Hydrogen production by steam reforming of liquefied natural gas (LNG) over mesoporous Ni-Al₂O₃ aerogel catalyst prepared by a single-step epoxide-driven sol-gel method

Bang, Yongju,Seo, Jeong Gil,Youn, Min Hye,Song, In Kyu Elsevier 2012 International journal of hydrogen energy Vol.37 No.2

<P><B>Abstract</B></P> <P>A mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst was prepared by a single-step epoxide-driven sol-gel method and a subsequent supercritical CO<SUB>2</SUB> drying method (NA-ES catalyst). For comparison, a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst was also prepared by a single-step alkoxide-based sol-gel method and a subsequent supercritical CO<SUB>2</SUB> drying method (NA-AS catalyst). Differences in physicochemical properties and catalytic activities of mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalysts in the steam reforming of liquefied natural gas (LNG) were investigated. Textural properties of Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalysts were affected by the preparation method. Nickel species were highly dispersed in alumina through the formation of nickel aluminate phase in both NA-ES and NA-AS catalysts. However, chemical states of Al atoms in both catalysts were quite different. In addition, nickel species in the NA-ES catalyst exhibited high reducibility and high dispersion compared to those in the NA-AS catalyst. In the steam reforming of LNG, NA-ES catalyst exhibited a better catalytic performance than NA-AS catalyst in terms of LNG conversion and hydrogen yield, although both catalysts showed a stable catalytic performance during the reaction without deactivation behavior. Furthermore, NA-ES catalyst with small average nickel diameter suppressed water-gas shift reaction. Reducibility and dispersion of nickel species served as important factors determining the catalytic performance of the catalysts.</P> <P><B>Graphical abstract</B></P> <P>In the steam reforming of liquefied natural gas (LNG), NA-ES catalyst (a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst prepared by a single-step epoxide-driven sol-gel method) showed better LNG conversion and hydrogen yield than NA-AS catalyst (a mesoporous Ni-Al<SUB>2</SUB>O<SUB>3</SUB> aerogel catalyst prepared by a single-step alkoxide-based sol-gel method).</P> <P>[DISPLAY OMISSION]</P> <P><B>Highlights</B></P> <P>► Hydrogen was produced by steam reforming of liquefied natural gas (LNG). ► A Ni-Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was prepared by an epoxide-driven sol-gel method (NA-ES). ► A Ni-Al<SUB>2</SUB>O<SUB>3</SUB> catalyst was prepared by an alkoxide-based sol-gel method (NA-AS). ► NA-ES showed higher LNG conversion and hydrogen yield than NA-AS.</P>

SIMPLIFICATION OF THE PHOTOCATALYST COATING BY SOL-GEL METHOD AND HYDROTHERMAL METHOD FOR THE INHIBITION OF BACTERIA AND FUNGI

Kevin PARK 국제과학영재학회 2015 APEC Youth Scientist Journal Vol.7 No.2

Photocatalysts are widely used via sol-gel and hydrothermal methods to coat surfaces such as windows and solar panels because of their ability to prevent microorganism growth. Although these methods are effective, they are sophisticated and costly. Thus, the focus of this research was to find a simple, easily-reproducible coating method that successfully coats TiO2 on a panel. First, modifications of the sol-gel method were applied using compounds such as AgBr, PEG (Polyethylene Glycol), and ZnO and the crystal formation on the panels were compared. It was found that when ZnO was added to the mixture, the surface tension of the coated surface increased and PEG additionally helped reduce cracks on the surface of the panel. Also, a simplified version of the hydrothermal coating method was employed and was successful in coating the surface of glass and metal panels evenly using the precipitates that formed during the process. Instead of using pressure with ZnO, NaOH was used in order to coat the glass panels.Out of the metals that were coated, it was observed that ZnO coated best on the surface of zinc. Both methods demonstrated the ability of photocatalysts to degrade methylene blue and prevent bacterial and fungal growth.

Sol-gel법으로 이산화티탄(TiO₂)을 저온소성 도포시킨 경량골재콘크리트의 아세트알데히드(CH₃CHO) 제거 특성

이승한(Lee Sung Han),여인동(Yeo In Dong),정용욱(Jung Yong Wook),장석수(Jang Suk Soo) 대한토목학회 2011 대한토목학회논문집 A Vol.31 No.2A

최근 대기오염 물질을 제거하기 위하여 TiO₂ 등의 광촉매 재료를 사용한 기능성콘크리트에 대한 연구가 활발히 이루어지고 있다. 이들 연구에서 TiO₂의 흡착은 콘크리트에 직접 혼합하거나, 현탁액을 표면에 직접 도포하는 방법을 사용하고 있다. 이 중 콘크리트에 TiO₂를 직접 혼합하는 방법은 TiO₂의 사용량에 비하여 효능이 떨어져 표면에 직접 도포하는 방법이 많이 이용된다. TiO₂의 표면도포는 광촉매의 활성화와 접착성 증대를 위하여 400℃이상의 고온 열처리를 실시하게 되며, 이는 콘크리트 수회생성물의 탈수 · 수축으로 내부균열을 발생시키는 원인이 되기도 한다. 이에 이 연구에서는 TiO₂의 저온도포가 가능한 Sol-gel법으로 TiO₂를 제조하였으며 펄라이트 사용 경량골재콘크리트에 저온 고정화하여 TiO₂도포 성능을 평가하였다. 또한 펄라이트 입경을 2.5~5.0 ㎜와 5.0 ㎜이상으로 구분하여 펄라이트 입경, TiO₂ 혼입방법과 혼입률 및 시간경과에 따른 CH₃CHO 제거 특성을 검토하였다. 실험결과, Sol-gel법으로 제조한 TiO₂를 120℃에서 저온 도포할 때 XRF 정량분석에서 TiO₂38%, SiO₂ 29%, CaO 18% 순으로 나타나 TiO₂ 도포율은 높게 나타났다. 또한 펄라이트 입경 2.5~5.0 ㎜에서 TiO₂를 저온도포한 경량골재콘크리트의 CH₃CHO 제거 특성은 Sol-gel법으로 제조된 TiO₂를 7% 표면 도포하였을 경우 94%로 나타나 10%를 혼입할 때 72%에 비해 약 20%정도 높게 나타났다. 또한 펄라이트 입경 5.0 ㎜이상에서 TiO₂를 10%로 치환하여 혼합하였을 경우 CH₃CHO 제거율은 69%로 펄라이트 입경 2.5~5.0 ㎜에 대한 72%와 비슷하게 나타나 펄라이트 입경이 CH₃CHO 제거율에 미치는 영향은 크지 않았다. 시간 경과에 따른 CH₃CHO 제거 특성은 전 시험편의 10시간 평균 제거율이 20시간 전체 제거율의 84% 수준으로 나타나 반응 초기에 제거율이 높은 것으로 나타났다. Recently studies on functional concrete with a photocatalytic material such as TiO₂ have actively been carried out in order to remove air pollutants. The absorbtion of TiO₂ from those studies is applied by it being directly mixed into concrete or by suspension coated on the surface. When it comes to the effectiveness, the former process is less than that of the latter compared with the TiO₂ lise. As a result, the direct coating of TiO₂ on materials' surface is more used for effectiveness. The Surface spread of it needs to have a more than 400℃ heat treat done to stimulate the activation and adhesion of photocatalysis. Heat treat consequently leads hydration products in concrete to be dehydrated and shrunk and is the cause of cracking. The study produces TiO₂ used Sol-gel method which enables it to be coated with a low temperature treat, applies it to pearlite using Lightweight Aggregate Concrete fixed with a low temperature treat and evaluates the spread performance of it. In addition to this, the size of pearlite is divided into two types: One is 2.5 ㎜ to 5.0 ㎜ and the other is more than 5.0 ㎜ for the benefit of finding out the removal characteristics of CH₃CHO whether they are affected by pearlite size, mixing method and ratio with TiO₂ and elapsed time. The result of this experiment shows that although TiO₂ produced by Sol-gel method is treated with 120 temperature, it maintains a high spread rate on the XRF(X ray Florescence) quantitative analysis which ranks TiO₂ 38 percent, SiO₂ 29 percent and CaO 18 percent. In the size of perlite from 2.5 ㎜ to 5.0 ㎜, the removal characteristic of CH₃CHO from a low temperature heated Lightweight concrete appears 20 percent higher when TiO₂ with Sol-gel method is spreaded on the 7 percent of surface. In other words, the removal rate is 94 percent compared with the 72 percent where TiO₂ is mixed in 10 percent surface. In more than 5.0 mm sized perlite, the removal rate of CH₃CHO, when TiO₂ is mixed with 10 percent, is 69 percent, which is similar with that of the previous case. It suggests that the size of pearlite has little effects on the removal rate of CH₃CHO. In terms of Elapsed time, the removal characteristic seems apparent at the early stage, where the average removal rate for the first 10 hours takes up 84 percent compared with that of 20 hours.

솔젤법에 의해 제작된 $TiO_2$ 솔과 $SiO_2$ 솔의 점도 특성에 대한 분석

유도현,You Do-Hyun 대한전기학회 2005 전기학회논문지C Vol.54 No.12

[$TiO_2$] sol and $SiO_2$ sol were prepared using sol-gel method. As $H_{2}O$/Alkoxide ratios increased, sol had cluster structure and as $H_{2}O$/Alkoxide ratios decreased, sol had linear structure. Gelation time of $TiO_2$ sol was faster than that of $SiO_2$ sol according to the time. In comparison with initial viscosity between $TiO_2$ sol and $SiO_2$ sol, $TiO_2$ sol was highest at $H_{2}O/Ti(OC_{3}H_{7})_{4}=5$, $SiO_2$ sol was almost constant according to $H_{2}O/Si(OC_{2}H_{5})_{4}$ ratios.

Sol-Gel법과 수열처리에 의한 단일 분포 기공을 갖는 Titania 나노 분말 제조

김현태,신상일,송기창,강용 한국화학공학회 2003 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.41 No.5

Sol-gel법에 의해 출발물질로 TTIP(titanium tetra-isopropoxide)를 사용하여 titania 분말을 제조하였으며, 이 분말을 autoclave에서 수열처리하여 그 물성을 고찰하였다. 수열처리에 의해 얻어진 분말은 많은 나노기공을 갖고 있었으며, 아나타제의 결정상이 나타났다. Sol-gel법에 의해 제조한 후 400℃이상에서 열처리하여 얻어진 titania 분말은 1차 입자들 사이의 기공(intra-particle pores)과 2차 입자들 사이의 기공(inter-aggregated pores)이 공존하는 bimodal의 기공분포를 보이는 반면, 200℃에서 수열처리한 분말은 1차 입자들 사이의 기공만 존재하는 monomodal의 기공분포를 나타내었으며, 크기도 매우 작아졌고(40-50 nm), 비표면적의 중가(50-100%)와 분말의 응집도 감소(30-40%)등 물성의 괄목할 만한 향상을 가져왔다. Titania powders were prepared from titanium tetra-isopropoxide (TTIP) by a sequence of sol-gel method and hydrothermal treatment The powders made by sol-gel method followed by hydmthermal treatment exhibited an anatase crystalline phase with numemus nano-size pores. The pore size distribution of the powders prepared by sol-gel method and calcination above 400 ℃ was bimodal with tine intra-particle pores (space between primary particles) and larger inter-aggregated pores (space between secondary particles). The powders by the hydrothermal treatment at 200℃ showed a monomodal pore size distribution with only intra-particle pores. The properties of titania powders could be improved by means of hydrothermal treatment considerably; the size could be reduced to 40-50 nm, specific surface area could be increased by 50-100% and the ratio of agglomeration could be reduced by 30-40%.

Sol-Gel법을 활용하여 합성된 실리콘 나노입자 첨가제를 포함한 콘택트렌즈 재료 연구

화지연,성아영 한국안광학회 2023 한국안광학회지 Vol.28 No.4

목적: 본 연구는 Sol-Gel 법으로 합성된 SiO2 나노입자를 첨가하고 사용하여 제조된 렌즈의 물성을 비교 및 분석하고 고 굴절률 콘택트렌즈 소재로서의 활용도를 알아보고자 하였다. 방법: SiO2 나노입자는 Sol-Gel 법을 활용하여 제조하였으며, 합성된 SiO2를 2-hydroxyethyl methacrylate(HEMA)와 N-vinyl-2-pyrrolidone(NVP)에 공중합 하여물성을 측정하였다. 결과: 물리적 특성을 측정한 결과, 굴절률은 1.4351~1.4554, 가시광선 투과율은 92.26~95.94%, 함수율은 30.16%~37.05%, 접촉각은 58.75o~68.85o, 그리고 인장강도는 0.066~0.144 kgf/mm2 값을 나타내었다. S그룹의 경우, 첨가비율이 증가할수록 굴절률은 감소하고 함수율은 증가하였으며, SN그룹의 경우, 첨가비율이 증가할수록 굴절률 및 함수율이 증가되는 결과를 나타내었다. 결론: SiO2 나노입자는 SEM-EDS를 통해 합성을 확인하였다. S그룹의 경우, 습윤성을 증가시키며, SN그룹의 경우, 습윤성이 감소되는 것으로 나타나 각각 고 함수 및 고 굴절률 콘택트렌즈의 소재로 유용하게 사용될 것으로 판단된다. Purpose: This study compared and analyzed the physical properties of lenses manufactured by adding SiO2 nanoparticles synthesized by the Sol-Gel method and investigated their utility as a high-refractive-index contact lens material. Methods: SiO2 nanoparticles were manufactured using the Sol-Gel method, and the physical properties were measured by copolymerizing the synthesized SiO2 with 2-hydroxyethyl methacrylate(HEMA) and N-vinyl-2-pyrrolidone(NVP). Results: Measurements of the physical properties yielded a refractive index of 1.4351. In academic writing, we avoid the use of tildes (~) to mean “approximately” or to indicate a range. –1.4554, visible light transmittance of 92.26-95.94%, water content of 30.16-37.05%, contact angle of 58.75-68.85o, and tensile strength of 0.066-0.144 kgf/mm2. In the S group, as the addition ratio increased, the refractive index decreased and the water content increased. In the SN group, both the refractive index and water content increased as the addition ratio increased. Conclusions: Surface analysis confirmed the synthesis of SiO2 nanoparticles through scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS). In the S and SN groups, wettability increased and decreased, respectively. Therefore, these materials are considered useful for high-water and high-refractive-index contact lenses, respectively.

졸-겔법에 의한 CuO-CeO 2 복합 산화물 촉매의 제조 및 CO의 선택적 산화반응에 응용

황재영(Jae-Young Hwang),함현식(Hyun-Sik Hahm) 한국유화학회 2017 한국응용과학기술학회지 Vol.34 No.4

고분자 전해질 연료전지의 연료에 포함된 일산화탄소의 선택적 산화를 위하여, 귀금속 촉매를 대체하기 위한 CuO-CeO 2 복합 산화물 촉매를 졸-겔법과 공침법으로 제조하였다. 졸-겔법으로 촉매 제조 시 Cu/Ce의 비와 가수분해 비를 변화시켰다. 제조한 촉매의 활성은 귀금속 촉매(Pt/γ-Al 2 O 3 )와 비교하였다. Cu/Ce의 비를 변화시키면서 제조한 촉매 중 Cu/Ce의 비가 4:16인 촉매가 가장 높은 CO 전환율(90%)과 선택도(60%)를 나타내었다. 촉매의 제조에서 가수분해 비가 증가할수록 촉매 표면적이 증가하였고, 아울러 촉매 활성 또한 증가하였다. 공침법으로 제조한 촉매와 1wt% Pt/γ-Al 2 O 3 촉매의 가장 높은 CO 전환율은 각각 82% 및 81%인 반면, 졸-겔법으로 제조한 촉매의 경우는 90%가 얻어졌 다. 이는 졸-겔법으로 제조한 촉매가 공침법으로 제조한 촉매나 귀금속 촉매보다 더 높은 촉매활성을 보임을 의미한다. CO-TPD 실험을 통하여, 낮은 온도(140℃)에서 CO를 탈착하는 촉매가 본 반응에서더 높은 촉매활성을 보임을 알 수 있었다. For the preferential oxidation of CO contained in the fuel of polymer electrolyte membrane fuel cell (PEMFC), CuO-CeO 2 mixed oxide catalysts were prepared by the sol-gel and co-precipitation methods to replace noble metal catalysts. In the catalyst preparation by the sol-gel method, Cu/Ce ratio and hydrolysis ratio were changed. The catalytic activity of the prepared catalysts was compared with the catalytic activity of the noble metal catalyst(Pt/γ-Al 2 O 3 ). Among the catalysts prepared with different Cu/Ce ratios, the catalyst whose Cu/Ce ratio was 4:16 showed the highest CO conversion (90%) and selectivity (60%) at 150℃. As the hydrolysis ratio was increased in the catalyst preparation, surface area increased, and catalytic activity also increased. The highest CO conversions with the CuO-CeO 2 mixed oxide catalyst prepared by the co-precipitation method and the noble metal catalyst (1wt% Pt/ɤ-Al 2 O 3 ) were 82 and 81% at 15 0℃, respectively, whereas the highest CO conversion with the CuO-CeO 2 mixed oxide catalyst prepared by the sol-gel method was 90% at the same temperature. This indicates that the catalyst prepared by the sol-gel method shows higher catalytic activity than the catalysts prepared by the co-precipitation method and the noble metal catalyst. From the CO-TPD experiment, it was found that the catalyst having CO desorption peak at a lower temperature (140℃) revealed higher catalytic activity.

Sol-Gel 법에 의한 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 다공성 결정화 유리의 제조 : (II) Sol-Gel 법에 의해 제조된 $Li_2O-Al_2O_3-TiO_2-SiO_2$ 계 괴상겔의 결정화

조훈성,양중식 한국세라믹학회 1995 한국세라믹학회지 Vol.32 No.4

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

졸 겔 법을 이용한 Cao-SiO₂계 겔의 합성 및 구조분석

이태형,이수정,황연,김일용,조성백,Lee, Tae-Hyung,Lee, Su-Jeong,Hwang, Yeon,Kim, Ill-Young,Ohtsuki, Chikara,Cho, Sung-Baek 한국세라믹학회 2008 한국세라믹학회지 Vol.45 No.10

It has been proposed that the Cao-$SiO_2$ binary system can be good basic composition of bioactive glasses and glass-ceramics. In the present study, various kinds of Cao-$SiO_2$ gels were prepared by sol-gel method in order to control the microstructure which are related to their dissolution rate, induction period of apatite formation in body environment. Characterization of the gels were done by wet chemical analysis, SEM observation, FT-IR spectroscopy and XRD. The gelation time decreased with CaO content. However, the volume of all the dried gel decreased to 50% of the wet gels irrespective of increasement of CaO content. All the Cao-$SiO_2$ gels were amorphous and contained a large amount of silanol groups on their surfaces after heat treatment up to $800^{\circ}C$. The interconnected structure of the gel changed to agglomerated spherical powders when Ca content exceed to 20 mol%. Most of the Cao-$SiO_2$ gel showed amorphous when heat-treated up to $900^{\circ}C$. However, quartz and cristobalite was produced when heat-treated at $1000^{\circ}C$ and resultant microstructure of the gel contained microporous structure.

Sol-Gel 법에 의한 Nanoporous Alumina Membrane용 Alumina Sol 제조

박자룡,김태환,성재석,송기창 한국화학공학회 2004 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.42 No.1

Sol-Gel법에 의해 출발물질로 aluminum isopropoxide(AIP)를 사용하여, 가수분해 및 해교과정을 거쳐 alumina(boehmite)졸을 제조하였다. 또한 이 졸을 건조오븐에서 건조시켜, 분말을 제조한 후 열처리온도에 따른 분말 결정상의 조성과 기공특성을 조사하였다. 100℃에서 열처리하여 제조된 분말은 boehmite상을 나타내었으며, 500℃에서 γ-alumina로 상전이 되었다. HCl/AIP=0.10의 조건으로 해교된 후 600℃로 열처리된 분말은 4nm의 평균기공 크기를 나타내었다. 또한 해교시 첨가된 HCl양이 증가됨에 따라 기공의 크기는 감소한 반면 열처리 온도가 증가됨에 따라 평균기공의 크기는 증가하였다. Alumina(boehmite) sol was prepared by the sol-gel method from aluminum isopropoxide(AIP) through bydrolysis and peptization processes. Powders were obtained by drying the sol in drying oven, and the powder properties, such as crystalline phase composition and pore structure, were studied as a function of heat-treatment temperatures. The powders showed boehmite phase at 100℃, and transformed to γ-alumina at 500℃. The powders, heat-treated at 600℃ after being peptized at HCl/AIP=0.10, 4㎚ in average pore diameter. The average pore diameter of the powders decreased with increasing HCl concentrations added uring peptization process, but increased with increasing heat-treatment temperatures.