Phosphoric acid chemical activation with

El-Sayed and Bandosz used three activated carbon samples of different origin, namely BPL from Calgon and MVP from Norit, both prepared from bituminous coal, and BAX from Westvaco, made from wood, using chemical activation with phosphoric acid for the adsorption of acetaldelyde. These carbons were washed in a soxhlet apparatus to remove water-soluble impurities and then oxidized with nitric acid. The adsorption of acetaldehyde was determined by inverse gas chromatography at infinite dilution and finite concentration. The heats of acetaldehyde adsorption at... 

In summary, as is the case with physical activation, highly activated carbons with narrow MPSDs can hardly be prepared by chemical activation with either phosphoric acid or zinc chloride. Therefore, they can neither satisfy the demand for improving some AC apphcations nor for finding new ones, as high-pressure gas storage (e.g., CO2, H2, natural gas) requires both high MPV and narrow MPSD. 

The largest producer in the USA is Calgon Carbon Corporation, with plants in several locations. Its annual capacity represents around 42% of the total production capacity of the country the main activation process is thermal and the precursors used are bituminous coal, coconut shell and charcoal. The second largest producer is Norit Americas, Inc., with around 23% of total capacity. Thermal activation is carried out with lignite and bituminous coal, and chemical activation (with phosphoric acid) is carried out with wood and peat. The third producer is Westvaco Corporation, with around 12%, sawdust being the main precursor for both thermal and chemical (with phosphoric acid) activation. Regeneration capacity of spent activated carbon has considerably increased in the last few years, this capacity being estimated to be now over 50,000 tonnes per year. 

In chemical activation processes, the precursor is first treated with a chemical activation agent, often phosphoric acid, and then heated to a temperature of 450 -700 °C in an activation kiln. The char is then washed with water to remove the acid from the carbon. The filtrate is passed to a chemical recovery unit for recycling. The carbon is dried, and the product is often screened to obtain a specific particle size range. A diagram of a process for the chemical activation of a wood precursor is shown in Fig. 3. 

The activity of Ti catalysts in SSP depends on the kind of stabilizer fed into the reactor. In the production of PET, phosphorous-containing chemicals are commonly added as stabilizers. These products improve the thermal stability, particularly in processing, which results in reduced degradation and discoloration and are therefore of importance with respect to quality. Such materials are added during the production of the prepolymer. These stabilizers are mainly based on phosphoric or phosphonic (phosphorous) acids or their esters. 

In some of the earliest recorded examples of adsorption, activated carbon was used as the adsorbent. Naturally occurring carbonaceous materials such as coal, wood, coconut shells or bones are decomposed in an inert atmosphere at a temperature of about 800 K. Because the product will not be porous, it needs additional treatment or activation to generate a system of fine pores. The carbon may be produced in the activated state by treating the raw material with chemicals, such as zinc chloride or phosphoric acid, before carbonising. Alternatively, the carbon from the carbonising stage may be selectively... 

Activation is often conducted by processing with steam or chemical agents. Carbons activated by steam can be prepared from raw materials such as coal, peat, or lignite, which are carbonized and reacted with high-temperature water steam, in the process where fraction of carbon atoms are gasified, leaving beside porous structure. Chemically, carbon can also be activated with phosphoric acid. So-called mesocarbon microbeads (MCMBs) were produced from coal tar pitch in the Osaka... 

Axially chiral phosphoric acid 3 was chosen as a potential catalyst due to its unique characteristics (Fig. 2). (1) The phosphorus atom and its optically active ligand form a seven-membered ring which prevents free rotation around the P-0 bond and therefore fixes the conformation of Brpnsted acid 3. This structural feature cannot be found in analogous carboxylic or sulfonic acids. (2) Phosphate 3 with the appropriate acid ity should activate potential substrates via protonation and hence increase their electrophilicity. Subsequent attack of a nucleophile and related processes could result in the formation of enantioenriched products via steren-chemical communication between the cationic protonated substrate and the chiral phosphate anion. (3) Since the phosphoryl oxygen atom of Brpnsted acid 3 provides an additional Lewis basic site, chiral BINOL phosphate 3 might act as bifunctional catalyst. 

Chemically pure reagents were used. Cadmium was added as its sulfate salt in concentrations of about 50 ppm. Lanthanides were added as nitrates. For the experiments with other metal ions so-called "black acid from a Nissan-H process was used. In this acid a large number of metal ions were present. To achieve calcium sulfate precipitation two solutions, one consisting of calcium phosphate in phosphoric acid and the other of a phosphoric acid/sulfuric acid mixture, were fed simultaneously in the 1 liter MSMPR crystallizer. The power input by the turbine stirrer was 1 kW/m. The solid content was about 10%. Each experiment was conducted for at least 8 residence times to obtain a steady state. During the experiments lic iid and solid samples were taken for analysis by ICP (Inductively Coupled Plasma spectrometry, based on atomic emission) and/or INAA (Instrumental Neutron Activation Analysis). The solid samples were washed with saturated gypsum solution (3x) and with acetone (3x), and subsequently dried at 30 C. The details of the continuous crystallization experiments are given in ref. [5]. 

Activated carbon is manufactured from carbonaceous materials, such as petroleum coke, sawdust, lignite, coal, peat, wood, charcoal, nutshells, and fruit pits. Activation is a physical change wherein the surface of the carbon is increased by the removal of hydrocarbons by any one of several methods. The most widely used methods involve treatment of the carbonaceous material with oxidizing gases such as air, steam, or carbon dioxide, and the carbonization of the raw material in the presence of chemical agents such as zinc chloride or phosphoric acid. 

During a treatment with chemically reacting agents, these may penetrate into the pore system where they react to form deposits, which may lead to a narrowing of the pores as well as to a change in the catalytic activity. Boric acid, trimethylborate, phosphoric acid and triphcnylphosphinc may serve as examples for suitable reacting agents. Such methods have been applied successfully to the selective production of p-xylene b ... 

Activation always involves some form of chemical attack. However, chemical activation is a term often used to indicate the prior impregnation of the precursor with a chemical agent such as phosphoric acid or zinc chloride before heat treatment. Physical activation, on the other hand, signifies the heat treatment of the char in a mildly reactive atmosphere such as steam or carbon dioxide. This type of process is preferably referred to as thermal activation (Baker, 1992). The apparent distinction between chemical and physical is somewhat unsatisfactory for two reasons first, it implies a fundamental difference in the mechanism of activation and second, it does not allow for the many procedures which involve both types of treatment. 

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