Detailed Chemical Kinetic Modeling of Pyrolysis of Ethylene, Acetylene, and Propylene at 1073-1373 K with a Plug-Flow Reactor Model

ABSTRACT: This study examines the predictive capability of our recently proposed reaction mechanism (Norinaga and Deutschmann, Ind Eng Chem Res 2007, 46, 3547) for hydrocarbon pyrolysis at varying temperature. The conventional flow reactor experiments were conducted at 8 kPa, over the temperature range 1073-1373 K, using ethylene, acetylene, and propylene as reactants to validate the mechanism. More than 40 compounds were identified and quantitatively analyzed by on-and off-line gas chromatography. The chemical reaction schemes consisting of 227 species and 827 reactions were coupled with a plug-flow reactor model that incorporated the experimentally measured axial temperature profile of the reactor. Comparisons between the computations and the experiments are presented for more than 30 products including hydrogen and hydrocarbons ranging from methane to coronene as a function of temperature. The model can predict the compositions of major products (mole fractions larger than 10 −2 ) in the pyrolysis of three hydrocarbons with satisfactory accuracies over the whole temperature range considered. Mole fraction profiles of minor compounds including polycyclic aromatic hydrocarbons (PAHs) up to three ring systems, such as phenanthrene, anthracene, and phenylnaphthalene, are also fairly modeled. At temperatures lower than 1273 K, larger PAHs were underpredicted and the deviation became larger with decreasing temperature and increasing molecular mass of PAHs, while better agreements were found at temperatures higher tha

Compos. Sci. Technol.

Chemical vapor deposition and infiltration of pyrolytic carbon for the production of carbon fiber reinforced carbon is studied by modeling approaches and computational tools developed recently. Firstly, the development of a gas-phase reaction mechanism of chemical vapor deposition (CVD) of carbon from unsaturated light hydrocarbons (C2H4, C2H2, and C3H6) is presented. The mechanism consisting of 827 reactions among 227 species is based on existing information on elementary reactions and evaluated by comparison of numerically predicted and experimentally determined product compositions taking into account 44 stable gas-phase compounds formed in a tubular flow reactor. Secondly, a model and a computer code for two-dimensional transient simulations of chemical vapor infiltration (CVI) from methane into carbon fiber reinforced carbon are presented. The chemical model is based on a reduced multi-step reaction scheme for pyrolytic carbon deposition, which is derived from a mechanism based on elementary reactions, and a hydrogen inhibition model of pyrolytic carbon deposition. The coupled governing equations of mass transfer, chemical vapor deposition, surface growth, and gas-phase and surface chemical reactions are numerically solved by a finite element method (FEM). The computer code is applied to reveal densification processes of felts with fiber volume fractions of 7.1 % and 14.2%. Numerically predicted bulk density distributions agree well with experimental results. (c) 2007 Elsevier Ltd. All rights reserved.Chemical vapor deposition and infiltration of pyrolytic carbon for the production of carbon fiber reinforced carbon is studied by modeling approaches and computational tools developed recently. Firstly, the development of a gas-phase reaction mechanism of chemical vapor deposition (CVD) of carbon from unsaturated light hydrocarbons (C2H4, C2H2, and C3H6) is presented. The mechanism consisting of 827 reactions among 227 species is based on existing information on elementary reactions and evaluated by comparison of numerically predicted and experimentally determined product compositions taking into account 44 stable gas-phase compounds formed in a tubular flow reactor. Secondly, a model and a computer code for two-dimensional transient simulations of chemical vapor infiltration (CVI) from methane into carbon fiber reinforced carbon are presented. The chemical model is based on a reduced multi-step reaction scheme for pyrolytic carbon deposition, which is derived from a mechanism based on elementary reactions, and a hydrogen inhibition model of pyrolytic carbon deposition. The coupled governing equations of mass transfer, chemical vapor deposition, surface growth, and gas-phase and surface chemical reactions are numerically solved by a finite element method (FEM). The computer code is applied to reveal densification processes of felts with fiber volume fractions of 7.1 % and 14.2%. Numerically predicted bulk density distributions agree well with experimental results. (c) 2007 Elsevier Ltd. All rights reserved

CFD simulation of CVD reactors in the CH3SiCl3(MTS)/H2 system using a two-step MTS decomposition and one-step SiC growth models

In this study, we report on a computational fluid dynamics (CFD) simulation of the chemical vapor deposition reactor of silicon carbide (SiC) in the methyltrichlorosilane (MTS, CH3SiCl3)/H2 system. The formation of SiC thin film is controlled by various process parameters, such as temperature and pressure. In this study, we propose a reaction mechanism of MTS decomposition to SiC growth on a substrate surface for CVD reactors in the CH3SiCl3(MTS)/H2 system. The reaction mechanism has two gas-phase pyrolysis reactions and one SiC film formation reaction. However, we individually build and validate MTS decomposition and SiC growth models to reduce uncertainty. An in-house version of reactingFoam, a reactive flow solver within OpenFOAM v2006, was used as the simulation tool. Our model accurately reproduced MTS decomposition for T = 1100–1350 K and [H2]/[MTS] = 2.65–14 at p = 101,325 Pa. Then, the MTS decomposition model was coupled with the SiC growth model, and the coupled model was applied to the SiC deposition data. The model could reproduce multiple datasets through validation studies

Production of ketones from pyroligneous acid of woody biomass pyrolysis over an iron-oxide catalyst

Catalytic upgrading of pyroligneous acid, by-product from slow pyrolysis of woody biomass for char production, was carried out using zirconia-supported iron-oxide catalysts under a steam atmosphere at temperatures ranging from 623 to 723 K, and the effect of ZrO2 content in the ZrO2-FeOX catalysts on catalytic activity and ketone yields was investigated. It was demonstrated that hydroxyacetone and carboxylic acids (acetic and propionic acids) in the pyroligneous acid were converted into aliphatic ketones (acetone and 2-butanone) via a ketonization reaction over the ZrO2-FeOX catalyst. However, reaction inhibition by metal impurities in the pyroligneous acid such as potassium (K) and magnesium (Mg) was also observed. These metal impurities could be removed from the pyroligneous acid without changing the organic composition by using an ion-exchange resin. The removal of the metal impurities was effective in increasing the ketone yields. Moreover, as the W/F value (W: Amount of catalyst, and F: Flow rate of the pyroligneous acid in the feed) increased, the ketone yield increased up to approximately 30 C mol%, and the ketone fraction in the liquid product reached 55 C mol%