Isothermal Integral Reactor Research Articles

Synthesis of 1,3-butadiene from ethanol/acetaldehyde over ZrO2-MgO-SiO2 catalyst: The thermodynamics and reaction kinetics analysis

The catalytic conversion of ethanol into 1,3-butadiene has once again attracted widely attention. However, the kinetics of 1,3-butadiene synthesis from ethanol are rarely reported. In this work, the kinetics of 1,3-butadiene synthesis from ethanol and acetaldehyde over ZrO2-MgO-SiO2 catalyst developed by our research group were studied. The study was carried out in an isothermal integral reactor at temperatures of 573–613 K with various space velocity. The kinetics of two main side reactions, dehydration of ethanol to ethylene and ether, were also measured. It was assumed that the aldol condensation rate determining step followed the Langmuir-Hinshelwood mechanism and the Eley-Rideal mechanism respectively, from which the corresponding kinetics models were derived. The results showed that the aldol condensation step followed the Langmuir-Hinshelwood mechanism over ZrO2-MgO-SiO2 catalyst, and the activation energy was calculated to be 54.6 kJ/mol. The obtained kinetics models were verified under the conditions of different ethanol/acetaldehyde molar ratio. The discrepancy between calculated outlet flow rates of key components and the experimental values was within ± 16%, indicating the validity of the obtained kinetics models. The research results can provide some theoretical guidance for the reactor design of 1,3-butadiene synthesis from ethanol.

Kinetics of Hydrogenation of Acetic Acid to Ethanol

The intrinsic kinetic behaviour of catalytic hydrogenation of acetic acid in vapour phase was studied over a multi-metallic catalyst. The rate expression was derived from the sequence of elementary reaction steps based on a Langmuir-Hinshelwood-model involving two types of active sites. Experiments were carried out in a fixed bed reactor, which is similar to an isothermal integral reactor designed to excluding the negative effects of internal and external diffusion. The reaction conditions investigated were as follow:reaction temperature 275-325 ºC, reaction pressure1.5-3.0 MPa, liquid hourly space velocity (sv) 0.3-1.2 h-1, molar ratio of hydrogen to acetic acid (H/AC) 8:20. The results show that conversion of acetic acid increases with increasing the reaction temperature and pressure, but decreases with increasing the space velocity and H/AC. Furthermore, reducing the reaction pressure and increasing reaction temperature, space velocity and H/AC can improve the reaction selectivity of acetic acid to ethanol. The established kinetic model results agreed with experimental results. The relative difference between the calculated value and the experimental value is less than 6 %. The values of model parameters are consistent with the three thermodynamic constraints. The study provided evidence that the intrinsic kinetic model is suitable both mathematically and thermodynamically, and it could be useful in guiding reactor design and optimization of operating conditions.

Deactivation Model of the Catalyst Used in Methanol to Olefin Process

The change of activity of the SAPO-34 zeolite catalyst in the methanol to olefin process( MTO) was studied after the catalyst started to lose activity in the fixed-bed isothermal integral reactor. The effect of temperature,space speed and time on stream on the change of catalyst activity was investigated. The deactivation function showed a good agreement with the experimental data. By analyzing the deactivation function,the relations between time when the deactivation speed was fast and both temperature and space velocity were obtained. The deactivation process obeyed the deactivation mechanism on the inhomogeneous surface. After the SAPO-34 zeolite started to lose activity,the effect of deactivation time was greater than the effect of space speed and reaction temperature.

Intrinsic kinetics of one-step dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst

The reaction kinetics of the dimethyl ether synthesis from hydrogen-rich synthesis gas over bi-functional catalyst was investigated using an isothermal integral reactor at 220–260°C temperature, 3–7 MPa pressure, and 1,000–2,500 mL/g·h space velocity. The H2/CO ratio of the synthetic gas was chosen between 3 : 1 and 6 : 1. The bi-functional catalyst was prepared by physically mixing commercial CuO/ZnO/Al2O3 and γ-alumina, which act as methanol synthesis catalyst and dehydration catalyst, respectively. The three reactions, including methanol synthesis from CO and CO2 as well as methanol dehydration, were chosen as independent reactions. The Langmuir-Hinshelwood kinetic models for dimethyl ether synthesis were adopted. Kinetics parameters were obtained using the Levenberg-Marquardt mathematical method. The model was reliable according to statistical and residual error analyses. The effects of different process conditions on the reactor performance were also investigated.

Kinetic model of the MTG process taking into account the catalyst deactivation. Reactor simulation

A kinetic model for the deactivation of catalyst (based on a HZSM5 zeolite) in the transformation of methanol into gasoline is proposed from results obtained in an isothermal fixed bed integral reactor. The kinetic model takes into account the effect of the composition of the lumps of oxygenates, light olefins and rest of products on the catalyst deactivation along the reactor. The model allows for simulating the integral reactor and for studying the influence of the operating conditions on selectivity towards different lumps in the MTG process. The resukts have been experimentally proven in an isothermal integral reactor and are in agreement with the results of coke deposition along the reactor.

Calculation of the kinetics of deactivation by coke of a silica-alumina catalyst in the dehydration of 2-ethylhexanol

The kinetics of deactivation by coke deposition of a silica-alumina catalyst in the dehydration of 2-ethylhexanol has been studied, from experiments following temperature-time sequences in an isothermal integral reactor, in automated reaction equipment. The data analysis method has consisted of simultaneously solving the mass conservation equation for the reactant and the kinetic equation of deactivation. The validity of the kinetic model calculated, which is a separable one of the Langmuir-Hinshelwood-Hougen-Watson type, and the experimental method of data analysis has been proven by comparing the results of reactor simulation with experiments carried out under different reaction conditions. The application of this rigorous method has been compared with the application, for the same reaction system, of simplified methods conventionally used in the literature for differential or integral reactor data analysis. The results show the interest of the experimental procedure proposed and of the data analysis method, which reduce the experimentation, lead to reproducible results, and do not have the limitations determined for the simplified methods of data treatment.

Calculation of the kinetics of deactivation by coke in an integral reactor for a triangular scheme reaction

The kinetics of deactivation by coke deposition has been studied for a SiO 2-Al 2O 3 catalyst in the isomerization of n-butenes in the 150-240°C temperature range. The kinetic model is a separable one, with a kinetic equation of the Langmuir—Hinshelwood—Hougen—Watson type for each one of the steps of the main reaction and of the deactivation reaction. The deactivation corresponds to the blockage of active sites by coke coming from degradation of cis-butene and trans-butene. The experimentation has been carried out in an isothermal integral reactor by working with a linear sequence of temperature—time. The treatment of the deactivation data for kinetic parameter calculation consists in rigorously solving the design equation for plug flow reactor; this method takes into account the effect of the composition of all the components on deactivation. The kinetic model has been verified by comparing the experimental results with those foreseen in the simulation of the isothermal operation and with different sequences of temperature-time. The procedure for both obtaining and analysing the deactivation kinetics data is particularly useful for complex reaction systems. In these systems, simplified methods for experimentation and calculation used to isolate the effect of composition on deactivation are not applicable.

Action of activated coke as a catalyst: oxydehydrogenation of ethylbenzene to styrene

Oxidative dehydrogenation of ethylbenzene to styrene has been carried out in an isothermal integral reactor on several samples of alumina having different superficial acidities. Variations in the acidity were achieved by doping of the alumina with sodium and were measured by temperature-programmed desorption (TPD) of ammonia. An active catalytic coke was formed on the alumina during reaction. In order to determine the degree of condensation, crystallinity, and characteristics of the functional groups responsible for the catalytic activity of the active coke, analyses were conducted by oxidation at programmed temperature (TPO), X-ray transmission, and electronic paramagnetic resonance (EPR). Changes in the C/H/O ratio of the coke, estimated by quantitative organic analysis, produce changes in the catalytic activity and in the styrene yield. The evidence of the presence of oxygenated species in the coke and the participation of this oxygen in oxidative dehydrogenation suggested a redox-type reaction mechanism.

Low-Temperature-Oxidation Reaction Kinetics and Effects on the In-Situ Combustion Process

Abstract The kinetics of low-temperature oxidation (LTO) of crude oils in porous media was studied. Isothermal integral reactor data were analyzed to obtain rate equations for the over-all rate of the partial oxidation reactions at temperatures below partial oxidation reactions at temperatures below 500 deg. F. The reaction order with respect to oxygen was found to be between 0.5 and 1.0. The order of the reaction was dependent upon the crude but independent of the properties of the porous medium. The activation energy of the reaction was insensitive to the type of crude or porous medium and is in the neighborhood of 31,000 Btu/lb mol. LTO reactions were found to be in the kinitics-influenced region. The measured reaction rates for a 19.9 deg. API and a 27.1 deg. API crude indicated higher oxidation rates under similar reaction conditions for the higher API gravity crude. Light crudes appear to be m ore susceptible to partial oxidation at low temperatures because of the react ed oxidation reactions rather than by carbon oxidation. Other information includes the fraction of reacted oxygen utilized in carbon atom oxidation by the LTO reaction and the molar ratio of CO2 and CO produced in the low-temperature region. Effect of partial oxidation of the crude on the in-situ combustion process was studied by experimentally simulating the zones preceding the combustion front where temperatures and injection rates of linear reservoir model were programmed with time according to a predesigned schedule. Oxidation of the crude at temperatures below 400 deg.F had significant effects on the behavior of the crude-oil/water system in the porous medium at elevated temperatures and on the fuel available for combustion. A substantial decline in the recoverable oil from the evaporation and cracking zones, an increase in fuel deposition, and drastic changes in fuel characteristics and coked sand properties were obtained when the crude was subjected to LTO during the simulation process. Introduction The application of thermal energy to petroleum reservoirs as a means of increasing crude oil recovery has been given a great deal of attention. In underground combustion, thermal energy is induced by the partial burning of the crude oil in situ. The production of heat by the exothermic oxidation reactions of the hydrocarbons constitutes a unique feature of the in-situ combustion process. The chemical reactions and the accompanying heat released create a new temperature profile and cause drastic redistribution in the reservoir fluid saturations. With oxygen available in the transient zones of variable temperature and hydrocarbon saturations, several oxidation reactions of differing nature can take place during an underground combustion process. Because of the complex composition of process. Because of the complex composition of crudes and the great number of reaction products that can be produced, it is convenient to classify the hydrocarbon oxidation reactions ascombustion reactions that take place in the high-temperature combustion zone (above 600 deg. F) with CO2, CO, and H2O as the principal reaction products andpartial oxidation or low-temperature products andpartial oxidation or low-temperature (LTO) reactions that occur in zones where the temperature is lower than 600 deg. F. Several partial oxidation reactions are known to take place, producing primarily water and oxygenated producing primarily water and oxygenated hydrocarbons such as carboxylic acid aldehydes, ketones, alcohols, and hydroperoxides. High-temperature combustion reactions are desirable because they generate most of the heat required for the in-situ combustion process. Partial oxidation reactions, on the other hand, are in most cases undesirable because of their adverse effect on the viscosity and distillation characteristics of the crude. SPEJ P. 253

Kinetics of Oxidation of Coke on Silica-Alumina Catalysts

The kinetics of the oxidation of coked silica-alumina catalysts in an air-nitrogen stream was studied under differential reactor conditions at atmospheric pressure and from 467°C to 560°C. The rates of the reaction were evaluated from the experimental data, according to a proposed kinetic model which includes coupled reactions of carbon and hydrogen in coke, and the catalytic oxidation of the carbon monoxide formed. They were then correlated with variables such as carbon content, hydrogen content, oxygen partial pressure, etc.In addition, to examine the applicability of the rate equations obtained, the product concentration profiles for various contact times of the feed gas were observed under isothermal integral reactor conditions, and were compared with the calculated values from the material balance equations combined with the rate equations.