TY - JOUR T1 - Preparation of Cubic Pt Nanoparticles deposited on Alumina and their Application to Propene Hydrogenation JF - Chemcatchem Y1 - 2010 A1 - El-Sayed, Mostafa A A1 - Yoo, J. W. VL - 2 SN - 1867-3880 N1 - El-Sayed, Mostafa A. Yoo, Jung Whan M3 - 10.1002/cctc.200900247 ER - TY - JOUR T1 - Propylene hydrogenation over cubic Pt nanoparticles deposited on alumina JF - BULLETIN-KOREAN CHEMICAL SOCIETY Y1 - 2004 A1 - Yoo, J. W. A1 - Lee, S.M. A1 - Kim, H.T. A1 - El-Sayed, Mostafa A AB - Pt nanoparticles loaded on alumina through an impregnation at room temperature was prepared using K2PtCl4 and acrylic acid as capping material. Transmission electron microscopy showed that the deposited Pt particles indicate ca. 80% cubic shapes with a narrow distribution of 8-10 nm in size. Propylene hydrogenation over the catalyst has been carried out to evaluate their catalytic performance by the values of activation energy. It is determined from the initial rate, reaction order, and rate constant and is found to be 9.7 ± 0.5 kcal/mol. This value has been discussed by comparing to those of encapsulated- and truncated octahedral Pt nanoparticles deposited on alumina, respectively, to study influence of the particle size and shape, and capping material used on the activation energy. PB - Korean Chemical Society VL - 25 SN - 0253-2964 UR - http://www.journal.kcsnet.or.kr/main/j_search/j_abstract_view.htm?code=B040616&qpage=j_search&spage=b_bkcs&dpage=ar CP - 6 ER - TY - JOUR T1 - Shape control of platinum nanoparticles by using different capping organic materials JF - BULLETIN-KOREAN CHEMICAL SOCIETY Y1 - 2004 A1 - Yoo, J. W. A1 - Lee, S.M. A1 - Kim, H.T. A1 - El-Sayed, Mostafa A KW - Cube KW - Nanoparticle KW - Platinum KW - Transmission electron microscopy KW - Truncated octahedra AB - No Abstract VL - 25 UR - http://newjournal.kcsnet.or.kr/main/j_search/j_abstract_view.htm?code=B040315&qpage=j_search&spage=b_bkcs&dpage=ar CP - 3 ER - TY - JOUR T1 - Propene hydrogenation over truncated octahedral Pt nanoparticles supported on alumina JF - Journal of Catalysis Y1 - 2003 A1 - Yoo, J. W. A1 - Hathcock, D. J. A1 - El-Sayed, Mostafa A AB - Colloidal Pt nanoparticles synthesized by a 1 : 5 concentration ratio of K2PtCl4 to polyacrylate were loaded on nanoporous alumina using the impregnation method at room temperature. The deposited Pt particles, present on the external surfaces of the support, were characterized by transmission electron microscopy, which indicated predominantly truncated octahedral (TO) shapes with a mean diameter of 10 nm. Their catalytic performance in the hydrogenation of propene at 30-80 degreesC was studied as a test reaction. The initial rate, reaction order, rate constant, activation energy, and turnover frequency were determined. The activation energy was found to be 8.4 +/- 0.2 kcal/mol, which is slightly lower than results reported for other platinum systems (10-14 kcal/mol). The TO platinum nanoparticles have atom-high surface steps, ledges, and kinks, and these atomic-scale fine structures are expected to decrease the activation energy. The reactivity of the surface atoms in this nanoparticle is so high that above 50 degreesC side reactions leading to complete surface poisoning take place within a few minutes. The effect of the polymer concentration of the polyacrylate-capped TO Pt/Al2O3 on the hydrogenation catalytic activity was also investigated. (C) 2003 Elsevier Science (USA). All rights reserved. VL - 214 SN - 0021-9517 N1 - Yoo, JW Hathcock, DJ El-Sayed, MA M3 - 10.1016/s0021-9517(02)00136-7 ER - TY - JOUR T1 - Characterization of pt nanoparticles encapsulated in Al2O3 and their catalytic efficiency in propene hydrogenation JF - Journal of Physical Chemistry A Y1 - 2002 A1 - Yoo, J. W. A1 - Hathcock, D. J. A1 - El-Sayed, Mostafa A AB - Pt nanoparticles supported in nanoporous Al2O3 catalyst are prepared by reduction of K2PtCl4 solution using 112 in the presence of Al2O3 and poly(acrylic acid) as capping; material. After thorough washing with water to remove Pt nanoparticles located on the external surface of the Al2O3 and drying at 70 degreesC for 12 h, they were used in propene hydrogenation to evaluate catalytic activity as measured by the value of the activation energy in the temperature range between 30 and 90 degreesC. The Pt nanoparticles are characterized by using transmission electron microscopy (TEM). The particles in Pt/Al2O3 are found to be encapsulated and uniformly dispersed inside the Al2O3; however, the size and shapes are not clearly seen. After extraction of the Pt nanoparticles from the Al2O3 channels by using an ethanol-diluted HF solution, various shapes such as truncated octahedral, cubic, tetrahedral, and spherical with a size around 5 nm are observed. The encapsulated particles have various shapes but are smaller in size than those prepared in K2PtCl4 solution with polyacrylate in the absence of Al2O3. Using FT-IR studies, the capping material initially used in Pt/Al2O3 is not found in the Al2O3 channels. This might be due to the fact that the polymer (average MW 2100) is too large to be accommodated within the Al2O3 pores. The nanopores of Al2O3 have several roles in the synthesis of these nanoparticles. It allows for uniform dispersion and encapsulation of Pt nanoparticles. It controls the Pt sizes with narrow distribution that is determined by the pore dimension (5.8 nm). It protects against metal particle aggregation and produces various shapes even in the absence of the capping material. Using these Pt nanoparticles, the catalysis of hydrogenation of propene gas was studied. The initial rates, reaction order, rate constants, and activation energy for the hydrogenation are determined by use of mass spectrometric techniques. The activation energy is found to be 5.7 kcal/mol, which is about one-half that previously reported for catalysis by Pt metal deposited in SiO2 and TiO2 synthesized by using H2PtCl6 and Pt(allyl)(2) by impregnation method. VL - 106 SN - 1089-5639 N1 - Yoo, JW Hathcock, D El-Sayed, MA M3 - 10.1021/jp0121318 ER -