Inhibition of dibenzothiophene hydrodesulfurization by di-aza heterocycles
- PDF / 205,305 Bytes
- 4 Pages / 595 x 794 pts Page_size
- 93 Downloads / 161 Views
Catalysis Letters Vol. 99, Nos. 3–4, February 2005 (Ó 2005) DOI: 10.1007/s10562-005-2096-6
Inhibition of dibenzothiophene hydrodesulfurization by di-aza heterocycles Teh C. Ho* and J. Sobel Corporate Strategic Research Laboratories ExxonMobil Research and Engineering Co. Annandale, NJ 08801
Received 23 August 2004; accepted 30 September 2004
The hydrodesulfurization of dibenzothiophene over a sulfided CoMo/Al2 O3 catalyst can be severely inhibited by 1,10phenanthroline. The catalyst’s hydrogenation activity is totally suppressed and cannot be fully recovered upon stripping of adsorbed nitrogen species. The bulk of the hydrogenolysis activity is suppressed but can be completely recovered upon stripping. Implications of these observations are discussed, including the possibility of a chelating-enhanced adsorption mechanism. KEY WORDS: Hydrodesulfurization; Catalyst poisoning; Nitrogen compounds; Di-aza Heterocycles; Mono-aza Heterocycles.
1. Introduction Indigenous nitrogen species in petroleum distillates have long been known to inhibit catalytic hydrodesulfurization (HDS) of organosulfur species. Recently, this effect has received much attention because governments worldwide are mandating substantial sulfur reduction in refinery products such as diesel and gasoline. For instance, the sulfur specification for on-road diesel in the U.S. is 15 ppmw in 2006, down from the current 500 ppmw. A fair amount of research has been done on the inhibiting effects of six- and five-membered nitrogen heterocycles containing only one nitrogen atom per molecule, or mono-aza heterocycles [1] and references therein]. To the best of our knowledge, no work has been reported on the inhibiting effects of heterocycles containing two nitrogen atoms. Such di-aza heterocycles are present in diesel fuel, for instance, benzo[c]cinnolines [2]. Di-aza heterocycle structures are different from those of mono-aza heterocycles as do reactivities. In this study we use 1,10-phenanthroline (PN) as a probe molecule with which to gain some understanding of the inhibiting effects of di-aza heterocycles in diesel HDS. The reaction considered is the HDS of dibenzothiophene (DBT) over a commercial sulfided CoMo/Al2 O3 catalyst.
2. Experimental PN, DBT and tetralin are available commercially (Aldrich). The composition and physical properties of the CoMo/Al2 O3 catalyst are: CoO, 3.5%; MoO3 , 1 Retired * To whom correspondence should be addressed. E-mail: [email protected]
12.5%; nitrogen BET surface area, 285 m2 /g; and Pore volume, 0.52 cc/g. Prior to use, the catalyst was crushed and sieved to 20–40 mesh granules and then sulfided at 360 C for 1 h at atmospheric pressure with a 10% H2 Sin-H2 gas mixture. The catalyst charge was 2.5 cc. Reactions were conducted in a vertical fixed-bed reactor made of a 3/8 in i.d. 316 stainless-steel pipe. It was equipped with a calibrated feed burette, pump, gas– liquid separator, and product collector. In all runs a large excess of hydrogen was used, corresponding to a gas-to-liquid ratio of 32 k mol H2 /m3 liquid fe
Data Loading...
