Aromatics process conditions

Commercial cmde lecithin is a brown to light yeUow fatty substance with a Hquid to plastic consistency. Its density is 0.97 g/mL (Uquid) and 0.5 g/mL (granule). The color is dependent on its origin, process conditions, and whether it is unbleached, bleached, or filtered. Its consistency is deterrnined chiefly by its oil, free fatty acid, and moisture content. Properly refined lecithin has practically no odor and has a bland taste. It is soluble in aflphatic and aromatic hydrocarbons, including the halogenated hydrocarbons however, it is only partially soluble in aflphatic alcohols (Table 5). Pure phosphatidylcholine is soluble in ethanol. 

The alkylcyclopentane (AGP) to aromatics process (ACP ACH Ar) is less efficient than ACH dehydrogenation, owing to the slowness of the first step and to ACP ring opening. Under conditions where cyclohexane is converted to benzene with close to 100% efficiency, only 50—75% of methylcyclopentane may be converted to benzene. 

Fischer-Tropsch A process for converting synthesis gas (a mixture of carbon monoxide and hydrogen) to liquid fuels. Modified versions were known as the Synol and Synthol processes. The process is operated under pressure at 200 to 350°C, over a catalyst. Several different catalyst systems have been used at different periods, notably iron-zinc oxide, nickel-thoria on kieselgtihr, cobalt-thoria on kieselgiihr, and cemented iron oxide. The main products are C5-Cn aliphatic hydrocarbons the aromatics content can be varied by varying the process conditions. The basic reaction was discovered in 1923 by F. Fischer and... 

In field investigations it has been shown that the elimination efficiency of aromatic sulfonates is strongly dependent on the process conditions of the individual facility [26]. In a long-term study conducted over one year in a waterworks, where the treatment consisted of three... 

A comparison of the feed and product compositions achievable by this approach is shown in Figure 16.8, which shows the depletion of multi-ring aromatics from the feed in favor of a variety of single ring aromatics with short alkyl chains. A more challenging approach that leads to a higher-value product involves optimization of the catalyst and process conditions to maximize xylene and toluene production for aromatic complex feeds [60]. 

It is necessary, however, to maximize the intermediate olefin product at the expense of the aromatic/paraffin product which makes up the gasoline ( ). The olefin yield increases with increasing temperature and decreasing pressure and contact time. Judicious selection of process conditions result in high olefin selectivity and complete methanol conversion. The detailed effect of temperature, pressure, space velocity and catalyst silica/alumina ratio on conversion and selectivity has been reported earlier ( ). The distribution of products from a typical MTO experiment is compared to MTG in Figure 4. Propylene is the most abundant species produced at MTO conditions and greatly exceeds its equilibrium value as seen in the table below for 482 C. It is apparently the product of autocatalytic reaction (7) between ethylene and methanol (8). 

A highly aromatic product boiling above 400° F. (the yield of which depends on the feed stock boiling range and on the process conditions)... 

Many other azeotropic separations are known. Butadiene, styrene, benzene, and xylenes are examples of compounds that may be segregated from refinery streams by this means. In fact, any separation of nonaromatic from aromatic hydrocarbons lends itself to this method, but requires the selection of the proper azeotrope former and processing conditions. In bench scale operations, azeotropy has been applied up to and including the lubricating oil range. 

The reaction of / -butoxycarbonyl hydrazones 263 with selenium oxychloride in CH2CI2 from — 20 °C to room temperature gave 2,3-dihydro-l,2,3-selenadiazoles 264 in 71-77% yields (Equation 33). Under these mild conditions, the aromatization process did not occur, and only 2,3-dihydro compounds were observed. The advantage of this reaction is the ease of workup. Pure compounds 264 were obtained simply by addition to the reaction mixture of an aqueous saturated solution of NaHCC>3 and subsequent evaporation of the organic solvent <2003JOC1947>. 

The oxidation of butane (or butylene or mixtures thereof) to maleic anhydride is a successful example of the replacement of a feedstock (in this case benzene) by a more economical one (Table 1, entry 5). Process conditions are similar to the conventional process starting from aromatics or butylene. Catalysts are based on vanadium and phosphorus oxides [11]. The reaction can be performed in multitubular fixed bed or in fluidized bed reactors. To achieve high selectivity the conversion is limited to <20 % in the fixed bed reactor and the concentration of C4 is limited to values below the explosion limit of approx. 2 mol% in the feed of fixed bed reactors. The fluidized-bed reactor can be operated above the explosion limits but the selectivity is lower than for a fixed bed process. The synthesis of maleic anhydride is also an example of the intensive process development that has occurred in recent decades. In the 1990s DuPont developed and introduced a so called cataloreactant concept on a technical scale. In this process hydrocarbons are oxidized by a catalyst in a high oxidation state and the catalyst is reduced in this first reaction step. In a second reaction step the catalyst is reoxidized separately. DuPont s circulating reactor-regenerator principle thus limits total oxidation of feed and products by the absence of gas phase oxygen in the reaction step of hydrocarbon oxidation [12]. 

Palomo75 report that various aromatic aldehydes can be converted to nitriles in 94-97% yield by refluxing the aromatic aldehyde, hydroxylamine hydrochloride, and magnesium sulfate in toluene or xylene, with p-toluencsulfonic acid as catalyst for 1.5 to 3 hr. The microwave-assisted process may prove better for aliphatic aldehydes and may be made even more attractive if the above process conditions could be refined to reduce or eliminate NMP—for instance, if both aldehyde and nitrile form a homogeneous liquid at the reaction temperature. 

The newly developed 600 MHz NMR Spectrometer is used to characterize coal-derived liquids and their chromatographically separated fractions. The distinct and well resolved proton resonance lines in both aromatic and aliphatic regions and IR analysis have been used to identify the major compounds and compound types. Double resonance technique has been applied for the chemical shift identification of donor protons (or-CHg, p-CH,) of partially hydrogenated polynuclear aromatic compounds. An NMR difference technique is applied to determine specific compositional changes in upgraded liquids derived under identical process conditions, but from different coal sources. 

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