US3810771A - Asphalt compositions - Google Patents

Abstract

AN IMPROVED ASPHALT PAVING COMPOSITION IS OBTAINED BY ADDING TO A PETROLEUM ASPHALT COAL WHICH HAS BEEN SOLVENT TREATED IN THE PRESENCE OF HYDROGEN.

Description

llVlay 14, 1974 H BEUTHER EVAL ASPHALT COMPOS ITIONS Filed Nov. 29, 1966 .lllll' May 14, 1974 H. BEUTIHr-:R E'rAL 3,80,77l

ASPHALT COMPOSITIONS Filed Nov. 29, 1966 5 Sheets-Sheet 2 INVENToRs /a/ef 14,1%. efe.

BEUTHER ET AL ASPHALT COMPOSI'IONS Filed Nov. 29, 1966 3 Sheets-Sheet 3 fUnited States Patent Oce 3,810,771 ASPHALT COMPOSI'I'IONS Harold Beuther, Gibsonia, and Alfred M. Henke, Springdale, Pa., assignors to Gulf Research & Development, Pittsburgh, Pa.

Continuation of abandoned application Ser. No. 597,792, Nov. 29, 1966. This application June 15, 1970, Ser. No. 48,885

Int. Cl. Cc 3/08; C08h 13/00, 17/22 U.S. Cl. 106-278 7 Claiml ABSTRACT 0F THE DISCLOSURE An improved asphalt paving composition is obtained by adding to a petroleum asphalt coal which has been solvent treated in the presence of hydrogen.

This application is a continuation of application Ser. No. 597,792 filed Nov. 29, 1966, now abandoned.

This invention relates to asphalt compositions having improved temperature susceptibility that are suitable for paving and other purposes and to lmethods of producing such compositions. This invention relates particularly to the production of such asphaltic products from petroleum residues.

Petroleum asphalts are obtained mainly as the residue on distillation of certain petroleum crude oils. They have certain empirical characteristics determined by their particular use, as for example, paving, roofing and waterproofing. One of the most important characteristics of asphalt is its flow or rheologcal properties. Various empirical tests are used in measuring these flow characteristics. It is customary to define these flow characteristics of asphaltic materials by means of measurements and ratios such as penetration and ductility values, melting point and temperature susceptibilities, the latter being represented by the ratio of penetrations at various temperatures, for instance at 39.2 F. and at 77 F. These measurements are made by standard methods of test of the American Society for Testing Materials. For example, penetration values are obtained by measuring the distance of penetration of various asphaltic materials by a specified needle loaded with a specified weight at a specified ternperature for a specified time. (See A.S.T.M. method No. -D5-25, Penetration of Bituminous Materials). Melting points (softening points) are commonly determined by the ball and ring method, which consists of filling a ring with asphalt and placing a steel ball of specified weight in the center of the asphalt and then uniformly heating the asphalt until the ball drops through. (See A.S.T.1M. method No. D36, Softening Point for Bituminous Materials). The above methods are used for the determinations given herein.

The properties represented by the above measurements are important from the standpoint of the present invention. In formulating asphalt compositions suitable for road paving operations it is desirable to improve the ability of the asphalt to withstand heavy loads and rather severe shocks. Penetration is a measure of consistency and hardness, serving primarily to classify asphalts into commercial grades of various degrees of hardness. The temperature susceptibility (penetration ratio) indicates the susceptibility of an asphalt product to change of hardness with change in temperature, that is, its rate of softening. It is therefore desirable to increase the temperature susceptibility of a paving asphalt as expressed by the above indicated ratio over the ratio present in the average commercial petroleum asphalt.

It is therefore an object of this invention to produce petroleum asphalts suitable for road paving having an improved ability to withstand heavy loads and shocks. It is a further object of this invention to increase the tem- 3,810,771 Patented May 14, 1974 perature susceptibility of a petroleum asphalt. It is another object of this invention to produce petroleum asphalt compositions having an improved ability to withstand heavy loads and severe shocks and having a high temperature susceptibility, at a relatively inexpensive cost. These and other objects of this invention are accomplished by adding a coal, that has been treated in the presence of available hydrogen so as to solubilize at least a portion thereof, to a petroleum residue. By the term coal we mean bituminous, subbituminous and lignite coal. In one preferred l embodiment of this invention coal, as defined above, which has been subjected to a solvent deashing process and which has had the ash physically removed from it, is added to a petroleum residue.

In another preferred embodiment of this invention, coal which has been subjected to a solvent treatment of the kind indicated above without having ash physically removed is added to a petroleum residue.

We have found that the addition of coal of the type described which has been treated by the aforementioned procedures when added to petroleum asphalt residues, increases the temperature susceptibility of the asphalt residue appreciably, thereby rendering it highly suitable for use as a road paving material.

In the accompanying drawings, FIG. I illustrates a comparison of the improved temperature susceptibility of deashed coal-asphalt blends with those of commercially available asphalts; FIG. II illustrates the effect of the addition of deashed coal on the penetration-softening point relationship of an asphalt residue; and FIG. III illustrates by means of a flow plan a preferred method of deashing the coal employed in this invention.

Coal, a sedimentary deposit, invariably contains mineral impurities. The residue from these 4mineral impurities after coal has been burned is called ash. Selective mining and coal cleaning processes can do a fairly effective job of removing free mineral impurities but they are not effective in removing inherent ash, that is, the mineral particles that are finely dispersed throughout the coal. Several prior art extraction methods have been developed to remove this inherent ash from coal, such as those disclosed in U.S. 2,686,152 to Franke. Probably the best known prior art method for accomplishing this type of extraction is that proposed by Alfred -P'ott Hans Broche, originators of the Pott-Broche process, wherein an extraction on low grade solid carbonaceous fuel is carried out with organic solvent at elevated temperatures. Thereafter, according to this process, the residue is removed by filtration on centrifuging and the resulting extract is then destructively distilled to a solid residue. Any suitable deashing process such as those just described may be ernployed in this invention.

Our preferred extraction method, shown in PIG. III, comprises a procedure wherein a raw feed fuel, such as Kentucky No. 1l coal which has been ground by a suitable means such as a hammer mill (preferably the coal is finely ground to approximately percent through 200 mesh U.S. Standard) is fed by means of a conveyor or the like to an agitated tank 1 where it is mixed with solvent (obtained from previous processing) at a ratio of about 0.6/1 to 4/1 solvent to coal. If desired, the coalsolvent slurry in tank 1 may be heated to any suitable temperature which will flash olf any moisture which may be present in the coal.

The solvent used in this extraction is derived from the coal being dissolved, and its composition may vary, depending on the analysis of the coal being used as feedstock. In general, however, the solvent employed is a highly aromatic solvent obtained from previous processing of coal, in the manner described herein, and will generally have a boiling range of about 302 F. to 1382 F., a density of about 1.1 and a carbon to hydrogen mole ratio in the range from about 1.0 to 0.9 to about 1.0 to 0.3. Generally, any good organic solvent for coal may be used as the initial starting solvent in the process. A typical solvent is, for example, middle oil obtained from coal and having a boiling range of 374 F. to 572 F. A solvent found particularly useful as a start-up solvent is anthracene oil (defined in Chambers Technical Dictionary, MacMillan, Great Britain, 1943, p. 40, as follows: A coal-tar fraction boiling above 518 F., consisting of anthracene, phenanthrene, chrysene, carbazole, and other hydrocarbon oils). However, the selection of a specific start-up solvent is not particularly critical since during the process dissolved fractions of the raw feed coal form substantial quantities of additional solvent which when added to the solvent originally fed into the system provide a total amount of solvent which is greater than the original amount. Other solvents which may satisfactorily be employed are those which are commonly utilized in the Pott-Broche process. Examples of these are polynuclear aromatic hydrocarbons such as naphthalene and chrysene and their hydrogenated products such as tetralin (tetrahydronaphthalene), decalin, etc. or one or more of the foregoing in admixture with a phenolic compound such as phenol or cresol.

The ratio of solvent to coal in the slurry mixed in slurry tank 1 will be in the range of 0.6/1 to 4/1 by weight with a preferred range of 1/1 to 2.3/1 by weight. Ratios of solvent to coal of less than 0.6/1 (i.e. 0.5/1) produce slurries which are of the consistencies of tar upon dissolution of the coal in the solvent, thus rendering them difiicult to move in the system and which frequently cause clogging of the system. Ratios of solvent to coal greater than 4/1 may be used but provide no functional advantage in the solution process and suffer the additional disadvantage of requiring additional energy or work for the subsequent separation of solvent from the deashed coal product for recycling in the system.

The slurry formed in tank 1 is then fed by means of any suitable method, for example a positive displacement pump 2, to a preheater 3 and then into a dissolver 4 which is suitably heated to maintain the slurry at its elevated temperature. It is essential that hydrogen be added to the slurry ahead of the preheater 3 or dissolver 4 (FIG. III shows addition before the slurry is introduced to the preheater) at a partial pressure of at least 500 p.s.i. The hydrogen employed is normally that recycled from previous processing together with any fresh make-up hydrogen required to provide the necessary hydrogen content. Although there is no critical upper limit to the hydrogen pressure employed, for practical reasons the pressure employed will normally be in the range of 500 to 1500 p.s.i. with 1000 p.s.i. preferably employed.

The hydrogen pressure fuel-solvent slurry is treated in the preheater rapidly to raise the temperature thereof to a temperature in the range of about '698 F. to about 932 F. and preferably 707 F. to about `824 F.

The length of time in which the solution of the hydrogen pressured slurry is continued in dissolver 4 is important to obtaining a satisfactory deashed product. Although the duration of solubilization treatment will vary for each particular carbonaceous fuel treated, it has been found that the mechanics of the solution provide an accurate guide for the residence time of the slurry in dissolver 4. In this regard the viscosity of the solution obtained during processing of the slurry increases with time in dissolver 4, followed by a decrease in viscosity as the solubilizing of the slurry is continued and then followed by a subsequent increase in the viscosity of the solution on extended holding in the dissolver 4. A criterion used for determining the completion of the solution process is the relative viscosity of the solution formed which is the ratio of the viscosity of the solution to the viscosity of the solvent, as fed to the process, both -viscosities being measured at 210 F. Accordingly, the term Relative Viscosity as used herein is defined as the viscosity at 210 F. of the solution formed divided by the viscosity of the` solvent at 210 F. fed to the system.

As the solubilizing of the slurry proceeds, the Relative Viscosity of the solution first rises above a value of 20 to a point at which the solution is extremely viscous and in a gel like condition. After reaching the maximum Relative Viscosity, well above the value of 20, the Relative Viscosity, begins to decrease to a minimum after which it again rises to higher values. It is important, for the production of a preferred deashed coal, to allow the solubilization to proceed until the Relative Viscosity, (following the initial rise in Relative Viscosity) decreases to a value of at least 10 and to separate the resultant solution from undissolved residue of the coal before the Relative Viscosity again rises above 10. Normally, the decrease in Relative Viscosity will be allowed to proceed to a value less than 5 and preferably in the range of 11/2 to 2.

It is believed that during solubilization the coal depolymerizes in the presence of hydrogen to form fractions which are soluble in the solvent. As the coal is depolymerized, the solubilization is accompanied by the evolution of hydrogen sulfide, water, carbon dioxide, methane, propane, butane and other higher hydrocarbons which will comprise part of the atmosphere in dissolver 4. In addition, the depolymerization of the coal consumes hydrogen up to a weight equivalent to about 2.0% of the weight of the feed, and under preferred conditions in an amount of about 0.5 to 1% of the feed.

Upon completion of the solubilization in dissolver 4 the resultant solution is then charged to a filter 5, for separation of the coal solution from undissolved residue (i.e. mineral matter) of the feed. The filter 5 is a conventional rotary drum pressure filter suitably adapted for pressure let down and venting of gases. It is to be understood that although a rotary drum filter has been described as being utilized in conjunction with this embodiment, other means of separation may be employed, as for example centrifuges and the like.

The gases vented from filter 5, containing principally unconsumed hydrogen, are then passed through line 10 into a gas treating unit 6 in which hydrogen sulfide and carbon dioxide are scrubbed out in any suitable manner, as for example by caustic solution. The remaining gas may be given any further purification treatment desired. The hydrogen sulfide-free and carbon dioxide-free hydrogen-containing gas recovered is then recycled to the process by feeding to fresh slurry being fed to preheater 3, with all make-up hydrogen being supplied through line 12 by fresh hydrogen. Analysis of the recovered gases has shown that the over-all consumption of hydrogen throughout the system is quite low with the actual consumption of hydrogen being not greater than 2% (based on the feed) and quite often as low as 0.5%.

The filter cake or residue obtained in filter 5 is withdrawn therefrom for additional processing as desired, as for example solvent recovery. In practice, further processing of the filter cake is desired since, in addition to mineral matter, it may contain from between 40 to 50% by weight of solvent that can be recovered by pyrolytic distillation. If the filter cake is processed for the recovery of the solvent, the recovered solvent may be recycled into the system for the preparation of additional slurry for feeding into the system.

The filtrate from filter 5 is then pumped by means of a suitable pump 7 at a temperature of about 518 to 806 F. through suitable nozzles into a simple vacuum flash evaporator 8 for removal of the majority of the solvent. Th e flashed solvent from evaporator 8 may be passed to a still 9 as shown in FIG. III, or recycled directly to the system (not shown in FIG. III). Itis to be understood that solvent recovery may be accomplished by a variety of methods such as wiped film evaporation, and thus, other means may also be employed if desired for recovery of solvent.

The remaining product from evaporator 8, which is liquid at this point, may be used as such, or if may be pumped onto a continuous rotating steel belt 11 where it is cooled and solidfied. This product, which solidifies upon cooling, is very brittle and breaks into flakes as it finally falls from the belt. Other methods may also be used to recover the product, as for example spray cooling or prilling, or again, if desired, the product may be maintained in the liquid state and used as such.

The solidified prod-uct recovered from evaporator 8 is a brittle hydrocarbon material having little resemblance to the feed coal charged into the system. As with the filter cake, a substantial amount of recoverable solvent remains in the product ranging from about 15 to 60%. The changed nature of this product is believed readily evident from the following properties which are set forth in conjunction with corresponding properties of Kentucky No. 11 coal.

TABLE 1.-ANALYS1S OF PROCESS PRODUCT COMPARED WITH KENTUCKY NO. 11 COAL As will be noted from the above analysis, the percentage of carbon has increased, and the percentages of sulfur and oxygen are substantially lower.

The petroleum residues which may be employed in this invention have a boiling range beginning from about 670 F. to 1100 F., a preferred feed stock being a Kuwait vacuum residue. Operating temperatures for blending the deashed coal with the residue may range from 200 to 800 F., the preferred range being 300 to 400 F. Atmospheric pressures are employed during blending operations. The contacting time for blending operations can range from 12 to 18 hours but can be reduced below this range depending upon the type of mixing equipment employed. The percentage of deashed coal added to the residue to achieve the improved properties can vary from 3 to 50% by weight, a preferred range being `from about 5 to 20% by weight.

The invention will further be described with reference to the following specific examples.

EXAMPLE I A 5% deashed coal-asphalt residue blend was prepared by placing 950 grams of Kuwait vacuum tower bottoms (KVTB) having the inspection data shown in Table II,

in a 2 liter beaker where its temperature was raised to 300 F., while stirring with an Eppenbock homo-mixer, a close tolerance, high-shear, high speed homogenizer. To the KVTB, 50 grams of deashed coal ground to 4 mesh size was slowly added. The deashed coal was prepared by the preferred process previously described herein. Kentucky No. 11 coal was employed at a 3/1 by weight solvent to coal ratio, the start-up solvent being anthracene oil. Solubilization operating conditions were conducted at 792 F. at 1,000 p.s.i. hydrogen pressure, and the liquid space velocity in the dissolver was 0.96. Following the dissolution the pressure was let down to 50 p.s.i. and the material ltered through a rotary precoat pressure filter. The filtered material was reheated to 806 F. and an amount of solvent equal to that originally added ashed ol under vacuum. The liquid product was pumped to a continuous steel belt where it was cooled to room temperature and recovered as a solid material. The coal-asphalt mixture was kept under a nitrogen blanket to prevent any repolymerization of the deashed coal. After 1`1/2 hours the temperature ofthe deashed coal-asphalt mixture TABLE 1I.-INSPECTION DATA OF KUWAIT VACUUM TOWER BOTTOMS Specific gravity, API 11.3 Viscosity:

SUS at 275 F- 982 SUS at 300 F 541 softening point,D36, F 100 Penetration D5-25 at- 39.2 F., 200 gm., 60 sec 55 77 F., 100 gm., 5 sec 227 Sulfur, percent by weight 5.17

EXAMPLE II A 10% deashed coal-asphalt blend -was prepared in a similar manner as in Example I except that 900 grams of KVTB were used with 100 grams of deashed coal. The deashed coal was prepared in the same manner as in Example I. The KVTB was heated to 500 F. before addition of the deashed coal and was mixed at this temperature for a total of 18 hours. Product inspection data for this blend is contained in Table III.

TABLE III Properties KVTB 5% blend 10% blend softening point, D36 100 108 140 Penetration sit- 39.2 F., 200 gm., 00 $80.... 55 43 15 77 F., 100 gm., 5 Sec... 227 132 36 Penetration ratio-39.2 F 7 F.

The temperature susceptibility as defined herein is expressed as penetration ratio which is computed as follows:

Pen. ratio Pen. value at 39.2 F. with a 200 gm. ball for 60 sec. Pen. value at 77 F. with a 100 gm. ball for 5 sec.

From the data contained in Table III it will be seen that the penetration ratio (temperature susceptibility) for the KVTB without any deashed coal added was 24. With 5% of deashed coal added, the penetration ratio was 32 and with 10% of deashed coal added the penetration ratio was 58. Thus it can be seen that with the addition of relatively small amounts of deashed coal to the petroleum residue the penetration ratio (temperature susceptibility) may be increased by more than 142%, thereby improving the ability of the asphalt to withstand heavy loads and shocks, a particularly desirable property in paving compositions.

A comparison between the improved temperature susceptibility of deashed coal-asphalt blends and straight run KVTB and other commercially available samples of 100 penetration asphalts was made. FIG. I shows a plot of penetration ratio (temperature susceptibility) versus penetration at 77 F. for the average of 119 samples of commercial asphalt, 5% and 10% deashed coal-asphalt blends, and straight run KVTB. As will be seen from FIG. I, the penetration ratio for the deashed blends at a penetration of is about 21 units above the KVTB and about 12 units above the commercial asphalts. This represents an increase in temperature susceptibility of 75% and 32% respectively.

It should be pointed out that while the addition of deashed coal raised the penetration ratio of a Kuwait residue, the penetration softening point relationship of the Kuwait residue was not changed, as is demonstrated in FIG. II. The addition of 5% by weight of deashed coal raised the softening point from F. to 108 F. and 10% by Weight raised the softening point from 100 F. to 140 F. However, the penetration values follow the curve for the original residue.

7 EXAMPLE In Experiments were conducted to determine the superiority of ltered solvent depolymerized coal as an asphalt hardening agent compared with untreated powdered coal. The deashed coal employed was Kentucky No. 11 and was solvent treated in the manner described in Example I. The asphalt employed was a steam refined paving asphalt made to a specification of 40,-50 tenths of a millimeter penetration at 77 F. (40/50 penetration grade). In preparing coal-asphalt blends, 20% by weight of deashed coal (Kentucky No. 11) and 20% by weight of a 200 mesh powdered Kentucky No. 1l coal were mixed with separate samples of asphalt. The penetration and softening points of the respective samples were determined and compared with the corresponding values for the original asphalt. These results are shown in Table IV.

l Beyond scope of method 300).

From the foregoing results, it will be seen that the preferred blend of asphalt plus 20% deashed coal has the highest temperature susceptibility value i.e. 50, compared to those of the asphalt and asphalt plus powdered coal which had not been solvent depolymerized. Furthermore, the addition of powdered coal to asphalt had a degrading effect upon the asphalts temperature susceptibility, lowering it from a value of 35 to 14.

EXAMPLE IV In another embodiment, a solubilized coal was prepared as described in Example I, except that after dissolution the solubilized coal-solvent mixture was passed to evaporator 8 without filtration in iilter unit 5 so that the ash content of the coal remained in the mixture. The ash-containing, hardened, solubilized coal product was ground to pass a 4 mesh screen and mixed in the amount of 5 percent by weight with the petroleum asphalt described in Example I, to obtain an asphalt having an improved penetration ratio.

It is to be understood that the above indicated examples are illustrative only and are not intended as limiting the scope of the invention. Thus, there can be substituted in the foregoing examples other asphalts, solubilized coals derived from other coals with the same or other solvents, all as disclosed herein. Likewise, the solubilized coals of this invention can be employed in other proportions than those ultilized in the examples.

What is claimed is:

1. An improved asphalt composition consisting essentially of a petroleum asphalt and from about 3 to about 50% by weight based upon the improved asphalt composition of a product obtained by treatment of a member selected from the group consisting of bituminous, sub-bituminous and lignite coals, in the presence of hydrogen at a hydrogen partial pressure from about 500 p.s.i. to about 1500 p.s.i., with a solvent selected from the group consisting of polynuclear aromatic hydrocarbons hydrogenated polynuclear aromatic hydrocarbons boiling in the range from about 302 and 1382 F., having a density of about 1.1 and having a carbon to hydrogen mol ratio in the rang from about 1.0 to 0.9 to about 1.0 to 0.3, and mixtures of these with a material selected from the group consisting of phenol and cresol in a solvent to coal ratio from about 0.6/1 by weight to about 4/1 by weight to about 4/1 by weight at a temperature from about 698 F. to about 932 F. elective to facilitate solubilization of the coal, and separating the solvent from the treated coal product.

2. The composition of claim 1 wherein the petroleum asphalt has a boiling range beginning about from 670 F. to about l100 F.

3. The composition of claim 1 wherein the treated coal is present in an amount of from about 5% by weight to about 10% by weight, and the asphalt is present in an amount of from about by weight to about 90% by weight.

4. The composition of claim 1 wherein the solvent employed in treating the coal is anthracene oil.

5. The composition of claim 1 wherein the hydrogen pressure is 1000 p.s.i., the solvent to coal ratio is from about 1/1 by weight to about 2.3/1 by weight and the solubilization temperature is from about 707 F. to about 824 F.

6. The composition of claim 1 wherein the solubilization of the coal provides a coal extract and an undissolved solid residue containing ash and wherein the said undissolved solid residue containing ash is physically separated from the coal extract.

7. The composition of claim 1 wherein the solubilization is conducted so as to permit the relative viscosity of the solution which is formed first to rise to a value above about 20 and thereafter to decline to a value less than about 10, and the solution is then separated from undissolved residue prior to the time that the relative viscosity again rises to a value above about 10.

References Cited UNITED STATES PATENTS 2,319,326 5/1943 Jenkner. 2,686,152 8/1954 Franke. 3,341,344 9/ 1967 Ginsberg et al.

JOSEPH L. SCHOFER, Primary Examiner H. I. LILLING, Assistant Examiner U.S. Cl. X.R.

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