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Highly stable Pd2+ species anchoring on ethylenediamine-grafted-MIL-101(Cr) as a robust oxidation catalyst†
(2022-02-01)
Makmeesub, Nuttapong
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Ritvirulh, Chonlada
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Choojun, Kittisak
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Sattayaporn, Suchinda
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Resasco, Daniel E.
Highly stable Pd2+ species were anchored on ethylenediamine-grafted MIL-101(Cr). Ethylenediamine (0.3-1.2 mmol g−1) was first grafted onto MIL-101(Cr), then Pd2+ (0.03-0.2 mmol Pd per g) was incorporated by double-solvent adsorption. Fourier transform infrared, inductively coupled plasma-optical emission spectroscopy, transmission electron microscopy and CHN analysis confirmed the incorporation of ethylenediamine and Pd2+ in MIL-101(Cr). X-ray photoelectron and Raman spectroscopy suggested that one amino moiety of ethylenediamine coordinated with the Cr3+ nodes of MIL-101(Cr). The other served as an anchoring site for the incorporated Pd2+ species. In situ X-ray absorption near-edge structure analysis showed that the strong interaction between Pd2+ and ethylenediamine, within the confinement of the MIL-101(Cr) structure, effectively prevented reduction to Pd0, even in the presence of H<inf>2</inf> at 150 °C. At relatively low temperatures, the catalysts with ethylenediamine : Pd2+ molar ratios of 10 provided a higher activity for styrene oxidation (TOF ∼30 h−1), as compared to previous reports. The presence of ethylenediamine as an anchoring ligand also inhibited the reduction of Pd2+ by the feed (styrene) and minimized leaching of the active Pd2+ species under oxidizing and acidic conditions. The Pd2+ species anchoring on ethylenediamine-grafted-MIL-101(Cr) exhibited an improved catalytic activity and stability, as compared to typical liquid-phase oxidation catalysts.
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Reversible Hydrogenation-Dehydrogenation of Acetylpyridine-Pd-MIL-101(Cr) for Chemical Hydrogen Storage
(2020-10-07)
Makmeesub, Nuttapong
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Ritvirulh, Chonlada
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Choojun, Kittisak
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Chen, Teng Hao
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Poo-Arporn, Yingyot
3-Acetylpyridine (AcP), as an organic hydrogen carrier, and Pd nanoparticles, as a catalyst, were incorporated into MIL-101(Cr) for chemical hydrogen storage. AcP was first grafted into MIL-101(Cr), and then Pd (0.5-4.0 wt %) was encapsulated by a double-solvent adsorption process. Thermogravimetric analysis, inductively coupled plasma-optical emission spectrometry, X-ray photoelectron spectroscopy, transmission electron microscopy, in situ X-ray adsorption near-edge structure analysis, 1H nuclear magnetic resonance (NMR), and elemental analysis suggested the existence of AcP and Pd nanoparticles (NPs) inside the MIL-101(Cr) cages. The chemical hydrogen storage of samples was evaluated by H2 temperature-programmed reaction. In situ Fourier transform infrared and 1H NMR techniques verified the hydrogenated and dehydrogenated forms of AcP upon hydrogen uptake. Reversible hydrogenation/dehydrogenation can be readily regulated by H2 partial pressure and temperature. The chemical hydrogen storage could be accomplished only when AcP and Pd NPs were adjacently present. The chemical hydrogen storage was enhanced with an increased Pd loading up to 0.33 mmol H2·g-1 per cycle. With the manipulation of hydrogenation and dehydrogenation temperatures at 150 °C, the chemical hydrogen storage can be maintained for up to 10 cycles. The material reported herein is one of the noncryogenic chemical hydrogen storages that can be operated at constant temperature and atmospheric pressure.
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Effect of extra-framework cesium on the deoxygenation of methylester over CsNaX zeolites
(2011-12-15)
Danuthai, Tanate
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Sooknoi, Tawan
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Jongpatiwut, Siriporn
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Rirksomboon, Thirasak
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Osuwan, Somchai
The deoxygenation of methyl octanoate has been investigated over Cs-containing NaX zeolite catalysts at atmospheric pressure with He carrier gas and methanol as a co-feed. By varying the preparation procedures, different amounts of extra-framework Cs were left on the catalyst. The presence of extra-framework Cs affects the acid-basic characteristics of the catalysts and consequently their activity, stability, and particularly the product selectivity. That is, when the amount of extra-framework Cs increases, the corresponding increase in basicity enhances decarbonylation activity as well as catalyst stability. In this case, the deoxygenation of methyl octanoate on CsNaX catalysts was found to yield heptenes and hexenes as main products via surface decomposition of octanoate-like species. When the amount of extra-framework Cs was reduced, the hexene yield readily increased. The enhancement in hexene production can be ascribed to both, a decreased basicity that reduces decarbonylation and to a greater space available within the zeolite cavity for formation of a rather bulky cyclic-like intermediate that leads to hexene. In addition, weakly acidic sites, generated after the excess Cs was removed, resulted in relatively higher yield of inner-olefin product. When Cs was not present in the catalyst (i.e., NaX), other products such as aromatics and coupling compounds were observed. These compounds are less desirable for transportation fuel applications. © 2011 Elsevier B.V. All rights reserved.
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Conversion of 1-tetralone over HY zeolite: An indicator of the extent of hydrogen transfer
(2010-12-01)
Prasomsri, Teerawit
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Galiasso Tailleur, Roberto E.
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Alvarez, Walter E.
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Sooknoi, Tawan
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Resasco, Daniel E.
The conversion of pure 1-tetralone and its mixtures with n-decane, decalin, tetralin, or 1,5-dimethyl tetralin (DMT) has been investigated over HY zeolite. The dominant reactions undergone by 1-tetralone are the dehydrogenation to 1-naphthol and the subsequent isomerization to 2-naphthol. In the presence of hydrocarbons, the hydrogen transfer/dehydration of naphthols is accelerated, and naphthalene is formed in different amounts, depending on the nature of the co-fed hydrocarbon. In this contribution, it is demonstrated how the product distribution from the tetralone conversion can be used as an indicator of the hydrogen transfer ability of a particular hydrocarbon, or mixture of hydrocarbons. The relative order of hydrogen transfer ability of the various hydrogen donating compounds, as inferred from the naphthalene-to-naphthol product ratio, is DMT > tetralin ≈ decalin > n-decane. This trend agrees well with the hydride dissociation energy of individual donors calculated by DFT. © 2010 Elsevier B.V. All rights reserved.
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Condensation reactions of propanal over CexZr 1-xO2 mixed oxide catalysts
(2010-09-15)
Gangadharan, Anirudhan
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Shen, Min
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Sooknoi, Tawan
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Resasco, Daniel E.
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Mallinson, Richard G.
Vapor phase condensation reactions of propanal were investigated over Ce<inf>x</inf>Zr<inf>1-x</inf>O<inf>2</inf> mixed oxides as a model reaction to produce gasoline range molecules from short aldehydes found in bio-oil mixtures. Several operating parameters were investigated. These included the type of carrier gas used (H<inf>2</inf> or He) and the incorporation of acids and water in the feed. Propanal is converted to higher carbon chain oxygenates on Ce <inf>x</inf>Zr<inf>1-x</inf>O<inf>2</inf> by two pathways, aldol condensation and ketonization. The major products of these condensation reactions include 3-pentanone, 2-methyl-2-pentenal, 2-methylpentanal, 3-heptanone and 4-methyl-3-heptanone. It is proposed that the primary intermediate for the ketonization path is a surface carboxylate. The presence of acids in the feed inhibits the aldol condensation pathway by competitive adsorption that reduces the aldehyde conversion. Water also promotes ketonization and inhibits aldol condensation by increasing the concentration of surface hydroxyl groups that enhance the formation of surface carboxylates with the aldehyde. Hydrogen enhances cracking and production of light oxygenates and hydrocarbons. The light oxygenates may in turn be reincorporated into the reaction path, giving secondary products. However, the hydrocarbons do not react further. Analysis of the fresh and spent catalysts by XPS showed varying degrees of reduction of the oxide under different operating conditions that were consistent with the reaction results. Changing the proportion of the parent oxides showed that increased Zr favored formation of aldol products while increased Ce favored ketonization. This occurs by shifting the balance of the acid-base properties of the active sites. © 2010 Elsevier B.V.
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A comparison of the reactivities of propanal and propylene on HZSM-5
(2010-05-04)
Hoang, Trung Q.
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Zhu, Xinli
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Sooknoi, Tawan
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Resasco, Daniel E.
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Mallinson, Richard G.
The reactivities of propanal and propylene have been compared over HSZM-5 zeolites (Si/Al = 45 and 25). Propanal is found to be much more reactive than propylene and to form mostly 2-methyl-2-pentenal and C<inf>9</inf> aromatics as early products in the reaction network. Propylene, in contrast, requires more severe conditions to form C<inf>6</inf> and C<inf>7</inf> aromatics. It is proposed that propanal undergoes acid-catalyzed aldol condensation to form 2-methyl-2-pentenal. This dimer undergoes further condensation to form the aldol trimer, which subsequently dehydrates and cyclizes into C<inf>9</inf> aromatics. In contrast, it is well known that propylene, like other olefins, undergoes aromatization via oligomerization and formation of a hydrocarbon pool. While in the conversion of propanal, propylene is also produced, it appears that it does not play a major role in the formation of aromatics under conditions of shorter space times and lower temperatures, at which propanal produces aromatics in significant amounts. © 2010 Elsevier Inc. All rights reserved.
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Conversion of 1- and 2-tetralone over HY zeolite
(2010-04-01)
Prasomsri, Teerawit
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Galiasso Tailleur, Roberto E.
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Alvarez, Walter E.
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Sooknoi, Tawan
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Resasco, Daniel E.
Conversion of 1- and 2-tetralone was investigated over acid HY zeolite under various reaction conditions in the vapor phase. Reactions were conducted in a fixed-bed reactor at 300, 400 and 500 °C in hydrogen atmospheric pressure. It was found that 1- and 2-tetralone are thermally unstable and thermal reaction has a contribution, particularly at high temperatures. The reactivity of 2-tetralone was significantly higher than that of 1-tetralone. This behavior is more pronounced in the presence of acid HY zeolite. For both isomers, the main products were naphthol, coupling compounds (4-ring), naphthalene and tetralin. Trace amounts of dihydronaphthalene, ring-contraction and ring-opening product were also observed. At high temperatures, isomerization and dehydration of naphthol were observed over the HY zeolite. It seems that on the acidic zeolite, hydrogen transfer plays a significant role in determining the reaction path. © 2010 Springer Science+Business Media, LLC.
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Conversion of propylene and propanal on HZSM-5
(2009-12-01)
Hoang, Trung Q.
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Zhu, Xinli
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Sooknoi, Tawan
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Resasco, Daniel E.
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Lobban, Lance L.
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Etherification of 2-methyl-pentanal on supported palladium
(2009-12-01)
Pham, Trung T.
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Crossley, Steven P.
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Sooknoi, Tawan
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Lobban, Lance L.
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Resasco, Daniel E.
Dialkyl ethers can be selectively produced from etherification of 2-methyl-pentanal and other oxygenates on supported Pd catalysts. Selectivities of 90% of ether were observed when feeding 2-methyl-pentanal and 2-methyl-pentanol at a molar ratio 1:1. Yields of up to 79 % have also been achieved. The reaction appears to be sensitive to metal particle features and molar feed ratios.
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Catalytic deoxygenation of benzaldehyde over gallium-modified ZSM-5 zeolite
(2009-11-15)
Ausavasukhi, Artit
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Sooknoi, Tawan
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Resasco, Daniel E.
The deoxygenation of benzaldehyde has been investigated over gallium-modified ZSM-5 catalysts. In the absence of H<inf>2</inf>, Ga/HZSM-5 catalyzes benzaldehyde decarbonylation resulting in benzene and CO. The active sites for this reaction are the strong Brønsted acid sites. In the presence of H<inf>2</inf>, the main product is toluene. It is believed that Ga cationic species (Ga+ / GaH<inf>2</inf>+) generated during H<inf>2</inf> reduction can promote the hydrogenation/hydrogenolysis reactions that give toluene and water. In the absence of H<inf>2</inf>, toluene can only be observed in transient experiments when the Ga/HZSM-5 catalysts are reduced. It is suggested that the GaH<inf>2</inf>+ species generated under H<inf>2</inf> play an important role in the hydrogenation/hydrogenolysis. However, they readily decompose to Ga+ in the absence of H<inf>2</inf>. The addition of water to the feed modifies the catalytic activity and selectivity of Ga/HZSM-5 catalysts. On the one hand, water generates additional Brønsted acid sites from the reaction of extra-framework Ga with chemisorbed water (GaO(OH)) and with defect hydroxyls of the zeolite framework (GaOHSi). These additional sites enhance the production of benzene but decrease the production of toluene, due to a decrease in the density of reduced Ga cationic species. © 2009 Elsevier Inc. All rights reserved.

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