Hydroisomerization reactors

Shell Gas B.V. has constructed a 1987 mVd (12,500 bbhd) Fischer-Tropsch plant in Malaysia, start-up occurring in 1994. The Shell Middle Distillate Synthesis (SMDS) process, as it is called, uses natural gas as the feedstock to fixed-bed reactors containing cobalt-based cat- yst. The heavy hydrocarbons from the Fischer-Tropsch reactors are converted to distillate fuels by hydrocracking and hydroisomerization. The quality of the products is very high, the diesel fuel having a cetane number in excess of 75. 

Hydroisomerization of n-octane was performed in a flow reactor, in the range of 473-533 K under pressure 1-20 bar, weight hourly space velocity of n-octane was 2,5 g/(g h) and the molar ratio of n-octane H2 =1 5. 

Kuba et al. (2003) monitored a WC>3/Zr02 catalysts with and without platinum during n-pentane isomerization and hydroisomerization at 523 K their equipment consisted of a reactor placed next to an integrating... 

From the thermodynamic point of view, the hydroisomerization reaction is not pressure sensitive. However, because the catalyst contains the acid function, hydrocarbon cracking is an unavoidable side reaction. The cracking reaction however should depend on the total pressure. Table 7.4 shows laboratory results obtained in a bench scale reactor at 250°C (482°F), H2/HC = 1 with a synthetic feedstock containing 50wt% of n.Cs, 25 of iCs, 20 of n C6, 5 of methylcyclopentane and no heptane (Feed 1). At a liquid hour space velocity (LHSV) of 2h an increase of the total pressure from 20 bar to 30 bar reduces the cracking selectivity S = Z C4/Z HC from 1.6 to 1.1 wt.-%, whereas at a LHSV of 1 h 1 no effect can be observed. 

Laboratory studies have shown that omega (MAZ structure type) based paraffin hydroisomerization catalyst shows higher activity than mordenite based catalyst and better selectivity, i.e. higher octane due to higher yield of di-branched paraffins compared to mordenite performance (17). The isomerization of a C5/C6 cut at 15 bar results in a final calculated RON of 80.4 for the alumina bound dealuminated PtH-MOR catalyst supplied by IFP with undisclosed (most likely similar) Si/Al ratio, measured at 265 °C compared to a RON value of 80.9 for an alumina bound dealuminated PtH-MAZ catalyst with bulk Si/Al = 16, measured at 250 °C. Both measurements were performed in a bench-scale tubular reactor with a volume of 50 cm3 of 2 mm diameter extrudates with WHSV of 1.5 h and H2/HC of 4. This... 

Isomerization of the waxy pyrolyzer stripper bottoms was carried out over a proprietary wax hydroisomerization catalyst. A commercial Pt-Pd on silica-alumina hydroflnishing catalyst was used in a second reactor downstream from the first to hydrogenate any unsaturated compounds to improve thermal and oxidative stability. 

Maloney ML, Gora L, McLeary EE, Jansen JC, and Maschmeyer TH. Hydroisomerization of hexane within a reactor composed of a tubular siUcaUte-l membrane packed with Pt-loaded chlorided alumina catalyst. Catal Commun 2004 5 297-300. 

Gora L and Jansen JC. Hydroisomerization of C-6 with a zeolite membrane reactor. J Catal 2005 230(2) 269-281. 

The hydroisomerization of n-pentane was conducted with a continuous flow type fixed bed reaction apparatus under pressurized conditions. The reactor was a stainless steel tube with an inner diameter of 6 mm. The feed material which had been deeply desulfurized was fed by a liquid pump. Products were analyzed by a gas chromatography. 

Jacobs et al. showed in a feasibility study that it is possible to obtain meaningful kinetic data using a high-throughput reactor [36]. Decane hydroisomerization was studied over Pt-loaded ultrastabilized Y type zeolites. Complete analysis of the complex product mixture could be achieved in 3.2 minutes using a multicapillary column, and the kinetic data obtained agreed well with those of a kinetic model derived for a conventional reactor. 

Decane hydroisomerization experiments were performed using a high-throughput reactor with 16 parallel reactor tubes [12]. Samples were impregnated with an aqueous [Pt(NH3)4]Cl2 solution to obtain a 0.5 wt.% nobel metal loading and then palletized in size between 125 and 250 pm. 50mg of catalyst was loaded in the reactors and activated in-situ at 400°C for Ih in O2, N2 and H2. A fixed contact time of 1656 kg s/mol was used along with a temperature step of 10°C. The reaction was performed at a total pressure of... 

P-18 - Conceptual process design of an all zeolite membrane reactor for the hydroisomerization of Cs/Cg... 

Membrane reactors provide opportunities for overcoming thermodynamic limits on the maximum attainable conversion of reversible reactions. A simple membrane reactor model has been employed to investigate the performance of Cs/C6 hydroisomerization process on zeolites and compare it to a state-of-the-art total isomerization (TIP) process. A RON of 88.0 was obtained, slightly higher and promising compared to the TIP process with RON of 86. 

Catalytic stability of a Pd/H-Mordenite catalyst for C5/C6 hydroisomerization was tested in a laboratory reactor for 1000 hours. The content, chemical composition and structure of the coke formed on the catalyst discharged from a pilot reactor working in an accelerated condition was characterized using XRD, EPR, MAS-NMR, FTIR and TPO techniques. The catalyst shows stable catalytic activity and selectivity during 1000 hours. The nature of the coke and its combustion behavior depended upon time on stream and varied with the catalyst bed length. As time on stream increased, coke initially formed on palladium metals and then moved to acidic sites on the support where polyaromatic or pseudographite-like structures were formed through further acid catalyzed reactions. 

Catalyst activity and selectivity were measured in a laboratory reactor that was 1350 cm in length and 3.9 cm in diameter. Hydroisomerization reactions were performed at a temperature of 260 °C, a WHSV of 2 h and a hydrogen/(n-hexane + n-pentane) molar ratio of 4, while maintaining a pressure of 1.96 MPa. 

During 1000 hours reaction, both activity and selectivity varied in a very narrow range, activity 83-88% for and 61-65% for Cs and selectivity 18-24 %. It is clearly shown that our catalyst has a relative long lifetime and is stable. Since this kind of catalyst for hydroisomerization in a stable operation condition can run for 1-2 years before complete deactivation, an accelerated deactivation test in our pilot plant reactor was therefore applied to estimate relative stability and coke formation. Detailed information concerning the accelerated deactivation test was reported elsewhere [15]. The following sections are the studies of the coke obtained from coked catalysts that have undergone the accelerated conditions. 

The reaction of cyclohexene over differently dealuminated H-Y samples at 370 K (isomerization to methylcyclopentene and hydroisomerization to methyl-cyclopentane, hydrogen transfer resulting in benzene and cyclohexane, cracking and coke formation) was monitored by Joly et al. [904] via in-situ IR spectroscopy in an IR flow-reactor cell coupled with a gas chromatograph. A good correlation was reported between the activity of the Bronsted acid sites and their strength... 

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