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Papers by P. Marchot

Journal of Sol-Gel Science and Technology, 1995

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique u... more A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(OiPr)4] and tetraethylorthosilicate [TEOS]: they are mixed in the same solvent and then directly hydrolysed. This one-step reaction is possible because of the use of 2-methoxyethanol, a protic polar solvent. This alcohol plays two different specific roles: it acts as a solvent as

Carbon, 2004

A kinetic study is presented for the synthesis of multi-walled carbon nanotubes in a semi-continu... more A kinetic study is presented for the synthesis of multi-walled carbon nanotubes in a semi-continuous chemical vapor deposition reactor. The study is based on the use of a mass spectrometer that allows the reaction rate to be inferred from the exhaust gas composition measurements. The tested reactor operating variables are the length and thickness of the catalytic bed, the total

Disorder and Mixing, 1988

We present a simple description of a gas-liquid flow through a packed bed under trickle flow cond... more We present a simple description of a gas-liquid flow through a packed bed under trickle flow conditions. A careful examination of the physics of the phenomena leads us to model the flow as a directed percolation process on a random network. Two accessibilities are introduced: the static accessibility resulting from the random distribution of the geometric properties of the packing and the dynamic accessibility resulting from energetical requirements. Under usual flow conditions (very far from the critical region) and for usual packing (no correlation between the two accessibilities) a simple model leads to the flow rate distribution. It is compared with experimental results obtained on a pilot scale trickling filter.

Non-Invasive Monitoring of Multiphase Flows, 1997

Publisher Summary This chapter describes gas-liquid flow imaging under trickle flow regime, which... more Publisher Summary This chapter describes gas-liquid flow imaging under trickle flow regime, which is one among the many hydrodynamic regimes, in which packed-beds may be operated. It occurs when the interactions between the co- or counter-current gas and liquid flows remain low. Simultaneous gas and liquid flows through unconsolidated beds of packing elements are encountered in a large variety of industrial processes. Roughly, these various applications may be divided in two categories. The first category groups processes aiming at bringing in contact gas and liquid reactants with a solid catalyst, in the pores of which the reaction(s) take(s) place. This field is covered by three phase (bio)reactor engineering. Typical examples are hydrodesulfurization in trickle bed reactors and biological treatment of waste water in trickling filters. The second category groups processes aiming at contacting a gas and a liquid to promote heat and/or mass transfer between these fluids. An inert solid packing is used to obtain a good distribution of the phases. Typical examples are gas-liquid absorption and distillation columns. The chapter discusses trickle bed reactors, trickling filters, absorption columns, liquid maldistribution, and tomographic techniques. It presents the results, which show that the high resolution, which can be obtained by computer assisted X-ray tomography allows the analysis of complex hydrodynamic phenomena occurring in different types of packed columns. The spatial distribution of the gas, liquid and solid phase saturations can be determined experimentally at a very small scale.

Colloids and Surfaces, 1984

Applied Catalysis, 1984

Oceanic polymetallic nodules could be used as a catalyst and adsorbent for hydrodemetallation and... more Oceanic polymetallic nodules could be used as a catalyst and adsorbent for hydrodemetallation and hydrodesulfurization of petroleum residua in a trickle bed reactor because of their particular composition and porous texture. A kinetic study of these reactions has been undertaken in a micro-pilot unit using operating conditions similar to those encountered in industrial reactors. The effect of the main operating parameters (pressure, temperature, mass flow rates) was investigated. Moreover, the evolution of the porous texture during reaction was examined and the performance of an industrial reactor estimated.

Chemical Engineering Journal, 2006

A Pd-Ag/SiO 2 xerogel catalyst prepared in one step by sol-gel process has been entrapped in cyli... more A Pd-Ag/SiO 2 xerogel catalyst prepared in one step by sol-gel process has been entrapped in cylindrical porous alumina foams of three different pore sizes in order to shape the catalyst under the appropriate form with suitable mechanical resistance to be used in an industrial fixed bed reactor. After drying, calcination and reduction, the Pd-Ag/SiO 2 xerogel catalyst pellets are immobilized inside the open porosity of the alumina foam. The localization of the xerogel catalyst in the alumina foams has been studied by X-ray tomography. The threedimensional porous structure was reconstructed from the consecutive cross-sections obtained by this technique. This method shows that the Pd-Ag/SiO 2 xerogel catalyst is uniformly dispersed inside the porosity of the alumina foams. Activity and selectivity of Pd-Ag/SiO 2 xerogel catalyst reference or catalyst entrapped in alumina foams have been studied for selective hydrodechlorination of 1,2-dichloroethane into ethylene. The specific reaction rate obtained with catalyst entrapped in alumina foams is smaller than the one obtained from corresponding catalyst powders. The catalytic activity decrease observed for Pd-Ag/SiO 2 xerogel catalyst entrapped in porous alumina foams most probably arises from diffusional limitations inside the porous texture of the alumina foams.

Journal of Sol-Gel Science and Technology, 1995

A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique u... more A new method to synthesize SiO2-TiO2 gels by sol-gel process has been developed. This technique uses tetraisopropylorthotitanate [Ti(OiPr)4] and tetraethylorthosilicate [TEOS]: they are mixed in the same solvent and then directly hydrolysed. This one-step reaction is possible because of the use of 2-methoxyethanol, a protic polar solvent. This alcohol plays two different specific roles: it acts as a solvent as

Carbon, 2004

A kinetic study is presented for the synthesis of multi-walled carbon nanotubes in a semi-continu... more A kinetic study is presented for the synthesis of multi-walled carbon nanotubes in a semi-continuous chemical vapor deposition reactor. The study is based on the use of a mass spectrometer that allows the reaction rate to be inferred from the exhaust gas composition measurements. The tested reactor operating variables are the length and thickness of the catalytic bed, the total

Disorder and Mixing, 1988

We present a simple description of a gas-liquid flow through a packed bed under trickle flow cond... more We present a simple description of a gas-liquid flow through a packed bed under trickle flow conditions. A careful examination of the physics of the phenomena leads us to model the flow as a directed percolation process on a random network. Two accessibilities are introduced: the static accessibility resulting from the random distribution of the geometric properties of the packing and the dynamic accessibility resulting from energetical requirements. Under usual flow conditions (very far from the critical region) and for usual packing (no correlation between the two accessibilities) a simple model leads to the flow rate distribution. It is compared with experimental results obtained on a pilot scale trickling filter.

Non-Invasive Monitoring of Multiphase Flows, 1997

Publisher Summary This chapter describes gas-liquid flow imaging under trickle flow regime, which... more Publisher Summary This chapter describes gas-liquid flow imaging under trickle flow regime, which is one among the many hydrodynamic regimes, in which packed-beds may be operated. It occurs when the interactions between the co- or counter-current gas and liquid flows remain low. Simultaneous gas and liquid flows through unconsolidated beds of packing elements are encountered in a large variety of industrial processes. Roughly, these various applications may be divided in two categories. The first category groups processes aiming at bringing in contact gas and liquid reactants with a solid catalyst, in the pores of which the reaction(s) take(s) place. This field is covered by three phase (bio)reactor engineering. Typical examples are hydrodesulfurization in trickle bed reactors and biological treatment of waste water in trickling filters. The second category groups processes aiming at contacting a gas and a liquid to promote heat and/or mass transfer between these fluids. An inert solid packing is used to obtain a good distribution of the phases. Typical examples are gas-liquid absorption and distillation columns. The chapter discusses trickle bed reactors, trickling filters, absorption columns, liquid maldistribution, and tomographic techniques. It presents the results, which show that the high resolution, which can be obtained by computer assisted X-ray tomography allows the analysis of complex hydrodynamic phenomena occurring in different types of packed columns. The spatial distribution of the gas, liquid and solid phase saturations can be determined experimentally at a very small scale.

Colloids and Surfaces, 1984

Applied Catalysis, 1984

Oceanic polymetallic nodules could be used as a catalyst and adsorbent for hydrodemetallation and... more Oceanic polymetallic nodules could be used as a catalyst and adsorbent for hydrodemetallation and hydrodesulfurization of petroleum residua in a trickle bed reactor because of their particular composition and porous texture. A kinetic study of these reactions has been undertaken in a micro-pilot unit using operating conditions similar to those encountered in industrial reactors. The effect of the main operating parameters (pressure, temperature, mass flow rates) was investigated. Moreover, the evolution of the porous texture during reaction was examined and the performance of an industrial reactor estimated.

Chemical Engineering Journal, 2006

A Pd-Ag/SiO 2 xerogel catalyst prepared in one step by sol-gel process has been entrapped in cyli... more A Pd-Ag/SiO 2 xerogel catalyst prepared in one step by sol-gel process has been entrapped in cylindrical porous alumina foams of three different pore sizes in order to shape the catalyst under the appropriate form with suitable mechanical resistance to be used in an industrial fixed bed reactor. After drying, calcination and reduction, the Pd-Ag/SiO 2 xerogel catalyst pellets are immobilized inside the open porosity of the alumina foam. The localization of the xerogel catalyst in the alumina foams has been studied by X-ray tomography. The threedimensional porous structure was reconstructed from the consecutive cross-sections obtained by this technique. This method shows that the Pd-Ag/SiO 2 xerogel catalyst is uniformly dispersed inside the porosity of the alumina foams. Activity and selectivity of Pd-Ag/SiO 2 xerogel catalyst reference or catalyst entrapped in alumina foams have been studied for selective hydrodechlorination of 1,2-dichloroethane into ethylene. The specific reaction rate obtained with catalyst entrapped in alumina foams is smaller than the one obtained from corresponding catalyst powders. The catalytic activity decrease observed for Pd-Ag/SiO 2 xerogel catalyst entrapped in porous alumina foams most probably arises from diffusional limitations inside the porous texture of the alumina foams.

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