Ethylene, from ethane

Dehydrogenation (Section 5 1) Elimination in which H2 is lost from adjacent atoms The term is most commonly en countered in the mdustnal preparation of ethylene from ethane propene from propane 1 3 butadiene from butane and styrene from ethylbenzene... 

A typical ethane cracker has several identical pyrolysis furnaces in which fresh ethane feed and recycled ethane are cracked with steam as a diluent. Figure 3-12 is a block diagram for ethylene from ethane. The outlet temperature is usually in the 800°C range. The furnace effluent is quenched in a heat exchanger and further cooled by direct contact in a water quench tower where steam is condensed and recycled to the pyrolysis furnace. After the cracked gas is treated to remove acid gases, hydrogen and methane are separated from the pyrolysis products in the demethanizer. The effluent is then treated to remove acetylene, and ethylene is separated from ethane and heavier in the ethylene fractionator. The bottom fraction is separated in the deethanizer into ethane and fraction. Ethane is then recycled to the pyrolysis furnace. 

Figure 3-12. Block diagram for producing ethylene from ethane.

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. 

We may use the reaction mechanism for the formation of ethylene from ethane (CjHg - C2H4 + H2), Section 6.1.2, to illustrate various types of steps in a typical chain reaction ... 

Dow Chemical in Midland, USA, the microprocess technologist Velocys in Plain City, USA, and PNNL in Richland, USA, as research institute in microreactor technology have a public funded project on high-intensity production of ethylene and other olefins by oxidation such as the formation of ethylene from ethane [1], A two-step reactor engineering is performed, starting with a bench-scale reactor with microchannel dimensions equal to the latter commercial unit and followed by numbering to the latter. An economic analysis with focus on reactor costs and energy consumption completes the project. 

Figure 7.5 Ethylene from ethane - sensitivity to oil price...

Ethylene from ethane Reduced reaction temperature, elimination of ethane recovery 4,655 34.95 0.163... 

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. 

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. 

Henry s Law constant is equal to the ratio of the vapor pressure of a species over the operating system pressure. If the number of stages required in a separation decreases with increasing Henry s Law constant, how can the Henry s Law constant be increased (i.e., of what thermodynamic variable is vapor pressure a function) Laboratory experiments were performed to assess the feasibility of separating ethylene from ethane. It was determined that the equilibrium solubilities of ethylene and ethane in an acidic copper(I) aqueous solution were similar. The rates of uptake of the two gases into the aqueous solution were measured independently and it was found that the rate of ethylene absorption is several times greater than that of ethane. Is this an example of an equilibrium- or a rate-controlled separation and why ... 

Equation (E4-3.9) was used along with A = 0.0205 ft. and Equations (E4-3.8) and (W-3.3) were used to obtain Figure E4-3.1, Using a bank of 100 pipes will give us the reactor volume necessary to make 300 million pounds per year of ethylene from ethane. The concemraiion and conversion profiles down any one of the pipes are shown in Figure B4-3.1. 

This process flourished, particularly in the United States, where an abundant supply of low cost ethylene from ethane and liquified petroleum gas (LPG) rapidly developed throughout the 1960s and 1970s. Today more than 96 0 of vinyl chloride in the United States is based on the balanced process. In Europe, ethylene based on cracking more expensive naphtha and gas oil favored the acetylene technology for vinyl chloride for a time, but, today, most European plants are also based on the balanced process. Of course, today, acetylene is almost nonexistent as a petrochemical feedstock and vinyl chloride plants worldwide are the balanced ethylene-based process. 

One can make the simple mechanistic assumption that ethylene- C is primarily formed from intermediates arising from insertion of [ iiCH] into primary carbon-hydrogen bonds. Then, by making the further assumptions that the total number of all [ CH] -insertion events is relatively constant in all hydrocarbons and that the insertions are indiscriminate, we can calculate the yield of ethylene- C for any hydrocarbon by using the ethylene- C yield from ethane as the maximum obtainable. The ratio of the yield of ethylene from any alkane relative to the yield of ethylene from ethane is then simply the number of primary hydrogen atoms n, in the compound under study, divided by the total number of primary (%), secondary (wj and tertiary (w,) hydrogens present. 

M. Teramoto, H. Matsuyama, T. Yamashiro, and Y. Katayama, Separation of ethylene from ethane by supported liquid membranes contained sUver nitrate as a carrier, J. Chem. Eng. Jpn. 19 (5) (1986) 419-424. 

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