有序双组分氧化物CoO-NiO/MCM-41催化剂的合成与表征

在碱性条件下用组装的方法得到了高负载量,均匀分布的CoO-NiO负载型MCM-41介孔材料,并采用XRD、BET、HREM等测试手段对样品进行了分析,结果表明,CoO,NiO双组分氧化物已成功地组装进入了MCM-41的有序孔道,在CoO,NiO组装过程中,CoO,NiO含量分别为7.53wt％和5.94wt％时,介孔材料的有序结构没有遭到破坏。     

MCM-41负载戊二酸锌催化剂催化CO2和环氧丙烷的共聚反应

制备了MCM-41负载戊二酸锌催化剂(ZnGA/MCM-41),并采用热重分析、红外光谱和X射线衍射对催化剂进行了表征。结果表明,ZnGA与载体间存在相互作用,ZnGA能以更小的粒径均匀分散到MCM-41的表面。实验研究表明,该催化剂对于CO2与环氧丙烷(PO)共聚反应显示出较高的催化效率,并得到高分子量的聚碳酸亚丙酯(PPC);通过调节负载量和催化剂的用量,最高催化效率达到了89.5g聚合物/g ZnGA;共聚产物的红外光谱和核磁数据表明,所得共聚产物具有接近完全交替(>97.4%)的碳酸酯结构。     

One-pot synthesis of the highly efficient bifunctional Ni-SAPO-11 catalyst

Hydroisomerization of linear alkanes to branched isomers is an important petrochemical process for production of gasoline with high octane number.Non-noble metal bifunctional catalysts used in this process always suffer from low metal dispersion and poor metal-acid synergy.Herein,a facile one-pot synthesis method was used to simultaneously regulate metal particle sizes and acidity of the Ni-SAPO-11 hydroisomerization catalyst.The physicochemical properties are investigated using XANES,EXAFS,TEM/STEM,FT-1R,XPS,UV-vis and NH3-TPD.Apart from the highly dispersed nickel nanoparticles with an average diameter of 8 nm,the framework Ni2+ions are generated via substituting framework Al3+ions of the SAPO-11.The formed NiP-OH structures have lower deprotonation energy(DPE)than the SiAl-OH ones,contributing more and stronger acid sites to the Ni-SAPO-11 catalyst.The great metal-acid synergy including high metal to acid sites ratio(nNi/nA)and close intimacy is obtained for the Ni-SAPO-11 catalyst.The Ni-SAPO-11 catalyst outperforms the counterpart prepared by the impregnation method and exhibits comparable activity and isomers selectivity to the Pt/SAPO-11 catalyst in the n-hexane hydroisomerization.     

负载型MoO3／β分子筛催化剂的丙烷氧化脱氢性能

以β分子筛为载体,采用浸渍法负载钼制备了MoO3／β筛催化剂,通过XRD、FTIR、BET、NH3-TPD进行表征,结果表明,样品中有活性组分氧化钼存在,也有不同酸性质的活性位存在,负载量对催化剂的表面积和孔径有影响;考察了催化剂对丙烷氧化脱氢制丙烯的催化性能,结果表明,单纯β分子筛载体有催化活性,不同钼负载量对催化性能有影响,考察负载量区间内反应转化率出现极值。     

Synthesis and characterization of mesoporous Si-MCM-41 materials and their application as solid acid catalysts in some esterification reactions

Mesoporous MCM-41 has been synthesized by sol–gel method at room temperature possessing good thermal stability, high surface area as well as retention of surface area at high temperature. The MCM-41 neutral framework has been modified and put to practical use by incorporating Al³⁺ in the siliceous MCM-41 framework and supporting 12-TPA (12-tungstophosphoric acid) onto MCM-41 by process of anchoring and calcination to induce Brønsted acidity in MCM-41 to yield Al-MCM-41 and 12TPA-MCM-41, respectively. The synthesized materials have been characterized for elemental analysis by ICP-AES, XRD, SEM, TEM, EDX, FT–IR and TGA. Surface area has been determined by BET method and pore size and pore size distribution determined by BJH method. Surface acidity has been evaluated by NH₃-TPD method. The potential use of Al-MCM-41 and 12TPA-MCM-41 as solid acid catalysts has been explored and compared by studying esterification as a model reaction wherein monoesters such as ethyl acetate (EA), propyl acetate (PA), butyl acetate (BA) and benzyl acetate (BzA) have been synthesized, optimizing several parameters such as catalyst amount, reaction time, reaction temperature and mole ratio of reagents.     

Esterification of levulinic acid into hexyl levulinate over dodecatungstophosphoric acid anchored to Al-MCM-41

Aluminum-substituted MCM-41 (Al-MCM-41) were hydrothermally synthesised and used as supports to fabricate the mesostructured H₃PW₁₂O₄₀ (HPW) solid acid catalysts via an impregnation method. The influences of various HPW loadings on the structures of the catalysts were verified by X-ray diffraction (XRD), nitrogen physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet–visible (UV–Vis) spectroscopy and Fourier-transform infrared spectroscopy (FT-IR) measurements and their acidities were evaluated by infrared of pyridine adsorption (Py-IR) and temperature-programmed desorption of ammonia (NH₃-TPD) measurements. The optimisation of the reaction conditions for levulinic acid esterification with n-hexanol such as the reaction temperature and time, the reactant molar ratio, and the catalyst dosages was performed to maximise the conversion of levulinic acid. The effects of various HPW loadings on the conversion of levulinic acid were investigated under the optimised and harsh reaction conditions. The reusability of the catalysts was also investigated. The results showed that these catalysts retained the hexagonal mesoporous structure of Al-MCM-41 and the Keggin characteristic of HPW, although their textural parameters decreased with increasing loading of HPW. In particular, the catalysts were found to be efficient in the esterification of levulinic acid with n-hexanol, resulting in hexyl levulinate which could replace the petroleum-derived chemical feedstocks.     

WO_3-SiO_2模型催化剂孔径对C_2H_4-C_(10)H_(20)歧化性能的影响

蒸发自组装30~150 nm单分散SiO2微球制备孔径均一的SiO2模型载体,采用等体积浸渍法制备WO3单层负载WO3-SiO2催化剂并对其进行低温氮吸附、压汞、程序升温氨脱附和扫描电子显微镜等表征,然后进行C2H4-C10H20歧化反应实验。结果表明,在相同的实验条件下,相同孔道结构的球形SiO2模型载体孔径对反应结果有重要的影响。催化剂孔径越大,起始乙烯转化率和丙烯选择性越高,反应失活也越快,即内扩散对C2H4-C10H20歧化反应有明显的影响。     

MoO3在介孔分子筛MCM-41上分散和存在状态的研究

在773K加热MoO₃和MCM-41的机械混合物,可以实现 MoO₃分散在介孔分子筛MCM-41表面,用透射电镜和选区电子衍射,配合XRD和液氮温度下氮吸附-脱附曲线和BJH孔径分布,研究了活性组分MoO₃在有序介孔材料MCM-41上的存在状态,以及MoO₃分散到MCM-41表面后MCM-41的结构变化情况.结果表明:当MoO₃的含量小于单层分散阈值,加热后MoO₃的XRD衍射峰彻底消失;用HRTEM观察不到分散在MCM-41表面或孔道中的MoO₃颗粒,而EDS能谱证明在MCM-41的孔道中有呈分散态的MoO₃存在.MoO₃的含量大于单层分散阈值,通过加热不能使MoO₃完全分散在MCM-41表面,而且XRD、HRTEM、氮吸附-脱附等温线和孔径分布都表明由于MoO₃的分散量较大,载体MCM-41的有序介孔结构遭到破坏.     

超细钨粉的制取及其氧化钨原料和钨粉的粒度测量

选取相成分单一的氢钨青铜（H0.33WO3）、铵钨青铜（NH4）0.5WO3）和紫钨（WO2.72）作为原料，研究钨原料对制取超细钨粉的影响，对氧化钨原料和超细钨粉的粒度测量方法作了比较，研究结果表明，紫钨由于有着特殊的结构，其制得的钨粉细而均匀，分散性好，可适合于做微晶硬质合金的原料。氧化钨原料的粒度（伪同晶颗粒尺寸，即二次颗粒）测量，推荐使用激光衍射法，超细钨粉粒度（一次颗粒）的炉前测量，BET法测球形当量径相当理想。     

杂多酸固载催化剂的合成及窄分子量纤维素制备的研究

通过水热合成法制备MCM-41型介孔分子筛,采用浸渍法负载磷钨酸于MCM-41介孔分子筛中,煅烧得到新型HPW/MCM-41固载催化剂。利用傅里叶红外光谱(FT-IR)、X射线衍射(XRD)、热重分析(TG)和扫描电镜(SEM)对固载催化剂进行表征;考察催化剂对棉纤维催化降解反应的性能。结果表明,新型HPW/MCM-41固载催化剂即持有了磷钨酸的Keggin结构,同时又保持了分子筛的完整介孔结构,具有催化、筛分双重性能。棉纤维催化降解反应数据显示,磷钨酸负载量、反应温度、催化剂用量、液固比及停留时间均影响HPW/MCM-41降解纤维素的性能。在单因素实验最佳反应条件下,棉纤维素降解产物的分子量分布较为均匀,降解产物的产率较优。     

Mn、Fe和Cu氧化物在低温等离子体催化氧化甲苯体系中的活性比较

采用等体积浸渍法制备了MnOx/γ-Al2O3、FeOx/γ-Al2O3和CuOx/γ-Al2O3催化剂,测定了不同催化剂在低温等离子体场内分解甲苯的活性,用X射线衍射(XRD)、氢气程序升温还原(H2-TPR)技术对催化剂进行表征。结果表明催化剂分解甲苯的活性的顺序是MnOx/γ-Al2O3>FeOx/γ-Al2O3>CuOx/γ-Al2O3。催化剂分解臭氧的实验表明,不同催化活性组分对臭氧的催化分解性能顺序与对甲苯的分解性能顺序是一致的。MnOx/γ-Al2O3催化剂的Mn负载量对其催化活性有明显影响,Mn的含量为1%(质量分数)时,催化剂的活性最高,当能量密度为19J/L时,其对甲苯催化氧化的转化率接近100%。催化剂表征结果表明当Mn含量为1%(质量分数)时,氧化锰在载体γ-Al2O3上最接近单层分散量,此时活性组分与载体表面的相互结合力最强,在载体上有很好的分散性,从而表现出对甲苯分解的最好性能。     

MoO3在介孔分子筛MCM-41上分散和存在状态的研究

在773K加热MoO3和MCM－41的机械混合物，可以实现MoO3分散在介孔分子筛MCM－41表面，用透射电镜和选区电子衍射，配合XRD和液氮温度下氮吸附－脱附曲线和BJH孔径分布，研究了活性组分MoO3在有序介 材料MCM－41上的存在状态，以及MoO3分散到MCM－41表面后MCM－41的结构变化情况。结果表明：当MoO3的含量小于单层分散阈值，加热后MoO3的XRD衍射峰彻底消失，用HRTEM观察不到分散在MCM－41表面或孔道中的MoO3颗粒，而EDS能谱证明在MCM－41的孔道中有呈分散态的MoO3存在。MoO3的含量大于单层分散阈值，通过加热不能使MoO3完全分散在MCM－41表面，而且XRD、HRTEM、氮吸附－脱附等温线和孔径分布都表明由于MoO3的分散量较大，载体MCM－41的有序介孔结构遭到破坏。     

SO24-／ZrMCM-48和H-ZrMCM-48的制备与催化性能

以正硅酸乙酯为硅源、硫酸锆为锆源、十六烷基三甲基溴化铵为模板剂,在氟化物存在的条件下,120℃下水热法合成ZrMCM-48介孔分子筛．分别用H2S04和NH4NO3对ZrMCM48进行修饰,得到酸性的SO24-／ZrMCM-48和H-zrMCM48介孔分子筛．通过x射线衍射仪（XRD）、NH3-TPD、N2吸附-脱附、透射电子显微镜（TEM）等方法对所得样品进行表征,并通过苯酚与叔丁醇的烷基化反应考察其催化性能．结果表明：ZrMCM-48、SO24-／ZrMCM-48和H-ZrMCM48都具有MCM48典型的立方介孔结构．经H2SO4和NH4NO3修饰后得到的样品的介孔有序性下降,ZrMCM48的弱酸中心较多,强酸中心相对缺乏;样品H-ZrMCM-48和SO24-／ZrMCM-48,除具有弱酸中心外,还有一定量的强酸中心,并且SO24-／ZrMCM-48比H-ZrMCM-48的强酸中心多．在相同的实验条件下,SO24-／ZrMCM-48催化剂的催化活性明显高于H-zrMCM48和zrMCM48,反应温度为140℃时,苯酚转化率高达91．6％．对于SO24-／ZrMCM-48催化剂,在低温时有利于选择性制备2,4-DTBP,高温时有利于选择性制备4-TBP．     

Effect of nanosized gold particle addition to supported metal oxide catalyst in methanol oxidation

Gold has rarely been utilized as a catalytic component because of its poor affinity to chemical species. It is however known that nanosized gold particles promote the dissociation of oxygen or hydrogen. In this study, alumina-supported metal oxide catalysts were prepared by impregnation method and applied to methanol oxidation. The dispersion form and size of the gold particles were observed by transmission electron microscopy (TEM). In the results, the maximum catalytic activity was obtained over the ZnO/Al2O3 catalyst, and the optimum loading was 4 wt%. Furthermore, nano-sized gold particles at various loadings were added to ZnO/Al2O3 catalyst by deposition method. The gold particles on Au/ZnO/Al2O3 catalyst were well dispersed and the catalyst activity was remarkably increased compared to ZnO/Al2O3 catalyst. The role of gold particles in the increased catalytic activity is discussed and a possible mechanism is presented.     

溶液燃烧法制备Ni-Al2O3催化剂用于CO2-CH4重整研究

采用溶液燃烧法制备了Ni含量为2wt%、4wt%、6wt%、8wt%和10wt%系列催化剂, 并对反应前后催化剂进行N₂吸附-脱附、XRD、H₂-TPR、TPH、Raman、TEM和TG-DTG等表征。与等体积浸渍法(以溶液燃烧法制备的Al₂O₃为载体)制备的催化剂相比, 溶液燃烧法制备的催化剂具有较大的比表面积, 孔径分布可分为2~4.5 nm和4.5~10 nm两段, 属典型的多级孔结构; NiO高度分散在载体上, 与载体具有较强的相互作用, 这种相互作用有利于提高催化剂的稳定性。催化剂210 h稳定性试验表明, 溶液燃烧法制备的Ni含量为8wt%试样的CH₄转化率维持在90%左右, 失活速率仅为0.035%/h, 优于浸渍法制备的相同Ni含量催化剂。     

Recycling of glass in synthesis of MCM-48 mesoporous silica as catalyst support for Ni<Subscript>2</Subscript>O<Subscript>3</Subscript> photocatalyst for Congo red dye removal

Glass was successfully recycled in the synthesis of mesoporous silica MCM-48 which was used as catalyst support for nickel oxide photocatalyst. The resulted products were evaluated using X-ray diffraction, scanning electron microscope and UV–Vis spectrophotometer. The precipitated nickel oxide is of Ni₂O₃ form and loading of it onto MCM-48 resulted in a reduction in the band gap energy from about 3.66 eV to about 2.4 eV. The role of MCM-48 as catalyst support for Ni₂O₃ in enhancing the adsorption capacity and photocatalytic properties of nickel oxide was evaluated through series of equilibrium studies and photocatalytic degradation of Congo red dye under visible light. Using of glass-based MCM-48 as catalyst support for Ni₂O₃ showed enhancing the adsorption capacity by 31.3 and 14.8% higher than the adsorption capacity of Ni₂O₃ and MCM-48, respectively. Also, the photocatalytic degradation percentage increased by about 67.3% relative to the Ni₂O₃ degradation percentage. The nature of MCM-48/Ni₂O₃ adsorption mechanism is chemisorption and occurs in multilayer form throughout the heterogeneous surface of the composite. The using of MCM-48 as support for Ni₂O₃ photocatalyst enhanced the adsorption capacity through increasing the total surface area. The loading process resulted in fixing of the Ni₂O₃ particles throughout the porous structure which producing more exposed active photocatalyst sites and active adsorption sites for the incident photons as well as preventing the nickel oxide particles from agglomeration. Based on the obtained results, supporting of Ni₂O₃ particles onto MCM-48 is promising active centers for the degradation of Congo red dye molecules.     

Facile synthesis of fully ordered L10-FePt nanoparticles with controlled Pt-shell thicknesses for electrocatalysis

We report a simple one-step approach for the synthesis of ～4 nm uniform and fully L10-ordered face-centered tetragonal (fct) FePt nanopartides (NPs) embedded in ～60 nm MCM-41 (fct-FePt NPs@MCM-41).We controlled the Pt-shell thickness of the fct-FePt NPs by treating the fct-FePt NPs@MCM-41 with acetic acid (HOAc) or hydrochloric acid (HC1) under sonication,thereby etching the surface Fe atoms of the NPs.The fct-FePt NPs deposited onto the carbon support (fct-FePt NP/C) were prepared by mixing the fct-FePt NPs@MCM-41 with carbon and subsequently removing the MCM-41 using NaOH.We also developed a facile method to synthesize acid-treated fct-FePt NP/C by using a HF solution for simultaneous surface-Fe etching and MCM-41 removal.We studied the effects of both surface-Fe etching and Pt-shell thickness on the electrocatalytic properties of fct-FePt NPs for the methanol oxidation reaction (MOR).Compared with the non-treated fct-FePt NP/C catalyst,the HOAc-treated and HCl-treated catalysts exhibit up to 34％ larger electrochemically active surface areas (ECASAs);in addition,the HCl-treated fct-FePt NP (with ～1.0 nm Pt shell)/C catalyst exhibits the highest specific activity.The HF-treated fct-FePt NP/C exhibits an ECASA almost 2 times larger than those of the other acid-treated fct-FePt NP/C catalysts and shows the highest mass activity (1,435 mA.mg~,2.3 times higher than that of the commercial Pt/C catalyst) and stability among the catalysts tested.Our findings demonstrate that the surface-Fe etching for the generation of the Pt shell on fct-FePt NPs and the Pt-shell thickness can be factors for optimizing the electrocatalysis of the MOR.     

WO3添加方式对V2O5/TiO2催化剂性能影响

以TiO2为载体,采用挤压成型法制备了钒系蜂窝整体式SCR脱硝催化剂,通过N2吸附-脱附(BET)、X射线衍射(XRD)、扫描电镜(SEM)、FT-Ra-man光谱等表征手段和催化活性测试对混合练泥工序中助催化剂WO3不同引入方式制备的催化剂进行了对比研究。实验结果表明,由钛钨粉制备的催化剂具有较大的比表面积及孔容积;而由偏钨酸铵制备的催化剂具有较均匀的微观结构形貌,活性物种分散性好,拥有更多的VO6八面体结构,且出现了WOx四面体结构,表现出良好的NH3-SCR活性和较宽的活性温度窗口,在空速为10000h-1,氨氮比为1.0时,活性温度范围内NO脱除率达到了93%。     

SCR烟气脱硝催化剂V_2O_5-WO_3/TiO_2性能研究

通过浸渍法制备了V2O5-WO3/TiO2催化剂,考察催化剂在SCR反应中的脱硝性能.结果表明,WO3的引入扩宽了催化剂的反应窗口,随着WO3含量增加,脱硝率略有上升,特别是在高温阶段.当WO3含量为8%时,催化剂具有最佳效果,在250~400℃范围内,NO脱除率都能达到95%以上,450℃时,脱硝率仍能达到89.19%.此外,进一步考察了空速值、氧浓度、氨氮比、NO初始浓度等不同条件下对催化剂活性的影响.     

Liquid phase hydrogenation of furfural to biofuel over robust NiCu/Laponite catalyst: A study on the role of copper loading

Sustainable production of biofuel and chemical feedstock through catalytic hydrogenation has now received increased attention due to the expeditious depletion of crude oil. In the present investigation, we developed a cost-effective and base metal-based NiCu/Laponite catalyst for liquid-phase hydrogenation of furfural into fuel range components. The robust catalysts were prepared by a simple co-impregnation method with constant loading of 5 wt% NiO with different wt.% of CuO (x) loadings (where x = 8, 10, 12 & 14%) on the Laponite support. The textural properties, surface acidity, and reduction of the synthesized catalysts were studied by employing various physicochemical characterizations such as XRD, N₂ sorption analysis, NH₃-TPD, H₂-TPR, and TGA. The obtained results revealed that optimum loading of 12% CuO and 5% NiO catalyst aids fine dispersion of copper and nickel oxide on the surface of the support. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images displayed the delamination of Laponite particles and dispersion of Ni-Cu catalyst on the support surface. The hydrogenation efficiency of the synthesized catalysts was tested in a bench top stainless steel autoclave reactor by liquid phase reaction condition of furfural at 150–210 °C under 10–25 bar H₂ pressure for 1–6 h. The excellent activity of 5Ni-12Cu/Laponite catalysts was compared and correlated with the physicochemical characteristics of the catalyst.