Catalytic Ethylene Oligomerization over Ni/Al-HMS: A Key Step in Conversion of Bio-Ethanol to Higher Olefins

Abstract

Al-modified hexagonal mesoporous silica (HMS) materials were synthesized using dodecylamine as a template according to the methods reported in the literature. FT-IR spectra proved that Al3+ ions entered in the HMS framework in Al-HMS (prepared by sol-gel reaction) but Al3+ ions existed in the extra-framework in Al/HMS (prepared by post-modification). NH3-TPD indicated that either Al-HMS or Al/HMS had solid acid sites on the surface, and the acidic strength of Al/HMS was stronger than that of Al-HMS. For ethylene oligomerization at 200 °C under 1 MPa, Ni/Al-HMS showed an ethylene conversion of 96.3%, which was much higher than that over Ni/Al/HMS (45.6%). The selectivity for C4H8, C6H12, C8H16, and C8+ was 37.7%, 24.5%, 24.0%, and 9.1% for ethylene oligomerization over Ni/Al-HMS, respectively. Ni/Al-MCM-41, which has been reported as an effective catalyst for ethylene oligomerization in the literature, showed a high ethylene conversion (95.2%) similar to that of Ni/Al-HMS in this study. However, the selectivity for C8H16 over Ni/Al-MCM-41 (16.3%) was lower than that over Ni/Al-HMS (24.0%) in the ethylene oligomerization. For ethanol dehydration at 300 °C under 1 MPa, a commercial H-ZSM-5 catalyst showed a high ethylene yield (91.2%) after reaction for 24 h using a feed containing 90 wt.% ethanol and 10 wt.% water. In this study, a two-step process containing two fixed-bed reactors and one cold trap was designed to achieve the direct synthesis of higher olefins from bio-ethanol. The cold trap was used to collect the water formed from ethanol dehydration. By using H-ZSM-5 as a catalyst for ethanol dehydration in the first reactor and using Ni/Al-HMS as a catalyst for ethylene oligomerization in the second reactor, higher olefins were continuously formed by feeding a mixture containing 90 wt.% ethanol and 10 wt.% water. The yields of higher olefins did not decrease after reaction for 8 h in the two-step reaction system.

Jet fuel range hydrocarbon synthesis through ethylene oligomerization over platelet Ni-AlSBA-15 catalyst

“…Sugar/starch-base bioethanol is now produced on a large scale and is one of the most successful commercial biofuels mainly used for automobiles by partially blending with gasoline. However, the needs of ethanol for automobiles is expected to be stagnant or decreased in the foreseeable future, due to the ethanol blend-wall limitation as well as the incoming of electric and hydrogen-fueled vehicles [7,8]. Thus, it is necessary to develop new technologies for utilizing the excess ethanol in advance.…”

“…Nicontaining catalysts are regarded as the promising heterogeneous catalyst for synthesizing higher olefins via the ethylene oligomerization as reported in many studies [12][13][14][15]. The ethylene oligomerization over Ni-based catalyst has been carried out in wide ranges of temperatures and pressures in both batch and flow reactors [8,[11][12][13]16]. The reaction conditions such as temperature, pressure and space velocity, as well as, the catalytic properties have a strong effect on the activity and selectivity [12].…”

“…This is due to the strong acidity of zeolite and limited mass transfer of oligomeric products in heterogeneous catalysis [2,14]. Coke is formed on the surface of acidic zeolite during the reaction, and then blocks the pores of zeolite causing the catalyst deactivation [8]. One of the approaches to overcome such a problem is to use a weak solid acidity catalyst with larger pores.…”

Catalytic Dehydration of Ethanol over WOx Nanoparticles Supported on MFI (Mobile Five) Zeolite Nanosheets

“…Presently, global ethylene production is around 150 million tons per year and is expected to increase [1]. Ethylene is widely used to produce ethylene glycol as antifreeze and many organic materials, such as ethylene dichloride, acetaldehyde, acetic acid, ethylene glycol, chloroethanol, and vinyl acetate [2][3][4]. Nowadays, over 90% of ethylene is produced using the naphtha steam cracking process at temperatures of 750 to 900 • C [2][3][4][5], which requires huge amounts of energy and generates massive amounts of carbon dioxide [6].…”

“…Ethylene is widely used to produce ethylene glycol as antifreeze and many organic materials, such as ethylene dichloride, acetaldehyde, acetic acid, ethylene glycol, chloroethanol, and vinyl acetate [2][3][4]. Nowadays, over 90% of ethylene is produced using the naphtha steam cracking process at temperatures of 750 to 900 • C [2][3][4][5], which requires huge amounts of energy and generates massive amounts of carbon dioxide [6]. To overcome these problems, large investments were made in the development of new catalytic pathways for sustainable ethylene production and these developments resulted in processes such as the catalytic dehydrogenation of light alkanes and the dehydration of bioethanol.…”