尼古丁气相转化反应机制的研究进展

尼古丁是烟草烟雾中的主要有机氮化合物之一,也是最主要的生物碱。在大气环境中,尼古丁会被羟基自由基等氧化,发生气相转化反应,生成二次有机气溶胶,对人体健康造成影响。本文综述了近年来尼古丁气相转化反应机制的相关研究。

反应控制相转化法制备PVDF/SMA-g-PEG共混超滤膜及性能研究

本文依据Schneier混合焓变理论计算预测、Flory-Huggins理论系统分析了聚偏氟乙烯(PVDF)/聚苯乙烯-马来酸酐(SMA)共混体系的相容性.结果表明,当PVDF/SMA共混质量比>88/12或<20/80时,体系为完全相容系统.此外,以m_(PVDF)∶m_(SMA)=88∶12为聚合物(质量分数为16%),二甲基乙酰胺(DMAc)为溶剂,聚乙二醇(PEG)(相对分子量为20000)为致孔剂和反应物,配制出均相聚合物溶液(50℃).根据酯化反应进程,终止反应,视反应体系为铸膜液,采用非溶剂诱导相转化法制备共混超滤膜.随着SMA与PEG之间发生酯化反应和接枝聚合物SMA-g-PEG的合成,溶液黏度从最初的780 mPa·s增至6580mPa·s(64 h),并出现凝胶化.以反应时间为48 h的铸膜液所制得的超滤膜,其纯水渗透率高达4807 L/(m^(2)·h·MPa),BSA截留率为96.6%,通量恢复率为78.9%,表现出优异的抗污染性能和分离性能.

静态顶空气相色谱技术

本文介绍了一种以顶空取样结合气相色谱分析的静态顶空气相色谱技术。重点是介绍在静态顶空气相色谱测定中的各种顶空分析技术,包括常规、全挥发、基于化学反应的相转化、挥发性示踪剂术,以及用于研究化学动力学多次顶空抽提气相色谱技术。本文还例举了一些顶空气相色谱技术的特殊应用。

2MgO·2B_2O_3·MgCl_2·14H_2O-7.8%H_3BO_3-H_2O体系多温相关系研究

研究了 2 Mg O· 2 B2 O3 · Mg Cl2 · 1 4 H2 O在不同温度下的 7.8% H3 BO3 水溶液中的相转化产物及其溶解度 . IR,XRD,TG及化学分析表明 ,相转化产物在 0～ 2 2℃范围内为 Mg O· 2 B2 O3 · 9H2 O;2 2～ 6 8℃为Mg O· 3B2 O3 · 7.5 H2 O;6 8～ 95℃为 Mg O· 3B2 O3 · 7H2 O;95～ 98.8℃为 Mg O· 3B2 O3 · 5 H2 O;1 0 0～ 1 1 0℃为 Mg O· B2 O3 · 3H2 O;1 1 0～ 1 2 0℃为 2 Mg O· B2 O3 · 2 H2 O;1 2 0～ 1 70℃为 2 Mg O· B2 O3 · 1 .5 H2 O;1 70～ 2 0 0℃为 2 Mg O·B2 O3 ·H2 O.提出了相转化反应原理 .

Reaction mechanism of roasting Zn_2SiO_4 using NaOH

The reaction kinetics of roasting zinc silicate using NaOH was investigated.The orthogonal test was employed to optimize the reaction conditions and the optimized reaction conditions were as follows:molar ratio of NaOH to Zn2SiO4 of 16:1,reaction temperature of 550°C,and reaction time of 2.5 h.In order to ascertain the phases transformation and reaction processes of zinc oxide and silica,the XRD phase analysis was used to analyze the phases of these specimens roasted at different temperatures.The final phases of the specimen roasted at 600°C were Na2ZnO2,Na4SiO4,Na2ZnSiO4 and NaOH.The reaction kinetic equation of roasting was determined by the shrinking unreacted core model.Aiming to investigate the reaction mechanism,two control models of reaction rate were applied:chemical reaction at the particle surface and diffusion through the product layer.The results indicated that the diffusion through the product layer model described the reaction process well.The apparent activation energy of the roasting was 19.77 kJ/mol.

Siderite pyrolysis in suspension roasting:An in-situ study on kinetics,phase transformation,and product properties

Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.

Oxidative coupling of α-bromoarylacetonitriles and oxidative decyanation of diarylacetonitriles catalyzed by solid-liquid phase transfer

Oxidative coupling of α-bromoarylacetonitriles and oxidative decyanation of diarylacetonitriles are efficiently realized by solid-liquid phase transfer catalysis using anhydrous K 3 PO 4 as base and TBAB as catalyst in acetone at room temperature. In this mild and convenient method, α,β-dicyanostilbenes and diarylketones were prepared in good to excellent yields.

Decoupling hydrogen production from water oxidation by integrating a triphase interfacial bioelectrochemical cascade reaction

Water electrolysis to produce H2 is a promising strategy for generating a renewable fuel.However,the sluggish-kinetics and low value-added anodic oxygen evolution reaction(OER)restricts the overall energy conversion efficiency.Herein we report a strategy of boosting H_(2)production at low voltages by replacing OER with a bioelectrochemical cascade reaction at a triphase bioanode.In the presence of oxygen,oxidase enzymes can convert biomass into valuable products,and concurrently generate H_(2)O_(2) that can be further electrooxidized at the bioanode.Benefiting from the efficient oxidase kinetics at an oxygen-rich triphase bioanode and the more favorable thermodynamics of H_(2)O_(2)oxidation than that of OER,the cell voltage and energy consumption are reduced by~0.70 V and~36%,respectively,relative to regular water electrolysis.This leads to an efficient H_(2)production at the cathode and valuable product generation at the bioanode.Integration of a bioelectrochemical cascade into the water splitting process provides an energy-efficient and promising pathway for achieving a renewable fuel.