Feedstocks structure

Table 4. Dimer Acid Feedstock—Structure Relationship...

REACTIVITY OF FEEDSTOCK STRUCTURE OF FEEDSTOCK COKING CONDITIONS... 

In our laboratories, we were concerned with yield of black production however, we were more concerned with the influence of feedstock structure on the quality of product produced. Molecular structures of feedstocks investigated were pure compounds and mixtures of pure and similar compounds including monocyclic aromatics with and without side chains, dicyclic aromatics, tricyclic aromatics, mixtures of higher molecular weight aromatics and high and low molecular weight paraffins. Some examples of the types of compounds studied are ... 

Almost all raw materials for Japan s chemical industries come from overseas sources. The largest among them is petrochemical feedstocks. In 1990, 97.5% of the feedstock for ethylene production was naphtha, while the remaining 2.5% was LPG. 72.5% of the naphtha was imported from overseas sources, out of which more than 70% came from the Middle East region. An extremely high naphtha ratio in the feedstock structure and its high dependence on the overseas sources constitute our concern for the future. 

Comparing the overall concentrations of these different carbons designated generally as structural patterns , measured before and after a process such as FCC or hydrocracking (see Chapter 10), enables the conversion to be monitored the simple knowledge of the percentage of condensed aromatic carbon of a feedstock gives an indication of its tendency to form coke. 

Rosin and tall oil-based tackifiers are derived from feedstock, which is typically obtained by extraction and distillation of the materials from shredded tree stumps or wood chips. A typical structure of one of the different products obtained through this process is this abietic acid structure shown in Fig. 14 as a representative of the rosin acid family. 

These observations consummated in a growth model that confers on the millions of aligned zone 1 nanotubes the role of field emitters, a role they play so effectively that they are the dominant source of electron injection into the plasma. In response, the plasma structure, in which current flow becomes concentrated above zone 1, enhances and sustains the growth of the field emission source —that is, zone 1 nanotubes. A convection cell is set up in order to allow the inert helium gas, which is swept down by collisions with carbon ions toward zone 1, to return to the plasma. The helium flow carries unreacted carbon feedstock out of zone 1, where it can add to the growing zone 2 nanotubes. In the model, it is the size and spacing of these convection cells in the plasma that determine the spacing of the zone 1 columns in a hexagonal lattice. 

Coke produced from delayed coking is described as delayed sponge, shot, or needle coke depending on its physical structure. Shot coke is the most common when running the unit under severe conditions with sour crude residues. Needle coke is produced from selected aromatic feedstocks. Sponge coke is more porous and has a high surface area. The properties and markets for petroleum cokes have been reviewed by Dymond. Table 3-4 shows the types of petroleum cokes and their uses. ... 

Pretreating the feedstocks with hydrogen is not always effective in reducing heavy metals, and it is expensive. Other means that proved successful are modifying the composition and the microporous structure of the catalyst or adding metals like Sb, Bi or Sn, or Sb-Sn combination. Antimony organics have been shown to reduce by 50% gas formation due to metal contaminants, especially nickel. ... 

The properties of the zeolite play a significant role in the overall performance of the catalyst. Understanding these properties increases our ability to predict catalyst response to changes in unit operation. From its inception in the catalyst plant, the zeolite must retain its catalytic properties under the hostile conditions of the FCC operation. The reaclor/regenerator environment can cause significant changes in chemical and structural composition of the zeolite. In the regenerator, for instance, the zeolite is subjected to thermal and hydrothermal treatments. In the reactor, it is exposed to feedstock contaminants such as vanadium and sodium. 

In the previous examples, the feed characterizing correlations in Chapter 2 are used to determine composition of the feedstock. The results show that the feedstock is predominantly paraffinic (i.e., 61.6% paraffins. 19.9% naphthenes, and 18.5% aromatics). Paraffinic feedstocks normally yield the most gasoline with the least octane. This confirms the relatively high FCC gasoline yield and low octane observed in the test run. This is the kind of information that should be included in the report. Of course, the effects of other factors, such as catalyst and operating parameters, will also affect the yield structure and will be discussed. 

The composition of AOS and IOS is determined by the choice of the olefin feedstock, by the way the feedstock is sulfonated and by manufacturing conditions. As will be shown later, the structural parameters such as hydrophobe chain length and branching, the ratio of alkene- to hydroxyalkanesulfonate, and (for AOS) the mono disulfonate ratio determine the physicochemical properties of AOS and IOS these in turn determine the performance of AOS and IOS in their end formulations. 

Feedstock recycling implies a change of the chemical structure of the material, where the resulting chemicals are used for another purpose than producing the original material ... 

An example of the large variety of monomer structures present in poly(HAMCL) is given in Fig. 2. Also different degrees of unsaturation in poly(HAMCL) can be established relatively easily [3-5,34-39]. For example, the compositional data in Table 1 for the repeat units show that about 16% of the mono-unsaturated double bonds are incorporated when oleic acid is used as feedstock. When tall oil fatty acids are used, over 40 % of the subunits of the resulting poly(HAMCL) are mono- or di-unsaturated, while the total degree of unsaturation of the alkyl side chains of linseed oil-based PHA is even higher (>65%). Moreover, a substantial part (about 30%) of these unsaturated linseed oil-based poly(HAMCL) subunits have up to three double bonds present. 

Minaev, V. Z. Zaidman, N. M. Spirina, G. A., et al., Effect of Pore Structure of Alumina-Cobalt-Molybdenum Catalyst on Activity and Stability in Hydrodesulfurization of Heavy Feedstocks. Chemistry and Technology of Fuels and Oils, 1975. 11(6) pp. 436-39. 

In addition to the use of composite anodes and cathodes, another commonly used approach to increase the total reaction surface area in SOFC electrodes is to manipulate the particle size distribution of the feedstock materials used to produce the electrodes to create a finer structure in the resulting electrode after consolidation. Various powder production and processing methods have been examined to manipulate the feedstock particle size distribution for the fabrication of SOFCs and their effects on fuel cell performance have also been studied. The effects of other process parameters, such as sintering temperature, on the final microstructural size features in the electrodes have also been examined extensively. 

Both wet-ceramic techniques and direct-deposition techniques require preparation of the feedstock, which can consist of dry powders, suspensions of powders in liquid, or solution precursors for the desired phases, such as nitrates of the cations from which the oxides are formed. Section 6.1.3 presented some processing methods utilized to prepare the powder precursors for use in SOFC fabrication. The component fabrication methods are presented here. An overview of the major wet-ceramic and direct-deposition techniques utilized to deposit the thinner fuel cell components onto the thicker structural support layer are presented below. 

Tall oil is made up mostly of resin acids with around 10% of neutral components. These resin acids are isomers or structurally close relatives of abietic acid (Figure 2.9) and are used as antislip agents, as a chemical feedstock and as paper-sizing agents (see Chapter 7). 

As previously mentioned, Davis (8) has shown that in model dehydrocyclization reactions with a dual function catalyst and an n-octane feedstock, isomerization of the hydrocarbon to 2-and 3-methylheptane is faster than the dehydrocyclization reaction. Although competitive isomerization of an alkane feedstock is commonly observed in model studies using monofunctional (Pt) catalysts, some of the alkanes produced can be rationalized as products of the hydrogenolysis of substituted cyclopentanes, which in turn can be formed on platinum surfaces via free radical-like mechanisms. However, the 2- and 3-methylheptane isomers (out of a total of 18 possible C8Hi8 isomers) observed with dual function catalysts are those expected from the rearrangement of n-octane via carbocation intermediates. Such acid-catalyzed isomerizations are widely acknowledged to occur via a protonated cyclopropane structure (25, 28), in this case one derived from the 2-octyl cation, which can then be the precursor... 

This protonated cyclopropane is found at B3LYP/6-31G to be 15.99 kcal/mol above the 1,5-p-H-bridged 23, the most stable structure of the 2-octyl cation. This transition-state is thus significantly smaller than the calculated transition-states that we have obtained for the dehydrocyclization mechanisms (29.60 kcal/mol for structure 24), and therefore in at least qualitative agreement with the observation of Davis (8) that an equilibration of n-octane with at least some other isooctanes is set up prior to significant dehydrocyclization of the feedstock. 

While a majority of laboratory-scale dehydrocyclization studies involve carefully chosen feedstocks, often a single alkane, commercial operators use a naphtha fraction consisting of a complex mixture of hydrocarbons. At least some of these will be incapable of easily undergoing direct dehydrocyclization and need to be isomerized into reactive structures if aromatics are to be formed. The work of Davis suggests that the acidity of dual function catalysts is an important added factor in these isomerizations, one which likely complements the different set of isomerizations that may be catalyzed by the platinum function. 

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