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Catalytic Upgrading of Biomass Pyrolysis Oxygenates with Vacuum Gas Oil (VGO) using a Davison Circulating Riser Reactor Mark William Jarvis, Jessica Olstad, Yves Parent, Steve Deutch, Kristiina Iisa, Earl D. Christensen, Haoxi Ben, Stuart K. Black, Mark R Nimlos, and Kimberly A. Magrini Energy Fuels, Just Accepted Manuscript • DOI: 10.1021/acs.energyfuels.7b02337 • Publication Date (Web): 02 Jan 2018 Downloaded from http://pubs.acs.org on January 3, 2018
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Energy & Fuels
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Catalytic Upgrading of Biomass Pyrolysis
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Oxygenates with Vacuum Gas Oil (VGO) using a
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Davison Circulating Riser Reactor
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Mark W. Jarvis*1, Jessica Olstad1, Yves Parent1, Steve Deutch1, Kristiina Iisa1, Earl
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Christensen1, Haoxi Ben1, Stuart Black1, Mark Nimlos1, Kim Magrini1
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1. National Renewable Energy Laboratory, National Bioenergy Center, 15523 Denver West Parkway, Golden, CO 80401
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ABSTRACT
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The objective of this work was to investigate and quantitate the changes in hydrocarbon product
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composition while evaluating the performance and operability of NREL’s Davison Circulating Riser
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(DCR) reactor system when biomass model compounds are co-fed with traditional fluid cat cracking
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(FCC) feeds and catalyst: vacuum gas oil (VGO) and equilibrium zeolite catalyst (E-Cat). Three
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compounds (acetic acid, guaiacol, and sorbitan monooleate) were selected to represent the major classes
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of oxygenates present in biomass pyrolysis vapors. These vapors can contain 30-50% oxygen as
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oxygenates, which create conversion complications (increased reactivity and coking) when integrating
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biomass vapors and liquids into fuel and chemical processes long dominated by petroleum feedstocks. We
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used these model compounds to determine the appropriate conditions for co-processing with petroleum
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and ultimately pure pyrolysis vapors only as compared with standard baseline conditions obtained with
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VGO and E-Cat only in the DCR. Model compound addition decreased the DCR catalyst circulation rate,
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which controls reactor temperature and measures reaction heat demand, while increasing catalyst coking
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rates. Liquid product analyses included 2-dimensional gas chromatography time of flight mass
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spectroscopy (2D GCxGC TOFS), simulated distillation (SIM DIST), 13C NMR, and carbonyl content
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with aggregated results indicating that the model compounds were converted during reaction, and despite
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functional group differences, product distributions for each model compound were very similar. In
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addition, we determined that adding model compounds to the VGO feed did not significantly affect the
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DCR’s operability or performance. Future work will assess catalytic upgrading of biomass pyrolysis
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vapor to fungible hydrocarbon products using upgrading catalysts currently being developed at NREL and
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at Johnson Matthey.
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INTRODUCTION
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The ongoing requirement for renewable liquid fuels and high value chemicals, including specialty
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oxygenates for fuel additives, continues to drive research that can integrate plant-based feedstocks within
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the existing petroleum refining infrastructure. The Bioenergy Technologies Office (BETO) as part of the
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United States Department of Energy (DOE) has a mission to transform the market to include biomass-
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derived liquid fuels and products. In support of this goal, this work reports on the incorporation of
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biomass pyrolysis compounds into hydrocarbon products using a Davison Circulating Riser Reactor
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(DCR) system operated with standard FCC conditions: VGO co-feed and equilibrium zeolite catalyst.
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These experiments provided the basis for assessing the impact of biomass oxygenate feeds on DCR
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operating conditions and their incorporation into liquid product. Model compounds comprising some of
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the major functional groups (methoxy phenols, sugars, and acids) found in biomass pyrolysis vapors were
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co-fed with a mixture of VGO and kerosene (used to solubilize the model compounds for mixing with
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VGO) with comprehensive product analysis used to determine incorporation extent and impact on
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composition. Results from DCR upgrading are refinery useable as these systems are extensively used by
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the petroleum industry to assess FCC catalysts and upgraded petroleum products. Assessing the impact of
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Energy & Fuels
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biomass pyrolysis oxygenates on FCC operations and hydrocarbon product composition is the first step to
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producing refinery insertable biogenic hydrocarbons for co-processing to gasoline and diesel fuels.
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Many technologies have been explored and modified for upgrading bio-oil liquids to fuels and chemicals
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and all require catalysts at some point in the process. Technologies range from hydrotreating raw
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pyrolysis oil to co-processing bio-oil products with traditional fluid catalytic cracking feeds using varied
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experimental systems. For technologies like hydrodeoxygenation (HDO), an understanding of the
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underlying mechanism has emerged through detailed model compounds studies, which has led to rational
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catalyst design and improvement.1 Most reports used zeolites for cracking and deoxygenating biomass
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pyrolysis liquids and numerous comprehensive reviews of biomass thermochemical conversion to oil
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provide specific details.2-5
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While catalytic upgrading is a promising method to increase the energy density of biomass-derived
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liquids, several properties of biomass pyrolysis liquid make processing difficult or complex. These
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properties include high oxygen content, low pH, high viscosity that increases with aging, and
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immiscibility with petroleum feedstocks. Bio-oil properties can be improved with hydrotreating or HDO
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methods to yield distillable products.6 These reactions usually require hydrogen at elevated pressure (200-
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300 bar), which increases process cost and may be better suited for producing high value chemicals and
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fuel additives. The final products from these processes contain some oxygen (up to ~8 wt%) though they
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may be suitable as fuel blend components or as refinery feedstocks. The types of oxygenated groups
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present in the treated product, carboxylic acids, carbonyls, aryl ethers, phenols and alcohols, vary with
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extent of deoxygenation. The phenolic functionality appears to be the most difficult to upgrade;7-8 more
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research and integration studies are needed.9 Another route that has been considered is catalytic pyrolysis
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to produce a catalytic pyrolysis oil (CPO) with lower oxygen content and a reduced set of oxygen
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functional groups comprising alcohols, phenols, and acids. Further upgrading of CPO by co-processing
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with VGO in a bench scale FCC-type reactor increased the organic product yield to 30 wt% compared to
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24 wt% for the pyrolysis/HDO route in which polycyclic aromatic products and alkylphenols increased 3 ACS Paragon Plus Environment
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compared to HDO/VGO co-processing.10 Very few reports however focus on pyrolysis vapor phase
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upgrading, which can be less complex than upgrading the liquid phase as alkali and char particles can be
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easily removed from the feed stream using hot gas filters as is done in NREL’s DCR.
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Co-processing guaiacol and acetic acid with VGO has recently been studied in an Advanced Cracking
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Evaluation (ACE™) unit, a small fluidized bed system 11 that is comparable to DCR processing at the
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laboratory scale. With commercial equilibrium catalyst, guaiacol addition increased product selectivity to
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gasoline while acetic acid increased olefin, CO, and CO2 production. Proton and carbon NMR product
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analysis showed an increase in aromaticity with C/O ratio. While complete conversion of acetic acid was
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achieved, guaiacol cracking was incomplete with VGO with results showing a cracking order of
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guaiacol+VGO > acetic acid+VGO > VGO. Agblevor et al.12 recently used an ACE system to co-process
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15 wt% pyrolysis oil with 85 wt% standard gas oil to produce hydrocarbon fuels with negligible oxygen
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content. They postulate that hydrogen transfer occurred from standard gas oil cracking to the pyrolysis
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oil that eliminated the need for external hydrogen addition. Other work has also shown that hydrogen
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transfer occurs during co-processing bio-oil with petroleum as evidenced by increased aromatic and
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saturated aliphatic yields.13 Petrobras recently reported successful gasoline production from 10 wt% pine
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wood pyrolysis oil co-fed with petroleum products in their large-scale research FCC. They noted that the
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feeding issues observed in numerous small-scale reactors are not problematic when using their larger
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scale unit (150 kg/h) 14
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The objective of this work was to study the effect of adding biomass model compounds (5-10 wt%) with
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standard feeds (vacuum gas oil and kerosene) on DCR process parameters, operability and product
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chemistry. Impacts on liquid product composition, coke formation, and light gas yield will be discussed.
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Acetic acid, guaiacol, and sorbitan monooleate were selected to investigate how these three primary
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oxygenate functionalities, comprising methoxy phenols, sugars, and acids, influenced both DCR
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operations and upgraded product. These experiments provided the operating parameters for future
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upgrading experiments with actual biomass pyrolysis vapors using a refinery accepted FCC system. 4 ACS Paragon Plus Environment
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Energy & Fuels
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Overall, the co-processing of biomass fast pyrolysis oxygenates was not found to significantly affect the
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operability or the performance of the DCR reactor and the product liquid hydrocarbons did not differ
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significantly from VGO FCC upgrading. This is one of the first reports of co-processing work to be
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conducted with a DCR system.
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METHODS
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Catalyst and Feedstock
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The catalyst used in this study was a low-metals equilibrium FCC catalyst (E-Cat) which was supplied by
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Equilibrium Catalyst, Inc. This catalyst is a faujasite (Type Y zeolite) that had been used in FCC refining
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operations and is the catalyst choice for baselining DCR operations with VGO standard feedstock.
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Modern FCC catalysts are fine powders with a bulk density of 0.80 to 0.96 g/cm3 and an average particle
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size of 60 to 100 µm. The design and operation of an FCC unit is largely dependent upon the chemical
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and physical properties of the catalyst with desirable properties comprising 1) good stability to high
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temperature and to steam, 2) high activity, 3) large pore sizes, 4) good resistance to attrition, and 5) low
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coke production. Current FCC catalysts consist of four major components: crystalline zeolite, matrix,
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binder, and filler. Zeolite is the primary active component and can range from about 15 to 50 wt% of the
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catalyst.16
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The catalytic sites in the zeolite are strong acids (equivalent to 90% sulfuric acid) and provide most of the
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catalytic activity. The acidic sites are provided by the alumina tetrahedral crystal structure. The matrix
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component of an FCC catalyst contains amorphous alumina which also provides catalytic sites and in
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larger pores that allows entry for larger molecules than does the zeolite. This property enables cracking of
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higher-boiling, larger feedstock molecules than are cracked by the zeolite. The binder and filler
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components provide the physical strength and integrity of the catalyst. The binder is usually silica sol and
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the filler is usually a clay (kaolin). Nickel, vanadium, iron, copper and other metal contaminants, present
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in FCC feedstocks in the parts per million range, all have detrimental effects on the catalyst activity and
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performance, which is why a low metals E-Cat was used for this work. 5 ACS Paragon Plus Environment
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The properties and compositions of the E-Cat and VGO used in this work are shown in Tables 1-2. Both
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are used to baseline DCR operations for gasoline production. After each oxygenate run, standard
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VGO/E-Cat upgrading was performed to ensure that DCR operation and product gasoline composition
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remain unchanged. The E-Cat is a low metals content (33 ppm Ni, 80 ppm V) equilibrium catalyst of 78
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µm particle size. A small amount of particles < 40 µm is required for continuous catalyst circulation.
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The VGO was a low metal, low sulfur content material with a standard molecular weight of 430 g/mole,
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API of 24.7, K Factor of 12.01, and Refractive Index of 1.5. Aromatic and naphthenic ring contents were
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17.6 and 20.3wt %, respectively; paraffinic content was 62.1 wt%. Carbon, hydrogen and nitrogen
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contents from CHN analysis were 87.42 wt% C, 13.17 wt% H2 and 0.09 wt% N.
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Table 1. E-Cat Properties and Metals Content Physical Properties Total Surface Area (m2/g) 171 Average Bulk Density (g/cc) 0.87 Particle Volume (cc/g) 0.35 0-40 (wt%) 5 0-80 (wt%) 52 Average Particle Size (µm) 78 Metals Content (wt%) Al2O3 SiO2 Na2O RE2O3 Ni (ppm) V (ppm) SO4 Fe TiO2 MgO P2O5 CaO
44.2 50.6 0.31 3.25 33 80 0.33 0.5 1.1 0.05 0.09 0.08
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Table 2. VGO Properties. VGO API (ºAPI) Specific Gravity K Factor Refractive Index
24.7 0.9059 12.01 1.5037 6 ACS Paragon Plus Environment
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Energy & Fuels
Density Boiling Point (°C) Flash Point (°C) Average Molecular Weight(g/mol) Arom Ring Carbons Ca (wt%) Naphthenic Ring C Cn (wt%) Paraffinic Carbons Cp (wt%) Total Carbon (wt%( Sulfur (wt%) Basic Nitrogen (wt%) Total Nitrogen (wt%) Conradson Carbon (wt%) Zn (ppm)*
---------430 17.6 20.3 62.1 87.4 0.35 0.046 0.14 0.32 0.1
*Other metals (Ni, V, Ca, K, Mg, Al, Ba, Cr, Cu, Fe, Mn, Pb, Sb) were below detection limits.
1 2
The oxygenated model compounds evaluated in this study were acetic acid, guaiacol, and sorbitol
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monooleate, all of which are found in biomass-derived pyrolysis products. Kerosene was chosen as a
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miscible solvent for both oxygenates and VGO as the oxygenates are not soluble in pure VGO. The
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DCR is equipped to feed both VGO and kerosene, as kerosene has a greatly reduced coke rate and is
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used to clean the system of VGO residuals between experiments. Further, both acetic acid and
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guaiacol are soluble in kerosene while sorbitol monooleate is insoluble. Sorbitan monooleate was
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chosen as an alternative to sorbitan monooleate for its solubility in kerosene. Sorbitan monooleate is a
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sorbitan monooleate fatty acid ester; it has the same basic structure as sorbitan monooleate, but has
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been dehydrated, bound into a ring structure, and contains an extra hydrocarbon chain. A solution
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containing 90 wt% kerosene and 10 wt% model compounds was prepared for each of the kerosene –
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oxygenate feeds. For co-feeding with VGO, the kerosene-oxygenate mixture was co-fed with 50 wt%
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VGO, with the overall feed containing 5 wt% oxygenate. Descriptions of each feed mixture are
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shown in Table 3.
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Table 3. DCR feed types. Feed 1 2 3 4 5 6 7 8 9
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Sample K V VK KA VKA KG VKG KS VKS
Composition Kerosene VGO VGO/Kerosene (50/50) Kerosene + Acetic Acid (10 wt%) VGO/Kerosene + Acetic Acid (5 wt%) Kerosene + Guaiacol (10 wt%) VGO/Kerosene + Guaiacol (5 wt%) Kerosene + Sorbitan Monooleate (10 wt%) VGO/Kerosene + Sorbitan Monooleate (5 wt%)
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Catalytic Cracking and Upgrading
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The upgrading experiments were carried out in a Davison Circulating Riser (DCR) comprised of three
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reaction vessels (regenerator, riser, and stripper) as shown in Figure 1. The licensing agreement from WR
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Grace prohibits mention of vessel dimensions but a general description of these systems show 2-story
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vessels (https://grace.com/catalysts-and-fuels/en-us/Documents/113-
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Flexible%20Pilot%20Plant%20Technology%20for%20Evaluation%20of%20Unconventional%20Feedsto
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cks%20and%20Processes.pdf). The DCR is operated adiabatically as are industrial FCC units. VGO is
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fed using an ISCO high pressure pump with dual cylinders. The model compound mixtures are fed using
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an Ismatec compact gear pump. Air is introduced into the regenerator for in situ catalyst regeneration, and
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the resulting flue gas is analyzed to determine coke deposition on the catalyst. The product stream is sent
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through a reflux condenser; all resulting liquids are collected for later analysis, and residual product gases
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are analyzed by gas chromatography.
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For these experiments, the system pressure was set at 25 psig and the total liquid feed rate at 1 kg/hr.
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Steam was fed to the bottom of the riser and the stripper, each at a rate of 30 g/hr. The regenerator,
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stripper, riser outlet, and the feed pre-heater temperatures were set to 700°C, 500°C, 521°C, and 150°C,
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respectively. These operating temperatures were chosen because they are commonly used in industrial
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FCC processes.
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Energy & Fuels
1 Figure 1. Schematic of the Davison Circulating Riser (DCR).
2 3
Product Analysis
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All product samples were diluted in dichloromethane solvent (Fisher, HPLC grade) and analyzed directly.
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Comprehensive liquid product analysis was conducted with 1) two dimensional gas chromatography time
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of flight mass spectrometry using a LECO Pegasus system using conditions shown in Table 4 and
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equipped with a Gerstel autosampler; 2) quantitative 13C NMR with a Bruker 400 MHz NMR
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spectrometer employing an inverse gated decoupling pulse sequence (zgig), 90° pulse angle, a pulse delay
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of 50 s, and 1024 scans used for all the standards and samples; 3) carbonyl analysis using a titration
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method developed by Faix; 17 and 4) simulated distillation conducted with ASTM method D2887 using an
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Agilent 7890A gas chromatograph (GC) equipped with a cool on-column injection port, flame ionization
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detector, and a Restek MXT-1HT capillary column (100% polydimethyl siloxane, 10m x 0.53 mm, 2.65
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µm df). The GC program was set following the recommendations in Table 1 of method D2887. 9 ACS Paragon Plus Environment
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Distillation points were calculated following the correlation with ASTM method D86 provided in
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Appendix X5 of method D2887. Post-condensation product gases were analyzed using an Agilent
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Technologies 490 Micro gas chromatograph, using 10m MS5A, 10m PPQ, and 8m 5CB columns with
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results reported on a nitrogen-free basis.
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Table 4. GCxGC-TOFMS analysis conditions. Column Primary Secondary Injector Split 30:1; Oven Primary Secondary Modulator Modulator cycle timing Start – 596 sec runtime 596 – End runtime Transfer Line TOF mass range TOF acquisition rate Solvent delay
10m x 180µm; 0.18µm RTX-5 0.75m x 100µm; 0.10µm DB-1701 300°C 40°C – 1-minute hold; +10°C offset from primary +15°C offset from secondary Modulation period sec Hot time sec Cold time sec 4 0.7 1.3 4 0.85 1.15 250°C 29 – 350 amu 200 spectra / sec 54 sec
5 6
NMR Analysis
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All NMR spectral data reported in this study was recorded with a Bruker 400 MHz NMR spectrometer.
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Quantitative 13C NMR employing an inverse gated decoupling pulse sequence (zgig), 90° pulse angle, a
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pulse delay of 50 s, and 1024 scans were used for all the standards and samples. To determine the
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multiplicity of carbon atom substitution with hydrogen, distortionless enhancement by polarization
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transfer, or DEPT, experiments were performed. DEPT-135 13C-NMR employed a standard Bruker pulse
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sequence “dept135” with a 135° pulse angle, 2 s pulse delay, and 1000 scans. DEPT-90 13C-NMR
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employed a standard Bruker pulse sequence “dept90” with a 90° pulse angle, 2 s pulse delay, and 1000
14
scans.
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Carbonyl Analysis 10 ACS Paragon Plus Environment
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Energy & Fuels
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The original carbonyl analysis method was developed by Faix13 and has been modified to increase sample
2
size and decrease reactant volumes14. This method reacts the sample with hydroxylamine hydrochloride
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(NH2OH.HCl) in ethanol and the liberated hydrochloric acid can react with an excess of triethanolamine
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(TEA) solution also in ethanol. The unreacted TEA is then titrated with standardized hydrochloric acid to
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determine the amount of hydroxylamine hydrochloride originally consumed and hence the equivalent
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amount of carbonyl groups present. The estimated detection limit is near 0.1 mol carbonyl group / kg oil.
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RESULTS AND DISCUSSION
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DCR Operations with Petroleum Feedstocks
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Prior to the petroleum-oxygenate runs, replicate mass balance runs were conducted with VGO and
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mineral oil with E-Cat to assess DCR operational reproducibility and compared with typical gasoline
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components from PIANO analysis (Table 5) prior to the oxygenate addition experiments. Reproducibility
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was within normal DCR operations (±5%). The VGO/E-Cat runs were repeated after every non-standard
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feedstock run to ensure DCR operability and product compositions remained unchanged.
14 15 16
Table 5. Compound class distributions (PIANO) reported in weight % produced using petroleum feedstocks and E-Cat in FFC-DCR upgrading to monitor reproducible baseline system performance.
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Compound Class Mineral Oil Mineral Oil VGO VGO Gasoline Paraffin 3.7 3.5 3.9 4.1 8.2 Iso Paraffins 32.0 31.1 27.3 28.3 51.9 Aromatics 23.0 22.8 25.1 26.8 31.3 Naphthenes 10.8 10.7 7.5 7.2 5.0 Olefins 20.0 18.9 22.7 20.0 3.3 Unidentified 10.5 13.1 13.5 13.6 0.3 Oxygenate addition experiments were conducted using the same DCR operating conditions and the feeds
18
shown in Table 3. Visual inspection showed color differences in the products obtained from the various
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feed materials (Figure S1). The marked contrast between the two base feed materials, VGO and kerosene,
20
is attributed to their composition as kerosene contains a narrow range of linear hydrocarbons that are
21
easily cracked while VGO contains long chain hydrocarbons and complex multiring compounds that are
22
more difficult to crack and prone to coking. The slight color differences between the mixed feeds imply
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product compositions closer to one base feed material or another. However, these same color variances do
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not give much indication that the presence of the model compounds makes a large contribution to
3
compositional variability as determined by NMR and GCxGC TOFMS analyses as discussed below.
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Catalyst Coking and Circulation Rate
5
In typical DCR operation, setpoints for riser outlet temperature, VGO or co-feed flow rate, and
6
regenerator temperature are fixed while the catalyst circulation rate automatically adjusts to maintain the
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selected riser outlet temperature. Catalyst circulation rate as well indicates the heat requirement for
8
cracking these feedstocks as lower circulation rates deliver less heat to the riser indicating that more
9
exothermic cracking is occurring. Conversely, high circulation rates deliver more heat to the riser thus
10
indicating more endothermic cracking is occurring. Figure 2 shows the circulation rates and associated
11
coke rates for VGO and the oxygenate co-feeding experiments. Experiments using only the petroleum
12
feeds VGO (V), kerosene (K) and a 50/50 mixture (VK) exhibited coking rates that were approximately
13
proportional to VGO content. Kerosene is a “clean” feed with a narrow distribution of hydrocarbon chain
14
lengths that readily crack to shorter chain products. Conversely, VGO contains “heavy” hydrocarbons,
15
Conradson carbon and multi-ring compounds that are more recalcitrant to cracking and more prone to
16
coking, as shown in Figure 2. Within the kerosene-oxygenate series, coking rates increased with K < KA
17
< KS < KG; within the VKG-oxygenate series, increasing coking rates were VK < VKA < VKS < VKG.
18
In both series, guaiacol (2-methoxyphenol) displayed the highest coking rate, which may be related to its
19
aromatic ring structure and the recalcitrance of phenols to fluid cat cracking. Sorbitan monooleate
20
exhibited intermediate coking rates and acetic acid produced the lowest coking in both series of
21
feedstocks. In general, feeds containing the oxygenate compounds had higher coke rates than for feeds
22
without these compounds. This behavior has been seen with oxygenated compound reactions over other
23
acid catalysts. 11, 15-17
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Catalyst circulation rates indicate heat demand for cracking reactions and within the kerosene-oxygenate
25
series endothermicity increased as KG < KA < K < KS; within the VK-oxygenate series, endothermicity 12 ACS Paragon Plus Environment
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increases were similar to the K-oxygenates and increased as VKG < VKA < VK < VKS. Interestingly,
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the VK feed was less endothermic than either feed by itself.
Circula on Rate vs. Coke Rate 50 V 45 40 35 Coke Rate (g/hr)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
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VKG
VKS VKA
25
KG VK
20 15
KS KA
10
K
5 0 6000
6500
7000
7500
8000
8500
9000
9500
10000
Circula on Rate (g/hr)
3 4
Figure 2. Steady-state values for catalyst circulation and coke rates for each feed.
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GC Analysis of Product Gas Stream
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Post-condensation product gases were analyzed with an online gas chromatograph. The results are
7
reported on a nitrogen-free basis and are shown in Figure 3.
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A)
C)
Page 14 of 31
B)
D)
1 2 3
Figure 3. Gas chromatograph results for gas products from each of the feed types: (a) feeds K, VK, and V, (b) feeds with and without acetic acid, (c) feeds with and without guaiacol, and (d) feeds with and without sorbitan monooleate. Results are reported on a nitrogen-free basis.
4
Gas phase product analysis shows that there was a decrease in hydrogen content when the model
5
compounds were added to either kerosene or VGO, which has been observed by Graca et al. and Naik et
6
al. who focused on cracking VGO in the presence of oxygenated compounds, including acetic acid and
7
guaiacol. 8, 11 Graca suggested that hydrogen consumption is correlated with higher concentrations of
8
olefins, as shown by an increase in the olefin/paraffin ratio. Naik attributed the decrease in hydrogen to
9
hydrogenation reactions, as observed by the increased concentrations of paraffins and aromatics. There is
10
no clear trend in this study (ethylene increased but olefins, C3, and higher hydrocarbons decreased), so the
11
hydrogen consumption may be due to one or both proposed schemes. It is also possible that dilution
12
effects from oxygenate addition are impacting hydrocarbon species formed from kerosene or VGO.
13
Further work with bench scale studies will be used to understand the predominant hydrogenation
14
mechanism(s). We also observed that the presence of oxygenates caused a decrease in all species C3 and 14 ACS Paragon Plus Environment
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1
above, but increased methane production as also observed by Naik. 11 These GC results suggest that the
2
presence of oxygenated compounds in the feed may have an effect on the overall product composition.
3
Mass Fraction Yields
4
To obtain mass balances for each experiment, the DCR system was run until the internal reflux condenser
5
temperature reached steady state. At steady state, the liquid collection was diverted to a clean tank, and
6
product was collected for one hour. Coke and gas average production rates were calculated as previously
7
described and the hydrocarbon and aqueous phase products were collected over the steady state period
8
and weighed. The results presented are the average of two mass balance runs. Further, the KG, VKG, and
9
the VKA experiments were repeated once, with two mass balance runs for each experiment. The effect of
10
model compound addition on the gas, coke, and liquid fractions (both hydrocarbon and aqueous) is shown
11
in Figure 4. Losses are primarily due to coke build up in the system outside of the regenerator and a small
12
percentage (~2-5%) of water and trace organics out of the regenerator flue. The regenerator was routinely
13
monitored for CO2 and CO only, as described in the methods section, to determine the coke rate. After
14
each experiment, air is introduced into the system to burn off any residual material (coke) that has built up
15
on reactor surfaces. The residual oxidation is evident from the temperature rise that occurs when air is
16
added to the riser and from on line analysis of regenerator flue gas that measures O2, CO, and CO2
17
concentrations, however light hydrocarbons are not analyzed. Because burnout is performed after each
18
experiment, plugging issues have not occurred. In addition to mass loss from coking, other contributions
19
to low mass closure are attributed to losses from 1) combustion water that is not measured, 2) escape of
20
hydrocarbon products from the regenerator from inefficient steam stripping (products remain on the
21
catalyst prior to regeneration), 3) light gas hydrocarbons escape during catalyst transfer from the stripper
22
to the regenerator, and 4) biomass-derived aerosols that do not condense in the stabilizer. The recent
23
addition of a fractional condensation train should minimize product losses from the regenerator as this
24
collection system is more efficient than the efflux condenser used in this work.
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Page 16 of 31
1 2 3
Figure 4. Mass balance across all experiments. Values based on 1 kg/hr total feed plus 60 g/hr of steam. AQ (aqueous); HC (hydrocarbon); Coke (from regenerator); Gas (from stripper).
4 5
Table 6. Error for feed types which had repeated experiments; a total of 4 mass balance runs was used for the calculations. These values are standard deviations reported as a percent. Feed Type
Gas
Coke
HC
AQ
VKG
7.3
6.6
3.6
112.6
VKA
2.0
5.5
7.2
20.1
KG
2.3
7.0
4.1
41.8
6 7 8
Table 7. Error for feed types that had a single experiment; a total of 2 mass balance runs was used for the calculations. These values are reported as percent difference. Feed Type
Gas
Coke
HC
AQ
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Page 17 of 31
VK
0.9
0.2
1.1
72.1
KA
8.5
0.1
13.6
43.0
VKS
0.9
0.1
2.4
56.6
K
0.6
2.0
1.2
12.9
KS
1.7
4.9
3.1
2.2
V
0.5
0.8
1.8
143.4
1 300.0
250.0
200.0
% Change from Control
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
150.0 Gas Coke 100.0 HC AQ 50.0
0.0 KA
VKA
KG
VKG
KS
VKS
-50.0
2
-100.0
3 4
Figure 5. Effect of model compound addition to mass balance fractions. Shown as % change from control conditions (K, and VK). AQ (aqueous); HC (hydrocarbon); Coke (from regenerator); Gas (from stripper).
5
As shown in Figure 5, the predominant effect of model compound addition was in the coke and aqueous
6
fractions. It is important to note that the model compounds were present in a higher concentration in the K
7
mixtures than the VK mixtures (10 wt% vs. 5 wt%). Hence, direct comparisons between the K and VK
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Page 18 of 31
1
runs will not be made. The higher concentration of model compounds and the simplified chemistry of the
2
kerosene (compared to VGO) allowed us to determine what operational changes would be required before
3
conducting the VGO experiments. Comparing the VK experiments, we observed small changes in the gas
4
and hydrocarbon yields for all model compound mixtures. The VKG mixture resulted in the same
5
hydrocarbon yield, while the VKA and VKS showed a 7.5% and 10.5% percent decrease, respectively,
6
from the control VK. Changes in total gas yields for the VK runs were similarly mild, with a 0.5%
7
increase with VKS, and 7.7% and 5.5% decrease from VKA and VKG. However, coke yields increased
8
10% with VKA and 24% and 22% with VKG and VKS. The aqueous phase yields were most strongly
9
impacted by the addition of acetic acid, with a 138% increase and a 33% increase with guaiacol. Sorbitan
10
monooleate addition showed an aqueous phase decrease of 60%. These runs had the lowest mass balance,
11
which is likely due to the low aqueous phase yield, as the gas, coke and HC phases were within normal
12
range.
13
Simulated Distillation
14
The distillation curves for the liquid product from each of the experiments is given in the Supplementary
15
Information. Figure S2A shows that the product distillation curves from feeds K, V and KV are relatively
16
close until 60 mass %, and then start to deviate: this is expected as kerosene (composed of carbon chains
17
that typically contain between 6 and 16 carbon atoms per molecule) does not contain the higher molecular
18
weight compounds of VGO. As shown in Figure S2B-D, the product distillation curves from the feeds
19
KA, KG, and KS experiments follow very closely to the feed K product distillation curve. This same
20
trend is also seen when looking at the product distillation curves with respect to feeds containing VGO.
21
These results suggest that adding these oxygenates to the petroleum feeds, at least at the tested
22
concentrations of 5 and 10 wt%, have no significant impact on the overall product composition.
23
2D GCxGC TOFMS Product Analysis
24
This two-dimensional chromatography method separates all of the major chemical classes from each
25
other in the 2nd dimension (vertical axis) with the exception of the olefins and naphthenic (saturated ring) 18 ACS Paragon Plus Environment
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1
compounds. The mono-olefins are found with the single ring naphthenic compounds. Di-olefins are
2
found in the 2-ring naphthenic compounds. Both linked ring (i.e. 1,1-biscyclohexane) and fused ring (i.e.
3
decahydronaphalene) elute in the same region along the 2nd dimension.
4
Paraffins and iso-paraffins always elute in the same 2nd dimension because they have similar polarity,
5
which is the analyte property that separates in the 2nd dimension of this column combination. They can be
6
easily differentiated by identification of the individual n-paraffin peaks, which are established by
7
comparison to the retention times to known standards. Remaining peaks will then be the iso-paraffins
8
which can be structurally diverse. Very light paraffins and iso-paraffins located at the lower right corner
9
of the chromatogram are poorly resolved along both dimensions because the column used for the 1st
10
dimension separation is optimized for the higher boiling point materials to provide a more general-
11
purpose method. Although a column optimized for separating these materials is available, it will not be
12
able to handle the highest boiling point materials found in unconverted VGO which typically elute in the
13
region of under and to the right of the 3-ring aromatic compounds.
14
Typical chromatograms of VGO and kerosene feedstocks are shown in Figure 6a-b. Figure 6c shows the
15
chromatogram of DCR product obtained from a mixture of VGO, kerosene and guaiacol. The kerosene-
16
derived product exhibits the characteristic straight chain hydrocarbons and paraffins and iso-paraffins
17
derived from the C6-C16 compounds in the feed. Figure 6b shows the upgraded heavier molecular weight
18
straight chain hydrocarbons and paraffins derived from VGO. Adding guaiacol to a mixture of kerosene
19
and VGO (Figure 6c) produces phenolics and the product suites from kerosene and VGO. The phenolics
20
were expected as previous work has shown that co-feeding either guaiacol18 or pyrolysis oils at 5 wt%
21
with VGO in FCC systems produce phenols in the hydrocarbon product19. With E-Cat, guaiacol as well
22
increased gasoline yields while reducing coke yield though coke on the catalyst increased18.
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Page 20 of 31
Kerosene Feedstock Naphthenic ISTD and olefins A) Kerosene feedstock
nC9 – nC14 & isoparaffin s
VGO
B) VGO feedstock
Feedstock VGO Feedsto ISTD Naphthenic and IST olefins ck D nC17 – nC30 & isoparaffin s 1-Ring Aroma cs
C) Products from VKG feedstock Phenolics 2-Ring Aroma cs
3-Ring Aroma cs
2-Ring Naphthalene Paraffin and Isoparaffin s
1-Ring Naphthenic and Olefins
1 2 3
Figure 6. GCxGC-TOFMS chromatograms: for feedstocks a) kerosene, b) VGO, and for DCR products obtained with c) VGO-kerosene-guaiacol (VKG) feed.
4
The determination of changes in product composition between the VK feed and a feed that included the
5
model compounds (feeds VKG, VKA, and VKS) was done by a peak by peak comparison of product
6
chromatograms. Peaks that showed large changes between the straight VK feed and the oxygenate
7
containing feeds were selected for further analysis (Figure 7).
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1 Figure 7. GCxGC TOFMS total area counts for product from VK, VKG, VKA, and VKS. Millions
2
8 7 6
GCMS TIC counts
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60
Energy & Fuels
5 Phenols
4
Carbonyls
3 2 1 0
3
VK
VKG
VKA
VKS
4 5 6
Figure 8. GCxGC TOFMS total area counts for oxygenates in product from VK, VKG, VKA, and VKS feeds. No carbonyls were observed with guaiacol addition. Similarly, no phenols were observed with acetic acid or sorbitan monooleate.
7
The following trends were observed in composition changes when oxygenated species were added to the
8
feed. Percent change from the control VK is reported with respect to the total MS area. None of the
9
starting oxygenated materials were found in the products. The effect of the oxygenates on the lighter,
10
lower boiling compounds is unclear because of the low resolution of these materials using the current 2D
11
GCxGC method. The guaiacol-spiked product was the only one containing phenol, which accounted for 21 ACS Paragon Plus Environment
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Page 22 of 31
1
1% of the total. For both acetic acid and sorbitan monooleate, these oxygenates were converted to
2
carbonyl compounds. Acetic acid was converted partially to butanone, while sorbitan monooleate
3
produced hexanone at 0.7% and 0.5%, respectively (Figure 8). The impact of guaiacol addition on the
4
yield of aromatic compounds is shown in Figure 9. While benzene and xylene were reduced (~10%),
5
toluene and tetralin yields increased by 7% and 20%, respectively. Acetic acid resulted in the greatest
6
aromatic reductions, with benzene, naphthalene, tetralin, and decalin decreasing by ~45%. The sugar
7
compound similarly showed strong reductions in tetralin and decalin, at 20% and 75%, with a negligible
8
impact on 1-ring aromatics. Figure 10 shows the effect of oxygenate addition on the alkanes and provides
9
some insight on the fate of the reduced aromatics. Guaiacol increased the yield of C8 alkanes by ~10%,
10
while acetic acid increased C10+ alkanes by ~20% and sorbitan monooleate produced ~35% more C7
11
species. Reductions in alkanes due to oxygenate addition were also observed. Guaiacol addition produced
12
20% less C6 and 30% lower yield of C9 and C10+ species. However, acetic acid only reduced C8 species by
13
~15%. Sorbitan monooleate increased C7 alkanes by ~35%, but reduced C8 and C10+ alkanes by ~50%.
14
The changes in liquid yield of alkenes are shown in Figure 11. The greatest impact of oxygenate co-feed
15
was observed in the alkenes. Guaiacol producing a nearly 160% increase in C6 species with only
16
moderate (20%) reductions in the C7-C10+ alkenes. Acetic acid displayed a trend of increasing C9 and C10+
17
alkenes by 30% and 70%, respectively, while decreasing C5 and C7 yields by 30% and C6 and C8
18
compounds by 20%. Sorbitan monooleate co-feed resulted mainly in alkene reductions with C7, C8, C9,
19
C10+ species reduced roughly 40% on average, with only C6 alkenes increasing modestly at 26%.
20
Figure 1. GCxGC TOFMS total area counts showing the impact of oxygenate addition on the yield of
21
aromatic compounds in the liquid product.
22 23
Figure 2. GCxGC TOFMS total area counts showing the impact of oxygenate addition on yield of alkanes
24
in the liquid product.
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1 2
Figure 3. GCxGC TOFMS total area counts showing the impact of the oxygenate addition on yield of
3
alkenes in the liquid product.
4 5 6
Figure 9. GCxGC TOFMS total area counts showing the impact of oxygenate addition on the yield of aromatic compounds in the liquid product.
7 8 9
Figure 10. GCxGC TOFMS total area counts showing the impact of oxygenate addition on yield of alkanes in the liquid product. 23 ACS Paragon Plus Environment
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Page 24 of 31
1 2 3
Figure 11. GCxGC TOFMS total area counts showing the impact of the oxygenate addition on yield of alkenes in the liquid product.
4
NMR Analysis
5
The quantitative 13C NMR for the VKG feed and feed/products are shown in Figure 12 and Figure 13. In
6
Figure 13 the VKG product spectra is overlaid (green) on the VK spectra. The quantitative results for all
7
analyses are presented in Table 8. In all cases, almost 70% of the carbon is present as aliphatic carbon,
8
and the remaining carbons are mostly aromatic. Importantly, the methoxy carbon peak (ppm ~55), and the
9
aromatic carbon hydroxy and methoxy (~146 and 147 ppm, resp.) are absent in the VKG product,
10
showing that guaiacol is completely converted. The unique peaks in green on Figure 13 at 116, 121, and
11
156 ppm can be attributed to phenol. For the VKA product sample, a small amount of ketone is present;
12
further examination of the spectra shows that the ketone is not from residual acetic acid but some other
13
compound. These results imply that all model compounds are converted during reaction and produce an
14
overall product slate that heavily deoxygenated and similar to the VK product.
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Energy & Fuels
1 2
Figure 12. Quantitative NMR for VGO, kerosene and guaiacol mixture (VKG feed).
3 4 5 6
Figure 13. Quantitative 13C NMR for VK products (red), and VKG products (green). There are several new peaks in the aromatic ranges for the samples with guaiacol feeding, which could be assigned to phenol like structures. All the methoxyl groups in the guaiacol have been completely decomposed.
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Page 26 of 31
Table 8. 13C NMR quantitative results for feed VK, VKA, VKG, and VKS products. Results are presented in carbon mol-%. Products from Feed Type
1
Aliphatic Carbons
C CH CH2 CH3 VK ~0 4.8 31.6 36.8 VKA ~0 2.6 28.2 33.3 VKG ~0 3.7 31.1 34.8 VKS ~0 5.5 28.4 34.8 *Overlap with some double bond carbons
Aromatic carbons* C 8.7 11.7 10 9.9
CH 17.8 23.7 20.1 21.1
Terminal double bond carbons
Ketone
=CH2 0.3 0.4 0.3 0.4
C=O ~0 0.1 ~0 ~0
2
Carbonyl Analysis
3
Results for the products from feeds VKA, VKG, and VKS showed that the carbonyl content was below
4
the detection limit. These results indicated that the oxygenated compounds studied do not form
5
breakdown products that retain oxygen as reactive carbonyl groups.
6
Taken together, DCR product analyses from oxygenate/VGO feeds show that guaiacol is converted to
7
phenolics and aromatics, all of the added oxygenates convert completely, and the upgraded products do
8
not differ significantly from product obtained with VGO feed. As well, DCR operating parameters and
9
conditions did not change significantly when oxygenates were added to the feed. Thus, this series of
10
experiments demonstrate the feasibility of conducting subsequent biomass pyrolysis vapor phase
11
upgrading experiments using a coupled pyrolyzer/DCR system and modified zeolites to produce fungible
12
hydrocarbon fuel intermediates.
13
CONCLUSIONS
14
Several oxygenated model compounds representative of biomass pyrolysis vapors (acetic acid, guaiacol,
15
and sorbitan monooleate) were co-fed with VGO and E-Cat into a DCR unit to evaluate biomass vapor
16
incorporation into FCC generated hydrocarbon products and assess impact on DCR operating conditions.
17
Analysis of steady-state operating conditions showed that catalyst circulation rate, the primary control of
18
reaction temperature in DCR reactors, decreased with oxygenate addition while E-Cat catalyst coke rate
19
increased in agreement with previous reports. Simulated distillation and 13C NMR analyses of liquid 26 ACS Paragon Plus Environment
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Energy & Fuels
1
products suggest that product distributions vary little with oxygenate addition. Carbonyl analysis indicates
2
that the model compounds do not convert to products that retain carbonyl groups. Contrastingly, 13C
3
NMR analysis showed some ketone in the VKA product though the concentration in the product was
4
quite low (0.1 mol-%).
5
Two dimensional GCxGC TOFMS was the only analytical technique that showed any distinguishable
6
differences among the products: guaiacol addition produced phenol and methyl phenols in the products,
7
which was not seen for VK feed or the other model compound feeds. The VKS feed resulted in lower
8
levels of high boiling point compounds (C10 to C16) when compared to the VK feed. Addition of all model
9
compound feeds produced elevated concentrations of toluene, xylenes, and trimethyl benzenes when
10
compared to the VK feed. The GC analysis of the VK feed gas phase products showed that the presence
11
of oxygenated compounds decreases hydrogen and all species C3 and larger, and increases methane
12
production.
13
The overarching conclusion is that addition of the oxygenated model compounds to VGO and kerosene
14
feeds had minimal impact on liquid hydrocarbon yield and composition. Acetic acid increased the
15
aqueous phase yield for K and VK feed. Coke formation increased with guaiacol under the K and VK
16
feed. Further work will determine the potential presence of ketones in the liquid products, and any
17
predominant reasons for hydrogen consumption.
18
This work, the first of its kind at the DCR scale, showed that adding biomass pyrolysis oxygenate model
19
compounds did not affect the DCR’s operability or performance. This conclusion is dependent on the
20
amount of model compound fed and method of feed introduction. Changing these parameters and
21
increasing the complexity of conditions may have an effect on the system that has yet to be determined.
22
Nevertheless, these baseline experiments show that 1) biomass oxygenates can be successfully co-
23
processed with VGO into fungible products and 2) feeding biomass pyrolysis vapors directly to the DCR
24
first with VGO then with progressively larger amounts of vapor is feasible.
27 ACS Paragon Plus Environment
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1
ASSOCIATED CONTENT
2
Supporting Information
3
The following files are available free of charge.
4
Photograph of liquid feeds and products. (PDF)
Page 28 of 31
5 6 7
S1. Products from upgrading guaiacol and petroleum feed types. Feed materials from left to right: K, V, VK, KG, and VKG.
8
Table S1. Catalyst Circulation and Coke Rate Data. (PDF) Table S1. Steady-state values for circulation and coke rates for each feed. Feed Circulation Rate (g/hr) Coke Rate (g/hr) K 8213 ± 299 8.5 ± 1.7 V 9402 ± 299 46.9 ± 1.7 VK 7864 ± 299 24.1 ± 1.7 KA 8061 ± 299 10.7 ± 1.7 VKA 7521 ± 260 26.5 ± 1.0 KG 7632 ± 248 23.2 ± 1.3 VKG 7181 ± 73 29.8 ± 1.2 KS 8534 ± 299 13.9 ± 1.7 VKS 8207 ± 299 29.4 ± 1.7
9 10
Simulated Distillation of feeds and products. (PDF)
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Energy & Fuels
A)
B)
C)
D)
1 2 3 4
S2. Simulated distillation curves for liquid products from each of the feed types: (a) feeds K, VK, and V, (b) feeds with and without acetic acid, (c) feeds with and without guaiacol, and (d) feeds with and without sorbitan monooleate.
5
AUTHOR INFORMATION
6
Corresponding Author
7
*Tel.: 303-384-7706, Fax: 303-384-6103. E-mail:
[email protected] 8
ACKNOWLEDGMENT
9 10
This work was supported by the U.S. Department of Energy, under Contract No. DE-AC3608GO28308 with the National Renewable Energy Laboratory.
11
REFERENCES
12 13 14 15 16 17 18 19
1. Ruddy, D. A.; Schaidle, J. A.; Ferrell III, J. R.; Wang, J.; Moens, L.; Hensley, J. E., Recent advances in heterogeneous catalysts for bio-oil upgrading via “ex situ catalytic fast pyrolysis”: catalyst development through the study of model compounds. Green Chem. 2014, 16 (2), 454-490. 2. Babu, B. V., Biomass pyrolysis: a state-of-the-art review. Biofuels, Bioprod. Biorefin. 2008, 2 (5), 393-414. 3. Czernik, S.; Bridgwater, A. V., Overview of Applications of Biomass Fast Pyrolysis Oil. Energy Fuels 2004, 18 (2), 590-598.
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4. Bridgwater, A. V., Upgrading biomass fast pyrolysis liquids. Environ. Prog. Sustainable Energy 2012, 31 (2), 261-268. 5. Mohan, D.; Pittman, C. U.; Steele, P. H., Pyrolysis of wood/biomass for bio-oil: a critical review. Energy Fuels 2006, 20 (3), 848-889. 6. Christensen, E. D.; Chupka, G. M.; Luecke, J.; Smurthwaite, T.; Alleman, T. L.; Iisa, K.; Franz, J. A.; Elliott, D. C.; McCormick, R. L., Analysis of oxygenated compounds in hydrotreated biomass fast pyrolysis oil distillate fractions. Energy Fuels 2011, 25 (11), 54625471. 7. Graça, I.; Comparot, J. D.; Laforge, S.; Magnoux, P.; Lopes, J. M.; Ribeiro, M. F.; Ribeiro, F. R., Effect of phenol addition on the performances of H–Y zeolite during methylcyclohexane transformation. Appl. Catal., A 2009, 353 (1), 123-129. 8. Graça, I.; Ribeiro, F. R.; Cerqueira, H. S.; Lam, Y. L.; de Almeida, M. B. B., Catalytic cracking of mixtures of model bio-oil compounds and gasoil. Applied Catalysis B, Environmental, 2009, 90 (3-4), 556-563. 9. Zacher, A. H.; Olarte, M. V.; Santosa, D. M.; Elliott, D. C.; Jones, S. B., A review and perspective of recent bio-oil hydrotreating research. Green Chem. 2014, 16 (2), 491-515. 10. Thegarid, N.; Fogassy, G.; Schuurman, Y.; Mirodatos, C.; Stefanidis, S.; Iliopoulou, E.; Kalogiannis, K.; Lappas, A., Second-generation biofuels by co-processing catalytic pyrolysis oil in FCC units. Appl. Catal., B 2014, 145, 161-166. 11. Naik, D. V.; Kumar, V.; Prasad, B.; Behera, B.; Atheya, N.; Singh, K. K.; Adhikari, D. K.; Garg, M. O., Catalytic cracking of pyrolysis oil oxygenates (aliphatic and aromatic) with vacuum gas oil and their characterization. Chem. Eng. Res. Des. 2014, 92 (8), 1579-1590. 12. Agblevor, F. A.; Mante, O.; McClung, R.; Oyama, S. T., Co-processing of standard gas oil and biocrude oil to hydrocarbon fuels. Biomass and Bioenergy 2012, 45, 130-137. 13. Faix, O., Andersons, B., Zakis, G., Determination of carbonyl groups of six round robin lignins by modified oximation and FTIR spectroscopyy. Holzforschung 1998, 52 (3), 268-274. 14. Black, S.; Ferrell, J. R., Determination of carbonyl functional groups in bio-oils by potentiometric titration: The faix method. Journal of Visualized Experiments 2017, 2017 (120). 15. Gayubo, A. G.; Aguayo, A. T.; Atutxa, A.; Aguado, R.; Bilbao, J., Transformation of Oxygenate Components of Biomass Pyrolysis Oil on a HZSM-5 Zeolite. I. Alcohols and Phenols. Industrial & Engineering Chemistry Research 2004, 43 (11), 2610-2618. 16. Gayubo, A. G.; Aguayo, A. T.; Atutxa, A.; Aguado, R.; Olazar, M.; Bilbao, J., Transformation of Oxygenate Components of Biomass Pyrolysis Oil on a HZSM-5 Zeolite. II. Aldehydes, Ketones, and Acids. Ind. Eng. Chem. Res. 2004, 43 (11), 2619-2626. 17. Cerqueira, H. S.; Caeiro, G.; Costa, L.; Ramôa Ribeiro, F., Deactivation of FCC catalysts. Journal of Molecular Catalysis A: Chemical 2008, 292 (1-2), 1-13.18. 18. Graça, I., Lopes, J. M., Ribeiro, M. F., Ramoa Ribeiro, F., Cerqueira, H. S., de Almeaida, M. B. B., Catalytic cracking in the presence of guaiacol. Applied Catalysis B: Environmental 2011, 101, 613-621. 19. de Rezende Pinho, A., de Almeida, M. B. B., Leal Mendes, F., Casavechia, L. C., Talmadge, M. S., Kinchin, C. M., Chum, H. L., Fast pyrolysis oil of pinewood chips coprocessing with vacuum gas oil in an FCC unit for second generation fuel production. Fuel 2017, 188, 462-473. 20. Corman, A., Huber, G. W., Sauvanaud, L., Connor, P. O., Processing biomass-derived oxygenates in theoil refinery: Catalytic cracking (FCC) reaction pathways and role of catalyst. Journal of Catalysis 2007, 247, 307-327.
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