A kinetic model for the first stage of pygas upgrading

Medeiros, José Luiz de; Araújo, O.Q.F.; Gaspar, Alexandre B.; Silva, M. A. P.; Britto, Jaildes Marques

doi:10.1590/s0104-66322007000100011

Cited by 11 publications

(6 citation statements)

References 9 publications

(9 reference statements)

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“…PYGAS is a product in the naphtha boiling range, with carbon numbers between C 5 -C 11 , with a high content of aromatics and olefins. It is used for blending with gasoline or as a raw material for the extraction of benzene, toluene and xylene (BTX) [3]. In this context, due to the increasing world trend towards the processing of heavier and cheaper raw materials for the generation of light olefins, the problem arises of finding use for growing stocks of PYGAS.…”

Section: Introductionmentioning

confidence: 99%

Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

Betti

Badano

Lederhos

et al. 2015

Reac Kinet Mech Cat

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This is a study on the kinetics of the liquid-phase hydrogenation of styrene to ethylbenzene over a catalyst of palladium supported on an inorganic-organic composite. This support has a better mechanical resistance than other commercial supports, e.g. alumina, and yields catalysts with egg-shell structure and a very thin active Pd layer. Catalytic tests were carried out in a batch reactor by varying temperature, total pressure and styrene initial concentration between 353-393 K, 10-30 bar, and 0.26-0.60 mol L -1 , respectively. Kinetic models were developed on the assumptions of dissociative hydrogen chemisorption and non-negligible adsorption of hydrogen and styrene. Final chemical reaction expressions useful for reactor design were obtained. The models that best fitted the experimental data were those ones that considered the surface reaction as the limiting step. In this sense a two-step Horiuti-Polanyi working mechanism with half hydrogenation intermediates gave the best fit of the experimental data. The heats of adsorption of styrene and ethylbenzene were also estimated.

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Section: Introductionmentioning

confidence: 99%

Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

Betti

Badano

Lederhos

et al. 2015

Reac Kinet Mech Cat

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“…However, the DE values microspheres containing EC (80.48%) showed that they were statistically more significant than commercial tablet (P < 0.05). The in vitro release profiles were fitted on various kinetic models in order to find out the mechanism of drug release (17,18). The fit parameters to Higuchi, first order, Peppas and zero order equations are given in Table 3.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Microencapsulation by Emulsion-Solvent Extraction/ Evaporation Technique Using Derivatives Cellulose and Acrylate-Methacrylate Copolymer as Carriers

Jelvehgari

Montazam

2012

Jundishapur J Nat Pharm Prod

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A B S T R A C T Background:Microencapsulation is a useful method to prolong a drug release from dosage forms and to reduce its adverse effect (1) among various available methods. The microencapsulation of hydrophilic active ingredients requires the use of a polar dispersing phase such as a mineral oil. Acetone/paraffin systems are conventionally used. Objectives: The current study aimed to investigate two different microencapsulation techniques comparatively, water in oil in oil (w/o/o) and oil in oil (o/o), for theophylline (TH) loaded ethylcellulose (EC), cellulose acetate butyrate (CAB), Eudragit RS and RL microspheres with regard to loading efficiency, release and degradation kinetics. Materials and Methods: Microspheres were prepared by the emulsification method by solvent diffusion/evaporation technique and different polymers which were incorporated into microspheres to control the release rate of drug. Theophylline (TH) was chosen as a model drug. The emulsion technique was investigated for to prepare theophylline microparticles. EC and CAB and acrylatemethacrylate copolymer corresponding to the above ratios were selected as microparticles wall materials. The effects of type polymers on the physical characteristics and dissolution of the microparticles were also studied. However, the TH loading efficiency (for w/o/o emulsion about 90.64% and o/o emulsion about 73.90/5 to 95.90%) and the TH release kinetics were influenced by the microencapsulation technique. Results:The results demonstrated that the o/o microspheres (containing of CAB) was most appropriate, providing a high encapsulation efficiency (95.90%) and low initial burst release (6.45%). The microspheres prepared with CAB polymer showed faster dissolution rate than other polymers with 0.75: 1 drug to polymer ratio. The double emulsion technique with EC as wall material gave the high dissolution efficiency (80.48%) of microcapsules. Conclusions: Eudragit RS microspheres showed higher yield (90%). The release of TH from CAB and Eudragit RL walled microcapsules was slow whilst the release from those of EC and Eudragit RS were faster. The type of polymer and the drug to polymer ratio were found to be the key factors affecting the release profile which could lead to microspheres with desired release behavior.

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“…In the first set of experiments, the temperature was fixed at 80 °C, which is inside the temperature range of 50 -130 °C used industrially (Medeiros et al, 2007). Five levels of H2 pressure (16,26,36,46, and 56 bar) and three levels of styrene concentration (0.3, 0.5 and 0.8 mol/L) were used.…”

Section: Styrene Hydrogenationmentioning

confidence: 99%

“…In the first one, styrene and diolefins are selectively hydrogenated under moderate conditions to prevent gum and coke formation. The reactor temperature and hydrogen pressure are in the range of 50 -130 °C and 20 -40 bar, respectively (Cheng et al, 1986;Medeiros et al, 2007). In the second stage, sulfur compounds are converted and mono-olefins are hydrogenated using higher temperatures (Mostoufi et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

Modeling Styrene Hydrogenation Kinetics Using Palladium Catalysts

Justino

Vale

Silva

et al. 2016

Braz. J. Chem. Eng.

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-The high octane number of pyrolysis gasoline (PYGAS) explains its insertion in the gasoline pool. However, its use is troublesome due to the presence of gum-forming chemicals which, in turn, can be removed via hydrogenation. The use of Langmuir-Hinshelwood kinetic models was evaluated for hydrogenation of styrene, a typical gum monomer, using Pd/9%Nb2O5-Al2O3 as catalyst. Kinetic models accounting for hydrogen dissociative and non-dissociative adsorption were considered. The availability of one or two kinds of catalytic sites was analyzed. Experiments were carried out in a semi-batch reactor at constant temperature and pressure in the absence of transport limitations. The conditions used in each experiment varied between 16 -56 bar and 60 -100 ºC for pressure and temperature, respectively. The kinetic models were evaluated using MATLAB and EMSO software. Models using adsorption of hydrogen and organic molecules on the same type of site fitted the data best.

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A kinetic model for the first stage of pygas upgrading

Cited by 11 publications

References 9 publications

Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

Kinetic study of the selective hydrogenation of styrene over a Pd egg-shell composite catalyst

Comparison of Microencapsulation by Emulsion-Solvent Extraction/ Evaporation Technique Using Derivatives Cellulose and Acrylate-Methacrylate Copolymer as Carriers

Modeling Styrene Hydrogenation Kinetics Using Palladium Catalysts

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