共查询到20条相似文献,搜索用时 15 毫秒
1.
以氧化铝(Al2O3)、ZSM-5、Beta和SAPO-11分子筛粉体为原料制备出不同的载体,在不同温度下考察了探针分子乙醇脱水转化反应。根据NH3-TPD方法测定载体的酸量和酸分布,以及载体负载贵金属Pt后C14~24长链烷烃异构化评价结果,探讨了载体表面酸、乙醇转化和异构化性能三者之间的关系。结果表明,载体表面酸与乙醇转化和异构化性能没有直接的关系,但乙醇转化和异构化性能之间有一定关联。载体上乙醇转化的稳定性较差、乙烯选择性低,则对应的贵金属催化剂异构化性能也较差;乙烯选择性高且稳定性好,可制备出性能优异的异构化催化剂。因此,作者提出区分固体酸的酸性和酸性质的必要性。酸性包含酸量、酸强度及分布等概念,酸性质指酸中心在催化反应中的行为,简称为酸功能。前者可由常规的表面酸方法表征,后者只能在反应条件下获得。数据表明了临氢异构化剂的酸功能可以采用乙醇转化反应进行表征。用乙醇转化作为模型反应表征载体的酸作用行为即酸功能,可以为异构催化剂载体的选择提供指导。 相似文献
2.
Reaction Mechanism of One-Step Conversion of Ethanol to 1, 3-Butadiene over Zn-Y/BEA and Superior Catalysts Screening 下载免费PDF全文
Shu-Xuan Dang Han-Xuan Liu Tao Ban Xin Gao Zheng-Qing Huang Dong-Yuan Yang Chun-Ran Chang 《化学物理学报(中文版)》2022,35(4):600-610
The one-step conversion of ethanol to 1, 3-butadiene has achieved a breakthrough with the development of beta zeolite supported dual metal catalysts. However, the reaction mechanism from ethanol to butadiene is complex and has not yet been fully elucidated, and no catalyst screening effort has been done based on central metal atoms. In this work, density functional theory (DFT) calculations were employed to study the mechanism of one-step conversion of ethanol to butadiene over Zn-Y/BEA catalyst. The results show that ethanol dehydrogenation prefers to proceed on Zn site with a reaction energy of 0.77 eV in the rate-determining step, and the aldol condensation to produce butadiene prefers to proceed on Y site with a reaction energy of 0.69 eV in the rate-determining step. Based on the mechanism revealed, six elements were selected to replace Y for screening superior combination of Zn-M/BEA (M=Sn, Nb, Ta, Hf, Zr, Ti; BEA: beta polymorph A) for this reaction. As a result, Zn-Y/BEA (0.69 eV) is proven to be the most preferring catalyst compared with the other six ones, and Zn-Zr/BEA (0.85 eV), Zn-Ti/BEA (0.87 eV), and Zn-Sn/BEA (0.93 eV) can be potential candidates for the conversion of ethanol to butadiene. This work not only provides mechanistic insights into one-step catalytic conversion of ethanol to butadiene over Zn-Y/BEA catalyst but also offers more promising catalyst candidates for this reaction. 相似文献
3.
采用无机溶胶法制备了用于乙醇燃料电池的PtTe/C催化剂;利用X射线衍射仪分析了催化剂的结构,采用循环伏安法和电化学阻抗法测试了PtTe/C催化剂对乙醇的电催化氧化性能.结果表明,与商业Pt/C催化剂相比,PtTe/C催化剂对乙醇的催化氧化效率明显较高,可使乙醇氧化峰电流密度提高27%,且具有更高的抗CO中毒能力. 相似文献
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Haili Pang Jinhua Chen Lei Yang Bo Liu Xinxian Zhong Xiaogang Wei 《Journal of Solid State Electrochemistry》2008,12(3):237-243
The electrooxidation of ethanol on Pt/ZSM-5 zeolite-C catalyst was investigated in sulfuric acid aqueous solution. Because
of high stability in general acidic solution, ZSM-5 zeolite particles were selected as the support and the second catalyst.
The micrograph and elemental composition of Pt/ZSM-5 zeolite particles were characterized by scanning electron microscopy
and energy disperse X-ray spectroscopy. The electrocatalytic properties of Pt/ZSM-5 zeolite-C catalyst for ethanol oxidation
have been investigated by cyclic voltammetry. Under the same Pt-loading mass and experimental conditions for ethanol oxidation,
Pt/ZSM-5 zeolite-C catalyst shows higher activity than Pt/C catalyst. Additionally, Pt/ZSM-5 zeolite-C catalyst possesses
good long-term cycle stability. The results indicate that Pt/ZSM-5 zeolite-C catalyst may have good potential application
in direct ethanol fuel cell. 相似文献
6.
Sara Chumillas Carlos Busó-Rogero José Solla-Gullón Francisco J. Vidal-Iglesias Enrique Herrero Juan M. Feliu 《Electrochemistry communications》2011,13(11):1194-1197
Formic acid and ethanol oxidations on spherical platinum nanoparticles dispersed on carbon with different loadings have been studied. The increasing loading of the catalyst leads to a lower diffusion flux of reactants in the internal parts of the catalyst layer, resulting in a lower apparent activity. In some cases, as in ethanol oxidation, it may also affect the diffusion of the products. As a practical consequence, the structure of the supporting layer and the catalyst loading should be optimized so that the maximum catalyst utilization is obtained. Finally, these diffusion effects may mask some important catalytic activity increase of the nanoparticles. In the case of formic acid, a significant increase in the activity is obtained for very small nanoparticles. 相似文献
7.
采用静电纺丝技术制备了碳纤维基纳米Pt-SnO2阳极催化剂(Pt/Sn原子比为3)。通过X射线衍射(XRD)、红外光谱(FT-IR)、扫描电子显微镜(SEM)等技术对该催化剂进行了表征,并采用循环伏安法对其在乙醇燃料电池中的阳极催化活性进行了评价。结果表明,纳米Pt-SnO2催化剂均匀地分散在碳纤维骨架上;随着烧结温度的升高,碳纤维载体的致密度越高、导电性能越好。电催化性能测试表明,烧结温度为800℃时催化剂的峰电流密度最大,达到0.11 A/cm2,抗中毒能力也最强。单电池的发电性能表明,在一定的乙醇浓度下,1.0 mL/min进样流速具有最优的发电效率。 相似文献
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Steam-reforming of ethanol for hydrogen production 总被引:1,自引:0,他引:1
Ahmed Bshish Zahira Yaakob Binitha Narayanan Resmi Ramakrishnan Ali Ebshish 《Chemical Papers》2011,65(3):251-266
Production of hydrogen by steam-reforming of ethanol has been performed using different catalytic systems. The present review
focuses on various catalyst systems used for this purpose. The activity of catalysts depends on several factors such as the
nature of the active metal catalyst and the catalyst support, the precursor used, the method adopted for catalyst preparation,
and the presence of promoters as well as reaction conditions like the water-to-ethanol molar ratio, temperature, and space
velocity. Among the active metals used to date for hydrogen production from ethanol, promoted-Ni is found to be a suitable
choice in terms of the activity of the resulting catalyst. Cu is the most commonly used promoter with nickel-based catalysts
to overcome the inactivity of nickel in the water-gas shift reaction. γ-Al2O3 support has been preferred by many researchers because of its ability to withstand reaction conditions. However, γ-Al2O3, being acidic, possesses the disadvantage of favouring ethanol dehydration to ethylene which is considered to be a source
of carbon deposit found on the catalyst. To overcome this difficulty and to obtain the long-term catalyst stability, basic
oxide supports such as CeO2, MgO, La2O3, etc. are mixed with alumina which neutralises the acidic sites. Most of the catalysts which can provide higher ethanol conversion
and hydrogen selectivity were prepared by a combination of impregnation method and sol-gel method. High temperature and high
water-to-ethanol molar ratio are two important factors in increasing the ethanol conversion and hydrogen selectivity, whereas
an increase in pressure can adversely affect hydrogen production. 相似文献
10.
Fuming Mei Exiang Chen Guangxing Li Aiqing Zhang 《Reaction Kinetics and Catalysis Letters》2008,93(1):101-108
Mg-Al-O-t-Bu hydrotalcite was synthesized and characterized by XRD, FT-IR and TGA-DTA. It was proved to be an active heterogeneous
catalyst for the transesterification of dimethyl carbonate (DMC) with ethanol. When the reaction was carried out over Mg-Al-O-t-Bu
hydrotalcite at 80°C, 7 h, molar ratio of ethanol to DMC 5:1, 1.0 wt.% of catalyst, the conversion of DMC was 86.4%, the selectivity
to diethyl carbonate (DEC) was 61.2%. This heterogeneous catalyst could be used 5 times without loss of its activity. 相似文献
11.
《印度化学会志》2023,100(2):100876
The direct ethanol fuel cell is a green and renewable power source alternative to fossil fuels and produces less emissions compared to a combustion engine. Ethanol can be generated in great quantity from renewable resources like biomass through a fermentation process. Bio-generated ethanol is thus attractive fuel since growing crops for biofuels absorbs much of the carbon dioxide emitted into the atmosphere from the oxidation of ethanol. The platinum and palladium were co-deposited on graphite substrate by the galvanostatic technique and employed as anode catalyst for ethanol electrooxidation. The information on surface morphology, structural characteristics and bulk composition of the catalyst was obtained using scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) spectroscopy. The cyclic voltammetry (CV) were used for the estimation of the electrochemically active surface area (ECSA) of the synthesized catalysts in alkaline medium. The CVs for ethanol oxidation revealed superior catalytic activity of Pt–Pd/C compared to Pd/C and Pt/C. The effect of OH? on ethanol oxidation at Pt–Pd/C catalyst was studied using cyclic voltammetry, quasisteady-state polarization, chronoamperometry, and electrochemical impedance spectroscopy (EIS). The Pt–Pd/C catalyst shows good stability and enhanced electrocatalytic activity is ascribed to the synergistic effect of higher electrochemical surface area, preferred OH? adsorption on the surface and palladium ad-atom contribution on the alloyed surface. 相似文献
12.
在HZSM-5分子筛催化乙醇脱水反应中观察到了停料效应:即当停止乙醇-水进料一定时间,恢复进料后乙烯选择性明显提高。通过考察不同反应条件下的停料效应,发现乙醇质量分数控制在55%附近、延长停料时间、升高反应温度和降低乙醇进料空速会提高停料效应强度,并较长时间维持高乙烯选择性。500 h的催化剂稳定性测试表明,停料效应可有效延长催化剂的使用寿命。结合含水乙醇脱水反应机理和实验结果,推测HZSM-5催化乙醇脱水停料效应产生的原因是停料时乙氧基中间体的积累和催化活性空位的再生。 相似文献
13.
Mann J Yao N Bocarsly AB 《Langmuir : the ACS journal of surfaces and colloids》2006,22(25):10432-10436
A direct ethanol fuel cell offers an attractive, fairly high density, energy source, if an electrochemical system can be developed that efficiently carries out the 12-electron oxidation of ethanol to carbon dioxide and water. To that end, new catalyst systems must be developed along with fuel cell operating conditions that encourage the complete oxidation of ethanol, as opposed to the presently available platinum on carbon systems that tend to produce acetaldehyde (two-electron oxidation) or acetic acid (four-electron oxidation) products. It is found that a composite nanoparticulate catalyst containing platinum and tin oxide or platinum indium tin oxide allows the partial conversion of ethanol to its 12-electron oxidation products. Catalysts of this type can be formed using a modified polyol process. Elevation of the operating temperature of a proton exchange membrane fuel cell using the indicated catalysts to 130 degrees C facilitates the production of carbon dioxide and provides an improved current-voltage response. 相似文献
14.
Only 15 mol% of l-proline in ethanol proved to be a very efficient catalyst for the one-pot synthesis of a wide variety of highly substituted pyridines at room temperature. The methodology is mild, efficient, high yielding, and the products can be directly recrystallized from hot ethanol. 相似文献
15.
S. P. Banzaraktsaeva E. V. Ovchinnikova V. A. Chumachenko 《Russian Journal of Applied Chemistry》2018,91(9):1486-1492
The indicators of ethanol to ethylene catalytic dehydration process on trilobe- and ring-shaped samples of an alumina catalyst were compared at the fixed parameters: thermal agent temperature and catalyst load. Experiments were performed in a flow-through reactor of a laboratory setup and in a tubular reactor of a pilot installation. The use of the less active ring-shaped catalyst ensures higher values of ethanol conversion, ethylene yield, and catalyst performance and significantly lower hydraulic resistance, compared to the more active trilobe-shaped catalyst. This is caused by lower intensity of the heat absorption on the less active catalyst and, correspondingly, to the higher temperature in the ring bed due to higher bed porosity. 相似文献
16.
浸渍顺序对Ag-Pd/Ce0.8Zr0.2O2催化剂活性及脱附性能的影响 总被引:1,自引:0,他引:1
采用不同的浸渍顺序制备了Ag-Pd/Ce0.8Zr0.2O2双组分催化剂,考察了催化剂对乙醇和CO氧化反应的催化活性,并对催化剂进行了TPD表征. 结果表明,浸渍顺序对催化剂的活性有很大的影响. 共浸渍催化剂的活性最高,其次为先浸渍钯后浸渍银的催化剂,先浸渍银后浸渍钯催化剂的活性最低. 催化剂上CO氧化活性与CO-TPD过程中CO2脱附峰的温度及强度有对应关系. 同时,乙醇氧化活性与C2H5OH-TPD过程中CO2脱附峰的温度有一定的对应关系. 这表明共浸渍催化剂的表面氧物种最活泼,最容易与吸附在催化剂表面的乙醇或CO发生氧化反应. 不同的浸渍顺序影响Ag或Pd的存在状态,共浸渍时有利于氧化态的形成; 但Ag状态的变化与催化剂上乙醇或CO氧化反应的活性没有对应关系. 相似文献
17.
Dr. Senthil Subramaniam Dr. Mond F. Guo Tanmayi Bathena Michel Gray Dr. Xiao Zhang Abraham Martinez Dr. Libor Kovarik Dr. Konstantinos A. Goulas Dr. Karthikeyan K. Ramasamy 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(34):14658-14665
Ethanol can be used as a platform molecule for synthesizing valuable chemicals and fuel precursors. Direct synthesis of C5+ ketones, building blocks for lubricants and hydrocarbon fuels, from ethanol was achieved over a stable Pd-promoted ZnO-ZrO2 catalyst. The sequence of reaction steps involved in the C5+ ketone formation from ethanol was determined. The key reaction steps were found to be the in situ generation of the acetone intermediate and the cross-aldol condensation between the reaction intermediates acetaldehyde and acetone. The formation of a Pd–Zn alloy in situ was identified to be the critical factor in maintaining high yield to the C5+ ketones and the stability of the catalyst. A yield of >70 % to C5+ ketones was achieved over a 0.1 % Pd-ZnO-ZrO2 mixed oxide catalyst, and the catalyst was demonstrated to be stable beyond 2000 hours on stream without any catalyst deactivation. 相似文献
18.
有机蒙脱土负载镍催化剂上乙醇重整制氢 总被引:1,自引:0,他引:1
有机蒙脱土负载镍催化剂上乙醇重整制氢 《燃料化学学报》2016,44(6):689-697
采用浸渍法制备了有机改性蒙脱土(OMt)负载的Ni/有机蒙脱土(Ni/OMt)催化剂,用于乙醇重整制氢;通过XRD、FT-IR、H2-TPR、SEM、XPS和氮吸附等手段对催化剂进行了表征分析。结果表明,与未改性的蒙脱土负载的Ni催化剂(Ni/MMT)相比,有机改性可显著提高其比表面积、孔容和金属Ni的分散度,降低碳沉积量,改善Ni/MMT催化剂的稳定性。Ni/OMt催化剂表现出较高的乙醇重整制氢催化性能,在773K下反应30 h,乙醇转化率保持在100%,氢气选择性为70%;而Ni/MMT催化剂在反应10 h即开始失活,碳沉积严重,同时产生副产物乙烯和乙醛。使用十六烷基三甲基溴化铵(CTAB)改性可促进Ni高分散在MMT层板上,抑制积炭对活性金属Ni包裹,提高其乙醇重整氢气选择性、降低乙烯和乙醛的选择性。 相似文献
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乙酸选择性加氢制乙醇反应性能研究 《燃料化学学报》2016,44(7):862-869
在固定床反应器上考察了反应温度、反应压力、乙酸(HAC)液体进料空速、H_2/HAC(总气体空速GHSV或H_2流量)对乙酸选择性加氢制乙醇反应的影响,研究了乙酸转化率、产物选择性、乙醇时空收率的变化规律,验证了自主开发催化剂的稳定性。结果表明,副产物的选择性受反应条件的影响,选择合适的反应条件可以抑制乙酸乙酯和丙酮的生成。原料与催化剂床层接触时间小于5s时,可以避免发生乙酸加氢分解脱羰反应生成甲烷气相产物,也避免了乙醇的进一步反应生成乙烷。在反应温度为280℃,反应压力为2.5 MPa,乙酸进料液时空速为0.72 h~(-1),H_2/HAC(mol ratio)为16的条件下,乙酸乙酯选择性为6%。900 h长周期实验表明,自主开发催化剂具有较好的工业应用前景。 相似文献