Dupont Electrochemicals

 

This de novo technological step developed within the Dupont research facility at Niagara Falls involved the bold commercialization of straight chain

  α, ω  disubstituted aliphatics, having the  C-4,  C-5,  C-6,  C-7  carbon atoms respectively all based on the manipulation of the furfural molecule.

A second phase to this research/development work was the semi-commercialization of no fewer than six parent and a host of heterocyclic molecules hitherto available only as laboratory curiosities. They were pyrrole and N-methylpyrrole, pyrrolidine, furan, dihydropyran, tetrahydropyran, tetrahydrothiophene, and most importantly tetrahydrofuran  (ref) QO had already commercialized both fufurfral and tetrahydrofurfural alcohols.      

 Set up as a completely free standing series of units was the plant to manufacture adiponitrile known chemically as 1,4-dicyanobutane,a thermally and air stable aliphatic dinitrile. The uniqueness of this plant was based on a renewable resource and the transformations of the furfural molecule. Manufactured  by Quaker Oats Co. in Peoria Illinois and shipped in tank car, by rail, to Niagara Falls. As I understood this, all of the technology was developed at Dupont’s Niagara research facility and was subject to many press releases and papers based on the potential of furfural as a raw material manufactured by a newly coined word called “Chemurgy”

A masterpiece of chemical development ; manufacturing Nylon a completely synthetic polymer from corncobs!

There were a host of other products which Dupont had developed

based on furfural see Oliver W. Cass, Industrial and Engineering Chemistry 40 #2 February (1948) see also Dunlop and Peters, The Furans,

 

U.S. Patent 2,776,981 (1957)  Leo Tyran E.I. Dupont Process and Catalyst for the production of Furan from Furfural

 

Why was this done at Niagara ?, my intuition tells me , because of the ease and experience in handling highly poisonous sodium cyanide

LD5015 mgm/kilogram (rats).

 

other products developed by Dupont based on this and similar technology.

Lysine

Dihydropyran

adiponitrile

N-methylpyrrole

Pyrrole

Tetrahydrofuran

4-chloro-I-butanol

1,4-diclorobutane

tetrahydrothiophene

4-chlorobutyronotrile

1,5-pentanediol

tetrahydropyran

delta-valerolactone

1,5-dichloropentane

5-chlorovaleronitrile

pimelic acid

1,5-cyanopentane

glutaric acid

5-amino-1-pentanol

 

 

The process was developed following a very straight forward line of attack from furfural using a continuous commercial process in a single process line in a newly built operation next to Dupont’s Electrochemical Facility. As stated before I was one of the fortunate few who had the rare privilege of personally visiting this facility in 1951. The first step in this process was the high temperature decarbonylation of furfural to furan

The equipment was located in an 1 wall open 3 walls closed open air building within 2 floors a platform on the second floor was located the reactor center which was heated to ~400° C with Dowtherm ,over a catalyst consisting of zinc and iron chromite, the room was very hot from the at necessary to effect this conversion and I don’t recall much insulation around the tubular reactor.

The reaction evolves carbon monoxide which was vented thru the refrigerated heat exchangers.

 

The major issue was the storage of very volatile furan b.p32oC

They had designed the process to store the furan in empty 1 ton chlorine cylinders for several reasons 1) ability to stand the vapor pressure

Because of the pressure rating of these cylinders 2) the ability to stand the abuse and reuse of these cylinders  3)  acting as a feed tank for the hydrogenation step. I can remember the cleaned  1 ton chlorine cylinders 7-8 of them representing 5 tons of furan painted silver and lined up horizontally on the ground floor outside the building next to the works lab.

We were not shown the catalytic hydrogenation of furan to tetrahydrofuran which I assume was done vapor phase and not liquid phase batch type. From the literature on this subject . They had by product electrolytic by product hydrogen available from neighboring companies since they did not generate hydrogen from their sodium metal operation in that plant.  THF was a big item with Dupont not only was it used as a feedstock for their Nylon operation but bas a solvent for a wide variety of polymers.  Since this process was costly and difficult it was only a matter of time before other routes were developed 10 years later.

For  hydrogenation, the Dupont group selected, as their method of choice, vapor phase hydrogenation with nickel on a silicaceous catalyst, for several reasons, firstly the pyrophoric nature of Raney Nickel reduced the fire an explosion risk because of the highly volatile nature of furan,

Looking into the literature in depth (at that time) one can approach tetrahydrofuran from two perspectives its chemical reactivity and its solvent power. The ring opening reactions of THF extensive as well as second, and third  generation products.

 

The principle reaction for the Nylon intermediate process was

1,4-dichlorobutane. With the proper choice of reaction conditions  and  recycling of by-products  substantially quantitative yields of 1,4-dcb could be obtained from THF.

1,4 dichlorobutane  is then reacted with 2 moles of sodium cyanide in a suitable solvent system, displacing 2 chlorine atoms with the formation of adiponitrile.