Catalytic hydroprocessing of SRC-II heavy distillate fractions. 7. Kinetics of hydrogenation, hydrodesulfurization, and hydrodeoxygenation of the neutral oils determined by analysis of compound classes and individual compounds

Abstract

A mathematical model is presented which describes mass and energy transport during rapid pyrolysis of fibrous cellulose particles. Radiative heat transfer within porous cellulose is modeled by using the method of zones. The kinetic model for pyrolysis developed by Bradbury et al. is extended to include secondary decomposition of condensible liquids (tars) formed. Solution of the governing equations shows that both mass-and heat-transfer resistances influence product composition from pyrolysis even for cellulose particles as small as 0.5 mm in diameter. Heating rate has little influence on product composition, but increasing the total pressure results in a decreased condensible product yield. Radiative heat transfer plays a minor role within the solid for the conditions simulated. The model is useful for identifying critical parameters and conditions in pyrolysis and for predicting trends in product yields.

Bruce Gates: A Career in Catalysis

“…As in the pure compound HDS work, HDS of the thiophenic compounds was shown to be about an order of magnitude faster than initial aromatic hydrogenation, , except for 4-methyldibenzothiophene, which is sterically inhibited. The 2-, 3-, and 4-ring aromatics that dominate the neutrals fraction are hydrogenated somewhat (the % of naphthenic carbon increases from ∼16 to ∼25% in 16 h), with evident equilibrium limitations . The phenolic compounds, concentrated in the weak acid fractions, undergo HDO at rates faster than for either aromatic hydrogenations, HDS, or HDN at typical conditions (350 °C, 12.2 MPa H 2 , 0.2 WHSV [gcat/(g feed*h)]).…”

“…117 For the neutral oils, HDS was the more important reaction, and here the reaction of DBT in the mixture was similar in rate to that of pure compound DBT 113 and therefore unaffected by the PAHs present. As in the pure compound HDS work, HDS of the thiophenic compounds was shown to be about an order of magnitude faster than initial aromatic hydrogenation, 113,115 except for 4-methyldibenzothiophene, which is sterically inhibited. The 2-, 3-, and 4-ring aromatics that dominate the neutrals fraction are hydrogenated somewhat (the % of naphthenic carbon increases from ∼16 to ∼25% in 16 h), with evident equilibrium limitations.…”

“…The phenolic compounds, concentrated in the weak acid fractions, undergo HDO at rates faster than for either aromatic hydrogenations, HDS, or HDN at typical conditions (350 °C, 12.2 MPa H 2 , 0.2 WHSV [gcat/(g feed*h)]). Both the HDO and HDS reactions were pseudo-first-order in the reactant, HDO about an order of magnitude higher rate constant than comparable HDS reactions, 10 –4 L/(gcat*s) being typical. ,, However, ethers and furans were far less reactive, − either in the weak acids or the neutral oils (∼20 times less here than phenolics). Tetralins, indans, cyclohexylbenzenes, cyclo- and dicycloalkanes, and two- and three-ring aromatics dominate the hydroprocessing products of the weak acids.…”

“…The model compound work led to more complex studies of HDS, HDN, and HDO of entire coal liquid fractions. − A first step was to be able to understand and quantify such complex mixtures by functional group analysis using combined NMR, elemental and mass spectral analysis, − after separation of the coal liquids into fractions by either LC or GC. , The catalyst here was presulfided Ni–Mo/Al 2 O 3 . The HDN rates of the primary N-containing fractions varied as strong bases (e.g., quinolines, biphenylamines, acridine) < weak bases (e.g., imidazoles, aminonaphthols, quinolinol, indolizines, carbazoles) < neutral resins (containing fewer N-containing compounds, but with carbazoles, quinolines, indanones, indoles, quinoxaline oxides, benzothiazoles) .…”

“…The 2-, 3-, and 4-ring aromatics that dominate the neutrals fraction are hydrogenated somewhat (the % of naphthenic carbon increases from ∼16 to ∼25% in 16 h), with evident equilibrium limitations. 115 The phenolic compounds, concentrated in the weak acid fractions, 114 undergo HDO at rates faster than for either aromatic hydrogenations, HDS, or HDN at typical conditions (350 °C, 12.2 MPa H 2 , 0.2 WHSV [gcat/(g feed*h)]). Both the HDO and HDS reactions were pseudo-first-order in the reactant, HDO about an order of magnitude higher rate constant than comparable HDS reactions, 10 −4 L/(gcat*s) being typical.…”