以培养研究型人才为导向的基础化学实验教学设计与实践

从培养研究型人才的角度出发,阐述了研究性教学模式在基础化学实验教学过程中的必要性。以"硫代硫酸钠溶液标定实验"为教学案例,引导学生主动探索,综合运用所学理论知识和技能,选择碘酸钾作为基准物,从酸度、加水量、反应时间和碘化钾溶液加入量四个方面考查实验条件和终点判断方法。实验设计和教学过程的实施,有助于培养学生系统的研究方法、严谨的科学思维和勇于探索创新的科学素养。

Improvement of catalytic stability for CO_2 reforming of methane by copper promoted Ni-based catalyst derived from layered-double hydroxides

Copper-promoted nickel-based metal nanoparticles (NPs) with high dispersion and good thermal stability were derived from layered-double hydroxides (LDHs) precursors that were facilely developed by a co-precipitation strategy. The copper-promoted Ni-based metal NPs catalysts were investigated for methane reforming with carbon dioxide to hydrogen and syngas. A series of characterization techniques including XRD, N2adsorption and desorption, H2-TPR, XPS, CO2-TPD, TEM, TGA and in situ CH4-TPSR were utilized to determine the structure-function relationship for the obtained catalysts. The copper addition accelerated the catalyst reducibility as well as the methane activation, and made the Ni species form smaller NPs during both preparation and reaction by restricting the aggregation. However, with higher copper loading, the derived catalysts were less active during methane reforming with CO2to syngas. It was confirmed that the catalyst with 1 wt% Cu additive gave the higher catalytic activity and remained stable during long time reaction with excellent resistance to coking and to sintering. Furthermore, the mean size of metal NPs changed minimally from 6.6 to 7.9 nm even after 80 h of time on stream at temperature as high as 700 °C for this optimized catalyst. Therefore, this high dispersed anti-coking copper-promoted nickel catalyst derived from LDHs precursor could be prospective catalyst candidate for the efficient heterogeneous catalysis of sustainable CO2conversion. © 2016 Science Press

Ordered mesoporous Sn-SBA-15 as support for Pt catalyst with enhanced performance in propane dehydrogenation

A series of Sn‐incorporated SBA‐15materials with high specific surface areas and highly orderedmesoporous structures were synthesized by a facile one‐pot method and used as catalyst supports.A reference sample was also prepared using a conventional impregnation method.The catalystswere characterized using various methods,and their activities in propane dehydrogenation wereinvestigated.The incorporation of Sn into the SBA‐15matrix led to strong interactions between Snspecies and the support,and these helped to maintain the oxidation states of Sn species during thereaction.Substitution with Sn changed the interfacial properties of the Pt species and improved thefunction and effect of the Sn promoter.The catalytic activities and stabilities of the Pt catalysts supportedon Sn‐incorporated SBA‐15were better than those of the impregnated sample.However,thecatalytic performance deteriorated when an excessive amount of Sn was introduced and the interactionsamong Pt,Sn species,and the support became weaker.The Pt/0.5Sn‐SBA‐15catalyst gavethe best propene selectivity,i.e.,98.5%,with a corresponding propane conversion of about43.8%.

Oxidative dehydrogenation of ethane with carbon dioxide over silica molecular sieves supported chromium oxides:Pore size effect

SBA-15 with varied pore size from 4 to 8 nm were synthesized by tuning the temperature of hydrothermal treatment,the supports were then used to load the active phase Cr Oxthrough a conventional impregnation method.The resulting catalysts were characterized by small/wide angle XRD,N_(2) adsorption/desorption,FT-IR,TEM-EDX,XPS,TPR and CO_(2)-TPD to study the feature of structure,surface chemical state,redox and basicity.It was found from these results that the metal species could be well dispersed on catalysts with larger pore size.Cr^(6+)species could enter into the framework by substituting the Si atoms of SBA-15,and Cr^(3+)mainly exist on extra framework.Pore size had profound effects on reducibility,surface composition and basicity.Cr^(6+)species were necessary to activate the C-H bonds of alkanes,while the basicity played an important role in activating C-O bonds of CO_(2).The best performances were achieved over the sample Cr supported on SBA-15 with a pore diameter of 7 nm in oxidative dehydrogenation of ethane in the presence of CO_(2).

Living and enantiomer-selective polymerization of allene initiated by Ni complex containing chiral phosphine

A new allylnickel(II) complex([S(R)]-N-[(1 S)-2-(diphenylphosphino)-1-phenylethyl]-2-methyl-2-propanesulfinamide)(2,2,2-trifluoroacetato-k O)(p-allyl)nickel(2) was designed and prepared by using chiral phosphine. 2 was revealed to efficiently initiate the polymerization of L-and D-N-(1-(dodecylamino)-1-oxopropan-2-yl)-4-(propa-1,2-dien-1-yloxy)-benzamide(L-1 and D-1) in a living/controlled chain growth manner. Polymerization kinetics of L-1 and D-1 indicated that L-1 preferentially polymerized over the antipode D-1 by a factor of 1.9. In block copolymerization of rac-1 using the poly-L-150 as the macroinitiator, the polymerization proceeded in enantiomer-selective manner. It was found that enantiomeric excess(ee) value of the recovered monomer increased with the monomer conversion and finally reached to the maximum of 34%. These results suggest this chiral phosphine complex exhibits enantiomer-selectivity for the polymerization of chiral allene derivative monomer.