C207铜基催化剂常压甲醇分解反应动力学(Ⅱ)催化剂效率因子正交配置解

在内循环无梯度反应器中常压下测定了工业颗粒C207催化剂甲醇分解反应宏观速率,测定了催化剂孔径分布和曲节因子,获得了催化剂效率因子的实测值。探讨了计算催化剂效率因子的甲醇单组分模型和多组分模型的正交配置解,颗粒催化剂存在中心平衡死区。在相同反应条件下,催化剂效率因子模型计算值与实测值的相对误差的绝对值的平均值在11%以内,结果表明计算模型是可行的。     

LB型节能高温变换催化剂曲节因子测定

采用改进的Wicke-Kallenbach扩散池,用稳态法在常压40 ℃和60 ℃下测定了LB型节能高温变换催化剂曲节因子和气体有效扩散系数,测定中各实验点氮气与二氧化碳的摩尔通量之比符合Graham理论,与理论值误差在5.0%之内,计算得到了曲节因子为2.603,以平均孔径计算的曲节因子为1.788,它们与气体流量和实验温度无关.     

甲醇合成铜基催化剂硫化氢中毒研究(Ⅱ)——表面中毒催化剂效率因子

在常压下内循环无梯度反应器中测定了工业颗粒C207铜基化剂在入口硫化氢含量7.19×10~(-4)通硫化氢4、8、12h后甲醇分解反应宏观速率,测定了催化剂孔径分布和曲折因子.由俄歇电子能谱测定获得,通H_2S 4h未中毒比半径x_c为0.938,通H_2S 8h为0.916,通H_2S 12h为0.896,与由本征失活动力学获得的计算值相符合.探讨了计算表面中毒催化剂效率因子的甲醇单组分模型和多组分模型的正交配置解,解决了颗粒催化剂存在表面中毒和中心平衡死区的效率因子的求解问题,中毒催化剂效率因子的实验值与模型计算值的相对误差,其绝对值的平均值在11%以内,表明表面中毒催化剂效率因子的计算模型是可行的.     

甲醇合成铜基催化剂硫化氢中毒研究(Ⅱ)——表面中毒催化剂效率因子

在常压下内循环无梯度反应器中测定了工业颗粒C207铜基化剂在入口硫化氢含量7.19×10~(-4)通硫化氢4、8、12h后甲醇分解反应宏观速率,测定了催化剂孔径分布和曲折因子.由俄歇电子能谱测定获得,通H_2S 4h未中毒比半径x_c为0.938,通H_2S 8h为0.916,通H_2S 12h为0.896,与由本征失活动力学获得的计算值相符合.探讨了计算表面中毒催化剂效率因子的甲醇单组分模型和多组分模型的正交配置解,解决了颗粒催化剂存在表面中毒和中心平衡死区的效率因子的求解问题,中毒催化剂效率因子的实验值与模型计算值的相对误差,其绝对值的平均值在11%以内,表明表面中毒催化剂效率因子的计算模型是可行的.     

多孔催化剂效率因子的多组分扩散模型 (Ⅱ)B109中温变换催化剂的效率因子

按照本文(Ⅰ)中提出的多孔催化剂效率因子的多组分扩散模型及其数值计算方法,本报计算了B109中温变换催化剂的效率因子,并与实验测定值进行了比较.测试了B109变换催化剂的孔隙率、孔径分布、曲节因子和常压下的本征动力学,并在内循环无梯度反应器中测试了常压下φ9.8×8.3mm圆柱状颗粒B109催化剂于各种气体组成和温度条件下只计入内扩散过程的宏观反应速率.由此获得十六种情况下效率因子的实验观察值为0.142至0.455,相同反应条件下模型预计值与实验观察值的相对误差为-0.25至0.06.比较的结果令人满意.     

反应条件下多孔催化剂上有效扩散系数及曲节因子的分析计算

采用CDS－810微反系统,在实验条件为：常压、氢苯比3.0-8.0、温度363.15K-453.15K时,进行了在四种不同粒度Ni/Al2O3催化剂上的气相苯加氢反应,利用实验数据计算了不同反应组成、不同反应速率时苯的有效扩散系数、反应死区及催化剂的曲节因子。计算结果表明：有效扩散系数不随反应速率改变,多孔催化剂的曲节因子可以看作多孔催化剂的结构参数,不随反应条件变化。     

铜基催化剂孔隙率对气体有效扩散系数的影响

研究了18种具有不同孔结构参数的粒状铜基甲醇合成催化剂孔隙率对有效扩散系数的影响。结果发现，催化剂微孔孔隙率增大，曲节因子亦增大，扩散阻力增加。将孔隙率与催化剂曲节因子关联，得到了半经验方程，用它可估算催化剂的曲节因子。     

SB—5型钴钼耐硫变换催化剂反应动力学的研究

本文对ＳＢ－５型钴钼耐硫变换催化剂进行了系统的动力学研究，获得了可信的本征动力学方程和催化剂的曲节因子，并在常压下测定了工业颗粒催化剂的宏观反应速率，所建立的内扩散效率因子模型的计算值与实验值相吻合。     

SB—5型钴钼耐硫变换催化剂反应动力学的研究

本文对ＳＢ－５型钴钼耐硫变换催化剂进行了系统的动力学研究，获得了可信的本征动力学方程和催化剂的曲节因子，并在常压下测定了工业颗粒催化剂的宏观反应速率，所建立的内扩散效率因子模型的计算值与实验值相吻合。     

多孔催化剂效率因子的多组分扩散模型(Ⅲ)——加压下WB-2中温变换催化剂的效率因子

在内循环无梯度反应器中研究37×10~5Pa(表)及13×10~5Pa(表)压力下工业粒度ф9×7mm.WB-2中温变换催化剂的宏观反应速率,测试了催化剂的孔径分布和曲节因子.本报应用常压下测得的本征动力学方程,对于十七组宏观实验速率,按照前报(Ⅱ)提出的简化多组分扩散模型,求取了效率因子的数值解,并与实验观察值作了比较.比较的结果令人满意.本报由此认为,对于中温变换这类压力不高的反应,研究其加压宏观动力学行为,不必进行加压宏观速率的实验测定.加压下的效率因子及宏观反应速率可在常压测得的本征动力学基础上借助本文提出的模型计算求得.     

Poisoning studies in a single-pellet catalytic reactor

Using a novel reactor configuration, the nonuniformity of a poison in a single catalyst pellet was studied. The activity of an n-alumina supported catalyst containing 0.25% platinum was measured using the cyclopropane hydrogenolysis reaction. The results show that the catalyst is progressively poisoned from the outside of the catalyst to the center plane nonuniformly. The data suggest a bimodal pore size distribution in the pellet.     

Ru/Al2O3催化剂表面分形分析

利用静态氮吸附仪在-196.15 ℃液氮气氛中,测定Ru/Al2O3催化剂的比表面积以及孔结构参数,研究了催化剂的孔容-孔径分布和吸附-脱附等温线。基于FHH多层吸附模型,利用全吸附数据计算出Ru/Al2O3催化剂的表面分形维数。结果表明,3种Ru/Al2O3催化剂的表面分形维数均约2.4,分形维数与比表面积和总孔体积无直接关联。     

Deactivation of hydrodesulfurization catalysts by metals deposition

Primary causes of deactivation of hydrodesulfurization catalysts are partial poisoning of the interior pore surface and pore-mouth plugging by deposition of metals from organo-metallic compounds in the reactor feed. A model is developed to account for both causes of deactivation. It can be used to predict which occurs first: complete surface poisoning or pore-mouth plugging. Equations are formulated for catalyst activity as a function of time for demetallization and also for desulfurization. The results depend upon particle geometry and geometry of deposited species, Thiele moduli for demetallization and desulfurization, and relative rates of desulfurization on fresh and partially poisoned catalytic surfaces. The treatment is for a single, isothermal catalyst particle.     

Morphological Analyses of Polymer Electrolyte Fuel Cell Electrodes with Nano‐Scale Computed Tomography Imaging

We report a three‐dimensional (3D), pore‐scale analysis of morphological and transport properties for a polymer electrolyte fuel cell (PEFC) catalyst layer. The 3D structure of the platinum/carbon/Nafion electrode was obtained using nano‐scale resolution X‐ray computed tomography (nano‐CT). The 3D nano‐CT data was analyzed according to several morphological characteristics, with particular focus on various effective pore diameters used in modeling gas diffusion in the Knudsen transition regime, which is prevalent in PEFC catalyst layers. The pore diameter metrics include those based on chord length distributions, inscribed spheres, and surface area. Those pore diameter statistics are evaluated against computational pore‐scale diffusion simulations with local gas diffusion coefficients determined from the local pore size according to the Bosanquet formulation. According to our comparison, simulations that use local pore diameters defined by inscribed spheres provide effective diffusion coefficients that are consistent with chord‐length based estimations for an effective Knudsen length scale. By evaluating transport rates in regions of varying porosity within the nano‐CT data, we identified a Bruggeman correction scaling factor for the effective diffusivity.     

Large pore heavy oil processing catalysts prepared using colloidal particles as templates

Macroporous FCC catalyst and macroporous HDS catalyst were prepared using polystyrene spheres as template. The size of the macropores can be tailored by controlling the size of template. The BET surface area and the pore volume of the macroporous catalysts are larger than those of catalysts prepared without template, and the more template used, the larger the surface area and pore volume obtained. When the same amount of template was used, the smaller diameter template produced a catalyst with larger surface area and pore volume. The increments in surface area and pore volume of the catalysts were greater than those predicted from the geometry of the template, indicating particle template could inhibit the shrinkage of the catalyst during drying. When used as heavy oil FCC catalysts and heavy oil HDS catalyst, the prepared macroporous catalysts are much more active than catalysts prepared without the template.     

Revisiting the concepts of competition between reaction and diffusion in poisoned catalysts

The competition between diffusion and first‐order irreversible reaction in poisoned catalysts is revisited. Two cases are considered for isothermal slab catalysts: uniform and shell‐progressive (or pore‐mouth) poisoning. Analytical concentration profiles are derived, and the implications on catalyst performance are evaluated in different regimes (chemical‐ or diffusion‐controlled) for different levels of poisoning. It was found that depending on the poisoning mechanism, the activity decay can be more or less pronounced. Being of particular concern is the pore‐mouth poisoning at high Thiele modulus, conditions under which catalyst performance is drastically affected. The reagent concentration profiles allowed the explanation of the phenomena occurring at the particle scale, in particular the effectiveness factors, observed reaction rates, and poisoning factors' dependence on the Thiele modulus and fraction of the poisoned catalyst; it was found that such relationships are dependent on the mechanism of deactivation. © 2012 Canadian Society for Chemical Engineering     

甲醇制烯烃用ZSM-5分子筛的研究进展

综述了甲醇制烯烃用ZSM-5分子筛催化剂的研究进展,包括甲醇制低碳烯烃的合成机理、ZSM-5分子筛的结构与酸性对合成低碳烯烃性能的影响以及分子筛的改性。重点探讨了ZSM-5分子筛的改性（如水热处理改性、磷改性、氟改性、硼改性、金属离子改性及其他化学改性）对催化剂表面酸性和孔径、低碳烯烃选择性和催化剂稳定性的影响,指出分子筛孔径/表面酸性的调控和MTO/MTP反应机理的研究是甲醇制低碳烯烃催化剂研究的发展方向。     

SCR脱硝催化剂抗砷中毒改性优化与再生研究进展

选择性催化还原（SCR）是目前应用最为广泛的烟气脱硝技术,催化剂是整个SCR脱硝系统的核心。在实际应用过程中,催化剂存在各种失活问题,其中砷中毒是催化剂失活的重要原因之一。本文详细阐述了SCR脱硝催化剂砷中毒的物理和化学失活机理,其中物理失活是由于As₂O₃在催化剂表面沉积、氧化造成催化剂孔道堵塞所致,而化学失活是由于砷氧化物破坏催化剂酸位点、改变活性基团形态、降低催化剂氨吸附及氧化还原能力所致。然后,系统介绍了抗砷中毒SCR脱硝催化剂的研发路线以及现有抗砷中毒催化剂优化改进的主要技术手段,主要包括调整催化剂孔隙结构、优化催化剂化学配方和烟气侧砷氧化物吸附固化等,其中MoO₃是优选的催化剂活性助剂,金属元素（如Bi、In、Sn、Mg）是主要的抗砷助剂,钙基物质是典型的烟气侧砷氧化物吸附添加剂。最后,对砷中毒废弃催化剂的再生技术进行了简要介绍,包括湿法清洗、热还原法、复合再生等,在实际工业应用中,主要以物理清扫、湿法清洗配合活性组分添加的复合再生方式实现中毒催化剂再生。本文可对未来抗砷中毒SCR脱硝催化剂的研发与优化提供重要支撑。     

JT-8型焦炉煤气加氢催化剂失活样品剖析

焦炉煤气深度净化是焦炉煤气综合利用的关键技术。采用XRF、颗粒抗压碎力、烧失重、压汞法孔结构、XRD和XPS等对JT-8型加氢催化剂新鲜样、使用样和焙烧样进行表征。加氢催化剂失活的主要原因是催化剂表面结焦积炭,形成致密板结层,隔绝了气体与催化活性位的有效接触,同时引起床层阻力降不断上涨。加氢催化剂使用样中含有大量的碳元素,质量分数从6.6%到29.4%均有分布;催化剂颗粒表面的碳原子百分数占76.23%~79.74%,其形态是类石墨炭形态(C—C、C—H)和高度聚合的有机碳形态(C—O、C=O),且以类石墨炭为主。使用样的微孔被堵塞,导致孔容和比表面积均大幅减少,平均孔径变大;焙烧后,一些小孔径的微孔结构可能被破坏,导致比表面积下降,平均孔径变大;结焦积炭严重的样品恢复率较差。