Petrochemicals naphtha

Europe. The demand for naphtha for petrochemical feed purposes in Europe continues to rise strongly. As a result, the prices for this commodity have risen over the past several years. Increased use of light North African crudes, providing a higher proportion of gasoline and potential petrochemical naphtha, has retarded but not stopped the rise in naphtha prices. 

Installation of more conversion equipment both in new refinery construction and as additions to existing hydroskimming facilities is already a trend. The production of more naphtha by providing new conversion units would, of course, make the additional naphtha more costly. In this connection a number of studies both our own and others (4) have attempted to determine the cost of incremental naphtha production. These indicate that in typically sized European hydroskimming refinery (operating on either Libyan or Arabian crudes) gasoline plus petrochemical naphtha yields can be increased by about 50% by installation of catalytic cracking. Based on today s prices for the other refinery products, the cost... 

The fiwdstocks used for pyrolysis vary widely and range from light saturated hydrocarbons such as ethane, propane, and even ethane/propane blends, to heavier petroleum cuts such as petrochemical naphtha and light and heavy gas oils. In this respect, the situation is clearly in favor of fight hydrocarbons in the United States, a country that is rich in natural gases containing methane as well as ethane and propane, and vHiich still mainly uses the latter two to manufacture ethylene, hi Europe and Japan, by contrast, petroleum cuts traditionally supply the steam cracker feedstocl (Table Zl). 

Other chemicals operations are in Sarawak. Offshore gas feeds a large methanol plant (660 kt/y) on Labuan Island and an ammonia plant at Bintulu. Also at Bintulu is the large Shell Gas to Liquids plant, which produces high valued linear-paraffins and wax as by-products. The naphtha fraction from the GTL plant is used as petrochemical naphtha. 

A typical naphtha cracking operation will use approximately 3.3 tonne naphtha per tonne of ethylene. Using this as a basis, the world demand for petrochemical naphtha is almost 200 million tonnes per year or almost 5 million barrels of naphtha per day. The ethane required is typically 1.3 toimes of ethane per tonne of ethylene. This translates into 41 million toimes of ethane per year. Most of this is derived from natural gas which (on a weight basis) contains about 10% ethane, hence some 400 million tonnes of natural gas is required to be processed to provide the world s petrochemical ethane or about 63 bcf/d of raw natural gas. 

The high temperature process is the only commercially proven process for the production of olefins and liquids from coal. Current developments favour a low temperature process which is commercially proven to produce liquids and wax from coal or gas. The low temperature process produces a waxy synthetic crude oil which is cracked to produce diesel of high cetane and naphtha. The naphtha, which has high level of Unear paraffins, is sold on the petrochemical naphtha market rather than conversion into gasoline. The conversion of this naphtha into olefins by steam cracking has been addressed in previous chapters. 

They are classified apart in this text because their use differs from that of petroleum solvents they are used as raw materials for petrochemicals, particularly as feeds to steam crackers. Naphthas are thus industrial intermediates and not consumer products. Consequently, naphthas are not subject to governmental specifications, but only to commercial specifications that are re-negotiated for each contract. Nevertheless, naphthas are in a relatively homogeneous class and represent a large enough tonnage so that the best known properties to be highlighted here. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Benzene, toluene, and xylene are made mosdy from catalytic reforming of naphthas with units similar to those already discussed. As a gross mixture, these aromatics are the backbone of gasoline blending for high octane numbers. However, there are many chemicals derived from these same aromatics thus many aromatic petrochemicals have their beginning by selective extraction from naphtha or gas—oil reformate. Benzene and cyclohexane are responsible for products such as nylon and polyester fibers, polystyrene, epoxy resins (qv), phenolic resins (qv), and polyurethanes (see Fibers Styrene plastics Urethane POLYiffiRs). 

Xylenes. The main appHcation of xylene isomers, primarily p- and 0-xylenes, is in the manufacture of plasticizers and polyester fibers and resins. Demands for xylene isomers and other aromatics such as benzene have steadily been increasing over the last two decades. The major source of xylenes is the catalytic reforming of naphtha and the pyrolysis of naphtha and gas oils. A significant amount of toluene and Cg aromatics, which have lower petrochemical value, is also produced by these processes. More valuable p- or 0-xylene isomers can be manufactured from these low value aromatics in a process complex consisting of transalkylation, eg, the Tatoray process and Mobil s toluene disproportionation (M lDP) and selective toluene disproportionation (MSTDP) processes isomerization, eg, the UOP Isomar process (88) and Mobil s high temperature isomerization (MHTI), low pressure isomerization (MLPI), and vapor-phase isomerization (MVPI) processes (89) and xylene isomer separation, eg, the UOP Parex process (90). 

Natural gas and crude distillates such as naphtha from petroleum refining are used as feedstocks to manufacture a wide range of petrochemicals that are in turn used in the manufacture of consumer goods. Basic petrochemicals are... 

Compounds considered carcinogenic that may be present in air emissions include benzene, butadiene, 1,2-dichloroethane, and vinyl chloride. A typical naphtha cracker at a petrochemical complex may release annually about 2,500 metric tons of alkenes, such as propylenes and ethylene, in producing 500,000 metric tons of ethylene. Boilers, process heaters, flares, and other process equipment (which in some cases may include catalyst regenerators) are responsible for the emission of PM (particulate matter), carbon monoxide, nitrogen oxides (200 tpy), based on 500,000 tpy of ethylene capacity, and sulfur oxides (600 tpy). 

Chemical and Other Specialty Manufacture A wide variety of products may be derived from petroleum feed stocks, including such diverse materials as alcohols, butyl rubber, sulfur, additives, and resins. Other specialties such as solvent naphthas, white oils, Isopars, Varsol, may also be produced. As indicated previously the respective chemical affiliate usually has responsibility for products broadly classified as petrochemicals. 

Aromatics are petrochemicals. Fixed-bed reforming of virgin naphthas is one source of these materials. Aromatics fiom the high temperature of coking of coal, the main source prior to 1940, now only account but for a small proportion of the total production. 

Upgrade lower-value materials such as heavy residues to more valuable products such as naphtha and LPG. Naphtha is mainly used to supplement the gasoline pool, while LPG is used as a fuel or as a petrochemical feedstock. 

Improve the characteristics of a fuel. For example, a lower octane naphtha fraction is reformed to a higher octane reformate product. The reformate is mainly blended with naphtha for gasoline formulation or extracted for obtaining aromatics needed for petrochemicals production. 

In Europe naphtha is the preferred feedstock for the production of synthesis gas, which is used to synthesize methanol and ammonia (Chapter 4). Another important role for naphtha is its use as a feedstock for steam cracking units for light olefins production (Chapter 3). Heavy naphtha, on the other hand, is a major feedstock for catalytic reforming. The product reformate containing a high percentage of Ce-Cg aromatic hydrocarbons is used to make gasoline. Reformates are also extracted to separate the aromatics as intermediates for petrochemicals. 

With the growing prominence of the petrochemicals industry this technology was, in turn, replaced by direct air oxidation of naphtha or butane. Both these processes have low selectivities but the naphtha route is still used since it is a valuable source of the co-products, formic and propanoic acid. The Wacker process, which uses ethylene as a feedstock for palladium/copper chloride catalysed synthesis of acetaldehyde, for which it is still widely used (Box 9.1), competed with the direct oxidation routes for a number of years. This process, however, produced undesirable amounts of chlorinated and oxychlorinated by-products, which required separation and disposal. 

Small olefins, notably ethylene (ethene), propene, and butene, form the building blocks of the petrochemical industry. These molecules originate among others from the FCC process, but they are also manufactured by the steam cracking of naphtha. A wealth of reactions is based on olefins. As examples, we discuss here the epoxida-tion of ethylene and the partial oxidation of propylene, as well as the polymerization of ethylene and propylene. 

In the late 1960s the biggest incentives were available in Puerto Rico. As a result, petrochemical investments in Puerto Rico may exceed 1,500,000,000 by 1975. The major baits were tax exemptions and free ports. Companies making products not produced in Puerto Rico previous to 1947 (true for nearly any chemical) could be granted 100% income tax exemptions for up to 17 years. They were also allowed to avoid the import duties on certain raw materials. For instance, in 1970 (naphtha), an important feedstock for producing petrochemicals, could be obtained on the world market at half its selling price in the United States.3,14... 

Propylene, a light olefin, is like ethylene one of the most important feedstocks for the petrochemical industry. In recent years the main way to obtain propylene and ethylene has been via cracking of naphtha. For this reason the cost of the corresponding polymers, mainly polypropylene and polyethylene, depends on the international oil price. One big challenge for modem chemistry is to look for an alternative production of feedstocks that is independent of the oil-industry. 

Ethylene is obtained by catalytic cracking of naphtha. It is one of the key petrochemical commodities worldwide used mostly in the production of polyethylene, ethyl benzene, ethylene oxide and others. The consumption of ethylene for the production of alcohols and other surfactant raw materials represents less than 10% of the total end uses of ethylene on a worldwide basis. 

Polymerization Polymerize Catalytic Unite two or more olefins Cracked olefins High-octane naphtha, petrochemical stocks ... 

The petrochemical industry also includes the treatment of hydrocarbon streams from the petroleum refining industry and natural gas liquids from the oil and gas production industry. Some of the raw materials used in the petrochemical industry include petroleum, natural gas, ethane, hydrocarbons, naphtha, heavy fractions. 

Introduction of zeolites into catalytic cracking improved the quality of the product and the efficiency of the process. It was estimated that this modification in catalyst composition in the United States alone saved over 200 million barrels of crude oil in 1977. The use of bimetallic catalysts in reforming of naphthas, a basic process for the production of high-octane gasoline and petrochemicals, resulted in great improvement in the catalytic performance of the process, and in considerable extension of catalyst life. New catalytic approaches to the development of synthetic fuels are being unveiled. 

The production ofp-xylene begins with petroleum naphtha, as does the production of the other mixed xylene components, benzene and toluene. Naphtha is chemically transformed to the desired petrochemical components and the individual components are recovered at required purity in what is known in the industry as an aromatics complex [12]. A generic aromatics complex flow scheme is shown in Figure 7.2. It is useful to briefly review the general flow scheme of this complex for subsequent discussion of the liquid adsorptive processes. The process blocks... 

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