skip to main content

Explore Research Products in the NSF-PAR

  • NSF Public Access
  • Search Results
  • Composite Hollow Fiber Membrane Reactor Containing Immobilized Organocatalysts and Palladium for Sustainable Chemical Transformation

This content will become publicly available on May 16, 2024

Title: Composite Hollow Fiber Membrane Reactor Containing Immobilized Organocatalysts and Palladium for Sustainable Chemical Transformation
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
Award ID(s):
2316143 2019350
NSF-PAR ID:
10466222
Author(s) / Creator(s):
Date Published:
Journal Name:
North American Membrane Society 2023
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ( , Journal of membrane science)
    null (Ed.)
    Sometimes NH₃ is stripped from process/effluent streams through hydrophobic porous hollow-fiber-membranes (HFMs) via a supported-gas-membrane (SGM) process and recovered in concentrated H₂SO₄ solution as (NH₄)₂SO₄. To recover relatively purified (NH₄)₂SO₄, one can avoid excess H₂SO₄ with a more dilute H₂SO₄ strip solution. Neglect of strip-side mass-transfer resistance for low-pH strip H₂SO₄ solutions is not desirable with higher-pH H₂SO₄ strip solutions. Small hollow-fiber membrane modules (HFMMs) were used with a higher-pH H₂SO₄ strip solution. Mass transfer was successfully modeled using reaction-enhanced mass transport in higher-pH H₂SO₄ solution. Employing larger-scale crossflow HFMMs, time-dependent ammonia removal from a large tank having ammonia-containing process effluent was modeled for batch recirculation operation. The larger-scale modules employ shell-side feed liquid in crossflow with an overall countercurrent flow pattern and acid flow in the tube side. Modeling ammonia transport without water vapor transfer can cause substantial errors in batch recirculation method. Water vapor transport was considered here for low-pH and high-pH H₂SO₄ strip solutions for ammonia-containing feed in a large tank. Model results describe literature-based experimentally observed mass transfer behavior in industrial-treatment systems well. Model calculations were also made for continuous ammonia recovery from industrial effluents by a number of series-connected HFMMs without any batch recirculation. 
    more » « less
  2. ; ; ; ; ; ; ; ; ; ( , AAAR 40th Annual Conference)
    Isoprene (C5H8) is the largest non-methane volatile organic compound emitted into the atmosphere. Isoprene reacts rapidly with ambient hydroxyl radicals (OH) and subsequent addition of O2 results in the formation alkyl peroxy (RO2) radicals. The fate of the initially formed RO2 radicals has been the focus of continuing theoretical and experimental research. Under pristine conditions where bimolecular reactions of RO2 are limited, the thermodynamically favored RO2 undergoes an intramolecular H-shift followed by reaction with O2 and elimination of HO2 to yield 4-hydroperoxy aldehyde (4-HPALD, C5H8O3), predicted to account for up to 13% of first-generation isoprene photochemical oxidation products. Mass spectrometric evidence has been reported for 4-HPALD, but lack of an authentic standard has precluded definitive confirmation of both the structure of 4-HPALD and its origin as a first-generation product of OH oxidation of isoprene. We report the synthesis and characterization of 4-HPALD and establish that it is a major product of isoprene oxidation. Synthetic 4-HPALD is isolated as the peroxyhemiacetal. As expected for the 4-hydroperoxy aldehyde, 1H NMR spectra show no evidence for equilibration with the carbonyl form, even in protic solvents, and gas-phase chemical analysis by CIMS also shows only a single form. OH oxidation of isoprene in an oxidation flow reactor coupled to an ion mobility source with an HR-CIMS detector unequivocally demonstrates 4-HPALD (and likely also 1-HPALD) as isoprene oxidation products. Although HPALDs have been discounted as significant contributors to SOA, oxidation of 4-HPALD in a potential aerosol mass (PAM) reactor in the presence of ozone and OH indicates 4-HPALD rapidly undergoes autooxidation reactions forming low-volatility particulate products. We have confirmed highly oxygenated compounds with compositions C5H8O6 and C5H10O6 likely from OH oxidation, and C5H10O7 and C5H10O8 compounds likely products of ozonolysis. The PAM oxidation experiment further demonstrates that the highly oxygenated, low-volatility products efficiently nucleate particles. 
    more » « less
  3. ; ; ; ; ; ; ; ; ; ( , Molecular Systems Design & Engineering)
    As wastewater reclamation and reuse technologies become more critical to meeting the growing demand for water, a need has emerged for separation platforms that can be tailored to accommodate the highly varied feed water compositions and treatment demands of these technologies. Nanofiltration (NF) membranes based on copolymer materials are a promising platform in this regard because they can be engineered at the molecular scale to address an array of separation process needs. Here, for example, a resilient NF membrane is developed through the design of a poly(trifluoroethyl methacrylate- co -oligo(ethylene glycol) methyl ether methacrylate- co -glycidyl methacrylate) [P(TFEMA-OEGMA-GMA)] copolymer that can be dip-coated onto hollow fiber supports. By exploiting the microphase separation of the oligomeric ethylene glycol side chains from the copolymer backbone and by elucidating the processing–structure–property relationships for the dip-coating process, membranes with pores 2 nm-in-diameter that exhibit a hydraulic permeability of 15.6 L m −2 h −1 bar −1 were generated. The GMA repeat units were functionalized post-coating with hexamethylene diamine to incorporate positively-charged moieties along the pore walls. This functionality resulted in membranes that rejected 98% of the MgCl 2 from a 1 mM feed solution. Moreover, the reaction with the diamine crosslinked the copolymer such that the membranes operated stably in ethanol, an organic solvent that damaged the unreacted parent membranes irreparably. Finally, the stability of the crosslinked P(TFEMA-OEGMA-GMA) copolymer resulted in membranes that could operate continuously for a 24 hour period in aqueous solutions containing 500 ppm chlorine without exhibiting signs of structural degradation as evidenced by consistent rejection of neutral probe solutes. These results demonstrate how resilient, charge-selective NF membranes can be fabricated from microphase separated copolymers by engineering each of the constituent repeat units for a directed purpose. 
    more » « less
  4. ; ; ; ; ; ; ; ( , Advanced Materials Interfaces)

    This study addresses the challenge of generalizable fabrication of metal‐organic framework (particularly zeolitic imidazolate frameworks (ZIF)) hollow fiber membranes that can allow a broader range of separations including hydrocarbon (“petrochemical”) as well as organics/water (“biorefining”) separations. We report a novel strategy that combines fluidic membrane processing with chemically inert carbon hollow fibers to produce robust ZIF membranes. Macroporous carbon hollow fibers are successfully fabricated by pyrolytic conversion of cross‐linked polymer hollow fibers. This step allows the use of a wide range of relatively aggressive fluidic processing solvents and conditions. Using these inert fiber supports, the fabrication of ZIF‐90 membranes is demonstrated and their butane isomer separations are investigated for the first time. Furthermore, ZIF membranes on carbon hollow fibers can be used in the separation of water/organic mixtures without the issue of fiber swelling or dissolution as seen in ZIF/polymer hollow fiber membranes. ZIF‐8/carbon membranes show stable operation spanning several days for dehydration of furfural and ethanol, with high water permeances and separation factors. In all cases, the ZIF membranes are prepared without any seeding, support modification, or postsynthesis procedures, thereby simplifying the fabrication process and increasing the potential for larger‐scale membrane fabrication.

     
    more » « less
  5. ; ; ; ; ( , Energy Science & Engineering)
    Abstract

    A comprehensive computational fluid dynamic (CFD) model of CEES‐developed polyethylenimine impregnated protonated titanate nanotubes (PEI‐PTNTs) was developed using the Multiphase Flow with Interphase eXchanges (MFiX) package to evaluate the performance of the PEI‐PTNTs in a 1‐MW pilot‐scale carbon capture reactor developed by the National Energy Technology Laboratory (NETL). In this CFD model, the momentum, continuity, and energy transport equations were integrated with the first‐order chemistry model for chemical kinetics of heterogeneous reactions to predict the adsorption of CO2onto amine‐based sorbent particles and the reactor temperature. Based on the amount of the CO2adsorption obtained in the small‐scale experiment, the coefficients for the chemical reaction equations of PEI‐PTNTs are adjusted. The adjusted PEI‐PTNTs model is applied to the simplified numerical model of 1‐MW pilot‐scale carbon capture system, which is calibrated through the comparison between our simulation results and the results provided by NETL. This calibrated CFD model is used for selecting the optimized flow rate of the gas phase. Our study shows that the optimized gas flow rate to absorb 100% CO2without loss is 1.5 kg/s, but if higher absorption rate is preferable despite some loss of CO2absorption in the reactor, a higher flow rate than 1.5 kg/s can be selected.

     
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email