Rates and equilibria of ester hydrolysis: Combination of slow and rapid reactions

The kinetics and thermodynamics of ester hydrolysis were studied experimentally in a laboratory-scale batch reactor by using ethyl formate as the model molecule. The effects of the reaction conditions, such as temperature, excess water, complexing agent and initial acid charge upon the ester hydrolysis process were investigated and a kinetic model was developed for the system. Autocatalytic kinetics was observed experimentally, which was due to the carboxylic acid formed during the reaction. The reaction rate was further enhanced and the equilibrium was shifted to the product side by adding a complexing agent into the reaction mixture. A mathematical model comprising the mass balances and rate equations were developed for the system by assuming quasi-equilibrium hypothesis for the reaction involving the complexing agent. A robust calculation scheme was developed for the estimation of the kinetic and thermodynamic parameters from experimental data. The proposed model was able to predict the experimental results satisfactorily.     

Cyclic poly(dimethylsiloxane) from kinetically controlled cyclodepolymerization of linear precursors in dilute solution

Cyclic poly(dimethylsiloxane) (PDMS), [(CH₃)₂SiO]_x or D_x, was prepared in high yield (>70% for x > 12) from commercially available linear α,ω-dihydroxy-PDMS by base-catalyzed unimolecular ring closure in dilute solution. Cyclization, which occurs with formation of charged linear byproducts, was confirmed by GPC, FTIR, MALDI-ToF and NMR spectroscopy. Product mixtures were analyzed with a newly developed dual-detector GPC method in which the linear byproducts were end-labeled with a UV-absorbing group and separately detectable with a UV detector. Alternatively, charged linear byproducts were removed with anion-exchange resin. Yields and molecular weight distributions of the cyclic products are consistent with Monte Carlo simulations of kinetically controlled cyclodepolymerization. Large cycles from this cyclodepolymerization route are obtained in much higher yields (>70% for x > 12) than those reported for the traditional base-catalyzed ring-chain equilibration of D₄ and D₅ (∼13% for x > 6) [1].     

聚酯缩聚催化剂用量的控制

缩聚催化剂会对聚酯后加工性能产生不良影响。选择溶解性能好的催化剂 ,降低酯化残存羧基量 ,提高缩聚温度 ,可减少催化剂用量     

聚酯生产中催化剂配制的改进

通过进行催化剂浓度的配比试验,并应用到实际生产,简化了生产中催化剂的配制作业,方便了操作,保证了高负荷下催化剂的供给。     

聚酯催化剂的研究进展

详细叙述了锑系、钛系、锗系、锡系、铝系和酶催化剂在聚酯反应中的应用情况,介绍了这些催化剂的分类和它们的优、缺点,指出高效环保型催化剂是聚酯催化剂发展的方向。     

聚酯催化剂研究的进展

介绍了聚酯催化剂的发展概况及新型催化剂的发展目标 ;分别对锑系催化剂、锗系催化剂和钛系催化剂目前的研制和应用情况进行了详细的论述     

西酞普兰对映体的手性色谱拆分及吸附平衡

以添加醇类和二乙胺的正己烷为流动相,考察了多糖类、酒石酸类和环糊精类手性固定相对西酞普兰外消旋体的拆分效果,优选合适的手性固定相、流动相和温度等色谱条件,在此基础上利用前沿色谱法测定了西酞普兰对映体的吸附等温线。优化的色谱操作条件为：Chiralpak AD-H柱为固定相,正己烷∶异丙醇∶二乙胺（95∶5∶0.1,体积比）为流动相,柱温35℃。西酞普兰对映体的吸附等温线为优惠型,采用Langmuir方程拟合,效果较好。本研究为模拟移动床（SMB）制备西酞普兰对映体提供重要的基础数据。     

钛系催化剂在聚酯行业应用现状及发展

分析了钛系催化剂的研制及应用现状,目前普遍使用的锑系催化剂已经不能满足行业发展需求,而新型钛系催化剂TY-2具有成本低、生产能耗低的优势,已经成功进行了工业化应用,产品品质指标合格。采用钛系催化剂取代锑系催化剂是今后聚酯行业发展的主要趋势。     

Phase equilibria in the Na2O-WO3 system

The Na₂O-WO₃ binary system is an important chemical system with various applications, such as catalysts, energy and corrosion resistant materials. In this study, phase equilibria and liquidus temperatures in the Na₂O-WO₃ binary system have been experimentally determined in air. The system was investigated at the temperature range from 550 to 830 °C using a high-temperature equilibration and quenching technique. The microstructure and compositions of the phases obtained in the quenched samples were then analyzed by an electron probe micro-analyzer (EPMA). Binary compounds Na₂W₂O₇, Na₂W₄O₁₃ and Na₂W₆O₁₉ have been identified and the liquidus temperature temperatures in these primary phase fields were determined. Two peritectic points in the system were confirmed and compared with previous data. The present study provided useful thermodynamic data including liquidus and solid solutions. Accurate phase equilibria data will be used as the base for the development of thermodynamic modelling.     

TY-2型钛系催化剂在聚酯生产中的应用和优化

介绍环保型钛系催化剂在5釜聚酯生产中的应用情况,在应用过程中出现产品b值升高等异常情况,通过调优化整反应参数,保证了聚酯产品品质优等。钛系催化剂按比例取代锑系催化剂生产聚酯的应用,结果表明:钛系催化剂能够不同程度地降低酯化和缩聚反应温度,进而降低生产能耗,同时有助于绿色环保产品的开发。     

高效催化剂在聚酯合成中的应用研究

选择乙二醇锑以及至少一种锰、锌、钴、铅等金属醋酸盐共同组成高效聚酯催化剂体系 ,研究其对缩聚反应的催化作用。实验证明 ,高效催化剂可明显加快缩聚反应速度 ,制得质量合格的PET切片。通过添加碱金属醋酸盐即可改善PET切片色泽 ,碱金属醋酸盐离子浓度 4.5～ 9μg/g较为合适 ,不需添加光学增白剂     

二氯甲烷-甲醇-丙酮-水体系汽液平衡测定和关联

二氯甲烷-甲醇-丙酮-水四元体系常见于化工、医药等行业生产的废液中,该体系分离回收的前提是进行汽液平衡数据的测定。现利用单级循环汽液平衡釜测定了二氯甲烷、甲醇、丙酮、水混合液中的6组二元体系在常压下的汽液平衡数据,同时对其进行了点对点法热力学一致性校验。实验中采用SP-6800型气相色谱仪分析汽液相组成,并运用Matlab中的非线性最小二乘法分别关联6组二元体系的汽液相组成,从而得到6对Wilson模型参数,并计算出相应的汽相组成。此外,还测定了二氯甲烷-甲醇-丙酮-水四元体系在100 kPa下的汽液平衡数据,并用关联出的6对模型参数计算该四元体系的汽液平衡数据。将计算结果与实验结果进行对比,实验值与计算值间的绝对偏差均小于0.05。实验结果表明Wilson模型的拟合精度高,适合于关联二氯甲烷、甲醇、丙酮、水体系。实验和计算结果为萃取精馏分离二氯甲烷、甲醇、丙酮、水混合液提供了一定的基础数据。     

钛锑复合催化剂聚酯切片的结晶性及可纺性

通过差示扫描量热分析和X射线衍射分析等研究了钛锑复合催化剂生产的聚对苯二甲酸乙二醇酯(PET)切片的结晶性能及其可纺性。结果表明:与常规锑系催化剂生产的PET切片相比,钛锑复合催化剂生产的PET切片的结晶速度慢,结晶度低,熔体降温结晶温度有所下降,冷结晶温度有所上升,可纺性好;钛锑催化剂的PET纤维的力学性能优于常规锑系催化剂的PET纤维。     

On the performance of HIAST and IAST in the prediction of multicomponent adsorption equilibria

The performance of the heterogenous ideal absorbed solution theory (HIAST) using a uniform energy distribution and the global ideal adsorbed solution theory (IAST) is studied on their predictability f multicomponent adsorption equilibria along with experimental data of gases on two activated carbons. Results show that HIAST may not always provide better predictability than IAST if the energy distribution parameters are not properly chosen, although it is reported in the literature that in most cases HIAST is superior to IAST.     

聚酯多元醇合成中催化剂的应用研究

以苯酐、己二酸和甲基丙二醇为原料合成了聚酯多元醇,在基本相同的反应条件下,分别采用乙二醇锑Sb2(EG)3、三氧化二锑(Sb2O3)、醋酸锌Zn(Ac)2、钛酸四丁酯(TBT)和钛酸四异丙酯(TPT)等催化剂进行聚酯多元醇的合成反应。研究结果表明,在本反应体系中TPT是最佳催化剂;随着聚酯多元醇理论相对分子质量的增大,反应越难以进行,因此催化剂用量应相应增加,但其质量分数以不超过0.04%为宜。     

聚酯高效催化剂的应用研究

选择乙二醇锑以及至少一种锰、锌、钙、钴、铅等金属醋酸盐共同组成高效催化剂,在1万t/a连续聚酯装置上研究它们对缩聚反应的催化作用。高效催化剂可明显加快缩聚反应速度,制备切片的质量指标达到国标优级品。可通过减少高效催化剂用量、增加碱金属醋酸盐添加量和提高生产负荷的方法降低切片二甘醇含量和端羧基值。技术经济分析表明高效催化剂有很好的应用前景。     

新型钛系聚酯催化剂的应用研究

研究了采用自制钛系聚酯催化剂,考察各聚合工艺及合成产品性能。结果表明:制备的钛系催化剂活性高、性能稳定、催化剂用量小。钛系催化剂合成的聚酯切片各项性能指标良好,成功通过工业化纺丝试验,提高了成品丝品质,钛系催化剂具有良好的工业应用前景。     

丙酮-水-丙酮连氮体系汽液平衡测定与关联

采用汽液双循环平衡釜,在常压（101.3 kPa）下测定了丙酮-丙酮连氮二元组分物系以及部分丙酮-水-丙酮连氮三元组分物系的汽液平衡数据。实验数据经Herington面积积分法检验符合热力学一致性。通过化工过程模拟软件,分别采用Wilson、NRTL、UNIQUAC 活度系数模型对丙酮-丙酮连氮二元组分物系实验数据进行关联得到模型参数。并对汽液平衡的计算值与实验值进行比较,3种模型都吻合良好,其中由NRTL方程关联得到的计算结果最为适合,平均温度偏差和汽相组成偏差分别为0.0639 K和0.0048。从三元汽液相平衡数据中拟合出了丙酮-丙酮连氮、丙酮-水、水-丙酮连氮之间的NRTL方程相互作用参数。为验证数据及其二元相互作用参数的可靠性,利用关联出的丙酮-丙酮连氮模型参数计算出汽相组成与丙酮-丙酮连氮的二元数据比较,二者符合较好。实验和关联的结果为精馏分离丙酮-水-丙酮连氮汽液平衡体系提供了一定的基础数据。     

锑系催化剂在聚酯缩聚工艺中的应用评价

本文以工业使用的实际经验 ,从反应活性和产品质量两个方面来评价锑系催化剂在聚酯缩聚工艺中的应用。同时 ,也对锑系催化剂的变换工业实验结果进行初步讨论     

Prediction of Enthalpy of Fusion of Non‐aromatic Energetic Compounds Containing Nitramine,Nitrate and Nitro Functional Groups

A new and reliable approach is introduced to predict enthalpy of fusion of non‐aromatic energetic compounds, which contain nitramine, nitrate and nitro functional groups. It is useful in diminishing hazardous synthesis and testing of energetic compounds. Simple relationship for predicting enthalpy of fusion can be expressed as a combination of the number of oxygen atoms and three structural parameters. Some experimental data of non‐aromatic energetic compounds were used to obtain the new correlation. The presented method has been tested with different non‐aromatic energetic compounds with complex molecular structures. The model can offer reliable predictions of enthalpy of fusion for non‐aromatic energetic compounds in comparison to the best available predictive methods. The enthalpy of fusion for some new non‐aromatic explosives such as CL‐20 and TNAZ was predicted.