Tubular reactors ethylene production

Figure 15—3 lays out the four-step process, starting with germinating the seed from which everything sprouts. Triethyl aluminum is created from aluminum, hydrogen, and ethylene in step one, which itself has several parts. Powdered aluminum in a toluene slurry is fir-st converted to diethyl aluminum hydride, HA1(C2H5)2, at 212—300 F and 1500 psi. This product is then fed to a tubular reactor with ethylene at 212 F and 300 psi to produce triethyl aluminum. Yields are about 90%. 

Gas-oil cracking was carried out in a fixed bed tubular reactor at atmospheric pressure and 482 °C. Average yields of the different products -diesel, gasoline, gases (methane, ethane, ethylene, C, C ), and coke- were measured at different levels of conversion jy varying the catalyst to oil ratio in the range 0.025-0.40 g.g, but always at 60 sec on-stream. The operational procedure has been detailed elsewhere (6). 

Set-up for Ethylene Glycol Lignin Production. A process development unit (PDU), previously described by Chornet and co-workers (11), was used for the experiments. A typical preparation consists of initially mixing 1-1.2 kg of wood meal with 10 1 of ethylene glycol. The mixture is allowed to stand overnight for imbibition to take place. To enhance solvent to substrate penetration, the slurry is homogenized at 200°C in the pretreatment section of the PDU. It is then pumped through the treatment section which consists of a tubular reactor at 220°C. The product slurry is collected in a receiver. The detailed procedure and choice of conditions above have been published elsewhere (11,12). 

The residence time is typically in the range of 15 - 60 s. The temperature and pressure are a little lower then in a tubular reactor. Pressures are in the range of 130 - 220 MPa, and the temperatures mostly do not exceed 260°C. When ethylene-vinyl acetate resins are produced, single autoclaves are run at temperatures which are 30 - 50°C lower then in the production of homopolyethylene. 

When ethylene-vinyl acetate copolymers are manufactured, the decomposition products also contain carbon monoxide and carbon dioxide. When decomposition takes place in a tubular reactor or in a multi-chamber or cascade of autoclaves, up to 50% of the decomposition gases can consist of undecomposed ethylene. 

The costs assume the production of pellets on 1997 German prices. Polymerization-grade ethylene is available at 5 MPa. The on-stream time is 8,000 h/a. The tubular reactors equipped with multiple feeds of ethylene and peroxide initiators are operated at 200 MPa. The initiators are a mix of dicyclohexyl peroxy dicarbonate, /-butylperoxy pivalate, /-butylperoxy 2-ethylhexanoate, and di(/-butyl)peroxide, which is fed in after the heating zone and at two further locations downstream. 

Figure 17.14. Some unusual reactor configurations, (a) Flame reactor for making ethylene and acetylene from liquid hydrocarbons [Patton et al., Pet Refin 37(li) 180, (1958)]. (b) Shallow bed reactor for oxidation of ammonia, using Pt-Rh gauze [Gillespie and Kenson, Chemtech, 625 (Oct. 1971)]. (c) Sdioenherr furnace for fixation of atmospheric nitrogen, (d) Production of acetic acid anhydride from acetic acid and gaseous ketene in a mixing pump, (e) Phillips reactor for low pressure polymerization of ethylene (closed loop tubular reactor), (f) Polymerization of ethylene at high pressure.

Figure 1.5 shows ways of designing tubular reactors to include heat transfer. If the amount of heat to be transferred is large, then the ratio of heat transfer surface to reactor volume will be large, and the reactor will look very much like a heat exchanger as in Fig. 1.5b. If the reaction has to be carried out at a high temperature and is strongly endothermic (for example, the production of ethylene by the thermal cracking of naphtha or ethane—see also Section 1.7.1, Example 1.4), the reactor will be directly fired by the combustion of oil or gas and will look like a pipe furnace (Fig. 1.5c).

Production of Ethylene by Pyrolysis of Ethane in an Isothermal Tubular Reactor... 

Effluent from the hydrogenation reactor is depressured to about 400 psig. This level of hydrogen is required to prevent the reverse reaction, diethylaluminum hydride decomposition, which results in plating of aluminum on the process equipment. Product diethylaluminum hydride, unreacted aluminum, and solvent are charged to the ethylation reactor. Ethylene is introduced and undergoes a rapid, exothermic reaction to form triethylaluminum. A tubular reactor with high heat transfer capabilities is required to control this reaction (12). 

Commercial production of ethanolamines (EOA) is by reaction of ethylene oxide with aqueous ammonia. The ethylene oxide reacts exothermically with 20% to 30% aqueous ammonia at 60 to 150°C and 30 to 150 bar in a tubular reactor to form the three possible ethanolamines (mono-ethanolamine - MEA, di-ethanolamine - DEA and tri-ethanolamine - TEA) with high selectivity. The product stream is then cooled before entering the first distillation column where any excess ammonia is removed overhead and recycled. In the second column, ammonia and water are removed and the EOA s are separated in a series of vacuum distillation columns. 

The industrial production of ethylene oxide is based on the direct oxidation of ethylene in the gas phase on a silver catalyst in cooled, tubular reactors. For a large excess of ethylene the reaction scheme can be simplified to ... 

Only peroxides are used as initiators and are added to the tubular reactor at several points. In combination with the unique CTR design, this process offers ethylene conversions up to 40%, at constant reactor pressure. A cleaning system nor a sequence system, for regularly fluctuating the reactor pressure during production, are not required. 

Stamicarbon bv Polyethylene, LDPE Ethylene Advanced Clean Tubular Reactor LDPE reliable, flexible and low-cost for any PE product lines sizes up to 200,000 tpy 9 2000... 

Theonly important current application of tubular reactors in polymer syntheses is in the production of high pressure, low density polyethylene. In tubular processes, the newer reactors typically have inside diameters about 2.5 cm and lengths of the order of I km. Ethylene, a free-radical initiator, and a chain transfer agent are injected at the tube inlet and sometimes downstream as well. The high heat of polymerization causes nonisothermal conditions with the temperature increasing towards the tube center and away from the inlet. A typical axial temperature profile peaks some distance down the tube where the bulk of the initiator has been consumed. The reactors are operated at 200-300°C and 2000-3000 atm pressure. 

Reactor designs are characterized as either homogeneous or heterogeneous. Typically, homogeneous reactors are well mixed stirred tanks (either batch or continuous), but can also be tubular reactors. They are widely used in the chemical industry from pilot plant to full-scale production. Examples include decomposition of azomethane, production of ethylene glycol, and the copolymerization of styrene and butadiene. 

EO is mainly produced by the direct oxidation of ethylene with air or oxygen in a packed-bed, multi tubular reactor with recycle [2]. Catalysts for EO production... 

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