复合分子筛催化剂上C9芳烃脱烷基的研究

将Ni负载在H-ZSM-5和H-MOR分子筛催化剂上，以异丙苯为模型化合物对分子筛催化剂加氢脱烷基性能进行评价。考察了分子筛复配比例、金属含量和酸浓度对催化剂活性的影响。结果表明，酸处理后的分子筛催化剂，异丙苯转化率和苯、甲苯、二甲苯(BTX)的收率有明显提高。当反应温度为340 ℃、压力0.8 MP和空速1 h^-1时，其转化率为81.5％，BTX收率为72.8％，选择性可达89.2％。     

分子筛催化C_9芳烃脱烷基的研究

将Bi、Ni、Mo、Pt分别负载在氢型ZSM-5、MOR、Y分子筛上,以异丙苯为模型化合物对分子筛催化加氢脱烷基性能进行评价,考察了不同金属的活性和分子筛结构。结果表明,不同分子筛载体上,不同金属脱烷基活性大小次序为:Pt>Mo>Ni>Bi;分子筛的孔结构可限制产物的形成,从而影响烷基转移反应和脱烷基反应二者的活性。此外,酸强度和密度的分布与金属同样重要,它们之间的平衡协同作用对催化剂的活性有着至关重要的作用。     

分子筛负载铂催化剂上四氢萘加氢裂解反应行为

四氢萘是多环芳烃加氢转化的产物或者中间体,其加氢裂解行为和规律的研究在重芳烃转化和脱除领域有着重要的意义。采用等体积浸渍法制备得到了氧化铝负载贵金属(Pt,Ir和Pd)催化剂和酸性分子筛(MOR和ZSM-5)负载铂双功能催化剂,考察了它们催化四氢萘加氢裂解的反应行为。氧化铝为载体时金属催化剂表面主要发生加氢及脱氢反应,其中金属Pt表现出最高的加氢和脱氢活性。双功能催化剂上四氢萘发生加氢裂化、异构化、氢转移及烷基化等复杂反应,金属Pt通过氢溢流作用提高了分子筛Br?nsted酸活性从而提高催化剂加氢裂解活性和选择性,但过量金属Pt会加剧苯环加氢而不利于单环芳烃的生成。分子筛孔道的限域作用对四氢萘的反应活性及产物分布有重要影响,相比Pt/ZSM-5催化剂,Pt/MOR表现出更高的裂解活性及异构化选择性。Pt/MOR催化剂上四氢萘加氢裂解主要通过异构-裂解路径进行,异构化活性及异构体构型决定了裂解活性及产物的分布。     

双组分金属类型对四氢萘加氢裂化反应性能的影响

以Beta分子筛为载体,采用等体积浸渍法制备不同双组分金属类型(Ni-Mo、Ni-W和Co-Mo)加氢裂化催化剂,利用XRD、BET、NH3-TPD、Py-IR和H2-TPR等对催化剂进行表征。在固定床连续加氢反应器上考察催化剂对四氢萘加氢裂化性能的影响,结果表明,催化剂CAT-a(Ni-Mo/Beta)有较适宜的比表面积和孔体积,酸量和酸强度最大,四氢萘转化率和BTX选择性最高。以Ni-Mo/Beta催化剂为研究对象,考察不同金属负载量对催化剂物化性质及四氢萘反应性能的影响,结果表明,Beta分子筛载体上金属负载质量分数18%的催化剂最适宜四氢萘加氢裂化多产BTX类物质。     

载体酸性对Pt/USY菲加氢制烷基金刚烷的影响

以Pt为活性组分、经不同浓度草酸铝处理的USY分子筛为载体,制备了Pt/USY催化剂,并用于菲一步加氢饱和反应和加氢异构反应体系。由于金属活性位点Pt上易发生加氢反应,USY载体酸性位点上易发生异构反应和裂解反应,实验分别考察了Pt颗粒、载体的酸强度和酸量对菲转化率和产物分布的影响。结果表明,活性金属Pt颗粒尺寸及分散度直接影响菲加氢饱和产物分布;草酸处理后制备的催化剂Pt/0.05-USY、Pt/0.1-USY较未经酸处理的Pt/USY更利于菲加氢反应。全氢蒽是菲向目标产物烷基金刚烷转化的关键中间产物,异构产物烷基金刚烷生成需在USY分子筛Br?nsted酸位点完成;随着催化剂载体酸量和酸强度的降低,裂解反应程度迅速减弱;菲加氢反应最终产物以加氢饱和反应产物为主;使用Pt/0.1-USY催化剂异构反应产物烷基金刚烷收率为2.3%。     

超声波碱处理改性对丝光沸石结构、酸性质及其催化性能的影响

基于丝光沸石(MOR)催化合成乙酸甲酯稳定性较差及传统碱处理MOR较难引入多级孔的特性,提出了利用超声波对MOR进行碱处理脱硅改性以制备多级孔MOR的技术。采用XRD、SEM、TEM、吡啶红外和N2吸-脱附等手段对催化剂进行了表征,分别考察了超声波在不同碱浓度处理改性条件下对分子筛催化剂骨架结构、酸性质、孔结构以及催化合成乙酸甲酯性能的影响。结果表明,通过超声波及合适浓度的Na OH碱溶液处理后,MOR分子筛的酸量、介孔孔容、比表面积都增加、孔径分布变宽,催化剂的活性和稳定性等催化性能得以改善。改性后的MOR催化剂二甲醚(DME)转化率由35.3%增加到44.8%,使用寿命大大延长,但碱液浓度过高会严重破坏MOR分子筛骨架结构,催化活性及稳定性快速下降。     

纳米梯级孔MOR分子筛的一步制备及其在重芳烃转化中的应用

在纳米mordenite(MOR)分子筛的制备基础上,以十六烷基三甲基溴化铵(CTAB)为介孔模板剂,一步水热晶化合成了具有微-介孔结构的纳米梯级孔MOR分子筛,考察了合成条件对MOR分子筛晶粒尺寸和孔结构的影响以及Pt/MOR催化剂催化异丙苯脱烷基的性能。结果表明:在晶化温度130℃,晶化时间48 h,水硅比18,碱硅比0.36和转速20 r/min条件下,制备的MOR分子筛晶粒大小约为30.0 nm;在合成体系中引入适量的CTAB可获得纳米梯级孔MOR分子筛,与纳米MOR分子筛相比,其具有较高的介孔面积和介孔体积以及适宜的酸量与酸强度。以纳米梯级孔MOR分子筛为载体制得的Pt/MOR催化剂显示出优异的加氢脱烷基性能。     

超声波碱处理改性对丝光沸石结构、酸性质及其催化性能的影响

基于丝光沸石（MOR）催化合成乙酸甲酯稳定性较差及传统碱处理MOR较难引入多级孔的特性,提出了利用超声波对MOR进行碱处理脱硅改性以制备多级孔MOR的技术。采用XRD、SEM、TEM、吡啶红外和N₂吸-脱附等手段对催化剂进行了表征,分别考察了超声波在不同碱浓度处理改性条件下对分子筛催化剂骨架结构、酸性质、孔结构以及催化合成乙酸甲酯性能的影响。结果表明,通过超声波及合适浓度的NaOH碱溶液处理后,MOR分子筛的酸量、介孔孔容、比表面积都增加、孔径分布变宽,催化剂的活性和稳定性等催化性能得以改善。改性后的MOR催化剂二甲醚（DME）转化率由35.3%增加到44.8%,使用寿命大大延长,但碱液浓度过高会严重破坏MOR分子筛骨架结构,催化活性及稳定性快速下降。     

不同载体和金属助剂负载Pt催化剂对丙烷催化氧化活性研究

制备了不同载体、不同金属助剂及不同贵金属Pt含量的蜂窝催化氧化催化剂,并评价了催化剂催化氧化含丙烷有机废气的活性:通过表面结构表征和活性评价实验,发现r-氧化铝作为载体时催化剂活性比分子筛和二氧化钛好;随着Pt含量的增加,催化剂的活性先升高后降低,Pt质量分数为0.2%时催化剂的活性最高;分别制备Pt/MO_x/Al_2O_3(M为铜、锰、钨、铈、锆、镧中的一种),在催化剂表面发现Pt聚集的颗粒,CeO_x的加入可改善贵金属的分布,Pt/CeO_x/Al_2O_3活性最佳,在400℃条件下,丙烷转化率达到95%以上,此时CeO_x的质量分数为1.0%。     

不同晶粒尺寸HZSM-5载Pt催化剂上氢气选择催化还原氮氧化物的研究

将微晶和纳晶HZSM-5分子筛作为催化剂载体应用于富氧条件下氢气选择催化还原氮氧化物(H₂-SCR)反应。研究发现,微晶HZSM-5载Pt催化剂表现出较好的H₂-SCR反应活性,100℃时NO_x转化率高达90%,N₂选择性也明显高于纳晶HZSM-5载Pt催化剂。利用XRD、SEM、NH₃-TPD、XPS和IR对纳晶和微晶HZSM-5及其载Pt催化剂晶型结构、表面形态、表面酸性以及原位反应表面物种进行表征。结果表明,Pt在纳晶和微晶HZSM-5载体上均高度分散,微晶HZSM-5载体上的总酸量多、酸强度强,有利于催化剂上Pt保持活性金属位,使得催化剂上活性金属Pt位数目较多,进而促进了还原剂H₂的活化及重要活性中间物种氨物种的生成和稳定,从而提高了NO_x转化率和N₂选择性。     

Low-temperature complete oxidation of BTX on Pt/activated carbon catalysts

The catalytic destruction of volatile organic compound (VOC) benefits from a low oxidation temperature due to less energy consumption. In this study, activated carbon-supported Pt catalysts were prepared for benzene, toluene and xylene (BTX) deep oxidation at below 200°C. Activated carbon can serve as a media for concentrating VOC. The carbon supports were heated to 400 or 800°C under N₂ flow and washed with HF acid to remove surface impurities and/or minerals. The 0.3 wt.% Pt/activated carbon catalysts were prepared by the incipient wetness method, followed by H₂ reduction at 300°C for 2 h. The catalytic oxidation was conducted with a BTX concentration ranging from 640 to 2000 ppmv in air at volume hour space velocity (VHSV) of approximately 21 000 h⁻¹. The light-off curves were very steep and the light-off temperatures ranged between 130 and 150°C, well below those of the Pt/Al₂O₃ catalyst. The oxidation activity was promoted because of a higher surface BTX concentration due to the adsorption capability of activated carbons. Moisture reduces the activity only slightly due to the hydrophobicity of activated carbon. Generally, the Pt catalysts with thermally-treated activated carbon had lower ignition temperatures. Experimental results indicated that high-temperature pretreatment of activated carbon could effectively increase the catalyst activity. Meanwhile, X-ray photoelectron spectroscopy (XPS)/secondary ion mass spectroscopy (SIMS) investigation revealed that the graphitized surface might play a role in catalytic activity. Finally, this work suggested a reaction mechanism based on the adsorption-migration of hydrocarbons to reveal the enhanced activity of activated carbon support.     

Pt/ZSM-35催化长链正构生物烷烃加氢裂化/异构化制航空煤油

以生物质油加氢脱氧得到的长链正构生物烷烃为原料，考察了H-MCM-49、H-ZSM-5、H-ZSM-22和 H-ZSM-35这4种不同分子筛催化剂的物化性质及其加氢裂化/异构化制生物航空煤油的性能。在此基础上，以H-ZSM-35分子筛为载体，制备并表征了一系列低负载量（0.1%、0.2%和0.3%）的Pt/ZSM-35双功能催化剂，以长链正构生物烷烃转化率、C₉~C₁₆产物选择性、生物航空煤油收率和异正比为指标，对其加氢裂化/异构化制生物航空煤油反应性能进行了评价，并对反应工艺条件进行优化。结果表明：H-ZSM-35的强酸中心强度高、酸量大，其结构中较小的孔口和较大的球型笼使其具有一定的容烃量和较好的择形性能，0.1%~0.3% Pt负载后， Pt/ZSM-35双功能催化剂表现出很好的加氢裂化/异构化活性和选择性。采用0.1% Pt/ZSM-35双功能催化剂在反应条件为320℃、1MPa、0.7h^-1、氢油比840∶1时，长链正构生物烷烃的转化率为84.3%，生物航空煤油收率达41.1%，产物异正比为1.34。81h长运转测试结果表明，该催化剂具有很好的稳定性。     

Aromatization of alkanes over Pt promoted conventional and mesoporous gallosilicates of MEL zeolite

Aromatization of hexane and propane was investigated over Pt promoted mesoporous gallium-containing HZSM-11 with controlled mesoporosity generated by desilication. Prepared catalysts were characterized by nitrogen adsorption, X-ray powder diffraction, scanning electron microscopy, Fourier transform infrared of chemisorbed pyridine, and NH₃ temperature programmed desorption confirming the development of intracrystalline mesoporosity of Ga-containing HZSM-11. The catalytic activities, which were compared in the aromatization of n-hexane and propane, increased upon desilication. The aromatization of n-hexane decreased in the following order, Pt/mesoporous GaZSM-11 ? Pt/conventional GaZSM-11 ? mesoporous GaZSM-11 > conventional GaZSM-11. Hexane conversion reached 70.1% over mesoporous Pt/GaZSM-11 with Si/Ga of 61, as compared with 29.6 and 24.9% for corresponding mesoporous and conventional GaZSM-11 (Si/Ga = 94), respectively, for experiments at liquid hour space velocity of 3.6 h⁻¹, and 540 °C. Comparison of BTX (benzene-toluene-xylene) selectivity at the conversion level of ∼21.0% revealed that Pt/mesoporous GaZSM-11 is more selective than corresponding mesoporous and conventional GaZSM-11. The BTX selectivity over Pt/mesoporous GaZSM-11 (Si/Ga = 94), which showed strong dependence on the conversion, reached 28.2%, whereas over corresponding mesoporous and conventional GaZSM-11catalysts reached 19.1% and 5.5%, respectively. A higher conversion and better selectivity can be attributed to the improved accessibility to the active extra-framework Ga species owing to the generation of mesopores inside the zeolite particles and shortening the contact time. It is worth mentioning that the prepared catalysts exhibited quite low activity in propane aromatization but exhibiting similar trends as for hexane aromatization.     

Preparation of high loading Pt nanoparticles on ordered mesoporous carbon with a controlled Pt size and its effects on oxygen reduction and methanol oxidation reactions

A series of ordered mesoporous carbon (OMC) supported Pt (Pt/OMC) catalysts with a controlled Pt size from 2.7 to 6.7 nm at high Pt loading around 60 wt.% have been prepared and their electrocatalytic activities for the electrode reactions relevant to the direct methanol fuel cells have been investigated. The Pt/OMC catalysts with a high dispersion (Pt size around 3 nm) could be prepared by the use of a modified, sequential impregnation–reduction method. The Pt/OMC catalysts containing larger Pt particles were obtained by increasing reduction temperature under hydrogen flow and Pt loading, and by performing impregnation–reduction in a single cycle. The oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) activities of Pt/OMC catalysts as a function of Pt size were investigated at room temperature in 0.1 M HClO₄ and (0.1 M HClO₄ + 0.5 M methanol), respectively. The specific activity of Pt/OMC for ORR steeply increased up to 3.3 nm and became independent of Pt size from 3.3 to 6.7 nm, and the mass activity curve exhibited maximum activity at 3.3 nm. The MOR activity of Pt/OMC also exhibited the similar trend with the ORR activity, as the maximum of mass activity was also found at 3.3 nm. The results of the present work indicate that the Pt catalysts of ca. 3 nm is an optimum particle size for both ORR and MOR, and this information may be translated into design of high performance membrane electrode assembly.     

SO_4~(2-)/M_xO_y型固体超强酸催化剂改性研究进展

介绍固体超强酸催化剂的发展、特点、应用及改性研究方向,研究催化剂酸强度低、催化剂易失活和稳定性差等问题,并提出解决方案。通过对国内外SO_4~(2-)/M_xO_y型固体超强酸催化剂的研究,分析向载体中引入稀土元素、分子筛、其他金属、纳米材料和交联剂对固体超强酸催化剂催化活性、热稳定性、酸性、比表面积和晶型等的影响,综述采用S2O2-8或硫酸盐替换SO_4~(2-)作为催化剂活性组分对催化剂的催化活性、酸强度及结构等的影响以及引入过渡金属(贵金属)形成的双官能团对催化剂结构与活性的影响,对制约SO_4~(2-)/M_xO_y型固体超强酸催化剂研究与工业化应用的催化剂寿命、稳定性、机械强度、合成方法、催化活性及催化剂再生等问题进行探讨。     

A Highly Effective Pt and H3PW12O40 Modified Zirconium Oxide Metal–Acid Bifunctional Catalyst for Skeletal Isomerization: Preparation, Characterization and Catalytic Behavior Study

A series of metal–acid bifunctional catalysts with varying quantities of platinum and tungstophosphoric acid (TPA) supported on zirconium oxide were prepared by co-impregnation method. In skeletal isomerization of n-pentane using catalyst with 1% Pt and 30% TPA loadings the conversion of the reactant which was close to the equilibrium conversion reached ca. 65% and the selectivity towards the product was as high as ca. 97% at atmospheric pressure and relatively low reaction temperature (200 °C). The phase structure, chemical structure, surface physicochemical properties, surface element oxidation states and hydrogen reduction behavior of the catalysts were well-characterized via XRD, FT-IR, N₂ adsorption–desorption determination (BET), XPS and TPR. The effects of Pt and TPA loadings, calcination temperature, reaction temperature and weight hourly space velocity (WHSV) on the catalytic performance were investigated. In addition, a long period catalytic stability test of the catalyst with optimal Pt and TPA loadings was carried out, which indicated that the bifunctional catalyst was in possession of good stability in skeletal isomerization along with high catalytic activity under the experimental conditions.     

Nickel impregnated Pt/H-β and Pt/H-mordenite catalysts for hydroisomerization of n-hexane

Nickel impregnated Pt/H-β and Pt/H-MOR catalysts with different Ni content were prepared and subjected to hydroisomerization of n-hexane in the presence of flowing H₂ gas. The states of Pt and Ni were identified by ESCA. The particle size measured by TEM shows that average particle size increases with increasing Ni loading. The acidity of the catalysts was measured by TPD of ammonia. The catalytic activity of Ni containing and Ni free Pt/H-β and Pt/H-MOR catalysts was compared and found that addition of Ni up to a threshold value (0.3 wt% for β and 0.1 wt% for MOR) increases the n-hexane conversion and dimethyl butanes selectivity due to better metal-acid synergism and decreases the amount of cracked products. When the Ni amount exceeds the threshold values the conversion decreases and cracked products increase. Further the Ni impregnation of Pt containing acidic supports increases the sustainability of the catalysts and was found to favor the protonated cyclopropane (PCP) intermediate mechanism in n-hexane isomerization. β zeolite was found to be a better potential support than mordenite and the isomerized product mixture shows better octane number.