US2310193A - Process for treating pitch - Google Patents

Description

Patented Feb. 2, 1943 rnoonss FOR TREATING PITCH Jacquelin E. Harvey, In, Atlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., 2. eorporation of Georgia No Drawing. Application May 8, 194-1, Serial No. 392,558

(or. rec ss) 3 Claims.

The present process relates to the production of valuable materials; more specifically to the joint production of superior solvents and polymerized products.

An object of the invention is the production of superior solvents and polymerized products from refined pitches, said pitches selected from the group boiling predominantly above, and above, 355 C.

Another object of the invention is, by subjecting-refined pitch to the action of a reducing gas to, among other things, induce newly formed solvent fractions; thereafter by continuing the process under selected conditions of process variables, to increase the solvent power of the overall induced low 'boiling fractions.

Still another object of the present process is the'polymerization of high boiling fractions of the starting feed stock while under the action of gas at elevated temperatures and pressures.

Yetanother object of the present process is to so coordinate process variables as to gasify a portion of newly formed low boiling products, the while polymerizing a portion of the higher boiling products, forbeneficial effects.

Another object of the present process is the provision of a polymerized high boiling product having, ascompared to'a product of comparable boiling range and produced by pyrolysis, superior plasticity, cohesion, resiliency, tack and/or-lowered variation in penetration due to temperature changes.

Another object of the present inventionis the provision of a high boiling material somewhat more resinous in nature than a material of comparable boiling range produced from the starting material by pyrolysis.

Other objects of the present invention will-become apparent from the following disclosures.

Among the group of materials that provide valuable aromatics, coal tar, low temperature tar, gas house tar and water gas tar are perhaps themost important, and because of the great volume of production tar, recovered from high temperature coke ovens, assumesa superior position as regards recoverable valuable aromatics.

In past years tar from high temperature coke ovens was the chief source of valuable aromatics. Because of its highrate of production and relative cheapness this tar occupied a superior position asthe parent material of valuable aromatics.

Atpresent however, the dominant position of coal tar as the-most-important-sourceof valuable aromatics, as for instance solvents, is seriously challenged. Dominant among the challengers of the coal tar industry is the petroleum industry.

For several decades the coal tar industry was the recognized source of such aromatic solvents asbenzol, toluol, etc. Currently the situation has changed. Thecondition now obtains that .the petroleum industry provides, by means of .the many processes and starting materials at its command, solvents of high aromatic content and of various boiling ranges, and, by one process is, or will be in theimmediate future, producing toluol suitable forunitration.

As regards the coal tar industry, not only does the condition obtain that the petroleumindustry is actually invading the solvent field formerly enjoyed exclusively by thecoal tar industry but information is available to conclusively-indicate that the petroleum industrywill continue to invade fields previously enjoyed lexclusively by the coal tar industry.

Accordingly, onemethod of attacking the ills of the coaltar industryas fiowing from petroleum competition-is to work-upor process the liquid volatiles coming from .the high-temperature coke ovens in such-a manner ,as tobetter meet the competition'named.

In the past, coal tarwas distilled to yield ('1 light 011,62) heavier solvents, (3) wood preservatives, and- (4) a pitch residual. The percentage of'the initial tar remaining as .apitch residual was, for the most-part, predicated on the amount of residue above 355 C. permissible in the wood preservative.

In the past decade trends in the wood preserving industry have been .such, that consumers, of coal tar derived wood preservative have demanded lower and lower residues above 355 C. In View of such aconditionobtaining, it is obvious that as consumers of tar derived wood preservative (creosote) demanded .or desired lower residues above 355 C., thepercentage of theinitialtar converted to pitch increased.

As is well known, pitch is among the lowest distillate in its entirety as a wood preservative.

Such operation provides for the smallest-amount of residual pitch, and is from the viewpointoi the tar distiller, .a afavorable ,operating procedure. However, thedesires of the creosote produc'er and point of the pitch (or coke), then fractionating the resultant distillate into (1) a creosote having a low residue above 355 C., as for'instance one having residue above 355 C. and ,(2) a residue refined pitch which at atmospheric temperature was either a heavy viscous oil or a solid mass.

This method of operation on the part of the tar distiller provided on the one hand'the low residue creosote of consumer demand, and on the other hand the low pitch or coke residual incidental to the primary tar distillation which is the desire of the tar distiller.

However, the refined pitch mentioned above and produced as a residual (or produced as a distillate as will immediately be apparent to those skilled in the art) from the heavy distillate recovered from the primary tar, has, as is a matter of record, been an article of great distress. Because of its distress position the refined pitch has, at times, been placed in inventory or sold at fuel value. v

If and when the tar distiller can market his refined pitch at a profit, the proposal to distill tar to the upper boiling point of hard pitch or coke, becomes commercial for the reason that the heavy distillate-so secured can be fractionated into low residue creosote and marketable refined pitch.

In my copending applications Serial Nos. 383,457-70 inclusive, filed March 14, 1941, I have described and claimed methods of processing the refined pitch with a reducing gas whereby to produce solvents having a preponderance of aromaticity. Tersely stated, the processes of the above named applications are predicated on subjecting the starting refined pitch to the action of a reducing gas for a period not in excess of the critical and recovering from the finally treated material a solvent having high solvent powers. If as'stated in the above numbered applications a period in excess of the critical be employed, reverse reactions occur, for the reason that fractional increment, hydrogen absorption and/ or depolymerization are not linear functions or" the time element, the critical time element being in the order of about three hours.

It is now discovered that by the process of the present invention especial benefits may flow from treating the starting refined pitch for periods of in excess of the critical, or under catalyzed conditions that provide for an approach to, or an apreferred to, a refined pitch is subjected to the action of hydrogen for a period of not in excess of the critical while employing a temperature of about 410 C. and a pressure of about 300 atmospheres. During the period of treatment, fractional increment, hydrogen absorption and/ or depolymerization are linear functions of the time element. However, if the critical period is exceeded, fractional increment, hydrogen absorption and/or depolymerization cease to be linear functions of the time element, and as a result of employing a time period in excess of the critical,

' there occurs loss of fractional increment, lowered hydrogen absorption on some fractions and/01' polymerization.

In accordance with the previous process the treated feed stock is distilled to recover a solvent having an aromaticity in the order of not substantially less than 50%. As a matter of comparison with the instant process, it will be assumed that in practicing a mode of the formerly named process the hydrogen treated feed stock was distilled to a point to recover 35% as a solvent having an aromaticity of not substantially less than 50%, whose solvency for convenienc will be designated as X.

At this point it is of importance to note that while the action of hydrogen proceeded in the former process whereby to make recoverable a low boiling solvent having an aromaticity of not substantially less than 50%, the high ends of the feed stock were simultaneously undergoing gas action that was conducive to depolymerization, or stated another way, the high ends were undergoing the action of gas that opposed polymerization. I

Thus, summarizing the former process, the reaction conditions were so controlled as to jointly provide (1) the induction of low boiling fractions from which were recoverable a solvent having an aromaticity of not substantially less than 50%, which solvent for purposes of comparison is represented as having a solvency of X, and, (2) gas action on high boiling fractions of the feed stock which wasconducive to depolymerization. The beneficiation of the feed stock noted in the former process stems from the employment of a time element not in excess of the critical.

As mentioned above, it is now discovered by the process of the present invention that especially novel benefits may be secured by employment of treatment .periods in excess of the critical, or employing catalyzed conditions that provide for an approach to, or an approximation of, conditions in the starting material under treatment which characterize employment of treatment periods in excess of the critical.

The following examples will serve to illustrate several modes of practicing the instant process, but such examples are not to be considered in any sense restrictive inasmuch as the disclosure herein made will suggest to those skilled in the art other and obviously suitable variations.

Example 1.A refined pitch characterized by content of molecular complexes and having an initial boiling point of in theorder of 355 C. is charged to an intermittent autoclave under a cold hydrogen pressure of atmospheres As catalytic materials are provided equal parts of molybdenum sulfide and iodoform; the aggregate of the catalyst representing 1.2% of the feed stock. The contents of the autoclave are heated to 410 C. and maintained at that temperature for 5 hours. If, periodically for the first part of the treatment, say for example, during the first 2% or 3 hours or thereabouts, an inspection is made-of the feed stock under treatment it will be found that fractional increment, hydrogen absorption and/or depolymerization are linear functions of the time element. It should be remembered that the refined pitch under treatment has a critical time element of in the order of about three hours, which, if exceeded, gives rise to reverse reactions, that is to say, loss of fractional increment, lowered hydrogen absorption on some fractions of the material under treatment and/ or polymerization.

During the period of inspection noted above, let it be assumed that if at the end of about three hours of treatment the process were stopped and the beneficiated refined pitch distilled to recover 30% as a solvent, the solvent so recovered would have a solvency of X. In view of the serious solvent competition offered by the petroleum industry and explained in detail in the foregoing, it becomes a desideratum when processing coal tar or fractions thereof for solvent recovery to eff'ect operating economies and/ or increase the solvent power of the resultant solvent. Accordingly, the instant process is predicated on, among other things, so controlling the time element that the newly formed liquid fractions reach a terminal low in solvency, and thereafter partake of a beneficiating hydrogen action that increases solvent power to at least X plus 1. Stated in another manner, if a time period of not in excess of the critical be employed, the 30% lowest boiling cut on the beneficiated feed stock would have a solvency which for convenience is evaluated as X. However, if as covered by the treatment period of the present example, the treatment be continued for a period in excess of the critical, say for 4, 5, or 6 hours or longer, the 30% lowest boiling cut on resultant beneficiated refined pitch would have a solvency at least as indicated by X plus 1.

It appears that the increase of solvent power of, as an example, the first 30% of the treated material processed for a period in excess of the critical, over the solvent power of, as an example, the first 30% of the material treated for less than the critical, resides in gasification of a portion of the newly formed low ends.

' Another method of practicing the present process wherein a refined pitch is subjected to the action of a reducing gas for a period in excess of V the critical, resides in recovering from the treated refined pitch a high boiling fraction thereof having induced therein cohesiveness in excess of a comparable fraction recovered from a refined pitch treated by the same process for a period of not in excess of the critical.

A refined pitch treated in accordance with the present process may have recoverable therefrom a high boiling portion of induced cohesiveness suitable for application in and to the arts employing a pitch of similar initial boiling point. Among such employments may be mentioned the saturation of felts, a base for various kinds of paints and protective coatings for metals, ma-

sonry and other structural materials; road binders and waterproofings; construction of pitch andfelt roofs; laminating membranes used in waterproofing foundations of buildings, tunnels, subways, and bridges; as pipe-dips; as a binder in constructing bituminous concrete and macadam pavements; for filling the joints of block pavements; and for manufacturing the better grades of bituminous paints. v

' the process of the instant invention a high boiling fraction recovered from a refined pitch previously subjected to the action of a reducing gas for a period in excess of the critical, has induced qualities of cohesion that make it especially usable as a superior substitute for pitches employed as in the instance of the above mentioned uses.

Example 2.-A refined pitch manufactured in accordance with the foregoing disclosures and having an initial boiling point of in the order of 380 C. is subjected to the action of a reducing gas for a period of four and one-half hours; temperature 420 C. and pressure 275 atmospheres; catalyst tin sulfide. If during the period of treatment, and periodically for a time extending through about the first three hours of treatment, inspection be made of the high boiling fractions of the starting material undergoing gas treatment, it will be ascertained that the high boiling fractions are progressively depolymerized or at least maintained in condition to be receptive to depolymerization.

As a matter of comparison let it be assumed that in the present example the process is carried on for only the period of three hours. The material treated for three hours is cooled, withdrawn from the treating vessel and the high boiling fractions thereof, as for instance the highest 30, 35 or 40% or more, evaluated for cohesion. In order to establish a basis for subsequent comparison, a cohesive value of Y is assigned to the recovered high boiling fractions.

The present example which provides for treating the refined pitch for a period of four and one-half hours is completed. The treated material is cooled, withdrawn from the process vessel and the high boiling portions thereof, as for instance the highest 30, 35 or 40% or more, evaluated for cohesion. The fraction named will be found to have a cohesive value of at least Y plus 1.

Thus, in accordance with the instant process a refined pitch when subjected to the action of a reducing gas for a period in excess of the critical has induced therein cohesive qualities which make it a superior product for purposes mentioned above, or others.

Example 3.-Another mode of practicing th present process is to jointly recover the superior solvent and the high boiling fraction of induced cohesion. Accordingly, in order to illustrate this mode of practicing the process, the following feed stock may be prepared: coal tar is distilled to the boiling point of a medium hard pitch; the distillate is fractionated to yield a creosote with no residue above 355 C. with the residual mass therefrom serving as a portion of the starting refined pitch of the instant example. The initial medium hard pitch is distilled with steam in the presence of F8203 and FeClz and the distillation continued as far as desired, as for instance to coke. The distillate from the medium hard pitch is added to the above named residual mass resulting from the fractionation of the first distillate recovered to provide the make-up of the starting material of the present process.

The starting material is subjected to the action of a reducing gas for a period of four hours. The pressure is 250 atmospheres and the temperature 400 C.

As a matter of comparison, the mass under gas action is inspected at the end of two and threequarter hours. The lowest boiling 30% of the beneficiated mass will be found to have a solyent power valueof X and the highest boiling 30% will be found to have a coheslon value of Y. The process run is continued to complete the aforementioned four hour period with production of fixed gases resulting from degradation of newly formed low boiling fractions liquid at atmospheric temperature. The reaction vessel and contents are cooled and the contents inspected. The lowest boiling 30% will be found to have a solvent power value of X plus 1 and the highest boiling 30% will be found to have a cohesion value of Y plus 1. The beneficiated material is fractionated to provide (1) a low boiling portion as a solvent of induced solvency, said solvent induction flowing from, among other things, the employment of the four hour time element, and (2) a high boiling portion having an enhanced cohesion value, said enhanced cohesion value flowing from, among other things, the employment of the four hour time element.

Example 4.-Yet another variation of the present process is possible as hereinafter described. A pitch produced from tar incidental to the distillation recovery of solvent, wood preservative or the like, is distilled to a predetermined point, as for instance to a harder pitch or coke. Steam or inert gas may be employed in the distillation. The distillate is subjected to the polymerizing action of heat while contacting at superatmospheric pressure one or more gas or gases chosen from the group consisting of hydrogen, carbon monoxide, carbon dioxide, nitrogen, steam, hydrocarbon gases, including mixtures thereof. The temperature is chosen from the range between 250 C. and 650 C., with the lower limit being so selected as to provide conditions conducive to polymerization, and the upper limit being so chosen as to preclude substantial amount of coking. The pressure is so chosen as to provide for carrying on the process in liquid phase, that is to say, so controlling the pressure that the phase condition of the materialunder treatment is preponderantly liquid. Necessarily, because of the varying temperatures that are possible of employment, the usable pressures cannot be stated as an arbitrary figure. A few trials when employing a chosen temperature will easily determine the necessary pressure. The time element is so chosen as to provide the desired amount of polymerization, as for instance, one hour; however, longer or shorter periods may be employed.

Example 5.-As representing a specific exemplification of the present process, the aforenamed pitch distillate is charged to a high pressure autoclave and a mixture of hydrogen and carbon monoxide in the percentage of and 15%, respectively, is pumped in to an upper limit of 150 atmospheres. Thereafter, the autoclave and contents are heated to 400 C. and there held for a period of two and one-quarter hours. The autoclave and contents are cooled. The contents are inspected. In a distillation range selected from the treated material for the purpose of cohesive evaluation, a cohesion value of at least Y plus 1 is arbitrarily assigned. A comparable boiling range on the crude starting feed stock will have a cohesive value of only Y. The entirety, or any selected portion thereof, of the beneficiated mass may be employed as a material having induced cohesive qualities.

Example 6.-Especial benefits flow from selecting a refined pitch and subjecting it to the action of a reducing gas for a period in excess of the critical whereby to (l) raise the solvent power of, as an example, the lowest boiling as compared to the lowest boiling 30% of the starting material beneficiated for a period less than the critical, and (2) to induce cohesive qualities in the higher boiling portion, as for instance, a higher or highest boiling 30%. In accordance with the instant example, the starting refined pitch may be processed in a manner similar to Example 3. Thereafter the entirety of the processed material may be used in toto. As an example of total employment of the treated material without fractionation is mentioned the following: In late years the use of a wood preservative which comprises a toxic material dissolved or dispersed in an oil, or the like, has been widespread with indications of increasing employment; As an example of such employment may be mentioned pentachlorphenol dissolved in suitable oils, alcohols or the like. The toxic chemical thus dissolved in the carrier is made to traverse, by pressure or otherwise, at least a portion of the interstices of the wood to be preserved. The carrier evaporates, generally in entirety, leaving the toxic chemical deposited for the preservation of the wood so treated. Not all oils are suitable to serve as carriers for the toxic chemical. It is generally desirable that the toxic chemical represent at least 5% of the solution. It will be found that the entirety of the product made in accordance with the instant example is effective in placing the toxic material in solution for subsequent application to the wood to be preserved with the added benefit that after application to the wood, the entirety of the carrier does not pass off but at least a portion of the newly formed high ends remain in the wood to reinforce the toxic value of the toxic chemical (formerly the solute) remaining in the wood.

Accordingly, the invention provides as a new matter of manufacture, a hydrocarbon or deriv ative thereof having enhanced solvency in the lower ends and added cohesive qualities in the higher ends.

In certain of the foregoing examples the instant process has been predicated on employment of a time element in excess of the critical with the benefit flowing therefrom that (1) the low liquid ends have a solvent power in excess of the low liquid ends treated under similar proc-- ess conditions but for a period not in excess of the critical, and (2) the highest boiling fractions have a cohesion value in excess of such value in the highest boiling fractions treated under similar process conditions but for a period not in excess of the critical. 7

It is also discovered that instead of employing time periods in excess of the critical to provide the benefits noted, catalysts may be utilized to secure an approximation, simulation, or partial simulation of said benefits.

Among such catalysts may be mentioned ceria, calcium oxide, calcium hydroxide, oxides and sulfides of metals employed at temperatures that induce gasification of low ends and polymerization of high ends; also employable at said'temperatures are halogens, halids and derivatives thereof.

In the practice of the instant process intermittent or continuous operation may be employed, and in the event of continuous operation, a single reaction chamber, a series thereof or a parallel arrangement thereof may be employed, including a multiplicity thereof.

Temperatures chosen between the limits of 250 C. and 600 0., preferably between 350 C.

and 475 C. may be advantageously employed when coordinated with the proper pressure.

Temperatures when employed with the chosen pressure should so promote reactions as to preclude serious carbon deposition, as for instance that percentage of carbon deposition that would close down continuous operation in a short period.

Pressures selected from the range of 20 atmospheres to as high as practicable may be employed, however, pressures of 100 atmospheres, or in excess thereof, in some instances, provide for good results.

By the term reducing gas as used herein is also meant to include any gas or gases capable of effecting reduction; or under process conditions effecting said reduction. Diluting and/or inert gases may also be employed.

Minor changes may be made within the scope of the appended claims without departing from the spirit of the instant invention.

I claim:

1. In the joint production of superior solvents and products of induced cohesion from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to provide a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., which process comprises: subjecting said higher boiling fraction to the action of a reducing gas in the presence of catalytic materials comprising a sulfide of a. metal and iodoform at a temperature selected between 350-475" 0., a pressure in excess of atmospheric and for such a length of time as to provide newly formed low boiling fractions of relatively low solvent power and reduction of at least a portion of the higher boiling materialsv in the feed stock; increasing the solvent power of said low boiling fractions and inducing cohesive qualities in said higher boiling materials by continuing the treatment to cover a total period of treatment in excess of about three hours under the conditions above named.

2. In the joint production of superior solvents from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to provide a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C., which process comprises: subjecting said higher boiling fraction to the action of a reducing gas in the presence of catalytic materials comprising a sulfide of a metal and iodoform at a temperature selected between 350475 0., a pressure in excess of atmospheric and for such a length of time as to provide newly formed low boiling fractions of relatively low solvent power; increasing the solvent power of the newly formed low boiling frac-' tions by continuing the treatment to cover a total period of treatment in excess of about three hours under the temperature and pressure conditions above named; and stripping low boiling fractions from the thus treated material to pro-' vide said low boiling material as a solvent.

3. In the production of high boiling materials of induced cohesion from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to provide a liqof the higher boiling materials in the feed stock;

inducing cohesive qualities in said higher boiling materials by continuing the treatment to cover a total period of treatment in excess of about three hours under the conditions above named; and stripping the thus treated material to provide a high boiling residue as a product of induced cohesion.

JACQUELIN E. HARVEY, JR.