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کاربرد نوع شرط:
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Kinetics,Propane dehydrogenation,Pt–based catalysts,Catalyst deactivation,Coke amount,Alkali metal
- چکیده:
- چکیده انگلیسی: The kinetics of catalyst deactivation and coke formation during dehydrogenation of propane over supported Pt–based catalysts and, in particular, the effect of alkali metal promoters on catalyst activity and stability were studied. The analysis of propane conversion data showed that there is an optimum level of alkali metal promoter loading for both catalyst activity and stability.A model based on individual site poisoning was proposed for coke deposition kinetics. The model showed fair fits for coke formation data with time on stream. While the rate constant of coke formation was slightly affected by loading of Na as the neutralizing promoter, the ultimate coke amount was strongly dependent on the Na loading. It was found that coke formation sites should be different from active sites for the main reaction.
- انتشار مقاله: 26-09-1391
- نویسندگان: Farnaz Tahriri Zangeneh,Abbas Taeb,Khodayar Gholivand,Saeed Sahebdelfar
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Kinetics,Silica,Aggregation,Aluminum fluoride,Heterogeneous reaction,Aluminum hydroxide,Fluosilicic acid,Effective diffusion coefficient
- چکیده:
- چکیده انگلیسی: The kinetic of the heterogeneous chemical reaction of aluminum hydroxide and fluosilicic acid was studied. It was found that the diffusion of the reactants through the porous silica coating to the aluminum hydroxide surface and the interfacial chemical reaction between the diffusing reactant and aluminum hydroxide platelets control the overall reaction rate. These two phenomena were studied and their contributions to the overall reaction rate were derived using experimental data. By combining these terms a relation for the overall reaction rate was obtained. The activation energy of the chemical reaction was calculated to be 12 kcal/mol and the activation energy of the diffusion into the silica coating was found as 28 kcal/mol. A numerical procedure was adjusted to determine the variation of the specific surface area of un-reacted core, its average particle size and the specific surface area for mass transfer
- انتشار مقاله: 30-07-1382
- نویسندگان: Mahmoud Bayat,Abbas Taeb,Saeed Rastegar
- مشاهده
- جایگاه : پژوهشی
- مجله: Iranian Journal of Chemistry and Chemical Engineering
- نوع مقاله: Journal Article
- کلمات کلیدی: Nucleation,Crystallization,Crystal growth,Aluminum fluoride,Surface interaction
- چکیده:
- چکیده انگلیسی: Crystallization of Aluminum fluoride at atmospheric pressure has been considered. Structure, size and shape of crystals formed during the crystallization process have been investigated. By applying the direct analysis method for the existed aluminum in solution, the aluminum fluoride nucleation process has been detected as a concentration valley at the outset of crystallization process. The linear rate of growth of aluminum fluoride crystals has been measured by taking SEM micrographs from crystals during crystallization process. The rate of crystal growth in longitudinal direction is about 10-9 m/s and nearly six times more than the rate of crystal growth in side direction. It is indicated that the aluminum fluoride nucleation process is repeated after completion of growth of initial crystals.
- انتشار مقاله: 14-07-1382
- نویسندگان: Mahmoud Bayat,Abbas Taeb,Saeed Rastegar
- مشاهده
- جایگاه : پژوهشی
- مجله: Advances in Environmental Technology
- نوع مقاله: Journal Article
- کلمات کلیدی: Solid-State method,Ball mill,Methanol,Green catalyst,environmental-friendly
- چکیده:
- چکیده انگلیسی: In this research study, methanol synthesis catalysts were manufactured with various mole ratios of metal carbonates (zinc, copper and aluminum carbonate) and ammonium hydrogen carbonate via a green solid-state method that employed a ball mill apparatus. Some parameters for the catalyst preparation, such as Al mole percent, Cu/Zn mole ratio, rotations milling speeds and aging time, were optimized to obtain the maximum catalyst activity. The prepared catalysts were compared with the best quality industrial catalyst under the same temperature and pressure condition in a titanium tabular fixed bed reactor. This novel method has many advantages in comparison to the conventional method. The main advantage of the solid-state method is that the methanol synthesis catalyst can be produced without using solvent. Furthermore, this new method reduces operating costs due to the elimination of the filtration and washing steps. Methanol synthesis catalytic activity was maximized at an optimized mole ratio of Cu/Zn of 1.9234 and an Al mole percent of 8 at the maximum grinding speed (450 rpm) during an aging time of 30 min, which showed higher activity (240 gCH3OH/kg cat.h) in comparison with an industrial catalyst sample (218 gCH3OH/kg cat.h). The production of a green catalyst, which requires less water and results in higher catalyst activity, can be widely used for methanol synthesis catalytic applications.
- انتشار مقاله: 07-12-1395
- نویسندگان: Neda Mirhosseini,Mohammad Reza Mirani,Reza Davarnejad,Marzie Hamidzade,Abbas Taeb
- مشاهده