在Pb-Bi-La-Mo/SiO_2催化剂上甲醇氧化的内扩散影响及甲醇扩散系数和催化剂曲折因子的测定

在30-40目的Pb_(0.88)Bi_(0.06)La_(0.02)Mo/SiO_2催化剂上甲醇氧化制甲醛的反应在动力学区域进行,其速度规律服从二步骤Redox机理动力学方程.当催化剂增大到3mm时,其动力学方程受内扩散影响严重,实验上测定了催化剂有效因子在0.28—0.12之间.作者对甲醇内扩散控制时的Redox机理动力学方程进行了理论上的推导和实验上的验证.实验上测定了受内扩散控制时的反应活化能,并从理论上指出动力学区域与内扩散区域活化能的关系.用动力学方法测定了甲醇在给定反应条件下的扩散系数和曲折因子.     

在Mo-Bi-P_(2.2)/SiO_2催化剂上丁烯异构化L-H三角反应机理复杂反应动力学

用玻璃外循环无梯度反应器研究了丁烯异构化L-H三角机理复杂反应动力学.X衍射分析指出Mo-B_1-P_2.2/SiO_2催化剂含有磷酸铋物相.用吸附指示剂正丁胺滴定法测定了催化剂的酸量.催化剂显中等强度的酸性.催化剂上吸附吡啶的红外光谱法测定了质子酸和路易斯酸.气相色谱法测定了1-丁烯、2-丁烯吸附热.讨论了1-丁烯异构化表观活化能与真活化能的关系.用正交设计法估计了动力学方程中的参数.异构化生成反-2-丁烯及顺-2-丁烯的动力学方程分别为式(11)、(12)所描述.     

钼系多组分催化剂上的丁烯-2氧化脱氢动力学

用玻璃流动循环反应器研究了Bi_（1.5）Fe_（3.0）Ni_（4.5）Co_1Cr_（0.5）Mo_（12）K_（0.3）（原子比）氧化物催化剂（SiO_2载体）上的丁烯-2氧化脱氢动力学,发现丁烯转化速度对丁烯及氧的反应级数m及n与温度及反应物浓度有关,而且m+n≈1。 根据Redox稳态机理可认为: ①催化剂被丁烯还原的速度与还原态催化剂再氧化的速度达到稳态。 ②丁二烯在催化剂的氧化态表面部分上可逆吸附起了阻碍丁烯转化的作用,并导出速度方程为: 计算出催化剂还原步骤的活化能E_1=4.53kcal/g-mol,催化剂再氧化步骤的活化能E_2=21kcal/g-mol（>400℃）及60kcal/g-mol（<400℃）,E_2在400℃附近转折。当丁二烯阻碍作用不显著时（相对于丁烯,丁二烯分压较小,或反应温度较高）方程可以简化为 本文还对常见的钼系催化剂的丁烯转化的活化能发生转折的原因进行了讨论。     

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。     

Cu/TiO2光催化正丁烷脱氢制丁烯

采用硼氢化钠还原法制备了Cu/TiO₂催化剂,考察Cu负载量、反应温度和反应时间对Cu/TiO₂光催化正丁烷脱氢制丁烯的影响。结果表明,室温下氙灯照射60 min, 0.5-Cu/TiO₂光催化正丁烷脱氢制丁烯产量为600.2μmol/(g-cat·h),选择性为95.3%,H₂产量为858.7μmol/(g-cat·h),丁烯产量和选择性随Cu负载量的变化不大。低温有利于光催化正丁烷脱氢,反应温度过高时,丁烯和H₂产量降低,丁烯选择性降低,裂解选择性增大。1-丁烯和2-丁烯相对选择性不随反应时间变化,未发现丁烯间的异构化反应。     

多元钼酸盐催化剂的丁烯-2氧化脱氢动力学的初步考察

在流动循环法装置上,对钼-铋-磷-铁-镍-钾六元体系催化剂的丁烯-2氧化脱氢和丁二烯氧化动力学进行了研究。研究结果表明,丁烯-2及丁二烯都能生成有机含氧化合物,丁烯-2不直接生成深度氧化产物(CO+CO_2),而是丁二烯可以直接生成深度氧化产物。并对实验数据按并行—串联机理进行了线性最小二乘法及非线性最小二乘法处理,导出了各反应步骤的幂函数动力学方程。     

CO2氛围中低碳烷烃制烯烃催化剂的研究进展

CO₂作为温和的氧化剂有效抑制了低碳烷烃催化转化过程中深度氧化的发生,然而其广泛应用还依赖于高效、高稳定性催化剂的研究与开发。本文就近年来国内外有关利用CO₂作为氧化剂在低碳烷烃催化转化反应方面的研究成果进行了综述,主要涉及甲烷氧化偶联制乙烯和乙烷催化剂;乙烷氧化脱氢制乙烯催化剂、丙烷氧化脱氢制丙烯催化剂和丁烷氧化脱氢制丁烯催化剂,分析讨论了CO₂作为氧化剂的作用和作用机制,并提出了研究展望。     

原料中杂质对异丁烷脱氢Pt-Sn-K/Al2O3催化剂性能的影响

采用固定床法考察了原料异丁烷中乙硫醇、甲醇、正丁烷和1-丁烯等杂质对Pt-Sn-K/Al₂O₃催化剂上异丁烷脱氢制异丁烯反应性能影响,反应产物使用气相色谱进行分析.实验结果表明,在异丁烷脱氢制异丁烯正常反应条件下,即温度580℃、压力0.1MPa、进料组成H₂/i-C₄H₁₀(体积比)= 2、总空速GHSV = 2000h^-1、GHSV(i-C4H10)= 667h^-1,乙硫醇、甲醇、正丁烷和1-丁烯对Pt-Sn-K/Al₂O₃催化剂的异丁烷转化率和异丁烯选择性均有较大的影响,且杂质含量越高,对催化剂的转化率和选择性影响越大.并对杂质造成催化剂失活的原因进行了分析.     

V-Mg-O催化剂上丁烷氧化脱氢动力学研究

制备了V－Mg-O催化剂,并测定了在该催化剂上进行丁烷氧化脱氢的反应动力学。应用BET和X射线衍射技术对催化剂进行了表征,在反应温度793－873K范围内,改变接触时间（W／F）和丁烷与氧气的分压进行了动力学实验。在所有的实验条件下,产物主要有脱氢产物（丁烯、丁二烯）、CO和CO2。提出了一个包括C4烯烃、COx生成反应的反应网络;从所测量的动力学数据中得到了合适的幂率型动力学方程。因为氧化脱氧反应的表观活化能比深度氧化反应的表观活化能大,在相同转化率时,C4烯烃选择性随着反应温度的提高而增加。     

丙烷CO_2氧化脱氢制丙烯研究进展

丙烷氧化脱氢反应不受热力学平衡限制,焓变小于零,为放热反应,可节省能源。但氧化脱氢制丙烯因为有O2存在,导致丙烷和丙烯深度氧化,使丙烯选择性下降。可通过以下途径改进:(1)通过添加助剂或改变活性组分限制丙烯的深度氧化;(2)改变反应气氛,用氧化性较弱的氧化剂(如CO2和N2O等)代替O2。近年来,在低碳烷烃脱氢领域以CO2为氧化剂的研究较多,CO2可以避免深度氧化。综述在丙烷氧化脱氢反应中通过引入CO2,将丙烷直接脱氢反应与逆水煤气反应进行偶合,打破了丙烷直接脱氢反应平衡,消除积炭,提高催化剂稳定性,推动反应向生成丙烯的方向进行,丙烯收率提高;在低温(270℃)区域,副反应可提高丙烷CO2氧化脱氢反应的丙烯平衡收率,丙烷二氧化碳脱氢反应的催化剂体系主要包括铬系催化剂、镓系催化剂、钒系催化剂及其他催化剂。     

用序贯实验设计法研究B02催化剂上丁烯氧化脱氢动力学

<正> 该催化剂虽已用于工业装置,但基本动力学数据的研究尚不充分,陈曙等利用外循环无梯度反应器,获得了该反应网络的半经验方程。作者应用经典方法由可能的28个候选模型中选出了较适宜的机理性模型。但由于经典法的实验安排是任意的,具有一定的盲目性,不保证每个实验数据均能充分反映模型之间的差别,实验测得数据虽很多,但有效数据较少。因而,筛选所得模型只是较适宜的,而不是最佳的。     

Oxidative Dehydrogenation of n-Butane: Activity and Kinetics Over VO x /Al2O3 Catalysts

The catalytic activity of a VO _x /Al₂O₃ catalyst for the oxidative dehydrogenation of n-butane is investigated. The effects of reaction temperature, oxygen to n-butane ratio and GHSV on the catalytic performance are examined and optimized. Interestingly, this simple catalyst gives good conversion and selectivity. Butane was 22–24 %, and the selectivity to C₄ alkenes was 56 %, of which 20–22 % to 1,3-butadiene. Moreover, the catalyst is stable for at least 72 h on stream. Kinetic studies show that the activation barriers for the formation of (butene + butadiene), CO and CO₂ amount to 70.2, 65 and 81.3 kJ/mol respectively.

     

膜控制氧化反应器中丁烯氧化脱氢的研究

在气体均布的无机膜控制氧化反应器上进行了丁烯氧化脱氢制丁二烯反应,并将其与固定床方式反应的实验结果进行了对比,结果表明在实验范围内膜反应器比传统的固定床反应更为有效。建立了描述控制氧化膜反应器操作性能的数学模型,并将模型求解值与实验值对比,吻合良好。     

Oxidative Dehydrogenation of n-Butane: Activity and Kinetics Over VO x /Al2O3 Catalysts

The catalytic activity of a VO _x /Al₂O₃ catalyst for the oxidative dehydrogenation of n-butane is investigated. The effects of reaction temperature, oxygen to n-butane ratio and GHSV on the catalytic performance are examined and optimized. Interestingly, this simple catalyst gives good conversion and selectivity. Butane was 22–24 %, and the selectivity to C₄ alkenes was 56 %, of which 20–22 % to 1,3-butadiene. Moreover, the catalyst is stable for at least 72 h on stream. Kinetic studies show that the activation barriers for the formation of (butene + butadiene), CO and CO₂ amount to 70.2, 65 and 81.3 kJ/mol respectively.     

Bis (2‐mercapto‐ethyl) amine modification of macroporous sulfonic resin catalyst in bisphenol‐a synthesis

A novel catalyst for bisphenol‐A synthesis was prepared by bis (2‐mercapto‐ethyl) amine adsorbed on macroporous sulfonic resin through neutralization reaction. The physicochemical properties of two resin catalysts before and after bis (2‐mercapto‐ethyl) amine absorption were compared by scanning electron microscope and nitrogen adsorption. The kinetic of the new catalyst preparation process was studied and it was found that this is a chemical adsorption and endothermic process. The adsorption rate is mainly controlled by the intraparticle diffusion, affected by boundary layer diffusion and chemical reaction as well. The thermodynamic activation parameters were calculated. Compared with unmodified catalyst, the modified resin catalyst showed higher selectivity and acetone conversion in the continuous bisphenol‐A synthesis process. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3816–3823, 2013     

The effect of catalyst particle size on the oxidative dehydrogenation of butenes to butadiene over bismuth molybdate

The oxidative dehydrogenation of but-1-ene to butadiene has been investigated in a continuous flow system using a range of different particle sizes. A but-1-ene to oxygen ratio of 2:1 was adopted in most experiments in order to avoid over-oxidation. The reaction rate was found to be first order in butene and zero order in oxygen in agreement with previous work. Particle size was found to have a profound influence on the rate of reaction and selectivity. The larger particle sizes operated at a temperature level above the ambient gas stream due to interphase effects. Allowance for this phenomenon enabled a revised activation energy of 41.42 kJ mol^?1 to be estimated which was independent of particle diameter.     

Selective Hydrogenation of 1‐Butene Rich Cuts: the Impact of the Intraparticle Diffusion Limitations on the Selectivity

The impact of intraparticle diffusion limitations on the selectivity of an industrial reactor for selective hydrogenation of 1‐butyne and 1,3‐butadiene contained in 1‐butene rich cuts was evaluated. To this end, a simple model of a trickle‐bed reactor was employed and actual process operating conditions were chosen. A kinetic model was chosen whose parameters correspond to a commercial catalyst. These parameters were calculated from experiments conducted under industrial operating conditions. The complex diffusion and reaction phenomena occurring inside catalyst pellets placed at different depths of the reactor are comprehensively described. 1‐Butene losses in the range 20–30 %, which are usual in commercial plants, were predicted. It was concluded that the operating pressure is crucial for enhancing process selectivity.