HZSM-5 zeolites undergoing the high-temperature process for boosting the bimolecular reaction in n-heptane catalytic cracking

High-temperature treatment is key to the preparation of zeolite catalysts.Herein,the effects of hightemperature treatment on the property and performance of HZSM-5 zeolites were studied in this work.X-Ray diffraction,N2physisorption,27Al magic angle spinning nuclear magnetic resonance(MAS NMR),and temperature-programmed desorption of ammonia results indicated that the hightemperature treatment at 650℃ hardly affected the inherent crystal and texture of HZSM-5zeolites but facilitated the conversion of framework Al to extra-framework Al,reducing the acid site and enhancing the acid strength.Moreover,the high-temperature treatment improved the performance of HZSM-5 zeolites in n-heptane catalytic cracking,promoting the conversion and light olefins yield while inhibiting coke formation.Based on the kinetic and mechanism analysis,the improvement of HZSM-5 performance caused by high-temperature treatment has been attributed to the formation of extra-framework Al,which enhanced the acid strength,facilitated the bimolecular reaction,and promoted the entropy change to overcome a higher energy barrier in n-heptane catalytic cracking.

Comparative Study on Soot Reduction, Soot Nanostructure and Oxidation Reactivity of n-heptane/DMC and Isooctane/DMC Inverse Diffusion Flames

Dimethyl carbonate(DMC)is an environmentally oxygenated compound which can be used efficiently for soot reduction.This paper compared the soot reduction,soot nanostructure and oxidation reactivity from inverse diffusion flames(IDFs)of the hydrocarbon fuels,namely n-heptane and isooctane doped with DMC.Effects of DMC additions on soot reduction were discussed.DMC addition is more effective for the soot reduction of n-heptane/DMC IDF than isooctane/DMC IDF.The morphology and nanostructures of soot particles were investigated by Transmission Electron Microscopy(TEM)and High Resolution TEM(HRTEM),and the soot graphitization and oxidation reactivity were analyzed by X-ray Diflfraction(XRD)and Thermogravimetric Analyzer(TGA),respectively.The results of HRTEM images showed that many larger aggregates were observed for the structures of soot particles from IDFs with DMC additions.The soot particles exhibited more liquid-like material,more amorphous,higher disorganized layers,and less graphitic than that of IDFs without DMC additions.With increasing of DMC blending rate,soot particles changed younger to have shorter fringe length,higher tortuosity,and greater fringe separation.Based on the XRD and TGA results,the degree of the soot graphitization level decreased;the soot mass lost significantly faster,and the soot become more reactive.

Experiment and modeling of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites

Since paraffins catalytic cracking was of significant importance to light olefins and aromatics production,this work was intended to gain insights into the feature and model of coke formation and catalyst deactivation in n-heptane catalytic cracking over HZSM-5 zeolites. 18 tests of n-heptane catalytic cracking were designed and carried out over HZSM-5 zeolites in a wide range of operating conditions. A particular attention was paid to the measurement of the conversion, product distribution, coke content, and the porosity and acidity of the fresh and spent HZSM-5 zeolites. It was found that alkene and aromatic promoted coke formation, and it reduced the pore volume and acid site of HZSM-5 zeolites, tailoring its performance in n-heptane catalytic cracking. The specific relationship between HZSM-5 zeolites, n-heptane conversion, product distribution and coke formation was quantitively characterized by the exponential and linear function. Based on the reaction network, the coupled scheme of coke formation and catalyst deactivation were specified for n-heptane catalytic cracking. The dual-model was proposed for the process simulation of n-heptane catalytic cracking over HZSM-5 zeolites. It predicted not only the conversion and product distribution but also coke content with the acceptable errors.

Effect of particle size of single-crystalline hierarchical ZSM-5 on its surface mass transfer in n-heptane catalytic cracking

Single-crystalline hierarchical ZSM-5 zeolites with different particle sizes(namely 100,140,and 200 nm)were successfully prepared by adjusting the amount of tetrapropylammonium hydroxide(TPAOH),and investigated in n-heptane catalytic cracking reaction.Diffusional measurements by zero-length column(ZLC)method showed that the apparent diffusivities of n-heptane decreased with the reduction of particle size,indicating the existence of surface barriers.Moreover,with the decrease of particle size,the additional diffusion path length increased,which meant the influence of surface barriers became more apparent.Despite the change of surface barriers,the intracrystalline diffusion still dominated the overall diffusion.Catalytic performance showed that the zeolite with smaller particle size had better stability.

DMC模型视域下学前教育APP游戏设计策略研究——以宝宝巴士世界APP为例

目的:随着计算机技术和智能移动设备的发展,开发商们纷纷通过游戏的方式介入儿童教育。但蓬勃发展的国内学前教育APP也暴露出一系列问题,根本原因是游戏化学习的设计实践欠缺理论指导,使得设计者在游戏中难以平衡教育性和娱乐性。文章探讨DMC模型视域下学前教育APP游戏设计策略,旨在为“游戏化+学前教育”的实践提供参考,推动教育领域持续创新与发展。方法:基于游戏化学习理论,以凯文·韦巴赫的DMC模型为分析框架,针对经典学前教育APP,深入分析其游戏化元素的结构和应用效果,从组建层、机制层和动力层三个层面构建游戏设计策略。结果:学前教育APP的游戏化设计须考虑多方面因素:内容型组件应少用文本,统一视觉风格并控制信息承载量;交互型组件须考虑儿童发育特征,设计适宜的交互手势和图标尺寸;机制层的反馈元素应及时、易懂且具有激励性;动力层则以情感元素为主,以帮助孩子成长为目的,并结合家长控制功能,约束孩子的行为,确保游戏环境的安全性和教育效果。结论:未来的研究可进一步探讨教育游戏的内在逻辑,并结合不同教育内容和用户群体应用DMC模型,以优化游戏化学习的实践和提高其设计的适用性。

碳酸二甲酯(DMC)生产过程风险分析及防范措施

聚碳酸酯和锂电池是我国产业结构和能源结构调整的重点发展产品。碳酸二甲酯(DMC)项目是开拓焦炉煤气应用的新领域,本文实验模拟了DMC生产过程,重点分析了DMC生产过程中的安全风险,并提出了防范措施。

DMC控制算法在单元机组协调控制系统中的应用

近年来,随着生活水平的不断提高,人们对电力的需求也日益增大,发电厂需要不断提高生产效率和技术水平来确保能够提供足够的电力供应。同时,单元机组的容量也不断扩大,而单元机组协调控制系统作为电厂控制的核心部位,具有非线性和时延性,传统的PID(Proportional-Integral-Derivative Control,比例积分微分控制)控制难以获得满意的控制效果。预测控制对模型的要求较低,并且采用滚动优化和反馈校正,具有较强的鲁棒性。因此,对动态矩阵控制算法(Dynamic Matrix Control,DMC)进行了深入研究,并且将动态矩阵控制算法(DMC)应用于协调控制系统中,结果表明,采用DMC控制算法对单元机组协调控制系统进行控制能获得较好的效果,提升了系统的响应速度,减小了系统响应时的超调量,是一种可行的控制方法。

发电厂封闭母线内DMC绝缘子的应用

现代大型发电厂所采用的封闭母线设计,虽然有效地防止了大型异物入侵的风险,然而其仍然面临着灰尘和潮气的侵扰。这些微小的环境因素能够逐渐侵蚀母线的绝缘层,导致其绝缘性能下降,进而威胁到整个电力系统的安全与稳定。因此,在保障大型发电厂封闭母线安全运行的过程中,必须充分考虑并应对灰尘和潮气等环境因素带来的潜在风险。

利用n-heptane详细模型对水乳化柴油燃烧的化学动力学研究

以4100QBZL-2型直喷柴油机为模拟对象,采用化学动力学计算软件CHEMKIN与LLNL的n-heptane详细氧化模型为基础,对柴油机燃用纯柴油,10%、20%、30%的水乳化柴油进行化学动力学模拟。数值模拟结果表明:水乳化柴油带来的滞燃期延长、着火滞后等现象,是乳化燃料中的水分在缸内的物理现象引起的。从纯化学动力学方面来看,掺入一定的水分可以促进H、O、OH、HO2等自由基在低温燃烧(LTC)阶段的生成,使得着火提前。通过敏感性分析可知,掺入的水分会对n-heptane氧LTC时期过氧烷基的异构化过程及过氧化氢酮的分解都会产生促进作用,从而导致n-heptane的快速分解及氧化。

基于DMC法的α-氨基酸-N-环内酸酐的绿色合成

针对传统方法合成α-氨基酸-N-环内酸酐(NCAs)毒性大、对环境不友好的问题,以氨基酸为原料,以乙酸锌为催化剂,以碳酸二甲酯(DMC)为环化剂,通过“一锅法”高效环保地合成了L-苯丙氨酸-N-羧基环内酸酐(Phe-NCA)、L-天冬氨酸-4-苄酯-羧基环内酸酐(H-Asp-Obzl-NCA)和Nε-苄氧羰基-L-赖氨酸环内酸酐(Cbz-Lys-NCA)等3种新型NCAs。通过GC-MS、NMR、FT-IR等对其进行定性表征;讨论了反应温度、反应物比例等因素对氨基酸转化率与NCAs产率的影响;并通过对比催化剂乙酸锌在反应前后的XPS和XRD等表征,分析乙酸锌的催化机理。结果表明:反应中氨基酸∶去质子碱∶催化剂的摩尔比为1:1.5:0.2,反应分别在160、120、140℃进行8 h后,去质子氨基酸与DMC在乙酸锌的作用下发生甲氧羰基化反应,进一步关环,Phe-NCA、H-Asp-Obzl-NCA和Cbz-Lys-NCA最佳产率可分别达到55.22%、56.30%和46.46%;乙酸锌的催化机理为Zn^(2+)与DMC中的羰基氧进行配位络合后实现氨基酸靶向甲氧羰基化,促进邻近COO-与羰基碳发生亲核取代,从而实现精准关环,得到NCAs。

污水处理溶解氧浓度DMC控制仿真研究

针对A2/O生物脱氮除磷工艺在传统PID算法下溶解氧浓度不能取得理想控制效果的问题,在建立溶解氧浓度动态近似模型的基础上,引入动态矩阵控制(DMC)算法并建立Simulink仿真模型。结果表明:DMC算法能够实现溶解氧浓度设定值的快速、无误差、小超调量跟踪,控制性能优异;此外,增大预测步程和控制步程有利于提升动态响应特性但会降低稳定性,而增大控制权矩阵系数可提升稳定性但会放缓动态响应。该结论对于DMC溶解氧浓度控制实际应用具有一定参考价值。

A Promising MoO_x-based Catalyst for n-Heptane Isomerization

The SiO2 and g-Al2O3 supported MoOx catalyst and a MoOx-SiO2 catalyst have been studied in a conventional fixed-bed flow reactor for n-alkanes isomerization. It is shown that the MoOx-SiO2 catalyst with SiO2 framework, in which the bulk MoOx phase is large enough to form typical mesoporous structure, is promising in terms of its advantages of both improved mechanical strength and high catalytic properties over the supported MoOx and bulk MoOx catalyst.

Effect of iridium loading on HZSM-5 for isomerization of n-heptane

The effect of iridium loading on the properties and catalytic isomerization of n-heptane over Ir-HZSM-5 is studied. Ir-HZSM-5 was prepared by impregnation method and subjected to isomerization process in the presence of flowing hydrogen gas. XRD and BET studies show that the presence of iridium stabilizes the crystalline structure of HZSM-5, leading to more ordered framework structure and larger surface area. TGA and FTIR results substantiate that iridium species interacts with OH group on the surface of HZSM-5. Pyridine FT-IR study verifies the interaction between iridium and surface OH group slightly increased the Bro¨nsted and Lewis acid sites without changing the lattice structure of HZSM-5. The presence of iridium and the increase of strong Lewis acid sites on HZSM-5 were found to bring an increase about 4.1%, 33.2% and 11.8% in conversion, selectivity and yield of n-heptane isomerization, respectively.

An asymmetric membrane of polyimide 6FDA-BDAF and its pervaporation desulfurization for n-heptane/thiophene mixtures

Polyimide（PI） is a type of important membrane material. A soluble polymer was synthesized from 4,4′-（hexafluoroisopropylidene） diphthalic anhydride（6FDA） and 2,2-bis[4-（4-aminophenoxy） phenyl] hexafluoropropane（BDAF） by the two-step polymerization method. The polymer was proved to be polyimide 6FDA-BDAF by the Fourier transform infrared（FT-IR）, the 1H-NMR and ^（19）F-NMR spectra. An asymmetric membrane was prepared with the synthesized polyimide 6FDA-BDAF, it was porous in the 50 μm height bulk and dense in a 3–5 μm height surface. The membrane was used to separate n-heptane/thiophene mixtures by pervaporation with sulfur（S） contents from 50 to 900 μg g^（–1）. The total flux was enlarged from 7.96 to 37.61 kg m^（–2） h^（–1） with temperature increasing from 50 to 90°C. The membrane＇s enrichments factor for thiophene were about 3.13 and dependent on the experimental conditions. The experimental results demonstrated that polyimide 6FDA-BDAF would be a potential membrane material for desulfurization and controlled release of the S-containing fertilizer.

CFBB燃烧系统耦合分析与DMC控制器设计

循环流化床锅炉(CFBB)燃烧系统耦合关系复杂且难以控制,该文将CFBB燃烧过程简化为一个二入二出对象,并针对其中最难控制工况下的标称参数模型进行控制。采用逆奈氏阵列法(INA方法)对CFBB系统的耦合性进行分析,得出利用单位矩阵静态解耦法对系统进行初步解耦的结论。考虑最小化CFBB系统的ITSE指标,提出一种基于遗传算法的CFBB系统DMC控制器参数寻优方法。仿真表明,提出的DMC参数寻优方法能快速响应主汽压和床层温度的变化,具有不错的鲁棒性和跟踪性能。

基于DMC算法的双容水箱液位控制系统研究与仿真

针对双容水箱液位控制系统,通过机理分析法建立了水箱的传递函数和增量状态方程数学模型,将增量状态方程用差分方法进行离散化不必进行线性处理,可避免系统误差,方程时序递推求解的过程可模拟双容水箱液位控制系统的实时仿真。用动态矩阵控制算法控制双容水箱的增量状态方程使液位达到设定值,并用Matlab脚本程序实现控制过程。仿真结果表明,DMC控制双容水箱系统取得较为理想的控制效果,满足控制需求,该实验仿真对研究与应用双容水箱、预测控制算法具有重要的参考价值。

SOLUBILITIES OF CARBON DIOXIDE IN MIXTURES OF n-DECANE-n-HEXADECANE AND n-HEPTANE-TOLUENE

Solubilities of CO2 in binary mixtures of n-decane-n-hexadecane and n-heptane-toluenewere measured in a glass apparatus by a synthetic method.Henry’s constants at several temperaturesand solvent compositions were reported.While the Henry’s constants of CO2 in mixtures of decaneand hexadecane can be satisfactorily predicted by a simple linear interpolation,prediction of Henry’sconstants for CO2 in mixtures of heptane and toluene requires excess Gibbs energy of the solvent mix-tures.The standard thermodynamic functions of solution（ΔH0,ΔG0,and ΔS0）were reported.

n-Heptane Isomerization over the Shaped Catalyst Pt/WO_(3)- ZrO_(2) and the Role of the Pseudo-Boehmite Binder

The present paper reports new results regarding the addition of pseudo-boehmite as a binder during the synthesis of shaped Pt/WO_(3)-ZrO_(2)-Al_(2)O_(3) (PtWZA) catalysts. Binder shaping can noticeably influence not only the structure and acidity of catalyst and improve its catalytic performance with regard to n-heptane isomerization, but the mechanical strength of the catalyst. A suitable binder content can improve the isomerization activity or selectivity by changing the acidity of PtWZA. The influence of the binder content depends on the WO_(3) content of the catalyst. PtWZA catalysts that contain 5%-15% binder on a dry basis exhibit favorable isomerization performance that depends on WO_(3) content. Suitable catalysts include Pt20WZ5A and Pt30WZ15A, which provide conversions of approximately 80%-90% and a selectivity of 90%. These new findings enrich researcher knowledge of the effect of the binder on the catalyst shaping process and are useful in the production of industrial catalysts.

A Novel MIL-101(Cr)Acidified by Silicotungstic Acid and Its Catalytic Performance for Isomerization of n-Heptane

The 0.4%Pt/xSTA-MIL-101(Cr)metal-acid bifunctional catalysts were prepared by impregnation using STA-MIL-101(Cr)as the support.The synthesized samples were verified to exhibit a typical octahedral structure of MIL-101(Cr)and the pore structure was arranged orderly.The specific surface area of the samples was extremely high and the samples were made of micro-mesoporous composite materials.Silicotungstic acid could retain its Keggin structure in the 0.4%Pt/xSTA-MIL-101(Cr)samples and the catalyst possessed moderately strong Brønsted acid sites.Besides,the dispersion of Pt particles in MIL-101(Cr)was relatively high.n-Heptane isomerization was first used as a probe to test the novel 0.4%Pt/xSTA-MIL-10(Cr)catalyst.Compared with the conventional silicate catalysts,the catalytic performance of 0.4%Pt/30%STA-MIL-101(Cr)was significantly improved with a n-heptane conversion of 58.93%and an iso-heptane selectivity of 95.68%,respectively,under conditions covering a reaction time of 2 h and a reaction temperature of 260°C.The catalyst could still maintain a relatively high catalytic performance after a reaction time of 5 h.Compared with the non-noble metal catalyst,the catalytic efficiency of 0.4%Pt/30%STA-MIL-101(Cr)is relatively high.The mechanism model of n-heptane isomerization over 0.4%Pt/xSTA-MIL-101(Cr)catalyst was established.

Numerical study of n-heptane/benzene separation by thermal diffusion column

In this article,numerical simulations are performed to investigate the performance of the thermal diffusion column for the separation of n-heptane/benzene mixture.The present work tried to optimize column by analyzing significant parameters such as feed flow rate,temperature and cut.In order to obtain the hydrodynamic and temperature and mass distribution inside thermal diffusion column,computational fluid dynamic(CFD) method is applied to solve the Navier-Stocks equations.Numerical simulations are conducted to study the main parameters in both stationary and time-dependent conditions.By using the separation work unit as a function of cut,the optimal cut for maximum SWU occurs within a limited range of 0.47-0.5 for feed rate between 0.5 and 4 g min^-1.Our findings reveal that the optimum feed rate in the range of optimum cut is about 1 g min^-1.In transient study,results show that the best cut for reaching to steady-state condition is θ=0.5.