Simulations hydrocarbon separation

Aromatic and Nonaromatic Hydrocarbon Separation. Aromatics are partially removed from kerosines and jet fuels to improve smoke point and burning characteristics. This removal is commonly accompHshed by hydroprocessing, but can also be achieved by Hquid-Hquid extraction with solvents, such as furfural, or by adsorptive separation. Table 7 shows the results of a simulated moving-bed pilot-plant test using siHca gel adsorbent and feedstock components mainly in the C q—range. The extent of extraction does not vary gready for each of the various species of aromatics present. SiHca gel tends to extract all aromatics from nonaromatics (89). 

Olefin Separation. U.O.P. s Olex Process. U.O.P. s other hydrocarbon separation process developed recently—i.e., the Olex process—is used to separate olefins from a feedstock containing olefins and paraffins. The zeolite adsorbent used, according to patent literature 29, 30), is a synthetic faujasite with 1-40 wt % of at least one cation selected from groups I A, IIA, IB, and IIB. The Olex process is also believed to use the same simulated moving-bed operation in liquid phase as U.O.P. s other hydrocarbon separation processes—i.e., the Molex and Parex processes. 

The simulated moving bed (SMB) technology was developed in the early 1960s by UOP for large-scale hydrocarbon separations in plants [1, 2], Recently, SMB is extensively used for the separation of enantiomers [3, 4], amino acids [5, 6], and protein desalting [7]. The SMB system simulated counter-current movement this is done with a series of packed bed by periodically advancing the input (feed, desorbent) and output port (raffinate, extract) along the solvent flow direction. 

However, ia some cases, the answer is not clear. A variety of factors need to be taken iato consideration before a clear choice emerges. Eor example, UOP s Molex and IsoSiv processes are used to separate normal paraffins from non-normals and aromatics ia feedstocks containing C —C2Q hydrocarbons, and both processes use molecular sieve adsorbents. However, Molex operates ia simulated moving-bed mode ia Hquid phase, and IsoSiv operates ia gas phase, with temperature swiag desorption by a displacement fluid. The foUowiag comparison of UOP s Molex and IsoSiv processes iadicates some of the primary factors that are often used ia decision making ... 

It is important to note that simulated distillation does not always separate hydrocarbons in the order of their boiling point. For example, high-boihng multiple-ring-type compounds may be eluted earher than normal paraffins (used as the calibration standard) of the same boiling point. Gas chromatography is also used in the ASTM D 2427 test method to determine quantitatively ethane through pentane hydrocarbons. 

Displacement-purge forms the basis for most simulated continuous countercurrent systems (see hereafter) such as the UOP Sorbex processes. UOP has licensed close to one hundred Sorbex units for its family of processes Parex to separate p-xylene from C3 aromatics, Molex tor /i-paraffin from branched and cyclic hydrocarbons, Olex for olefins from paraffin, Sarex for fruc tose from dextrose plus polysaccharides, Cymex forp- or m-cymene from cymene isomers, and Cresex for p- or m-cresol from cresol isomers. Toray Industries Aromax process is another for the production of p-xylene [Otani, Chem. Eng., 80(9), 106-107, (1973)]. Illinois Water Treatment [Making Wave.s in Liquid Processing, Illinois Water Treatment Company, IWT Adsep System, Rockford, IL, 6(1), (1984)] and Mitsubishi [Ishikawa, Tanabe, and Usui, U.S. Patent 4,182,633 (1980)] have also commercialized displacement-purge processes for the separation of fructose from dextrose. 

Sulfur compounds in the gas oil fractions from two bitumens (Athabasca oil sand and Cold Lake deposit)> a heavy oil (Lloydminster) from Cretaceous reservoirs along the western Canada sedimentary basin, and a Cretaceous oil from a deep reservoir that may be mature (Medicine River) are investigated. The gas oil distillates were separated to concentrates of different hydrocarbon types on a liquid adsorption chromatographic column. The aromatic hydrocarbon types with their associated sulfur compounds were resolved by gas chromatographic simulated distillation and then by gas solid chromatography. Some sulfur compounds were further characterized by mass spectrometry. The predominant sulfur compounds in these fractions are alkyl-substituted benzo- and dibenzothiophenes with short side chains which have few dominant isomers. 

There was a small amount of sulfur in the mononuclear aromatic hydrocarbon fractions, which did not show any appreciable resolution on the microcoulometric trace obtained during simulated distillation. According to the U.S. Bureau of Mines report (3) describing this type separation, thiophenes and cyclic sufides could be expected in this fraction. 

Distillations are perfect candidates for Raman process monitoring since many potential fluorescent or interfering species are reduced or removed. The Institut Francais du Petrole holds two relevant patents discussing the use of Raman spectroscopy to control the separation of aromatics by adsorption on simulated moving beds and the separation of isomers, particularly aromatic hydrocarbons with 8-10 carbon atoms such as para-xylene and orffio-xylene.67 68... 

Marin et al. (250) attempted to model a reactor similar to that used by Alonso and co workers. Their simulations were compared with simulations representing a fixed-bed reactor operated under similar conditions. They concluded that the membrane reactor (with the external fluidized bed) was a viable technology for n-butane oxidation, but that it offered only a modest increase in MA yields relative to those realized in a fixed-bed reactor. Nonetheless, the safer operating conditions which keep the O2 and hydrocarbon flows separate, particularly with the oxidation of butane to MA, are desirable. Presently, MA yields are chiefly governed by the explosive limits of butane in air (i.e., 1.8%). Increasing the butane concentration with an optimized membrane reactor may increase overall MA yields. 

The separation scheme for deasphaltened bitumen on silica [WOELM, activated at 140°C (4 hr)] is shown in Figure 1. The fractions obtained were loosely termed hydrocarbons. Polar I, II, and III. The IR spectra of these fractions, as shown in Figure 2, suggested that Polar I was very similar to the polyaromatic/neutral polar fraction from the API 60-based separation after removal of additional material from alumina with pure benzene. Also, simulated distillation curves for this fraction from either procedure are very similar (Figure 3). The IR spectra of the Polar II and III fractions show the presence of all the functional groups which can be distinguished in these complex mixtures and which... 

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