Chemically prepared manganese dioxides

Manganese dioxide has been nsed to carry out a range of chemical oxidations, and is the reagent of choice for the oxidation of allylic alcohols (Hndlicky 1990). There are several methods for its preparation that may acconnt for differences in its activity. Although it has seldom been exploited for the oxidation of contaminants, two widely different applications have been described ... 

Chemical manganese dioxide (CMD). This form of Mn02 is used for batteries it is available from I. C. Sample office (Cleveland, Ohio, 44101). Shioiri et al. report it is superior to commercial activated Mn02 (Aldrich) and more convenient than freshly prepared activated Mn02 for dehydrogenation of 2-(l-ami-noalkyl)thiazolidine-4-carboxylic acids to the corresponding thiazoles (thiazole amino acids). 

Quinone may be prepared by the oxidation of aniline with dichromate or manganese dioxide and sulfuric acid.1 This is a more feasible commercial method than the one given. However, the oxidation of hydroquinone is more rapid and convenient and, hence is more desirable for use in the laboratory. Various materials have been oxidized by chemical means to give quinone they are quinic acid,2 hydroquinone,3 benzidine,4 -phenylene-diamine,5 sulfanilic acid,6 / -phenolsulfonic acid,7 arbutin,8 aniline black,9 and the leaves of various plants.10 Quinone is also formed by several other methods by the fermentation of fresh grass 11 by the action of iodine on the lead salt of hydroquin-... 

In the laboratory oxygen may be prepared by several chemical methods that involve thermal decomposition of solid oxides or 0x0 salts. The most convenient method of preparing oxygen is to heat potassium chlorate in the presence of manganese dioxide catalyst ... 

Gemeay AH, Nishiya H, Kuwabata S, Yoneyama H. Chemical preparation of manganese dioxide/poly-pyrrole composites and their use as cathode active materials for rechargeable lithium batteries. J Electrochem Soc 1995 142 4190-4195. 

The actual cell voltage is about 1.5 V, it does not depend on the actual pH-value of the electrolyte solution as obvious from the absence of protons and hydroxide ions in the cell reaction equation. It slightly depends on the source of the used manganese dioxide. Initially naturally occurring manganese dioxide was used. The battery required a quality of less than 0.5% copper, nickel, cobalt, and arsenic to avoid undue corrosion of the zinc electrode. Currently synthetic manganese dioxide is prepared either by chemical (CMD) or electrochemical (EMD) procedures. For improved electrical conductivity graphite or acetylene black are added. Upon deep... 

Usually tapping density prepared from EMD is higher than that from chemical manganese dioxide (CMD). The typical tapping density of our product is 1.6 g/cm. ... 

II. The manganese dioxide catalysts were prepared using a newly developed ultrasonic nozzle reactor (Figure 2). The reactor behaves like a continuous stirred tank reactor. The product flows into a beaker glass of 500 ml volume. It is characterized directly without further steps of preparation by chemical reaction with a solution of hydrochloric-acid and hydrogen peroxide in water. 

Write the chemical equations for the preparation of potassium manganate and potassium permanganate from manganese dioxide, using potassium hydroxide, air, and carbon dioxide. 

Different preparations of activated manganese dioxide (Mn02) are reported in the chemical literature. Generally, the commercially available material destined for catalyst use has suffered particle size adjustment (through grinding), acid (or base) washing to add or subtract surface protons, and heat treatment to remove adsorbed water. It is not uncommon to find that different batches of commercially obtained material (even from the same supplier) have different activites. 

Preparation and Uses of Chlorine Chlorine is a major industrial chemical. It is prepared commercially by the electrolysis of aqueous sodium chloride. Chlorine can be prepared in small amounts for laboratory use by the reaction of chloride ion with a strong oxidizing agent, such as potassium dichromate or manganese dioxide. However, chlorine is readily available in steel cylinders for laboratory work. 

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