• Korean Chemical Engineering Research
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• v.44 no.4
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• pp.329-339
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• 2006

The production of lower olefins from methanol becomes an attractive process because of the rapid increase in crude oil price. This paper reivews the conversion mechanisms of methanol to hydrocarbons over zeolite and SAPO molecular sieve catalysts to understand the formation steps of lower olefins from methanol. The feasibility of the conversion mechanisms such as the direct mechanism based on well-defined intermediates and the hydrocarbon pool mechanism involving hydrocarbon moieties as an active centers is discussed with reepect to the induction period, the selectivity for products and the deactivation phenomena of the methanol conversion. The literature appeered since 1999 for the structure of the hydrocarbon pool and its catalytic role in the methanol conversion are summariged, and the prospect for the methanol-to-olefins process is described.

• Journal of the Korean Chemical Society
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• v.25 no.3
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• pp.172-176
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• 1981

The formation of $C_2-C_{10}$ hydrocarbons from methanol over shape-selective ZSM-5 zeolite catalysts is studied. It seems that $C_2-C_5$ olefins formed from methanol via dimethylether are transformed further to higher hydrocarbons containing higher concentration of aromatics by the acid sites of ZSM-5. Unique cross linked channel structure and its hydrophobicity seems to be mainly responsible for its high activity of ZSM-5 catalyst for the conversion of methanol.

• 한국전기화학회:학술대회논문집
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• 1999.04a
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• pp.27-27
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• 1999

• Clean Technology
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• v.14 no.3
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• pp.204-210
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• 2008

A series of $V_{2}O_{5}-TiO_2$ xerogel catalysts were prepared by nonhydrolytic sol-gel method and analysed by various characterization techniques. These catalysts showed much higher surface areas and total pore volumes than conventional V$V_{2}O_{5}-TiO_2$ xerogel and impregnated $V_{2}O_{5}/TiO_2$ catalysts. It was found that the textural property of $V_{2}O_{5}-TiO_2$ material varies with the method and conditions of synthesis. Surface vanadates and $TiO_2$ anatase phase are the crucial factors to obtain high catalytic activities. The selective oxidation of hydrogen sulfide in the presence of excess water and ammonia was studied over these catalysts. Xerogel catalysts prepared by non-hydrolytic sol-gel method showed very high conversion of $H_{2}S$ without harmful emission of $SO_2$. The highest catalytic activity shown by these $V_{2}O_{5}-TiO_2$ catalysts may be due to their high surface area and good dispersion of vanadia species in the titania matrix.

• Journal of the Korean Chemical Society
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• v.17 no.4
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• pp.275-285
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• 1973

The addition of one mole of aluminum chloride to three moles of sodium borohydride in tetrahydrofuran gives a turbid solution with enormously more powerful reducing properties than those of sodium borohydride itself. The reducing properties of this reagent were tested with 49 organic compounds which have representative functional groups. Alcohols liberated hydrogen immediately but showed no sign of hydrogenolysis of alkoxy group. Aldehydes and ketones were reduced rapidly within one hr. Acyl derivatives were reduced moderately, however, carboxylic acids were reduced much more slowly. Esters, lactones and epoxides were reduced readily than sodium borohydride or borane. Tertiary amide was reduced slowly, however, primary amide consumed one hydride for hydrogen evolution but reduction was sluggish. Aromatic nitrile was reduced much more readily than aliphatic nitrile. Nitro compounds were inert to this reagent but azo and azoxy groups were slowly attacked. Oxime was reduced slowly but isocyanate was only partially reduced. Disulfide and sulfoxide were attacked slowly but sulfide and sulfone were inert. Olefin was hydroborated rapidly.

• Korean Chemical Engineering Research
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• v.50 no.3
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• pp.398-402
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• 2012

The catalytic performance of some metal oxides in the vapor phase selective oxidation of $H_2S$ in the stream containing ammonia and water was investigated. Among the catalysts tested $Fe_2O_3/SiO_2$ was the most promising catalyst for practical application. It showed higher than 90% $H_2S$ conversion and very small amount of $SO_2$ emission over a temperature range of $240{\sim}280^{\circ}C$. The effects of reaction temperature, $O_2/H_2S$ ratio, amount of ammonia and water vapor on the catalytic activity of $Fe_2O_3/SiO_2$ were discussed to better understand the reaction mechanism. The $H_2S$ conversion showed a maximum at $260^{\circ}C$ and it decreased with increasing temperature over $280^{\circ}C$. With an increase of $O_2/H_2S$ ratio from 0.5 to 4, the conversion was slightly increased, but the selectivity to elemental sulfur was remarkably decreased. The increase of ammonia amount favored the conversion and the selectivity to elemental sulfur with a decrease in $SO_2$ production. The presence of water vapor decreased both the activity and the selectivity to sulfur, but increased the ATS selectivity.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3353-3358
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• 2007

The present paper is devoted to investigate dynamic effect and steady-state performance of methane autothermal reformer theoretically and numerically. In order to simplify the complicated phenomena in the system, axisymmetric heterogeneous reactor model is developed. As autothermal reaction takes places on catalyst surface between bulk gas and catalyst, volume averaging method is incorporated using porous medium approach. To understand the start-up process which occurs in the reactor is highly important. Therefore, in this paper we get various goverining equations to find out transient and steady solutions and time scale for start-up introducing dimensionless variables. Start-up is a significant issue in reforming reaction for automobile system and fueling of SOFC-based auxiliary power units. This paper deals with characteristics of heat and mass transfer and predicted light-off time in the reformer as oxygen to carbon ratio ($O_2$/C) and amount of feeding gas.

• Membrane Journal
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• v.7 no.3
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• pp.136-141
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• 1997

Humic acid has been extracted and purified from biologically nondegradable humic substances. Using the ion exchange capability of carboxylic acids which are the main component of the humic acids, a membrane was prepared with poly(viny1 alcohol). Its transport behavior of biologically active ions, $K^+$and $Na^+$, were investigated. The ion transport velocity increased with hydrogen ion concentration, especially, in the range of $10^-1$~$10^0$. The selectivity increased with increasing the concentrations of $K^{＋}$ and Na$^{＋}$, In particular, the transport velocity of $K^+$ increased twice compared to that of $Na^+$ at the 100 hydrogen ion concentration. In this regards, humic acid may be used as a new material for ion exchange membranes.

• Korean Chemical Engineering Research
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• v.48 no.6
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• pp.776-783
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• 2010

Co and Ni catalysts supported on $Al_2O_3$ for partial oxidation of methane producing hydrogen were synthesized using impregnation to incipient wetness. The activities of these catalysts for the partial oxidation of methane was investigated at 1 atm and $CH_4/O_2=2.0$ in the temperature range of $450{\sim}650^{\circ}C$. The reaction activity of $Ni/Al_2O_3$ and $Co/Al_2O_3$ catalysts with different loading was investigated. And the beneficial effects of Ni addition to $Co/Al_2O_3$ and the promotional effects of Ce and La addition to $Ni/Al_2O_3$ and $Co/Al_2O_3$ were investigated. These catalysts were characterized by XRD and SEM/EDX. Comparing catalyst loadings, 10 wt% Co and 10 wt% Ni were found to be optimal at the experimental conditions. The 10 wt% $Ni/Al_2O_3$ and 10 wt% $Co/Al_2O_3$ catalysts in partial oxidation of methane showed $CH_4$ conversions and CO selectivity close to the thermodynamic equilibrium levels, but showed lower $H_2$ selectivity than equilibrium level. The addition of Ni to $Co/Al_2O_3$ exhibited higher $H_2$ selectivity but beneficial effect was not observed in the $CH_4$ conversion. Addition of Ce to $Co/Al_2O_3$ and addition of La to $Ni/Al_2O_3$ a improved the $CH_4$ conversion level and $H_2$ selectivity.

• Membrane Journal
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• v.19 no.4
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• pp.261-267
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• 2009

Polyimide which is the glassy polymer has high chemical resistance, thermal stability and high mechanical property. In this study, the polyimide hollow fiber membranes were prepared by the dry-jet wet phase inversion in order to investigate the permeation porperties of the $H_2S$ and $CH_4$. The morphology of prepared hollow fiber membranes and their permeation behaviors of $H_2S$ and $CH_4$ before and after silicon coating were evaluated. The permeance of $H_2S$ and $H_2S/CH_4$ selectivity increased due to plasticization with increasing the feed pressure. The permeance of KSM03b and selectivity of KSM03d were highest among the three type membranes used this experiments. The permeance decreased but the $H_2S/CH_4$ selectivity increased with increasing the air gap. The permeance reduced after silicon coating. However, the selectivity increased and the selectivity of KSM03d was 275 at 7 atm.