Weldon Process

In acid solution, Mn02 is an oxidi2ing agent, and is used as such in industry. The classic example is the oxidation of chloride in HCl, which has been a convenient means of chlorine generation, both in the laboratory and in the old Weldon process for the manufacture of chlorine. 

Manganese(ll) chloride is a by-product in the manufacture of chlorine from manganese dioxide and hydrochloric acid (the Weldon process). 

Routes to chlorine from hydrogen chloride oxidation have been refined from the original commercial ventures of Weldon, which employed manganese dioxide (Eq. 8.54). The Weldon process permitted a maximum recovery of 50% of the chlorine in the hydrogen chloride consumed. Attempts to recycle the manganese (II) chloride met with mixed success [47]. 

During Roscoe s professorship in Manchester important developments in the Leblanc alkali process and its subsidiaries were occurring in Lancashire. The Weldon chlorine process was begun at St. Helens in 1866 and manufacture commenced in 1869. The Deacon process began about 1867 and slowly displaced the Weldon process the last English Deacon plant was shut down in 1929 but the process has been revived in a modern form using oxygen. 

Deacon published a theory of the chlorine process. The important method for purifying the hydrochloric acid gas from the saltcake furnaces was devised by Robert Hasenclever. Deacon s process came into general use only after his death, since the Weldon process was simpler and gave a more concentrated (85-90 per cent) gas. Deacon in 1872 warned Mond of the possibilities of the ammonia-soda process. He amassed a considerable fortune of over 3 100,000. Another chlorine process invented by Dunlop (1849), involving the oxidation of hydrochloric acid by nitric acid, has recently been revived. 

Recycling of manganese improved the overall process economics, and the process became known as the Weldon process [2], In the 1860s, the Deacon process, which generated chlorine by direct catalytic oxidation of hydrochloric acid with air according to Eq. (2) was developed [3],... 

This improved the economics, and the Weldon process operated for a time. A novel process for producing chlorine by the oxidation of hydrogen chloride with air, catalyzed by cupric chloride, then appeared ... 

Claus felt that the cyclic process could be simplified if the hydrogen sulfide were converted to sulfur by an iron catalyst in a kiln. It was later found that dried Weldon process mud or bauxite would operate as a catalyst at a lower temperature than ferric oxide. This not only extended the life of the kiln but also increased sulfur yield. Problems with blocked beds were overcome as technology evolved and proper reactors containing solid catalyst particles were developed. Thus, the modem Claus sulfur recovery process originated from the statutory obligation to remove sulfur from town gas in Victorian gas works. 

A more constrained opportunity for nitrate bioremediation arose at the US-DoE Weldon Spring Site near St. Louis, Missouri. This site had been a uranium and thorium processing faciUty, and treatment of the metal had involved nitric acid. The wastestream, known as raffinate, was discharged to surface inpoundments and neutralized with lime to precipitate the metals. Two pits had nitrate levels that requited treatment before discharge, but heavy rains in 1993 threatened to cause the pits to overflow. Bioremediation by the addition of calcium acetate as a carbon source successfully treated more than 19 million liters of water at a reasonable cost (75). 

The Weldon-Pechiney process for manufacturing CI2 from HCl involves the use of Mn02 as the oxidizing agent instead of the O2 employed in the Deacon reaction. 

Machines Based on Movement of Both Dye Liquor and Material. One example of a machine in which both yam and dye Hquor are moved is the Klauder-Weldon skein dye machine not only do the skeins turn, but the Hquor is pumped in small streams over the yam as the threads pass over the spindles. This process assures maximum uniformity and levelness. 

Weldon An early process for making chlorine by oxidizing hydrochloric acid (from the Leblanc process) with manganese dioxide. The mixture was heated with steam in stone tanks. Manganese was recovered from the liquor by precipitation with calcium hydroxide and subsequent oxidation by air ... 

The process was complicated by the formation of calcium manganite, CaMn206, known as Weldon mud. Invented by W. Weldon in 1866 and developed at St. Helens from 1868 to 1870. Operated in competition with the Deacon process until both were overtaken by the electrolytic process for making chlorine from brine. Weldon mud has been used as a catalyst for oxidizing the hydrogen sulfide in coal gas to elemental sulfur. 

Weldon et al.5 used Raman in the surface-enhanced mode (SERS) to monitor bacterial (P. acnes) hydrolysis of triglycerides in lipid mixtures that model sebaceous gland secretions. While technically not a process monitor, it paves the way for methods to monitor specific moieties in very complicated matrices. 

Weldon, M. K., Queeney, . T., Eng, J., Raghavachari, K. and Chabal, Y. J. The surface science of semiconductor processing gate oxides in the ever-shrinking transistor. Surface Science 500, 859 (2002). 

It is, however, a blemish that it produces less chlorine per unit of acid than native manganese ore of good quality and, as W. Weldon himself has said, it is a barbarous process that yields only one-third of the total chlorine of the acid treated, and thatthe other two-thirds are wasted as calcium chloride. 

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