Distillation heavy vacuum distillate

Feedstocks are light vacuum distillates and/or heavy ends from crude distillation or heavy vacuum distillates from other conversion processes visbreaking, coking, hydroconversion of atmospheric and vacuum residues, as well as deasphalted oils. 

The reactor effluent is separated by conventional distillation into recycle solvent, light gases, to 537°C bp distillate, and a heavy vacuum bottoms stream containing unconverted coal and ash. The recycle solvent is hydrogenated in a separate reactor and sent back to the Hquefaction reactor. 

Gas oils Utilized as straight-run distillate after desulfurization. Lighter atmospheric and vacuum gas oils are often hydrocracked or catalytically cracked to produce gasoline, jet, and diesel fuel fractions heavy vacuum gas oils can be used to produce lubestocks or as fluid catalytic cracking (FCC) feedstock... 

The single-stage plant (Figure 3) can be used to produce gasoline but is most advantageously used to produce middle distillate from heavy vacuum gas oils. The operation is again extinction recycle above a cut point which can be above 700°F. These two flow schemes represent... 

The atmospheric residuum is then fed to the vacuum distillation unit at the pressure of 10 mmHg where light vacuum gas oil, heavy vacuum gas oil, and vacuum residue are the products (Fig. 13.4). 

Hydrotreating is being employed extensively in the petroleum industry for processing a variety of feedstocks. Both straight-run and cracked petroleum products such as naphthas, kerosenes, middle distillates, gas oils (atmospheric and heavy vacuum types), cycle stocks, residues, asphalts, crudes, and shale oils may be so treated. The process primarily is employed as a pretreat previous to catalytic reforming or catal3d ic cracking. 

Today, the majority of ethylene is produced by thermal cracking of hydrocarbon feedstocks ranging fi-om ethane to heavy vacuum gas oils. Over 60% of the world s propylene is produced as a by-product of thermal cracking, with the balance being supplied from refinery sources and others. Raw materials are mosdy natural gas condensate components (principally ethane and propane) in the US and Mideast and naphtha in Europe and Asia. Alkanes/olefins are broken apart at high temperatures, often in the presence of a zeolite catalyst, to produce a mixture of primarily aliphatic alkenes and lower molecular weight alkanes. The mixture is feedstock and temperature dependent and separated by fractional distillation. 

Table 6. Two-step Hydrocracking of Heavy Vacuum Gas Oil. IFP Process - Case of maximum middle distillates production.

Low-value distillates, including heavy-cycle oils from FCC units, thermal and coker gas oils, and other heavy-vacuum gas oils, are cracked to produce naphtha, jet fuel, and diesel oils. The reaction mechanism is the same as in catalytic cracking and some aromatic products are also hydrogenated. 

Slurry-phase hydrocracking systems convert heavy vacuum residues however, these processes are not yet fully commercialized. The feed to this type of reactor is the petroleum residue plus a solid carrier (commonly known as additive). The purpose of the additive is to provide a surface for the deposition of converted asphaltenes and metals, as the residue is hydrocracked. Slurry reactors operate at high temperature and pressure, and residue conversions higher than 90% (Kressmann et al., 1998). Unfortunately, these units produce poor-quality, hydrogen-deficient distillate and vacuum products that cannot be used as fuel, unless blended with something else, for example, coal or heavy fuel oil, due to their high content of sulfur and metals (Ancheyta and Speight, 2007). 

SARA (Saturates, Aromatics, Resins, Asphaltenes) analysis is widely practiced on heavy fractions such as vacuum and atmospheric residues and vacuum distillates for two purposes ... 

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. 

During the production of mineral oils from vacuum distillates, one of the process steps, dewaxing , removes the high melting point materials in order to improve the oil s pour point. Dewaixing produces paraffins and waxes, the first coming from light distillates, and the second from medium or heavy distillates. 

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. 

Solvent deasphalting. This is an extraction of the heaviest fractions of a vacuum residue or heavy distillate. The extract is used to produce the bitumen. The separation is based on the precipitation of asphaltenes and the dissolution of the oil in an alkane solvent. The solvents employed are butane or propane or a butane-propane mixture. By selecting the proper feedstock and by controlling the deasphalting parameters, notably temperature and pressure, it is possible to obtain different grades of bitumen by this process. 

Vacuum distillation of the atmospheric residue complements primary distillation, enabli r.ecoyery of heavy distillate cuts from atmospheric residue that will un r o further conversion or will serve as lube oil bases. The vacuum residue containing most of the crude contaminants (metals, salts, sediments, sulfur, nitrogen, asphaltenes, Conradson carbon, etc.) is used in asphalt manufacture, for heavy fuel-oil, or for feed for others conversion processes. 

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). 

Heavy residues are not always converted. The use of low sulfur light crude and crudes having a reduced ultimate residue (higher ratio of gasoline + distillates/vacuum residue) as well as natural gas utilization has been intensified. 

After 5 hours the reaction is stopped and the flask cooled. The formyl-MDA can be isolated and hydrolyzed by any of the ways Strike just mentioned a few paragraphs back, but this method offers a third, very convenient way which should be tried. What the chemist does is forget about letting the flask and its contents cool. Instead, she removes the oil bath, places the flask back on the stirplate (distillation setup still attached), attaches a vacuum and distills off all the formamide. What remains is a dark, heavy formyl-MDA precipitate that is allowed to cool down while the chemist makes up a solution of 150g potassium hydroxide (KOH), 500mL ethanol and 125mL dH20. This solution is poured into the... 

After 7 days the solution is poured into 300mL cool dH20 in a 500mL flask and slowly distilled with no vacuum. The first 20mL of distillate that comes over will be clear heavy tetranitromethane. The chemist will know that all has distilled over when the last clear drops that come over will be water that will start to form a layer on top of the tetranitromethane. The product is washed with dilute NaOH, then water and dried through a very small amount of Na2S04 to give 16g pure tetranitromethane. 

METHOD 2 [89]--1M MDA or benzedrine and 1M benzaldehyde is dissolved in 95% ethanol (Everclear), stirred, the solvent removed by distillation then the oil vacuum distilled to give 95% yellow oil which is a Schiff base intermediate. 1M of this intermediate, plus 1M iodomethane, is sealed in a pipe bomb that s dumped in boiling water for 5 hours giving an orangy-red heavy oil. The oil is taken up in methanol, 1/8 its volume of dH20 is added and the solution refluxed for 30 minutes. Next, an equal volume of water is added and the whole solution boiled openly until no more odor of benzaldehyde is detected (smells like almond extract). The solution is acidified with acetic acid, washed with ether (discard ether), the MDMA or meth freebase liberated with NaOH and extracted with ether to afford a yield of 90% for meth and 65% for MDMA. That s not a bad conversion but what s with having to use benzaldehyde (a List chemical) Strike wonders if another aldehyde can substitute. 

That aqueous layer that was saved can be removed of most of its water by vacuum distillation, allowed to cool slightly then extracted with hot toluene. When the toluene cools, a few hundred more grams of catechol will crystallize out but will be contaminated with some heavy red bromo compounds. The crystals are filtered and vacuum distilled such that the pyrocatechol will distill over first, leaving the higher boiling bromo compounds behind. Yield is about 80% or 600g of catechol. 

---