Design of Transition-Metal/Zeolite Catalysts for Direct Conversion of Coal-Derived Dioxide to Aromatics (FE0031719) Iman Nezam, Gabriel S. Gusmão, Wei Zhou, Matthew J. Realff, Andrew J. Medford, Christopher W. Jones Georgia Institute of Technology, Atlanta, GA

The objective of this project is to develop a technology for the conversion of coal-derived CO2 directly into mixed aromatic chemicals that are currently sourced from petroleum. Aromatic chemicals such as , , and (BTX) face growing demand due to their expanding use in plastics and packaging, chiefly in poly(ethylene terephthalate) (PET). BTX is normally produced from oil in a petroleum refinery via multiple steps, involving several different reactions and separations. In this project we will explore a process intensification effort that begins the development of a new technology for the conversion of coal-derived CO2 directly into BTX in a single reactor. This approach involves hydrogenation of CO2 into methanol or short chain and related olefins, which subsequently encounter a second catalyst that converts the intermediate species to BTX in the same reactor. A BTX production technology based on this reaction scheme would significantly deviate from the state-of-the-art, allowing the use of CO2 as a feedstock, reducing the number of process steps and unit operations, and allowing smaller, more modular installations, which is commensurate with siting near large coal-fired power plants, minimizing costs of CO2 storage and transportation.

Motivation Approach

Benzene, Toluene, THEORETICAL Industrial Applications Precursor to Metal Alloy Screening value-added chemicals CO + H Methanol Medford’s Group 2 2 Olefins 흁Kinetic models (CatMAP)

ZnZrO Oxygenates ZSM-5 Coke Global Production (2010) 2050 Projection • Si/Al ratio BTX • Crystal size 100 million metric tons 200 million metric tons High CO2 + H2 Methanol Olefins BTX selectivity range Realff’s Group Techno-economic Jones’ Group Process Intensification Paraffins Oligomers CO Experiments / Optimization Characterization EXPERIMENTAL LCA Spectroscopy Current Production Technology Catalyst of naphtha Precious metals supported by high surface area materials with acidity

Carbon Dioxide (CO2) Computational Progress

• Domestic CO2 emission from coal combustion: 1500 million metric tons in 2017 • Comprehensive DFT-based mean-field microkinetic catalytic model on Cu(111) • Could fully support the BTX global market encompassing 28 adsorbate- and 13 gas-species in 42 elementary reactions. • [1] Grabow, L.C. and M. Mavrikakis, ACS Catal. CO to BTX (CO → Intermediate → BTX) Forward and reverse water-gas shift from 2 2 2011. Oxygenates formation: ethanol, formic acid, formaldehyde from [1], ethanol, acetic acid and acetaldehyde from Schumann, J. et al., ACS Catal. 2018. Two steps in a single reactor (CO2 from flue gas, some H2 source) formation: methane [1] and ethane from Martin Hangaard, H. et al., J. Catal. 2019. CO2 to Intermediates (MOH/DME): Metal Oxides (ZnZrOx) Oxygen dissociation from Falsig, H., et al., Top. Catal. 2014.

Oligomerization + Aromatization: MFI (H-ZSM-5) CH OH 3 (g) CH4 (g) Turn-over frequencies

(log10TOF) for methanol and

log methane on Cu(111) at static

10 gas phase concentration

Experimental Progress TOF 0.90:0.05:0.05 H2:CO2:CO

Process Setup: Typical Products Distribution: P [bar]

Zn/Zr=1/6, ZnZrOx/H-ZSM-5=1/2, Si/Al=80, H2/CO2=3 P=600 psi, T=320 oC WHSV=7200 mL/g cat./h Potential Energy Diagram

Temperature [K] CO2 to Methanol DFT-based formation energies for microkinetic model extended to Ag(211) additional transition metal catalysts

• Only olefins present are ethylene and propylene Au(211) → Not following the typical ASF distribution Cu(111) • Aromatics are mainly C9 perhaps due to the Grabow’s [1] small ZSM5 particle size (excess external Cu(111) surface area) Catalyst Temperature Dependence: Cu(211)

Zn/Zr=1/6, ZnZrOx/H-ZSM-5=1/2, Si/Al=80, H2/CO2=3 P=600 psi, WHSV=7200 mL/g cat./h Pd(211)

o

• Aromatics selectivity is maximized at 320 C Pt(211) Rh(211) (g)

• Olefin hydrogenation to paraffins becomes 2(g)

O*

O

2

2

OH*

+ H* +

+ H* +

-

+ 4H* + + 6H* + 6H* + 5H* + 5H* + 3H* +

+ 3H* + 2H* +

+ 4H* + + 3H* +

dominant at high temperatures 2H* +

*+ 3H* *+

+ 3H +

*

+ H +

2

2

2(g) 2(g)

H*

O

-

(g) (g)

2(g) 2(g) 3

OH*

-

CO

OH* + H + OH*

CO COO*

3

-

OH

O

OH* + H + OH* CH

• RWGS reaction is endothermic→ Increasing CO CO

3

HCOO* HCOOH 2

3

H* + OH* + H*

H

-

- O*+ OH* O*+

HCOOH*

O*+ OH* O*+

O* + OH* + O*

CH

OH* + OH*+ OH* 2

HCOO

2

H

3

O

CH 3 CH

selectivity with temperature CH

3

CH

CH

CH

-

CH

CH H Catalyst Acid Density Dependence: Current Status • Maximum aromatics selectivity is obtained at T=320 oC, WHSV=7200 mL/g cat./h,

Si/Al=300: 39.7% (STY= 1.04 mmol CO2/g cat/h) • DFT-based rates have been calculated for the main intermediate species for the CO2 hydrogenation on Cu(111). DFT-energies have been extended to the 211 facet of Ag, Au, Pd, Pt, Rh and Cu. w/o ZSM5 Next steps

H-ZSM-5-800 • Very low acid density is desired. Max • Studying the effect of diffusion path length on catalytic activity. 11 µmol/g H-ZSM-5-500 18 µmol/g 20 H-ZSM-5-300 40 aromatics selectivity at Si/Al=300 • DFT-based identification of target alloy catalysts for methanol production. 21 µmol/g H-ZSM-5-200 60 80 35 µmol/g H-ZSM-5-120 120 • CO selectivity is minimum at Si/Al 200 H-ZSM-5-80 66 µmol/g 300 H-ZSM-5-60 96 µmol/g ratio of 300-600 Intensity /a.u. Intensity 500

Intensity/a.u. 800 H-ZSM-5-40 156 µmol/g • High acid density promotes the Acknowledgments H-ZSM-5-20 185 µmol/g RWGS reaction The authors acknowledge the U.S. Department of Energy for financial • Low acid density reduces H- 440 µmol/g 10 20 30 40 50 60 support through grant DE-FE0026433. 100 200 300 400 2 /degree transfer rate for olefins synthesis Temperature /oC

NH3 TPD → Reduced CO selectivity