Desorbent Flow Rate Research Articles

Purification of rutin by supercritical fluid simulated moving bed chromatography

AbstractRecent studies have shown that rutin (Quercetin‐3‐O‐rhamnosylglucoside) may have an inhibitory effect on COVID‐19. Rutin can be extracted from Tartary buckwheat as an active pharmaceutical ingredient. Nevertheless, its purification is mainly hindered by Kaempferol‐3‐O‐rutinoside (K3R) due to their similar molecular structures. This study intends to propose a simulated moving bed (SMB) chromatography process of rutin and K3R to achieve continuous production. True moving bed (TMB) and SMB models were established to numerically analyze and optimize this process. The system consists of a four‐zone SMB with two columns in each zone. The effects of the switch interval, feed flowrate, desorbent flowrate, extract flowrate, raffinate flowrate, and recycle flowrate on the purity and yield of rutin and K3R were investigated and the optimized conditions were chosen as 5 min, 3.5, 40, 34, 9.5, and 24.5 L/min, respectively. Consequently, the purities of 99.64% and 99.25%, and the yields of 99.81% and 99.37% for rutin and K3R were obtained, respectively. The simulation results can provide a guidance for the future industrial application of SF‐SMB to separate rutin and K3R.

Separation of propane and propylene by desorbent swing adsorption using zeolite 13X and carbon dioxide

A new concept of the desorbent swing adsorption (DSA) process operating at a constant pressure is proposed. The developed process was applied to the separation of propane and propylene because propylene, a high-demand chemical, is produced from an energy-intensive and expensive process. The selection criterion of desorbent was the chemical having the adsorption affinity between propane and propylene, and carbon dioxide was selected as a case study. According to the sequential breakthrough experiments, propylene was separated from propane in the CO2 pre-filled bed. However, the desorption step utilizing CO2 flow played a key factor in the separation performance because a faster desorbent flowrate enhanced the desorption of adsorbed propylene and prolonged the breakthrough times of the components. A two-bed DSA process (60% propane and 40% propylene), containing rinse-out and rinse-in steps, achieved 94.427% purity for propane with 99.655% recovery and 8.816 mol/(kg·hr) productivity, and 99.999% purity for propylene with 96.644% recovery and 5.700 mol/(kg·hr) productivity. Unusual temperature variances in the DSA process (decreasing during the adsorption step and increasing during the desorption step) was opposite to that in conventional adsorptive processes. These temperature variances contributed to an enhanced separation performance and process safety (prevention of zeolite 13X poisoning and gas fires). The feasibility of the DSA process was demonstrated without further requirements for additional energy arising from compression or a vacuum. The optimization of the DSA process and subsequent desorbent recovery processes is a subject for further studies.

Multi-objective optimization of non-isothermal simulated moving bed reactor: Methyl acetate synthesis

Simulated moving bed reactor (SMBR) increases conversion of a reversible chemical reaction by introducing continuous counter-current in-situ adsorptive separation of reactants and/or products. Effects of temperature variance among different operating zones on the performance of a 4-column SMBR for reaction in the form of A↔B+C were evaluated based on multi-objective optimization. This article is focused on the model system of methyl acetate synthesis. A total of five representative cases with different temperature distributions in the range of 308–323 K were compared for six optimization problems with two or three objective functions along with practical constraints in terms of product purity, yield, unit throughput and solvent consumption. Pareto solutions were obtained for each problem. Under optimal conditions, a major fraction (over 85%) of the fed acid is converted in feed-section. For a given purity requirement, Cases 1 and 2 with 323 K in the feed section have similar unit throughput, higher than those of the other cases studied by about 10–40%. Compared with isothermally operated Case 1, Case 2 with a temperature gradient exhibited reduced solvent consumption (defined as the ratio of desorbent flowrate to maximum flowrate) by about 20% at 313 K. The superiority of non-isothermal operation resulting on reduced solvent consumption becomes more significant with decreased purity requirement and/or decreased unit throughput.

Optimal Operation of Simulated Moving Bed Technology on Utilization of Naphtha Resource

Simulated moving bed (SMB) technology has attracted more and more attention in recent decades. The simulated moving bed (SMB) technology on optimal utilization of naphtha resource was studied in this paper. A simulated moving bed equipped with 16 columns was used to separate normal paraffins from naphtha. The effects of temperature (T), switching time (ts), extract oil flow rate (LAD), feed flow rate (LF), and desorbent flow rate (LD) on the separation performance were investigated, and the desorbent recycle process was simulated by Aspen Plus. The results showed that the optimal conditions for simulated moving bed were operation temperature (T) of 170°C, switching time (ts) of 900 s, extract oil flow rate (LAD) of 10 mL/min, feed flow rate (LF) of 5 mL/min, and desorbent flow rate (LD) of 20 mL/min. Through the SMB and the desorbent recycle system, the purity of the de-solvent extract oil (DEO) reached 98% and the purity of the de-solvent raffinate oil (DRO) reached 92%, which were the high-quality feed for the ethylene cracking process and the catalytic reforming process, respectively.

Optimization of an improved single-column chromatographic process for the separation of enantiomers

This work addresses optimization of an improved single-column chromatographic (ISCC) process for the separation of guaifenesin enantiomers. Conventional feed injection and fraction collection systems have been replaced with customized components facilitating simultaneous separation and online monitoring with the ultimate objective of application of an optimizing controller. Injection volume, cycle time, desorbent flow rate, feed concentration, and three cut intervals are considered as decision variables. A multi-objective optimization technique based on genetic algorithm (GA) is adopted to achieve maximum productivity and minimum desorbent requirement in the region constrained by product specifications and hardware limitations. The optimization results along with the contribution of decision variables are discussed using Pareto fronts that identify non-dominated solutions. Optimization results of a similar simulated moving bed process have also been included to facilitate comparison with a continuous chromatographic process.

Three-zone simulated moving-bed (SMB) for separation of cytosine and guanine

Separation of guanine and cytosine base pairs in nucleotide is an interesting topic for investigation of DNA structure. Therefore, an understanding of nucleotide separation by chromatography is necessary to prepare DNA molecules. Guanine and cytosine separation in SMB was simulated by Aspen chromatography and it was experimented by assembled 3-zone simulated moving bed (SMB) with change of stream flow rates, sample concentration, and desorbent flow rate. The simulation of batch chromatography was also confirmed by HPLC experiments. Based on these, good operating conditions of SMB chromatography were determined. Three-zone SMB equipment was set up by connecting three C18-HPLC columns, four HPLC pumps, and six multiposition valves. Batch chromatography of cytosine and guanine was conducted to determine the isotherms of the two nucleotides. The outlet streams of SMB, raffinate and extract were sampled and analyzed by analytical HPLC system. The adsorption isotherms of cytosine and guanine were HC= 0.5 and H G =1.05. The highest experimental purity of cytosine and guanine in SMB was obtained as 94.9% and 89.8% with operating parameters of Q feed =0.2 mL/min, Q desorbent =0.6 mL/min, Q extract =0.2 mL/min, Q raffinate =0.6 mL/min, and switching time=7 min.

Theoritical analysis and simulation of five‐zone simulating moving bed for ternary mixture separation

AbstractIn the present work a mathematical model has been presented to study the behaviour of five‐zone simulating moving bed (SMB) system for the separation of a ternary mixture of certain amino acids. These are methionine, phenylalanine and tryptophan, possessing linear isotherms values. Safety margin method has been used to design the SMB system while triangle theory became the basis to calculate the operating conditions at fixed feed flow rate. It was found that for same safety factor (β) value in each zone, increase in β value causes the purity values of all product streams to increase up to a definite value. Further increase in β value shows the effect of decrease in separation efficiency, because of dominance of axial dispersion and mass transfer resistances. The effect of zone safety factor (zone flow rate βII, βIII and βIV) values on the separation performance of five‐zone SMB have also been investigated which remained an important issue in SMB current research. Increase in βII value results in rising tryptophan purity, phenylalanine purity improves due to increase in βIII value and increase in βIV value becomes the basis for enhancing methionine purity. In column profile study, the solute concentration profile diminishes due to increase in particular separation zone safety factor value. This happened due to low column switching time with high desorbent flow rate to the system. The developed mode was run in Aspen Chromatography vis 12.1. (2004) simulator for simulation studies.

Multifunctional Reactor for the Synthesis of Dimethylacetal

The synthesis of dimethylacetal (1,1-dimethoxyethane) was performed in a Simulated Moving Bed Reactor (SMBR) pilot unit LICOSEP 12-26 (Novasep, France) with 12 columns packed with the acid resin Amberlyst-15 wet (Rohm & Haas, France). For the operating conditions used, the performance parameters obtained were as follows: acetal purity, 91.41%; productivity rate, 5.17 kgacetal/(Ladsorbent day); and desorbent consumption, 7.11 Lmethanol/kgacetal. The effect of the switching time, feed composition, and desorbent flow rate in the performance of the SMBR was studied by means of two mathematical models approaches: the SMBR model (for the concentration profiles and performance parameters) and the True Moving Bed Reactor (TMBR) model (for the reaction separation regions).

Effects of desorbent flowrate on simulated moving bed process

Effects of desorbent flowrate on simulated moving bed process

Effects of desorbent flowrate on simulated moving bed process

This article presents the effects of the desorbent flowrate (or m1) on simulated moving bed (SMB) process performance at constant m2, m3 and m4, where the m-values (m j ) are defined as the net flowrate ratios of the zone, j, to the solid flowrate. A complete m-plane analysis of SMB systems (ComPASS) has been developed that illustrates how the desorbent flowrate is determined within the complete m-plane (i.e., fluid-solid flowrate ratio plane) to enhance the SMB process performance. The effects of desorbent flowrate are presented numerically for linear/equilibrium and nonlinear/nonequilibrium SMB processes. The results of the studies using ComPASS show that for linear/equilibrium SMB process, it is desirable to determine the minimum desorbent flowrate (m1) within the complete separation region. For the nonlinear/nonequilibrium SMB process, the desorbent flowrate can be determined at the minimum value which maximizes the raffinate purity.

Optimization of throughput and desorbent consumption in simulated moving-bed chromatography for paclitaxel purification

In simulated moving-bed (SMB) applications, throughput and desorbent consumption are two key factors that control process cost. For a given adsorbent volume and product purity requirements, throughput and desorbent consumption depend on desorbent composition, column configuration, column length to diameter ratio, and adsorbent particle size. In this study, these design parameters are systematically examined for paclitaxel purification. The results show that if adsorbent particle size, column dimensions and column configuration are fixed, the higher the product purity required, the lower the throughput. If product purity and yield are fixed, the larger the solute migration speed ratio, the higher the throughput, and the lower the desorbent consumption. If total bed volume and product purities are fixed, the longer the separation zones, the higher the throughput, but the higher the desorbent flow-rate. An intermediate configuration gives the minimum desorbent consumption. If there are no limits on pressure drop or zone flow-rate, the larger the column length to diameter ratio, the smaller the adsorbent particle size, the higher the throughput, and the lower the desorbent consumption. If the maximum zone flow-rate is controlled by the pressure drop limit and not by the standing waves requirement, the longer the columns, the lower the zone flow-rates and the lower the throughput. For 150-μm adsorbent particles and a maximum zone flow-rate of 300 ml/min, a design with optimal throughput and desorbent consumption is found for paclitaxel purification.

Continuous chromatographic separation process: simulated moving bed allowing simultaneous withdrawal of three fractions

Continuous counter-current chromatographic separation has been carried out in a simulated moving bed system (SMB). We have worked with a SMB pilot plant (8 columns, 4.4 litres of resin each) which allows the continuous withdrawal of two different fractions. A mixture of glucose-fructose has been separated. To calculate the concentration profile within the separator an axial dispersed plug flow model and an equilibrium stage model have been employed; software has been created to simulate the behaviour of the separator. The necessary parameters of the mode: the adsorption equilibrium constant, the height equivalent to a theoretical plate and the bed voidage, have been acquired experimentally from elution chromatography measurements. The results calculated by simulation give a good representation of the experimental concentration profiles; other separations like xylitol-arabitol have been simulated. The influence of some factors like desorbent flow-rate, feed flow-rate and the bed voidage have been studied using the software. Once the system has worked in a two withdrawal way, an extension of the pilot plant has been constructed so as to obtain a third one. The necessary parameters of the three withdrawal model will be studied.