skip to main content


Title: Scale-up of high-pressure F-T synthesis in 3D printed stainless steel microchannel microreactors: Experiments and modeling
Scale-up of Fischer-Tropsch (F-T) synthesis using microreactors is very important for a paradigm shift in the production of fuels and chemicals. The scalability of microreactors for F-T Synthesis was experimentally evaluated using 3D printed stainless steel microreactors, containing seven microchannels of dimensions 1000 µm × 1000 µm × 5cms. Mesoporous silica (KIT-6), with high surface area, containing ordered mesoporous structure was used to incorporate 10% cobalt and 5% ruthenium using a one-pot hydrothermal method. Bimetallic Co-Ru-KIT-6 catalyst was used for scale-up of F-T Synthesis. The performance of the catalysts was evaluated and examined for three different scale-up configurations (stand-alone, two, and four microreactors assembled in parallel) at both atmospheric pressure and 20 bar at F-T operating temperature of 240 °C using a syngas molar ratio (H2:CO) of 2. All three configurations of microreactors yielded not only comparable CO conversion (85.6–88.4%) and methane selectivity (~14%) but also similar selectivity towards lower gaseous hydrocarbons like ethane, propane, and butane (6.23–9.4%) observed in atmospheric F-T Synthesis. The overall selectivity to higher hydrocarbons, C5 + is in the range of 75–82% at 20 bars. A CFD model was used to investigate the effect of different design features and numbering up approaches on the performance of the microchannel reactor. The effect of the reactor inlet, the mixing internals and the channel designs on the dead zone %, the quality index factor, the cooling requirement and the maximum dimensionless temperature within the microreactor were quantified. There is no significant effect of increasing the channel width on the microreactor performance and operation of the microchannel reactor at lower Nusselt number that results in higher CO conversion. Increasing the channel width reduced the maximum temperature exhibited in the channel. Finally, the effect of increasing the y/x stacking ratio, i.e. having more reactor units in parallel compared to series, was investigated. Increasing the y/x ratio increased the cooling requirement and the maximum dimensionless temperature increase within the unit decreased the productivity. To minimize the productivity losses, numbering up in series is the better approach; however further analysis must be done to delineate heat removal requirements.  more » « less
Award ID(s):
1736173
NSF-PAR ID:
10317285
Author(s) / Creator(s):
Editor(s):
M.A. Bañares E. Groppo, PhD
Date Published:
Journal Name:
Catalysis today
ISSN:
0920-5861
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. In recent years, rising environmental concerns have led to the focus on some of the innovative alternative technologies to produce clean burning fuels. Fischer–Tropsch (FT) synthesis is one of the alternative chemical processes to produce synthetic fuels, which has a current research focus on reactor and catalyst improvements. In this work, a cobalt nanofilm (~4.5 nm), deposited by the atomic layer deposition (ALD) technique in a silicon microchannel microreactor (2.4 cm long × 50 µm wide × 100 µm deep), was used as a catalyst for atmospheric Fischer–Tropsch (FT) synthesis. The catalyst film was characterized by XPS, TEM-EDX, and AFM studies. The data from AFM and TEM clearly showed the presence of polygranular cobalt species on the silicon wafer. The XPS studies of as-deposited and reduced cobalt nanofilm in silicon microchannels showed a shift on the binding energies of Co 2p spin splits and confirmed the presence of cobalt in the Co0 chemical state for FT synthesis. The FT studies using the microchannel microreactor were carried out at two different temperatures, 240 °C and 220 °C, with a syngas (H2:CO) molar ratio of 2:1. The highest CO conversion of 74% was observed at 220 °C with the distribution of C1–C4 hydrocarbons. The results showed no significant selectivity towards butane at the higher temperature, 240 °C. The deactivation studies were performed at 220 °C for 60 h. The catalyst exhibited long-term stability, with only ~13% drop in the CO conversion at the end of 60 h. The deactivated cobalt film in the microchannels was investigated by XPS, showing a weak carbon peak in the XPS spectra. 
    more » « less
  2. Fischer–Tropsch (FT) synthesis was carried out in a 3D printed stainless steel (SS) microchannel microreactor using bimetallic Co-Ru catalysts on three different mesoporous silica supports. CoRu-MCM-41, CoRu-SBA-15, and CoRu-KIT-6 were synthesized using a one-pot hydrothermal method and characterized by Brunner–Emmett–Teller (BET), temperature programmed reduction (TPR), SEM-EDX, TEM, and X-ray photoelectron spectroscopy (XPS) techniques. The mesoporous catalysts show the long-range ordered structure as supported by BET and low-angle XRD studies. The TPR profiles of metal oxides with H2 varied significantly depending on the support. These catalysts were coated inside the microchannels using polyvinyl alcohol and kinetic performance was evaluated at three different temperatures, in the low-temperature FT regime (210–270 °C), at different Weight Hourly Space Velocity (WHSV) in the range of 3.15–25.2 kgcat.h/kmol using a syngas ratio of H2/CO = 2. The mesoporous supports have a significant effect on the FT kinetics and stability of the catalyst. The kinetic models (FT-3, FT-6), based on the Langmuir–Hinshelwood mechanism, were found to be statistically and physically relevant for FT synthesis using CoRu-MCM-41 and CoRu-KIT-6. The kinetic model equation (FT-2), derived using Eley–Rideal mechanism, is found to be relevant for CoRu-SBA-15 in the SS microchannel microreactor. CoRu-KIT-6 was found to be 2.5 times more active than Co-Ru-MCM-41 and slightly more active than CoRu-SBA-15, based on activation energy calculations. CoRu-KIT-6 was ~3 and ~1.5 times more stable than CoRu-SBA-15 and CoRu-MCM-41, respectively, based on CO conversion in the deactivation studies. Keywords: Fischer-Tropsch synthesis; mesoporous silica based catalysts; kinetic studies; 3-D printed microchannel microreactor 
    more » « less
  3. Abstract

    Microreactor-Assisted Nanomaterial Deposition (MAND) process offers unique capabilities in achieving large size and shape control levels while providing a more rapid path for scaling via process intensification for nanomaterial production. This review highlights the application of continuous flow microreactors to synthesize, assemble, transform, and deposit nanostructured materials for Solar Photovoltaics, the capabilities of MAND in the field, and the potential outlook of MAND.

    Microreactor-Assisted Nanomaterial Deposition (MAND) is a promising technology that synthesizes reactive fluxes and nanomaterials to deposit nanostructured materials at the point of use. MAND offers precise control over reaction, organization, and transformation processes to manufacture nanostructured materials with distinct morphologies, structures, and properties. In synthesis, microreactor technology offers large surface-area-to-volume ratios within microchannel structures to accelerate heat and mass transport. This accelerated transport allows for rapid changes in reaction temperatures and concentrations, leading to more uniform heating and mixing in the deposition process. The possibility of synthesizing nanomaterials in the required volumes at the point of application eliminates the need to store and transport potentially hazardous materials. Further, MAND provides new opportunities for tailoring novel nanostructures and nano-shaped features, opening the opportunity to assemble unique nanostructures and nanostructured thin films. MAND processes control the heat transfer, mass transfer, and reaction kinetics using well-defined microstructures of the active unit reactor cell that can be replicated at larger scales to produce higher chemical production volumes. This critical feature opens a promising avenue in developing scalable nanomanufacturing. This paper reviews advances in microreactor-assisted nanomaterial deposition of nanostructured materials for solar photovoltaics. The discussions review the use of microreactors to tailor the reacting flux, transporting to substrate surfaces via controlling process parameters such as flow rates, pH of the precursor solutions, and seed layers on the formation and/or transformation of intermediary reactive molecules, nanoclusters, nanoparticles, and structured assemblies. In the end, the review discusses the use of an industrial scale MAND to apply anti-reflective and anti-soiling coatings on the solar modules in the field and details future outlooks of MAND reactors.

    Graphical abstract

     
    more » « less
  4. Catalytically active asymmetric membranes were developed by crosslinking a polydimethylsiloxane (PDMS) thin layer onto a porous polyamide‐imide hollow fiber (PAIHF) support, followed by grafting of aminosilane with hydroxyl derived-PDMS/PAIHF, and finally palladium nanoparticles (PdNPs) immobilization using salicylic aldehyde. Aminosilane and salicylic aldehyde linkers were used to permanently immobilize PdNPs onto the PDMS surface through metal coordination chelation, which prevented their agglomeration and leaching from the catalytic membrane reactor (CMR) module. The obtained CMRs were used as a heterogeneous catalyst and continuous-flow membrane reactor for hydrogenation of 4-nitrophenol, aldol and nitroaldol condensation, Heck coupling, CO2 cycloaddition and hydroxyalkylation of aniline, and tandem reactions of glucose and fructose to 5-hydroxymethylfurfural (HMF). Our findings also revealed that the turnover frequency (TOF) and selectivity can be tuned and controlled by adjusting the chemistry and degree of cross-linkers, reaction solvents, and flow rates. Even though our polymeric hollow fiber microreactors showed relatively good performance at temperatures up to 150 °C, some amount of active spices (e.g., Pd nanoparticles) leached out from the microreactor due to polymer swelling, plasticization, and pore shrinkage during flow reaction, especially when exposed to polar aprotic solvents and aromatics, and deteriorated the stability of the immobilized catalysts. 
    more » « less
  5. Metal-mediated cross-coupling reactions offer organic chemists a wide array of stereo- and chemically-selective reactions with broad applications in fine chemical and pharmaceutical synthesis.1 Current batch-based synthesis methods are beginning to be replaced with flow chemistry strategies to take advantage of the improved consistency and process control methods offered by continuous flow systems.2,3 Most cross-coupling chemistries still encounter several issues in flow using homogeneous catalysis, including expensive catalyst recovery and air sensitivity due to the chemical nature of the catalyst ligands.1 To mitigate some of these issues, a ligand-free heterogeneous catalysis reaction was developed using palladium (Pd) loaded into a polymeric network of a silicone elastomer, poly(hydromethylsiloxane) (PHMS), that is not air sensitive and can be used with mild reaction solvents (ethanol and water).4 In this work we present a novel method of producing soft catalytic microparticles using a multiphase flow-focusing microreactor and demonstrate their application for continuous Suzuki-Miyaura cross-coupling reactions. The catalytic microparticles are produced in a coaxial glass capillary-based 3D flow-focusing microreactor. The microreactor consists of two precursors, a cross-linking catalyst in toluene and a mixture of the PHMS polymer and a divinyl cross-linker. The dispersed phase containing the polymer, cross-linker, and cross-linking catalyst is continuously mixed and then formed into microdroplets by the continuous phase of water and surfactant (sodium dodecyl sulfate) introduced in a counter-flow configuration. Elastomeric microdroplets with a diameter ranging between 50 to 300 micron are produced at 25 to 250 Hz with a size polydispersity less than 3% in single stream production. The physicochemical properties of the elastomeric microparticles such as particle swelling/softness can be tuned using the ratio of cross-linker to polymer as well as the ratio of polymer mixture to solvent during the particle formation. Swelling in toluene can be tuned up to 400% of the initial particle volume by reducing the concentration of cross-linker in the mixture and increasing the ratio of polymer to solvent during production.5 After the particles are produced and collected, they are transferred into toluene containing palladium acetate, allowing the particles to incorporate the palladium into the polymer network and then reduce the palladium to Pd0 with the Si-H functionality present on the PHMS backbones. After the reduction, the Pd-loaded particles can be washed and dried for storage or switched into an ethanol/water solution for loading into a micro-packed bed reactor (µ-PBR) for continuous organic synthesis. The in-situ reduction of Pd within the PHMS microparticles was confirmed using energy dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and focused ion beam-SEM, and TEM techniques. In the next step, we used the developed µ-PBR to conduct continuous organic synthesis of 4-phenyltoluene by Suzuki-Miyaura cross-coupling of 4-iodotoluene and phenylboronic acid using potassium carbonate as the base. Catalyst leaching was determined to only occur at sub ppm concentrations even at high solvent flow rates after 24 h of continuous run using inductively coupled plasma mass spectrometry (ICP-MS). The developed µ-PBR using the elastomeric microparticles is an important initial step towards the development of highly-efficient and green continuous manufacturing technologies in the pharma industry. In addition, the developed elastomeric microparticle synthesis technique can be utilized for the development of a library of other chemically cross-linkable polymer/cross-linker pairs for applications in organic synthesis, targeted drug delivery, cell encapsulation, or biomedical imaging. References 1. Ruiz-Castillo P, Buchwald SL. Applications of Palladium-Catalyzed C-N Cross-Coupling Reactions. Chem Rev. 2016;116(19):12564-12649. 2. Adamo A, Beingessner RL, Behnam M, et al. On-demand continuous-flow production of pharmaceuticals in a compact, reconfigurable system. Science. 2016;352(6281):61 LP-67. 3. Jensen KF. Flow Chemistry — Microreaction Technology Comes of Age. 2017;63(3). 4. Stibingerova I, Voltrova S, Kocova S, Lindale M, Srogl J. Modular Approach to Heterogenous Catalysis. Manipulation of Cross-Coupling Catalyst Activity. Org Lett. 2016;18(2):312-315. 5. Bennett JA, Kristof AJ, Vasudevan V, Genzer J, Srogl J, Abolhasani M. Microfluidic synthesis of elastomeric microparticles: A case study in catalysis of palladium-mediated cross-coupling. AIChE J. 2018;0(0):1-10. 
    more » « less