Hydrocracking Of N-hexadecane Research Articles

Reaction pathways control of long-chain alkanes hydroisomerization and hydrocracking via tailoring the metal-acid sites intimacy

Designing a bifunctional catalyst to achieve efficient hydroisomerization of long-chain alkanes is very essential for producing high-performance fuel and lubricant base oils. Herein, a bifunctional catalyst composed of an intimate mixture of ZSM-48 zeolite and alumina binder and with platinum (Pt) metal controllably deposited on zeolite or alumina was fabricated by a strong electrostatic adsorption method. The dependence of reaction pathways of hydroisomerization and hydrocracking of n-hexadecane on the metal-acid sites intimacy was investigated. High Brønsted acid density and suitable metal-acid sites intimacy favored to promote the catalytic activity. The selectivity, hydroisomerization mechanism and hydrocracking mechanism were significantly altered by tailoring the metal-acid sites intimacy. Too large or too small metal-acid sites intimacy was conducive to inhibit the occurrence of pore-mouth mode. A linear decease of the hydroisomerization selectivity with the increase of acid steps (nas) was observed. The catalyst with nanoscale intimacy of metal-acid sites (Pt/A-48) showed the highest catalytic activity and isomer selectivity (87%) and the least acid steps (nas = 1.4). This work provides a promising approach to fabricating highly efficient and shape-selective bifunctional catalysts for selective hydroisomerization of long-chain alkanes. A reaction network was proposed over the catalysts with different metal-acid intimacy.

Hydrocracking of n-hexadecane via liquid or gaseous water assisted pulsed spark discharge in liquid

In view of the problem that it is difficult to ignite discharge in the insulating liquid medium, the method of water assisted where the spark will occur was proposed. The introduction of water in any form lead to easier breakdown in the insulating liquid medium, and can also avoid carbon deposition caused by spark discharge, so as to achieve the purpose of reducing the discharge voltage. This paper also analyzes the liquid products after discharge, and it is found that the higher heating value of the liquid products was influenced by water state and peak voltage, which increased by 2.25% under the action of spark discharge. In addition, extending processing time may not be a good way to increase higher heating value of liquid products. This method not only solves the difficult problem of plasma generation in liquid medium, but also provides evidence for plasma-chemical reactions in heavy oil cracking and hydrogenation.

Role of zeolite content in Ni-Mo/β-USY zeolite catalyst on hydrocracking of n-hexadecane and vacuum gas oil in a batch reactor and a fixed-bed reactor

In this paper, different materials that involved amorphous silica–alumina and hydrothermally synthesized beta zeolite and treated Y zeolite (USY) were introduced as parts of the hydrocracking catalyst supports. The prepared supports were used for preparation of Ni-Mo/silica alumina–zeolite catalysts by wetness impregnation method. The prepared catalysts were characterized by BET, temperature programmed desorption (TPD), temperature programmed reduction (TPR), and field emission – scanning electron microscopy (FE–SEM) methods. Effect of zeolite type and content on hydrocracking of n-hexadecane and vacuum gas oil in a batch and a fixed-bed reactor was investigated. Also, the content of coke formed after reaction was measured by thermal gravimetric methods (TGA). Hydrocracking was done at 400 °C and 55 bar. The hydrocracking of vacuum gas oil results showed that in the Ni-Mo/10B-30USY catalyst containing higher USY zeolite with high total acidity, selectivity to middle distillate was higher than the other (90%). Moreover, the Ni-Mo/10B-30USY catalyst in hydrocracking of n-hexadecane had a higher yield (82%) and was more selective to heavier products (C9–C12). The findings indicated that in the Ni-Mo/10B-30USY catalyst, coke content was more than the other due to high acidity.

Role of Support in Hydrocracking of n-hexadecane over Sulfided NiMo Catalysts

Abstract The graphene nanosheets (GNS) have been considered as a support for the synthesis of catalysts applied in various catalytic reactions. In this research, the hydrocracking (HCK) of n-hexadecane as a model component of the long chain paraffin was carried out using synthesized Ni-Mo/GNS and commercial Ni-Mo/Al2O3-SiO2 catalysts in a fixed-bed reactor. The physico-chemical properties of catalysts were determined using XRF, TEM, XRD, TGA and NH3-TPD analysis. The effect of support on the conversion and product distribution in HCK of n-hexadecane was investigated. The stability of the catalysts in the presence of water and coke deposition was examined for the HCK of nonconventional feeds. The obtained results revealed that the active metals were anchored on the functionalized GNS and the stability of Ni-Mo/GNS was significantly increased compared to commercial catalyst. The obtained results indicated that the GNS-supported catalysts have a higher potential for HCK of n-hexadecane in comparison to commercial Ni-Mo/ Al2O3-SiO2 catalysts.

Synthesis of Nanostructured Catalytic Materials from Microemulsions

Since the 1980s [1,2], colloidal systems such as microemulsions (ME) have been widely investigated, especially for the synthesis of nanomaterials for various applications.[...]

Hydrocracking under Fischer–Tropsch conditions; the effect of CO on the mass transfer resistance by metal clusters

Over-cracking of Fischer–Tropsch wax remains an obstacle toward successful integration of FT synthesis and upgrading with high middle-distillate yields. The effect of syngas CO on the hydrocracking of n-hexadecane over Pd/H-MFI zeolites with different metal loadings has been investigated. Secondary cracking is minimized with increasing metal loading in Pd/H-MFI zeolite catalysts, and surprisingly a commensurate n-hexadecane conversion loss is observed, whereas in Pd/H-Y zeolites activity increases with metal loading. By means of tracer chromatography with cyclohexane, and using the solutions of the bidisperse model, it is demonstrated that metal loaded on the H-MFI zeolite lowers the micro- and macropore diffusivities. The presence of CO results in increased activity and concomitant secondary cracking on Pd/H-MFI with high metal loading, reminiscent of a Pd/H-MFI with low metal loading, showing that Pd is only partially poisoned. Pd/H-Y with CO displays lower activity like a Pd/H-Y with less Pd and Pt/H-MFI loses all hydrocracking activity. Severe secondary cracking in the presence of CO attests to an increased distance between metal and acid sites due to Pd migration from the micropores.

Hydroisomerization and hydrocracking over platinum loaded ZSM-23 catalysts in the presence of sulfur and nitrogen compounds for the dewaxing of diesel fuel

Hydroisomerization and hydrocracking of n-hexadecane in the presence of sulfur and nitrogen compound were investigated over four different platinum loaded ZSM-23 catalysts (Pt/ZSM-23, Pt–Pd/ZSM-23, Pt–Mg/ZSM-23 and Pt–Pd–Mg/ZSM-23). Sulfur and nitrogen compounds could poison metal and acid sites of bifunctional catalysts, respectively. In this study, effort has been made to improve the sulfur and nitrogen tolerance in the conversion of n-hexadecane by introducing palladium and magnesium as additives. Pt–Pd bimetallic catalysts increased the electron-deficiency of metal sites, leading to the improvement of sulfur tolerance. The addition of magnesium on platinum loaded ZSM-23 increased the concentration of Lewis acid sites and thereby the poisoning of nitrogen compound was discouraged. The applicability of Pt–Pd–Mg/ZSM-23 catalyst for dewaxing process was further examined using diesel feeds with sulfur compound such as dimethyl disulfide in a high pressure pilot plant. Pt–Pd–Mg/ZSM-23 catalyst showed good catalytic performance for dewaxing process in terms of diesel product yield and long-term stability.

Deactivation of a Pt/Silica–Alumina Catalyst and Effect on Selectivity in the Hydrocracking of n-Hexadecane

The deactivation behavior of a bifunctional catalyst consisting of platinum on amorphous silica–alumina was studied in the hydrocracking of n-hexadecane. The initial decline in activity and the change in selectivity were monitored at the following reaction conditions: pressure = 30 bar; temperature = 310 °C; hydrogen-to-hexadecane feed molar ratio = 10. Initially, hexadecane conversion and selectivity to cracking products decreased rapidly with time-on-stream, and stabilized after 40 h on stream. This could be related to an initial loss of metal surface area, which decreased the activity of monofunctional hydrogenolysis generating cracking products. The acidic function seemed to be unaffected under these reaction conditions. The stable catalyst was exposed to a lower hydrogen-to-hexadecane ratio to accelerate deactivation by coking. A decline in the activity of both functions was observed. The activity of the acidic function could be almost completely recovered by oxidative regeneration, while the metal activity was only partially recovered.

Hydrocracking of n-hexadecane on noble metal/silica–alumina catalysts

Bifunctional catalysts consisting of platinum or palladium on amorphous silica–alumina were prepared and tested in the hydrocracking of n-hexadecane (n-C16H34). Product selectivities toward mono-branched and multi-branched feed isomers and cracking products have been determined in a wide range of conversions, varying liquid hourly space velocity at constant operating parameters (pressure=30bar; temperature=310°C; H2/n-C16H34 feed molar ratio=10).A simple kinetic study is presented, in which the reactions are approximated by a network of pseudo first order irreversible reaction steps. The reaction network model was fitted to the experimental data, and kinetic constants for the different reaction steps were obtained. It could be concluded that mono-branched feed isomers are primary products in the hydrocracking/hydroisomerization reaction network; multi-branched isomers are formed mainly from mono-branched as a secondary product. On the platinum catalyst cracking products were formed as primary products, and it proved to be slightly more active than the palladium based one, at the same metallic molar loading. It could be shown that the platinum catalyst yields cracking products both via a bifunctional metal/acid mechanism and by monofunctional (metal only) hydrogenolysis. This second mechanism accounted for the higher activity of the platinum catalyst.

Noble Metal Wax Hydrocracking Catalysts Supported on High-Siliceous Alumina

Amorphous silica−aluminas formed by alumina obtained from the sililation of aluminum alkoxides with othosicilic acid were used as support material for the preparation of bifunctional hydrocracking catalysts. Bronsted acidity, which was observed for the support with 40% silica (Siral40), was absent in the material with 75% silica (Siral75). Impregnation with Pt or Pt and W, however, generated not only Bronsted acidity on Siral75 but also resulted in a higher platinum dispersion relative to Siral40. The PtW75 catalyst showed the behavior of ideal hydrocracking during hydrocracking of n-hexadecane. A high-quality diesel was obtained with high selectivity even at conversion levels above 90% during hydrocracking of Fischer−Tropsch wax. The performance of the PtW75 catalyst proved to be comparable or even better than the commercial catalyst tested.

Hydroisomerization and hydrocracking of long chain n-alkanes on Pt/amorphous SiO 2–Al 2O 3 catalyst

The hydroisomerization and hydrocracking of n-hexadecane, n-octacosane and n-hexatriacontane on a 0.3% platinum/amorphous silica–alumina (MSA/E) catalyst was investigated in a stirred microautoclave at 345, 360 and 380°C and between 2 and 13.1 MPa hydrogen pressure. For each n-paraffin, the reaction pathway and the kinetic parameters were determined. The results were used to elucidate the effect of chain length and operating conditions on isomerization and cracking selectivity. The conversion of the n-paraffins lead to the formation of a mixture of the respective isomers, as the main product, together with cracking products. At every temperature, the iso-alkane/ n-alkane ratio of cracking products increased considerably with increasing conversion degree. At the same conversion level, higher reaction temperatures lead to cracking products characterized by a lower iso-alkane/ n-alkane ratio. The conversion rate constants showed a considerable increase between n-C 16 and n-C 28, whereas a slight decrease between n-C 28 and n-C 36 was observed. The hydroisomerization selectivities showed a decrease as a function of chain length and with increasing conversion levels. The increase in reaction temperature leads to a small decrease in the isomerization selectivities only at low-medium conversion degrees and at the highest temperature investigated, while the effect of this parameter on the maximum yields achievable in iso-C16, iso-C28 and iso-C36 was negligible. The results indicate that the conversion of the n-paraffins follows a first-order kinetic in hydrocarbon while the order in hydrogen pressure was −1.1 ± 0.21 for n-C 16 and −0.66 ± 0.15 for n-C 28. Furthermore, an increase in hydroisomerization selectivity at higher hydrogen pressure for n-C 28 conversion was observed.

Hydroisomerization and Hydrocracking of n-Hexadecane over a Platinum-Promoted Sulfated Zirconia Catalyst

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTHydroisomerization and Hydrocracking of n-Hexadecane over a Platinum-Promoted Sulfated Zirconia CatalystRobert A. Keogh, Dennis Sparks, Jianli Hu, Irving Wender, John W. Tierney, Wei Wang, and Burtron H. DavisCite this: Energy Fuels 1994, 8, 3, 755–762Publication Date (Print):May 1, 1994Publication History Published online1 May 2002Published inissue 1 May 1994https://doi.org/10.1021/ef00045a032RIGHTS & PERMISSIONSArticle Views357Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (830 KB) Get e-Alerts Get e-Alerts

Kinetics of n-hexadecane hydrocracking on nickelmolybdenum/alumina catalysts

Composition of the products of n-hexadecane hydrocracking on Ni−Mb−Al catalysts has been determined. It is shown that the data of a single experiment can be used to obtain four rate constants for hydroisomerization and hydrocracking of n-hexadecane and its isomers.

The promotional effect of water in hydrocracking

The effects of water on the hydrocracking of n-hexadecane and of a certain hydrocracking feed using a rare-earth containing X zeolite and an acid Y catalyst have been examined. The results indicate that the partial pressure of water in the reaction system exerts a marked influence on both activity and selectivity which are quite different between the two catalysts tested. The effects manifest themselves quickly and are reversible by drying with hydrogen at 600 °F. To explain the observations, three concurrently operating mechanisms are proposed.