Seong-Poong Lee

Metal-free mild oxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran

The potential of 4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl (4-hydroxy-TEMPO radical) as an oxidant with [bis(acetoxy)-iodo]benzene (BAIB) and acetic acid (CH3COOH) as co-oxidants to convert 5-hydroxymethylfurfural (5-HMF) into 2,5-diformylfuran (2,5-DFF) was investigated. The effects of oxidant/acid dosages, choice of appropriate solvent, reaction temperature and time were determined to maximize the 2,5-DFF yield. Optimally, 66% 2,5-DFF yield was achieved in TEMPO/BAIB/CH3COOH system at 30 °C after 45 min in ethyl acetate. The reaction system is environmentally benign (metal-free) and energy efficient (mild at short reaction period). With scarce reports on 2,5-DFF production, the developed system provides an alternative route for a better access and wider application of this important platform chemical.

One-pot synthesis of 2,5-diformylfuran from fructose using a magnetic bi-functional catalyst

A magnetic bi-functional WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst was prepared to directly synthesize 2,5-diformylfuran (2,5-DFF) from fructose. The chlorosilylated SiO2@Fe3O4 (Cl-SiO2@Fe3O4) nanoparticles served as the platform for the two functionalities. Tungstic acid was generated via protonation of sodium tungstate, which was directly attached on the platform via nucleophilic –Cl displacement. Meanwhile, oxovanadium was complexed with a salten ligand which was functionalized on the Cl-SiO2@Fe3O4. Characterization results confirmed the successful preparation of the WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst. Under the optimal one-pot system, tungstic acid-mediated fructose dehydration afforded 82% 5-hydroxymethylfurfural (5-HMF) in 1 h. Upon co-oxidant H2O2 addition, in situ 5-HMF oxidation by the activated oxoperoxovanadium species produced 71% of 2,5-DFF after 15 h under ambient air. The stability of 5-HMF formation was found critical to 2,5-DFF production. Aside from the catalytic efficiency and process simplicity, the WO3HO-VO(salten)-SiO2@Fe3O4 nanocatalyst was readily retrieved magnetically and re-used multiple times with marginal losses in its activity.

Liquid–liquid extraction of Li+ using mixed ion carrier system at room temperature ionic liquid

AbstractAn environmentally benign technique for the separation and recovery of lithium (Li+) from aqueous streams, containing mixed metal ions was developed via liquid–liquid extraction (LLE). Hydrophobic room temperature ionic liquids (RTIL) were tested as the main extracting solvents. To increase the metal extraction, a proton-ionizable agent bis(2-ethylhexyl) phosphoric acid (DEHPA) was added into the RTIL. To enhance the metal uptake selectivity, three Li+-selective neutral ion carriers such as 6-hydroxy-dibenzo-14-crown-4, dibenzo-14-crown-4, and tri-n-octyl-phosphine (TOPO) were also used and tested as extractant additives. Among the tested RTILs, phosphonium-based CYPHOS IL 109 was the most stable extractant as it exhibited the lowest loss when contacted with water. Addition of proton-ionizable agent DEHPA in CYPHOS IL 109 afforded a high extraction of multivalent cations with negligible recovery of monovalent metals. On the other hand, the addition of neutral ion carrier TOPO in DEHPA/CYPHOS IL 10...

SBA-15 supported ionic liquid phase (SILP) with H2PW12O40− for the hydrolytic catalysis of red macroalgal biomass to sugars

A supported ionic liquid phase (SILP) catalyst for biomass hydrolysis was prepared via immobilization of an acidic ionic liquid (IL) with a phosphotungstic counter-anion H2PW12O40− (HPW) on ordered mesoporous silica (SBA-15). Characterization results from XRD, N2 physisorption, FT-IR, TGA and SEM/TEM image analyses confirmed the successful preparation of the SILP catalyst (SBA-IL–HPW). Meanwhile, its catalytic performance was evaluated in terms of sugar production from the hydrolysis of different biomasses in water. Under optimal hydrolysis conditions, SBA-IL–HPW yielded 73% D-galactose from agarose and 58% D-glucose from cellobiose. Moreover, SBA-IL–HPW effectively hydrolyzed the red macroalgae G. amansii as it afforded 55% total reducing sugar and 38% D-galactose yields. SBA-IL–HPW was easily separated from the hydrolysates after reaction and was re-used five times without significant loss of activity. Overall findings reveal the potential of SBA-IL–HPW as a durable, environmentally benign catalyst for sugar production from renewable resources.

Microwave-Assisted Synthesis of Dibenzo-Crown Ethers

The present invention relates to a method for preparing various dibenzo-crown ethers (DBC) including both of the symmetric and asymmetric atom ring structures. In the present invention, methods for preparing DBC using organic synthesis by using two microwaves are disclosed in which one is a preparation method using appropriate dihalide and one-port equimolar reaction of a base and catechol for preparing symmetrical DBC, and the other one is a preparation method using diphenol intermediates for preparing symmetrical or asymmetrical DBC. According to the present preparation method, the preparation of DCB can be done within 60 minutes, which were taken at least one day with a conventional method, and the yield of DBC can be improved than before.

Composite membranes with surface-modifying macromolecules for halogenated hydrocarbons removal from water in membrane extraction process

AbstractFlat sheet composite polysulfone (PSf) membranes blended with surface-modifying macromolecules (SMM) were prepared, characterized, and tested for halogenated hydrocarbons (HHC) (i.e. trichloroethylene, TCE) permeation and separation from water in an extractive membrane system. The fluorine end groups in SMMs facilitated its migration towards the membrane surface during membrane casting, whereas the polydimethylsiloxane component rendered the SMM organophilic which improved the surface affinity of the composite membrane towards TCE. Polydimethylsiloxane content in SMM, SMM content in PSf, and air-exposure of the casted blend solutions before membrane formation were found critical in obtaining an effective composite membrane. The presence of a selective SMM layer on the membrane surface was confirmed via contact angle measurement, Fourier-transform infrared spectrometry analysis, and field emission-scanning electron microscope. The most effective composite membrane (PSf with 15 wt% H-SMM and air exp...

Removal of odorous compounds emitted from a food-waste composting facility in Korea using a pilot-scale scrubber.

ABSTRACT Monitoring and control of odorous compound emissions have been enforced by the Korean government since 2005. One of the point sources for these emissions was from food waste composting facilities. In this study, a pilot-scale scrubber installed in a composting facility was evaluated for its performance in the removal of malodorous compounds. The exhaust stream contained ammonia and methylamine as the major odorants detected by the threshold odor test and various instrumental techniques (GC-FID, FPD, MS and HPLC/UV). For the scrubber operation, the column was randomly packed with polypropylene Hi-Rex 200, while aqueous sulfuric acid was selected as the scrubbing solution. To achieve 95% removal, the scrubber must be operated by using H2SO4 solution with pH at < 6.5, liquid to gas ratio > 4.5, gas loading rate < 1750 m3/m3-hr and contact time < 0.94 s. The scrubber performance was further evaluated by determining the mass transfer coefficients and then monitoring for 355 days of operation. The pilot-scale scrubber maintained > 95% ammonia and methylamine removal efficiencies despite the fluctuations in the inlet (from composting facility exhaust stream) concentration. The optimum operating conditions and scrubber performance indicators determined in this study provides a basis for the design of a plant-scale scrubber for treatment of composting facility gas emissions.