Emissions partial oxidation products

Emissions from methanol vehicles are expected to produce lower HC and CO emissions than equivalent gasoline engines. However, methanol combustion produces significant amounts of formaldehyde (qv), a partial oxidation product of methanol. Eormaldehyde is classified as an air toxic and its emissions should be minimized. Eormaldehyde is also very reactive in the atmosphere and contributes to the formation of ozone. Emissions of NO may also pose a problem, especiaHy if the engine mns lean, a regime in which the standard three-way catalyst is not effective for NO reduction. 

From [2] we present further information on the nature (so-called speciation) of the hydrocarbons emissions in the form of the relationship between fuel and exhaust (engine-out) composition (Fig. 5). It is evident that the fingerprints for compounds of C5 and higher (C5+) are comparable on a fuel-to-exhaust basis. Thus unbumed fuel is a major contributor to the C5+ engine-out profile. Lighter hydrocarbons (C4 ) are produced by the breakdown of larger molecules and other partial oxidation products will also form (e.g. aldehydes and ketones, which are not considered here). Figure 6 provides a more quantitative example of exhaust/fuel comparisons for C5+ components. 

Today, different processes (steam reforming, autothermal reforming, partial oxidation, gasification) are available and commercially mature for hydrogen production from natural gas or coal. These processes would have to be combined with technologies for C02 capture and storage (CCS), to keep the emissions profile low. A power plant that combines electricity and hydrogen production can be more efficient than retrofitted C02 separation systems for conventional power plants. 

Although liquid hydrogen, LH2, can be used as a fuel source, much of the recent fuel cell research is focusing on the partial oxidation of methanol, natural gas, ethanol, or gasoline to produce the necessary hydrogen. Catalysts that aid in the partial oxidation of these fuels yields a readily available, rich source of hydrogen. Water is the primary exhaust emission produced by fuel cell powered vehicles. If a carbon-based fuel source is utilized, then a carbon-containing by-product will also be produced. 

It is fair to state that by and large the most important application of structured reactors is in environmental catalysis. The major applications are in automotive emission reduction. For diesel exhaust gases a complication is that it is overall oxidizing and contains soot. The three-way catalyst does not work under the conditions of the diesel exhaust gas. The cleaning of exhaust gas from stationary sources is also done in structured catalytic reactors. Important areas are reduction of NOv from power plants and the oxidation of volatile organic compounds (VOCs). Structured reactors also suggest themselves in synthesis gas production, for instance, in catalytic partial oxidation (CPO) of methane. 

Conventional processes for hydrogen production are among major producers of C02 emissions. It has been proposed recently that C02 produced in steam reforming or partial oxidation processes could be captured and sequestrated in the ocean or underground. In our work we estimated that the total energy consumption for C02 sequestration (C02 capture, pressurization, transportation and injection), will most likely exceed 5,000 kJ per kg of sequestrated C02. Since about 80% of world energy production is based on fossil fuels, this could potentially result in the production of 0.20-0.25 kg of C02 per kg of sequestrated C02. 

Partial oxidation ammonia plants have the same emission sources except for the primary reformer flue gas. The plants have an auxiliary boiler to generate steam for power production and fired heaters, which on account of the sulfur content of the fuel oil release a flue gas containing S02 (< 1500 mg/m3). Other possible emissions are H2S (< 0.3 ppmv), CO (30 ppmv) and traces of dust. The NO, content of the flue gas depends on the configuration of the auxiliary boiler and on the extent electric power generation on the site as opposed to outside supply. The total NO, emission per tonne of product may be somewhat lower than for steam reforming plants. 

The reactor was fed with 1.6 Nl/min of 1000, 2000 and 4000 ppm of methane in air. The mixtures were obtained by mixing N-50 synthetic air and 2.5 % (vol.) CH4 in N-50 synthetic air (Air Products). 40 ppm of SO2 (from a cylinder of 370 ppmV SO2 in N-50 synthetic air. Air Products) were added when the effect of sulphur on the catalysts activity was studied. Flow rates were controlled by calibrated mass flow controllers (Brooks 5850 TR). Exhaust gas was analysed by gas chromatography (Hewlett Packard HP 5890 Series II). Methane in the inlet and outlet streams was analysed using a 30 m fused silica capillary column with apolar stationary phase SE-30, and a FID detector. CO and CO2 were analysed using a HayeSep N 80/100 and a molecular sieve 45/60 columns connected in series, and a TCD detector. Neither CO, nor partial oxidation were detected in any experiment, the carbon mass balance fitting in all the cases within 2%. Methane conversions were calculated both from outlet methane and CO2 concentrations, being both values very close in all the cases. Methane (2000 ppmV) and SO2 (40 ppmV) concentrations have been selected because they are representative of industrial emissions, such as coke oven emissions. 

Demonstrate the feasibility of the superadiabatic partial oxidation concept as a basis for developing an innovative process for production of economically viable quantities of hydrogen through the thermal, noncatalytic decomposition of hydrogen sulfide (H2S) in H2S-rich waste streams into hydrogen and elemental sulfur, without the input of additional energy (and no additional carbon dioxide [CO2] emissions). 

The combustion of gasoline air mixtures in the combustion chamber of spark ignited engines leads essentially to the fonnation of total oxidation products, but also to CO, H2, NO, a hydrocarbon (HC) mixture and SO2. Several HC emissions formation mechanisms are possible to explain the origin of tlie hydrocarbon mixture [1,2], such as flame quenching at tlie cylinder walls or at crevice entrance, adsorption-desorption in the oil film and incomplete combustion (partial or complete misfire) particularly during transient operations. The HC that are not combusted (about 1 % of the gasoline) are either exliausted unmodified or... 

The production of hydrogen by steam-reforming of methane or by partial oxidation of heavy residues (POX) inevitably leads to an increase in self-consumption and additional emissions of CO2. 

Highly Ecological Hydrogen Production by Partial Oxidation of Hydrocarbons without CO2 Emission Plasma Generation of Carbon Suboxides... 

Fossil-fueled vehicles give rise to emissions of unburned fuel and partially oxidized hydrocarbons [102,106]. Prominent are the BTEX suite of aromatics - benzene, toluene, ethylbenzene, and xylenes. These compounds are ubiquitous in the environment, present in essentially every hive atmosphere we test and often among the most prominent peaks in the chromatogram. To date, it has not been possible to position a bee colony that avoids capture of significant amounts of BTEX. We also detect more biorefractive fuel components in hive air - polycyclic aromatics and biphenyls commonly associated with diesel products [114]. Incompletely burned fuel residuals [102] were also evident as noted in the Oxygenates portion of Table 2.5. These comprised aldehydes, ketones, alcohols, and oxides. 

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