Production of linear alkylbenzene over Ce containing Beta zeolites

Ce-encapsulated Beta zeolite was synthesized by a one-pot hydrothermal method with citric acid complexing Ce in the absence of Na species.Additional citric acid can effectively prevent the deposition of Ce species during the hydrothermal synthesis of zeolites,leading to uniform distribution of Ce cluster in the framework of Beta zeolites.Moreover,the sodium-free synthesis system resulted that the Brønsted acid sites were mainly located on the straight channels and external surface of Beta zeolites,improving the utilization of Brønsted acid sites.In addition,Ce encapsulated Beta zeolites showed enhanced activity and robust stability in the alkylation of benzene with 1-dodecene based on the synergistic effect between Ce species and Brønsted acid sites,which pave the way for its practical application in the production of alkylbenzene.

NiMo/Al_2O_3 catalyst containing nano-sized zeolite Y for deep hydrodesulfurization and hydrodenitrogenation of diesel

Two mixed-matrix NiMo/Al2O3 catalysts containing nano-and micro-sized zeolite Y have been prepared to explore the size effect of zeolite Y particle on the hydrodesulfurization（HDS）and hydrodenitrogenation（HDN）activities of fluid catalytic cracking（FCC）diesel.They were characterized by SEM,BET,XRD,H2-TPR,NH3-TPD and HRTEM.The results show that the catalyst containing nano-sized zeolite Y possesses larger average pore diameter,higher pore volume,weaker and lesser acid sites,more easily reducible metal phases,shorter MoS2 slabs and more slab layers than the catalyst containing micro-sized zeolite Y.The catalysts were also evaluated with a high-pressure fixed-bed reactor using real FCC diesel as feed.The results display that the catalyst containing nano-sized zeolite Y bears higher HDS and HDN activities and exhibits higher relative rate constant for the removal of total sulfur or nitrogen than the one containing micro-sized zeolite.

Synthesis of zeolite Beta containing ultra-small CoO particles for ethylbenzene oxidation

Zeolite Beta containing ultra-small CoO particles was synthesized from a one-step hydrothermal process. The synthesis route involves the pre-mixture of hydrofluoric acid with tetraethylammo- nium hydroxide （in a molar ratio of 1.3-1.5：1） before the addition of a silicon and cobalt source.Investigations by scanning electron microscopy, X-ray diffraction, UV-Vi s spectroscopy, X-ray pho-toelectron spectroscopy, H 2 -temperature-programmed reduct i on and transmi ssi on el ectron mi -croscopy confirm the presence of ultra-small CoO particles in the zeolite Beta structure. The ul-tra-small CoO particles in zeolite Beta present high stability against both oxidation and reduction atmospheres at high temperatures. The catalytic performance of the CoO-containing zeolite Beta catalysts was compared with other Co-containing zeolites by evaluating ethylbenzene oxidation reactivity. The CoO-containing zeolite Beta exhibits high ethylbenzene conversion and high selectiv-ity to acetophenone and 1-phenylethanol. The high activity of this catalyst system can be attributed to the high dispersion of the ultra-small CoO particles in the Beta structure.

Adsorptive desulfurization over hierarchical beta zeolite by alkaline treatment

Hierarchical beta zeolites with SiO2/Al2O3 molar ratios of 16 to 25 were obtained by alkaline treatment in NaOH solution. The effects of treatment temperature on crystallinity, textural properties and chemical composites were studied by XRD, N2 sorption, FT-IR and XRF techniques. The desulfurization performance of parent and alkaline-treated beta zeolites was investigated by static absorption in four model fuels, containing four sulfur compounds of different molecular sizes like thiophene （TP）, 3-methylthiophene （3-MT）, benzothiophene （BT） and dibenzothiophene （DBT）, respectively. The crystallinity was observed to be successfully maintained when the treatment temperature was below 50 ℃. Mesoporosity of beta zeolite was evidently developed with alkaline treatment. The formation of mesopore remarkably improved the desulfurization performance for TP, 3-MT, BT and DBT, especially for DBT with larger molecular diameter. Though the addition of toluene in the model fuels resulted in a significant drop of the desulfurization performance of mesoporous beta zeolite, the introduction of cerium ions to some extent mitigated the effect of toluene, which means that both the adsorbent’s porous structure and the adsorption mode are responsible for the desulfurization performance. The adsorbent of cerium ion-exchanged mesoporous beta showed about 80% recovery of desulfurization after the first regeneration.

Surface dealuminated Beta zeolites supported WO3 catalyst and its catalytic performance in tetralin hydrocracking

In this study,selective dealumination of Beta zeolites was performed through partially removing the templating agent in Beta zeolites by calcination and then removing the aluminum on the external surface of Beta zeolites with acid treatment.Hydrocracking catalysts were prepared by loading WO_(3)onto these dealuminated Beta zeolites.It was shown that the surface SiO_(2)/Al_(2)O_(3)of selectively dealuminated Beta zeolites was higher than that of conventionally dealuminated samples for the same bulk SiO_(2)/Al_(2)O_(3),and the hydrogenation activity of the catalyst of the selectively dealuminated Beta zeolites was lower than that of conventionally dealuminated Beta zeolites.The experimental results for tetralin hydrocracking to BTX showed that the catalysts based on the selectively dealuminated Beta zeolites had higher BTX selectivity and lower coke formation rate than that the catalysts based on the conventionally dealuminated Beta zeolites.

Catalytic performance of Cu-and Zr-modified beta zeolite catalysts in the methylation of 2-methylnaphthalene

2,6-Dimethylnaphthalene(2,6-DMN) is a commercially important chemical for the production of polyethylenenaphthalate and polybutylene naphthalate. However, its complex synthesis procedure and high production cost significantly reduce the use of 2,6-DMN. In this study, the synthesis of 2,6-DMN was investigated with methylation of 2-methylnaphthalene(2-MN) over metal-loaded beta zeolite catalysts including beta zeolite, Cu-impregnated beta zeolite and Zr-impregnated beta zeolite. The experiments were performed in a fixed-bed reactor at atmospheric pressure under a nitrogen atmosphere. The reactor was operated at a temperature range of 400–500 °C and varying weight hourly space velocity between 1 and 3 h^(-1).The results demonstrated that 2,6-DMN can be synthesized by methylation of 2-MN over beta type zeolite catalysts.Besides 2,6-DMN, the product stream also contained other DMN isomers such as 2,7-DMN, 1,3-DMN, 1,2-DMN and 2,3-DMN. The activity and selectivity of beta zeolite catalyst were remarkably enhanced by Zr impregnation, whereas Cu modification of beta zeolite catalyst had an insignificant effect on its selectivity. The highest conversion of 2-MN reached81%, the highest ratio of 2,6-DMN/2,7-DMN reached 2.6 and the highest selectivity of 2,6-DMN was found to be 20% by using Zr-modified beta zeolite catalyst.

Preparation and Characterization of Zeolite Beta with Low SiO_2/Al_2O_3 Ratio

Zeolite beta with a low SiO2/Al2O3 ratio was synthesizcd by a novel two-step process. The synthesized sample was characterized with XRD, SEM, FTIR, and N2 adsorption-desorption and solid-state MAS NMR. The results showed that aluminium species were inserted into the framework of zeolite beta. The BET surface area, volume, and particle size of the zeolite beta sample decreased with decreasing SiO2/Al2O3 ratio. Our process was proved an efficient route to synthesize zeolitc beta with a low SiO2/Al2O3 ratio.

Synthesis of Single Crystals of Zeolite Betaby Using Two Silica Sources

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Etherification of HMF to biodiesel additives: The role of NH4+ confinement in Beta zeolites

The role of NH4^+ ion confinement in the catalytic etherification of HMF(5-hydroxymethylfurfural) with ethanol to biodiesel additives was evidenced by studying the catalytic behavior of NH4^+-Beta zeolites with SiO2/Al2O3 ratios of 25 and 75.In order to affect the strength and distribution of the acidic sites, as well as the mobility of NH4^+ ions in the zeolites cages, a secondary level of porosity was introduced in the NH4^+-Beta, presenting a different stability versus alkaline treatment, by using a thermal or an ultrasound assisted method.By analyzing the catalytic behavior in these two series of samples with respect to the changes in porosity by nonlocal density functional theory, structure by XRD, amount of acid sites by FT-IR and mobility of NH4^+ cations by measurements of reversible NH4^+ exchange capacity, was evidenced a decrease in catalytic performances both in terms of rate of HMF depletion and productivity to the main products, when confinement of the ammonium ions is lost due to the introduction of mesoporosity.The high capability of ammonium ions release, associated to the mono-dentate configuration,and the minor confinement effect inside the zeolite pore system, due to the more opened pores structure of mesoporous zeolites, hinders both the direct etherification of HMF to EMF [5-(ethoxymethyl)furan-2-carbaldehyde] and the parallel reaction pathway via acetalization, favoring the rapid desorption of the HMFDEA [5-(hydroxymethyl)furfural diethyl acetal] product out of the crystal and the consequent inhibition of the consecutive reactions to EMFDEA [5-(ethoxymethyl)furfural diethyl acetal] and EMF.

Beta@ZIF-67复合材料的制备及对聚乳酸塑料的催化降解性能

以聚乳酸(PLA)为代表的可降解塑料被认为是传统石油基塑料的合适替代品.然而,PLA自然降解的时间较长,同时伴随着CO_(2)的排放.因此,升级回收PLA更有利于实现可持续发展.本文通过将沸石咪唑酯骨架(ZIF-67)生长在Beta沸石表面,制备了一种Beta@ZIF-67复合材料.该材料可以实现废弃PLA塑料的高效催化降解,在180℃下反应4 h即可将日常生活中所用PLA塑料完全转化为乳酸甲酯(产率高达76.4%).这种高催化效率得益于复合材料开放的孔道结构和较大的比表面积,以及ZIF-67(Lewis酸/碱)与Beta分子筛(Brønsted酸)所提供活性位点的协同作用.本研究为沸石分子筛复合催化剂的设计合成及用于聚乳酸塑料催化降解提供了新的途径.

Deactivation mechanism of beta-zeolite catalyst for synthesis of cumene by benzene alkylation with isopropanol

The alkylation of benzene with isopropanol over beta-zeolite is a more cost-effective solution to cumene production. During the benzene alkylation cycles, the cumene selectivity slowly increased, while the benzene conversion presented the sharp decrease due to catalyst deactivation. The deactivation mechanism of betazeolite catalyst was investigated by characterizing the fresh and used catalysts. The XRD, SEM and TEM results show that the crystalline and particle size of the beta-zeolite catalyst almost remained stable during the alkylation cycles. The drop in catalytic activity and benzene conversion could be explained by the TG, BET,NH_3-TPD and GC–MS results. The organic matters mainly consisted of ethylbenzene, p-xylene and 1-ethyl-3-(1-methyl) benzene produced in the benzene alkylation deposited in the catalyst, which strongly reduced the specific surface area of beta-zeolite catalyst. Moreover, during the reaction cycles, the amount of acidity also significantly decreased. As a result, the catalyst deactivation occurred. To maintain the catalytic performance,the catalyst regeneration was carried out by using ethanol rinse and calcination. The deactivated catalyst could be effectively regenerated by the calcination method and the good catalytic performance was obtained.

Crystallization behavior of zeolite beta from acid-leached metakaolin

Well-crystallized zeolite beta was synthesized by using acid-leached metakaolin as the silica-alumina source and tetraethylammonium hydroxide structure-directing agent.The influence of the composition of the reaction mixture on product crystallinity was investigated,and the crystallization process was studied by examining solid samples obtained at different synthesis times.Results showed that the acid-leached metakaolin was fully converted into soluble aluminum and silicon species,which is crucial for the formation of well-crystallized zeolite beta.At the beginning of the crystallization process,these soluble aluminum and silicon species formed a aluminum-rich intermediate structure with layer morphology.With the crystallization proceeding,more silicon species were incorporated into the zeolite beta framework and the layered structure was changed into spherical particles of zeolite beta with high SiO 2 /Al 2 O 3 ratio and crystallinity.

响应面模型用于Beta分子筛催化剂蜂窝状整体式成型的研究

Beta分子筛由于具有独特的三维十二元环孔道结构,可提供更多活性组分附着位点,是在实际应用中具有优异性能的工业催化剂。在工业使用中,蜂窝整体式催化剂具有通量高、流场均匀、压降小、不易堵塞的优点,是气固或者液固催化反应的最优解决方案。但由于Beta分子筛吸水率高,收缩率大,导致蜂窝成型困难,严重限制了Beta分子筛的工业应用。基于此,选择拟薄水铝石(SB粉)为黏结剂、硝酸为胶溶剂、田菁粉为助挤剂,在水粉比为0.6的条件下制备一系列蜂窝整体式成型Beta分子筛催化剂,基于响应面法,评价了各原料的配比对蜂窝整体式催化剂机械强度的影响,得到了催化剂的机械强度与3个因素(黏结剂用量、胶溶剂用量、助挤剂用量)之间关系的二阶多项式近似模型函数。将试验结果与预测值进行对比,证明了预测模型的可靠性,并利用该模型找到最优的Beta分子筛蜂窝成型条件为SB粉质量分数36.1%、硝酸质量分数8.4%、田菁粉质量分数4.7%。

La掺杂改性Co-Beta催化丙烷脱氢

钴基催化剂在高温反应中易团聚烧结,且对其活性中心认识不足。为此设计了一种新型CoLa双金属催化剂,通过稀土金属La隔离并稳定钴物种,从而提高催化剂的反应活性。通过调控La在材料中的掺杂量,建立不同分散度与催化性能之间的构-效关系,以深入了解活性中心。采用XRD、XPS、化学吸附、探针分子红外等表征手段对催化剂中Co物种的存在形式、化学环境和尺寸大小等催化相关性质进行分析。结果表明,La的掺杂可以促进Co物种的分散,并增强Co物种与载体之间的相互作用。

An IR Study on Adsorption of CO and NO on Copper Ion-exchanged Zeolite Beta

Thee adsorption of CO and NO on copper ion-exchanged zeolite Beta was investigated using IR method.It was found that the thermalvacuum pretreatment procedure could result in the reduction of Cu2+ions in zeolite Beta.The adsorption of CO on Cu+sites in zeolite Beta closely follows Langmuir isotherm.Another Cu+species may form during the reaction between water and CO.The catalytic decomposition of NO on the zeolite was observed at room temperature,indicating that the decomposition reaction may occur between two coordinated NO ligands of the same dinitrosyhc complex.Furthermore,the appearance of two series of NO adsorption bands reveals that copper ions existing at different cation sites may have different effect on the adsorption and decomposition of NO molecules.

Cubic Mesoporous Aluminosilicate with Primary Structure Units of Zeolite Beta in the Pore Wall

Mesoporous aluminosilicate with cubic ordered structure was synthesized by two-step crystallization, which showed stronger acid sites and more effective activity for catalytic alkylation of 2, 4-ditert-butylphenol with tert-butanol than conventional H-AlMCM-48 materials.

Theoretical Study on a 42 T Model of Beta Zeolite by Density Functional Theory Simulation

Density functional theory was applied to study the structure of Beta zeolite. A model cluster containing 41Si atoms, 1 Al atom, 70 O atoms and 29 H atoms was constructed. The model structures were optimized using the Becke＇s three-parameter hybrid method with the Lee-Yang-Parr correlation functional （B3LYP） and the 6-31G basis set applying the Gaussian03 program package. The NMR parameters were calculated to validate the rationality of the model. It was found that in the optimization models, all O-H bond lengths were in range of 0.984-0.985A^°, among which the model with O-H bond length of 0.98478A^° was more stable than the others. The ^1H and ^27Al chemical shifts of the most stable model were 4.03434 and 55.74 ppm, which were pretty consistent with Larry＇ s experimental data of 4.1 and 54 ppm. The relationship between other structure parameters and total relative electric energy has also been found. All the results exhibit that the 42 T （the total number of Si and Al atoms is 42） model has common properties of the standard of zeolite Beta.

Sn-beta分子筛的合成和应用进展

综述了Sn-beta分子筛合成方法及其近年来在热门研究领域(葡萄糖转化制备乳酸甲酯、丙烷脱氢制备丙烯、乳酸制备L-丙交酯)的进展。对不同方法制备的Sn-beta分子筛优缺点、Sn物种状态及其催化性能间的关系进行了阐述,指出了目前Sn-beta分子筛存在的问题,对其未来发展方向进行了展望。