Surface treatment of a polypropylene film with a nitrogen DBD at medium pressure

Surface treatment of polymer films is usually necessary to improve surface wetting and adhesion characteristics. Traditional liquid chemical processes have several disadvantages in contrast to dry finishing processes, like plasma technology. Dielectric barrier discharges at atmospheric pressure are extensively studied for surface treatment, however, almost no research has been done on surface treatment with a dielectric barrier discharge at medium pressure. Therefore, in this paper, a polypropylene (PP) film is plasma-treated with a dielectric barrier discharge (DBD) in nitrogen at medium pressure (5.0 kPa). The surface properties of the plasma-treated samples are examined using contact angle measurements, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results show that the surface wettability is significantly enhanced after plasma treatment. The incorporation of nitrogen on the surface is significant (10 at%), demonstrating the ability of the used DBD set-up to generate nitrogen-containing functional groups on the PP surface. Nevertheless, a considerable amount of oxygen (10 at%) is incorporated onto the PP surface underlining the extreme reactivity of oxygen active species and the difficulty in overcoming the air contamination problem. Moreover, AFM analysis reveals that the nitrogen plasma creates large changes in the surface morphology of the PP film due to the selective etching of the amorphous regions of the polymer film

Characterization and hydrodesulfurization activity of CoMo catalysts supported on sol-gel prepared Al2O3

A series of CoMo/Al2O3 catalysts was prepared by impregnation on a series of alumina powders synthesized by the sol-gel method with different hydrolysis ratios R (defined as [H2O] / [aluminum-tri-sec-butoxide (ASB)]; R = 3, 4, ..., 12, 13). The oxide precursors were characterized and subsequently tested in the hydrodesulfurization (HDS) of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT). Mainly due to their large pore diameters of ca. 6 nm, the catalysts prepared from the alumina with hydrolysis ratio R = 7 ~ 10 showed higher HDS activity compared with the activities of the other prepared catalysts. The effect of the pore diffusional limitation was more significant than expected, due to the ink-bottle shape of the pores of the prepared catalysts with hydrolysis ratio R 10. Due to highly dispersed CoMo active phase, the HDS activity of the prepared catalysts with hydrolysis ratio R = 8 and 9 for thiophene was similar to that of a reference industrial catalyst that was designed and manufactured for deep HDS of diesel fuel fractions. Furthermore, the HDS activity of the prepared catalysts with hydrolysis ratio R > 5 for DBT was higher than that of the reference industrial catalyst. For 4,6-DMDBT, however, the reference industrial catalyst showed higher HDS activity compared with the activities of the prepared catalysts. Relatively high HDS activity was observed for the prepared catalysts with R = 9 and 10 with cylindrical pore shape and with a high proportion of strong acid sites. The strong acidity supposedly enhanced the hydrogenation activity of the catalysts that was essential for the HDS of 4,6-DMDBT

Description of coordinatively unsaturated sites regeneration over MoS2-based HDS catalysts using 35S experiments combined with computer simulations

By combining experimental results and computer simulations, we previously showed that the coordinatively unsaturated sites (CUS) formation over MoS2 is most likely to occur on the MoS2 metallic edge through the departure of an H2S molecule. In the present paper, we aimed at examining the H2S departure from MoS2 catalysts promoted with Co and Ni. The [35S]DBT HDS experiments results showed that over CoMoS/Al2O3 and NiMoS/Al2O3 catalysts, the activation energy of the H2S release reaction is essentially the same with respective values of 7.4 kcal.mol-1 and 7.9 kcal.mol-1. Considering the H2S departure activation energy in the case of the non-promoted MoS2 surface (10 ~ 12 kcal.mol-1), this result illustrates the synergetic effect between Mo and Co or Ni in terms of CUS regeneration easiness. Further, preliminary computer simulations results showed that for S atoms bridged between Co atoms, a mechanism implying H2S departure from the metallic edge cannot be reasonably envisaged. Moreover, on the sulfur edge the H2S release activation energy is too high (~ 13.5 kcal.mol-1) if we consider experimental results on CoMo/Al2O3 catalysts but not incompatible with the experimental value obtained over Co/Al2O3 catalysts (ca. 10 kcal.mol-1), which suggests that the mechanism on the promoted catalyst differs from that on the un-promoted one

Nuevos precursores Al-X-Mo/W (X = Al, Co, V) vía síntesis reticular: Caracterización por 27Al NMR y Raman Microprobe. Aplicación en desulfurización oxidativa (ODS)

Se investigó la actividad de nuevos precursores trimetálicos obtenidos por síntesis reticular, en dos diferentes reacciones de desulfurización oxidativa (ODS): difenilsulfuro a difenilsulfona en presencia de H2O2 y de dibenzotiofeno DBTs mediante terbutilhidroperóxido (t-BuOOH). Se prepararon diversas fases de fórmula general A113-[XMo6] (X= Al (III), Co(III), V(V) y Al13-P[WO4]n combinando el isopolication Keggin [AlO4Al12(OH)24(H2O)12]7+ (Al13) e iso ó heteropolimetalatos del tipo: [XMo6O24H6]3-; [Co2Mo10H4]6-; [WO4]n , [PW9O34]9-, [V2W4]6-. La caracterización se llevó a cabo por XRD, 27Al NMR, FTIR y Raman Microprobe. La estabilidad térmica se estudió por TGA-DTA. Los tests catalíticos se realizaron en batch entre 75 y 80 °C. Los resultados preliminares indican que la actividad ODS aumenta con la densidad electrónica del sustrato, siendo mayor para difenilsulfuro que para DBT. Los catalizadores a base de heteropolimolibdatos presentan una mejor performance en ambas reacciones, mientras el heteroátomo parece mejorar la polarización del enlace Mo-O2t. Catalizadores a base de iso y politungstatos no mostraron actividad excepto aquel conteniendo P como heteroátomo. Asimismo se comprobó por Raman Microprobe, que las fases empleadas conservan su estructura después de la reacción, mostrando la interesante posibilidad de reutilización

Improvement of HDS catalysts through the modification of the oxidic precursor with 1,5-pentanediol: Gas phase sulfidation and thiophene conversion

AbstractThe performance, in thiophene HDS, of a CoMo/Al2O3 catalyst was successfully improved through chemical modification of its oxidic precursor by impregnation with 1,5-pentanediol solution. The gas phase activation with a H2/H2S mixture was followed by thermogravimetric analysis coupled with a rapid chromatograph; the catalysts were characterized at different steps of the activation using X-ray photoelectron spectroscopy (XPS). It appeared that the addition of the organic agent retards the sulfidation of the supported metals, leading to a simultaneous sulfidation of Co and Mo atoms. This induces the formation of smaller MoS2 slabs and thus an increase in the number of active CoMoS sites, directly correlated with the better HDS performance of the modified solid. The role of 1,5-pentanediol is likely to inhibit, at low temperature, the adsorption of H2S on the solid and thus the sulfidation of the supported metals

Characterization and Hydrodesulfurization Activity of CoMo Catalysts Supported on Boron-Doped Sol-Gel Alumina

A series of hydrodesulfurization (HDS) catalysts was prepared by impregnation of Co and Mo on sol-gel B-Al2O3 supports with B/Al ratios of 0, 0.02, 0.04, 0.08, 0.20, 0.32, 0.49, and 0.61. The thiophene HDS and dibenzothiophene (DBT) HDS activities were both maximal for the catalyst with B/Al = 0.04, with respective values 70% and 42% higher than those for an industrial reference catalyst. These maxima in HDS activity correlated with the previously reported presence of isolated BO4 surface species. These BO4 species were responsible for a local maximum in the acidity of the B-Al2O3 supports when B/Al = 0.04. In contrast, the formation of mixed oxides (A9B2 and A2B) or B2O3 that also resulted in enhanced acidity of the B-Al2O3 supports had a detrimental effect on the HDS activity. The 4,6-dimethyldibenzothiophene (4,6-DMDBT) HDS activity over the CoMo/B-Al2O3 catalysts decreased when the B/Al ratio was increased. This was attributed to the strong direct desulfurization character of the CoMo catalysts supported on the B-Al2O3 supports, because high hydrogenation ability toward the C=C double bonds is essential prior to sulfur removal from 4,6-DMDBT. The excellent performance in the thiophene and DBT HDS of the CoMo/B-Al2O3 catalysts is particularly useful for ultra-deep HDS of light fractions

Catalyseurs à base de molybdène supporté sur alumine [gamma] et zéolithe HY (caractérisation des phases oxydes et sulfures)

Les précurseurs oxydes de catalyseurs d'hydrotraitement (Co)Mo/alumine ou zéolithe ont été caractérisés par spectrométries Raman, RMN et EXAFS aux seuils K du Mo et du Co. Lors de l'imprégnation du support avec une solution d'heptamolybdate d'ammonium, la formation d'un composé aluminomolybdate de type Anderson a été confirmée pour l'alumine et mise en évidence pour le support zéolithique HY, avec consommation de la phase alumine amorphe de la zéolithe. En l'absence de cette dernière, il y a précipitation d'heptamolybdate d'ammonium. Les espèces sont conservées au séchage ; à la calcination, l'aluminomolybdate évolue en une phase de type molybdate d'aluminium de surface, alors que l'heptamolybdate se transforme en MoO3. Les espèces formées lors de l'imprégnation sont présentes dans la porosité inter-granulaire, alors que par vaporisation de MoO3, on a formation de dimères localisés dans la structure zéolithique. L'étude des précurseurs promus par le cobalt a permis de montrer que l'évolution du molybdène est identique dans le cas d'une préparation par co-imprégnation. L'imprégnation de cobaltomolybdate permet d'éviter la formation de l'ion aluminomolybdate et de préserver l'interaction Mo-Co, mais, quel que soit le précurseur, l'effet nivelant des étapes de calcination-réhydratation a été mis en évidence. L'étude EXAFS en fonction du taux de couverture en soufre des feuillets de MoS2 dans les catalyseurs Mo/Al2O3 sulfurés a mis en évidence les limites de l'EXAFS pour la détermination de la taille de cristallites de MoS2, information accessible par la technique AWAXS, qui fournit également des renseignements sur l'empilement des feuillets...LILLE1-BU (590092102) / SudocSudocFranceF