Activated carbon production methods

In some instances removal of ruthenium from the desired product has proved difficult. To overcome this problem, there are several reported ways to remove the ruthenium catalyst after the olefin metathesis reaction is complete. The first and most common is addition of a modifier or adsorbent followed by chromatography. The additives include dimethyl sulfoxide (DMSO), triphenylphos-phine oxide,74 or activated carbon.75 Although this is generally not suitable for commercial production, it can be quite effective. A convenient alternative is the use of Brockmann I basic alumina, followed by simple filtration through a bed of filter agent such as activated carbon. This method is capable of reducing ruthenium levels down to less than 20 ppm.76... 

Another option would be to employ an alternative method for plastic carboiuzation that would overcome the problem of low yields posed by classic carboiuzation and activation methods. A possible route would be the employment of pressurized pyrolysis. For purposes other than activated carbon production, hydrocarbon precursors have been heated under pressure to produce solid carbon products with high yields and high purity [92-94]. As an example, exceptionally hard carbon microspheres have been produced from PET waste via the closed autoclave method. This autogenic method has been patented for the production of carbon spheres for use in batteries [95]. Pol et al. further explained their method in a more extensive article [96]. In order... 

A wide range and a number of purification steps are required to make available hydrogen/synthesis gas having the desired purity that depends on use. Technology is available in many forms and combinations for specific hydrogen purification requirements. Methods include physical and chemical treatments (solvent scmbbing) low temperature (cryogenic) systems adsorption on soHds, such as active carbon, metal oxides, and molecular sieves, and various membrane systems. Composition of the raw gas and the amount of impurities that can be tolerated in the product determine the selection of the most suitable process. 

Another method employed is the treatment of aqueous solutions of aminophenols with activated carbon (81,82). During this procedure, sodium sulfite, sodium dithionite, or disodium ethylenediaminotetraacetate (82) is added to increase the quaUty and stabiUty of the products and to chelate heavy-metal ions that would catalyze oxidation. Addition of sodium dithionite, hydrazine (82), or sodium hydrosulfite (83) also is recommended during precipitation or crystallization of aminophenols. 

Color None Decaying organic material and metallic ions causing color may cause foaming in boilers hinders precipitation methods such as iron removal, hot phosphate softening can stain product in process use Coagulation, filtration, chlorination, adsorption by activated carbon... 

Phenol is the starting material for numerous intermediates and finished products. About 90% of the worldwide production of phenol is by Hock process (cumene oxidation process) and the rest by toluene oxidation process. Both the commercial processes for phenol production are multi step processes and thereby inherently unclean [1]. Therefore, there is need for a cleaner production method for phenol, which is economically and environmentally viable. There is great interest amongst researchers to develop a new method for the synthesis of phenol in a one step process [2]. Activated carbon materials, which have large surface areas, have been used as adsorbents, catalysts and catalyst supports [3,4], Activated carbons also have favorable hydrophobicity/ hydrophilicity, which make them suitable for the benzene hydroxylation. Transition metals have been widely used as catalytically active materials for the oxidation/hydroxylation of various aromatic compounds. 

Anhydrous alpha dextrose may be obtained by drying the hydrate in a stream of warm air.6 For a very pure grade of the anhydrous product a better method is used which consists of crystallizing from solution in a vacuum pan at a temperature above 50°C.1314 This temperature is the hydrate-anhydrous transition point. Dextrose from the first crystallization of the starch conversion liquor is dissolved in water to give about a 60 % solution which is treated with a small quantity of activated carbon... 

Recently investigated methods of treating waste waters contaminated with 1,3-DNB or 1,3,5-TNB and related products include biological treatment, stripping, solvent extraction, and activated carbon adsorption (HSDB 1994). 

Despite its efficiency in numerous cases optical resolution is by no means a trivial operation. In each case the optimum method has to be found by laborious trial and error procedures the optical purity of the material has to be secured and its absolute configuration has to be established before the compound can be used in a synthetic sequence. These drawbacks of optical resolution led chemists to start their syntheses from optically active natural products (the so-called chiral carbon pool ). A variety of suitable ex-chiral-pool compounds including carbohydrates, amino acids, hydroxy acids, and terpenoids are shown. 

---