- Library Home /
- Search Collections /
- Open Collections /
- Browse Collections /
- UBC Theses and Dissertations /
- A study of the catalytic reaction of olefins with methane
Open Collections
UBC Theses and Dissertations
UBC Theses and Dissertations
A study of the catalytic reaction of olefins with methane Liu, Qingdong
Abstract
The catalytic reaction of CH₄ with C₃H₆, referred to as CH₄/C₃H₆ homologation or coupling, was investigated in an attempt to selectively produce C₄ hydrocarbons. The CH₄/C₃H₆ coupling reaction was conducted over various Ni catalysts at temperatures in the range 300 °C to 375 °C and 101 kPa. The effects of process variables, catalyst promoters and different supports on the CH₄/C₃H₆ coupling reaction were examined. In addition, the role of the carbonaceous species deposited on the catalyst surface during catalyst reduction in CH₄ and during the CH₄/C₃H₆ coupling reaction, was investigated. In preliminary experiments, Ni catalysts supported on AI₂O₃ were modified by K and P, and used for the CH₄/C₃H₆ coupling reaction. The calcined catalysts were reduced in CH₄ at 600 °C for 1 hour before reaction. Compared with Ni/Al₂0₃ catalyst, the Ni/K/Al₂0₃ and Ni/P/Al₂0₃ catalysts showed higher C₃H₆ conversion and C₄ selectivity. The maximum selectivity of 10.0 mole % to the desired C₄ product was achieved over the Ni/K/Al₂0₃ catalyst at 350 °C and 101 kPa with a feed gas composition of 90 mol % CH₄/IO mol % C₃H₆. The C₃H₆ conversion decreased significantly with time-on-stream. During catalyst reduction in CH₄, decomposition of CH₄ occurred and a large amount of carbonaceous species deposited on the catalyst surface. Subsequently, during the CH₄/C₃H₆ coupling reaction, additional carbonaceous species were deposited on the catalyst surface. The presence of two types of carbonaceous species were identified using temperature programmed surface reaction (TPSR) in H₂ . The first type of carbonaceous species was relatively active, and reacted with H₂ at low temperature, in the range 192 °C to 237 °C. A second type of carbonaceous species was relatively inactive, and reacted with H₂ at high temperature, in the range 547 °C to 667 °C. The amount of the low temperature carbonaceous species present on the catalyst surface after the CH₄/C₃H₆ coupling reaction, was shown to correlate with the C₄ yield. The significance of the treatment of catalyst in CH₄ before reaction was shown to be less important than what was claimed in previous studies. The CH₄ reduced catalyst surface had higher C₃H₆ conversion than H₂ reduced catalysts but the C₄ selectivity was unchanged. A model of the carbonaceous species deposition process on the catalyst surface was proposed. The effect of supports on the CH₂/C₃H₆ coupling reaction was also investigated. Different reaction paths were proposed. The major reactions over non-zeolite supported Ni catalysts were C₃H₆ decomposition and C₃H₅ hydrogenation with a low activity for homologation. The C₃H₅ conversion was high and C₃H₆ metathesis and olefin dimerization were the dominant reactions over the Na-Y supported Ni catalyst. The high activity of the Ni/Na-Y catalyst was a consequence of the acidic property of the Na-Y support. After the acidic property of the Ni/Na-Y catalyst was neutralized, the catalyst activity decreased dramatically and evidence for the C₃H₆ homologation was apparent. Results of the present study have shown that C₄ selectivity, particularly 1-butene, was formed by the homologation reaction: CHX + C₃H₆ -> 1-C₄H₈, where CHX is a surface carbon species generated either from catalyst reduction in CH₄ or from C₃H₆ decomposition reactions that occur during reaction. Most importantly, the present study has shown that gas phase CH₄ does not homologate C₃H₆ directly at the conditions studied. The maximum C₄ selectivity of 10 %, obtained using Ni/K/Al₂0₃ catalyst operated at 350 °C and 1O1kPa, was also very low which together with the fact that direct CH₄/C₃H₆ homologation did not occur, point to the need for a multi-step reaction if this approach is to be utilized for direct CH₄ upgrading.
Item Metadata
Title |
A study of the catalytic reaction of olefins with methane
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
1998
|
Description |
The catalytic reaction of CH₄ with C₃H₆, referred to as CH₄/C₃H₆ homologation or
coupling, was investigated in an attempt to selectively produce C₄ hydrocarbons. The CH₄/C₃H₆
coupling reaction was conducted over various Ni catalysts at temperatures in the range 300 °C to
375 °C and 101 kPa. The effects of process variables, catalyst promoters and different supports
on the CH₄/C₃H₆ coupling reaction were examined. In addition, the role of the carbonaceous
species deposited on the catalyst surface during catalyst reduction in CH₄ and during the
CH₄/C₃H₆ coupling reaction, was investigated.
In preliminary experiments, Ni catalysts supported on AI₂O₃ were modified by K and P,
and used for the CH₄/C₃H₆ coupling reaction. The calcined catalysts were reduced in CH₄ at 600
°C for 1 hour before reaction. Compared with Ni/Al₂0₃ catalyst, the Ni/K/Al₂0₃ and Ni/P/Al₂0₃
catalysts showed higher C₃H₆ conversion and C₄ selectivity. The maximum selectivity of 10.0
mole % to the desired C₄ product was achieved over the Ni/K/Al₂0₃ catalyst at 350 °C and 101
kPa with a feed gas composition of 90 mol % CH₄/IO mol % C₃H₆. The C₃H₆ conversion
decreased significantly with time-on-stream.
During catalyst reduction in CH₄, decomposition of CH₄ occurred and a large amount of
carbonaceous species deposited on the catalyst surface. Subsequently, during the CH₄/C₃H₆
coupling reaction, additional carbonaceous species were deposited on the catalyst surface. The
presence of two types of carbonaceous species were identified using temperature programmed
surface reaction (TPSR) in H₂ . The first type of carbonaceous species was relatively active, and
reacted with H₂ at low temperature, in the range 192 °C to 237 °C. A second type of carbonaceous species was relatively inactive, and reacted with H₂ at high temperature, in the
range 547 °C to 667 °C. The amount of the low temperature carbonaceous species present on the
catalyst surface after the CH₄/C₃H₆ coupling reaction, was shown to correlate with the C₄ yield.
The significance of the treatment of catalyst in CH₄ before reaction was shown to be less
important than what was claimed in previous studies. The CH₄ reduced catalyst surface had higher
C₃H₆ conversion than H₂ reduced catalysts but the C₄ selectivity was unchanged. A model of the
carbonaceous species deposition process on the catalyst surface was proposed.
The effect of supports on the CH₂/C₃H₆ coupling reaction was also investigated. Different
reaction paths were proposed. The major reactions over non-zeolite supported Ni catalysts were
C₃H₆ decomposition and C₃H₅ hydrogenation with a low activity for homologation. The C₃H₅
conversion was high and C₃H₆ metathesis and olefin dimerization were the dominant reactions
over the Na-Y supported Ni catalyst. The high activity of the Ni/Na-Y catalyst was a consequence
of the acidic property of the Na-Y support. After the acidic property of the Ni/Na-Y catalyst was
neutralized, the catalyst activity decreased dramatically and evidence for the C₃H₆ homologation
was apparent.
Results of the present study have shown that C₄ selectivity, particularly 1-butene, was
formed by the homologation reaction: CHX + C₃H₆ -> 1-C₄H₈, where CHX is a surface carbon
species generated either from catalyst reduction in CH₄ or from C₃H₆ decomposition reactions
that occur during reaction. Most importantly, the present study has shown that gas phase CH₄
does not homologate C₃H₆ directly at the conditions studied. The maximum C₄ selectivity of 10
%, obtained using Ni/K/Al₂0₃ catalyst operated at 350 °C and 1O1kPa, was also very low which
together with the fact that direct CH₄/C₃H₆ homologation did not occur, point to the need for a multi-step reaction if this approach is to be utilized for direct CH₄ upgrading.
|
Extent |
6314844 bytes
|
Genre | |
Type | |
File Format |
application/pdf
|
Language |
eng
|
Date Available |
2009-06-02
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
|
DOI |
10.14288/1.0058632
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
1998-05
|
Campus | |
Scholarly Level |
Graduate
|
Aggregated Source Repository |
DSpace
|
Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.