• Title, Summary, Keyword: alkali catalyst

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Synthesis of Alkoxy Modified Silicone Using Alkali Catalyst

  • Lee, Kangseok;Shim, Sang Eun
    • Elastomers and Composites
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    • v.51 no.2
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    • pp.99-105
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    • 2016
  • Alkoxy modified silicone (PAMS) was synthesized from hydroxyl-terminated polydimethylsiloxane (OH-PDMS) and vinyltrimethoxysilane (VTMO) under alkali catalyst (NaOH and KOH) at room temperature ($25^{\circ}C$) via condensation polymerization. Then, the structural verification of the synthesized PAMS was confirmed using $^1H$-NMR and FT-IR spectroscopy. The reaction rate of PAMSs was studied in terms of the concentration variation of alkali catalyst. The reaction rate increased with the concentration of alkali catalyst, but no correlation between conversion and concentration of alkali catalyst was observed.

Chemical Poisoning of Ni/MgO Catalyst by Alkali Carbonate Vapor in the Steam Reforming Reaction of DIR-MCFC

  • 문형대;임태훈;이호인
    • Bulletin of the Korean Chemical Society
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    • v.20 no.12
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    • pp.1413-1417
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    • 1999
  • Chemical poisoning of Ni/MgO catalyst was induced by hot alkali carbonate vapor in molten carbonate fuel cell (MCFC), and the poisoned (or contaminated) catalyst was characterized by TPR/TPO, FTIR, and XRD analysis. Carbonate electrolytes such as K and Li were transferred to the catalyst during DIR-MCFC operation at 650 ℃. The deposition of alkali species on the catalyst consequently led to physical blocking on catalytic active sites and structural deformation by chemical poisoning. TPR/TPO analysis indicated that K species enhanced the reducibility of NiO thin film over Ni as co-catalyst, and Li species lessened the reducibility of metallic Ni by chemical reaction with MgO. FTIR analysis of the poisoned catalyst did not exhibit the characteristic ${\vector}_1$$(D_{3h})$ peaks (1055 $cm^{-1},\;1085\;cm{-1})$ for pure crystalline carbonates, instead a new peak (1120 $cm^{-1})$ was observed proportionally with deformed alkali carbonates. From XRD analysis, the oxidation of metallic Ni into $Ni_xMg_{1-x}O$ was confirmed by the peak shift of MgO with shrinking of Ni particles. Conclusively, hot alkali species induced both chemical poisoning and physical deposition on Ni/MgO catalyst in DIR-MCFC at 650 ℃.

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Vapor-phase Oxidation of Alkylaromatics over V/TiO2 and VSb/Al2O3 Catalysts: Effect of Alkali Metals

  • Yoon, Ji-Woong;Jhung, Sung-Hwa;Chang, Jong-San
    • Bulletin of the Korean Chemical Society
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    • v.28 no.12
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    • pp.2405-2408
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    • 2007
  • Oxidation of alkylaromatics including toluene and p-methoxytoluene has been carried out over alkali metal (AM)-containing catalysts such as AM-V/TiO2 and AM-VSb/Al2O3 in vapor-phase using oxygen as an oxidant. The selectivity for partial oxidations increases with incorporation of an alkali metal or with increasing the basicity of alkali metals (from Na to Cs), irrespective of the supports or reactants. However, the conversion is nearly constant or slightly decreasing with the addition of alkali metals in the catalyst. The increased selectivity may be related with the decreased acidity even though more detailed work is necessary to understand the effect of alkali metals in the oxidation. The AM-VSb/Al2O3 may be suggested as a potential selective catalyst for vapor-phase oxidations.

The deactivation behavior of SCR catalyst by alkali and alkali earth metal (알칼리 및 알칼리 토금속에 의한 SCR 촉매 비활성 거동)

  • Han, Seungyun;Shin, Min-Chul;Lee, Heesoo
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.26 no.6
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    • pp.238-242
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    • 2016
  • The effect of the alkali, alkali earth metal elements on selective catalytic reduction(SCR) catalyst deactivation behavior were investigated in terms of microstructure, surface area, pore volume and De-NOx test. Poisoned SCR catalyst were manufactured by injection of $K_2CO_3$, $Na_2CO_3$, $Ca(CH_3COO)_2{\cdot}H_2O$, $C_4H_6MgO_4{\cdot}4H_2O$, $H_3PO_4$ solutions in the new SCR catalyst at $350^{\circ}C$ for 6 hours. New and poisoned catalysts surface were similar. But specific surface area, pore volume decrease from Na, Mg, K, Ca, P compared to new SCR catalyst. Especially, Na poisoned catalyst surface area and pore size extremely decreased by $10.20m^2/g$, $0.061cm^2/g$. De-NOx test results of new and poisoned catalysts at $150{\sim}450^{\circ}C$ indicated that alkali metal (K, Na) poisoned SCR catalysts have the lowest De-NOx efficiency, alkali earth metal poisoned SCR catalysts (Ca, Mg) De-NOx efficiency are higher than alkali metal poisoned SCR catalysts. P poisoned SCR catalyst De-NOx efficiency is similar new SCR catalyst. It were considered that physical deactivation of SCR catalyst was affected by SCR catalyst surface area and pore volume change.

Poisoning of the Ni/MgO Catalyst by Alkali Carbonates in a DIR-MCFC (용융탄산염 연료전지에서 알칼리 탄산염에 의한 Ni/MgO 촉매의 피독)

  • Moon, Hyeung-Dae;Kim, Joon-Hee;Ha, Heung Yong;Lim, Tae-Hoon;Hong, Sung-Ahn;Lee, Ho-In
    • Applied Chemistry for Engineering
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    • v.10 no.5
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    • pp.754-760
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    • 1999
  • The properties of the catalyst for a direct internal reforming type molten carbonate fuel cell were examined by ICP, BET, CHN, EDS, and $H_2$ chemisorption. Potassium and lithium, the components of carbonate electrolyte, were transported to the catalyst during the operation of fuel cell, and the amounts of the deposited alkali elements were reduced in the order of inlet, outlet, and the middle. From the direct correlation between the amount of alkali and the physical properties such as BET surface area and Ni dispersion, and from the observation of the lump of the alkali species on the poisoned catalyst, it was confirmed that the physical blocking of the catalyst by alkali deposition was the main reason for the deactivation. Although the amount of alkali species was greater at the inlet than at the oulet, the catalyst sampled from the outlet had lower activity. This was caused by the chemical interaction between the alkali species and the catalyst at the outlet where temperature was highest in the cell body, which was detected by FT-IR analyses.

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Biodiesel Production from Waste Cooking Oil Using Alkali Catalyst and Immobilized Enzyme 1. Fatty Acid Composition (알칼리 촉매와 고정화 효소를 이용한 폐식용유로 부터 바이오 디젤 생산 1. 지방산 조성)

  • Shin, Choon-Hwan
    • Journal of Environmental Science International
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    • v.19 no.10
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    • pp.1247-1256
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    • 2010
  • Since biodiesel as bioenergy is defined as ester compounds formed by esterification of animal/vegetable oils, in this study three vegetable cooking oils (market, waste and refined waste ones) were esterified by reactions of alkali catalyst and immobilized enzyme. The fatty acid composition of the formed ester compounds was analyzed to investigate the feasibility of biodiesel production. By lipolysis (i.e, hydrolysis of Triglyceride (TG)), all three vegetable oils used in this study were found to produce Diglyceride (DG), Monoglyceride (MD) and Fatty acid ethylester (FAEE). However, the amount of produced FAEE (which can be used as an energy source) was in the increasing order of market cooking oil, waste one and refined waste one. With NaOH catalyst, FAEE was produced about 24.92, 17.63 and 11.31 % for the respective oils while adding Lipozyme TL produced FAEE about 43.54, 38.16 and 24.47 %, respectively. This indicates that enzyme catalyst is more effective than alkali one for transesterification. In addition, it was found that the composition of fatty acids produced by hydrolysis of TG was unchanged with alkali and immobilized enzyme reactions. Thus it can be expected that stable conditions remain in the course of mixing with gasoline whose composition is similar to that of the fatty acids.

Effect of Acetate Promotor on the Pd-Au/SiO2-catalyzed Synthesis of Vinyl Acetate from the Reaction of Ethylene with Acetic Acid (Pd-Au/SiO2 촉매에 의한 에틸렌과 아세트산으로부터 비닐 아세트산염의 생성반응에 대한 아세트산염의 촉진 효과)

  • Atashi, Hossein;Motahari, Kazem;Tabrizi, Farshad Farshchi;Sarkari, Majid;Fazlollahi, Farhad
    • Journal of the Korean Chemical Society
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    • v.55 no.1
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    • pp.92-97
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    • 2011
  • The effect of Group I alkali acetate promoters on vinyl acetate (VA) synthesis was evaluated. Catalyst product selectivity and ethylene conversion are compared to the unpromoted catalyst in the fixed-bed reactor with oxidation reaction of ethylene and acetic acid in gaseous phase over Pd-Au/$SiO_2$ catalyst. It was found that: a) the promoters were stabilized on the catalyst surface, b) common effect for the alkali promoted Pd-Au catalysts increaseed in product selectivity and ethylene conversion compared to unpromoted catalyst (these effects increase from top to the bottom of Group I). These promoting effect is due to the common-ion effect of acetate, present in the reaction, resulting in an increase in the activity of the catalyst. In addition a complementary theory for the effect of Au in the structure of the catalyst is proposed the imposition of distribution of palladium particles through decreasing the particle's diameter.

Effect of Alkali Promoter in CO Hydrogenation Using Co/NaY Catalyst (Co/NaY 촉매를 이용한 CO 수소화 반응에 있어서 알칼리 첨가제의효과)

  • Myong-Mo Sung;Min-Young Youn;Yunsoo Kim;Hang Nam Paik
    • Journal of the Korean Chemical Society
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    • v.32 no.5
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    • pp.501-506
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    • 1988
  • The effects of alkali promoters on the activity and selectivity of Co/NaY catalyst have been investigated. The catalysts were prepared by impregnating NaY with aqueous solutions of alkali compounds and a benzene solution of $Co_2(CO)_8$. Hydrocarbon synthesis was studied in a flow reactor under the reaction conditions : temperature = 200∼250$^{\circ}C$, space velocity = 120∼$160hr^{-1}$, pressure = 1 atm, $H_2$/CO = 1. As the basicity of alkali promoter increases, the olefin selectivity, probability of chain growth, and CO$_2$ formation increase and methane formation decreases. The activity of CO hydrogenation increases with the pH of alkali solutions.

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A Study on the Sulfur-Resistant Catalysts for Water Gas Shift Reaction II. Effect of Alkali Metal Salt on the Activity of CoMo Catalyst (황에 저항성을 가지는 수성가스 전환반응 촉매의 연구 II. CoMo 촉매의 활성에 미치는 알칼리 금속염의 영향)

  • Kim, Joon Hee;Lee, Ho In
    • Journal of the Korean Chemical Society
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    • v.42 no.6
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    • pp.696-702
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    • 1998
  • The effect of alkali metal salt on the activity of Co-Mo catalyst which has high resistance to sulfur poisoning for water gas shift reaction(WGSR) was studied. Two groups of catalysts were prepared to investigate the effects of anion and cation in alkali metal salts. For K-doped catalysts made with various potassium salts having different anion, the catalytic activity was explained to depend mainly on the BET surface area. Among the catalysts prepared by various nitrates of alkali metal as precursor, the Li-doped catalyst showed the best activity, and the others did not make significant differences giving relatively low activities. And the change of BET surface area by varying the loading of alkali metal showed a similar trend to that of activity. In this case, the activity was dependent on both BET surface area and the ratio of $Mo^{6+}$ with a tetrahedral coordination symmetry to $Mo^{6+}$ with an octahedral one, $Mo^6+[T]/Mo^{6+}[O]$ value.

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The Effect of Alkali Metal Ions (Na, K) on NH3-SCR Response of V/W/TiO2 (알칼리 금속 이온(Na, K)이 V/W/TiO2의 NH3-SCR 반응인자에 미치는 영향)

  • Yeo, Jonghyeon;Hong, Sungchang
    • Applied Chemistry for Engineering
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    • v.31 no.5
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    • pp.560-567
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    • 2020
  • In this study, we investigated that the effect of alkali metals [Na(Sodium) and K(Potassium)], known as representative deactivating substances among exhaust gases of various industrial processes, on the NH3-SCR (selective catalytic reduction) reaction of V/W/TiO2 catalysts. NO, NH3-TPD (temperature programmed desorption), DRIFT (diffuse reflectance infrared fourier transform spectroscopy analysis), and H2-TPR analysis were performed to determine the cause of the decrease in activity. As a result, each alkali metal acts as a catalyst poisoning, reducing the amount of NH3 adsorption, and Na and K reduce the SCR reaction by reducing the L and B acid points that contribute to the reaction activity of the catalyst. Through the H2-TPR analysis, the alkali metal is considered to be the cause of the decrease in activity because the reduction temperature rises to a high temperature by affecting the reduction temperature of V-O-V (bridge oxygen bond) and V=O (terminal bond).