Ethylene Production

• Ethylene has world-wide demand in excess of 150 MM tons per year [1]

• Fundamental change in US supply of hydrocarbons

• Primarily produced by steam cracking of ethane or naphtha

C2H6 + Heat ⇆ C2H4 + H2

C6H14(l) + Heat ⇆ 3.C2H4 + H2

• Members of the Li research group• Department of Energy ARPA-E Award Number

DE-AR0000327• EcoCatalytic Technologies• The Analytical Instrumentation Facility (AIF)• PSRI

• CL-ODH has the potential to reduce the energy demand for ethylene production by 52% and 82% using naphtha and ethane respectively

• It also provides a corresponding drop in CO2/NOx emissions• Second Law analysis reveals 67% reduction in exergy loss• The newly constructed 10 kWth circulating fluidized bed reactor (CFB)

will be used to validate reaction data for CL-ODH.

CL-ODH Modeling Study

Conclusions and Future Work

Modeling Results and Scale-Up

Acknowledgments

Product Yield (%)

Cracker ODH Cracker ODH

Ethane 35.0 15.0 3.3 2.1

Methane 3.4 6.0 11.5 7.7

Acetylene 0.5 0.2 0.7 0.3

Ethylene 56.1 65.0 27.3 32

Propylene 1.2 2.4 12.3 16.2

Propane 0.1 0.3 0.3 0.6

Butadiene 2.1 2.4 4.1 4

Butenes 0.2 2.4 2.8 7.5

C5+s 0.6 0.5 18 23

Aromatics 0.6 2.9 19.7 2

CO 0.0 1.5 0 1.3

CO2 0.0 1.5 0 3.3

Light Alkane Valorization to Ethylene via Chemical Looping Vasudev Pralhad Haribal, Luke Neal, Seif Yusuf, Fanxing Li*

Department of Chemical & Biomolecular Engineering, North Carolina State University

Energy Demand Distribution (GJ/ton ethylene)

[1]Stangland, Eric E. (2018), Annual review of Chemical and Biomolecular Engineering (0)[2]Ren, T., Patel, M., & Blok, K. (2006), Energy, 31(4), 425–451.[3]Yusuf, S., Neal, L. M., & Li, F. (2017), ACS Catalysis, 7(8), 5163–5173.[4]Haribal, V. P., Neal, L. M., & Li, F. (2017), Energy, 119, 1024–1035.[5] Haribal, V. P., Chen, Y., Neal, L., & Li, F. (2018). Engineering.

1 kg/day cold model in collaboration with PSRI demonstrated satisfactory hydrodynamics

Lab-scale fluidized bed testing was done with the material and ethane for >1400 cycles

46%

45%

9%

23%50%

27%

15.2 2.7 15.5

32.5Ethane to ethylene

Naphtha

• Pilot-scale cold-flow model of a circulating fluidized bed reactor (CFB) designed and tested in conjunction with PSRI

82% Reduction[4] Naphtha to ethylene

52% Reduction[5]

Compression

Reactor

Separation

Ethane Naphtha

• Simulations are performed in AspenPlus, a software package for modeling chemical reactors

• Product distributions from our previous work are used to determine yields[3]

• Results are compared to traditional cracking

• Coupled with Second Law analysis

• Downstream energy demand is significantly reduced due to higher conversions and less hydrogen going to the compressor.

Reactor temperatures can reach 1100°CThe reaction is highly endothermic (17-30 GJ/ton of ethylene

formed)Purification of the ethylene product is very energy intensive

• Energy demand is met through combustion of natural gas at high temperatures causing significant CO2 and NOx emissions, with more than 1.2 tons of CO2 produced per ton of ethylene[2]

• Unfortunately, this process has several key drawbacks:

US production of crude oil and other fuels[1}

Steam

cracking

Exergy Loss

• Oxygen is donated from the crystal lattice of an oxygen carrier in a endothermic reaction

• Heat is produced in a separate reactor when air re-oxidizes the oxygen carrier

• CL-ODH does not need demand pure oxygen: eliminates air separation

Chemical Looping ODH

Mg6MnO8, a Mixed Ionic Electronic Conductor(MIEC), allows fast transport of bulk lattice oxygen to the surface, supplying enough oxygen to drive the reaction.

• Gas chromatography shows that un-promoted, this model oxygen carrier burns ethane in the 800-900°C range

• Doped with alkali salts, however, it demonstrates excellent selectivity to ethylene

• In chemical looping oxidative dehydrogenation (CL-ODH) the oxygen needed for ODH is supplied by a metal oxide

Performance at 850 ºC

ReducerODH

OxidizerRegeneration

C2H4 + H2O

CnH2n+2 Air

N2 + Heat

MeOx-1

MeOx

Heat

+

ODH

Regeneration

MagnesiumManganeseOxygen

Mg6MnO8 Crystal Structure

General Mechanism using Mg6MnO8

Temperature programed reduction (TPR), shows that doping suppresses activation of ethane for deep oxidation at lower temperatures, while allowing hydrogen combustion.[2,3]

Ethane TPR

CH3CH3 ⇆ CH2CH2 + H2

H2 + Mn3O4 ⟶ H2O + 3∙MnO

3∙MnO + ½ O2 ⟶ Mn3O4 + Heat

Thermal cracking of ethane

Selective H2 combustion

Sequence of Reactions

Thermal cracking of ethane vs ODH

Hydrogen Combustion

Hydrogen Combustion

Hydrogen Combustion

Regeneration