Low temperature oxidation of methane over Pd/SnO2 catalyst

Catalytic activities of supported Pd were investigated for low temperature oxidation of methane. Pd/SnO₂ catalysts demonstrated excellent activity for methane oxidation in spite of their low surface area. The catalytic activity of Pd/SnO₂ was strongly affected by the preparation procedure. Impregnation of Pd on SnO₂ using aqueous solution of Pd(CH₃COO)₂ was most effective in enhancing the catalytic activity. The catalytic activity was also improved when well-crystallized SnO₂ was employed as a support material. TEM observations revealed that catalytic activity is strongly influenced by the dispersion state of Pd. For the active catalysts, strong interaction between Pd and SnO₂ support was observed in the adsorption of oxygen.     

Multiplicity in the partial oxidation of propylene over a copper-molybdena catalyst

Measurement of rates of formation of acrolein and acetaldehyde in the partial oxidation of propylene over a copper molybdate catalyst were made under steady-state and transient modes. These measurements disclosed a rate of product formation multiplicity apparently attributable to the oxidation state of the catalyst and not to surface phenomena usually thought to be the source of hysteresis in catalytic systems.     

以SDB为载体的疏水催化剂在化学工业中的研究进展

在反应物、反应介质或产物中有水的一些催化反应过程中,水对亲水性催化剂的活性及寿命影响很大。疏水性催化剂可以克服由于水对活性组分覆盖而使催化剂的活性减弱及寿命降低等不足。SDB（苯乙烯-二乙烯基苯共聚物）以其独特的疏水性能,近年来在疏水催化剂制备方面愈来愈得到广泛的关注。本文综述了近年来以SDB为载体的疏水催化剂在核化工及合成饱和酸/酯、烯酸/酯等化学品方面的研究进展,展望了其良好的应用前景。     

Direct partial oxidation of methane over ZSM-5 catalyst: Zn-ZSM-5 catalyst studies

Extended studies on Zn-ZSM-5 catalyst for the production of liquid hydrocarbons in the direct partial oxidation (DPO) of CH₄ with O₂ are reported. Previously, it was reported that metal-containing ZSM-5 catalysts could produce C₅₊ hydrocarbons from pure CH₄/O₂ feeds without feed additives. Zn-ZSM-5 produced the highest C₅₊ yields of the catalysts tested. This work shows that the method of introducing Zn onto the catalyst, ion-exchange versus impregnation, does not significantly alter C₅₊ yields if low Zn content is maintained ( 0.4–0.5 wt%). Liquid hydrocarbon yields in this system doubled after 8 h on stream while overall C₂₊ yields increased by over 300%. Mechanistic implications of these findings are discussed. Finally, processing a natural gas feed over Zn-ZSM-5 gave higher C₅₊ yields over CH₄ feed but these yields were not improved over previously published results using HZSM-5.     

络合还原法制备的Pd/C催化剂对甲酸氧化的电催化性能

分别以硼氢化钠和乙二醇为还原剂,经络合还原法制备了炭载钯（Pd/C）催化剂。透射电镜（TEM）和X射线粉末衍射谱（XRD）结果表明,以乙二醇为还原剂制备的Pd/C催化剂中Pd粒子具有较小的粒径、均匀的粒径分布和较大的相对结晶度,Pd粒子的平均粒径和相对结晶度分别为4.2±2 nm和1.88。电化学测试结果显示,以乙二醇为还原剂制备的Pd/C催化剂具有较大的电化学活性面积,对甲酸氧化表现出较高的电催化活性和稳定性。     

NiO/MgO整体式催化剂上甲烷部分氧化制备合成气

甲烷部分氧化制备合成气反应过程具有反应速率快、能耗低和H₂与CO物质的量比适用于合成甲醇及F-T合成等优点,是一种有希望替代传统水蒸汽重整的方法。研究在NiO/MgO蜂窝陶瓷整体式催化剂上的甲烷部分氧化过程,主要考察涂层载体、活性组分Ni含量、涂层载体前驱体、焙烧温度和还原温度对催化剂反应性能的影响。采用XRD、H₂-TPR和N2吸附等表征前驱体及其负载活性组分NiO后的晶相、还原特性和吸附性能。结果表明,采用浸渍法制备催化剂时,Mg(NO₃)₂为涂层载体MgO前驱体,在NiO负载质量分数20%、焙烧温度（500~600） ℃和还原温度750 ℃条件下制备的催化剂NiO/MgO-N性能较好,活性较稳定;以NiO/MgO-N为催化剂,在反应温度800 ℃、n(O₂)∶n(CH₄)＝0.5和空速9 723 h^-1条件下,CH₄转化率94.4%,H₂选择性99.9%,CO选择性92.9%。     

Pd/Ce基催化剂催化氧化氯苯的性能

采用等体积浸渍法制备Pd/Al₂O₃系列催化剂,考察不同Pd负载量对催化剂催化氯苯活性的影响,结果表明0.75%Pd/Al₂O₃催化剂活性最优,采用BET、H₂-TPR、SEM等对催化剂进行表征分析,表明添加Ce后氧化能力增强,催化氧化效率提高。对催化产物进行分析,使用离子色谱分析了无机Cl^-生成情况及其选择性,使用GC-MS定性分析了有机副产物,发现350℃时有少量苯生成。同时考察了焙烧温度、氯苯浓度、空速对催化活性的影响,结果表明焙烧温度过高或过低都会影响催化剂的活性,在550℃焙烧的催化剂活性更优,400℃时氯苯转化率为96%;氯苯入口处质量浓度在1500～6000mg/m³时,浓度升高,催化氯苯活性降低;空速在15000～30000h^-1时,空速对氯苯催化活性影响不大,但继续提高空速会明显降低催化活性。     

Methanol partial oxidation on carbon-supported Pt and Pd catalysts

Different Pt and Pd catalysts supported on an activated carbon were prepared by using different metal precursors. Prepared catalysts were pretreated at 400 °C under different atmospheres to decompose the precursor compound and reduce the metal. After pretreatments, the supported catalysts were characterized by H₂ chemisorption, X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy to know their metal dispersion, particle size, distribution and oxidation state. Afterwards, the catalysts were tested in methanol partial oxidation with two different O₂/CH₃OH molar ratios. Results obtained in this reaction were compared with those obtained for methanol decomposition in inert atmosphere. For Pt catalysts, there was an increase in methanol conversion and hydrogen production and a decrease in carbon monoxide production under oxidizing conditions. Both methanol conversion and partial oxidation reactions appear to be sensitive to Pt particle structure in the particle size range studied. Results obtained under oxidizing conditions differed between Pd and Pt catalysts. Finally, catalytic activity in methanol partial oxidation was more affected by Pt than Pd particle size in the size range studied.     

Pd/NaY催化苯甲醇无溶剂选择性氧化反应

采用离子交换法将[Pd(NH₃)₄]²⁺交换到NaY分子筛中,经焙烧和氢气还原制备金属钯粒径可调变的Pd/NaY催化剂。在(120~500) ℃改变焙烧温度,可以获得金属钯粒径(1.3~11.9) nm的Pd/NaY催化剂。Pd/NaY催化剂能够催化苯甲醇的无溶剂选择性氧化反应,对含不同钯粒径的Pd/NaY催化剂上醇选择性氧化研究发现,在1.6%Pd/NaY催化剂用量0.1 g、反应温度100 ℃、苯甲醇用量48.5 mmol和O₂流速3 mL·min^-1条件下,苯甲醇转化的真实转化频率随粒径变化在3.2 nm处呈最大值,该反应为结构敏感反应。     

VOC deep oxidation over Pt catalysts using hydrophobic supports

The active hydrophobic-supported Pt catalysts were synthesized for VOC deep oxidation at low temperature (less than 200°C). The destruction of VOC could cost less at lower temperature due to less energy consumption. The advantage using hydrophobic support was that moistures from atmosphere and oxidation would not be adsorbed on the surface. Thus the active sites would not be cloaked and catalyst activity could be maintained, especially at low temperature. The hydrophobicity of supports was characterized by wetting angles. Porous SDB (styrene divinylbenzene copolymer) was found near 113°, indicating high hydrophobicity. Three Pt catalysts were prepared on SDB and activated carbons by incipient wetness method. Specific surface areas were measured by nitrogen adsorption. The thermal stability of SDB catalyst was examined by TGA, and found no degradation below 200°C in air. The surface compositions of catalysts were analyzed by EDS. XRD showed that Pt was well dispersed on supports after hydrogen reduction at 160°C. The chemical states of Pt were investigated by XPS, and suggested that the oxidized Pt^IV might be the active sites in the reaction. The deep oxidation of toluene/air mixture was carried out to test the activity of catalysts. Pt/SDB showed the highest activity among the catalysts and could completely oxidize 90 ppm toluene/air at VHSV=21 000 h⁻¹, 150°C. Redox mechanism was proposed to reveal the enhanced kinetic rates. The results suggested that the rate of toluene oxidation might be enhanced due to the fact that water, one of the products, was expelled from the hydrophobic surface.     

钯炭催化剂在PTA生产中使用寿命的探讨

总结辽化聚酯厂PTA装置Pd/C催化剂的使用情况 ,着重分析了影响Pd/C催化剂使用寿命的原因 ,并探讨了在实际生产中延长Pd/C催化剂使用寿命的方法     

延长Pd/C催化剂使用寿命

本文围绕延缓Pd/C催化剂中Pd晶粒的烧结及减少Cu、Fe等离子对催化剂的污染的原理方面进行了工艺实验 ,提出了在使用初期 ,采取比原来值高的H2 供应量 ;中期控制在设计范围内 ;在使用后期 ,特别是超过设计寿命时 ,采取强化工艺 ,提高H2 分压 ,有效地保护Pd晶粒的活性中心 ,以延缓Pd/C催化剂中的Pd烧结及减少杂质离子的污染。并对受到污染而活性下降的Pd/C催化剂用碱洗恢复活性的方法进行了有关实验 ,常温下先用 2 0 %NaOH溶液浸泡 4h ,再用 5 %NaOH溶液浸泡 4h ,即能够有效地去除污染物 ,恢复催化剂的活性。延缓Pd/C催化剂中的Pd烧结和碱洗均能延长Pd/C催化剂使用寿命     

空气气氛下RuO2/ZSM-5催化醇的部分氧化反应

通过原位反应法制备了RuO₂/ZSM-5催化剂，并用XRD、XPS和TEM对合成的催化剂进行了表征，结果表明，RuO₂主要以20 nm左右的微晶分散在载体中，原位反应引入钌物种，没有改变载体ZSM-5的结构，大部分钌为四价。催化试验表明，在以空气为氧化剂的温和条件下，RuO₂/ZSM-5不仅可有效地催化芳香醇和带烯丙基的醇类（激活醇）氧化生成醛酮，而且对一些非激活醇也有较好的催化效果。     

整装式铝泡沫负载Pd催化剂Pd/AlOOH/Al-foam及其催化甲烷燃烧性能

以三维网络结构的铝泡沫板作为骨架基体和铝源,利用水热氧化法制备整装式拟薄水铝石(Al OOH/Al-foam)纳米阵列,随后通过丙酮辅助-初湿浸渍法,制备出整装式铝泡沫负载Pd催化剂Pd/Al OOH/Al-foam,用于低浓度甲烷催化燃烧反应。在制备条件优化过程中,发现催化剂性能受到纳米阵列的形貌特征、物相组成以及焙烧温度等因素的影响。其中,表面富含羟基的拟薄水铝石可促进Pd颗粒的均匀分散,也增强载体和Pd之间的相互作用,进而提高甲烷燃烧的低温活性。稳定性测试初期活性下降较快,主要原因是表层Al_2O_3纳米阵列载体和Pd纳米颗粒自身的不稳定性导致的Pd颗粒烧结。     

延长Pd/C催化剂使用寿命的途径

影响钯 炭催化剂使用寿命的因素主要有催化剂失活 ,运输、装填过程中的磨损 ,工艺操作条件等。延长催化剂的使用寿命的途径有正确的运输、装填方法 ,定期冲洗 ,定期碱洗和分阶段调整氢气加入量     

Pd/AC催化剂催化分解甲酸反应条件的研究

采用水浴振荡法,研究了振荡速度、催化剂粒径、催化剂用量、反应温度、反应时间等因素对Pd/AC催化剂催化分解甲酸活性的影响,得出了Pd/AC催化剂催化分解甲酸的优化条件。结果表明,在振荡速度为200 r/min、内/外扩散影响消除的条件下,将1.0 g150~180μm的Pd/AC催化剂与100 mL浓度为0.1 mol/L的甲酸水溶液进行分解反应,发现最佳反应温度为80℃,反应时间为60 min,Pd/AC催化剂催化分解甲酸的分解率可达到95%,在此优化条件下,Pd/AC催化剂对含甲酸的工业废水的分解率达80%。     

Pd/C催化剂催化邻硝基苯胺加氢制备邻苯二胺

卤代芳胺是重要的有机中间体,广泛应用于合成染料、农药、医药、香料及橡胶助剂等。卤代芳香硝基化合物通过液相催化加氢制备卤代芳胺的技术以其环境友好、产品质量稳定和工艺先进而受到重视。用负载型贵金属催化剂催化芳香硝基化合物选择加氢制备相应的芳胺有广泛的应用价值。采用邻硝基苯胺为原料,Pd/C为催化剂,低压催化加氢还原合成邻苯二胺,考察不同溶剂、反应压力、反应温度和反应时间对产物收率的影响。结果表明,在甲醇为溶剂、反应温度100 ℃、反应压力0.8 MPa和反应时间100 min条件下,邻苯二胺平均收率为97%。与传统硫化碱还原或铁粉化学法还原工艺相比,以甲醇为溶剂,Pd/C催化剂催化加氢法在减少废水和降低成本等方面有较大优势。     

PTA加氢精制Pd/C催化剂活性降低原因及处理

洛阳PTA装置氧化母液回收系统投用后,进口钯/碳(Pd/C)催化剂使用过程中活性降低,对其原因进行分析和探讨,通过对催化剂床层进行翻床处理,并使用脱离子水清洗,确保该床催化剂的正常使用。     

Reaction pathways in the selective oxidation of propane over a mixed metal oxide catalyst

The catalytic properties of a Mo–V–Te–Nb–O mixed metal oxide catalyst were investigated in the selective oxidation of propane and its corresponding partial oxidation intermediates. Propane oxidation pathways are proposed based on experimental findings.     

LiLaNiO_x/γ-Al_2O_3催化剂上甲烷加压部分氧化制合成气

考察LiLaNiO_x/γ—Al_2O_3催化剂对甲烷加压[(0.2～1.0)MPa]部分氧化制合成气反应的催化性能。结果表明,LiLaNiO_x/γ—Al_2O_3催化剂具有优良的甲烷部分氧化催化性能,在850℃和1.0 MPa条件下,甲烷转化率和CO选择性分别达76.2%和82.5%。在100 h连续实验中,反应活性及选择性保持不变,显示出较高的催化稳定性。采用XRD、XPS和TG—DTA方法对反应前后催化剂的晶体结构、表面性能以及抗积炭性能进行表征,结果表明,LiLaNiO_x/γ-Al_2O_3催化剂具有较高的结构稳定性和抗积炭性能。