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1.
Jie Du Yajing Zhang Kangjun Wang Fu Ding Songyan Jia Guoguo Liu Limei Tan 《RSC advances》2021,11(24):14426
Dimethyl ether (DME) can be directly synthesized from carbon dioxide and hydrogen by mixing methanol synthesis catalysts and methanol dehydration catalysts. The activity and selectivity of the catalyst can be greatly affected by the promoter; herein, we presented a series of CuO–ZnO–Ga2O3/HZSM-5 hybrid catalysts, which were prepared by the coprecipitation method. The effect of the Ga2O3 content on the structure and performance of the Ga-promoted Cu–ZnO/HZSM-5 based catalysts was thoroughly investigated. The results showed that the addition of Ga2O3 significantly increased specific surface areas and Cu areas, decreased the size of Cu particles, maintained the proportion of Cu+/Cu0 on the surface of the catalyst, and strengthened the metal–support interaction, resulting in high catalytic performance.The additive Ga2O3 improved the catalytic performance of CuO–ZnO/HZSM-5 catalysts for hydrogenation of CO2 to DME. 相似文献
2.
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
3.
As deep space exploration moves farther and farther away, thermal control coating of the in-orbit spacecraft will suffer a serious vacuum-ultraviolet radiation environment, which seriously threatens the reliability of the spacecraft in orbit. Therefore, it is important to improve the vacuum-ultraviolet resistance performance of the thermal control coating. In this work, the inorganic Al2O3–ZnO–Y2O3 thermal control coating was in situ fabricated on a 6061 aluminum alloy surface by PEO technology, and its vacuum-ultraviolet resistance performance was investigated. The results show that the Al2O3–ZnO–Y2O3 thermal control coating has a good resistance performance to vacuum-ultraviolet radiation, which is mainly because the large extinction coefficients of the ZnO and Y2O3 materials in the ultraviolet band are conducive to improving the ultraviolet resistance performance. Furthermore, the life prediction model of the Al2O3–ZnO–Y2O3 thermal control coating shows that its Δαs value first slightly increases and then tends to be stable with the increase of ultraviolet irradiation time from 0 ESH to 25 000 ESH, and the maximum variation of Δαs is about 0.0536. This work provides a material basis and technical support for the thermal control system of spacecraft with long life and high reliability.The Al2O3–ZnO–Y2O3 thermal control coating in situ fabricated by PEO technology, shows a good resistance performance to vacuum-ultraviolet radiation. Further, its life prediction model at vacuum-ultraviolet irradiation is preliminarily established. 相似文献
4.
In this study, different magnesium, copper, lanthanide single metal, and composite multimetal oxide catalysts were prepared via the coprecipitation route for the aerobic oxidation of cumene into cumene hydroperoxide. All catalysts were characterized using several analytical techniques, including XRD, SEM, EDS, FT-IR, BET, CO2-TPD, XPS, and TG-DTG. La2O3–CuO–MgO shows higher oxidation activity and yield than other catalysts. The results of XRD and SEM studies show that the copper and magnesium particles in the catalyst are smaller in size and have a distribution over a larger area due to the introduction of the lanthanum element. The CO2-TPD results confirmed that the catalyst has more alkali density and alkali strength, which can excite active sites and prevent the decomposition of cumene hydroperoxide. XPS results show that due to the promotional effect of La2O3, there are more lattice and active oxygen species in the catalyst, which can effectively utilize the lattice defects under the strong interaction between metal oxides for rapid adsorption and activation, thus improving the oxidation performance. Besides, La2O3–CuO–MgO exhibits good stability and crystalline structure due to its high oxygen mobility inhibiting coking during the cycle stability test. Finally, the possible reaction pathway and promotional mechanism on La2O3–CuO–MgO in cumene oxidation are proposed. We expect this study to shed more light on the nature of the surface-active site(s) of La2O3–CuO–MgO catalyst for cumene oxidation and the development of heterogeneous catalysts with high activity in a wide range of applications.The La2O3–CuO–MgO catalyst acts on the oxidation of cumene and shows excellent catalytic activity through the coordination of surface and interior. 相似文献
5.
Reactive adsorption desulfurization (RADS) of Fluidized Catalytically Cracked (FCC) gasoline on reduced and unreduced NiO/ZnO–Al2O3–SiO2 adsorbents was studied. Various characterizations such as powder X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), the H2/O2 pulse titration (HOPT), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) are used to evaluate the effects of hydrogen pretreatment of the adsorbents. XRD and HOPT results indicate that NiO is hard to be reduced to Ni0 under the conditions of RADS. H2-TPR shows that NiO might be reduced to Ni0 at the temperature of 598 °C, much higher than the temperature of RADS. The Ni 2p3/2 spectrum of Ni0 is not observed for the reduced adsorbent, but the main peak of Ni 2p3/2 of NiS is found for the spent adsorbent. The unreduced NiO/ZnO–Al2O3–SiO2 adsorbent performs a better desulfurization than the reduced adsorbent at the beginning of desulfurization process. NiO and Ni0 are assumed as the main active components and present a good desulfurization ability in RADS. Finally, a change in the RADS mechanism is presented and discussed.A possible reaction mechanism of desulfurization on NiO/ZnO–Al2O3–SiO2 is discussed. 相似文献
6.
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
7.
Stefan Wild Sabrina Polierer Thomas A. Zevaco David Guse Matthias Kind Stephan Pitter Karla Herrera Delgado Jrg Sauer 《RSC advances》2021,11(5):2556
Catalyst systems for the conversion of synthesis gas, which are tolerant to fluctuating CO/CO2 gas compositions, have great potential for process-technical applications, related to the expected changes in the supply of synthesis gas. Copper-based catalysts usually used in the synthesis of methanol play an important role in this context. We investigated the productivity characteristics for their application in direct dimethyl ether (DME) synthesis as a function of the CO2/COx ratio over the complete range from 0 to 1. For this purpose, we compared an industrial Cu/ZnO/Al2O3 methanol catalyst with a self-developed Cu/ZnO/ZrO2 catalyst prepared by a continuous coprecipitation approach. For DME synthesis, catalysts were combined with two commercial dehydration catalysts, H-FER 20 and γ-Al2O3, respectively. Using a standard testing procedure, we determined the productivity characteristics in a temperature range between 483 K and 523 K in a fixed bed reactor. The combination of Cu/ZnO/ZrO2 and H-FER 20 provided the highest DME productivity with up to 1017 gDME (kgCu h)−1 at 523 K, 50 bar and 36 000 mlN (g h)−1 and achieved DME productivities higher than 689 gDME (kgCu h)−1 at all investigated CO2/COx ratios under the mentioned conditions. With the use of Cu/ZnO/ZrO2//H-FER 20 a promising operating range between CO2/COx 0.47 and 0.8 was found where CO as well as CO2 can be converted with high DME selectivity. First results on the long-term stability of the system Cu/ZnO/ZrO2//H-FER 20 showed an overall reduction of 27.0% over 545 h time on stream and 14.6% between 200 h and 545 h under variable feed conditions with a consistently high DME selectivity.Catalyst systems for the conversion of synthesis gas, which are tolerant to fluctuating CO/CO2 gas compositions, have great potential for process-technical applications, related to the expected changes in the synthesis gas supply. 相似文献
8.
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
9.
The influence of aging of precipitates on the physical and catalytic properties of a copper/zinc oxide-aluminium (Cu/ZnO–Al) catalyst with an optimized composition (low Al concentration, Cu/Zn/Al = 68/29/3) prepared using co-precipitation has been investigated in detail. The change in the structure of precipitates with aging (from amorphous zincian georgeite to crystalline zincian malachite) strongly influences the micro- and nano-structure (Cu and ZnO crystallite size, exposed copper surface area, Cu–ZnO interactions and stability of ZnO) of the final Cu/ZnO–Al catalysts obtained after calcination and reduction of the precipitates. The results of catalytic activity in methanol synthesis from syngas show the higher intrinsic activity of the catalysts derived from aged zincian malachite precipitates as consequence of the increase in the exposed copper surface area and the Cu–ZnO contacts. The stability of catalysts under the reaction conditions was also improved in the catalysts derived from precipitates aged after crystallization of malachite. The catalyst derived from the precipitate removed close to the point of crystallization of malachite shows very poor activity in the methanol synthesis as consequence of its segregated large Cu crystallites in low contact with ZnO derived from the absence of carbonate retention after calcination of the precipitate and the presence of sodium species after conventional washing which favour the strong sintering and crystallization of Cu during reduction.The catalysts derived from precipitates aged after crystallization of zincian malachite show higher activity and stability 相似文献
10.
Yaxian Zhao Jincheng Du Xin Cao Chong Zhang Gang Xu Xvsheng Qiao Yong Liu Shou Peng Gaorong Han 《RSC advances》2021,11(12):7025
We investigated the short- and medium-range structural features of sodium aluminosilicate glasses with various P2O5 (0–7 mol%) content and Al/Na ratios ranging from 0.667 to 2.000 by using molecular dynamics simulations. The local environment evolution of network former cations (Si, Al, P) and the extent of clustering behavior of modifiers (Na+) is determined through pair distribution function (PDF), total correlation function (TDF), coordination number (CN), Qxn distribution and oxygen speciation analysis. We show that Al–O–P and Si–O–Al linkage is preferred over other connections as compared to a random model and that Si–O–Si linkage is promoted by the P2O5 addition, which is related to structural heterogeneity and generates well-separated silicon-rich and aluminum–phosphorus-rich regions. Meanwhile, due to the relatively high propensity of Al to both Si and P, heterogeneity can be partly overcome with high Al content. A small amount of Si–O–P linkages have been detected at the interface of separated regions. Clustering of Na+ is also observed and intensified with the addition of P2O5. Based on the simulated structural information, a modified random network model for P2O5-bearing sodium aluminosilicate glass has been proposed, which could be useful to optimize the mobility of sodium ions and design novel functional glass compositions.(A) A modified structural model proposed for P2O5-bearing sodium aluminosilicate glasses. (B) Degree of preferred connection (DPC) of different T–O–T network linkage for LAP, MAP and HAP glass compositions with various P2O5 content. 相似文献
11.
Zaireen Fatima Chandkiram Gautam Ajeet Singh Sarvesh Kumar Avinashi Bal Chandra Yadav Afroj Ahmed Khan 《RSC advances》2022,12(49):31585
The present work mainly focuses on the fabrication of a porous glass 40SiO2–35H3BO3–19V2O5–6P2O5via a melt-quenching technique. The structural, morphological, and sensing behaviour of the glass sample was investigated successfully. The calculated density and molar volume of the fabricated glass are 2.4813 ± 0.124 g cm−3 and 35.7660 ± 1.708 cm3 mol−1. XRD, SEM and TEM analyses confirmed the amorphous nature of the glass. FTIR results revealed the O–H bond formations, which indicate that the presence of water molecules is probably due to the porous nature of the glass. Further, BET analysis confirmed the mesoporous nature of the glass sample with a mean pore diameter of 7 nm. The sensing response of the synthesized glass at 1000 ppm concentration of CO2 was found to be 3.05 with a response time 22.6 s and recovery time 25.8 s. Hence, this porous glass can be easily synthesized, is affordable, and was found to be useful for CO2 gas sensing applications.The present work mainly focuses on the fabrication of a porous glass 40SiO2–35H3BO3–19V2O5–6P2O5via a melt-quenching technique. 相似文献
12.
In this study, a CaO–SiO2–Al2O3–MgO–FeO–CaF2(–Cr2O3) slag was chosen according to the compositions of the stainless steel slag for industrial production, and a CaO block was added to the molten slag after the synthetic slag was fully melted. The influences of unmelted lime on the distribution of elements and the structure of product layers at the lime/slag boundary, particularly the existing state of chromium oxide in the chromium-bearing stainless steel slag, were deeply discussed by scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and FactSage 7.1. The experiment results indicated that when the unmelted lime existed in the CaO–SiO2–Al2O3–MgO–FeO–CaF2 slag system, two product layers of periclase (MgO) and dicalcium silicate (Ca2SiO4) at the boundary of the CaO block were formed. However, when the CaO block was added in the CaO–SiO2–Al2O3–MgO–FeO–CaF2–Cr2O3 stainless steel slag, besides MgO and Ca2SiO4 product layers, needle-shaped calcium chromite (CaCr2O4) was also precipitated around the CaO block. Moreover, a small amount of Cr dissolved in the periclase phase. Eh–pH diagrams showed that the CaCr2O4 and MgO phase unstably existed in a weak acid aqueous solution. Therefore, the existence of unmelted lime in the stainless steel slag could enhance the leachability of chromium.The effect of unmelted lime on the distribution of elements and structure of product layers in CaO–SiO2–MgO–Al2O3–FeO–CaF2(–Cr2O2) stainless steel slag and the action of unmelted lime phase mechanism in experimental slags was conducted. 相似文献
13.
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
14.
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
15.
Achim M. Diem Kevin Hildenbrand Leila Raafat Joachim Bill Zaklina Burghard 《RSC advances》2021,11(3):1354
The increasing demand for high energy, sustainable and safer rechargeable electrochemical storage systems for portable devices and electric vehicles can be satisfied by the use of hybrid batteries. Hybrid batteries, such as magnesium–lithium-ion batteries (MLIBs), using a dual-salt electrolyte take advantage of both the fast Li+ intercalation kinetics of lithium-ion batteries (LIBs) and the dendrite-free anode reactions. Here we report the utilization of a binder-free and self-supporting V2O5 nanofiber-based cathode for MLIBs. The V2O5 cathode has a high operating voltage of ∼1.5 V vs. Mg/Mg2+ and achieves storage capacities of up to 386 mA h g−1, accompanied by an energy density of 280 W h kg−1. Additionally, a good cycling stability at 200 mA g−1 over 500 cycles is reached. The structural integrity of the V2O5 cathode is preserved upon cycling. This work demonstrates the suitability of the V2O5 cathode for MLIBs to overcome the limitations of LIBs and MIBs and to meet the future demands of advanced electrochemical storage systems.This work shows the feasibility of a self-supporting V2O5 nanofiber-based cathode for magnesium–lithium-ion batteries reaching an energy density of 280 W h kg−1. 相似文献
16.
Jun-Hao Zhou Chen-Yue Yuan Ya-Li Zheng Hai-Jing Yin Kun Yuan Xiao-Chen Sun Ya-Wen Zhang 《RSC advances》2021,11(61):38486
Tandem catalysis, in which a CO2-to-C2 process is divided into a CO2-to-CO/*CO step and a CO/*CO-to-C2 step, is promising for enhancing the C2 product selectivity when using Cu-based electrochemical CO2 reduction catalysts. In this work, a nanoporous hollow Au/CuO–CuO tandem catalyst was used for catalyzing the eCO2RR, which exhibited a C2 product FE of 52.8% at −1.0 V vs. RHE and a C2 product partial current density of 78.77 mA cm−2 at −1.5 V vs. RHE. In addition, the C2 product FE stably remained at over 40% over a wide potential range, from −1.0 V to −1.5 V. This superior performance was attributed to good matching in terms of the optimal working potential and charge-transfer resistance between CO/*CO-production sites (Au/CuO) and CO/*CO-reduction sites (CuO). This site pair matching effect ensured sufficient supplies of CO/*CO and electrons at CuO sites at the working potentials, thus dramatically enhancing the formation rate of C2 products.C2 product FE of 52.8% was achieved in eCO2RR at −1.0 V vs. RHE using a nanoporous hollow Au/CuO–CuO tandem catalyst due to the matching of optimal working potentials and charge-transfer resistances of the CO-production sites and CO-reduction sites. 相似文献
17.
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
18.
A. Barrera F. Tzompantzi J. Campa-Molina J. E. Casillas R. Prez-Hernndez S. Ulloa-Godinez C. Velsquez J. Arenas-Alatorre 《RSC advances》2018,8(6):3108
The photocatalytic activity in the degradation of 4-chlorophenol (4-ClPh) in aqueous medium (80 ppm) using 2.0 wt% Ag/Al2O3–Gd2O3 (Ag/Al–Gd-x; where x = 2.0, 5.0, 15.0, 25.0 and 50.0 wt% of Gd2O3) photocatalysts prepared by the sol–gel method was studied under UV light irradiation. The photocatalysts were characterized by N2 physisorption, X-ray diffraction, SEM, HRTEM, UV-Vis, XPS, FTIR and fluorescence spectroscopy. About 67.0% of 4-ClPh was photoconverted after 4 h of UV light irradiation using Ag/γ-–Al2O3. When Ag/Al–Gd-x photocatalysts were tested, the 4-ClPh photoconversion was improved and more than 90.0% of 4-ClPh was photoconverted after 3 h of UV light irradiation in the materials containing 15.0 and 25.0 wt% of Gd2O3. Ag/Al–Gd-25 was the material with the highest efficacy to mineralize dissolved organic carbon, mineralizing more than 85.0% after 4 h of UV light irradiation. Silver nanoparticles and micro-particles of irregular pentagonal shape intersected by plane nanobelts of Al2O3–Gd2O3 composite oxide were detected in the Ag/Al–Gd-25 photocatalyst. This material is characterized by a lowest recombination rate of electron–hole pairs. The low recombination rate of photo-induced electron–hole pairs in the Ag/Al–Gd-x photocatalysts with high Gd2O3 contents (≥15.0 wt%) confirmes that the presence of silver nanoparticles and microparticles interacting with Al2O3–Gd2O3 composite oxide entities favors the separation of photo-induced charges (e− and h+). These materials could be appropriate to be used as highly efficient photocatalysts to eliminate high concentrations of 4-ClPh in aqueous medium.Ag/Al2O3–Gd2O3 showed high efficacy to photodegradate 4-chlorophenol, the strong interaction between silver nano-particles and micro-particles and Al2O3–Gd2O3 entities favors the decrease in the recombination rate. 相似文献
19.
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
20.
Hetong Li Yuchun Zhang Peng Fu Ranran Wei Zhiyu Li Lei Dai Andong Zhang 《RSC advances》2022,12(37):24014
Fe-based oxygen carriers (OCs) are widely used in chemical looping steam reforming (CLSR) due to excellent resistance to carbon buildup, low toxicity, and high activity. In this study, a type of nano NiO–Fe2O3/Al2O3 Fe-based OC that can easily be reduced by fuels and re-oxidized by air was developed for use in glycerol CLSR. It was synthesized by co-precipitation and impregnation. Based on the quadratic regression orthogonal model, a quadratic polynomial function was established to investigate the effects of temperature (T), water/carbon ratio (S/C), and loading (M) on hydrogen content (HL) and hydrogen selectivity (S). The OCs were characterized by XRD, XPS, SEM/EDX-mapping, TEM, and H2-TPR to determine their physicochemical properties. XPS shows the Fe phase highly interacted with the Al2O3 supporting matrix by forming Fe aluminates in NiO–Fe2O3/Al2O3. The S (85.33%) and HL (78.41%) were obtained under the optimal conditions T = 600 °C, S/C = 1.0 mol mol−1 and M = 0. A hydrogen content fluctuation within 4% was obtained under T = 700 °C, S/C = 1.0 mol mol−1, and M = 2.5%, which means the cycle stability is perfect because of the addition of Ni. This study provides a basis for the development of efficient oxygen carriers in the CLSR system.A nano NiO–Fe2O3/Al2O3 Fe-based OC was developed for CLSR hydrogen production experiments in a modified device. Ni promoted Fe-Al2O3 is effective and stable. 相似文献