离子交换树脂吸附胞嘧啶核苷三磷酸的动力学和热力学研究

根据CTP在离子交换树脂上的吸附容量和分离因数的大小,确定Duolite A-30树脂适合CTP与CDP及CMP之间的分离.CTP在Duolite A-30树脂上的吸附动力学和热力学研究表明,在283.15～303.15K之间,CTP的质量浓度在7.5g/L以上时,Duolite A-30树脂对CTP的吸附主要受颗粒扩散的控制,其有效扩散系数为D=3.47×10-7cm2/s,溶液的质量浓度≤1.0g/L时,CTP与Duolitc A-30树脂之间的交换速率主要受液膜控制,其液膜扩散系数为Kf=4.112×10-4/s.热力学参数Eα=9.008kJ/mol,△H=5.17kJ/mol·K,△S283.15K=80.28J/mol·K.     

柠檬酸在D354树脂上的动态交换过程

在３５℃下，实验测定了柠檬酸溶液在Ｄ３５４树脂固定床离子交换柱中的穿透曲线，研究了进口浓度、进口流速及柱高对穿透曲线的影响。用简单线性推动力模型描述固定床动态过程，考察了轴向返混对穿透曲线的影响，并从穿透曲线回归得到总传质系数，模型计算值与实验数据符合良好。同时还研究了用强酸顶替法洗脱柠檬酸。     

胸腺五肽在NH-1树脂上的离子交换过程研究

研究了胸腺五肽(TP5)在NH-1树脂上的离子交换过程.结果表明,在pH 2.O的条件下,其等温吸附过程符合Langmuir等温吸附方程,最大吸附量为221.07mg/g wet resin;静态吸附动力学的研究结果显示,NH-1树脂对TP5的吸附过程主要受颗粒扩散控制影响,TP5的颗粒内扩散系数为4.50×10-9cm2/s;对比Nernst-Planck与Fick动力学模型,可用Fick动力学模型来描述TP5在NH-1树脂内的颗粒扩散行为,其有效扩散系数为5.58×10-9cm2/s;采用固定床吸附数学模型,对TP5离子交换柱行为进行模拟,该数学模型考虑了颗粒扩散、轴向返混、非线性平衡以及液膜扩散.结果显示,模拟数据与实验结果具有较好的符合.     

固定床离子交换树脂对K+吸附特性的研究

以固定床离子交换树脂对K~+的吸附过程进行研究,考察了固定床中不同时间及轴向高度中KCl溶液浓度的变化、轴向各区域内树脂对K~+吸附量和吸附率的变化以及KCl溶液表观输送速度和原料液初始浓度对固定床吸附K~+的影响。结果显示,固定床轴向各区域内树脂对K~+吸附量均随时间而增大,而对K~+的吸附率随时间逐渐减小;随着KCl溶液表观输送速度的增大,穿透时间缩短,树脂对K~+的吸附量增加,但对K~+的吸附率由48.43%降至43.02%;相同轴向高度下穿透时间随KCl浓度的增加而缩短,树脂对K~+的吸附量随KCl浓度的增加而变大,对K~+的吸附率由37.75%增至55.20%。     

基于BP神经网络研究儿茶素在ADS-8树脂固定床的吸附过程

以信阳毛尖茶叶浸提液为原料,研究儿茶素在ADS-8树脂固定床的吸附过程及优化吸附条件。试验基于BP神经网络建立吸附模型,通过仿真分析上样浓度、柱径比和流速对穿透时间、穿透体积的影响。模型的模拟值与试验值的相关系数为0.992,模拟值与试验值没有显著差异。最佳工艺条件为上样浓度1.5mg/mL,柱径比17:1,流速3.0mL/min。建立的模型可用于模拟儿茶素在ADS-8树脂固定床的吸附过程,结果为吸附树脂法制备儿茶素提供一定的参考。     

红霉素在大孔树脂SP825上的固定床吸附动力学研究

通过大孔吸附树脂SP825对红霉素进行动态吸附,研究了进料浓度、温度、床层高度和高径比等因素对穿透曲线的影响,采用同时考虑液膜扩散阻力、孔内扩散阻力和轴向扩散的综合速率模型对吸附过程进行模拟,计算得到相关动力学参数。结果表明,进料浓度的增加对红霉素固定床吸附过程不利,温度和床层高径比的增加可以提高固定床吸附效率,而床层高度的变化对固定床吸附过程影响不大。     

氨基酸螯合吸附树脂对苯酚的吸附行为研究

合成了一种L-酪氨酸修饰的螯合吸附树脂(AJS-02),并与超高交联树脂NDA-150作对比,研究了其对苯酚的吸附和脱附行为.静态实验结果表明,在研究的浓度范围内,吸附平衡数据符合Langmuir等温吸附方程且吸附为放热过程.溶液的初始浓度为100 mg/L、吸附温度为288 K时,苯酚在AJS-02和NDA-150上的平衡吸附量分别为76.98和91.97 mg/g,苯酚在两种树脂上的吸附是比表面积和表面官能团共同作用的结果.动力学数据表明吸附动力学符合液膜扩散方程和颗粒内扩散方程,液膜扩散为吸附速率的主要控制步骤.动态吸附-脱附实验表明,AJS-02树脂对苯酚的动态穿透吸附量和饱和吸附量分别为5.26×10-2和6.60×10-2mmol/mL,采用95%乙醇作脱附剂,脱附率可达91.5%以上.     

聚乙烯基吡啶树脂吸附乳酸的研究

在35℃下,实验测定了乳酸在聚乙烯基吡啶上的吸附等温线,测定了乳酸水溶液在以聚乙烯基吡啶为吸附剂的固定床吸附柱中的穿透曲线,研究了乳酸浓度、进口流速及柱高对穿透曲线的影响。用Freundlich模型关联了吸附等温线,用线性推动力模型描述吸附柱的动态过程并从实验穿透曲线回归得到了总传质系数,模型计算值与实验数据符合良好。     

金的离子交换与吸附化学(Ⅱ)——大孔交联聚甲基丙烯酸酯MET-802对金的吸附平衡和柱穿透

研究了盐酸溶液中AuCl_4~-在MET-802(相当于AmberliteXAD-7)树脂上的吸附平衡和柱穿透过程。测算出0.25～1.00mol/L盐酸范围内AuCl_4~-对Cl~-的选择系数,确认AuCl_4~1在柱穿透时的传质为液膜扩散主控,液膜厚度6=5.8×10~(-2)(v)~(-0.65),与AuCl_4~-的浓度及树脂粒度无关,HETP服从Snyder方程h=1.8×10~2γ_0(v)~(0.35)。     

L-酪氨酸在732阳离子交换树脂上吸附平衡与动力学研究

研究搅拌槽中732阳离子交换树脂吸附L-酪氨酸的交换平衡和动力学特性,考查了搅拌速度、温度、料液初始pH值、树脂粒径和料液初浓度对离子交换过程的影响.在研究的温度和浓度范围内,该离子交换等温线符合Henry等温式.搅拌速度为350rpm时,可以将外传质阻力忽略.料液初始pH值介于2.5～5.5 时,对交换量影响不大,而料液中Na 的存在会降低树脂的交换量.在忽略外传质阻力的条件下,采用不同粒径计算方法对动力学曲线影响很小.用间歇搅拌槽吸附动力学模型拟合出无外传质阻力条件下、不同初始浓度条件下离子交换的表面扩散系数Ds.结果表明,随着初始浓度的增大,Ds的数量级始终在10-8左右.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.