Kinetic investigations of the deactivation by coking of a noble metal catalyst in the catalytic hydrogenation of nitrobenzene using a catalytic wall reactor

The vapour phase hydrogenation of nitrobenzene to aniline is a highly exothermic reaction deactivated by coking of the palladium catalyst supported on -alumina carrier. For studying the deactivation of the catalyst a catalytic wall reactor was used in order to ensure isothermal reaction conditions for the kinetic measurements. Furthermore, the catalytic wall reactor allowed the determination of axial coke profiles by total carbon analysis of different wall segments. On the assumption that the main reaction and the deactivation of the catalyst can be assumed separable both the steady state and the unsteady state kinetics were studied. Nitrobenzene was identified as the relevant coke precursor whereas aniline has neither an influence on the main reaction nor on the deactivation. It could be shown that the hydrogenation of nitrobenzene to aniline follows a Langmuir–Hinshelwood mechanism considering the surface reaction of the adsorbed nitrobenzene molecule and one adsorbed hydrogen atom as the rate determining step. The differentiation of coke on the active sites and coke on the support must be taken into account to model the kinetics of coke formation with sufficient accuracy.     

骨架镍催化剂制备及其催化烯基芳烃加氢性能的研究

考察了成型时拟薄水铝石和合金粉的比例、胶溶剂硝酸质量分数,水粉比及焙烧温度对骨架镍催化剂侧压强度的影响,采用XRD和TG-DTA等手段对催化剂进行表征。结果表明,催化剂侧压强度随着拟薄水铝石和合金粉的比例、胶溶剂硝酸质量分数、水粉比以及焙烧温度的提高呈现先增加后减小的规律,在拟薄水铝石与合金粉质量比1.5、胶溶剂硝酸质量分数6%和水粉比0.21 mL.g-1条件下成型,860℃空气中焙烧,得到侧压强度最好的催化剂,以苯乙烯、甲基苯乙烯加氢为探针反应,对催化剂的加氢性能进行评价,结果表明,在反应压力2 MPa、温度80℃、原料空速2 h-1和V(H2)∶V(油)=300∶1条件下,苯乙烯与甲基苯乙烯在考察的500 h运转周期内,转化率接近100%,且催化剂活性保持稳定。     

硝基苯加氢制备苯胺的催化体系研究进展

介绍了硝基苯加氢反应的铜系、钯系及其他催化体系及近年来的研究进展。     

硝基苯催化加氢Pt-MoS2/C催化剂的制备及使用寿命的研究

采用浸渍法制备Pt/C和Pt-MoS2/C催化剂,用于催化硝基苯加氢反应。采用BET、压汞仪等测试方法测定新鲜催化剂和重复使用后的催化剂的比表面积和孔容。结果表明,比表面积下降27.3%,微孔孔容下降13.2%,总孔容下降5.8%。催化剂失活的主要原因为有机物覆盖在催化剂表面,造成表面积下降和孔堵塞。负载MoS2可使Pt/C催化剂延缓比表面积下降和孔堵塞,寿命显著提高,可循环使用14次左右。     

KF/膨润土催化剂的制备及其在活泼亚甲基烷基化中的应用

钙基膨润土钠化后,负载一定量KF,焙烧制得KF/膨润土催化剂。以溴代正丁烷与乙酰乙酸乙酯的烷基化反应为探针反应,考察了催化剂制备条件及反应工艺条件对收率的影响。结果表明,在溴代正丁烷0.02 mol、乙酰乙酸乙酯0.01 mol、催化剂用量0.4 g和85 ℃条件下反应4.0 h,2-正丁基乙酰乙酸乙酯收率达38.6%,体现出催化剂对活泼亚甲基的烷基化反应具有良好活性。     

硝基苯液相催化加氢制苯胺催化剂研究进展

介绍了硝基苯液相催化加氢制苯胺的工艺过程,同时对该工艺所用催化剂体系(非贵金属类催化剂和贵金属类催化剂)进行了详述.非贵金属催化剂不仅存在对苯胺选择性差还存在对环境污染的问题;贵金属催化剂活性高,但成本也较高.开发催化活性高、稳定性好、寿命长、损耗低且环境友好型催化剂是硝基苯液相加氢催化剂发展的主研方向.     

Ni/bentonite catalysts prepared by solution combustion method for CO2 methanation

A 20 wt% Ni/bentonite catalyst was prepared by a solution combustion synthesis (SCS), which exhibited higher activity for the CO₂ methanation than that of an impregnation method (IPM), and the catalyst prepared by SCS showed a CO₂ conversion of 85% and a CH₄ selectivity of 100% at 300℃, atmospheric pressure, and 3600 ml·(g cat)^-1·h^-1, and the catalyst exhibited stable within a 110-h reaction. The results showed higher metallic Ni dispersion, smaller Ni particle size, larger specific surface area and lower reduction temperature in the Ni/bentonite prepared by SCS than that of IPM. And the Ni/bentonite prepared by the SCS moderated the interaction between NiO and bentonite.     

A solvent-free,selective liquid phase hydrogenation of nitroarenes to aniline in slurry bubble mode on porous NiMo bimetallic catalyst

Ni Mo bimetallic catalysts were prepared by a solid reaction method. On the Ni Mo catalyst, the selective liquid phase hydrogenation of nitrobenzene to aniline was achieved in slurry bubble mode. And the high yields(98.9%) were obtained under the conditions of 80 °C, solvent-free and atmospheric pressure. The effect of Mo on the catalytic behavior of Ni based catalyst was investigated. The characterization displayed that the inclusion of Mo could improve the specific surface area and pore volume, and the solid reaction method made metal Mo enrichment on the surface of catalyst. These two aspects should be responsible for excellent catalytic performance of Ni Mo catalyst. In sum, we described a simple and efficient Ni Mo catalyst and provided a facile and green procedure for liquid phase hydrogenation of nitrobenzene to aniline.     

Acid-treated bentonite-supported Ni catalysts via rapid microwave-assisted drying for nitrobenzene hydrogenation

Acid-treated bentonite-supported Ni catalysts were prepared using a microwave-assisted drying process, characterized and used for the hydrogenation of nitrobenzene to aniline. Microwave-assisted drying of the catalyst reduced the drying time from 3?h with a traditional heating method to 10?min; after drying by microwave irradiation, the acid-treated bentonite-supported Ni catalysts were more stable due to a smaller crystallite size, a higher dispersion of metallic Ni and stronger interactions between Ni and the acid-treated bentonite support than the traditional drying method. Catalytic studies conducted at 300°C with a nitrobenzene liquid hourly space velocity of 3.6?mL?g^?1?h^?1 and a H₂ gas hourly space velocity of 4,800?mL?g^?1?h^?1 indicated that the catalyst prepared using the microwave heating method maintained a nitrobenzene conversion of >99.9% with an aniline selectivity >93% during a 60-h reaction. In addition, the catalyst dried using a traditional method only functioned for 16?h.     

负载型Pd/SBA—15催化剂催化性能研究

将负载型催化剂Pd/SBA—15用于催化邻氯硝基苯加氢。考察了反应温度、催化剂用量对Pd/SBA—15催化性能的影响,并考察了催化剂的使用寿命。实验结果表明,Pd/SBA—15催化剂表现出很好的催化性能,有望应用于工业生产。     

非晶态Ni-P合金上硝基苯催化加氢制苯胺的本征动力学

Ni-P非晶态合金催化剂因其晶体结构的特殊,具有较好的催化活性。以硝基苯液相催化加氢合成苯胺为目标反应,运用Matlab软件并借助Levenberg-Marquardt算法估计反应动力学模型的参数,根据参数估计结果筛选动力学机理模型,对新型Ni-P非晶态合金催化剂的本征动力学进行研究,为催化剂的进一步开发和反应器设计提供理论依据。结果表明,Ni-P非晶态合金催化剂的颗粒较小,过程内扩散的影响可以忽略不计,当搅拌速率达到600 r·min^-1时,反应过程的外扩散影响也可忽略。在（373.15~403.15） K、氢压1.0 MPa、非晶态Ni-P催化剂质量0.2 g、硝基苯质量2.0 g和无水乙醇质量8.0 g条件下,硝基苯分子不吸附,硝基苯分子与解离吸附的氢原子在催化剂表面反应,苯胺脱附为硝基苯加氢合成苯胺反应的速率控制步骤,本征动力学模型为：r_j=kc_A/1+b_H2α_H2p_H2,表面反应的指前因子为1.08×105 min^-1,活化能为51.81 kJ·mol-1,氢气吸附热为64.12 kJ·mol^-1。     

浸渍液pH对镍物种存在状态及催化剂加氢催化性能的影响

以HZSM-5为载体,硝酸调节浸渍液的pH,采用等体积浸渍法制备含Ni质量分数0.5%的Ni/HZSM-5催化剂,结合XRD、TEM、BET、NH3-TPD及H2-TPR等表征手段,考察浸渍液pH对Ni物种存在状态及催化剂加氢催化性能的影响.结果表明,pH为2.5时,Ni物种以3种形式存在,载体外表面较大颗粒(8 nm...     

负载型膨润土固体碱催化剂的制备及在生物柴油合成中的应用

提出了一种负载型膨润土固体碱催化剂的制备方法,并将此催化剂用于生物柴油合成的酯交换反应。该催化剂通过碱性钙基膨润土在半干条件下负载氢氧化钠制得。催化剂制备的单因素实验结果表明：当氢氧化钠与碱性钙基膨润土的质量配比为0.6、负载时间为18 h、温度为60 ℃及碱性钙基膨润土中OH−含量为1.5 mmol/g时,催化剂中氢氧化钠负载量达到4.10 mmol/g。将该催化剂用于生物柴油酯交换反应,反应转化率可达97.4%,反应完成后生物柴油无需洗涤,避免了三废的大量排放,减少了对环境的污染。     

H2气氛中TiOx的形成及其对Ni/TiO2催化剂顺酐液相加氢性能的影响

采用等体积浸渍法制备了Ni/TiO₂催化剂,利用N₂物理吸附、H₂-TPR、XRD、H₂-TPD及CO-TPSR等表征手段研究H₂气氛中随着热处理温度升高,Ni/TiO₂催化剂结构和织构变化规律,并考察催化剂的顺酐液相加氢性能。研究表明,随着热处理温度的升高,催化剂C-C键加氢活性逐渐增高,而CO加氢活性先增高后降低。产生这一现象的原因与TiO_x物种随H₂气氛中热处理温度的升高而逐渐增多有关。     

膨润土上负载AlCl３固体酸催化剂的制备

以无水三氯化铝为原料,并以处理过的膨润土为载体,采用液固溶剂法制备固体酸催化剂。用载铝量为检验指标,通过单纯型搜索法寻优,探讨各种因素对载铝量的影响,并分析了主次因素。     

硝基苯液相催化加氢制苯胺催化剂研究进展

介绍了苯胺生产中硝基苯液相催化加氢制苯胺工艺,着重介绍了液相加氢催化剂体系中的镍系催化剂和贵金属催化剂的研究进展。液相催化加氢多采用贵金属催化剂和高活性、制备工艺复杂的催化剂,生产成本较高,开发价廉、高效并能满足绿色化工要求的新型催化剂是今后工作的重点。     

镍/三氧化二铝油脂加氢催化剂研究

以铝酸钠和硫酸铝为原料制备铝胶,然后将可溶性镍盐、稀土硝酸盐与碱性沉淀剂中和后,加入到上述铝胶中,经水洗、干燥、还原即制得油脂加氢催化剂。氧化铝载体比表面积为(300±10)m2/g时,催化剂活性最高;综合考虑温度对氧化铝载体比表面积及催化剂过滤性能的影响,选取85℃为最佳温度;还原气中氮气、氢气体积比为3∶1时,得到的催化剂活性最好。该催化剂的活性评价结果表明,其性能已达到进口产品的水平。     

复合改性膨润土的制备及吸附苯胺的特性

选用不同碳链长度及不同类型的表面活性剂与聚合羟基铝对膨润土进行复合改性,表明长碳链表面活性剂制备的复合改性样品相对于短碳链表面活性剂制备的复合改性样品对苯胺有较好的吸附效果,阴离子表面活性剂制备的复合改性样品比阳离子表面活性剂制备的复合改性样品对苯胺有更好的吸附效果。采用正交试验得到的最优复合改性样品吸附苯胺,表明样品对苯胺的吸附符合准二级动力学模型(R2≈1),粒内扩散并不是控制吸附的惟一限速步骤,Freundlich等温线模型比Langmuir等温线模型更适合描述吸附过程,吸附过程为吸热物理过程(△Hθ=9.39 k J·mol-1)。     

Ni/Al2O3-MxOy催化剂催化松香加氢的催化性能及产物组成

研究了Ni/Al2O3-MxOy,催化剂催化松香氢化反应的催化性能,结果表明Ni/Al2O3-MxOy催化剂催化松香氢化具有较好的催化性能,枞酸转化率可达98%以上,氢化产物达到国家普通氢化松香(特级)标准.产物主要组分与Pd/C催化剂催化所得的氢化产物基本相同.     

硝基苯催化加氢制对氨基苯酚工艺研究

介绍了硝基苯催化加氢制对氨基苯酚的工艺路线 ,并对其影响因素进行了探讨 ,得出最佳制备工艺 ,即在 85℃、硫酸含量 1 7%、体积比 6 .6、氢压 0 .2MPa、反应时间 2h等条件下 ,硝基苯转化率为81 .9% ,对氨基苯酚选择性 98.9%。