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1.
采用催化加氢技术脱除F-T合成水相中羧酸、醛、醇、酮、酯含氧化合物,考察了Ru/ZrO2、Ru/TiO2、Ru/SiO2和Ru/Al2O3 4种Ru催化剂的反应性能.相对于酸、醇,水中的醛、酮、酯更易被转化.其中Ru/ZrO2和Ru/TiO2具有良好的加氢脱羰活性,在200℃、9.8 MPa、3.0 h-1空速下,酸、醛、醇、酮、酯均转化为C1~C6的烷烃,总转化率达92%.同条件下,虽然Ru/Al2O3对酸、醛、酮、酯的转化活性较高(>87%),但对醇的转化不到30%,具有选择性转化特点.H2-TPR和NH3-TPD结果表明,Ru/Al2O3催化剂的金属活性位与载体酸性位的协同作用有利于羧酸的加氢反应,能抑制醇的加氢脱羰活性;而金属-载体相互作用较弱和酸度较低的催化剂有利于羧酸、醇发生加氢脱羰反应.Ru/Al2O3催化剂运行500 h后失活,XRD、SEM和N2-物理吸附表明,载体结构物相和织构性质的改变以及活性组分的流失是导致催化剂失活的主要因素.  相似文献   

2.
Ru/TiO2 catalysts were prepared by spray reaction (SPR) and conventional impregnation (IMP) methods. The catalytic activities of SPR fine particles were much higher than those of IMP catalysts for CO2 hydrogenation. A high temperature reduction greatly promoted the activity of SPR catalyst. A model of surface structure was proposed which exhibits the enhancement of decoration and the formation of more boundaries over spr-Ru/TiO2. The high activity of SPR catalyst is attributed to the occurrence of new active sites at the metal–support perimeters and not any SMSI phenomenon. EXAFS reveals that the Ru atom was interacting with TiO2 by oxygen atom so strongly on the SPR catalysts that a part of the Ru atoms, located near the internal interface between Ru particles and TiO2 support, existed as Run+ (n<4) cations even if SPR catalyst was subjected to a high temperature reduction. These Run+ cations are responsible for the inhibition of SMSI formation over SPR catalysts.  相似文献   

3.
Catalytic wet air oxidation (CWAO) technology can efficiently treat organic wastewater, but the performance of existing catalysts, especially its stability, is far from industrial applications. In this study, ZrO2 was used to modify TiO2 support to form the stable Ru/TiO2-ZrO2 catalysts. It was found that the Ru/TiO2-ZrO2 catalysts showed excellent performance for catalytic wet air oxidation of phenolsulfonic acid wastewater. They gave high total organic carbon (TOC) conversions (>90%) and remained stable in 5 consecutive running in the Ti/Zr ratio range from 9∶1 to 7∶3. On the other hand, TOC conversion decreased from 99.1% to 65.3% in 5 consecutive cycles for the conventional Ru/TiO2 catalyst. The characterization results of XRD, BET, XPS, H2-TPR and ICP-OES indicated that ZrO2 can enter the lattice of TiO2 to form TiO2-ZrO2 solid solution, which prevented the transformation of TiO2 from anatase to rutile. In addition, the modification of ZrO2 strengthened the interaction between Ru and the support, which effectively inhibited the leaching of Ru metal. The stable support structure and good anti-loss performance are the main reasons for the excellent reaction performance of Ru/TiO2-ZrO2 catalyst.  相似文献   

4.
催化湿式氧化(CWAO)技术可高效处理有机废水,但现有催化剂的性能,尤其是其稳定性距工业应用还有很大差距。利用ZrO2对TiO2载体进行掺杂调变,研制出了具有良好稳定性的Ru/TiO2-ZrO2催化湿式氧化催化剂。结果表明, Ru/TiO2催化剂在进行连续5次催化湿式氧化降解苯酚磺酸(phenolsulfonic acid,PSA)废水的反应后,总有机碳(total organic carbon,TOC)转化率由99.1%降低至65.3%;而Ru/TiO2-ZrO2催化剂在Ti/Zr质量比为9∶1~7∶3范围内,能表现出优良的反应性能,在连续5次反应后, TOC转化率稳定保持在90%以上。X射线仪衍射(XRD)、N2吸脱附(BET)、X射线扫描微探针电子能谱仪(XPS)、氢气程序升温还原(H2-TPR)和电感耦合等离子体发射光谱(ICP-OES)表征结果表明:ZrO2能够进入TiO2的晶格,TiO2-ZrO2固溶体的生成阻止了TiO2由锐钛矿相向金红石相的转变。另外,ZrO2的调变加强了Ru与载体的相互作用,有效抑制了活性金属Ru的流失。稳定的载体结构和良好的抗流失性能是Ru/TiO2-ZrO2催化剂具有优良反应性能的主要原因。  相似文献   

5.
Kinetic studies show deactivation of TiO2 catalysts during aqueous-phase and gas-phase photooxidation of trichloroethene (TCE). Temperature-programmed desorption (TPD) and X-ray photoelectron spectroscopy (XPS) were used to examine adsorbed species on TiO2 photocatalyst surfaces after reaction, and TPD was used to determine how reactants and products adsorb on the TiO2 surface. Used and deactivated catalysts were analyzed after participating in either aqueous-phase or gas-phase photooxidation of TCE. The XPS spectra showed little difference between the surface composition of fresh TiO2 and that of a deactivated catalyst from the aqueous-phase photoreactor. Chlorine was observed only on catalysts used in the gas-phase photocatalytic decomposition of TCE. Differences due to photoreaction were observed in TPD spectra of water, carbon monoxide, and carbon dioxide. Both the total amount desorbed and the temperature of desorption of carbon monoxide and carbon dioxide were quite different for used and deactivated catalysts from the two photoreactions. Apparently strongly bound species, such as carbonates, accumulated on the surface and formed carbon monoxide upon high-temperature decomposition. Small amounts of chlorinated compounds desorbed from the used and deactivated catalysts following gas-phase photoreaction. Dichloroacetyl chloride (DCAC), a reaction intermediate, can adsorb strongly on TiO2 and readily displaces TCE. Thermally decomposed DCAC reduces the number of available adsorption sites for DCAC and TCE. An interesting low-temperature oxygen desorption peak was observed from catalysts treated with H2O2, which improves catalytic activity. This feature indicates that H2O2 is stable on TiO2 at room temperature and decomposes at 420 K.  相似文献   

6.
Changbin Zhang  Hong He   《Catalysis Today》2007,126(3-4):345-350
The TiO2 supported noble metal (Au, Rh, Pd and Pt) catalysts were prepared by impregnation method and characterized by means of X-ray diffraction (XRD) and BET. These catalysts were tested for the catalytic oxidation of formaldehyde (HCHO). It was found that the order of activity was Pt/TiO2  Rh/TiO2 > Pd/TiO2 > Au/TiO2  TiO2. HCHO could be completely oxidized into CO2 and H2O over Pt/TiO2 in a gas hourly space velocity (GHSV) of 50,000 h−1 even at room temperature. In contrast, the other catalysts were much less effective for HCHO oxidation at the same reaction conditions. HCHO conversion to CO2 was only 20% over the Rh/TiO2 at 20 °C. The Pd/TiO2 and Au/TiO2 showed no activities for HCHO oxidation at 20 °C. The different activities of the noble metals for HCHO oxidation were studied with respect to the behavior of adsorbed species on the catalysts surface at room temperature using in situ DRIFTS. The results show that the activities of the TiO2 supported Pt, Rh, Pd and Au catalysts for HCHO oxidation are closely related to their capacities for the formation of formate species and the formate decomposition into CO species. Based on in situ DRIFTS studies, a simplified reaction scheme of HCHO oxidation was also proposed.  相似文献   

7.
负载型铟基催化剂二氧化碳加氢动力学研究   总被引:2,自引:1,他引:1       下载免费PDF全文
曹晨熙  陈天元  丁晓旭  黄海  徐晶  韩一帆 《化工学报》2019,70(10):3985-3993
探讨了载体对铟基催化剂上CO2加氢动力学的影响。通过浸渍法制备了不同载体的负载型In基催化剂,仅ⅣB族元素(Ti,Zr,Hf)氧化物负载的In基催化剂表现出明显的CO2加氢活性,其中In1/HfO2和In1/ZrO2催化剂具有较高的甲醇选择性,而In1/TiO2催化剂主要起催化逆水气变换反应的作用。通过稳态动力学、高压原位漫反射红外和程序升温实验等动力学手段,证明反应条件下In1/ZrO2和In1/HfO2上的关键表面反应中间体是甲酸盐与甲氧基,甲醇主要通过表面甲酸盐的逐步加氢生成。In1/HfO2具有最强的氢解离与加氢能力,因此最有利于甲醇合成。In1/TiO2在CO2加氢中表面无明显含碳中间物种,高CO选择性可能与界面氧空缺位点促进redox循环以及甲酸盐中间体分解相关。  相似文献   

8.
The catalytic activity of supported noble metal catalysts (Pt, Rh, Ru, and Pd) for the WGS reaction is investigated with respect to the physichochemical properties of the metallic phase and the support. It has been found that, for all metal-support combinations investigated, Pt is much more active than Pd, while Rh and Ru exhibit intermediate activity. The turnover frequency (TOF) of CO conversion does not depend on metal loading, dispersion or crystallite size, but depends strongly on the nature of the metal oxide carrier. In particular, catalytic activity of Pt and Ru catalysts, is 1-2 orders of magnitude higher when supported on “reducible” (TiO2, CeO2, La2O3, and YSZ) rather than on “irreducible” (Al2O3, MgO, and SiO2) metal oxides. In contrast to what has been found in our previous study over Pt/TiO2 catalysts, catalytic activity of dispersed Pt does not depend on the structural and morphological characteristics of CeO2, such as specific surface area or primary crystallite size.  相似文献   

9.
Hydrotreating of Maya heavy crude oil over high specific surface area CoMo/TiO2–Al2O3 oxide supported catalysts was studied in an integral reactor close to industrial practice. Activity studies were carried out with Maya crude hydrodesulfurization (HDS), hydrodemetallization (HDM), hydrodenitrogenation (HDN), and hydrodeasphaltenization (HDAs) reactions. The effect of support composition, the method of TiO2 incorporation, and the catalyst deactivation are examined. Supported catalysts are characterized by BET specific surface area (SSA), pore volume (PV), pore size distribution (PSD), and atomic absorption. It has been found that sulfided catalysts showed a wide range of activity variation with TiO2 incorporation into the alumina, which confirmed that molybdenum sulfided active phases strongly depend on the nature of support. The pore diameter and nature of the active site for HDS, HDM, HDN, and HDAs account for the influence of the large reactant molecules restricted diffusion into the pore, and/or the decrease in the number of active sites due to the MoS2 phases buried with time-on-stream. The textural properties and hysteresis loop area of supported and spent catalysts indicated that catalysts were deactivated at the pore mouth due to the metal and carbon depositions. The atomic absorption results agreed well regarding the textural properties of spent catalysts. Thus, incorporation of TiO2 with γ-Al2O3 alters the nature of active metal interaction with support, which may facilitate the dispersion of active phases on the support surface. Therefore, the TiO2 counterpart plays a promoting role to HDS activity due to the favorable morphology of MoS2 phases and metal support interaction.  相似文献   

10.
Pt supported on γ-Al2O3, TiO2 and ZrO2 are active catalysts for the CO2 reforming of methane to synthesis gas. The stability of the catalysts increased in the order Pt/γ-A12O3 < Pt/TiO2 < Pt/ZrO2. For all catalysts, the decrease in activity with time on stream is caused by carbon formation, which blocks the active metal sites for reaction. With Pt/TiO2 and Pt/ZrO2, deactivation started immediately after the start of the reaction, while the Pt/γ-A12O3 catalyst showed an induction period during which carbon was accumulated without affecting the catalytic activity.  相似文献   

11.
The oxidation of perchloroethylene (PCE) was investigated over chromium oxide catalysts supported on SiO2, SiO2–Al2O3, activated carbon, mordenite type zeolites, MgO, TiO2 and Al2O3. Supported chromium oxide catalysts were more active than any other metal oxide catalysts including noble metal examined in the present study. PCE removal activity of chromium oxide catalysts mainly depended on the type of supports and the content of metal loaded on the catalyst surface. TiO2 and Al2O3 containing high surface areas were effective for the high performance of PCE removal, since the formation of well dispersed Cr(VI) active reaction sites for the present reaction system, was enhanced even for the high Cr loading on the catalyst surface. CrOx catalysts supported on TiO2 and Al2O3 also exhibited stable PCE removal activity at a low feed concentration of PCE of 30 ppm up to 100 h at 350°C. However, significant catalyst deactivation was observed at high PCE concentration of 10 000 ppm. CrOx/TiO2 revealed stronger water tolerance than CrOx/Al2O3 due to the surface hydrophobicity.  相似文献   

12.
The catalytic oxidation of sulfur dioxide to sulfur trioxide over several binary (MxOy/TiO2) and ternary (V2O5/MXOY/TiO2) supported metal oxide catalysts was systematically investigated. The supported metal oxide components were essentially 100% dispersed as surface metal oxide species, as confirmed by Raman spectroscopy characterization. The sulfur dioxide oxidation turnover frequencies of the binary catalysts were all within an order of magnitude (V2O5/TiO2>Fe2O3/TiO2>Re2O7/TiO2  CrO3/TiO2  Nb2O5/TiO2>MoO3/TiO2  WO3/TiO2). An exception was the K2O/TiO2 catalysts, which is essentially inactive for sulfur dioxide oxidation. With the exception of K2O, all of the surface metal oxide species present in the ternary catalysts (i.e., oxides of V, Fe, Re, Cr, Nb, Mo and W) can undergo redox cycles and oxidize SO2 to SO3. The turnover frequency for sulfur dioxide oxidation over all of these catalysts is approximately the same at both low and high surface coverages. This indicates that the mechanism of sulfur dioxide oxidation is not sensitive to the coordination of the surface metal oxide species. A comparison of the activities of the ternary catalysts with the corresponding binary catalysts suggests that the surface vanadium oxide and the additive surface metal oxide redox sites act independently without synergistic interactions. The V2O5/K2O/TiO2 catalyst showed a dramatic reduction in the catalytic activity in comparison to the unpromoted V2O5/TiO2 catalyst. The ability of K2O to significantly retard the redox potential of the surface vanadia species is primarily responsible for the lower catalytic activity of the ternary catalytic system. The fundamental insights generated from this research can potentially assist in the molecular design of the air pollution control catalysts: (1) the development of catalysts for low temperature oxidation of SO2 to SO3 during sulfuric acid manufacture (2) the design of efficient SCR DeNOx catalysts with minimal SO2 oxidation activity and (3) improvements in additives for the simultaneous oxidation/sorption of sulfur oxides in petroleum refinery operations.  相似文献   

13.
采用化学还原法制备Ni-P/TiO2非晶态催化剂,以α-蒎烯加氢反应为探针反应,考察了催化剂制备条件对其催化性能的影响,得到适宜的制备条件为载体与NiCl2?6H2O质量比为3∶1,P/Ni摩尔比为2.5∶1,反应温度为25℃,pH为11。结果表明:该条件下制备的催化剂对α-蒎烯加氢具有较高的催化活性,α-蒎烯转化率为99.89%,顺式蒎烷选择性为98.48%,收率为98.37%,且可重复使用8次。以XRD、BET、DSC、XPS、TEM为表征手段,对催化剂失活前后的结构及形貌进行了分析,结果表明:新鲜催化剂为粒径均一的球形颗粒,粒径约为100nm,分散性较好,引入TiO2有效提高了Ni-P粒子的热稳定性,将其晶化温度分别提高了78℃、190℃和115.1℃,而失活催化剂的分散度、Ni0含量均有下降,出现了活性组分流失、氧化及团聚等现象,这可能是导致催化剂失活的主要原因。  相似文献   

14.
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TiOx物种随H2气氛中热处理温度的升高而逐渐增多有关。  相似文献   

15.
采用改进溶胶-凝胶法制备的TiO_2-Al_2O_3作复合载体,制备不同柠檬酸引入方式改性的CoMo/TiO_2-Al_2O_3加氢脱硫催化剂。利用低温N_2吸附-脱附、XRD、SEM和H_2-TPR等对催化剂进行表征,并采用固定床反应器对催化剂加氢脱硫性能进行评价。结果表明,后处理法制备的催化剂比表面积相对较大,孔道结构较好,活性金属组分以无定形形态均匀分散在载体表面,一定程度上减弱了其与载体间的相互作用;该催化剂可以延缓Co硫化,并且络合生成较多易于硫化还原的Mo物种,利于MoS_2在催化剂表面的堆叠,生成更多的Co-Mo-S(Ⅱ)活性相,因而相应的CoMo催化剂对噻吩加氢脱硫转化率显著提高。  相似文献   

16.
Various partial oxidation products were identified on the surface of TiO2 and an 8% SiO2–TiO2 binary catalyst used for the photocatalytic oxidation of gas-phase toluene. Using in situ FTIR spectroscopy, benzaldehyde and benzoic acid were identified on the surface of the deactivated photocatalysts. Additional GC/MS analysis of methanol-extracted surface species confirmed the presence of benzaldehyde and benzoic acid and detected small concentrations of benzyl alcohol. Apparently, benzaldehyde is the main partial oxidation product that is further oxidized to benzoic acid. Benzoic acid is strongly adsorbed on the surface of the catalyst. There seems to be a correlation between the accumulation of benzoic acid on the surface and catalyst deactivation. The presence of gas-phase water in the reactive mixture seems to retard the formation of benzoic acid.

The SiO2–TiO2 photocatalyst is more active and appears to deactivate slower than TiO2. This binary oxide is photocatalytically active even in the absence of gas-phase oxygen. It also seems to have a higher toluene adsorption capacity than TiO2. The acidity of the different oxides was examined using FTIR spectroscopy of adsorbed pyridine. The results indicate that no pure metal oxide displays Brønsted acidity but when SiO2 is cofumed with TiO2, Brønsted acidity of intermediate strength is generated. The generation of new surface sites may be responsible for the increased activity. The mechanism of this promotion effect is not clearly understood and further studies are required to elucidate it.  相似文献   


17.
Co–Mo model sulfide catalysts, in which CoMoS phases are selectively formed, were prepared by means of a CVD technique using Co(CO)3NO as a precursor of Co. It is shown by means of XPS, FTIR and NO adsorption that CoMoS phases form selectively when the Mo content exceeds monolayer loading. A single exposure of MoS2/Al2O3 to a vapor of Co(CO)3NO at room temperature fills the edge sites of the MoS2 particles. It is suggested that the maximum potential HDS activity of MoS2/Al2O3 and Co–Mo/Al2O3 catalysts can be predicted by means of Co(CO)3NO as a “probe” molecule. An attempt was made to determine the fate of Co(CO)3NO adsorbed on MoS2/Al2O3. The effects of the support on Co–Mo sulfide catalysts in HDS and HYD were investigated by use of CVD-Co/MoS2/support catalysts. XPS and NO adsorption showed that model catalysts can also be prepared for SiO2-, TiO2- and ZrO2-supported catalysts by means of the CVD technique. The thiophene HDS activity of CVD-Co/MoS2/Al2O3, CVD-Co/MoS2/TiO2 and CVD-Co/MoS2/Al2O3 is proportional to the amount of Co species interacting with the edge sites of MoS2 particles or CoMoS phases. It is concluded that the support does not influence the HDS reactivity of CoMoS phases supported on TiO2, ZrO2 and Al2O3. In contrast, CoMoS phases on SiO2 show catalytic features characteristic of CoMoS Type II. With the hydrogenation of butadiene, on the other hand, the Co species on MoS2/TiO2, ZrO2 and SiO2 have the same activity, while the Co species on MoS2/Al2O3 have a higher activity.  相似文献   

18.
采用等体积浸渍法制备了单贵金属Ru/TiO2和双金属Ru-Ce/TiO2系列催化剂,测试了其对氯苯的催化活性,并通过N2吸脱附、扫描电镜(SEM)、程序升温还原(H2-TPR)进行表征,旨在考察稀土元素Ce掺杂对Ru/TiO2催化氯苯性能的影响。结果表明,Ce的引入可使其在降低贵金属含量的基础上仍保持高的催化效率,且极大地提高了低温催化活性。0.4%Ru-1.0%Ce/TiO2与0.4%Ru/TiO2相比,其T10T90分别降低了50℃和60℃。H2-TPR表明引入Ce为催化剂提供了更多的表面氧空位,形成Ru-O-Ce增强了其氧化还原能力。掺杂Ce未改变Ru/TiO2催化剂的结构形貌,仍保持介孔结构,但若负载量过多,会堵塞部分孔道,阻碍污染物吸附及反应,降低催化性能。  相似文献   

19.
为提高钌基催化剂的高温稳定性,本文采用液相共浸法制备了一系列Ru-CeO x /TiO2复合氧化物催化剂,探究了CeO2对钌基催化剂在HCl氧化过程中催化性能的影响。通过TEM、XRD、N2吸附-脱附、Raman、XPS等表征手段分析催化剂结构及组成,结合催化剂在HCl催化氧化反应中的催化性能,研究了不同Ce负载量对RuO2/TiO2体系的作用规律。结果表明,引入Ce之后改变了活性相RuO2与载体TiO2的相互作用,形成了Ce-O-Ru结构,对钌基催化剂的活性产生一定的负面作用;但是由于抑制了Ru活性位点的烧结失活,同时高浓度的Ce3+物种有利于氧物种的吸附与活化,使含适量Ce的Ru-CeO x /TiO2复合氧化物催化剂能够在较高温度(370℃、400℃)下保持良好的高温稳定性与催化活性,最终确定摩尔比以Ru∶Ce=1∶1较为适宜。  相似文献   

20.
采用化学还原法制备了RuCu/TiO2双金属催化剂,并探究了Ru和Cu的协同作用对催化湿式氧化(CWAO)无害化处理氨氮废水催化性能的影响。研究结果表明,Cu的添加可有效改善Ru/TiO2催化剂的N2选择性,而Ru的存在可有效提高Cu/TiO2催化剂的催化活性。反应条件为0.5 MPa、150℃、[NH3]0=1000 mg·L-1、pH=12、模拟废水处理量为33 L·(kg cat)-1·h-1时,1Ru2Cu/TiO2能使废水的氨氮转化率和N2选择性分别高达87.7%和85.9%。表征结果表明:Ru和Cu的协同在催化氧化氨氮废水过程中起了关键作用,主要体现在:Ru和Cu的强相互作用导致1Ru2Cu/TiO2催化剂具有良好的抗流失性能,进而使得催化剂具有良好的稳定性;Ru和Cu的电子转移使得1Ru2Cu/TiO2具有适中的亲氧性能,有效提高了催化剂的催化活性。  相似文献   

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