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Post Deformation at Room and Cryogenic Temperature Cooling Media on Severely Deformed 1050-Aluminum
M. Sarkari Khorrami,M. Kazeminezhad 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2
The annealed 1050-aluminum sheets were initially subjected to the severe plastic deformation through two passes of constrainedgroove pressing (CGP) process. The obtained specimens were post-deformed by friction stir processing at roomand cryogenic temperature cooling media. The microstructure evolutions during mentioned processes in terms of grainstructure, misorientation distribution, and grain orientation spread (GOS) were characterized using electron backscattereddiffraction. The annealed sample contained a large number of “recrystallized” grains and relatively large fraction (78%) ofhigh-angle grain boundaries (HAGBs). When CGP process was applied on the annealed specimen, the elongated grainswith interior substructure were developed, which was responsible for the formation of 80% low-angle grain boundaries. TheGOS map of the severely deformed specimen manifested the formation of 43% “distorted” and 51% “substructured” grains. The post deformation of severely deformed aluminum at room temperature led to the increase in the fraction of HAGBsfrom 20 to 60%. Also, it gave rise to the formation of “recrystallized” grains with the average size of 13 μm, which werecoarser than the grains predicted by Zener–Hollomon parameter. This was attributed to the occurrence of appreciable graingrowth during post deformation. In the case of post deformation at cryogenic temperature cooling medium, the grain sizewas decreased, which was in well agreement with the predicted grain size. The cumulative distribution of misorientationwas the same for both processing routes. Mechanical properties characterizations in terms of nano-indentation and tensiletests revealed that the post deformation process led to the reduction in hardness, yield stress, and ultimate tensile strengthof the severely deformed aluminum.
Ajamein, Hossein,Sarkari, Majid,Fazlollahi, Farhad,Atashi, Hossein Korean Chemical Society 2011 대한화학회지 Vol.55 No.5
In Fischer-Tropsch Synthesis, because of few reactants ($H_2$, CO), scarce operating parameters affected on efficiency especially the selectivity of products. In this research, effect of operating parameters on the selectivity of Co-Mn-$TiO_2$ Fischer-Tropsch synthesis catalyst were studied by design of experimental procedure and Taguchi method. According to this research, interactions between operating factors have a crucial effect on light products selectivity. Among these interactions, (temperature${\times}$feed ratio) has the main influence on light hydrocarbons selectivity. It was concluded that temperature and feed ratio ($H_2$/CO) were the most integral operating parameters for much greater selectivity of light hydrocarbons.
Development of a kinetic model for Fischer–Tropsch synthesis over Co/Ni/Al2O3 catalyst
Farhad Fazlollahi,Majid Sarkari,Akbar Zare,Ali Akbar Mirzaei,Hossein Atashi 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.4
In the present research an active Co–Ni/Al2O3 catalyst was prepared by impregnation method for synthesis of light olefins in Fischer–Tropsch synthesis. After studying the effects of using optimized operating conditions on catalyst performance, the kinetic experimental study was performed in a differential micro-fixed-bed-reactor by altering reaction temperature (230–270 8C), pressure (2–12 bar),gas hourly space velocity (2000–7200 h-1) and H2/CO feed molar ratio (1–3). Based on Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach, seven different two-parameter kinetic models were considered. The kinetic data of this study were fitted accurately by a simple form -rCO ¼APCOPH2 =ð1 þ bPCOP0:5H2Þ2 that assumed the following kinetically relevant steps, where CO dissociates via interaction with adsorbed hydrogen; the first hydrogenation step of the surface carbon was reversible and fast, while the second one was slow and rate determining. The kinetic parameters were determined using Levenberg–Marquardt (LM) method and the apparent activation energy and heat of adsorption were 78.70 kJ/mol and -14.16 kJ/mol, respectively.
Atashi, Hossein,Motahari, Kazem,Tabrizi, Farshad Farshchi,Sarkari, Majid,Fazlollahi, Farhad Korean Chemical Society 2011 대한화학회지 Vol.55 No.1
비닐 아세트산염 합성에 대한 1족 알칼리금속 아세트산염의 촉진 효과를 조사하였다. Pd-Au/$SiO_2$ 촉매를 사용한 경우와 사용하지 않은 경우에 대해 에틸렌과 아세트산 간의 기체상 반응에 대해 생성물 선택성과 에틸렌 전환을 비교하였다. 촉진제가 촉매 표면을 안정화시켰으며, 생성물 선택성과 에틸렌 전환을 촉진하였다. 이 촉매 효과는 1족에서 위에서 아래로 내려갈수록 증가하였다. 이것은 아세트산염의 공통이온효과 때문이다. The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/$SiO_2$ catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle's diameter.
Hossein Atashi,Kazem Motahari,Farshad Farshchi Tabrizi,Farhad Fazlollahi,Majid Sarkari 대한화학회 2011 대한화학회지 Vol.55 No.1
The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/SiO_2 catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle’s diameter.
Kinetic study of Fischer–Tropsch process on titania-supported cobalt–manganese catalyst
H. Atashi,F. Siami,A.A. Mirzaei,M. Sarkari 한국공업화학회 2010 Journal of Industrial and Engineering Chemistry Vol.16 No.6
An active cobalt–manganese catalyst was prepared by co-precipitation method, and was also tested for hydrogenation of carbon monoxide to light olefins. The catalyst was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area techniques. The kinetic experiments on a well-characterized Co–Mn/TiO2 catalyst were performed in a fixed-bed micro-reactor, and were also conducted in a temperature range of 190–280 8C, pressure range of 1–10 bar, H2/CO feed ratio (mol/mol) range of 1–3 and a space velocity range of 2700–5200 h1. Two kinetic expressions based on Langmuir–Hinshelwood–Houngen–Watson (LHHW) mechanism were observed to fit the experimental data accurately for Fischer–Tropsch synthesis reaction. The kinetic parameters were estimated with non-linear regression method. Activation energies obtained were 35.131 and 44.613 kJ/mol for optimal kinetics models.
Kazem Motahari,Hossein Atashi,Farhad Fazlollahi,Farshad F. Tabrizi,Majid Sarkari 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.1
While qualitative interpretation of the experimental results is often limited to the identification of global mechanistic phenomena, kinetic modeling is a more powerful tool for the identification of the chemical reaction network that can describe the experimental results. In this paper, kinetic study of vinyl acetate (VA) synthesis was performed in a fixed bed reactor with oxidation of ethylene and acetic acid in gaseous phase over Pd/Au/SiO2 catalyst under the industrial relevant reaction condition as follows: temperature of 120–165 8C, at constant pressure of 8 bar and the ratio of catalyst mass to the feed (W/F) was maintained at 70 g/mol min. Variation in partial pressure and concentration of reactants have led us to determine the rate limiting step and therefore proposing a new rate low based on Langmuir-Hinshelwood–Hougen–Watson (LHHW) approached consistent with experimental observation while adapted through mathematical formulation with high reliance. So, the kinetic parameters were determined by the Levenberg–Marquardt algorithm. Effect of temperature has also been surveyed showing a decreased in selectivity due to the difference in reaction constants of main and side reaction rate and an increase rate due to the increase in apparent activation energy.