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Steam Catalytic Reactions on Vacuum Residue for Producing Petroleum Fuels

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Abstract
ABSTRACT
Humans are facing the biggest energy challenges, transportation fuels especially. In
this study, the effect factors of catalytic characters on the catalytic upgrading of petroleum
residues in supercritical water, researched to produce more petroleum transportation fuels,
were deeply investigated.
In the first study, NiK/yCe x Zr 1-x O 2 -macroporous Al 2 O 3 catalysts (y = 0, 10, 20, and
30; x = 0.73-0.92) were synthesized by dispersing different amounts of Ce x Zr 1-x O 2 phase
onto macroporous -Al 2 O 3 as supports, and then subsequently impregnating Ni and K into
the supports, which possessed advantageous properties, such as a high surface area, ordered
macropores and high oxygen storage capacity. Moreover, the introduction of Ni and K
metals into these supports created more oxygen vacancies in them. We applied these
catalysts to the cracking of vacuum residue with steam. It was found that the variation of
the liquid yield with the amount of Ce x Zr 1-x O 2 phase showed a volcano pattern. The
macropores in the supports played an important role in enhancing the diffusion of large
molecules to the active sites, while the high oxygen storage capacity over the Ce x Zr 1-x O 2
phase improved the oxidative cracking rate, thereby increasing the lighter oil fraction from
the vacuum residue.
In the second study, a NiK/CeO 2 catalyst was employed to investigate the
interaction between Ni metal and CeO 2 support and its effect on oxidative cracking of
vacuum residue. In the reaction results, a large amount of light oils, including naphtha,
diesel and VGO, was produced through oxidative cracking over CeO 2 , and the quality of
the liquid products was significantly improved by hydrogenation. The interaction between
Ni metal and CeO 2 support induced the formation of a Ce y Ni 1-y O 2- solid solution and
increased the number of oxygen vacancies, thus enhancing the oxidative cracking of
vacuum residue. Further, the addition of NiK into the supports provided Ni metallic sites

for hydrogenation, producing more liquid products with a high H/C ratio. As a result,
NiK/CeO 2 catalyst showed a higher diesel yield (22.87%) than that without catalyst
(9.14%).
In the third study, NiK/ceria-zirconia (CZ) and NiK/ceria-zirconia-alumina (CZ-A)
catalysts were investigated in order to further understand the roles of mixed-oxide supports
in the steam catalytic cracking of vacuum residue (VR). Compared to thermal cracking,
higher conversions and liquid yields were achieved over the catalysts. Steam decomposition
occurring over the CZ and ZrO 2 phases provided an alternative hydrogen and oxygen
sources for hydrogenation and oxidative cracking, respectively. The introduction of Ni into
the CZ support induced the formation of Ce x (Zr-Ni) 1-x O 2-δ solid solution and the isolation of
the ZrO 2 phase via a strong metal-support interaction, resulting in greater oxygen vacancy
in the bulk structure. In contrast, the strong interaction of CZ and Ni phases with Al 2 O 3
induced higher dispersions of CZ and Ni phases in the NiK/CZ-A catalyst, which resulted
in a greater density of oxygen vacancies on the surface and higher CeO 2 reducibility. As a
result, the quality of the liquid products and naphtha yields were significantly improved by
hydrogenation over the nickel metallic sites and oxidative cracking through the metal-
support interaction.
In the fourth study, steam oxidative cracking route of 1-methylnaphthalene were
investigated through the combination of oxidation and hydrogenation over nickel-
containing mixed oxide catalysts. Depending on the used supports, several types of active
sites for oxidation, hydrogenation, and steam decomposition were generated by various
metal–support and support–support interactions. The steam-reforming routes were
dominant without nickel, resulting in high gas selectivity due to a full-cracking process.
With nickel, steam oxidative cracking routes were strongly enhanced by a synergistic
combination between hydrogenation occurring on the Ni metallic sites and oxidation over

mobile lattice oxygens in a Ce x Zr 1-x O 2 solid solution, resulting to the higher selectivity of
liquid products than that of gas products. Among the prepared catalysts, an optimal
interaction between Ni and Ceria-Zirconia-Alumina mixed oxide support caused not only
an increase of oxygen vacancies in solid solutions, but also the formation of smaller Ni
metallic nanoparticles, resulting in reinforcement of steam oxidative cracking of 1-methyl
naphthalene.
Finally, the hierarchically macro-mesoporous grainy aluminas containing the novel
properties were prepared for being a support in xK/Ni-Al 2 O 3 catalyst which are applied to
study 1-methyl naphthalene steam reforming. The impact of a hierarchically ordered macro-
mesoporous structure on steam reforming of 1-methyl naphthalene at the low temperature
(600 o C) was investigated over xK/Ni-MeAl (mesoporous alumina-supported nickel &
potassium) and xK/Ni-MaAl (macro-mesoporous alumina-supported nickel & potassium)
catalysts in a fixed-bed reactor system. The hierarchical ordered macro-mesoporous
structure in Al 2 O 3 support played an important role in enhancing the reactant diffusion to
the active sites promoted both the catalytic cracking and steam reforming, resulting in high
gas yields and 1-methyl naphthalene conversion. The introduction of potassium on Ni-
MeAl and Ni-MaAl supports created more nickel active sites enhancing significantly the
steam reforming rate. In addition, using macro-mesoporous alumina as support also
increased the nickel site dispersion, leading to enrichment of potassium location on alumina,
which makes the catalytic deactivation being slow down.
Author(s)
도 티 리엔
Issued Date
2020
Awarded Date
2020-02
Type
Dissertation
URI
https://oak.ulsan.ac.kr/handle/2021.oak/6385
http://ulsan.dcollection.net/common/orgView/200000284742
Affiliation
울산대학교
Department
일반대학원 화학공학전공
Advisor
Professor Eun Woo Shin
Degree
Doctor
Publisher
울산대학교 일반대학원 화학공학전공
Language
eng
Rights
울산대학교 논문은 저작권에 의해 보호받습니다.
Appears in Collections:
Chemical Engineering > 2. Theses (Ph.D)
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