扩散过程对气固反应影响的模型研究北大核心

将固体反应物视为由一系列分配特征的孔隙组成,同时考虑固体颗粒内外扩散、化学反应及产物层扩散过程,建立气固反应随机孔隙模型。微分方程组利用数值计算的方法求解,采用基于勒让德多项式的正交配置方法将扩散方程转化为代数方程,并用四阶龙格库塔方法积分得到转化率与反应时间关系。模拟了舍伍德数、体积比、毕沃模数和席勒模数发生变化时对反应转化率及反应速率的影响。结果表明,生成物固体摩尔体积大于反应物摩尔体积会导致反应物不能完全转化;增加产物层扩散阻力或颗粒内气体扩散阻力可以减弱孔隙闭合的影响,提高固体反应物的转化率,而在相同转化率条件下会使气固反应反应速率降低。     

COREX预还原竖炉反应进程的物理模拟

COREX工艺主要由预还原竖炉和熔化气化炉两部分组成,预还原竖炉作为气-固逆流式反应器,炉内铁氧化物的还原情况至关重要,关系到整个流程的生产效益.本文通过建立1∶20的半圆周冷态模型,利用硅胶吸水逐渐变色的特性进行预还原竖炉内气-固反应进程的可视化模拟实验,测定了不同气体流量下填充床内铁矿石的还原情况.结果表明炉内径向铁矿石还原率相差较大,随着气体流量增大而炉内气-固反应进程加快,反应进程在轴向、径向上很不均匀.     

扩散过程对气固反应影响的模型研究

将固体反应物视为由一系列分配特征的孔隙组成,同时考虑固体颗粒内外扩散、化学反应及产物层扩散过程,建立气固反应随机孔隙模型。微分方程组利用数值计算的方法求解,采用基于勒让德多项式的正交配置方法将扩散方程转化为代数方程,并用四阶龙格库塔方法积分得到转化率与反应时间关系。模拟了舍伍德数、体积比、毕沃模数和席勒模数发生变化时对反应转化率及反应速率的影响。结果表明,生成物固体摩尔体积大于反应物摩尔体积会导致反应物不能完全转化;增加产物层扩散阻力或颗粒内气体扩散阻力可以减弱孔隙闭合的影响,提高固体反应物的转化率,而在相同转化率条件下会使气固反应反应速率降低。     

煤气化过程中单颗粒吸收剂脱硫反应模型概述

对煤气化过程中吸收剂脱硫反应的气固反应模型进行了概述.气固反应模型大致可分为未反应缩核模型,晶粒模型、孔模型及逾渗模型等几种基本型式.未反应缩核模型结构比较简单,可以作为其它模型的基础和组成部分,晶粒模型应用较为广泛且已经得到了充分的发展和改进,孔模型侧重于颗粒内部孔隙特性对反应影响的分析,逾渗模型则基于孔模型将逾渗理论引入来描述脱硫反应过程.     

高温焦油沥青的热解反应及显微结构变化

本文用非等温热重法研究了山西焦化厂高温焦油沥青及其组分的热解反应。用Ｃｏａｔｓ和Ｒｅｄｆｅｒｎ法对结果进行了数学处理。以１４种典型的气－固反应模型为基础，用最小二乘法进行了模型筛选。考察了不同反应气氛下不同组分的热解反应规律，研究了不同组分热解过程中显微结构的变化。结果表明，正已烷不溶，苯可溶组分与原料沥青具有相似的反应规律，热解后生成的是细镶嵌的中间体。     

高温悬浮态气固反应试验台的开发与应用

开发的高温、悬浮态气固反应试验台，是目前国内较先进的气固反应动力学试验装置，它能够比较接近生产实际状况地对各种粉体物料进行悬浮态气固反应动力学研究，所得规律可用来定量地指导工业反应器的设计和操作。     

碱—白云石反应机理与预防

根据颗粒堆积原理计算了碱－白云石反应引起的固相框架体积的变化，并用图象分析技术研究了反应产物间的孔隙体积。研究了碱－白云反应 ，从热力学和通过实验分析了溶液ＰＨ值对碱－白云石反应程度与速率的影响。通过监测白云岩粉末样压实体和基本不含粘土及石英的白云灰岩在碱溶液中的膨胀行为，研究了碱－白云石反应本身的膨胀性。评估了低碱度的硫铝酸盐水泥对碱－白云反应的抑制作用。结果表明：球形产物如呈最紧密堆积，则固体     

含固体微粒悬浮液的化学吸收动力学的研究

以氢氧化钙悬浮液吸收二氧化碳气体为例,对固体粒子参与化学反应的气液固三相反应过程进行了研究,提出气液固三相反应动力学模型,为验证模型的正确性,对上述反应过程的速率进行了实验测定,实验结果与模型计算结果相吻合。     

银氧化铜复合材料的反应合成判据

进行了反应合成法制备AgCuO材料的热力学计算和数据分析．结果表明，当反应温度小于500K时，合成反应属于固一固间的置换反应；当反应温度大于500K时，合成反应属于固-气间的氧化反应．通过计算500～1200K范围内Ag2O的分解氧分压、Cu的氧分压，确定Ag-Cu合金氧化反应的最终产物为AgCuO，而不存AgCuO相．氧分压的分析为制定反应合成法制备AgCuO材料的工艺参数提供了理论依据，采用氧分压条件作为银金属氧化物反应合成的判据是完全可行的．     

TiO2表面的光催化反应的研究与进展

综述了TiO2 表面的光催化反应以及TiO2 催化剂表面液 -固界面间和气 -固界面间的光氧化反应     

Interfacial reaction between solid nickel and liquid zinc

Interfacial reactions between solid nickel and liquid zinc at 450-650 ℃ for 30-600 s were studied. The morphology and growth behavior of intermetallic compound layers at the interface between solid nickel and liquid zinc were observed and analyzed by SEM and EDS. The results show that γ and 8 phases are formed at 450 ℃ at the Ni/Zn interface, and at 550 ℃ and 650 ℃ only ）,phase is formed at the interthce and some δ phase particles will be participated during solidification on the surface of γphase layer. The β1 phase is absent under experimental conditions. Many cracks occur in the layers due to the difference in thermal expansion coefficients of these phases. It is found that the kinetics of the intermetallic compounds growth follows a parabolic law of time, as controlled by the diffusion mechanism. The apparent activation energies are 113.9 kJ/mol for the growth of γphase and 125.87 kJ/mol for γ1 phase, respectively.     

低温固相反应法合成钇铝石榴石粉体的研究

以分析纯六水合硝酸钇、四水合碱式乙酸铝为原料,柠檬酸为配合剂,通过碾磨发生低温固相化学反应制备前驱体,然后用煅烧的方式获得钇铝石榴石（YAG）产物。采用FTIR和TG／DSC对前驱体的组成及其热分解过程进行分析,采用XRD和SEM对产物Y3Al5O12粉末进行表征。结果表明,可在全固相条件下通过低温固相反应得到钇和铝原子级混合的前驱体,该前驱体煅烧到800℃即可形成纯净无中间产物的YAG晶体粉末,且随温度的升高,其逐渐转化为结晶良好、尺寸均匀的钇铝石榴石粉体。     

Acting mechanism of F, K, and Na in the solid phase sintering reaction of the Baiyunebo iron ore

The effect of F,K,and Na on the solid phase reaction of the Baiyunebo iron ore was investigated by differential thermal analysis (DTA) and X-ray diffraction(XRD).It has been identified that alkaline elements K and Na in the Baiyunebo ore instigate the formation of low melting point compounds Na_2SiO_3 and Na_2O·Fe_2O_3 and the generation of molten state in the solid phase sintering.Element F in the Baiyunebo ore facilitates the formation of cuspidine compound 3CaO·2SiO_2·CaF_2 in the solid phase reaction...     

邻菲咯啉与氯化亚铁固相配位反应 的热化学研究

以一定比例的混合溶液作为量热溶剂，利用具有恒定温度环境的反应热量计，分别测定了反应物与产物的溶解焓，并利用所设计的热化学循环，得到该固相配位反应在25 ℃ 标准状态下的反应焓变.     

Synthesis of mesoporous chromium aluminophosphate (CrAlPO) via solid state reaction at low temperature

Mesoporous chromium aluminophosphate（CrAlPO）was successfully synthesized via solid state reaction（SSR）route at low temperature in the presence of a cationic surfactant cetyltrimethyl ammonium bromide（CTAB）and inorganic sources such as AlCl₃·6H₂O,CrCl₃·6H₂O and NaH₂PO₄·2H₂O.Characterizations by means of powder X-ray diffraction（XRD）,N₂ adsorption-desorption,high resolution transmission electron microscopy（HR-TEM）,scanning electron micrography（SEM）,energy dispersion spectroscopy（EDS）,thermo-gravimetry（TG）,Fourier transform infrared spectroscopy（FT-IR）,and ultraviolet visible light spectroscopy（UV-Vis）were carried out to understand both the pore characteristics and electron transition route of these obtained materials.The experimental results show that the meso-CrAlPO materials with various Cr/Al molar ratios possess a mesostructure and a specific surface area of 193 to 310 m² /g corresponding to an average pore size of 5.5 to 2.2 nm,respectively.The maxium content of Cr in meso-CrAlPO materials synthesized via SSR route can achieve 16.7wt%,being significantly higher than that of the meso-CrAlPO prepared via a conventional sol-gel route.Meanwhile,the formation mechanism of the meso-CrAlPO was also proposed.     

新型固体碱催化剂及其催化制备生物柴油的工艺研究

研究了等体积浸渍法制备负载型N/M固体碱催化剂及催化剂催化制备生物柴油的工艺。运用扫描电镜SEM和晶体衍射仪XRD对催化剂进行表征,结合生物柴油转化率,得出催化剂制备最佳工艺为:N负载量10%,煅烧温度600℃,煅烧时间5h。采用响应曲面法中的Box-Behnken模式对影响生物柴油转化率的4个主要因素(反应温度、催化剂用量、反应时间、醇油质量比)进行优化,建立生物柴油转化率的二次多项回归模型,并对回归方程系数进行显著性检验和方差分析,结果表明模型有效可靠,且得出新型固体碱催化制备生物柴油的最佳工艺为:反应温度60℃、催化剂用量为油质量的3%、反应时间5h、醇油质量比2∶5。模型预测最高生物柴油转换率92.43%,与实测值吻合。     

SO2-4/TiO2-HZSM-5固体超强酸催化合成TMPOT

为了制备具有较高酯化率和抗乳化性能的三羟甲基丙烷油酸酯(TMPOT),采用溶胶凝胶法制备了SO^2-₄/TiO₂-HZSM-5固体超强酸催化剂,用于催化合成三羟甲基丙烷油酸酯,探讨了酸醇摩尔比、催化剂用量、反应时间、反应温度和不同种类催化剂对产物酯化率和抗乳化性能的影响.结果表明,SO^2-₄/TiO₂-HZSM-5固体超强酸催化剂的催化活性较高.当酸醇摩尔比为3.1∶1、催化剂用量为反应物总质量的2%、反应时间为8 h、反应温度为200 ℃时,三羟甲基丙烷油酸酯的酯化率高达97.6%,对产物进行抗乳化性能测试时所需的油水分离时间为5 min,且抗乳化性能较好.     

Coating of LiNi1/3Mn1/3Co1/3O2 cathode materials with alumina by solid state reaction at room temperature

Alumina coated LiNi1/3Mn1/3Co1/3O2 particles were obtained by a simple method of solid state reaction at room temperature. The reaction mechanism of solid state reaction at room temperature was investigated. The structure and morphology of the coating materials were investigated by XRD, SEM and TEM. The electrochemical performances of uncoated and Al2O3-coated LiNi1/3Co1/3Mn1/3O2 cathode materials were studied within a voltage window of 3.00-4.35 V at current density of 30 mA/g. SEM, TEM and EDS analytical results indicate that the surface of LiNi1/3Mn1/3Co1/3O2 particles is coated with very fine Al2O3 composite, which leads to the improved cycle ability though a slight decrease in the first discharge capacity is observed. It is proposed that surface treatment by solid state reaction at room temperature is a simple and effective method to improve the cycle performance of LiNi1/3Co1/3Mn1/3O2 particles.     

EFFECTS OF PARTICLE SHAPES ON THE KINETICS OF SOLID REACTIONS

In the paper,the effects of powder particleshapes on the kinetics of solid reaction (K. S. R) and errorscaused by the current methods based on spherical particlemodels have been studied. It has been found that particleshaeps have significant effects on kinetics of the solid reaction(K. S. R). However it has now not been involved in the pre-sent kinetic equations as a factor. The ball models used by thepresent kinetic equation have led to great errors not only in de-termination of the reaction constants but also in judgement ofreaction types. This is a problem that has not been much recog-nized and needs to be solved immediaitly.