T302锌锰系脱硫剂脱除H_2S在的宏观动力学

用热重法研究了T302锌锰系脱硫剂脱除H_2S的宏观动力学行为.实验表明,该过程对H_2S为一级反应.在200～400℃的温度范围,反应初期为表面反应控制,中后期转移为颗粒扩散控制.宏观动力学行为可用等效粒子模型来描述.表面反应及固体扩散活化能分别为11.842、20.865kJ/mol.对反应存在最佳温度及固体扩散活化能大于表面反应活化能进行了讨论.     

T305型脱硫剂脱除H_2S的颗粒的宏观动力学研究——(Ⅰ)脱硫动力学特征

采用热重法研究了工业用大颗粒 T305脱硫剂在温度为200～400℃,H_2S 浓度为5～20g/Nm~3条件下脱除 H_2S 的颗粒的宏观动力学。通过扫描电子显微拍照(SEM)、电子探针分析和热重数据证明,脱硫过程主要受颗粒产物层扩散控制,指出脱硫过程存在最佳温度 T_(opt),分析了 T_(opt)存在的原因。     

活性炭脱除煤气中H_2S的气氛影响及动力学研究

用活性炭对模拟煤气中的H2S进行催化氧化脱除,考察了反应温度、氧硫比以及煤气气氛组成对活性炭催化氧化脱除H2S行为的影响.结果表明,最佳催化脱硫温度约为180℃,氧硫比为1∶2.煤气气氛中,CO,CO2和H2含量的增加降低了活性炭的硫容,而水蒸气含量的提高则有利于脱硫反应的进行,提高了反应的脱硫效率和活性炭的硫容.对其动力学行为进行研究,结果表明,脱硫反应过程属于表面反应控制过程,给出了脱硫反应动力学方程及动力学参数.     

固体超强酸S_2O_8~(2-)/TiO_2-Al_2O_3催化合成乙酸戊酯的动力学研究

研究了以固体超强酸S2O82-/TiO2-A l2O3为催化剂合成乙酸戊酯的反应,在反应温度分别为100,108,116℃下,测出合成乙酸戊酯的动力学方程参数,建立了动力学方程式,并与无催化剂酯化反应的活化能及动力学方程式进行了比较。结果表明,最佳合成条件为:醇酸摩尔比1.3∶1,催化剂用量1 g,带水剂用量10 mL。固体超强酸S2O82-/TiO2-A l2O3使反应活化能明显降低,是合成乙酸戊酯的有效催化剂。     

铁基载氧体的沼气化学链燃烧反应动力学研究

化学链技术能够实现碳基燃料燃烧所释放的CO₂的全捕获，可为我国早日实现“双碳”目标提供一种全新的视角。首先理论推导得到铁基载氧体CH₄还原反应的改进动力学模型；对Fe₂O₃与CH₄之间的反应系统进行了热力学计算，为后续反应操作温度的选择提供理论指导；在固定床反应器中通过改变混合气流速，研究外扩散对反应过程的影响，当气体流速达到180 mL·min^-1以后，表观反应速率不再增加，表明外扩散影响消除；在消除外扩散及灰尘扩散影响的前提下进行表面反应动力学测定，回归获得反应活化能E=147.574 kJ·mol^-1和指前因子k₀=6.399 5×10⁷s^-1，并建立了表面反应动力学方程式；在温度为680℃时，延长反应时间至1 h，反应不再进行，据此确定对应于该温度下的反应的固体产物，该固体产物以Fe₂O₃·n FeO形式虚拟表示，进而...     

在Mo-Bi-Ce/SiO_2催化剂上丁烯-2氧化脱氢的内扩散影响

用玻璃流动外循环无梯度反应器研究了Mo—Bi—Ce/SiO_2催化剂上丁烯-2氧化脱氢的内扩散影响.确定了催化剂的有效因子,多孔催化剂的有效因子随反应温度的升高而减小.在内扩散区域的反应活化能为丁烯-2扩散活化能、动力学区域反应活化能的算术平均值.在内扩散区域的丁烯氧化脱氢生成丁二烯的选择性用经验式描述.     

高炉铝酸钙炉渣浸出过程动力学

研究了高炉铝酸钙炉渣的浸出动力学,考察了搅拌强度、浸出反应温度、浸出剂初始浓度及炉渣粒度对浸出速率的影响. 结果表明,浸出过程符合一级反应的收缩未反应核模型,宏观动力学方程为1+2(1-xB)-3(1-xB)2/3= 1.108exp(-1906/T)t,表观活化能为15.84 kJ/mol,过程速率为固膜内扩散速率控制. 通过实验数据验证,表明所得模型能较好地描述炉渣的浸出过程.     

FeCl_2·2H_2O焙烧过程动力学研究

用固定床研究了FeCl_2·2H_2O焙烧过程的动力学行为,变量包括温度、物料颗粒尺寸、气流速度和气流中含水量,讨论了过程的控制步骤,估算了表观反应速率常数和表观活化能,并用热分析校核了结果.     

HCl-NaCl浸出铅锑合金氧化吹炼渣过程中锑的浸出动力学

用液-固多相反应的收缩未反应核模型研究了在HCl-NaCl浸出铅锑合金氧化吹炼渣过程中锑的浸出动力学. 详细考察了浸出温度、盐酸浓度、颗粒粒度对锑的反应速率的影响. 研究结果表明,从铅锑合金氧化吹炼渣中浸出锑过程的控制步骤为固膜扩散,表观反应级数为0.2775. 在实验选取的温度范围内,反应的表观活化能为7.656 kJ/mol. 根据研究结果,建立了浸出锑的宏观动力学方程.     

1-丁烯与H2S反应制备仲丁硫醇动力学研究

以Al2O3为载体,采用等体积浸渍法制备了P2O5-MoO3/Al2O3催化剂。在排除内外扩散影响的条件下,研究了1-丁烯与H2S在P2O5-MoO3/Al2O3催化剂上反应生成仲丁硫醇反应的本征动力学。在反应温度120~180℃、压力0.2 MPa的条件下,考察了反应温度、1-丁烯分压和硫化氢分压对反应速率的影响。对1-丁烯在P2O5-MoO3/Al2O3催化剂上的催化硫化机理进行了探讨。实验结果表明,1-丁烯与H2S在P2O5-MoO3/Al2O3催化剂上的反应机制是1-丁烯与H2S发生共吸附后由表面反应控制的二级催化反应,根据该机理得到反应动力学方程为A B2A A B B A(1)kp p r K p K p根据实验数据得到其指前因子k0=3.3×109,活化能Ea=60.78 kJ/mol。     

T305脱硫剂脱除H2S反应宏观动力学行为

用热重法研究了T305氧化锌脱硫剂脱除H₂S反应的宏观动力学。研究表明,脱硫反应动力学行为可用等效粒子模型猫迷。给出了该模型的各参数估值,分析了孔扩散、粒子内扩散及烧结对反应行为的影响。     

ON THE ANALYSIS OF NONCATALYTIC GAS-SOLID KINETICS DATA HAVING WEAK TEMPERATURE DEPENDENCE

Noncatalytic gas-solid reactions should exhibit strong temperature dependence when the rate is controlled by surface kinetics. However, there are a number of examples in the literature where apparent activation energies less than 10 kcal/mol have been reported as being representative of intrinsic kinetics. This conclusion is often based on electrobalance data in which large gas Row rates were used to eliminate mass transfer resistance and the fact that fractional conversion-time results are consistent with the surface kinetics control version of a gas-solid reaction model.

The oxidation of FeS was studied in an electrobalance reactor as a function of O₂ mol fraction, temperature, and gas flow rate. The global rate was first-order in O₂ and weakly dependent on temperature and flow rate. Data analysis used the approximate solution to the grain model. The single-resistance surface kinetics variation of the model provided good match with the conversion-time data, but the apparent activation energy was only about 7 kcal/mol. A two-resistance mass transfer-product layer diffusion variation provided equally good match with the data, and the dependence of reaction coefficients on reaction variables was in general agreement with theory.     

ON THE ANALYSIS OF NONCATALYTIC GAS-SOLID KINETICS DATA HAVING WEAK TEMPERATURE DEPENDENCE

Noncatalytic gas-solid reactions should exhibit strong temperature dependence when the rate is controlled by surface kinetics. However, there are a number of examples in the literature where apparent activation energies less than 10 kcal/mol have been reported as being representative of intrinsic kinetics. This conclusion is often based on electrobalance data in which large gas Row rates were used to eliminate mass transfer resistance and the fact that fractional conversion-time results are consistent with the surface kinetics control version of a gas-solid reaction model.

The oxidation of FeS was studied in an electrobalance reactor as a function of O₂ mol fraction, temperature, and gas flow rate. The global rate was first-order in O₂ and weakly dependent on temperature and flow rate. Data analysis used the approximate solution to the grain model. The single-resistance surface kinetics variation of the model provided good match with the conversion-time data, but the apparent activation energy was only about 7 kcal/mol. A two-resistance mass transfer-product layer diffusion variation provided equally good match with the data, and the dependence of reaction coefficients on reaction variables was in general agreement with theory.     

Application of the shrinking core model to the kinetics of zinc oxide desulfurization

The kinetics of H_2S removal by zinc oxide desulfurizer was studied through thermogravimetricanalysis.The experimental results show that desulfurization rate was controlled,at high temperatureand low conversion,by the chemical reaction rate,and at low temperature and high conversion by thegrain diffusion rate.The reaction is first order with respect to H_2S concentration in the differentcontrolled stages.The kinetic behavior can be modeled through the employment of the shrinking coremodel.The values of the model parameters were determined.The variation tendencies with temperatureand concentration of H_2S at the controlled stages were discussed.     

Diffusion of Water into Silica Glass at Low Temperature

Diffusion of water into silica glass was measured in the temperature range of 200° to 750° by treating the glass in air containing a constant water vapor pressure and analyzing the concentration profile using a Fourier transform infrared spectrometer. In the short-time diffusion heat treatments, the surface concentration was lower and the apparent diffusion coefficient was higher than the corresponding steady-state values. The temperature dependence of the steady-state diffusion coefficient showed two different activation energies. Above ∼550° the diffusion coefficients were similar to the published results with an activation energy of ∼80 kJ/mol, while below ∼550°, the diffusion coefficient was higher than the value obtained by extrapolation from higher temperatures, and the activation energy was ∼40 kJ/mol. Correspondingly, the water solubility–temperature relation showed a sudden change at around the same temperature: at temperatures above this temperature the solubility increased with decreasing temperature, while at lower temperatures the trend was reversed. It was suggested that this observed peculiarity was caused by the initial nonequilibrium reaction between water and SiO₂ glass and a change in enthalpy of the glass–water reaction.     

Effect of polarization type on properties of Ni–W nanocrystalline electrodeposits

Nickel–tungsten nanocrystalline coatings were electrodeposited from a Watts type bath onto a copper substrate, at different current densities selected from activation, mixed and diffusion controlled regions in the cathodic scan plot at room temperature. The results confirm that tungsten codeposition proceeds via the adsorption and reduction of complexes produced in the bulk of solution. The coatings obtained were single phase solid solutions and their grain sizes increased with current density. A cauliflower-type surface morphology with highest hardness was obtained when the current density was in the activation controlled region. The surface morphology obtained in the mixed controlled region was distorted, and then converted to a nodular morphology in the diffusion controlled region. In the mixed control region, coatings with the highest corrosion resistance were obtained due to the lowest exchange current density for water reduction.     

Reaction of TiO2-Al-C in the Combustion Synthesis of TiC-Al2O3 Composite

Reaction mechanisms and the thermal structure in the reaction zone during the combustion of TiO₂, Al, and C to form TiC-Al₂O₃ composite were studied. The reaction between each component was studied and the combustion wave structure and real-time temperature profile were analyzed. Titanium aluminide species, present in the aluminothermic reduction of TiO₂, did not occur in the presence of C, because of the high thermodynamic stability of TiC. The activation energies of the exothermic reaction in the 3TiO₂-4Al-3C system were determined by DSC analysis. This suggests that the combustion reaction is mainly controlled by carbon diffusion through solid TiC. The combustion wave was observed to propagate in an unstable mode. The temperature profiles in the reaction zone were of the sawtooth type and the products were of layered structure.     

活化煤气化粗渣盐酸浸取机理研究

考察了颗粒粒径、盐酸浓度和浸取温度3个条件对活化煤气化粗渣（简称活化渣）中铝、铁、钙离子浸取率的影响,并对浸取机理进行了研究。实验结果表明,活化渣为钙铝黄长石（2CaO·Al2O3·SiO2）与三氧化二铁（Fe2O3）的固溶体,与盐酸反应后颗粒粒径不断减小,钙离子较铝、铁离子优先浸出,其浸取过程符合化学反应控制的缩芯模型,相应的表观活化能为71.3 kJ/mol;钙离子浸出后活化渣颗粒成为疏松多孔材料,铝、铁离子的浸取过程则符合 Avrami模型,二者的浸取反应均受内扩散控制,表观活化能分别为24.7 kJ/mol和22.5 kJ/mol。