Cracking, naphtha

During World War II, production of butadiene (qv) from ethanol was of great importance. About 60% of the butadiene produced in the United States during that time was obtained by a two-step process utilizing a 3 1 mixture of ethanol and acetaldehyde at atmospheric pressure and a catalyst of tantalum oxide and siHca gel at 325—350°C (393—397). Extensive catalytic studies were reported (398—401) including a fluidized process (402). However, because of later developments in the manufacture of butadiene by the dehydrogenation of butane and butenes, and by naphtha cracking, the use of ethanol as a raw material for this purpose has all but disappeared. 

The combination of low residence time and low partial pressure produces high selectivity to olefins at a constant feed conversion. In the 1960s, the residence time was 0.5 to 0.8 seconds, whereas in the late 1980s, residence time was typically 0.1 to 0.15 seconds. Typical pyrolysis heater characteristics are given in Table 4. Temperature, pressure, conversion, and residence time profiles across the reactor for naphtha cracking are illustrated in Figure 2. 

Steam cracking raffinate from aromatic extraction units is similar to naphtha cracking. However, because raffinates have more isoparaffins, relatively less ethylene and more propylene is produced. 

The plastic samples used in this study were palletized to a form of 2.8 3.2min in diameter. The molecular weights of LDPE and HDPE were 196,000 and 416,000, respectively. The waste catalysts used as a fine powder form. The ZSM-5 was used a petroleum refinement process and the RFCC was used in a naphtha cracking process. The BET surface area of ZSM-5 was 239.6 m /g, whose micropore and mesopore areas were 226.2 m /g and 13.4 m /g, respectively. For the RFCC, the BET surface area was 124.5 m /g, and micropore and mesopore areas were 85.6 m /g and 38.89 m /g, respectively. The experimental conditions applied are as follows the amount of reactant and catalyst are 125 g and 1.25-6.25 g, respectively. The flow rate of nitrogen stream is 40 cc/min, and the reaction temperature and heating rate are 300-500 C and 5 C/ min, respectively. Gas products were vented after cooling by condenser to -5 °C. Liquid products were collected in a reservoir over a period of... 

The industrial use of 1,3-dienes and of their electrophilic reactions has strongly stimulated the field in recent years. Because of the low cost of butadiene, abundantly available from the naphtha cracking process, very large scale applications in the synthesis of polymers, solvents and fine chemicals have been developed, leading to many basic raw materials of the modem chemical industry. For example, the primary steps in the syntheses of acrylonitrile and adiponitrile have been the electrophilic addition of hydrocyanic acid to butadiene24. Chlorination of butadiene was the basis of chloroprene synthesis25. 

The actual configuration of the reactor may take various forms depending on the precise requirements of the process. For example, for a high-temperature homogeneous gas-phase reaction such as naphtha cracking, the reactor may be simply a long tube in a furnace [Fig. 6(a)]. In other cases, the single tube is replaced by a number of tubes in parallel as shown in Fig. 6(b). 

Isoprene occurs in the environment as emissions from vegetation, particularly from deciduous forests, and as a by-product in the production of ethylene by naphtha cracking. In the United States, the total emission rate of isoprene from deciduous forests has been estimated at 4.9 tonnes per year, with greatest emissions in the summer. The global annual emission of isoprene in 1988 was estimated to be 285 000 thousand tonnes. Isoprene is produced endogenously in humans. It has also been found in tobacco smoke, gasoline, turbine and automobile exhaust, and in emissions from wood pulping, biomass combustion and rubber abrasion (United States National Library of Medicine, 1997). 

Exposure to isoprene occurs in the production of the monomer and in the production of synthetic rubbers. Isoprene occurs in the environment due to emissions from vegetation and the production of ethylene by naphtha cracking. 

Figure 7 shows the effect on ethylene production cost from naphtha cracking with BTX aromatics value increases as a parameter. (The basis we have used for determining the effect of aromatics price increases is given in Table XII). Figure 7 indicates that a 5 /gal increase in BTX... 

The philosophy of process intensification has been traditionally characterized by four words smaller, cheaper, safer, slicker. And indeed, equipment size, land use costs, and process safety are among the most important PI incentives. But process intensification can (and should) also be placed in a broader context—the context of sustainable technological development. Several years ago DSM published a picture symbolizing its own vision of process intensification (32), in which skyscraping distillation towers of the naphtha-cracking unit are replaced by a compact, clean, and tidy indoor plant (see Figure 3). The importance of PI for sustainable development and its role in the company s responsible business has been further stressed in a recent publication by the company s CEO, Peter Elverding (33). Here,... 

Somewhat similar are the so-called adductive crystallization processes, often (wrongly) called extractive crystallization, where reactions of complex/ adduct formation are used to separate compounds that are otherwise difficult to separate. Examples of adductive crystallization include separation of p- and m-cresols (137), separation of o- and p - n i troch I oro ben zcn cs (138), separation of quinaldine and isoquinoline (139), separation of nonaromatic compounds from naphtha-cracking raffinate (140), and separation of p-cresol from 2,6-xylenol (141). Other examples of reactive crystallization/precipitation reported in the literature are listed in Table 5. 

Nowadays, it is believed worldwide that n-paraffins, which are extracted from kerosene, will be more advantageous raw material than ethylene from naphtha cracking in view of both resource saving and process economics. 

Illes et al. [44] developed a reaction model for naphtha cracking which involves an nth-order decomposition of naphtha, considered as a single constituent. 

Isobutylene is present as 20-30% of the C4 fraction from the naphtha cracking process. A number of different upgrading reactions with isobutylene have been carried out industrially (with and without prior separation from the C4 fraction). One of these includes the acid-catalyzed oligomerization... 

SCT from Naphtha Cracking SCT from Gas Oil Cracking SCT from Desulfurized Gas Oil Cracking... 

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. 

Unstable byproducts are formed in naphtha cracking, and these are hydrotreated in order to increase their stability. One of the important reactions occurring is the saturation of diolefins. 

As any organic chemist will tell you, the conversion of an amino acid to the corresponding ester also requires more than one equivalent of a Bronsted acid. This is because an amino acid is a zwitterion and, in order to undergo acid catalysed esterification, the carboxylate anion needs to be protonated with one equivalent of acid. However, it was shown [38] that amino acids undergo esterification in the presence of a catalytic amount of zeolite H-USY, the very same catalyst that is used in naphtha cracking, thus affording a salt-free route to amino acid esters (Fig. 1.11). This is a truly remarkable reaction in that a basic compound (the amino ester) is formed in the presence of an acid catalyst. Esterification of optically active amino acids under these conditions (MeOH, 100 °C) un-... 

CDTECH Butadiene C4+ from naphtha cracking Selective hydrogenation of C4 acetylenes in a distillation column to produce low acetylene feed for butadiene extraction 2 1998... 

Lurgi 01 Gas Chemie GmbH Butadiene, 1,3 C4 cut from naphtha cracking Extractive distillation using N-methylpyrrolidone as solvent has high yield, low utilities 24 2001... 

Like many countries in the Far East, there is a relatively high demand for propylene. To maximise propylene production from naphtha cracking, the process plant is operated at low severity. In order to maintain design levels of ethylene, more naphtha feedstock is required, with the naphtha requirement being about 3.8 times the weight of ethylene produced. This creates a large demand of about 750,000 to... 

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