Naphtha feedstocks

In most of the rest of the world the olefins industry was originally based on naphtha feedstocks. Naphtha is the dominant olefins feedstock in Europe and Asia. In the middle 1980s several large olefins complexes were budt outside of the United States based on gas Hquids feedstocks, most notable in western Canada, Saudi Arabia, and Scotiand. In each case the driving force was the production of natural gas, perhaps associated with cmde oil production, which was in excess of energy demands. 

Should these projects come to fruition, the Middle East producers will be the lowest cost producers for a wide range of petrochemicals and derivatives. The major portion of the products would be exported to the world markets and so will impact on the world price. This will be a particular concern to most producers in Europe and the Far East with feedstock (naphtha) linked to the prevailing crude oil price. The cracking operations in the Middle East in 2008 are listed in Table 1.5. 

These authors studied the possibility of blending LDPE and PP into the feedstock of a naphtha cracker. Such units have huge yearly capacity, of the order of 400 000 tonne ethylene or about 1 Mton of feedstock (naphtha). Most plastics pyrolysis units have only a modest scale, ranging from an annual 2000 to 20 000 tonne. This difference in scale obviously reflects in differences in cost, since labour is almost identical for small, medium, or large plant, whereas investment cost I of petrochemical plant typically varies with capacity C as (R = reference basis) ... 

Figure 3a. Methane yields as a function of molecular collision parameter. Feedstock naphtha.

The main reactions for liquid feedstocks (naphthas, gas oils, etc.) are sometimes summarized according to the types and amounts of paraffins (n-paraffins and iso-paraffins), olefins, naphthenes (monocyclic naphthenes and multicyclic naphthenes), and aromatics (naphthenic aromatics and pure aromatics). The basic chemistry and modeling efforts have been reported by numerous investigators including Dente et... 

Reforming units specifically used for the production of aromatics are called BTX reformers. The acronym BTX is based upon the desire to produce benzene, toluene, and xylenes as petrochemical feedstocks. Naphthas for theses units consist substantially of naphthenes and paraffins of six to eight carbons. The desired reaction is aromatization through dehydrogenation of the naphthenes and cy-clization and dehydrogenation of the paraffins to the analogous aromatic. Characterization of Products. 

Refining is the processing of crude oil into a relatively small number of complex mixtures of hydrocarbons of high quality. The main products are fuels such as gasoline, diesel oil, jet fuel, and heating oil, but refineries also produce the major feedstocks (naphtha and LPG) for the petrochemical industry, and, therefore, crude oil is also the basis of industrial organic chemistry. The main objectives of a refinery can be briefly summarized as follows. 

Ethylene is produced utilizing a steam-cracking process carried out at 750-950°C (steam cracking is the most energy-consuming process in the chemical industry), with primarily two feedstocks, naphtha and ethane, although other feedstock such as propane, butane and gas oil are also used. 

During the 1950s the petroleum industry experienced a rapid development. A new abundant and cheap feedstock, naphtha, became available for the chemical industry and all ethylene needed for polyethylene and other chemical products started to be made from fossil feedstock. Combined with the development of cracker technology this has led to the very cost-effective steam crackers operated today. A typical size of a cracker built today has an ethylene production capacity of up to 1 metric tonnes/year. Gradually ethane and propane obtained either by separation from natural gas or from flare gas in oilfields have been used as feedstock. In areas with large oilfields and low population the latter provides a cheap feedstock. This is an important reason why most of today s investments in cracker capacity are made in the Middle East. 

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