物质封闭循环的反应路径综合方法

为了达到目标废物的零排放,综合物质封闭循环的反应路径方案很有意义,这一问题往往通过多产品的联产来实现. 在相关物质所构成的简单计量系数反应方程网络的基础上,构造优化数学模型,得出了最优的物质封闭循环的反应路径.     

化工过程反应路径综合方法的研究进展

反应路径综合是过程综合的核心,对减小过程的环境影响、提高过程安全性等起到关键作用。本文介绍了已有反应路径综合方法,并着重阐述了考虑环境因素和安全因素的综合方法的研究进展,重点阐明了这些方法的实现手段以及实例应用情况,分析了它们的优点和不足。对几种具有代表性的反应路径综合方法的特色以及存在的问题进行了评价,得到反应路径综合研究的重点主要有以下3方面:基于反应路径综合的成熟方法,寻求集成本质安全的策略方法将有利于实现反应路径的本质安全;应用多目标优化方法获取反应路径综合的多目标最优解是重要的研究方向之一;着眼于全局过程系统,注重环境影响最小化的反应路径综合的实现和应用研究具有重要现实意义。     

简单计量系数反应方程

对反应路径综合问题提出了简单计量系数反应方程的概念,通过对反应原子矩阵的数学变换可以直接枚举出物理意义明确的所有简单计量系数反应方程,从中即可容易地筛选出所需的反应路径方案. 为进一步解决更为复杂的反应路径综合问题奠定了基础.     

考虑动力学的反应路径多目标优化方法

提出了一种考虑动力学影响和环境约束的反应路径综合方法. 引入平衡温距的概念来估计反应的动力学属性.可从多种备选物质之中找到生产某种指定产品的较好的反应路径和相应的原料.根据原子平衡方程综合反应路径,建立模糊规则来评价反应的平衡温距,并求解带有模糊参数的多目标机会约束规划模型,得到一系列经济、环境上均优化可行的反应路径.用合成氨联产尿素的实例对该方法进行了说明.     

集成模糊安全评价的反应路径综合

为在过程早期获取本质安全性较好的反应路径,将模糊安全评价集成于反应路径综合形成有效方法。根据反应路径综合阶段信息选择指标,通过设定指标的隶属度函数,建立模糊推理系统,且应用层次分析法（analytic hierarchy process,AHP）求得指标的权重因子,形成了模糊评价方法。为消除中间变量的影响,分别建立单、双输入变量的模糊推理系统。将它集成于反应路径综合,通过原料筛选规则,模糊安全评价,建立以安全为目标的优化模型,求解得到优良的反应路径组合。应用于萘甲胺反应路径综合实例,定量得到了反应路径及其目标函数值,并对两种模糊系统的综合结果进行了比较。     

反应路径和反应器网络同步寻优

反应过程优化主要包括反应路径综合和反应器网络综合,反应路径综合研究原料到目标产物的化学转化途径,反应器网络综合的任务在于寻求适宜的反应器类型、尺寸以及反应器单元间的连接关系,并确定各反应器的最优操作条件。传统的研究将二者孤立,文中以功能性催化剂排列为切入点,提出了同步优化反应路径和反应器网络的超级结构法。通过优化生产目标产物反应过程中多种功能性催化剂的排列,得到生产目标产物的最优反应路径,并同步优化得到装填特定功能性催化剂反应器的网络结构。用提出的方法优化设计了对二甲苯的生产工艺流程,得到装填功能性催化剂反应器的网络,与装填单催化剂的反应器相比,等反应时间下,对二甲苯产率提高22.73%,实例验证了方法的有效性。     

丁炔二醇加氢制1,4-丁二醇反应动力学研究

用质量分数为0.41%Pd/γ-Al_2O_3催化剂,在间歇高压反应条件下进行丁炔二醇加氢制1,4-丁二醇的动力学研究.用动力学实验数据,对假设的机理速度方程进行筛选和鉴别.然后,对复杂的连串平行反应过程构成的微分方程组用Runge-Kutta法进行最优估值并求得各步反应的活化能.     

基于模糊HSE评价的多目标反应路径综合方法

为在过程早期获取HSE综合性质优良的反应路径,提出了基于模糊HSE评价的多目标反应路径综合方法。全面考虑HSE因素,形成了HSE指标结构,通过设定指标的隶属度函数,建立模糊推理系统,应用层次分析法（analytic hierarchy process,AHP）确定指标的权重因子,形成了模糊HSE评价方法。基于模糊HSE评价体系,建立以安全、环境和健康为目标函数的多目标优化模型,求解得到优良的反应路径组合。应用于萘甲胺反应路径综合实例,定量得到了反应路径及其HSE目标函数值,为过程早期的路径优选提供定量数据。     

Cu/SiO2催化硝基环己烷加氢反应路径

以用于硝基环己烷还原制环己酮肟的铜基催化剂为研究对象,在釜式反应器中研究了蒸氨水热法制备的Cu/SiO2催化剂催化硝基环己烷还原制环己酮肟过程中的主、副反应历程,重点考察了反应体系中水的存在对反应路径及目标产物选择性的影响.结果表明:该反应过程中环己酮肟水解反应基本不会发生,但外源水量的增加会显著促进环己酮的生成.由此...     

二苯并噻吩在Ni-Mo-W/γ-Al2O3上加氢脱硫机理的研究

研究了二苯并噻吩(DBT)在Ni-Mo-W/γ/Al2O3上的加氢脱硫(HDS)反应产物分布、可能的反应网络以及温度对产物分布的影响,揭示了HDS反应的可能机理.研究发现,DBT在Ni-Mo-W/γ-Al2O3上的HDS反应主要通过直接氢解路径和加氢路径进行,且后者的速率是前者的两倍.考察了芳烃(萘)、硫化物(硫化氢)和氮化物(喹啉)三种物质对DBT在Ni-Mo-W/γ-Al2O3催化剂上HDS反应的影响,结果表明,芳烃对反应有较弱的抑制作用,并且对两个路径的抑制作用相当.氮化物喹啉对反应有较强的抑制作用,其主要是通过竞争吸附作用抑制加氢路径.硫化物H2S对反应也有一定的抑制作用,其抑制直接氢解脱硫路径,但对加氢路径有一定的促进作用.     

尿素合成均相反应理论的提出、实现和应用

系统论述了尿素合成过程的机理,详细讨论了尿素合成塔中的混合过程和反应过程,重点针对水溶液全循环法尿素合成工艺中存在的主要问题进行了客观评价,指出了目前普遍存在的工艺缺陷,给出了可行的解决方案。利用本文提出的"均相反应理论",有望对尿素合成的理念带来全新的认识,对于传统的工艺设计带来全新的改变,达到提高反应效率和节约能源的目的。     

On the tuning of predictive controllers: Impact of disturbances,constraints, and feedback structure

The impact of problem formulation modifications on predictive controller tuning is investigated. First, the proposed tuning method is shown to adapt to disturbance characteristic changes and thus, takes full economic advantage of the scenario. The second topic concerns point‐wise‐in‐time constraints and the impact of constraint infeasibility. Specifically, we shift the tuning question from selection of nonintuitive weighting matrix parameters to that of a few key parameters and results in a rather intuitive trade‐off between expected profit and expected constraint violations. Finally, we show that simple modifications will allow for the consideration of various feedback structures, including computational delay and partial state information. The overall conclusions of the work are that the results of the automated algorithm will help build an intuitive understating of the dynamics of the process and ultimately result in a higher level trade‐off between profit and constraint observance. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3473–3489, 2014     

Automatic data-driven stoichiometry identification and kinetic modeling framework for homogeneous organic reactions

Data-driven and knowledge-driven methods are two approaches used in studying reaction kinetics. This article proposes a hybrid-modeling framework for homogeneous synthesis reactions, which combines the advantages of high level of automation in the data-driven approach and improved accuracy in the knowledge-driven approach. A constrained enumeration method is proposed to generate possible candidate stoichiometries, and dynamic response surface methodology, target factor analysis, and mass balance are used together for identifying stoichiometries one-by-one, without the necessity of an expert-generated candidate list. Then, the previously screened stoichiometries are formed into different groups that represent candidate reaction systems, and the group (or groups) with the greatest likelihood will be identified, based on kinetic fitting and reaction dynamic criteria. This framework has been demonstrated by several examples of different reaction systems. The true reaction stoichiometries are all correctly identified, and the accurate kinetic models are obtained, showing satisfactory performance of the proposed method.     

甲烷等离子体转化合成碳二烃反应过程和过渡态理论

The direct synthesis of C2 hydrocarbons （ethylene, acetylene and ethane） from methane is one of the most important task in C1 chemistry. Higher conversion of methane and selectivity to C2 hydrocarbons can be realized through plasma reaction. In order to explore the reaction process and mechanism, the possible reaction paths （1）--（4） were proposed on coupling reaction of methane through plasma and studied theoretically using semi-PM3 method [PM3 is parameterization method of modified neglect of diatomic overlap （MNDO）] including determining the transition state, calculating the activation energy and thermodynamic state functions and analyzing the bond order and intrinsic reaction coordinate. The reaction heat results indicate that the reactions （2） and （4） are exothermic, while reactions of （1） and （3） are endothermic. The activation energy results show that activation energy for reactions （1） and （2） was much lower than that of reaction paths （3） and （4）. Therefore, paths （1） and （2） is the favorable reaction path energetically. More interestingly by comparing the intrinsic reaction coordinated （IRC） of the reaction paths （1） and （2）, it is found that the variations of bond lengths in reaction path （1） has a crucial effect on the potential energy, while in reaction path （2）, the adjustment of the system geometry also contributes to the whole potential energy of the system.     

Attainable regions for a reactor: Application of ΔH–ΔG plot

This paper describes a technique that can be used to analyze the reactions that take place in a reactor via mass balances, a graphical representation and interpretation of basic thermodynamic principles. This allows for the chemical species taking part in the reactions being considered, to create lines that define attainable boundaries in a GH plot. The end result is an attainable area that satisfies the conditions for an attainable region in a GH plot. The simultaneous methanol synthesis from syngas with the Water Gas Shift (WGS) reaction is used to illustrate this approach. Considering the investigation, one can readily see that at higher temperatures the reaction was not feasible thermodynamically at 1 bar, but at increased pressure the reaction could again become favorable and thermodynamically feasible. This paper also shows that the introduction of either water or CO₂, or both, to the feed opens up the mass balance region, resulting in WGS activity and generating more reaction path alternatives. Again, the change in Gibbs free energy across the reactor and the reaction pathways leading to product are interlinked.