• 청정기술
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• 제16권3호
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• pp.220-228
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• 2010

과당(fructose)로부터 간단한 공정을 통하여 바이오디젤보다 우수한 청정에너지 연료로 알려진 5-하이드록시메틸퍼퓨랄(HMF)을 제조하는 청정공정을 개발하였다. 이 연구에서는 중심원소와 배위원소가 치환된 네 종류의 헤테로폴리산 $H_nXM_{12}O_{40}$ (중심원소 X = P, Si, 배위원소 M = W, Mo.)을 과당으로부터 HMF로 전환하는 탈수반응에 적용하고, 그 반응활성을 비교하였다. 헤테로폴리산의 산 세기는 중심원소가 P, 배위원소가 W일 때 더 높았으며 산 점의 수는 이와 반대되는 경향을 보였다. 과당의 HMF로의 탈수반응은 헤테로폴리산의 산 특성과 음이온의 연성(softness)과 밀접한 관련이 있으며, 촉매 활성점과 전환율이 상쇄 작용하여 네 종류의 헤테로폴리산 촉매는 서로 비슷한 활성을 보였다. 또한 반응에 사용된 헤테로폴리산을 반응온도보다 높은 $200^{\circ}C$에서 열처리한 후에도 그 결정구조가 유지되는 것을 확인하였으며, 이를 통하여 헤테로폴리산의 반응활성이 안정적으로 유지됨을 확인할 수 있었다.

• Korean Chemical Engineering Research
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• 제47권2호
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• pp.163-168
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• 2009

본 연구에서는 양이온, 중심원소, 배위원소가 치환된 Keggin 형 및 Wells-Dawson 형 헤테로폴리산 촉매의 NDR(negative differential resistance) 거동을 STM(scanning tunneling microscopy)을 이용하여 살펴보았다. 헤테로폴리산 촉매의 NDR 전압과 산화환원능력 사이에는 일정한 상관관계가 있었다. 촉매의 구조적 차이에 상관없이 산화환원능력이 높은 헤테로폴리산 촉매는 보다 낮은 음전압에서 NDR 거동을 나타내었다. 이처럼 NDR 전압은 촉매의 산화환원능력을 대변하는 하나의 correlating parameter로 활용될 수 있었다.

• 한국수소및신에너지학회논문집
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• 제20권3호
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• pp.194-201
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• 2009

The e1ectrocatalytic properties of heteropolyacids(HPAs) entrapped in covalently cross-linked sulfonated polyetheretherketone(CL-SPEEK/HPA) membranes have been studied for water electrolysis. The HPAs, including tungstophosphoric acid(TPA), molybdophosphoric acid(MoPA), and tungstosilicic acid(TSiA) were used as additives in the composite membranes. The MEA was prepared by a non-equilibrium impregnation-reduction(I-R) method, using reducing agent, sodium borohydride(NaBH4) and tetraamineplatinum(II) chloride(pt(NH$_3$)$_4$Cl$_2$). The electrocatalytic properties of composite membranes such as the cell voltage were in the order of magnitude CL-SPEEKlMoPA40 (wt%) > /TPA30 > /TSiA40. In the optimum cell applications for water electrolysis, the cell voltage of PtlPEM/Pt-Ru MEA with CL-SPEEKlTPA30 membrane was 1.75 V at 80$^{\circ}$C and I A/cm$^2$ and this voltage carried lower than that of 1.81 V of Nafion 117. Consequently, in regards of electrochemical and mechanical characteristics and oxidation durability, the newly developed CL-SPEEKITPA30 composite membrane exhibited a better performance than the others, but CLSPEEKlMoPA40 showed the best electrocatalytic activity (1.71 Vat 80$^{\circ}$C and 1 A/cm$^2$) among the composite membranes.

• 대한화학회지
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• 제55권1호
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• pp.14-18
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• 2011

methacrylic acid과 ethylene glycol과의 에스테르화 반응을 ZSM-5에 지지된 heteropolyacids [HPA: $H_4SiW_{12}O_{40}$(STA)와 $H_3PW_{12}O_{40}$(PTA)] 하에서 수행하였다. 비교를 위하여, 지지하지 않은HPA, $H_2SO_4$, $BF_3$와 PTSA 하에서 같은 반응을 수행하였다. 연구한 촉매 중에서, HPA는 $H_2SO_4$, $BF_3$와 PTSA와 비교하여 더 좋은 활성을 보여주었다. 촉매 활성을 HPA지지 ZSM-5 촉매와 비교하였는데, 그 결과 ZSM-5위에 지지된 30 wt% PTA는 bulk PTA와 거의 같은 활성을 나타내었다. 이 반응은 methacrylic acid에 관하여 1차 속도 법칙을 따랐으며, 반응 생성물은 $^1H$-NMR과 FT-IR을 이용하여 확인하였다.

• 공업화학
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• 제9권7호
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• pp.1018-1022
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• 1998

본 연구에서는 테트라하이드로퓨란(THF)의 개환중합반응에 의해 변형된 12-몰리브도인산의 특성 및 촉매 반응성을 살펴보았다. 기상 에탄올 전화반응에서 THF에 의해 변형된 12-몰리브도인산은 모산 촉매보다 매우 우수한 전환율 및 생성물 수율을 보였다. 변형된 12-몰리브도인산의 증가된 반응성은 변형된 헤테로폴리음이온의 구조적 유연성과 약화된 수소결합에 기인하는 것으로 판단된다. THF는 양성자 또는 결정수를 매개로 헤테로폴리산과 상호작용을 하는 것으로 나타났는데, 결정수를 중심으로 한 THF와 헤테로폴리음이온간의 상호작용이 변형된 12-몰리브도인산의 촉매 활성을 결정하는 주된 요인이었다.

• Journal of Ginseng Research
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• 제48권4호
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• pp.366-372
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• 2024

Background: The biological activity and pharmacological effects of rare ginsenosides have been proven to be superior to those of the major ginsenosides, but they are rarely found in ginseng. Methods: Ginsenoside Rb1 was chemically transformed with the involvement of methanol molecules by a synthesized heterogeneous catalyst 12-HPW@MeSi, which was obtained by the immobilization of 12-phosphotungstic acid on a mesoporous silica framework. High-performance liquid chromatography coupled with mass spectrometry was used to identify the transformation products. Results: A total of 18 transformation products were obtained and identified. Methanol was found to be involved in the formation of 8 products formed by the addition of methanol molecules to the C-24 (25), C-20 (21) or C-20 (22) double bonds of the aglycone. The transformation pathways of ginsenoside Rb1 involved deglycosylation, addition, elimination, cycloaddition, and epimerization reactions. These pathways could be elucidated in terms of the stability of the generated carbenium ion. In addition, 12-HPW@MeSi was able to maintain a 60.5% conversion rate of Rb1 after 5 cycles. Conclusion: Tandem and high-resolution mass spectrometry analysis allowed rapid and accurate identification of the transformation products through the characteristic fragment ions and neutral loss. Rare ginsenosides with methoxyl groups grafted at the C-25 and C-20 positions were obtained for the first time by chemical transformation using the composite catalyst 12-HPW@MeSi, which also enabled cyclic heterogeneous transformation and facile centrifugal separation of ginsenosides. This work provides an efficient and recyclable strategy for the preparation of rare ginsenosides with the involvement of organic molecules.

• Journal of Microbiology and Biotechnology
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• 제30권4호
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• pp.540-551
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• 2020

Sporotrichosis is a chronic and subacute mycosis causing epidemiological outbreaks involving sick cats and humans in southeastern Brazil. The systemic disease prevails in cats and in humans, with the symptoms restricted to the skin of immunocompetent individuals. Under these conditions, the prolonged treatment of animals and cases of recurrence justify the discovery of new treatments for sporotrichosis. This work addresses the antifungal activity of silver salts of Keggin-type heteropolyacid salts (Ag-HPA salts) such as Ag₃[PW₁₂O₄₀], Ag₆[SiW₁₀V₂O₄₀], Ag₄[SiW₁₂O₄₀] and Ag₃[PMo₁₂O₄₀] and interactions with the antifungal drugs itraconazole (ITC), terbinafine (TBF) and amphotericin B (AMB) on the yeast and mycelia forms of Sporothrix spp. Sporothrix spp. yeast cells were susceptible to Ag-HPA salts at minimum inhibitory concentration (MIC) values ranging from 8 to 128 ㎍/ml. Interactions between Ag₃[PW₁₂O₄₀] and Ag₃[PMo₁₂O₄₀] with itraconazole and amphotericin B resulted in higher antifungal activity with a reduction in growth and melanization. Treated cells showed changes in cell membrane integrity, vacuolization, cytoplasm disorder, and membrane detachment. Promising antifungal activity for treating sporotrichosis was observed for the Ag-HPA salts Ag₃[PMo₁₂O₄₀] and Ag₃[PW₁₂O₄₀], which have a low cost, high yield and activity at low concentrations. However, further evaluation of in vivo tests is still required.

• 한국수소및신에너지학회논문집
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• 제21권1호
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• pp.26-34
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• 2010

The electrocatalystic prperties of Pt-Co and Pt-Ni with heteropolyacids (HPAs) entrapped in covalently cross-linked sulfonated poly(ether ether ketone) (CL-SPEEK)/HPA membranes were investigated for water electrolysis. The HP As, including molybdophosphoric acid (MoPA), and tungstophosphoric acid (TPA) were both used as membrane additives and electrocatalysts. The membrane electrode assembly (MEA) was prepared by a nonequilibrium impregnation-reduction (I-R) method. $Pt(NH_3)_4Cl_2$, $NiCl_2$ and $CoCl_2$ as electrocatalytic materials and $NaBH_4$ as reducing agent were used. I order to enhance electrocatalytic activity, the catalyst layer prepared above was electrodeposited (Dep) with HP A. Surface morphologies and physico-chemical properties of MEA were investigated by means of SEM, EDX and XRD. The electrocatalytic properties of composite membranes such as the cell voltage and coulombic charge in CV were in the order of magnitude: CL-SPEEK/MoPA40 (wt%) > CL-SPEEK/TPA30 > Nafion117. In the optimum cell applications for water electrolysis, the cell voltage of Pt/CL-SPEEK-MoPA40/Pt-Co (Dep-MoPA) and Pt/CL-SPEEK-TPA30/Pt-Co (Dep-TPA) was 1.75 Vat $80^{\circ}C$ and $1\;A/cm^2$ and voltage efficiency was 87.1%. Also, the observed activity of Pt-Co (84:16 atomic ratio by EDX) is a little higher than that of Pt-Ni (86: 14). The current density peak of electrodeposited electrodes were better a little than those of unactivated electrodes based on the same membranes.