NASA/TM—2013–217496

Atmosphere Resource Recovery 

and Environmental Monitoring Trace 

Contaminant Control Through FY 2012

December 2013

J.L. Perry and M.W. Pruitt

Marshall Space Flight Center, Huntsville, Alabama

R.M. Wheeler and O. Monje

Kennedy Space Center, Cape Canaveral, Florida
	




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i

NASA/TM—2013–217496

Atmosphere Resource Recovery 

and Environmental Monitoring Trace 

Contaminant Control Through FY 2012

J.L. Perry and M.W. Pruitt

Marshall Space Flight Center, Huntsville, Alabama

R.M. Wheeler and O. Monje

Kennedy Space Center, Cape Canaveral, Florida

December 2013

National Aeronautics and

Space Administration

Marshall Space Flight Center • Huntsville, Alabama 35812
ii

Available from:

NASA STI Information Desk

Mail Stop 148

NASA Langley Research Center

Hampton, VA 23681–1299, USA

757–864–9658

This report is also available in electronic form at

<http://www.sti.nasa.gov>

TRADEMARKS

Trade names and trademarks are used in this report for identification only. This usage does not constitute an official 

endorsement, either expressed or implied, by the National Aeronautics and Space Administration.
iii

TABLE OF CONTENTS

1. BACKGROUND AND TECHNOLOGY DESCRIPTION .............................................. 1

 1.1 Carbon Bed Assembly .................................................................................................. 1

 1.2 Catalytic Oxidizer Assembly ......................................................................................... 2

 1.3 Sorbent Bed Assembly .................................................................................................. 2

 1.4 Opportunities for International Space Station Trace Contaminant

 Control System Improvement ....................................................................................... 2

2. PROGRESS: PLANNED, ACTUAL, AND RESULTS ..................................................... 3

 2.1 Fixed Bed ...................................................................................................................... 3

 2.2 High-Temperature Catalytic Oxidizer ........................................................................... 4

 2.3 Orion Trace Contaminant Control Bed ........................................................................ 4

 2.4 Heat Melt Compactor Contaminant Control System ................................................... 5

3. FUTURE WORK ............................................................................................................... 7

 3.1 Orion Trace Contaminant Control Bed ........................................................................ 7

 3.2 High Flow Rate Carbon Bed ........................................................................................ 7

 3.3 Orion Smoke Eater ....................................................................................................... 7

 3.4 Photocatalytic Oxidation System .................................................................................. 7

 3.5 Sorbent Testing and Evaluation .................................................................................... 8

APPENDIX A—BENCH-SCALE CHARACTERIZATION OF CANDIDATE 

SORBENTS AND CATALYSTS (TRACE CONTAMINANT 

CONTROL: CARBON DIOXIDE AND WATER REMOVAL) ................ 9

 A.1 Overview—Candidate Sorbent and Catalyst Testing by Kennedy Space Center .......... 9

 A.2 Silicalite ....................................................................................................................... 9

 A.3 Immobilized Amines (G10 and Polyethyleneimine-Silane) ........................................... 10

 A.4 Low-Temperature Carbon Monoxide Catalysts ........................................................... 11

 A.5 Honeywell Photocatalyst Evaluation ........................................................................... 12

APPENDIX B—BENCH-SCALE DEVELOPMENT OF A CATALYST FOR 

SELECTIVE CONVERSION OF AMMONIA TO NITROGEN .............. 15

 B.1 Summary ...................................................................................................................... 15

 B.2 Synthesis of a Low-Temperature, Platinum-Based Catalyst for

 Ammonia Removal ...................................................................................................... 16 

 B.3 Study of Ammonia Removal Using Closed-Loop Fourier Transform 

 Infrared Spectrometer .................................................................................................. 18
iv

TABLE OF CONTENTS (Continued)

 B.4 Low-Temperature, Platinum-Based Catalyst Testing .................................................... 20

 B.5 Future Development of Low-Temperature, Platinum-Based Catalyst .......................... 23

REFERENCES ....................................................................................................................... 25
v

LIST OF FIGURES

1. XPS analysis of TDA Research catalyst before and after an ethanol challenge: 

(a) New and (b) used .................................................................................................... 12

2. LTP catalyst samples .................................................................................................... 17

3. RVCS block diagram ................................................................................................... 18

4. Custom gaseous NH3 generator .................................................................................. 19

5. RVCS chamber NH3 concentration dynamic ............................................................... 20

6. RVCS chamber NH3 concentration decay profile ......................................................... 21

7. Temperature influence on N2O concentration in the RVCS chamber ........................... 22
vi

LIST OF TABLES

1. Event timeline for Honeywell PCO catalyst testing ...................................................... 13

2. NH3 removal rate corrected for RVCS chamber leakage .............................................. 22
vii

LIST OF ABBREVIATIONS, ACRONYMS, AND SYMBOLS

ARC Ames Research Center

ARREM Atmosphere Resource Recovery and Environmental Monitoring

ARS atmosphere revitalization system

CBA carbon bed assembly

CCS contaminant control system

CDRA carbon dioxide removal assembly

CO carbon monoxide

CO2 carbon dioxide

COA catalytic oxidizer assembly

E-chamber exploration chamber

FF PCO fast flow photocatalytic oxidation

FTIR Fourier transform infrared

FY fiscal year

GC gas chromograph

GCMS gas chromatograph mass spectrometer

H2O water

HMC heat melt compactor

HTCO high-temperature catalytic oxidizer

ISS International Space Station

KSC Kennedy Space Center
viii

LIST OF ABBREVIATIONS, ACRONYMS, AND SYMBOLS (Continued)

LiOH lithium hydroxide

LTP catalyst low-temperature, platinum-based catalyst

MSFC Marshall Space Flight Center

N2 nitrogen

N2O nitrous oxide

NaOH sodium hydroxide

NETL National Energy Technology Laboratory

NH3 ammonia

NH4Cl ammonium chloride

NO nitric oxide

NOx nitrogen oxide

NO2 nitrogen dioxide

PCI Precision Combustion, Inc.

PCO photocatalytic oxidation

PEI polyethyleneimine

Pt platinum

RVCS regenerable volatile organic compound control system

rNH3 ammonia removal rate corrected for chamber leak rate

SBA sorbent bed assembly

SCO selective catalytic oxidation
ix

LIST OF ABBREVIATIONS, ACRONYMS, AND SYMBOLS (Continued)

TCC trace contaminant control

TCCS trace contaminant control system

TRL Technology Readiness Level

UOP Universal Oil Products

UV ultraviolet

UVA ultraviolet A

UVC ultraviolet C

V-chamber vacuum chamber

VOC volatile organic compound

XPS x-ray photoelectron spectroscopy
x
1

TECHNICAL MEMORANDUM

ATMOSPHERE RESOURCE RECOVERY AND ENVIRONMENTAL MONITORING 

TRACE CONTAMINANT CONTROL THROUGH FY 2012

1. BACKGROUND AND TECHNOLOGY DESCRIPTION

 This Technical Memorandum presents the results of work accomplished during fiscal year 

(FY) 2012 for the Advanced Exploration Systems Atmosphere Resource Recovery and Environmental Monitoring (ARREM) project in the trace contaminant control (TCC) functional area.

 TCC has been a concern of spacecraft designers and operators from early in the progression 

of manned spaceflight. Significant technological advancement has occurred since the first designs 

were implemented in the 1960s, culminating in the trace contaminant control system (TCCS) currently in use aboard the International Space Station (ISS) as part of the atmosphere revitalization 

system (ARS).

 Within the ARS, the TCCS can be considered an independent system. The TCCS draws 

inlet air directly from the cabin through a port in the face of its rack and exhausts treated air out 

into the cabin via a dedicated outlet within the rack. The system was designed for 5.25 crew persons, and due to its parallel operation with a similar Russian system, provides ample contaminant 

elimination capability to the ISS.

 The TCCS consists of three primary subsystems: (1) The carbon bed assembly (CBA), 

(2) the catalytic oxidizer assembly (COA), and (3) the sorbent bed assembly (SBA).

1.1 Carbon Bed Assembly

 The CBA is a 24-in-long bed filled with 22.7 kg (50 lb) of Barnebey-Sutcliffe® Type 3032 

coconut shell activated carbon treated with phosphoric acid 10% by weight. The CBA is responsible for purifying the cabin air of most large molecular weight chemical compounds and ammonia 

(NH3). The CBA accomplishes the bulk of contaminant removal by means of physical adsorption, a process in which compounds are entrapped by angstrom-sized pores on a material surface. 

The CBA removes NH3 from the cabin air, and the phosphoric acid impregnation on the carbon 

accomplishes this through chemical adsorption.
2

1.2 Catalytic Oxidizer Assembly

 The COA consists of a recuperative heat exchanger, a heating element, and a catalytic 

reactor. The catalytic reactor is filled with 0.5 kg of 0.5% palladium on alumina pellets and operates at a mean temperature of 400 °C. Incoming air is heated to reactor operating temperatures 

by the recuperative heat exchanger and heating element, and the reactor exhaust is cooled in the 

recuperative heat exchanger prior to entering the final subsystem.

1.3 Sorbent Bed Assembly

 The SBA consists of a single bed filled with 1.4 kg of lithium hydroxide (LiOH) pellets. 

The purpose of the SBA is to prevent any acid gases that are generated in the catalytic reactor from 

escaping into the cabin atmosphere. The SBA accomplishes acid gas removal through chemical 

adsorption.

1.4 Opportunities for International Space Station Trace Contaminant

Control System Improvement

 For the ARREM TCC task, several advancements to these legacy technologies were pursued and utilized in FY 2012. First, a new activated carbon was required to fill the role of the CBA 

due to the discontinuation of the Barnebey-Sutcliffe Type 3032 product. Equivalent or upgraded 

capability was sought via commercially available products.

 Similarly, FY 2012 efforts sought to eliminate the need for the SBA. The LiOH pellets in 

the SBA are known to degrade during operation and cause pressure drop increases in the TCCS. 

Chemical adsorbent media alternatives to LiOH were sought in the pursuit of an option that would 

preserve pressure drop characteristics throughout bed operation.

 Thirdly, TCC task efforts sought to utilize an upgrade to the traditional pelletized COA 

reactor. Built by Precision Combustion, Inc. (PCI) for NASA as a Small Business Innovative 

Research (SBIR) phase II in the mid-2000s, the ultra-short channel Microlith® reactor supplants 

the original pelletized bed with a tightly spaced matrix of conductive material coated in catalyst. 

Previous testing of this unit has shown that light-off time (time elapsed between system activation 

and system efficacy) is greatly reduced compared to the legacy reactor.
3

2. PROGRESS: PLANNED, ACTUAL, AND RESULTS

 FY 2012 accomplishments for the ARREM TCC task can be aligned with five areas of 

focus: (1) The fixed bed, (2) the high-temperature catalytic oxidizer (HTCO), (3) the Orion TCC 

bed, (4) the heat melt compactor (HMC) contaminant control system (CCS), and (5) sorbent and 

catalyst evaluation.

2.1 Fixed Bed

 Planned progress for the fixed bed began with identifying a suitable replacement for the 

sorbent in the ISS TCCS CBA, Barnebey-Sutcliffe Type 3032, coconut shell activated carbon; 

calculating the contaminant capacity of the fixed bed given the new sorbent’s bulk density and the 

conditions of the ISS cabin atmosphere; packing a heritage bed housing with the newly selected 

sorbent and conducting pressure drop testing; and integrating the bed into the exploration chamber 

(E-chamber) in parallel with the condensing heat exchanger and a metering bypass valve.

 Actual progress for the fixed bed included successful completion of all planned tasks. Examining earlier NH3-targeting sorbent testing conducted at Ames Research Center (ARC) by Luna et 

al.,1 Molecular Products Chemsorb® 1425 was chosen as the replacement for Barnebey-Sutcliffe 

Type 3032. Analysis of the fixed bed contaminant capacity was performed assuming that the 

adsorption equations defined for Barnebey-Sutcliffe Type 3032 applied to Chemsorb 1425. Pressure 

drop testing was conducted on the packed bed, and the bed was integrated into the E-chamber in 

parallel with the condensing heat exchanger and a metering bypass valve.

 Results from the fixed bed analysis indicated that the bed should last 136 days before saturating with methanol, the most demanding compound considered in the analysis after carbon monoxide (CO), hydrogen, methane, and formaldehyde, all of which are readily oxidized in the catalytic 

reactor.

 The Chemsorb 1425 that was ordered for testing unexpectedly arrived in mesh sizes 12 × 20, 

much finer than the Barnebey-Sutcliffe Type 3032 at 4 × 8. As a result, pressure drop through the 

bed was much higher than anticipated, and the bed could only reach a maximum flow rate of 5 cfm 

with the assistance of a blower.

 The placement of the fixed bed in the E-chamber, in parallel with the condensing heat 

exchanger, enables direct comparison of the Chemsorb 1425’s performance with the BarnebeySutcliffe Type 3032 since both the TCCS CBA and the fixed bed ingest cabin air at standard 

humidity; additionally, the placement of the fixed bed in parallel with a metering bypass valve 

allows for testing of the bed at various flow rates.
4

2.2 High-Temperature Catalytic Oxidizer

 Planned progress for the HTCO using Microlith reactor technology included removing 

the unit from an old test fixture in the vacuum chamber (V-chamber), verifying unit functionality, 

determining optimal system placement in the overall E-chamber architecture, and integrating the 

unit into the E-chamber for cycle 1 testing.

 Actual progress for the HTCO included successful completion of all planned tasks. The unit 

in the V-chamber was removed from the old test fixture and confirmed to be operational. Optimal 

placement for the HTCO was determined to be downstream of the carbon dioxide removal assembly (CDRA) zeolite 5A beds in the cabin air return flow path. At this particular location in the 

E-chamber architecture, the gas stream is very dry, reducing the heating burden on the HTCO heaters. The HTCO was then installed in the E-chamber in advance of cycle 1 testing.

 Results from preliminary operational data for the HTCO Microlith unit indicate that 

the thermocouples within the unit are improperly labeled; this has yielded unexpected results in 

both the reactor’s thermal cycling and in the thermal response time. Examination of the data led 

to selection of a different thermocouple for control of the unit’s heaters, and system behavior is 

expected to return to nominal.

2.3 Orion Trace Contaminant Control Bed

 For the Orion TCC bed, planned progress included designing a bed sized for the Orion 

cabin atmosphere, approximating the design with available legacy hardware, determining optimal 

bed placement in the E-chamber architecture, and integrating the bed into the E-chamber.

 Actual progress for the Orion TCC bed yielded successful completion of all planned tasks. 

Published contaminant generation rates for both metabolic processes and equipment offgassing 

were coupled with projected Orion crew size and estimated equipment manifest to create a projected Orion cumulative contaminant load. The TCC bed was sized assuming a 30-day mission, 

and that the cabin atmosphere must be controlled to the 30-day spacecraft maximum allowable 

concentration for each published contaminant. 

 Once the bed was sized, heritage sorbent bed hardware was packed with a sorbent, Chemsorb 1425, and an ambient temperature CO catalyst, Carulite® 300. Optimal bed location was 

determined to be downstream of the CDRA zeolite 5A beds in the cabin air return flow path, 

upstream of the HTCO. This particular placement provides protection to the HTCO from any 

NH3 that bypassed the fixed bed prior to CDRA; furthermore, it provides a very dry operating 

environment for the Carulite 300, which requires low humidity to function.

 Results from the Orion TCC bed are forthcoming, as the E-chamber is not yet operating 

with contaminant injection capability.
5

2.4 Heat Melt Compactor Contaminant Control System

 Planned progress for the HMC CCS included calculating an estimated total contaminant 

load emitted by the compactor for a 1-yr mission, evaluating potential control technologies against 

the quantity and composition of the contaminant load, making a recommendation to the HMC 

project, and delivering a report capturing all data and calculations supporting the recommendation.

 Actual progress for the HMC CCS bed accomplished all planned tasks. ARC provided 

preliminary effluent data from a test run of the HMC unit at ARC. The data included probable 

contaminants present in the effluent, gas chromatograph mass spectrometer (GCMS) peak heights 

for the probable contaminants, and bulk contaminant concentration values. Listed probable contaminants were assumed to be present, recorded peak heights were assumed to uniformly relate to 

compound concentration, and the bulk contaminant emission plot was assumed to be symmetrical 

about the period of greatest emission. On the basis of those assumptions, contaminant load data 

were generated for a 1-yr mission, assuming the HMC would operate daily.

 Two technologies were considered to treat the load: (1) A sorbent bed of activated carbon 

and (2) thermal catalytic oxidation. The sorbent bed analysis examined the performance of 

a treated activated carbon and an untreated activated carbon: Chemsorb 1425 and Chemsorb 1000, 

respectively. The second technology, thermal catalytic oxidation, was analyzed using data from 

previous HTCO Microlith testing and extrapolated ISS-scale system performance to the lower flow 

rates required for the HMC. Upon completion of the technology evaluation, the HMC project was 

advised to pursue a sorbent bed design filled with Chemsorb 1425.

 Data and calculations used to support the recommendation were captured in a report 

entitled “Estimated Characteristics of a Trace Contaminant Control System for the Heat Melt 

Compactor,” completed in June 2012.2 Data and conclusions from the report were presented at 

the HMC Preliminary Design Review in August 2012. Also, a contract was initiated with PCI to 

begin design of a Microlith catalytic reactor sized for the HMC in the event that further compactor 

effluent analysis should indicate catalytic oxidation is necessary.

 Results from the initial HMC effluent analysis determined that the five predominant contaminants were acetoin, ethyl acetate, benzaldehyde, hexanal, and 3-methyl-1-butanol. Assuming 

GCMS peak magnitude directly correlated to contaminant concentration, the relative presence of 

each contaminant was found to be approximately 53%, 19%, 16%, 7%, and 5%, respectively, of the 

bulk contaminant concentration. 

 Results from the treatment technology evaluation showed that while untreated carbon 

required less sorbent mass to process the full load, the treated carbon provided additional capability as a means of NH3 removal in the event of NH3 generation in the HMC. Furthermore, the 

increase in required sorbent mass over untreated activated carbon was marginal at less than 50 g. 

Results from the Microlith catalytic reactor analysis projected that a unit sized for the HMC would 

likely achieve 97% oxidation efficiency at 90 W power consumption and would likely require 10 min 

to achieve light-off, or initiation of oxidation.
6

 Given the catalytic oxidizer’s significant power requirements compared to the unpowered 

sorbent bed, and the greater capability of the treated activated carbon over the untreated activated 

carbon, a sorbent bed packed with treated activated carbon was recommended. Such a configuration provided capability to remove NH3 and other contaminants from the effluent stream while 

avoiding any additional power requirements.

 The trace contaminant load and its variation will be characterized during FY 2013, and the 

catalytic oxidizer’s design will be revisited based on that characterization. Fabrication is planned 

for late FY 2013 and early FY 2014.
7

3. FUTURE WORK

 In the next few years, ARREM work for the TCC task will continue to advance NASA’s 

airborne contaminant mitigation capabilities. Work in the next fiscal year will involve a variety of 

technologies and systems, including an Orion TCC bed, a high flow rate activated carbon system, 

an Orion smoke eater, a photocatalytic oxidation (PCO) system, and sorbent and catalyst testing 

and evaluation.

3.1 Orion Trace Contaminant Control Bed

 The Orion TCC bed will compare directly to the system that is currently planned for the 

Orion vehicle. The bed design will employ multiple layers of sorbents and catalysts to effectively 

control the concentration of trace contaminants in the Orion cabin atmosphere. Myriad sorbent 

and catalyst evaluations will be performed to determine suitable candidates for inclusion in the 

Orion TCC bed.

3.2 High Flow Rate Carbon Bed

 The high flow rate activated carbon system will be evaluated against the current ISS paradigm of treating a small flow rate with very high single-pass efficiency. By contrast to the ISS 

TCCS, a high flow rate activated carbon system will process cabin air at greatly elevated flow rates, 

though at a lower single-pass efficiency. The high flow capacity of the system will permit its possible incorporation into the ISS ductwork, eliminating requirements for a dedicated blower and 

potentially decreasing the volatile organic compound (VOC) burden for which the water recovery 

system is responsible.

3.3 Orion Smoke Eater

 The Orion smoke eater will be designed to operate in the event of an Orion cabin fire, 

extracting particulates and chemical contaminants from the cabin atmosphere at a much higher 

rate than would be possible with the standard Orion TCC bed. The bed will employ multiple layers 

of sorbents and catalysts specially selected to target the products of combustion, such as CO.

3.4 Photocatalytic Oxidation System

 PCO technology is a direct competitor with HTCO, the technology currently in use aboard 

the ISS. Both processes oxidize low molecular weight compounds across a variety of chemical 

classes and are used in conjunction with adsorption beds for TCC systems, as low molecular weight 

compounds are not readily adsorbed. The benefit of PCO technology is ambient temperature 

operation; by contrast, HTCO requires significant power input to reach operating temperatures 

above 300 °C and can even generate contaminants in the presence of certain compounds. PCO 

technology assessment will be conducted at Kennedy Space Center (KSC).
8

3.5 Sorbent Testing and Evaluation

 Sorbents and catalysts will continue to be evaluated at KSC in support of various TCCS 

development efforts. As media are identified for potential integration into a TCCS, KSC personnel 

will assess media performance using an assortment of challenge compounds that represent particular metabolic or equipment offgassing loads. Data from KSC testing will guide sorbent and catalyst 

selection throughout system development.
9

APPENDIX A—BENCH-SCALE CHARACTERIZATION OF CANDIDATE 

SORBENTS AND CATALYSTS (TRACE CONTAMINANT CONTROL: 

CARBON DIOXIDE AND WATER REMOVAL)

A.1 Overview—Candidate Sorbent and Catalyst Testing by Kennedy Space Center

Research Milestones

 Two candidate sorbents and two catalysts were tested in FY 2012:

• Evaluate TCC by silicalite.

• Evaluate carbon dioxide (CO2) and water (H2O) removal by immobilized amines.

• Evaluate ethanol removal by low-temperature CO catalysts.

• Evaluate ethanol removal with Honeywell PCO catalysts.

A.2 Silicalite

 Silicalites (HiSiv 1000 and HiSiv 3000) are sorbents manufactured by Universal Oil Products (UOP) Honeywell that do not adsorb much CO2 at 0.6% CO2 and continue to adsorb VOCs 

at high moisture contents because they are hydrophobic.

Research Goals

• Evaluate the adsorptive capacities of HiSiv 3000 for gas mixtures (ethanol-acetone-toluene 

and dichloromethane-xylene) with 70%–80% relative humidity and 7 and 23 °C, respectively.

• Evaluate the adsorptive capacities of HiSiv 1000 for gas mixtures (ethanol-acetone-toluene 

and dichloromethane-xylene) with 70%–80% relative humidity and 7 and 23 °C, respectively.

• Measure adsorptive capacity data (umol/g) for calculating the size of single-pass silicalite beds. 

Equipment

• Simulated cabin air gas streams (humidified gas mixtures) were supplied to 5 g of silicalite in the 

0.5-in-diameter heated sorbent bed of the regenerable volatile organic compound control system 

(RVCS) testbed. 

• Gas mixture analysis conducted using Fourier transform infrared (FTIR) spectrometer.

Procedures 

• The UOP silicalites were loaded with VOCs at 1.5 SLPM in the 0.5-in-diameter RVCS bed.

• The silicalites were regenerated before use with reverse flow of nitrogen (N2) and thermal 

ramping up to 260 °C for ≈4 hr. 

• The tests were run for 3 hr to ensure maximum adsorption was reached.
10

Key Results

• HiSiv 3000 did not adsorb xylene, and absorption capacities followed acetone >> toluene > ethanol > dichloromethane. HiSiv 3000 was dusty after removal from the bed. 

• HiSiv 1000 adsorption was acetone >> ethanol >> toluene > xylene/dichloromethane. More toluene was adsorbed when dry. Dichloromethane showed rollover with water vapor. HiSiv 1000 was 

not dusty after removal from the bed.

• A data summary was sent to Marshall Space Flight Center (MSFC) in February as requested.

• Additional silicalite characterization was not possible due to flooding of the Space Life Sciences 

Lab.

A.3 Immobilized Amines (G10 and Polyethyleneimine-Silane)

 CO2 adsorptive capacities of immobilized amines (G10 and polyethyleneimine- (PEI-) 

silane), synthesized by the National Energy Technology Laboratory (NETL), were evaluated at 

various loading temperatures. 

Research Goals

• Measure breakthrough curves for CO2 adsorption of G10 at 20, 40, and 60 °C using low flow 

rates. 

• Measure breakthrough curves for CO2 adsorption of PEI-silane at 20, 40, and 80 °C using low 

flow rates. 

• Study the effect of humidity on the CO2 adsorption of G10. 

Equipment

• Simulated cabin air gas streams (0.6% CO2) were supplied to 5 g of immobilized amines 

in the 0.5-in-diameter heated sorbent bed of the RVCS testbed. 

• Gas mixture analysis conducted using FTIR spectrometer.

Procedures 

• The immobilized amines were loaded with CO2 at 0.5 SLPM in the 0.5-in-diameter RVCS bed.

• The immobilized amines were regenerated before use with reverse flow of N2 at 100 °C for 1 hr. 

Key Results

• The data collected were sent to the University of South Carolina to corroborate their modeling 

efforts at explaining mechanisms of CO2 absorption by these immobilized amines. 

• The data were shared with NETL and MSFC to evaluate the possible use of these immobilized 

amines as substitutes for SA9T.
11

A.4 Low-Temperature Carbon Monoxide Catalysts

Research Goals

• Evaluate low-temperature CO catalysts for removal of VOCs.

• Two gold-based commercial catalysts (TDA Research, Inc. and Novax Material and Technology 

Co.) and one platinum- (Pt-) tin, oxide-based catalyst were studied.

Equipment

• Simulated cabin air gas stream (humidified ethanol). 

• Gas mixture analysis conducted using a gas chromograph (GC) and an FTIR spectrometer.

Procedures 

• VOCs were tested over oxidation catalysts to determine the conversion rates. The catalysts were 

exposed to ethanol at concentrations less than 20 ppm and at a flow rate of 0.6 SLPM. Maximum allowable concentration limit for ethanol is 1,000 ppm in an enclosed space. VOCs vent 

into a carbon filter. 

• Three catalysts were tested. Catalysts prepared by TDA Research, Inc. and Novax Material 

and Technology Co. are gold-based catalysts; the third one is a Pt-tin-oxide catalyst. 

• Ethanol was generated with an impinger. Nitrogen gas flows through a flow meter into 15 mL 

of ethanol and generates a gas stream of 20 ppm of VOCs that flows at 0.6 SLPM through 

20–50 mg of catalyst. The ethanol concentrations were sampled before and after the tube containing the catalyst. 

• The gas samples were analyzed with a GC and FTIR. Catalyst samples, used and new, 

were analyzed with x-ray photoelectron spectroscopy (XPS).

Key Results

• Studied all three catalysts, but TDA performed the best. No intermediates were formed and it 

lasted longer.

• Ethanol thermocatalytic removal using a gold/iron-oxide (TDA Research) catalyst at room 

temperature (TDA Research catalyst was previously tested at ARC for low-temperature CO 

oxidation). Initial ethanol removal was rapid for the first 2–3 hr followed by saturation/poisoning 

of the catalyst. Figure 1 shows that the XPS analysis of the carbon region before (fig. 1(a)) and 

after (fig. 1(b)) indicates formation of carbonyl species on the surface of the catalyst with 

a reduced concentration CO indicative of a surface reaction with no ethanol absorption.
12

300

700

800

900

1,000

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

299 298 297 296 295 294 293 292 291 290 289 288 287 286 285 284 283 282 281 280 279 278 277 276

300

1,100

1,200

1,300

1,400

1,500

1,600

1,700

1,800

1,900

2,000

2,100

2,200

299 298 297 296 295 294 293 292 291 290 289 288 287 286 285 284 283 282 281 280 279 278 277 276

Binding Energy (eV)

Binding Energy (eV)

Counts/s Counts/s (a)

(b)

Figure 1. XPS analysis of TDA Research catalyst before and after an ethanol challenge: 

(a) New and (b) used.

A.5 Honeywell Photocatalyst Evaluation

A collaborative effort was initiated with Honeywell regarding the manufacture of doped 

photocatalyst coupons for testing at KSC (table 1). The effort has been slow, tedious, and ongoing. 

Testing was not possible in FY 2012 as the catalyst coupons had not been delivered by Honeywell.

Research Goals

• Measure PCO degradation of ethanol and acetone using ultraviolet A (UV) (UVA) 

and ultraviolet C (UVC) radiation using Honeywell doped PCO catalyst coupons 

in the fast flow photocatalytic oxidation (FF PCO) of the Solar Simulator testbed.

• Measure PCO degradation of ethanol in presence of VOC mixtures.

• Study the effect of humidity PCO degradation of ethanol. 
13

Table 1. Event timeline for Honeywell PCO catalyst testing.

Date Purpose Document

4/2011 Contacted Honeywell with collaborative ideas AVO_Ideas_ARSystems

11/2011 Established NDA with Honeywell NDA

5/2012 Suggested test plan of Honeywell catalysts Test Plan

8/2012 Requested quote for coupon fabrication Informal request

9/2012 Awaiting quote for Honeywell catalyst coupons –

Equipment

• Vacuum-sealed, ultraviolet- (UV-) irradiated, FF PCO reactor bed.

• Simulated cabin air gas stream supplied to the FF PCO bed in the RVCS testbed. 

• Gas mixture analysis conducted using FTIR spectrometer.

• UVA and UVC supplied by the Solar Simulator Testbed.

Procedures 

• Honeywell catalyst would be regenerated by vacuum desorption for 1 hr during UVC irradiation. 

• Load Honeywell calayst with a known amount of ethanol and irradiated by UV in a closed-loop 

photocatalytic reactor.

• Rates of intermediate formation during PCO will be measured using FTIR as a function 

of moisture present in the gas stream.

• The effects of toluene and xylene on intermediate formation will be studied.
14
15

APPENDIX B—BENCH-SCALE DEVELOPMENT OF A CATALYST FOR SELECTIVE 

CONVERSION OF AMMONIA TO NITROGEN

B.1 Summary

Research Goals

• Demonstrate that NH3 (2–5 ppm) from spacecraft cabin gas streams can be converted to N2

using selective catalytic oxidation (SCO). 

• Develop a low-temperature, platinum-based catalyst (LTP catalyst) for SCO.

• Demonstrate that LTP catalyst reduces the temperature required for NH3 removal.

• Demonstrate that LTP catalyst does not produce toxic nitrogen oxides (NOx) (nitric oxide (NO) 

and nitrogen dioxide (NO2)) and reduces nitrous oxide (N2O) formation.

• Study the effect of water vapor and temperature on NH3 removal from spacecraft gas streams 

using SCO. 

Equipment

• Gas mixture analysis was conducted using FTIR spectrometry in the RVCS testbed. The RVCS 

was modified by adding a 66-L semisealed chamber. 

• Permeation tubes for the gas generator were expensive and could not supply enough NH3, thus 

a custom NH3 generator was designed, tested, and implemented.

• The LTP catalyst was contained within the 0.5-in-diameter bed of the RVCS. Bed temperatures 

were controlled between 23 and 220 °C. The fine powder was contained using 100 mesh screens.

Procedures 

• The LTP catalyst was synthesized at the Air Revitalization Lab, KSC.

• The RVCS was configured to run in closed-loop mode to measure NH3 removal rate and NO, 

N2O, and NO2 production using several LTP catalyst formulations at various temperatures. 

• The NH3 generator was used to supply 17 ppm and 450 ppm NH3 to 66 L of air recirculated 

through 3.2 g of LTP catalyst contained in the heated RVCS sorbent bed.

Key Results

• ARREM-funded FY 2012 work at KSC developed LTP catalyst that oxidizes NH3 into N2 and 

only produces trace amounts of N2O at 150 °C. The ability of the LTP catalyst to remove NH3

from cabin air at low temperatures (150 °C) was demonstrated.

• The LTP catalyst is a fine powder that causes a large pressure drop when used in a catalyst bed.

• The LTP catalyst powder is also hard to contain within the catalyst bed volume as it passes 

through 50–100 mesh screens.
16

B.2 Synthesis of a Low-Temperature, Platinum-Based Catalyst for Ammonia Removal

B.2.1 Overview

 Air revitalization technologies maintain a safe atmosphere inside spacecraft by the removal 

of CO2, NH3, and trace contaminants. NH3 onboard the ISS is produced by crew metabolism, 

payloads, or accidental release of thermal control refrigerant. TCC onboard the ISS is accomplished not only by the TCCS, but also by other Environmental Control and Life Support System 

subassemblies. These additional removal routes include absorption by humidity condensate in the 

temperature and humidity control condensing heat exchanger and adsorption by the CDRA. 

 Currently, the ISS relies on removing NH3 via humidity condensate and hooded respirators 

(during emergencies). A better approach to cabin NH3 removal is SCO because it builds on existing 

thermal catalytic oxidation concepts that have flight experience and could be more readily incorporated into the existing TCCS process equipment architecture on the ISS.

 SCO of NH3 is carried out via the mechanism shown in equations (1)–(3): 

 2NH3 + 3/2O2 → N2 + 3H2O + 151 kcal , (1)

 2NH3 + 2O2 → N2O + 3H2O + 132 kcal , (2)

and

 2NH3 + 5/2 O2 → 2NO + 3H2O + 108 kcal . (3)

 At low temperatures (<500 °C), all three N2-containing products (N2, N2O, and NO) are 

formed simultaneously in various proportions in the presence of many catalysts. The challenge of 

implementing SCO is to reduce formation of undesirable byproducts like NOx (N2O and NO).

 An LTP catalyst was developed at KSC in FY 2012 for converting NH3 to H2O and N2 gas 

by SCO. This SCO catalyst could significantly reduce the upstream sorbent bed size of TCCS to 

address only organo-silicone compounds, which currently also adsorbs NH3. 
17

B.2.2 Low-Temperature, Platinum-Based Catalyst Synthesis

 The LTP catalyst (fig. 2) was synthesized by doping ZSM-5 with diamine-Pt-nitrite. The Pt 

was doped using various impregnation methods. After impregnation, the LTP catalyst was dried at 

120 °C overnight and calcined at 500 °C for 6 hr in a muffler furnace.

Figure 2. LTP catalyst samples. 
18

B.3 Study of Ammonia Removal Using Closed-Loop Fourier Transform Infrared Spectrometer

B.3.1 Regenerable Volatile Organic Compound Control System Modifications

 The RVCS testbed (fig. 3) was modified by adding a 66-L semisealed chamber and an NH3

generator. The RVCS was reconfigured in a closed-loop mode to test the SCO NH3 removal rate 

using the LTP catalyst. An NH3 generator was devised to supply NH3 concentrations ranging from 

1 to 700 ppm to a 66-L chamber. A pump recirculates chamber air among the chamber, FTIR, and 

catalyst bed. The FTIR measures NH3, NO, N2O, and NO2 production during SCO.

Chamber

66 L

Heated

LTP

Catalyst

Closed Loop

Pump

NH3

Gen.

FTIR

Figure 3. RVCS block diagram.
19

B.3.2 Ammonia Generation Methods

 NH3 permeation tubes for the KIN-TEKTM gas generator of the RVCS were expensive and 

could not supply enough NH3, thus a custom NH3 generator was designed, tested, and implemented. NH3 was generated by supplying ammonium chloride (NH4Cl) solutions of known molarity onto excess sodium hydroxide (NaOH) pellets. NH3 is released into a 2-L NH3 generator (fig. 4) 

as an NH4Cl solution is delivered to NaOH pellets via syringe. NO2 was found to be generated via 

this prodedure. The NH3 generated in the NH3 generator can be swept into the 66-L chamber as 

needed to bring the NH3 concentration in the chamber to the same initial concentration.

Figure 4. Custom gaseous NH3 generator.
20

B.4 Low-Temperature, Platinum-Based Catalyst Testing

B.4.1 Platinum Content

The amount of Pt dopant was varied, and the amount of NO produced at 165 °C was found 

to increase as the amount of Pt was decreased.

B.4.2 Chamber Gas Composition—Ammonia Removal Experiment

The 66-L chamber was filled with lab air, which contains atmospheric NO, and with water 

vapor. Initially, the gas was recirculated bypassing the catalyst bed. Then, the gas was mixed with 

NH3 generated in the NH3 generator (fig. 5), and NH3 concentration (right axis) rose up to 18 ppm 

after 1 hr. The gas generator introduced up to 0.1 ppm of NO and NO2. The chamber was then 

recirculated, bypassing the bed, and the concentration of most gases (NH3, CO2, NO, and NO2) 

decreased at the chamber leak rate. At 1.8 hr, the gas generator increased the NH3 concentration, 

and the air was circulated through the LTP catalyst bed. At 3.2 hr, the NH3 was increased again 

and allowed to flow through the bed. NH3 was added to the 66-L chamber with the NH3 generator 

and leak rate measured in the first 1.7 hr. NH3 removal by the LTP catalyst was measured after 

1.7 hr.

1

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

0

20

15

10

5

0

25

012345

Time (hr)

Concentration (ppm)

Ammonia Concentration (ppm)

Carbon Dioxide

Nitrogen Dioxide 

Nitrous Oxide

Nitric Oxide 

Ammonia

Figure 5. RVCS chamber NH3 concentration dynamic.
21

B.4.3 Chamber Leak Rates

The 66-L chamber was found to be leaky, thus its leak rate had to be determined in order 

to accurately determine NH3 removal rates. NH3 concentration in the chamber (Cch) will decrease 

due to a concentration gradient to a lower external concentration (Cext). The chamber leak rate was 

determined by fitting NH3 concentration data to equation (4):

Leak (%/hr) = (100/Δt) × ln(([Cch1] – [Cext1]) / ([Cch2] – [Cext2])) . (4)

NH3 concentration in the 66-L chamber decreased when the LTP catalyst bed was not present due to the chamber leak rate. The NH3 removal obtained from changes in chamber concentration must be corrected for the leak rate. The chamber leak rate (fig. 6) was found to be 30%–33%/hr, 

and it was sensitive to the recirculating flow rate of the closed-loop system. The chamber leak rate 

was also confirmed by using changes in chamber CO2 concentration.

22

13

14

15

16

17

18

19

20

21

12

0 0.2 0.4 0.6 0.8 1

Time (hr)

Ammonia Concentration (ppm)

No Bed - 0.14 SLPM

No Bed - 0.3 SLPM

8/30 - 21 °C

8/30 - 50 °C

8/29 - 100 °C

Figure 6. RVCS chamber NH3 concentration decay profile.
22

B.4.4 Ammonia Removal Versus Ammonia Concentration

The NH3 removal rate corrected for chamber leak rate (rNH3) was determined at 150 °C 

and 1.4% water vapor using two NH3 concentrations (table 2). The rNH3 was 3.3 mg/g/hr at 

17 ppm and rose to 53 mg/g/hr. The NH3 removal rates for a 500-g bed of LTP catalyst at 150 °C 

were 1.7 g/hr and 27 g/hr at 17 ppm and 420 ppm, respectively. N2O concentration in the 66-L 

chamber increased dramatically as the LTP catalyst bed temperature exceeded 170 °C.

Table 2. NH3 removal rate corrected for RVCS 

chamber leakage.

Ammonia Concentration 

(ppm)

Chamber Leak Rate

(mg/g/hr)

Bed Removal Rate

(g/hr)

17 3.3 1.7

420 53 27

B.4.5 Temperature Effects

The N2O concentration in the 66-L chamber was 0.35 ppm from a catalyst bed temperature of 20 to 150 °C (fig. 7). N2O concentration in the 66-L chamber increased dramatically as the 

LTP catalyst bed temperature exceeded 170 °C. It rose to 0.47 ppm at 170 °C and was 1.8 ppm at 

200 °C. Nitric oxide and NO2 formation was not detected during NH3 removal via SCO with the 

LTP catalyst. 

2

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

0

50 70 90 110 130 150 170 190 210

Bed Temperature (°C)

Nitrous Oxide Concentration (ppm)

Nitrous Oxide

Figure 7. Temperature influence on N2O concentration in the RVCS chamber.
23

B.4.6 Pressure Drop

 The bed containing 3 g of LTP catalyst decreased the flow rate through it by 50%. The 

talcum powder consistency of the LTP catalyst resulted in a large pressure drop. It was also hard to 

contain with 100 mesh screens. The powder was found outside the bed on several occasions.

B.5 Future Development of Low-Temperature, Platinum-Based Catalyst

B.5.1 Microlith Development

 The LTP catalyst is a fine powder, which leads to high pressure drop and poor containment. 

Future work should aim to reduce pressure drop and improve reliability. PCI was contacted for 

exploring the possibility of coating the LTP catalyst onto Microlith metal mesh elements. A nondisclosure agreement was established with PCI, and they submitted a statement of work. This work 

is being proposed as a KSC Center Investment Fund proposal. The current Technological Readiness Level (TRL) of the LTP catalyst is 2. The expected TRL after incorporating it onto Microlith 

is 3.
24
25

REFERENCES

1. Luna, B.; Somi, G.; Winchester, J.P.; et al.: “Evaluation of Commercial Off-the-Shelf Sorbents 

and Catalysts for Control of Ammonia and Carbon Monoxide,” Paper Presented at AIAA 

2010, 40th International Conference on Environmental Systems, Barcelona, Spain, July 11–15, 

2010.

2. Pruitt, M.W.; and Perry, J.L.: “Estimated Characteristics of a Trace Contaminant Control 

System for the Heat Melt Compactor,” NASA Marshall Space Flight Center, AL, 12 pp., 

June 2012. 
26

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