共查询到20条相似文献,搜索用时 13 毫秒
1.
Kyriakos N. Papageridis Nikolaos D. Charisiou Savvas Douvartzides Victor Sebastian Steven J. Hinder Mark A. Baker Ayesha A. AlKhoori Sara I. AlKhoori Kyriaki Polychronopoulou Maria A. Goula 《RSC advances》2021,11(15):8569
The present study provides, for the first time in the literature, a comparative assessment of the catalytic performance of Ni catalysts supported on γ-Al2O3 and γ-Al2O3 modified with La2O3, in a continuous flow trickle bed reactor, for the selective deoxygenation of palm oil. The catalysts were prepared via the wet impregnation method and were characterized, after calcination and/or reduction, by N2 adsorption/desorption, XRD, NH3-TPD, CO2-TPD, H2-TPR, H2-TPD, XPS and TEM, and after the time-on-stream tests, by TGA, TPO, Raman and TEM. Catalytic experiments were performed between 300–400 °C, at a constant pressure (30 bar) and different LHSV (1.2–3.6 h−1). The results show that the incorporation of La2O3 in the Al2O3 support increased the Ni surface atomic concentration (XPS), affected the nature and abundance of surface basicity (CO2-TPD), and despite leading to a drop in surface acidity (NH3-TPD), the Ni/LaAl catalyst presented a larger population of medium-strength acid sites. These characteristics helped promote the SDO process and prevented extended cracking and the formation of coke. Thus, higher triglyceride conversions and n-C15 to n-C18 hydrocarbon yields were achieved with the Ni/LaAl at lower reaction temperatures. Moreover, the Ni/LaAl catalyst was considerably more stable during 20 h of time-on-stream. Examination of the spent catalysts revealed that both carbon deposition and degree of graphitization of the surface coke, as well as, the extent of sintering were lower on the Ni/LaAl catalyst, explaining its excellent performance during time-on-stream.Highly selective and stable Ni supported on La2O3–Al2O3 catalyst on the deCO/deCO2 reaction paths for the production of renewable diesel. 相似文献
2.
The dehydrocyclization–cracking of methyl oleate was performed by ZnZSM-5–Al2O3 hierarchical composite-supported Pt catalysts in the range of 450–550 °C under 0.5 MPa hydrogen pressure. Most catalysts converted methyl oleate completely and produced aromatics with more than 10 wt% yield as well as valuable fuels even at 450 °C. The reactivity of catalysts changed remarkably depending on the addition method of Pt, while supporting Pt of 0–0.16 wt% did not affect the pore structure of each catalyst. When Pt was introduced into the composite support by the conventional impregnation method, remarkable hydrocracking proceeded through the decarboxylation and decarbonylation of methyl oleate and the successive conversion of C17 fragments and gave the significant amounts of gaseous products. Nevertheless, the selectivity for the aromatics of the gasoline fraction was relatively high and the yields of aromatics reached maximum 19% at 500 °C under 0.5 MPa, suggesting that gaseous olefins would be cyclized through the Diels–Alder reaction on ZnZSM-5 in the composite support. In contrast, when Pt was introduced into catalysts by ion-exchange with ZnZSM-5, the significant conversion of methyl oleate was inhibited and produced liquid fuels in a wide range.The ideal reaction route in the dehydrocyclization–cracking of methyl oleate catalyzed by Pt/ZnZSM-5–Al2O3 is to produce xylene, toluene, and hydrogen through decarboxylation. 相似文献
3.
Lvesheng Sun Shunxin Cao Yun Huang Yiming Zhang Youhong Xiao Guojun Dong Yu Su 《RSC advances》2019,9(52):30340
In this experiment, a TiO2–Ce0.9Zr0.1O2 support with core–shell structure was successfully prepared by a precipitation method and VOX/TiO2–Ce0.9Zr0.1O2 catalyst was prepared by an impregnation method, and the catalyst was used to catalyze the NH3-SCR of NO. Based on the results of HRTEM, XRD, BET, H2-TPR, NH3-TPD, XPS, Py-IR, it was speculated that due to the interaction between TiO2 and Ce0.9Zr0.1O2, more oxygen vacancies and Ce3+ are generated, which are beneficial to the existence of low-valence V by electron transfer between high valence state V and Ce3+and increase the acidic sites on the catalyst surface. The catalytic activity (>97%) of the VOX/TiO2–Ce0.9Zr0.1O2 catalyst is superior to the current commercial catalyst (V2O5–WO3/TiO2) and has a higher N2 selectivity (>97.5%) at 40 000 h−1 GHSV and 250–400 °C.VOX/TiO2–Ce0.9Zr0.1O2 catalyst exhibits high activity and selectivity in a wide temperature window. 相似文献
4.
Alberto Alvarez-Fernandez Frdric Nallet Philippe Fontaine Cian Cummins Georges Hadziioannou Philippe Barois Guillaume Fleury Virginie Ponsinet 《RSC advances》2020,10(67):41088
In the field of functional nanomaterials, core–satellite nanoclusters have recently elicited great interest due to their unique optoelectronic properties. However, core–satellite synthetic routes to date are hampered by delicate and multistep reaction conditions and no practical method has been reported for the ordering of these structures onto a surface monolayer. Herein we show a reproducible and simplified thin film process to fabricate bimetallic raspberry nanoclusters using block copolymer (BCP) lithography. The fabricated inorganic raspberry nanoclusters consisted of a ∼36 nm alumina core decorated with ∼15 nm Au satellites after infusing multilayer BCP nanopatterns. A series of cylindrical BCPs with different molecular weights allowed us to dial in specific nanodot periodicities (from 30 to 80 nm). Highly ordered BCP nanopatterns were then selectively infiltrated with alumina and Au species to develop multi-level bimetallic raspberry features. Microscopy and X-ray reflectivity analysis were used at each fabrication step to gain further mechanistic insights and understand the infiltration process. Furthermore, grazing-incidence small-angle X-ray scattering studies of infiltrated films confirmed the excellent order and vertical orientation over wafer scale areas of Al2O3/Au raspberry nanoclusters. We believe our work demonstrates a robust strategy towards designing hybrid nanoclusters since BCP blocks can be infiltrated with various low cost salt-based precursors. The highly controlled nanocluster strategy disclosed here could have wide ranging uses, in particular for metasurface and optical based sensor applications.Large area Al2O3–Au raspberry-like nanoclusters and other complex structures have been created by iterative block-copolymer self-assembly, paving the way to a new generation of on-demand metallic architectures. 相似文献
5.
Ruifeng Wang Lungang Chen Xinghua Zhang Qi Zhang Yuping Li Chenguang Wang Longlong Ma 《RSC advances》2018,8(71):40989
Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water. In this study, mixed oxides Al2O3–TiO2, Al2O3–MoO3 and Al2O3–Co3O4 were synthesized by co-precipitation using aqueous solution of NaOH as precipitant. Ru catalysts supported on mixed oxides were prepared by impregnation method and their catalytic performances were tested in the hydrogenation of LA to GVL on a fixed bed reactor. The physicochemical properties of the catalysts were characterized by XRD, H2-TPR, NH3-TPD, and BET techniques. The TiO2 component significantly affected the acidity of the catalyst, and thus its catalytic activity for the GVL yield was affected. The desired product GVL with a yield of about 97% was obtained over the Ru/Al2O3–TiO2 catalyst under mild conditions (WHSV = 1.8 h−1, T = 80 °C). Moreover, the catalyst Ru/Al2O3–TiO2 exhibited excellent thermal stability in the test period of time.Novel catalytic material with high catalytic activity and hydrothermal stability plays a key role in the efficient conversion of levulinic acid (LA) to γ-valerolactone (GVL) in water. 相似文献
6.
Yaseen Muhammad Ata Ur Rahman Haroon Ur Rashid Maria Sahibzada Sidra Subhan Zhangfa Tong 《RSC advances》2019,9(18):10371
Sulfur compounds in fuel oils are a major source of atmospheric pollution. This study is focused on the hydrodesulfurization (HDS) of dibenzothiophene (DBT) via the coupled application of 0.5 wt% Pd-loaded Co–Mo/Al2O3 and Ni–Mo/Al2O3 catalysts with ionic liquids (ILs) at ambient temperature (120 °C) and pressure (1 MPa H2). The enhanced HDS activity of the solid catalysts coupled with [BMIM]BF4, [(CH3)4N]Cl, [EMIM]AlCl4, and [(n-C8H17)(C4H9)3P]Br was credited to the synergism between hydrogenation by the former and extractive desulfurization and better H2 transport by the latter, which was confirmed by DFT simulation. The Pd-loaded catalysts ranked highest by activity i.e. Pd–Ni–Mo/Al2O3 > Pd–Co–Mo/Al2O3 > Ni–Mo/Al2O3 > Co–Mo/Al2O3. With mild experimental conditions of 1 MPa H2 pressure and 120 °C temperature and an oil : IL ratio of 10 : 3.3, DBT conversion was enhanced from 21% (by blank Ni–Mo/Al2O3) to 70% by Pd–Ni–Mo/Al2O3 coupled with [(n-C8H17)(C4H9)3P]Br. The interaction of polarizable delocalized bonds (in DBT) and van der Waals forces influenced the higher solubility in ILs and hence led to higher DBT conversion. The IL was recycled four times with minimal loss of activity. Fresh and spent catalysts were characterized by FESEM, ICP-MS, EDX, XRD, XPS and BET surface area techniques. GC-MS analysis revealed biphenyl as the major HDS product. This study presents a considerable advance to the classical HDS processes in terms of mild operating conditions, cost-effectiveness, and simplified mechanization, and hence can be envisaged as an alternative approach for fuel oil processing.Synergistic application of ionic liquids with Pd loaded Co–Mo@Al2O3 and Ni–Mo@Al2O3 catalysts for efficient hydrodesulfurization of dibenzothiophene at ambient conditions. 相似文献
7.
Yushan Wu Jianghui Lin Guangyuan Ma Yanfei Xu Jianli Zhang Chanatip Samart Mingyue Ding 《RSC advances》2020,10(4):2067
The selectivity and activity of a nickel catalyst for the hydrogenation of carbon dioxide to form methane at low temperatures could be enhanced by mesoporous Al2O3–CeO2 synthesized through a one-pot sol–gel method. The performances of the as-prepared Ni/Al2O3–CeO2 catalysts exceeded those of their single Al2O3 counterpart giving a conversion of 78% carbon dioxide with 100% selectivity for methane during 100 h testing, without any deactivation, at the low temperature of 320 °C. The influence of CeO2 doping on the structure of the catalysts, the interactions between the mesoporous support and nickel species, and the reduction behaviors of Ni2+ ions were investigated in detail. In this work, the addition of CeO2 to the composites increased the oxygen vacancies and active metallic nickel sites, and also decreased the size of the nickel particles, thus improving the low temperature catalytic activity and selectivity significantly.The addition of CeO2 to form Ni composite catalysts increased the oxygen vacancies and active metallic nickel sites thus improving the low temperature CO2 methanation performance. 相似文献
8.
Yingxin Liu Kai Liu Meihua Zhang Kaiyue Zhang Jiao Ma Shuwen Xiao Zuojun Wei Shuguang Deng 《RSC advances》2021,12(1):602
Highly active and thermally stable Cu–Re bimetallic catalysts supported on TiO2 with 2.0 wt% loading of Cu were prepared via an incipient wetness impregnation method and were applied for liquid phase selective hydrogenation of levulinic acid (LA) to γ-valerolactone (GVL) in H2. The effect of the molar ratios of Cu : Re on the physico-chemical properties and the catalytic performance of the Cu–Re/TiO2 catalysts was investigated. Moreover, the influence of various reaction parameters on the hydrogenation of LA to GVL was studied. The results showed that the Cu–Re/TiO2 catalyst with a 1 : 1 molar ratio of Cu to Re (Cu–Re(1 : 1)/TiO2) exhibited the highest performance for the reaction. Complete conversion of LA with a 100% yield of GVL was achieved in 1,4-dioxane solvent under the reaction conditions of 180 °C, 4.0 MPa H2 for 4 h, and the catalyst could be reused at least 6 times with only a slight loss of activity. Combined with the characterization results, the high performance of the catalyst was mainly attributed to the well-dispersed Cu–Re nanoparticles with a very fine average size (ca. 0.69 nm) and the co-presence of Cu–Re bimetal and ReOx on the catalyst surface.Herein, we report a highly efficient and recyclable Cu–Re(1 : 1)/TiO2 bimetallic catalyst for liquid phase hydrogenation of levulinic acid to γ-valerolactone. 相似文献
9.
A series of MOx–Cr2O3–La2O3/TiO2–N (M = Cu, Fe, Ce) catalysts with nitrogen doping were prepared via the impregnation method. Comparing the low-temperature NH3-SCR activity of the catalysts, CeCrLa/Ti–N (xCeO2–yCr2O3–zLa2O3/TiO2–N) exhibited the best catalytic performance (NO conversion approaching 100% at 220–460 °C). The physico-chemical properties of the catalysts were characterized by XRD, BET, SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS. From the XRD and SEM results, N doping affects the crystalline growth of anatase TiO2 and MOx (M = Cu, Fe, Ce, Cr, La) which were well dispersed over the support. Moreover, the doping of N promotes the increase of the Cr6+/Cr ratio and Ce3+/Ce ratio, and the surface chemical adsorption oxygen content, which suggested the improvement of the redox properties of the catalyst. And the surface acid content of the catalyst increased with the doping of N, which is related to CeCrLa/TiO2–N having the best catalytic activity at high temperature. Therefore, the CeCrLa/TiO2–N catalyst exhibited the best NH3-SCR performance and the redox performance of the catalysts is the main factor affecting their activity. Furthermore, in situ DRIFTS analysis indicates that Lewis-acid sites are the main adsorption sites for ammonia onto CeCrLa/TiO2–N and the catalyst mainly follows the L–H mechanism.A series of MOx–Cr2O3–La2O3/TiO2–N (M = Cu, Fe, Ce) catalysts with nitrogen doping were prepared via the impregnation method. 相似文献
10.
Zhiyuan Li Na Li Nan Wang Bing Zhou Jun Yu Boyu Song Pan Yin Yusen Yang 《RSC advances》2022,12(9):5509
The water–gas shift reaction (WGSR) plays a pivotal role in many important industrial processes as well as in the elimination of residual CO in feed gas for fuel cells. The development of a high-efficiency low-temperature WGSR (LT-WGSR) catalyst has attracted considerable attention. Herein, we report a ZnO-modified Cu-based nanocatalyst (denoted as Cu@ZnO/Al2O3) obtained via an in situ topological transformation from a Cu2Zn1Al-layered double hydroxide (Cu2Zn1Al-LDH) precursor at different reduction temperatures. The optimal Cu@ZnO/Al2O3-300R catalyst with appropriately abundant Cu@ZnO interface structure shows superior catalytic performance toward the LT-WGSR with a reaction rate of up to 19.47 μmolCO gcat−1 s−1 at 175 °C, which is ∼5 times larger than the commercial Cu/ZnO/Al2O3 catalyst. High-resolution transmission electron microscopy (HRTEM) proves that the reduction treatment results in the coverage of Cu nanoparticles by ZnO overlayers induced by a strong metal–support interaction (SMSI). Furthermore, the generation of the coating layers of ZnO structure is conducive to stabilize Cu nanoparticles, accounting for long-term stability under the reaction conditions and excellent start/stop cycle of the Cu@ZnO/Al2O3-300R catalyst. This study provides a high-efficiency and low-cost Cu-based catalyst for the LT-WGSR and gives a concrete example to help understand the role of Cu@ZnO interface structure in dominating the catalytic activity and stability toward WGSR.The water–gas shift reaction (WGSR) plays a pivotal role in many important industrial processes as well as in the elimination of residual CO in feed gas for fuel cells. 相似文献
11.
Hongli Wu Meng Zou Lisheng Guo Fengyun Ma Wenlong Mo Yuming Yu Inamullah Mian Jingmei Liu Shuangjie Yin Noritatsu Tsubaki 《RSC advances》2020,10(7):4166
A series of Ni–La/Al2O3 catalysts for the syngas methanation reaction were prepared by a mechanochemical method and characterized by thermogravimetric analysis (TG-DTA), X-ray fluorescence (XRF), X-ray diffraction (XRD), N2 adsorption–desorption, H2 temperature-programmed reduction (H2-TPR), and X-ray photoelectron spectroscopy (XPS). The calcination temperatures (350–700 °C) had significant impacts on the crystallite sizes and interactions between NiO and Al2O3. The catalyst calcined at 400 °C (cat-400) showed a 12.1% Ni dispersion degree and the maximum bound state of NiO (54%) through the Gaussian fitting of H2-TPR. Cat-400 also achieved the highest CO conversion, CH4 selectivity and yield. Cat-400 exhibited good stability and catalytic activity in a lifetime testing of 200 h. The deactivation of cat-400 was mainly caused by carbon deposition according to the data from XRD, TG-DTG and XPS.Calcination temperature affects the existing types of NiO, and the influence of the three NiO types on the catalytic activity of samples is bound type ≫ free type > combined type. 相似文献
12.
In the direct synthesis of 2-propylheptanol (2-PH) from n-valeraldehyde, a second-metal oxide component Co3O4 was introduced into NiO/Nb2O5–TiO2 catalyst to assist in the reduction of NiO. In order to optimize the catalytic performance of NiO–Co3O4/Nb2O5–TiO2 catalyst, the effects of the Ni/Co mass ratio and NiO–Co3O4 loading were investigated. A series of NiO–Co3O4/Nb2O5–TiO2 catalysts with different Ni/Co mass ratios were prepared by the co-precipitation method and their catalytic performances were evaluated. The result showed that NiO–Co3O4/Nb2O5–TiO2 with a Ni/Co mass ratio of 8/3 demonstrated the best catalytic performance because the number of d-band holes in this catalyst was nearly equal to the number of electrons transferred in hydrogenation reaction. Subsequently, the NiO–Co3O4/Nb2O5–TiO2 catalysts with different Ni/Co mass ratios were characterized by XRD and XPS and the results indicated that both an interaction of Ni with Co and formation of a Ni–Co alloy were the main reasons for the reduction of NiO–Co3O4/Nb2O5–TiO2 catalyst in the reaction process. A higher NiO–Co3O4 loading could increase the catalytic activity but too high a loading resulted in incomplete reduction of NiO–Co3O4 in the reaction process. Thus the NiO–Co3O4/Nb2O5–TiO2 catalyst with a Ni/Co mass ratio of 8/3 and a NiO–Co3O4 loading of 14 wt% showed the best catalytic performance; a 2-PH selectivity of 80.4% was achieved with complete conversion of n-valeraldehyde. Furthermore, the NiO–Co3O4/Nb2O5–TiO2 catalyst showed good stability. This was ascribed to the interaction of Ni with Co, the formation of the Ni–Co alloy and further reservation of both in the process of reuse.NiO–Co3O4/Nb2O5–TiO2 catalyst with a Ni/Co mass ratio of 8/3 and NiO–Co3O4 loading of 14% shows the best catalytic performance. 相似文献
13.
High-temperature arsenic resistance catalysts of CeLa0.5Fex/Ti (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) series were prepared and measured under a simulation condition of arsenic poisoning. The as-prepared catalysts were characterized by XRD, SEM, TEM, and XPS. The specific surface area and pore size of the catalysts were measured. At x = 0.2, the catalyst shows the best arsenic resistance and catalytic performance. The active temperature range of the CeLa0.5Fe0.2/Ti catalyst is 345–520 °C when the gas hourly space velocity is up to 225 000 mL g−1 h−1. Compared with commercial vanadium-based catalysts, CeLa0.5Fe0.2/Ti shows much better catalytic performance. The introduction of Fe will improve the dispersion of CeO2 and increase the concentration of Ce3+ and unsaturated active oxygen on the surface. The NH3-TPD and H2-TPR results show that the CeLa0.5Fe0.2/Ti catalyst has more acidic sites and more excellent redox performance than CeLa0.5Fe0/Ti. The CeLa0.5Fe0.2/Ti catalyst might have application prospects in the field of selective catalytic reduction of NOx with NH3.The NO conversion of the CeLa0.5Fe0.2/Ti is obviously better than that of the commercial vanadium-based catalyst with regard to arsenic resistance and it has good N2 selectivity, and good SO2 resistance. 相似文献
14.
Bimetallic nanocatalysts have been used for the development of organic reactions, owing to the synergistic effect between the transition metals. A new procedure for synthesizing amines by the reduction of imines with H2 at atmospheric pressure and room temperature in the presence of PdCo–Fe3O4 nanoparticles is reported. The straightforward procedure, mild reaction conditions, high turnover number, and recyclability extend the scope of this reaction to practical applications.A catalytic procedure that has mild reaction conditions, high turnover number, and the recyclability of the catalyst is presented, whereby the synthesis of amines through the reduction of imines employing PdCo–Fe3O4 under atmospheric pressure of H2 is achieved. 相似文献
15.
Ni–Co–Al2O3 composite coatings were prepared by pulsed electrodeposition and electrophoresis–electrodeposition on aluminum alloy. The content of Al2O3 particles of the Ni–Co–Al2O3 composite coating prepared by electrophoresis–electrodeposition was significantly higher than the composite coating prepared by pulsed electrodeposition. The composite coating prepared by electrophoresis–electrodeposition exhibited a better anti-wear performance than that prepared by pulsed electrodeposition. The morphology, composition and microstructure of the composite coatings were determined by means of X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The hardness and friction properties of the samples were tested on the microhardness tester and the friction and wear loss tester respectively.Ni–Co–Al2O3 composite coatings were prepared by pulsed electrodeposition and electrophoresis–electrodeposition on aluminum alloy. 相似文献
16.
Li Lan Xin Huang Weiqi Zhou Hongmei Li Junhuai Xiang Shanhu Chen Yaoqiang Chen 《RSC advances》2021,11(12):7015
For catalytic systems consisting of Pt as the active component and CeO2–Al2O3 as the support material, the metal–support interaction between the Pt and CeO2 components is widely applied to inhibit aggregation of Pt species and thus enhance the thermal stability of the catalyst. In this work, a highly thermostable Pt catalyst was prepared by modifying the synthesis procedure for conventional Pt/CeO2/Al2O3 (Pt/Ce/Al) catalyst, that is, the CeO2 component was introduced after deposition of Pt on Al2O3. The obtained CeO2/Pt/Al2O3 (Ce/Pt/Al) catalyst exhibits significantly different aging behavior. During the hydrothermal aging process, redispersion of Pt species from the surface of Al2O3 to the surface of CeO2 occurs, resulting in a stronger metal–support interaction between Pt and CeO2. Thus, the formed Pt–O–Ce bond could act as an anchor to retard aggregation of Pt species and help Pt species stay at a more oxidative state. Consequently, excellent reduction capability and superior three-way catalytic performance are acquired by Ce/Pt/Al-a after hydrothermal aging treatment.Ce/Pt/Al undergoes redispersion of Pt upon hydrothermal aging, resulting in higher dispersion and consequently superior three-way catalytic performance of Ce/Pt/Al-a. 相似文献
17.
Heterojunction formation and heteroatom doping could be viewed as promising strategies for constructing composite photocatalysts with high visible light catalytic activity. In this work, we fabricated a carbon, nitrogen and sulfur co-doped TiO2/g-C3N4 (CNS-TiO2/g-C3N4) Z-scheme heterojunction photocatalyst composite via one-step hydrothermal and calcination methods. Compared with pure TiO2 and g-C3N4, the CNS-TiO2/g-C3N4 Z-scheme heterojunction photocatalyst possessed excellent degradation performance under visible light irradiation. Due to the formation of the Z-scheme heterostructure, the utilization rate of the photogenerated electrons–holes generated by the catalyst was increased, which enhanced the catalytic activity. Moreover, the heteroatom doping (C, N and S) could efficiently tailor the band gap of TiO2 and facilitate electron transition, contributing to enhancing the degradation ability under visible light. The CNS-TiO2/g-C3N4-2 exhibited a superior photocatalytic degradation efficiency (k = 0.069 min−1) for methyl orange dye (MO), which is higher than those of pure TiO2 (k = 0.001 min−1) and g-C3N4 (k = 0.012 min−1), showing excellent photocatalytic activity against organic pollutants.The CNS-TiO2/g-C3N4 photocatalyst with excellent visible light catalytic activity was successfully manufactured, benefiting from the construction of the Z-scheme heterojunction and the co-doping of heteroatoms (C, N and S). 相似文献
18.
Xuan Ge Hang Sun Kun Dong Yanqi Tao Qi Wang Yazhong Chen Genlei Zhang Peng Cui Ye Wang Qinghong Zhang 《RSC advances》2019,9(26):14592
Mechanically mixed γ-Al2O3 and HZSM-5 (Si/Al = 50) with different mass ratio were utilized as support for Cu–Co higher alcohol synthesis catalysts prepared through incipient wetness impregnation. The textural and structural properties were studied using Ar low temperature adsorption and desorption, H2-temperature programmed reduction (H2-TPR), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscope (TEM) and catalytic performance measurements. The results indicated that the mechanically mixed HZSM-5 and γ-Al2O3 supported copper–cobalt catalysts were superior to either γ-Al2O3 or HZSM-5 supported ones with the same metal loading. The results revealed that using HZSM-5 and γ-Al2O3 mechanically mixed benefited the dispersion of metallic phases and stronger synergetic functions between smaller nanoparticles containing copper and/or cobalt, which is essential for HAS from CO hydrogenation. Under working conditions of P = 5.0 MPa, T = 300 °C, V(H2) : V(CO) : V(N2) = 4 : 2 : 1 and GHSV = 7200 mL g−1 h−1, mechanically mixed HZSM-5 and γ-Al2O3 supported catalysts showed higher catalytic activity than those over single support. For CuCo catalysts upon support containing 50.0 wt% HZSM-5 and 50.0 wt% γ-Al2O3, the CO conversion was 21.3% and the C2+ alcohol selectivity was 41.8%.CuCo bimetallic catalysts over the mixed supports showed smaller average particle size, better dispersion of cobalt and copper species, and good activity for higher alcohols synthesis. 相似文献
19.
Lijun Liu Boxiong Shen Meng Si Peng Yuan Fengju Lu Hongpei Gao Yan Yao Cai Liang Hongjie Xu 《RSC advances》2021,11(31):18945
Mn-Based catalysts supported on γ-Al2O3, TiO2 and MCM-41 synthesized by an impregnation method were compared to evaluate their NO catalytic oxidation performance with low ratio O3/NO at low temperature (80–200 °C). Activity tests showed that the participation of O3 remarkably promoted the NO oxidation. The catalytic oxidation performance of the three catalysts decreased in the following order: Mn/γ-Al2O3 > Mn/TiO2 > Mn/MCM-41, indicating that Mn/γ-Al2O3 exhibited the best catalytic activity. In addition, there was a clear synergistic effect between Mn/γ-Al2O3 and O3, followed by Mn/TiO2 and O3. The characterization results of XRD, EDS mapping, BET, H2-TPR, XPS and TG showed that Mn/γ-Al2O3 had good manganese dispersion, excellent redox properties, appropriate amounts of coexisting Mn3+ and Mn4+ and abundant chemically adsorbed oxygen, which ensured its good performance. In situ DRIFTS demonstrated the NO adsorption performance on the catalyst surface. As revealed by in situ DRIFTS experiments, the chemically adsorbed oxygen, mainly from the decomposition of O3, greatly promoted the NO adsorption and the formation of nitrates. The Mn-based catalysts showed stronger adsorption strength than the corresponding pure supports. Due to the abundant adsorption sites provided by pure γ-Al2O3, under the interaction of Mn and γ-Al2O3, the Mn/γ-Al2O3 catalyst exhibited the strongest NO adsorption performance among the three catalysts and produced lots of monodentate nitrates (–O–NO2) and bidentate nitrates (–O2NO), which were the vital intermediate species for NO2 formation. Moreover, the NO–TPD studies also demonstrated that Mn/γ-Al2O3 showed the best NO desorption performance among the three catalysts. The good NO adsorption and desorption characteristics of Mn/γ-Al2O3 improved its high catalytic activity. In addition, the activity test results also suggested that Mn/γ-Al2O3 exhibited good SO2 tolerance.The Mn/γ-Al2O3 catalyst exhibited excellent performance for NO conversion in the presence of a low ratio of O3/NO, which was due to the coexistence of Mn3+ and Mn4+ and abundant chemically adsorbed oxygen. 相似文献
20.
Bionic design is efficient to develop high-performance lightweight refractories with sophisticated structures such as hollow ceramic fibers. Here, we report a four-stage procedure for the preparation of Al2O3–ZrO2(Y2O3) hollow fibers using the template of cogon—a natural grass. Subsequently, to optimize the thermal performance of the fibers, four sets of preparation parameters, namely, x(Al2O3), solute mass ratio of the mixture, dry temperature, and sintering temperature were investigated. Through an orthogonal design, the optimal condition of each parameter was obtained as follows: x(Al2O3) was 0.70, solute mass ratio of the mixture was 15 wt%, dry temperature was 80 °C, and sintering temperature was 1100 °C. Overall, Al2O3–ZrO2(Y2O3) hollow fibers show relatively low thermal conductivity (0.1038 W m−1 K−1 at 1000 °C), high porosity (95.0%), and low density (0.05–0.10 g cm−3). The multiphase compositions and morphology of Al2O3–ZrO2(Y2O3) hollow fibers, which may contribute to their thermal properties, were also discussed.Lightweight Al2O3–ZrO2(Y2O3) hollow fibers with low thermal conductivity were prepared by a natural template—cogon grass. 相似文献