共查询到20条相似文献,搜索用时 15 毫秒
1.
Jiangyin Lu Yancong Liu Na Li Key Laboratory of Oil Gas Fine Chemicals of Ministry of Education Xinjiang University Urumqi Xinjiang China 《天然气化学杂志》2011,(4):423-427
A series of Fe/HZSM-5 catalysts with different iron loadings were prepared by impregnation method.Characterization was performed by N2 adsorption-desorption,X-ray diffraction(XRD),NH3 temperature-programmed desorption(NH3-TPD),temperature-programmed reduction (TPR),temperature-programmed oxidation(TPO)and thermogravimetry(TG)analysis.Iron content in the synthesized samples varied from 1.1 wt%to 20 wt%.The obtained samples have been used for ethanol conversion into light olefins.It was found that the amount of strong acidity at 300 -5 50-C on Fe-modified samples was decreased,going with another new acid site appearance at 550- 600-C and that Fe/HZSM-5 catalysts were highly selective towards light olefins,especially the 9FZ sample.In addition,Fe-modified catalysts suppressed the conversion of ethanol to aromatics and paraffins and enhanced their anti-carbon deposit ability. 相似文献
2.
采用水热法合成了相同粒径、不同硅铝比的ZSM-5分子筛,并通过浸渍法将Fe基(Fe-Cu-K)催化剂负载于ZSM-5上,系统考察了分子筛硅铝比变化对合成气制烯烃(FTO)反应的影响。结果表明,反应条件、分子筛酸性对CO转化率和低碳烯烃选择性有显著影响。当ZSM-5分子筛硅铝比为50时负载型催化剂有着最高的CO转化率(84.71%)和低碳烯烃选择性(32.08%)。H2-TPR结果表明,硅铝比为50的Z50/FeCuK中Fe物相的还原度最高。原位漫反射红外光谱(DRIFTS)、热重差热分析(TG-DTA)、X射线粉末衍射(XRD)等结果表明,Z50/FeCuK催化剂表面吸附的碳酸盐和烃类吸附物种最多,且其反应后形成了较多的FeCx晶相。最后对反应条件进行了优化,结果表明,温度为310 ℃,H2/CO (volume ratio)=2和压力为1.0 MPa时FTO的催化性能最优。 相似文献
3.
Six catalysts consisting of mixtures of catalysts for methanol synthesis and its conversion to hydrocarbons were prepared by mechanical mixing, impregnation, and coprecipitation, followed by extrusion. Phase changes occurring during various stages of preparation and after use were followed by x-ray diffraction. The catalysts were found to be nontrivial bifunctional catalysts which selectively convert synthesis gas directly to low molecular weight hydrocarbons in the range of C1 to C4. Methanol and dimethylether were detected as intermediates. Olefins were formed, and their further hydrogenation yielded products with high paraffinic content. Carbon dioxide retards the conversion of synthesis gas to hydrocarbons, whereas steam retards the hydrogenation of olefins. On heating the commercial zinc chromite catalyst, dehydration, reduction, and solid-state reactions occur with the formation of ZnO-ZnCr2O4 solid solution. Exchanging cations within the zeolite component did not affect the space lattice, but these ions tend to occupy special sites, and during service more order was detected. Copper ions tend to diffuse in ZnO, forming a solid solution, and during service metallic copper was produced. 相似文献
4.
5.
T. Inui 《Reaction Kinetics and Catalysis Letters》1987,35(1-2):227-236
Conversion of light olefins to gasoline was investigated for various metallosilicates having the pentasil pore-opening structure. The metallosilicate was prepared by replacing the Al ingredient of the H-ZSM-5 with various metal salt at the stage of gel formation. Among various metallosilicates H–Fe-silicate was most effective and stable for the selective formation of high octane-number gasoline. The causes of this high catalytic performance was attributed to its proper acid strength and low diffusion resistance. 相似文献
6.
7.
K/MgFeZn-HTLcs催化CO加氢制低碳烯烃性能研究 《燃料化学学报》2016,44(4):449-456
以MgFeZn-HTLcs为前驱体,制备了不同Mg/Fe/Zn物质的量配比、K改性的K/MgFeZn-HTLcs催化剂,用于CO加氢直接制低碳烯烃反应。采用N2吸附-脱附、SEM、TG、XRD、XPS、H_2-TPR等手段对催化剂进行了表征。结果表明,MgFeZnHTLcs前驱体具有典型的层状结构,孔径分布均一;经焙烧、K改性后仍具有一定的层状结构,但比表面积显著减小,平均孔径增大;新鲜催化剂物相以金属氧化物和铁酸盐为主,反应后K/MgFeZn-HTLcs催化剂主要以Fe_5C_2、MgCO_3和ZnO相存在,K/2Fe-1Zn催化剂主要物相为ZnFe2O_4。在CO加氢反应中,K/MgFeZn-HTLcs催化剂具有较高的C=2-4烯烃选择性和较低的C+5含量,与K/2Fe-1Zn催化剂相比,产物分布明显改善;K/2Mg-2Fe-1Zn催化剂上O/P比值达5.15,C=2-4含量占总烃质量的48.56%。 相似文献
8.
9.
10.
11.
12.
13.
Zn助剂对铁基催化剂费托合成制低碳烯烃性能的影响 总被引:3,自引:0,他引:3
低碳烯烃(C2=–C4=)是十分重要的基础化工原料,目前主要采用热裂解或催化裂解石脑油、蜡油等工艺路线生产。近年来,针对全球范围的石油危机及我国富煤贫油这一基本的国情,以煤、天然气(页岩气)和生物质等丰厚的碳资源,经合成气制取低碳烯烃的工艺路线备受关注。其中,合成气经由甲醇或二甲醚间接制取烯烃技术(MTO/MTP)已经工业化;与之相比,费托合成直接生产低碳烯烃(FTO)工艺流程短、投资和操作费用低,具有良好的工业发展前景。目前,费托合成催化剂活性组分的研究主要集中于Fe, Co, Ni和Ru等元素,其中Fe基催化剂具有较高低碳烯烃选择性、较低甲烷选择性和制造廉价等优势,更适合于FTO反应。最近,人们大多聚焦于对负载型铁基催化剂的研究,但传统非负载型铁催化剂由于其制备简单、价格低廉,仍然具有巨大的开发前景。近来,我们组报道了采用微波水热法制备的Zr助剂改性Fe-Zr催化剂应用于CO加氢研究,提高了催化剂的活性,与传统Mn改性铁基催化剂相比, CO2选择性明显降低。目前,已有研究小组对Zn助剂提高铁基催化剂烯烃选择性进行报道,但反应过程中的严重积碳问题却少有研究。我们在Fe-Zr催化剂的基础上,进一步研究了Zn助剂在提高铁基催化剂低碳烯烃选择性、改善产物分布和降低反应过程积碳方面的作用。
我们分别采用微波水热法和浸渍法对铁基催化剂进行了Zn改性,并将其用于费托合成制取低碳烯烃反应。运用扫描电镜(SEM)、X射线衍射(XRD)、N2物理吸附(BET)、H2程序升温还原(H2-TPR)和X射线光电子能谱(XPS)技术手段对催化剂的物理和化学性质进行了表征。结果表明,两种方法改性后的铁基催化剂具有高低碳烯烃选择性和稳定性,重质烃(C5+)含量降低,且保持低CO2选择性。此外,采用两种方法Zn改性的铁基催化剂展现出了不同的特性。 XRD结果表明,反应前两种方法制备的样品α-Fe2O3物相晶粒大小均为15–18 nm,反应后浸渍法制备的样品对应物相(ZnFe2O4)晶粒大小约为25 nm、而微波水热法制备的样品约为20 nm,说明微波水热法改性的催化剂有效分散了Fe活性组分; H2-TPR结果显示,两种Zn助剂加入方法对催化剂Fe组分的还原行为有不同程度影响,体现了活性组分间不同的相互作用; XPS结果表明, Zn助剂改变了催化剂Fe活性位的化学性质,在微波水热法制得催化剂的表面Zn含量更低、分散度更高,而Zn助剂的加入对Zr组分没有明显影响。所有催化剂经200 h在线活性测试后,采用传统浸渍法制备的催化剂表面有大量积碳生成;而采用微波水热改性铁基催化剂积碳量明显减少,表现出更高的催化活性与稳定性。 相似文献
我们分别采用微波水热法和浸渍法对铁基催化剂进行了Zn改性,并将其用于费托合成制取低碳烯烃反应。运用扫描电镜(SEM)、X射线衍射(XRD)、N2物理吸附(BET)、H2程序升温还原(H2-TPR)和X射线光电子能谱(XPS)技术手段对催化剂的物理和化学性质进行了表征。结果表明,两种方法改性后的铁基催化剂具有高低碳烯烃选择性和稳定性,重质烃(C5+)含量降低,且保持低CO2选择性。此外,采用两种方法Zn改性的铁基催化剂展现出了不同的特性。 XRD结果表明,反应前两种方法制备的样品α-Fe2O3物相晶粒大小均为15–18 nm,反应后浸渍法制备的样品对应物相(ZnFe2O4)晶粒大小约为25 nm、而微波水热法制备的样品约为20 nm,说明微波水热法改性的催化剂有效分散了Fe活性组分; H2-TPR结果显示,两种Zn助剂加入方法对催化剂Fe组分的还原行为有不同程度影响,体现了活性组分间不同的相互作用; XPS结果表明, Zn助剂改变了催化剂Fe活性位的化学性质,在微波水热法制得催化剂的表面Zn含量更低、分散度更高,而Zn助剂的加入对Zr组分没有明显影响。所有催化剂经200 h在线活性测试后,采用传统浸渍法制备的催化剂表面有大量积碳生成;而采用微波水热改性铁基催化剂积碳量明显减少,表现出更高的催化活性与稳定性。 相似文献
14.
Photolysis of an alkylmercuric halide in the presence of diphenyl-diselenide yields the corresponding alkylphenylselenium intermediate, which can be converted into an olefin on treatment with sodium periodate. 相似文献
15.
Xinxing Wang Wen Chen Tiejun Lin Jie Li Fei Yu Yunlei An Yuanyuan Dai Hui Wang Liangshu Zhong Yuhan Sun 《催化学报》2018,39(12):1869-1880
Co2C-based catalysts with SiO2, γ-Al2O3, and carbon nanotubes (CNTs) as support materials were prepared and evaluated for the Fischer-Tropsch to olefin (FTO) reaction. The combination of catalytic performance and structure characterization indicates that the cobalt-support interaction has a great influence on the Co2C morphology and catalytic performance. The CNT support facilitates the formation of a CoMn composite oxide during calcination, and Co2C nanoprisms were observed in the spent catalysts, resulting in a product distribution that greatly deviates from the classical Anderson-Schulz-Flory (ASF) distribution, where only 2.4 C% methane was generated. The Co3O4 phase for SiO2- and γ-Al2O3-supported catalysts was observed in the calcined sample. After reduction, CoO, MnO, and low-valence CoMn composite oxide were generated in the γ-Al2O3-supported sample, and both Co2C nanospheres and nanoprisms were identified in the corresponding spent catalyst. However, only separated phases of CoO and MnO were found in the reduced sample supported by SiO2, and Co2C nanospheres were detected in the spent catalyst without the evidence of any Co2C nanoprisms. The Co2C nanospheres led to a relatively high methane selectivity of 5.8 C% and 12.0 C% of the γ-Al2O3- and SiO2-supported catalysts, respectively. These results suggest that a relatively weak cobalt-support interaction is necessary for the formation of the CoMn composite oxide during calcination, which benefits the formation of Co2C nanoprisms with promising catalytic performance for the sustainable production of olefins via syngas. 相似文献
16.
A. G. Dedov O. A. Shlyakhtin A. S. Loktev G. N. Mazo S. A. Malyshev S. I. Tyumenova A. E. Baranchikov I. I. Moiseev 《Doklady Physical Chemistry》2017,477(2):209-211
New catalysts have been developed for the production of synthesis gas via a resource-saving and environmentally friendly process—dry reforming of methane. The catalysts are fabricated from NdCaCo1–xNi x On precursors (x = 0, 0.2, 0.4, 0.6, 0.8, 1) synthesized by a ceramic method. According to X-ray powder diffraction, when reacting with an equimolar CH4/CO2 mixture at 800–900°С, the precursors are converted into a mixture of neodymium and calcium oxides and cobalt and nickel metals. The catalyst based on NdCaNiO n at 850°С has ensured high conversions of methane (91%) and CO2 (86%) at СО and hydrogen yields of 88 and 78%, respectively. At 940°С, the yield of CO is close to the quantitative one (97%). 相似文献
17.
Etienne Baranoff 《Journal of organometallic chemistry》2009,694(17):2661-1073
This brief review describes applications of cyclometallated iridium complexes for energy saving organic light-emitting devices (OLED’s) and energy generating molecular photovoltaic cells. The first part consists of a short overview of the methods to modulate emitted color and quantum yield in neutral and ionic complexes for light-emitting diodes. And in the second part, we report initial results of cyclometallated iridium complexes for solar cell applications. 相似文献
18.
19.
20.
O. L. Eliseev M. V. Tsapkina O. S. Dement’eva P. E. Davydov A. V. Kazakov A. L. Lapidus 《Kinetics and Catalysis》2013,54(2):207-212
The promotion of supported cobalt catalysts for the synthesis of hydrocarbons from CO and H2 with alkali metals was studied. The catalysts were characterized by X-ray diffraction analysis, oxygen titration, and the temperature-programmed desorption (TPD) of CO. Catalytic tests showed that the introduction of alkaline promoters increases selectivity for higher hydrocarbons, decreases selectivity for methane, and also increases the concentration of olefins in the gasoline fraction of products. The promoting effect depends on the catalyst preparation method. The TPD of CO was used to demonstrate that the greatest amount of CO was adsorbed on the surface of a catalyst promoted with potassium; in this case, the strength of CO binding on this catalyst reached a maximum. The data of the TPD of CO correspond to the highest selectivity of a cobalt-potassium catalyst for the formation of higher hydrocarbons. 相似文献