Methylation of 2-methylnaphthalene with methanol to 2,6-dimethylnaphthalene over HZSM-5 modified by NH4F and SrO

The methylation of 2-methylnaphthalene (2-MN) into 2,6-dimethylnaphthalene (2,6-DMN) was investigated over the solid acid catalysts.The results show that HZSM-5 modified by NH_4F has better catalytic performance than parent HZSM-5 due to the decrease in the acidity.When NH_4F/HZSM-5 is further modified by SrO,its catalytic activity decreases due to the decrease in the total acid amount and acidic strength.As a result,the comprehensive modification of NH_4F and SrO leads to the increase in the 2,6- DMN selectivity (2,6-DMN to DMN),up to 64.8% when 2-MN conversion is 10%.We calculated the ESP charge by density functional theory and the results show that the 6-position in 2-MN has higher ESP charge value than 7-position.The formation of 2,6-DMN is favored energetically as compared to that for 2,7-DMN.This suggests during the alkylation of 2-MN inside the ZSM-5 channel,the formation of 2,6-DMN is favored electronically than that of 2,7-DMN.Hence,lowering the acidity of catalyst is a key factor to obtain high selectivity of 2,6-DMN.     

Study on the adsorption of 1,5-, 1,6- and 2,6-dimethylnaphthalene on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites

Adsorption of the equilibrium mixture of 1,5-, 1,6- and 2,6-dimethylnaphthalene (DMN) was investigated on a series of alkaline and alkaline earth ion-exchanged faujasite zeolites using pulse test and breakthrough techniques. It was found that the adsorption of the DMNs would proceed through a complex mechanism governing by at least molecular diffusion, acid-base interaction, preferential interaction with cation and molecular displacement. All ion-exchanged faujasite zeolites only provided rejective systems for 2,6-DMN and some of them were potential adsorbents for the 2,6-DMN purification.     

水蒸气处理改性的SAPO-11分子筛催化合成2,6-二甲基萘的研究

采用水蒸气对SAPO-11分子筛进行改性.通过XRD、SEM、NH3-TPD以及N2吸脱附等表征手段对改性前后SAPO-11分子筛的结构、酸性进行表征,并研究了改性后分子筛催化合成2,6-二甲基萘反应性能的影响规律.结果表明,水蒸气处理使SAPO-11分子筛发生骨架脱铝,酸中心数量减少,比表面积和孔体积有所下降,从而使2,6-二甲基萘的选择性、2,6-二甲基萘与2,7-二甲基萘的比值及催化稳定性提高.     

Beta zeolite colloidal nanocrystals supported on mesoporous MCM-41

Zeolite-based composite materials prepared by the embedding of the beta zeolite nanophase from aqueous colloidal solution into matrices of preformed Si(Al)MCM-41 mesoporous molecular sieves have been characterized by different methods (XRD, SEM, FTIR, N2 adsorption, and TPD of NH3). Their potential as catalysts for toluene disproportionation has been compared to mechanical mixtures of freeze-dried nanobeta crystallites with Si(Al)MCM-41 mesoporous materials. It is found that the zeolite catalyst efficiency is not substantially changed by the presence of mesopores belonging to the matrix. It is suggested that formation of intergrown aggregates from the colloidal nanobeta particles provides own highly developed textural mesoporosity that makes the contribution of the diffusional alleviation of the support negligible.     

Cu改性SAPO-11分子筛催化萘和甲醇甲基化反应的研究

分别采用水热合成法和浸渍法对SAPO-11分子筛进行Cu改性.通过X射线衍射(XRD)、扫描电镜(SEM)、NH_3-程序升温脱附(NH_3-TPD)、H_2-程序升温还原(H_2-TPR)、~(29)Si固体核磁共振(~(29)SiMAS NMR)以及N_2吸附-脱附(N_2adsorption-desorption)等表征手段对改性前后SAPO-11分子筛的结构、酸性进行表征,并研究了改性后分子筛催化合成2,6-二甲基萘反应性能的影响规律.结果表明,经水热合成法进行Cu改性的SAPO-11分子筛结晶度升高,酸中心数量增加,比表面积和孔体积上升,从而使萘的转化率、2,6-二甲基萘的选择性、2,6-二甲基萘与2,7-二甲基萘的比值及2,6-二甲基萘的收率提高.     

Highly efficient two-step selective synthesis of 2,6-dimethylnaphthalene

2,6-Dimethylnaphthalene (2,6-DMN), a key raw material for poly(ethylene naphthalate) (PEN), was selectively synthesized via a two-step process in an overall 66% yield from commercially available 4-bromotoluene and 3-methyl-3-buten-1-ol. The ligand-free Heck reaction of the starting materials produced γ-(p-tolyl)-substituted aldehyde that was cyclized with an acid to give 2,6-DMN after in situ oxidation. No other isomers of 2,6-DMN were found.     

Isomerization of dimethylnaphthalenes over zeolites

A dimethylnaphthalene (DMN) isomer mixture from a reforming unit was reacted at 350°C and atmospheric pressure over H-mordenites (Si/Al ranging from 5 to 100), a partially decationated NaY (Si/Al=2.4) and a slightly dealuminated HY (Si/Al=5), with the aim of increasing the 2,6- and 2,7-DMN content by isomerization. The best results were obtained on H-mordenite with Si/Al=10, where shape selective effects made possible to double the amount of the valuable isomers while limiting to a negligible extent the side reactions of disproportionation and dealkylation.     

Methylation of 2-methylnaphthalene over metal-impregnated mesoporous MCM-41 for the synthesis of 2,6-triad dimethylnaphthalene isomers

Research on Chemical Intermediates - 2,6-Dimethylnaphthalene (2,6-DMN) is one of the key intermediates for the production of polyethylene naphthalate (PEN), which demonstrates superior properties...     

Liquid phase acylation of 2-methylnaphthalene catalyzed by H-beta zeolite

Liquid phase Friedel–Crafts acylation of 2-methylnaphthalene (2-MN) has been investigated over zeolite catalyst. The influence of zeolite structures, substituents on naphthalene, acylating agents and solvents on the acylation has been discussed. 2-Methyl-6-butyrylnaphthalene (2,6-BMN), a promising precursor of 2,6-naphthalenedicarboxylic acid (2,6-NDCA), has been synthesized by the acylation of 2-MN using butyric anhydride (BA) as an acylating agent and H-beta zeolite as a catalyst. The influence of the preparative methods and dosage of H-beta zeolite, the molar ratio of reactants, the reaction temperature and reaction time on the catalytic butyrylation was also studied. The H-beta zeolite exchanged for four times and calcined at 550 °C possessed relatively better catalytic performance. Under the optimized condition, the conversion of BA reached 78.3% and the selectivity for 2,6-BMN was 53.1%.     

Selective Synthesis of 2,6-Dimethylnaphthalene by Transalkylation in the Presence of Acid Ionic Liquids[Cnmim]Cl-AlCl3

A highly selective synthesis of 2,6-dimethylnaphthanlene(2,6-DMN) by transalkylation between 2-methylnaphthanlene(2-MN) and 1,2,4,5-tetramethylbenzene(TeMB) was performed with 1-alkyl-3-methylimidazo- lium aluminum chloride([Cnmim]Cl-AlCl3) ionic liquids(ILs) as catalysts. The influences of the alkyl group as the organic cation, the acidic strength of [C4mim]Cl-AlCl3 ILs as well as the reaction conditions on the catalytic performance were investigated. [C4mim]Cl-AlCl3 ILs[x(AlCl3)=71%] exhibited high activity and selectivity toward 2,6-DMN. The selectivity to 2,6-DMN and the 2,6-DMN/2,7-DMN ratio reached up to 68.2% and 3.7:1, respectively. The UV-Vis spectrum of TeMB treated by different ILs shows that the protonated degree of TeMB dependeds on the acidity strength of ILs, which has a significant impact on the reaction results. The high protonated degree of TeMB is advantageous to enhancing the conversion of transalkylation and the large stereo-hindrance effect of TeMB is favorable to improving the selecivity to 2,6-DMN.     

Effect of the catalyst MCM-41 on the kinetic of the thermal decomposition of poly(ethylene terephthalate)

The aim of this work is to determine the activation energy for the thermal decomposition of poly(ethylene terephthalate)—PET, in the presence of a MCM-41 mesoporous catalyst. This material was synthesized by the hydrothermal method, using cetyltrimethylammonium as template. The PET sample has been submitted to thermal degradation alone and in presence of MCM-41 catalyst at a concentration of 25% in mass (MCM-41/PET). The degradation process was evaluated by thermogravimetry, at temperature range from 350 to 500 °C, under nitrogen atmosphere, with heating rates of 5, 10 and 25 °C min^?1. From TG, the activation energy, determined using the Flynn–Wall kinetic method, decreased from 231 kJ mol^?1, for the pure polymer (PET), to 195 kJ mol^?1, in the presence of the material (MCM-41/PET), showing the catalyst efficiency for the polymer decomposition process.     

A novel method for synthesis of mesoporous ZSM-5 from iron ore tailings

Mesoporous ZSM-5 was prepared from iron ore tailings (IOT) using a two-step process. Mesoporous MCM-41 was first synthesized using cetyltrimethylammonium bromide (CTAB) as mesoporous template and IOT as silica source. The CTAB in the as-synthesized MCM-41 was used as the mesoporogen to produce the mesoporous ZSM-5, by recrystallizing the amorphous walls of MCM-41 with tetrapropylammonium bromide (TPABr) as the structure-directing agent via solid-phase conversion. To evaluate the textural properties of mesoporous ZSM-5, the as-synthesized samples were characterized using x-ray diffraction, scanning electron microscopy, transmission electron microscopy, ²⁹Si, ²⁷Al magic angle spinning nuclear magnetic resonance spectroscopy, and nitrogen adsorption. The results show that phase separation between the surfactant and zeolite crystals was avoided in the solid-phase conversion process, which transforms the as-synthesized MCM-41 to mesoporous zeolite. Therefore, the synthetic route presented herein provides a novel method for the synthesis of mesoporous ZSM-5 from IOT.

     

MCM-41-HY复合分子筛的合成及其在深度加氢脱硫中的应用

在水热条件下合成了包覆型MCM-41-HY复合分子筛.采用XRD、N2气吸附和SEM等方法对其进行了表征.结果表明,MCM-41-HY复合分子筛和MCM-41与H型Y沸石(HY)的机械混合物明显不同,在复合分子筛MCM-41-HY中,中孔相MCM-41附晶生长在HY沸石上,将HY包覆起来.以二苯并噻吩为模型化合物,考察了该材料担载NiMo催化剂的加氢脱硫活性.结果表明,MCM-41-HY复合分子筛与MCM-41和HY的机械混合物担载NiMo催化剂的加氢脱硫(HDS)活性相当,但MCM-41-HY复合分子筛担载NiMo催化剂的裂化活性较低.其裂化活性不同的原因在于其载体孔道结构和酸性位的分布不同.     

Synthesis, characterization, and catalytic properties of stable mesoporous molecular sieve MCM-41 prepared from zeolite mordenite

Mesoporous molecular sieves (denoted as M-MCM-41) with ordered hexagonal structure have been successfully synthesized from the assembly of precursors from preformed zeolite Mordenite with CTAB surfactant micelle in alkaline media. The samples were characterized by XRD, N₂ adsorption, IR and DTG. The materials exhibit highly hydrothermal stability, as compared with conventional MCM-41. Characterization results indicate that the mesoporous walls of M-MCM-41 contain the secondary building units similar to those in microporous crystal of zeolite Mordenite. In catalytic dealkylation of C10⁺ aromatic hydrocarbon, M-MCM-41 shows higher activities in comparison with Mordenite and MCM-41, which would be ascribed to the combination of advantages of both MCM-41 (large pores) and Mordenite (strong acidity). Furthermore, this synthesis strategy could be used as a new general method for the preparation of hydrothermally stable mesoporous aluminosilicate materials under alkaline conditions.     

Synthesis of ITQ-2 zeolite under static conditions and its properties

Zeolite ITQ-2 can be synthesized by swelling the layers of MCM-22 precursor. It has a single delami-nated structure of MWW with thickness of 2.5 nm. It shows disordered properties in long range and ordered in short range, which is a promising catalytic ma…     

Metal-Chelate Immobilization of Lipase onto Polyethylenimine Coated MCM-41 for Apple Flavor Synthesis

An enzyme immobilized on a mesoporous silica nanoparticle can serve as a multiple catalyst for the synthesis of industrially useful chemicals. In this work, MCM-41 nanoparticles were coated with polyethylenimine (MCM-41@PEI) and further modified by chelation of divalent metal ions (M = Co²⁺, Cu²⁺, or Pd²⁺) to produce metal-chelated silica nanoparticles (MCM-41@PEI-M). Thermomyces lanuginosa lipase (TLL) was immobilized onto MCM-41, MCM-41@PEI, and MCM-41@PEI-M by physical adsorption. Maximum immobilization yield and efficiency of 75 ± 3.5 and 65 ± 2.7% were obtained for MCM@PEI-Co, respectively. The highest biocatalytic activity at extremely acidic and basic pH (pH = 3 and 10) values were achieved for MCM-PEI-Co and MCM-PEI-Cu, respectively. Optimum enzymatic activity was observed for MCM-41@PEI-Co at 75 °C, while immobilized lipase on the Co-chelated support retained 70% of its initial activity after 14 days of storage at room temperature. Due to its efficient catalytic performance, MCM-41@PEI-Co was selected for the synthesis of ethyl valerate in the presence of valeric acid and ethanol. The enzymatic esterification yield for immobilized lipase onto MCM-41@PEI-Co was 60 and 53%, respectively, after 24 h of incubation in n-hexane and dimethyl sulfoxide media.

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Graphical Abstract Divalent metal chelated polyethylenimine coated MCM-41 (MCM-41@PEI-M) was used for immobilization of Thermomyces lanuginosa lipase catalyzing green apple flavor preparation

     

Mesoporous materials with zeolite framework: remarkable effect of the hierarchical structure for retardation of catalyst deactivation

Hierarchical MFI zeolite was synthesized following a synthesis route using organic-inorganic hybrid surfactants; the resultant zeolite with mesoporous/microporous hierarchical structure exhibited remarkably high resistance to deactivation in catalytic activity of various reactions such as isomerization of 1,2,4-trimethylbenzene, cumene cracking, and esterification of benzyl alcohol with hexanoic acid, as compared with conventional MFI and mesoporous aluminosilicate MCM-41.     

EFFECT OF CRYSTALLIZATION TEMPERATURE ON MCM-41 SYNTHESIS

在Ｎａ２ＯＳｉＯ２ＣＴＡＢＨ２Ｏ四元水热体系中系统地考察了晶化温度对中孔ＭＣＭ４１分子筛合成及其骨架结构的影响。实验结果表明，提高晶化温度虽然能明显加快晶化速率，缩短晶化时间，但同时样品的结晶度和中孔骨架结构的有序度却被迅速破坏。这些特点与传统沸石的合成过程完全不同，其原因主要是合成ＭＣＭ４ｌ时所用的模板剂及其在合成中所起的模板作用与传统沸石完全不同。相对低的晶化温度（如１００℃）有利于高质量和高热稳定性的中孔ＭＣＭ４ｌ分子筛的合成。     

MCM-41 mesoporous silica: a highly efficient and recoverable catalyst for rapid synthesis of α-aminonitriles and imines

In this work, pure MCM-41 mesoporous silica with active mesoporous sites has been successfully applied, as a highly efficient and recoverable catalyst, for the rapid and convenient synthesis of α-aminonitriles and imines. Various imines, as the intermediate of the Strecker reaction, were simply prepared from condensation of a wide range of aldehydes and amines in the presence of low loading of MCM-41 mesoporous silica under solvent-free conditions at room temperature in high to quantitative yields. Furthermore, the corresponding α-aminonitrile derivatives were prepared through the three-component Strecker reaction using trimethylsilylcyanide catalyzed by MCM-41 as a bifunctional heterogeneous mesoporous solid catalyst.