Selective methane chlorination to methyl chloride by zeolite Y-based catalysts

Joo, Hyeonho,Kim, Daeho,Lim, Kwang Soo,Choi, Yong Nam,Na, Kyungsu Elsevier 2018 SOLID STATE SCIENCES Vol.77 No.-

<P><B>Abstract</B></P> <P>The CH<SUB>4</SUB> chlorination over Y zeolites was investigated to produce CH<SUB>3</SUB>Cl in a high yield. Three different catalytic systems based on Y zeolite were tested for enhancement of CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity: (i) HY zeolites in H<SUP>+</SUP>-form having various Si/Al ratios, (ii) Pt/HY zeolites supporting Pt metal nanoparticles, (iii) Pt/NaY zeolites in Na<SUP>+</SUP>-form supporting Pt metal nanoparticles. The reaction was carried out using the gas mixture of CH<SUB>4</SUB> and Cl<SUB>2</SUB> with the respective flow rates of 15 and 10 mL min<SUP>−1</SUP> at 300–350 °C using a fixed-bed reactor under a continuous gas flow condition (gas hourly space velocity = 3000 mL g<SUP>−1</SUP> h<SUP>−1</SUP>). Above the reaction temperature of 300 °C, the CH<SUB>4</SUB> chlorination is spontaneous even in the absence of catalyst, achieving 23.6% of CH<SUB>4</SUB> conversion with 73.4% of CH<SUB>3</SUB>Cl selectivity. Under sufficient supplement of thermal energy, Cl<SUB>2</SUB> molecules can be dissociated to two chlorine radicals, which triggered the C-H bond activation of CH<SUB>4</SUB> molecule and thereby various chlorinated methane products (i.e., CH<SUB>3</SUB>Cl, CH<SUB>2</SUB>Cl<SUB>2</SUB>, CHCl<SUB>3</SUB>, CCl<SUB>4</SUB>) could be produced. When the catalysts were used under the same reaction condition, enhancement in the CH<SUB>4</SUB> conversion was observed. The Pt-free HY zeolite series with varied Si/Al ratios gave around 27% of CH<SUB>4</SUB> conversion, but there was a slight decrease in CH<SUB>3</SUB>Cl selectivity with about 64%. Despite the difference in acidity of HY zeolites having different Si/Al ratios, no prominent effect of the Si/Al ratios on the catalytic performance was observed. This suggests that the catalytic contribution of HY zeolites under the present reaction condition is not strong enough to overcome the spontaneous CH<SUB>4</SUB> chlorination. When the Pt/HY zeolite catalysts were used, the CH<SUB>4</SUB> conversion reached further up to 30% but the CH<SUB>3</SUB>Cl selectivity decreased to 60%. Such an enhancement of CH<SUB>4</SUB> conversion could be attributed to the strong catalytic activity of HY and Pt/HY zeolite catalysts. However, both catalysts induced the radical cleavage of Cl<SUB>2</SUB> more favorably, which ultimately decreased the CH<SUB>3</SUB>Cl selectivity. Such trade-off relationship between CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity can be slightly broken by using Pt/NaY zeolite catalyst that is known to possess Frustrated Lewis Pairs (FLP) that are very useful for ionic cleavage of H<SUB>2</SUB> to H<SUP>+</SUP> and H<SUP>−</SUP>. Similarly, in the present work, Pt/NaY(FLP) catalysts enhanced the CH<SUB>4</SUB> conversion while keeping the CH<SUB>3</SUB>Cl selectivity as compared to the Pt/HY zeolite catalysts.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Selective chlorination of CH<SUB>4</SUB> with Cl<SUB>2</SUB> molecule was studied using zeolite Y-based catalysts. </LI> <LI> CH<SUB>4</SUB> conversion increased with HY zeolites having acidity, but CH<SUB>3</SUB>Cl selectivity decreased. </LI> <LI> CH<SUB>4</SUB> conversion increased further with Pt/HY zeolites, but CH<SUB>3</SUB>Cl selectivity decreased further. </LI> <LI> Pt/NaY with Frustrated Lewis Pairs improved CH<SUB>4</SUB> conversion and CH<SUB>3</SUB>Cl selectivity simultaneously. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

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민영(Young Min) 한국언론학회 2016 한국언론학보 Vol.60 No.2

Attending to the increasing user selectivity in news exposure, this study investigates the causes and political consequences of partisan and news selectivity. Particularly, this study assesses the level of partisan selectivity in news exposure by considering both selective approach and selective avoidance. From a nation-wide online survey (N = 1,193) in the congressional by-elections in April 2015, the following results were drawn. First, ideological intensity and political interest appeared to be the two most important predictors of partisan selectivity. News selectivity was higher among male, aged, and politically engaged citizens. Second, stronger partisan selectivity led to more polarized attitudes toward political parties and politicians. News selectivity exerted a marginally significant impact on alleviating the extremity in citizens’ attitudes toward politicians. Third, partisan selectivity did not significantly facilitate political participation nor increase political knowledge. News selectivity, in contrast, showed some meaningful effects on enhancing alternative political participation and general political knowledge.

분리막 투과도와 분리도 인자의 시스템 설계 효과 연구

신미수(Mi-Soo Shin),장동순(Dongsoon Jang),이용국(Yongguk Lee) 대한환경공학회 2016 대한환경공학회지 Vol.38 No.12

분리막의 제조에 있어서 높은 분리도와 투과도가 요구되지만 투과도와 분리도는 반비례하는 경향이 있으므로 현실적으로 가능하지 않다. CO₂ 포집의 비용절감 측면에서 살펴보면 분리막의 재질 자체보다는 투과도와 분리도가 분리막의 모듈이나 시스템의 성능이 미치는 영향이 더 중요하다고 할 수 있다. 예로 들어 CO₂ 13%와 N₂ 87%인 혼합기체를 분리도를 5로 고정시킨 후 유량의 10%가 분리막을 통하여 투과된다고 가정하면 투과한 10% 중에 CO₂ 4.28%, N₂가 5.72%로서 투과한 기체중 이산화탄소의 농도가 42.8%가 된다. 이 경우 이산화탄소의 순도는 42.8%이며 첫 번째 투과에 의해 얻은 이산화탄소의 회수량은 4.28/13 = 32.9%가 된다. 만일 투과도와 분리도를 두배로 증가시킬 경우 이산화탄소의 순도는 64.5%, 이산화탄소 회수량은 12.9/13 = 99.2%로 나타났다. 이 경우 대부분의 CO₂가 회수되었으며 이것이 의미하는 바는 주입된 이산화탄소가 투과되지 않고 그대로 통과하여 빠져나가는 양은 거의 제로에 가까운 경우로서 이산화탄소 분리에는 이상적인 설계나 운전조건이라 할 수 있다. 일정한 주입농도에서 주어진 투과도에 대하여 이산화탄소를 100% 회수하는 임계 분리도가 존재함을 알 수 있으며, 임계 분리도 이상 높아질 경우 이산화탄소 회수되는 양이나 순도 향상에 별다른 영향이 없음을 시사하고 있다. 이상의 결과에서 주어진 이산화탄소의 농도에 대해서 분리막을 이용한 분리에서 이산화탄소를 100% 투과시키는 임계 투과도와 분리도가 설계와 운전조건의 최적화를 위하여 절대적으로 중요함을 알 수 있다. Manufacturing membrane materials with high selectivity and permeability is quite desirable but practically not possible, since the permeability and selectivity are usually inversely proportional. From the viewpoint of reducing the cost of CO₂ capture, module performance is even more important than the performance of membrane materials itself, which is affected by the permeance of the membrane (P, stagecut) and selectivity (S). As a typical example, when the mixture with a composition of 13% CO₂ and 87% of N₂ is fed into the module with 10% stage cut and selectivity 5, in the 10 parts of the permeate, CO₂ represents 4.28 parts and N₂ represents 5.72 parts. In this case, the CO₂ concentration in the permeate is 42.8% and the recovery rate of CO₂ in this first separation appears as 4.28/13 = 32.9%. When permeance and selectivity are doubled, however, from 10% to 20% and from 5 to 10, respectively, the CO₂ concentration in the permeant becomes 64.5% and the recovery rate is 12.9/13 = 99.2%. Since in this case, most of the CO₂ is separated, this may be the ideal condition. For a given feed concentration, the CO₂ concentration in the separated gas decreases if permeance is larger than the threshold value for complete recovery at a given selectivity. Conversely, for a given permeance, increasing the selectivity over the threshold value does not improve the process further. For a given initial feed gas concentration, if permeance or selectivity is larger than that required for the complete separation of CO₂, the process becomes less efficient. From all these considerations, we can see that there exists an optimum design for a given set of conditions.

결혼이민자의 선별성과 출산: 개인효과와 지역효과를 중심으로

황성식,유정균 통계청 2018 통계연구 Vol.23 No.4

The main purpose of this study is to explore the effects of immigrant selectivity on marriage immigrant’s fertility in Korea. This paper adopts selectivity in both individual and regional level to investigate the direct effect of selectivity and the selective effect by residence. Micro data from the 2009 National Multi-Cultural Family Survey and various aggregated level data are combined to calculate the immigrant selectivity in individual and regional level. The results of cross-classified multi-level analyses reveal that the selectivity of marriage immigrants negatively impact on their fertility. The variation according to the proportion of marriage immigrants and same ethnic immigrants in residential area declined when regional level selectivity is controlled. It is also reported that the neighborhood effects turned to be more significant for the immigrants with low selectivity. These results imply that the immigrant selectivity not only affects the individual difference in fertility behavior, but also explains the regional variation in fertility when measured in aggregated level. 이 논문은 이민 전 지위의 개념인 선별성을 통해 결혼이민자들의 출산을 설명한다. 특히, 결혼이민자의 선별성을 개인수준과 지역수준에서 측정하여 선별성이 출산에 미치는 영향과 더불어 거주지역에 따른 선별효과를 파악하고자 하였다. 이 논문에서는 선별적인 이민자일수록 성취에 대한 동기를 지니며, 이에 따라 낮은 출산수준을 보일 것으로 가정하였다. 아울러 지역수준의 선별효과가 존재하는지 살펴보고, 이를 통제할 경우 거주지역 특성의 효과는 감소하는지를 확인하고자 하였다. 분석을 위하여 『2009년 다문화가족 실태조사』의 원자료를 활용하였으며, 여러 집합적인 수준의 자료들을 사용하여 개인수준과 지역수준에서의 선별성 및 거주지역의 특성을 계산하였다. 교차다층모형을 실시한 결과, 출신국가에서의 지위가 높은 이민자들일수록 출산수준이 낮은 것으로 나타났다. 지역수준에서 계산된 선별성을 투입하자 외국인 아내 비중과 같은 민족 비중의 효과는 감소하는 것으로 밝혀졌다. 또한, 거주지역의 외국인 아내 비중과 같은 민족 비중의 효과는 선별성이 낮은 집단에서 더욱 뚜렷하게 관찰되었다. 이러한 결과는 결혼이민자의 선별성에 따라 이들의 행동양식이 상이하다는 점을 제시할 뿐 아니라, 거주지역에 따른 선별효과가 내재함을 시사해준다.

Kinetic CO₂ selectivity in clathrate-based CO₂ capture for upgrading CO₂-rich natural gas and biogas

Lim, Jiyeon,Choi, Wonjung,Mok, Junghoon,Seo, Yongwon Elsevier 2019 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.369 No.-

<P><B>Abstract</B></P> <P>Upgrading CO<SUB>2</SUB>-rich natural gas or biogas through CO<SUB>2</SUB> capture is essential to reduce greenhouse gas emissions and to increase its energy density. In this study, clathrate-based CO<SUB>2</SUB> capture from CO<SUB>2</SUB>-rich natural gas or biogas was investigated with a primary focus on kinetic CO<SUB>2</SUB> selectivity. The time-dependent CO<SUB>2</SUB> selectivity during clathrate formation for pure water, tetrahydrofuran (THF, 5.6 mol%) solution, and tetra-n-butylammonium chloride (TBAC, 3.3 mol%) solution was examined through direct composition analysis and <I>in situ</I> Raman spectroscopy. In pure water, the CO<SUB>2</SUB> composition in the clathrate phase was much higher at the early stage of clathrate formation than that at equilibrium, indicating that CO<SUB>2</SUB> is kinetically and thermodynamically selective. For both the THF (5.6 mol%) and TBAC (3.3 mol%) solutions, the CO<SUB>2</SUB> composition in the clathrate phase was almost constant during clathrate formation. However, the TBAC (3.3 mol%) solution showed significantly higher CO<SUB>2</SUB> composition (∼74%) throughout the reaction, whereas the THF (5.6 mol%) solution exhibited enrichment of CH<SUB>4</SUB> in the clathrate phase. The experimental results clearly demonstrate that CO<SUB>2</SUB> selectivity is dependent on both kinetics and equilibrium of clathrate hydrates and that the addition of thermodynamic promoters, such as THF and TBAC, can affect kinetic CO<SUB>2</SUB> selectivity as well as equilibrium CO<SUB>2</SUB> selectivity in the clathrate phase.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Clathrate growth kinetics and time-dependent CO<SUB>2</SUB> selectivity were investigated. </LI> <LI> At the early stage of clathrate formation in pure water, CO<SUB>2</SUB> selectivity was higher. </LI> <LI> Clathrate CO<SUB>2</SUB> composition was not changed during THF and TBAC clathrate formation. </LI> <LI> CO<SUB>2</SUB> selectivity was dependent on both the kinetics and equilibrium of clathrates. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Directed Molecular Engineering of Mig6 Peptide Selectivity between Proto-oncogene ErbB Family Receptor Tyrosine Kinases

Zhijun Qiao,Shuai Wang 한국생물공학회 2021 Biotechnology and Bioprocess Engineering Vol.26 No.2

The ErbB signaling pathway plays important roles in normal physiology and cancer, which consists of four proto-oncogene receptor tyrosine kinases ErbB1/EGFR, ErbB2/Her2, ErbB3/Her3, and ErbB4/Her4. Selective targeting of different ErbB kinases would result in distinct therapeutic effects, but traditional small-molecule inhibitors generally exhibit a strong cross-reactivity over these kinases due to the very high conservation in kinase’s active site. Instead of developing small-molecule drugs to selectively target the conserved active site of ErbB kinases, we herein attempt to design peptide agents for selectively disrupting the dimerization event of these kinases at their asymmetric dimer interfaces that have a relatively low homology. Three hotspot peptides S1P1, S1P2, and S1P3 are split from the functional segment 1 (Seg1) of mitogen-inducible gene 6 (Mig6), a natural EGFR-inhibitory protein that has been observed to inactivate the kinase by disrupting its dimerization. We demonstrate that the Mig6 peptides not only inhibit EGFR, but also bind Her2, Her3, and Her4, although the peptide affinities to the four ErbB kinases are different considerably, exhibiting a typical selectivity. The S1P2 peptide locates in the core binding region of Mig6 Seg1 and contributes significantly to the segment interaction with kinases. An iteration algorithm is employed to guide the directed molecular engineering of S1P2 peptide selectivity towards each of the four kinases. Hundreds of parallel evolution running yield a series of peptide candidates with potential selectivity, which are then substantiated by fluorescence-based assays. The designed EGFR-selective peptide S1P2-p1EGFR is determined to have a moderate affinity to EGFR (Kd = 56 μM) and a high selectivity for EGFR over Her2, Her3, and H4 (FEGFR = 10.1-fold), which is improved considerably relative to wild-type S1P2 peptide (FEGFR = 2.7-fold). Structural examination observes different noncovalent interaction modes at the complex interfaces of S1P2-p1EGFR with EGFR and other three kinases, revealing a molecular origin of the peptide selectivity.

Involvement of Amino Acids Flanking Glu7.32 of the Gonadotropin-releasing Hormone Receptor in the Selectivity of Antagonists

Chengbing Wang,Da Young Oh,코식마이티,권혁방,Jun Cheon,황종익,성재영 한국분자세포생물학회 2008 Molecules and cells Vol.25 No.1

The Glu/Asp7.32 residue in extracellular loop 3 of the mammalian type-I gonadotropin-releasing hormone receptor (GnRHR) interacts with Arg8 of GnRH-I, conferring preferential ligand selectivity for GnRH-I over GnRH-II. Previously, we demonstrated that the residues (Ser and Pro) flanking Glu/Asp7.32 also play a role in the differential agonist selectivity of mammalian and non-mammalian GnRHRs. In this study, we examined the differential antagonist selectivity of wild type and mutant GnRHRs in which the Ser and Pro residues were changed. Cetrorelix, a GnRH-I antagonist, and Trptorelix-2, a GnRH-II antagonist, exhibited high selectivity for mammalian type-I and nonmammalian GnRHRs, respectively. The inhibitory activities of the antagonists were dependent on agonist concentration and subtype. Rat GnRHR in which the Ser-Glu-Pro (SEP) motif was changed to Pro-Glu-Val (PEV) or Pro-Glu-Ser (PES) had increased sensitivity to Trptorelix-2 but decreased sensitivity to Cetrorelix. Mutant bullfrog GnRHR-1 with the SEP motif had the reverse antagonist selectivity, with reduced sensitivity to Trptorelix-2 but increased sensitivity to Cetrorelix. These findings indicate that the residues flanking Glu7.32 are important for antagonist as well as agonist selectivity.

Involvement of Amino Acids Flanking Glu^7.32 of the Gonadotropin-releasing Hormone Receptor in the Selectivity of Antagonists

Wang, Cheng bing,Oh, Da young,Maiti, Kaushik,Kwon, Hyuk bang,Cheon, Jun,Hwang, Jong iIk,Seong, Jae young Korean Society for Molecular Biology 2008 Molecules and cells Vol.25 No.1

The Glu/Asp^7.32 residue in extracellular loop 3 of the mammalian type-I gonadotropin-releasing hormone receptor (GnRHR) interacts with Arg⁸ of GnRH-I, conferring preferential ligand selectivity for GnRH-I over GnRH-II. Previously, we demonstrated that the residues (Ser and Pro) flanking Glu/Asp^7.32 also play a role in the differential agonist selectivity of mammalian and non-mammalian GnRHRs. In this study, we examined the differential antagonist selectivity of wild type and mutant GnRHRs in which the Ser and Pro residues were changed. Cetrorelix, a GnRH-I antagonist, and Trptorelix-2, a GnRH-II antagonist, exhibited high selectivity for mammalian type-I and non-mammalian GnRHRs, respectively. The inhibitory activities of the antagonists were dependent on agonist concentration and subtype. Rat GnRHR in which the Ser-Glu-Pro (SEP) motif was changed to Pro-Glu-Val (PEV) or Pro-Glu-Ser (PES) had increased sensitivity to Trptorelix-2 but decreased sensitivity to Cetrorelix. Mutant bullfrog GnRHR-1 with the SEP motif had the reverse antagonist selectivity, with reduced sensitivity to Trptorelix-2 but increased sensitivity to Cetrorelix. These findings indicate that the residues flanking Glu^7.32 are important for antagonist as well as agonist selectivity.

The effect of counter-ions on the ion selectivity of potassium and sodium ions in nanopores.

Tang, Dai,Kim, Daejoong Pergamon Press 2014 Bio-medical materials and engineering Vol.24 No.1

<P>The ion selective transport plays an important role in the function of cell membranes, and promotes the application of artificial permeable membranes. This phenomenon has been studied in case for different diameters and functional groups of nanopores. In this work, we focus on the effect of anions on cation selectivity, in particular the influence of various halide ions on K+ and Na+ selectivity. We adopted molecular dynamics simulations with non-charged nanopores under constant temperature and uniform concentration. The results show K+-selectivity in the solution with Cl- and Na+-selectivity in the solution with Br- and I-. This selectivity, on the contrary, disappears in the solution with F-. We also investigate the change of the hydration shell of ions and cation-anion interactions between in the bulk region and in the nanopores, which could explain this selective phenomenon.</P>

참조기 (Larimichthys polyactis) 유자망에 있어서 SELECT모델에 의한 적정 망목선택성 곡선 추정

김성훈 ( Seong Hun Kim ),박성욱 ( Seong Wook Park ),이경훈 ( Kyoung Hoon Lee ),양용수 ( Yong Su Yang ) 한국어업기술학회 2012 수산해양기술연구 Vol.48 No.1

The mesh selectivity of a drift net for yellow croaker (Larimichthys polyactis) was examined in field experiments with six different net mesh size (40, 45, 50, 55, 60 and 65mm) from April to December, 2008 in the coastal areas of Jeollanam-do in Korea. The total catch of 6,748 consisted of yellow croaker (n〓6,310; 89.1% of total catch), common mackerel (n〓158; 5.6%) and other species (n〓280; 9.6%). The selectivity curve for yellow croaker was fit by the models of selectivity curve in SELECT method. The optimal mesh size for 50% retention for minimum landing size (191mm) of yellow croaker was estimated as 49.6mm- 51mm by selectivity curves. And the bi-normal model for the selectivity curve was found to fit the data best.