Dimethyl ether (DME, CH 3 OCH 3 ) is the simplest of ethers and is considered one of the leading candidates in the quest for a substitute for petroleum-based fuels. In this work, we analyzed the one-step synthesis of DME in a shell-and-tube type fixed-bed reactor. We have conducted simulations using a one-dimensional steady-state model of a heterogeneous catalyst bed. This model considered heat and mass transfer between the catalyst pellets and reactants and the effectiveness factor of the catalysts, together with the reactor cooling through the reactor tube wall. The reactor simulation was carried out under steady-state conditions. Thereafter, we compared the data of simulation results with the data obtained from the operation of a pilot-scale reactor and found acceptable agreement between the two data sets. Moreover, we analyzed effectiveness factors of the catalyst pellet and along the length of the reactor where we also analyzed temperature profiles and concentrations of the components. The analyses showed that complex reactions, when coupled with pore diffusion within the catalyst pellets, result in unusual values of the effectiveness factor along the length of the reactor. Given these results, the reactor demonstrated high performance for such variables as CO conversion and DME yield. On the contrary, operations over a high temperature range are unavoidable even though this type of reactor has been in general use. Eventually more effective cooling strategies in the operation of this type of reactor should be developed and studied.
A reaction network and kinetic model for the dehydration of 2,3-butanediol (2,3-BDO) to 1,3-butadiene (1,3-BD) and methyl ethyl ketone (MEK) on an amorphous calcium phosphate catalyst are proposed. The kinetic parameters of the model were estimated using experimental data obtained from a laboratory-scale fixed-bed reactor operated under isothermal conditions. Experiments were performed using a mixture of 2,3-BDO, 3-buten-2-ol (3B2OL), and N 2 as feed, at temperatures ranging from 304 to 334.5 °C and gas hourly space velocity (GHSV) ranging from 1780 to 2222 h −1 . 2,3-BDO conversion varied from 6 to 100%; the selectivity of 1,3-BD ranged from 5 to 33 wt %, and the selectivity of MEK ranged from 31 to 34 wt %. Kinetic models based on the simple power law and Langmuir−Hinshelwood−Hougen−Watson model were developed to describe the dehydration of 2,3-BDO to 1,3-BD and MEK. Statistical and physicochemical criteria are used to contrast the performance of the two kinetic approaches. The power law model showed the highest capacity to represent the tendency of experimental data obtained by changing temperature and GHSV. The kinetic parameters indicate the following: (i) The reaction orders (n 1 , n 3 , n 4 = 0.0187; n 2 = 0.146) are very close to 0, meaning that reactor performance for 2,3-BDO dehydration is mainly determined by the temperature of the reactor not by the concentrations of reactants. (ii) The reaction routes that produce 1,3-BD demand activation energy that is higher than that of the others, explaining the quickly changing rate of 3B2OL and 1,3-BD selectivity and slowly changing rate of MEK and 2MPL selectivity with increasing temperature.
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