Ethylene separation from ethane using

Ethylene has been separated from ethane by a silver nitrate solution passing countercurrent in a hollow fiber poly-sulfone.165 This separation has also been performed with the silver nitrate solution between two sheets of a polysilox-ane.166 A hydrated silver ion-exchanged Nafion film separated 1,5-hexadiene from 1-hexene with separation factors of 50-80.167 Polyethylene, graft-polymerized with acrylic acid, then converted to its silver salt, favored isobutylene over isobutane by a factor of 10. Olefins, such as ethylene, can be separated from paraffins by electroinduced facilitated transport using a Nafion membrane containing copper ions and platinum.168 A carbon molecular sieve made by pyrolysis of a polyimide, followed by enlargement of the pores with water at 400 C selected propylene over propane with an a-valve greater than 100 at 35°C.169... 

Separation of Ethylene from Ethane Using Perfluorosulfonic Acid Ion-Exchange Membranes... 

As a general rule difficult or expensive separations should be performed last, since by that time less total material will be involved. Consider Table 4-1, which gives the product mix obtained in a cracking furnace of an ethylene plant and the normal boiling points of the compounds. Suppose it is desired to separate the six groups listed in the table using distillation. The separation of ethylene from ethane and propylene from propane will be the most difficult because they have the smallest boiling-point differences. Therefore, these steps should be performed last. 

The volumetric expansion parameter S may thus be taken as 0.9675. The product distribution will vary somewhat with temperature, but the stoichiometry indicated above is sufficient for preliminary design purposes. (We should also indicate that if one s primary goal is the production of ethylene, the obvious thing to do is to recycle the propylene and ethane and any unreacted propane after separation from the lighter components. In such cases the reactor feed would consist of a mixture of propane, propylene, and ethane, and the design analysis that we will present would have to be modified. For our purposes, however, the use of a mixed feed would involve significantly more computation without serving sufficient educational purpose.)... 

About half the propane produced annually in the U.S. is used as a domestic and industrial fuel. When it is used as a fuel, propane is not separated from the related compounds, butane, ethane, and propylene. Butane, with boiling point -0.5 °C (31.1 °F), however, reduces somewhat the rate of evaporation of the liquid mixture. Propane forms a solid hydrate at low temperatures, and this causes great inconvenience when a blockage occurs in a natural-gas line. Propane is used also as so-called bottled gas, as a motor fuel, as a refrigerant, as a low-temperature solvent, and as a source of propylene and ethylene. 

C2 units are also found in solid-state compounds with C-C separations that depend on formal electron count. These are viewed as deprotonated ethyne, ethylene or ethane using a popular solid-state idea the Zintl-Klemm concept. This concept is based on the simple idea that the metals transfer their valence electrons to the non-metal atoms thereby generating filled anion-centered bands at low energy, well separated from empty cation-based bands. Of course, this concept fails when the electronegativities of the metal and non-metal are not very different,... 

Teramoto M, Matsuyama H, Yamashiro T, and Okamoto S. Separation of ethylene from ethane by a flowing liquid membrane using silver nitrate as a carrier. J Mem Sci, 1989 45(1-2) 115-136. 

In 1864, ethylene was first expressed graphically in its modem form with a double bond connecting the two carbon atoms (CH2=CH2). This was adopted by Wanklyn to represent the constitutional formula of rosaniline (6), and made public in September of that year at the annual meeting of the British Association for the Advancement of Science, held in Bath. Wanklyn s ethylene-type formula showed two carbon atoms separated from the four hydrogen atoms by a bracket18. The ethylene type, unlike other type formulas, was used only to express the constitutions of coal-tar dyes. Wanklyn argued that the constitutions of the members of the rosaniline series could be expressed by his ethylene type by virtue of known reduction and replacement reactions. Thus he compared the conversion of 6 into colorless leucaniline (10) with the ready reduction of ethylene (ethene) (11) to ethane (12), both of which involved the addition of two hydrogen atoms (Scheme 4)19 21. 

Gas separation membrane technologies are extensively used in industry. Typical applications include carbon dioxide separation from various gas streams, production of oxygen enriched air, hydrogen recovery from a variety of refinery and petrochemical streams, olefin separation such as ethylene-ethane or propylene-propane mixtures. However, membrane separation methods often do not allow reaching needed levels of performance and selectivity. Polymeric membrane materials with relatively high selectivities used so far show generally low permeabilities, which is referred to as trade-off or upper bound relationship for specific gas pairs [1]. 

A new type of configuration, the flowing liquid membrane (FLM) was studied by Teramoto et al. [20]. In this case, the membrane liquid phase is in motion as the feed and strip phase. In this type of system a plate-and-frame and spiral-wound configuration with flat membrane was used. The scheme of the FLM configuration is drawn in Fig. 7.3A. The hquid phase flows (FLM) between two hydrophobic microporous membranes. The two membranes separate the hquid membrane phase from feed and strip phases. In Fig. 7.3B, it is reported the classical plate-and-frame module employed for the separation of ethylene from ethane [20]. The liquid membrane convection increased the membrane transport coefficient in gas separation. However, the membrane surface packing density (membrane surface area/ equipment volume) is much lower in spiral-wound system than in hollow fiber. 

Ethylene for polymerization to the most widely used polymer can be made by the dehydration of ethanol from fermentation (12.1).6 The ethanol used need not be anhydrous. Dehydration of 20% aqueous ethanol over HZSM-5 zeolite gave 76-83% ethylene, 2% ethane, 6.6% propylene, 2% propane, 4% butenes, and 3% /3-butane.7 Presumably, the paraffins could be dehydrogenated catalyti-cally after separation from the olefins.8 Ethylene can be dimerized to 1-butene with a nickel catalyst.9 It can be trimerized to 1-hexene with a chromium catalyst with 95% selectivity at 70% conversion.10 Ethylene is often copolymerized with 1-hexene to produce linear low-density polyethylene. Brookhart and co-workers have developed iron, cobalt, nickel, and palladium dimine catalysts that produce similar branched polyethylene from ethylene alone.11 Mixed higher olefins can be made by reaction of ethylene with triethylaluminum or by the Shell higher olefins process, which employs a nickel phosphine catalyst. 

Natural gas consists of approximately 90%-95% methane 5%-10% ethane and a mixture of other relatively low-boiling alkanes, chiefly propane, butane, and 2-methylpropane. The current widespread use of ethylene as the organic chemical industry s most important building block is largely the result of the ease with which ethane can be separated from natural gas and cracked into ethylene. 

Figures 147-150 show representative separations obtained under the conditions of Table 130. Interference from ethane in the ethylene dichloride determinations can be avoided by using longer columns or by eliminating ethane, prior to the analysis, by bubbling nitrogen at room temperature through the sample. Under these conditions neither the lead alkyls nor the scavengers are swept through because of their higher boiling points. Variations in the sample volume can be easily estimated. The quantitative elimination of ethane is very difficult, but the ethane content is quickly reduced to a small concentration that does not interfere because of partial separation from ethylene dichloride.

The world s 140 million metric tons of annual ethylene capacity almost exclusively employs steam cracking of hydrocarbon feedstocks [5]. The majority of the feedstocks come from petroleum refining, such as by cracking of naphtha, but some producers use liquefied natural gas as a feedstock. In Brazil, where sugar cane is plentiful, Braskem has built a 200,000 metric ton per year ethylene plant based upon the dehydration of sugar-derived ethanol [6]. In the United States, natural gas liquids, a mixture of ethane, propane, butane, and other hydrocarbons, are available from shale deposits. The ethane is separated and cracked to make ethylene. Depending on the cost of oil and natural gas, this can be an economic advantage. In 2012, about 70% of United States ethylene production was from ethane [7]. 

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