• Bulletin of the Korean Chemical Society
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• 제23권6호
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• pp.803-807
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• 2002

The conversion of dimethyl ether(DME) has been carried out over $\gamma-alumina$, silica-alumina, and modified $\gamma-aluminal$ catalysts. Especially, the water effect has been investigated on purpose to develop a suitable catalyst for one-step synthesis of DME from $CO_2$ hydrgenation, The $\gamma-Al_2O_3$ modified with 1 wt% silica is more active and less deactivated by water than unmodified one. $CO_2has$ no effect on catalytic dehydration of methanol to DME.

• 공업화학
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• 제1권1호
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• pp.35-43
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• 1990

일련의 $TiO_2-SiO_2$촉매를 $TiCl_4$와 $Na_2SiO_3$혼합용액을 공침전시켜 제조하였으며 이중 일부의 촉매는 1N $H_2SO_4$로 처리하여 촉매표면을 개질하였다. 개질된 촉매의 촉매활성은 개질 안된 촉매보다 높은 촉매활성을 나타내었으며 cumene dealkylation 반응에서 보다 2 - propanol dehydration 반응에서 더욱 효과가 크게 나타났다. 개질 안된 촉매의 상기 두 반응에 대한 촉매활성은 산의 양과 관계가 있었다. $TiO_2-SiO_2$촉매는 비교적 많은 양의 약한 산자리와 작은 양의 강한 산자리를 가졌기 때문에 cumene dealkylation 반응에서 보다 2 - propanol dealkylation 반응에 더 높은 촉매활성을 나타내었다. 촉매활성에 미치는 $H_2SO_4$의 개질효과는 $TiO_2$ 함량에 비례하였으며 $92-TiO_2-SiO_2/SO_4^2$가 2 - propanol dealkylation 반응에 가장 큰 촉매활성의 증가를 나타내었다.

• Bulletin of the Korean Chemical Society
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• 제31권11호
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• pp.3283-3290
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• 2010

The gas-phase dehydration of glycerol to acrolein was carried out over 10 wt % HSiW catalysts supported on different supports, viz. $\gamma-Al_2O_3$, $SiO_2-Al_2O_3$, $TiO_2$, $ZrO_2$, $SiO_2$, AC, $CeO_2$ and MgO. The same reaction was also conducted over each support without HSiW for comparison. Several characterization techniques, $N_2$-physisorption, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), the temperature-programmed desorption of ammonia ($NH_3$-TPD), temperature-programmed oxidation (TPO) with mass spectroscopy and CHNS analysis were employed to characterize the catalysts. The glycerol conversion generally increased with increasing amount of acid sites. Ceria showed the highest 1-hydroxyacetone selectivity at $315^{\circ}C$ among the various metal oxides. The supported HSiW catalyst showed superior catalytic activity to that of the corresponding support. Among the supported HSiW catalysts, HSiW/$ZrO_2$ and HSiW/$SiO_2-Al_2O_3$ showed the highest acrolein selectivity. In the case of HSiW/$ZrO_2$, the initial catalytic activity was recovered after the removal of the accumulated carbon species at $550^{\circ}C$ in the presence of oxygen.

• Bulletin of the Korean Chemical Society
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• 제31권12호
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• pp.3679-3683
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• 2010

Niobium oxide ($Nb_2O_5$) and phosphated $Nb_2O_5$ were synthesized and used as catalysts for sorbitol dehydration to isosorbide. The characterization results of $N_2$ adsorption, XRD and $NH_3$-TPD revealed that the phosphoric acid modification could well prevent the crystallization of $Nb_2O_5$. And the amorphous phosphated $Nb_2O_5$ catalysts kept the relatively large surface area and stable acidity at high calcination temperature. The catalytic results showed that the selectivity to isosorbide could be dramatically enhanced over phosphated $Nb_2O_5$. The excellent catalytic performance with 100.0% sorbitol conversion and 62.5% isosorbide selectivity were obtained over the 0.8P/NBO-400 catalyst. Comparing with $Nb_2O_5$ catalysts, phosphated $Nb_2O_5$ catalysts regenerated through a simple calcination process showed no significant activity loss after recycling three runs.

• Bulletin of the Korean Chemical Society
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• 제22권12호
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• pp.1309-1315
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• 2001

Zirconium sulfate supported on zirconia catalysts were prepared by impregnation of powdered $Zr(OH)_4$ with zirconium sulfate aqueous solution followed by calcining in air at high temperature. The characterization of prepared catalysts was performed using Fourier transform infrared (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and by the measurement of surface area. The addition of zirconium sulfate to zirconia increased the phase transition temperature of $ZrO_2$ from amorphous to tetragonal due to the interaction between zirconium sulfate and zirconia, and the specific surface area and acidity of catalysts increased in proportion to the zirconium sulfate content up to 10 wt% of $Zr(SO_4)_2$. Infrared spectra of ammonia adsorbed on $Zr(SO_4)2}ZrO_2$ showed the presence of Bronsted and Lewis acid sites on the surface. $10-Zr(SO_4)_2}ZrO_2$ calcined at $600^{\circ}C$ exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by ammonia chemisorption method.

• Bulletin of the Korean Chemical Society
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• 제25권5호
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• pp.657-664
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• 2004

Titanium sulfate supported on $TiO_2$was prepared by impregnation of powdered $TiO_2$with an aqueous solution of titanium sulfate followed by calcining in air at high temperature. For Ti$(SO_4)_2/TiO_2$ samples calcined at 300 $^{\circ}C$, no diffraction lines of titanium sulfate are observed at $Ti(SO_4)_2$loading up to 30 wt%, indicating good dispersion of $Ti(SO_4)_2$ on the surface of $TiO_2$. The acidity of the catalysts increased in proportion to the titanium sulfate content up to 20 wt% of $Ti(SO_4)_2$. 20 wt% $Ti(SO_4)_2/TiO_2$ calcined at 300 $^{\circ}C$ exhibited maximum catalytic activities for 2-propanol dehydration and cumene dealkylation. The catalytic activities for these reactions, were correlated with the acidity of catalysts measured by ammonia chemisorption method.

• 청정기술
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• 제22권1호
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• pp.9-15
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• 2016

Al/(Al+Zr)의 몰 비를 달리하여 xAl-yZr 산화물 촉매를 공침법으로 제조하였고, 모델반응으로 이소프로판올 탈수반응을 수행하였다. 제조된 촉매는 X-선 회절분석, 시차 열분석법, 질소 흡착법, 암모니아 승온탈착법, 이소프로판올 승온탈착법 등의 특성분석을 수행하였다. 지르코니아에 알루미늄 종을 첨가하면 상대적으로 넓은 비표면적을 갖는 작은 입자를 얻을 수 있으며 지르코니아의 결정상변화를 억제시켰다. 암모니아 승온탈착으로 알루미늄의 몰 비가 증가함에 따라 상대적인 산양이 증가함을 확인하였고, 이소프로판올탈수반응에서 촉매 활성 또한 증가하였다. 이러한 촉매활성은 촉매의 비표면적, 산점, 상대적으로 용이한 이소프로판올의 탈착과 연관시킬 수 있었다.

• Korean Chemical Engineering Research
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• 제53권1호
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• pp.121-126
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• 2015

본 연구의 목적은 정수 슬러지로부터 제조된 다공성 물질의 촉매 기능을 평가하기 위한 것이다. 촉매의 구조적 특성은 질소 흡착-탈착 등온선, 주사 전자 현미경 및 X선 회절을 이용하여 조사하였다. 정수 슬러지로부터 제조된 촉매는 메조 기공과 미세 기공을 동시에 보유하고 있으며, 촉매의 비표면적은 $157m^2/g$이다. 촉매의 산특성은 암모니아 승온탈착법과 피리딘 흡착 적외선 분광법으로 분석하였다. 고정층 촉매 반응기에서 2-부탄올의 탈수 반응을 수행한 결과, $350^{\circ}C$의 반응 온도에서 1-부텐, 트랜스-2-부텐 및 시스-2-부텐의 수율은 각각 25.6 wt%, 19.2 wt% 및 29.9 wt%이었다. 정수 슬러지로부터 제조된 촉매의 2-부탄올 탈수 반응 활성은 브뢴스테드 산점와 루이스 산점으로 이루어진 산점을 보유한 것에 기인한다. 부탄올의 탈수 반응에 의해 $C_4$ 올레핀을 제조하는 반응에서 정수 슬러지로부터 제조된 촉매의 활용 가능성을 확인하였다.

• Bulletin of the Korean Chemical Society
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• 제11권5호
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• pp.403-406
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• 1990

Two types of new silica catalysts modified with benzenesulfonic acid derivatives were prepared by esterification or phenylation followed by sulfonation. Both catalysts thus prepared were tested as acid catalysts for 2-propanol dehydration and cumene dealkylation reactions. B catalyst () were more active than A catalyst (). Highter catalytic activity for B catalyst may be accounted for by higher resistance to water, higher acid strength, more acidity, and better thermal stability as compared with A catalyst.

• Bulletin of the Korean Chemical Society
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• 제27권11호
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• pp.1844-1850
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• 2006

Two types of catalyst samples were prepared, one sulfated zirconia and the other silica doped sulfated zirconia. The acidity tests indicate that sulfated zirconia doped with silica has higher concentration and strength of acidic catalyst sites than undoped sulfated zirconia. The acidic surface sites have been characterized using FTIR, NMR, pyridine adsorption, TPD, XRD and nitrogen adsorption. Doping with silica increased the concentration of surface Lewis and Brfnsted acid sites and resulted in generation of proximate acid sites.The activity test indicates that doping sulfated zirconia with silica increases both the acidity and catalytic activity for liquid phase dehydration of methanol at 413-453 K. Methanol is sequentially dehydrated to dimethyl ether and ethylene over both catalysts. Significant amounts of propylene are also formed over the silica-doped catalyst, but not over the undoped catalyst.