Simulated Moving Bed Technology Research Articles

Research Progress on the Typical Variants of Simulated Moving Bed: From the Established Processes to the Advanced Technologies

Simulated moving bed (SMB) chromatography is a highly efficient adsorption-based separation technology with various industrial applications. At present, its application has been successfully extended to the biochemical and pharmaceutical industrial sectors. SMB possesses the advantages of high product purity and yield, large feed treatment capacity, and simple process control due to the continuous operation mode and the efficient separation mechanism, particularly for difficult separation. Moreover, SMB performs well, particularly for multi-component separation or complicated systems’ purification processes in which each component exhibits similar properties and low resolution. With the development of the economy and technology, SMB technology needs to be improved and optimized to enhance its performance and deal with more complex separation tasks. This paper summarizes the typical variants or modifications of the SMB process through three aspects: zone variant, gradient variant, and feed or operation variant. The corresponding modification principles, operating modes, advantages, limitations, and practical application areas of each variant were comprehensively investigated. Finally, the application prospect and development direction were summarized, which could provide valuable recommendations and guidance for future research in the SMB area.

Raising the Research Octane Number using an optimized Simulated Moving Bed technology towards greater sustainability and economic return

The scale of CO2 emissions from light-duty vehicle (LDV) fleets worldwide has led governments to mandate substantive improvements in vehicle fuel economy, thereby mitigating climate change. Raising the Research Octane Number (RON) of fuel through isomerization, alongside mandates to recalibrate existing LDV engines, promises to contribute substantially to climate action. This study has aimed to develop a highly efficient adsorption separation technology for isomerization refining that can contribute significantly to the sustainability and economics of the overall “well-to-wheel” outcome for LDV fleets globally. This study developed a rigorous dynamic model for a Simulated Moving Bed (SMB), comparing the SMB to conventional distillation as the next best alternative. The SMB was optimized using a genetic algorithm, maximizing RON and Gross Margin as objective functions. This study showed that SMB effectively separates high octane components from low octane components, producing a fuel with a RON of 95 when maximizing the RON, thereby enabling lower emissions associated with recalibrated LDV engines. Compared to 11 MW of steam duty associated with conventional distillation, the SMB unit utilized 3.4 MW and 5.7 MW of electricity when optimizing the RON and the Gross Margin respectively, appreciably reducing comparative greenhouse gas emissions. Finally, compared to conventional distillation as measured by Gross Margin, the optimized SMB unit increased the economic return by 47% when maximizing the RON and by 82 % when maximizing the Gross Margin. In summary, this study motivated for rapid capital investment into retrofitting isomerization facilities with SMB unit operations, replacing outmoded distillation as the primary separation technology. Future work will focus on optimizing the separation technology alongside the overall isomerization process using a rigorous techno-economic analysis as the objective function for optimization.

Discrimination of xylene isomers in a stacked coordination polymer.

The separation and purification of xylene isomers is an industrially important but challenging process. Developing highly efficient adsorbents is crucial for the implementation of simulated moving bed technology for industrial separation of these isomers. Herein, we report a stacked one-dimensional coordination polymer {[Mn(dhbq)(H2O)2], H2dhbq = 2,5-dihydroxy-1,4-benzoquinone} that exhibits an ideal molecular recognition and sieving of xylene isomers. Its distinct temperature-adsorbate-dependent adsorption behavior enables full separation of p-, m-, and o-xylene isomers in both vapor and liquid phases. The delicate stimuli-responsive swelling of the structure imparts this porous material with exceptionally high flexibility and stability, well-balanced adsorption capacity, high selectivity, and fast kinetics at conditions mimicking industrial settings. This study may offer an alternative approach for energy-efficient and adsorption-based industrial xylene separation and purification processes.

Simulated-moving-bed technology for purification of the prebiotics galacto-oligosaccharides

A commercial galacto-oligosaccharide (GOS) syrup with prebiotic properties was purified with simulated moving bed (SMB) chromatography to separate undesired side products induced by synthesis reaction mechanism. A promising polystyrene-divinylbenzene resin stationary phase has been characterized with regard to its selective adsorption behavior. The chosen chromatographic system allows a pseudo binary separation of the multi-component GOS syrup mixture exploiting a multi-column continuous chromatographic process. Suitable SMB operation parameters were estimated by means of the equilibrium (triangle) theory, further optimized by modelling the separation in more detail and finally validated experimentally. Changes of temperature, concentration of the feed as well as in the instrumental configuration (open loop, closed loop and 3 zones) were examined with a classical SMB plant in lab scale size. Highly purified GOS products could be obtained with purities up to >99% in the extract and raffinate fractions. A quantitative description of the transfer from batch chromatography to the continuous separation process via SMB technology is provided, indicated significant potential for a scale-up.

Optimization of the Production of 1,1-Diethoxybutane by Simulated Moving Bed Reactor

Simulated moving bed technology is applied in the field of pharmaceutical, petrochemical and fine chemistry. It shows capability in separating multicomponent mixtures up to high purities. In this work, an attempt was made to optimize the production of 1,1-diethoxybutane (DEB), using the simulated moving bed technology. A fixed bed model is made with good agreement with experimental results. This fixed bed model was expanded to a simulated moving bed model. This model was used to determine the optimum conditions regarding the switching time and flowrates in each section. From this model, the optimum switching time was found to be 2.4 min, and the ratio of liquid flowrate over the solid flowrate in Section 1Section 2Section 3 and Section 4 of the SMBR was found to be 4.24, 1.77, 3.03 and 1.35, respectively. Under those conditions, the productivity was 19.8 kg DEB per liter of adsorbent per day, and the desorbent consumption was 6.1 L of ethanol per kg of DEB. The results were obtained with a minimum purity of the extract and raffinate of 97%.

Towards polymer grade ethylene production with Cu-BTC: gas-phase SMB versus PSA

The recovery of ethylene as a product from ethylene/ethane mixtures by adsorptive processes has been attracting great interest due to the high operating and capital costs of the cryogenic distillation traditionally practiced. This search for novel economical ways to separate olefins from paraffins by adsorptive processes has motivated the appearance of improved materials. The trend of developing new materials, such as metal–organic frameworks (MOF) and the challenge of improving the existing technologies, such as pressure swing adsorption (PSA) and simulated moving bed (SMB) leave the horizon open for new alternatives. In the present work, PSA and SMB in gas phase were tested to produce ethylene at high purity on Cu-BTC MOF in beads form. For the first time, the olefin/paraffin separation by SMB technology, using a MOF as adsorbent, was achieved. Both technologies were successfully implemented experimentally and simulated. In the best cycle performed by VPSA for the 20/80 ethane/ethylene feed composition, the ethylene was obtained with a purity of 98.0% at a recovery of 70.2% and a productivity per unit mass of stationary phase of 1.55 molC2 h−1 kg−1adsorbent. Additionally, for the 50/50 ethane/ethylene mixture only 43.2% of the ethylene is recovered at a purity of 95.4% and a productivity of 0.52 molC2 h−1 kg−1adsorbent. In the two cycles performed by SMB, to separate 39/61 ethane/ethylene mixture, ethylene was obtained with a purity of 95%, a recovery above 90% and productivity between 0.50 and 0.66 molC2 h−1 kg−1adsorbent. All the experiments were well predicted by the axial dispersion flow model with the LDF approximation.

Enhanced Simulated Moving Bed Reactor Process for Butyl Acrylate Synthesis: Process Analysis and Optimization

A novel process design based on the simulated moving bed technology for the synthesis of butyl acrylate (BAc) was investigated in order to get a more competitive industrial process. For that, a fixed-bed reactor was coupled with a simulated moving bed reactor. Reactive separation regions were determined for different conditions of process configurations and feed compositions allowing the optimal operating parameters to be found. Furthermore, the process integration was accomplished and the desorbent (n-butanol) recovery was also investigated ensuring the minimal BAc purity required (99.5% w/w). The viability and competitiveness of this process were evaluated after an economic analysis which showed that it required similar production costs and energy consumption as well for the highest production capacity when compared with other state-of-the-art processes for the BAc synthesis, presented so far.

Development of gas‐phase SMB technology for light olefin/paraffin separations

The separation of ethylene from ethane is particularly complex due to their similar physical properties. Cryogenic distillation is the most common technology employed for this separation and is one of the most expensive operations in industry, being the driving force for the ongoing research to find a more cost‐effective alternative. In the present work, a gas‐phase simulated moving bed (SMB) bench unit was employed to produce polymer‐grade ethylene from ethane/ethylene mixtures, using binderless 13X zeolite beads as adsorbent, and propane as desorbent. The achieved performance parameters demonstrated the high efficiency of the current technology, since ethylene was obtained with a purity of 99.8%, a recovery of 99.8%, and a productivity of 59.7 kgC2H4·h−1· . Considering the encouraging results obtained it is fair to say that the gas‐phase SMB is a competitive and strong candidate as alternative to the conventional process, especially when combined with enhanced performance adsorbents, such as binderless zeolites. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2490–2500, 2016

Molasses separation using improved SMB distributor

There is potential for wide ranging applications of simulated moving bed (SMB). Several new concepts have been proposed in order to improve the performance and extend the range of application of classical SMB technology by exploiting various additional degrees of freedom. Improving SMB processes aims to reduce production costs and increasing efficiency, thus, this effort results in several configurations of SMB equipment designs with more degrees of freedom than the classical SMB processes.SMB modeling will play a significant role in designing the right process configurations for the separation of value – adding ingredients in the food industry and other branches.We aim to modify our SMB station by using set of valves (electronically controlled valves) instead of the existing rotary valve, by this way a new flows distributor with additional degrees of freedom for binary separation of saccharides and salts, the new configuration will be tested for saccharides separation (molasses) and evaluating the efficiency of the processes.

Hybrid Process for o‐ and p‐Xylene Production in Aromatics Plants

AbstractA new hybrid process for the production of o‐ and p‐xylene is proposed to replace the traditional plant of aromatics in refineries. The proposed process comprises a simulated moving bed (SMB) unit and two crystallizers. The SMB technology as the first unit of the suggested process is applied for the separation of xylene isomers and was investigated by simulation of an industrial size unit, using experimentally measured adsorption equilibrium data on MIL‐53(Al)‐shaped material. The separation of p‐xylene from o‐xylene with m‐xylene as desorbent is the key characteristic of this method. An industrial‐scale SMB unit could provide extract and raffinate streams with very high purities.

Web-based multi-dimensional education system for the simulated moving bed process

This paper describes the development of an operator-education program for a simulated moving bed (SMB) pilot plant that separates para-xylene isomer from mixed xylenes. The education program was motivated from reliable and safe operations for a newly developed SMB technology, in particular, a priori education on preventing accidents such as explosion, fire and toxic material release, most of which result from the lack of understanding of the processes being operated. This SMB process education program has overall SMB process description, sixteen operating screen and response procedure for accident of leak and explosion. The proposed system was implemented based on client/server architecture in company-wise LAN environment and applied previously operator heuristics. In addition, it features multi-dimensional animation for virtual reality of process flow, using multi-media techniques. Operators are expected to benefit from education that is free of time and space constraints. The education system for the pilot plant will contribute to keeping the full scale SMB operation workforce performing at a high level of proficiency as well as refreshing the operational skills of senior operators.

Simulated moving bed purification of flaxseed oil orbitides: unprecedented separation of cyclolinopeptides C and E.

The purification and enrichment of most natural products with potential pharmaceutical applications has been performed mainly employing conventional batch-mode chromatographic processes. There is a growing interest in use of simulated moving bed (SMB) chromatography for natural product enrichment as this method enables conservation of mobile phase, while increasing productivity of chromatography medium. SMB increases yield while decreasing cost. Cyclolinopeptides C ([1-9-NaC],[1-MetO]-CLB, 3) and E ([1-8-NaC],[1-MetO]-CLE, 8) were extracted as a mixture from flaxseed oil and then enriched using a three-zone simulated moving bed. The current research extends the SMB technology to enrichment of cyclolinopeptides (CLs), a group of biologically active hydrophobic cyclic peptides that occur in flaxseed oil. Of interest are [1-9-NaC],[1-MetO]-CLB (3) and [1-8-NaC],[1-MetO]-CLE (8) that provide synthetic scaffolds for modified CLs. The influence of flow rate (feed, desorbent, and extract) on the separation of [1-9-NaC],[1-MetO]-CLB (3) and [1-8-NaC],[1-MetO]-CLE (8) was investigated.

Gas phase SMB for propane/propylene separation using enhanced 13X zeolite beads

A gas phase simulated moving bed technology using improved 13X zeolite beads and isobutane as desorbent is assessed for the separation of propane/propylene. Adsorption equilibrium (via gravimetric method) and dynamics (via breakthrough curves) were determined in order to validate the mathematical model used to describe the adsorption process. Simulation results have shown that it is possible to separate propylene from a mixture with propane using gas phase SMB technology. The results indicate that high purity propylene (99.99 % desorbent free basis) can be recovered up to 99.96 % with a productivity of 17.6 mol kg−1 h−1, with propane being also recovered at high levels (99.98 %) and high purity (99.89 % desorbent free basis). Comparing the SMB simulation results obtained for this new 13X zeolite beads with those obtained with a commercial 13X zeolite characterized elsewhere, it was found that the productivity of the process was raised by 25 %, with half desorbent consumption.

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.

Reverse Shape Selectivity in the Liquid-Phase Adsorption of Xylene Isomers in Zirconium Terephthalate MOF UiO-66

Powder, agglomerates, and tablets of the microporous zirconium(IV) terephthalate metal-organic framework UiO-66 were evaluated for the selective adsorption and separation of xylene isomers in the liquid phase using n-heptane as the eluent. Pulse experiments, performed at 313 K in the presence of n-heptane, revealed the o-xylene preference of this material, which was further confirmed by binary and multicomponent breakthrough experiments in the presence of m- and p-xylene, resulting in selectivities at 313 K of 1.8 and 2.4 with regards to m-xylene and p-xylene, respectively. Additionally, because p-xylene is the less retained isomer, UiO-66 presents a selectivity pattern that is reverse of that of the xylenes' molecular dimension with respect to shape selectivity. The shaping of the material as tablets did not significantly change its selectivity toward the o-xylene isomer or toward p-xylene, which was the less retained isomer, despite a loss in capacity. Finally, the selectivity behavior of UiO-66 in the liquid n-heptane phase makes it a suitable material for o-xylene separation in the extract (heavy product) or p-xylene separation in the raffinate (light product) by simulated moving bed technology.

Techno‐economic evaluation of an inclusion body solubilization and recombinant protein refolding process

Expression of recombinant proteins in Escherichia coli is normally accompanied by the formation of inclusion bodies (IBs). To obtain the protein product in an active (native) soluble form, the IBs must be first solubilized, and thereafter, the soluble, often denatured and reduced protein must be refolded. Several technically feasible alternatives to conduct IBs solubilization and on-column refolding have been proposed in recent years. However, rarely these on-column refolding alternatives have been evaluated from an economical point of view, questioning the feasibility of their implementation at a preparative scale. The presented study assesses the economic performance of four distinct process alternatives that include pH induced IBs solubilization and protein refolding (pH_IndSR); IBs solubilization using urea, dithiothreitol (DTT), and alkaline pH followed by batch size-exclusion protein refolding; inclusion bodies (IBs) solubilization using urea, DTT, and alkaline pH followed by simulated moving bed (SMB) size-exclusion protein refolding, and IBs solubilization using urea, DTT and alkaline pH followed by batch dilution protein refolding. The economic performance was judged on the basis of the direct fixed capital, and the production cost per unit of product (P(C)). This work shows that (1) pH_IndSR system is a relatively economical process, because of the low IBs solubilization cost; (2) substituting β-mercaptoethanol for dithiothreithol is an attractive alternative, as it significantly decreases the product cost contribution from the IBs solubilization; and (3) protein refolding by size-exclusion chromatography becomes economically attractive by changing the mode of operation of the chromatographic reactor from batch to continuous using SMB technology.

Chiral Separation of Ketoprofen Enantiomers by Preparative and Simulated Moving Bed Chromatography

The pharmaceutical industry is now directed to the market of more safety and efficient drugs, based on single enantiomers. Ketoprofen, still used as a racemic pharmaceutical drug, belongs to the profens class, one of the most representative of the non-steroidal anti-inflammatory drugs. This work presents the chiral separation of ketoprofen enantiomers by simulated moving bed technology, using a laboratory scale unit (the FlexSMB-LSRE®) with six columns, packed with the Chiralpak AD® stationary phase (20 μm). A comparative study between a mobile phase composed of a traditional high hydrocarbon content (10%ethanol/90%n-hexane/0.01%TFA) and a strong polar organic composition (100%ethanol/0.01%TFA) is presented. The study includes the measurement of the adsorption isotherms, elution, and frontal chromatography experiments, carried out on a SMB column for both compositions. The results obtained allowed the prediction and optimization of the SMB operation. Using pure ethanol as solvent and a racemic feed concentration of 40 g/L, purities above 98.6% on both outlet streams were obtained, with a productivity of 3.84 gfeed/(Lbed.hr) and a solvent consumption of 0.78 Lsolvent/gfeed. The results obtained in the experimental separation of ketoprofen enantiomers by SMB chromatography indicates that pure ethanol presents better performances than the classic high hydrocarbon content composition.

Simulated moving bed technology to improve the yield of the biotechnological production of lactobionic acid and sorbitol

This work presents an analysis on the suitability of the Simulated Moving Bed (and pseudo-SMB) technology on separating the mixture obtained from the lactose oxidation catalyzed by glucose-fructose oxidoreductase and glucono-α-lactonase enzymes. These enzymes from the Zymomonas mobilis bacteria are able to oxidize lactose in presence of fructose to its respective organic acid—lactobionic acid—and sorbitol. Some alternative arrays of chromatographic systems, as fixed bed column, SMB unit, 4 section pseudo-SMB, have been explored to separate the multi-component mixture, in such way to make possible the product recovery and the recycle of substrates to the enzymatic reactor. This study involved the definition of appropriate operating conditions and the prediction of the performance of the separation units, or arrangement of units, through modeling and simulations tools. To define the proper operating conditions, inequalities from equilibrium theory and the concept of the separation volume analysis have been considered. In this analysis, equilibrium and kinetic parameters for the compounds adsorbing on DOWEX 50W-X4 resin, in K+ and Ca+2 ion-loadings, have been obtained from chromatographic methods (pulse and adsorption-desorption techniques). The enzymatic kinetic of production of lactobionic acid and sorbitol using permeabilized cells of Z. mobilis is shown. The strategy of keeping the highest value of reaction rate by the integration of a chromatographic system proved to be viable when it was found the feasibility to apply the SMB system in cascade.

Size-exclusion simulated moving bed chromatographic protein refolding

Size-exclusion chromatographic refolding (SECR) has successfully proven its capability to refold a variety of proteins using a range of gel filtration column materials. Several approaches have also been undertaken to improve the refolding yield of these systems, mostly under batch operation. Although, these approaches may lead to an increase on refolding yield, it is not expected that they will lead to significant increases in other important process indicators, such as volumetric productivity, specific eluent consumption and product concentration in the product stream; as these indicators are strongly dependent on the mode of operation. To overcome the shortcomings of batch chromatography, the size-exclusion refolding reactor may be operated in a continuous mode, with the aid of Simulated Moving Bed (SMB) technology. Albeit, SMB technology has inherent advantages over batch chromatography, these have been proven mainly in the context of conventional purifications and are still to be addressed in the context of chromatographic refolding reactors. In this work we report the on-column refolding of an industrially relevant protein, produced in inclusion bodies, by batch size-exclusion chromatography (SEC) and simulated moving bed size-exclusion chromatography (SMBSEC). The presented study encompasses: (1) a statistical design of experiments (DOE) to study the combined effect of the mobile phase pH (9.0–11.20) and the feed concentration of denatured and reduced protein ( C f, D& R =2.50–7.50 mg ml −1) on the refolding yield of the model protein; (2) a mechanistic analysis of the SMBSECR data, using a detailed model that accounts for both separation and refolding; and (3) a detailed comparison of the SMBSECR against the SECR, based both on quantitative and qualitative criteria. Our work showed that: (1) refolding yields of 50% are attainable by tuning pH and C f, D& R , and that the positive effect of pH is strongly dependent on the C f, D& R ; (2) the modeling tool captured well the SMBSECR behavior, based solely on the effect that C f, D& R has on the reaction rates; and (3) the volumetric productivity of the SMBSECR is about 53 times higher than that of the SECR, the specific solvent consumption is approximately 1/10th of that of the SECR, and the concentration of the product (i.e., native protein), leaving the SMBSECR, is roughly 4.5-fold higher than the one leaving the SECR. Accordingly, the comparison revealed the significant advantages that SMB technology has to offer to the design of chromatographic refolding reactors.

Simulated moving bed technology applied to coal gasification

An alternative technology to conventional coal gasification is discussed in order to improve the performances of the existing processes. The concept of simulated moving bed (SMB) is applied to coal gasification: a number of fixed-bed reactors are connected in series and a suitable switching policy is applied so that each fixed-bed is cyclically operated both as a combustion and a gasification reactor. A possible combustion-gasification scheme is designed and simulated considering both chemical kinetics and mass-transfer phenomena. Sensitivity studies are carried out on a number of performance parameters: the syngas production efficiency, the H 2/CO molar ratio, the cold gas efficiency, the amount of CO 2 emitted per unit of syngas produced and the total productivity. The simulated performances of the newly proposed process are compared to those of conventional gasifiers.