聚甲醛二甲醚反应热力学分析

聚甲醛二甲醚(DMM2—8)是一种有潜在应用价值的绿色柴油添加剂,可以采用三聚甲醛和甲醇为原料合成。用基团贡献法对聚甲醛二甲醚合成反应体系中主要反应的反应焓变、反应Gibbs自由能变和反应平衡常数以及多种基础热力学数据进行了估算。结果表明:在298.15—473.15 K,反应体系中三聚甲醛分解为甲醛单体的反应为吸热反应,升高温度有利于反应的进行,而甲醛与甲醇反应生成DMM2—8的反应为放热反应,随温度升高反应逐渐向不可自发进行转变;以上两步反应耦合后,在整个温度范围内为放热反应,升高温度使反应平衡常数减小,但反应均可自发进行。     

Thermodynamic analysis of steam reforming of glycerol for hydrogen production at atmospheric pressure

Thermodynamic chemical equilibrium analysis of steam reforming of glycerol(SRG)for selective hydrogen production was performed based on the Gibbs free energy minimisation method.The ideal SRG reaction(C₃H₈O₃+3H₂O→3CO₂+7H₂)and a comprehensive set of side reactions during SRG are considered for the formation of a wide range of products.Specifically,this work focused on the analysis of formation of H₂,CO₂,CO and CH4 in the gas phase and determination of the carbon free region in SRG under the conditions at atmospheric pressure,600 K–1100 K and 1.013×10⁵–1.013×10⁶ Pa with the steam-to-glycerol feed ratios(SGFR)of 1:5–10.The reaction conditions which favoured SRG for H₂ production with minimum coke formation were identifies as:atmospheric pressure,temperatures of 900 K–1050 K and SGFR of 10:1.The influence of using the inert carrier gas(i.e.,N₂)in SRG was studied as well at atmospheric pressure.Although the presence of N₂ in the stream decreased the partial pressure of reactants,it was beneficial to improve the equilibrium yield of H₂.Under both conditions of SRG(with/without inert gas),the CH4 production is minimised,and carbon formation was thermodynamically unfavoured at steam rich conditions of SGFR>5:1.     

氢/氩热等离子体裂解煤碳-氢-氧-氩多相多组分体系的热力学分析

采用Gibbs自由能极小化法对等离子体裂解煤制乙炔碳-氢-氧-氩多相多组分体系的化学反应平衡组成进行了计算,结果表明,在C-H-Ar平衡体系中,惰性组分氩的存在降低了乙炔的最高平衡产率,氩在5000 K以下基本不电离,典型组成为C:H:Ar=1:13.39:0.6的液化石油气裂解反应体系的最佳反应温度区间为2800~3200 K. 在C-H-Ar-O多相平衡体系中,氧作为杂质同样降低了乙炔的平衡产率,体系中氧以CO的形式存在,典型组成为C:H:O:Ar=1:8.638:0.160:3.339的煤裂解反应体系的最佳反应温度区间为3000~3200 K.     

等离子体裂解煤制乙炔碳-氢体系的热力学平衡分析

碳-氢多相多组份体系的化学反应平衡组成可用Gibbs自由能极小化法求得. 计算表明：把C-H体系视为单相体系是不合理的，只有在多相体系下的计算结果才是真正意义上的热力学平衡组成，两种体系在生成乙炔的最佳温度范围和平衡组成两方面都有较大的差别. 得出C-H体系中生成乙炔的最佳温度范围是3400~3800 K的高温区域.     

费托合成反应体系的热力学计算与分析

利用Benson基团贡献法和ABWY法估算了费托合成产物的标准生成焓、标准熵和摩尔定压热容,对费托合成反应体系的热力学性质进行了详尽的计算,得到不同反应温度下的反应焓、吉布斯自由能以及反应平衡常数等热力学性质。分析了不同反应步骤的热力平衡与限度,对反应生成烷烃、烯烃、含氧有机化合物的热力学可能性与生成顺序进行了判断,考察了温度和H2与CO摩尔比对合成气平衡转化率的影响。结果表明:费托合成反应是放热反应,低温时大部分反应在热力学上都能够自发地进行,并运行到很高的程度;高温时(大于635 K)生成烷烃、烯烃、醇及酸的大部分反应在热力学上不能自发进行;随着温度的升高,平衡转化率降低,随着H2与CO摩尔比的增大,平衡转化率升高;且所获的热力学数据对费托合成工艺研究及相关催化剂研发等具有重要的参考价值。     

电子级多晶硅生产工艺的热力学分析

基于Gibbs自由能最小原理,对SiHCl3法生产电子级多晶硅闭环工艺的3个反应子系统分别进行了化学反应平衡计算,重点对SiHCl3还原反应子系统进行了热力学分析. 对于SiHCl3还原反应子系统,适宜的操作温度为1323~1473 K,压力为0.1 MPa;温度高于1323 K,H2/SiHCl3比大于6.6,低压下有利于SiHCl3还原生产多晶硅. 针对传统的SiHCl3还原需要高温下电加热给过程操作带来的诸多不便,提出了用Cl2部分氧化使SiHCl3还原反应体系实现能量耦合的新工艺,即反应过程不需外部加热就可完成,从而节约电耗,同时还发现平衡时体系中加入的Cl2能反应完全,不会影响后序工艺的进行. 对于SiCl4转化反应子系统,高压、低H2/SiCl4比有利于生成SiHCl3.     

生物质粗燃气自热重整调变的热力学分析

运用吉布斯自由能最小化方法对生物质粗燃气自热重整过程进行了热力学分析,研究了重整反应过程中的温度,O2/CH4摩尔比及焦油摩尔分数等因素对平衡产物组成的影响规律。研究结果表明:低温有利于CO歧化与加氢反应,而高温促进了CH4和CO2的转化,提高合成气H2+CO摩尔分数,降低H2/CO摩尔比。O2/CH4摩尔比的增加有利于生物质燃气从部分氧化反应向完全氧化反应转变,促进了CH4的重整反应而抑制了CO2的转化;O2/CH4摩尔比的增加降低了合成气H2+CO摩尔分数,降低了H2/CO摩尔比,在重整后的生物质粗燃气中,n(H2)/n(CO)≈1。积碳量随温度升高和O2/CH4摩尔比的增加逐渐减少,随着焦油(C10H8)物质的量的增加而增加。焦油物质的量增加提高了合成气中H2与CO摩尔分数,是重整反应的重要原料。优化的生物质燃气自热重整反应条件为温度1 023 K,O2/CH4摩尔比0.7,焦油摩尔分数<1%。     

甲醇制低碳烯烃反应体系的热力学计算与分析

采用原子矩阵法确定了甲醇制低碳烯烃独立的反应数,采用Gibbs自由能最小化方法,建立了计算烯烃产物之间平衡关系的数学模型,简化了计算过程。计算了甲醇制低碳烯烃各独立反应的Gibbs自由能及烯烃产物之间的平衡关系。热力学分析表明,甲醇制低碳烯烃反应主要为动力学控制,提高反应温度、降低反应压力和加水有利于乙烯平衡组成增加和乙烯与丙烯总平衡组成的增加,丙烯平衡组成随温度、压力变化存在最大值。计算数据与文献值比较表明,该法计算结果可靠,对甲醇制低碳烯烃的实验室研究及工业化生产有指导意义。     

化学热力学分析中短缺组分概念的应用问题

本文从吉布斯自由概念的定义出发，指出了ΔＧ、ΔＧＴ在热力学分析中的使用条件。本着准确，直观，便利的应用原则，提出了应用于化学热力学分析中的短缺组分概念，并给出了这一概念的应用实例。     

Modified equilibrium modelling of coal gasification with in situ CO2 capture using sorbent CaO: Assessment of approach temperature

Gasification process has become more attractive around the globe due to the energy crisis and environmental issues. An equilibrium model based on minimization of Gibbs energy is developed to predict the product gas composition of an air-blown coal gasifier. This paper further proposes a method for modifying the thermodynamic equilibrium model. The presented method includes the introduction of an approach temperature which corresponds to the deviation from equilibrium condition. The major components in produced gas, H₂, H₂O, CH₄, CO, CO₂, and N₂ have been determined and compared with the pure equilibrium modelling as well as the experimental data. Comparison with experimental measurements revealed that the modification of the equilibrium model has significantly reduced the error in predicting the product gas composition. In situ CO₂ capture using sorbent (CaO) is also investigated in order to enhance the hydrogen production and also to address the environmental regulations on Green House Gas (GHG) emissions. The effect of important process parameters on the product gas composition is studied and the temperature of 1200 K, pressure of 1 bar, air ratio of 0.4, and sorbent to feed ratio of 2.2 have been predicted as the optimum operating conditions for the purpose of maximum hydrogen production.     

噻吩水热裂解平衡计算及反应过程分析

采用乘子法,结合Gibbs自由能最小的概念,计算注蒸汽热采地层条件下,噻吩水热裂解反应体系的平衡组成.根据实验数据和计算结果分析反应过程,认为噻吩水热裂解过程中发生了水解、热解、加氢脱硫、加氢饱和及水煤气转换等反应.平衡计算结果表明,当水/噻吩摩尔进料比小于4时,提高进料比有利于脱硫,并生成更多气体;提高反应温度、降低反应压力有利于提高气体产量,但不利于脱硫.当水/噻吩摩尔进料比大于4时,噻吩平衡转化率达100%,温度、压力、进料比对平衡组成的影响很小.     

Simultaneous calculation of chemical and phase equilibria using convexity analysis

Chemical and phase equilibria were considered for closed multicomponent reactive systems at: (a) constant pressure and temperature; (b) constant pressure and enthalpy. Equilibrium at constant P and T was found by minimization of G, while equilibrium at constant P and H was found by maximization of S or minimization of −S, all with respect to the number of moles of each component in each phase. Both cases could be handled as optimization problems, satisfying the restrictions imposed by mole or atom balances, and non-negativity of number of moles. Convexity analyses were carried out, and the conditions were found in order to guarantee global minimum, for one liquid phase, one gas phase, and a number of solid phases. The minimum point was then found either by analytical methods or by direct minimization methods. These strategies were tested for a number of cases, with good results.     

二氧化碳和水蒸气重整制甲醇的热力学分析

二氧化碳和水蒸气重整制甲醇是有效利用二氧化碳资源的重要途径,具有重要的经济和环保意义。从热力学角度进行分析,找出合理的反应条件,以提高甲醇的选择性和收率,对指导CO2和H2O反应具有重要意义。文中基于Gibbs最小自由能原理对该体系的热力学平衡进行了相关计算,分析了温度、压力、原料配比H2O/CO2等条件对该反应体系平衡组成的影响。结果表明:改变温度对体系的平衡组成影响不大,而体系的平衡组成随着压力和原料配比H2O/CO2的增大而增大。得到优化反应条件为初始原料摩尔比n(H2O)/n(CO2)为7∶3,温度约为500 K,压力为8 MPa。这对二氧化碳水蒸气重整制甲醇反应条件的优化具有一定的指导价值。     

Comparative Study on Thermodynamic Analysis of CO2 Utilization Reactions

Thermodynamic analysis of dimethyl ether (DME) and methane synthesis from CO₂ hydrogenation, and dry reforming of methane was performed using Gibbs free energy minimization. The effects of temperature, pressure, and feed composition on conversion, selectivity, and yield were investigated for each process. High pressure, high H₂/CO₂ ratio, and low temperature favored DME production. The yield of methane during CO₂ methanation increased at lower temperature, higher pressure, and H₂/CO₂ ratio. The yield of synthesis gas improved at higher temperature. Comparison of the three processes demonstrated that the CO₂ conversion was highest during CO₂ methanation reaction if the fraction of CO₂ mol in the feed was less than 0.3. Above this value in the feed, dry reforming allowed the highest CO₂ conversion.     

碳酸二甲酯与苯酚酯交换合成碳酸二苯酯热力学分析

用分子模拟软件M aterial stud io、工艺过程模拟软件ChemCAD结合Benson基团贡献法,计算了碳酸二甲酯与苯酚酯交换合成碳酸二苯酯的反应焓变、反应熵变、吉布斯自由能变及平衡常数。结果表明,该反应为吸热反应,升高温度有利于DPC的生成。反应的热力学平衡常数很小,为了提高DPC收率,必须及时移走副产物甲醇。     

Thermodynamic analysis of carbon dioxide reforming of methane in view of solid carbon formation

A thermodynamic equilibrium analysis on the multi-reaction system for carbon dioxide reforming of methane in view of carbon formation was performed with Aspen plus based on direct minimization of Gibbs free energy method. The effects of CO₂/CH₄ ratio (0.5-3), reaction temperature (573-1473 K) and pressure (1-25 atm) on equilibrium conversions, product compositions and solid carbon were studied. Numerical analysis revealed that the optimal working conditions for syngas production in Fischer-Tropsch synthesis were at temperatures higher than 1173 K for CO₂/CH₄ ratio being 1 at which about 4 mol of syngas (H₂/CO = 1) could be produced from 2 mol of reactants with negligible amount of carbon formation. Although temperatures above 973 K had suppressed the carbon formation, the moles of water formed increased especially at higher CO₂/CH₄ ratios (being 2 and 3). The increment could be attributed to RWGS reaction attested by the enhanced number of CO moles, declined H₂ moles and gradual increment of CO₂ conversion. The simulated reactant conversions and product distribution were compared with experimental results in the literatures to study the differences between the real behavior and thermodynamic equilibrium profile of CO₂ reforming of methane. The potential of producing decent yields of ethylene, ethane, methanol and dimethyl ether seemed to depend on active and selective catalysts. Higher pressures suppressed the effect of temperature on reactant conversion, augmented carbon deposition and decreased CO and H₂ production due to methane decomposition and CO disproportionation reactions. Analysis of oxidative CO₂ reforming of methane with equal amount of CH₄ and CO₂ revealed reactant conversions and syngas yields above 90% corresponded to the optimal operating temperature and feed ratio of 1073 K and CO₂:CH₄:O₂ = 1:1:0.1, respectively. The H₂/CO ratio was maintained at unity while water formation was minimized and solid carbon eliminated.     

十二烷基甘油醚羧酸盐阴离子表面活性剂的合成及性能研究

研究了十二烷基甘油醚羧酸盐阴离子表面活性剂的合成条件。首先制备了中间产物十二烷基甘油醚,然后与氯乙酸钠反应制得终产物。考察了反应温度、反应时间、物料摩尔比、氢氧化钠用量及反应方法对反应的影响,得出反应的适宜条件为:浓度为50%的氢氧化钠碱液,n(十二烷基甘油醚)∶n(氯乙酸钠)=1∶1.2,以环己烷作带水剂,100℃下反应6 h,活性物含量达87.6%。测定了该表面活性剂的一系列性能,结果显示,该表面活性剂具有高表面活性,较低的临界胶束浓度和良好的增溶性、稳泡性。     

叔丁醇气相脱水生产异丁烯反应热力学分析

研究了叔丁醇(TBA)气相脱水生成异丁烯过程所涉及主、副反应的热力学,采用平衡常数计算法得出主、副反应在不同温度下的标准摩尔焓变、标准摩尔生成吉布斯自由能变和标准平衡常数等热力学数据。采用吉布斯自由能最小化法,从热力学角度讨论了反应温度、压力、惰性稀释和水蒸气稀释对TBA脱水反应的影响规律,可为工业化TBA脱水工艺开发提供借鉴。热力学分析结果说明了TBA脱水反应易在高温低压下进行,异丁烯平衡产率对温度和压力的变化更为敏感,TBA原料含水量对异丁烯平衡产率几乎无影响,以热力学角度而言,无需对TBA原料进行干燥处理。     

Star-Shaped Poly(furfuryl glycidyl ether)-Block-Poly(glyceryl glycerol ether) as an Efficient Agent for the Enhancement of Nifuratel Solubility and for the Formation of Injectable and Self-Healable Hydrogel Platforms for the Gynaecological Therapies

In this paper, we present novel well-defined unimolecular micelles constructed a on poly(furfuryl glycidyl ether) core and highly hydrophilic poly(glyceryl glycerol ether) shell, PFGE-b-PGGE. The copolymer was synthesized via anionic ring-opening polymerization of furfuryl glycidyl ether and (1,2-isopropylidene glyceryl) glycidyl ether, respectively. MTT assay revealed that the copolymer is non-cytotoxic against human cervical cancer endothelial (HeLa) cells. The copolymer thanks to furan moieties in its core is capable of encapsulation of nifuratel, a hydrophobic nitrofuran derivative, which is a drug applied in the gynaecology therapies that shows a broad antimicroorganism spectrum. The study shows high loading capacity of the copolymer, i.e., 146 mg of nifuratel per 1 g of copolymer. The load unimolecular micelles were characterized using DLS and TEM microscopy and compared with the reference glyceryl glycerol ether homopolymer sample. The presence of numerous 1,2-diol moieties in the shell of PFGE-b-PGG macromolecules enabled the formation of reversible cross-links with 2-acrylamidephenylboronic acid-based polyacrylamide. The obtained hydrogels were both injectable and self-healable, which was confirmed with a rheological study.     

超稳Y型分子筛的骨架硅铝比对甘油气相脱水反应的影响

以铵交换和高温水热处理法制备了不同硅铝比的超稳Y型分子筛（USY）,利用X射线衍射、扫描电镜、氮气吸附脱附和吡啶红外等技术对USY进行了表征。以USY为催化剂,考察了USY的骨架硅铝比对气相甘油脱水制丙烯醛的影响。X射线衍射和扫描电镜结果表明,铵交换和高温水热处理只是提高USY的硅铝比,相对结晶度略有降低,而对Y型分子筛的结构和形貌没有影响。氮气吸附-脱附和吡啶红外结果表明,随USY骨架SiO₂/Al₂O₃比提高,总酸量和B酸酸量逐渐降低,L酸酸量有所增多,介孔孔体积和平均孔径有所增大。气相甘油脱水反应结果表明,催化剂织构性质对甘油转化率和丙烯醛选择性的影响大于酸性的影响,因而SiO₂/Al₂O₃比为29的USY催化剂的反应性能最好,甘油转化率和丙烯醛收率分别达到了84.5%和51.8%。