Stavros G. Poulopoulos

Regulated and unregulated emissions from an internal combustion engine operating on ethanol-containing fuels

In the present work, the effect of ethanol addition to gasoline on regulated and unregulated emissions is studied. A 4-cylinder OPEL 1.6 L internal combustion engine equipped with a hydraulic brake dynamometer was used in all the experiments. For exhaust emissions treatment a typical three-way catalyst was used. Among the various compounds detected in exhaust emissions, the following ones were monitored at engine and catalyst outlet: methane, hexane, ethylene, acetaldehyde, acetone, benzene, 1,3-butadiene, toluene, acetic acid and ethanol. Addition of ethanol in the fuel up to 10% w/w had as a result an increase in the Reid vapour pressure of the fuel, which indicates indirectly increased evaporative emissions, while carbon monoxide tailpipe emissions were decreased. For ethanol-containing fuels, acetaldehyde emissions were appreciably increased (up to 100%), especially for fuel containing 3% w/w ethanol. In contrast, aromatics emissions were decreased by ethanol addition to gasoline. Methane and ethanol were the most resistant compounds to oxidation while ethylene was the most degradable compound over the catalyst. Ethylene, methane and acetaldehyde were the main compounds present at engine exhaust while methane, acetaldehyde and ethanol were the main compounds in tailpipe emissions for ethanol fuels after the catalyst operation.

4 – Adsorption and Ion Exchange

Publisher Summary This chapter deals with the phenomena of adsorption and ion exchange, and highlights their role in environmental protection. Activated carbon, silica gel, and alumina are the most popular adsorbent materials in industry due to the fact that they provide large surface areas per unit weight. Activated carbon is produced from coconut shell, wood, and bone, whereas silica gel is made of hydrated silicon dioxide. Alumina can be either mined or produced by precipitated aluminum oxide and hydroxide. There are a number of cases where carbon adsorption is preferably used in water treatment—if compounds are not compliant for biodegradation, if the molecule contains branched chairs, has a large molecular weight, and low polarity, and generally, in the case of removing organic and inorganic species, for concentrations lower than 5000 and 1000 mg/L, respectively. Besides the applications of water treatment, activated carbon is called into action for the removal of volatile organic compounds, such as solvents, toxic gases, and odors from gaseous waste streams. Ion exchange shares many characteristics with adsorption, such as mass transfer from the fluid to the solid phase; there are, however, some significant differences. In ion exchange, the ions removed from the liquid phase are replaced by ions from the solid phase. So, there actually occurs an exchange of ions and not only a removal in the latter process. This principle is the basis of use of ion exchange in removing the effects of pollution in air and water.

Treatment of industrial oily wastewaters by wet oxidation

In the present work, the homogeneous wet oxidation (WO) of an oily wastewater (COD approximately 11,000 mg l(-1)), composed mainly of alcohols and phenolic compounds, was studied in a high-pressure agitated autoclave reactor in the temperature range of 180-260 degrees C and oxygen pressure 1 MPa. Temperature was found to have a significant impact on the oxidation of the contaminants in the wastewater. Among the compounds contained in the wastewater, ethylene glycol showed great resistance to wet oxidation. Temperatures above 240 degrees C were required for its effective degradation. Organic acids, mainly acetic acid, were the intermediate products of the wet oxidation process and their conversion to carbon dioxide was very slow. A generalised model based on a parallel reaction scheme was used to interpret the experimental data obtained. The activation energies obtained were in the range of 90-130 kJ mol(-1).

Photo-assisted oxidation of an oily wastewater using hydrogen peroxide

The primary objective was to study the purification of an oily wastewater from a lubricant production unit using ultraviolet irradiation and hydrogen peroxide. The influence of hydrogen peroxide concentration, initial pH of the solution and of the addition of ferric ions on the chemical oxygen demand (COD) was examined. In each case, the concentration of the compounds contained in the oily wastewater was determined. It was shown that a 20-45% COD removal was achieved with 830-1660 mg l(-1) H(2)O(2). Gas chromatography-mass spectrometry analysis showed that the organic compounds of the wastewater decomposed to organic acids that were very resistant to photo-oxidation. Among these compounds, ethylene glycol remained almost unchanged by the attack from hydroxyl radicals. Acidic pH and Fe(III) addition enhanced significantly the photo-oxidation of the wastewater.

The Effect of Adding Oxygenated Compounds to Gasoline on Automotive Exhaust Emissions

In the present work, the effect of adding ethanol or methyl tertiary butyl ether (MTBE) to gasoline on the regulated and unregulated emissions from an internal combustion engine with a typical three-way catalyst was studied. The addition of ethanol to fuel (10% w/w) increased both the research octane number and the Reid vapor pressure of the fuel, whereas adding 11% w/w MTBE caused an increase only in the research octane number of the fuel. When the fuel contained MTBE, less hydrocarbons, carbon monoxide, and acetaldehyde were emitted in the tailpipe. The increased emissions of acetaldehyde and ethanol were the main disadvantages of using ethanol.

Acetaldehyde Yield and Reaction Products in the Catalytic Destruction of Gaseous Ethanol

The catalytic destruction of ethanol (0.5% v/v) over a typical three-way catalyst (Pt/Rh/Ce) and two base catalysts (1% CuO and 10% CuO on γ-Al2O3) was studied in a continuous flow reactor, under atmospheric pressure. The effect of the temperature (100--500 °C) and of the oxygen concentration (0--10% v/v) on the operation of the tested catalysts and on the product profiles is presented. The formation of acetaldehyde during the catalytic destruction of ethanol, the main concern of ethanol addition to fuels, was extremely dependent on the oxygen concentration. It is noteworthy that more acetaldehyde was produced during the oxidation of ethanol in oxygen deficit conditions than during its decomposition in the absence of oxygen. Copper addition on γ-Al2O3 enhanced acetaldehyde formation, while less acetaldehyde amounts were produced over the noble metal catalyst.

Photo-assisted Oxidation of Chlorophenols in Aqueous Solutions Using Hydrogen Peroxide and Titanium Dioxide

Abstract In the present work, the efficiency of phenol and chlorophenol degradation under irradiation using hydrogen peroxide as oxidant and titanium dioxide powder as photo-catalyst was investigated. In the absence of titanium oxide, increased concentrations of hydrogen peroxide resulted in higher conversions. Generally, phenol was the most readily oxidized compound, whereas in excess of hydrogen peroxide, the more chlorine atoms were present in the ring, the less degradable the chlorophenol was, in terms of initial rate of oxidation. In the case of 4-chlorophenol, the catalytic photo-oxidation efficiency with hydrogen peroxide and titanium oxide was dependent on the catalyst concentration exhibiting a maximum at 0.025–0.05 g L−1 titanium oxide. The combined use of titanium oxide and hydrogen peroxide resulted in higher degree of oxidation compared to results obtained when using hydrogen peroxide. Finally, the presence of Fe(III) proved to be beneficial for the photo-catalytic oxidation only in the presence of hydrogen peroxide.

Air and Water Pollution

Human activities negatively influence the environment and nature in many ways. The production of undesirable wastewater, waste gas, and liquid plus solid residues seems to be inevitable during chemical processes. This chapter focuses on air and water pollution. Under this topic, it discusses issues of releases from chemical processes and environmental problems arising from other activities. Emphasis is given on the current environmental situation in Europe. There are many problems associated with air pollution, starting from photochemical smog, ozone formation, and acid rain at a regional level, to the greenhouse effect and ozone layer depletion at a global level. These problems have an adverse impact on both environment and public health. Water pollution is generally defined as any physical, chemical, or biological alteration in water quality that has a negative impact on living organisms. However, there is a tolerance limit for each pollutant, since zero-level pollution is economically and technically unpractical. Chemical engineering is the field of science that combines chemistry with technology and is able to provide solutions to most environmental problems. The environment is going to set the pace in chemical engineering evolution, because, if destruction and pollution are not stopped, the environment, life on Earth will be in danger—at least life as it is known today. Sustainability is the proposal for a better future, where economic development can coexist with social cohesion and environmental protection.

PHOTOCATALYTIC DESTRUCTION OF METHYL TERT-BUTYL ETHER IN THE GAS PHASE USING TITANIUM DIOXIDE

ABSTRACT The efficiency of the photocatalytic destruction of methyl tert-butyl ether (MTBE) in the gas-phase using UV light and titanium dioxide was studied. TiO2 was coated on the inner side of the photoreactor. Specifically, the effect of residence time (0.17–2.22 min), MTBE concentration (500–5000 ppm), oxygen concentration (0–20,000 ppm) and water vapor on MTBE conversion was examined. Acetone and tert-butyl formate were detected in the photoreactor effluent. The formation of by-products from MTBE decomposition was determined with gas chromatography–mass spectrometry. The residence time affected dramatically the MTBE photo-oxidation as well as by-products existence and configuration. The increase in MTBE concentration at the reactor inlet and the addition of water vapor to the reactants resulted in decreased MTBE conversions. Increasing oxygen concentration up to 10,000 ppm enhanced the photocatalytic process but a further increase to 20,000 ppm had an adverse impact on MTBE decomposition. In all cases, the by-product formation profiles were extremely dependent on photocatalysis parameters studied.

Speciated Hydrocarbon and Carbon Monoxide Emissions from an Internal Combustion Engine Operating on Methyl Tertiary Butyl Ether-Containing Fuels

ABSTRACT In the present work, engine and tailpipe (after a three-way catalytic converter) emissions from an internal combustion engine operating on two oxygenated blend fuels [containing 2 and 11% weight/weight (w/w) methyl tertiary butyl ether (MTBE)] and on a nonoxygenated base fuel were characterized. The engine (OPEL 1.6 L) was operated under various conditions, in the range of 0-20 HP. Total unburned hydrocarbons, carbon monoxide, methane, hexane, ethylene, acetaldehyde, acetone, 2-propanol, benzene, toluene, 1,3-butadiene, acetic acid, and MTBE were measured at each engine operating condition. As concerns the total HC emissions, the use of MTBE was beneficial from 1.90 to 3.81 HP, which were by far the most polluting conditions. Moreover, CO emissions in tailpipe exhaust were decreased in the whole operation range with increasing MTBE in the fuel. The greatest advantage of MTBE addition to gasoline was the decrease in ethylene, acetaldehyde, benzene, toluene, and acetic acid emissions in engine exhaust, especially when MTBE content in the fuel was increased to 11% w/w. In tailpipe exhaust, the catalyst operation diminished the observed differences. Ethylene, methane,and acetaldehyde were the main compounds present in exhaust gases. Ethylene was easily oxidized over the catalyst,while acetaldehyde and methane were quite resistant to oxidation.