Comparison of ginger oil conversion over MFI, BEA, and FAU Yang He, Sean E. Barnes, Daniel W. Crunkleton, Geoffrey L. Price ⇑ Department of Chemical Engineering, University of Tulsa, Tulsa, OK 74114, USA article info Article history: Received 26 September 2011 Received in revised form 6 January 2012 Accepted 14 January 2012 Available online 1 February 2012 Keywords: Ginger oil Catalytic cracking BEA FAU MFI abstract The catalytic cracking of ginger oil in a fixed-bed tubular reactor with a weight hourly space velocity 1.0 h À1 at temperatures ranging from 300 °C to 450 °C has been accomplished over zeolites MFI, BEA, and FAU having different SiO 2 /Al 2 O 3 ratios. Gasoline fraction yields have been observed along with liquid, gas, and coke yields. Trends in the various yields have been correlated to zeolite structure, SiO 2 /Al 2 O 3 ratio, and reaction conditions where possible. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Biofuels have recently been gaining interest all over the world primarily because of the limited amounts of fossil fuels which are easy and environmentally feasible to produce [1–6]. Biofuels also have important advantages such as sustainability, renewabil- ity, and carbon neutrality. Numerous studies have focused on the production of gasoline-range hydrocarbons from renewable oil sources by catalytic cracking, such as canola oil [7–12], palm oil [13–20], and various other vegetable oils [21–23]. All of these oils are edible and utilizing edible products for the production of trans- portation fuels could lead to food shortages and price increases [24]. An emerging option for producing fuel from non-food sources is oils produced from algae. Algae do not compete with food crops for farmland or water because algae can be grown on non-arable land using brackish water [25]. In previous studies, it has been shown that oil extracted from Botryococcus braunii can be cracked to gas- oline-range hydrocarbons or hydrocracked to diesel/jet fuel [26,27]. Oil extracted from algae generally contains a variety of components, including lipids, carotenoids, sterols, tri-, di-, and mono-glycerides, free fatty acids, chlorophylls, and phospholipids [28,29], and, of particular interest for this study, terpenes [1]. Terpenes are a class of chemical compounds formed via linking multiple isoprene (C 5 H 8 ) units, and they vary in structure from open acyclic chains, to mono-, bi-, and tri-cyclic, and other config- urations [1]. One example of a terpene is squalene, which is pro- duced by B. braunii for building cellular membranes and extra cellular polymer matrix that holds the algal colony together [30]. Terpenes, which are naturally occurring hydrocarbons, can be used for transportation fuels if they can be produced economically. Currently, it is believed that through genetic modification of algae, significant amounts of terpenes can become part of algae oils [31]. Of the classes of terpenes, only the monoterpenes (generally having the molecular formula C 10 H 16 ) are in the gasoline range, and, being at the upper end of the appropriate molecular weight for gasoline, only small amounts could be included in gasoline frac- tions if vapor pressure and boiling curve specifications for modern gasolines are to be met. The sesquiterpenes (generally having the molecular formula C 15 H 24 , see Fig. 1) are roughly twice the molec- ular weight of average gasoline molecules and are clearly too heavy to be used directly in gasoline. However, catalytic cracking could be used to break down sesquiterpenes into gasoline range molecules. Terpenes have carbon backbones that are branched due to the branching in the monomer, isoprene. In turn, branched hydrocarbons are known to have higher octane numbers than an equivalent molecular weight linear hydrocarbon chain. Catalytic cracking generally increases skeletal isomerization of paraffins and olefins, so we expect that products of the catalytic cracking of sesquiterpenes could be excellent for gasoline. In a previous paper, we showed that squalene could be effectively cracked by zeolite catalysts to produce light hydrocarbons that have many desirable gasoline-range properties [32]. In this present work, the catalytic cracking of a ginger oil feed- stock was performed. Zeolites MFI, BEA, and FAU have been used to catalytically crack the sesquiterpene fraction of ginger oil into lighter hydrocarbons. 0016-2361/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.fuel.2012.01.033 ⇑ Corresponding author. Tel.: +1 918 631 2575. E-mail address: [email protected](G.L. Price). Fuel 96 (2012) 469–475 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel
Transcript
Fuel 96 (2012) 469–475
Contents lists available at SciVerse ScienceDirect
Fuel
journal homepage: www.elsevier .com/locate / fuel
Comparison of ginger oil conversion over MFI, BEA, and FAU
Yang He, Sean E. Barnes, Daniel W. Crunkleton, Geoffrey L. Price ⇑Department of Chemical Engineering, University of Tulsa, Tulsa, OK 74114, USA
a r t i c l e i n f o a b s t r a c t
Article history:Received 26 September 2011Received in revised form 6 January 2012Accepted 14 January 2012Available online 1 February 2012
Keywords:Ginger oilCatalytic crackingBEAFAUMFI
0016-2361/$ - see front matter � 2012 Elsevier Ltd. Adoi:10.1016/j.fuel.2012.01.033
The catalytic cracking of ginger oil in a fixed-bed tubular reactor with a weight hourly space velocity1.0 h�1 at temperatures ranging from 300 �C to 450 �C has been accomplished over zeolites MFI, BEA,and FAU having different SiO2/Al2O3 ratios. Gasoline fraction yields have been observed along with liquid,gas, and coke yields. Trends in the various yields have been correlated to zeolite structure, SiO2/Al2O3
ratio, and reaction conditions where possible.� 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Biofuels have recently been gaining interest all over the worldprimarily because of the limited amounts of fossil fuels whichare easy and environmentally feasible to produce [1–6]. Biofuelsalso have important advantages such as sustainability, renewabil-ity, and carbon neutrality. Numerous studies have focused on theproduction of gasoline-range hydrocarbons from renewable oilsources by catalytic cracking, such as canola oil [7–12], palm oil[13–20], and various other vegetable oils [21–23]. All of these oilsare edible and utilizing edible products for the production of trans-portation fuels could lead to food shortages and price increases[24].
An emerging option for producing fuel from non-food sources isoils produced from algae. Algae do not compete with food crops forfarmland or water because algae can be grown on non-arable landusing brackish water [25]. In previous studies, it has been shownthat oil extracted from Botryococcus braunii can be cracked to gas-oline-range hydrocarbons or hydrocracked to diesel/jet fuel[26,27]. Oil extracted from algae generally contains a variety ofcomponents, including lipids, carotenoids, sterols, tri-, di-, andmono-glycerides, free fatty acids, chlorophylls, and phospholipids[28,29], and, of particular interest for this study, terpenes [1].Terpenes are a class of chemical compounds formed via linkingmultiple isoprene (C5H8) units, and they vary in structure fromopen acyclic chains, to mono-, bi-, and tri-cyclic, and other config-urations [1]. One example of a terpene is squalene, which is pro-
ll rights reserved.
duced by B. braunii for building cellular membranes and extracellular polymer matrix that holds the algal colony together [30].Terpenes, which are naturally occurring hydrocarbons, can be usedfor transportation fuels if they can be produced economically.Currently, it is believed that through genetic modification of algae,significant amounts of terpenes can become part of algae oils [31].
Of the classes of terpenes, only the monoterpenes (generallyhaving the molecular formula C10H16) are in the gasoline range,and, being at the upper end of the appropriate molecular weightfor gasoline, only small amounts could be included in gasoline frac-tions if vapor pressure and boiling curve specifications for moderngasolines are to be met. The sesquiterpenes (generally having themolecular formula C15H24, see Fig. 1) are roughly twice the molec-ular weight of average gasoline molecules and are clearly too heavyto be used directly in gasoline. However, catalytic cracking couldbe used to break down sesquiterpenes into gasoline rangemolecules. Terpenes have carbon backbones that are brancheddue to the branching in the monomer, isoprene. In turn, branchedhydrocarbons are known to have higher octane numbers than anequivalent molecular weight linear hydrocarbon chain. Catalyticcracking generally increases skeletal isomerization of paraffinsand olefins, so we expect that products of the catalytic crackingof sesquiterpenes could be excellent for gasoline. In a previouspaper, we showed that squalene could be effectively cracked byzeolite catalysts to produce light hydrocarbons that have manydesirable gasoline-range properties [32].
In this present work, the catalytic cracking of a ginger oil feed-stock was performed. Zeolites MFI, BEA, and FAU have been used tocatalytically crack the sesquiterpene fraction of ginger oil intolighter hydrocarbons.
Key to the diagram 1 Nitrogen cylinder 2 Gas regulator 3 Valve 4 Mass flow controller 5 Syringe pump 6 Reactor 7 Furnace 8 Catalyst 9 Thermocouple 10 Glass cylinder 11 Ice-cooled condenser 12 Liquid Product 13 Micro GC
Fig. 2. Schematic of experimental apparatus used to crack ginger oil.
470 Y. He et al. / Fuel 96 (2012) 469–475
2. Experimental
2.1. Ginger oil
Raw ginger oil was obtained from Ananda Apothecary in aromapurity. The raw ginger oil was then distilled into five fractions byboiling point. The lightest fraction contained a significant fractionof monterpenes, so it was discarded. The second lightest fractionwas used for all catalytic cracking experiments. The primary com-ponents of this cut were sesquiterpenes, and a GC–MS analysis ofthis fraction is given in Table 1.
2.2. Catalysts and characteristics
Zeolites were obtained from Sud-Chemie and Zeolyst Interna-tional. Sud-Chemie zeolites were T-4546 and BEEZ00050 extru-dates which are BEA (Zeolite-Beta) phases with manufacturerreported SiO2/Al2O3 ratios of 25 and 150, respectively. The otherzeolites were purchased from Zeolyst International and wereprovided in powdered form. Of those purchased from Zeolyst,two were FAU (a.k.a. faujasite or Zeolite-Y) materials, CBV780and CBV720 with manufacturer reported SiO2/Al2O3 ratios of 80and 30 respectively, two were MFI (a.k.a. ZSM-5) materials,CBV5524G and CBV28014 with manufacturer reported SiO2/Al2O3
ratios of 50 and 280 respectively, and one was a BEA material,CP811C-300 with manufacturer reported SiO2/Al2O3 ratio of 300.
The five powdered zeolites purchased from Zeolyst were boundand extruded into extrudates with 20% Al2O3 as a binder followinga procedure previously reported [24]. A microbalance (Perkin–El-mer TGA 7) was used to determine the proton site density of each
Table 1Chemical composition of ginger oil distillate fraction 2.
catalyst in the extrudate form using 1-propanamine (NPA) as theadsorbing species. Details of this procedure can be found else-where [33].
This represents a set of seven zeolites in extrudate form whichwe refer to as H-BEA-25, H-BEA-150, H-BEA-300, H-FAU-30,H-FAU-80, H-MFI-50, and H-MFI-280. The ‘‘H-’’ prefix reminds usthese are all protonated forms of the zeolite, the three digit middlecode designates the phase using the International Zeolite Associa-tion recognized abbreviations, and the appendage give the manu-facturer’s reported SiO2/Al2O3 ratio. Catalysts and their particularcharacteristics are given in Table 2.
2.3. Catalytic reactor and experimental procedure
The catalytic cracking experiments were conducted at atmo-spheric pressure in a continuous down-flow, fixed-bed stainlesssteel reactor (11 mm I.D. and 521 mm overall length) using thesame reactor setup as in a previous report [24] and shown inFig. 2. Ginger oil was pumped by a syringe pump into the reactorat a fixed rate with nitrogen gas as a co-feed. Two thermocoupleswere used to measure the temperature of the reactor on the out-side and inside of the reactor near the center of the catalyst bed.The catalyst bed temperature was taken as the reaction tempera-ture. Temperatures were controlled by a LabVIEW-based controlprogram.
Experiments typically began with 10 g of catalyst loaded in thereactor at night, then the reactor was heated to reaction tempera-ture (in the range of 300–450 �C) and held at that temperatureovernight with a nitrogen flow rate of 46.5 ml/min to dry the cat-alyst. Ginger oil cracking started with ginger oil fed by a syringepump at a fixed flow rate of 0.194 ml/min into the reactor withthe nitrogen co-feed. Experiments typically ran 1 h correspondingto 10 g of ginger oil being fed. Thus, the weight hourly space veloc-ity (WHSV) was 1.0 h�1. A liquid fraction was collected at the efflu-
Table 3Overall mass balance obtained for gas, liquid, and coke.
Fig. 3. Vapor product yield obtained for the cracking reaction over each zeolite as afunction of temperature.
0%
10%
20%
30%
40%
50%
60%
70%
80%
300 350 400 450Li
quid
Yie
ld
Temperature (oC)
H-BEA-25H-BEA-150
H-BEA-300
H-FAU-30
H-FAU-80
H-MFI-50
H-MFI-280
Fig. 4. Liquid product yield obtained for the cracking reaction over each zeolite as afunction of temperature.
Y. He et al. / Fuel 96 (2012) 469–475 471
ent of the reactor after leaving the furnace in a glass condenserthermostated with ice. The offgas from the condenser was thenanalyzed by a four-channel MicroGC (Agilent G2804A) every4 min. All reactions were nominally at atmospheric pressure.
2.4. Product analysis
Amounts of gaseous products were calculated under theassumption of ideal gas behavior, and the method of measuringthe gas product has been previously reported [24]. Basically, N2
gas was used an internal standard, and flows of all other gases weredetermined relative to the flow of N2. Flows were integrated overtime to yield a weight of each species identified by the MicroGC.Calibration of the MicroGC was done regularly using a mixture ofknown composition provided by DCG Partnership 1, Ltd.
The condensed liquid product consisted of a broad range of or-ganic products, and we refer to it as Organic Liquid Product (OLP).OLP was characterized first by simulated distillation (SimDis) usinga Hewlett Packard 5890 series II GC with a 10 m � 0.530mm � 3.0 lm capillary column (Agilent DB-2887) and a flame ion-ization detector. The gasoline fraction was taken as the fractionboiling below 225 �C as determined by SimDis. The OLP wasfurther analyzed with an Agilent 5975 GC–MS system with a50 m � 0.2 mm � 0.5 lm capillary column (Agilent PONA) includ-ing an effluent split to FID for quantitative analysis to identify andquantify major components.
2.5. Overall mass balance
For all the experiments, we work on a N2-free basis, so the totalmass fed was the ginger oil, which was 10 g for all runs. In all cases,no ginger oil components were detected in the products, so conver-sion was 100%. Total mass out included the gas and liquid prod-ucts, and coke which forms on the catalyst. Any runs which did
not have a material balance with 5% (i.e., between 9.5 and 10.5 gof total products collected) were discarded and the run repeated.Seven different zeolites over four different temperatures (300,350, 400 and 450 �C) were run and products analyzed. The overallmass balance obtained for each run is shown in Table 3.
3. Results
3.1. Product yield comparisons
Figs. 3–6 provide a comparison of the product yields obtainedover each zeolite at the four different reaction temperatures. Fromthese figures, it is clear that for all zeolites, vapor products andcoke yields increased with reaction temperature, while the liquidproduct yield decreased with increasing temperature withoutany exceptions. Comparing individual zeolites, H-MFI-280produced the least vapor product, about 30%, while the H-MFI-50vapor product yield did not change significantly with increasingtemperature, averaging about 35% over the four temperatures. H-FAU-30 produced the lowest OLP yield while H-MFI-280 generallygave the highest liquid product yield of all the catalysts. For cokeyield, H-FAU-30 and H-FAU-80 were the highest, while H-MFI-50and H-MFI-280 were the lowest, compared to the other zeolites.
Looking at the gasoline range yields in Fig. 6, there is no cleartrend with temperature, but most catalysts gave better gasolineyields at 350 or 400 �C. MFI zeolites consistently produced thehighest gasoline fraction yields regardless of the temperature,while FAU catalysts generally performed poorly in gasoline yield.
Since the highest gasoline range yield was on H-MFI-280 at400 �C, we prepared Fig. 7 to compare the vapor, liquid, coke,and gasoline yields at 400 �C. The figure was arranged so thatliquid yield increased from lowest to highest going from left toright. In Fig. 7, note that vapor product yields fall in a relativelynarrow range, 35–37%, except for H-MFI-280 which is not that
0%
5%
10%
15%
20%
25%
30%
35%
300 350 400 450
Cok
e Yi
eld
Temperature (oC)
H-BEA-25
H-BEA-150
H-BEA-300
H-FAU-30
H-FAU-80
H-MFI-50
H-MFI-280
Fig. 5. Yield of coke during the cracking reaction over each zeolite as a function oftemperature.
0%
10%
20%
30%
40%
50%
60%
300 350 400 450
Gas
olin
e Yi
eld
Temperature (oC)
H-BEA-25
H-BEA-150
H-BEA-300
H-FAU-30
H-FAU-80
H-MFI-50
H-MFI-280
Fig. 6. Overall gasoline fraction yield from the cracking reaction as a function oftemperature.
0%
10%
20%
30%
40%
50%
60%
25 150 300
Prod
uct Y
ield
SiO2/Al2O3
VaporLiquid
CokeGasoline
Fig. 8. Product yields over H-BEA at 400 �C as a function of SiO2/Al2O3 ratio of thezeolite.
0%5%10%15%20%25%30%35%40%45%
0803Pr
oduc
t Yie
ld
SiO2/Al2O3
VaporLiquid
CokeGasoline
Fig. 9. Product yields over H-FAU at 400 �C as a function of SiO2/Al2O3 ratio of thezeolite.
Fig. 7. Product yields for cracking reaction for all zeolite catalysts at 400 �C.
472 Y. He et al. / Fuel 96 (2012) 469–475
far off the range of other catalysts at 29%. H-FAU-30 and H-FAU-80produced considerably more coke than other catalysts at 24% and20% respectively, at 400 �C. H-MFI-280, the catalyst yielding theleast coke, gave only 3% coke. Gasoline range yields in Fig. 7follow almost the same trend as the liquid yield, increasing contin-uously from left to right, with H-BEA-25 being the only outlier, andits gasoline range yield is only slightly less than H-FAU-80 situatedto its left in the figure. Following the general trends from left toright in Fig. 7, liquid and gasoline range yields increase, while coke(H-BEA-150 being the only outlier) and vapor yields decrease. Coke
especially decreases strongly from left to right, and decreasingcoke correlates extremely well with increasing liquid yield.
3.2. Effect of SiO2/Al2O3
Three different SiO2/Al2O3 ratios of beta zeolites, two differentSiO2/Al2O3 ratios of FAU and two different SiO2/Al2O3 ratios of H-MFI zeolites have been used, allowing for an examination of the ef-fect of this physical property on product yields. Different SiO2/Al2O3 ratios provide different densities of acid sites, which affectthe catalytic cracking reactions especially by altering the probabil-ities that bi-molecular interactions at acid sites can take place. Figs.8–10 compare the product yields of each zeolite as a function ofSiO2/Al2O3 ratio at 400 �C. These figure emphasize the trendsdiscussed in the above, but they also clearly show that for a givenzeolite phase, higher SiO2/Al2O3 ratios produce less coke. Lowercoke yields generally translate to higher liquid yields.
3.3. Vapor phase product distribution
Based on the above results it is apparent that the SiO2/Al2O3 ratiohas an impact on the overall yields of various products for a givenzeolite phase. Each of these cracking reactions produce variousamounts of vapor and liquid products at the each of the reactiontemperatures are shown in Tables 4–7, which gives the comprehen-sive yields of the products produced for all experiments.
Methane and ethane increase strongly with increasing temper-ature in general for all catalysts. Methane, and to a lesser extent,ethane, are relatively unreactive under the conditions applied inthese experiments, and once they are formed, they will notundergo further reactions to an appreciable extent. Therefore, itis expected that these compounds would increase steadily withtemperature.
Table 4Product yields for catalytic cracking of ginger oil over MFI, BEA, and FAU at 300 �C.
Catalyst H-MFI-50
H-MFI-280
H-BEA-25
H-BEA-150
H-BEA-300
H-FAU-30
H-FAU-80
Yield of components in the gas product (wt.% of ginger oil converted to thecomponent)
Fig. 10. Product yields over H-MFI at 400 �C as a function of SiO2/Al2O3 ratio of thezeolite.
Y. He et al. / Fuel 96 (2012) 469–475 473
Total gas phase paraffin yields are much greater than total ole-fins yields. Olefins are known to be much more reactive than par-affins under these conditions, so this is also not a surprising result.
One very noticeable result is the yield of propane on the MFImaterials, especially at the lower temperatures used in this study.At 300 �C, 22.2 wt.% of the overall product is propane. A similarlylarge yield of propane was also observed from a canola oil feed-stock under very similar conditions in one of our recent reports[24]. The only reasonable explanation for this high yield is a spec-ificity based upon the shape selectivity of MFI because all thematerials have the ability to perform strong acid chemistry. At alltemperatures used in this study, both individual gas phase olefinsand total gas phase olefins are significantly greater on the higher
SiO2/Al2O3 ratio material H-MFI-280 than H-MFI-50. This resultsuggests that a significant pathway for the reaction of light olefinsinvolves multiple acid sites on MFI.
4. Discussion
The preponderance of molecules in the ginger oil feedstock usedin this study can be described crudely as a C6 ring with a methylgroup on one side of the ring and a multiply-branched, unsaturatedC8 chain on the other side of the C6 ring in the para position to themethyl group. This description applies to curcumene, zingiberene,sesquiphellandrene, and bisabolene and the detailed differences inthose species basically are based upon the location of unsaturatedC–C bonds in the molecules, while in curcumene, the ring is aro-matic rather than being partially unsaturated. Acid catalysis isknown to cause rapid double-bond migration in hydrocarbons,especially under the thermal conditions employed in this study,so the detailed differences in structure of the primary moleculesin the ginger oil feedstock are insignificant in terms of the productmolecules which we expect from acid cracking.
We can therefore consider what kinds of products we might ex-pect from the basic skeletal structure of the primary moleculeswhich exist in our ginger oil feedstock. Focusing first on the fateof the C6 ring side of the molecule, in the case of curcumene, thering is already aromatic and that ring will likely remain intact. Inthe other molecules, the rings are already partially dehydrogenat-ed, so it is likely the ring will wind up dehydrogenating to an aro-matic ring rather than undergoing a ring opening reaction. Thus, inall cases, one end of the ring is likely to be or become aromatic. Themethyl group on one side of the C6 ring will likely remain as the C6
Table 6Product yields for catalytic cracking of ginger oil over MFI, BEA, and FAU at 400 �C.
Catalyst H-MFI-50
H-MFI-280
H-BEA-25
H-BEA-150
H-BEA-300
H-FAU-30
H-FAU-80
Yield of components in the gas product (wt.% of ginger oil converted to thecomponent)
ring undergoes aromatization because the tertiary carbeium ionwhich could form at the methyl group branch of the C6 ring cannoteliminate a methyl group by beta-scission at that point. Thebranched C8 chain on the other side of the C6 ring will likelyundergo several different reaction routes in the early stages ofthe reaction. Because this side chain is both branched and unsatu-rated, many possibilities for carbenium ion formation can be envis-aged. Such carbenium ions can undergo a wealth of reactions, butcracking under the shape selective confines of the zeolite is highlylikely. Scission of the C8 side chain at the C6 ring, which would re-sult in a molecule of toluene and a multiply-unsaturated andbranched C8 carbenium ion, is a clear possibility. Indeed, all thecatalysts give toluene in the highest yields among the aromaticproducts. The C8 side chain can also undergo beta-scission at otherpoints, leaving a methyl-, ethyl-, etc. group attached to the C6 ring,and with the methyl group on the other side, such processes wouldlead to xylenes, methyl-ethyl-benzene, etc. These are exactly thepreponderance of products we have seen in high yields in thisstudy.
Fig. 7 is perhaps the most important result of this paper. It con-nects high coke yields to low liquid yields, suggesting that catalystswhich have a lower propensity to produce coke are desirable from astandpoint of producing liquid range components which areparticularly useful for fuels and petrochemicals. Fig. 7 also givesus insight into the effect of SiO2/Al2O3 ratio and the effect of thezeolite channel structure on the overall yields. Both FAU and BEAhave 3-dimensional 12-ring pore openings. These two phases allowfor passage of larger molecules and passage of multiple moleculesbetter than the 10-rings pores in the MFI structure. As we seeclearly, FAU and BEA catalysts produce more coke than MFI and thiscan be attributed to coke formation resulting from condensation of
multiple molecules. In addition to the 12-ring 3-dimensional porestructure, FAU, unlike BEA, contains a supercage where there iseven more space to accommodate interactions of multiple mole-cules. Molecules larger than the pore mouth can form in the super-cage, resulting in being trapped in the cage. This is likely the reasonthat FAU coke levels exceed BEA by roughly a factor of 2. Finally, wenote that for any given phase, a higher SiO2/Al2O3 results in lowercoke yields which suggests that coke formation comes from theinteraction of multiple molecules at or near proton sites. HigherSiO2/Al2O3 dilutes the proton sites resulting in lower coke yields.Compared to FAU and BEA, MFI gives the highest yields of liquidproducts because of the combined effects of smaller pore size andhigh SiO2/Al2O3 resulting in the least interaction of multiple reac-tive molecules which give rise to coke formation.
5. Conclusions
Catalytic cracking of sesquiterpenes to yield products suitablefor liquid transportation fuels can be done successfully. Biosyn-thetic pathways to sesquiterpenes therefore represent a renewableroute to liquid fuels. Zeolites that favor coke formation are less suit-able from a standpoint of giving higher liquid yields. Zeolites withlow SiO2/Al2O3 ratios and having pore structures which reduceinteractions of multiple molecules are favored. FAU, widely usedin fluid catalytic cracking processes, has been shown to give pooryields of liquids from ginger oil and are basically unsuitable for thisprocess. MFI gives the highest liquid yield but also gives the highestyield of benzene which is undesirable for gasoline. However, if aro-matics for renewable petrochemicals are a goal, MFI appears theclear choice. Finally, high SiO2/Al2O3 BEA appears to be a goodchoice for high liquid yields for fuels if benzene is undesired.
Y. He et al. / Fuel 96 (2012) 469–475 475
Acknowledgements
The authors gratefully acknowledge Sud-Chemie for providingtwo of the BEA materials used in this study and to the Departmentof Energy (DE-SC0005315) for financial support.
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