美罗培南合成用钯炭催化剂的失活及再生研究

采用物理吸附、X射线衍射、扫描电镜、X射线能谱及等离子体发射光谱法对在美罗培南合成过程中失活的Pd/C催化剂比表面积、孔容、孔径、钯粒径形貌、表面元素及钯含量的变化进行分析,对催化剂的失活原因及再生方法进行研究。结果表明,催化剂在反应过程中吸附体系物质对钯活性中心的覆盖包裹及金属钯的少量流失是催化剂失活的主要原因。以30%四氢呋喃水溶液在超声条件下洗涤可以部分去除催化剂表面沉积的有机物,同时补加质量分数30%催化剂时,再次使用时效果较好。     

钯碳催化剂的应用和失活原因及再生

对钯碳催化剂在精细化工中加氢的应用、催化剂失活的多种原因和再生进行了分析，把催化剂的失活原因归纳为活性组分流失、中毒、堵塞、烧结四大类，文章提出了对催化剂的再生，利用甲醛溶液还原可以有效再生失活钯碳催化剂：     

EDS表面分析研究Pd／C催化剂的失活原因

利用Ｘ射线能谱仪及原子吸收研究了对苯二甲酸加氢精制过程中失活的钯炭催化剂的失活原因,结果表明,原料中的含硫化合物,以二甲苯氧化工段的催化剂四溴乙铵,设备腐蚀和溶剂水中的离子均会沉积在钯炭催化剂的表面,引起催化剂加氢活性的下降,利用ＥＤＳ分析把炭催化剂及断面的元素沉积是分析催化剂失活原因的有效方法。     

铜催化剂在涉氢反应中的失活机制和稳定策略

铜基催化剂对C==O、C—H、O—H和H—H等化学键具有独特活性能力，因而被广泛应用于CO_x、醛、酸、酯加氢和醇脱氢等涉氢反应中。然而铜纳米颗粒塔曼温度较低，容易发生颗粒聚集长大而导致催化剂不可逆失活，限制了铜基催化剂的广泛应用。本文首先从表面能、金属物种表面迁移等角度入手系统地介绍了铜基催化剂的失活机理。然后，根据失活原因回顾了铜基催化剂在增强金属与载体相互作用、空间物理固定和合金化等方面的多种稳定策略。最后，通过现有结果分析了未来铜基催化剂的发展方向，指出可以通过失活机理的深入研究，借鉴新材料合成工艺和方法，制备廉价的新型铜基催化剂，为涉氢反应催化剂长寿命运行奠定基础。     

催化剂制备与研究 中低温煤焦油加氢裂化催化剂的表征与分析

通过对反应前后的煤焦油加氢裂化催化剂进行表征与分析,研究影响中低温煤焦油加氢催化剂失活的原因,以煤焦油组分特点为依据,分别考察加氢裂化催化剂的活性元素、积炭、金属沉淀、分散度和中心酸性等对催化剂寿命的影响。结果表明,煤焦油加氢催化剂的失活原因主要为积炭失活、金属沉积和水热失活;催化剂中较低的金属钙含量、良好的水热稳定性及较低的L酸含量有利于催化剂寿命的提高。     

中低温煤焦油加氢裂化催化剂的表征与分析

通过对反应前后的煤焦油加氢裂化催化剂进行表征与分析,研究影响中低温煤焦油加氢催化剂失活的原因,以煤焦油组分特点为依据,分别考察加氢裂化催化剂的活性元素、积炭、金属沉淀、分散度和中心酸性等对催化剂寿命的影响。结果表明,煤焦油加氢催化剂的失活原因主要为积炭失活、金属沉积和水热失活;催化剂中较低的金属钙含量、良好的水热稳定性及较低的L酸含量有利于催化剂寿命的提高。     

关于精对苯二甲酸(PTA)生产用钯碳催化剂的制备研究

本文主要对精对苯二甲酸(PTA)生产用钯碳催化剂的制备与再生进行了分析。首先对新鲜催化剂制备与催化剂活性评价进行了分析,接着对制备过程对催化剂活性的影响进行了分析,主要是吸附周期及还原过程的影响,最后对钯催化剂寿命延长及再生进行了研究,钯碳催化剂寿命延长失活与钯碳催化剂再生能够再生失活钯碳催化剂。     

催化氧化葡萄糖中失活钯铋炭催化剂再生方法探讨

探讨了钯铋炭催化剂失活的原因。认为其中活性组分钯的聚集、被氧化、流失及助剂铋的流失是主要因素。在不添加活性组分钯的前提下．采用不同的方法对失活催化剂进行再生实验,使用失活催化荆催化氧化葡萄糖4h葡萄糖的转化率达到20％左右．先氧化后还原处理的催化剂催化氧化葡萄糖4h葡萄糖的转化率达到64％以上,催化剂得到再生。     

醋酸氯化液氢解制氯乙酸用Pd/C催化剂的失活研究

醋酸氯化液加氢脱氯制备氯乙酸反应中,Pd/C催化剂活性和稳定性决定生产成本。对浸渍还原法制备的钯负载质量分数0.8%的Pd/C催化剂进行评价实验。结果表明,在无氯化氢条件下,催化剂活性和稳定性较好;在含氯化氢条件下,催化剂活性和稳定性下降。采用SEM、XRD、原子吸收、BET和DTA等手段对使用前后的催化剂进行表征。结果表明,氯化氢加速Pd晶粒烧结长大和活性组分金属Pd流失是催化剂失活的主要原因。在催化剂使用过程中,表面积炭物的形成也导致催化剂失活。     

制氢装置转化催化剂失活原因分析及对策

中石化西安分公司制氢装置转化催化剂在短期生产运行过程中,因催化剂积碳导致转化炉管表面出现大面积花斑,近半数炉管出现红管,炉管差压增大,转化出口甲烷含量超标,芳烃穿透.对催化剂失活原因进行细致分析后表明:装置开停车频繁;转化催化剂多次积碳-烧碳使催化剂表面剥蚀破碎、跑损严重为主要原因.针对失活原因制定了相应对策.     

The activity and stability of Pd/C catalysts in benzene hydrogenation

Carbon black supported Pd catalysts were prepared by an incipient wetness impregnation method and tested for benzene hydrogenation. The catalytic activity is subjected to serious deactivation. However, the deactivation is found to depend on the test procedure. When the reaction is performed under constant flow of benzene and hydrogen during a stepwise temperature-ascending-descending test sequence, no deactivation is observed. Deactivation occurs when the reaction gas is replaced by a He purge during temperature changes in the test sequence. The Pd/C catalysts prepared from different precursors show similar activation energy and similar TOF as oxide-supported Pd catalysts when deactivation is confined by applying suitable experimental procedures. EXAFS, TEM, and TGA results suggest that both Pd sintering and carbonaceous residue are responsible for the deactivation.     

Pd/C催化剂的失活机理与回收再生研究进展

Pd/C催化剂广泛应用于加氢脱卤反应,但其失活机理及再生处理存在一定的问题和难点。综述了Pd/C催化剂的制备工艺、失活机理及回收再生工艺的研究进展,对传统钯氨络合工艺、还原法、吸附法和超临界流体再生Pd/C催化剂技术进行了分析讨论,对应用存在的问题及今后的研究方向做了展望。     

Effect of Pd precursor salt on the activity and stability of Pd-doped hexaaluminate catalysts for the CH4 catalytic combustion

This study reports the influence of palladium salt precursor on the catalytic activity of palladium-doped hexaaluminate catalysts for the combustion of 1 vol% CH₄ in the presence of CO₂ and H₂O as inhibitors. Thermal stability of the catalysts is evaluated in long-term catalytic test at 700 °C. The hexaaluminate supports were synthesized using two different procedures: conventional coprecipitation and solid/solid diffusion procedure. Palladium impregnation was carried out by two different routes using Pd(NO₃)₂ in water or Pd(acac)₂ in toluene as impregnation solution. It was observed that using Pd(acac)₂ as precursor allows to attain higher dispersion of the active phase (Pd particles size <3 nm). Compared to the catalysts obtained by impregnation of Pd(NO₃)₂, higher catalytic activities are then obtained. Nevertheless, a deactivation of the samples obtained using Pd(acac)₂ is observed. At the end of the stability test, almost similar catalytic activity is obtained whatever the palladium precursor. Reduction–reoxidation experiment showed that this deactivation is irreversible, and TEM analysis suggest that this deactivation is related to the sintering of Pd particles under reaction over samples synthesized using Pd(acac)₂ as precursor.     

An investigation on Pd/C industrial catalysts for the purification of terephthalic acid

Commercial 0.5% Pd/C catalysts for the production of purified terephthalic acid (PTA) have been investigated by several physical techniques (SEM-EDS, CO chemisorption, XRD) and by activity tests performed in conditions strictly similar to those of industrial operation. These catalysts show a strongly external Pd distribution, pointing to high Pd concentrations in the outer layers of the carrier. It was found that Pd sinters very easily and that a rough proportionality exists between catalytic activity and Pd surface area. Pd sintering was shown to be an important cause of deactivation for PTA catalysts. However, in some cases deactivation occurs by sulphur poisoning, with the formation of a Pd sulphide (Pd₄S).     

Hydrogenation of 2-Ethylanthraquinone over Pd/SiO2 and Pd/Al2O3 in the Fixed-Bed Reactor. The Effect of the Type of Support

The effects of the type of support and Pd concentration profile in alumina and silica supported egg-shell catalysts and their performance in the hydrogenation of 2-ethylanthraquinone (eAQ) were studied in 'Anthra' (AQ) and 'All-Tetra' systems. The activity and deactivation of catalysts were determined in the fixed-bed reactor. Solution saturated with hydrogen, (concentration of active quinones 60g/dm³, eAQ in the AQ system, 30% of eAQ and 70% of H₄eAQ–2-ethlytetrahydroanthraquinone, in the All-Tetra system) was circulated through the catalyst bed at temperature 50°C and pressure 5bar. The contents of eAQ, active quinones, H₄eAQ and degradation products were determined in the course of hydrogenation by GC method. The egg-shell palladium catalysts (1–2wt% Pd) prepared by the precipitation of palladium hydroxide onto alumina and silica supports pre-impregnated with various alkaline (NaHCO₃, NaH₂PO₄, Na₂SiO₃) solutions were used in the hydrogenation experiments. Pd concentration profile inside the grains of catalysts was characterized by scanning electron microscopy. A difference between alumina and silica carriers with respect to the course of side reactions producing degradation products was found. Degradation of quinones in the hydrogenolytic reactions predominated on alumina supported catalysts, while the catalysts with silica favoured the hydrogenation of aromatic rings resulting in H₄eAQ-active quinone. As a crucial factor for the decrease in the activity during the hydrogenation run, the reactivity of catalyst in the hydrogenolytic reactions was established. Alumina supported catalysts exhibited much higher deactivation than those of silica supported ones. Silica carrier as well as silica species introduced onto alumina under pre-impregnation with Na₂SiO₃ exhibited an advantageous role in the catalyst performance, in terms of activity and deactivation.     

苯甲酸加氢用钯碳催化剂的制备、失活及再生研究

研究了苯甲酸加氢用钯碳催化剂的制备、失活及再生。提出了钯碳催化剂的制备关键、加入甲烷化助剂可以延长钯碳催化剂寿命、利用超临界流体再生方法可以有效再生失活钯碳催化剂。     

Deactivation of metal exchanged zeolite catalysts during exposure to chlorinated hydrocarbons under oxidizing conditions

Deactivation of modified cation exchanged zeolite catalysts was studied during complete oxidation of methylene chloride, trichloroethylene and carbon tetrachloride over a temperature range of 175 to 400°C. Coking was found to be the cause of deactivation. However, the catalysts could be completely regenerated by oxidation in air at 450°C. Two different formulations of modified cobalt exchanged Y zeolite catalysts were tested to determine the coking and deactivation rates. Increased cation content increased deactivation and coking over a period of about 1000 hours. Changing the type of zeolite from larger pore Y to medium pore mordenite increased deactivation. The type of chlorinated feed also affected coking and deactivation with the rate of deactivation increasing in the order of trichloroethylene> methylene chloride> carbon tetrachloride. Both coking and deactivation increased with decreasing temperature. Higher space velocity produced more deactivation for trichloroethylene oxidation at 275°C. Based on these results a mechanism for coking is proposed with CO as the possible reaction intermediate that leads to the formation of coke.     

Pd/Al2O3催化剂用于连续重整汽油全馏分加氢的失活分析

研究了负载在氧化铝载体上的贵金属Pd基催化剂在重整生成油选择性加氢脱烯烃反应中的性能。结果表明,在连续重整生成油全馏分的选择性加氢实验中，采用现有工业常用的工艺条件，单使用Pd作活性组分的Pd/Al₂O₃催化剂不能满足产品质量要求。探讨了切割馏分油加氢反应中催化剂失活原因，并对失活前后的催化剂采用XRD、SEM和FTIR等手段进行分析表征。结果表明，造成催化剂失活原因是催化剂表面油品中重组分等热敏类物质强吸附或聚合作用的结果。改进后的双金属Pd基催化剂UDO-01可用于重整生成油全馏分的选择性加氢脱烯烃反应，加氢后产品的溴价小于200 mg Br·(100 g-油)^-1,芳烃损失小于0.5%，且表现出好的稳定性。