Dispersion hydrocarbon

Increased agitation of a given acid—hydrocarbon dispersion results in an increase in interfacial areas owing to a decrease in the average diameter of the dispersed droplets. In addition, the diameters of the droplets also decrease to relatively low and nearly constant values as the volume % acid in the dispersions approaches either 0 or 100%. As the droplets decrease in si2e, the ease of separation of the two phases, following completion of nitration, also decreases. 

E.I. duPont de Nemours and Company Aqueous Explosive Compositions Containing a Partially Nitrated Aromatic Hydrocarbon Dispersed by a Monoamide... 

In conclusion we have successfully demonstrated that the Lewis acid nature of boron in BN nanotubes can be exploited to functionalize and solubilize their nanostructures through interaction with Lewis bases. The solubilized nanotubes retain the nanotube features and the hydrocarbon dispersions are stable up to a few days. It is noteworthy that the interaction of the BN nanotubes with the Lewis bases at room temperature suffices to provide good dispersions of the BN nanotubes in hydrocarbon solvents. We also note that any carbon impurity due to carbon nanotubes used as templates in the preparation of the BN nanotubes settles to the bottom after interaction of the BN nanotubes with a Lewis base, thereby providing a means of separation of carbon and BN nanotubes. 

Good hydrocarbon dispersion in hydrofluoric acid is an impxjrtant factor In producing alkylate rich in trimethylpentanes and thus favors olefin isomerization (to isobutene), isobutene dimerization, and maximizes hydrogen transfer and primary alkylation reactions. Excess olefin polymerization to form residue is suppressed by good dispersion. 

Hydrocarbon Disperson. Hydrocarbon dispersion (in HF catalyst) was found to be an important factor in producing alkylates of different composition and quality from the same olefin under the same reaction conditions. As the degree of dispersion was changed from poor to excellent by improving mass transfer, alkylate composition underwent drastic changes. These changes are summarized in Table VI. (Detailed alkylate compositions are in Table XI). 

There seems a strong possibility that olefin isomerization and dimerization could take place in the catalyst phase and that alkylation could take place in the hydrocarbon phase. When hydrocarbon dispersion is poor, i.e., droplets are large, a moss transfer limitation exists, and olefin Isomerization and dimerization are reduced. This results in a product containing large amounts of residue, which may be due to secondary alkylation of, say, an Isobutene molecule with an isooctyl carbonium Ion to produce a dodecyl carbonium Ion which can then undergo hydride transferor scission. Under conditions of good hydrocarbon dispersion (small droplets with large amount of surface area), the reactions yield less heavies and scission products and more of the desirable trimethylpentanes. 

The interfacial area between the acid/hydrocarbon dispersions is the location at which most, if not... 

Stratco Reactors. These reactors designed by Stratco, Inc. produce about 34% of the alkylate produced worldwide (P. Pyror, personal communication). In 2003, Stratco was purchased by E.I. du Pont de Nemours, Inc. A reactor, often called a Contactor, is a horizontal cylindrical vessel, as shown in Fig. 1, with the following features. An impeller at one end recirculates the acid/hydrocarbon dispersion many times (on average) over a U-tube bundle to regulate the temperature of the dispersion at about 5-10°C. A cylindrical circulation shell located in the reactor provides an annular space so that the dispersion flows from one end of the reactor to the other, where it makes a 180° turn and flows back over the tube bundle. 

The reactors designed by Phillips Petroleum (now Conoco-Phillips) and UOP produce about 32% and 20%, respectively, of all alkylate produced worldwide (P. Pyror, personal communication). The HF/ hydrocarbon dispersions in these reactors have much larger interfacial areas (probably by a factor of about 10) as compared to areas in sulfuric acid/hydrocarbon dispersions.f This is a major reason why the kinetics of alkylation is much higher with HF. 

Conoco-Phillips Reactor. This reactor is basically a vertical tube in which the HF/hydrocarbon dispersion... 

A typical antifoam consists of an oil (polydimethylsiloxane or hydrocarbon), dispersed hydro-phobic solid particles (e.g., hydrophobized silica), or a mixture of both. The oil-solid mixtures are often called antifoam compounds. The weight concentration of the solid particles in compounds is around several percent (typically between 2 and 8). A strong synergistic effect between the oil and the solid particles is observed in the compounds — in most cases, the latter are much more efficient than either of their individual components, if taken separately. The compounds are used at a concentration below 0.1 wt%, whereas the oils are used at higher concentrations (up to several percent) due to their lower antifoam efficiency. The antifoams are usually preemulsified in the form of oil drops or mixed oil-solid globules of micrometer size. 

Aquamix. [Harwich] Halogenat hydrocarbon dispersions, chlorinated paraffins emulsions flame retardants, stabilizers, accelerattxs, activators, vulcanizing agents, antioxidants, tackifiers for plastics. 

Bitumin is a naturally occurring, almost black material that is also obtained in mineral-oil refining. It consists of high-molecular-weight hydrocarbons dispersed in oil-like material. 

A microemulsion is water/hydrocarbon dispersion stabilized by an ionic surfactant such as a soap, alkyl sulphate or sul-phonate and most often also contains a cosurfactant in the form of a medium chain length alcohol (pentanol). Of these four components water, surfactant and cosurfactant are called the structure forming elements since they form colloidal association structures similar to the microemulsions with no hydrocarbon present. The formulation and preparation of microemulsions is greatly enhanced by a knowledge of these composition dependent structures, hence an introductory description of them will be given. 

Fig. 10.39. Extraction of benzoic acid from hydrocarbons by water in packed towers, hydrocarbons dispersed.

Emulsified fracturing fluids are typically very viscous polymer oil-inwater emulsions that may consist of60-70% hquid hydrocarbon dispersed in 30-40% aqueous solution or gel. The hydrocarbon phase may be diesel fuel, kerosene, or even crude oils and condensates. The aqueous phase may consist of gelled fresh water, a KCl solution or an acid solution. Emulsion fracturing fluids may be applied to oil or gas wells, particularly in low pressure formations susceptible to water blockage, and for bottom-hole temperatures of up to about 150 °C. They can provide excellent fluid loss control, possess good transport properties and can be less damaging to the reservoir than other fluids. However, emulsions are more difficult to prepare and can be more expensive. 

Larger interfacial areas in the acid hydrocarbon dispersions. As already indicated, transfer occurs mainly at the interfaces. Hence, the rate of transfer to H transfer to i-Cg s is promoted, which minimizes the formation of f-Ci2+ and i-Ci6+. Two methods of obtaining larger areas include, first, higher levels of agitation and, second, select ratios of acid/ hydrocarbon in the dispersions. It was found (10) that the maximum interfacial areas occurred with acid/hydrocarbon volumetric ratios of 65 35 to 75 25. The dispersions are always acid continuous in commercial units. 

Second, isoparaffins containing tertiary C—H bonds can react, or in a sense be alkylated, when mixed with olefins in the presence of acid catalysts. TMPs can react forming first C12—C20 cations. Mechanism 2- and 3-type reactions then occur. The quality of alkylate is often significantly reduced, and some CPs are also produced. To minimize these undesired reactions of especially TMPs, two procedures should be employed. Reactors are needed that minimize contact between TMPs and olefins. In addition, acid/hydrocarbon dispersions should be separated quickly as soon as the alkylation reactions are completed. Less information is available on undesired reactions when HF is used as the catalyst. 

Predictions for HF/hydrocarbon dispersions at 10°C were also made using VisiMix 2000 (see Table 1). Droplet diameters were smaller by factors of about 7-11 than those for sulfuric acid/hydrocarbon dispersions. The HF phase has a much lower viscosity and also a lower density than those of sulfuric acid. The much greater interfacial areas with HF/hydrocarbon dispersions are thought to be a major factor affecting the much more rapid alkylation reactions that occur when HF is used as the catalyst plus the significant differences in products obtained. 

The reactor, or Contactor, is basically a special type of a continuous-flow stirred tank reactor, as shown in Figure 1 (6). It is a cylindrical vessel positioned horizontally in which the acid/hydrocarbon dispersion is repeatedly circulated over and around heat transfer coils (tube bundle). The impeller employed to promote the dispersion of the feed mixture of isobutane and olefins in the acid phase is located at one end of the reactor. The impeller causes the dispersion to enter the annular region between the shell of the reactor and the tube bundle the dispersion flows rapidly in this region, which extends over most of the length of the reactor. As the dispersion reaches the exit end of the annulus, a small portion of the dispersion is withdrawn and fed to the decanter, which is discussed later. The remainder of the dispersion leaving the annular region makes a 180° turn at the end of the reactor and flows back toward the impeller. As it returns, the dispersion passes over and around U-shaped heat transfer coils that remove the exothermic heats of reaction and the energy added to the reactor by the impeller. 

In each reactor zone, an acid/hydrocarbon dispersion enters from the previous zone. In the second zone plus all later zones, the hydrocarbon droplets in the entering dispersion contain mainly isobutane and alkylate. The hydrocarbon droplets that are initially obtained as the feed mixture of isobutane and olefin is injected into each zone are obviously of different composition as compared with other droplets in the zone. Coalescence of droplets, followed by their fragmentation, obviously occurs in each zone. Such a coalescence-fragmentation sequence promotes mixing of hydrocarbons in the droplets (12,13). Such a sequence causes higher isobutane/olefin ratios, which results in improved alkylation processes. On the negative side, olefins and alkylate are also mixed and small amounts of trimethylpentanes (TMPs) and olefins react with the loss of quality (14). 

The acid/hydrocarbon dispersion leaving the cascade reactor flows to the decanter (or settler) as shown in Figure 2. After the acid separates, it is recycled to the reactor. Not shown in Figure 2 are lines to discard a small fraction of the acid leaving the decanter and to provide fresh (or make-up) acid. In both cascade and Stratco units, the acid is recycled on the average numerous times before it is rejected. 

Isoalkyl sulfates are also key intermediates in conjunct polymer production (27). Better operation of the decanter minimizes acid consumption (6). Rapid separation of acid/hydrocarbon dispersion leaving the reactor is highly desired. 

In large plants of UOP design, a second reactor is often connected to the first reactor. In such an arrangement, the HF hydrocarbon dispersion from the first reactor flows in series through the second reactor where more feed hydrocarbons are injected. Several years ago, the liquid HF inventories in UOP plants were about 5-6 pounds of HF per barrel of alkylate per day. Considerable effort has recently been made to reduce these inventories in order to reduce the potential dangers of the unit. The current levels in UOP plants are unknown. 

PMMA is mostly homo- or copolymerized in aliphatic hydrocarbon dispersions, using different rubbers, polysiloxanes, long-chain polymethacrylates, or different block and graft copolymers as stabilizers. An interesting variant of the dispersion polymerization of acrylates is carried out in supercritical carbon dioxide [45,46]. Transition-metal-mediated living radical suspension polymerization is discussed in Ref. [47]. Common radical initiators are described in Refs. [48] and [49]. The entire field is reviewed extensively in Ref. [50]. 

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