Pt含量及活化温度对固体超强酸催化剂异构化性能的影响

本文制备了固体超强酸Pt- S2O82-/ZrO2-Al2O3催化剂,采用XRD、TPR、TG-DTA 、FT-IR等表征手段对催化剂进行了表征,并在高压微反－色谱联合装置上,考察了Pt质量分数和活化温度对催化剂正戊烷异构化性能的影响. 结果表明,Pt能使催化剂的还原温度降低;增强载体表面氢气的溢流效应,提高酸强度;Pt质量分数0.10%、活化温度300℃的催化剂异构化活性最高,在反应温度220℃、压力2.0MPa、氢烃摩尔比4:1、质量空速1.0h-1时,异戊烷产率达62.3%. 在100h内异戊烷收率可稳定在55%左右,选择性在98.0％以上.     

MgO/NaY催化剂上葡萄糖水中异构制取果糖的研究

The MgO/NaY catalysts prepared by impregnation method were used for the conversion of glucose to fructose in water medium.The effects of MgO loading,reaction temperature,glucose concentration and reaction time on the catalytic performance for the reaction were studied.The activity testing results indicated that fructose could be generated effectively by controlling the components of the catalyst and reaction conditions.The maximal fructose yield of 33.8% with the selectivity of 67.3% was achieved over the 10% MgO/NaY catalyst at 100 ℃ for 2 h.Moreover,the catalysts were characterized by XRD,BET,and CO₂-TPD techniques.The structural property of NaY with higher surface area facilitated glucose conversion,and the modulated basicity of the catalyst with MgO addition contributed to the formation of fructose in the tautomerization of aldose to ketose.     

Surface-relief-grating formation behavior of two hyperbranched azo polymers

In this work,surface-relief-grating formation behavior was studied by using two hyperbranched azo polymers.The hyperbranched polymers containing pseudo-stilbene type azo chromophores throughout the hyperbranched structure were synthesized by step-growth polycondensation of AB₂ type monomers.The AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）-phenylazo） benzoic acid（BAA）,was prepared through azo-coupling reaction between N,N’-bis（2-chloroethyl）aniline and 4- aminobenzenic acid.The another AB₂ monomer,4-（4’-（bis（2-chloroethyl）amino）phenylazo）-3-nitro-benzoic acid（BANA）, was prepared through azo-coupling reaction between N,N-bis（2-chloroethyl）aniline and 3-nitro-4-aminobenzcnic acid.The hyperbranched polymers（PBAA and PBANA） were prepared through nucleophilic substitution reaction of BAA and BANA, respectively.The polymers synthesized were characterized by using spectroscopic methods and thermal analysis.The photoinduced dichroism and photo-induced surface-relief-grating（SRG） formation of the hyperbranched polymers were investigated upon irradiation with Ar⁺ laser at 488 nm.PBAA shows typical photoinduced dichroism SRG formation behavior.On the contrary,PBANA does not show the photoresponsive properties.The results indicate that the nitro at the ortho position of azo group of PBANA shows the effect of inhibiting the photoinduced variations.The effect can be attributed to the blockage of the trans-cis isomerization of the azobenzene moieties by the steric hindrance.     

Comparative study of kinetics isomerization of substituted polyacetylene (Cl,F and I): Ab initio and DFT calculations

Ab initio and DFT methods were used to investigate the interconversions of substituted polyacetylene conformers C₁₀H₆X₆ (X=F, Cl and I) in the vapour phase. The rates of this geometrical isomerization have been calculated and the Arrhenius parameters evaluated. In the case of unsubstituted polyacetylene as the reference, the B3LYP Arrhenius parameters obtained are A₁=2.99 × 10¹⁷ s^–1 and E_a=17.30 kcal mol^–1. The values of the equilibrium constant for the reaction have also been determined at various temperatures between 300 and 500 K and the value of the energies change calculated. The results also suggest that the straightforward kinetics characterizing the majority of substituted polyacetylene isomerizations above 300 K. The isomerization energies are positive and the barrier heights ΔE_barrier are expected to be sensitive for the magnitude of halogens effects. According to geometries features the Cis → Trans isomerization in the gas phase occurs by a rotational mechanism.     

Isomerization of n-Hexane Over Platinum Ion-Exchanged Zeolite Beta

Zeolite Beta was synthesized from appropriate gels and crystallized under the controlled temperature and pressurized conditions. For isomerization of n-hexane, platinum ion-exchanged zeolite Beta exhibited high activity and selectivity for 2,2-dimethylbutane (2,2-DMB), 2,3-dimethylbutane (2,3-DMB), 2-methylpentane (2-MP) and 3-methylpentane (3-MP). As high as 72% of n-hexane conversion and 98% of product selectivity were obtained at 250°C, 1600 h^–1 for 20 min on stream. The influences of reaction temperature and space velocity were also studied. Pt/H-Beta zeolite was recommended as one of the promising catalyst for n-hexane isomerization due to its high activity and stability. The combined effect of the stronger acidity possessed by H-Beta and the dehydrogenation role played by Pt was believed to be responsible for the good catalytic performance of Pt/H-Beta.     

链状双杂芳基乙烯化合物的合成与光化学性质研究

合成了1,n-双[4-[2-[2-(5-甲基苯并唑基)]乙烯基]苯氧基]烷烃(a:n=3;b:n=4;c:n=6)和2,2'-双[4-[2-[2-(5-甲基苯并唑基)]乙烯基]苯氧基]乙醚(d)4个新化合物.用元素分析、红外、紫外、核磁共振谱和质谱表征了其结构.用紫外吸收光谱跟踪研究了Ⅰa_Ⅰd在紫外灯照射下的变化,发现上述化合物在高压汞灯照射下可同时发生反顺异构化和[2+2]分子内光二聚两种反应,反顺异构化反应迅速可逆,而光二聚反应进行缓慢且不可逆.增加链长有助于提高分子内光二聚反应的速率.分子内光二聚反应不受空气中氧的影响的事实表明其是经激发单线态历程进行的.还发现分子内光二聚体在短波紫外光照射下容易进行逆[2+2]光解开环反应.上述化合物分子内光二聚和光解开环反应可以反复进行多次,表明该类化合物具有较高的光稳定性.     

溶剂效应的TLSER描述及其在几类异构化反应中的应用

建立了适合于描述党溶剂效应的理论线性溶剂化能相关(TLSER)模型。并用该模型对四类异构化反应在不同溶剂下的反应自由能或活化自由能与溶剂的分子结构之间的关系进行了研究,确证了模型的合理性。     

HAsS2异构体结构与稳定性

在MP2/6-311++G(d,p)和QCISD(t)/6-311++G(3df,2p)(单点)水平下计算得到9个异构体和10个过渡态的HAsS₂体系势能面.异构体cis-HSAsS(E1)的能量最低,其次是trans-HSAsS(E2)、具有AsSS三元环的立体HAs(S)S(C_{s,E3)和HAs(S)S(C2v,E4)结构的异构体,能量分别比cis-HSAsS高1.46,60.78和93.63kJ/mol.根据体系的势能面,异构体E1,E2,E3和E4具有一定的动力学稳定性.AsH和S2第一步反应产物将会异构化为具有较高动力学稳定性的异构体E3,而SH和AsS第一步反应产物将会异构化为E1.计算结果与HNO2,HNS2,HPO2,HPS2和HAsO2等价电子相同的分子的势能面进行了比较.}     

反式-2-取代硫代氨基脲基-4-芳基-5,5-二甲基-2-氧-1,3,2-二氧磷杂环己烷的立体选择性合成及立体化学研究

首先合成了重要的磷酰异硫氰酸酯中间体3, 然后便捷、高产率且立体选择性地合成了反式-2-取代硫代氨基脲基取代的新型六元磷杂环, 其立体化学通过2D NOESY NMR确证. 所有合成的化合物均进行了元素分析和光谱表征, 其中目标产物的13C NMR表征为1,3,2-二氧磷杂环己烷衍生物的碳骨架表征提供了难得的依据. 在溶剂DMSO-d6中, 所有产物均异构化, 生成磷原子的差向异构体. 这一研究结果证明了C4—H 以及31P NMR谱图与立体结构的相关性.     

Substituent effects on the isomerization of hydrazone switches driven by the intramolecular hydrogen bond

In this work, the substituent effects on hydrogen bonding in one kind of hydrazone-based switch are revealed. The E/Z isomerization ratios of these hydrazones and their intramolecular hydrogen bond strengths in the Z form were evaluated using NMR technique. Linear correlations between these parameters and Hammett empirical values for substituent effects are explored as well.