Coprocessing of Catalytic-Pyrolysis-Derived Bio-Oil with VGO in a

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Co-processing of Catalytic Pyrolysis Derived Bio-oil with VGO in a Pilot Scale FCC Riser Chenxi Wang, Mingrui Li, and Yunming Fang Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.5b03008 • Publication Date (Web): 03 Mar 2016 Downloaded from http://pubs.acs.org on March 5, 2016

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Industrial & Engineering Chemistry Research

Co-processing of Catalytic Pyrolysis Derived Bio-oil with VGO in a Pilot Scale FCC Riser Chenxi Wang, Mingrui Li, Yunming Fang* National Energy R&D Research Center for Biorefinery, Department of Chemical Engineering, Beijing University of Chemical Technology, 100029, Beijing, China

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ABSTRACT: A catalytic pyrolysis derived bio-oil, which was characterized by higher H/Ceff ratio and lower oxygen content in comparison to fast pyrolysis derived bio-oil, was co-processed with VGO in a pilot scale FCC riser. The addition of the bio-oil up to 10 wt.% gave nearly equivalent oxygenate content and also similar selectivities of gasoline, bottom oil, and coke to those in VGO catalytic cracking alone, suggesting the catalytic pyrolysis derived bio-oil was a suitable feedstock for FCC co-processing. However, the dry gas, including hydrogen and light alkane, was significantly decreased in the co-processing experiment mainly due to the hydrogen transfer between bio-oil and VGO. Radiocarbon analysis of the product showed that 7% carbon of gasoline was derived from the bio-oil when 10 wt.% bio-oil was added to VGO. The co-processing of biomass catalytic pyrolysis and FCC was highly promising for biomass conversion into biofuel.

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1. INTRODUCTION There is increasing interest in bio-transportation fuel production. The main challenge of biofuel production is the huge difference between biomass feedstock and fuel products. Deep changes of both phase and chemical composition are needed for the conversion of biomass into hydrocarbon fuel. Up to date, a lot of technologies such as gasification/F-T synthesis, 1 pyrolysis/oil upgrading, and fermentation have been developed and evaluated for biofuel production.2-5 Among the above options, pyrolysis has some advantages such as high efficiency in phase transformation (the liquid bio-oil yield up to 70%), low capital investment, and distributed production. High oxygen and unsaturated degree, however, make the so-called bio-oil low energy density as well as low thermal and chemical stability.6 Hence, bio-oil must be upgraded to total or partial elimination of oxygen and unsaturated degree before it can be used as a conventional liquid transportation fuel.7 Currently, several approaches, e.g., hydro-deoxygenation (HDO) which removes the oxygen under a high hydrogen pressure with a catalyst,8-10 zeolite cracking which rejects the oxygen as CO, CO2, and H2O, and aqueous-phase reforming, have been developed and tested for the bio-oil upgrading.11 However, the technologies and cost issues of these upgrading methods limit their use. FCC is a core technology in modern oil refinery with excellent heavy oil processing capacity.12,13 Its principal function is to convert high molecular weight hydrocarbons obtained from crude oil distillation into more valuable products like gasoline. Co-processing of bio-oil in standard oil refinery units especially FCC units was considered as a promising pathway for bio-oil upgrading and widely studied in the past several years.14,15 These studies pointed out

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both the promising and challenging aspects of bio-oil co-processing in FCC unit. 16-19 Bio-oil and heavy oil are both very complex mixtures of different chemicals. It is thus very difficult to understand the reaction mechanism especially the bio-oil/heavy oil interaction during the co-processing. Fogassy et al. compared the molecular size of different typical oxygenates in bio-oil with the pore-opening in typical FCC catalyst, and further linked to the VGO/bio-oil co-processing performance to share light on the bio-oil and heavy oil interaction during co-processing. They found that most of the oxygenated compounds from bio-oil (after upgrading by mild hydro-processing), like the heaviest VGO molecules, cannot enter the zeolite pores. Therefore a pre-cracking step in outer-surface of zeolite or extra-framework aluminum (EFAL) deposits for steamed samples is necessary. Another key mechanistic feature they found is the competition for hydrogen (protons or hydrides) through the zeolite interface, required by the oxygenated cracking process16. The mixed nature of bio-oil and heavy oil also resulted in high challenge on the determination of the bio-carbon percentage in the final product. Recently, modern radiocarbon (C14) analysis was successfully used for this purpose in FCC co-processing by Fogassy et al.20 The main challenge in FCC co-processing of bio-oil is the low quality of bio-oil derived from fast pyrolysis. It was found that the quality of bio-oil produced by fast pyrolysis was too low to be co-processed in a standard FCC process.17, 18 Hydro-processing is always necessary to remove the most reactive components in bio-oil for the successful co-processing. Hence most of the reported co-processing experiments are based on the hydrogenation stabilized bio-oil.21 For example, Mercader et al. reported the successful co-processing of hydrogenation stabilized bio-oil in a lab scale FCC unit. In spite of the relatively high oxygen

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content and the different properties of the hydrogenation stabilized bio-oil samples, they all could be successfully co-processed with heavy oil (Long Residue) at high blend ratio (20 wt.%), yielding near normal FCC products without an excessive increase of undesired coke and dry gas.17,18 Catalytic pyrolysis, which upgrades the biomass pyrolysis vapor with catalyst in-situ, is a technology recently widely studied for high quality bio-oil production and is a promising technology for the production of bio-oil that can be used for FCC co-processing.22 When proper catalyst and conditions are used, the resulting bio-oil with some expense of liquid yield has lower oxygen content and is more stable than the bio-oil from fast pyrolysis. Zhang et al. reported that using a spent Fluid Catalytic Cracking (FCC) catalyst, the demethoxylation and alkylation function of catalyst leads to the formation of more alkyl-phenols such as cresol in catalytic pyrolysis derived oil other than guaiacol like polyphenols in bio-oil from fast pyrolysis.23 It was also reported that the catalysts significantly influence the liquid yield, and more coke forms in the deep deoxygenation reaction of catalytic pyrolysis.24-27 Carlson et al., Cheng et al., and Zhang et al. carried out a series of studies on aromatics production with modified ZSM-5 zeolite as catalyst.28-30 They reported that biomass can be directly converted into aromatics using ZSM-5 as catalyst.28 They further reported that p-xylene is selectively produced from direct biomass catalytic pyrolysis using Ga/ZSM-5 with narrowed pore size.29 Agblevor et al. reported a fractional catalytic pyrolysis pathway for biomass where the cellulose and hemi-cellulose fractions were mainly converted into gas.31 The research activities and challenges on biomass catalytic pyrolysis were recently summarized by several excellent review papers 32,33. Agblevor et al.

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successfully proved the possibility for co-processing of catalytic pyrolysis derived oil in FCC unit.15 Very recently, Schuurman et al. studied the co-processing of catalytic pyrolysis oil and VGO in lab scale FCC cracker and claimed that the bio-oil derived from catalytic pyrolysis performs similarly to hydro-deoxygenated bio-oil when co-catalytic cracking with heavy oil like VGO.34 However, up to now the co-processing experiments reported were mainly based on the Lab scale catalytic cracking units. A pilot scale experiment is hence obviously important before such co-processing scheme can be scaled up to commercial reality. Recently, co-processing experiment of raw bio-oil and gas oil in a pilot scale FCC unit was carried out by Rezende et al.19 Obviously different results from the pilot riser and Lab scale advanced cracking evaluation (ACE) unit were found. The coke selectivity in the pilot scale riser is much lower than that in ACE unit. The authors attributed the reasons to optimization of feedstock pre-heating and thermal shock effect. However, the bio-carbon selectivity in gasoline product is only about 2% due to the low carbon percentage in raw bio-oil. In this paper, we reported the co-processing of catalytic pyrolysis derived bio-oil with VGO in a pilot scale FCC riser. The general performance of catalytic pyrolysis derived bio-oil in FCC co-processing, product distribution, and bio-carbon distribution were investigated in detail.

2. EXPERIMENTAL 2.1 Materials A commercial lignocellulosic biomass obtained from beech wood (44.18 wt.% carbon, 6.69 wt.% hydrogen, 46.58 wt.% oxygen, 1.45 wt.% ash; 59.7 mg/kg Na, 216 mg/kg K) was

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used in the current study. The catalyst used in this study was a commercial FCC equilibrium catalyst collected in an industrial FCC unit located in one of the China petro refineries. Table 1 shows the physicochemical characteristics of the catalyst. A VGO from a local refinery with properties shown in Table 2 was used as heavy oil. 2.2 Biomass Fast Pyrolysis and Catalytic Pyrolysis Both biomass fast pyrolysis and catalytic pyrolysis were carried out in a pilot scale riser reactor. 5% Fe/ZSM-5 prepared by impregnation of ZSM-5 (Zeolyst 5524G) with Fe(NO3)3 was used as catalyst for the catalytic pyrolysis step. The pyrolysis reactor was schematically shown in Figure 1S of Supporting Information. The unit was designed similarly to a FCC riser but the catalyst was regenerated offline. In such unit, the biomass was fed from the feed hopper to the hot reaction section using a screw feeder, where it was mixed with the solid heat carrier (sand or catalyst) loaded in the heat carrier vessel. The heat carrier vessel was separated into two vessels arranged vertically like a double hopper. The heat carrier vessel was heated to 650 °C in order to provide the heat required for biomass cracking. A pre-mixing zone was designed in the bottom part of the pyrolysis reactor to ensure good mixing and heat transfer. The pyrolysis was taking place once the biomass was mixed with sand or catalyst and transported into the main riser. The residence time of vapors in the riser was about 2 s, and the pyrolysis temperature was controlled to 500 °C. The mixture of biomass pyrolysis vapors and solid heat carrier or catalyst then entered the cyclonic head of the stripper tangentially, where oil vapor and catalyst solids were separated. The spent catalyst was kept in a catalyst vessel and regenerated offline. The bio-oil was recovered from

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the condensate system. 2.3 Riser Reactor Platform The FCC co-processing experiments were conducted in an automated Pilot-Plant FCC unit schematically shown in Figure 1. The pilot plant was operated in a full catalyst circulation mode with continuous regeneration and consisted of a riser reactor (7 mm inner diameter and about 9 m height), stripper, lift line, and fluidized bed as the regenerator (78 mm inner diameter). The catalyst circulation was achieved with two slide valves, and it was controlled in a manner similar to that in a commercial FCC unit. The inside of the entire system was considered as an isothermal zone, of which the temperature was controlled independently at many points as shown in Fig.1. The reaction temperature was kept at 525 °C, which is a typical reaction condition of commercial FCC operation. The catalyst to oil ratio was controlled between 5 and 8 in all the co-processing experiments. For catalyst stripping, steam was used at the bottom of the stripper vessel. The separation of the produced gaseous and other liquid products was conducted using a specially designed refrigerated stabilizer. The liquid products, mainly C5 and heavier compounds, were condensed and collected. In each FCC pilot-plant test, the liquid product was collected in a receiver located at the bottom of the separating tower. Meanwhile, the gas products were gathered in a gasbag. The amount of coke formed on the catalyst was calculated from the carbon dioxide production during the regeneration period, as measured by carbon dioxide analyzer. In order to confirm the repeatability, all experiments were carried out twice in our study. 2.4 Characterization Methods The gas products were analyzed on Agilent 7890A gas chromatography (GC) system

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designed for analyzing refinery gas. The GC system contains 3 detectors (2 TCD and 1 FID) and 7 columns to quickly analyze the gas samples. Liquid products were firstly analyzed by GC/MS system (Agilent 7890A/5975C). LECD Pegasus®4D GC×GC- TOF/MS instrument was also used for detailed chemical composition analysis of obtained liquid products. In such analysis, the first column is nonpolar or weakly-polar and the second one is a polar column. As a consequence, the compounds were separated respectively according to the differences of their boiling points and polarities. The two dimensional GC analysis conditions are given in Table 1S of Supporting Information. The

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C (renewable carbon) concentration in the liquid product was determined in an

accelerator mass spectrometer (AMS) comprised of the isotope ratio mass spectrometer using the ASTM D6866-12 method (method B). The liquid product was converted into solid carbon sample before the analysis, which was done by converting the samples into carbon dioxide through combustion then into carbon monoxide in the presence of zinc and further reducing carbon monoxide into graphite via a catalytic reaction with iron. The radiocarbon contents are expressed as pMC (percent Modern Carbon) and then transferred to bio-carbon ratio according to the procedure shown in literature.20

3. RESULTS AND DISCUSSION 3.1 Comparison of Bio-oil Derived from Fast Pyrolysis and Catalytic Pyrolysis The bio-oil derived from catalytic pyrolysis has an obvious difference in yield, elemental distribution, and chemical composition when compared with fast pyrolysis oil. Table 3 gives the bio-oil yield and elemental distribution of bio-oil samples. The bio-oil yield in catalytic pyrolysis dropped to 26.8% from 46.4% in fast pyrolysis. A dramatic increase of

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carbon and hydrogen contents in bio-oil samples was observed in catalytic pyrolysis derived bio-oil. The oxygen content in catalytic pyrolysis derived bio-oil is only 19.5%, which is much lower than that of bio-oil obtained in fast pyrolysis. The reduction in oxygen content is further supported by the chemical composition analysis. Table 4 shows the chemical composition of bio-oil derived from fast pyrolysis and catalytic pyrolysis determined by 2D GC×GC-TOF/MS. It should be noted that the percentage calculated by area can only be considered as semi-quantitative results and expression of the composition change in bio-oil obtained under different conditions. The bio-oil derived from catalytic pyrolysis contains no detectable acidic compounds, while there is about 9.2% in fast pyrolysis derived bio-oil. The pH value of bio-oil derived from fast pyrolysis and catalytic pyrolysis is 2.60 and 3.71, respectively. The lower acidity of catalytically derived bio-oil is very important for both oil storage and avoiding possible corrosion of processing equipment. Oxygenates with more than one oxygen-containing functional group, and sugars are also reduced obviously in catalytic pyrolysis derived bio-oil. The furans, aromatic oxygenates other than phenol and sugar content in catalytic pyrolysis derived bio-oil is 2.7%, 31.0% and 0.5%, while there is 13.0%, 41.0% and 17.6% of the fast pyrolysis derived bio-oil, respectively. The percentages of phenols, mono-aromatics, and poly-aromatics in catalytic pyrolysis derived bio-oil are obviously increased. For instance, the content of mono-aromatics is increased to 12.7% from 1.5% in catalytic pyrolysis derived bio-oil. Thus, it can be concluded that the primary bio-oil vapor was upgraded in-situ to reduce the acid content and highly oxygenated molecules during the catalytic pyrolysis step. As a consequence of the change in chemical composition, the H/Ceff of catalytic pyrolysis derived bio-oil also increased to 0.81 from 0.17 of the fast

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pyrolysis derived bio-oil. The bio-oil produced in present study has good balance on quality and carbon yield, and would be interesting feedstock for FCC co-processing. 3.2 Co-processing of Catalytic Pyrolysis Derived Bio-oil with VGO in FCC Pilot Riser The E-cat and VGO feedstock is gathered from a working refinery to well represent our experiment. As shown in Table 1, the E-cat is typical FCC catalyst with surface area, Re2O3 and V, Ni content being 158 m2/g, 1.8 wt.%, 1000 ppm and 2200 ppm, respectively. The properties of VGO feed are shown in Table 2. It has no detectable asphaltene and low wax (1.9%) content. The calculated UOPK value of the VGO feed is 12.3, which indicates the good cracking property of the VGO feed. Before the co-processing experiment, the miscibility of bio-oil in VGO was firstly checked visually. The bio-oil from fast pyrolysis is poor in miscibility with heavy oil, and pre-heating of the bio-oil always results in bio-oil repolymerization. Hence two different feeding lines for bio-oil and heavy oil are necessary for a FCC co-processing unit according to previous publication.19 The change in chemical composition caused by catalytic reaction leads to different miscibility of bio-oil in heavy oil. Although the miscibility of catalytic pyrolysis derived bio-oil in heavy oil at room temperature is still limited, a slight increase in the temperature, e.g., 60 °C, enables them to mix well. Due to the good miscibility of catalytic pyrolysis derived bio-oil and VGO, the oil feedstock was introduced through one feed line in our experiments. Several different blends of catalytic pyrolysis derived bio-oil and VGO were firstly carried out to test the effect of blending ratio on the co-processing performance. It was found that the co-processing experiment can be performed without any plug problem and riser coke issue with a bio-oil content below 10%. As shown in Table 5, the oil conversion, gasoline and

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coke selectivity have linear relationship when similar catalyst to oil ratio (~5) is used. When 15% catalytic pyrolysis derived oil was blended into VGO and used as co-processing feedstock, riser coke and feeder blockage (indicated by PT 3 increasing in Figure 1) were sometimes observed. It should be noted that higher blending degree of catalytic pyrolysis derived bio-oil can possibly be used in larger pilot or commercial FCC unit, since larger unit has larger riser diameter and thus lower possibility for the bio-oil injection to the riser wall. Another possibility for increasing bio-oil blend is using separate feed line to introduce bio-oil to the bottom part of riser where the temperature is highest. In this way, the large oxygenates in bio-oil could be cracked into smaller ones through thermal shock effect. The 10% catalytic pyrolysis derived oil, and 90% VGO was then used as main feedstock to study the co-processing performance at different catalyst to oil ratios. Four different ratios of catalyst to oil (5.1, 6.3, 7.2, and 8.7) were used. Obviously, higher conversion of bio-oil/VGO mixture than that of pure VGO is found at the same C/O ratio as shown in Table 6, resulting from a higher reactivity of bio-oil/VGO mixture. Further study is necessary to confirm if the higher reactivity of bio-oil and VGO blend is general for all biomass and VGO. Figure 2 and Table 2S show the selectivities of main group of products, dry gas, LPG, gasoline, LCO, bottom, coke, and water. A clear decrease in the dry gas yield was found. With similar conversion (70%), the dry gas yield was 4.7% for VGO catalytic cracking while only 2.6% for catalytic pyrolysis derived bio-oil and VGO co-processing. The gasoline, bottom, and coke yields during 10% bio-oil co-catalytic cracking were almost the same as those obtained with pure VGO. The selectivity of LCO was even slightly higher (0.5% at about 70% conversion) than that from pure VGO. Figure 3 further shows the yields of CO,

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CO2, water, and hydrogen during catalytic pyrolysis oil and VGO co-processing. Similar to dry gas selectivity, the hydrogen yield also decreased. With 70% conversion, the hydrogen yield was 0.09% for VGO catalytic cracking while only 0.05% for catalytic pyrolysis derived bio-oil and VGO co-processing. In VGO catalytic cracking experiment, there was no formation of CO, CO2, and H2O. In VGO/bio-oil co-catalytic cracking experiment, CO, CO2, and water were also found in minor selectivity, potentially caused by the lower oxygen degree of the mixed feedstock. Besides the similar gasoline and LCO yields found during the co-processing experiment, another interesting finding is the complete deoxygenation of bio-oil. After co-processing experiment, common 1D GC/MS could detect any oxygenates due to the serious overlap between the peaks derived from oxygenates and hydrocarbons. Hence 2D GC×GC-TOF/MS was used in this experiment to further test the oxygenate content. The results for 10% bio-oil co-processing experiment are shown in Figure 4 and Table 7. Note that the oxygenate content of liquid hydrocarbon derived from co-processing is only 0.22%, and the liquid product from pure VGO catalytic cracking also contains 0.19% oxygenates. The existence of oxygenates like phenols in pure VGO cracking is due to the reaction between oxygen entrained in the regenerated catalyst and the hydrocarbon feed. The very close value of oxygenate in VGO and VGO/bio-oil mixture cracking experiment indicates the complete deoxygenation of bio-oil feed. Due to the low H/Ceff of the bio-oil derived from catalytic pyrolysis, the deoxygenation during FCC co-processing is relied to the following three pathways: oxygen ejection of bio-oxygenate

alone

through

decarbonylation

and

decarboxylation,

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bio-oxygenate


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hydrogenation through either hydrogen transfer between the bio-oxygenate and hydrocarbon or hydrogenation of bio-oxygenate by hydrogen in dry gas, and the dehydration of bio-oxygenate over the acid sites. The first reaction pathway was supported by the formation of CO and CO2, which were both observed in the co-processing experiment, indicating the presence of decarbonylation and decarboxylation reaction. However, the amount of CO and CO2 were much lower than those of raw bio-oil co-processing reported by Rezende et al23. This is possibly because some decarbonylation and decarboxylation occurred in the catalytic pyrolysis step. The hydrogenation mechanism was supported by the changes in H2 and light alkane contents in dry gas. The formation of water is a clear evidence for the presence of dehydration reaction. The complete deoxygenation of bio-oil during co-processing is also directly linked to the chemical composition. According to 2D GC×GC-TOF/MS analysis, there are more mono-functional oxygenates, like phenol, in the catalytic pyrolysis derived bio-oil. As shown in Figure 2S of Supporting Information, the phenols can be converted into aromatics through one-step transfer hydrogenation. While other bio-oxygenates with more than one oxygen containing functional groups such as eugenol need two or more adsorption and transfer hydrogenation steps. The less transfer hydrogenation step not only reduces the coking possibility but also decreases the active site competing with hydrocarbon feed. Similar to the Lab scale co-catalytic cracking experiment with hydrogenation stabilized bio-oil and catalytic pyrolysis derived oil as bio-feedstock, 34 more aromatics were found in the gasoline and LCO fractions. The increase of aromatics was considered as a result of bio-oxygenate co-processing such as competitive adsorption on active sites and hydrogen

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transfer.16 However, in our case, a part of the aromatics can be introduced directly from catalytic pyrolysis derived bio-oil. The competitive effect for aromatics formation is thus much lower than the co-processing of raw bio-oil, catalytic pyrolysis oil, and even bio-oil after mild hydro-processing. The renewable carbon content in liquid product is of great importance for a successful co-processing concept. Table 8 shows the bio-carbon content in each liquid fraction of the co-processing products in two reproduced experiments with a conversion of 70%. The renewable carbon in gasoline product is about 7%, which is much higher than that from raw bio-oil co-processing and is similar to that from co-processing experiment of hydrogenation stabilized bio-oil on small scale. The higher renewable carbon in gasoline fraction is directly connected to the higher carbon percentage (73.1% vs 42.4%) of catalytic pyrolysis derived bio-oil than raw bio-oil. It is interesting to find that the bio-carbon in LCO fraction is slightly higher than gasoline cut (7.3%). Considering there are 9% poly-aromatics in the bio-oil derived from catalytic pyrolysis, it is easy to understand the high bio-carbon content in LCO fraction. 3.3 Discussion on Biofuel Production from Catalytic Pyrolysis and FCC Co-processing When integrated the co-processing step to the complete biofuel production process from lignocellulosic biomass, it can be found that the catalytic pyrolysis coupled with FCC co-processing pathway is a promising processing technology. In such a biofuel production process, biomass is firstly converted into stable bio-oil by catalytic pyrolysis and FCC co-processing of the bio-oil derived from catalytic pyrolysis into oxygen free hydrocarbon biofuel. Here we clearly proved that the oxygen in catalytic pyrolysis derived oil can be

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completely removed by co-processing with VGO. Such a technology shows very interesting feature regarding oxygen removing pathway. In terms of biomass, oxygen can be removed through CO, CO2, and H2O. A rational combination of carbon ejection (CO, CO2) and hydrogen addition (H2O) should be realized for high carbon selectivity and minimal hydrogen consumption. In the above mentioned technology, the oxygen was removed in catalytic pyrolysis through CO, CO2, and H2O, while mainly removed by H2O in FCC co-processing. It is interesting to compare this process with other existing biofuel production technologies starting from biomass catalytic pyrolysis (including FCC co-processing). In most FCC co-processing studies, a hydro-processing upgrading step is included to improve the bio-oil properties (H/Ceff >1.2). The co-processing of bio-oil obtained after upgrading was successfully proved in Lab scale FCC unit (both MAT and fluidized ACE unit). However, some issues such as the decrease in quality of VGO cracking product, and the reaction site competed by bio-oxygenate have also been reported.16 Moreover, the bio-oil HDO step is not a commercial technology and is still under development.17 Another drawback is the expensive noble metal catalyst such as Ru/C is always used in the HDO step.18 Hence eliminating the costly hydrogenation step by a catalytic pyrolysis step is more competitive. Schuurmau et al.22 successfully proved the co-processing of catalytic pyrolysis derived bio-oil with VGO in a microscale FCC unit. Here we further demonstrated such co-processing in a pilot FCC riser. Moreover, our results first reported that the oxygen in bio-oil can be removed almost completely in the FCC co-processing studies. The difference in oxygen content between our result and other Lab scale cracking experiments can be understood from at least two aspects: 1) the difference of operation scale and the benefits of thermal shock effect in pilot scale unit,

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and 2) higher quality of the starting bio-oil in our investigation. Another potential upgrading method for catalytic pyrolysis derived bio-oil is hydro-deoxygenation. Recently, our group has reported an advanced biofuel production pathway through catalytic pyrolysis and hydro-deoxygenation.35 A clear synergy between catalytic pyrolysis and hydro-processing step such as removal of oxygen and increase of carbon yield was proved. It was found that catalytic pyrolysis step lowers down the difficulty in hydro-deoxygenation step. A remaining drawback of that process is again the expensive hydrogen and its high pressure involved in the hydro-deoxygenation step. In the present study, the hydro-deoxygenation step was replaced by FCC co-processing, which has mature infrastructure and operational experience. This new biofuel production pathway can reserve the merits of previous catalytic pyrolysis/hydro-deoxygenation process and simultaneously introduce the above mentioned new advantages.

4. CONCLUSION From the experimental results of the present pilot-plant study, it is shown that the catalytic pyrolysis derived bio-oil is very promising as a blend during VGO catalytic cracking. With the high quality of bio-oil used in the present study, the co-processing experiment can be carried out with 10% blend of catalytic pyrolysis bio-oil. The mixture is more crackable than pure VGO in comparable condition. The gasoline, bottom, and coke selectivities from co-processing are almost the same as those of VGO catalytic cracking alone under similar conversion. The dry gas, including hydrogen and light alkane reduces obviously in the co-processing experiment because of the hydrogen transfer between bio-feedstock and VGO. The co-processing experiments also lead to the formation of CO, CO2, and water; however,

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their amounts in catalytic pyrolysis derived bio-oil co-processing case are much lower than those from fast pyrolysis oil co-processing. The reason for this is the part oxygen removal in catalytic pyrolysis step. 2D GC-TOF/MS results indicate that the oxygenate content in co-processing experiment is almost the same as in VGO cracking. Radiocarbon analysis reveals that 7% carbon of gasoline come from catalytic pyrolysis derived bio-oil when 10% catalytic pyrolysis derived bio-oil is used in the mixed feedstock. The successful co-processing, complete deoxygenation, and high bio-carbon content make the biomass catalytic pyrolysis/FCC co-processing process highly suitable for biomass conversion into biofuel. ■ AUTHOR INFORMATION Corresponding Author Tel. & Fax: +86-10-64429057. E-mail address: [email protected] (Yunming Fang)

Notes Acknowledgement: Financial support for this work was provided by Nature Science Foundation of China under Project No.21206183 and is greatly acknowledged.

Supporting Information The Supporting Information is available free of charge on the ACS Publications website. Fast (catalytic) pyrolysis process (Figure 1S), conditions of GC*GC-TOF-MS analysis (Table 1S), yield and products selectivities of co-processing experiments (Table 2S), proposed reaction mechanism of catalytic pyrolysis derived bio-oil in FCC co-processing (Figure 2S) (PDF).

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Table 1. Properties of the FCC catalyst Physical

Micropore

Mesopore

volume

area

(m2/g)

(m2/g)

0.05

53.0

Surface area

properties

(m2/g)

Value

158

Al2O3

Re2O3

V

Ni

(wt.%)

(wt.%)

(mg/kg)

(mg/kg)

45.0

1.8

1000

2200

22


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Table 2. Properties of the VGO feeds used in this study Properties

Value

API°

26.3

Density

S

N

Ni

V

CCR

ASTM 2887 (wt.%/°C)

(g/ml)

(ppm)

(ppm)

(ppm)

(ppm)

(wt.%)

5%

50%

95%

FBP

0.85

849

380

0.9

Coprocessing of Catalytic-Pyrolysis-Derived Bio-Oil with VGO in a

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