A METHOD OF REMOVING SUBSTANCES FROM FOSSIL DERIVED HYDROCARBON LIQUIDS

Abstract: A method of separating high molecular weight fractions of and inorganic ingredients (eg aluminum, silicon, nickel, phosphorous, boron, vanadium, chromium, copper, titanium, zinc, lead, iron, nitrogen, magnesium, calcium and sulphur) from hydrocarbon liquids (eg spent diesel lubrication oil, crude oil or pipeline blend crude oils and heavy oils, and bitumen), wherein, at a viscosity less than 600 centipoise, the hydro­ carbon liquid (2) is passed through a membrane (18), having at least an outer layer (34) on the high pressure side comprising a microporous, polysulfone, poly­ acrylonitrile, polyamide or polyvinylidene fluoride membrane, at a pressure differential in the range 1 to 100 atmospheres oil to 10 MPa. The microporous structure is such that it provides the said at least outer layer with a molecular cut off less than 20,000 when measured in an aqueous medium. The viscosity of the hydrocarbon liquid may be reduced by heating (14) or a solvent (8) for the hydrocarbon involved in the separation. The microporous structure preferably provides the said at least outer layer with a molecular weight cut off of less than 4,000 when measured in oil.

Description: This invention relates to a method of removing contaminants with relatively high molecular weights and inorganic substances from fossil derived, hydrocarbon liquids. It has already been proposed in United States Patent Number 4,093,540, dated June 6, 1978, "Purification Process", A.K.S. Gupta, to refine dilute glyceride oil compositions by contacting them, in solution in an organic solvent, with a semi-permeable (e.g. polysulphone or polyacrylonitrile) membrane to separate constituents of different molecular weights into retentate and permeate fractions. The removal of, say, phosphatides (lecithins) from, say, a hexane solution of crude vegetable oil by the Gupta process is possible because lecithins, when dissolved in hexane, form molecular aggregates known as micelles with a molecular weight as high as 200,000. While the Gupta process has been found useful for separating these high molecular weight aggregates, it is not possible to form such high molecular weight aggregates with hexane from high molecular weight fractions of fossil derived hydrocarbon liquids or inorganic substances, present therein as solutions and suspensions, and so the Gupta process is not useful as a separation process in this instance, unless, as taught by Gupta, these substances (e.g. bitumen, calcium or magnesium) are present chemically associated with the phospholipids, which is never the case. This is borne out by the fact that Gupta teaches that copper is not removed by his process. There is a need for a process where high molecular weight fractions and/or inorganic substances, present as solutions and suspensions and not chemically associated with phospholipids, are removed from fossil derived hydrocarbon liquids. DE-A-2417452 discloses the use of an ultrafiltration membrane having a molecular weight cut off of between 5000 and 300 000 when measured in an aqueous medium for removing dissolved metal compounds from a used lubricating oil. According to the present invention there is provided a method of removing substances from fossil derived, hydrocarbon liquid, comprising passing a feed comprising a fossil derived hydrocarbon liquid containing at least one substance selected from the group consisting of relatively higher molecular fractions of the fossil derived, hydrocarbon liquid, and inorganic substances, the feed having a viscosity of less than about 600 centipoise (0.6 Pas), across a high pressure side of a microporous membrane, at pressure differential in the range of about one atmosphere to about 100 atmospheres (i.e. 0.1 to 10.0 MPa), at least an outer layer of the membrane, on the high pressure side thereof, being of at least one lyophilic, hydrocarbon liquid stable, organic, polymeric material which is a polysulphone or a polysulphone and at least one material selected from polyacrylonitrile, polyamides and polyvinylidene fluoride, said at least outer layer having a microporous structure that provides the said at least an outer layer with a molecular weight cut off of less than about 20,000 when measured in an aqueous medium, and less than 4,000 when measured in hydrocarbon liquid, so that hydrocarbon liquid depleted in the said at least one substance permeates the membrane leaving liquid hydrocarbon enriched in the said at least one substance as a retentate on the high pressure side of the membrane. The hydrocarbon liquid feed may contain asphaltenes and the permeate may be essentially asphaltene free. The viscosity of the hydrocarbon liquid feed may be reduced to less than about the said 600 centipoise (0.6 Pas) by heating the hydrocarbon liquid. This will ease the processability and reduce the pressure drop of the hydrocarbon liquid feed on the retentate side of the membrane. The viscosity of the feed hydrocarbon liquid may also be reduced to less than about the said 600 centipoise (0.6 Pas) by diluting the hydrocarbon liquid feed with a solvent therefor. Separated solids in the retentate may be separated from the remaining retentate, and then the remaining retentate is recirculated to the membrane for further separation. The retentate may be enriched with at least one inorganic substance selected from the group consisting of nickel, vanadium, chromium, copper, aluminium, boron, titanium, zinc, lead, iron, nitrogen, silicon, phosphorus, magnesium, calcium and sulphur present in the hydrocarbon liquid. Preferably the viscosity of the hydrocarbon liquid permeate is less than about 50 percent of that of the hydrocarbon liquid feed. In one embodiment of the present invention the hydrocarbon liquid feed is passed across the retentate side of the membrane with the hydrocarbon liquid feed having a viscosity of less than about 400 centipoise (0.4 Pas), and the microporous structure of the said outer layer provides that layer with a molecular weight cut off of less than about 10,000 in an aqueous medium. This is particularly useful for removing, for example, asphaltenes from tar sand bitumen in addition to removing inorganic substances therefrom. In the accompanying drawings which are provided for a better understanding of the present invention: Figure 1 shows a flow diagram of apparatus used to verify the present invention, Figure 2 is a graph of the molecular weight distribution of a light oil before and after the separation of inorganic substances therefrom, and Figure 3 is a graph of the molecular weight distribution of a heavy oil before and after the separation of inorganic substances therefrom. In Figure 1, there is shown a tank 1, containing fossil derived, aromatics and aliphatics containing, hydrocarbon liquid 2, a stirrer 4 in the hydrocarbon liquid 2, a tank 6 containing a solvent 8 for the hydrocarbon liquid 2, pumps 10 and 12, a heat exchanger 14, a membrane separating device 16 having a microporous membrane 18, a tank 20 containing retentate 22, a centrifugal separator 24, pumps 26, 28 and valves 30 to 33. At least an outer layer 34 on the high pressure side of the membrane 18 is of at least one lyophilic, hydrocarbon liquid stable, organic, polymeric material, and has a microporous structure that provides that said at least an outer layer with a molecular weight cut off of less than about 20,000 when measured in an aqueous medium. One method of providing such a membrane 18 is described and claimed in United States Patent No. 4,451,424, for casting polysulfone membranes, and other methods of producing such membranes in other materials are well known to persons skilled in the art. In operation, hydrocarbon liquid 2, together with a solvent 8, such as naphtha, mixed therewith by stirrer 4, if it is necessary to reduce the viscosity of the hydrocarbon liquid 2 in this manner, is pumped by the pump 12 through the heat exchanger 14 to provide a pressure differential in the range one to 100 atmospheres (about 101 to 10100 kPa) at the membrane 18 of the membrane separating device 16. The heat exchanger 14 may heat the hydrocarbon liquid 2 to, in conjunction with the solvent 8, or in place thereof, reduce the viscosity of hydrocarbon liquid 2 if this is necessary. In operation, the hydrocarbon liquid 2 containing e.g. at least one inorganic substance is pumped by pump 12 through the heat exchanger into the separating device 16, to the side of the membrane 18 having outer layer 34. As previously stated, if necessary, the viscosity of the hydrocarbon liquid 2 can be reduced to less than about 600 centipoise (0.6 Pas) by mixing the solvent 8 with the hydrocarbon liquid 12 using the stirrer 4. The viscosity of the hydrocarbon liquid 2 can also, if necessary, be reduced to less than about 600 centipoise (0.6 Pas) by heating the hydrocarbon liquid using the heat exchanger 14 alone or in combination with the addition of solvent 8 thereto. It is necessary for the viscosity of the hydrocarbon liquid to be reduced to less than about 600 centipoise (0.6 Pas) in order that the hydrocarbon liquid can be pumped across the outer layer 34 of the membrane 18 to pass through the membrane at a pressure differential in the range of one to 100 atmospheres and in order that the membrane 18 will not become blinded by the hydrocarbon liquid. The hydrocarbon liquid is forced through the membrane 18 leaving behind a retentate enriched with the inorganic substance or substances. The retentate flows across the membrane and is collected in the tank 20. If desired, retentate 22 may be pumped by pump 26 from the tank 20 to the centrifugal separator 24, where solid substances are removed from the retentate and returned to the tank 20. The retentate with solid substances removed therefrom is pumped by the pump 28 to the tank 1 to be processed once more. Throughout the test results which follow, 1 centipoise (CPS) = 0.001 Pas. The following tables give the results of tests carried out to verify the present invention using the apparatus shown in Figure 1. Each table gives the results of different tests carried out for the removal of inorganic substances for a particular fossil derived, hydrocarbon liquid using similar or different membranes in each text in a table. In the following Table 1, new and used diesel lubricating oil was passed at a pressure of 1.0 ± 0.1 Bar (10⁵ ± 10⁴ Pa) at 60°C through the membranes specified at the particular fluxes given. Test No. 3 is provided for comparative purposes. The following Tables II to XII give the results of tests for different fossil derived, free flowing, hydrocarbon liquids using flat polysulfone membranes on polyester supports. Where the membrane numbers are followed by U, such as 2U, this indicates that these membranes were made from polysulfone marketed under trade name UDEL 3500 by Union Carbide Corporation. Where the membrane numbers are followed by V, such as 3V, this indicates that these membranes were made from polysulfone marketed under the trade name VICTREX by Imperial Chemical Industries, London, England. In the Tables the separation results given for chromium and vanadium were measured using a method that was unreliable below 2 ppm and so these results are given merely to show that separation of chromium and vanadium occurred. In the following Table II the feed was Venezuela crude oil, fed at a flow rate of 0.192 Kg/second, and at a temperature of 30°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of crude oil used in each test was 9.0 liters having a mean viscosity at 30°C of 10.0 CPS. In the following Table III the feed was the Venezuelan crude oil retentate from the test of the same designation in Table II, which was the remaining concentrated 60% by volume of the feed for Table II. In Table III the flow rate of the feed pressure for each test was 0.065 Kg/second, at a temperature of 37°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of oil used in each test was 5.0 liters having a means viscosity at 37°C of 25.5 CPS. In the following Table IV the feed was Texas crude oil, fed at a flow rate of 0.270 Kg/second, and at a temperature of 20°C. The feed pressure for each test was between 2.0 MPa and 2.5 MPa. The volume of crude oil used in each test was 5.0 liters having a mean viscosity at 20°C of 5.1 CPS. In the following Table V the feed was crude oil from Leduc, Alberta, Canada, fed at a flow rate of 0.264 Kg/second, and at a temperature of 24°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of crude oil used in each test was 9.0 liters having a mean viscosity at 24°C of 56.5 CPS. In the following Table VI the feed was from the Leduc crude oil retentate from the test of the same designation in Table V, which was the remaining concentrated 50% by volume of the feed from Table V. In Table VI, the flow rate of the feed for each test was 0.129 Kg/second, and at a temperature of 24°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of oil used in each test was 4.5 liters having a mean viscosity at 24°C of 16.5 CPS. In the following Table VII the feed was that known as Mydale crude oil from Venezuela, fed at a flow rate of 0.110 Kg/second, and at a temperature of 50°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of crude oil used in each test was 9.0 liters having a mean viscosity at 50°C of 19.5 CPS. Referring now to Figure 2, there is shown a graph of the molecular weight distribution of the test designated 6U in Table VII, obtained by a high performance liquid chromatograph. In Figure 2 molecular weight M is plotted against elution volume V, ----- is for the feed which had a weight averaged molecular weight of 576, and ― is for the permeate which had a weight averaged molecular weight of 320. In the following Table VIII, the feed was the Mydal crude oil retentate from the test of the same designation in Table VII, which was the remaining concentrated 40% by volume of the feed for Table VII. In Table VIII the flow rate of the feed for each test was 0.042 Kg/second, at a temperature of 60°C. The feed pressure was between 2.0 MPa and 3.5 MPa. The volume of oil used in each test was 4.0 liters having a mean viscosity at 60°C of 98.7 CPS. In the following Table IX the feed was that known as Boundary Lake crude oil from British Columbia, Canada, fed at a flow rate of 1.39 Kg/second, and at a temperature of 25°C. The feed pressure was between 1.5 MPa and 2.0 MPa. The volume of crude oil used in each test was 7.0 liters having a mean viscosity at 25°C of 8.5 CPS. In the following Table X the feed was the Boundary Lake retentate from the test of the same designation in Table IX, which was the remaining concentrated 57% by volume of the feed for Table IX. In Table X the flow rate of the feed for each test was 0.103 Kg/second, and at a temperature of 35°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of the oil used in each test was 4.0 liters having a mean viscosity at 35°C of 17.5 CPS. In the following Table XI the feed was a Canadian pipeline blend of crude oils, of unknown origin, fed at a flow rate of 0.210 Kg/second, and at a temperature of 30°C. The feed pressure for each test was between 2.0 MPa and 2.5 MPa. The volume of the crude oil used in each test was 9.5 liters having a mean viscosity at 30°C of 5.1 CPS. In the following Table XII the feed was the pipeline blend crude oils retentate from the test of the same designation in Table XI, representing the remaining concentrated 47% of the initial feed of Table XI. In Table XII the flow rate of the feed for each test was 0.132 Kg/second, and at a temperature of 30°C. The feed pressure was between 2.0 MPa and 2.5 MPa. The volume of the oil used in each test was 5.0 liters having a mean viscosity at 30°C of 15.4 CPS. The following Tables XIII to XXI give results of tests carried out on various tar sands bitumen to verify the present invention for different membranes. In the following Table XIII, the feed was Athabasca Tar Sands bitumen obtained from the Solvent Extraction Spherical Agglomeration (SESA) process. The flow on the retentate side of the membranes was 3 liters/minute at a pressure of 9 bars (9 X 10⁵ Pa) and at 20°C. For comparison, the analysis of oil upgraded by the conventional method of solvent extraction and centrifugation called Maltenes is shown. It is evident that the conventional method for removing asphaltenes is not effective in removing nitrogen, sulphur, nickel and vanadium which are the most important contaminants. In the following Table XIV, the feed was Lloyd Primary Bitumen fed at a flow rate of 0.31 Kg/s at a temperature of 38°C and a pressure between 2.0 MPa and 2.6 MPa on the retentate side of the membranes. The volume of oil used was 8.5 liters having a mean viscosity of 85 CPS at 38°C. In the following Table XV, the feed was Lloyd Primary Bitumen from Table XIV after removal of 4.5 liters of permeate fed at a flow rate of 0.028 Kg/s at a temperature of 42°C and a pressure between 2.0 MPa and 3.4 MPa on the retentate side of the membranes. The volume of oil used was 4 liters having a mean viscosity of 295 CPS at 42°C. In the following Table XVI, the feed was Cold Lake Bitumen diluted by 34% naphtha, fed at a flow rate of 0.126 Kg/s at a temperature of 46°C and a pressure between 2.0 MPa to 2.5 MPa on the retentate side of the membranes. The volume of oil used was 5.5 liters having a mean viscosity of 27.2 CPS at 46°C. In Figure 3 there is shown a graph of the molecular weight distribution of the Cold Lake Bitumen test designated U6 in Table XVI obtained by the previously mentioned high performance liquid chromatograph. In Figure 3 the molecular weight M is plotted against elution volume. The line ----- is for the feed hydrocarbon which has a weight average molecular weight of 814 and line ― is for the permeate which has a weight average molecular weight of about 400. In the following Table XVII, the feed was Cold Lake Bitumen from the test in Table XVI after removal of 2.5 liters of permeate. The feed was introduced at a flow rate of 0.985 Kg/s at a temperature of 45°C and a pressure between 2.0 MPa to 3.0 MPa on the retentate side of the membranes. The volume of oil used was 3 liters having a mean viscosity of 89.6 CPS at 45°C. In the following Table XVIII the feed was Carbonate Trend Bitumen diluted by 41% with naphtha and fed at a flow rate of 0.034 Kg/s at a temperature of 25°C and a pressure between 2.4 MPa to 2.9 MPa on the retentate side of the membranes. The volume of oil used was 8 liters having a mean viscosity of 80.8 CPS at 25°C. In the following Table XIX the feed was Carbonate Trend Bitumen from the test described in Table XVIII after removal of 50% of the feed as permeate. The now concentrated feed was fed at a flow rate of 0.02 Kg/s at a temperature of 35°C and a pressure between 2.0 MPa to 3.5 MPa on the retentate side of the membranes. The volume of oil used was 4 liters having a mean viscosity of 392.5 CPS at 35°C. In the following Table XX the feed was Athabasca Bitumen from the hot water extraction process with a dilution of 37% with naphtha fed at a flow rate of 0.1 Kg/s at a temperature of 35°C and a pressure flow between 2.0 MPa and 2.5 MPa on the retentate side of the membranes. The volume of oil used was 6.5 liters having a mean viscosity of 21.9 CPS at 35°C. In the following Table XXI the feed was Athabasca Bitumen concentrate from the test of Table XX after removal of 3 liters of permeate, fed at a flow rate of 0.025 Kg/s at a temperature of 34°C and a pressure flow between 2.0 MPa and 2.7 MPa on the retentate side of the membranes. The volume of oil used was 3.5 liters having a mean viscosity of 122.8 CPS at 34°C. The tests showed that when the microporous structure provided the outer layer on the retentate side with a molecular weight cut off greater than about 20,000 > membrane 9V, when measured in an aqueous medium, the microporous structure was more susceptible to plugging giving lower separation factors for the constituents and lower permeate fluxes. The test results also indicated that using feeds having higher viscosities than those given in the Tables would give larger pressure drops with the equipment used on the retentate side of the membrane, causing more difficult pumping of hydrocarbon past the membrane which in turn would give lower permeation rates, and so the viscosities would have to be decreased for higher recoveries of the upgraded oil. The viscosity may be reduced by heating the oil or by adding a recoverable solvent, such as naphtha or hydrocarbon concentrates, such as those obtained from natural gas, provided that they are mainly aliphatic in nature. Higher viscosities could be accommodated by equipment with larger spacings on the retentate side of the membrane and by the use of larger pipe sizes in the construction of the equipment. It was also evident from the tests that a retentate obtained from a fossil derived hydrocarbon liquid by the present invention may be enriched with at least one inorganic substance selected from groups IIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB, IIIB, IVB, VB and VIB of the Periodic Table as specified by the International Union of Pure and Applied Chemistry. Important inorganic substances included in this list and demonstrated to be separable in the previous examples are boron, nickel, vanadium, chromium, copper, aluminum, titanium, zinc, lead, iron, nitrogen, silicon, phosphorus, magnesium, calcium and sulphur, which were chosen to act as examples and are not meant to limit the present invention to these elements. In the case of oil from oil shale or bitumen from tar sands, inorganic substances such as polyaromatic hydrocarbons, e.g. asphaltenes gums and waxes, may also be retained in the retentate obtained by the present invention.

Claims: A method of removing substances from fossil derived, hydrocarbon liquid, comprising passing a feed comprising a fossil derived hydrocarbon liquid containing at least one substance selected from the group consisting of relatively higher molecular fractions of the fossil derived, hydrocarbon liquid, and inorganic substances, the feed having a viscosity of less than about 600 centipoise (0.6 Pas), across a high pressure side of a microporous membrane, at pressure differential in the range of about one atmosphere to about 100 atmospheres (i.e. 0.1 to 10.0 MPa), at least an outer layer of the membrane, on the high pressure side thereof, being of at least one lyophilic, hydrocarbon liquid stable, organic, polymeric material which is a polysulphone or a polysulphone and at least one material selected from polyacrylonitrile, polyamides and polyvinylidene fluoride, said at least outer layer having a microporous structure that provides the said at least an outer layer with a molecular weight cut off of less than about 20,000 when measured in an aqueous medium, and less than 4,000 when measured in hydrocarbon liquid, so that hydrocarbon liquid depleted in the said at least one substance permeates the membrane leaving liquid hydrocarbon enriched in the said at least one substance as a retentate on the high pressure side of the membrane. A method as claimed in claim 1, wherein the hydrocarbon liquid feed contains asphaltenes and the permeate is essentially asphaltene-free. A method as claimed in claim 1 or claim 2, wherein the viscosity of the feed is brought to less than about the said 600 centipoise (0.6 Pas) by heating the hydrocarbon liquid. A method as claimed in any one of claims 1 to 3, wherein the viscosity of the feed is brought to less than about the said 600 centipoise (0.6 Pas) by diluting the hydrocarbon liquid with a solvent therefor. A method as claimed in any one of claims 1 to 4, wherein separated solids in the retentate are separated from the remaining retentate, and then the remaining retentate is recirculated to the membrane for further separation. A method as claimed in any one of claims 1 to 5, wherein the retentate is enriched with at least one inorganic substance selected from the group consisting of nickel, vanadium, chromium, copper, aluminium, boron, titanium, zinc, lead, iron, nitrogen, silicon, phosphorus, magnesium, calcium and sulphur present in the hydrocarbon liquid. A method as claimed in any one of claims 1 to 6, wherein the viscosity of the hydrocarbon liquid permeate is less than about 50% of that of the feed. A method as claimed in any one of claims 1 to 7, wherein the feed is passed across the retentate side of the membrane with the feed having a viscosity of less than about 400 centipoise (0.4 Pas), and the microporous structure of the said at least outer layer provides that layer with a molecular weight cut off of less than about 10,000 in an aqueous medium.

Inventors: HAZLETT, JOHN D., KUTOWY, OLEH, TWEDDLE, THOMAS A.
Applicants: NATIONAL RESEARCH COUNCIL OF CANADA/ CONSEIL NATIONAL DE RECHERCHES DU CANADA
Application year: 1986
Main classification: C10G31
IPC codes: F02B3, C10G31, C10M175