Jin-Soo Hwang

Fischer–Tropsch on Iron with H2/CO and H2/CO2 as Synthesis Gases: The Episodes of Formation of the Fischer–Tropsch Regime and Construction of the Catalyst

Fischer–Tropsch synthesis experiments have been performed with reduced precipitated Fe-Al-Cu-K2O catalysts, using a H2/CO and a H2/CO2 synthesis gas. Samples of the reaction products and of the catalyst were taken at distinct run lengths. The product samples were analyzed in detail and from their composition the kinetic data of elemental reaction steps (growth, branching, desorption as olefin or paraffin) calculated, applying the extended model of “nontrivial surface polymerization”. The catalyst samples were characterized by BET, XRD, Mössbauer spectroscopy, XPS and TPD in hydrogen and thus specifically phase changes of e.g. alpha iron, iron oxides, and iron carbides observed.It has been measured how the product composition changed with time, up to the steady state of synthesis. Several episodes with their own kinetic regimes were identified. These were then correlated with compositional and structural changes of the catalyst. This is addressed as “construction of the true iron Fischer–Tropsch catalyst”.

Production of γ-butyrolactone from biomass-derived 1,4-butanediol over novel copper-silica nanocomposite

γ-Butyrolactone was produced highly selectively from biomass-derived 1,4-butanediol by vapor-phase dehydrocyclization over novel copper-silica nanocomposite catalyst. Compared with usual Cu(12)/SiO2, the highly Cu-loaded SiO2 nanocomposite (80 wt%) exhibited high catalyst performance with 98% yield on 400 h stream without significant deactivation even in the absence of H2.

Preparation and application of nanocatalysts via surface functionalization of mesoporous materials

Surface immobilization of active species onto mesoporous materials is gaining importance, especially in the design of functionalized mesoporous materials as a nanocatalyst through heterogenization of homogeneous catalytic systems. This article summarizes recent work on the synthesis, characterization and catalytic performance of the functionalized mesoporous catalysts performed by the present authors. A cationic rhenium(I) complex was encapsulated into mesoporous Al-MCM-41 molecular sieve using a ion-exchange method, yielding a new photocatalyst to be active for photocatalytic reduction of CO2. Surface functionalization of mesoporous silica SBA-15 with sulfonic acid groups was investigated to give a solid acid catalyst. The chemically modified Fe-containing mesoporous materials, which are active for hydroxylation of phenol, were prepared by a surface-grafting method that iron salts are immobilized onto mesoporous Si-MCM-41 with the help of 3-aminopropyltrimethoxysilane as a linker. A cobalt(III) complex was heterogenized onto mesoporous silica SBA-15 containing carboxylic groups in order to utilize as a solid catalyst for the liquid-phase oxidation of aromatic hydrocarbons.

A Facile Synthesis of Highly Functionalized 4-Arylcoumarins via Kostanecki Reactions Mediated by DBU

An efficient synthesis of 4-arylcoumarins has been accomplished via Kostanecki reactions of 2-hydroxybenzophenones with acetic anhydride employing DBU at ambient temperature. Using the same strategy, several 2-acyloxybenzophenone derivatives were readily converted to 3,4-difunctionalized coumarins. This protocol offers a notable improvement in reaction conditions for coumarin synthesis and takes advantage of its synthetic capability, especially for highly functionalized 4-arylcoumarins with structural diversity.

Microwave synthesis, characterization and catalytic properties of titanium-incorporated ZSM-5 zeolite

Titanium-incorporated ZSM-5 zeolites (Si/Al = 50–200 and Si/Ti = 70) were successfully synthesized in a one-step sol-gel process under microwave irradiation. The characteristics of Ti-ZSM-5 zeolites were investigated using X-ray power diffraction, UV/Vis-DRS, FT-IR spectroscopy and solid-state 27Al-NMR to monitor the physico-chemical properties. Simultaneously, the acidic properties were characterized by the NH3-TPD profile. The characterization results revealed that the Ti4+ and Al3+ ions were well incorporated into the framework of Ti-ZSM-5 zeolite. The prepared zeolite was moderately active but selective in the dehydration of methanol to dimethyl ether.

Photocatalytic activation of CO2 under visible light by Rhenium complex encapsulated in molecular sieves

The photocatalytic activation of CO2 over molecular sieve-encapsulated cationic rhenium complex has been investigated under visible light (λ>350 nm). The cationic rhenium complex, [Re(I)(CO)3(bpy)(py)]+(bpy=2,2′bipyridine, py=pyridine), has been encapsulated by ion-exchange method using the aqueous solution of [Re(I)(CO)3 (bpy)(py)]+PF6- into the microporous NaY and the mesoporous A1MCM-41 molecular sieve acting as supramolecular heterogeneous host. To confirm the encapsulation of [Re(IXCO)3(bpy)(py)]+ into the pores of molecular sieve, XeNMR and FT-IR spectroscopies have been applied before and after the [Re(I)(CO)3(bpy)(py)]+ encapsulation. To investigate the photophysical and photochemical properties, molecular sieve-encapsulated cationic rhenium complex has been studied by UV-Visible diffuse reflectance spectroscopy (UV-DRS) with photoirradiation (λ>350 nm) at room temperature. By monitoring the photoreaction of CO2 over the photocatalysts, the conversion of CO2 into CO and carbonate species has been observed by usingin-situ FT-IR and time-resolved mass spectroscopy. From the experimental results, the photocatalytic activation mechanism of CO2 on the catalyst under visible light (λ>350 nm) could be proposed via the photo-induced reaction of two electrons and two protons, resulting from water decomposition.

Direct hydroxylation of aromatics with a mixture of H2 and O2 gases over Fe- and Pd-incorporated zeolites

The hydroxylation of benzene and phenol with in-situ-generated oxidant was performed under mild reaction conditions over the bicatalytic system which has dual abilities of direct H2O2 generation and the hydroxylation activity by combining Pd-zeolite with redox zeolites such as TS-1, Ti-MCM-41, V-MCM-41 and Fe-zeolite. The amount of H2O2 formed directly from H2 and O2 increases with increasing Pd loading over zeolite up to 0.6% and subsequently decreases slightly as the Pd loading increases. The optimum amount of H2O2 produced is 6.4 mmol. Over Pd/HBEA + Fe/Y, when H2 : O2 = 40 : 40 ml/min is supplied, phenol conversion increases from 4.6% at 2 h to 13.6% at 8 h with high catechol selectivity in the range of 65–79%. The hydroxylation activities over redox catalyst with H2O2 are compared. Hydroxylation activity is improved by encapsulating FePc onto Y zeolite. In terms of TON, FePc/Y exhibits 3.5 times higher capacity than Fe/Y.

Catalytic formation of hydrogen peroxide from H2 and O2 over hydrogen transfer agent-anchored Pd°/beta zeolites

Hydrogen transfer agents (HTAs) have been successfully anchored on Pd°/H-beta zeolite and exhibit enhanced catalytic activity in the formation of H2O2 from H2 and O2 at atmospheric pressure compared with that of the Pd°/H-beta and the HTA included catalysts.