Hydrogenate steam cracked naphtha

Residues (petroleum), coker scrubber, condensed-ring-arom-containing Residues (petroleum), hydrogenated steam-cracked naphtha, atm tower, vacuum, light... 

A high purity hydrogen and a low purity methane stream result. The 95% hydrogen may be used directly to hydrogenate steam cracked naphtha or directly consumed elsewhere in the refinery. The methane stream goes to fuel. 

Residues (petroleum), hydrogenated steam-cracked naphtha... 

Depending upon the refinery needs, the raw C5 plus steam cracked naphtha may be sent to isoprene extraction, treated to remove gum forming diolefins and sent to the refinery gasoline pool, or else completely hydrogenated and then fed to an aromatics extraction unit. 

Figures 4 and 5 show the sulfur specific chromatograms (S-GCxGC) of the two above FCC and SCN samples. The sulfiir compounds were also resolved by the GCxGC process into sulfur classes with distinct bands for mercaptans + sulfides, thiophenes, and benzothiophenes. Note that there was a sulfur conm nd in the steam cracked naphtha at approximately X=55 min, Y=110 s. This unknown compound was also found to contain carbon, hydrogen, and oxygen by further GCxGC/AED analysis. Further characterization of the compound may be possible by GC/Mass Spectrometry (GC/MS) using a comprehensive GCxGC/GC/MS set up very similarly to that described in this paper.

Both of these reactions have very important industrial uses (Section 14.3.9). In order to obtain alkene streams of sufficient purity for further use, the products of steam-cracking or catalytic cracking of naphtha fractions must be treated to lower the concentration of alkynes and alkadienes to very low levels (<5ppm). For example, residual alkynes and dienes can reduce the effectiveness of alkene polymerisation catalysts, but the desired levels of impurities can be achieved by their selective hydrogenation (Scheme 9.4) with palladium catalysts, typically Pd/A Os with a low palladium content. A great deal of literature exists,13,37 particularly on the problem of hydrogenating ethyne in the presence of a large excess of... 

The primary source of isoprene today is as a by-product in the production of ethylene via naphtha cracking. A solvent extraction process is employed. Much less isoprene is produced in the crackers than butadiene, so the availability of isoprene is much more limited. Isoprene also may be produced by the catalytic dehydrogenation of amylenes, which are available in C-5 refinery streams. It also can be produced from propylene by a dimerization process, followed by isomerization and steam cracking. A third route involves the use of acetone and acetylene, produced from coal via calcium carbide. The resulting 3-methyl-butyne-3-ol is hydrogenated to methyl butanol and subsequently dehydrogenated to give isoprene. The plants that were built on these last two processes have been shut down, evidently because of the relatively low cost of the extraction route. 

Table 23 gives the main physicochemical properties of a number of naphtha cuts derived from Kirkuk and Hassi-Messaoud crudes. The steam cracking of these naphthas yields a wide variety of products, ranging from hydrogen to highly aromatic heavy liquid fractions. 

H-Oil unit are processed for sulfur recovery and then sent for separation through the gas recovery facilities associated with the steam cracker. Remaining unconverted residue from the H-Oil operation is used as a fuel oil component for plant fuel. Ethylene is manufactured by steam cracking of ethane, propane, naphtha, and distillate, and products from these operations are separated in conventional gas recovery facilities. Hydrogen for H-Oil is partially supplied by by-product recovery from steam cracker and H-Oil off-gases supplemented by steam reforming of methane. The heavy oils produced in steam cracking of naphtha and distillate are blended with the H-Oil residue to yield plant fuel. 

In the USA, and to some extent in Great Britain and Norway, ethane is the dominant feedstock for steam cracking. It is recovered from wet natural gas and gives high yields of ethylene, hydrogen and methane. From naphtha, the preferred feedstock in Europe and Japan, additional principal products are propylene, C4 hydrocarbons and pyrolysis naphtha as well as highly aromatic pyrolysis tar. 

Typically steam cracking of naphtha produces ethene (32%), propene (13%) and butadiene (4.5%). By-products consist of aromatics (13.5%), methane, hydrogen, gasoline and fuel oil (total 37%). The exact proportions are a function of temperature. A process by which the olefins are separated is described on p. 89. 

Furnace carbon black is produced from the incomplete combustion of what is called carbon black oil feedstock, which consists of heavy aromatic residue oils. In the United States this oil is commonly the bottoms from catalytic cracker units. They are commonly referred to as cat cracker bottoms and contain relatively low hydrogen content (and conversely high carbon content). In Europe and other locations, the carbon black oil used is commonly a byproduct of high-temperature steam cracking of such products as naphtha, gas condensate, and gas oil to produce ethylene, propylene, and other olefins. Here, no catalysts are used in the cracking process. These types of carbon black oils are mainly unsaturated hydrocarbons. A third source of carbon black feedstock is coal tar, which is commonly used in China to manufacture carbon black. 

Butenes are usually derived from Crack-C4 from naphtha steam cracking [27]. After the removal of butadiene (by extraction) and isobutene (by conversion into methyl t-butylether) from the crude stream, the so-called Raffinate II contains 1-butene (50-65%), cis/trons-2-butene, and the isomeric butanes. Raffinate II is the cheapest source of butenes, and their most valuable hydroformylation product is n-pentanal, whereas the isomers 2-methylbutyraldehyde and 3-methylbutyraldehyde are less in demand and lower in value. The main application for -valeraldehyde is its transformation into 2-propylheptanol (2-PH) by aldolcondensation and subsequent hydrogenation of the product (Scheme 14.4) [28, 29]. like 2-EH, 2-PH is also an important plasticizer alcohol. n-Valeraldehyde is also used as an ingredient in flavoring mixtures. w-Valeraldehyde can be converted into -valercarboxylic ester by subsequent oxidation and esterification with tertiary valeric alcohol, providing a useful lubricant and a substitute for Freon. 

Reforming, In refining, a catalytic process in which naphtha molecules are cracked, rearranged, and/or recombined for the purpose of increasing the octane number of the naphtha. Reforming is also the process of converting hydrocarbons and steam to synthesis gas (carbon monoxide and hydrogen). 

Hydrogen production from fossil fuels is based on steam reforming of natural gas, thermal cracking of natmal gas, partial oxidation of heavier than naphtha... 

A typical steam cracker consists of several identical pyrolysis furnaces in which the feed is cracked in the presence of steam as a diluent.The cracked gases are quenched and then sent to the demethanizer to remove hydrogen and methane. The effluent is then treated to remove acetylene, and ethylene is separated in the ethylene fractionator. The bottom fraction is separated in the de-ethanizer into ethane and C3, which is sent for further treatment to recover propylene and other olefins. Typical operating conditions of ethane steam cracker are 750-800°C, 1-1.2 atm, and steam/ethane ratio of 0.5. Liquid feeds are usually cracked at lower residence time and higher steam dilution ratios compared to gaseous feeds. Typical conditions for naphtha cracking are 800° C, 1 atm, steam/hydrocarbon ratio of 0.6-0.8, and a residence time of 0.35 sec. Liquid feedstocks produce a wide spectrum of coproducts including BTX aromatics that can be used in the production of variety of chemical derivatives. 

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