Synergistic effect for bimetallic Ru-Tc catalysts of cyclohexane dehydrogenation

Catalytic properties of the Ru-Tc/support (-Al₂O₃, Y₂O₃, and SiO₂) systems in the dehydrogenation of cyclohexane have been studied. The catalytic activity of the bimetallic catalysts depends on the nature of the support. A nonadditive increase in the catalytic activity of the bimetallic catalysts in comparison with monometallic samples was established. The value of the synergistic effect depends on the ratio between the amounts of the supported metals and the nature of the support. By using the diffuse reflectance spectra in UV- and visible regions and hydrogen chemisorption techniques, the modifying influence of the ionic metal species on the catalytic properties was shown.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1959–1963, August, 1996.     

Effect of cerium addition on catalytic performance of PtSnNa/ZSM-5 catalyst for propane dehydrogenation

The effect of cerium addition on the catalytic performance of propane dehydrogenation over PtSnNa/ZSM-5 catalyst has been investigated by reaction tests and some physicochemical characterization such as XRD,BET,TEM,XPS,NH 3-TPD,H 2 chemisorption,TPR and TPO techniques.It has been found that with suitable amount of cerium addition,the platinum dispersion increased,while the carbon deposition tended to be eliminated easily.In these cases,the presence of cerium could not only realize the better distribution of metallic particles on the support,but also strengthen the interactions between Sn species and the support.Additionally,XPS spectra confirmed that more amounts of tin could exist in oxidized form,which was advantageous to the reaction.In our experiments,PtSnNaCe(1.1 wt%)/ZSM-5 catalyst exhibited the best catalytic performance.After running the reaction for 750 h,propane conversion was maintained higher than 30% with the corresponding selectivity to propylene of about 97%.     

Selective deposition of Sn on the Pt surface of Pt/ZnAl2O4 catalyst and addition effect on isobutane dehydrogenation

Pt−Sn bimetallic catalysts were prepared by a CVD technique in which Sn was added by passing volatile organometallic compounds over Pt/ZnAl₂O₄ in a H₂ flow. Mixed Pt−Sn sites improve the activity of isobutane dehydrogenation, while Sn on the support improves the selectivity.     

纳米碳材料负载铂催化剂在环己烷脱氢反应中的催化性能研究

制备了纳米碳材料负载铂的催化剂,通过N₂吸附、TEM、XRD技术分别对载体的BET比表面积和催化剂结构、形貌和粒径大小进行了表征。考察了不同催化剂在环己烷脱氢反应中的催化性能以及温度对纳米碳颗粒负载铂催化剂活性的影响。结果表明,锚定在不同碳载体上的铂有较好的分散性,粒径较小,粒度分布范围较窄并且具有相同的晶型结构。孔状纳米碳颗粒负载铂催化剂的活性高于碳纳米管和高比表面的活性炭负载铂催化剂,并且在低温条件下已经显示了较高的活性,尤其是中空碳颗粒负载铂催化剂在环己烷脱氢反应中显示了好的活性和稳定性。     

钡改性对Cr_2O_3/Al_2O_3催化剂异丁烷脱氢性能的影响

采用浸渍法制备了不同BaO负载量的Cr_2O_3/Al_2O_3催化剂,利用XRD、BET、NH3-TPD和O2-TPO等表征方法对钡改性前后的催化剂进行了分析;在反应温度560℃、反应压力0.1MPa、催化剂用量10mL、GHSV=400h-1的条件下,在固定床反应器上考察了其异丁烷脱氢反应的性能。结果表明,钡的引入影响了活性组分Cr2O3的分散,导致了催化剂比表面积的降低,但影响并不显著;钡的引入降低了催化剂表面的酸性、减少了反应过程中催化剂的积炭,改善了催化剂的选择性,提高了催化剂的稳定性。当BaO负载量为3%时,催化剂的性能最佳。     

Improvements in selectivity and stability of Rh catalysts modified by SnBu4. dehydrogenation of isobutane to isobutene

RhSn/SiO₂ bimetallic catalysts prepared via an organometallic route have proved to be very active and selective toward several hydrogenation reactions. In this work these catalysts were studied for the dehydrogenation of isobutane to isobutene. It was found that Rh/SiO₂ monometallic catalysts had a null selectivity to isobutene, and this selectivity increased up to more than 90% after the addition of tin, using SnBu₄ as precursor.     

Effect of calcination conditions on the properties of a catalyst for ethylbenzene dehydrogenation

Summary The effects of calcination conditions on the properties of the catalyst for dehydrogenation of ethylbenzene were studied by using TG, DTA, and XRD. The formation temperature of polyferrite was higher than 600°C. The strength of the catalyst changed during calcination. Higher temperature enhanced the strength and improved the activity of catalyst. The calcination model has great influences on the catalyst performance. Multi-stage calcination improved the catalyst activity.     

Synergistic effect between solid wastes and intumescent flame retardant on flammability and smoke suppression of thermoplastic polyurethane composites

Phosphorus tailings and fly ash both are solid wastes and do harm to the environment. Here, they were added into thermoplastic polyurethane (TPU) matrices together with intumescent flame retardants (IFR), and the synergistic effects between IFR and phosphorus tailings or fly ash for improving the flame retardancy of TPU were investigated. The cone calorimeter test (CCT) results indicated that adding phosphorus tailings or fly ash substitute for part of IFR could obtain a better flame retardant effect. The peak heart release rate (PHRR) of TPU/25 wt% IFR composites exhibited a reduction of 77% than that of neat TPU, and the total smoke production presented a reduction of 16%. However, the PHRR value and total smoke production of the sample TPU/20 wt% IFR/5 wt% phosphorus tailings were reduced by 91% and 57%, respectively, compared to that of neat TPU. The dense char promoted by the presence of IFR and phosphorus tailings or fly ash delayed the diffusion of volatile pyrolysis products and transmission of heat and oxygen to the underlying material. Therefore, a certain amount of phosphorus tailings or fly ash can be used as synergistic agents with IFR to enhance the fire safety of TPU materials. From another aspect, it also provides a promising way for recycling use of phosphorus tailings and fly ash.     

Effect of particle size in the hydrogenation of crotonaldehyde on supported Pt and Pt-Sn catalysts

The present work reports the effect of metal particle size on the selectivity to crotyl alcohol (S_UOL) in the liquid phase hydrogenation of crotonaldehyde over SiO₂ and a-Al₂O₃-supported Pt and Pt-Sn catalysts. It was demonstrated that, for the monometallic catalysts, a higher particle size led to a higher S_UOL, while for the bimetallic catalysts, this effect was not so important.     

Isobutane dehydrogenation over chromia alumina catalysts prepared from MIL-101: Insight into chromium species on activity and selectivity

Various mesoporous chromia alumina catalysts were prepared by five different methods based on a metal-organic framework MIL-101 and their catalytic performances over isobutane dehydrogenation were investigated. The highly dispersed chromium species were produced on catalyst KCr Al-I1 with largest specific surface area of 198 m2 g-1prepared with aluminium isopropoxide(Al(i-OC3H7)3) by ultrasonic impregnation method. However, the catalyst KCr Al-I2 synthesized by stirring impregnation possessed crystalline α-Cr2O3 phase, which was poorly dispersed. Two types of Cr-rich and Al-rich Crx Al2-xO3 solid solutions, designated as Cr Al-I and Cr Al-II phase, were formed over the catalysts KCr Al-I3(prepared by Al(i-OC3H7)3with nitric acid regulation), KCr Al-C4(prepared by aluminium chloride hexahydrate) and KCr Al-N5(prepared by aluminium nitrate nonahydrate). Catalytic evaluation results revealed that KCr Al-I1 exhibited the high isobutane conversion due to its highly dispersed chromium species. However, KCr Al-I3, KCr Al-C4 and KCr Al-N5 showed the higher isobutene selectivity(95.2%-96.4%) on account of the formation of chromia alumina solid solutions in the catalysts. Moreover, the solid solution over the chromia alumina catalysts could greatly suppress the coke formation.     

Isobutane dehydrogenation over chromia alumina catalysts prepared from MIL-101:Insight into chromium species on activity and selectivity

Various mesoporous chromia alumina catalysts were prepared by five different methods based on a metal-organic framework MIL-101 and their catalytic performances over isobutane dehydrogenation were investigated. The highly dispersed chromium species were produced on catalyst KCrAI-I1 with largest specific surface area of 198 m2-g-1 prepared with aluminium isopropoxide （Al（i-OC3HT）3） by ultrasonic im- pregnation method. However, the catalyst KCrAI-I2 synthesized by stirring impregnation possessed crystalline a-Cr203 phase, which was poorly dispersed. Two types of Cr-rich and Al-rich CrzA12_zO3 solid solutions, designated as CrAI-I and CrAI-II phase, were formed over the catalysts KCrAI-I3 （prepared by Al（i-OC3HT）3 with nitric acid regulation）, KCrA1-C4 （prepared by aluminium chloride hexahydrate） and KCrA1-N5 （prepared by aluminium nitrate nonahydrate）. Catalytic evaluation results revealed that KCrAI-I1 exhibited the high isobutane con- version due to its highly dispersed chromium species. However, KCrAI-I3, KCrA1-C4 and KCrA1-N5 showed the higher isobutene selectivity （95.2%-96.4%） on account of the formation of chromia alumina solid solutions in the catalysts. Moreover, the solid solution over the chromia alumina catalysts could greatly suppress the coke formation.     

Synergetic effect between NiO and Ni3V2O8 in propane oxidative dehydrogenation

The oxidative dehydrogenation (ODH) of propane was investigated on Ni-V-O catalysts in a wide range of vanadium contents (5-40%). The addition of a small amount of vanadium significantly increased the catalytic activity of NiO for oxidative dehydrogenation of propane to propene. The formation of propene has a good correlation with the coexistence of NiO and Ni₃V₂O₈. This result strongly suggests that a synergetic effect exists between them in Ni_XV_1-XO_Y (X = 0.95 to 0.6). The best results were obtained with a high Ni/V ratio (e.g. X = 0.95 to 0.85). The active sites and selective oxygen species are discussed. The influence of the catalyst preparation technique and the redox properties of the catalyst were also examined.     

Synergistic effect between phosphorus tailings and aluminum hypophosphite in flame‐retardant thermoplastic polyurethane composites

The massive accumulation of phosphorus tailings (PT) not only occupies land resources and also causes great threat to ecological environment and human security. It is of great significance to explore the resource utilization of PT in some fields. Herein, aluminum hypophosphite (AHP) and PT are blended together to enhance the flame retardancy of thermoplastic polyurethane (TPU) composites, and the synergistic effects between AHP and PT are investigated systematically. Cone calorimeter test (CCT) results indicate that the peak heat release rate (PHRR) and total heat release (THR) of the samples containing 25 wt% AHP are decreased by 89% and 68%, respectively, and the total smoke release (TSR) show a reduction of 58.8%, in comparison with those of neat TPU. For the sample TPU/22.5AHP/2.5PT, the PHRR, THR, and TSR are decreased by 91.2%, 70%, and 63%, respectively. Scanning electron microscopy (SEM) analysis results demonstrate that the addition of PT can facilitate the generation of dense and compact char layers, preventing the release of heat and smoke effectively. All the abovementioned results indicate that the synergistic effects are existed between AHP and PT for enhancing the fire safety of TPU composites, which can provide a new way for the utilization of PT.     

丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na+助剂组分的作用

用微型催化反应装置结合X射线衍射(XRD)、H₂化学吸附、NH₃吸附-程序升温脱附(NH₃-TPD)和H₂-程序升温还原等多种物理化学手段研究了丙烷脱氢负载型PtSnNa/SUZ-4催化剂中Na⁺助剂组分的作用。结果表明,Na⁺组分可中和SUZ-4载体表面的强酸中心、提高催化剂的Pt金属分散度、抑制脱氢产物的裂解和积炭的生成,从而提高催化剂的丙烷脱氢选择性和反应稳定性。但是过量Na⁺组分的存在会削弱Sn物种与载体之间的相互作用,使其易被还原,导致催化剂丙烷脱氢活性显著下降。     

Effect of aluminum modification on catalytic properties of PtSn-based catalysts supported on SBA-15 for propane dehydrogenation

The catalytic properties of PtSn-based catalysts supported on siliceous SBA-15 and Al-modified SBA-15, such as Al-incorporated SBA-15 (AlSBA-15) and alumina-modified SBA-15 (Al2O3/SBA-15), for propane dehydrogenation were investigated. Al2O3/SBA-15 was prepared either by an impregnation method using aluminum nitrate aqueous solution, or by the treatment of SBA-15 with a Al(OC3H7)3 solution in anhydrous toluene. N2-physisorption, FT-IR spectroscopy, solid-state 27Al MAS NMR spectroscopy, hydrogen chemisorption, XRF, NH3 temperature-programmed desorption, X-ray photoelectron spectroscopy and TPO were used to characterize these samples. Among these catalysts, the PtSn-based catalyst supported on Al2O3/SBA-15, which was grafted with Al(OC3H7)3, exhibited the best catalytic performance in terms of activity and stability The possible reason was due to the high Pt metal dispersion and/or the strong interactions among Pt, Sn, and the support.     

高浓度杂多酸溶液催化性能的研究1: 一种新型异丁烷/丁烯烷 基化催化剂

在异丁烷、丁烯烷基化反应中研究了一种由杂多酸和醋酸组成的新型液体催化剂的催化性能,醋酸作为溶剂对杂多酸具有共协效应,系统研究了形成活性相的条件,杂多酸结晶水含量对活性相的形成和催化活性均有显著影响,这一催化体系具有与硫酸可比的催化活性。     

Hydrotalcite-supported gold catalyst for the oxidant-free dehydrogenation of benzyl alcohol: studies on support and gold size effects

Gold nanoparticles with uniform mean sizes (≈3 nm) loaded onto various supports have been prepared and studied for the oxidant-free dehydrogenation of benzyl alcohol to benzaldehyde and hydrogen. The use of hydrotalcite (HT), which possesses both strong acidity and strong basicity, provides the best catalytic performance. Au/HT catalysts with various mean Au particle sizes (2.1-21 nm) have been successfully prepared by a deposition-precipitation method under controlled conditions. Detailed catalytic reaction studies with these catalysts demonstrate that the Au-catalyzed dehydrogenation of benzyl alcohol is a structure-sensitive reaction. The turnover frequency (TOF) increases with decreasing Au mean particle size (from 12 to 2.1 nm). A steep rise in TOF occurs when the mean Au particle size becomes smaller than 4 nm. Our present work suggests that the acid-base properties of the support and the size of Au nanoparticles are two key factors controlling the alcohol dehydrogenation catalysis. A reaction mechanism is proposed to rationalize these results. It is assumed that the activation of the β-C-H bond of alcohol, which requires the coordinatively unsaturated Au atoms, is the rate-determining step.     

生物质和废塑料混合热解协同特性研究

选取聚丙烯(PP)和竹屑作为废塑料与生物质的典型代表,在热重分析仪和固定床台架上研究了塑料掺混比例对混合热解失重特性、动力学机理、产物分布行为等特性的影响,并分析了混合热解时生物质和废塑料间的协同作用机制。结果表明,随着塑料掺混比例的增加,混合热解终止温度由501℃降低至471℃,主要热解温度区间缩短;混合热解所需活化能呈现先减小后增大的趋势,在塑料掺混比例为0.25时取得最小值。通过对比实验数据和理论数据发现,生物质与废塑料混合热解具有很强的协同作用:该协同作用降低了生物质反应所需能量,增加了废塑料反应所需能量,降低了混合热解过程的总活化能;此外,协同作用促进大分子挥发分转化为小分子气体,促进芳烃、烷烃等烃类生成,抑制CO₂、苯酚、羧酸、呋喃和酮类等含氧物质生成。     

Tetradecanol dehydrogenation over CuO catalyst supported on BaO, CaO and MgO

Bimetallic Cu/Mg, Ca, Ba mixed oxide compounds acted as catalyst in the dehydrogenation of tetradecanol into tetradecanal, and were characterized by thermal gravimetric analysis, surface area, X-ray diffraction, temperature-programmed reduction and desorption of CO₂. Alkaline earth oxides increased the total basic site concentration in the order of Mg>Ca>Ba. A correlation was found between the total basic site concentration and initial dehydrogenation rate. This revised version was published online in June 2006 with corrections to the Cover Date.     

Design and synthesis of the honeycomb PtSnNa/ZSM-5 monolithic catalyst for propane dehydrogenation

A novel PtSnNa/ZSM-5 monolithic catalyst was designed and synthesized for the propane dehydrogenation reaction, which was a significant transformation in industry. Experimental results showed that although the propane conversion and the propylene selectivity gradually fell down along with the reaction time, the descent speed of the PtSnNa/ZSM-5 monolithic catalyst was slower than that of the granule catalyst and the propane conversion and propylene selectivity of the reaction with monolithic catalyst still remained at a high level after 12 hr. The monolithic catalyst had regular pore structure that facilitated the separation of the product from the catalyst and reduced the limitation on internal and external diffusion and mass transfer, and led to the high catalytic activity and stability. The catalyst could be easily fabricated and was of highly industrial application potential.