Acid Strength Controlled Reaction Pathways for the Catalytic Cracking of 1-Pentene to Propene over ZSM-5

Abstract

The influence of acid strength was evaluated toward the selectivity to propene on conversion of 1-pentene. For the catalytic cracking of 1-pentene, the main reaction pathways and the molar ratio of propene to ethene (P/E ratio) were controlled by acid strength with the appropriate amount of total acid sites. The results showed that the P/E ratio increased with decreasing amounts of strong acid sites, since the activation energies of individual reaction pathways were influenced by acid strength to a different extent. Strong acid sites could promote pathway I′ (C 5 2− → C 2 2− + C 3 2− ) and pathway II′-1 (C 6 2− → C 2 2− + C 4 2− ), while weak acid sites preferred pathway II′ (2C 5 2− → C 10 + → C 4 2− + C 6 2− ) and pathway II′-2 (C 6 2− → 2C 3 2− ), since pathways II′ and II′-2 underwent some energetically favorable routes (tertiary− secondary, secondary−secondary) of carbenium ion intermediates. By manipulation of the acid strength distribution on ZSM-5, the P/E ratio and selectivity of propene could be significantly improved, suggesting that this can provide an important guideline for improving such a process. In addition, we also designed a coupled process combing butene and pentene coconversion, as pentene and butene could be produced during C 4 2− and C 5 2− catalytic cracking. The coupled process could offer a promising solution to gain high selectivity of propene from C 4 and C 5 olefin cracking.

A Systematic Study of Isomorphically Substituted H‐MAlPO‐5 Materials for the Methanol‐to‐Hydrocarbons Reaction

“…This conclusion is in line with literature reports, which showed that only strongly acidic zeolites could crack C 5 + alkenes to light C 2 and C 3 alkenes, whereas less-acidicz eotypes favored oligomerization followed by cracking to higher alkenes. [56,57] Interestingly,M iyaji et al showedt hat 2-methyl-2butene and 1-pentene were not cracked in am onomolecular mechanism over H-SAPO-5, [75] in line with the resultspresented in Figure 5. Furthermore, Meusinger et al studied cracking of n-hexanea nd n-butane overH -MgAlPO-5, H-CoAlPO-5, and H-SAPO-5.…”

Coated sulfated zirconia/SAPO-34 for the direct conversion of CO2to light olefins

“…35 This type of acidity has been reported as responsible for the direct cracking of C 5+ olefins via the classical β-scission mechanism. [36][37][38] Again, in line with the literature 29 additional Brønsted-like acid sites are generated after pretreatment of the ZrS/SAPO-34 composite with water vapor as, overall, a shift in the main desorption peak to higher temperatures is observed (see yellow spectra in Fig. 2A).…”

“…3A). [36][37][38] As expected, after boiling, the 27 Al spectrum of the ZrS/ SAPO-34 is consistent with the fresh SAPO-34 material itself, indicating the internal rearrangement to regain Brønsted acid sites. However, 27 Al is a quadrupolar nucleus and its NMR line-shape typically suffers from residual second-order quadrupolar interactions.…”

Strategies to Enhance the Catalytic Performance of ZSM-5 Zeolite in Hydrocarbon Cracking: A Review

“…The strong acid sites prefer to crack 1-pentene to ethylene. Then, the ratio of propylene to ethylene can be controlled between 1.2 and 7.9 by adjusting the acid strength of ZSM-5 zeolite [112].…”