Ammonia synthesis using nonAmmonia synthesis using non--thermal thermal plasma with plasma with RuRu--based catalystsbased catalysts

Roger RuanRoger Ruan11, , ZhipingZhiping LeLe11, , ShaoboShaobo DengDeng11, Paul Chen, Paul Chen11 , , XiangyangXiangyang LinLin11, Mike Reese, Mike Reese22, and Greg Cuomo, and Greg Cuomo22

11Department of Department of BioproductsBioproducts and and BiosystemsBiosystems Engineering, Engineering, 22West Central Research and Outreach Center, West Central Research and Outreach Center,

University of MinnesotaUniversity of Minnesota

IntroductionIntroductionAmmonia is one of the most valuable industrial Ammonia is one of the most valuable industrial chemicals and agricultural fertilizer. More recently chemicals and agricultural fertilizer. More recently it is considered as a direct fuel or hydrogen carrier. it is considered as a direct fuel or hydrogen carrier. Traditionally ammonia is synthesized from Traditionally ammonia is synthesized from hydrogen and nitrogen gases under high pressure hydrogen and nitrogen gases under high pressure and temperature with the help of catalysts. This and temperature with the help of catalysts. This process (Haber process) is usually carried out in process (Haber process) is usually carried out in large scales. large scales. There is a clear need for a more active catalytic There is a clear need for a more active catalytic system or a new route for ammonia synthesis at system or a new route for ammonia synthesis at milder operating conditions to address the interest milder operating conditions to address the interest of smaller distributed ammonia production systems, of smaller distributed ammonia production systems, to fully and more efficiently utilized the wind to fully and more efficiently utilized the wind energy, for example.energy, for example.

ObjectivesObjectivesDevelop efficient nonDevelop efficient non--thermal plasma (NTP) thermal plasma (NTP) systems for synthesis of NHsystems for synthesis of NH33 from renewable from renewable hydrogen such as wind hydrogen. hydrogen such as wind hydrogen.

Evaluate different catalysts and promoters and Evaluate different catalysts and promoters and the synergy effect with nonthe synergy effect with non--thermal plasma.thermal plasma.

Study NTP Study NTP processing parameters such as applied processing parameters such as applied voltage, frequency, gas ratio, and residence time. voltage, frequency, gas ratio, and residence time.

What is NTP?NTP species include: energetic electrons, photons, atoms, and molecules, highly reactive radicals, ozone, etc. Ozone is the most widely used NTP species.NTP is generated though electrical discharge in gas (in atmosphere or liquid).

HV Power

Electrode

Electrode

Plasma

NonthermalNonthermal Plasma (NTP)Plasma (NTP)

Generation of highly reactive speciesGeneration of highly reactive species

e + Oe + O22 OO22++ + 2e+ 2e

OO++ + O + 2e+ O + 2eO* + O + eO* + O + eOO-- + O+ O

e + Ne + N22 NN22++ + 2e+ 2e

NN++ + N + 2e+ N + 2eNN22* + e* + eN* + N + eN* + N + e

O* + HO* + H22O O 2OH2OH

O + OO + O22 + O+ O22 OO33 + O+ O22

e + He + H22O O H + OHH + OH

NONOxx + O + O NO or NONO or NO22NONOxx + OH + OH HNOHNO33NONOxx + N + N NN22 + O+ O22SOSOxx + O + H+ O + H22OO HH22SOSO44SOSOxx + 2OH + 2OH HH22SOSO44NHNH33 + O + O NN22 + H+ H22OOHH22S + OH S + OH SOSO22 + H+ H22O O COCOxx + O + O COCO22 + CO+ CO

Effects of NTP on gaseous compoundsEffects of NTP on gaseous compounds

O + O + VOCsVOCs COCOxx + H+ H22O + byproductsO + byproducts

OH + OH + VOCsVOCs COCOxx + H+ H22O + byproductsO + byproducts

OO33 + + VOCsVOCs COCOxx + H+ H22O + byproductsO + byproducts

e + Oe + O22 + + VOCsVOCs COCOxx + H+ H22O + byproductsO + byproductsdepending on depending on VOCsVOCs

Effects of NTP on gaseous compoundsEffects of NTP on gaseous compounds

Pulsed Corona Discharge Reactors

Silent discharge reactors

NTP Reactors

Packed-Bed NTP reactor

Pilot NTP surface disinfection system

Materials and MethodsMaterials and MethodsNew approach for ammonia production from New approach for ammonia production from renewable hydrogen and energyrenewable hydrogen and energy

Wind Generated Electricity

Electrolysis of Water

Hydrogen

NTP-Assisted NH3 Synthesis Reactor

Nitrogen

Ammonia

Biomass conversion

Materials and MethodsMaterials and MethodsSchematic diagram of the experimental apparatusSchematic diagram of the experimental apparatus

(1) nitrogen; (2) hydrogen; (3) mass flow

controller; (4) dryer; (5) gas purification; (6) temperature

control instrument;

(7) inner electrode; (8) outer electrode; (9) catalyst bed; (10) plasma reactor; (11) power supply; (12) compressor;

and (13) ammonia

storage tanks.

Materials and MethodsMaterials and MethodsNonNon--Thermal Plasma Assisted NHThermal Plasma Assisted NH33SynthesisSynthesis

N2 N2 →→ 2N(ad)2N(ad)H2 H2 →→ 2H(ad)2H(ad)N(adN(ad) + ) + H(adH(ad ))→→ NH(adNH(ad))NH(adNH(ad) + ) + H(adH(ad) ) →→ NH2(ad)NH2(ad)NH2(ad) + NH2(ad) + H(adH(ad) ) →→ NH3(ad)NH3(ad)

Results and DiscussionResults and DiscussionAmmonia synthesis under different catalystAmmonia synthesis under different catalyst

0

0.5

1

1.5

2

2.5

3

3.5

4

NTP NTP + MgO NTP + Ru /MgO NTP + Cs-Ru/MgO

Am

mon

ia y

ield

(%)

Results and DiscussionResults and DiscussionEffect of applied voltage on ammonia formationEffect of applied voltage on ammonia formation

6.2

6.4

6.6

6.8

7

7.2

7.4

7.6

4000 5000 6000 7000 8000

Voltage (v)

Am

mon

ia y

ield

(%)

catalyst: Cs-Ru/MgO-TiO2; frequency: 8000Hz; N2 and H2 total flow rate: 60ml/min.

Results and DiscussionResults and DiscussionAmmonia formation as a function of temperatureAmmonia formation as a function of temperature

44.5

55.5

6

6.57

7.58

8.5

180 210 240 270 300

Reaction temperature (C)

Am

mon

ia y

ield

(%)

catalyst: Cs-Ru/MgO-TiO2; VN2:VH2=1:3, N2 and H2 total flow rate: 60ml/min, voltage: 5000V, frequency :10000Hz.

Results and DiscussionResults and DiscussionEffect of ratio of N2/H2 on ammonia formationEffect of ratio of N2/H2 on ammonia formation

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

0.04 0.04 0.05 0.05 0.05

Ratio of N2/H2

Am

mon

ia y

ield

(%) catalyst:

Cs-Ru /MgO-TiO2; voltage :5000V, frequency:10000Hz; N2 and H2 total flow rate: 60ml/min

Results and DiscussionResults and DiscussionAmmonia formation as a function of time in an Ammonia formation as a function of time in an NTP reactor with catalystsNTP reactor with catalysts

4

6

8

10

12

14

5 50 95 140 185 230

Reation time (min)

Am

mon

ia y

ield

(%)

Comparison Between Traditional Thermochemistry and NTP Assisted Catalysis.

CH4, NH3, CO2, N2O, NO, ……-CO2, H2, NH3(3) CO + N2 + H2O

Reactants

Traditional high

temperature and high pressure

Low temperature and atmospheric pressure

Without NTP With NTP

(1) N2 + H2 NH3 - NH3

(2) N2 + H2O - - NH3, N2O

(4) CO + H2O CO2, H2 - CH4, CO2, H2

FTFT--IR spectrum of reaction of N2 and IR spectrum of reaction of N2 and H2O on H2O on RuRu--PtPt--Cs/MgOCs/MgO catalystcatalyst

FTFT--IR spectrum of reaction of N2, CO, IR spectrum of reaction of N2, CO, and H2O.and H2O.

FTFT--IR spectrum of reaction of CO and H2O.IR spectrum of reaction of CO and H2O.

NH3, CH4, other hydrocarbons

NTP Assisted Catalysis ReactionsNTP Assisted Catalysis Reactions

ConclusionsConclusionsThe nonThe non--thermal plasma generated by thermal plasma generated by dielectric barrier discharge can ionize and dielectric barrier discharge can ionize and dissociate Ndissociate N22 and Hand H22 molecules to form a large molecules to form a large number of activated species, which react to number of activated species, which react to produce ammonia molecules. produce ammonia molecules.

ConclusionsConclusionsThe concentration of ammonia produced The concentration of ammonia produced depends on applied voltage, frequency, depends on applied voltage, frequency, temperature, and the catalysts and promoters. temperature, and the catalysts and promoters. The highest concentration reached 12.6% in The highest concentration reached 12.6% in this study.this study.

ConclusionsConclusions

The The RuRu--based catalyst had high catalytic based catalyst had high catalytic activity at low temperature. It also indicated activity at low temperature. It also indicated that ammonia synthesis with nonthat ammonia synthesis with non--thermal thermal plasma and promoted catalyst was much less plasma and promoted catalyst was much less temperature dependent than with other temperature dependent than with other catalytic processes.catalytic processes.

ConclusionsConclusionsHigh reaction activities can be attained even High reaction activities can be attained even when the feed gas composition varied to a when the feed gas composition varied to a large extent.large extent.Ammonia synthesis by nonAmmonia synthesis by non--thermal plasma thermal plasma with promoted catalysts should have a great with promoted catalysts should have a great potential to become an innovative commercial potential to become an innovative commercial technology.technology.

Thanks!Thanks!

Questions?Questions?

Roger Ruan, Professor and Director

Center for Biorefining and

Department of Bioproducts and Biosystems Engineering

University of Minnesota

1390 Eckles Avenue

St. Paul, MN 55108

ruanx001@umn.edu