Raw Materials Precursors

Raw Materials Selection. The selection of the appropriate raw (precursor) materi s is the first and critical step in the manufacturing process. It determines to a great degree, the properties and the cost of the final product. The characteristics of these raw materials such as the particle size and ash content of cokes, the degree of carbonization of pitch, the particle structure of lampblack, and the impurities and particle size of natural graphite must be taken into account. 

Raw materials can be divided into four generic categories fillers, binders, impregnants, and additivesJ l I l 

Fillers. The filler is usually selected from carbon materials that graphitize readily. As mentioned in Ch. 4, such materials are generally cokes, also known in industry as soft fillers . They graphitize rapidly above 2700°C (the graphitization process is described in Sec. 2.4 below). Other major fillers are synthetic graphite from recycled electrodes, natural graphite, and carbon black (see Ch. 10). 

Petroleum coke is the filler of choice in most applications. It is a porous by-product of the petroleum industry and an almost-pure solid carbon at room temperature. It is produced by destructive distillation without the addition of hydrogen, either by a continuous process (fluid coking) or, more commonly, by a batch process (delayed coking). 

The batch process consists of heating high-boiling petroleum feedstocks under pressure to approximately 430°C, usually for several days.I l This promotes the growth of mesophase-liquid polycylic crystals. The material is then calcined up to 1200°C, to remove almost all the residual hydrogen, and finally ground and sized. 

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High carbon yielding resins are sometimes employed as raw material precursors for specialty carbons. Various chemical additives are also used in low concentrations to improve the processabiHty or to control puffing during graphitization. 

The kind of manufacture, transportation, and distribution infrastructure required to support a hydrogen-based fuel cell vehicle will be tied directly to the form of hydrogen used on board the vehicle. For example, on-board storage of molecular hydrogen allows a broad spectrum of raw material precursors to manufacture hydrogen. With a chemical carrier, however, molecular hydrogen may not be needed, and the manufacture, transportation, distribution, and storage systems would be quite different. 

HPLC is widely used in the chemical and plastics industries. Applications in the chemical industry are quite similar to those for testing pharmaceutical ingredients. They include assay and purity testing of synthetic chemicals such as raw materials, precursors, monomers, surfactants, detergents, and dyes.27,28 In the plastics industry, GPC is used for polymer characterization in product research and quality control. RPC is used in the determination of polymer additives. 

The deaning agents ability to remove residues of raw materials, precursors, by-products, intermediates, or APIs ... 

There are over 8000 chemicals that exhibit commercially significant optical properties. Some of these are natural products such as indigo, chlorophyll, and cochineal, but the majority are synthesized in a series of steps involving dye intermediates (any of the 3000 or more organic and inorganic chemicals used as raw material precursors to manufactured dyes, the most important of which are benzene and naphthalene). Coal tar dyes refers to the dyestuffs originating from the complex mix of hydrocarbons (benzene, toluene, xylene, pyrene, naphthalene, anthracene, etc.) present in coal tar (8007-45-2). Petroleum has succeeded coal as the dominant source of dye intermediates. Dyes, pigments, and dye intermediates include... 

Some hquid defoamers are preemulsified relatives of paste defoamers. In addition to the fatty components mentioned above, kerosene [8008-20-6] or an organic cosolvent such as 2-propanol have been used to enhance stabiUty of the oil—water emulsion and the solubiUty of the defoamer s active ingredients. These cosolvents are used less frequently as concerns increase about volatile organic emissions (VOCs) from the paper machine. Additionally, the use of ultrapure mineral oil in defoamers has become commonplace. Concern about the creation of 2,3,7,8-tetrachlorodibenzodioxin (TCDD) and 2,3,7,8-tetrachlorodibenzofuran (TCDF) in the pulping process has led to the discovery of unchlorinated precursor molecules, especially in recycled mineral oil and other organic cosolvents used in defoamer formulations (28). In 1995 the mineral oil that is used is essentially free of dibenzodioxin and dibenzofuran. In addition, owing to both the concern about these oils and the fluctuating cost of raw materials, the trend in paper machine defoamers is toward water-based defoamers (29). 

Cycloahphatic amine production economics are dominated by raw material charges and process equipment capital costs. Acetone (isophorone), adiponitnle, aniline, and MDA are all large-volume specification organic intermediates bordering on commodity chemicals. They are each cost-effective precursors. 

The precursors of dyes are called dye intermediates. They are obtained from simple raw materials, such as ben2ene and naphthalene, by a variety of chemical reactions. Usually, the raw materials are cycHc aromatic compounds, but acycHc precursors are used to synthesi2e heterocycHc intermediates. The intermediates are derived from two principal sources, coal tar and petroleum (qv). 

A further source of C9 material is coal tar. Structures of the two resins precursors are roughly similar, except the presence of small quantities of coumarone in coal tar feedstream. There is a significant difference in the concentrations of individual monomers coal-tar-based raw material is richer in indene (styrene/indene ratio =1 7) than the petroleum-based feedstream (styrene/indene ratio =1 1). 

Natural gas and crude oils are the main sources for hydrocarbon intermediates or secondary raw materials for the production of petrochemicals. From natural gas, ethane and LPG are recovered for use as intermediates in the production of olefins and diolefms. Important chemicals such as methanol and ammonia are also based on methane via synthesis gas. On the other hand, refinery gases from different crude oil processing schemes are important sources for olefins and LPG. Crude oil distillates and residues are precursors for olefins and aromatics via cracking and reforming processes. This chapter reviews the properties of the different hydrocarbon intermediates—paraffins, olefins, diolefms, and aromatics. Petroleum fractions and residues as mixtures of different hydrocarbon classes and hydrocarbon derivatives are discussed separately at the end of the chapter. 

The physicochemical properties of carbon are highly dependent on its surface structure and chemical composition [66—68], The type and content of surface species, particle shape and size, pore-size distribution, BET surface area and pore-opening are of critical importance in the use of carbons as anode material. These properties have a major influence on (9IR, reversible capacity <2R, and the rate capability and safety of the battery. The surface chemical composition depends on the raw materials (carbon precursors), the production process, and the history of the carbon. Surface groups containing H, O, S, N, P, halogens, and other elements have been identified on carbon blacks [66, 67]. There is also ash on the surface of carbon and this typically contains Ca, Si, Fe, Al, and V. Ash and acidic oxides enhance the adsorption of the more polar compounds and electrolytes [66]. 

Methanol is used in industry as a raw material for formaldehyde (40-50%), as a solvent, and for producing, for example, acetic acid by hydroformylation. The latter is used, for example, to make precursors for polymers. 

Sitosterol is an abundant and low-cost raw material for the production of pharmaceutical steroids. 4-Androstene-3,17-dione, the precursor for the synthesis of corticosteroid hormones, can be derived from the side-chain cleavage of/3-sitosterol. Immobilized cells of Mycobacterium sp. NRRL B-3805 on Celite matrix (80-120 mesh) was found to be effective in cleaving the side chain of /3-sitosterol (5gL ) with a molar conversion yield of 70% in 50 h [30],... 

Raw materials were ground to a particle size less than 630 pm. Physical mixtures of solid KOH and a given precursor at 2 1, 3 1, 4 1 and 5 1 weight ratios were activated in the temperature range of 600-900°C for 1-5 h under argon flow of 15 dm3/h. The treatments were carried out in a horizontal furnace using a nickel boat placed in a 36 mm diameter quartz tube. The heating rate was 10°C/min. The resultant materials were washed with 10% solution of HC1 and distilled water and next were dried at 110°C for 6 h. 

Although the above classes of raw materials are the most widely used, depending on the precursor chemical approach and desire for a specific level... 

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