Conversion of n-Octene over Nanoscale HZSM-5 Zeolite

Abstract

Transformation of n-octene has been investigated over nanoscale HZSM-5 at different reaction temperature and contact time. The results show that the main reaction was isomerization of n-octene over 200°C. Hydrogen transfer reaction also occurred at 200°C, but the products were alkanes and cycloolefins instead of aromatics. The aromatization was promoted by high temperature. The maximum selectivity of i-paraffins occurred between 300 and 350°C. Propene, butene and pentene were the primary cracking products. These olefins were oligomerized and cracked to produce a wide distribution of olefins with different carbon atoms. These intermediates then were quickly transformed into aromatics and alkanes by hydrogen transfer over acid sites at high reaction temperature. Propane and butane can be transformed into methane and ethane at long contact time above 400°C.

An Initial Study of the Catalytic Reforming of Crop Oil‐Derived 1‐Alkenes with HZSM‐5 to Aromatic Hydrocarbons

“…) were formed in a lower abundance. Furthermore, the C 8 –C 10 aromatics range turned out to be the most abundant range in contrast to that reported in previous studies where C 6 –C 8 BTEX were the most abundant products resulting from the zeolite‐facilitated reforming reactions (Bhan and Delgass, ; Fegade et al, ; Hodala et al, ; Long et al, , ; Nash et al, ; Olson et al, ; Smiešková et al, ), although a relatively large C 9 aromatic fraction was observed in the case of n ‐octene conversion (Long et al, ), corroborating the results obtained in our study.…”

“…It was also noted that large amounts of higher‐MW alkylnaphthalene and indane diaromatics were produced, with C 15 naphthalene (i.e., C 5 substituted) being the most abundant. These products were not observed previously in smaller‐size alkene reforming (Bhat and Halgeri, ; Hodala et al, ; Long et al, , ; Maslyanskii et al, ; Nash et al, ; Olson et al, ). Also, acyclic dienes were identified only in Experiments 9 and 10 by their library match, based on the fragmentation pattern, which was different from those of the corresponding isomers, cycloalkenes and acyclic alkynes (the computer‐generated library match was confirmed by the manual case‐to‐case matching of the available MS spectra).…”

“…As for the aromatic products, their average size was larger than that of BTEX, which are formed when C 2 (adsorbed ethene) intermediates are postulated to dominate the reaction mechanism (Asomaning et al, , ; Bhat and Halgeri, ; Fegade et al, ; Hodala et al, ; Kubátová et al, ; Long et al, , ; Mäki‐Arvela et al, ; Maslyanskii et al, ; Nash et al, ; Olson et al, ; Stanciulescu et al, ; Štávová et al, ). Small‐sized primary intermediates definitely form, as the gas‐phase product yield increases with a decrease of the TCR.…”

“…Toluene and xylenes were shown to be the major products from the aromatization of n ‐octene over nanoscale HZSM‐5 catalysts (Long et al, ). Similar to light alkene aromatization, n ‐octene aromatization over nanoscale HZSM‐5 catalysts produced greater yields of xylenes at lower temperatures, whereas benzene and toluene dominated the products at higher temperatures (Long et al, ). A similar trend was observed by Nash et al for 1‐hexane and 1‐octene conversion using Ga‐doped HZSM‐5 (Nash et al, ), although the two studies on 1‐octene conversion showed significant differences both in the aromatics yield (30–45% vs. 10–20% and 50–75% (Long et al, ;Long et al, ; Nash et al, )) and selectivity (xylenes vs. toluene being the main aromatic product (Long et al, ; Nash et al, )).…”

The Aromatization of Propene Via Nano-Size HZSM-5

“…Initially, creating such a varied cavity size design required the use of removable organic templates, but the seminal work of [10] provided a simple template-free nano-size zeolite synthesis protocol. This advancement led to a number of successful applications demonstrating the advantages of using nano-size zeolite catalysts, including but not limited to aromatics' production and ranging from alkene isomerization to triglyceride transesterification [7,[11][12][13][14][15][16][17][18][19].…”