Ethyl process

Mild steel is a satisfactory constmction material for all equipment in Ziegler chemistry processes except for hydrolysis. If sulfuric acid hydrolysis is employed, materials capable of withstanding sulfuric acid at 100°C are requited lead-lined steel, some alloys, and some plastics. Flow diagrams for the Vista and Ethyl processes are shown in Eigures 3 and 4, respectively. 

The Ziegler process produces linear alcohols with an even number of carbon atoms and is based on the polymerization of ethylene under catalytic conditions, generally with triethylaluminum as in the Alfol and the Ethyl processes. The distribution of alkyl chains depends on the version of the process employed but the alcohols obtained after fractionation can be equivalent to those obtained from fats and oils or have purpose-made distributions depending on the fractionation conditions. 

Ethyl Process Development Center Baton Rouge, LA 5,500 0 250 0 5.750 0 0... 

Plant sterols such as stigmasterol typically contain an extra ethyl group when compared with cholesterol. Now this is not introduced by an electrophilic ethylation process instead, two successive electrophilic methylation processes occur, both involving SAM as methyl donor. Indeed, it is a methylene derivative like that just seen in ergosterol formation that can act as the alkene for further electrophilic alkylation. After proton loss, the product has a side-chain with an ethylidene substituent the side-chains of the common plant sterols stigmasterol and sitosterol are then related by repeats of the reduction and dehydrogenation processes already seen in ergosterol formation. 

The Chevron/Gulf process also uses triethylaluminum but in a catalytic reaction at higher temperature. Reaction conditions exert a strong effect on product distribution. Under the proper conditions (200-250°C, 140-270 atm) the rates of insertion and chain transfer (displacement) are comparable, ensuring frequent p-hydrogen elimination. A broader product distribution compared with that of the two-step ethyl process is obtained. 

In the mid 1950 s, Dr. Karl Ziegler (4) and his associates at the Max Planck Institute carried out fundamental research which provided the basis for schemes to synthesize even carbon-numbered, linear alcohols similar to natural alcohols. Commercial plants were built by Conoco in 1962, Condea in 1964, and Ethyl in 1965. The Conoco and Condea processes are virtually identical and different from the Ethyl process. 

Both the Conoco and Ethyl processes use these four basic steps, and Ethyl adds a transalkylation step to control product distribution. 

The following discussion is based on an interpretation of patent literature. The Ethyl process consists of five basic steps instead of four. 

Figure 4. Ethyl process (based on patent literature)...

The aluminum trialkoxides are then hydrolyzed with dilute sulfuric acid in the Ethyl process (23)- This forms free alcohol and an aqueous aluminum sulfate solution which are separated by phase split. The aqueous aluminum sulfate is sold. Product alcohols are washed with caustic to remove traces of acid, dried, and fed to conventional distillation train. The product alcohols are sold by Ethyl under the trade name of EPAL alcohols. 

In this stoichiometric reaction sequence, a Poisson distribution of a-oletin products is obtained. The main disadvantage of this process is the large amount of aluminium alkyls needed in an industrial plant. To overcome this drawback, improvements of the process were developed by several companies. Only the two most important examples, the Gulf process and the Ethyl process, will be described in more detail. Shell developed a different route based on a nickel complex catalyst. Though other processes based on different transition metal catalysts have been developed, only the three processes mentioned above became important [16]. 

Two processes have been commerdalized on the basis of the oligomerization of ethylene, one by Conoco Chemical and the second by Ethyl Corporation. They differ in the distribution curve of the different alcohols formed. Whereas Conoco s Alfol alcohols range from C2 to C22 with about 55 per cent C12 or above (Fig. 9.S), the alcohol distribution of the Ethyl process is narrower and comprises 85 par cent C 2 - Tins change in the distribution curve results from the insertion of an additional stage of transalkylation by triisobutyUluminum. 

The synthesis of a-olefins from ethylene has been conducted by two general routes. By one route, triethylaluminum reacts with ethylene to form longer chain alkylaluminum compoimds (Equation 22.25). On average, nine moles of ethylene are incorporated into one triethylaluminum to generate trioctylaluminum. These alkylaluminum products are then treated with ethylene at higher temperature to eliminate the olefin and regenerate triethylaluminum. This process is called "the ethyl process." ... 

Olefin Chain Composition from the Ethyl Process... 

The Ethyl process was costly relative to the simple one-step process, which is likely the reason for Ethyl selling their plant to BP that was later shut down in 2002 because it could not compete with the other process routes such as the simpler single-step and 0x0 processes. 

Chemical Co. [283-287], Ethyl Corp. [288], and by Shell Oil Co. [288-291]. The Gulf and Ethyl processes use EtsAl as catalyst although they differ in some details. In the Ethyl process, in contrast to the Gulf process, the products are recycled to increase the amount of the most desirable linear a-olefins C6-Ci4. This leads, unfortunately, to higher branched olefin content in the yield as a result of higher a-olefins reactions with alkylaluminum compounds. 

The Ethyl process [292] is carried out at 100°C under 210 psig pressure, and the Gulf process at 190 C under 4000 psig uses 14% EtsAl in heptane solution as catalyst. The ethylene conversion reaches 85%. 

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