Naphtha from refineries

Table 7 shows the yield distribution of the C4 isomers from different feedstocks with specific processing schemes. The largest yield of butylenes comes from the refineries processing middle distillates and from olefins plants cracking naphtha. The refinery product contains 35 to 65% butanes olefins plants, 3 to 5%. Catalyst type and operating severity determine the selectivity of the C4 isomer distribution (41) in the refinery process stream. Processes that parallel fluid catalytic cracking to produce butylenes and propylene from heavy cmde oil fractions are under development (42). 

Feed stock for the first sulfuric acid alkylation units consisted mainly of butylenes and isobutane obtained originally from thermal cracking and later from catalytic cracking processes. Isobutane was derived from refinery sources and from natural gasoline processing. Isomerization of normal butane to make isobutane was also quite prevalent. Later the olefinic part of the feed stock was expanded to include propylene and amylenes in some cases. When ethylene was required in large quantities for the production of ethylbenzene, propane and butanes were cracked, and later naphtha and gas oils were cracked. This was especially practiced in European countries where the cracking of propane has not been economic. 

Like ethylene (q.v.), propylene can also be isolated from refinery gas but propylene (propene) is also manufactured by steam cracking of hydrocarbons as for ethylene and the best feedstocks are propane, naphtha, or gas oil (Fig. 1). 

Ethylene is produced commercially in a variety of different processes. Feed stocks for these various processes range from refinery gas, ethane, propane, butane, natural gasoline, light and heavy naphthas to gas and oil and heavier fractions. Prepare three different qualitative flow sheets to handle a majority of these feed stocks. What are the advantages and disadvantages of each selected process ... 

Naphtha cracking provides about 4.3 million tonnes of propylene per year, which is out of a total demand for propylene in excess of 5.3 million tonnes per year. The difference (about 20%) is made up by propylene extracted from refinery off-gases, particularly FCC operations (used to produce gasoUne from heavier feed stocks such as heavy gas-oil or residua). 

As stated above, some of the chemicals and compounds produced in a refinery are destined for further processing and as raw material feedstocks for the fast growing petrochemical industry. Such nonfuel uses of crude oil products are sometimes referred to as its nonenergy uses. Petroleum products and natural gas provide two of the basic starting points for this industry methane from natural gas, and naphtha and refinery gases. 

Hydrogen plants in refineries typically have to operate on a variety of feedstocks ranging from refinery off-gas to naphtha. Without the prereformer, the tubular reformer should be designed for a steam carbon ratio being safe for the operation on naphtha. With a prereformer, the steam to carbon ratio can be reduced from typically 3.5 to 2.5, and the average heat flux can be increased, thus reducing the size of the tubular reformer. Typically,... 

GTC Technology Benzene saturation Full-range ECC naphtha Application of extractive distillation technology for simultaneous recovery of BTX and thio-phenic sulfur species from refinery or petrochemical aromatic-containing streams 1 2008... 

Some of the products from refineries, such as naphtha, are termed intermediates they are not used directly instead they are sold to chemical plants which use them to make a wide range of... 

The feedstock available (natural gas, residual gases from refineries, LPG (Liquefied Petroleum Gas), naphtha, heavy oils, distillation residues, pitch, coal, carbon dioxide, oxygen) and process utilities (steam, cooling water,...). 

Aromatics [benzene, toluene, and xylene (BTX)] are obtained from refinery and petrochemical light naphtha streams. Aromatics are produced in the reforming process and in steam cracking. Extraction or various extractive distillation processes are used to isolate and separate aromatics from the naphtha streams. Typical extraction processes are based on tetraethylene glycol, sulfolane, N,N -methylpyrolidene, or morpholine. They produce a mixture of aromatics that are subsequently separated by distillation, extractive distillation, or—in the case of xylene isomers—differential adsorption or fractional crystallization. 

Today, the majority of ethylene is produced by thermal cracking of hydrocarbon feedstocks ranging fi-om ethane to heavy vacuum gas oils. Over 60% of the world s propylene is produced as a by-product of thermal cracking, with the balance being supplied from refinery sources and others. Raw materials are mosdy natural gas condensate components (principally ethane and propane) in the US and Mideast and naphtha in Europe and Asia. Alkanes/olefins are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes. The mixture is feedstock and temperature dependent and separated by fractional distillation. 

The feedstock can be olefin-rich light hydrocarbons in the carbon range C4 to Cg, and the ideal feedstocks are C4 and C5 streams generated in the steam cracker. Diolefins and acetylenes in the feedstock can be partially hydrogenated to olefins, or the diolefins extracted for other petrochemical applications. Other possible feedstocks are MTBE Rafifinate-2, aromatics plant raffinate and refinery streams that are rich in olefins, such as light naphthas from an FCCU, coker or visbreaker. Refinery streams do not require pretreatment or hydrogenation of dienes - there is no limit on feed aromatic or diene content. 

Europe and Asia obtain propylene mainly from steam cracking of liquid petroleum feedstocks such as naphtha or from FCC units (fluid catalytic cracking). Also, propylene can be obtained from cracking of gas oil from refineries. Propylene can also be produced from cracking of propane and butane, to a lesser extent. This latter process is more feasible if the cost of propane is relatively low. 

I blocked valve C shown in Fig. 49.4, waited a few minutes, and obtained a sample of product naphtha from the hot drum. Lab analysis showed that the amount of jet fuel in the naphtha product had dropped from 20 to 10 percent. Another victory to report to the plant manager of the Coastal Refinery in Aruba. 

From 1950, the demand for nitrogen fertilizers in North America led to the construction of many more ammonia plants all based on the steam reforming process. Modifications to the primary reforming catalysts by the incorporation of potash to reduce the level of caibon deposition have enabled operators in those parts of the World with no readily available supply of natural gas to use naphtha or refinery off-gases as feed for the primary reformer, and this has increased the versatility of the process even further. ... 

We cite isomerization of Cs-Ce paraffinic cuts, aliphatic alkylation making isoparaffinic gasoline from C3-C5 olefins and isobutane, and etherification of C4-C5 olefins with the C1-C2 alcohols. This type of refinery can need more hydrogen than is available from naphtha reforming. Flexibility is greatly improved over the simple conventional refinery. Nonetheless some products are not eliminated, for example, the heavy fuel of marginal quality, and the conversion product qualities may not be adequate, even after severe treatment, to meet certain specifications such as the gasoline octane number, diesel cetane number, and allowable levels of certain components. 

Olefins are produced primarily by thermal cracking of a hydrocarbon feedstock which takes place at low residence time in the presence of steam in the tubes of a furnace. In the United States, natural gas Hquids derived from natural gas processing, primarily ethane [74-84-0] and propane [74-98-6] have been the dominant feedstock for olefins plants, accounting for about 50 to 70% of ethylene production. Most of the remainder has been based on cracking naphtha or gas oil hydrocarbon streams which are derived from cmde oil. Naphtha is a hydrocarbon fraction boiling between 40 and 170°C, whereas the gas oil fraction bods between about 310 and 490°C. These feedstocks, which have been used primarily by producers with refinery affiliations, account for most of the remainder of olefins production. In addition a substantial amount of propylene and a small amount of ethylene ate recovered from waste gases produced in petroleum refineries. 

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