US2291319A - Producing solvents from refined coal tar pitch - Google Patents

Description

July 28, 1942- J. E. HARVEY, JR 2,291,319

PRODUCING SOLVENTS FROM REFINED COAL TAR FITCH Filed March 14,` 1941 3mm/vrom l Patented July 28, 1942 PRODUCING SOLVENTS FROM REFINED COAL TAR PITCH Jacquelin E. Harvey, Jr.,rAtlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Application March 14, 1941, Serial No. 383,469

Claims. (Cl. 196--53) The present process relates to the production of valuable liquids from hydrocarbons, said hydrocarbons characterized by content of oxygenated compounds and sulphur.

This application is a continuation in part of my application Serial No. 352,668, iiled August 14, 1940, for Production of valuable material, copending herewith, as to all matter common to the two applications.

An object of the invention is the production of refined solvents of lowered corrosivity from hydrocarbons of higher boiling range.

Another object of the present invention is the production of rened solvents of lowered corrosivity from liquid and solid hydrocarbons characterized by content of oXygenated compounds and sulphur.

A more specific object of the present invention is the conversion of tars of aromatic content and fractions thereof characterized by content of oxygenated compounds and sulphur, substantially in entirety, if desired, of the material remaining liquid, into rened solvents of superior solvency and lowered corrosivity.

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

The tars forming suitable starting materials for the present process are tars and their fractions derived from coal and petroleum, including gases, and are characterized by content of aromatics, oxygenated compounds, and sulphur.

Coal tar and fractions thereof will be shown as a starting material of the example cited, but it will be immediately apparent that other tars or fractions thereof characterized by content of aromatics, oxygenated compounds and sulphur, serve as suitable starting materials.

Coal tar is a destructive distillate of coal, generally having a predominance of fractions boiling above 190 C. and a typical specic gravity of 1.120. Said tar in its higher boiling range represents molecular complexes that may be viewed as a multiplicity of ring structures.

If desired, to the end that coal tar, or fractions thereof, in the substantial entirety thereof remaining nally liquid under process conditions, be converted into rened solvents of lowered corrosivity of the present process, said molecular complexes may be progressively or step-wise reduced in size, and, among other things, the present invention is predicated on such teaching.

As far as applicant understands the theory of the present invention, same is predicated on the following:

First: by depolym-erizing the molecular com- `plexes in step-wise manner, they are finally brought down to the refined solvents of lowered corrosivity of the present invention.

Second: that by impressing reaction conditions on said molecular complexes, they are converted into solvents whose solvency is directly measurable and usable as opposed to the absence of such characteristics in the molecular complexes contained in the starting material, and,

Third: to conform to the present invention, said molecular complexes must be depolymerized under conditions that induce no substantial percentage of normally liquid products that are other than aromatic. By the term substantial aromaticity as used herein and in the appended claims is meant that the solvents of the present invention are in the order of 50% aromatic or more.

Viewed broadly, the present invention provides a process wherein among other things, coal tar or the like, o r fractions thereof, characterized by content of oxygenated compounds and sulphur content, is subjected to the action of hydrogen to lower corrosivity, afterwards to the action of hydrogen while contacting an oxide catalyst andr a catalyst material selected from the group consisting of halogens, halids, and derivatives thereof, including substitution and addition products thereof, under controlled conditions whereby the high molecular complexes of the starting material may beV reduced in step-wise manner to provide refined solvents of lowered corrosivity and are characterized by lowered and controlled boiling range and .directly measurable and usable solvency as opposed to the absence of similar characteristics in said molecular compleXes containing in the starting material.

By providing the presence of a catalytic material adapted to influence the decomposition of oxygenated compounds contained in the starting material, the step-wise induction of solvency is enhanced. Included among .those catalytic materials adapted to inliuence the decomposition of oxygenated compounds contained in the starting material, are halids, halogens and derivatives thereof` including substitution and addition products thereof.

The invention will be understood from the following description of illustrative steps comprising various methods of securing the objects of the invention, when read in connection with the accompanying drawing wherein the ligure is a diagrammatic sketch of an apparatus for carrying out a form of the process of the invention and wherein the nature of the step carried out in each chamber and the contents thereof are indicated by legend.

The following examples will serve to illustrate general principles upon which the practice of the y present invention is based, as well as the process of the present invention.

Example 1.-Coal tar, specic gravity 1.120 and 3% distilling at 210 C. and characterized by sulphur content and content of oxygenated compounds is treated with hydrogen at 400 C. and 200 atmospheres pressure to lower sulphur content thereby lowering corrosivity. The coal tar of reduced sulphur content is passed through a high pressure reaction vessel at a temperature of 405 C. and a pressure of 300 atmospheres. Flow of hydrogen is 15,000 cubic feet per barrel tar. The time of contact is one hour and the catalyst molybdenum oxide and tin chloride. The beneficiated coal tar flowing from the reactor is distilled to an upper limit of 210 C. to recover the rened solvent of loweredcorrosivity as a dis-A tillate. The residue resulting from said solvent recovery is of a more liquid nature than a comparable cut on the starting materiaLindicating that the high boiling ends formerly described as including multiplicity of rings had either been saturated or partially saturated, thus provid-ing the initial step in the step-wise conversion of substantial entirety of the tar remaining finally liquid into the refined solvent of lowered corrosivity'of the present invention. It will be found that no such percentage of liquidV chainv structures has been induced as would preclude production of solvents having an aromaticity of at least substantially 50%, and that no substantial percentage of carbonaceous deposition was formed in the reaction chamber. i Undue coking isundesirable.

The residue resulting from reiined solvent recoveryV may be recycled forconversion to the rened solvent of the present invention orused as an article of commerce.

Thus, under the action of hydrogen while contacting an oxide catalyst and a catalytic material selected from the group consisting of halogens, halids and derivatives thereof including substitution and addition products thereof, the starting material under temperature and pressure conditions chosen from inexcess of 250 C. and atmospheric, respectively, is converted to refined solvents of lowered corrosivity boiling, as an example, below 210 C., said refinedY solvents being characterized by at least substantially 50% aromatic content, and being further characterized by being products produced while step-wise reduction of a multiplicity ofY rings is being effected; said solvents are also further characterized by being those productsV iiowing from ring reduction, including in size. The reduction being effected-under coordinated time, temperature and pressure conditions that preclude substantial* deposition, as for instance, 25%. Said carbonaceous deposition referring to any time or period of the process wherein controls are impressed for multiplicity of ring reduction for'nal formation of the refined solvent of lowered corrosivity of the present invention.

After formation of the refined solventoflowered corrosivity and the removal thereof from the parent and beneficiated material, said refined solvent may be fractionally cut-as desired, or the cut or cuts may be effected at the time of recovery from the parent material.

Viewed broadly, the present invention'provides aprocess for subjecting tarsl and fractions thereof boiling substantially above 190 C. and characterized by content of oxygenated compounds and sulphur, and derived from coal, petroleum or gas, to the action of hydrogen, as heretofore explained, one or more times, so controlled as to induce solvent fractions of usable and measurable quality as opposed to the absenceof such characteristics in the ring multiples contained in the starting material.

The present invention may be practiced in a discontinuous manner, or in a continuous manner in a high pressure reaction chamber, a series of reaction chambers, a parallelism of reaction chambers, including a multiplicity thereof.

rather characterized by substantial aromaticityy as heretofore described, and the solventsv so produced may serve as substitutes for the boilingrange or ranges of benzene, toluene, xylene and the various naphthas and plasticizers. Heavy naphthas proposed as solvents are currently available having an end point in the order of 360 C. The present inventionprovides for cutting the solvent from the parent material at any point desired with subsequent fractionation into desired cuts as may be dictated by commercial necessity; residue may ber recycled as aforetaught.

The phase condition of the present process isv liquid phase and is not that phase that gasiies all starting material. Thev term liquid phase as used herein and in the appended claims may not be technically correct, but isi meant to differentiate from processes-that gasify all materials processed. Y v

The starting materials of thev present process are not circumscribed by limitation in carbon content, being merely limitedby the nature oftars and fractions thereof available as the starting material. Tars of more than usual carbon content may be depolymerized under less severe conditions at rst with severer conditions progressively applied until maximum reaction conditions are attained.

Many modes of practicing the present inventionV are possible. Forinstance, tar may be stripped of any percentage of low boiling ends and the residual mass then treated in accordance with the process to provide the rei-ined solvent of lowered corrosivity of the present invention.

Thus, pitches hard or softxare among the Starting materials of the present process; also included in the starting materials are those oxygenated compounds and sulphur content produced by the petroleum industry are usable and desirable starting materials.

Those skilled in the art know that hydrogenations proceed at lowered pressures, however commercial recoveries of the refined solvent of the present process are best effected at elevated pressures; thus the present invention includes use of pressures as high as practicable. The time element of treatment in the iirst cycle of hydrogen action is that period necessary for reduction of sulphur content, while in the second cycle of hydrogen action, treatment may be as short as one hour, or more, or less.

The starting materials of the present process include tars of aromatic content or fractions thereof characterized by content of oxygenated compounds and sulphur, at least once refined by hydrogen, or other means.

The solvent of the present invention is varied in boiling range and includes the ranges of any or all of the following:

Product: Boiling range, C. Benzol '78-120 Toluol 100-150 Hi-flash naphtha 150-200 High boiling crudes 175-360 Heavy naphtha 150-290 Plasticizers 16o-360 Instead of controlling the process to provide a low boiling point of '78 C., as for instance in the benzol shown, processing may be controlled to produce lower boiling products. Controls of lesser intensity produce solvents of higher initial point, while controls of greater intensity produce solvents of lower boiling point.

The solvent of the present process may be characterized by containing fractions boiling at least 150 to 200 C.

Broadly considered, the present process provides a method for converting tars of aromatic content and fractions thereof including creosote, topped tars, stripped tars and various pitches characterized by sulphur content and molecular complexes, to refined solvents of lowered corrosivity by the controlled action of hydrogen under conditions that induce no substantial percentage of liquid chain structures or carbon deposits as heretofore explained.

The catalysts of the present invention are oxides and a catalytic material selected from the group consisting of halogens, halids, and derivatives including substitution and addition products thereof; oxides of metals of the 6th and 8th periodic groups are usable, however all oxide catalysts may be used. Diflicultly reducible oxides are preferred.

Example 2. It has been discovered when subjecting certain mixtures of refined coal tar fractions to the action of hydrogen in accordance with the present proc-ess for the production of solvents and/or plasticizers that the formerly accepted teaching that product increment, depolymerization and/or hydrogen absorption are linear functions of the time, is not followed.

When subjecting a mixture of crude coal tar fractions boiling predominantly above 250 C. or 275 C. to the action of hydrogen, research has disclosed that the newly induced products, depolymerization and/or hydrogen absorption ,are linear functions of the time. As an example, when the above mixture of crude coal tar fractions is subjected to the actionof hydrogen for 2, and 8-hourI periods, the newly 'induced products, depolymerization and/or hydrogen absorption are linear functions of the time element.

One of the preferred starting materials of the present process is a mixture of refined coal tar fractions boiling predominantly above 355 or 380 C. Such a starting material is conveniently the final residue resulting from evaporating coal tar to dryness or substantial dryness and then stripping wood preservative from the distillate. This final residue mass of refined coal tar fractions is an especially suitable reiined coal tar pitch to be used as starting material of the present process. However, in contradistinction to the mixture of crude tar fractions boiling predominantly above 250 or 300 C., when the aforenamed preferred starting material is subjected to the action of hydrogen for production of solvents and/or plasticizers, the newly induced fractions, depolymerization and/or hydrogen absorption are not, as described for the other mixture of crude tar fractions, linear functions of the time. A critical period of treatment by or with hydrogen exists, and which if exceeded causes loss of newly induced fractions, polymerization and/or lessened hydrogen absorption on certain fractions of the preferred starting material under treatment.

The critical time element because of the obvious possible variations in the characteristics of the aforenamed refined coal tar pitch cannot be spoken of as an arbitrary figure. It can be stated, however, that if the refined coal tar pitch were to be subjected to the action of hydrogen for such a length of time, which for the other crude coal tar fractions would illustrate that the newly induced fractions, depolymerization and/or hydrogen absorption were linear functions of the time element, loss of induced products, polymerization and/or lessening of hydrogen absorption would occur. When treating the refined coal tar pitch by or with hydrogen, the critical time element is in the order of about three hours.

In the disclosures made herein and in the ap- 'pendedV claims distillate removal of low boiling portions from the beneiiciated material is considered the equivalent of fractional removal by gas movement, solvent action or the like. The converse also obtains.

A refined coal tar pitch selected from the group boiling predominantly above, and above, 355 C. and characterized by .sulfur content and content of oxygenated compounds is treated with hydrogen at 390 C. and 200 atmospheres pressure thereby lowering sulfur content and corrosivity, at least providing for lowered corrosivity in a final product, the while inducing no substantial percentage of solventl increment. The refined pitch of lowered sulfur content is passed through a high pressure reaction vessel at a temperature of 430 C. and a pressure of 300 atmospheres. The flow of hydrogen is in the order of 15,000 cubic feet per barrel feed stock. The time of contact is two hours, and the catalytic material molybdenum oxide and iodoform. The beneficiated reiined coal tar pitch flowing from the reactor is distilled to an upper limit of 300 C. to recover the refined solvents of lowered corrosivity as a distillate. The beneiiciated refined coal tar pitch as iiowing from the hydrogen action last named will be found to be characterized by lowered oxygen content, specific gravity andviscosity. The residue resulting from said solvent recovery is of a more liquid nature than a comparable cut on the starting material, indicating that the high boiling end which may be described as including multiplicity of ring structures had been, at least, either saturated or partially saturated, thus providing the initial step in the stepwise conversion Vof substantially the entirety of the refined coal tar pitch remaining liquid under process conditions into the refined solvent of lowered corrosivity of the present process.

The residue resulting from the recovery of the refined solvent from the beneciated rened pitch may be recycled for conversion to additional refned solvents.

In the instance of the solvent recovered to an upper limit of 300 C. as above described, the solvent cut may be divided to provide solvents of various boiling ranges as may be dictated by necessity. In the event a deep out is taken on the beneciated refined coal tar pitch to provide the solvent and/or solvents of the present process the upper boiling portion of the deep cut may provide a product having induced plasticizing properties.

When subjectingf a refined pitch to the action of hydrogen for theV production of solvents in accordance with the present process, the hydrogen action characterized by solvent increment is controllably held at or below the critical time period, and if such is exceeded adverse reaction will occur. As an example, if the critical time period is exceeded, instead of fractional increment, depolymerization and/or hydrogen absorption being linear functions of the time element, the reverse will obtain. In other words, if the critical time period is exceeded, fractional increment, depolymerization and/or hydrogen absorption will not be linear functions of the time element, it having been found, among other things, that a period in excess of that which is critical will provide for loss of fractional increment and /or poly- Vmerization.

The critical time element in the instance of treating the refined coal tar pitch'with hydrogen is in the order of about three hours, andV the present process is predicated onl the employment of the critical, or less than the critical, time element.

The refined solvents of lowered corrosivity as being the conversion products of the refined pitch are of superior quality and are characterized by a preponderance of ring structures.

In the first cycle of hydrogen action that reduces sulphur content, said reduction of sulphur may be accomplished in the presence of a catalyst. Catalysts effective in the presence of hydrogen are usable, as for instance, the oxides and/or sulides Vof molybdenum, vanadium, uranium, cobalt, tin, manganese, tungsten, or the like.

In the disclosures herein made the removing of low boiling fractions by gas movement or pressure release is considered the equivalent of distillation.

When reference is made to high molecular complexes contained in the starting material, and when the starting material contains low boiling fractions that are not considered high molecular complexes, it is of course obvious that the high molecular complexes contained in the starting material are to a certain extent depolymerized by the solvent present.

It will be seen that by reduction of sulfur content of the material under treatment during ,any stage of hydrogen action, the` oxide catalyst used during subsequent stages is at least partially protected from the effect of the sulfur.

The decomposition influencer which it is desired to have present in the reaction zone is generally taken between 0.1 and 4 or 5 percent, based on the feed stock, and is preferably taken between 0.1 and 1.5 percent.

Halogens, halids and derivatives thereof are Y employed for catalytic purposes noted in the foregoing; however, also may be employed substances furnishing under the process conditions a halogen or a hydrogen halid. Ammonium chloride Vmay be employed, also halogen compounds of coal tar oils, or the like as for instance the iodides or bromides. Also'may be employed acids such as nitric, sulphuric, sulphonic, formic and acetic.

The addition of the decomposition influencer may be made prior to the entry of the feed stock into the reaction chamber, or at any suitable time, as for instance after the charging stock has been heated.

When practicing the process, the hydrogen step characterized by reduction of molecular complexes may be carried forward at lowered temperatures; however temperatures in excess of 350 C. are preferred. The upper limit of temperature usableA is defined as that temperature that precludes substantial carbonaceous deposition, as for instance coking.

An especially attractive form of practicing the present process is to first depolymerize the starting material with a solvent, as for instance, but not in a restrictive sense, a refractory solvent. As an example of such solvent employment may be mentioned the depolymerization of the refined coal tar pitch by use of a suitable solvent. The solvent may be employed in quantities up to volume for volume, or more. After the depolymerizing step, the solvent and solute are then subjected to the action of hydrogen in accordance with the process. Solvents having at least the power to place a substantial portion of the starting feed, as for instance the reiined coal tar pitch, in solution are preferred. Such solvents may conveniently be secured from the tar or petroleum industries.

Gas flows may be chosen, as an example, between the limits of l5,000-25,000 cubic feet per barrel feed; however other ows causing n0 adverse reactions may be employed.

Equivalent amounts of compounds furnishing halogen or hydrogen halid may be employed.

The evaluation of solvent power is conveniently accomplished by finding the well-known aniline point or kauributanol number. The evaluation of plasticizing properties is conveniently accomplished by recourse to methods suggested in chapter VI, The technology of solvents by Dr. Otto Jordon, Mannheim,.Germany, translated by Alen D. Whitehead, Chemical Publishing Company of New York, Incorporated, New York, New York.

Minor changes may be made in the foregoing without departing from the spirit of the invention.

I claim:

1. The process of producing a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, and fractionating the overhead material to recover 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 hydrogen whereby to lower sulfur content whilst precluding substantial solvent-increment; subjecting the material of lowered sulfur content to the action of hydrogen at a temperature and pressure in excess of 250 C. and atmospheric, respectively, while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions, to provide a solvent.

2. The process of producing a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, fractionating the overhead material to recover 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 hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; subjecting the material of lowered sulfur content to the action of hydrogen while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; and fractionating the beneficiated material to provide low boiling fractions as a solvent.

3. The process of claim 2 with the inclusion of recycling the residue.

4. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, fractionating the overhead material to recover 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 hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; subjecting the material of lowered sulfur content to the action of hydrogen at a pressure and temperature in excess of atmospheric and 250 C., respectively, while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid polymerization, to provide a solvent.

5. In the production of a solvent from the refined pitch produced by stripping high temperature coal tar to at least about substantial dryness, fractionating the overhead material to recover 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 hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; subjecting the material of lowered sulfur content to the action of hydrogen at a pressure in excess of atmospheric and a temperature in excess of 250 C. while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid lowered hydrogen absorption, to provide a solvent.

6. The process of producing a solvent which comprises: evaporating high temperature coal tar to at least about substantial dryness; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; subjecting said higher boiling fraction to the action of hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; and subjecting the material of lowered sulfur content to the action of hydrogen while contacting as Catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions, to provide a solvent.

7. The process of producing a solvent which comprises: evaporating high temperature coal tar to at least about substantial dryness; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; subjecting said higher boiling fraction to the action of hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; subjecting the material of lowered sulfur content to the action of hydrogen while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid loss of newly induced fractions; and fractionating the beneficiated material to provide low boiling fractions as a solvent.

8. The process of claim 7 with the inclusion of recycling the residue.

9. The process of producing a solvent which comprises: evaporating high temperature coal tar to at least about substantial dryness; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; subjecting said higher boiling fraction to the action of hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; and subjecting the material of lowered sulfur content to the action of hydrogen at a pressure in excess of atmospheric while contacting as catalytic materials an oxide and a material selected from the group consisting of halogens, halids and derivatives thereof for a period not in excess of about three hours, whereby to avoid polymerization, to provide a solvent.

10. The process of producing a solvent which comprises: evaporating high temperature coal tar to at least about substantial dryness; fractionating the overhead material to recover a liquid useful as a wood preservative, and a higher boiling fraction boiling predominantly above 355 C.; subjecting said higher boiling fraction to the action of hydrogen whereby to lower sulfur content whilst precluding substantial solvent increment; and subjecting the material of lowered sulfur content to the action of hydrogen while contacting a catalytic material selected from the group consisting of halogens, halids and derivatives thereof at a pressure in excess of atmospheric and a temperature in excess of 250 C. for a period not in excess of about three hours, whereby to avoid lowered hydrogen absorption, to provide a solvent.

JACQUELIN E. HARVEY, JR.

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