Isotopic Tracer Studies of Thiophene Desulfurization Reactions Using Hydrogen from Alkanes on H-ZSM5 and Co/H-ZSM5

Li, Wei; Yu, Sara Y.; Iglesia, Enrique

doi:10.1006/jcat.2001.3309

Cited by 15 publications

(23 citation statements)

References 16 publications

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“…Hydrocarbon selectivities measured with and without thiophene are compared for each alkane in Table 3; these comparisons are presented at similar alkane conversion levels, because primary and secondary reaction path- Table 3 Comparison of product selectivities (on a per total carbon basis of both reactants) during pure alkane and alkane-thiophene reactions on H-ZSM5 (Si/Al = 14. ways prevalent during alkane reactions can lead to significant effects of reactant conversion and reactor residence time on product distributions. For each alkane, the presence of thiophene led to higher selectivities to aromatic products, as reported previously for propane reactants [3]. Isotopic tracing of reaction products formed from mixtures of thiophene and 13 C-labeled propane on H-ZSM5 and Co/H-ZSM5 showed that these higher aromatics selectivities were only partially caused by the contribution of thiophenic carbons to these aromatic products.…”

Section: Resultssupporting

confidence: 82%

“…Thiophene-derived intermediates desorb to form hydrocarbons and hydrogen sulfide selectively during propane-thiophene reactions, without the direct involvement of gas phase H 2 molecules formed during concurrent propane dehydrogenation and dehydrocyclodimerization reactions. These reaction pathways were confirmed using 13 C and 2 H isotopic tracer studies [3,4]. Previous studies have shown that hydrodesulfurization of thiophene can also be carried out using hydrogen on cation-exchanged zeolites [1,2,[5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 60%

“…Isotopic tracing of reaction products formed from mixtures of thiophene and 13 C-labeled propane on H-ZSM5 and Co/H-ZSM5 showed that these higher aromatics selectivities were only partially caused by the contribution of thiophenic carbons to these aromatic products. The aromatics selectivity of the propane dehydrocyclodimerization reaction itself also increased when thiophene was present as a scavenger for propane-derived hydrogen and hydrogen-rich intermediates [3]. Reactions among unsaturated products of thiophene and hydrogen-rich intermediates formed from alkanes lead to synergistic effects that increase the rate of both alkane dehydrocyclodimerization and thiophene desulfurization reactions.…”

Section: Resultsmentioning

confidence: 99%

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Catalytic desulfurization of thiophene on H-ZSM5 using alkanes as co-reactants

Waku

Iglesia

2003

Applied Catalysis A: General

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Propane, n-hexane, n-decane, and hydrogen were used as co-reactants in the desulfurization of thiophene catalyzed by H-ZSM5 at 673 K. These co-reactants lead to hydrogen-rich intermediates, which are required for the removal of unsaturated fragments formed in thiophene decomposition reactions. Thiophene desulfurization rates increased with increasing alkane chain size, suggesting that the availability of hydrogen-rich intermediates increases with increasing alkane reactivity. Desulfurization rates with alkane co-reactants were significantly higher than those achieved with hydrogen. Sulfur is predominately removed as hydrogen sulfide (>80% S-selectivity) in the presence of alkane co-reactants, but much lower hydrogen sulfide selectivities were obtained when hydrogen was used and when thiophene decomposed in the absence of any co-reactants. The presence of thiophene did not alter the nature of the cracking, dehydrogenation, oligomerization, and cyclization pathways typical of alkane reactions or the overall rates of propane conversion on H-ZSM5. The selectivity for alkane conversion to aromatics, however, increased when alkane reactions occur concurrently with thiophene desulfurization, indicating that thiophene-derived intermediates contribute to the formation of aromatics by scavenging alkene intermediates formed from the alkane co-reactants. The higher alkene/alkane ratios observed during alkane reactions in the presence of thiophene are consistent with the scavenging of hydrogen-rich intermediates by thiophene-derived species via reactions that form aromatic molecules containing carbon atoms from both alkane and thiophene reactants.

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Section: Resultssupporting

confidence: 82%

Section: Introductionmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 99%

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Catalytic desulfurization of thiophene on H-ZSM5 using alkanes as co-reactants

Waku

Iglesia

2003

Applied Catalysis A: General

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“…This seems to confirm that cations do not influence the pathways involved in thiophene- propane reactions. 3 No inorganic sulfides were apparent in any of the samples, as also concluded from the nearly unchanged structure of Co cations during reaction. Co cations are stable against sulfidation and reduction during thiophene-propane reactions in which H 2 S is formed and present.…”

Section: In Situ Co K-edge Xanesmentioning

confidence: 63%

“…Previous mechanistic studies have also shown that Co cations influence the rate but not the pathways of desulfurization reactions using propane or H 2 as a hydrogen source. 3 The total amounts of hydrocarbon products desorbed from H-ZSM5 and Co/H-ZSM5 in He and in H 2 are reported in Table 1. Reactions of adsorbed thiophene using He as the carrier gas led to a larger number of products, because the absence of H 2 favors reactions among thiophene-derived adsorbed intermediates, and to the formation of a wide range of larger organosulfur compounds (Table 1).…”

Section: Temperature Programmed Desorption Of Pre-adsorbed Thiophenementioning

confidence: 99%

Kinetic, infrared, and X-ray absorption studies of adsorption, desorption, and reactions of thiophene on H-ZSM5 and Co/H-ZSM5

García‐Martínez

et al. 2002

Phys. Chem. Chem. Phys.

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Temperature programmed desorption and infrared and X-ray absorption near-edge spectroscopies were used during adsorption and reactions of thiophene in order to probe adsorbed intermediates and catalytic structures responsible for thiophene reactions with propane or H 2 on H-ZSM5 and Co/H-ZSM5. Infrared spectra showed that thiophene interacts with acidic OH groups in H-ZSM5 via hydrogen bonding at ambient temperature. No additional bands were detected on Co/H-ZSM5, suggesting the absence of specific interactions with Co cations. During adsorption at ambient temperatures, infrared bands assigned to CH 2 groups near C=C bonds or Satoms and to S-H species were detected and H-ZSM5 and Co/H-ZSM5 acquired colors typical of thiophene oligomers. Slightly above ambient temperatures, benzene and H 2 S formed from pre-adsorbed thiophene. These results indicate that hydrogen-bonded thiophene undergoes ring opening or oligomerization near ambient temperature on acidic OH groups in H-ZSM5. Some of the adsorbed thiophene (20-50%) interacts weakly with channel walls or with residual Na cations and desorbs unreacted. The remaining adsorbed thiophene desorbs as H 2 S, aromatic hydrocarbons, and organosulfur compounds, such as methylthiophene and benzothiophene, or forms irreversibly adsorbed unsaturated organic deposits. In situ infrared studies during thiophene and thiophene-propane reactions at 773 K on H-ZSM5 and Co/H-ZSM5 showed that surface coverages of thiophene-derived intermediates were low on acidic OH groups and Co cations. Co K-edge X-ray absorption near-edge spectra measured during these reactions confirmed that Co 2+ cations do not reduce or sulfide; their local environment, however, changes slightly, apparently because of interactions of strongly adsorbed species with Co cations. Sulfur K-edge X-ray absorption spectra detected small amounts of organosulfur species, but no inorganic sulfides, after thiophene, thiophene-H 2 , and thiophene-propane reactions, consistent with the observed stability of exchanged cations against reduction and sulfidation. S : Al ratios were less than 0.04 at. on all samples; these amounts represent less than 1% of the S-atoms removed from thiophene as H 2 S during catalytic propane-thiophene reactions.

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Sensitivity and economic analysis of a catalytic distillation process for alkylation desulfurization of fluid catalytic cracking (FCC) gasoline

Guo

2014

J of Chemical Tech & Biotech

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BACKGROUND The issues of gasoline desulfurization are becoming more important because the regulated sulfur limits are being set lower and lower. Among the new desulfurization technologies, the olefin alkylation of thiophenic sulfur (OATS) process is more attractive than hydrodesulfurization because of its mild operating conditions and low loss of octane number. In this work, a sensitivity analysis and an economic analysis of a catalytic distillation process for alkylation desulfurization of fluid catalytic cracking (FCC) gasoline are presented. The objective is to evaluate the effects of various design and operating parameters on the OATS process by using a realistic FCC gasoline fraction. RESULTS A sensitivity analysis performed for operating pressure, reflux ratio, bottom flow rate, feed conditions, number of separate stages, number of reactive stages, catalyst weight, feed location, reactive zone position, and an economic analysis based on total annual costs (TAC) for these variables were studied. CONCLUSION The results show the qualitative environmental and economic effect of several design variables and operating conditions on the OATS process and provide a direction to the further design. In addition, more attention should be paid to feed flow rate control. © 2014 Society of Chemical Industry

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Isotopic Tracer Studies of Thiophene Desulfurization Reactions Using Hydrogen from Alkanes on H-ZSM5 and Co/H-ZSM5

Cited by 15 publications

References 16 publications

Catalytic desulfurization of thiophene on H-ZSM5 using alkanes as co-reactants

Catalytic desulfurization of thiophene on H-ZSM5 using alkanes as co-reactants

Kinetic, infrared, and X-ray absorption studies of adsorption, desorption, and reactions of thiophene on H-ZSM5 and Co/H-ZSM5

Sensitivity and economic analysis of a catalytic distillation process for alkylation desulfurization of fluid catalytic cracking (FCC) gasoline

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