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عنوان فارسی مقاله:
اصلاح بخار مدل پلاستیکی هیدروکربن در اثر حرارت و غیر فعال کردن کاتالیزور
عنوان انگلیسی مقاله:
Steam reforming of plastic pyrolysis model hydrocarbons and catalyst deactivation
سال انتشار : 2016
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مقدمه انگلیسی مقاله:
1. Introduction
Plastic materials have contributed to the development and progress of the society for the last 150 years. The annual increase in plastic consumption has caused an increasingly environmental issue associated with their management. In 2014, 25.8 million tonnes of post-consumer plastics waste were recovered in Europe, of which 70% were treated by recycling and energy recovery processes and 30% were still land filled [1]. Among plastic waste valorisation routes, thermochemical processes have the best perspective for their large scale implantation in order to recover fuels, chemicals, monomers and H2, with low contaminant emission [2–5]. Although gasification is the most usual process, it is generally directed to syngas production and the concentration of H2 obtained is reduced and depends greatly on the gasifying agent used. The lower temperature used in the pyrolysis strategy improves energy efficiency of the process [6] compared to the gasification strategy. Besides, pyrolysis process is flexible and can treat mixed plastics of municipal solid waste [7], automobile recycling [8], electronics and computers [9] or construction [10].Pyrolysis of plastic waste has been widely studied using different reactors such as batch reactors, fluidized beds, spouted beds, screw kilns and son on [11]. Fluidized beds reactors have been largely applied [12,13], but the vigorous movement of the solid in the conical spouted bed reactor (CSBR) avoids the defluidization of the bed by agglomeration of particles coated with fused plastic [14]. Moreover, pyrolysis in a CSBR was studied by feeding several plastic materials, such as polyolefins [15], PET [16], PS [17,18] and PMMA [19]. In the pyrolysis of different plastics, the circumstances and composition of the volatiles are considerably different. Thus, in the pyrolysis of polyolefins, which account for 62% of plastics in municipal solid wastes, the volatile stream is greatly dependent on pyrolysis temperature and residence time of the volatiles in the reactor. Thereby, polyolefin pyrolysis can be directed to the production of: i) waxes (low temperature and low residence time); ii) BTX aromatics (high temperature and high residence time); iii) light olefins (high temperature and low residence time) [15]. Polystyrene pyrolysis stream is mainly composed of aromatic hydrocarbons (monomer, dimer and trimer and other mono and polyaromatic hydrocarbons) and several studies have been carried out optimizing operating conditions for maximizing styrene recovery [18,20]. Regarding PET pyrolysis, the volatile stream is heterogeneous and composed of CO, CO2, oxygenated compoundsand aromatics [16,21]. It should be noted that PET pyrolysis gives way to the formation of a sticky carbon residue remaining in the pyrolysis reactor. In the production of H2 from plastic wastes, two strategies are of interest: i) steam gasification using a reforming catalyst in situ or in-line [11,12]; ii) pyrolysis and in-line steam reforming of the hydrocarbons produced [6,22]. The products obtained in the pyrolysis-reforming strategy are greatly dependent on the intermediates formed in the first step, which are conditioned by the operating conditions, i.e., feed, catalyst used and so on [23,24]. H2 production from HDPE pyrolysis-catalytic steam reforming was studied in a previous work [25]. HDPE pyrolysis was carried out in a CSBR and the volatiles formed were fed in-line to a fluidized bed reactor, where a Ni based commercial catalyst was placed. Under the optimum conditions, i.e., 700 ◦C, space time of 16.7 gcat min gHDPE−1 and steam/plastic ratio of 5, the H2 yield was 92.5% of that corresponding to stoichometry, which accounts for a H2 production of 38.1 g per 100 g of HDPE in the feed. These results are encouraging, but the technological development of this strategy for plastic waste valorization involves challenges, as are: i) valorization of heterogeneous plastic wastes and ii) deactivation of the catalyst. These aspects have been approached in this paper by conducting the steam reforming of model hydrocarbons of pyrolysis volatiles corresponding to different plastics in order to ascertain the effect the type of hydrocarbon has on H2 yield and catalyst deactivation. In the steam reforming of fossil fuels, the catalyst is deactivated not only by coke deposition but also by sulphur poisoning andmetal sintering [26–29]. In the case of hydrocarbons, the main cause of Ni based catalyst deactivation is coke deposition and three types of cokes have been distinguished, i.e., gum, whisker carbon and pyrolytic carbon [30]. Several studies focus on the influence of operating conditions and prove that coke formation is minimized by increasing reforming temperature and steam/carbon ratio [31–33]. Furthermore, the nature of the hydrocarbon in the feed has great influence on the amount and type of coke deposited [34,35].
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کلمات کلیدی:
Deactivation and Testing of Hydrocarbon-Processing Catalysts - ACS ... pubs.acs.org/isbn/9780841234116 Jun 6, 1996 - Deactivation and Testing of Hydrocarbon-Processing Catalysts .... Experimental Methods and Models for Prediction of Performance. Thomas S. Steam reforming of plastic pyrolysis model hydrocarbons and catalyst ... https://www.researchgate.net/.../308090778_Steam_reforming_of_plastic_pyrolysis_mo... Steam reforming of plastic pyrolysis model hydrocarbons and catalyst deactivation on ResearchGate, the professional network for scientists. Modeling of Catalyst Deactivation - ResearchGate https://www.researchgate.net/publication/228437072_Modeling_of_Catalyst_Deactivation Modeling of Catalyst Deactivation on ResearchGate, the professional network ... the kinetics of catalyst deactivation in the hydrocarbon transformation reactions. Kinetic Modeling of Hydrocarbon Processing and the Effect of Catalyst ... www.tandfonline.com/doi/abs/10.1080/01614940701803960 by GF Froment - 2008 - Cited by 50 - Related articles Previously derived fundamental rate equations for coke formation and catalyst deactivation are applied to the modeling of a number of commercial processes: ... [PDF]Steam reforming of plastic pyrolysis model hydrocarbons and catalyst ... iranarze.ir/wp-content/uploads/2016/10/E2113.pdf Sep 9, 2016 - faster catalyst deactivation than paraffinic compounds (tetradecane and .... model hydrocarbons of pyrolysis volatiles corresponding to differ-. [PDF]Catalyst deactivation www.fhi-berlin.mpg.de/.../manfred_baerns__catalyst_deactivation__110121.pdf 21.01.2011. Lecture Series Heterogeneous Catalysis: Catalyst Deactivation. Deactivation ... undesired reactions of hydrocarbon reactants, intermediates, and products ... Models for crystalline growth due to sintering by movements of atoms. Catalyst Deactivation 1997 - Page 319 - Google Books Result https://books.google.com/books?isbn=008052866X G.A. Fuentes, C.H. Bartholomew - 1997 - Technology & Engineering A. Model. for. Catalyst. Deactivation. in. Industrial. Catalytic. Reforming ... production of aromatic hydrocarbons, as well as being employed to enhance octane ...
