Cracker feed

Hydrofining usually involves only minor molecular changes of the feed with hydrogen consumption in the range of about 100 to 1,000 cu.ft./bbl. Typical applications include desulfurization of a wide range of feeds (naphtha, light and heavy distillates, and certain residua) and occasional pretreatment of cat cracker feeds. 

Superficially the Oryx GTL refinery design has much in common with the SMDS process, but there are important differences. There is no separate hydrotreater, which limits production of chemicals, such as waxes. The hydrocracker employs the Chevron Isocracking technology, which is based on a sulfided supported base-metal catalyst that was designed for crude oil conversion. The operating conditions of the hydrocracker are also more severe (>350°C, 7 MPa) than those required by the SMDS process (300-350°C, 3-5 MPa). Only intermediate products are produced (Table 18.13),5 with the naphtha slated as cracker feed and the distillate as blending component for diesel fuel. 

Assuming that demand for petroleum continues to increase at a rate of 1.2% per annum to 2010,37 and that all gasoline and diesel produced by U.S. refineries will have a sulfur content of less than 30 ppm, desulfurization of gasoline and diesel to these low levels will require extensive hydrotreating of both catalytic cracker feed and product of distillate. 

Hydrotreating Hydrogenation Catalytic Remove impnrities, satnrate HCs Residuals, cracked HCs Cracker feed, distillate, lube... 

Figure 3 Crude fractionation (crude distillation, three stages). An atmospheric fractionating stage produces lighter oils. An initial vacuum stage produces lube oils. A second vacuum stage fractionates bottoms from the other stages to produce asphalt and catalytic cracker feed. (From Ref. 5.)...

The selection of steam cracker feedstock is mainly driven by market demand as different feedstock qualities produce different olefins yields. One of the commonly used feed quality assessment methods in practice is the Bureau of Mines Correlation Index (BMCI) (Gonzalo et al., 2004). This index is a function of average boiling point and specific gravity of a particular feedstock. The steam cracker feed quality improves with a decrease in the BMCI value. For instance, vacuum gas oil (VGO) has a high value of BMCI and, therefore, is not an attractive steam cracker feed. The commonly used feedstocks in industry are naphtha and gas oil. 

This paper discusses developments in solvent extraction with emphasis on applications to petroleum fractions in the kerosene and heavier boiling range. Many of these techniques have been extended to the refining of gasoline, Diesel fuels, catalytic cracker feed and cycle stocks, and butadiene. 

Application The MaxEne process increases the ethylene yield from naphtha crackers by raising the concentration of normal paraffins (n-paraffins) in the naphtha-cracker feed. The MaxEne process is the newest application of UOP s Sorbex technology. The process uses adsorptive separation to separate C5-Cn naphtha into a rich n-paraffins stream and a stream depleted of n-paraffins. 

Application Upgrade natural gas condensate and other contaminated streams to higher-value ethylene plant feedstocks. Mercury, arsenic and lead contamination in potential ethylene plant feedstocks precludes their use, despite attractive yield patterns. The contaminants poison catalysts, cause corrosion in equipment and have undesirable environmental implications. For example, mercury compounds poison hydrotreating catalysts and, if present in the steam-cracker feed, are distributed in the C2-C5+ cuts. A condensate containing mercury may have negative added-value as a gas field product. 

At the present time, butane is also used to supplement liquid steam cracker feeds. Considered independently at very high severity (95 per cent conversion), it allows z final ethylene yield of 35 molar per cent after ethane recycling. 

N) and aromatics (A). The octane rating (RON) is typically 55 or higher. Some straight-run naphtha contains high levels of aromatics which do not make good cracker feed. It has been proposed that such naphtha could be pre-treated to remove the aromatics prior to the cracking operation. This would improve ethylene yields and provide additional aromatics for downstream operations. ... 

As shown, it is possible to recover directly high amounts of olefins similar to that of a naphtha crackers from polyolefin wastes. For selling, the olefins have to be cleaned up in distillation plants. To avoid problems with HCl from unexpected PVC fractions, it is safer to produce from polyolefins a waxy material which can be analyzed and, if free from HCl and chloroorganic compounds, mixed with naphtha and used as cracker feed. This was the concept of BP Chemicals. The test runs were made in our Hamburg laboratory plant (LWS3) [15]. Detailed material balances for experiments are provided in Table 17.7... 

T he expansion of the petrochemical industry and the accompanying increase in the demand for ethylene, propylene, and butadiene has resulted in renewed interest and research into the pyrolytic reactions of hydrocarbons. Much of this activity has involved paraffin pyrolysis for two reasons saturates make up most of any steam cracker feed and since the pioneering work of Rice 40 years ago, the basic features of paraffin cracking mechanisms have been known (1). The emergence of gas chromatography as a major analytical tool in the past 15 years has made it possible to confirm the basic utility of Rice s hypotheses (see, for example, Ref. 2). 

Solvent deasphalting Solvent-enhanced precipitation process to remove asphaltenes from heavy lube base stocks and for improving the feed quality of catalytic cracker feed. 

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