Study of the catalytic reactions of ethylene oligomerization in subcritical and supercritical media over a NiBEA catalyst

Abstract

We report a study of the catalytic reactions of ethylene oligomerization over nickel impregnated in aluminum silicate using subcritical and supercritical media. We found the BET surface area decreases with increasing nickel loading, indicating the deposition of NiO particles in the catalyst surface. We compared the performance of the NiBEA catalyst with the protonated form of the commercial support used during the preparation and showed that, although the protonated form promotes the oligomerization of ethylene, the corresponding oligomers do not desorb from the catalyst surface. Conversely, the introduction of nickel in the catalyst facilitates the desorption of the oligomers. Additionally, we used FTIR and GC-MS/FID to characterize the adsorbed and desorbed oligomers, and develop reaction pathways for the ethylene oligomerization over the NiBEA catalyst. We found that both adsorbed and desorbed oligomers are aliphatic, and the non-desorbed products constitute the coke. Additionally, we found that pressure and temperature both increase the oligomerization and desorption rates of adsorbed oligomers. Under

Effects of Ethene Pressure on the Deactivation of Ni‐Zeolites During Ethene Oligomerization at Sub‐ambient Temperatures

“…Alkene oligomerization carried out under near‐supercritical conditions has been proposed to attenuate deactivation via the solvation of carbonaceous species that serve as coke precursors, [11–15] reminiscent of regeneration treatments using supercritical alkane phases to remove coke from zeolite catalysts during hydrocarbon processing [16–20] . Mitigated deactivation was reported during ethene oligomerization on Ni−H‐Beta and Ni−Al‐SBA‐15 under supercritical conditions by Jan et al., [13] and during heavier alkene (e. g., 1‐butene, 1‐hexene) oligomerization on H‐FER, H‐MFI, and H‐FAU under near‐supercritical conditions [12,14] .…”

Novel Ni-SIRAL Catalyst for Heterogeneous Ethylene Oligomerization

“…The XRD patterns of the nickel catalysts show the absence of boehmite peaks due to the transformation of boehmite into γ-Al 2 O 3 after calcination at 550 °C and the presence of very weak diffractions at 37.3, 43.3, and 62.9°, characteristic of (110), (200), and (220) fcc-planes of NiO crystals . The weak intensity of NiO diffractions indicates that if NiO crystallites were formed during impregnation, they are relatively small for both catalyst samples (2.8 and 4.9 wt % nickel) …”

“…Ni-SIRAL 40 HPV catalysts (abbreviated as Ni-SIRAL) with different nickel loadings were produced via impregnation of SIRAL with Ni­(NO 3 ) 2 ·6H 2 O, using a procedure reported in our previous publications. , Briefly, a nickel nitrate (Ni­(NO 3 ) 2 ) solution was prepared by mixing a given mass of Ni­(NO 3 ) 2 ·6H 2 O with 100 mL of deionized waterthe mass of Ni­(NO 3 ) 2 ·6H 2 O used was determined based on the target nickel loading on the SIRAL support (Figure S1, Supporting Information). Then, the Ni­(NO 3 ) 2 solution was dripped onto the pristine SIRAL support under agitation at room temperature for 6 h. Afterward, the solution was vacuum-filtered to recover the solid fraction.…”

“…Research at the University of Washington has extensively studied the oligomerization of ethylene over nickel-based solid catalysts. − We reported the production of liquid products over the Ni–H-β and provided visual evidence that supercritical ethylene promotes coke dissolution during the reaction. , High pressures are required for supercritical ethylene oligomerization because of the high ethylene critical pressure, 50.4 bar. Most of the liquid obtained under supercritical conditions comprised C 10 + alkenes with a small fraction of cycloalkanes (less than 1.0 wt %).…”

“…For the coke solubility effect to occur, coke dissolution rates in supercritical ethylene have to surpass product formation rates on the catalyst; otherwise, carbon deposits may form on the catalyst surface. , High reaction rates at supercritical conditions over a catalyst that contains a low pore volume led to the accumulation of products on the catalyst, thus causing pore plugging. Catalyst deactivation was observed even when we used the Ni–H-βa catalyst that contains a substantial fraction of mesopores (approximately 40%)for the oligomerization of supercritical ethylene .…”