Transformation of but-1-ene into aromatic hydrocarbons over ZSM-5 zeolites

Abstract

The yield of aromatic hydrocarbons from but-1-ene increases greatly when zinc cations are incorporated into ZSM-5 zeolites. Thus, the selectivities to aromatics were 38.6 % and 77.8 YO over H-ZSM-5 and Zn-ZSM-5, respectively, at 773 K. For both zeolites, the main aromatic products are benzene, toluene and xylenes. A variety of aromatic products implies that the interconversion among alkenes precedes their aromatization over ZSM-5 zeolites. The ratio of alkanes to aromatics was close to 3 over H-ZSM-5, indicating that aromatics are formed by the successive deprotonation and hydride transfer to carbenium ions from oligomerized products. On the other hand, the ratio was 0.9 over Zn-ZSM-5, indicating that the direct dehydrogenation of intermediate alkenes is involved in aromatization. Over Hborosilicate, the formation of alkanes and aromatics is negligible. The aromatization activity developed on incorporating zinc cations into the borosilicate, indicating the essential rol of zinc species in aromatization. The dehydrogenation activity of zinc species is further confirmed by the high selectivity to butadiene from but-1-ene at low contact time over Znborosilicate.

Oligo-Aromatization of Light Hydrocarbons from Petroleum Refining Processes Over ZnO/MFI Microporous Material

“…The major role of acid sites is to function as a proton source for alkanes, leading to the formation of carbocations and for interaction with alkenes (π-complex) often resulting in oligomerization. A large number of scientific papers and patents are related to the aromatization of light alkanes and alkenes C2 -C4, of liquefied petroleum gas (LPG) and of light and heavy naphtha [16][17][18][19][20][21][22][23][24][25][26][27][28][29]. Many types of zeolites structures were tested for the aromatization of lower saturated and unsaturated hydrocarbons: ZSM-5 (MFI) , ZSM-11 (MEL), LTL [80], ZSM-22 (TON), MCM-22 (MWW) , BETA (BEA) , AlPO4-5; -11 (AFI, AEL) and EU-1 (EUO) .…”

“…The catalysts investigated contain as dehydrogenating metal (metallic, ionic, oxide); gallium [1, 18-25, 28, 30-47, 49, 50], zinc [19-23, 28, 31-36, 43-45, 47, 50-80], platinum [21,25,28,31,83], cobalt [76], molybdenum [55], nickel, iron [76], copper [65], palladium, ruthenium, rhenium, silver, Zn-Ni, Zn-Cu, Zn-Ga, Ga-Pt, Ga-In. The review of studies showed that only the medium pore zeolites ZSM-5 modified with metals as Ga, Pt, Zn and LTL zeolite in K or Ba form modified with Pt or Zn appear to be the most effective catalysts for alkane / alkene aromatization reaction [17][18][19][20][21][22][23][24][25][26][27][28].…”

Decarboxylation of Lactones over Zn/ZSM‐5: Elucidation of the Structure of the Active Site and Molecular Interactions

“…Thus water is not only required to reduce "carbon" deposition, but also acts as ac atalyst to produce CO 2 and butene from GVL over the ZnÀOH and Brønsted acidic sites in ac ooperative manner.B utene,o nce formed, is known to undergo aromatization over H-ZSM-5-based materials to give aromatic compounds;this has been well studied and will not be further discussed. [21] As mentioned, the Zn/ZSM-5 catalyst is at ypical microporous acidic zeolite.I te xhibits slow but progressive deactivation over 310 ho fo n-stream testing.H owever,t he deactivated Zn/ZSM-5 catalyst can be fully regenerated through calcination in air at 600 8 8Cf or 1h.T he same concentration of Zn (0.99 Zn per unit cell) was obtained, by adding up the SOFs of Zn-1 and Zn-2 (Table S5). Similarly, the derived coordination numbers and corresponding ZnÀO distances from SXRD refinement and EXAFS (Table 1a nd Table S6) of the regenerated sample also clearly indicate the structural integrity of the active sites in Zn/ZSM-5 after prolonged testing (see Sections S6 and S7 and Figure S9).…”

Decarboxylation of Lactones over Zn/ZSM‐5: Elucidation of the Structure of the Active Site and Molecular Interactions

“…Thus water is not only required to reduce “carbon” deposition, but also acts as a catalyst to produce CO 2 and butene from GVL over the Zn−OH and Brønsted acidic sites in a cooperative manner. Butene, once formed, is known to undergo aromatization over H‐ZSM‐5‐based materials to give aromatic compounds; this has been well studied and will not be further discussed …”