Selection of raw materials

Products such as diethylene glycol and triethylene glycol, obtained by side reactions in the preparation of ethylene glycol, are sometimes used but they 

Maleic anhydride is commonly prepared by passing a mixture of benzene vapour and air over a catalyst (e.g. a vanadium derivative) at elevated temperatures (e.g. 450°C). It is a crystalline solid melting at 52.6°C (the acid melts at 130°C). 

Fumaric acid may be prepared by heating maleic acid, with or without catalysts. It is also obtained as by-product in the manufacture of phthalic anhydride from naphthalene. The acid is a solid melting at 284°C. Fumaric acid is sometimes preferred to maleic anhydride as it is less corrosive, it tends to give lighter coloured products and the resins have slightly greater heat resistance. 

The prime function of the saturated acid is to space out the double bonds and thus reduce the density of cross-linking. Phthalic anhydride is most commonly used for this purpose because it provides an inflexible link and maintains the rigidity in the cured resin. It has been used in increasing proportions during the past decade since its low price enables cheaper resins to be made. The most detrimental effect of this is to reduce the heat resistance of the laminates but this is frequently unimportant. It is usually produced by catalytic oxidation of o-xylene but sometimes naphthalene and is a crystalline solid melting at 131°C. 

Isophthalic acid (m.p. 347°C), made by oxidation of /n-xylene, has also been introduced for resins. The resins have higher heat distortion temperatures and flexural moduli and better craze resistance. They are also useful in the preparation of resilient gel coats. 

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Products used for boosting or building alkalinity in BW generally are relatively simple formulations and may or may not contain tannins, antifoamers, phosphates, polymers, and the like. Where these adjuncts are included, the selection of raw materials generally is made on the basis of ensuring compliance with G6 USDA approval, for application in USDA-inspected plants. 

The representation of hard-block domain structure shown in Scheme 4.8, implying rigid, crystallike molecular order, can be misleading because hard blocks are, at best, microcrystalline (as are soft blocks). Although microcrystallinity can be readily obtained, it requires careful selection of raw materials,... 

All safety related matters, such as the selection of raw materials, are not considered in the synthesis phase but are given by the user. Also the generation of universal synthesis rules considering safety is not easy. Therefore it is important to analyze the alternative designs by inherent safety indices which describe e.g. flammability, toxicity, process conditions. 

Indeed, the selection of raw materials from the pharmaceutical perspective is severely restricted by toxicity concerns, and Attwood and Florence (1998) suggested that only a few nonionic surfactants such as polysorbates 80 and 20 may be suitable for oral administration, with the possibility of some phospholipids serving the same function. Since that time a small number of other nonionic surfactants (e.g., cremo-phores) have been evaluated. 

Petroleum refining involves many interrelated processes, most of which have a wide range of possible operating conditions. Many refiners are also able to exercise considerable choice in the selection of raw materials for processing. This is important, since the many available crude oils differ markedly in their refining characteristics. 

The selection of raw materials and the method of preparation of the catalyst base are important in determining the final quality of the catalyst. Impregnating almost any iron oxide with potassium hydroxide and drying it will yield a catalyst of some activity, but care must be exercised both in selecting the raw materials and in the method of preparation, if a superior catalyst is to be obtained. Generally, the purer the components the better the catalyst, but substantial quantities of impurities such as silicon dioxide, aluminum oxide, and carbon can be tolerated. Suitable raw materials are obtainable at low cost, and satisfactory methods of preparation are simple and inexpensive. 

To recapitulate, the synthesis reaction in the fluid bed is quite complex. For successful operation it is necessary to provide a satisfactory catalyst and environment. This in turn requires care in the selection of raw materials for the catalyst, in its preparation and preconditioning, and in the control of the reactor feed. A combination which led to an intolerable rate of disintegration of the catalyst is shown in the first column of Table I. The results of two experiments at a lower level of selectivity which proved operable are shown in the second and third columns. The difference in operability of experiments A And B seems to stem from a variation in catalyst selectivity per se, whereas the difference... 

The extraction of vegetable plant-material requires careful selection of raw materials, in connection with chemical analysis, because the content of the vegetables to be extracted can vary substantially. Also the possibility of high concentrations of undesired substances - either contained within them, or contaminations such as pesticides - can influence the product quality enormously. Exhaustive extraction is not always possible with acceptable effort, owing to the vegetable structure, and the extraction efficiency using low-quality raw materials may be too poor to allow economic processing. 

The procedure towards an environmentally benign process starts with the selection of raw materials in addition to conventional raw materials from the petrochemical industry based on low- to medium-boiling aliphatic and aromatic hydrocarbons, replenishable raw materials from nature are increasingly available nowadays. In the simplest cases, these can be carbon sources, such as glucose and sucrose for fermentation, but also more complex molecules, frequently obtained from the chiral pool or through inexpensive fermentation from carbon sources, such as glutamic acid or citric acid. Table 20.2 lists a selection of raw materials from the chiral pool, with their estimated costs per kilogram. 

Finally, the future prominence of fluorine s role in agrochemicals will depend upon improved chemical processes for the industrial production of a wide array of fluorine-containing starting materials and intermediates. In addition to ensuring lowered costs and increased selection of raw materials, improvement in fluorine processes should also take into consideration the use of greener chemistry. 

The selection of raw materials takes into account the price variation versus purity, with constraints on undesired species. Table 10.5 shows the choice. Acetic acid is of high purity with small amounts in acetaldehyde and formic acid. Ethylene is of high purity too, with severe specifications on CO and sulfur in order to protect the catalyst, but small amounts of ethane are allowed. 

The two openings visible in the ceiling of the room today measure approximately 60 cm x 60 cm (the eastern opening),54 and 40 cm x 40 cm (the western opening).55 Both led to a wooden shaft in which a small chimney made of planks had been built. This shaft was closed by means of a lid, also made of wood, on the roof of the hut. Measured from the ceiling of the room, the chimney is approximately 1.15 m in height. Its present condition (except with regards to the size and selection of raw materials), corresponds to the draft of the cost estimate dated November 18, 1942 so that the actual structure, as built, was modified later. This is shown by the fact that, inside the room, the... 

With proper selection of raw materials which do not require pulverization, it is possible to formulate suspensions for high production with minimum process time. 

Some effervescent tablet products are successfully produced by direct compression (e.g., acetylsalicylic acid products). Direct compression normally requires careful selection of raw materials to achieve a free-flowing, non-segregating, compressible mixture. Effervescent products present the same problems as conventional products in direct compression. 

Legal requirements. Government requirements like the Federal Motor Vehicle Safety Standard (FMVSS) 105 and 135 in the United States and ECE R13 in Europe and South America are normally specified to cover vehicle stopping distance under cold, hot, high-speed, thermal and water fade and recovery conditions, and inoperative power assist. Additional requirements are imposed on the selection of raw materials by health, safety, and environmental regulations. These are the minimum requirements that need to be satisfied by a brake system. 

To this point, only the aspects concerning the technical success of the scale-up process have been treated, but it is evident that the final production process will only be successful if the catalyst can be produced in a cost-effective way. Therefore, it is important to select from the first development work the manufacturing routes that can give the lowest cost and concentrate the R D effort accordingly in the future development and test period. The raw material cost normally constitutes 60-80% of the direct cost and, therefore, the selection of raw material is an important task. The initial experiments are perhaps made on analytical... 

The late Middle Ages, with the emerging knowledge of chemistry and mineralogy, marked the start of the specific development of ceramic materials and, parallel to this, a more systematic selection of raw materials and development of technologies. 

FIGURE 60.11 Structural formula selection of raw material examples. 

As discussed in Chapter 3, the selection of raw materials and chemical reactions is often suggested by chemists, biologists, biochemists, or other persons knowledgeable about the chemical conversions involved. In recent years, with the tremendous increase in awareness of the need to avoid handling hazardous and toxic chemicals, in connection with environmental and safety regulations (as discussed in Sections 1.3 and 1.4), raw materials and chemical reactions are often selected to protect the environment and avoid the safety problems that are evident in Material Safety Data Sheets (MSDSs). For example, recall that when the vinyl chloride... 

CaP synthesis methods and their technological parameters can significantly impact stoichiometry of the synthesis product, its grade of crystallization, particle size, bioceramic phase composition, thermal stability, microstructure and mechanical properties. The important technologic parameters that impact properties of calcium phosphate synthesis product and then also of bioceramic, are temperature of synthesis, pH of synthesis environment, reagent type and concentration, as well as selection of raw materials, their purity and quality. All of the above mentioned also brings a significant impact on the tissue response of these bioceramic implants. 

The important relationship that generally exists between the careful study and selection of raw materials and the purity of the finished products cannot be too strongly emphasized, and may be assumed to apply to the methods presented throughout this article. 

The selection of raw materials depends on different questions such as the type of the desired odor, the users focused on, the particular application, the stability of the finished product, the approximate price desired for the final product, etc. 

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