• Membrane Journal
• /
• v.15 no.4
• /
• pp.330-337
• /
• 2005

Water selective silica membranes were prepared fur use as membrane reactor for synthesis of dimethyl ether (DME) by methanol dehydration. Silica membranes formed on a Porous SUS tube by ultrasonic spray Pyrolysis (USP) and chemical vapor deposition (CVD) using tetraethoxysilane (TEOS) as precursor. The CVD-derived membranes formed higher level of trade-off line between water permeance and water/methanol selectivity than that of the USP-derived membranes. The membrane reactor possessing water permeance of $1.2\times10^{-7}\;mol\;{\cdot}\;m^{-2}\;{\cdot}\;S^{-1}\;{\cdot}\;Pa^{-1}$ and water/methanol selectivity of 10 exhibited increase in methanol conversion of about $20\%$ comparing to conventional reactor system. These findings led us to conclude that the dehydration membrane reactor simultaneously separating the water vapour produced in the reaction zone was effective in increasing the reaction conversion.

• Transactions of the Korean hydrogen and new energy society
• /
• v.29 no.1
• /
• pp.1-10
• /
• 2018

The amount of biogas increases as the amount of organic waste increases. Recently, biogas from organic waste have been made much efforts to utilize as a energy. In particular, the concentration of $CH_4$ and $CO_2$ generated from sewage sludge and livestock manure treatment are 60-70% and 30-35%, and $CH_4$ and $CO_2$ generated from food wastes are 60-80% and 20-40%. In case of landfill gas, $CH_4$ and $CO_2$ have a concentration of 40-60% and 40-60% respectively. Therefore, in order to use the biogas more widely, it is necessary to convert the biogas to methanol, LNG or DME. In this study, experiments were conducted to produce hydrogen and carbon monoxide through various biogas reforming reactions on $Ni/Ce-ZrO_2/Al2O3$ catalysts. The experiment of synthetic gas synthesis was carried out on a wide concentrations of methane and carbon dioxide, which were the major constituents of biogas from various organic wastes. The effect of $(O_2+CO_2)/CH_4$ (=R') on the yields of hydrogen and carbon monoxide, the conversion rate of methane and carbon dioxide was investigated. Also simulation for syngas synthesis on the $CO_2$ reforming of $CH_4$ was computed by employing total Gibbs free energy minimization method using PRO/II simulator, and compared with the experimental results on wet and dry reforming reaction of biogas.

• Journal of the Korean Electrochemical Society
• /
• v.10 no.2
• /
• pp.150-154
• /
• 2007

Redox complexes to transport electrodes from biomaterial to electrodes are very important part in commercial biosensor industry. A novel osmium redox complex was synthesized by the coordinating pyridine group with osmium metal. A novel osmium complex is described as $[Os(dme-bpy)_2(ap-im)Cl]^{+/2+}$. We have been studied the electrochemical characteristics of this osmium complex with electrochemical techniques such as cyclic voltammetry and chronoamperommetry. In order to immobilize osmium redox complexes on the electrode, we deposited gold nano-particles on screen printed carbon electrode(SPE). The electrical signal converts the osmium redox films into an electrocatalyst for glucose oxidation. The catalytic currents were monitored that the catalytic currents were linearly increased from 1 mM to 5 mM concentrations of glucose.

• Journal of Energy Engineering
• /
• v.10 no.1
• /
• pp.49-54
• /
• 2001

최근 자동차용 청정 연료로서의 이용 가능성으로 주목받는 디메틸에테르를 액상 혼합 반응기에서 직접 합성 가스로부터 합성하였다. 메탄올 함성촉매와 감마알루미나의 혼성촉매를 사용한 결과, $H_2$/CO=1일 때, 메탄올 함성 촉매와 탈수촉매의 비가 8:2인 경우, 가장 높은 메탄옥 환산 생산량을 보였다. 또한 공간속도의 변화에 따른 디메틸에테르, 메탄올, 이산화탄소, 메탄 등 각 생성물에 대한 선택도의 변화는 거의 없이 일정하였다. 메탄옥 합성 반응 촉매만을 사용한 경우, 생성물 중 각 성분의 선택도는 반응가스의 공간속도에 따라 달라졌는데, 반응가스의 공간속도가 작아지면 생성물 중 디메틸에테르의 선택도는 변화가 없었으나, 이산화탄소의 발생량이 많고 메탄올의 생성이 적어졌다. 동일한 반응 조건에서 액상 반응과 시강 반응을 비교한 결과, DME 수율이 액상의 경우가 더 높았다.

• 한국가스학회:학술대회논문집
• /
• 2007.04a
• /
• pp.33-36
• /
• 2007

합성가스는 C1화학을 시작하는 반응원료 물질로 최근 DME(dimethyl-ether), 메탄올, GTL(gas to liquid), CTL(coal to liquid), 암모니아 생성 공정 등 많은 화학공정에 사용되고 있다. 합성가스를 생산하는 방법은 천연가스 개질반응과 석탄의 가스화반응, 그리고 원유의 정제 등을 통해 얻을 수 있다. 삼중개질반응은 천연가스와 산소, 수증기, 이산화탄소를 원료로 $1000^{\circ}C$ 이상의 고온에서 반응시켜 합성가스를 생산하며, 균일반응계와 불균일반응계로 이루어져 있다. 균일반응계에서는 천연가스와 산소가 주로 반응하며, 원료로 투입된 대부분의 산소는 균일반응계에서 소모되어 일산화탄소와 이산화탄소를 생성한다. 삼중개질반응의 균일반응계에서는 산소와 천연가스와의 반응으로 많은 발열이 발생하여 전체 반응계의 온도를 유지할 수 있도록 해준다. 본 연구에서는 산소로 인한 삼중개질반응의 온도 조절과 균일반응계의 온도 분포를 위치에 따라 관찰해 보았으며, 실험과 모사를 통해 비교해 보았다.

• Applied Chemistry for Engineering
• /
• v.34 no.5
• /
• pp.548-555
• /
• 2023

SAPO-34 catalysts were modified with polyethylene glycol (PEG) and Pb to improve their catalytic lifetime and selectivity for light olefins in the conversion of dimethyl ether to olefins (DTO). Hierarchical SAPO-34 catalysts and PbAPSO-34 catalysts were synthesized according to changes in the molecular weight of PEG (M.W. = 1000, 2000, 4000) and the molar ratio of Pb/Al (Pb/Al = 0.0015, 0.0025, 0.0035), respectively. By introducing PEG into the SAPO-34 catalyst crystals, an enhanced volume of mesopores and reduced acidity were observed, resulting in improved catalytic performance. Pb was successfully substituted into the SAPO-34 catalyst frameworks, and an increased BET surface area and concentration of acid sites in the PbAPSO-34 catalysts were observed. In particular, the concentrations of the weak acid sites, which induce a mild reaction, were increased compared with the concentrations of strong acid sites. Then, the P2000-Pb(25)APSO-34 catalyst was prepared by simultaneously utilizing the synthesis conditions for the P2000 SAPO-34 and Pb(25)APSO-34 catalysts. The P2000-Pb(25)APSO-34 catalyst showed the best catalytic lifetime (183 min based on DME conversion > 90%), with an approximately 62% improvement compared to that of the unmodified catalyst (113 min).

• Polymer(Korea)
• /
• v.39 no.3
• /
• pp.453-460
• /
• 2015

Engineering the polylactide via stereocomplexation with supercritical fluid (SCF) technology paved way to fabricate polymers with enhanced thermal and mechanical properties. We aimed to establish a SCF medium with excellent solubility for PLA without any additional solvent/co-solvent. We, therefore, employed supercritical dimethyl ether to synthesize 100% stereocomplex polylactide from high molecular weight homopolymers with an excellent yield. The remarkable solubility of the homopolymers in dimethyl ether is the key for quick conversion to s-PLA. This study proves a rapid synthesis route of dry s-PLA powder with sc-DME at 250 bar, $70^{\circ}C$ and 1.5 h, which are reasonably achievable processing parameters compared to the conventional methods. The degree of stereocomplexation was evaluated under the effect of pressures, temperatures, times, homopolymer-concentrations and molecular weights. An increment in the degree of stereocomplexation was observed with increased temperature and pressure. Complete conversion to s-PLA was obtained for PLLA and PDLA with $M_n{\sim}200kg{\cdot}mol^{-1}$ with a total homopolymer to total DME ratio of 6:100% w/w at prescribed reaction conditions. The degree of stereocomplexation was determined by DSC and confirmed by XRD. Considerable improvement in thermo-mechanical properties of s-PLA was observed. DSC and TGA analyses proved a $50^{\circ}C$ enhancement in melting transition and a high onset temperature for thermal degradation of s-PLA respectively.

• 한국신재생에너지학회:학술대회논문집
• /
• 2009.06a
• /
• pp.451-454
• /
• 2009

Production and application of biodiesel are expected to grow steadily in the coming years and thus output of its by-product, crude glycerin, will accordingly increase as well. In the present study, gasification of biodiesel by-product as a renewable energy was performed in an entrained flow gasifier to investigate the gasification performance with the operating conditions. Crude glycerin shows a high heating value of 6,000 kcal/kg and low ash and sulphur content. Gasification was conducted in a temperature range of $950\;{\sim}\;1500\;^{\circ}C$. The variation of syngas composition with excess air ratio of 0.17 ~ 0.7 for air or oxygen as a gasification agent was investigated. From the results, syngas heating value, carbon conversion and cold gas efficiency of more than $2500\;kcal/Nm^3$, 95% and 65% were achieved, respectively. The temperature dependency of syngas composition, carbon conversion, and cold gas efficiency shows a similar tendency to excess air ratio at the temperature corresponding to the excess air ratio. The $H_2/CO$ ratio of the product gas was varied from 1.25 to 0.7 with the excess air ratio and this gas composition was favorable for DME synthesis. The optimum excess air ratio for gasification of biodiesel by-product was evaluated to be an approximately 0.35 to 0.4. The present results indicate that crude glycerin can be utilized as a feedstock for gasification to make syngas.

• Journal of the Korean Chemical Society
• /
• v.33 no.1
• /
• pp.135-142
• /
• 1989

Methyl tert-butyl ether(MTBE) was synthesized from vapor phase reaction of methanol with iso-butylene over HZSM-5 catalysts, and effects of SiO$_2/Al_2O_3$ ratio in the HZSM-5 catalysts and reaction conditions on products distribution have been examined. Acid strength and acid type of each catalyst with different SiO$_2/Al_2O_3$ ratio were measured using pyridine adsorption followed by temperature programmed desorption(TPD) and IR analysis. Reactants and products adsorption characteristics on different acid sites have also been examined. As the SiO$_2/Al_2O_3$ ratio of HZSM-5 catalyst was increased, selectivity to MTBE was improved as a result of decrease in dimethylether(DME) formation at the strong acid sites. Conversion and selectivity to MTBE were also greatly enhanced as $i-C_4H_8/CH_3OH$ reactant ratio was increased, and overall about 80$^{\circ}$C was adequate for the MTBE synthesis. The properties of deposited coke on spent catalysts were examined by TG, DTA and IR spectrum analysis, indicating the amount of the coke deposit in the order of HY > H-Mordenite > HZSM-5. Even if the coke deposited on H-Mordenite was little more in amount than to that on HZSM-5, the former deactivated quickly due to its non-interconnected channel structure. For HY, owing to its lange pore size, significant $i-C_4H_8$ polymerization was occured, and rapid deactivation and severe coke formation has resulted within few hours.