Pilot-scale Reactive Distillation Column Research Articles

Esterification of glycerol and acetic acid in a pilot-scale reactive distillation column: Experimental investigation, model validation, and process analysis

Abstract The esterification of glycerol with acetic acid is associated with an unfavorable chemical equilibrium and complex cascade reactions behavior. This results in a challenging and cost-intensive process currently used for triacetin (TAG) production. Reactive distillation (RD) as an integration technology was proposed for TAG production in this paper to improve both efficiency and TAG yield. To design such a column for industrial-scale application, a series of pilot-scale experiments and theoretical investigations were performed. Experiments varying decisive operating parameters were successfully performed showing that complete glycerol conversion and high purity of TAG could be easily achieved, validating reactive distillation as a potential candidate for TAG production. A rigorous model based on the chemical kinetics and phase equilibrium was established and validated by good agreement of the simulation results and the experimental data. The model was then applied to investigate the process synthesis, design and optimization of this integration sustainable process. The results indicate the optimal operating ranges for the design of an industrial-scale RD process to get high TAG purity in the bottom stream with considerably less energy consumption.

Application of Economics Optimizing Control to a Two-step Transesterification Reaction in a Pilot-Scale Reactive Distillation Column

The challenges in the chemical process industry of tighter environmental and safety constraints, a higher economic efficiency and an operation in a more dynamic environment motivate the utilization of optimizing control where economic policies are integrated into a (often nonlinear) model predictive control scheme. This so-called one-layer approach or dynamic real-time optimization (D-RTO) has the advantage that the processes are dynamically steered towards the most profitable region. High-fidelity dynamic process models are a basic prerequisite for a good controller performance, and building such models is a challenge. Using highly complex models also may lead to long computation times and thus feedback delays. These issues are in practice avoided by applying only steady-state optimization based on nonlinear models (RTO) and/or using simplified models in MPC. However, the development of computational methods that are able to solve large-scale dynamic optimization problems efficiently have paved the way for applications of economics optimizing control to complex chemical processes. In this contribution, we will demonstrate that a real complex pilot-scale chemical processes, a two-step transesterification realized by reactive distillation that is described by a large DAE model can be operated at the economic optimum by using direct optimizing control. We discuss the problem formulation and the numerical methods used and show experimental data that were obtained at the real process.

Novel process integration for biodiesel blend in membrane reactive divided wall (MRDW) column

Abstract The paper proposes a novel process integration for biodiesel blend in the Membrane assisted Reactive Divided Wall Distillation (MRDW) column. Biodiesel is a green fuel and grade of biodiesel blend is B20 (%) which consist of 20% biodiesel and rest 80% commercial diesel. Instead of commercial diesel, Tertiary Amyl Ethyl Ether (TAEE) was used as an environment friendly fuel for blending biodiesel. Biodiesel and TAEE were synthesized in a pilot scale reactive distillation column. Dual reactive distillation and MRDW were simulated using aspen plus. B20 (%) limit calculation was performed using feed flow rates of both TAEE and biodiesel. MRDW was compared with dual reactive distillation column and it was observed that MRDW is comparatively cost effective and suitable in terms of improved heat integration and flow pattern.

Synthesis of dimethyl carbonate and propylene glycol in a pilot-scale reactive distillation column: Experimental investigation, modeling and process analysis

The transesterification of propylene carbonate with methanol to produce the two valuable products dimethyl carbonate and propylene glycol is associated with an unfavorable chemical equilibrium and complex thermodynamic behavior. This results in a challenging and cost-intensive process currently used for their production. The application of reactive distillation, which integrates chemical reaction and distillation into one single column is considered as potential candidate to improve efficiencies and product yields within chemical-equilibrium-limited systems. However, the design of such a column for industrial-scale applications is challenging as it needs the integration of model-based approaches with reliable experimental data. This paper presents an experimental and theoretical investigation of the simultaneous production of dimethyl carbonate and propylene glycol in a pilot-scale reactive distillation column. Experiments varying decisive operating parameters were successfully performed showing the feasibility of simultaneously producing dimethyl carbonate and propylene glycol in a reactive distillation column. The experimental results were used to select and validate a modeling approach for the simulation of the reactive distillation process. The successfully validated non-equilibrium stage model was applied to perform a process analysis pointing out the trends of both the reactant conversions and the product purities. The simulation results showed the option of achieving high propylene carbonate conversions while recovering an azeotropic mixture of dimethyl carbonate and methanol in the distillate. These results define the operating range for the economic optimization and establishment of an industrial-scale reactive distillation process for this chemical system.

Esterification of Acrylic Acid and n-Butanol in a Pilot-Scale Reactive Distillation Column—Experimental Investigation, Model Validation, and Process Analysis

Due to a high risk of polymerization and complex thermodynamic behavior of the chemical system, the current production process for n-butyl acrylate synthesis is cost-intensive and challenging. Reactive distillation integrates chemical reactions and distillation into one unit at the same time and is one of the best-known examples of process intensification. To facilitate industrial application of this concept for the production of n-butyl acrylate, reliable experimental data are required. This article presents an experimental and theoretical investigation of the synthesis of n-butyl acrylate using reactive distillation. Experiments were conducted in a pilot-scale reactive distillation column, and the decisive operational parameters were varied. To predict the experimental results, a nonequilibrium-stage model was applied and the model was validated using the experimental data. The validated model was then used to perform a process analysis, showing trends in the conversion of acrylic acid and n-butanol and the purity of n-butyl acrylate that can be used for prospective optimization studies.

The inhibition of acrylic acid and acrylate ester polymerisation in a heterogeneously catalysed pilot-scale reactive distillation column

Due to a complex thermodynamic behavior and a high risk of polymerisation, the current production process for n-butyl acrylate is challenging and cost-intensive. The process intensification for the esterification reaction between acrylic acid and n-butanol to synthesise n-butyl acrylate in a reactive distillation column has not been studied much experimentally and is addressed in this paper. A main challenge that currently hinders the implementation of this promising process is the risk of polymerisation of acrylic acid and n-butyl acrylate. This article presents an experimental investigation of the inhibition period of acrylic acid and n-butyl acrylate polymerisation, which is dependent on the amount of inhibitor added, the temperature and the gas phase composition. Hydroquinone monomethyl ether and phenothiazine are the most common inhibitors and are hence used within this study. The liquid–liquid separation is also studied together with the experimental investigation of the inhibition period. Furthermore, the dilution of the inhibitor in a pilot-scale reactive distillation column is investigated together with the development of startup and shutdown procedures. The results of the experimental and theoretical investigations are used to develop a concept to avoid any polymerisation occurring in a pilot-scale reactive distillation column. This concept was used to successfully conduct a pilot-scale reactive distillation experiment.

Transesterification of dimethyl carbonate with ethanol in a pilot-scale reactive distillation column

Reactive distillation (RD) is currently used to increase reactant conversion and the purity of the target product. Our work focuses on the application of RD to reaction systems that feature more than one target product. In such systems, an RD column acts as a multipurpose reactor to produce several target products with high selectivities by changing the operating conditions. A promising example of such a multiple-product system is the consecutive transesterification of dimethyl carbonate with ethanol to form the target products ethyl methyl carbonate and diethyl carbonate. This article presents for the first time a comprehensive experimental study on that reaction system in a pilot-sale RD column. Data reconciliation tests confirm the reliability of the experimental results. The effect of decisive operating parameters on the RD column's behavior was extensively studied, and the potential of an RD column to act as a multipurpose reactor was experimentally verified.

Experimental model validation for n-propyl propionate synthesis in a reactive distillation column coupled with a liquid–liquid phase separator

In the synthesis of some organic esters, reactive distillation coupled with a liquid–liquid phase separator is often used to increase the product purity or to recover the reactants. In this article, we present a comprehensive experimental and theoretical study on the heterogeneously catalysed synthesis of n-propyl propionate by reactive distillation and a subsequent liquid–liquid phase separator. The experiments were performed in a pilot-scale reactive distillation column. Data-reconciliation tests proved that the experimental results obtained comprise a complete, reliable set of composition and temperature profiles along the pilot-scale reactive distillation column and can be used for further model validation. A nonequilibrium-stage model was applied to predict the experimental results. Simulation studies demonstrated that the composition and temperature profiles in the rectifying section of the column were highly sensitive to the composition of the reflux stream entering the column. Deviations between the experimental and predicted composition profiles in the rectifying section were identified. An explanation for the deviations is given in this article.

Reactive distillation — experimental data for propyl propionate synthesis

AbstractA set of experimental data for heterogeneously catalysed esterification of propan-1-ol and propionic acid to propyl propionate in a pilot scale reactive distillation column is presented. The catalytic section of the column was equipped with the structured packing Katapak SP-11. Both, rectifying and stripping, sections consisted of the non-reactive structured Sulzer BX packing. As catalyst, the strongly acidic ion-exchange resin Amberlyst 46 was used. The experimental results show concentration as well as temperature profiles along the column height and therefore exhibit reliable data for model validation purposes.

Inference of conversion and purity for ETBE reactive distillation

Reactive distillation (RD), an unconventional and attractive technique, has been applied in fuel ether production. A typical application of RD is the synthesis of the widely used methyl tert-butyl ether (MTBE). RD has also been found to have potential to produce high quality ethyl tert-butyl ether (ETBE), a potential alternative to MTBE. A RD process integrates conventional reaction and separation into a single unit, resulting in extra complexity and dual process objectives, i.e. maximization of reactant conversion and purity of products. The conversion and the purity are thus important variables to be controlled in RD of ETBE. Unfortunately, both of them are not economically and reliably available for closed-loop control. This study aims to develop an effective method to infer the conversion and the purity from multiple temperature measurements that are easily available on-line and in real time. Nonlinear inferential models are recommended for ETBE synthesis with a ten-stage pilot scale RD column. The models are two-variable third-order regressive models, in which the temperature measurements of the reboiler and the bottom reactive section are employed. Experimental design, model identification, and model testing are also investigated.