(411f) Co-Processing of Methane and Higher Alkanes in a Staged Autothermal Reactor

Staged autothermal reactors have previously been shown to enable ethanol and methanol dehydration reactions to occur at 100 milliseconds or less without a need for external heat input [1-2]. We aim to extend the staged autothermal reactor concept to hydrocracking and hydroisomerization of higher hydrocarbons. A reactor was fabricated containing a 0.5 wt % Pt/γ-Al₂O₃ stage mixed with 10 g of either H-BEA, HZSM-5, or USY and situated downstream of a 1 wt % Rh - 1 wt % Ce /α-Al₂O₃ stage.  CH_4, fed upstream to the Rh-Ce stage, formed oxidation products H₂, CO, CO₂, and H₂O and released energy that heated the downstream zeolite stage. Hexane, decane, and 2-decanone were fed to the reactor between the two stages to avoid undesired oxidation reactions on the Rh-Ce stage.  Temperatures were changed by varying the separation distance between the stages.  Conversion of decane over USY and HBEA was approximately twice as high as the conversion over HZSM-5 from 300 °C to 460 °C.  The 12-member ring pore size of HBEA and USY reduces diffusion limitations of reactant molecules traveling through to an acid site leading to an increase in conversion [3]. The selectivity of aromatics formed from 2-decanone increased from 5% at 300 °C to 25% at 460 °C over HZSM-5.  Aromatic formation may be promoted by an increased initial propene selectivity formed by 2-decanone hydroprocessing.  At high conversions, more propene is consumed to form aromatics. Over all zeolites studied, selectivity of C₅-₆  compounds decreased with conversion while C_2-3 compounds increased, indicating a series reaction was occurring. C_5-6 products form first from decane and are then further decomposed.  The increase in yield of C₅₊ products and the presence of branchedisomers indicates the feasibility of integrating a hydroprocessing catalyst with a partial oxidation catalyst in a single-pipe autothermal reactor.

¹M.J. Skinner, E.L. Michor, W. Fan, M. Tsapatsis, A. Bhan, and L.D. Schmidt. ChemSusChem  4 (2011) 1151-1156.

²H. Sun and L.D. Schmidt. Applied Catalysis A, General 404 (2011) 81-86.

³Z. Wang, A. Kamo, T. Yoneda, T. Komatsu, T. Yashima. Applied Catalysis A, General 159 (1997) 119-132