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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.
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.
Intrinsic kinetics of the Fischer-Tropsch synthesis over an impregnated cobalt-potassium catalyst
Hossein Atashi,Mohsen Mansouri,Seyyed Hossein Hosseini,Mohammad Khorram,Ali Akbar Mirzaei,Masoud Karimi,Ghobad Mansouri 한국화학공학회 2012 Korean Journal of Chemical Engineering Vol.29 No.3
The optimal amount of 15 wt%Co/10 wt%K/Al2O3 catalyst was prepared using the impregnation technique in order to study the kinetics of the Fischer-Tropsch synthesis. The rate of synthesis was measured in a fixed-bed micro reactor with H2/CO feed ratio of 1-3 and space velocity in the range of 2,700-5,200 h−1 under reactor pressure of 8 bar and a temperature range of 210-240 oC. The experimental data were best fitted by a Langmuir-Hinshelwood-Hougen-Watson (LHHW) approach rate in the form of −rCO=(k2K1PCOPH2)/(1+K1PCO). Furthermore, the data were fitted fairly well by a power law equation in the form of −rCO=kPCO 1.32PH21.42. The activation energies for LHHW approach model and power law equation were obtained as 138.5 kJ/mol and 87.39 kJ/mol, respectively.
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.
Kinetics studies of nano-structured cobalt–manganese oxide catalysts in Fischer–Tropsch synthesis
Mohsen Mansouri,Hossein Atashi,Farshad Farshchi Tabrizi,Ali Akbar Mirzaei,Ghobad Mansouri 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.4
The nano-structured cobalt/manganese oxide catalyst was prepared by thermal decomposition of [Co(NH3)4CO3]MnO4 precursor, and was tested for the Fischer–Tropsch reaction (hydrocarbon forming)in a fixed-bed micro-reactor. Experimental conditions were varied as follow: reaction pressure 1–10 bar,H2/CO feed ratio of 1–2 and space velocity of 3600 h1 at the temperature range of 463.15–523.15 K. On the basis of carbide and/or enolic mechanisms and Langmuir–Hinshelwood–Hougen–Watson (LHHW)type rate equations, 30 kinetic expressions for CO consumption were tested and interaction between adsorption HCO and dissociated adsorption hydrogen as the controlling step gave the most plausible kinetic model. The kinetic parameters were estimated with non-linear regression method and the activation energy was 80.63 kJ/mol for optimal kinetic model. Kinetic results indicated that in Fischer–Tropsch synthesis (FTS) rate expression, the rate constant (k) has been increased by decreasing the catalyst particle size. The catalyst characterization was carried out using different methods including powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) surface area measurements.
Mehdi Shiva,Hossein Atashi,Farhad Farshchi Tabrizi,Ali Akbar Mirzaei,Maryam Arsalanfar 한국공업화학회 2013 Journal of Industrial and Engineering Chemistry Vol.19 No.1
The study addresses an enhanced approach for study of kinetics and mechanism of CO hydrogenation over Fe–Co catalyst. Kinetic models for rate of methane, paraffin and olefin formation have been developed by LHHW approach and information that obtained from UBI_QEP calculations.
Bioleaching kinetics of copper from copper smelters dust
Fereshteh Bakhtiari,Hossein Atashi,Mortaza Zivdar,Seyedali Seyedbagheri,Mohammad Hassan Fazaelipoor 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.1
The smelting factory of Sarcheshmeh Copper Complex in Iran produces about 50 tons per day of copper dust containing 36% Cu, 22.2% Fe and 12.2% S. The dust is currently recycled to the smelters. Thismethod is not desirable in terms of operation, and energy consumption. A mixed culture of mesophilic bacteria was used to examine the bioleaching of copper from the dust. The effect of various parameters such as pulp density, nutrients, temperature, and the amount of pyrite added to the bioleaching media were examined in the dust bioleaching tests. It was shown that the bacteria contributed effectively in the leaching of copper from the dust. The collected data showed that at pH 1.8 and the pulp density less than 7%, the dissolution of copper followed shrinking core kinetic model and the process was limited by diffusion of lixiviant. With the pulp density of 7%, however, the process showed to be reaction limited.
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.
Mansouri, Mohsen,Atashi, Hossein,Khalilipour, Mir Mohammad,Setareshenas, Naimeh,Shahraki, Farhad Korean Chemical Society 2013 대한화학회지 Vol.57 No.6
The effect of operating conditions (temperature and the partial pressures of H2 and CO) on the reaction rate of Fischer-Tropsch synthesis (FTS) were investigated by carrying out experiments according to a Box-Behnken design (BBD), and were mathematically modeled by using response surface methodology (RSM). The catalyst used was a nano-structured cobalt/manganese oxide catalyst, which was prepared by thermal decomposition. The rate of synthesis was measured in a fixed-bed micro reactor with $H_2/CO$ molar feed ratio of 0.32-3.11 and reactor pressure in the range of 3-9.33 bar at space velocity of $3600h^{-1}$ and a temperature range of 463.15-503.15 K, under differential conditions (CO conversion below 2%). The results indicated that in the present experimental setup, the temperature and the partial pressure of CO were the most significant variables affecting reaction rate. Based on statistical analysis the quadratic model of reaction rate of FTS was highly significant as p-value 0.0002.
Comparison of CFD results and experimental data in a fixed bed Fischer–Tropsch synthesis reactor
Ali Reza Miroliaei,Hossein Atashi,Ramin Karimzadeh,Farhad Shahraki 한국공업화학회 2012 Journal of Industrial and Engineering Chemistry Vol.18 No.6
Hydrogenation of carbon monoxide in a fixed bed Fischer–Tropsch reactor has been simulated using computational fluid dynamics. The geometry of fixed bed reactor was modeled using the discrete packing method. The effects of reaction temperature, feed flow rate and H2/CO ratio on CO conversion and product selectivity were investigated. The mass fraction of products was also predicted by using the CFD model at different H2/CO ratios. It was observed that the CO conversion increased with increasing temperature,while decreased with increasing mass flow rate. The selectivity and mass fraction of products also increased with increasing temperature and H2/CO ratio.