EFFECTS OF SELECTED CATALYSTS ON KINETIC PARAMETERS OF THE CARBON-STEAM REACTION

A comparison has been made between the catalytic effects of two groups of elements on the steam gasification of carbon: the alkaline earths and noble transition metals of Group VIII. Spectroscopically pure graphite was selected as a model carbon because it consists of well-defined crystals with a large number of atoms located in basal planes, which, without a catalyst, are of low reactivity. Moreover, foreign atoms which can enhance or inhibit catalysis are eliminated. Local overheating is prevented by the endothermic reaction with steam.

It is not possible to distinguish unambiguously reaction-rate increases associated with a lowering of the activation energy and those caused by an increase of the reaction-site density. Thus conclusions about the mode of catalyst action are by necessity tentative. However, evidence from electron micrographs, in connection with elemental maps and theoretical calculations indicates that catalysis in the case of alkaline earths can be explained essentially by an increase of the reaction-site density. A close contact between these catalysts and the carbon surface is preserved during the reaction. In contrast, metals of Group VIII have a tendency to coalesce and to become isolated from the graphite surface. Here a lowering of the activation energy is a distinct possibility due to intercalation of these metals and weakening of the C-C bonds which are to be severed in the carbon gasification.     

用于估计动力学参数的微型反应装置

动力学参数估值的较好方法是使用微型反应器进行测定．本文讨论了多种实验用的微型反应器，它们可适用于很宽的流作状态．使用温度范围在0-1000℃以上，压力范围为0．1～10MPa或更高．     

浆态F—T法宏观反应动力学的参数估计

利用浆态床 F-T 合成反应,经长周期试验数据估算宏观反应动力学参数。用多组分数学模型,考虑了反应器内催化剂浓度间歇变化,并引入催化剂活性修正因子,采用正交排列与单纯形方法进行计算。最后用得到的动力学参数进行模拟计算,合成气转化率预报值与实测值相对误差2.5%,最大误差7.7%。可以认为采用的数学模型及动力学参数可以描述用沉淀铁催化剂,进行浆态床 F-T 合成反应的结果。     

催化裂化反应动力学参数识别与优化

以十二集总动力学模型为基础，讨论了催化裂化反应的参数识别思想，应用参数识别方法，对轻烷烃和轻燃料油催化裂化反应网络中的反应速率常数和时变失活函数进行了计算，并对模型计算值与实验值作了比较，二者吻合较为满意，在此基础上，研究了基于集总模型的优于问题用所建立的优化方法，得出了优化参数，提高了催化裂化装置的效率。     

改性双马来酰亚胺树脂固化反应动力学参数的计算

本文通过差示扫描量热(DSC)和凝胶化两种方法,分别计算了烯丙基苯基化合物改性双马来酰亚胺(BMI)树脂固化反应动力学参数。前者通过多元线性同归,可求得表观活化能(E)、频率因子(A)和反应级数(n);后者只求得表观活化能,但二者结果一致。结果还表明,随树脂中改性剂含量提高,活化能降低。     

甲缩醛合成催化剂的筛选和工艺条件

针对由甲醇、甲醛溶液合成甲缩醛反应。采用不同制备方法制备了四种不同组成的硅酸铝固体酸催化剂,在间歇操作方式下,通过改变催化剂用量、反应温度、原料甲醇和甲醛的摩尔配比以及反应原料中甲醛初浓度.考察了反应混合物中反应物和产物浓度随时间的变化关系以及反应的选择性和收率,得出了实验操作范围内适宜的催化剂组成、制备方法和反应工艺条件。     

ADVANCED CHEMICAL OXIDATION OF 2,4,6 TRICHLOROPHENOL IN AQUEOUS PHASE BY FENTON'S REAGENT-PART II: EFFECTS OF VARIOUS REACTION PARAMETERS ON THE TREATMENT REACTION

Part I of this paper examined the effects of the amounts of oxidant and catalyst on the rates and extents of oxidation of 2,4,6-Trichlorophenol (TCP), in aqueous phase, by Fenton's Reagent. In this part the effects of various reaction parameters, e.g. temperature, pH, oxidation state of catalyst (ferrous versus ferric), mode of addition of oxidant to the reactor (single batch versus multiple increments), and the presence of dissolved oxygen (D.O.) have been examined. The progress of each reaction has been monitored by the rate and extent of release of free chloride ions in the aqueous solution. All the experiments were conducted using optimum molar ratios of the oxidant (hydrogen peroxide) to the substrate (TCP), and the catalyst (ferrous ions) to the oxidant of 5.5:1 and 0.10:1 respectively, as defined in Part I.     

间苯二甲酸二缩水甘油酯固化动力学的研究

以DSC为主要测试手段,对间苯二甲酸二缩水甘油酯(DGPA)的不同固化体系进行了研究,得出了固化曲线,并根据经验公式求出了DGPA的固化动力学参数。结果表明,DGPA树脂因固化剂不同,固化动力学参数存在较大差异,其固化活性低于DER331树脂;此外,对于不同固化体系,不同升温速率下,固化剂活性对固化物玻璃化温度影响较大,固化剂活性越高,玻璃化温度越低。     

聚酯高效催化剂缩聚反应动力学研究

研究了常规的Sb2 O3 、复合催化剂和C - 94三种催化剂对于PET缩聚反应的宏观动力学。结果表明 ,在相同条件下复合催化剂和C - 94的催化活性明显高于常规的Sb2 O3 催化剂 ;C -94的表观活化能明显高于复合催化剂和常规催化剂 ,其催化PET缩聚反应过程的温度效应显著 ;在有效搅拌条件下 ,三种催化剂在高真空阶段仍有较高的催化活性 ,过程是化学反应控制的。     

影响BaTiO_3半导瓷PTC效应的动力学参数的研究

采用钛酸盐半导瓷晶界层功力学理论模型,对影响BaTiO_3PTC效应的动力学参数进行了研究,计算机模拟结果与实验结果具有相同的规律。     

过渡态模型和反应动力学介质效应的研究

研究了 C_5H_5N+CH_3I 和(CH_3CO)_2O+C_2H_5OH 两个反应的过渡态模型及其动力学溶剂效应。结果表明,体系中含有各向异性的芳环分子时,由于位置效应粒子间产生了强烈的相互作用,因此提出了新的求取过渡态分子参量的方法,并应用了不同的过渡态模型及其相应的分子参量来描述这种相互作用,更接近实际地反映了过渡态模型的性质与动力学介质效应的内在关系,以及反应物和过渡态与溶剂分子之间的相互作用。计算了上述反应在各种纯溶剂和混合溶剂中,不同温度下的速率常数。结果与实验值能较好地符合。     

改性双马来酰亚胺树脂固化反应动力学的研究

用 PE DSC-7仪器测定了 N,N,N′,N′—四烯丙基二苯甲烷二胺改性双马来酰亚胺树脂的比热容,并借助DSC-7动力学软件得到该树脂的固化反应级数n=1.39±0.10、反应活化能E_a=138±7.77kJ/mol和表观频率因子InZ=28.6±1.921/sec;还预测了树脂的固化反应程度(d),固化反应温度(T)和固化反应时间 (t)三者间相互关系,并计算了凝胶化温度(Tgel)、固化温度(Tcure)和后处理温度(Ttreat)。     

潜伏性热固性树脂体系动力学参数的研究

本文通过对二种潜伏性热固性树脂(环氧树脂)体系动力学参数的分析讨论。结果认为,理想的潜伏性热固性树脂体系的特征是具有较高的反应活化能(Ea)和频率因子(A);或者具有变活化能—既在室温下具有较高的反应活化能。     

ON APPLICATION OF THE METHOD OF KINETIC INVARIANTS TO THE DESCRIPTION OF DISSOLUTION ACCOMPANIED BY A CHEMICAL REACTION

The dissolution, accompanied by chemical reaction, of monodisperse solid particles has been analysed. The resulting model, which accounts for the variation of mass transfer coefficient with the size of the dissolving particles, yields an approximate analytical form of a kinetic function. Rigorous numerical and approximate analytical solutions have been obtained for the governing system of nonlinear ordinary differential equations. The transient nature of the dissolution process as well as the accuracy of the analytical solution is brought out by the rigorous numerical solution. The analytical solution is fairly accurate for the major part of the range of operational times encountered in practice.     

催化剂对劣质煤燃烧性能的影响

主要利用热分析法研究了催化剂NaClO4,MnO2和BaCO3对劣质煤燃烧性能的影响.结果表明,三种催化剂均可以提高劣质煤的挥发分释放量;各催化剂对煤粉的着火特性和燃尽指数都有不同程度的促进作用,其影响大小排序为:NaClO4>BaCO3>MnO2和BaCO3>MnO2>NaClO4;加入各催化剂后,煤粉的放热量均得到了提高.主要作用机理是:催化剂促进煤中挥发分的析出,降低煤的着火温度并且促进氧气与焦炭的充分接触,从而加速煤的燃烧过程.     

TPR研究焦炭溶损反应动力学参数求解方法

提出了一种由程序升温热分析（ＴＰＲ）实验结果获得焦炭溶损反应动力学参数的方法。该方法基于数学原理和计算程序，不需将热分析得到的ＴＧ线转化为ＤＴＧ线．在ＰＣ机上可方便快捷地由ＴＧ试验结果获得动力学参数．应用实例证明了该方法的实用价值．     

EFFECTS OF CARBON DEPOSITS ON THE SPECIFIC ACTIVITY OF NICKEL AND NICKEL BIMETALLIC CATALYSTS

The effects of carbon formation on methanation activity of nickel and nickel bimetallic catalysts were investigated. Carbon was deposited on these catalysts at 675-700 K, 1 atm, H₂/CO = 2 and space velocities of 80,000 to 200,000 h^-1 over a period of 6-24 hours. Specific methanation activities were measured before and after carbon depositing treatments at 500-575 K, 1 atm H₂/CO = 4 and space velocities of 100,000 h^-1. The results show that Ni/Al₂O₃ loses 20-60% of its initial activity within 10-15 hours of treatment. Platinum and cobalt promoted nickel are significantly more resistant to deactivation by carbon. However, Ni-MoO₂ is highly susceptible to deactivation, losing essentially all of its activity within a few hours. Data showing the effects of reaction conditions, metal concentration and catalyst composition on the extent of deactivation and the effects of deactivation on catalyst strength are presented and discussed     

EFFECTS OF CARBON DEPOSITS ON THE SPECIFIC ACTIVITY OF NICKEL AND NICKEL BIMETALLIC CATALYSTS

The effects of carbon formation on methanation activity of nickel and nickel bimetallic catalysts were investigated. Carbon was deposited on these catalysts at 675-700 K, 1 atm, H₂/CO = 2 and space velocities of 80,000 to 200,000 h^?1 over a period of 6-24 hours. Specific methanation activities were measured before and after carbon depositing treatments at 500-575 K, 1 atm H₂/CO = 4 and space velocities of 100,000 h^?1. The results show that Ni/Al₂O₃ loses 20-60% of its initial activity within 10-15 hours of treatment. Platinum and cobalt promoted nickel are significantly more resistant to deactivation by carbon. However, Ni-MoO₂ is highly susceptible to deactivation, losing essentially all of its activity within a few hours. Data showing the effects of reaction conditions, metal concentration and catalyst composition on the extent of deactivation and the effects of deactivation on catalyst strength are presented and discussed     

粒度对煤燃烧和热解动力学影响的量化研究

以六方石墨原子簇模拟纳米煤颗粒,采用量子化学AM1方法,研究了粒度对煤燃烧和热解动力学参数的影响规律.结果表明,粒度对煤粒燃烧和热解动力学参数有显著影响,Ea随着煤粒粒径的减小而减小,R则随粒径减小而增大,并且Ea和lnR均与粒径的倒数呈线性关系,这些影响规律与文献报道的实验结果一致.     

基于汽油烯烃转化的催化裂化动力学模型

以催化裂化反应机理为基础,把FCC原料及产品按馏程和化学组成进行集总划分.考虑氢转移、芳构化等二次反应,通过对反应网络的合理简化,提出了一种分子水平的动力学模型.通过参数估计求取18个动力学速度常数,建立集总动力学模型以预测汽油的化学结构组成.研究结果表明：该模型能较好预测不同条件下的产率分布,而且可以预测汽油组成分布,有助于降低汽油烯烃含量的研究.