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    Direct conversion of carboxylic acid to olefins over Pt-loaded, oxygen-deficient alkali hexatitanate catalysts with ketonization-hydrogenation-dehydration activity
    (2021-09-01)
    Promchana, Pratya
    ;
    Boonchun, Adisak
    ;
    T-Thienprasert, Jiraroj
    ;
    Sooknoi, Tawan
    ;
    Maluangnont, Tosapol
    The production of long chain olefins from fatty acids via decarbonylation is limited by low olefins selectivity at high conversion. Here, we reported the direct acid-to-olefins conversion via the ketonization-hydrogenation-dehydration sequence at 400 °C and atmospheric 10 %H<inf>2</inf>/Ar. The oxygen vacancy defects (V<inf>O</inf>) were essential in acetic acid ketonization over the oxygen-deficient alkali hexatitanate A<inf>2</inf>Ti<inf>6</inf>O<inf>13-</inf><inf>x</inf> (A[dbnd]K, Na and Li) catalysts, as evidenced from the activity of reduced vs non-reduced catalysts. The presence of V<inf>O</inf> was deduced spectroscopically with XPS and DRUV-VIS, and the ease of V<inf>O</inf> formation was ranked via the DFT calculations. The ketonization activity was proportionated to the square of the V<inf>O</inf> content (x<sup>2</sup>), consistent with the bimolecular reaction mechanism. The Pt-loaded K<inf>2</inf>Ti<inf>6</inf>O<inf>13-</inf><inf>x</inf> enabled the direct acid-to-olefins transformation as shown by a complete conversion of two model compounds (heptanoic acid and lauric acid) with ∼30–40 % yield of long chain olefins. Heptanoic acid (C<inf>7</inf>) underwent ketonization to 7-tridecanone (a C<inf>13</inf> ketone) prior to the hydrogenation-dehydration to 7-tridecene, a C<inf>13</inf> olefin. The strong metal-support interaction (SMSI) between Pt and K<inf>2</inf>Ti<inf>6</inf>O<inf>13-</inf><inf>x</inf> inhibited further hydrogenation of the olefin to a low-value alkane. For lauric acid (C<inf>12</inf>), 12-tricosene (a C<inf>23</inf> olefin) was produced analogously. The catalytic activity and products selectivity over Pt-loaded K<inf>2</inf>Ti<inf>6</inf>O<inf>13-</inf><inf>x</inf> significantly depended on the Pt content (0–1.0 wt%). The simultaneous C[sbnd]C coupling and oxygen removal prior to the subsequent hydrogenation and dehydration is a potential approach toward the production of long chain olefins with the (2n-1) carbon atoms from C<inf>n</inf>-fatty acids.
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    Light-response characteristics of platinum doped silicon photodetector
    (2013-11-04)
    Nararug, Budsara
    ;
    Ueamanapong, Surada
    ;
    Srithanachai, Itsara
    ;
    Janprapha, Supakorn
    ;
    Suwanchatree, Ai Lada
    The purposeof this research article is present electrical characteristic of Pt-doped silicon photodetector compare with undoped silicon photodetector. The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Pt-doped detector were investigated. In this experiment, the results of Pt-doped detector show that the dark currentisobviously decreased and the photocurrent is decreased about 9 to 10 orders. Furthermore, the capacitance characteristic isslightly increased about 0.15 pF. The effects platinum on silicon indicated the carrier in silicon have been changed. © (2013) Trans Tech Publications, Switzerland.
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    Enhanced silicon bandgap by platinum diffusion for UV detector
    (2013-03-01)
    Ueamanapong, Surada
    ;
    Srithanachai, Itsara
    ;
    Atiwongsangtong, Narin
    ;
    Klunngien, Nipapan
    ;
    Poyai, Amporn
    This research article proposes a new method that enables silicon to respond to light in the UV wavelength range by doping Platinum (Pt), which is an impurity atom, into silicon. It is widely recognized that silicon semiconductor can respond to visible light. Silicon photodetector can thus detect merely the light with wavelengths of visible light and near IR. The effect of Pt on photocurrent of a metal-semiconductor-metal (MSM) photodetector was investigated. The undoped and Pt-doped silicon photodetectors in this experiment were fabricated to test the current characteristics. It was found that Pt-doped photodetectors can respond to the light wavelength of 365 nm. The energy bandgap (E<inf>g</inf>), a parameter related to the optical response of semiconductor, of Pt-doped silicon was obtained by extracting from Arrhenius plot of generation current of silicon p-n junction. The result was shown that E<inf>g</inf> of Pt-doped silicon is increased with the introduction of Pt. E<inf>g</inf> of silicon is typically 1.12 eV; however, the E<inf>g</inf> in this study is approximated at 1.7 eV. © 2013 American Scientific Publishers All rights reserved.