Residue, distillation

The field of application for liquid chromatography in the petroleum world is vast separation of diesel fuel by chemical families, separation of distillation residues (see Tables 3.4 and 3.5), separation of polynuclear aromatics, and separation of certain basic nitrogen derivatives. Some examples are given later in this section. 

Figure 3.12 shows the spectrum of carbon 13 obtained from a distillation residue and Table 3.10 gives average parameters for two FCC feedstocks as measured by NMR. 

In the 1970 s, heavy fuel came mainly from atmospheric distillation residue. Nowadays a very large proportion of this product is vacuum distilled and the distillate obtained is fed to conversion units such as catalytic cracking, visbreaking and cokers. These produce lighter products —gas and gasoline— but also very heavy components, that are viscous and have high contaminant levels, that are subsequently incorporated in the fuels. 

The distillation of crudes chosen for their yield in heavy fractions is the most common means. Bitumen is extracted from the residue from a vacuum distillation column (a few dozen mm of mercury), the latter being fed by atmospheric distillation residue. Unlike the practice of a decade ago, it is now possible to obtain all categories of bitumen, including the hard grades. 

Influence of the feed coke produced from distillation residue is less structured, less crystalline than that from a cracking residue. If the residue feeding the unit is highly contaminated with sulfur and metals, it is still coke, but is disqualified for certain applications. 

Properly speaking, steam cracking is not a refining process. A key petrochemical process, it has the purpose of producing ethylene, propylene, butadiene, butenes and aromatics (BTX) mainly from light fractions of crude oil (LPG, naphthas), but also from heavy fractions hydrotreated or not (paraffinic vacuum distillates, residue from hydrocracking HOC). 

Health and Safety Factors. Because of their high vapor pressures (methyl vinyl ether is a gas at ambient conditions), the lower vinyl ethers represent a severe fire hazard and must be handled accordingly. Contact with acids can initiate violent polymerization and must be avoided. Although vinyl ethers form peroxides more slowly than saturated ethers, distillation residues must be handled with caution. 

Commercially, a small amount of the 4,4 -MDA is isolated by distillation from PMDA. Depending on the process employed, the removal of MDA can be partial (as is done with the isocyanates) or total. Partial removal of MDA gives some processiag latitude but yields of 4,4 -MDA are reduced. Distillation residues from PMDA manufacture that contain less than 1% MDA pose a disposal problem. Processes for the regeneration of MDA by heating these residues ia the presence of aniline and an acid catalyst have been patented (33—35). Waste disposal of PMDA is expensive and reclamation processes could become commercially viable. The versatility of the isocyanate process, however, can be used to avoid the formation of low MDA content distillation residues. 

A number of processes have been devised for purifying thionyl chloride. A recommended laboratory method involves distillation from quinoline and boiled linseed oil. Commercial processes involve adding various high boiling olefins such as styrene (qv) to react with the sulfur chlorides to form adducts that remain in the distillation residue when the thionyl chloride is redistilled (179). Alternatively, sulfur can be fed into the top of the distillation column to react with the sulfur dichloride (180). Commercial thionyl chloride has a purity of 98—99.6% minimum, having sulfur dioxide, sulfur chlorides, and sulfuryl chloride as possible impurities. These can be determined by gas chromatography (181). 

It is incorrect to refer to bitumen as tar or pitch. Although the word tar is somewhat descriptive of the black bituminous material, it is best to avoid its use in referring to natural materials. More correctly, the name tar is usually appHed to the heavy product remaining after the destmctive distillation of coal (qv) or other organic matter. Pitch is the distillation residue of the various types of tar (see Tar and pitch). 

Even though the simple distillation process has no practical use as a method for separating mixtures, simple distillation residue curve maps have extremely usehil appHcations. These maps can be used to test the consistency of experimental azeotropic data (16,17,19) to predict the order and content of the cuts in batch distillation (20—22) and, in continuous distillation, to determine whether a given mixture is separable by distillation, identify feasible entrainers/solvents, predict the attainable product compositions, quaHtatively predict the composition profile shape, and synthesize the corresponding distillation sequences (16,23—30). By identifying the limited separations achievable by distillation, residue curve maps are also usehil in synthesizing separation sequences combining distillation with other methods. 

The vapor is thea withdrawa from the stiH as distillate. The changing Hquid composition is most coavenieafly described by foUowiag the trajectory (or residue curve) of the overall composition of all the coexistiag Hquid phases. An exteasive amouat of valuable experimental data for the water—acetoae—chloroform mixture, including biaary and ternary LLE, VLE, and VLLE data, and both simple distillation and batch distillation residue curves are available (93,101). Experimentally determined simple distillation residue curves have also been reported for the heterogeneous system water—formic acid—1,2-dichloroethane (102). 

Bunker-fuel specifications for merchant vessels are described by ASTM D 2069, Standard Specification for Marine Fuels. Deep draft vessels carry residual (e.g., No. 6 fuel oil) or distillate-residual blend for main propulsion, plus distillate for start-up, shutdown, maneuvering, deck engines, and diesel generators. Main-propulsion fuel is identified principally by its viscosity in centistokes at 373 K. Obsolete designations include those based on Redwood No. 1 seconds at 100°F (311 K) (e.g., "MD 1500 ) and the designations "Bunker A for No. 5 fuel oil and "Bunker B and "Bunker C for No. 6 fuel oil in the lower-and upper-viscosity ranges, respectively. 

Black, viscous residuum direc tly from the still at 410 K (390°F) or higher serves as fuel in nearby furnaces or may be cooled and blended to make commercial fuels. Diluted with 5 to 20 percent distillate, the blend is No. 6 fuel oil. With 20 to 50 percent distillate, it becomes No. 4 and No. 5 fuel oils for commercial use, as in schools and apartment houses. Distillate-residual blends also serve as diesel fuel in large stationaiy and marine engines. However, distillates with inadequate solvent power will precipitate asphaltenes and other high-molecular-... 

Benzene-1,2-dithiol [17534-15-5] M 142.2, m 24-25 , 27-28 , b 110-112 , pKEst(i) -6.0, p K s,(2) 9.4. Likely impurities are the oxidation products, the disulfides which could be polymeric. Dissolve in aq NaOH until the soln is alkaline. Extract with Et20 and discard the extract. Acidify with cold HCl (diluted 1 1 by vol with H2O) to Congo Red paper under N2 and extract three times with Et20. Dry the Et20 with Na2S04, filter, evaporate and distil residue under reduced press in an atmosphere of N2. The distillate solidifies on cooling. [UV J Chem Soc 3076 7 955 J Am Chem Soc 81 4939 7957 Org Synth Coll Vol V 419 1973.]... 

NaHC03 H2O, dry (MgS04), filter, evaporate and distil residue. Identified by hydrolysis to the acid and determining the neutralisation equiv (theor 80.0). The acid has m 155-157° efferv [Hauser, Abramovitch and Adams J Am Chem Soc 64 2715 1 942 Bush and Beauchamp J Am Chem Soc 75 2949 1953]. 

Pivaloyl chloride (trimethylacetyl chloride) [3282-30-2] M 120.6, b 57.6"/150mm, 70.5-71/250mm, 104"/754mm, 104-105"/atm, 105-108"/atm, d 1.003, n p 1.4142. First check the IR to see if OH hands are present. If absent, or present in small amounts, then redistil under moderate vac. If present in large amounts then treat with oxalyl chloride or thionyl chloride and reflux for 2-3h, evap and distil residue. Strongly LACHRYMATORY - work in a fumecupboard. Store in sealed ampoules under N2. [Traynham and Battiste J Org Chem 22 1551 1957, Grignard reactns Whitmore et al. J Am Chem Soc 63 647 1941.]... 

This procedure is then repeated again. Distillation of the combined residues using a nitrogen leak (Note 16) yields 54 g. of the product as a yellowoil, b.p. 66-68° (1.1 mm.) (Note 17). The distillation residue, when washed through a short acidic alumina column with light petroleum ether and the solvent evaporated, yields an additional 5 g. of product total yield 59-68 g., 67-78% (Notes 18, 19). 

Types of fuels ineluded True distillates (naphtha, kerosene, no. 2 diesel, no. 2 fuel oil, JP-4, JP-5) High-quality etudes, slightly eontaminated distillates Navy distillate Residuals and low-grade etude (No. 5 fuel. No. 6 fuel. Bunker C)... 

The distillate is extracted with five 50-cc. portions of benzene, and the benzene solution is dried thoroughly with powdered sodium hydroxide and distilled (Note 5). Most of the amine distfls at 184-186°, but the fraction distilling at 180-190° is sufficiently pure for most purposes (Note 6). The yield of this fraction is 80-88 g. By combining the benzene fore-run with the distillation residue, extracting with dilute acid, and recovering the amine as above, an additional 10-12 g. of material can be obtained (Note 7), making the total yield po-ioo g. (60-66 per cent of the theoretical amount based on the acetophenone taken) (Note 8). 

NOTE - Petrochemical plants also generate significant amounts of solid wastes and sludges, some of which may be considered hazardous because of the presence of toxic organics and heavy metals. Spent caustic and other hazardous wastes may be generated in significant quantities examples are distillation residues associated with units handling acetaldehyde, acetonitrile, benzyl chloride, carbon tetrachloride, cumene, phthallic anhydride, nitrobenzene, methyl ethyl pyridine, toluene diisocyanate, trichloroethane, trichloroethylene, perchloro-ethylene, aniline, chlorobenzenes, dimethyl hydrazine, ethylene dibromide, toluenediamine, epichlorohydrin, ethyl chloride, ethylene dichloride, and vinyl chloride. 

There are numerous applications in solvent recovery processes where evaporation equipment are employed. Figure 14 provides an example of a process scheme for toluene-di-isocyanate recovery. This is an example of continuous vacuum evaporation of distillation residues. 

The reaction mixture comprising 2,2,2-trifluoroethyl vinyl ether, 2,2,2-trifluoroethanol and potassium 2,2,2-trifluoroethylate was fractionally distilled, whereupon crude 2,2,2-trifluoroethyl vinyl ether was obtained which boiled at 42° to 45°C at 760 mm. More 2,2,2-trifluoroethyl vinyl ether was obtained when the distillation residue was returned to the bomb and reacted with acetylene in the same manner as hereinabove described. 

In the distillation residue (5.7-6.3 g.) remain other byproducts, presumably l,l-dimethallyl-2-propanone, 3-methallyl-2,4-pentanedione, and 3,3-dimethallyl-2,4-pentanedione (indicated by vapor phase chromatography). The checkers carried out v.p.c. analyses using an 8-ft. column of 5% silicone oil XE-60 on Diatoport S at 100° for analysis of the distillate and 175° for analysis of the residue. 

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