Petroleum chemicals Separation

This section describes the major industrial processes within the petroleum refining industry, ineluding the materials and equipment used, and the processes employed. The section is necessary for an understanding of the interrelationships between the industrial processes, the types of air emissions, and control and pollution prevention approaehes. Deseriptions of eommonly used production processes, assoeiated raw materials, by-produets produeed are first deseribed. Petroleum refining is the physieal, thermal, and chemical separation of erude oil into its major distillation fraetions, which are then further proeessed through a series of separation and eonversion steps into finished petroleum produets. The primary products of the industry fall into three major categories ... 

The MADEP (Hutcheson et al. 1996 MADEP 1997) and the TPHCWG (1997a, 1997b, 1997c) approaches both assume additivity of the indicator compounds and the hydrocarbon fractions in assessing the potential for adverse effects of TPH on health. In contrast, the ASTM approach tends to assess each individual TPH indicator chemical separately and without regard to the presence of other petroleum hydrocarbons and the potential for additivity or interactions, although it does not preclude a consideration of these factors. 

A recent court decision in Britain that petroleum and natural gas are two separate materials shows the need for mentioning both in a definition of petroleum chemical, if for no other reason than to avoid misunderstanding outside the petroleum industry (68). 

The following definition is suggested Petroleum chemicals comprise chemicals, marketable chemical mixtures, and elements intended for chemical use, which occur naturally in petroleum or natural gas, or result from refining these, or are obtained from them by synthesis or reaction, and which are separable by known methods, and are now obtained or give promise of being obtained commercially within limits imposed by the necessity of profit petroleum chemicals are the resulting chemicals themselves, and not their further secondary or tertiary derivatives. (While this definition is long, no briefer one seems adequate.)... 

Methods of separation of hydrocarbons became more diversified. Fractional distillation was improved by the use of azeotropic and extractive distillation. Continuous adsorption on solids such as active charcoal or silica gel was established. Liquid-hquid solvent extraction, already used in petroleum refining, was adapted to the concentration and purification of some of the raw materials for petroleum chemicals finally, the formation of physical complexes, the so-called clathrate compounds, which permit separation of hydrocarbons of different shapes, is being developed as a new separation method, now known as extractive crystalhzation. 

When components entering a multistage vapor-liquid separation column are mutually reactive, chemical reactions and phase separation can occur simultaneously in what is generally described as reactive distillation. This phenomenon is found in several operations in the petroleum, chemical, and petrochemical industries. 

The trade literature touted SCF technology as a panacea for the chemicals, petroleum, and foods industries it was going to solve all sorts of problems in energy reduction, waste treatment, chemicals separation, and biotechnology. Quotes from some of these articles attest to the unbridled and, in our opinion, unwarranted enthusiasm for this new technology. 

Separation processes are central to the petroleum, chemical, petrochemical, pulp, pharmaceutical, mineral, and other industries. Major portions of capital and operating expenses of such industries are associated with one or more separation processes consequently, the impact of separation process technology on corporate profitability is great in most of these industries. The growth of new industries, based on biotechnology or electronics, for example, requires the development of new separation techniques and application of historically successful technology in new environments. 

The rotating disk contactor has had extensive application in petroleum refining and organic chemical separations. A modified version, with holes in the horizontal stator disks to promote countercurrent flow, has been used in the recovery of uranium from solutions used in cleaning process equipment [D4, L2]. 

The molar flow rate of the supply of constituent j to the unit 0 CR) will be called F j and the molar flow rate of constituent j leaving the separation unit (j R CR, P, CP, BP) will be called Fj. In the petroleum chemical industry, chemically complex reactants are used (naphtha, LPG. ..), and it is much more common to carry out mass balances. Wqj and Wj are the mass-flows of constituent j supplying the process and leaving the separation unit, respectively. 

Metal oxide catalytic materials currently find wide application in the petroleum, chemical, and environmental industries, and their uses have significantly expanded since the mid-20th century (especially in environmental applications) [1,2], Bulk mixed metal oxides are extensively employed by the chemical industries as selective oxidation catalysts in the synthesis of chemical intermediates. Supported metal oxides are also used as selective oxidation catalysts by the chemical industry, as environmental catalysts, to selectively transform undesirable pollutants to nonnox-ious forms, and as components of catalysts employed by the petroleum industry. Zeolite and molecular sieve catalytic materials are employed as solid acid catalysts in the petroleum industry and as aqueous selective oxidation catalysts in the chemical industry, respectively. Zeolites and molecular sieves are also employed as sorbents for separation of gases and to trap toxic impurities that may be present in water supplies. Significant molecular spectroscopic advances in recent years have finally allowed the nature of the active surface sites present in these different metal oxide catalytic materials to be determined in different environments. This chapter examines our current state of knowledge of the molecular structures of the active surface metal oxide species present in metal oxide catalysts and the influence of different environments upon the structures of these catalytic active sites. 

The field of application for liquid chromatography in the petroleum world is vast separation of diesel fuel by chemical families, separation of distillation residues (see Tables 3.4 and 3.5), separation of polynuclear aromatics, and separation of certain basic nitrogen derivatives. Some examples are given later in this section. 

The complexity of petroleum products raises the question of sample validity is the sample representative of the total flow The problem becomes that much more difficult when dealing with samples of heavy materials or samples coming from separations. The diverse chemical families in a petroleum cut can have very different physical characteristics and the homogeneous nature of the cut is often due to the delicate equilibrium between its components. The equilibrium can be upset by extraction or by addition of certain materials as in the case of the precipitation of asphaltenes by light paraffins. 

In the petroleum refining and natural gas treatment industries, mixtures of hydrocarbons are more often separated into their components or into narrower mixtures by chemical engineering operations that make use of phase equilibria between liquid and gas phases such as those mentioned below ... 

Proof of the existence of benzene in the light oil derived from coal tar (8) first estabHshed coal tar and coal as chemical raw materials (see Eeedstocks, COAL chemicals). Soon thereafter the separation of coal-tar light oil into substantially pure fractions produced a number of the aromatic components now known to be present in significant quantities in petroleum-derived Hquid fuels. Indeed, these separation procedures were for the recovery of benzene—toluene—xylene (BTX) and related substances, ie, benzol or motor benzol, from coke-oven operations (8) (see BTX processing). 

Polymerization in Hquid monomer was pioneered by RexaH Dmg and Chemical and Phillips Petroleum (United States). In the RexaH process, Hquid propylene is polymerized in a stirred reactor to form a polymer slurry. This suspension is transferred to a cyclone to separate the polymer from gaseous monomer under atmospheric pressure. The gaseous monomer is then compressed, condensed, and recycled to the polymerizer (123). In the Phillips process, polymerization occurs in loop reactors, increasing the ratio of available heat-transfer surface to reactor volume (124). In both of these processes, high catalyst residues necessitate post-reactor treatment of the polymer. 

Petroleum Waxes. Waxes derived from petroleum are hydrocarbons of three types paraffin [64742-43-4] (clay-treated) sernimicrocrystaUine or intermediate and microcrystalHne [64742-42-3] (clay-treated). SernimicrocrystaUine waxes are not generally marketed as such (7). Others include acid-treated, chemically neutrali2ed, and hydrotreated and paraffin and hydrocarbon waxes, untreated. The quaHty and quantity of the wax separated from the cmde oil depends on the source of the cmde oil and the degree of refining to which it has been subjected prior to wax separation. Petroleum waxes are produced in massive quantities throughout the world. Subject to the wax content in the cmde, paraffin and, to a substantially lesser degree, microcrystalHne wax are produced in almost all countries of the world that refine cmde oil. Production capacity in the United States and imports for the years 1990 to 1995 are Hsted in Table 2. Canada suppHes over 50% of the petroleum wax imported into the United States (3). 

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