Aromatics removal from liquid fuels

Aromatic and Nonaromatic Hydrocarbon Separation. Aromatics are partially removed from kerosines and jet fuels to improve smoke point and burning characteristics. This removal is commonly accomplished by hydroprocessing, but can also be achieved by liquid —liquid extraction with solvents, such as furfural, or by adsorptive separation. Table 7 shows the results of a simulated moving-bed pilot-plant test using silica gel adsorbent and feedstock components mainly in the C1Q—1C15 range. The extent of extraction does not vary greatly for each of the various species of aromatics present. Silica gel tends to extract all aromatics from nonaromatics (89). 

Since about 1991, diesel oxidation catalysts have been generally applied to passenger cars in the European Union and to some medium and heavy duty trucks in the USA. Their principle of operation is shown in Fig. 101. The amount of carbon monoxide, hydrocarbons and aldehydes is reduced by oxidation of these components to carbon dioxide and water. The mass of particulate matter emitted is reduced by the oxidation of the liquid hydrocarbons, which are adsorbed on the particulates. These liquid hydrocarbons originate both from the fuel and the lubricating oil, and are commonly denoted as the soluble organic fraction (SOF). The adsorbed polynuclear aromatic hydrocarbons are also removed by oxidation. 

Environmental limits on the aromatic content of gasoline and diesel fuel have led to a further application of supported nickel hydrogenation catalysts. Benzene can be completely removed from light Ce reformate or other similar streams by liquid phase hydrogenation, before blending into the refinery gasoline pool. 

The replacement of conventional catalytic processes for purification of mixtures by processes involving extraction with ionic liquids has also been envisioned. For example, the extractive removal of sulfur compounds from fuels has shown promising leads for high selectivity for aromatic sulfur compounds, and removal of such compounds has been a major challenge in conventional heterogeneous hydrodesulfurization catalysis (27,296). 

Reactor effluent is separated into liquid and vapor products (4). Liquid product is sent to a stabilizer (5) to remove light ends. Vapor from the separator is compressed and sent to a gas-recovery section (6) to separate 90%-pure hydrogen byproduct. A fuel gas byproduct of LPG can also be produced. UOP s latest R-270 series catalyst maximizes aromatics yields. 

Solid-state C NMR techniques provide a powerful means by which to obtain information about the carbon structure of fossil fuel materials. Indeed, CP/MAS measurements have been applied to coals and oil shales almost from their inception around 1976. Solid-state NMR measurements are now made routinely in fossil Riel research, particularly in coal structure studies. For oil shales, solid-state NMR methods are particularly useful because the measurements can be made on raw shale, without the need to remove the mineral matter, which generally accounts for >85 wt% of the rock. However, because of the reduced emphasis in developing oil shale deposits commercially, applications of NMR in oil shale research are now not as common as in the past. Nevertheless, NMR measurements have provided valuable information about various aspects of oil shales. For example, the extent of aromatization of aliphatic carbon moieties during conversion can be obtained by combining solid- and liquid-state NMR measurements with mass balance data. Such information is difficult to obtain by other methods and provides insight into the chemical processes associated with fossil fuel conversion. 

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