Catalytic properties of Ni–B and Ni–P ultrafine materials

The ultrafine Ni–B and Ni–P amorphous alloy catalysts were prepared by the chemical reduction method. The catalysts were characterized with respect to ICP‐AES, XRD, nitrogen sorption, DSC, SEM, TEM and XPS. Nitrobenzene hydrogenation was used to compare their hydrogenation abilities. The different metalloids of boron and phosphorus bound to the nickel metal for the Ni–B and Ni–P catalysts result in the distinct different surface area, amorphous structure and hydrogenation activity of the catalysts. Ni–B had a larger surface area than Ni–P. The specific activity per surface area of Ni–P was greater than that of Ni–B. The different activities between the Ni–P and Ni–B can be attributed to the difference of the electron density on the nickel metal; boron donates electrons to the nickel metal and phosphorus accepts electrons from the nickel metal. The catalysts were easier to oxidize when they were exposed to air. This would result in the lower activity. However, the activity could be recovered in the reaction process due to the presence of hydrogen in the reaction system. © 2000 Society of Chemical Industry     

一锅水热-浸渍法制备Pd-Fe/SiO2催化剂及其蒽醌加氢性能增强

以正硅酸乙酯为硅源,Pluronic三嵌段共聚物P123或四丙基氢氧化铵（TPAOH）为结构调节剂,采用一锅温和水热法成功地合成了Fe-修饰的SiO₂;并以其为载体,采用等体积浸渍法制备了负载型0.3% Pd-3% Fe/SiO₂催化剂。采用XRD、N₂吸附-脱附、CO脉冲吸附法、微型浆态床反应器和高效液相色谱对产物的物相结构、织构性质和2-乙基蒽醌加氢性能进行了表征和测试。结果表明,该催化剂具有较规整的孔道、较窄的孔径分布和适中的比表面积;在蒽醌加氢反应中,该催化剂的氢化效率可达13.1g/L、选择性可达66.1%,并且反应4h时的氢化效率仍高达11g/L。相比之下,典型的工业Pd-催化剂反应1.5h后便因副反应过多而无法进行,且氢化效率仅有5.4g/L,选择性仅有26.2%。研究还发现,以P123为结构调节剂时,掺杂Fe可以提高催化剂的选择性;而以TPAOH为结构调节剂时,掺杂Fe可以同时显著地改善催化剂的活性和选择性。     

Preparation of Pdshell–Aucore/SiO2 catalyst and catalytic activity for acetylene hydrogenation

Various Pd shell thicknesses (0.12–1.5 nm) were synthesized on preformed Au particles of 5 nm size by seeded growth technique (15–80 at% Pd) using sodium citrate and tannic acid. The sols were characterized by UV–vis spectroscopy, TEM and high-resolution TEM (HRTEM) measurements. HRTEM confirmed the pseudomorphic growth of the Pd shell on the Au core. The Au/Pd core/shell particles were fixed onto SiO₂ (Aerosil 200) support by PDDA polycation. The catalytic activity in acetylene hydrogenation and selectivity of competition between acetylene and propene were tested after O₂ and H₂ pretreatment. The samples even in “as prepared” state hydrogenated acetylene. The thin Pd layer (15–30 at% Pd) on Au provided higher hydrogenation activity than the thick Pd shell. However, thermal treatment of the samples in H₂ stream causing Au/Pd intermixing shifted the activity maximum to higher Pd concentration (68–80 at% Pd). Comparison of the TOF (1/s) and selectivity values allowed us to conclude that the homogenized particle with 68–80 at% Pd shows better hydrogenation activity and selectivity than the thin Pd shell (15–30 at% Pd) on the Au core.     

Glucose hydrogenation on Co–B amorphous alloy catalysts and the promoting effect of metal additives

Two kinds of ultrafine Co–B amorphous alloy catalysts, denoted as P‐1 Co–B and P‐2W Co–B, were prepared by chemical reduction with borohydride in aqueous or 50% (v/v) ethanol/water solution, respectively. In comparison with the corresponding Co‐based crystalline catalysts and Ni‐based catalysts, these catalysts exhibited higher activity during the liquid phase glucose hydrogenation, possibly due to the unique amorphous characteristics and the lower d‐band electron density, which was favorable for hydrogen dissociative chemisorption. Addition of Cr‐, Mo‐ or W‐promoters could further increase the conversion of Co–B amorphous catalyst, which was mainly attributed to the dispersion effect of promoters and the adsorption and polarization of carbonyl groups by these promoters. The different effects of W‐ from Cr‐ and Mo‐promoters on the conversion were observed and are discussed. © 2001 Society of Chemical Industry     

Cu/SiO2 catalyst prepared by electroless method

Cu/SiO₂ catalysts prepared by an electroless deposition method were investigated and compared with those by an impregnation method. Copper contents varied from 5% to 15% and SiO₂ was used as support. All catalysts were characterized by BET, DSC, SEM and TPR and tested by an n-butanol dehydrogenation reaction for activities and stabilities. BET analysis showed that the catalysts prepared by the two methods present larger average pore size and less surface area than those of the fresh SiO₂, indicating that smaller pores may get blocked during the course of preparation. This blockage is more severe in the impregnation method. SEM photos showed that the electroless method produces smaller copper crystals than the impregnated method. The reaction activity was found to be in the order of the calcined electroless copper catalyst>the fresh electroless copper catalyst>impregnated copper catalyst. © 1998 Society of Chemical Industry     

添加ZrO2的Pd/Al2O3催化剂及其催化蒽醌加氢性能

以四氯合钯（II）酸（H2PdCl4）为前体,活性氧化铝（Al2O3）为载体,硝酸锆（Zr（NO3）4）为添加组分,采用不同方式的分步浸渍法制备了添加ZrO2的Pd/Al2O3催化剂。考察了制备方法和反应条件对催化剂蒽醌加氢催化性能的影响,发现催化剂活性与制备方法有关。当对添加锆的载体进行适当焙烧,控制Pd负载量为0.3%,还原温度低于300℃时,催化剂的蒽醌加氢活性较高,与未添加ZrO2的催化剂相比提高了约20%。X射线衍射（XRD）、氮气物理吸附（BET）、透射电镜（TEM）、X光电子能谱（XPS）和程序升温还原（TPR）等表征对催化剂物相结构、比表面积、表面形貌及组分间相互作用的分析表明,ZrO2的掺杂提高了载体Al2O3的高温稳定性,改善了催化剂中活性组分Pd与载体间的相互作用,促进了Pd在载体表面的分散,从而提高了催化活性。     

High temperature water–gas shift reaction over hollow Ni–Fe–Al oxide nano-composite catalysts prepared by the solution-spray plasma technique

The effect of Fe content in Ni–Fe–Al oxide nano-composites prepared by the solution-spray plasma technique on their catalytic activity for the high temperature water–gas shift reaction was investigated. The composites showed a hollow sphere structure, with highly dispersed Fe–Ni particles supported on the outer surface of the spheres. When the water–gas shift reaction was performed over an Ni–Al oxide composite catalyst without Fe, undesired CO methanation took place predominantly compared to the water–gas shift reaction, and significant amounts of hydrogen were consumed. When appropriate amounts of Fe were added to the Ni–Al oxide composite catalyst during the plasma process, methanation was suppressed remarkably, without serious loss of activity for the water–gas shift reaction. The catalyst was characterized by STEM, XRD and H₂ chemisorption measurements.     

High-performance Al2O3 ceramics prepared by DCC-HVCI via microwave heating

A novel and rapid fabrication method for Al₂O₃ ceramics by the DCC-HVCI method via microwave heating was proposed. Effects of microwave heating temperature on coagulation time, micromorphology, as well as performance of the green body and ceramic sample were studied. As the microwave heating temperature rises, the coagulation time gradually reduced and compressive strength of green sample decreased while relative density and flexural strength of ceramics rose at the beginning and then dropped. The 50 vol.% Al₂O₃ suspension was coagulated and demolded after treating at 60°C for 800 s by microwave heating. The compressive strength of green samples reached 1.12 ± 0.13 MPa. The relative density of Al₂O₃ ceramic samples reached 99.39%. And the flexural strength of Al₂O₃ ceramics reached 334.55 ± 26.41 MPa. The Weibull modulus of Al₂O₃ ceramics reached 19. In contrast with the ceramic samples heated through water bath, the ceramic samples treated through microwave possessed uniform microstructures. Microwave heating could reduce the coagulation time by 77%. Meanwhile, it could significantly raise the compressive strength of green bodies by 65%. Additionally, it could increase the flexural strength of ceramics by 30%.     

溶胶-凝胶法制备草酸二甲酯加氢Cu/SiO2催化剂及性能

以正硅酸乙酯为硅源,采用溶胶-凝胶法制备草酸二甲酯加氢合成乙二醇的Cu/SiO₂催化剂,并考察老化时间对Cu/SiO₂催化剂活性与结构的影响。用N2物理吸附、XRD、FT-IR和H₂-TPR等技术对Cu/SiO₂催化剂性能与结构进行表征。结果表明,溶胶-凝胶法制备的Cu/SiO₂催化剂中有层状硅酸铜形成,铜物种均匀分布在载体SiO₂上,易被还原,活性较高。合理的老化时间可抑制SiO₂对催化剂表面活性位的包覆,提高活性。在200 ℃、2.0 MPa、氢酯物质的量比60∶1、草酸二甲酯空速1.0 h^-1和老化时间1.5 h的条件下,草酸二甲酯转化率达99.51%,乙二醇选择性93.60%。
     

ZrO2/SiO2催化剂的制备及其氧化脱硫性能研究

以己内酰胺-八水氧氯化锆低共熔溶剂为添加组分,采用溶胶-凝胶法合成含锆的硅胶,再经过高温煅烧得到n-ZrO₂/SiO₂ （n=2%,4%,6%） 负载型催化剂。并用红外光谱（FT-IR）、X射线衍射（XRD）、扫描电镜（SEM）、N₂吸附-脱附、X射线光电子能谱（XPS）对其进行结构表征,确定ZrO₂成功负载到SiO₂上。以ZrO₂/SiO₂为催化剂和吸附剂,H₂O₂为氧化剂组成催化氧化脱硫体系,并应用于模拟油脱硫。分别考察了氧化锆负载量、反应温度、氧硫比、催化剂加入量及不同类型的硫化物对脱硫效果的影响。实验结果表明,在反应温度为70℃、n（H₂O₂）/n（S）=4（摩尔比）、4%-ZrO₂/SiO₂的加入量为0.2 g的最佳反应条件下,氧化脱硫体系对二苯并噻吩（DBT）、4,6-二甲基二苯并噻吩（4,6-DMDBT）和苯并噻吩（BT）的脱除率分别为98.7%、93%和65.9%。且4%-ZrO₂/SiO₂回收利用5次后,DBT脱除率仍可达到91.8%。     

Oxidative carbonylation of methanol to dimethyl carbonate over CuCl/SiO2–TiO2 catalysts prepared by microwave heating: The effect of support composition

Copper(I) chloride catalysts with a loading of 20 wt%, supported on silica–titania mixed oxides with Si/Ti ratios of 1, 5, 10 and 50 were prepared by conventional and microwave heating methods and tested in the oxidative carbonylation of methanol to dimethyl carbonate (DMC). X-ray diffraction (XRD), nitrogen adsorption, X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) were used to examine the bulk and surface properties of the CuCl/SiO₂–TiO₂ catalysts. Quantum-chemical calculations were performed to explore the interaction of CuCl with the silica–titania support. Microwave heating showed some significant advantages over the conventional heating method, with markedly reduced preparation temperature and time, and provided improved catalytic activity in the oxidative carbonylation of methanol. The catalytic behavior of CuCl/SiO₂–TiO₂ in the test reaction studied was strongly dependent on the support composition. Incorporation of tetrahedral Ti(IV) species into the silica matrix could enhance the interaction of copper species with the oxide support. The improved catalytic performance of CuCl/SiO₂–TiO₂ in the DMC synthesis can be understood by the existence of the strong coordination interactions between the Cu⁺ centers of CuCl and the bridging oxygen atoms at the Si–O–Ti bonds in the silica–titania support.     

Pd/C催化剂对生物质基丁酮催化加氢制取仲丁醇

研究了生物质基丁酮经Pd/C催化加氢制备仲丁醇的工艺条件,考察了反应时间、反应温度、氢压和催化剂用量对仲丁醇收率的影响。结果表明,Pd/C可催化丁酮进行加氢反应,主要产物为仲丁醇。在一定温度条件下,仲丁醇收率随温度的升高而增大,但超过一定范围,继续增加反应温度,收率反而下降。加氢压力1 MPa,反应8 h后,90 ℃、120 ℃和150 ℃条件下仲丁醇收率分别为53.1%、52.8%和45.5%;增大氢压,仲丁醇收率反而明显降低。增加催化剂用量,反应速率加快,反应时间缩短,但对最终仲丁醇收率的影响不大。     

Some New Perspective on the Reaction Mechanism of MgO–SiO2–H2O System

The application of MgO–SiO₂–H₂O system, one of the most popular basic refractories, is greatly limited because of the hydration of MgO. In this work, the phase and morphological development of MgO–SiO₂–H₂O system during aging were analyzed using various techniques. It is found that Mg(OH)₂ initially appears and the amount increases after 10 days aging at room temperature. At elevated temperature, the heat treatment can facilitate the hydration reaction. Mg(OH)₂ covers the surface of silica fume particles. The combination product connects with each other and distributes homogeneously around MgO particles to produce M–S–H gels, which inhibit the further hydration.     

Carbon nanotube-supported Pd–ZnO catalyst for hydrogenation of CO2 to methanol

A type of Pd–ZnO catalysts supported on multi-walled carbon nanotubes (MWCNTs) were developed, with excellent performance for CO₂ hydrogenation to methanol. Under reaction conditions of 3.0 MPa and 523 K, the observed turnover-frequency of CO₂ hydrogenation reached 1.15 × 10⁻² s⁻¹ over the 16%Pd_0.1Zn₁/CNTs(h-type). This value was 1.17 and 1.18 times that (0.98 × 10⁻² and 0.97 × 10⁻² s⁻¹) of the 35%Pd_0.1Zn₁/AC and 20%Pd_0.1Zn₁/γ-Al₂O₃ catalysts with the respective optimal Pd_0.1Zn₁-loading. Using the MWCNTs in place of AC or γ-Al₂O₃ as the catalyst support displayed little change in the apparent activation energy for the CO₂ hydrogenation, but led to an increase of surface concentration of the Pd⁰-species in the form of PdZn alloys, a kind of catalytically active Pd⁰-species closely associated with the methanol generation. On the other hand, the MWCNT-supported Pd–ZnO catalyst could reversibly adsorb a greater amount of hydrogen at temperatures ranging from room temperature to 623 K. This unique feature would help to generate a micro-environment with higher concentration of active H-adspecies at the surface of the functioning catalyst, thus increasing the rate of surface hydrogenation reactions. In comparison with the “Parallel-type (p-type)” MWCNTs, the “Herringbone-type (h-type)” MWCNTs possess more active surface (with more dangling bonds), and thus, higher capacity for adsorbing H₂, which make their promoting action more remarkable.     

Cu／SiO2催化剂的制备及在环己醇脱氢制环己酮反应中的催化性能

采用共沉淀法制备了不同铜／硅物质的量比的Cu／SiO2催化剂,结果表明：在n（Cu）：n（si）=1：2时,DH-0．5-400催化剂在环己醇脱氢制环己酮的反应中表现出优异的催化活性。考察了不同焙烧温度对环己醇脱氢制环己酮的影响。结果表明：焙烧温度400℃时,制备的DH-0．5-400催化剂上的环己酮得率为52．9％,高于其他催化剂。采用XRD和BET对催化剂进行了表征,根据结果,在催化剂中氧化铜是以均匀、高分散的微小纳米粒子或以簇的形式存在,结果增加了与反应物的接触机会,致使DH-0．5-400催化剂显示出高的催化性能和环己酮选择性。     

Synthesis of high rubber styrene–EPDM–acrylonitrile graft copolymer and its toughening effect on SAN

High rubber styrene–EPDM–acrylonitrile (AES) was prepared by the graft copolymerization of styrene (St) and acrylonitrile (AN) onto ethylene–propylene–diene terpolymer (EPDM) in n‐heptane/toluene cosolvent using benzoyl peroxide as an initiator. The effects of reaction conditions, such as reaction temperature, initiator concentration, EPDM content, the solvent component, and reaction time, on the graft copolymerization are discussed. In addition, according to the research on mechanical properties of the SAN/AES blend, a remarkable toughening effect of AES on SAN resin was found. By means of scanning electron microscopy, the toughening mechanism is proposed to be crazing initiation from rubber particles and shear deformation of SAN matrix. Uniform dispersion of rubber particles, as shown by transmission electron microscopy, is attributed to the good compatibility of SAN and AES. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 416–423, 2004     

硝基苯催化加氢Pt-MoS2/C催化剂的制备及使用寿命的研究

采用浸渍法制备Pt/C和Pt-MoS2/C催化剂,用于催化硝基苯加氢反应。采用BET、压汞仪等测试方法测定新鲜催化剂和重复使用后的催化剂的比表面积和孔容。结果表明,比表面积下降27.3%,微孔孔容下降13.2%,总孔容下降5.8%。催化剂失活的主要原因为有机物覆盖在催化剂表面,造成表面积下降和孔堵塞。负载MoS2可使Pt/C催化剂延缓比表面积下降和孔堵塞,寿命显著提高,可循环使用14次左右。     

Preparation and characterization of sol–gel Al2O3/Ni–P composite coatings on carbon steel

Ceramic films have been applied to improve the resistance against high temperature oxidation of carbon steels. Alumina film was prepared on carbon steel surface by a dip coating technique. Electroless Ni–P plating film has been pre-deposited as an intermediate layer to improve the adherence of the film to carbon steel substrate. The oxidation kinetics of coated sample was investigated by measuring weight gain at 800 °C for 100 h. The surface and cross-section morphology of samples before and after oxidation were characterized by scanning electron microscopy (SEM). The composition and element distribution at the interface of the coated samples were analyzed by energy dispersive spectroscopy (EDS) and EMAX.The results show that the composite coating is uniform. The alumina coating adhesion strength to the substrate is up to 20 ± 2 N in scratch test because the alumina film presents interdiffusion of nickel and aluminum during heat treatment. The oxidation resistance test indicates higher oxidation resistance of as-coated carbon steel comparing to uncoated ones.