Mesopore expansion of surfactant-directed nanomorphic zeolites with trimethylbenzene

Jo, C.,Jung, J.,Ryoo, R. Elsevier 2014 Microporous and mesoporous materials Vol.194 No.-

The synthesis of zeolite using multiammonium surfactants as the hierarchical structure-directing agent has been investigated with a particular focus on mesopore expansion by trimethylbenzene (TMB) addition during the synthesis of nanosponge beta, MTW and MRE zeolites. The results showed that mesopore diameters of these zeolites could be increased according to the amount of TMB added to the zeolite synthesis reaction mixture but only when the Na<SUP>+</SUP> content was sufficiently high. The expansion was reversed when the synthesis mixture was reheated following TMB removal by solvent extraction. The thickness of the mesopore walls did not change during the consecutive pore expansion and shrinking processes. A transmission electron microscopic investigation revealed that the process is likely occurring through recrystallization of the zeolite frameworks, as promoted by Na<SUP>+</SUP>. The mesopore diameter of the nanosponge beta zeolite could be increased to 15nm using this method. This zeolite exhibited four times the adsorption capacity for lysozyme (molecular dimension: 2.0x2.5x4.3nm<SUP>3</SUP>) at 298K, compared to the TMB-untreated zeolite, which possessed 3.8nm mesopores.

Crosslinked enzyme aggregates in hierarchically-ordered mesoporous silica: A simple and effective method for enzyme stabilization

Kim, Moon Il,Kim, Jungbae,Lee, Jinwoo,Jia, Hongfei,Na, Hyon Bin,Youn, Jong Kyu,Kwak, Ja Hun,Dohnalkova, Alice,Grate, Jay W.,Wang, Ping,Hyeon, Taeghwan,Park, Hyun Gyu,Chang, Ho Nam Wiley Subscription Services, Inc., A Wiley Company 2007 Biotechnology and bioengineering Vol.96 No.2

<P>α-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of α-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for 2 weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity. Biotechnol. Bioeng. 2007;96: 210–218. © 2006 Wiley Periodicals, Inc.</P>

HZSM5 Assisted Upgradation of Kraft Lignin Derived Bio-oil

( Ashutosh Agarwal ),( Masud Rana ),( Seong-jae Park ),( Jeong-hun Park ) 한국폐기물자원순환학회(구 한국폐기물학회) 2019 ISSE 초록집 Vol.2019 No.-

Hierarchical and non-hierarchical mono and bimetallic Ni and/or Zn-HZSM5 catalysts were synthesized and compared for upgrading of Kraft lignin derived liquefaction bio-oil in a batch reactor at 300 ℃ for 1h under H2 atmosphere in supercritical ethanol. N₂ adsorption-desorption isotherms, FE-SEM, XPS, ICP-OES and XRD techniques were used to characterize the synthesized catalysts. HZSM5 crystalline structure was not significantly influenced by the incorporation of Ni and Zn. GC-MS and elemental analysis were used to analyze the upgraded bio-oils. After bio-oil upgrading, the amounts of 4-ethylguaiacol and 4- propylguaiacol increased considerably because of reduction in the amounts of unsubstituted guaiacol, 4-methylguaiacol, 4- propenylguaiacol and homovanillic acid. Hydrogenation, alkylation and deoxygenation were the prominent reaction mechanisms responsible for bio-oil upgrading. Highest HHV_Boie (~29.93 MJ/Kg) was obtained for non-hierarchical 15Ni5Zn-HZSM5 and hierarchical 20Zn-HZSM5 catalysts. Hierarchical and non-hierarchical catalysts favored hydrogenation and deoxygenation, respectively.

Tunable synthesis of hierarchical mesoporous silica via porogen-carrying organosilicates

Cho, W.,Lee, H.I.,Shim, B.S.,Cha, B.J.,Kim, J.M.,Char, K. Elsevier 2017 Microporous and mesoporous materials Vol.239 No.-

We describe the synthesis and characterization of hierarchically porous organic-inorganic hybrid silica with periodic 2-D hexagonal order and tunable location of secondary nanopores through co-condensation of tetraethylorthosilicate (TEOS) and a new type of amphiphilic organosilicate precursors. Our amphiphilic organosilicates offer unique tunability of secondary micropores by carefully controlled bond molecular structure and number of bonds between hydrophobic adamantylphenols pore-generating moieties and siloxane precursors. Small angle X-ray scattering (SAXS) and microscopy results show a good structural order of the organic-inorganic hybrid silica. In addition, <SUP>29</SUP>Si CP-MAS NMR spectra confirm the successful incorporation of organosilicate precursors into a silica framework. The primary cylindrical mesopores (~6.4 nm) were originated from the cooperative self-assembly of Pluronic P123 triblock copolymer templates while smaller meso-/micropores were derived from adamantylphenols groups. We have previously demonstrated that adam-graft SQ had an affinity for hydrophobic PO core blocks to be located close to PO segment, which resulted in small pores next to primary mesopores and the resultant increment of mesopore size as well as wrinkled silica walls. On the contrary, the secondary small pores were mainly generated within a silica network while the size of the primary mesopores unaffected with the addition of adam-bridge SQ due to its selective incorporation into a silica framework. Moreover, the organic-inorganic hybrid silica prepared with adam-bridge SQ showed higher thermal stability than that of adam-graft SQ and SBA-15 type mesoporous silica. It is attributed to more Si?O?Si bonds formed from the bridged structure as well as enhanced hydrogen-bonding interaction between adam-bridge SQ hybrid silica and P123 templates.

Dry-gel synthesis of mesoporous MFI zeolite nanosponges using a structure-directing surfactant

Han, Seung Won,Kim, Jaeheon,Ryoo, Ryong Elsevier 2017 Microporous and mesoporous materials Vol.240 No.-

<P><B>Abstract</B></P> <P>The synthesis of mesoporous MFI zeolite nanosponges was investigated in a dry-gel conversion process using C<SUB>18</SUB>H<SUB>37</SUB> N<SUP>+</SUP>(CH<SUB>3</SUB>)<SUB>2</SUB> C<SUB>6</SUB>H<SUB>12</SUB> N<SUP>+</SUP>(CH<SUB>3</SUB>)<SUB>2</SUB> C<SUB>4</SUB>H<SUB>9</SUB> as a micropore-mesopore hierarchical structure-directing surfactant. The initial synthesis mixture was converted at 333 K to a mesoporous material exhibiting a structure similar to that of MCM-41. The mesoporous material was filtered, dried at 373 K, and subsequently heated at 423 K in an autoclave with controlled humidity. In this process, precise control of the relative chamber humidity and the pH of the precursor gel was necessary to achieve full crystallization of the zeolite. The final product was composed of three-dimensional networks of 2.5-nm thick MFI nanolayers and exhibited a high surface area and narrow distribution of mesopore diameters centered at 4 nm. The zeolite crystallization behavior at 423 K was investigated after various heating times with X-ray diffraction, gas adsorption, and electron microscopy. The results indicated that under controlled humidity, crystallization took place through a pseudomorphic transformation, where the initial gel morphology was maintained throughout. The overall quality of the dry-gel product was similar to that of a conventional hydrothermal product. The Si/Al ratios of the zeolite could be controlled over the range of 50 ∼ ∞. Furthermore, in a 100-g synthesis batch, the dry-gel method had the advantage of compact autoclave size for large-scale synthesis.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mesoporous MFI zeolite nanosponges were synthesized by dry-gel conversion at relative chamber humidity above 80%. </LI> <LI> At 80% humidity, zeolite formation took place through a pseudomorphic transformation. </LI> <LI> The dry-gel synthesis allowed significant reduction of autoclave volume and pressure. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Investigation on the morphology of hierarchical mesoporous ZSM-5 zeolite prepared by the CO2-in-water microemulsion method

Chunlei Wang,Juntao Yan,Jianfen Li,Jianmin Sun 한국화학공학회 2014 Korean Journal of Chemical Engineering Vol.31 No.9

A series of hierarchical mesoporous ZSM-5 zeolites with different morphology were successfully syn-thesized by the CO2-in-water microemulsion method, and mesoporosity was formed without organotemplate. The dif-ferent synthesis conditions, including silica alumina molar ratio, stirring time and compressed CO2 pressure, were sys-tematically investigated to discuss the influence of these conditions on the morphology of ZSM-5 zeolite. The resultingsamples were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), inductively coupledplasma (ICP) and nitrogen adsorption-desorption measurement. XRD results indicated that compressed CO2 route forthe synthesis of MFI zeolites had a fast crystallization rate and good crystallinity. SEM images showed that the ZSM-5hierarchical mesoporous ZSM-5 zeolite had a uniform chain-like crystal morphology, whereas silicalite-1 displayed amonodisperse crystal morphology. In addition, the nitrogen adsorption-desorption measurement provided sufficientevidence for the presence of hierarchical mesopores in ZSM-5 zeolite.

Hierarchical faujasite zeolite-supported heteropoly acid catalyst for acetalization of crude-glycerol to fuel additives

Amin Talebian-Kiakalaieh,Sara Tarighi 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.79 No.-

Glycerol acetalization in the presence of aldehydes/ketals and acid catalysts leads to production of fueladditives,which could improve clean fuel ignition, promote combustion process, and reduce fuel gellingin the engine. In this study, hierarchical faujasite zeolite-supported heteropoly acid catalysts (HR/Y) wereprepared followed by impregnation of 10, 20 and 30 wt% phosphotungstic acid (HPW). The synthesizedcatalysts (HR/Y-Wx) were characterized using XRD, FTIR, FESEM, EDX, TEM, NH3-TPD and N2physisorption analyses. The impregnated hierarchical zeolites along with NaY zeolite were used ascatalysts in crude-glycerol acetalization to produce a fuel additive, 4-hydroxymethyl-2,2-dimethyl-1,3-dioxolane (solketal). The catalysts possessed high thermal stability, large specific surface area, large porediameter (mesoporous structure) and strong acidic sites. The highest solketal yield of 97.85% at 100%crude-glycerol conversion was obtained over the HR/Y-W20 catalyst. Optimization studies revealed thatthe best solketal yield of 97.87% at complete reaction conversion could be achieved at 40 C with 10 wt%catalyst weight and 10/1 MR of AC/Gl in 2 h. The synthesized catalyst even maintained its activity after 30h reaction time due to its mesoporous structure and strong acidity. The impact of real impurities (e.g. water, methanol, and NaCl) on catalyst activity was evaluated and the results revealed that crude-glycerolacetalization over HR/Y-W20 acid catalyst was promising for solketal production with >86% solketal yieldat >97% glycerol conversion in the presence of high concentrations of impurities (15 wt% water, 10 wt%methanol, and 15 wt% NaCl). Results confirmed that the prepared HR/Y-W20 catalyst can be a potentialcandidate for future large scale research and development.

Hierarchical K/LTL zeolites: Synthesis by alkali treatment, characterization and catalytic performance in Knoevenagel condensation reaction

Nilesh P. Tangale,Shilpa K. Sonar,Prashant S. Niphadkar,Praphulla N. Joshi 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.40 No.-

The hierarchical K/LTL zeolites prepared by post-synthesis modification with aqueous 1.5 M KOHsolution by varying alkali volume to K/LTL zeolite (10–70 ml/g) ratios, were examined in Knoevenagelcondensation. The physico-chemical properties of the catalysts were thoroughly evaluated by PXRD,FTIR, ICP, CO2-TPD, XPS, N2 adsorption/desorption and 29Si and 27Al MAS-NMR. Among all the samples,hierarchical K/LTL prepared by treating K/LTL with 50 ml aqueous 1.5 M KOH solution per gram of K/LTLdisplayed about 1.5 fold higher catalytic activity as compared to parent K/LTL, presumably because ofcombined effect of enhanced basicity and molecular diffusion through pore channels.

Synthesis of hierarchical MFI zeolite and its methanol to hydrocarbon reactions

김진성,최정규 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

By using a structure directing agent of tetra-n-butylphosphonium hydroxide, two type MFI catalysts (Si/Al: ∼30) with different mesoporosity were synthesized. The resulting ZSM-5 catalysts were formed via the interconnection of very thin lamellae; (1) high mesoporosity (H_30) and (2) low mesoporosity (L_30). From pyridine-based acid titration results, we could reveal that internal Brønsted acid sites of H_30 and C_75 (commercial ZSM-5 with Si/Al: ~75) were similar, but H_30 has a large amount of external Brønsted acid sites. The methanol to hydrocarbons (MTH) reaction performance demonstrates that H_30 preferred to produce propene over ethene compared to C_75, while L_30 showed a very poor MTH performance. Further, H_30 has very short diffusional length then C_75. Accordingly, H_30 allowed for achieving the ratio of propene to ethene as high as ∼9.1. And moreover, when ceria was doped at H_30, the stability for the MTH reaction and a propene to ethene ratio were improved much more.

Porous Silica Particles As Chromatographic Separation Media: A Review

정원조 대한화학회 2014 Bulletin of the Korean Chemical Society Vol.35 No.12

Porous silica particles are the most prevailing raw material for stationary phases of liquid chromatography. During a long period of time, various methodologies for production of porous silica particles have been proposed, such as crashing and sieving of xerogel, traditional dry or wet process preparation of conventional spherical particles, preparation of hierarchical mesoporous particles by template-mediated pore formation, repeated formation of a thin layer of porous silica upon nonporous silica core (core-shell particles), and formation of specific silica monolith followed by grinding and calcination. Recent developments and applications of useful porous silica particles will be covered in this review. Discussion on sub-3 μm silica particles including nonporous silica particles, carbon or metal oxide clad silica particles, and molecularly imprinted silica particles, will also be included. Next, the individual preparation methods and their feasibilities will be collectively and critically compared and evaluated, being followed by conclusive remarks and future perspectives.