Development of a dynamic nonequilibrium cell model for reactive distillation tray columns

Dynamic behaviour of reactive distillation tray columns described with a nonequilibrium cell model

Kinetics and structural design of ZSM-5@SiC foam catalytic packing in RD column for ethyl levulinate synthesis

Economic optimization of a reactive distillation column with multiple reactive sections for silane production

Rigorous design and economic optimization of reactive distillation column considering real liquid hold-up and hydraulic conditions of industrial device

Optimization and heat integration of hybrid R-HIDiC and pervaporation by combining GA and PSO algorithm in TAME synthesis

This paper aims to present the feasibility of conducting the transesterification of propylene glycol ether (PM) with methyl acetate (MeAc) in a reactive distillation (RD) column to improve the reaction conversion. The essential thermodynamic and reaction kinetic data of the reaction system were measured for the feasibility study. There is only one azeotrope, MeAc–MeOH, in the reaction system, and the NRTL model could describe well the thermodynamic behavior of this system. The transesterification of PM with MeAc is an endothermic reaction with activation energy E = 55.704 kJ·mol–1. The feasibility was analyzed by residue curve maps (RCM), showing that full conversion of PM could be realized by RD with a mole ratio of MeAc–PM larger than 2.882. The intensification effect was experimentally verified in a batch RD column. Finally, some important parameters are given through the conceptual design to develop a continuous RD column for the transesterification of PM with MeAc.

Fatty acid methyl esters derived from renewable sources such as vegetable oils has gained importance nowadays as an alternative fuel for diesel engines. The present study is aimed to produce biodiesel from non-edible oil (Karanja oil of Indian origin) both in batch and continuous reactors. The purpose of the study is the comparison of Karanja biodiesel production with different reactor types under variable reaction characteristics. Therefore, two types of continuous reactors were used: helical tube reactor and reactive distillation (RD) column. Experiments were carried out to obtain suitable operating parameters in batch- and continuous-flow reactors. For batch reactor, suitable operating conditions obtained are: 7:1 methanol-to-oil molar ratio, 0.8% (by weight of oil) catalyst (KOH), 65°C reaction temperature, and 1-h reaction time, at which the maximum yield obtained is 96%. In continuous helical tube reactor, maximum yield of 92.6% was obtained at 6.6 mL/min of flow rate at the same operating conditions of batch reactor. In continuous RD column, maximum yield of biodiesel 96.6% was obtained at the same operating conditions except methanol-to-oil molar ratio (5:1) because of recycling of methanol into the column. The residence times in the helical tube reactor and RD column were 4 and 8 min, respectively, as compared to 1 h in the batch reactor for almost the same yield.

Reactive distillation (RD) in the face of azeotrope(s) in the separation of a mixture from an RD column might need debottlenecking design and more columns to obtain high-purity products. Under such circumstances, the integration of heat with the process becomes an effective consideration for reducing costs. In this study, an RD process to produce ethyl acetate and n-butanol from ethanol and n-butyl acetate by conducting a transesterification reaction is presented. The products from the RD column include n-butanol and an ethanol/ethyl acetate mixture. Designs with alternative configurations are used to illustrate plantwide designs of the process with heat integration/coupling. Among these alternatives are two with three columns and one with two columns. In the three-column configurations, separation of ethanol/ethyl-acetate mixtures from the top product of the RD column is conducted by extractive distillation or pressure-swing distillation. The other configuration consists of an RD column followed by a conventional distillation column operated at high pressure. Systematic design procedures are used to optimize the flowsheets of different configurations by minimizing the total annual cost. Heat integration and thermal coupling technologies are used in these three configurations to attempt to provide more economical designs. The results show that the selection of separation system depends on whether heat integration/coupling is considered. In this case, the two-column reactive distillation process with heat integration yields high-purity products and the lowest total annual cost.

<p>In the present study, two distinctly different approaches are followed for modeling of reactive distillation column, the equilibrium stage model and the nonequilibrium stage model. These models are simulated with a computer code developed in the present<br> study using MATLAB programming. In the equilibrium stage models, the vapor and liquid phases are assumed to be in equilibrium and allowance is made for finite reaction rates, where as in the nonequilibrium stage models simultaneous mass transfer and reaction rates are considered. These simulated model results are validated from the experimental data reported in the literature. The simulated results of equilibrium and nonequilibrium models are compared for concentration, temperature and reaction rate profiles in a reactive distillation column for Methyl Tert Butyle Ether (MTBE) production. Both the models show similar trend for the concentration, temperature and reaction rate profiles but the nonequilibrium model predictions are higher and closer to the experimental values reported in the literature.</p>

This paper introduces multiple esterification reactions of three alcohols occurring in a single reactive distillation (RD) column and reports significant energy savings by combining three reactions in the single unit. To realize a feasible integration of the three reactions, the removal of the common water product from the unstable heterogeneous azeotrope should be possible through liquid–liquid decantation in the eight-component system. For this multireaction system, only the direct sequence can produce three esters with a purity higher than 99.0 mol % due to the behavior of liquid–liquid phase equilibrium. We demonstrate an economic evaluation of the direct sequence of a single RD column simultaneously producing the three esters by comparing the direct sequence with the two parallel RD sequences in the same design basis. The total annual cost of the triple esterification direct sequence is reduced by 21.3–25.2% compared to that of the parallel esterification system.

The reactive double dividing-wall distillation column (R-DDWDC) can simultaneously integrate and effectively coordinate reaction–separation coupling (RSC) and separation–separation coupling (SSC), thereby offering greater technical advantages and development potential than the conventional reactive distillation column and the reactive single dividing-wall distillation column. However, the application of two dividing walls and the introduction of external recycle flows inevitably lead to multiple candidate configurations of the R-DDWDC, and this significantly adds complexity and computational burden to its synthesis and design. To address the issue, we propose an effective methodology for developing the R-DDWDC, which involves a two-step strategy: the first step is to determine the configuration of external recycle flows by searching for the RSC from non-sharp separation to sharp separation of reaction mixtures, and the second step is to adjust the arrangement of the dividing walls to intensify the SSC. The former serves to provide the greatest flexibility for the inclusion of the SSC, and the latter helps to achieve full coordination with the RSC, thereby allowing the determination of the optimal design with low complexity and computational intensity. The methodology is fundamentally a conceptual design and structural optimization framework that can be implemented using either generic process simulation platforms or custom computational programs. Four representative examples, including the metathesis of 2-pentene; the acetalization of ethanol with butanal; the transesterification of propylene glycol monomethyl ether with methyl acetate; and the esterification of lactic acid with methanol, are selected to assess the derived procedure, and the obtained results confirm its simplicity and efficiency. Because the procedure proposed in this work is independent of the number of components contained in reaction mixtures and their relative volatility rankings, it can be regarded as a general methodology for developing other complicated reactive dividing-wall distillation columns.

The study aims to reveal the possibility of reactive distillation (RD) in the 2-methoxy-2-methylheptane (MMH) production process. MMH is getting more industrial and academic interests as a gasoline additive to replace methyl tert-butyl ether. Traditionally, MMH is obtained by carrying out the reaction in the reactor followed by three distillation columns. The high yield of MMH could be achieved by keeping the large reactor size or by using the large excess of 2-methyl-1-heptene (MH). Both former and latter strategies are associated with the high capital and operating costs. To solve these problems, this study proposed an innovative RD configuration to take synergistic benefits of reaction and separation involved. This innovative RD configuration allows the production of MMH with significantly lower capital, operating and total annual costs. For desired MMH yield, the result demonstrates that the proposed RD configuration can reduce energy, capital, and total annual costs up to 7.7, 31.3, and 17.1%, respectively, compared to a conventional process. Furthermore, the influence of some important design parameters on the RD column performance was also explored to overcome the temperature limitation of acid resin catalyst inside the reactive zone of the RD column.

Environment concerns related to the use of fossil fuels are reflected in proposals for new conversion technologies to produce biofuels from biomass. The biofuels produced in this context have the same characteristics as petroleum derivatives, however, with reduced greenhouse gas emissions and with no sulfur in their molecular structures. In this context, a reactive distillation (RD) column was designed, constructed, installed, and operated using process intensification principles. It was applied in the production of biodiesel, using residual frying oil as the raw material, by the transesterification reaction, in a continuous regime. The process started with alcohol in excess in the reboiler, located in the bottom of the RD, which was heated through the combustion of liquefied petroleum gas (LPG) to produce ethanol vapor, which was recirculated in the column until stabilization. In this stage, the reagents were inserted into the feed tanks. Thus, the tank valves were opened for each reactant. The reaction products were recovered during the experiment from the bottom of the column and they were distilled to obtain two phases, biodiesel and glycerol. The results obtained from this study show that the use of an RD column can produce biodiesel in a continuous regime.

Kinetic analysis for the acid-catalyzed dimerization of C4 olefins was performed in a batch reactor, and a suitable rate model was developed. It was further used in the rate-based simulation model of a continuous reactive distillation (RD) column. The results obtained were compared with the experimental observations made on a pilot-scale high-pressure RD column. An important outcome of the present work is that RD can be used efficiently to enhance the selectivity of C8 dimers, thereby avoiding the formation of trimers and tetramers. The use of polar components (such as water or alcohols), as selectivity enhancers, is not necessary.

In this paper, design of a complete reactive distillation (RD) system has been developed. The reactive distillation system in the study is the production of ethyl acetate (EtAc) via esterification of acetic acid (HAc) with ethanol (EtOH) using sulphuric acid as homogeneous catalyst. A suitable NRTL model parameter set for calculating of liquid activity coefficients has been established with excellent prediction of the compositions and temperatures for the four azeotropes in this system. In the VLE calculations, vapor association of acetic acid due to dimerization has also been considered. A reactive distillation column with an overhead decanter can be designed to achieve over 93 wt% of ethyl acetate composition at organic phase top product stream while the bottom product stream is designed to be rich in acetic acid so that it can be recycled and mixed with fresh acid make-up stream to serve as acid feed to the reactive distillation column. Since the purity of the optimum top organic product is still not good enough for the ethyl acetate product specification in industry, an additional column is designed to purify the ethyl acetate product of the reactive distillation column to over 99.5 wt%. The top draw of the second column will be recycled back to the decanter. In summary, the overall optimum design of this ethyl acetate reactive distillation system includes two columns (including the reactive distillation column and the second column), one decanter, and two recycle streams. The optimum operating condition of the overall system will also be studied to minimize the total operating cost of the overall system while meeting product specifications.