US3532618A

US3532618A - Pour point depressant made by hydrovisbreaking and deasphalting a shale oil

Info

Publication number: US3532618A
Application number: US751054A
Authority: US
Inventors: Donald K Wunderlich; John H Frankovich
Original assignee: Sinclair Oil Corp
Current assignee: Sinclair Oil Corp
Priority date: 1968-08-08
Filing date: 1968-08-08
Publication date: 1970-10-06
Anticipated expiration: 1987-10-06

Description

US. Cl. 208-14 13 Claims ABSTRACT OF THE DISCLOSURE A process for producing a pour point depressant for shale oil which comprises mixing a deasphalting solvent, under deasphalting conditions, for instance, at a temperature of up to about 250 F. at a pressure up to about 500 p.s.i.g., with a shale oil which has had its viscosity and pour point lowered as a result of contact with hydrogen under hydrovisbreaking conditions. The mixture of shale oil and deasphalting solvent is then separated into deasphalted shale oil and a heavier portion containing the pour point depressant for shale oil. Compositions comprised of shale oil and the pour depressant are also disclosed.

This invention relates to the pour point reduction of shale oils. More particularly, this invention relates to a process for producing a pour point depressant for shale oils from a shale oil which has had its pour point lowered as a result of contact with hydrogen under hydrovisbreaking conditions.

Quantity production of shale oil by retorting or underground heat drive will take place in remote sections of the country such as Colorado. Before the shale oil can be used in conventional refining processes, it must be subjected to severe catalytic hydrotreatment to lower the concentration of nitrogen-containing and olefinic compounds. If the catalytic hydrogen treatment were performed at the shale oil production site, the construction of complex facilities in remote areas would be required where construction costs are high and skilled labor is scarce. A more economical approach is to pipeline the untreated shale oil to refineries located in industrial areas of the country and to catalytically hydrotreat the shale oil at these locations. The problem in this approach is that the physical properties of shale oil make pipelining difficult since the viscosity of the shale oil is high and, more importantly, the shale oil pour point is very high.

It is possible to reduce both viscosity and pour point of shale oil by a viscosity-breaking process known in the art as visbreaking; however, we have found that this method is not practical since the pourpoint of the visbroken shale oil is not stable and increases upon storage. The visbreaking process is also not practical since the solid deposits, e.g. coke, which form in the viscositybreaking reaction chamber reduce the volume of the reaction chamber and cause plugging in lines carrying the shale oil product of reduced viscosity from the reactor.

It has now been found that a pour point depressant for shale oil can be obtained from a shale oil which has had its pour point lowered as a result of contact with hydrogen under hydrovisbreaking conditions. It has also been found that when hydrogen is contacted with the shale oil during the viscosity-breaking process, there is greater pour point and viscosity reduction, stability of nited States Patent G M 3,532,618 Patented Oct. 6, 1970 ICC pour point upon storage, higher conversion of the 1050 F. plus bottoms to lighter material, and higher API gravity and higher hydrogen content in the resulting shale oil of lowered viscosity and pour point. This process can be called hydrovisbreaking. In addition, it has also been found that the formation of solid deposits, e.g. coke, is decreased by contacting the shale oil with hydrogen during the viscosity-breaking process in the reaction zone.

In accordance with the present invention, a pour point depressant for shale oil and its fractions having pour points above about 20 F., is produced by a process which comprises contacting a deasphalting solvent, under deasphalting conditions, for instance at a temperature up to about 250 F. and a pressure up to about 500 p.s.i.g., with a shale oil which has had its viscosity and pour point lowered as a result of contact with hydrogen under hydrovisbreaking conditions. The mixture of shale oil and deasphalting solvent is then separated into a lighter portion containing the deasphalting solvent, deasphalted shale oil of intermediate pour point and a heavier portion containing the pour point depressant for shale oil, the heavier portion being essentially insoluble in the deasphalting solvent.

The deasphalting solvent is of relatively low boiling point and thus the solvent can be separated from the deasphalted shale oil of intermediate pour point by distillation and solvent reused in the deasphalting treatment. The deasphalting'solvent can be an aliphatic hydrocarbon containing about 3 to 7 carbon atoms and preferably saturated. Suitable hydrocarbon solvents in clude, for instance, propane, butane and pentane. The deasphalting solvent can be contacted with the hydrovisbroken shale oil at a solvent to oil ratio of, for instance, about 0.2 to 10: 1, preferably about 0.5 to 5:1, by volume.

The shale oil of lowered viscosity and pour point can be produced by a process which comprises heating shale oil in contact with molecular hydrogen under hydrovisbreaking conditions, for instance, at a temperature of about 600 to 1000 F., preferably about 700 to 900 F., under a pressure of about 500 to 3000, preferably about 500 to 1500 p.s.i.g. The hydrogen can be contacted with the shale oil at a ratio of, for instance, about 250 to 10,000, preferably about 500 to 3000 s.c.f. hydrogen per bbl. of shale oil. The shale oil and hydrogen are maintained under hydrovisbreaking conditions under essentially liquid phase conditions for a time sufficient to substantially lower the viscosity and pour point of the shale oil. This time is often called the cold oil time which is defined as the heated reactor volume divided by the oil feed rate in volumes per minute at ambient conditions. Suitable cold oil times include generally up to about 30 minutes and say at least about 3, preferably about 5 to 15, minutes.

In this invention, the term shale oil encompasses full range shale oils, shale oil residuals such as atmospheric reduced shale oils, vacuum reduced shale bottoms, and other shale oils which have not been distilled as overhead after removal from oil shale by retorting. Shale oil usually has an initial pour point above about F. and a viscosity above about 30 kv. at 122 F. The hydrovisbreaking process reduces the pour point of the shale oil to generally at least below about 0 F., preferably below about 25 F. A viscosity reduction of the shale oil accompanies the pour point reduction and the viscosity is usually reduced to below about 25 kv. at 122 F. Hydrogen containing vapor can be separated from the resulting liquid shale oil at an elevated pressure, e.g. approximately the treating pressure, to facilitate recycle to the treating zone and reduce compression costs. The hydro-containing vapor can be cooled and separated into a liquid shale oil portion and a vapor portion containing hydrogen. This liquid shale oil portion can be combined with the liquid shale oil product taken from the reaction zone. The vapor portion containing hydrogen can be recycled into contact with shale oil heated under the hydrovisbreaking conditions. There can be little, if any, hydrogen consumption in this process and most of the hydrogen used in the process can be obtained by recycle. As a result, the requirement for makeup hydrogen is small and compression costs are minimal.

In the system of the present invention, raw, hot, shale oil and hydrogen are sent into a viscosity-breaking furnace. The heated mixture of shale oil and hydrogen is withdrawn from the viscosity-breaking furnace and is transferred to a soaking drum wherein most of the thermal cracking occurs. Hydrogen-containing vapor is taken overhead from the soaking drum. The withdrawal of hydrogen-containing vapor while the shale oil and hydrogen are maintained in the soaking drum minimizes the thermal cracking of the light hydrocarbons contained in the stream and permits maximum thermal cracking on the bottoms contained in the soaking drum at a given equipment cost. The hydrogen-containing vapor is transferred into and through a heat exchanger where it is cooled and then sent into a flash drum. A vapor portion containing hydrogen is withdrawn from the flash drum and is recycled and combined with hydrogen entering the process.

Liquid shale oil of lowered viscosity and pour point is withdrawn from the soaking drum and is transferred into and through a heat exchanger where it is cooled. The cooled liquid shale oil is of lowered viscosity and pour point. A liquid shale oil portion is withdrawn from the flash drum and is combined with liquid shale oil of lowered viscosity and pour point. The combined liquid shale oil portion and liquid shale oil of lowered viscosity and pour point are then sent to a solvent deasphalting unit which can be successive batch treating units, a packed tower, a baffle tower, a bubble cap tower or rotating disk contractor, etc. The deasphalting solvent is transferred into the deasphalting unit. Deasphalting shale oil of intermediate pour point and the deasphalting solvent are withdrawn and transferred to a deasphalting solvent extraction'unit. The deasphalting solvent is recovered in the deasphalting solvent extraction unit and is recycled to be combined with makeup intermediate pour point is Withdrawn from the deasphalting solvent extraction. The pour point depressant for shale oil is withdrawn from the deasphalting solvent unit.

The pour point depressant can then be added to shale oils having a pour point of above about 20 F. to obtain shale oil compositions of lowered pour point. The amount of depressant added to the shale oil is small but suflicient to provide a substantial pour depressing effect, for instance, to reduce the pour point of the oil by at least about 20 F., preferably to about 10 F. or lower. This amount will often be about 0.1 to 10 or more weight percent of the shale oil to be pour depressed, preferably about 1 to 5 weight percent. The shale oils pour depressed can be for example, the various oils which can be used as feeds to the hydrovisbreaking operation.

The following example illustrates the process of the invention.

EXAMPLE I Raw shale oil was passed up-flow, in contact with hydrogen under hydrovisbreaking conditions, through a inch, schedule 40 pipe which was held at reaction temperature in an electrically heated furnace. Feedstock properties, reaction conditions and product inspections are contained in Table I.

deasphalting solvent. Shale oil of 0 TABLE I Raw shale Hydrovis oil breaking Reactor temperature, F 825 Pressure, p.s.i.g 1, 000 Gas ratio, s.c.f./b 2, 000 Oil feed rate, gn1./l1r 300 Cold oil time, min Wt. percent liquid recovery 100 94. 0

Feed Product Liquid Inspections:

Gravity, All l8. 9 19. 7 Pour point, F +85 -45 Viscosity, kv. at 122 F 31.01 14. Percent Ramsbottom carbon 4. 5 5. 46 Wt. percent hydrogen 11. 27 11. 11

Raw shale Hydrovisoil breaking ASIN (vac.) distillation, F.:

Trap, ml

The shale oil of lowered viscosity having a pour point of 45 F. produced by the hydrovisbreaking process was mixed at ambient temperature and pressure with an equal volume of normal pentane. After thorough mixing, the mixture was centrifuged and a heavy viscous layer amounting to 2.5 weight percent of the shale oil of lowered viscosity and pour point was centrifuged from the lighter deasphalted shale oil layer. This heavy viscous layer contained the pour point depressant for shale oil. The deasphalting solvent contained in the deasphalted shale oil layer was evaporated from the deasphalted shale oil. The resulting deasphalted shale oil had a pour point of 0 F. The removal of the heavy viscous layer, therefore, actually increased the pour point of the shale oil of lowered visocsity and pour point from the initial value of -45 F. to 0 F. The heavy viscous layer obtained from the deasphalting step and containing the pour point depressant was mixed thoroughly with a volume of raw shale oil having a pour point of P. which was equal to the volume of shale oil of reduced pour point and viscosity from which the heavy viscous layer was obtained. The resulting mixture of raw shale oil and the heavy viscous layer containing the pour point depressant had a pour point of 0 F. Thus, the pour point depressant of the present invention was effective in reducing the pour point of raw shale oil from +85 F. to 0 F.

What is claimed is:

1. A process for producing a pour point depressant for shale oil which comprises contacting a deasphalting solvent, under deasphalting conditions with shale oil which has had its pour point lowered to less than about 0 F. as a result of contact with hydrogen under hydrovisbreaking conditions, separating said mixture of shale oil and deasphalting solvent into a lighter portion con taining said solvent and deasphalted shale oil, and a heavier portion which is a pour point depressant for shale oil.

2. The process of claim 1 in which the shale oil contacted with the deasphalting solvent has a pour point below about -25 F.

3. The process of claim 2 wherein the deasphalting solvent is contacted, under deasphalting conditions, with shale oil which has had its pour point lowered as a result of contact with hydrogen under hydrovisbreaking conditions including a temperature of about 700 to 900 F. and a pressure of about 500 to 3000 p.s.i.g.

4. The process of claim 3 wherein the deasphalting solvent is a saturated aliphatic hydrocarbon containing about 3 to 7 carbon atoms.

5. The process of claim 4 wherein the deasphalting solvent is n-pentane.

6. The process of claim 4 wherein the deasphalting solvent is contacted with the shale oil of lower viscosity and pour point at a solvent to oil ratio of about 0.5 to 5:1 by volume.

7. The pour depressor made by the process of claim 1.

8. The pour depressor made by the process of claim 2.

9. The pour depressor made by the process of claim 4.

10. A composition comprising shale oil having a pour point of at least about 20 F. having added thereto a small amount, sufficient to depress the pour point of the oil by at least about 20 F. of the pour depressor made by the process of claim 1.

11. A composition comprising shale oil having a pour point of at least about 20 F. having added thereto a small amount, suflicient to depress the pour point of the oil by at least about 20 F. of the pour depressor made by the process of claim 2.

12. A composition comprising shale oil having a pour point of at least about 20 F. having added thereto a UNITED STATES PATENTS 2,943,050 6/1960 Beavon 208-96 3,053,750 9/1962 Beuther 20896 3,106,521 10/1963 Huntington 20811 3,369,992 2/1968 Henke et al. 20814 FOREIGN PATENTS 995,106 6/1965 Great Britain.

HERBERT LEVINE, Primary Examiner US. Cl. X.R.