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عنوان فارسی مقاله:
کاهش برنامه ریزی شده دمای اصلاح کاتالیزور بخار نیکل با گلوکز
عنوان انگلیسی مقاله:
Temperature-programmed reduction of nickel steam reforming catalyst with glucose
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Chemical looping reforming (CLR) is a novel reforming technology for syngas production from hydrocarbons with low heat demand [1–5]. A typical CLR process is performed by circulating oxygen carrier (normally supported metal oxide) between two reactors. In a fuel reactor, the oxygen carrier is first reduced by fuel, and then catalyses steam reforming of fuel [6]. In an air reactor, the reduced oxygen carrier is re-oxidized and then sent back to the fuel reactor for a new cycle. The heat required for the steam reforming is supplied by the internal combustion. A key issue for CLR technology is the selection of suitable oxygen carriers. Supported NiO has been suggested as a promising oxygen carrier due to its high reduction reactivity and adequate catalytic activity on steam reforming [6–8]. In fact, alumina supported NiO (NiO/-Al2O3) is a common catalyst for industrial steam reforming process [9]. It has also been selected as a model steam reforming catalyst in some research [10,11]. Similar to other transition metal catalysts, the NiO catalyst requires reduction to give active phase (i.e. metallic Ni) priorto their use [12]. In industry, the catalyst reduction is usually conducted with either hydrogen-containing gases or natural gassteam mixtures. Reduction conditions are important as they have influences on subsequent catalytic activity [10]. For instance, high temperatures and rapid reduction may result in lower Ni dispersions and less activity, the introduction of carbon or sulphur may accelerate catalyst deactivation [13,14]. Therefore, reduction mechanisms and possible affecting factors have been extensively investigated using hydrogen or light hydrocarbons as reducing agents [15–22]. Richardson et al. [10,11,16] carried out a series of studies on H2 reduction of NiO/-Al2O3 catalysts. A reduction mechanism was proposed as follows. (1) Hydrogen is dissociated, first on NiO and then rapidly on the surface of Ni clusters as they become available. (2) Hydrogen atoms rupture Ni O bonds, producing Ni0 atoms and H2O molecules. This process is retarded or accelerated by foreign cations in NiO lattice or on vicinal surface. (3) Nickel atoms diffuse across the support surface away from reduction centres. Water retained on the surface retards nucleation by limiting the diffusion. (4) Nickel atoms nucleate into metallic clusters, after an induction period if the overall reduction rate is low (e.g. at low temperatures). (5) Nickel clusters grow into crystallites. In addition to chemical reaction, nucleation and mass transfer, the fate and activity of radicals formed by the dissociation of reductant moleculesalso play a role in determining reduction kinetics, as suggested by Syed-Hassan et al. [18,23]. The conventional fuel for syngas generation by steam reforming or CLR is natural gas. There is a growing interest in exploiting biomass as substitute of fossil fuel to produce fuels and chemicals. Some bio-liquids such as bio-diesel and bio-ethanol could be utilized as transport fuels after a simple pre-treatment. In contrast, bio-oil must be upgraded by complex chemical processes (e.g. hydrodeoxygenation, zeolite upgrading [24]) if it is to be used in vehicles, which increases energetic and economic costs. This is determined by the properties of bio-oil that include high oxygen content, complex composition, low heating value, high viscosity, incomplete volatility, and chemical instability. Alternatively, biooil can be converted into syngas by steam reforming [25,26]. The conversion of bio-liquids to syngas is a promising route to utilize biomass resources as syngas has a wide application (the production of ammonia, methanol, alkanes and hydrogen), although the storage of syngas is not as easy as that for liquid fuels. Syngas production by bio-oil steam reforming followed by water gas shift has been considered as a promising way for sustainable H2 production, which is of importance to accomplish ‘hydrogen economy’ in future. Some bio-liquids (e.g. sunflower oil [2], waste cooking oil [27,28], scrap tyre oil [29], and bio-oil [30]) have been tested in a CLR process. Feasibility of bio-oil CLR was proved but bottlenecks still existed. For scrap tyre pyrolysis oil in which a considerable amount of sulphur was present [29], the H2 yield decreased as the cycle number increased. Analysis of the reacted catalyst indicated this was most likely due to catalyst deactivation by carbon deposition and sulphur poisoning. Catalyst deactivation upon cycling was also observed during the CLR of biomass pyrolysis oil as indicated by the drop in fuel conversion [30]. The reduction rate of catalyst also decreased with cycling. Solutions to these problems include preparing catalysts more tolerant to carbon deposition, pre-treating feedstock to remove sulphur, and investigating the mechanism of catalyst reduction with bio-feedstock. As a typical bio-feedstock for CLR, bio-oil is obtained by fast pyrolysis of biomass and comprised of numerous hydrocarbons. Most of bio-oil components have a tendency to decompose at operating temperatures (600–900 ◦C). Both types of pyrolysis products (volatiles and char) are potential reductant for oxygen carriers. Therefore, multiple reaction channels exist simultaneously during CLR, making research on reduction mechanism difficult. Rather than evaluating the global reduction process during CLR, the objective of this study is to reveal the reactivity between a NiO catalyst and char from glucose pyrolysis, which is part of the complex reaction network. Glucose was selected as a model compound of biomass as it is the basic building block of cellulose and one of bio-oil components [25,26]. A slow temperature-programmed rise anda continuousflow ofinert gas were employedinthis study. Such a condition decoupled glucose pyrolysis and catalyst reduction, enabling the reduction to be studied separately. Reduction characteristics and mechanism were discussed. The work presented here is part of a series on the reduction of a NiO catalyst with various bio-compounds and has been covered in the thesis of the first author [8]. Such a study has an implication both for exploiting biomass resources via chemical looping technology and for gaining an insight into solid reduction mechanism.
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کلمات کلیدی:
Supporting data for “Temperature-programmed reduction of nickel ... archive.researchdata.leeds.ac.uk/71/ Aug 18, 2016 - Cheng, Feng (2016) Supporting data for “Temperature-programmed reduction of nickel steam reforming catalyst with glucose”. University of ... [PDF]Temperature-programmed reduction of nickel steam reforming catalyst ... iranarze.ir/wp-content/uploads/2016/10/E2108.pdf Nickel oxide. Reforming catalyst. Glucose char. Reduction. TGA-FTIR. a b s t r a c t. Temperature-programmed reduction (TPR) of a NiO/-Al2O3 steam reforming ... [PDF]Nickel-based Catalysts for Gasification of Glucose in Supercritical Water ir.lib.uwo.ca/cgi/viewcontent.cgi?article=1104&context=etd by MBI Chowdhury - 2010 - Cited by 2 - Related articles Title: Supercritical water gasification and partial oxidation of glucose: Effect ...... Minowa et al.71 showed the importance of Ni catalyst on the steam reforming and. Catalytic Gasification of Glucose over Ni/Activated ... - ACS Publications pubs.acs.org/doi/pdf/10.1021/ie8012456 by IG Lee - 2008 - Cited by 67 - Related articles Dec 19, 2008 - steam gasification of biomass,17 or hydrothermal treatments of glucose16,18 and ... Amin et al.16 found commercial nickel reforming catalysts. Integrated Catalytic Process for Conversion of Biomass to Hydrogen ... pubs.acs.org/doi/full/10.1021/ef060054f by SM Swami - 2006 - Cited by 84 - Related articles Jump to Glucose Reforming - The low Pd−Ni catalyst contained 0.1% Pd and 3% Ni, whereas ... the amount of char formation for glucose steam reforming. Reduction of model steam reforming catalysts: NiO/α-Al2O3 https://www.researchgate.net/.../229236205_Reduction_of_model_steam_reforming_cat... Temperature-programmed reduction of nickel steam reforming catalyst with glucose. "Therefore, reduction mechanisms and possible affecting factors have been ... Developments in Thermochemical Biomass Conversion: Volume 1 / https://books.google.com/books?isbn=9400915594 A.V. Bridgwater, D.G.B. Boocock - 2013 - Science ... Jr. (1993) Hydrogen production by steam reforming glucose in supercritical ... wet cellulose into methane using reduced nickel catalyst and sodium carbonate.
