Naphtha from distillation

Natural gas and crude distillates such as naphtha from petroleum refining are used as feedstocks to manufacture a wide range of petrochemicals that are in turn used in the manufacture of consumer goods. Basic petrochemicals are... 

Pure Commercial Benzene, obtained from coal-tai naphtha, should distil w lthin one degiee (80—Si ), and solidify completely when cooled to 0°. Other tests are as follow s shaken with concentrated sulphuric acid for a few minutes, the acid should not darken, and a drop of bromine water should not be immediately decolourised. A single distillation over a few small pieces of sodium, which absorb any traces of water, is usually a sufficient purification. If the benzene impart a brown or black colour to the sulphuric acid, it must be repeatedly shaken with about 20 per cent, of the acid until the lattev becomes only slightly yellow on standing. This is done in a stoppered separating funnel, and after shaking fora few minutes the mixture is allow ed to settle, and the low er layer of acid diawn off. The benzene is then shaken tw o 01 three times with water to free it from acid, carefully separated from the aqueous layer, and left in contact with fused calcium chloride until the liquid becomes clear. It is then decanted, frozen in ice, and any liquid (carbon bisulphide, paraffins) carefully drained off, and die benzene finally distilled over sodium. 

Liquid Petroleum fractions are light naphtha, heavy naphtha, kerosine and gas oil. The bottom product from distillation units is the residue. These... 

Naphtha from atmospheric distillation is characterized by an absence of olefinic compounds. Its main constituents are straight and branched-chain paraffins, cycloparaffms (naphthenes), and aromatics, and the ratios of these components are mainly a function of the crude origin. 

Heavy naphtha from atmospheric distillation units or hydrocracking... 

Kerosine, a distillate fraction heavier than naphtha, is normally a product from distilling crude oils under atmospheric pressures. It may also he obtained as a product from thermal and catalytic cracking or hydrocracking units. Kerosines from cracking units are usually less stable than those produced from atmospheric distillation and hydrocracking units due to presence of variable amounts of olefinic constituents. 

Products from coking processes vary considerably with feed type and process conditions. These products are hydrocarbon gases, cracked naphtha, middle distillates, and coke. The gas and liquid products are characterized by a high percentage of unsaturation. Hydrotreatment is usually required to saturate olefinic compounds and to desulfurize products from coking units. 

The feed to a catalytic reformer is normally a heavy naphtha fraction produced from atmospheric distillation units. Naphtha from other sources such as those produced from cracking and delayed coking may also be used. Before using naphtha as feed for a catalytic reforming unit, it must be hydrotreated to saturate the olefins and to hydrodesulfurize... 

Oxygenate refining was limited to chemicals recovery from the Fischer-Tropsch aqueous product and acidic isomerization of the C5-C6 naphtha. The naphtha and distillate range oxygenates were removed by hydrodeoxygenation (HDO) in hydrotreaters, before further refining. 

SPD [Slurry phase distillate] A process for making diesel fuel, kerosene, and naphtha from natural gas. Developed by Sasol and first commercialized in South Africa in 1993. A joint venture with Haldor Topsoe for the further development and commercialization of the process was announced in 1996. Commercialization in Nigeria was announced in 1998. 

Removal of naphtha and distillate fractions from the crude oil under atmospheric pressure distillation requires charge temperatures to be maintained below the cracking temperature of the crude oil components. This temperature will vary but can typically range from 750°F to 800°F (398.9°C to 426.7°C). Occasionally, even lower temperatures may be required. Above these temperatures, crude oil components can begin to thermally crack and foul processing equipment. 

Severe hydroprocessing to remove sulfur from naphtha and distillate fractions produces hydrogen sulfide. Although most hydrogen sulfide is removed as off-gas or stripped from fuel streams, the possibility exists for low levels of hydrogen sulfide to remain in fuel fractions. 

The first fraction listed is the 550°F-f- heavy oil produced by hydrogenation of the 550°-850°F heavy oil from distillation and coking of the in situ crude oil. This is the same fraction listed in Tables I and II as the syncrude heavy oil fraction. The second fraction listed in Table VII is the 350°-550°F light oil produced in the foregoing hydrogenation, and the third fraction is the 175°-350°F heavy naphtha produced in the same hydrogenation. 

The 175°-350°F naphthas from the two previous hydrogenation runs were combined with the total naphtha from the third distillation of in situ crude shale oil and coker distillate. The combined naphthas were then hydrogenated in a continuous 48-hr run. Operating conditions and product yields are shown in Table VIII. Under the conditions used, only 4.3 wt % of the charge was converted to products boiling below 175°F. 

The next processing stage, hydrodesulfurization, is where most of the sulfur, some of the nitrogen, and the residual metals are removed. A limited amount of conversion also takes place. From the final reactor, the gas phase is separated, hydrogen is recirculated to the reaction section, and the liquid products are sent to a conventional fractionation section for separation into naphtha, middle distillates, and heavier streams. 

H-Coal naphthas and distillates derived from Illinois No. 6 (Burning Star Mine) and Wyodak coals were supplied by Hydrocarbon Research, Inc. The naphthas and distillates were blended in the appropriate proportions to obtain a whole syncrude derived from each coal. Properties of these syncrudes are shown in Table I. For comparison, Table I also shows properties of the SRC-II syncrude used in the study described in the previous chapter. The SRC-II syncrude was derived from a West Virginia coal (Pittsburgh Seam, Blacksville No. 2 Mine of the consolidated Coal Company). The H-Coal and SRC-II syncrudes are not directly comparable because the coals used to derive these syncrudes differ. 

For the motor and BTX naphthas from the base crude mix, the preprocessor (1) determines the amount of each component present in the crude, (2) computes the fraction distilled overhead for each component at the naphtha cutpoints specified for the crude distillation unit, (3) constructs for each naphtha the composition of the material remaining between the initial and final boiling points, and (4) computes the blended compositions of the motor and BTX naphthas from the base crude mix. 

The lighter distillates and naphtha from oil shale and coal can be refined by processes used for petroleum, except that more severe hydrotreatment will be required to remove nitrogen and the other nonhydrocarbon impurities that poison catalysts and cause product instabiltiy. 

Once the synthetic crude oils from coal and oil shale have been upgraded and the heavy ends converted to lighter distillates, further refining by existing processes need not be covered in detail except to note the essential character of the products. The paraffinic syncrude from oil shale yields middle distillates which are excellent jet and diesel fuel stocks. The principal requirements are removal of nitrogen to the extent necessary for good thermal stability of the fuels and adjustment of cut points to meet required pour or freeze points, limited by the presence of waxy straight-chain paraffins. The heavy naphtha from shale oil can be further hydrotreated and catalytically reformed to acceptable octane number, but with considerable loss of volume because of the only moderate content of cyclic hydrocarbons, typically 45-50%. On the other... 

Based on correlations, the naphthas from the shale oil hydrotreater can be readily upgraded to high-octane gasolines by catalytic reforming. The middle distillate fractions will require some additional hydrotreating... 

The new developments in catalyst improvements and in process optimization have brought new opportunities to directly process virgin naphtha from atmospheric distillation along with benzene and benzene precursors extracted from reformer feeds. This can eliminate the need for a separate naphtha hydrotreater as well as sepa-... 

Feedstock. A hydrotreated, straight-run naphtha from a North Sea crude was used as a base feedstock in the test program. By distillation (according to ASTM D-2892, with 15 theoretical plates and a reflux ratio of 5 1) three naphthas with different initial boiling points (IBP) and three naphthas with different final boiling points were produced. The boiling point properties of the base and the derived naphthas are given in Table I. The composition of the different naphthas was determined by GC analysis. 

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