Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

Akhmedov, Vagif M.; Al-Khowaiter, Soliman H.

doi:10.1080/01614940601128427

Cited by 211 publications

(114 citation statements)

References 378 publications

(412 reference statements)

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“…Thus, the hydroisomerisation of n-C7 to mono-and multibranched isomers is an important area which merits research. The reactions of hydrocarbons over acidic zeolite catalysts are accompanied by the formation of coke, which causes catalysts to deactivate and leads to changes in product distribution [10][11][12][13].…”

Section: Introductionmentioning

confidence: 99%

The time-on-stream stability of some selected bifunctional nanoporous-based catalysts in n-heptane hydroisomerisation

et al. 2013

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In this work, some commercial nanoporousbased catalysts, such as USY, beta and mordenite zeolites loaded with Platinum metal acting as bifunctional catalysts, were used for hydroisomerisation experiments in a fixedbed reactor at the atmospheric pressure and at feed space time 5.12 h -1 to hydroisomerise n-heptane over a temperature range of 210-270°C. The study aimed to evaluate the changes with time-on-stream in the catalytic activity, product selectivity and manner of deactivation of metalloaded zeolite catalysts, at constant contact time of 5.13 h -1 and a hydrogen-to-n-heptane molar ratio fixed at 9. Various analytical techniques were used to characterise fresh and aged catalysts. Results show that pore architecture is the most important factor affecting coke formation and deactivation in zeolite catalysts, and those catalysts with three-dimensional pore structures lacking cavities or cages were best able to resist deactivation. In addition, it was found that those catalysts with high Si/Al ratios and those which had been acid-leached or steamed showed better activity, higher selectivity towards isomeric products and better time stability. Moreover, the balance between the number of metal sites and the number of acid sites played an important role in determining the activity, selectivity and stability of the bifunctional catalysts.

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“…44 For this reason, the catalysts were promoted with Mn and the effects of Mn-promotion is shown in Figure 8(a), (b). The CO-conversion (%) is calculated according to the normalization method given below.…”

Section: Ft Catalytic Performancementioning

confidence: 99%

Effect of Manganese Promotion on Al-Pillared Montmorillonite Supported Cobalt Nanoparticles for Fischer-Tropsch Synthesis

Ahmad¹,

Hussain²,

Muhammad³

et al. 2013

Bulletin of the Korean Chemical Society

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The effect of Mn-promotion on high surface area Al-pillared montmorillonite (AlMMT) supported Co nanoparticles prepared by hydrothermal method have been investigated. A series of different weight% Mnpromoted Co nanoparticles were prepared and characterized by XRD, TPR, TGA, BET and SEM techniques. An increase in the surface area of MMT is observed with Al-pillaring. Fischer-Tropsch catalytic activity of the as prepared catalysts was studied in a fixed bed micro reactor at 225 o C, H 2 /CO = 2 and at 1 atm pressure. The data showed that by the addition of Mn the selectivity of C 1 dropped drastically while that of C 2 -C 12 hydrocarbons increased significantly over all the Mn-promoted Co/AlMMT catalysts. The C 13 -C 20 hydrocarbons remained almost same for all the catalysts while the selectivity of C 21+ long chain hydrocarbons decreased considerably with the addition of Mn. The catalyst with 3.5%Mn showed lowest C 21+ and highest C 2 -C 12 hydrocarbons selectivity due to cracking of long chain hydrocarbons over acidic sites of MMT.

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“…Among the probable candidates, keeping hydrothermal stability of the catalyst in mind, zeolites Beta has remained the catalyst of choice. Readers are referred to relatively recent works [1,2] for introduction to paraffin isomerization and review articles by Valavarasu and Sairam [3], and Akhmedov et al [4] for details and comprehensive intricacies of various commercial processes. Now, when the molecular size of product increases as a result of the reaction, it is worth expecting that (a) smaller crystal size, preferably in nanometer size affording smaller diffusion length and enhanced external surface area and (b) generation of mesoporosity in zeolites crystals would be beneficial for the reaction.…”

Section: Introductionmentioning

confidence: 99%

Combined influence of alkaline earth metals and CO2 on performance of hierarchical zeolite Beta in n-hexane isomerization

Shinde¹,

Chakraborty²,

Parikh³

2018

Appl Petrochem Res

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The present work deals with isomerization of straight chain paraffin, n-hexane with an aim to make up loss in gasoline quantity as well as octane. This is due to its reduced benzene content warranted by its carcinogenic nature. Performance of impregnation of alkaline earth metals (Mg, Ca, Sr, and Ba) on Pt/desilicated (and dealuminated) zeolites Beta was studied and found that isomer selectivity as high as 99% with stable catalytic performance is achievable. Furthermore, replacing part of hydrogen (15%) with carbon dioxide in hydrogen as carrier gas improves hexane conversion. Hexane conversion increased as Mg-< Ba-< Ca-< Sr-Pt/deSi Beta. Observed performance parameters have been explained on the basis of reported variation in acidity due to both alkaline earth metals and CO 2 .

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“…Normal heptane is one important feedstock that can undergo isomerization, cracking, or aromatization in zeolites to produce valuable petrochemicals [40,41], e.g., propylene and ethylene. Besides, the surface barriers for mass transfer of n-heptane in ZSM-5 have not been explored to the best of our knowledge.…”

Section: Introductionmentioning

confidence: 99%

Probing the Nature of Surface Barriers on ZSM-5 by Surface Modification

Guo

Sun

et al. 2017

Chemie Ingenieur Technik

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The nature of external surface barriers in the zeolite ZSM-5 was explored by comparing mass transfer of n-heptane in samples with different crystal sizes, surface structure, and composition. These different surface properties were achieved by HF acid etching and SiO 2 deposition on an as-synthesized ZSM-5 crystal sample. HF etching does not reduce surface barriers. SiO 2 deposition on the same sample reduces surface barriers significantly. These insights into the nature of surface barriers could be used to guide the rational design of zeolitic materials with better mass transport properties.

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“…On the other hand, the isomerization of alkanes over zeolites without platinum metals is less well characterized because such zeolites are not always appropriate for the skeleton isomerization of linear alkanes, and loading of platinum metals on zeolites under hydrogen atmosphere enhances the activation of alkanes for isomerization 2)～5) . However, such cooper- , Kiyotada AOYAMA 1) , Kenichi KOMURA 1) , Yoshihiro KUBOTA 1), 2) Yoichi NISHIMURA 3) , and Yoshihiro SUGI August 19, 2011) Beta zeolite (BEA) samples with different SiO2/Al2O3 ratios were synthesized by the dry gel conversion method (DGC) using tetraethyl ammonium hydroxide (TEAOH) as a structure directing agent (SDA). Catalytic properties of BEA for the isomerization and cracking of hexane were evaluated by comparing with the typical zeolites, mordenite (MOR), ZSM-5 (MFI), and ZSM-22 (MWW) with SiO2/Al2O3 ratios of [30][31][32][33][34][35][36][37][38][39][40].…”

mentioning

confidence: 99%

Isomerization and Cracking of Hexane over Beta Zeolites Synthesized by Dry Gel Conversion Method

Pusparatu

Haga

Aoyama

et al. 2012

J. Jpn. Petrol. Inst.

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Recent Advances and Future Aspects in the Selective Isomerization of High n‐Alkanes

Cited by 211 publications

References 378 publications

The time-on-stream stability of some selected bifunctional nanoporous-based catalysts in n-heptane hydroisomerisation

Effect of Manganese Promotion on Al-Pillared Montmorillonite Supported Cobalt Nanoparticles for Fischer-Tropsch Synthesis

Combined influence of alkaline earth metals and CO2 on performance of hierarchical zeolite Beta in n-hexane isomerization

Probing the Nature of Surface Barriers on ZSM-5 by Surface Modification

Isomerization and Cracking of Hexane over Beta Zeolites Synthesized by Dry Gel Conversion Method

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