The kinetics of the reaction between CO2 and diethanolamine in aqueous ethyleneglycol at 298 K: a viscous gas—liquid reaction system for the determination of interfacial areas in gas—liquid contactors

The reaction between CO2 and diethanolamine (DEA) in aqueous ethyleneglycol (ETG) at 298 K has been studied over the complete composition range. The application of this reaction as a viscous gas—liquid system for the determination of interfacial areas in gas—liquid contactors by the chemical method is discussed. The reaction kinetics have been determined by mass transfer experiments of CO2 into solutions of DEA in aqueous ETG. To this end laboratory-scale stirred cell reactors with a flat surface have been used. In accordance with the same reaction in water at 298 K the reaction between CO2 and DEA in aqueous ETG at 298 K can be described by the zwitterion mechanism of Caplow. Special attention has been paid to the reversibility of the reaction between CO2 and DEA. Calculation show that the influence of the reversibility on the mass transfer rate can be neglected for partial pressures of CO2 below 3 kPa. It is demonstrated that the reaction between CO2 and DEA in aqueous ETG can be used for the determination of interfacial areas in gas—liquid contactors at higher viscosities

The protective properties of thin alumina films deposited by metal organic chemical vapour deposition against high-temperature corrosion of stainless steels

Coatings of Al2O3 were deposited on Incoloy 800H and AISI 304 by means of metal organic chemical vapour deposition. Diffusion limitation was the rate-determining step above 420 °C. Below this temperature, the activation energy of the reaction appeared to be 30 kJ mol−1. Coating with Al2O3 increases the sulphidation resistance by at least 4–10 times. The sulphidation resistance is influenced by the growth rate of the coating and by the thermomechanical properties of the coating - substrate combination. The sulphidation resistance also depends on the growth rate of the coating. The weight gain of coated specimens is about 10–14 times less than that of uncoated specimens. Treatment of the coated samples in air at 850 °C results in a still higher sulphidation resistance. This is due to the chromium oxide grown into the cracks in the coating during the treatment. These cracks are the result of mechanical stresses at irregularities

Thin alumina and silica films by chemical vapor deposition (CVD)

Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ceramic coatings. The influence of several process steps on the deposition rate and surface morphology is discussed. The deposition of SiO2 at atmospheric pressure is kinetically limited below 833 K and is a mixed first and second order reaction with an activation energy of 155 kJ.mole-1. The deposition of Al2O3 is kinetically limited below 673 K and is a first order reaction with an activation energy of 30 kJ.mole-1 at atmospheric pressure. The deposition of Al2O3 is kinetically limited below 623 K and is a second order reaction at low pressure (3 torr) with an activation energy of 30 kJ.mole-1. The decomposition of both precursors involves a B-hydroge n elimination reaction by which DADBS decomposes to acetic acid anhydride, 2-methyl propane, SiO2 and H2O, while ATI decomposes to 2-propanol, propane, Al2O3 and H2O

Thin alumina and silica films by chemical vapor deposition

Alumina and silica coatings have been deposited by MOCVD (Metal Organic Chemical Vapor Deposition) on alloys to protect them against high temperature corrosion. Aluminium Tri-lsopropoxide (ATI) and DiAcetoxyDitertiaryButoxySilane (DAOBS) have been used as metal organic precursors to prepare these ceramic coatings. The influence of several process steps on the deposition rate and surface morphology is discussed. The deposition of SiO2 at atmospheric pressure is kinetically limited below 833 K and is a mixed first and second order reaction with an activation energy of 155 kJ.mole-1. The deposition of Al2O3 is kinetically limited below 673 K and is a first order reaction with an activation energy of 30 kJ.mole-1 at atmospheric pressure. The deposition of Al2O3 is kinetically limited below 623 K and is a second order reaction at low pressure (3 torr) with an activation energy of 30 kJ.mole-1. The decomposition of both precursors involves a B-hydroge n elimination reaction by which DADBS decomposes to acetic acid anhydride, 2-methyl propane, SiO2 and H2O, while ATI decomposes to 2-propanol, propane, Al2O3 and H2O

Formation of thin oxide films by metal-organic chemical vapour deposition

A summary is given of the metal-organic vapour deposition, performed during the last eight years at the University of Twente (The Netherlands), of thin alumina, silica, and titania films at atmospheric and at low pressure on stainless steels. Alumina films were produced from aluminium-tri-sec-butoxide (ATSB) and aluminium-tri-iso-propoxide (ATI), silica films from di-acetoxy-di-t-butoxy-silane (DADBS), and titania films from titanium-tetra-iso-propoxide (TTIP). These investigations can be separated into a number of projects: 1) mechanistic aspects of the decomposition chemistry of the precursors, 2) kinetics of the deposition processes, 3) chemical properties, and 4) mechanical properties of the thin oxide films