Reducing coke formation and extending lifetime of the HZSM-5 catalyst via co-pyrolysis of high density polyethylene with

switchgrass(Panicum virgatum)

Frankie Lazauskas, Drexel University, Department of Biodiversity, Earth, and Environmental Sciences

2

Background: Pyrolysis

• Thermochemical decomposition of organic matter in the absence of oxygen which can produce solid, liquid, and gas products

• Biomass fast pyrolysis oil is a complex mixture of many oxygenated hydrocarbons and water (Acids, esters, ketones, aldehydes, sugars, furans, phenols, 15-30% water)

• Other issues with biomass pyrolysis oil include its high acidity, low heating value, thermal instability, and high oxygen/low hydrogen content(compared to petroleum oil)

3

Background: Catalytic Fast Pyrolysis(CFP)

• Same as fast pyrolysis, except products pass over a reactive catalyst bed

• Often a zeolite catalyst, such as HZSM-5, that selectively makes deoxygenated aromatic hydrocarbons

• CFP of biomass creates coke while losing H, this coke formation eventually leads to deactivation of the catalyst

4

Background: Agricultural Plastic Waste

• Many different plastics used for agricultural needs such as hay bale covers, pesticide/insecticide containers, transportation/storage of crops, etc.

• 521 million pounds of agricultural plastic waste every year in the U.S alone with about 70% being polyethylene

• Disposal Solutions

• Incineration, burial, and landfills come with many environmental concerns

• Simply recycling them can be difficult/expensive(toxins from pesticides)

• Co-pyrolysis feedstock

5

Objective

• How does addition of HDPE affect product formation?

• Does addition of HDPE have an effect on coke formation and the lifetime of the catalyst?

6

Materials & Methods

• CDS pyrolyzer(CDS Pyroprobe 5250-T) and external reactor(CDS 5250-TR)

• Agilent GC/MS(6890N)

• Quartz tube with ~1mg of sample(Switchgrass, HDPE, and 1:1 mixture) stuffed with quartz wool to prevent loss of sample

7

Materials & Methods

• Pyrolysis done at 650°C with either 30 sample or 60 sample runs

• Gases transferred to external reactor and passed over HZSM-5 bed with ~15mg of catalyst at 500°C

• Products then analyzed by GC/MS

8

Materials & Methods

• Spent catalyst with quartz wool removed post-run

• Quartz wool separated from spent catalyst

• Spent catalyst heated to 650°C, weight loss recorded for determining coke formation on HZSM-5

9

Results: Coke Formation

1:1 Switchgrass HDPE

10

Results: HZSM-5 Lifetime and Product Formation (Switchgrass Alone)

BTEX is the sum of the aromatic

compounds Benzene, Toluene,

Ethylbenzene, p-Xylene, and o-Xylene.

11

Results: HZSM-5 Lifetime and Product Formation (HDPE Alone)

12

Results: HZSM-5 Lifetime and Product Formation (1:1 Mix of HDPE and Switchgrass)

13

Results: Deactivation of HZSM-5

• Production of acetic acid increased as more sample was run over HZSM-5 for all switchgrass runs

• No acetic acid detected in any of the HDPE runs

• Only 1 out of 4 of the mixed runs showed any acetic acid production(highest value ~12)

0 10 20 30 40 50 60 700

5

10

15

20

25

30

Acetic Acid for all SWG runs

SWG_A1-30SWG_B1-30SWG_C1-60SWG_D1-60

Amount of Sample Catalyst Exposed To(mg)

Are

a/M

ass(

mg)

/100

0000

0

Conclusions

• Addition of HDPE reduces coke formation which helps to delay deactivation of HZSM-5

• HDPE increased yield of stable aromatic hydrocarbons compared to biomass alone with a synergistic effect(1:1 ratio showed consistently higher yields)

Future Directions

• Understanding chemical pathways for the observed synergistic effect in mixed samples testing of other biomass/plastic combinations

• Different/smaller ratios of plastic to biomass, how much plastic is needed to still utilize this effects?

• Potential options for external reactor that is compatible with Shimadzu GC/MS models could mitigate many of the maintenance issues that hindered this project

Acknowledgements

Special thanks to

Dr. Akwesi Boateng, Dr. Charles Mullen, Tom Coleman and the entire pyrolysis team!

Questions?