Single-Step Catalytic Conversion of Ethanol to n-Butene-rich Olefins and 1,3-Butadiene Chemical Coproduct Robert Dagle1, Vanessa Dagle1, Zhenglong Li2, 1 2 July 31, 2019 Three takeaways from this talk . PNNL and ORNL have developed effective Butadiene Uses catalysts and processes for conversion of ethanol to fuels and co-products. We present a flexible catalytic process for the single-step conversion of ethanol to either butadiene or n-butenes using a n-Butene Uses mixed oxide catalyst (PNNL). We present the catalytic processing for producing either C5+/BTX hydrocarbons or C3+ olefins using zeolite catalysts (ORNL). Bioenergy Technologies Office | ChemCatBio (CCB) is a national-lab led R&D consortium dedicated to overcoming catalysis challenges for biomass conversion . ChemCatBio is a node in DOE’s Energy Materials Network. It strives to accelerate the development of catalysts and related technologies for the commercialization of biomass-derived fuels and chemicals by leveraging unique capabilities of the US DOE national laboratories. The team comprises over 100 researchers from 8 national labs and has published more than 90 peer-reviewed manuscripts over its four years of operation. Advanced synthesis Analysis and Evaluation across and Characterization Simulation Scales Bioenergy Technologies Office | Ethanol - an attractive feedstock . Ethanol is commercially produced from renewable biomass & waste sources. Current trend positive to future competitive ethanol production: . Ethanol “blendwall” . Advancement in production efficiency . Feedstock diversification ACS Catal. 2014, 4, 1078-1090 Bioenergy Technologies Office | 4 PNNL & ORNL have found effective processes for converting ethanol to fuels and co-products Being Commercialized ethylene butenes Jet/Diesel Range & Biochemical or Hydrocarbons Thermochemical Conversion PNNL Gasoline/Jet C5+ HCs BTX ORNL & Prior Research (ChemCatBio) ORNL C5+/BTX Green Chemistry, 2017, 19, 4344 C4+ Precursors PNNL n-butanol Top Catal, 2016, 59, 46 + higher alcohols Catal Today, 2016, 269, 82 Ethanol PNNL Green Chemistry, 2016, 18, 1880 isobutene Catal.Sci.Technol.2016, 6, 2325 PNNL Current Research (ChemCatBio) Applied Catal B. 2018, 236, 1576 PNNL & ORNL butadiene Catalysis Today, 2019, DOI: 10.1016/j.cattod.2019.05.042 Oligomerization + & Hydrogenation + Jet/Diesel Range n-butenes Fractionation Hydrocarbons Bioenergy Technologies Office | Single-step conversion of ethanol to isobutylene leads to the unavoidable formation of CO2 Catal.Sci.Technol.2016, 6, 2325 Single-step Green Chemistry, 2016, 18, 1880 ZnxZryOz Mechanism ethanol OH -H2 Ethanol -CO2 Isobutylene acetaldehyde O +O2 O acetic acid Ketonization OH releases CO2 -H2O -CO2 O acetone 33% carbon Conversion: 100% . Isobutylene Sel: 42.4 % yield to CO2 . CO2 Sel: 32.2 % (theoretical) + O isobutylene acetaldehyde Isobutylene production from ethanol is limited due to formation of CO2 PNNL Bioenergy Technologies Office | Butadiene uses, production technologies, and market outlook Butadiene Production: 11 MT/Year. Butadiene Uses: synthetic rubbers, elastomers, polymer resins. Production technologies . Extraction from C4 hydrocarbons- ethylene steam cracker (SC) - BD is a by-product - 95% BD production . Dehydrogenation of n-butane & n-butene . Processing of renewable sources Market outlook . The quantity of BD produced from SC depends of cracking feedstock. Low cost ethane obtained from shale gas is the preferred feedstock in USA . - Decline of BD co-production 7 Bioenergy Technologies Office | Producing butadiene from ethanol can be cost competitive with current butadiene prices, with sufficiently low cost ethanol US Delivered Prices for Butadiene PPI adjusted to 2016 Ethanol Scale 50 M gal/year, 10% ROI e.g. $1.50/gal ethanol feedstock➞ $0.68/lb Butadiene selling price (~ current market price) PNNL Bioenergy Technologies Office | 8 PNNL Designed an Ethanol to Butadiene Catalyst with 1.5x Yield Over State of the Art on Ag/ZrO2/SiO2 . Historically, ethanol to butadiene catalyst yields low . Ag/ZrO2/SiO2 multifunctional catalyst system developed that selectively enables single-step conversion of ethanol to butadiene . Significantly more active than literature benchmark catalyst . Produces butadiene with 89% ethanol conversion and 74% selectivity 1 Dagle, V. L. et. al. Applied Catalysis B 2018, 236, 576–587. 2 Ivanova et. al., E. J. Catal. 2014, 316, 121–129. PNNL Bioenergy Technologies Office | 9 We found SBA-16 to be the Best SiO2 Support for Ethanol to Butadiene over Ag/ZrO2/SiO2 Butadiene Conversion Lewis acid sites SiO support selectivity 2 (%) (µmoles/g) . Screened catalysts using SiO2 (%) with different properties (e.g. SG Davisil 636 82.7 65.2 32.2 surface area, porosity) SG Alfa Aesar 48.7 29.3 35.0 SG Davisil 646 76.1 75.3 22.8 SG Davisil 645 29.5 41.6 21.6 . Greatly influenced activity and After ion- 79.6 73.4 27.8 selectivity to butadiene exchange SG Davisil 923 84.8 56.8 31.0 SG KSKG-GOST- 84.7 78.3 26.1 3956-76 SG KSMG-GOST- 100.0 0.0 NA 3956-76 Fumed silica 37.1 39.2 NA Cabosil EL90 The choice of SiO2 support is Fumed silica 39.2 29.6 5.0 Aerosil 380 key in effective catalyst design SBA-15 97.8 46.6 NA for butadiene production SBA-16 99.0 70.5 26.4 -1 1Ag/4ZrO2/SiO2 activity. WHSV: 0.23hr , PEtOH: 24.3% in N2, P: 1 atm, T: 325°C. Dagle, V. L. et. Al. Applied Catalysis B 2018, 236, 576–587 PNNL Bioenergy Technologies Office | 10 Mechanism & Role of Catalyst Components were Confirmed over this Catalytic System 80 10 4Ag/4ZrO2/SiO2 Intermediate Species butadiene 8 . Both acetaldehyde and crotonaldehyde are 60 intermediates involved in BD formation acetaldehyde . Conversion and selectivity profiles supports 6 the aldol condensation mechanism 40 followed by MPV reaction. 4 20 crotonaldehyde 2 Crotonaldehyde Selectivity (%) Selectivity Crotonaldehyde Role of Ag, ZrO2, and SiO2 0 0 . ZrO acid sites are responsible for (%) Selectivity Acetaldehyde/Butadiene 0 20 40 60 80 100 2 Conversion (%) -1 undesired ethanol dehydration to T=325°C, P= 1 atmosphere, WHSV = 0.37-38.0 hr , 50% Ethanol/N2 ethylene and DEE Catalyst EtOH Conv. Selectivities (%) . Ag responsible for the (%) C = DEE BD AcH dehydrogenation of ethanol to 2 acetaldehyde SiO2 7.2 26.4 2.2 0 69.6 4ZrO2/SiO2 14.8 47.9 46.9 0 2.6 . Addition of ZrO2 to Ag/SiO2 does not have a significant impact on the 4Ag/SiO2 88.3 1.5 0.1 0.9 61.4 conversion 4Ag/4ZrO2/SiO2 89.2 5.5 3.0 73.6 6.7 -1 Dagle, V. L. et. Al. Applied Catalysis B 2018, 236, 576–587. T = 325°C, P = 1 atmosphere, WHSV = 0.47 hr , 50% EtOH/N2, SiO2: Davisil 646 PNNL Bioenergy Technologies Office | 11 SiO2 Support Affects Surface Area, Ag Dispersion, and Subsequent Ethanol Conversion Catalyst Conversion (%) . Addition of ZrO2 to Ag/SiO2 SiO2 7.0 does not have a significant 4ZrO /SiO 14.8 impact on the conversion 2 2 4Ag/SiO2 88.3 . Conversion increases with 4Ag/4ZrO /SiO 89.2 catalyst surface area 2 2 -1 T = 325°C, P = 1 atmosphere, WHSV = 0.47 hr , 50% EtOH/N2, SiO2: Davisil 646 . Same Ag loading of 1% for all catalysts 1%Ag/4%ZrO2 – varied SiO2 supports Increase in conversion is due to increased Ag dispersion Dagle, V. L. et. Al. Applied Catalysis B 2018, 236, 576–587 PNNL Bioenergy Technologies Office | 12 SiO2 Support Interaction with ZrO2 Affects Catalyst Acidity and Subsequent Butadiene Selectivity . 0.04 Presence of Lewis acid sites 1448 1607 . Butadiene selectivity decreases as 1598 1491 Lewis acid site concentration 1578 4Ag/10ZrO2/SiO2 increases Absorbance 4Ag/4ZrO2/SiO2 . Evidence of a relationship between 4Ag/2ZrO2/SiO2 butadiene selectivity and acid sites 4Ag/1ZrO2/SiO2 1650 1610 1560 1510 1460 1410 concentration. Wavenumbers ( cm-1) 80 Conversion: ~80% 70 The interaction between ZrO2 and SiO2 varies greatly depending on the 60 SiO2 support which affects the 50 quantity of the acid sites and the 1Ag/4ZrO2/SiO2* butadiene selectivity Butadiene Selectivity (%) 40 4Ag/xZrO2/SiO2-646 *Various Silicas 30 10 20 30 40 Dagle, V. L. et. Al. Applied Catalysis B 2018, 236, 576–587 Lewis acid sites concentration (umoles/g) PNNL Bioenergy Technologies Office | 13 Ag Particle Size Affects Selectivity in Ethanol to Butadiene Reaction Two DFT models considered: DFT Calculation Results . Dispersed Ag representative of small Ag particles Catalyst ΔG ethylene ΔG acetaldehyde . Ag nanoparticle (NP) surface representative of larger Ag particles Dispersed 1.93 -2.69 Ag/ZrO2/SiO2 NP Ag/ZrO2/SiO2 -0.74 -0.63 DFT calculations suggested: ZrO2/SiO2 -1.36 - . Larger Ag particles favor ethylene formation through ethanol dehydration . Smaller Ag particles favor formation of Experimental Results acetaldehyde for butadiene . Experimental Results Validate Calculated DFT Trends Greater Ag dispersion inhibits the formation of dehydration side products 1.9nm 3.2nm CCPC: Consortium for Computational Physics and Chemistry PNNL Bioenergy Technologies Office | 14 Single step formation of butenes from ethanol over Ag/ZrO2/SiO2 is observed under reducing conditions A Flexible Process for Production of Butadiene or Olefins fuels Precursors Selectivity (C mol %) Total Feed Conv (%) C -C C = C = C = Butadiene DEE 2 5 Oxy Olefins 2 3 4 alkanes + DEE EtOH in 99.0 5.8 2.8 11.2 70.5 2.6 3.4 3.7 92.9 inert EtOH in reducing 93.9 25.7 2.0 57.7 0.0 6.0 6.1 2.5 91.4 environment . Butadiene formed in inert environment . Butene-rich olefins formed in reducing environment . Olefin double bonds remain even under reducing environment, provided suitable catalyst and processing conditions. Impact: Producing butene-rich olefins directly from ethanol reduces a unit operation thereby representing a major improvement to the state of the art. PNNL Bioenergy Technologies Office | 15 Butenes mostly produced from butadiene intermediate Space Velocity Profile Possible Pathways 80 60 Acetaldehyde acetaldehyde butenes Ethanol 40 Acetaldol electivity (%) electivity S 20 butadiene Crotonaldehyde 0 0 20 40 60 80 100 Crotyl Conversion (%) Alcohol H2 Butadiene Preliminary operando NMR & catalytic performance: Butyraldehyde .