A kinetic study of Pd–Au catalyzed synthesis of vinyl acetate from oxidation of ethylene and acetic acid in heterogeneous gas reaction

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.

Effect of Acetate Promotor on the Pd-Au/SiO₂-catalyzed Synthesis of Vinyl Acetate from the Reaction of Ethylene with Acetic Acid

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.

Effect of Acetate Promotor on the Pd-Au/SiO2-catalyzed Synthesis of Vinyl Acetate from the Reaction of Ethylene with Acetic Acid

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.

Designing a Fuzzy Expert System with a Hybrid Approach to Select Operational Strategies in Project-Based Organizations with a Selected Competitive Priority

Ehsan Javanrad,Alireza Pooya,Mohsen Kahani,Nasser Motahari Farimani 대한산업공학회 2017 Industrial Engineeering & Management Systems Vol.16 No.1

This research was conducted in order to solve the problem of selecting an operational strategy for projects in projectbased organizations by designing a fuzzy expert system. In the current research, we first determined the contributing parameters in operational strategy of project-based organizations based on existing research literature and experts’ opinion. Next, we divided them into two groups of model inputs and outputs and the rules governing them were determined by referring to research literature and educational instances. In order to integrate rules, the revised Ternary Grid (revised TG) and expert opinions were applied according to a hybrid algorithm. The Ultimate rules were provided in Fuzzy Inference System format (FIS). In this FIS, proper manufacturing decisions are recommended to the user based on selected competitive priority and also project properties. This paper is the first study in which rules and relations governing the parameters contributing operational strategy in project-based organizations are acquired in a guided integrated process and in the shape of an expert system. Using the decision support system presented in this research, managers of project-based organizations can easily become informed of proper manufacturing decisions in proportion with selected competitive priority and project properties; and also be ensured that theoretical background and past experiences are considered.

Modeling the Dependency of Suction Stress Characteristic Curve on Void Ratio in Unsaturated Soils

A. A. Heshmati,M. R. Motahari 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.1

Geotechnical problems associated with unsaturated soils are common in semi-arid climates, where the upper soil layers arenaturally unsaturated. Once a soil becomes unsaturated, its mechanical properties become different from its saturated counterpart. The main part of effective stress in unsaturated soils resulting from the soil moisture can be defined by the Suction StressCharacteristic Curve (SSCC). Although, the suction stress characteristic curve is determined from shear strength tests, but recentworks show that the SSCC can be connected to the Soil Water Characteristic Curve (SWCC). This paper presents a simple and novelapproach to model the effect of void ratio changes on SSCC in unsaturated soils. The proposed approach can be easily utilized withexisting Soil Water Characteristic Curve (SWCC) equations to model any changes in suction stress for unsaturated soils. The mainadvantage of the suggested method is in fact its dependency to just one parameter, simply calibrated by the conventional waterretention tests. This characteristic is so applicable in hydro mechanical constitutive models of unsaturated soils. Finally, theefficiently predicting of the experimental results implicitly demonstrates the applicability of effective stress principle using theconcept of Suction Stress Characteristic Curve (SSCC) for unsaturated soils.

Practical evaluation of rapid tests for assessing the Chloride resistance of concretes containing Silica Fume

Amirreza Pilvar,Ali Akbar Ramezanianpour,Hosein Rajaie,S. Mahmoud Motahari Karein 사단법인 한국계산역학회 2016 Computers and Concrete, An International Journal Vol.18 No.4

The present study is an exploratory research that appraises and compares the performance of four rapid tests for assessing the chloride penetration of concrete; Rapid Chloride Permeability Test (RCPT), Rapid Chloride Migration Test (RCMT), Surface Electrical Resistivity (SR) and Modified Rapid Chloride Permeability Test (MRCPT). Due to the concern raised by some researchers on that the conductivity of the pore solution impinges upon the results on some of these rapid tests, silica fume was used as supplementary cementitious material in proportions of 7.5% and 15%. All four methods exhibited substantial reduction in the chloride permeability of concrete mixtures containing silica fume compared to the control mixture at the ages of 28 and 90 days. The variations in performance caused by silica fume usage were significant for RCPT and SR methods, moderate for RCMT and marginal for MRCPT. Results show that the variation in the conductivity of the pore solution significantly alters the results of SR and RCPT tests, and marginally alters those of MRCPT.

Designing a Fuzzy Expert System with a Hybrid Approach to Select Operational Strategies in Project-Based Organizations with a Selected Competitive Priority

Javanrad, Ehsan,Pooya, Alireza,Kahani, Mohsen,Farimani, Nasser Motahari Korean Institute of Industrial Engineers 2017 Industrial Engineeering & Management Systems Vol.16 No.1

This research was conducted in order to solve the problem of selecting an operational strategy for projects in project-based organizations by designing a fuzzy expert system. In the current research, we first determined the contributing parameters in operational strategy of project-based organizations based on existing research literature and experts' opinion. Next, we divided them into two groups of model inputs and outputs and the rules governing them were determined by referring to research literature and educational instances. In order to integrate rules, the revised Ternary Grid (revised TG) and expert opinions were applied according to a hybrid algorithm. The Ultimate rules were provided in Fuzzy Inference System format (FIS). In this FIS, proper manufacturing decisions are recommended to the user based on selected competitive priority and also project properties. This paper is the first study in which rules and relations governing the parameters contributing operational strategy in project-based organizations are acquired in a guided integrated process and in the shape of an expert system. Using the decision support system presented in this research, managers of project-based organizations can easily become informed of proper manufacturing decisions in proportion with selected competitive priority and project properties; and also be ensured that theoretical background and past experiences are considered.