Grantee Research Project Results
Final Report: Novel Catalytic Air Cleaner for Removal of VOCs and Particulates From Indoor Air
EPA Contract Number: 68D99073Title: Novel Catalytic Air Cleaner for Removal of VOCs and Particulates From Indoor Air
Investigators: Scott, David J.
Small Business: UItramet
EPA Contact: Richards, April
Phase: I
Project Period: September 1, 1999 through March 1, 2000
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (1999) RFA Text | Recipients Lists
Research Category: SBIR - Air Pollution , Small Business Innovation Research (SBIR) , Air Quality and Air Toxics
Description:
The ever-growing concern over air quality has led to considerable legislation to control atmospheric concentrations of ozone, nitrogen oxides, sulfur oxides, and volatile organic compounds. However, much work remains before an acceptable measure of indoor air quality is adopted. This is due in part to the lack of universal standards for indoor air quality. These issues and the abundant evidence of so-called sick building syndrome will lead to the need for indoor air quality regulations and the means to attain those standards. The development of innovative and cost-effective control measures for indoor air pollutants has thus become nearly as important as those already developed for atmospheric pollutants.Over the past three decades, the low temperature catalytic oxidation of volatile organic compounds (VOCs) has been improved considerably as part of emission control efforts for combustion engine exhaust generated from transportation and energy production sources. State-of-the-art devices, however, require a minimum temperature of 200-300?C to achieve conversion rates of more than 50%. The removal of relatively small amounts of VOCs at or near room temperature is far more challenging. No existing catalyst system is known to exhibit a sufficiently high catalytic activity in the 0-200?C temperature range while exhibiting adequate lifetime to accomplish this goal. New technologies must be developed to either find sufficiently active catalysts or somehow enhance existing catalytic activity by several orders of magnitude.
To achieve these goals, Ultramet pursued an approach based on the recently discovered phenomenon that the activity of a metal catalyst can be increased by at least two orders of magnitude via non-Faradaic electrochemical modification of catalytic activity (NEMCA). The NEMCA effect involves the use of a small electric potential to modify the surface of a metal catalyst by inducing spillover of ions of hydrogen and oxygen from a supporting solid electrolyte onto a metal catalyst surface. These ions are able to greatly reduce the activation energy for dissociative adsorption of molecules and their reaction with each other such that rapid and complete oxidation of VOCs is achieved near room temperature. The ions on the catalyst surface enhance dissociative adsorption of many molecules such as VOCs and oxygen, leading to highly reactive molecule fragments and atoms. The surface metal atoms function as redox centers aiding the various reduction and oxidation processes.
In this project, Ultramet demonstrated the feasibility of a catalytic air filtration element utilizing an open-cell foam substrate coated with a mixed metal oxide electrolyte/metal catalyst system exhibiting complete conversion of VOCs near room temperature and under high flow rate conditions. Subscale catalyst performance was characterized, and the life of the air filter system and its compatibility with current heating, ventilation, and air conditioning systems was evaluated and shown to be feasible. In addition, the open-cell structure of the foam substrate can act as an efficient particulate filter, and particulate collection efficiency was characterized as well.
Summary/Accomplishments (Outputs/Outcomes):
Of the more than 24 electrolyte/catalyst systems evaluated, three individual systems stood out for various reasons, including their low temperature oxidation, high rate of reaction, and overall performance. All of these systems exhibited efficiencies of at least 10% and as high as 40% at 100?C, which is noteworthy when the residence time of the contaminant within the system, the rate of reaction, and the overall efficiency are taken into account.At the outset of the project, dodecane (*) had been selected as the baseline contaminant of interest in conjunction with the EPA project officer. However, available instrumentation at Ultramet was unable to quantify the concentration of this compound, and propylene (*) was used as an alternative. The target operating conditions were defined as follows:
- Propylene concentration: 100 ppmv
- Gas face velocity: 50 ft/min
- Relative humidity: 10-30%
- 25% conversion temperature, single-pass mode: ambient (y23?C)
Test results for systems #1 and #2 indicated that complete conversion of propylene was achieved under the following conditions:
- Propylene concentration: 100 ppmv
- Gas face velocity: 50 ft/min
- Relative humidity: 10-30%
- >98% conversion temperature, single-pass mode: >175?C
- Residence time: 0.1 sec
Test results for system #3 indicated that complete conversion of propylene was achieved under the following conditions:
- Propylene concentration: 100 ppmv
- Gas face velocity: 50 ft/min
- Relative humidity: 10-30%
- >98% conversion temperature, single-pass mode: >200-250?C
- Residence time: 0.1 sec
Low temperature oxidation efficiency was exemplified by system #2, whose y40% efficiency was achieved at 100?C while the other systems operated at about 10% efficiency:
- Propylene concentration: 100 ppmv
- Gas face velocity: 50 ft/min
- Relative humidity: 10-30%
- 40% conversion temperature, single-pass mode: 100?C
- Residence time: 0.1 sec
Characterization of particulate collection had several unexpected results. High PM collection efficiencies for 0.03- and 0.5-µm particle sizes were most likely the result of electrostatic attraction of the submicron particles to each other, resulting in formation of a filter cake in the foam. Removal efficiencies for 10-, 25-, and 50- µm particles were <20% for all foam ppi numbers, not warranting further effort in this area.
Conclusions:
The successful completion of this project demonstrated the feasibility of this innovative air cleaner and its potential for reducing VOCs and particulates in indoor air. In potential follow-on work, Ultramet would optimize the system with regard to surface area and electrolyte and catalyst type. Specifically, three electrolyte/catalyst systems would be optimized for the low temperature removal of common indoor contaminants such as formaldehyde, tetrachloroethylene, and 1,3-butadiene. These systems would revolve around dissimilar electrolytes and catalysts that will produce various intermediates and final products of destruction. Gas chromatograph/mass spectrometer (GC/MS) analysis of the output gas streams would be performed to speciate any intermediates and the final byproducts of the catalyzed reaction, if any. This would also allow for the precise control of low concentration gas streams to better simulate the actual indoor air environment. Particular emphasis would be placed on the design and scaleup of this innovative air cleaner system. Testing at a selected installation would be conducted to evaluate the performance of the system and identify any necessary modifications required to proceed to demonstration of a pilot-scale air filtration system.In addition, Ultramet would team with experts in the field such as Engelhard and/or Johnson Matthey, with whom Ultramet is currently working in other catalyst projects, to test optimized catalyst designs. Ultramet and Honda R&D Americas Inc. have been jointly investigating radial flow catalytic systems that increase the efficiency and reduce the size of catalytic converters for automobile applications. These collaborative efforts would greatly benefit the potential follow-on effort, leading directly to commercialization in a wide range of areas such as indoor air cleaners, HVAC air purification, and catalytic converters for automobiles.
This technology can result in smaller, more efficient, and economical air cleaners capable of meeting future, more demanding indoor air standards. Additionally, automobiles, diesel trucks, locomotives, watercraft, and stationary power plants can easily employ the NEMCA-based catalysis technology at very low cost. Also, NEMCA-based water treatment systems can potentially completely remove organic pollutants from effluent wastewater streams and purify drinking water supplies.
Existing state-of-the-art components and systems for indoor air filtration and cleaning range in price from tens to thousands of dollars. In addition, many of the available systems are not practical for small-scale installations. The proposed system can be fabricated to accommodate any size installation, from a window-mounted home air conditioner to an industrial air purification system. It may be manufactured at reasonable cost for most applications, with the value-added benefit of removing VOCs and other contaminants as well as filtration of particulates.
Supplemental Keywords:
indoor air pollution; sick building syndrome; air cleaner; air filter; heating, ventilation, and air conditioning (HVAC) systems; water treatment systems; catalytic converters., Scientific Discipline, Air, Water, Sustainable Industry/Business, particulate matter, air toxics, cleaner production/pollution prevention, Wastewater, Chemistry, Technology for Sustainable Environment, mobile sources, indoor air, New/Innovative technologies, Engineering, Chemistry, & Physics, stationary sources, automotive coating, indoor air pollution control, particulates, wastewater treatment, metal catalysts, air pollutants, indoor VOC compounds, locomotive, stratospheric ozone, novel catalyst systems, electric utilities, filtration technology, pollution control technologies, VOCs, filtration, particulate emissions, air pollution control, automotive combustion, air pollution, automotive exhaust, catalysts, automobiles, emission controls, auto emissions, trucks, indoor air quality, power generation , Volatile Organic Compounds (VOCs), contaminant removal, air emissions, pollution prevention, automotive coatings, removal, power generationThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.