2O/SiO2摩尔比为2.4～6.0以及高温焙烧硅铝胶有利于合成高结晶度的纳米富铝β沸石;硅铝胶固体焙烧后能产生易于转化为β沸石晶核的Al四配位结构,而部分六配位Al在晶化过程中缓慢溶入β沸石晶核中而最终生成纳米富铝β沸石。     

Catalytic reforming of methane by carbon dioxide over nickel-exchanged zeolite catalysts

A series of nickel-exchanged catalysts based on ZSM-5, USY, and Mordenite zeolites has been prepared by the ionic exchange method. The NiZeol catalysts have been characterized by XRD and BET. The exchange levels and nickel contents of the catalysts have been determined by chemical analysis. The acidity of the zeolite supports has been investigated using NH₃ adsorption microcalorimetry. The number of acidic sites was found to decrease according to the following sequence: HUSY > HZSM-5 > HMOR. The temperature programmed reduction studies showed that the most reducible catalyst is NiZSM-5. The Ni-exchanged zeolites presented good catalytic performance in the methane reforming by CO₂. At a temperature of 650°C, CH₄ conversions of 71 and 54% were achieved on NiUSY and NiZSM-5 respectively. At 400°C, CO₂ FTIR adsorption has shown that CO₂ decomposes into CO and oxygen on NiZSM-5 which explains its reactivity at such a low temperature, while no decomposition of this probe molecule was observed on the NiUSY catalyst. The catalytic performance was found to vary in the following sequence at 650°C: NiUSY > NiZSM-5 > NiMOR. Moreover, the catalytic performances were found to depend strongly on the CO₂/CH₄ ratio in the feed and were markedly improved for CO₂/CH₄ greater than 1.     

Pervaporation performance of PDMS-NiY zeolite hybrid membranes in the desulfurization of gasoline

PDMS-Ni²⁺Y zeolite hybrid membranes were fabricated and used for the pervaporation removal of thiophene from model gasoline system. The structural morphology, mechanical stability, crystallinity, and free volume characteristics of the hybrid membranes were systematically investigated. Molecular dynamics simulation was employed to calculate the diffusion coefficients of small penetrants in the polymer matrix and the zeolite. The effect of Ni²⁺Y zeolite content on pervaporation performance was evaluated experimentally. With the increase of Ni²⁺Y zeolite content, the permeation flux increased continuously, while the enrichment factor first increased and then decreased possibly due to the occurrence of defective voids within organic–inorganic interface region. The PDMS membrane containing 5.0 wt% Ni²⁺Y zeolite exhibited the highest enrichment factor (4.84) with a permeation flux of 3.26 kg/(m² h) for 500 ppm sulfur in feed at 30 °C. The effects of operating conditions on the pervaporation performance were investigated in detail. It has been found that the interfacial morphology strongly influenced the separation performance of the hybrid membrane, and it was of great significance to rationally modify the interfacial region in order to improve the organic–inorganic compatibility.     

Hydrogen production by conversion of methane over nickel-supported USY-type zeolite catalysts

Hydrogen production by conversion of methane over Ni-supported zeolite catalysts was investigated, and Ni-supported USY-type zeolite (Si/Al₂ = 14.0, 360) was found to have longer catalytic lifetime than Ni-supported silica (Cab-O-Sil) catalyst, which had been reported to have the longest catalytic lifetime for this reaction.     

Deep desulfurization of FCC gasoline by selective adsorption over nanosized zeolite-based adsorbents

Deep desulfurization of FCC gasoline by selective absorption was performed on various ion-exchanged nanosized Y zeolites. It was found that the metal ion as well as calcination conditions have significant influence on the absorption performance. The highest S absorption capacity was obtained on a HCuCeY sample calcined in N₂ atmosphere.     

Fabrication of polyaniline with hierarchical structures in alkaline solution

Nanosheet- or nanorod-based microspheres and nanorod-based microrods of polyaniline (PANI) with hierarchical structures were successfully prepared by oxidation polymerization of aniline in alkaline solution. Temperature was found to have important influence on the morphology of PANI hierarchical structures and their building blocks. The concentration of alkali (NaOH) could be used to guide the morphological evolution of PANI, from leaf-like structures to nanosheet-based particles, and to nanorod-based microspheres and nanorod-based microrods with increasing concentration of NaOH in synthesis. The chemical structures of product were characterized by FTIR, UV-vis spectra and XRD, and its solubility was also studied in this report.