甲基噻吩在HY分子筛上的吸附、脱附及转化行为

由NH₄Y分子筛制备了HY分子筛,运用N₂吸附、NH₃-TPD和Py-FTIR等手段表征HY分子筛的物化性能;采用智能重量分析仪(IGA)方法研究了甲基噻吩(2-甲基噻吩、3-甲基噻吩)在HY分子筛上的吸附-脱附行为;采用程序升温脱附-质谱(TPD-MS)联用手段研究了甲基噻吩在HY分子筛上的转化行为。结果表明,在200 ℃下 2-甲基噻吩和3-甲基噻吩在HY分子筛中的强B酸上发生强化学吸附作用,与B酸结合后生成了甲基噻吩的碳正离子结构进而发生了歧化反应、脱烷基反应以及裂化反应;与2-甲基噻吩不同的是,3-甲基噻吩与HY通过一定的氢转移反应生成了3-甲基四氢噻吩,且200 ℃吸附条件下3-甲基噻吩比2-甲基噻吩更容易发生裂化反应。     

Effect of weak base modification on ZSM‐5 catalyst for methanol to aromatics

The effect of weak base modification on the catalytic performance of ZSM‐5 catalyst for conversion of methanol to aromatics was investigated. The catalysts were characterized using X‐ray diffraction, X‐ray fluorescence, N₂ adsorption–desorption, NH₃ temperature‐programmed desorption, Fourier transform infrared spectroscopy, scanning electron microscopy and thermogravimetry. The results showed that catalysts treated with weak base (NaHCO₃, Na₂CO₃ and NH₃⋅H₂O) exhibited a pore structure with interconnected micropores and mesopores. The existence of mesopores was beneficial for improving the diffusion of reactants and products, and the coke deposition resistance capacity of treated catalysts was enhanced greatly. Meanwhile, compared to traditional ZSM‐5 zeolite, the ratio of Brønsted to Lewis (B/L) acid sites of ZSM‐5/NH₃⋅H₂O (B/L = 7.35) zeolite slightly increased but the amount of acid sites reduced, while those of ZSM‐5/NaHCO₃ (B/L = 0.127) and ZSM‐5/Na₂CO₃ (B/L = 0.107) significantly reduced. Further, the catalyst treated with NH₃⋅H₂O solution was evaluated in the methanol to aromatics reaction and led to an enhanced aromatization reaction rate. The liquid hydrocarbons product distribution exhibited higher aromatic hydrocarbons yield (56.12%) and selectivity (40.28%) of benzene, toluene and xylene (BTX) with isoparaffin content reducing to 26.17%, which could be explained by appropriate B/L acid sites ratio, higher pore volumes and higher surface area.     

Base-induced Brönsted Acid Sites on Dealuminated HY Zeolite: A Solid-state NMR Spectroscopy Study

Using trimethylphosphine (TMP) and d₅-pyridine(deuterated pyridine) as the basic probe molecules, the concentrations of Brönsted acid sites on both HY zeolite and dealuminated HY zeolite have been quantitatively determined using solid-state ¹H and ³¹P magic-angle spinning (MAS) NMR. After adsorption of the probe molecules, the concentration of Brönsted acid sites on the dealuminated HY zeolite increases by about 25%, whereas that in the parent HY sample remains almost unchanged. The increase in the concentration of Brönsted acid sites is due to the appearance of base-induced Brönsted acid sites in the dealuminated HY zeolite. The terminal SiOH in the vicinity of the aluminum atom is “induced” to form a bridging hydroxyl group (SiOHAl) in the presence of the basic probe molecules. The mechanism of formation of the induced Brönsted acid sites has also been discussed.     

New Method for the Temperature‐ Programmed Desorption (TPD) of Ammonia Experiment for Characterization of Zeolite Acidity: A Review

In this review, a method for the temperature‐programmed desorption (TPD) of ammonia experiment for the characterization of zeolite acidity and its improvement by simultaneous IR measurement and DFT calculation are described. First, various methods of ammonia TPD are explained, since the measurements have been conducted under the concepts of kinetics, equilibrium, or diffusion control. It is however emphasized that the ubiquitous TPD experiment is governed by the equilibrium between ammonia molecules in the gas phase and on the surface. Therefore, a method to measure quantitatively the strength of the acid site (?H upon ammonia desorption) under equilibrium‐controlled conditions is elucidated. Then, a quantitative relationship between ?H and H₀ function is proposed, based on which the acid strength ?H can be converted into the H₀ function. The identification of the desorption peaks and the quantitative measurement of the number of acid sites are then explained. In order to overcome a serious disadvantage of the method (i.e., no information is provided about the structure of acid sites), the simultaneous measurement of IR spectroscopy with ammonia TPD, named IRMS‐TPD (infrared spectroscopy/mass spectrometry–temperature‐programmed desorption), is proposed. Based on this improved measurement, Brønsted and Lewis acid sites were differentiated and the distribution of Brønsted OH was revealed. The acidity characterized by IRMS‐TPD was further supported by the theoretical DFT calculation. Thus, the advanced study of zeolite acidity at the molecular level was made possible. Advantages and disadvantages of the ammonia TPD experiment are discussed, and understanding of the catalytic cracking activity based on the derived acidic profile is explained.     

Liquid‐phase α‐Pinene Isomerization over Fe‐doped Sulfated Zirconia Prepared by a Hydrothermal Treatment‐assisted Process

A series of Fe‐doped (0.5%–3%) sulfated zirconia have been prepared by a hydrothermal treatment‐assisted process. Textural and structural characterizations of the as‐synthesized materials were performed by means of N₂ adsorption, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy and thermogravi‐ metric analysis. Temperature‐programmed desorption of ammonia was used to determine the acidity of the samples. The effects of Fe‐doping on the structure, acidity and catalytic activity of sulfated zirconia for liquid‐phase α‐pinene isomerization were investigated. The incorporation of small amounts of Fe into sulfated zirconia results in the increase of sulfate content and the number of acid sites, which is responsible for the enhanced activity of Fe‐doped catalysts in comparison with the undoped one. Meanwhile, hydrothermal treatment helps to improve the activity of the catalyst.     

Nanoscale lanthanum oxide catalysts for self-condensation of acetone: preparation via self-assembly on anodic aluminum oxide,structure, and properties

A novel structured La₂O₃/AAO solid base catalyst was prepared by supporting lanthanum oxide (La₂O₃) on the surface of anodic aluminum oxide (AAO) under hydrothermal conditions. Catalytic activity of the catalyst was tested using self-condensation of acetone to diacetone alcohol as a probe reaction. The conversion of acetone reached 4.14% with the diacetone alcohol selectivity of 98%. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy disperse spectroscopy (EDS), thermogravimetric analysis (TGA), N₂ adsorption-desorption (BET), and temperature programmed desorption (CO₂-TPD). XRD patterns and SEM images indicated that La₂O₃ nanoscale particles with high crystallinity were uniformly distributed over the AAO surface. The results of CO₂-TPD showed that the calcination temperature led to the formation of medium-strength basic sites, strong basic sites, and to an increase of the basic strength. The strong basic sites and large basic strength are an important factor that influences the catalytic activity in the self-condensation of acetone to diacetone alcohol.     

Oxygen Sorption and Desorption Properties of Selected Lanthanum Manganites and Lanthanum Ferrite Manganites

Temperature‐programmed desorption (TPD) with a carrier gas was used to study the oxygen sorption and desorption properties of oxidation catalysts and solid‐oxide fuel cell (SOFC) cathode materials (La_0.85Sr_0.15)_0.95MnO_3+δ (LSM) and La_0.60Sr_0.40Fe_0.80Mn_0.20O_3‐δ (LSFM). The powders were characterized by X‐ray diffractometry, atomic force microscopy (AFM), and BET surface adsorption. Sorbed oxygen could be distinguished from oxygen originating from stoichiometry changes. The results indicated that there is one main site for oxygen sorption/desorption. The amount of sorbed oxygen was monitored over time at different temperatures. Furthermore, through data analysis it was shown that the desorption peak associated with oxygen sorption is described well by second‐order desorption kinetics. This indicates that oxygen molecules dissociate upon adsorption and that the rate‐determining step for the desorption reaction is a recombination of monatomic oxygen. Typical problems with re‐adsorption in this kind of TPD setup were revealed to be insignificant by using simulations. Finally, different key parameters of sorption and desorption were determined, such as desorption activation energies, density of sorption sites, and adsorption and desorption reaction order.     

Production of propene from 1-butene metathesis reaction on tungsten based heterogeneous catalysts

A new propene production route from 1-butene metathesis has been developed on heterogeneous 10WO₃/Al₂O₃-HY catalysts with different HY contents. It is found that the catalysts play bi-functionally first for the isomerization of 1-butene to 2-butene and then for the cross-metathesis between 1-butene and 2-butene to propene and 2-pentene. The combination of HY zeolite and Al₂O₃ is prerequisite for the production of propene. The propene yield keeps increasing with the HY content in the range of 10–70 wt%, where 10WO₃/Al₂O₃-70HY exhibits the highest propene yield. The MS-H₂-TPR and MS-O₂-TPO characterizations indicate that the increase of HY content in the catalysts weakens the interaction between W species and supports, whereas enhance the probability of coking on the metal species and acid sites.     

Microwave Hydrothermal Synthesis and Acidity of Nanosize Gallosilicate Mesoporous Molecular Sieves

A range of nanosize alkaline‐free gallosilicate mesoporous molecular sieves (GaMMS) were synthesized using microwave hydrothermal method and various analytical and spectroscopic techniques were employed to systematically investigate the structure, coordination geometry of gallium, acidic properties and catalytic activity. These nanosize GaMMSs exhibit high surface area (240 ～ 720 m²/g), pore volume (1.06 ～ 1.49 m³/g), narrow pore size distribution and nano‐particle size between 20 and 100 nm and four‐coordinated gallium site mainly, which were characterized by XRD, N₂ adsorption/desorption, TEM, ⁷¹Ga MAS‐NMR and ICP‐AES. Mesoporosity, mesostructure and nanosize can be controlled simply by microwave irradiation time and temperature. Pyridine‐IR result reveals the coexistence of Lewis and Brönstead acid sites in these nanosize GaMMS while NH₃‐TPD profiles suggest nanosize one has stronger acid site and contains more acid sites than the conventional one. Catalytic performance was evaluated using the catalytic cumene cracking test. The result indicates that the nanosize GaMMS shows a much higher activity than that of conventional GaMCM‐41, probably due to higher concentrations of H‐form sites, external surface and fast diffusion.     

Nano‐MoO3‐modified MCM‐22 for methane dehydroaromatization

The work reported was aimed at a simple method to improve the catalytic activity of Mo/HMCM‐22 in methane aromatization. The catalysts were characterized using X‐ray diffraction, scanning electron microscopy, N₂ adsorption–desorption, NH₃ temperature‐programmed desorption, infrared spectra of pyridine adsorption, X‐ray photoelectron spectroscopy and thermogravimetric analysis. Physicochemical measurements indicated that Mo species with smaller size in HMCM‐22 would sublimate more easily and form Mo species at the atomic/molecular level and then interact well with the internal Brønsted acid sites to form Mo–O–Al active species. Catalytic results confirmed that nano‐MoO₃‐modified HMCM‐22 showed higher methane conversion and aromatics yield (13.1 versus 8.9%) than commercial MoO₃‐modified HMCM‐22 (11.0 versus 7.5%). In addition, nano‐MoO₃‐modified HMCM‐22 showed better durability compared with commercial MoO₃‐modified MCM‐22. Copyright © 2015 John Wiley & Sons, Ltd.     

富氧条件下乙炔选择催化还原NOx

Acetylene as a reducing agent of metal exchanged HY catalysts, for selective catalytic reduction of NO in the reaction system of 0.16% NO, 0 （C2H2-SCR） was investigated over a series 08% C2H2, and 9.95% O2 （volume percent） in He. 75% of NO conversion to N2 with hydrocarbon efficiency about 1.5 was achieved over a Ce-HY catalyst around 300 ℃. The NO removal level was comparable with that of selective catalytic reduction of NOx by C3H6 reported in literatures, although only one third of the reducing agent in carbon moles was used in the C2H2-SCR of NO. The protons in zeolite were crucial to the C2H2-SCR of NO, and the performance of HY in the reaction was significantly promoted by cerium incorporation into the zeolite. NO2 was proposed to be the intermediate of NO reduction to N2, and the oxidation of NO to NO2 was rate-determining step of the C2H2-SCR of NO over Ce-HY. The suggestion was well supported by the results of the NO oxidation with O2, and the C2H2 consumption under the conditions in the presence or absence of NO.     

Gold Nanoclusters Confined in a Supercage of Y Zeolite for Aerobic Oxidation of HMF under Mild Conditions

Au nanoclusters with an average size of approximately 1 nm size supported on HY zeolite exhibit a superior catalytic performance for the selective oxidation of 5‐hydroxymethyl‐2‐furfural (HMF) into 2,5‐furandicarboxylic acid (FDCA). It achieved >99 % yield of 2,5‐furandicarboxylic acid in water under mild conditions (60 °C, 0.3 MPa oxygen), which is much higher than that of Au supported on metal oxides/hydroxide (TiO₂, CeO₂, and Mg(OH)₂) and channel‐type zeolites (ZSM‐5 and H‐MOR). Detailed characterizations, such as X‐ray diffraction, transmission electron microscopy, N₂‐physisorption, and H₂‐temperature‐programmed reduction (TPR), revealed that the Au nanoclusters are well encapsulated in the HY zeolite supercage, which is considered to restrict and avoid further growing of the Au nanoclusters into large particles. The acidic hydroxyl groups of the supercage were proven to be responsible for the formation and stabilization of the gold nanoclusters. Moreover, the interaction between the hydroxyl groups in the supercage and the Au nanoclusters leads to electronic modification of the Au nanoparticles, which is supposed to contribute to the high efficiency in the catalytic oxidation of HMF to FDCA.     

Selective hydroisomerization of n-dodecane over platinum supported on zeolites

In this study, in order to develop catalysts for the selective isomerization of higher paraffin, the hydroisomerization reaction of n-dodecane was performed as a model reaction. Pt/ZSM-48, Pt/HZSM-5, Pt/HY, and Pt/SAPO-11 were examined for the selective hydroisomerization of n-dodecane. The catalysts were characterized via X-ray powder diffraction, N₂ adsorption, and the temperature-programmed desorption of ammonia. Among the catalysts studied, the Pt/HZSM-48 catalyst exhibited the best isomerization selectivity in the hydroisomerization reaction of n-dodecane, which is attributed to the moderate acid sites and medium-sized pores present in the HZSM-48. The highest iso-dodecane yield was obtained at a reaction temperature of 280 °C in the Pt/HZSM-48 catalyst. The optimal selectivity of the n-dodecane hydroisomerization over the Pt/SAPO-11 catalyst was obtained at approximately 300 °C, which was slightly higher than that of the Pt/HZSM-48 catalyst.     

Retracted: Acid‐Catalyzed Aquation of Ni(II)‐Hydrazone Complexes: Kinetics and Solvent Effect

Complexes of the type [Ni(L)(H₂O)]Cl₂·nH₂O, where L = 2‐pyridyl‐3‐isatinbishydrazone ligands, have been synthesized and characterized on the bases of elemental analysis, molar conductance, IR, electronic spectra, and thermal analysis (TGA and DTA). Acid‐catalyzed aquation of the Ni(II) isatin‐bishydrazone complexes was followed spectrophotometrically in various water–methanol and water–acetone mixtures at temperature 298 K. Kinetic behavior of the acid aquation is a linear rate law, indicating that the acid‐catalyzed aquation of these complexes in water–methanol and water–acetone mixtures follows a rate law with k_obs = k₂[H⁺]. The effect of the mole fraction of the ganic solvent, i.e., methanol and acetone, on the acid aquation has been analyzed; the decrease in the rate constant values with increasing of the methanol or acetone ratios is attributable to the effect of the co‐organic solvent on the initial states of the acid aquation by the destabilization of the H⁺ ion.     

Silicalite-1修饰的HY型分子筛及其对纤维素水解的催化性能

采用silicalite-1对HY型分子筛进行修饰,得到具有核壳结构的复合分子筛HY/silicalite-1。通过X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、N2的吸附-脱附及吡啶吸附红外(Py-FTIR)等手段对不同晶化时间合成的HY/silicalite-1复合分子筛进行了表征,研究了复合分子筛对纤维素水解的催化性能。结果表明,晶化时间直接影响复合分子筛的晶体生长规律和两组分的相对含量,最佳晶化时间为16-24 h,所得到的复合分子筛外貌呈核壳结构,silicalite-1附晶生长在HY型分子筛的表面;随着晶化时间的延长,复合分子筛的表面由胶浊状变为光滑,最终变为鳞片状;其B酸量先减少后增加,而L酸量则先增加后减少。其中,晶化时间为24 h的HY/silicalite-1复合分子筛B酸量最大,L酸量最小,对纤维素水解反应具有良好的催化性能,葡萄糖收率由HY型分子筛催化获得的28.0%大幅提高至45.8%。     

Coloring–decoloring behavior of fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid oligomer/acetone composite in methanol

A reddish‐brown fluoroalkyl end‐capped 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS) oligomer/acetone composite was prepared by heating the white oligomer powder with acetone at 80 °C for 3 h. The color was not observed in the corresponding non‐fluorinated AMPS oligomer/acetone composite, which was prepared under similar conditions. The coloring was probably caused by the formation of acetone polyaldol condensation products in the fluorinated oligomeric gel network cores. The colored R_F‐(AMPS)_n‐R_F/acetone composite powders were stable and did not exhibit any color change after 2 years in natural light at room temperature. The colored composite powders dissolved in methanol to give a reddish‐brown solution at room temperature. However, the retro‐polyaldol condensation decolored the solution after 1 day at room temperature. This is the first example of the retro‐aldol polycondensation of acetone under mild conditions. The decoloration increased by between 38‐ and 70‐fold under UV irradiation, compared with that in dark conditions. The coloring–decoloring behavior was consistent and repeatable; therefore our fluorinated oligomer/acetone composites are promising candidates for new fluorinated coloring materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2555–2564     

Porous Organic Zirconium Phosphonate as Efficient Catalysts for the Catalytic Transfer Hydrogenation of Ethyl Levulinate to γ‐Valerolactone without External Hydrogen

Organic hybrid zirconium phosphonate materials (ZrATMP, ZrEDTMPS, ZrDTPMPA, and ZrHEDP) were synthesized through reaction of organic phosphonic acid sodium salt and ZrOCl₂ in water, which exhibited high catalytic activity on the conversion of ethyl levulinate (EL) to γ‐valerolactone (GVL) in the presence of isopropanol. The obtained catalysts were characterized by FT‐IR, TGA, XRD, BET, XPS, ICP‐AES, SEM, TEM, NH₃‐TPD, and CO₂‐TPD. The results demonstrate that the number of acid sites and basic sites between the layers of the catalysts play a very important role in promoting the conversion of EL to GVL and that the functional groups that exist in phosphates could regulate the number of acid and basic sites. Meanwhile, the catalysts could be easily separated from the reaction system and reused at least five times without any obvious decrease in activity or selectivity.     

Selective Conversion of Cellobiose and Cellulose into Gluconic Acid in Water in the Presence of Oxygen,Catalyzed by Polyoxometalate‐Supported Gold Nanoparticles

Gold nanoparticles loaded onto Keggin‐type insoluble polyoxometalates (Cs_xH_3?xPW₁₂O₄₀) showed superior catalytic performances for the direct conversion of cellobiose into gluconic acid in water in the presence of O₂. The selectivity of Au/Cs_xH_3?xPW₁₂O₄₀ for gluconic acid was significantly higher than those of Au catalysts loaded onto typical metal oxides (e.g., SiO₂, Al₂O₃, and TiO₂), carbon nanotubes, and zeolites (H‐ZSM‐5 and HY). The acidity of polyoxometalates and the mean‐size of the Au nanoparticles were the key factors in the catalytic conversion of cellobiose into gluconic acid. The stronger acidity of polyoxometalates not only favored the conversion of cellobiose but also resulted in higher selectivity of gluconic acid by facilitating desorption and inhibiting its further degradation. On the other hand, the smaller Au nanoparticles accelerated the oxidation of glucose (an intermediate) into gluconic acid, thereby leading to increases both in the conversion of cellobiose and in the selectivity of gluconic acid. The Au/Cs_xH_3?xPW₁₂O₄₀ system also catalyzed the conversion of cellulose into gluconic acid with good efficiency, but it could not be used repeatedly owing to the leaching of a H⁺‐rich hydrophilic moiety over long‐term hydrothermal reactions. We have demonstrated that the combination of H₃PW₁₂O₄₀ and Au/Cs_3.0PW₁₂O₄₀ afforded excellent yields of gluconic acid (about 85 %, 418 K, 11 h), and the deactivation of the recovered H₃PW₁₂O₄₀–Au/Cs_3.0PW₁₂O₄₀ catalyst was not serious during repeated use.     

Synthesis and Characterization of New Material——La/Zr/MMT Employed in Acetone Oxidation

A new material of zirconium pillared montmorillonite added with lanthanum （denoted as La/Zr/MMT） was prepared for acetone oxidation. Surface properties of the catalysts were investigated by means of XRD, TEM, TG-DTA and BET methods. The XRD result indicated that the interlayer space of the montmorillonite was enlarged from 1.57 to 4.85 um after the treatment with zirconium pillaring and the addition of lanthanum. N2 adsorption-desorption result showed that by the process of zirconium pillaring, the specific surface area of the sample was increased to 128.0 m^2/g, which was two times almost as large as pure montmorillonite. Simultaneously, the thermal stability was also enhanced. The activity of the new material on the total oxidation of acetone was investigated, and the results indicated that the catalytic activity of the montmorillonite was greatly improved. Over the sample of La/Zr/MMT, the T98 of acetone was obtained at 350 ℃, while it needs 400 ℃ over the pure montmorillonite. After 0.1% Pd was supported on the sample of La/Zr/MMT, the T98 decreased from 350 to 280 ℃, indicating the montmorillonite is a promising material for the control of some types of the volatile organic compounds such as acetone.     

On the synergistic catalytic properties of bimetallic mesoporous materials containing aluminum and zirconium: the Prins cyclisation of citronellal

Bimetallic three‐dimensional amorphous mesoporous materials, Al‐Zr‐TUD‐1 materials, were synthesised by using a surfactant‐free, one‐pot procedure employing triethanolamine (TEA) as a complexing reagent. The amount of aluminium and zirconium was varied in order to study the effect of these metals on the Brønsted and Lewis acidity, as well as on the resulting catalytic activity of the material. The materials were characterised by various techniques, including elemental analysis, X‐ray diffraction, high‐resolution TEM, N₂ physisorption, temperature‐programmed desorption (TPD) of NH₃, and ²⁷Al MAS NMR, XPS and FT‐IR spectroscopy using pyridine and CO as probe molecules. Al‐Zr‐TUD‐1 materials are mesoporous with surface areas ranging from 700–900 m² g^?1, an average pore size of around 4 nm and a pore volume of around 0.70 cm³ g^?1. The synthesised Al‐Zr‐TUD‐1 materials were tested as catalyst materials in the Lewis acid catalysed Meerwein–Ponndorf–Verley reduction of 4‐tert‐butylcyclohexanone, the intermolecular Prins synthesis of nopol and in the intramolecular Prins cyclisation of citronellal. Although Al‐Zr‐TUD‐1 catalysts possess a lower amount of acid sites than their monometallic counterparts, according to TPD of NH₃, these materials outperformed those of the monometallic Al‐TUD‐1 as well as Zr‐TUD‐1 in the Prins cyclisation of citronellal. This proves the existence of synergistic properties of Al‐Zr‐TUD‐1. Due to the intramolecular nature of the Prins cyclisation of citronellal, the hydrophilic surface of the catalyst as well as the presence of both Brønsted and Lewis acid sites synergy could be obtained with bimetallic Al‐Zr‐TUD‐1. Besides spectroscopic investigation of the active sites of the catalyst material a thorough testing of the catalyst in different types of reactions is crucial in identifying its specific active sites.