Ga改性的HZSM-5分子筛甲醇芳构化催化反应性能

以浸渍法和水热合成法向ZSM-5分子筛中引入Ga助剂对其进行改性。采用XRD、XPS、NH₃-TPD和SEM等技术对改性前后的分子筛进行了表征。结果表明,采用两种不同引入方式引入Ga助剂对分子筛的晶体结构、孔径及形貌影响均很小,而对分子筛酸性的影响与Ga的引入方式有关。其中,浸渍法引入Ga对分子筛的酸性影响不明显,只是其中的强酸位略有减少。而水热合成法引入Ga会显著增加分子筛的弱酸及强酸的酸量。在固定床反应器上考察了Ga的引入对HZSM-5催化剂甲醇芳构化催化性能的影响。结果表明,水热合成法引入Ga较浸渍法引入Ga更能提高甲醇芳构化反应的活性和芳烃选择性。此外,Ga改性HZSM-5分子筛对其甲醇芳构化反应中积炭反应的抑制起到积极作用。     

Zn改性SAPO-34/HZSM-5复合分子筛及其催化甲醇芳构化性能研究

采用机械混合法制备SAPO-34/HZSM-5复合分子筛,以浸渍法向复合分子筛引入Zn助剂对其进行改性,借助X射线衍射(XRD)、N2吸附-脱附、NH3程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-FTIR)和程序升温氧化(TPO)等手段对改性前后的复合分子筛进行表征。结果表明,Zn助剂的引入对复合分子筛的晶体结构、孔径影响较小,对复合分子筛的表面酸性影响较大。与改性前相比,改性后的复合分子筛的反应稳定性略差。最后,将Zn改性前后的复合分子筛用于甲醇芳构化反应,考察其芳构化性能。结果表明,Zn改性的SAPO-34/HZSM-5复合分子筛具有较好的芳构化活性。在反应温度为460℃、反应压力0.5 MPa、空速(LHSV)1.2 h-1条件下,BTX(苯、甲苯和二甲苯)的收率可达40.8%。     

Zn改性SAPO-34/HZSM-5复合分子筛及其催化甲醇芳构化性能研究

采用机械混合法制备SAPO-34/HZSM-5复合分子筛,以浸渍法向复合分子筛引入Zn助剂对其进行改性,借助X射线衍射(XRD)、N2吸附-脱附、NH3程序升温脱附(NH3-TPD)、吡啶吸附红外光谱(Py-FTIR)和程序升温氧化(TPO)等手段对改性前后的复合分子筛进行表征。结果表明,Zn助剂的引入对复合分子筛的晶体结构、孔径影响较小,对复合分子筛的表面酸性影响较大。与改性前相比,改性后的复合分子筛的反应稳定性略差。最后,将Zn改性前后的复合分子筛用于甲醇芳构化反应,考察其芳构化性能。结果表明,Zn改性的SAPO-34/HZSM-5复合分子筛具有较好的芳构化活性。在反应温度为460℃、反应压力0.5 MPa、空速(LHSV)1.2 h-1条件下,BTX(苯、甲苯和二甲苯)的收率可达40.8%。     

甲醇芳构化制对二甲苯催化剂的研究进展

近些年由煤基甲醇芳构化制备对二甲苯成为研究热点,因特殊的分子结构ZSM-5分子筛成为该反应常用的催化剂。为了提高反应的催化活性及对二甲苯的选择性,ZSM-5分子筛需要有合适的孔径和表面酸中心。故引入金属与非金届元素改性ZSM-5分子筛,将改性后的分子筛用于甲醇芳构化制备对二甲苯的实验研究。     

改性HZSM-5分子筛催化醛氨缩合反应

采用离子交换方法制备了不同金属离子改性HZSM-5分子筛的M/HZSM-5(M分别为Co,Pb,Cd和Zn),利用原位红外和氨气-程序升温脱附法(NH3-TPD)研究了催化剂的酸性,并考察了改性前后催化剂在醛氨缩合反应中的催化活性.结果表明,改性盾得到的Co/HZSM-5,Pb/HZSM-5和Gd/HZSM-5的催化活性提高,Zn/HZSM-5催化活性下降.HZSM-5分子筛通过金属离子改性后,HZSM-5的骨架结构没有被破坏,金属离子均匀地分布在分子筛表面.分子筛的酸性强弱、酸量和酸中心类型的分布均发生了一定的变化,在金属离子含量基本相同的情况下,不同的金属离子对分子筛表面酸性的调变能力不同.     

碱改性对甲醇芳构化催化剂Zn/La-HZSM-5性能的影响

采用碱处理对Zn/La-HZSM-5分子筛进行改性,调变分子筛的酸性和择形性能,评价其在甲醇芳构化反应中的性能。采用N_2低温吸附-脱附、NH_3-TPD和XRD等方法表征催化剂。结果表明,碱处理的Zn/La-HZSM-5分子筛催化剂孔体积和比表面积增加,酸量碱处理后降低,Zn改性后增加,催化剂的催化性能显著改善。0.3 mol·L~(-1 )NaOH溶液处理的Zn/La-HZSM-5分子筛催化剂在0.1 Mpa、TOS=10 h、WHSV=0.8 h~(-1)、437℃的反应条件下轻质芳烃收率41.82%,具有较高的芳烃收率和反应稳定性。     

小晶粒HZSM-5分子筛合成及甲醇制芳烃催化性能

在HZSM-5分子筛合成过程中,通过加入表面活性剂、降低水热反应温度成功制备出晶粒尺寸为200 nm左右的小晶粒HZSM-5(S-HZ)分子筛,并与传统方法制备的微米级HZSM-5(M-HZ)分子筛进行比较。采用XRD、N_2等温吸附-脱附、SEM、TEM、NH_3-TPD和TG对催化剂的结构、形貌、晶粒尺寸、酸性和积碳量进行表征,并用多用途固定床管式反应器对催化剂进行甲醇芳构化(MTA)催化性能评价。结果表明,与M-HZ分子筛相比,S-HZ分子筛具有更大的比表面积和孔体积,改善了分子筛催化剂的扩散性能和容碳能力,使其表现出更好的芳烃收率和催化稳定性。     

不同硅铝比HZSM-5催化正己烷耦合甲醇芳构化

在温度为400℃,压力为0.50 MPa,质量空速为1 h~(-1),甲醇与正己烷质量比为7/3的条件下,在50 mL固定床反应器中考察了5种不同硅铝比HZSM-5分子筛催化正己烷耦合甲醇芳构化反应的活性和稳定性,并对HZSM-5分子筛进行了X射线衍射(XRD)、N_2吸-脱附、NH_3程序升温脱附(NH_3-TPD)、扫描电镜(SEM)和吡啶吸附红外光谱(Py-IR)表征。研究结果表明:硅铝比低的HZSM-5分子筛作为催化剂时,产物中芳烃的选择性较大;硅铝比高的HZSM-5分子筛作为催化剂时,其反应稳定性较好。硅铝比为15时,芳烃选择性为49.7%,催化剂寿命为144 h;硅铝比为75时,芳烃选择性为27.7%,催化剂寿命为384 h。表征结果显示:不同硅铝比HZSM-5分子筛是由纳米尺寸的小晶粒构成,均具有MFI晶型结构,比表面积和孔体积相近;高硅铝比HZSM-5分子筛的中强酸量和Br?nsted酸量较小,反应温和,催化剂稳定性较好,不同硅铝比HZSM-5分子筛的酸量差异可能是造成催化性能不同的主要原因。     

微孔-双介孔核壳型HZSM-5@BMMs催化甲醇芳构化

采用外延法,以HZSM-5为核,双介孔分子筛BMMs为壳制备了多级孔核壳型HZSM-5@BMMs甲醇芳构化(MTA)催化剂。采用XRD、BET、NH3-TPD、SEM和TEM对催化剂进行了表征。结果表明:HZSM-5@BMMs具有明显的核壳结构和微孔-双介孔多级孔孔道,孔径集中分布于0.9、2.2和5.3 nm,其比表面积(510.8 m2/g)和孔容(0.399 cm3/g)均高于HZSM-5的比表面积(408.4 m2/g)和孔容(0.190 cm3/g),而酸量(0.573 mmol/g)和酸强度均低于HZSM-5的酸量(0.883 mmol/g)和酸强度。相同反应条件下HZSM-5@BMMs寿命比HZSM-5增加38 h,最高芳烃收率为25.7%,最高BTX(轻质芳烃:苯、甲苯、二甲苯)选择性为55.3%。     

磷的引入对Zn-ZSM-5催化剂甲醇芳构化性能的影响

在锌改性ZSM-5分子筛的基础上引入第二组分磷,以调变分子筛的酸性和择形性能,并对催化剂的甲醇芳构化性能进行评价。采用氨程序升温脱附、N2低温吸附-脱附、X射线衍射等对催化剂进行表征。结果表明,添加磷物种后催化剂的水热稳定性明显提升,磷改善分子筛表面酸中心强度和分布,提高了催化剂的轻质芳烃选择性。P/Zn-ZSM-5分子筛催化剂在压力0. 1 MPa、反应时间240 min、空速0. 8 h-1和反应温度437℃的条件下,BTX收率为40. 29%,具有较高的芳烃收率和反应稳定性。     

Novel catalysts based on titanium dioxide/silicon dioxide for poly(ethylene terephthalate)

A series of titanium dioxide/silicon dioxide based poly(ethylene terephthalate) (PET) polycondensation catalysts were synthesized with different Si/Ti molar ratios and various amounts of polyvinylpyrrolidone (PVP). The composition, structure, and catalytic activities of the catalysts and the properties of the PET samples catalyzed by these catalysts were characterized with thermogravimetric analysis, electron probe microanalysis, X‐ray diffraction, X‐ray photoelectron spectroscopy, and so forth. The results indicated that the Si/Ti molar ratios of the catalysts could be well controlled by the synthesis processes used in this study, whereas the content of PVP was influenced by the amount of titanium dioxide. The activities of the catalysts greatly depended on the Si/Ti molar ratios and coordinative effects between titanium and PVP. Some of the catalysts possessed ultrahigh activities, and the corresponding PET material had excellent properties.© 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Novel flame‐retardant epoxy based on zinc methylethyl phosphinate

A novel flame retardant zinc methylethylphosphinate (Zn(MEP)) was used to fill epoxy resins (EPs). The structure of Zn(MEP) was conformed with Fourier transform infrared, hydrogen nuclear magnetic resonance and phosphorus nuclear magnetic resonance, and X‐ray fluorescent and X‐ray diffraction. The flammability, decomposition behavior, and glass transition temperature (T_g) of cured EP/Zn(MEP) were investigated. Zn(MEP) is stable below 406°C. EP containing 20 phr of Zn(MEP) achieves 27.5% of limiting oxygen index and UL‐94 V0 rating. Scanning electron microscopy‐energy‐dispersive X‐ray and Fourier transform infrared spectroscopy investigations show that a condensed char layer with carbon‐rich and phosphorus‐rich components was formed during heating Zn(MEP)/EP, the atomic ratio of P to Zn on the surface of the char is reduced compared with the initial sample. The P‐rich components and lower atomic ratio of P/Zn on the char surface implies that the Zn(MEP) acts in both condensed phase and gas phase. TGA investigation shows that there are interactions between Zn(MEP) and EP when they are copyrolyzed. The interactions lead to a modification in degradation process and promote the char forming. Compared with aluminum diethylphosphinate Zn(MEP) filled EP shows lower limiting oxygen index but higher T_g. In addition, the interactions between polymer and additive are different when aluminum diethylphosphinate instead of Zn(MEP) is added into EP. Copyright © 2013 John Wiley & Sons, Ltd.     

Promoted Fe2O3‐Al2O3‐CuO Chromium‐Free Catalysts for High‐Temperature Water‐Gas Shift Reaction

Promoted Fe₂O₃‐Al₂O₃‐CuO (FAC) chromium‐free catalysts were prepared for high‐temperature water‐gas shift reactions and characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller method (BET), temperature‐programmed reduction (TPR), and transmission electron microscopy (TEM) techniques. The catalytic results revealed that among the investigated promoted catalysts with Ce, La, Zn, Y, and Mn as promoters, the Mn‐promoted sample showed higher activity compared to the other promoted catalysts. Increasing the Mn content improved the surface area and catalytic activity. The FAC catalyst promoted with a high Mn content exhibited maximum activity and relatively high stability in high‐temperature water‐gas shift reaction.     

Preparation of nanocrystalline Ni/Al2O3 catalysts with the microemulsion method for dry reforming of methane

Mesoporous nanocrystalline nickel‐alumina catalysts with high surface area were prepared by a microemulsion (ME) method and were employed in methane reforming with carbon dioxide for syngas production. The catalysts were characterized by X‐ray diffraction (XRD), Brunauer‐Emmett‐Teller surface area analysis (BET), temperature‐programmed reduction (TPR), temperature‐programmed oxidation (TPO), and scanning electron microscopy (SEM) techniques. The results showed that the catalysts possessed mesoporous structure with high surface area (> 250 m² · g^?1) and small crystallite size (～5 nm). The catalytic results revealed high activity and stability for the prepared catalysts. In addition, the effect of feed ratio and GHSV on catalytic performance was investigated.     

Calcined Zn/Al hydrotalcites as solid base catalysts for glycolysis of poly(ethylene terephthalate)

In this research, glycolysis of poly(ethylene terephthalate) (PET) with ethylene glycol (EG) was carried out using Zn/Al mixed oxide catalyst. These mixed oxides were prepared by calcining crystalline Zn/Al hydrotalcites at different calcination temperatures. The samples and corresponding precursors were characterized by X‐ray diffraction, BET, Fourier‐transform infrared spectra, thermogravimetry/differential thermal analysis, and Hammett titration method. The experimental results showed that Zn/Al mixed oxides obtained from hydrotalcites were found to be more active than their individual oxides for glycolysis of PET. The relationship between catalytic performance and chemical–physical features of catalysts was established. In addition, a study for optimizing the glycolysis reaction conditions, such as the weight ratio of EG to PET, catalyst amount and reaction time, was performed. The conversion of PET and yield of bis(2‐hydroxyethyl terephthalate) (BHET) reached about 92% and 79%, respectively, under the optimal experimental conditions. Moreover, it should be noted that Zn/Al mixed oxide not only provided an effective heterogeneous catalyst for glycolysis of poly(ethylene terephthalate), but also presented a novel method for decolorization of discarded colored polyester fabric. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41053.     

Physicochemical and catalytic properties of iron‐promoted Raney‐nickel catalysts obtained by mechanical alloying

Raney‐type catalysts were prepared by means of a two‐step procedure: (i) mechanical alloying of the metals and (ii) alkaline aluminum leaching. Mechanical alloying is a novel alternative related to the synthesis of skeletal Ni catalysts. Catalysts characterization was performed by atomic absorption, X‐ray diffraction, electron microscopy, and Mössbauer spectroscopies. Textural studies were also carried out. Binary Al–Ni and ternary Al–Ni–Fe alloys were produced by mechanical alloying from pure metallic powders; in particular, the intermetallic α‐(AlNi) phase was formed with a fine microstructure as a non‐equilibrium phase; then, aluminum was selectively removed. After aluminum leaching the α‐(AlNi) phase was transformed into the more stable nickel fcc structure. The effect of iron addition to the Ni–Al catalysts depends on iron concentration and reduction temperature; both parameters determine catalysts composition and activity. This work reports physicochemical properties and benzene hydrogenation activity of these materials, compared with conventional catalysts obtained by melting and leaching.     

The Promoting Effect of Europium on PtSn/C Catalyst for Ethanol Oxidation

Well‐dispersed PtSnEu/C and PtSn/C catalysts were prepared by the impregnation–reduction method using formic acid as a reductant and characterised by X‐ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS). The synthesised catalysts with different atomic ratios of Pt/Sn/Eu have the Pt face centered cubic (fcc) structure and their particle sizes are 3–4 nm. The PtSnEu/C catalyst is composed of many Pt (0), SnO₂, Eu(OH)₃, a small amount of Pt(II) and partly alloyed PtSn, but no metallic Eu. The electrochemical measurements indicate that in comparison with Pt₃Sn₁/C catalyst, the Pt₃Sn₁Eu₁/C catalyst for ethanol oxidation has more negative onset potential, smaller apparent activation energy and lower electrochemical impedance so that it exhibits very high catalytic activity. Its peak current density increases by 135% and 40%, compared with Pt₃Sn₁/C and Pt₁Ru₁/C (JM) catalysts, respectively. This is because the Eu(OH)₃ formed by adding Eu to PtSn/C catalyst can provide the OH group which is in favour of the removal of adsorbed intermediates and ethanol oxidation.     

Morphology of Poly(1‐olefin)s from Poly(1‐octene) to Poly(1‐eicosene)

Poly(1‐olefin)s from poly(1‐octene) to poly(1‐eicosene) synthesized by isospecific metallocene catalysts are investigated by wide and small angle X‐ray scattering (WAXS and SAXS) and by atomic force microscopy. The crystal structure of poly(1‐eicosene) is determined and the scattering peaks are assigned. Additionally, 1‐dodecene is polymerized using a constrained geometry catalyst and the obtained atactic polymer is compared with the isotactic species. Using this sample it is possible to determine the amorphous halo in the small angle regime at room temperature. For poly(1‐decene), poly(1‐dodecene), and poly(1‐hexadecene) a long period can be measured by small angle X‐ray scattering which coincides with the results from AFM measurements.     

4,6-二氨基间苯二酚合成工艺中Pd/C催化剂失活原因分析

通过采用原子吸收、XBD、物理吸附、DSC—TGA等分析手段对在4,6-二氨基间苯二酚合成过程中发生失活的Pd／C催化剂的活性组分、比表面积、孔容及孔径的变化、热失重和晶相结构进行分析,以及对失活催化剂进行再生处理,对催化荆的失活原因进行了研究。结果表明：催化剂在反应过程中发生了积炭失活,通过用碱溶液或有机溶荆进行洗涤可以部分去除催化剂表面沉积的有机物,使催化剂的表面得以改善;在后处理过程中催化剂中的金属钯由于与HCl反应生成PdCl2造成金属钯的大量流失是使催化剂发生失活的主要原因。     

One‐Step Sonochemical Synthesis of Reduced Graphene Oxide/Pt/Sn Hybrid Materials and Their Electrochemical Properties

Low frequency ultrasound (20 kHz) was used for the reduction of graphene oxide (GO), Pt and Sn precursors with simultaneous loading of Pt and Sn monometallic and Pt–Sn bimetallic nanoparticles on the surface of reduced GO (rGO). The physicochemical characterizations of the catalysts were carried out using transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), energy dispersive X‐ray spectroscopy (EDX), and selected area electron diffraction (SAED) techniques. The reduced monometallic and bimetallic nanoparticles were spherical in shape with diameters around 2–6 nm, uniformly embedded on rGO sheets of few layers thickness. The electrocatalytic activities of the synthesized materials were evaluated by cyclic voltammetric studies.