A simple co-impregnation route to load highly dispersed Fe(III) centers into the pore structure of SBA-15 and the extraordinarily high catalytic performance

Highly dispersed iron centers supported on SBA-15 were successfully prepared via a simple incipient wetness co-impregnation route by casting furfuryl alcohol (FA) solution of iron (III) acetylacetonate (Fe(acac)₃), which were used as carbon and iron sources, respectively, into the pore structure of SBA-15, followed by the subsequent removal of carbonized FA. Various techniques such as XRD, TEM, N₂ sorption, UV–vis, XPS and EPR, were employed to characterize the prepared catalysts. It was shown that both Fe₂O₃ nanoclusters and isolated iron species were present and highly dispersed onto the pore surface of SBA-15, due to the presence of abundant carbon source co-impregnated, with well-maintained, highly ordered and open mesoporous structure. A great number of acidities was introduced by the loading of Fe₂O₃, and the catalytic performance was tested on the Friedel–Crafts benzylation of benzene by benzyl chloride. Under the optimized reaction condition, the catalyst showed a superior catalytic performance with a 100% yield of monoalkylated product within 1.5 min at 60 °C. The catalyst demonstrated high reusability and stability, the yield of diphenylmethane was still higher than 90% after 6 runs. Moreover, the catalyst was still active at the temperature as low as 40 °C. Such a strategy is verified applicable to prepare other well-dispersed metal oxides, i.e. Mn_xO_y loaded into the pore structure of mesoporous materials.     

Effect of furfuryl alcohol addition on the cure of furfuryl alcohol resin used in the glassy carbon manufacture

Glassy carbon can be manufactured practically without pores, named Monolithic Vitreous Carbon (MVC) or presenting up to 98% in transport pore volume, foam form, denominated Reticulated Vitreous Carbon (RVC). The glassy carbon processing is affected by some processing parameters, among them it can be cited the resin viscosity. The present work involves the optimization of RVC manufacture by monitoring the polyurethane (PU) foam impregnation with furfuryl alcohol resin with different viscosity values, which were obtained by dilution of the resin with different amounts of furfuryl alcohol. The resin samples used in the PU impregnation were characterized by thermal and rheological analyses. These results were correlated with scanning electron microscopy observations and compression test results of the impregnated polyurethane foam. The results show that the rheological behavior of the resin has significant influence on the polymerization step, affecting the homogeneity of impregnated foam and, consequently, its final properties, mainly the mechanical one. The impregnated foam prepared with the furfuryl alcohol resin diluted with 10% of furfuryl alcohol (η = 11.4 Pa s) showed higher compression values (0.26 MPa). © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Iron (III) oxide nanoparticles within the pore system of mesoporous carbon CMK-1: intra-pore synthesis and characterization

Iron (III) oxide nanoparticles were synthesized inside the pore system of mesoporous carbon CMK-1. This intra-pore synthesis was carried out using several cycles of wet impregnation, drying and calcination procedures. The existence of iron (III) oxide nanoparticles within the pore system was proved by powder X-ray diffraction, nitrogen physisorption, preservation of the host structure by Raman spectroscopy and transmission electron microscopy. Finally, the local structure of the iron oxide was determined by X-ray absorption spectroscopy.     

糠醇基介孔碳对水中双酚A的吸附性能研究

采用3种多孔碳材料C-1、C-2和C-3对双酚A进行静态吸附实验,选用具有集中介孔分布、比表面积较大的C-3在不同温度和pH条件下对双酚A进行吸附。结果表明,当双酚A初始质量浓度为60 mg/L、温度为30℃时,C-3对双酚A的饱和吸附量达到279.4 mg/g。在相同条件、等电点附近,C-3对双酚A的去除率达到最大值47.4%,饱和吸附量达到284.5 mg/g。C-3对双酚A的吸附遵循拟二级动力学方程。     

不同制备条件对SBA-15介孔氧化硅的形貌、比表面积和孔径分布的影响

研究了表面活性剂用量、水解过程中维持搅拌或静置、水热或微波辐射陈化等反应条件或因素对合成SBA-15的形貌、比表面积以及孔径大小和分布的影响及规律。结果表明,在P123中增加CTAB表面活性剂的用量,所得SBA-15形貌由棒状逐渐转变为球型颗粒;硅源水解过程中,搅拌会使产物倾向于呈现棒状颗粒,而静置水解则有利于成球颗粒的形成。与水热陈化处理相比,微波能快速方便地合成形貌规则、比表面积大且孔径较均一的SBA-15。     

糠醛加氢制糠醇中γ-Al2O3负载Cu-Zn催化剂的改性研究

采用浸渍法制备Co改性γ-Al₂O₃负载的Cu-Zn催化剂，考察Cu-Zn负载量、Co含量及反应温度等对催化剂性能的影响。结果表明，在413 K、氢气流速0.5 mL·s^－1 和糠醛空速2 h^-1 条件下,当催化剂Cu-Zn/γ-Al₂O₃（Co）中n(Cu)∶n(Zn)∶n(Al)∶n(Co)＝1.0∶2.0∶3.0∶0.51时，糠醇的选择性100％，糠醛转化率94.6％，比使用单纯Cu-Zn/γ-Al₂O₃催化剂的最佳转化率提高11％。     

清洁催化氧化苯甲醇合成苯甲醛新途径

以30%的双氧水为氧源,Na2WO4·H2O为催化剂,在酸性配体存在而无任何溶剂和相转移催化剂的条件下,清洁催化氧化苯甲醇合成苯甲醛。研究了不同配体及其用量对反应的影响。     

金属离子Al~(3+)对SBA-15分子筛形貌的调控作用研究

以异丙醇铝为铝源,在高浓度酸性环境下,通过Al3+调控SBA-15的形貌与性质。在强酸条件下,所得样品的实际n(Si)∶n(Al)都远高于配料n(Si)∶n(Al),且样品的Brnsted酸为0,Lewis酸也较低,铝元素无论是以嫁接还是骨架配位形式都难以嵌入到SBA-15的体相中。随着配料n(Si)∶n(Al)降低,SBA-15由线粒状向端粒颗粒状发展;当配料n(Si)∶n(Al)=5和2.5时,SBA-15仍然具有有序结构,但是二维有序性不强。当n(Si)∶n(Al)=20时,所得材料具有最高的比表面积、孔容及孔径,其值分别为827m2/g,1.25cm3/g,6.06nm。无机硅物种和有机高分子表面活性剂相互作用及体系Al3+浓度导致的胶束空间限制这两方面是Al3+对SBA-15的形貌形成的原因。     

Effect of different lanthanum source and preparation method on the lanthanum-doped mesoporous SBA-15 synthesis

Lanthanum-substituted mesoporous SBA-15 molecular sieve has been prepared by direct synthesis and post-synthesis procedures using lanthanum nitrate or lanthanum chloride as lanthanum source. Characterizations by atomic absorption, X-ray diffraction, nitrogen adsorption, UV–Vis spectra analysis, FT–IR spectroscopy and scanning electron microscopy have been carried out to evaluate the efficiency of the incorporation of lanthanum by these procedures. Results showed that Lanthanum was well incorporated into the hexagonal framework of SBA-15 molecular sieves by these two procedures. These LaSBA-15 mesoporous molecular sieves retain the hexagonal order and physical properties of siliceous SBA-15 material. Compared to lanthanum chloride, the lanthanum nitrate is a suitable lanthanum source, which can match the hydrolysis rate of silicon precursor and composite materials possess larger specific surface area, uniform mesopore size distribution.     

苯磺酸化SBA-15催化乙二胺四亚甲基膦酸合成研究

以介孔二氧化硅SBA-15为载体,TMPS为接枝剂,氯磺酸为磺化剂制得表面苯磺酸改性的固体酸催化剂SBA-15-ph-SO3H。利用小角XRD、TEM、红外光谱、酸量测定的手段对合成的催化剂进行了表征。将该催化剂应用于催化乙二胺四亚甲基膦酸的合成反应,结果表明,在低温80℃、催化剂用量0.5 g/mol的条件下反应3 h,乙二胺四亚甲基膦酸的转化率为74%,重复使用5次,催化性能无明显下降。     

Novel efficient and green approach to the synthesis of glutaraldehyde over highly active W-doped SBA-15 catalyst

In the present work, we demonstrate for the first time the use of W-doped SBA-15 catalyst prepared by a novel in situ synthesis method as highly efficient catalyst for the direct production of glutaraldehyde via selective oxidation of cyclopentene by using non-aqueous hydrogen peroxide as the green oxidant. It is suggested that the presence of a high surface concentraiton of WO_x species dispersed on well ordered hexagonal pore walls of SBA-15 support is essential to the superior performance of the catalyst for the selective oxidation of cyclopentene.     

近期糠醛催化加氢制糠醇催化剂研究热点

综述了近10年来催化剂在糠醛加氢制糠醇反应中应用的研究成果及催化剂的研究热点,展望了催化剂的发展方向。     

合成条件对SBA-15介孔分子筛晶体结构及水热稳定性影响

以X射线衍射(XRD)为表征手段,研究了SBA-15介孔分子筛合成过程中酸类型、加料顺序和搅拌时间对介孔分子筛晶体结构的影响,结果表明:不同酸合成的SBA-15介孔分子筛的结晶度顺序为高氯酸盐酸硫酸氢氟酸。同时研究了焙烧法和溶剂萃取法去除模板剂对SBA-15介孔分子筛水热稳定性的影响,结果表明:焙烧法去除模板剂后得到的分子筛的水热稳定性更高。     

Effect of different synthesis methods on the structural and catalytic performance of SBA-15 modified by aluminum

Two different aluminum-containing mesoporous Al/SBA-15 were prepared by post-synthesis method and direct synthesis method using P123 as structure directing agent and aluminum isopropoxide as the aluminum source. Samples were characterized in detail by XRD, N₂ adsorption, TEM,²⁷Al MAS NMR, and the acidic properties were performed by FT-IR of pyridine adsorption (Py-IR). The results show that Al/SBA-15 prepared by the direct synthesis method possessed higher BET surface area and larger pore volume. The acidic properties were investigated in Friedel–Crafts alkylation of phenol tert-butylation. The different synthesis method leads to distinct coordination of Al and intensity of acidity. Kinetics of the alkylation over Al/SBA-15 was also investigated. These results indicated that Al/SBA-15, prepared by post-synthetic grafting method, has more activity ability than the corresponding one synthesized by direct method since they contain more Lewis acid sites and Brönsted acid sites. The catalysts preserved almost their initial catalytic activity after four reuses.     

Effect of addition of alkali metal salts in hydrothermal synthesis and post heat-treatment on porosity of SBA-15

SBA-15 was hydrothermally synthesized at 80 °C for 48 h, and then the surfactant template for mesopore formation was removed by extraction with ethanol, washing with nitric acid, and heating at 200 °C. Addition of alkali metal chlorides to a synthesis gel of SBA-15 increased its mesopore diameter in the following order: no added salt < LiCl < KCl < CsCl. The micropore volume did not change with the addition of any alkali metal and was around 0.17 mL g^–1. These results suggest that alkali metal salt is inside the mesopore with a micelle template. When a small amount of potassium chloride was impregnated in SBA-15 after extraction and washing, micropore volume reduced almost to zero with heating at 400 °C in dry air, and the mesopore diameter and pore wall thickness were reduced by a larger amount than for non-impregnated SBA-15. It is likely that the micropores in the mesopore wall vanish due to condensation of silanols and/or reconstruction of siloxane bonds on the micropore wall, which are catalyzed by alkali metal halides.     

A comparative investigation on the properties of Cr-SBA-15 and CrOx/SBA-15

High-surface area and well-ordered mesoporous Cr-incorporated SBA-15 (Cr-SBA-15) and SBA-15-supported chromia (CrO_x/SBA-15) with Cr surface density = 0.05–1.11 Cr-atom/nm² have been prepared, respectively, using the one-step synthesis and incipient wetness impregnation method, and characterized by AAS, XRD, BET, ESEM, TEM, XPS, laser Raman, UV-Vis, FT-IR, and H₂-TPR. It is observed that the Cr-SBA-15 and CrO_x/SBA-15 samples showed an evolution of surface morphology from long chain-shaped to short rod-like and further to an irregularly spherical architecture at elevated Cr content, which might arise from the interaction of Cr ions or CrO_x domains with SBA-15. There were co-presence of tetrahedrally coordinated mono- and poly-chromate (Cr⁶⁺) as well as octahedrally coordinated Cr³⁺ species in Cr-SBA-15 and CrO_x/SBA-15, with the Cr⁶⁺ species being dominant at Cr surface density ≤0.22 Cr-atom/nm² in Cr-SBA-15 and Cr ≤0.54 Cr-atom/nm² in CrO_x/SBA-15, whereas the amount of the Cr³⁺ species increased markedly at Cr surface density ≥0.53 Cr-atom/nm² due to the formation of crystal Cr₂O₃ phase. Maximal Cr incorporation into Cr-SBA-15 and one monolayer surface CrO_x coverage on CrO_x/SBA-15 occurred at Cr surface density ≤0.53 Cr-atom/nm² and <1.11 Cr-atom/nm², respectively. The CrO_x/SBA-15 samples exhibited better reducibility than the Cr-SBA-15 samples, with the best reducibility exhibited at Cr surface densities of 0.54 and 0.12 Cr-atom/nm², respectively.     

Templated pyrolytic carbon: the effect of poly(ethylene glycol) molecular weight on the pore size distribution of poly(furfuryl alcohol)-derived carbon

Poly(ethylene glycol), which has a negligible carbon yield upon pyrolysis, was used as a template to study the controlled formation of mesoporosity in pyrolytic carbons. A series of carbons was produced from mixtures of poly(ethylene glycol) and poly(furfuryl alcohol) with 25, 50 and 75% composition by weight and an M_n of 300 to18?500 g/mol of template. Polydisperse dextran adsorption reveals a maximum in uptake for 8000 g/mol and 50% templated carbons, while materials from 75% mixtures or those from less than 2000 g/mol template yielded negligible dextran uptake. These results correlated well with the intensity ratio of a broad peak between 7 and 11° 2θ in the X-ray diffraction spectrum and the 002 diffraction peak and also qualitatively with micrographs of the internal microstructure of the carbons. The results suggest a templating process dominated by both the molecular size of the template and the rate of expulsion of decomposed template material during the formation of the solid.     

SBA-15介孔分子筛的功能化新应用进展

SBA-15介孔分子筛,具有规则的孔径分布,大的孔径和较厚的孔壁,可以作为载体材料,且在反应中能提供特殊的微环境,因此在催化与纳米材料领域具有非常广阔的应用前景.针对SBA-15的应用现状,本文集中探讨了现阶段SBA-15在介孔碳的合成、色谱填料基体、纳米化学反应器等新兴领域的应用研究进展,并对今后SBA-15的发展以及研究方向进行了展望.     

Synthesis of pigments based on the CuO-Cr2O3-Al2O3 system using the precipitation method

Compositions of ceramic pigments for coloring glaze and flux coatings have been developed using the powder method and the coprecipitation method. Comparative parameters of chromophore properties of the obtained pigments are given. The expediency of using the coprecipitation method in the synthesis of ceramic pigments is demonstrated.     

A new route to synthesis of sulphonato-salen-chromium(III) hydrotalcites: Highly selective catalysts for oxidation of benzyl alcohol to benzaldehyde

The Mg–Al layered-double hydroxides (LDHs) intercalated by three kinds of sulphonato-salen-chromium(III) complexes were prepared and characterized by FTIR, UV–vis, XRD and elemental analysis. It was found that the homogeneous complexes were successfully intercalated into the LDH interlayer via the method of anion exchange followed by coordination with chromium(III) chloride. And the resulting LDH hosted chromium complexes were shown to be effective heterogeneous catalysts for the solvent-free oxidation of benzyl alcohol (BzOH) to benzaldehyde (BzH) using 30% H₂O₂ as oxidant. Furthermore, owing to the different local environment of the central metal ion chromium(III), the catalyst with the backbone of o-C₆H₄ displayed the highest catalytic performance followed by the NH(CH₂CH₂)₂ with the (CH₂)₂ showing the lowest BzH yield. In addition, a tentative mechanism was also discussed.