Degradation of toluene vapor using vacuum ultraviolet photolytic a way to reduce air pollution

Changes of outlet toluene concentration inlet concentration at 200 ppm after apply VUV radiation .... Changes of outlet toluene concentration inlet concentration at 150 ppm after apply V

THAI NGUYEN UNIVERSITY

UNIVERSITY OF AGRICULTURE AND FORESTRY

Study Mode: Full-time

Major: Environmental Science and Management Faculty: Advanced Education Programs Office Batch: 2014 - 2018

Thai Nguyen, 25/09/2018

ACKNOWLEDGEMENT

I would like firstly to emphasize the sincere appreciation to lecturers in the Advance Education Program as well as lecturers in Thai Nguyen University of Agriculture and Forestry, who have lectured me profound knowledge not only for

my subjects but also for my soft skills and gave me a chance to do my thesis abroad

In addiction, I would like to thank all supports and help from Department of Environmental Engineering, Falculty of Engineering, King Mongkut’s University Technology of Thonbori for the time I conducted my research in Thailand

He also helps me a lot in spending much tim checking my thesis report

Finally, I would like to express my gratitude to my family and friends, who always beside me all the time Their help support and encouragements created the pump leading me to my success

Sincerely Khanh

Le Ngoc Khanh

TABLE OF CONTENT

ACKNOWLEDGEMENT i

TABLE OF CONTENT ii

LIST OF FIGURES iv

LIST OF TABLES v

LIST OF ABBREVIATIONS vi

DOCUMENTATION PAGE WITH ABSTRACT vii

PART I INTRODUCTION 1

1.1 Research rationale 1

1.2 Reasearch’s Objectives 2

1.3 Research questions and hypothesis 2

1.4 Limitations 3

1.5 Definitions 3

1.5.1 Toluene 3

1.5.2 Standard of toluene 5

PART II LITERATURE REVIEW 7

PART III METHOD 10

3.1 Materials 10

3.2 Method 10

3.2.1 Experiment setup 10

3.2.2 Calculate flow rate of gas based on a retention time 11

3.2.3 Experimental setup 13

PART VI RESULT AND DISSCUSION 14

4.1 Result 14

4.1.1 Reduction of outlet concentration of 200 ppm and C/Co(%) 14

4.1.2 Reduction of outlet concentration of 150 ppm and C/Co(%) 16

4.1.3 Reduction of outlet concentration of 100 ppm and C/Co(%) 19

4.2 Disscusion 21

4.2.1 Reduction of outlet concentration 21

4.2.1.1 Inlet concentration of 200 ppm 21

4.2.1.2 Inlet concentration of 150 ppm 22

4.2.1.3 Inlet concentration of 100 ppm 23

4.3 Removal efficiecy 23

4.3.1 C/Co efficiency at 200 ppm inlet concentration 23

4.3.2 C/Co efficiency at 150 ppm inlet concentration 24

4.3.3 C/Co efficiency at 100 ppm inlet concentration 25

4.3.4 Comparison of removal efficiency of toluene 25

PART V CONCLUSION 27

REFERENCE 28

PART VI APPENDICES 32

LIST OF FIGURES

Figure 1.1 Chemical properties of toluene 3 Figure 1.2 Schematic diagram of experiment setup 11 Figure 1.3 Size of reactor 12 Figure 1.4 Changes of outlet toluene concentration (inlet concentration at 200 ppm)

after apply VUV radiation 22 Figure 1.5 Changes of outlet toluene concentration (inlet concentration at 150 ppm)

after apply VUV radiation 22 Figure 1.6 Changes of outlet toluene concentration (inlet concentration at 100 ppm)

after apply VUV radiation 23 Figure 1.7 Changes of removal efficiency at the inlet concentration of 200 ppm 24 Figure 1.8 Changes of removal efficiency at the inlet concentration of 150 ppm 24 Figure 1.9 Changes of removal efficiency at the inlet concentration of 100 ppm 25 Figure 1.10 Comparison of toluene removal efficiency for the inlet concentrations

of 100, 150, and 200 ppm 26

LIST OF TABLES

Table 1.1 Physical properties of toluene 4 Table 1.2 Occupational Exposure Limits of toluene from USA 5 Table 1.3 Maximum allowable concentration of some hazardous substances in

ambient air in Viet Nam (Legal 2006) 6 Table 1.4 List of materials used in the experiment 10 Table 1.5 Calculate the flow rate based on retention time 12 Table 1.6 Degradation and removal efficiency of outlet concentration of 200 ppm 14 Table 1.7 Degradation and removal efficiency of outlet concentration of 150 ppm 17 Table 1.8 Degradation and removal efficiency of outlet concentration of 100 ppm 19

LIST OF ABBREVIATIONS

VUV Vacuum Ultraviolet

VOC Volatile organic compounds

CNS Central nervous system

PID Photoionization detection

OSHA PEL The Occupational Safety and Health Administration

STEL Short-term exposure limit

NIOSH IDLH The National Institute for Occupational Safety and Health

immediately dangerous to life or health ACGIH TLV American Conference of Governmental Industrial Hygienists

threshold limit value AIHA ERPG-2 American Industrial Hygiene Association emergency response

planning guideline WHO World Health Organization

PEL Permissible exposure limit

DOCUMENTATION PAGE WITH ABSTRACT

Thai Nguyen University of Agriculture and Forestry

Degree Program Bachelor of Environmental Science and Management

Thesis Title Degradation of Toluene Vapor using Vacuum

Ultraviolet Photolytic : A Way to Reduce Air

Pollution Supervisor (s) Nguyen Hung Quang

Supervisor’s signature (s)

Abstract

Vacuum ultraviolet is a simple way to destruct volatile organic compounds (VOCs) In this paper, we are experiment the concentration of toluene during 30 minutes open VUV lamp Results indicate that the toluene removal efficiency is only 11 % in the VUV process This process is depend on the influence concentration of toluene, the concentration of toluene increased, removal efficiency decreased and the concentration decreased, removal efficiency increased

VUV radiation Flow rate Removal efficiency Toluene concentration VUV

PART I INTRODUCTION 1.1 Research rationale

Organic compounds are chemicals that contain carbon and are usually found

in all living things Volatile organic compounds, sometimes referred to as VOCs, are organic compounds that easily become vapors or gases (high vapor pressure) Most of VOCs has a low boiling point of less than 15 C However, some VOCs may also contains some other substitutes such as hydrogen, oxygen, fluorine, chlorine, bromine, sulfur or nitrogen, which may cause more harmful effects to human VOCs are commonly released from burning fuel, such as gasoline, wood, coal, or natural gas They are also emitted from oil and gas fields and diesel exhaust They are also released from solvents, paints, glues, and other products that are used and stored at home and at work

A number of petrochemical industry and some other types of industry also produces or uses many types of VOCs in their processes Loss of those chemicals into air has been investigated more than 500 tons per year from industrial sector in Thailand Exposure with multi VOCs may associate with various syndromes, such

as fatigue, nausea, impaired vigilance, confusion, drowsiness, irritant-induced asthma, and some respiratory symptoms High exposure of VOCs at short period may cause various actual effects, whereas many species of VOCs has a close-link to

be a major cause of cancer (called “carcinogen”) For example, formaldehyde and benzene are considered by many authorities to be probable human carcinogens

Nowadays, there are totally 5 conventional techniques to control VOCs emission from various types of industry, which are absorption, adsorption, incineration/oxidation, bio-filtration, and condensation Each technique has their own advantages and limitations Absorption commonly limits on VOC gas solubility in the selected liquid used in thes system Smaller liquid droplet may increase the solubility of the gas Adsorption is a promising technology, which always provides high removal efficiency, but the cost of operation and dispose is also high Incineration/oxidation is generally applied for VOCs emission at high concentration, which high enough to be self-ignition Lower concentration may also increase operation costs due to additional co-fuel in the system Bio-filtration is a

cheapest technology, which has low investment and operation cost The microorganism including bacteria and fungi are immobilized in the biofilm and degrade the pollutant in the system Due to the system rely mainly on microbial growth, bio-clogging may be found for sometime The condensation is one of the recycling technologies to condense the gaseous pollutants (VOC) to become liquid under high pressure and/or low temperature However, pollutant concentration should be high for cost effectiveness

Vacuum Ultraviolet, or VUV, (has wavelengths shorter than 200 nm) are strongly absorbed by molecular oxygen in the air Longer wavelengths of about 150–200 nm can propagate through nitrogen, which is highly active for VOCs oxidation A VUV lamp emits UV light at a wavelength of 185 nm and generated energetic photons that can activate oxygen and water vapor to produce numerous reactive species such as O(D), O(P), hydroxyl radicals (OH) and Ozone VUV has been used to destruct various VOCs including benzene, toluene Nevertheless, its application is greatly limited by the formation of O3 byproduct and low degradation capacity and mineralization rate for VOC destruction

In this study, VUV was applied to remove toluene vapor from synthesis gas,

as a case study Oxidation of VOCs was performed under VUV radiation in a continuous flow reactor

1.2 Reasearch’s Objectives

To assess the efficiency of toluene removal using VUV radiation in a continuous flow reactor

1.3 Research questions and hypothesis

1 A breach-scale experiment was set up at the Department of Environmental Engineering, King Mongkut’s University of Technology Thonburi (KMUTT) A 3-L stainless reactor was selected in the study

2 Toluene vapor was simulated using a toluene generator developed under this study

3 A continuous flow experiment was

4 The removal efficiency was assessed using measurement at inlet and outlet of the reactor

5 A multi-gas detector (MultiRae) was used for measurement of toluene concentration based on photoionization detection (PID)

6 Optimum inlet concentration was also studied by vary an inlet gas flow rate The target inlet toluene concentrations under this study were 100, 150, and 200 ppm

1.4 Limitations

The old VUV lamp is used that may ganerate the weak radiation, which

affect to the result of this experiment Reactor design should be mentioned because

we do not have enough time to design the reactor

Time is also a limitation to conduct this experiment because the internship was taken place on only three and half of a month It took time to study about this new field of air pollution and searched the information about VUV, also knowledge

Figure 1.1 Chemical properties of toluene

Table 1.1 Physical properties of toluene

Physical state and appearance Clear liquid

Vapor density at 0°C 3.1 (Air = 1)

Log K (octanol/water coefficient) 2.72

Flammability classification Flammable liquid

Toluene is used as an additive in gasoline mixtures to increase octane ratings,

in benzene production, and as a solvent in paints, coatings, inks, adhesives, and cleaners Additionally, toluene is used in the production of nylon, plastics, and polyurethanes Toluene was once used as a medicinal anthelmintic agent against

roundworms and hookworms.Toluene (methylbenzene) is a natural substance of gasoline and crude oil It is also used for synthesis of benzene and other chemicals, including graphic pigments, paints, and solvents It is a highly lipophilic white matter toxin resulting in loss of myelin in cerebral and cerebellar white matter, as well as in diffuse cerebral and cerebellar atrophy

Toluene is irritating to the skin, eyes, and respiratory tract It can cause systemic toxicity by ingestion or inhalation and is slowly absorbed through the skin The most common route of exposure is via inhalation Symptoms of toluene poisoning include CNS effects (headache, dizziness, ataxia, drowsiness, euphoria, hallucinations, tremors, seizures, and coma), ventricular arrythmias, chemical pneumonitis, respiratory depression, nausea, vomiting, and electrolyte imbalances

1.5.2 Standard of toluene

The American Conference of Governmental Industrial Hygienists (ACGIH) (1997) has recommended 188 mg/m3 as the 8-h time-weighted average threshold limit value, with a skin notation, for occupational exposures to toluene in workplace air Values of 100– 380 mg/m3 are used as standards or guidelines in other countries (International Labor Office, 1991) The World Health Organization has established a provisional international drinking water guideline for toluene of 700 μg/L (WHO, 1993)

Table 1.2 Occupational Exposure Limits of toluene from USA

OSHA PEL ( Occupational Safety and

Health Administration permissible

exposure limit)

200 ppm (averaged over an 8-hour work-shift)

OSHA STEL (short-term exposure limit) 500 ppm (10-minute exposure)

NIOSH IDLH (immediately dangerous

to life or health)

500 ppm

ACGIH TLV (threshold limit value) 50 ppm (averaged over an 8-hour

work-shift) AIHA ERPG-2 (emergency response

planning guideline) (maximum airborne

concentration below which it is believed

that nearly all individuals could be

exposed for up to 1 hour without

experiencing or developing irreversible

or other serious health effects or

symptoms which could impair an

individual's ability to take protective

action)

300 ppm

Table 1.3 Maximum allowable concentration of some hazardous substances in

ambient air in Viet Nam (Legal 2006)

Inorganic substances Chemical formula The average time Allowable

concentration Toluene

Unit: Microgram per

cubic meter (μg/m3)

1.5.3 Vacuum ultraviolet Vacuum Ultraviolet, or VUV, wavelengths (10 -

200 nm) are strongly absorbed by molecular oxygen in the air, though the longer wavelengths of about 150–200 nm can propagate through nitrogen, which are highly active for VOCs oxidation A VUV lamp emits UV light at wavelength of

185 nm and generates energetic photons that can activate oxygen and water vapor to produce numerous reactive species such as O(D), O(P), hydroxyl radicals (OH) and Ozone VUV has been used to destruct various VOCs including benzene, toluene Nevertheless, its application is greatly limited by the formation of O3 byproduct and low degradation capacity and mineralization rate for VOC destruction

PART II LITERATURE REVIEW

Nowadays, air pollution is one of the most serious problems in the world It refers to the contamination of the atmosphere by harmful chemicals or biological materials especially VOCs, SO2 and NO2 pollutants Base on this issues, Chinese’s researcher was found the way to reduced VOCs gaseous pollutant by using VUV radiation and catalyst

Huang and Leung (2014) had conducted the enhanced degradation of gaseous benzene under vacuum ultraviolet (VUV) radiation over TiO2 (titanium dioxide) modified by transition metals They found that, the highest benzene removal efficiency achieved 58% with photocatalysts as Mn/Tio2, Co/TiO2, Ni/TiO2and P25 have the same benzene removal efficiency (50%) But it was declined to 45% for both Fe/TiO2 and undoped TiO2 This is because benzene could not able to

be destructed There was no ozone produced in radiation of 254 nm UV lamp This indicated that the effect of direct photo-oxidation and catalytic ozonation of benzene were absent In the study, water vapor played a dual role in benzene oxidation in the VUV-PCO process Catalytic is mostly responsible for benzene abatement at low humidity while 185 nm photooxidation is the dominant pathways at high humidity

Huang (2016) studied the photo catalytic oxidation of gaseous benzene under VUV radiation over TiO2/Zeolites catalysts 100% benzene removal efficiency was achieved over TiO2/zeolite due to the contribution of absortion in initial stage The benzene absorption capacity does not only depend on BET (Brunauer-Emmett-Teller theory) surface area but also pore diameter of zeolite The product of benzene photocatalytic oxidation was only CO2

Zhao(2013) evaluated the health risk of vacuum ultraviolet (VUV) photolysis

of naphthalene (NP) in indoor air, intermediates were detected by gas chromatograph–mass spectrometry and proton transfer reaction-mass spectrometry His result shown the accumulation of VOCs, especially highly harmful aldehydes, resulted in an increased of health risk influence index (ᶯ ) to 150 after VUV irradiation of 2.81 min, while the mineralization of VOCs led to a sharp reduce of (ᶯ ) to 28 after VUV irradiation of 7.01 min It could be concluded that the mineralization of VOCs was a key factor to alleviate the health risk of photolysis

The results will give a safe and economical application of VUV photolysis technology in indoor air purification

Chaolin Li(26 February 2014) researched on Photolysis of low concentration H2S under UV/VUV irradiation emitted from high frequency discharge electrodeless lamps The photolysis of low concentration of H2S malodorous gas was studied under UV irradiation emitted by self-made high frequency discharge electrodeless lamp with atomic mercury lines at 185/253.7 nm In their study, researcher have shown that a high efficiency for H2S removal (>90%) in the presence of low [H2S] (3.1–29.6 mg m^-3) at various gas residence time (2.9–23.2 s) More importantly, the significant effects of relative humidity and oxygen concentration on H2S removal demonstrated that the media played an significant role in the photolysis processes, which is to some extent capable of probing into the mechanisms of photolysis Possible mechanisms for photolysis includes: direct photolysis by UV/VUV light and indirect photolysis mediated by ozone and hydroxyl radicals

Huiling Huang and Haibao Huang(6 January 2016) examined the Efficient degradation of gaseous benzene by VUV photolysis combined with ozone-assisted catalytic oxidation: Performance and mechanism In this study, they are the first combining an efficient Mn/ZSM-5 catalyst with VUV photolysis to eliminate O3 and improved VOC degradation efficiency via ozone-assisted catalytic oxidation (OZCO) Results indicate that the benzene removal efficiency was only 48% with

83 ppm residual O3 in the VUV photolysis process However, both benzene and O3 were completely removed after the adoption of the Mn/ZSM-5 catalyst The possible degradation pathways and mechanism in such a novel VUV-OZCO process was proposed according to the identified products This study provided an efficient and potential process with promising insights for the degradation of VOCs

In our study, toluene was selected as the representative VOCs due to its high toxicity and photochemical activity Toluene was testes in a closed system under vacuum ultraviolet radiation The concentrations of toluene at inlet and outlet were observed Noted that the outlet concentration was start measured when VUV lamp turn on

Toluene is a compound of the benzene series At room temperature, toluene

is a clear-to-amber colorless liquid with a pungent, benzene-like odor Although it is

a liquid at room temperature, toluene’s low vapor pressure results in extensive volatilization It is flammable with a flash point of 4.4 oC Toluene is strongly reactive with a number of chemical classes, particularly nitrogen-containing compounds, and may react with some plastics ACGIH (2000) has recommended an 8-hour time-weighted average (TWA) of 50 ppm (189 mg/m3) for toluene to protect against effects on the central nervous system OSHA (1993) has promulgated an 8-hour permissible exposure limit (PEL) of 200 ppm (754 mg/m3)

The principal source of toluene exposure for the general population is gasoline, which contains 5% to 7% toluene by weight Toluene is released to the atmosphere during the production, transport, and combustion of gasoline Not surprisingly, toluene concentrations are highest in areas of heavy traffic, near gasoline filling stations, and near refineries Toluene is short-lived in ambient air because of its reactivity with other air pollutants Toluene is used in aviation gasoline and high-octane blending stock, and as a solvent for paints, coatings, gums and resins Other sources include tobacco smoke, petroleum and coal production, use as a chemical intermediate, and for styrene production

The highest concentrations of toluene usually occur in indoor air from the use of common household products (paints, paint thinners, adhesives, synthetic fragrances and nail polish) and cigarette smoke The deliberate inhalation of paint or glue may result in high levels of exposure to toluene, as well as to other chemicals,

PART III METHOD 3.1 Materials

The list of materials used in this experiment is shown below

Table 1.4 List of materials used in the experiment

measurement of outlet toluene concentration Removal efficiency of toluene was estimated Valve#1, #2 and #3 were installed to control volume of gas passing into the pipe A 3-L stainless reactor was selected in the study to reduce the toluene adsorption effect on the surface of reactor

Figure 1.2 Schematic diagram of experiment setup

3.2.2 Calculate flow rate of gas based on a retention time

To study changes of efficiency due to a retention time, a target flow rate was calculated based on a retention time in the reactor at 0.5, 1, 2, 3, and 4 minutes Detail calculation is shown as below

Table 1.5 Calculate the flow rate based on retention time

Retention time (min) Volume (m³) Flow rate(m³/min) Flow

Figure 1.3 Size of reactor

Based on the volume of reactor, the target flow rate was calculated as shown

in Table 1.5 A rotameter was installed to control a flow rate of gas passing through the reactor

3.2.3 Experimental setup

Step 1: Set the inlet toluene concentration at 100 ppm and controll the concentration to be stable within 30 minutes Check the toluene concentration for every 1 minute during the control period (30 minutes)

Step 2: Check the leakage of the system (with VUV lamp but not turn on) by measuring the outlet concentration for every 1 minutes during 30 minutes The outlet concentrations are expected to be equal with the inlet one

if the outlet concentrations stable at 100 ppm, the experiment can be

started by turn on the VUV lamp

if the concentration is not stable 100 ppm, the inlet concentrations should be recheck again by going back to Step 1

Step 3: Activated carbon was installed to clean the remaining toluene at the outlet

Step 4: Start the experiment by turn on the VUV lamp and measure the outlet concentrations for every 1 minute during 30 minutes

Step 5: Adjust the inlet toluene concentrtions at 150 and 200 ppm, respectively and start step 1, 2, 3 and 4 again After the experiment, the system efficiencies for

toluene removal were calculated

The experiment was taken place at laboratory of the Department of Environmental Engineering, Faculty of Engineering We conducted 3 sample of toluene concentration at 100, 150 and 200 ppm respectively For each sample, the concentration is measured 30 times before we turned on VUV lamp and 30 times with VUV lamp turned on