Hercules-Distillers process

The stirred flow reactor is frequently chosen when temperature control is a critical aspect, as in the nitration of aromatic hydrocarbons or glycerine (Biazzi-process). The stirred flow reactor is also chosen when the conversion must take place at a constant composition, as in the copol3rmerization of butadiene and styrene, or when a reaction between two phases has to be carried out, or when a catalyst must be kept in suspension as in the polymerization of ethylene with Ziegler catalyst, the hydrogenation of a-methylstyrene to cumene, and the air oxidation of cumene to acetone and phenol (Hercules-Distillers process). 

Herm/es/Djnamit JS obe/Process. On a worldwide basis, the Hercules Inc./Dynamit Nobel AG process is the dorninant technology for the production of dimethyl terephthalate the chemistry was patented in the 1950s (67—69). Modifications in commercial practice have occurred over the years, with several variations being practiced commercially (70—72). The reaction to dimethyl terephthalate involves four steps, which alternate between liquid-phase oxidation and liquid-phase esterification. Two reactors are used. Eirst, -xylene is oxidized with air to -toluic acid in the oxidation reactor, and the contents are then sent to the second reactor for esterification with methanol to methyl -toluate. The toluate is isolated by distillation and returned to the first reactor where it is further oxidized to monomethyl terephthalate, which is then esterified in the second reactor to dimethyl terephthalate. 

The oldest cresol production method used in the United States is through the recovery of fractional distillates from coal tars. Most domestic cresols are formed via catalytic and thermal cracking of naphtha fractions during petroleum distillation. Since 1965, quantities of coal tar and petroleum isolates have been insufficient to meet the rising demand. Consequently, several processes for the manufacture of the various isomers have been developed. One General Electric facility produces o-cresol at an annual capacity of 10,000 tons by the methylation of phenol in the presence of catalysts. The Sherman-Williams Company uses the toluene sulfonation process and maintains an annual capacity for p-cresol of 15,000 tons. The Hercules Powder Company produced p-cresol until 1972 by the cymene- cresol process. 

In 1957 Hercules Inc. started the first unit that produced concentrated nitric acid for commercial sales using magnesium nitrate as the extractive agent. In this process (see Figure 2) the weak nitric acid product from an AOP is fed to the appropriate tray of a distillation column. A concentrated solution of magnesium nitrate and water is fed to the proper tray in sufficient quantity to enrich the vapors to a concentration greater than 68 wt % nitric acid. The overhead product from the column is concentrated (98-99.5 wt %) nitric acid. A portion of the concentrated nitric acid is returned as reflux to aid in rectification. The... 

The cumene process, sometimes referred to as the Hock process, was made possible by the discovery of cumyl hydroperoxide and of its cleavage to phenol and acetone [1]. Shortly after World War II the reaction was developed into an industrial process by the Distillers Co. (BP Chemicals) in the United Kingdom and Hercules in the USA. The first commercial plant was started in Montreal, Canada, in 1952 by M.W Kellogg. 

Phenol. The manufacture of phenol by the oxidation of benzene is described by Denton (21) and by Simons and McArthur (107). The literature on phenol by the oxidation of cumene is partly covered in the reports of Frank (33), Hawkins (43), and Kharasch (57), mentioned earlier. A brief description and flow sheet of the process is given in Chemical Engineering (16). The patents in this field are mainly held by The Distillers Co., Ltd., Hercules Powder Co., and Allied Chemical and Dye Corp. In this phenol process large amounts of acetone are obtained as a coproduct. It should also be noted that the process may be directed to the production of cumene hydroperoxide and a,a dimethylbenzyl alcohol. Krieble (61) and Kenyon and Boehmer (55) describe the preparation of phenol by the chlorination and sulfonation processes. 

THE ENTRY INTO PETROCHEMICALS Because the early 1950s were a period of rapid innovation in polymer/petrochemical technology, Hercules was able to build a new learning base in that industry and become a first mover in one of the most versatile of the new commodities, polypropylene (PP). Its strategy was excellent. The company worked closely with European inventors and companies that, like Hercules, had not been involved in the new technology s wartime development. After pioneering the invention of a new process for phenol resins, it joined with Britain s Distillers Company to commercialize and license the process. Its first plant came on-stream in 1952.4... 

A third advanced purification step must be added, due to the evolving requirements of users who demand increasnely pure phenoL The main process holders are Allied Chemical, BP (British Petroleum) (Distillers), Chevron, Power Gas. Hercules, Rhone-Poulenc, SIR (Societa Italiana Resine) and HOP [Universal Oil Products) (Cumox process). 

In the Chemische Werke Witten process, which was further developed by Dynamit Nobel and Hercules, p-xylene, air and the catalyst are fed continuously into the oxidation reactor, to which recirculated p-methylbenzoic acid methyl ester is also added. Oxidation is effected at a temperature of 140 to 170 °C and a pressure of 4 to 7 bar. The heat of reaction is removed by the vaporization of water and excess p-xylene. The further reaction with methanol is carried out at 200 to 250 °C under slightly raised pressure (20 bar) in the esterification reactor, to keep the reaction mixture in the liquid-phase. The esterification products flow to the crude ester column, where p-methylbenzoic add methyl ester is separated from the crude dimethyl terephthalate. p-Methylbenzoic acid methyl ester is recycled to the oxidation reactor, where oxidation of the second methyl group occurs. The crude dimethyl terephthalate is purified to fiber grade quality by distillation and crystallization from methanol, and subsequent redistillation in a column with around 30 trays. The yield of dimethyl terephthalate (m.p. 141 °C) is generally about 87 mol%. 

As in all alkylation reactions the catalyst used to produce cumene from propylene and benzene is a strong acid and a number of processes have been introduced. The first were developed by Distillers and Hercules in 1953 ... 

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