Influence of zeolite pore structure on product selectivities for protolysis and hydride transfer reactions in the cracking of n-pentane

Abstract

The conversion of n-pentane was carried out to examine the effects of reaction conditions on changes in product selectivities at 823 K, using zeolites with 10- and 12-membered rings. We also investigated the influence of the pore structure of these zeolites on their catalytic activities for both protolysis and hydride transfer reactions. In the first half of this work, we examined the influence of acidic proton concentration and n-pentane pressure on the reaction rates for protolysis and hydride transfer reactions using ZSM-5 zeolites. The rates of hydride transfer reactions were more influenced by pentane pressure compared to protolysis reactions, and were proportional to the square of n-pentane pressure and the concentration of acidic protons. In the second half of this work, the influence of the zeolite pore structure on changes in product selectivities with n-pentane conversion and that on the rates of protolysis and the hydride transfer reactions were revealed using various zeolites with 10- and 12-membered rings. The catalytic activities of zeolites for the protolysis and hydride transfer reactions were influenced more by the spatial volume of the zeolite cavity than the acid strength of protons on the zeolite.

Ketal Sugar Conversion Into Green Hydrocarbons by Faujasite Zeolite in a Typical Catalytic Cracking Process

“…After the protolytic reaction (Kotrel et al, 2000) (in low conversion and differential conditions) n-hexane is converted into molecular propylene/propane, ethylene/butanes and ethane/butenes ratios close to one. Higher rate of hydrogen transfer reaction decreases the olefin concentration (Miyaji et al, 2015) and both propylene/propane and total light olefins/total light paraffins (in wt.%) ratio may be used to indicate the hydrogen transfer (HT) reaction. Both ratios increased from USY to USY-D500 and further increased were observed to USY-D500-Silica.…”

酵素およびゼオライトの空洞内でのアルカン転化反応における生成物選択性―空洞容積が生成物への選択性に及ぼす影響―

“…The selectivities for alkenes, hydrogen, and alkanes in the primary reactions (i.e., the protolysis reactions) for n-pentane cracking were not correlated with the turn over frequencies (TOFs) of the zeolites with both 10-membered rings and 12-membered rings 30) . The TOF is a measure of the acid strength.…”

“…8), and the selectivities for hydrogen and pentane, methane and butenes, and propane and ethene decreased slightly (data provided in Ref. 30)). These variations were smaller than those of the selectivities for ethane and propene.…”

“…To investigate the dependence of the catalytic performance on the pore structure of the zeolite, conversion of n-pentane was carried out using various zeolites at 823 K with 10.1 kPa of n-pentane 30) . Various zeolites with 10-and 12-membered rings (Table 3) were hydrothermally synthesized using various structuredirecting agents 30) , and used as catalysts.…”

“…Various zeolites with 10-and 12-membered rings (Table 3) were hydrothermally synthesized using various structuredirecting agents 30) , and used as catalysts. The product selectivities were examined over a wide range of conversion values from zero to about 90 %.…”