GOVPH

 

Marlon T. Conato

Sex: Male

Education: 

University of Houston, Doctor of Philosophy (Ph.D), 2012

Field of Specialization

Organic Chemistry 

Analytical Chemistry

Mass Spectrometry

Nanotechnology

Gas Chromatography

UV/Vis Spectroscopy

Researches:

Article title: Synthesis and characterization of mordenite-type zeolites via hydrothermal method using silica gel and sodium aluminate as Si and Al sources at varying temperature

Authors: Mon Bryan Zambale Gili, Marlon T. Conato

Publication title: Journal of Physics Conference Series 1191:012038, March 2019

Abstract:

Mordenite-type zeolites were prepared via hydrothermal method using silica gel and sodium aluminate as Si and Al sources respectively. The temperature was varied from 150 °C up to 190 °C to determine the minimum temperature to obtain crystalline mordenite using a 23 mL Teflon-lined stainless-steel autoclave. The samples were characterized using XRD, FTIR and SEM. With the given experimental conditions, mordenite-type zeolites with good crystallinity and excellent purity were produced at 190 °C. Amorphous materials with notable peaks that correspond to mordenite planes were produced at 170 °C. The sample produced at 150°C was completely amorphous. FTIR revealed that all the three samples contain bands associated to aluminosilicate vibrational groups. However, a significant decrease in the intensities of vibration bands associated to hydroxyl (HO⁻) stretching and water bending were observed as the temperature is decreased. From the SEM, the sample treated at 190°C was composed of particles with strikingly linear edges having an average grain size of ~38.0 µm. Most particles are hexagonal in shape. Particle components of the samples synthesized at 170 °C and 150 °C have irregular sizes and shapes.

 

Article title: Adsorption uptake of Philippine natural zeolite for Zn 2+ ions in aqueous solution

Authors: Mon Bryan Zambale Gili, L. Olegario-Sanchez, Marlon T. Conato

Publication title: Journal of Physics Conference Series 1191-:012042, March 2019

 

Abstract:

The Philippine natural zeolite (PNZ) was characterized and subjected to Zn²⁺ adsorption tests in aqueous solutions to determine its adsorption uptake and to understand its adsorption behaviour. The PNZ was characterized using XRD, SEM, BET-analysis and TG-DTA. XRD showed significant peaks indexed to natural mordenite-type zeolite along with other natural zeolites and minerals. SEM micrographs revealed a rough and corrugated surface morphology of the sample. BET physisorption analysis showed a surface area of 222.63 m²/g. From the analytical tests report given by the supplier, the Si/Al ratio (SAR) was computed to be equal to 4.29 based on the silica and alumina content of the PNZ. Adsorption kinetic and thermodynamic studies were done to determine the adsorption mechanism and adsorption capacity of PNZ for Zn²⁺ ions in aqueous solution. From the adsorption kinetic curve, the PNZ attained chemical equilibrium after 50 min. Pseudo-second-order kinetic model was the most applicable kinetic model providing the highest correlation with the data. Langmuir model better described the adsorption isotherm of the PNZ than Freundlich model. The theoretical maximum cation exchange capacity of PNZ was computed as 27.17 mg Zn²⁺/g according to the Langmuir model.

 

Article title: Facile Fabrication of a Potential Slow-Release Fertilizer Based on Oxalate-Phosphate-Amine Metal-Organic Frameworks (OPA-MOFs)

Authors: Ken Aldren Sumaya Usman, Salvador Buenviaje, Yasmin Edañol, Marlon T. Conato, et al.

Publication title: Materials Science Forum 936:14-19, October 2018

 

Abstract:

 

This work demonstrates a simple, reproducible and scalable method of producing a potential slow-release fertilizer material. In this study, oxalate-phosphate-amine metal organic frameworks (OPA-MOFs) powder was synthesized from the hydrothermal treatment of ferric chloride (FeCl 3 •6H 2 O), orthophosphoric acid (H 3 PO 4), oxalic acid dihydrate (H 2 C 2 O 4 •2H 2 O), and a common fertilizer, urea (CO(NH 2) 2). Being a structure directing agent (SDA)-type of MOF, the material is expected to slowly release urea via cation exchange, and eventually trigger the collapse of the framework, thus resulting to the subsequent release of the phosphates and iron-oxalate complexes. Elemental analysis revealed that the synthesized samples contains a promising amount of incorporated nitrogen and phosphorus. In this particular study, increasing in the amount of urea during the synthesis however revealed minimal change in the %N in the final product which tells us that maximum loading has already been achieved. P and N release experiments shall still be done both in vitro and in actual soil samples to monitor the release delivery kinetics and efficiency of the OPA-MOFs for fertilizer release applications.

Full text available by request to the author

 

Article title: Organic-Free Synthesis of a Highly Siliceous Faujasite Zeolite with Spatially-Biased Q 4 ( n Al) Si Speciation

Authors: Matthew D. Oleksiak, Koki Muraoka, Ming-Feng Hsieh, Marlon T. Conato, et al.

Publication title: Angewandte Chemie International Edition 129(43), September 2017

 

Abstract:  

Designing zeolites with tunable composition and acid siting is a significant challenge for applications in adsorption and catalysis. In their Communication (DOI: 10.1002/anie.201702672), W. Chaikittisilp, J. D. Rimer, and co-workers report on the synthesis of high-silica faujasite (HOU-3) with a Si/Al ratio of 3 and show that the Al locations within the structure are biased and not random.

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Article title: Oxidative Coupling of Methane over Mixed Metal Oxide Catalysts: Steady State Multiplicity and Catalyst Durability

Authors: Geofrey Goldwin Jeba, Marlon T. Conato. Jeffrey D. Rimer, Michael P. Harold

Publication title: Chemical Engineering Journal 331, August 2017

 

Abstract:

Exothermic heat effects are a crucial factor in determining the performance and stability of catalysts for the oxidative coupling of methane (OCM). Fixed bed temperature rise, steady state multiplicity, and catalyst durability are investigated over a range of feed conditions for the mixed metal oxides Cs/Sr/MgO, Cs/Ba/MgO, Cs/Sr/La2O3, and Na2WO4-Mn/SiO2. A comparison with previous studies on doped metal oxides catalysts for OCM clearly indicates that doping not only improves the performance but also significantly improves the catalyst stability. We experimentally demonstrate for the first time hysteresis behavior for Cs/Sr/La2O3 powder catalyst. Our results show that the catalyst stability depends on the magnitude of temperature rise in the catalyst bed. At a lower space velocity of 3,600 cc/h/g, the catalysts exhibit moderate temperature rise (<50 °C) at complete O2 conversion and sustained activity for extended time-on-stream (50–72 h). The performance of Cs/Sr/MgO and Cs/Ba/MgO are comparable to Na2WO4-Mn/SiO2 (∼19% C2+ yield). While Cs/Sr/La2O3 activates at lower temperature, its maximum C2+ yield (∼14%) is lower. At a higher space velocity of 14,400 cc/h/g, a significant temperature rise of ∼300 °C and ignition-extinction behavior is encountered. Under these demanding conditions, improved OCM performance is observed for Na2WO4-Mn/SiO2 (35% methane conversion, C2+ selectivity 60%) but the catalyst deactivates due to the high bed temperature (930 °C). In comparison, methane conversion of ∼25% and C2+ selectivity of ∼38% is observed for Cs/Sr/La2O3 at a feed temperature of 395 °C. Despite a bed temperature of 830 °C, the Cs/Sr/La2O3 catalyst is stable for 50 h. The findings show the importance of heat effects in both promoting OCM catalyst performance and leading to deleterious catalyst deactivation.

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Article title: Synthesis Strategies for Ultrastable Zeolite GIS Polymorphs as Sorbents for Selective Separations

Authors: Matthew D. Oleksiak, Arian Ghorbanpour, Marlon T. Conato, B. Peter McGrail, et al.

Publication title: Chemistry- A European Journal 22(45), October 2016

 

Abstract: 

New approaches to tailor the synthesis of zeolite polymorphs can lead to breakthroughs in applications spanning from separations to adsorption. A comparison of small-pore zeolite GIS polymorphs P1 and P2 revealed marked differences in their thermal stability. Moreover, adsorption experiments and DFT studies collectively showed that GIS polymorphs are promising materials for selective separation of small molecules.

 

Article title: Nucleation of FAU and LTA Zeolites from Heterogeneous Aluminosilicate Precursors

Authors: Matthew D. Oleksiak, Jennifer Soltis, Marlon T. Conato, R. Lee Penn, Jeffrey D. Rimer

Publication title: Chemistry of materials 28(14), June 2016

 

Abstract:

The nucleation of many natural, biogenic, and synthetic crystals involves the initial formation of metastable precursors that provides a kinetic pathway for an amorphous-to-crystalline transformation. This nonclassical mechanism is believed to be the dominant crystallization pathway for microporous zeolites. Despite significant research on zeolite growth mechanisms, molecular level details regarding the assembly, physicochemical properties, and structural evolution of amorphous (alumino)silicate precursors remain elusive. Here we use a combination of diffraction, scattering, and microscopy techniques to characterize the amorphous precursors that assemble and evolve during the synthesis of zeolites FAU and LTA – two materials that are widely used in commercial applications such as catalysis, adsorption, separations, and ion-exchange. Nucleation occurs by a two-step mechanism involving the initial formation of aggregates that serve as heterogeneous sites for nucleation. Using commercially-relevant colloidal silica as a reagent, we observe that precursors are comprised of heterogeneous silica and alumina domains due in part to the negligible dissolution of silica during room temperature aging. This indicates substantial Si-O-Si bond breakage must occur during hydrothermal treatment with concomitant exchange of soluble alumina species to achieve a final crystalline product with Si/Al ratio = 1.0 – 2.5. All syntheses were performed with molar compositions of Si/Al ≥ 2.0, which favors the formation of FAU; however, we observe that certain growth conditions are capable of creating a “false” environment (i.e., Al-rich regions) that favors LTA nucleation, followed by intercrystalline transformation to FAU. Time-resolved ex situ transmission electron microscopy of extracted solids during zeolite crystallization indicates that nucleation occurs on the exterior surface of precursors. This observation is consistent with our proposed hypothesis that posits exterior surfaces are more energetically favorable sites for nucleation compared to the particle interior on the basis of confinement effects. Given that numerous zeolite syntheses involve the initial formation of metastable precursors with heterogeneous composition, the pathway for nucleation proposed in this study may prove to be generalizable to other zeolite structures and related materials.

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Article title: Framework Stabilization of Si-Rich LTA Zeolite Prepared in Organic-Free Media

Authors: Marlon T. Conato, Matthew D. Oleksiak, B. Peter McGrail, Radha Kishan Motkuri, et al.

Publication title: Chemical Communications 51(2), October 2014

 

Abstract:

Zeolite HOU-2 (LTA type) is prepared with the highest silica content (Si/Al = 2.1) reported for Na-LTA zeolites without the use of an organic structure-directing agent. The rational design of Si-rich zeolites has the potential to improve their thermal stability for applications in catalysis, gas storage, and selective separations.

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Article title: Control of nucleation and crystal growth kinetics of MOF-5 on functionalized gold surfaces

Authors: Marlon T. Conato and Allan J. Jacobson

Publication title: Microporous and Mesoporous Materials 175, July 2013

 

Abstract:

 

Self-assembled monolayers (SAMs) on gold (Au) substrates have been used to prepare metal–organic framework (MOF) thin films. Both highly-oriented single crystals (∼100 μm) and dense films of zinc terephthalate (MOF-5) were grown by room-temperature pretreatment of Au-SAM substrates with Zn2+ ions to control nucleation and crystal growth in MOF-5 synthesis solutions. The particle size distribution in the film samples (1 × 104–5 × 104 μm2) was determined by image analysis of optical micrographs collected at different times during crystallization in order to study the crystal growth kinetics. An induction period of 2–3 d was observed before the onset of crystal growth. The crystal sizes saturate at a mean cross sectional area of 2.0–2.5 × 104 μm2.

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Article title: Synthesis and crystal structures of complexes based on the ligand meso-1,4-phenylenebis(hydroxyacetic acid)

Authors: Marlon T. Conato, Xiqu Wang, Allan J. Jacobson

Publication title: Inorganica Chimica Acta 401, May 2013

 

Abstract:

The syntheses and crystal structures of compounds based on the ligand 1,4-phenylenebis (hydroxyacetic acid) (H2L) are reported for the first time. Three chain structures based on H2L and divalent metal cations were synthesized and characterized and their structures determined by single-crystal X-ray diffraction. The compounds PbL (1), CoL(H2O)2·2H2O (2), and ZnL(H2O)2·2H2O (3) have similar infinite chains of metal centers bridged by 1,4-phenylenebis(hydroxyacetic acid). The coordination spheres of the transition metal ions are completed by coordinating water molecules in the isostructural compounds 2 and 3. The non-covalent secondary bonding requirement of Pb2+ in 1 and interchain hydrogen bonds in 2 and 3 lead to different packing of the chains.

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Article title: Microporous, Homochiral Structures Containing Iron Oxo-Clusters Supported by Antimony(III) Tartrate Scaffolds

Authors: Qiang Gao, Xiqu Wang, Marlon T. Conato, Tatyana Makarenko, et al.

Publication title: Crystal Growth & Design 11(10), October 2011

 

Abstract:

A chiral cluster compd., dipotassium bis-(μ-tartrato)-diantimony(III), K2Sb2L2 (H4L = L-tartaric acid), was used as a secondary building unit to react with Fe(III) perchlorate and Fe(II) sulfate in H2O and DMF in the presence of NaN(CN)2 or 4,4'-bipyridine. Three distinct homochiral structures were obtained: H3Na7[Fe4Sb6(μ4-O)6(μ3-O)2(L-tartrate)6]·14H2O (1), H5K3[Me2NH2]2[Fe7Sb6(μ4-O)6(μ3-O)2(L-tartrate)6]2·28H2O (2), and Na3K5[Me2NH2]4[Fe6Sb6(μ4-O)6(μ3-O)2(L-tartrate)6]2·30H2O (3). All of these compds. contain Fe oxo-clusters sandwiched by Sb3(μ3-O)(L-tartrate)3 SBUs. 1 Consists of isolated [Fe4Sb6(μ4-O)6(μ3-O)2(L-tartrate)6]10- clusters, which are interconnected by Na+ ions into 2-dimensional homochiral layers. The structure of 2 features [Fe7Sb6(μ4-O)6(μ3-O)2(L-tartrate)6]5- clusters. The clusters are further linked into neg. charged honeycomb layers. Both types of clusters are found in 3 and are also assembled into neg. charged honeycomb layers. The accessibility of the microporosity of 2 was demonstrated by adsorption of 2-butanol. The magnetic properties of the compds. were measured from 5 to 300 K and indicate predominantly antiferromagnetic exchange interactions. [on SciFinder(R)]

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Article title: Amine-Templated Anionic Metal-Organic Frameworks with the 4,4 '-(Hexafluoroisopropylidene) Bis(benzoic acid) Ligand

Authors: Xiqu Wang, Lumei Liu, Marlon Conato, Allan J. Jacobson

Publication title:  Crystal Growth & Design 11(6), July 2011

 

Abstract:

Three compds. with anionic metal-org. frameworks [M3(hfbba)4]2-, M = Mn2+ or Co2+, H2hfbba = 4,4'-(hexafluoroisopropylidene)bis(benzoic acid), were synthesized by solvothermal techniques in the presence of different amines. Their structures were detd. from single crystal x-ray data. All three structures are based on linear trimers of metal oxide polyhedra. (C6H11NH3)2Mn3(hfbba)4, 1, has a 3D structure with large cages that are filled by pairs of cyclohexylammonium cations. ((C4H11)2NH2)2Co3(hfbba)4, 2, has a complex layered structure with intralayer lateral channels. One half of the dibutylammonium cations are located inside the channels and are orientationally disordered, while the other half of the dibutylammonium cations are located in the interlayer spaces and are ordered. (H2tdpip)Co3(hfbba)4,3, tdpip = 4,4'-trimethylenedipiperidine, also has a layered structure with the H2tdpip cations located between the layers. The magnetic properties of all compds. were detd. from 10 to 300 K.

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Papers Presented

 

Title: Synthesis and characterization of zinc adeninate metal-organic frameworks (bioMOF1) as potential anti-inflammatory drug delivery material

Authors: Ken Aldren Sumaya Usman, Salvador Buenviaje, Joselito M. Razal, Marlon T. Conato, et al.

Conference title: AIP Conference Proceedings 1958(1), May 2018

 

Abstract:

Zn8(ad)4(BPDC)6O•2Me2NH2 (bioMOF1), a porous metal–organic framework with zinc-adeninate secondary building units (SBUs), interconnected via biphenyldicarboxylate linkers, shows great potential for drug delivery applications due to its non-toxic and biocompatible components (zinc and adenine). In this study, bioMOF1 crystals synthesized solvothermally at 130°C for 24 hours, were characterized thoroughly and loaded with a known anti-inflammatory drug, nimesulide (NIM). The crystalline nature of the material was confirmed using powder x-ray diffraction crystallography (PXRD) along with morphology assessment using focused-ion beam/field emission scanning electron microscopy (FIB/FESEM). NIM was introduced to the crystals via solvent exchange accompanied with vigorous stirring and quantified using thermogravimetric analysis (TGA) with loading saturation of ∼30% attained during the 2nd to 3rd day of drug immersion. Drug release in phosphate buffer saline and in deionized water was done to monitor the kinetic of drug release in vitro. The drug release showed a controlled discharge profile which slowed down at the 24th and 48th hour of release. Drug release in buffer showed a faster release of drug from the material, which means that the presence of cations in the solution could further trigger the release of drug. Slow drug release was observed for all of the set-ups with maximum % drug release of 24.47%, and 16.14% for the bioMOF1 in buffer and bioMOF1 in water respectively for the span of 48 hours.

 

Title: N/Fe-TiO2 doped nanoparticles loaded on bentonite for increased photocatalytic activity for the degradation of organic pollutants

Authors: Mel BryanL. Esprenilla, Ryan Carl Santos Magyaya, Marlon T. Conato

Conference title: 8th International Conference on Nanoscience and Nanotechnology 2017, May 2017

 

Abstract:

Photocatalyst materials based on Philippine bentonite-titanium oxide composites and their ability to degrade organic pollutants is reported. Nanosized-titanium dioxide (TiO2) was synthesized by sol-gel method from titanium tetraisopropoxide. This was then incorporated in the Philippine bentonite via hydrothermal methods. In order to shift the absorbance of the TiO2 to the visible region doping was done using iron and nitrogen ions. The hydrodynamic radius of the synthesized TiO2 was analyzed using a zeta-sizer and was found to be around 70 nm. The photocatalytic efficiency of the TiO2/bentonite, N-TiO2/bentonite, Fe-TiO2/bentonite and N-Fe-TiO2/bentonite was evaluated using a photocatalytic reactor. It was found out that the N-Fe-TiO2/bentonite to be the most efficient with 22% degradation of the model pollutant after 80 minutes. FT-IR analysis was done to determine the bonding of the different components. Scanning electron microscopy and atomic force microscopy analysis was also performed to characterize the products.

 

Title: Synthesis and characterization of 12-aminolauric acid-modified montmorillonite for catalytic application

Authors: Cris Angelo Manahan Pagtalunan, Florentino C. Sumera, Marlon T. Conato

Conference title: 8th International Conference on Nanoscience and Nanotechnology 2017, May 2017

 

Abstract:

The simple cation-exchange preparation of 12-aminolauric acid-modified montmorillonite (ALA-Mt), an aluminosilicate clay modified with the alkylammonium surfactant, is reported. Different loadings of 12-aminolauric acid (12-ALA) from 100 to 400 times the cation exchange capacity (CEC) in montmorillonite (Mt) was prepared and studied. Successful intercalation of the organic surfactant was monitored by the increase in basal (d001) spacing of the organoclay compared to the pure Mt. The clay mineral composite have increased surfactant loading resulting to lower degradation temperatures, rougher surface morphology, increased particle size, and increased organophilicity of the organoclay compared to the native Mt. The improved properties of ALA-Mt present it as an attractive catalyst material for polymerization reactions.

 

Title: Hydrothermal synthesis, crystal structures, and enantioselective adsorption property of bis(L-histidinato)nickel(II) monohydrate

Authors: Christian Paul L. Ramos, Marlon T. Conato

Conference title: 8th International Conference on Nanoscience and Nanotechnology 2017, May 2017

 

Abstract:

Despite the numerous researches in metal-organic frameworks (MOFs), there are only few reports on biologically important amino acids, histidine in particular, on its use as bridging ligand in the construction of open-framework architectures. In this work, hydrothermal synthesis was used to prepare a compound based on Ni²⁺ and histidine. The coordination assembly of imidazole side chain of histidine with divalent nickel ions in aqueous condition yielded purple prismatic solids. Single crystal X-ray diffraction (XRD) analysis of the product revealed structure for Ni(C6H8N3O2)2 • H2O that has a monoclinic (C2) structure with lattice parameters, a = 29.41, b = 8.27, c = 6.31 Å, β = 90.01 ˚. Circular dichroism – optical rotatory dispersion (CD-ORD), Powder X-ray diffraction (PXRD) and Fourier transform – infrared spectroscopy (FT-IR) analyses are conducted to further characterize the crystals. Enantioselective adsorption analysis using racemic mixture of 2-butanol confirmed bis(L-histidinato)nickel(II) monohydrate MOF crystal’s enantioselective property preferentially favoring the adsorption of (S)-2-butanol isomer.

 

Title: Synthesis of Zeolite Catalysts in the Absence of Organic Structure-Directing Agents

Authors: Matthew D. Oleksiak, Marlon Conato, Jeffrey D. Rimer

Conference title: AlChe Annual Meeting, November 2014

 

Title:Reaction Studies on Na2WO4-Mn/SiO2 Catalyst : Oxidative Coupling of Methane

Authors: Fnu Aseem, Geofrey Goldwin, Marlon T. Conato, Jeffrey D. Rimer , Michael P. Harold, Ken Blackmon

Conference title: AlChe Annual Meeting, November 2014

 

Title: Controlling Polymorphism in Organic-Free Syntheses of Zeolites

Authors: Matthew D. Oleksiak, Marlon T. Conato, Jeffrey D.  Rimer

Conference title: AlChe Annual Meeting, November 2014