US2291296A - Treatment of high temperature coal tar - Google Patents

Description

July 28 l942- J. E. HARVEY, JR 2,291,296

TREATMENT 0F HIGH TEMPERATURE COAL' TAR FiledJune 20, 1940 #mwa/57mm@ CWA/wam (SMF/0E 04740157) Patented July 28, 1942 TREATMENT OF HIGH TEMPERATURE COAL TAR Jacquelin E. Harvey, Jr., Atlanta, Ga., assignor of one-half to Southern Wood Preserving Company, East Point, Ga., a corporation of Georgia Application June 20, 1940, Serial No. 341,595

2 Claims.

The present invention relates to the joint production of useful products, and more specifically relates to the joint production of useful products from high boiling fractions of tar, including pitches and the so-called residual tar.

An object of the invention is the joint production of wood preservatives and solvents from high boiling fractions of tar, including pitch, and constitutes an improvement on Patent 2,082,885, granted to me on June 8, 1937.

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

Patent 2,082,885 describes a method for the production of wood preservatives from pitch to the end that said pitch, substantially in its entirety, is converted into a wood preservative of enhanced value and controllable specications, as for instance those specifications meeting A. W. P. A. requirements. Such a process made available to creosote manufacturers a method whereby coal tar, or the like, could be converted substantially in its entirety, as for instance 80% or better, into wood preservatives, with the added benefit that said process eliminated the final production of pitch incidental and inherent to wood preservative (creosote) production from coal tar or the like by conventional distillation or extraction methods.

It is well known in the industry that this country has for years imported millions of gallons of creosote from abroad even though the raw parent material of creosote-coal tar or the like-was and is domestically produced in such quantities as to make available by conventional distillation methods an amount of creosote to provide national sufficiency. However, this country did not take advantage of the adequate raw material supplycoal tar or the like-to the end that national sufficiency in creosote be realized, for the reason that distillation recovery of cleosote from tar resulted in the production of in the order of 50% pitch which was at times a distress product.

The process described in Patent 2,082,885 provides, as aforesaid, a method for substantially total conversion of coal tar, or the like, into rened wood preservatives by. iirst, distilling said tar for creosote recovery and, Second. the C011- version of the resultant pitch by the action of hydrogen, substantially in entirety, into rened wood preservative. Thus a method was PIOVd@d for substantially volume for volume conversion of refined wood preservative from coal tar, or the like.

With such a process available, smaller quantities of coal tar, or the like, would be required to the end that national suiciency in reiined wood preservatives, as for instance creosote or creosote-coal tar solutions or their modifications, be secured. With an average annual coal tar production of 500-600 million gallons and an annual average consumption of refined tar wood preservatives of 200 million gallons, and employing the process of U. S. Patent No. 2,082,885, it is apparent that 30G-400 million gallons of tar would be available for other purposes.

It is now found that instead of converting pitch, substantially in entirety, to wood preservatives as described in Patent No. 2,082,885, pitch may be converted, substantially in entirety, jointly into solvents of superior quality and wood preservatives of enhanced toxic value.

By describing the solvents of the present invention as being of superior solvency is meant that said solvents are in the order of approximately 50% aromatic, or more, and as is well known in the art can only be accomplished by precluding excessive destruction of the aromatic nuclei in the starting material. When assigning to the wood preservatives of the present invention an enhanced toxic value, is meant that the toxicity of said wood preservatives is in excess of the toxicity -of said starting material and thus, as is also well known in the art, cannot be provided if excessive rupture of destruction of the aromatic nuclei in the starting material take place.

The present invention to the end that the starting materials oi the process be converted substantially entirely to said solvents and wood preservatives, insofar as applicant understands saine, is predicated on:

First, that the molecular complexes of the starting material, as hereinafter explained, are converted in step wise manner to produce the products and/or product of the present invention.

Second, that the reduction including in size, of said molecular complexes be accomplished under a partial pressure of at least a fractional atmosphere of hydrogen sulde.

Ihe 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 aforementioned.

in each chamber and the contents thereof are indicated by legend.

Example 1.-A tar pitch boiling substantially 15% at 355 C. was subjected to the action of hydrogen in a continuous manner in a high pressure reaction chamber, under the influence of a molybdenum sulfide catalyst, at 400 C. and 300 atmospheres pressure. Time of contact was 2 hours. Inspection of the beneciated product during the first portion of the run showed a yield of distilling to 205 C. and approximately 22% distilling from 205 C. to 355 C.

The product recovered up to 205 C. was the solvent of the present invention and boiled predominantly between 165 C. 205 C. and had an aromaticity of in the order of 50%; the product boiling substantially between 205-355 C. was the wood preservative of the present invention and had a toxicity comparable to conventional creosote, and a toxicity in excess Yof its parent material. As is usually recognized the pitches have little or no toxicity. The residue incidental to the recovery of 'said Wood preservative may be used as an article of commerce or recycled, with or without addition of other starting material for compensation for diminution in volume incidental to product recovery. n Y

At the end of the'36th hour of the use of the catalyst, the conversion of the starting pitch to products of the present invention was reduced. Research disclosed that the cause of such reduction was due to failure of Vthe catalyst. to be maintained in substantial sulde form, that is to say, the catalyst appeared 'to be converted to other form, at least to a degree. By adding 1/2 of 1% sulfur to the starting material (pitch), it was found that substantially the initial high rate of reaction was established, and continued substantially so thereafter.

Thus, the 'initiating and continuance Vwithout substantial reduction, other than that incidental to catalystage, of reaction conditions that produce the solvents and wood preservatives of the present invention are predicated' on the maintenance of a hydrogen'sulfide partial pressureof at least *afra'ctional atmosphere. At times the partial pressure of hydrogen'sulde maybe as high as one atmosphere, orhigher. The `partial pressure of hydrogen sulde of the present invention, is that partial pressure required to maintain the sulde catalyst in substantial suliide form.

Somestarting 'materials' of the present process may'have suiiicient sulphur therein contained to supply theneeds incidental to-the suliide catalyst being maintained in substantial sulfide form. Other starting feeds may require the addition of sulphur. The amount of sulphur necessary to maintain the sulfide catalyst in substantial -sulfide form Will readily be found after a fevv trials,.

and in the event of sulphur deiiciency, the same is added.

Viewed broadly, the present invention provides a process for the conversion cfa high boiling iraction of tar into solvents of superior solvency and wood preservatives of enhanced toxic value, wherein said high boiling tar fraction is subjected to the action oi' hydrogen `a'ridhydrogen sulphide, in the presence of a sulde catalyst, whereby said tar high boilingfraction,`substan tially, in entirety is converted in stepvvise Vmanner to the solvents and wood preservatives'as It canbe explained that the action of sulfur in the instant process also has the, unexpected effect of reducing the toxicity blanketing elect of the residual above 270 C. in the wood preservative produced, as compared to a product produced by a similar process without sulfur. It is recognized in the art that the toxicity of a tar .derived wood preservative is proportional to the percentage distilling below 270 C. However, it is also recognized in the art that the residual above 270 C. in the wood preserving oil lowers or has a toxicity blanketing effect on the overall wood preservative. The inclusion of hydrogen sulde in the instant process reduces the well known toxicity blanketing effect in the residual above 270 C. in the wood preserving oil.

Example 2.--Various methods of practicing the present process are possible, as will immediately become apparent to those skilled in the art.

For instance, the pitch of Example l may be treated in the first cycle for the recovery of the solvents and wood preservatives of the present invention, thereafter recycling the residue, with or without the addition of added starting material, for conversion only to wood preservative.

Example 3.-The present process is also adapted to convert specific high boiling fractions of tar into the solvents and wood preservatives oi the present invention, as for instance wax oil and high residue recovered Vfrom Vhigh residue creosote; also selected high fractions, including pitch, from petroleum aro-matics.

High residue recovered from high-residue creosote, said high residue v.boiling substantially 97% above 3803 C. and having a colre residue in excess of 4% Was'adjusted to sulphur content by adding an amount 'of sulphur thereto that under process conditions Vgave atleast a partial atmosphere hydrogen -sulride partial pressure. Said high-residue was chargedtoa high pressure bomb and charged with hydrogen to 2000 lbs. Heat was then applied to an upper limit of 410 C., meanwhile agitating` the bomb. The run continued 8 hours. At the end of said y8 hour period the bomb was allowed vvto cool and recharged with fresh hydrogen to 2000lbs. Identical reaction controls were r'eihstituted and the run continued for an additional 8 hours. At the end of said period the 'beneciated material was withdrawn vfrom theV bomb, dissolved and occluded gas removed, Hand `distilled for solvent and wood preservative recovery. The distillation cut Was made at 200 C., with the 'distillate serving as the solvent "of the presentinvehtion and the'residue'a's wood preservative. The solvent boiled pr'ed'o'iniriaritlt7 bet'v'veen 50 C. and 200 C.`and"had an aromaticity ofin the order of 50%. TheV woodprservative had a'cokeresidue within nwood Ypreservative Vspecification limits, a toxicity inexcess of 'its parent material and a Vpermissible initial boiling point 4in view oi' specifications' extant.

As noted in the foregoing, the beneficiat'e'd material flowing from the process controls of the present invention may be Vfractionated `to produce (a) the solvent as 'a distillate and the residue thereof las a wood preservative or (b) the solvent and wood preservatives as distillates with the 'residue VresultingV therefrom used 'as an article of'coinmer'ce or recycled.

The starting materials of the present process are high" boiling fractions'of aromatic tars and tars'of aromatici content, includingpitches, acid or neutral, crude or'rened, as-for instancefone or more times refined by hydrogen.

Also suitable starting materials of the present process are residual tars, by which is meant tars from which have been removed certain high boiling solvents.

The ter-m liquid phase as used herein and in the appended claims is used to diierentiate from the gas phase which gasiiies substantially all or substantially the entirety of the feed material. The term liquid phase may not be technically correct, inasmuch as a certain portion does exist in vapor phase, however, as used herein, the liquid phase predominates.

The process is also adapted to be practiced in continuous or intermittent operation; reaction chambers may consist of a simple chamber, a multiplicity thereof, in series or parallel.

All sulde hydrogenating catalysts are usable, as for instance those of the 6th periodic group;

especially eiective are the sulfides of vanadium,

tungsten, tin, molybdenum and uranium; sulfide catalysts in admixture with other materials possessing hydrogenating qualities or not; deposited on carriers, extruded, in various shapes, comminuted or in proper` form to aid surface contact; promoted or not; with halogen deriva` tives or not; all hydrogenating catalysts of sulfide form.

As is well known, hydrogenations proceed at only slightly elevated temperatures and pressures; however, elevated temperatures are desirable, and the preferred pressure is 200-400 atmospheres. However, pressures as high as 1000 atmospheres or higher are usable. Temperatures chosen between 200 C. and 650 C. are the practicable process limits, however, good operation may be had between 375 C. and 425 C.

The point of fractionation between the solvent and the wood preservative is flexible. As an example, commercial solvents are of varying boiling ranges and end points, and by a like token, commercially acceptable wood preservatives are of varying initial boiling points; thus inasmuch as in the present invention, the end point of the solvent approximates the initial boiling point of the wood preservative, the distillation cut may be at various points. Some commercial solvents on the market have the following end points:

Commercial solvent:

End point, C.

Benzol 120 Toluol 150 High-Hash naphtha 200 Heavy naphthas above 200 Some commercial wood preservatives on the market have the following initial boiling points:

Southern Pine Shingle Stain Oil 92 C.

rThus, from the foregoing it will be seen that there is no iniexible point at which the solvent and wood preservative must be separated; further, it will be strictly understood that the foregoing solvent end points and wood preservative initial boiling points are illustrative only, and that the cut may be made at any point as determined by manufacturing necessities.

Also, when recovering the wood preservative as a distillate, the end point may be at any desired point consistent with consumer acceptance. Accepted and specification wood preservatives seldom limit end point. Thus, the present invention may be applied to produce the wood preservative as a distillate whose end point is that end point desired. In the following are listed several accepted wood preservatives having no limitation on end point.

Woon PRESERVING IMPREGNANTS Specification 1. American Wood Preservers Association:

a. Up to 210 C., not more than 5%. b. Up to 235 C., not more than 25%.

2. American Wood Preservers Association:

a. Up to`210 C., not more than 1%. b. Up to 235 C., not more than 10%. c. Up to 355 C., not less than 65%.

.3. American Wood Preservers Association:

a. Up to 235 C., not more than 11/2 b. Up to 300 C., not more than ll/2%. c. Up to 355 C., not less than 45%.

4. American Wood Preservers Association:

a. Up to 210 C., not more than 8%. b. Up to 235 C., not more than 35% 5. American Wood Preservers Association:

a. Up to 210 C., not more than 10%. b. Up to 235 C., not more than 40%.

6. American Wood Preservers Association:

a. Up to 210 C., not more than 5%. b. AUp to 235 C., not more than 15%.

7. Prussian Ry.:

a. Up to 150 C., not more than 3%. b. Up to 200 C., not more than 10% c. Up to 235 C., not more than 25%.

8. National Paint, Varnish & Lacquer Association;

a. 5% at 162 C. b. 97% at 270 C.

9. Southern Pine Shingle Stain Oil:

a. 5% at 137 C. b. at 257 C.

10. Neville Shingle Stain Oil:

a. I. B. P., C. b. 5% at 205 C. c. 95% at 292 C.

Thus, from the foregoing it will be seen that the listed specifications place no arbitrary end point on the wood preservatives; generally, the end point is determined by customer preference.

summarizing: The present invention provides a process for the conversion of high boiling fractions of tar, including pitch, into solvents and wood preservatives of superior solvency and enhanced toxic value, said solvents and Wood preservatives being characterized as being substantially total conversion products of said high boiling fractions, and being further characterized in that said conversion was effected under the influence of hydrogen and a hydrogen sulfide partial pressure of at least a partial atmosphere while in the presence of a sulfide catalyst.

Pitclies and high boiling tar fractions at least once rened by hydrogen are especially adapted as starting materials of the present process.

Solvents may be used to reduce carbon concentration in any of the starting materials prior to treatment by the process of the present invention.

By the term beneicated as used herein and in the appended claims, is meant the starting material at least once subjected to the process controls of the present invention. The high boiling materials may be passed through a reaction chamber under conditions that refine but fail to produce the products of the present invention in a commercial manner; thereafter the refined material may be subjected to process controls that produce the products of the present invention.

The solvents of the present invention vary in their lower boiling range in accordance with impressed controls; controls may be impressed to provide solvents boiling as low as 50 C., or lower. The overall solvents so produced may be fractionated to provide various cuts.

When processing high boiling fractions oi' relatively high carbon content, or others, impressed process conditions may be less vigorous at rst, and after a certain depolymerization has been effected, increasing process controls up to an optimum.

The wood preservatives of the present invention include the usual shingle stain wood preserving oils.

By the phrase without substantial reduction when applied to catalyst activity is not meant to include reduction in activity due to age.

Concerning the conversion of the molecular complexes contained in the starting material: the highest boiling fractions of the starting material may be viewed as a multiplicity of rings or molecular complexes. These multiplicity ci' rings are converted in step-wise fashion to the products of the present invention. By the term stepwise is meant progressively; such progressive conversion, in accordance with the present invention, institutes and maintains without substantial reduction, the depolymerizing hydrogenation of the present invention by the joint action of hydrogen and hydrogen suliide, in the presence of a sulphide catalyst.

The oils and/or solids also contained in the starting materials, other than said molecular complexes, are also converted to cons 'tuency in the products of the present invention.

The sulfide catalysts of the present invention include those catalysts of other forms, converted to suldes prior to or during the process.

Minor changes may :be made in the steps of the process Within the scope of the following claims Without departing from the spirit of the invention.

I=claim:

1. In the joint production of solvents and Wood preservatives from a mixture of high temperature-coal tar Vfractions boiling not in excess of about 15% at 355C., the process which comprises: subjecting said material to the action of hydrogen in the presence of a sulfide catalyst with the time so coordinated with a temperature above 400 C. and a pressure selected between the limits of about 200-400 atmospheres as to provide newly formed low boiling solvent'fractions having an aromatic content of at least about 50%, said newly formed low boiling solvent fractions boiling :below and contiguous to other newly formed fractions of induced toxicity; maintaining a hydrogen sulfide partial pressure by adding sulfur containing material equivalent to about one-half of one percent sulfur; stripping the treated material of low boiling lfractions to provide a low boiling solvent having an aromatic content of at least about 50% thereby .providing as a residue an oil of the Wood preserving type having not more than about 10% boiling below 210 C. nor less than about 45% boiling up to 355 C.

2. In the joint production of solvents and wood preservatives from a mixture of `high temperature coal tar fractions boiling not in excess ofabout 15% at 355 C., the .process -which comprises: subjecting said material vto the action of hydrogen in the presence of a sulfide catalyst with the time so coordinated with a temperature above 400 C. and a pressureselected between the limits of about 200-400 .atmospheres as to provide newly formed .low boiling solvent fractions having an `aromatic content of at least about 50%, said newly formed low boiling solvent fractions boiling below and contiguous to other newly formed fractions of induced toxicity; maintaining a hydrogen sulfide partial' pressure Iby adding sulfur containing material equivalent to about one-half of one -percent sulfur; stripping the treated material to lprovide la relatively low boiling solvent having an aromatic content of at least about 50% and a relatively high boiling oil of the wood preserving type boiling not more than about 10% at 210 C. nor less than about at 355 C.

J ACQUELIN E. HARVEY, J n.

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