VIETNAM JOURNAL OF CHEMISTRY DOI: 10.15625/0866-7144.2016-00259
54(2) 194-198
REUSE OF SPENT FCC OF DUNG QUAT REFINERY FOR CRACKIN WASTED COOKING OIL IN LIQUID PHASE
T r a n Thi Nhu Mai'", T r a n Chi C o n g ' , Nguyen V a n M a n h ' , L u u V a n B a c ' , G i a n g Thi P h u o n g Ly^, Q o a c h Vien D u o n g '
'Hanoi University of Science, Vietnam National University in Hanoi, Hanoi, Vietnam
^Hanoi University of Science and Technology, Hanoi, Vietnam Received 7 August 2015; Accepted for publication 26 April 2016
Applications of pretreated spent FCC catalyst in wasted cooking oils cracking were investigated. TTieqwi catalyst was obtained from commercial FCC unit in Dung Quat refinery. The spent FCC catalyst vras iBmcWtefe?
heavy metals by reflux with 5 % concentration solution of enthanedioic ^ i d by magnetic stirring for 5 h o u r s a ^ /
"C. The obtained results showed that 56% Fe and 30 % Ni were removed. Treated spent FCC catalyst was used irf- cracking wasted cookmg oils in liquid phase at 370 "C, 400 °C and 420 °C for 45 minutes with rate of s % % being 400 rpm. At 400 °C liquid and gas products yield was higher than at 370 °C (82 % and 12 % in comparis^gi with 80 % and 10 %), respectively, as a consequence, unconverted products at 400 °C were smaller than at 370 %' (2.5 % versus 6.3 %). The GC-MS results showed that the obtained products are mainly straight chain alkan^as green diesel.
Keywords. Spent FCC, regenerated FCC, ^ e n diesel, catalytic cracking.
1. INTRODUCTION
In the past few decades, fossil ftiels, mainly petroleum-based liquid fuels, natmal gas and coals, have played an important role in fulfilling the energy demand. However, because of their non-renewable nature, these fossil fiiels are projected to be exhausted in the near future. This situation has worsened with the rapid increasing in energy demand with significant worldwide population growth," therefore, the demand for clean, reliable, and yet economically feasible renewable energy sources has led researchers to search for new sources [1]. In this respect, plant biomass is the only current sustainable source of organic carbon, biofliels, and iiiels derived from plant biomass [2], such as plant oil, more commonly denoted as vegetable oils, which are castor, soybean, cotton, peanut oils, or any other vegetable oils, pure or wasted [3].
Triglycerides are the main component in vegetable oils, in which the long hydrocarbon chains m Its structure are similar to crude oil. Three fatty acid chains connected via the carboxyl group to a glycerol backbone. The physical and chemical properties of vegetable oils depend strongly on their fatty acid composition [4]. Vegetable oils can be
used directly in diesel engines, however, there are &
number of disadvantages of pure vegetable oiisj including high viscosity, low volatility and e n ^ L problems (coking on the injectors, carbon d e p o s ^ ? oil ring sticking...). The most common way # • upgrading vegetable oils to fiiel is transesterificafiC;
of triglycerides into bio-diesel. Kaliaguine et dj;, synthesized the mesoporous silica fimctionalized with TBD in order to obtain the high activity catrfyst in the transesterification of vegetable oil \SjSJi.
However, biodiesel produced by this methad^, requires a large amount of methanol, the complot pre-processing and strict material quality [7]. M , ' altemative option for the conversion of v e g e t ^ oils into transportation fuels might be thiBU^™^' caUlytic cracking [8].
The co-feeding of vegetable oils widi 1 feedstocks to fluid catalytic cracking (FCC) « can be an interesting application [9]. Catal.
cracking method for quality of mixture p r o d u c t s ^ well as mineral fuels (gasoline, diesel) and 1 requirements of the pretreatment process of mat are less strict. Spent FCC fiom the Dung Quat:|
refmery after regeneration is suitable for i cracking process. Most of these spent c a t a l y ^ h been removed as landfill, while metals such as B
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Fe in catalyst ate ha2mlous wastes. Therefoie, researches on die process for lecycUng and reutiUzation of spent FCC catalyst have received a lot of considerable attentions. Xm Pu et al. were successfiil in discarding contammated heavy metals by using organic acid [10].
In this sttidy, research group regenerated spent FCC catiilyst deactivated partiy by heavy metals such as Ni, Fe tittough washing witti oxalic acid.
The metals, mainly nickel and mm accumulated on the surface of FCC catalyst promote dehydrogenation and condensation reactions leading to enhance tiie formation of coke. The reseatt:h group used tieated spent FCC catalyst for cracking wasted cooking oils wifli free fatty acid factor as 67.
2. EXPERIMENTAL 2.L Pretreatment of spent FCC
The spent catiilyst was obtiiined from commercial FCC unit in Dung Quat refinery.
Contaminated heavy metals such as Fe, Ni were lemoved by reflux wifli 5 % concentiation solution of oxalic acid by magnetic stirring for 5 hours at 75
"C[10].
2.2. Characterization
The structtire of FCC was characterized by XRD specttoscopy using XRD-Siemens D5005 at Hanoi University of Science. The elemental composition of
Tran Thi Nhu Mai, etal.
FCC was detentuned by EDX in Hanoi University of Science and Technology.
23. Liquid cracking system
The reaction was catried out m the liquid crackmg system at 370 °C, 400 °C and 420 °C for 45 minutes wiUi rate of stirring was 400 r/min. The mixture rractants contained wasted cookmg oils with a fi^e fatty acid number 67 and the spent FCC after pretteattnent The ratio of FCC catidyst witii wasted cookmg oil is 5 wt%. The gas products were collected in a glass bottle conttiining brute water, tiie liquid products were analyzed by GC-MS. GC- MS HP 6890 with a mass specttometiy detector MS HP 5689 (American) at pettoleum center- Faculty of Chemistiy-HUS.
3. RESULTS AND DISCUSSION 3.1. FCC characterization 3.1.1. XRD of regenerated FCC
The XRD difftactogram shows that the major components of FCC catalyst ftom Dung Quat refinery contain Zeolite Y and y- AI203. However in flie difftactogram of regeneiated FCC, some crystalline phase characterization peaks of zeolite Y were slightly shifted in comparison with flie ft^sh FCC catiilyst
Fresh FCC Regenerated
FCC 28 20 d
Table 6.3 6.3 14.102
.• The particular 20 angles 10.5
10.5 8.954
12 12 7.328
15.6 16 5.586
of original and regenerated FCC 18.8
19 4.672
20.4 21 4.303
23.9 24 3.699
27 27.5 3.247
31.5 32 2.813
45.6 45.6 1.987 3.1.2. EDX of spent and regenerated FCC
The EDX spectium of spent FCC indicated tiiat tite amount of Fe, Ni accounted for large value, 3.97
% of Fe and 1.07% of Ni. The analysis results in regeneiated FCC showed fliat flie content of Fe and Ni elements was declmed significantly, about 56%
and 32%, respectively. The pretieattnent witii oxalic acid could not remove tiie heavy metals completely however, the presence of small amount of Ni and Fe might enhance dehydrogenation process resulting in olefins formation.
3.1.3 BET surface and micro-pore area and pore volume
BET surface and micro-pore area and pore volume of regenerated and spent FCC eatiilysts are summarized in table 2 R) investigate flie effect of regeneration process on zeolite and matrix surface area The data of table 2 mdicated ttiat after regeneration, the porous structural data of FCC decreases noticeably, especially tiie BET surface area (decrease approximately 44 %). However, flie size of micro-pore of regenerated FCC is well suited for the wasted cookmg oil cracking.
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Table 2: Surface area and pore characteristics of regenerated and spent FCC Sample
BET surface area (m7g) Micro-pore area (mVg) Micro-pore volume
(cmVg) Adsorption cumulative
surface area of pores between 17-3000 A
(mVg) Adsorption cumulative volume of pores between
17-3000 A (cm'/g) Fresh FCC 211.5298
96.8410 0.050714
138.163
0.295817 Regenerated
FCC 119.5154 72.9697 0.0384 56.157
0.2148
Reuse of spent FCC of Dung Quat r\
3.2. The liquid-phase cracking Table 3 describes the liquid products of Q cracking of wasted cooking oils which analyzed by GC-MS method. The results j that the main components are die denvatives^
paraffinic hydrocarbon, C10-C19.
Nonetheless, there are some fi«e f a ^ acids sn^
as cis-9 octadecenoic acid, hexadecanoic acid ^ remained in the products. It can be explamed t ^ ^ the decarbo^lation reaction did not take place completely. It can be elucidated that mcieasuui temperature enhanced decarboxylation lem^oQ When the temperature rose to 420 "C the componait of unconverted fatty acid went down.
Table 3: Some major components in liquid products at 370°C, 400"C and 420''C Nomenclature
Heptane (CyHie) Octane (CgHig)
370 °C (%) 400 °C (%) 420 °C (%) 0.77
Nonane (C9H20) Decane (C10H22) Undecane(C!iH2<) 1-Undecene (CJ1H22) Dodecane (C11H26) 1-Tridecene (Ci3H26) Tridecane(Ci3H28) I-Tetradecene (CHHJS) Tetradecane (CuHjo) 1-Pentadecene (C1JH20) Pentadecane (C1SH32) 1-Hexadecene (C16H32) Hexadecane(Ci6H34) 8-Heptadecene (C^Hs^) l-Heptadecene(Ci7H34) Heptadecane (C17H36) Undecyl cyclohexane (CnHji) Hexadecanoic acid (CiiH3tCOOH) Cis-9 octadecenoic acid (C17H33COOH) Cyclopropanenonanoic acid (CiiH2iC0Om Pentadecanoic acid (CnHiiCOOH)
4.02 2.47
5.54 5.89
2.55 3.23 4.58 4.97 10.93 5.46 8.42 12.26 3.98 6.38 2.99 7.31
l.OI
n r o ^ c ^ ^ i . ' r ! ' ' ^ ' ' ^ ' ! ' ' ' ' " * " . * ^ " ^ ' ' " ' ' ' ' " ' ' ^ ^^*'^^"« 'S * « '^y'^l'^t'O" reaction of F S S ; i r s t i n r S c t t i'^'^!^ ""^^^^^^^^ hydrocarbon chain such as hCC catalyst m reactions, hi addition, the possible heptadecene.
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By using fliis temperature in tiie liquid-phase cractang system, flie liquid products are obtitined 81.5 % at 400 "C in comparison with 79.7 % at 370 C. Ci3-C[9 segments was contained as the large mgredientii, which have high cetime number such as n-hexadecane and n-hexadecene of 100 and 91 respectively as green diesel and was obtiiined about
Tran Thi Nhu Mai, et ai 45.2 % at 370 °C and 48.8 % at 400 °C. The main reason is the influence of temperatiire in cracking reaction. By incteasing tiie temperattire between 370-420 °C, hydrogenated triglycerides were degraded into monoglycerides, diglycerides and ftee fatty acids which were lately ttansformed into deoxygenated products.
'table 4: Product composition of catidytic cracking reaction at different conditions, 370 'C. 400 "C, 420 °C Temperature
Sample Water (wt%) Unconverted oils (wt%)
Gas product (wt%) Free fatty acid number 34
400 "C
4.1 2.5
30
420 °C
6.2 0.9 13.5 17
6.0 1.2 13.4 17
3^
5.6 1.0 13.1
20 Table 4 intt-oduces flie components of flie
cracking produetii from 5 samples in a series of 30 experiments being carried out continuously without changing of catalyst at 420 °C; and the fliird sample at 370 and 400 °C conditions. It can be seen fliat free fatty^acid numbers were lower titan fliose at 370 and 400 °C, which is expected that catalytic activity of regenerated FCC was enhanced and achieved equivalent stiite after few rounds of experiments (count to tiie 3"" sample). The presence of higher amount of water (5.6 %) and gas products (13.1 %) at 420"c; could be explained by an increase of dehydration and decarboxylation process when temperature was raised up.
5.5 1.1 13.2 23
5.4 1.1 13.0
26 The decarboxylation pafllway (1) converts flie carboxylic acid group in flie ftee fatty acids to sti^ight chain alkanes by releasing COj
R-CHj-COOH -» R-CH3 -I- CO, (1) R-CH2-COOH -I- Ha ^ R-CHj + CO -1- HjO (2) On flie oflier hand, tile presence of Hj production ftom cracking reactions might lead to tiie secondary reaction which is decarbonylation (2) releasing water and CO as by-products. The decarbonylation pathway produces alkanes by reaction of tiie carboxylic group in tiie free fatty acids with hydrogen and forming CO and water. The possible mechanisms of formation of products in flie experiments were illustiated in figure 5.
HiC=CH, + CH,-CH"CH Ethylene Prapylene
Figure 5: Probable pathways of products formation fi-om catalytic cracking triglycerides ui wasted cooking oil
(.CONCLUSIONS fi„,^ „ ^ ^^^ ^^ ^^^^^.^^ contiiminated ,nthisresea.h,spentFCCcatalystinDungQuat "SvI^T^t^^l^ t Z t t ' " ! :
197
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treatment, 56 % and 32 % respectively. In addition, XRD results of regenerated FCC catalyst indicated that the pretreatment did not alter the structure of the original catalyst.
The products in the cracking wasted cooking oil process catalyzed by regenerated FCC were analyzed by GC-MS. Using the liquid phase catalytic cracking, the obtained products are the main of straight chain alkanes from C|o-C]9 and high yield of liquid products, 79.7 % at 370 °C; 81.5 % at 400 "C; 80.0 % at 420 "C in which green diesel accounted for 45.2 %, 48.8 % and 50.8 % respectively. These results support for the advantages of liquid phase cracking process in order to yield higher liquid products as green diesel for fiiel. The increasing of temperature may enhance the decarboxylation as well as the dehydration reactions.
The cracking reaction with vegetable oil in different temperature 370 "C, 400 °C and 420 "C indicated that the regenerated FCC catalyst was efficient to achieve an appreciable amount of diesel as well as high quanti^ of liquid products.
Acknowledgements. This research was fimded by ministry of Science and Technology and also partially fimded by DT-PTNTD-2012-G project
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Corresponding author: Tran Thi Nhu Mai
Faculty ofChemistiy, Hanoi University of Science Vietaam National University in Hanoi, Hanoi, Vietaam 19 Le Thanh Tong, Hoan Kiem, Hanoi
E-mail: [email protected].