Search results for "Propene"
showing 10 items of 67 documents
Counterintuitive Mechanisms of the Addition of Hydrogen and Simple Olefins to Heavy Group 13 Alkene Analogues
2013
The mechanism of the reaction of olefins and hydrogen with dimetallenes ArMMAr (Ar = aromatic group; M = Al or Ga) was studied by density functional theory calculations and experimental methods. The digallenes, for which the most experimental data are available, are extensively dissociated to gallanediyl monomers, :GaAr, in hydrocarbon solution, but the calculations and experimental data showed also that they react with simple olefins, such as ethylene, as intact ArGaGaAr dimers via stepwise [2 + 2 + 2] cycloadditions due to their considerably lower activation barriers vis-à-vis the gallanediyl monomers, :GaAr. This pathway was preferred over the [2 + 2] cycloaddition of olefin to monomeric…
Steam catalytic cracking of naphtha over ZSM-5 zeolite for production of propene and ethene: Micro and macroscopic implications of the presence of st…
2012
One option to produce more ethene and propene can be to crack naphtha type fractions in dedicated smaller FCC units. We present here the results obtained for high temperature steam catalytic cracking (SCC) of a representative naphtha product (n-heptane) with ZSM-5. It has been found that under those conditions the presence of steam produces an irreversible dealumination of the zeolite as well as a reversible deactivation due to the interaction of water with active sites with a negative effect on protolytic cracking. A kinetic decay model that takes into account the two phenomena has been developed. The apparent activation energy is lower in the presence of steam. It appears that whilst the …
Keggin heteropolyacid supported on TiO2 used in gas-solid (photo)catalytic propene hydration and in liquid-solid photocatalytic glycerol dehydration
2017
Abstract (Photo)catalytic propene hydration to 2-propanol and glycerol dehydration to acrolein were carried out by using Keggin heteropolyacids (HPAs) supported on TiO 2 . Binary materials have been prepared by impregnation of H 3 PW 12 O 40 , H 3 PMo 12 O 40 and H 4 SiW 12 O 40 , on TiO 2 Evonik P25. Moreover, a binary material consisting of H 4 SiW 12 O 40 and TiO 2 was prepared via a hydrothermal treatment and tested for the same reactions. All the materials were characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with energy dispersive X-ray (EDX) measurements, diffuse reflectance spectroscopy (DRS), Raman spectroscopy and Fourier transform …
Supported H3PW12O40 for 2-propanol (photo-assisted) catalytic dehydration in gas-solid regime: The role of the support and of the pseudo-liquid phase…
2016
Abstract Catalytic and photocatalytic 2-propanol dehydration was carried out by using a supported Keggin heteropolyacid H3PW12O40 (PW12). Binary materials were prepared by impregnation and/or solvothermal treatment by using commercial supports: SiO2 (Mallinckrodt), TiO2 (Evonik P25) and multiwall carbon nanotubes (Sunnano) or home solvothermically prepared SiO2 and TiO2. All the materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy observations (SEM) coupled with EDX microanalysis, specific surface area measurements, diffuse reflectance spectroscopy (DRS), FTIR and Raman spectroscopy. (Photo)catalytic 2-propanol dehydration was studied in gas-solid regim…
Selectivity in Propene Dehydrogenation on Pt and Pt3Sn Surfaces from First Principles
2013
Propene can be produced via dehydrogenation of propane on Pt-based catalysts; however, the catalysts are plagued by low selectivity toward propene and high coke formation. The selectivity can be improved and the coke formation reduced by alloying Pt with Sn. The alloying is known to weaken the binding of propene, which in part explains the improved performance. We conducted density functional theory calculations to study the dehydrogenation of propene on flat and stepped Pt and Pt3Sn surfaces. The steps on Pt dehydrogenate propene readily, whereas, on Pt3Sn, the steps are inert because they are decorated with Sn. Our results indicate that the high selectivity and low coking on the Pt–Sn cat…
Phosphororganische Verbindungen, 64: Allyl‐Propenyl‐Umlagerungen Das elektrochemische Verhalten einiger Propenylverbindungen
1970
Allyl-aryl-sulfone, Allyl-diphenyl-phosphinoxid, Allylphosphonsaure-diathylester, Allyl-triphenyl-phosphoniumbromid und Allyl-triphenyl-arsoniumbromid lagern sich an basischem Al2O3 in die entsprechenden 1-Propenyl-Verbindungen um. Allyl-diphenyl-phosphin und Diallyl-phenyl-phosphin isomerisieren sich unter Mitwirkung von Natriumathylat zu den entsprechenden 1-Propenyl-Verbindungen. Die Allyl- und 1-Propenyl-Verbindungen werden IR- und NMR-spektroskopisch sowie polarographisch charakterisiert. — Bei der kathodischen Spaltung von 1-Propenyltriphenyl-phosphoniumbromid entstehen 92% Triphenylphosphin und Propen. 1-Propenyl-phenyl-sulfon wird elektrochemisch in Propen und Benzol-sulfinsaure auf…
Enhanced (photo)catalytic activity of Wells-Dawson (H6P2W18O62) in comparison to Keggin (H3PW12O40) heteropolyacids for 2-propanol dehydration in gas…
2016
Abstract Catalytic and photocatalytic 2-propanol dehydration to propene at atmospheric pressure and a temperature range of 60–120 °C were carried out in gas-solid regime by using bare and supported Keggin H 3 PW 12 O 40 (PW 12 ) and Wells-Dawson H 6 P 2 W 18 O 62 (P 2 W 18 ) heteropolyacids (HPAs). Binary materials were prepared by impregnation of the HPAs on commercial SiO 2 and TiO 2 . The Wells-Dawson was in any case more active than the Keggin heteropolyacid and the differences were enhanced when the supported samples were used. In particular, Wells-Dawson HPA supported on TiO 2 and under irradiation showed the highest activity. The HPA species played the key role both in the catalytic …
Photo-assisted degradation of 2-propanol in gas–solid regime by using TiO2 impregnated with heteropolyacid H3PW12O40
2009
Abstract Commercial and home prepared TiO2 samples impregnated with tungstophosphoric acid (H3PW12O40) were used for the photo-assisted degradation of 2-propanol in gas–solid regime. The characterization results evidenced a good coverage of the polyoxometalate (POM) onto the surface of TiO2 along with a marginal effect of the presence of the POM on the specific surface area, morphology and cristallinity of the samples. Propene was the main intermediate product revealed in 2-propanol photocatalytic degradation by using as photocatalysts the samples containing the POM, whereas propanone was mainly obtained when the photocatalysts was bare TiO2, both commercial or home prepared. Acetaldehyde w…
Mo-containing tetragonal tungsten bronzes. The influence of tellurium on catalytic behaviour in selective oxidation of propene
2009
Abstract Te-free and Te-containing multicomponent Mo-based catalysts presenting tetragonal tungsten bronze (TTB) structure have been prepared, characterized and tested for the selective oxidation of propene. The catalysts were prepared hydrothermally and heat treated at 700 °C. The structural characterization performed by means of XRD, FTIR, SAED and HRTEM confirms the incorporation of tellurium to the TTB structural framework and shows that its presence does not modify in essence the crystalline structure. However, the incorporation of Te strongly modifies the catalytic performance, and the highest yield to acrolein has been achieved on catalysts with Te/Mo atomic ratios in bulk of 0.03. T…
Theta-1 zeolite catalyst for increasing the yield of propene when cracking olefins and its potential integration with an olefin metathesis unit
2017
[EN] There is a need for on-purpose propene production technologies beyond energy-intensive steam cracking. Hexene is a compound with limited value that can be found in several streams in the refinery and can readily crack on zeolites at lower temperatures and shorter contact times than those used for cracking alkanes. Cracking over ZSM-5 zeolite yields high selectivity to light olefins. These results are improved by Theta-1 zeolite, which can yield a remarkable propene molar selectivity of 180% (90 wt%) at 90% conversion, close to the maximum thermodynamic yield. Moreover, crystal engineering allowed its TOF to increase by more than 50%. Based on these results we also identified some prosp…