US2049000A - Manufacture of asphalt and lubricating oils - Google Patents

Description

July 28, 1936.

R. B. DAY

MANUFACTURE OF ASPHALT AND LUBRICATING OILS Filed Feb. 26, 1.934

Patented July 28, 1936 ir ST MANUFACTURE OF ASPHALT AND LUBRICATDIG OES Application February 26, 1934, Serial No. 712,887

3 Claims.

This invention relates more particularly to the manufacture of asphalt and lubricating oils from cracked residua.

It is more specically concerned with a process of treating cracked residua to increase the yield of asphalt and lubricating oils recoverable therefrom and combines a heat treatment under accurately controlled conditions along with the subsequent use of particular solvents for effecting segregation of the asphaltic and lubricating constituents.

The heavy tar-like residua produced in cracking and distilling operations vary in character to a considerable extent. They consist of mixtures of hydrocarbons of a definitely uid character and compounds of a solid or semi-solid asphaltic character which may be looked upon as heavy hydrocarbon polymeric derivatives containing oxygen and sulphur which possess the commonly recognized characteristics of asphalts or pitches, that is, relatively high melting point, adhesiveness and a limited ductility. The physical properties of a cracked residuum such as viscosity, melting point, etc., and chemical properties such as tendency toward coking and resistance to oxidizing and weathering iniiuences are determined by the character and relative amounts of their fluid and solid components.

A large number of cracked residua.,V particularly those which are the result of deep or intensive cracking to produce maximum yields of gasoline, approach a solid consistency at ordinary temperatures and have too high viscosity, too high xed carbon content and too large a percentage of suspended cokey or carbonaceous material to permit their use as fuel oil in the ordinary type of atomizing burners. When employed directly as a road oil or asphalt, the presence of the uid components of the mixture, which in.

clude some light oils and lubricating fractions of varying viscosity, renders their action under severe conditions uncertain, so that frequently heavy cracked residuaare not suitable for such purposes.

The principal objects of thepresent invention are the production from cracked residua of maximum yields both of marketable asphalt and lubricating oil fractions, with the elimination of solid'coke-like substances and light oils which have at the most only a fuel value.

In one specic embodiment the invention comprises the prolonged digestion of cracked residua at temperatures Within the approximate range of `550 to 850 F., to effect substantial completion of polymerization reactions, followed by the separate recovery from the polymerized material of asphalt and lubricating oil fractions by means of their diierential solubility in selected solvents. t'

The sequence of steps by which the objects of invention are accomplished may be disclosed in connection with the description of a characteristic plant operation, and to assist in this description the attached drawing has been provided which shows diagrammatically in side elevation and using conventional gures an arrangement of interconnected elements in which the process may be conducted.

Referring to the drawing linel containing control valve 2 indicates4 a supply line. for cracked residuum, which may come' from intermediate storage or be supplied directly and continuously from a concurrently operating cracking plant. The first step' of the process is necessarily a batch operation on account of the long period of heating which has generally been found to be necessary for completing the polymerization reactions which were initiated in the cracking zone. While digester 3 is shown as a single unit it represents any number of such units connected in parallel which may be employed in the rst step of the process to insure a proper supply of polymerized residuum at all times for the succeeding steps of the process which are preferably conducted continuously.

' Digester 3 is positioned over a furnace 3' which is heated by the combustion of oil or other uid fuelintroduced to a burner by way of line 4 containing control valve 5. The digester is preferably insulated at all points except those immediately exposed to the hot combustion gases and the oil is maintained at the temperature of approximately 550 to 850 F., as previously stated. 'I'he exact temperature best for any given residuum in consideration of the overall yields of asphalt and lubricating oil will be a matter of experiment, since 'the composition of cracked residua varies over avide-range depending upon the character of the original oil cracked, the severity of temperature, pressure and time conditions imposed and special plant operating conditions. Moderate superatmospheric pressures up to approximately pounds per square inch may be employed with advantage in treating some residua.

During the digestion of the residuum a small amount of cracking may occur although the principal effect is the polymerization of the highly unsaturated constituents and the distillation of relatively small amounts .of low boiling distillates,

which leave the still through vapor line 6 containing control valve 1, and 1lndergo reuxing in a tower 8. The nxed gases .md low boiling vapors pass from the tower through a line 9 containing slightly superatmospheric pressure) is usually small andof the order of 5 to 10% by volume of the stock subjected to the digesting step. This distillate may be further fractionated to recover any gasoline boiling range fractions, the intermediate stocks being used as a light fuel or charging stock to the cracking plant.

After the period of digestion, which may range from 12 to 48 hours in different cases, the residuum is drawn from the digester, cooled to approximately atmospheric temperature and subjected to the action of selective solvents. As a rule the solvent extraction may be performed in one stage since the coke formed will settle quickly after the heat is taken from the bottom of the digester and a homogenous licuid is withdrawn for the solvent extraction.

parafiin naphtha of Van average boiling point corresponding to a mixture of pentanes and hexanes, though if suitable equipment is provided to permit the use of pressure, butanes and propane may be used. The invention is not limited to the use of any particular class of solvents and may employ any single solvent or mixture of solvents which may be found suitable for effecting the desired results.

The iiuid residuum is drawn from the digester through line I9 containing control valve 29 and transferred by a pump 2I by way of line 22 containing control valve 23 to a cooler 24 in which the temperature is only reduced to a point which will permit the use of the light solvent without undue losses and must not be brought too low in view of the tendency of the residuum to solidify or become too viscous for pumping. If desired,

some of the solvent may be admited at an intermediate point in the cooling coil.

The cooled residuum, with or without addition of a small amount of solvent, passes through line 25 containing control valve 26 and meets a stream of solvent from line 3l containing control valve 32. Line 3I is supplied with make-up solvent by way of line 28, control valve 29 and pump-30 and by recovered solvent from line 96, the production of which will be described in proper sequence. The volume of solvent used upon diierent pretreated cracked residua will vary from approximately 0.5 to 2.0 volumes based on the volume of residuum though obviously this range of volumes is subject to great variations due to the `differences .in the character of the residua which may be treated and the diierent types of solvents which may be employed. When using an 86 A. P. I. paraffin naphtha the volume commonly employed is from 1.5 to 2.5 volumes per volume of residuum.

'I'he residuum and solvent then pass through some type of mixing device indicated at 21 as a tube of moderate diameter containing filling or bailling material to create turbulence and then The solvent mostA vgenerally preferred for the segregation of the asphaltic and lubricating constituents is a light pass through aline 26 containing a control valve 21' to a settling tank 33. In this tank zone 34 -indicates an upper clear layer of a solution of'oil in solvent, 35 indicates an intermediate zone containing suspended material and 36 a zone of settled asphalt. shown at 33 may be employed in parallel in case it is further necessary or expedient to Warm the settled asphalt to insure suiicient fluidity for its ready pumping. If the material can be drawn continuously, parallel settlers may not be neces.- sary. The settler is provided with a gas vent line 31 containing control valve 38 for the release of any fixed gas accumulations and this line may Lbe connected to the solvent recovery vapor line if desired although this is not shown in the drawing.

The settled asphalt, mixed with a certain amount of adhering solvent and` oil may be drawn through a line 39 containing control Valve 40 to a pump 4I and subjected to any further processing steps necessary for the production of a finished product. Ordinarily this will consist in simply distilling oil? any solvent or oil. Thus pump 4I discharging through line 42 containing control valve 43 may pass the asphalt through a tubular heating element 44 disposed to receive heat from a furnace 45, the heated material passing to line 4G containing control valve 41 to a fractionator 48. The conditions of distillation in this tower are so controlled that the solvent and light oils are driven oli to pass through vapor line 49, control valve 50, condenser 5I, line 52 and con.- trol valve 53 to a receiver 54 which is provided with the customary gas release line 55 containing control valve 56 and liquid draw line 51 containing control valve 58. If found expedient the liquid l products may be worked up for solvent recovery Settling drums of the typecontaining control valve 60 to a receiver 6I which is again provided with a customary gas release line 62 containing control Valve 63 and a liquid draw line 6,4 containing control valve 65 leading to some intermediate storage. lDepending upon rthe temperature 'employed in the fractionator, this may be a product of varying consistency. It may be subjected to any further refining steps necessary for producing a finished material.

For the recovery of lubricating oil stocks the upper clear layer 34 in'settler 33 is removed by Way of line 66 containing control valve 61, taken by pump 68 and discharged by way of line 69 containing control valve 10 through the solvent recovery plant comprising heating elementl and a subsequent fractionator 15. 'Ihe heating unit 1I is disposed to receive heat from furnace 12 and the products are discharged by way of line 13 ycontaining control valve 14 at`a temperature suiiicient to enable the recoveryof the solvent as an overheadv vapor and the lubricating stocks as a tower reiiux, the latter passing out through draw line 86 containing control valve 81 to receiver 88 provided with a gas release line 89 containing control valve 90 and a liquid draw line 9| containing control valve 92. Stocks produced at this point may be worked up into finished lubricating oils in any desired manner such as, for example, vacuum distillation to produce cuts of diierent viscosities, solvent extraction, sulphurlc acid treatment, chilling and pressing to-remove parafn kor treatment with clay to improve color.

Solvent yvapors from fractionator 15 pass through vapor line 7S containing control valve 'il andare condensed during passage through condenser 'le from which they iiow through line 'lS containing control valve 80 to receiver tl provided with a fixed gas release line containing control valve t3 and a liquid draw line il@ containing control valve t5.

In the usual operation of the process all the overhead produced at this point will be returned to the solvent extraction step by Way o a line S3 containing control valve 9d, a recirculating pump 95 and a discharge line t containing control valve ill and leading to solvent line 3l pre'- viously described.

The following example is given to show the general character of the results obtainable by the use of the process, and while it isentirely representative, it is only one of a large number and the scope of the invention is not limited by the specific data given..

A Mid-Continent cracked residuurn having an A. i3. i. gravity or' 8.9 was digested for 2li hours at a temperature of lilly F., and a pressure oil 50 pounds per square inch. Following the digestion the residuurn was cooled and mixed with approxiz mately 2 volumes oi a close-cut paradlnic distillate fraction having the approximate boiling range oi pentane., The soluble and insoluble matsrials were separated and Worlsed up according to the general process outlined in connection with the drawing and the iollovring, table sliorvs the comparison between the yields of various products obtained from the untreated and the treated residuum by the solvent extraction step.

Uhh-cated Treated residuuin residuum ercent asphalt by pentane precipitation.. 12 42 Percent wax by chilling to 20 F. in l-l volumes in pantano l Percent overhead at 500 F... 5 l5 Percent oi 100 V. I. finished lubr lil 26 Percent heavy unsaturated oils 57 9 An inspection of the data reveals the iact that the asphalty content has been increased, the paraffin content slightly decreased, and the lubricating oil fraction increased by a considerable percentage. The increase of overhead at500 il. from to 15% indicates a slight cracking and it is evident from the decided drop in the percent age of heavy unsaturated oils from 57% to 9% that the". have been converted into the asphalt and lubricating oil fractions. The asphalt produced by the polymerizing step compared either with the asphalt recoverable by solvent action from the untreated residuum or with asphalt of corresponding penetration prepared from straight run residuum has a much lower susceptibility factor, that is, there is less change in penetration, meltingpoint and ductility as temperatures are' increased.

The character and value of the invention is obvious from a consideration of the preceding specication and single instance of results obtained, but neither is to be construed as imposing undue limitations upon its scope.

I claim as my invention:

l. A process for the treatment of liquid residue from a hydrocarbon cracking process which comprises, subjecting sald residue to prolonged digestion, at temperatures within the approximate range of 550 F. and 850 F., under non-hydrogenating conditions and Without substantial cracking thereof, to eiect polymerization reactions and to increase the asphalt and lubricating oil lcontent thereof, subjecting the thus treated cracked residue to the action oi a solvent, separating the undissolved material comprising asphalt from the supernatant liquid from which asphaltio components have been separated, andremoving and recovering the solvent and the dissolved oil by distillation of the solvent.

2. A process for the treatment oi liquid residue from a hydrocarbon cracking process which comn prises, subjecting said residue to prolonged digestion at temperatures within the approximate range of 550 F. and 850 F., under non-hydrogenating conditions and without substantial# 'cracking thereof, to eect polymerization reactions and to increase the ahphalt and lubricating oil content thereof, subjecting the thus treated cracked residue to the action of a solvent,.cornprising a relatively low-boiling hydrocarbon separating the undiolved material comprising asphalt vfrom ,the supernatant liquid from which asphaltic components have been separated, and removing and recovering the solvent and the dissolved oil by distillation of the solvent.

3. A process for the treatment oi liquid residue from a hydrocarbon cracking process which cornprises, subjecting said residue to prolonged digestion at temperatures within the approximate range or 550 F. and 850 F., under non-hydrogenating conditions and Without substantial cracking thereof, to eect. polymerization reactions and to increase the asphalt and lubricating oil content thereof, subjecting the thus treated cracked resi'due to the action of a solvent, comprising a rela= tively low-boiling hydrocarbon, separating the undissolved material comprising `asphalt from the supernatant liquid from which asphaltic cornponente have been separated, removing and recovering the solvent and the dissolved oil by distillation of the solvent-and producing lubricating oil from the dissolved oil by subjecting the same to chemical treatment.

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