Catalytic Cracking of Soybean Oil for Biofuel over γ-Al2O3/CaO Composite Catalyst

In this paper, we report the catalytic cracking of soybean oil for biofuel over γ-Al₂O₃/CaO composite catalysts. The influence of catalysts, cracking temperature and weight hourly space velocity (WHSV) on the products distribution were investigated. The maximum yield (70.0 wt.%) of biofuel with low acid value (6.7 mg KOH g^-1) and oxygen content (5.6%), as well as high calorific value (44.2 MJ kg^-1) was achieved over 35 wt.% γ-Al₂O₃/CaO at 480 ºC and 3.72 h^-1. The paper focused on the variation of biofuel composition and cracking pathway caused by γ-Al₂O₃/CaO composite catalysts via gas chromatography-mass spectrometry (GC-MS) and thermogravimetric (TG) analysis. Calcium oxide would react with fatty acid to yield calcium carboxylates at 300-350 ºC, which were subsequently decomposed into hydrocarbons (57.9 wt.%) and ketones (22.6 wt.%) at 415-510 ºC. As for 35 wt.% γ-Al₂O₃/CaO, the addition of γ-Al₂O₃ was beneficial to generate alkenes (38.2 wt.%), arenes (10.6 wt.%) and alcohols (12.3 wt.%) with ketones decreasing (16.5 wt.%) via γ-hydrogen transfer reaction and disproportination.

Keywords:
soybean oil; catalytic cracking; γ-Al₂O₃/CaO catalysts; biofuel

Authorship

Zhi Zheng

College of Chemical Engineering, Zhejiang University of Technology, 310014 Hangzhou, Zhejiang, P. R. ChinaZhejiang University of TechnologyChinaHangzhou, Zhejiang, ChinaCollege of Chemical Engineering, Zhejiang University of Technology, 310014 Hangzhou, Zhejiang, P. R. China

Biodiesel Laboratory of China Petroleum and Chemical Industry Federation, 310014 Hangzhou, Zhejiang, P. R. ChinaChemical Industry FederationChinaHangzhou, Zhejiang, ChinaBiodiesel Laboratory of China Petroleum and Chemical Industry Federation, 310014 Hangzhou, Zhejiang, P. R. China

Zhejiang Province Key Laboratory of Biofuel, 310014 Hangzhou, Zhejiang, P. R. ChinaZhejiang Province Key Laboratory of BiofuelChinaHangzhou, Zhejiang, ChinaZhejiang Province Key Laboratory of Biofuel, 310014 Hangzhou, Zhejiang, P. R. China

https://orcid.org/0000-0002-4540-3271

Tong Lei

Jun Wang

Yi Wei

Xuejun Liu

Fengwen Yu ^**e-mail: yufw@zjut.edu.cn

Jianbing Ji

*e-mail: yufw@zjut.edu.cn

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables | Formulas

Figures (7)
Tables (6)
Formulas (5)

Fatty acid	Content / wt.%
Palmitic acid (C_16:0)	12.5
Stearic acid (C_18:0)	2.9
Oleic acid (C_18:1)	34.8
Linoleic acid (C_18:2)	49.1
Others	0.6

Property	Density^a a Determined at 20 °C. / (kg m^-3)	Calorific value / (MJ kg^-1)	Viscosity^a a Determined at 20 °C. / cSt	C / %	H / %	O / %
Soybean oil	922	38.6	58.3	77.9	10.9	11.2

Comparison group	Yield of product / wt.%				Distribution of OLP / wt.%
Comparison group	OLP	Water	Solid	Gas	HC^b b HC represents hydrocarbon;	OC^c c OC represents oxygenated compounds; OLP: organic liquid product; A/C: γ-Al2O3/CaO.	C / %	H / %	O / %
Thermal	82.5	2.8	0.4	14.3	46.7	53.3	78.0	11.4	10.6
γ-Al₂O₃	63.6	6.1	10.2	20.1	75.9	24.1	83.2	12.3	4.5
50 wt.% A/C	64.6	5.3	10.6	19.5	70.9	29.1	82.1	11.9	6.0
35 wt.% A/C	70.0	4.9	10.5	14.6	66.5	33.5	82.5	11.9	5.6
20 wt.% A/C	68.8	3.6	8.3	19.3	62.7	37.3	82.6	12.2	5.2
10 wt.% A/C	68.1	3.1	7.2	21.6	65.1	34.9	82.0	12.0	6.0
CaO	67.1	2.3	9.8	20.8	57.9	42.1	81.4	11.7	6.9

Property	Acid value / (mg KOH g^-1)	Calorific value / (MJ kg^-1)	Density (20 ºC) / (kg m^-3)	Kinematic viscosity (20 ºC) / (mm² s^-1)
Thermal	104.7	41.2	880.1	12.2
γ-Al₂O₃	13.5	44.2	809.8	6.3
50 wt.% A/C	8.2	44.3	810.3	7.1
35 wt.% A/C	6.7	44.2	810.6	8.0
20 wt.% A/C	4.7	43.5	828.3	6.1
10 wt.% A/C	7.0	43.9	854.6	8.5
CaO	6.3	43.4	849.9	8.4
Biodiesel^a a According to ASTM6751-03;	0.8	38.0	860-900	1.9-6.0
Diesel^b b according to GB/T19147-2003. A/C: γ-Al2O3/CaO.	–	43.0	820-860	3.0-8.0

Compound	Molecular formula	Relative content / wt.%
Compound	Molecular formula	Thermal	g -Al₂O₃	CaO	35 wt.% A/C
Alkane
Octane	C₈H₁₈	1.7	2.7	2.0	2.8
Nonane	C₉H₂₀	–	1.5	–	2.9
Decane	C₁₀H₂₂	0.6	1.0	0.8	1.0
Undecane	C₁₁H₂₄	0.6	1.1	0.8	1.1
Dodecane	C₁₂H₂₆	3.8	1.1	6.5	1.3
Tridecane	C₁₃H₂₈	0.9	1.4	1.2	1.6
Tetradecane	C₁₄H₃₀	0.9	1.2	1.0	1.4
Pentadecane	C₁₅H₃₂	2.3	2.5	2.3	2.8
Heptadecane	C₁₇H₃₆	1.1	1.1	1.1	2.1
Alkene
2-Octene	C₈H₁₆	2.5	1.4	2.4	2.6
1-Nonene	C₉H₁₈	2.3	1.4	2.2	3.0
1-Decene	C₁₀H₂₀	1.6	2.0	1.6	2.0
1-Undecene	C₁₁H₂₂	1.9	2.2	1.6	2.1
5-Undecene	C₁₁H₂₂	0.6	3.5	2.0	1.9
3-Dodecene, (Z)-	C₁₂H₂₄	1.5	4.3	0.3	2.1
1-Tetradecene	C₁₄H₂₈	3.6	2.7	4.5	3.6
7-Tetradecene	C₁₄H₂₈	–	2.2	–	–
1-Pentadecene	C₁₅H₃₀	1.6	2.0	1.6	2.3
17-Pentatriacontene	C₃₅H₇₀	–	–	2.6	–
Arene
Toluene	C₇H₈	1.3	2.4	1.2	1.6
Ethylbenzene	C₈H₁₀	0.7	1.2	0.8	1.0
Benzene, butyl-	C₁₀H₁₄	0.4	1.1	0.6	0.8
Benzene, pentyl-	C₁₁H₁₆	1.2	2.0	1.1	1.6
Benzene, 1-methylbutyl-	C₁₁H₁₆	–	1.3	0.8	1.3
Benzene, hexyl-	C₁₂H₁₈	–	1.3	0.9	1.2
Benzene, 1,3-dimethylbutyl-	C₁₂H₁₈	–	1.2	0.9	1.1
Fatty acid
Heptanoic acid	C₇H₁₄O₂	3.6	–	–	–
Octanoic acid	C₈H₁₆O₂	2.1	–	–	–
n-Decanoic acid	C₁₀H₂₀O₂	2.8	–	–	–
n-Hexadecanoic acid	C₁₆H₃₂O₂	8.3	–	–	0.7
cis-Vaccenic acid	C₁₈H₃₄O₂	6.8	–	1.8	–
Oleic acid	C₁₈H₃₄O₂	6.7	–	–	–
Ester
Butyl acetate	C₆H₁₂O₂	3.8	–	2.3	1.9
7-Methyl-Z-tetradecen-1-ol acetate	C₁₇H₃₂O₂	–	–	1.2	2.1
Z,Z-3,15-Octadecadien-1-ol acetate	C₂₀H₃₆O₂	3.1	1.1	0.9	–
Ketone
2-Hexanone	C₆H₁₂O	–	0.5	0.6	0.7
2-Heptanone	C₇H₁₄O	–	0.5	1.0	1.0
2-Octanone	C₈H₁₆O	0.7	1.3	2.3	2.2
2-Nonanone	C₉H₁₈O	–	0.8	1.3	1.4
3-Nonanone	C₉H₁₈O	–	–	0.4	0.5
2-Fluorenone	C₁₀H₂₀O	–	–	–	1.3
4-Fluorenone	C₁₀H₂₀O	–	–	0.3	–
2-Undecenone	C₁₁H₂₂O	–	–	2.6	–
2-Dodecone	C₁₂H₂₄O	–	–	2.3	–
6-Dodecone	C₁₂H₂₄O	–	–	0.2	–
7-Tridecanone	C₁₃H₂₆O	–	–	0.4	–
7-Hexadecanone	C₁₆H₃₂O	–	–	0.4	–
2-Heptadecanone	C₁₇H₃₄O	2.9	3.3	5.4	6.0
2-Nonadecanone	C₁₉H₃₈O	1.4	1.2	2.3	2.5
Z-5-Methyl-6-heneicosen-11-one	C₂₂H₄₂O	–	1.2	–	–
Alcohol
E-2-Octen-1-ol	C₈H₁₆O	–	–	2.5	–
Trans, trans-nona-2,4-dienol	C₉H₁₆O	–	1.1	–	0.8
2-Methyl-1-undecanol	C₁₂H₂₆O	–	–	–	2.9
E-2-Hexadecacen-1-ol	C₁₆H₃₂O	1.4	2.2	0.6	–
1-Hexadecanol	C₁₆H₃₄O	–	1.7	0.3	2.1
E-2-Octadecadecen-1-ol	C₁₈H₃₆O	2.0	2.6	2.8	1.7
12-Methyl-E, E-2,13-octadecadien-1-ol	C₁₉H₃₆O	1.8	1.6	–	3.1
Behenic alcohol	C₂₂H₄₆O	–	0.4	0.6	1.5

T_max^a / °C	The maximum mass loss rate / (wt.% °C^-1)
T_max^a / °C	SO	SO + A	SO + C	SO + A/C
333	–	–	–13.63	–10.21
408	–	–	–5.13	–8.06
430	–49.51	–34.06	–	–
475	–	–	-40.45	–35.49