US2082885A - Method of producing a wood preservative or the like - Google Patents

Description

June 8, 1937. .La HARVEY, JR 2,082,885

METHOD 0F PRODUCING A WOOD PRESERYATIV OR'THE LIKE Filed April 2, 1935 Patented June 8, 1937.

METHOD oF PRODUCING A Woon PaEsERvATIvE on 'ma LIKE JacquelinE. Harvey, Jr., Cogdell, Ga., assignor of one-half to Southern Wood Preserving Company, Atlanta, Ga., a corporation of Georgia Application Aprile, 1935, serial No. 14,378

s'claims. (ci. 19e-62)l This invention relates to a process of produc,- `ing a Wood preservative or the like and has as an object the carrying on of hydrogenation in such a manner as to exercise a controlof the characteristics of Vthe finished product.

It is a further object of the invention .to provide a process for hydrogenation of pitch in suchA a manner as to iinally convert the entire quantity into a synthetic creosote having less than 10 distilling to'200 C., and not less than 50% dis-` tilling to 355 C., whenA distilled according to American Wood Preservers Association' standard distillation of creosote, Schedule 11E.

Creosote is the distillate recovered from coal tar, or the like. In past years, upwards ofV 50% creosote was recovered4 from coal tar,but as the present trend of the industry is toward lower residues, vthat is, the proportion above 355 C., smaller and smaller recoveries ofcreosote from coal tar are nowbeing made. For instance', to.

condition in mind, it has long been a desideraturn i, -lin the art to recover by simple distillation from coal tar, or the like, as much creosote as possible. Various investigators have proposed various procedures, one of the most notable being the Barrett direct. recovery still which has recovered V approximately '70% creosote from coal tar-but with a recovery of approximately "70%, the residue in the resultant creosote above 355 C., is 40 53%. Even when the recovery of creosote from coal tar in the Barrett direct recovery still has being dropped to 55%, the residue above 355 C.,

is only slightly under 50%.

The Barrett direct recovery still recovers as much creosote from c'oal tar as any otherv method heretofore known and more cheaply.V V

When recovering approximately '70% creosote from coal tar, the residue above 355 C. in the creosote is approximately 53%.` Many creosote consumers will not permit a creosote having such a high residue; therefore, as the' trend vof the industry is toward creosotes having only 30% residue above 355 C., producers must decrease.

r the percentage recovery of creosote from coal 55 tar in the order of 25 to 35%.

. wood preservative.

4-I have found that I vcan recover 80 to 100% of creosote from coal tar or the like, neglecting normal manufacturing losses.v When practicing my invention for the recovery of volume for volume of creosote from coal tar, I can control the' residue in the creosote above 355 ,from zero to any'desired pointgr I claim as pioneer in the art my process for producing substantially volume for volume of 'creosote from coal tar, wherein not more than 10% will distill at 200 C., and wherein the residue above 355 C. can be controllably held from zero to any desired percentage.

Coal tar in the trade means the tar resulting from distillation of coal in a high temperature coke oven. This is the material now preferred for treatment by my process. Other usable starting materials are gas house tar, low' temperaturedistillation tar, and rosin oil pitch.

Inasmuch as the rststep in production ofwood preservative from any of the above materials is the recovery by distillation of any fractions present of permissible wood preservative, the inventionV here resolves itself into the production of wood preservative from pitch.

By-l permissible creosote is meant a material which lwill meet the tests setl up by'the trade.v At present among these tests is the requirement that 'not more -than 5% shall dstill at 200 C.

tion, therefore, contemplates any modification of the extent ,of hydrogenation at the successive steps described below to agree with any such modification.

I havel attimes secured more than vol'- umetric eiliciencyv of creosote from coal tar-'or eries,-I have vheld. the amount distilling up to 200 C. below 5%, and the jamount of residue above 355 C.`;from zero to any desired percentA age; v y

. I may take a coal tar or the like and by simple distillation recover from it a distillate falling 'within the specifications of a permissible creosote.

This simple distillation leaves a residuum of 4pitch in the'still which because of its physical and other characteristics is not acceptable as a I have found that by taking the residual matter and subjecting it for a'time to hydrogenating conditions, I can simple distil from said residual mass an oil falling within the the like, and this recovery is more the rule than the exception. And, when practicing such recov -1 This oil is the desired creosote.

After the newlyv formed oil has been removed, the resultant residual mass may again be hydrogenated to produce a similar distillate and such procedure may be carriedonuntil said residual mass has completely disappeared. The mechanics of the operation make possible the total conversion of the residual mass into an acceptable wood preservative. The requirements -for recovery of 100% or over of permissible wood preservative are: rst, that the hydrogenation shall be carried out under such conditions as not to induce a fraction that is not commercially feasible of hydrogenation to creosote; and lsecond, that at no time is the hydrogenation carried to an extent to produce a fraction having a boiling point lower than is permissible in the desired product as in such a case said fraction must be removed and discarded so* far as .the desired use is concerned.

By the word pitch as used herein and in the claims is meant any or all the material of coal tar not permissible in a wood preservative creosote. For instance, it is possible to distill off 75% to 80% of the coal tar and to label the disv tillate creosote but under present conditions the 'said creosote would not be permissible as a wood preservative. However if 80% cut is again distilled to yield a permissible wood preservative creosote, the residueof said last distillation is regarded as` pitch in the sense used herein and in shown in the accompanying drawing in which the figure is a diagrammatic showing of a ow sheet. In the drawing a still is shown at I, which may be of anydesired character having an outlet for vapors at 2, and a charging inlet for fresh material at 3. Residues from the distillation are drawn at `4 under influence o'f pump' 5, and hydrogen or hydrogen carrying gas may be supplied by pump 6 from any source. The residues and gas then pass through heater 1, through the h ydrogenation. chamber 8, to and vthrough a high pressure gas separation chamberl 9, then to and through a low pressure gas separator I0, from whichlatter the hydrogenated liquid passes back to the still. Pressure regulating and reducing valves are shown at II and I2.

The gases from separators- 9 and I0 are passed into reilux condensers I3 and IIIa respectively and escape at I5 and I6 from which points the escapling gases may be led toapparatus, not shown, to recover hydrogen 'for reuse.

The fresh material introduced to the still at 3 may be pitch as defined herein. However in many cases it may be desirable to introduce coal tar at 3 both initially and thereafter to keep up the supply as the volume of material is reduced by hydrogenation and distillation, allowing the creosote 'distilled from the coal tar direct. .to mingle with the synthesized creosote'produced by the process of the invention. J y

`It vwill be understood that the gas recovery apparatus connected "at- I5 and I6 must be ar- .ranged to preserve the desired pressures in 9 and I0, which fact I have illustrated by indi,-

cating reducing ,pressure regulation valves at I1 l completeseparation of entrained gas from the hydrogenated liquid, agitators I9 and v20 may be 2,082,885 limitations of a specied and desired creosote. u

placed ln the separators 9` and I0 respectively. The bale plates 2I in hydrogenating chamber 8 may be depended upon for agitation of the gas and liquid therein but it will be obvious that any agitator may be utilized.

In the following I set' forth fully several examples of steps for substantially a hundred per cent volumetric recovery of desired creosote from coal tar or the like: y

ErampZe 1.-I take a given coal tar and subject it to simple distillation until all permissible wood preservative creosote has been recovered which under present trade requirements means until a creosote is recovered which will distill approximately 5% up to 200 C., and that will have aresidue of not substantially more than 20% at 355 C. The resultant pitch, as is well known, will have a specicvgravity in the order of 1.23 and approximately nothing oil? at 355 C. as well as having substantially no toxic value as a wood preservative. This pitch is charged to an autoclave designed to withstand high pressure) and temperature, and subjected to a temperature of from 300 to 500- C., and a hydrogen pressure of from 20 to 300 atmospheres while, las is .usual with such processes, keeping the contents within the ranges of temperature and hydrogen pressure` named, this result will be found to be accomplished in from one to ten hours. It is at present preferred to operate at from 350 to 400 C. and with hydrogen pressures ofabout 200 atmospheres under which conditions the result named will be found' to be accomplished in a time of'the order of four hours.

After hydrogenating as and to the extent described, the contents oil the autoclave are discharged into a suitable distilling apparatus and distilled up to a temperature of substantially '355 C. until approximately nothing further is coming oi. 'I'his distillation will be found to yield approximately 12% as a distillate which is the wood preservative creosote desired, which under the conditions set forth will give of! notJ The residue from the distilling operation may then be charged back toy the autoclave and the cycle repeated, enabling a ltotal conversion of the pitch into creosote. As is Well known, the usual coal tar pitches have a hydrogen content of substantially 4% to ,6.5%. Analysis of the result of the above described process will show a hydrogen 7^content oi substantially 7%. This means that vthe process as described adds to the pitch.from .5 to 3% hydrogen.

It is impossible to produce volume for /volume of creosote frompitch in va single'cycle of hydrogenation since if the pitch be hydrogenated in a single step to the point that it will all pass over at 355 C., the resultant distillate will contain an undue amount (more than 5%) that will distill at 200 C. and this low boillngiractlon lmust be eliminated and discarded for the purpose intended. Therefore volume for volume \in.

superior to creosotedistilled from coaltar from which Vdistillation the pitchvisthe residue.

The limits of temperature and pressure given are important. A lower temperature or pressure or both are operable but the ,time required is greatly extended and the process therefore ceases to be commercially feasible at present.

It is a known and accepted fact that the fungicidal power of a creosote decreasesas the boiling point increases. It is also a known and accepted factthat lthe neutral hydrocarbons are fully as effective as the phenolic compounds of similar distillation range. That this is accepted as fact is borne out' by an article by F. I-I. Rhodes Vand F. T. Gardner of Cornell University which was published in February 1930 issue of Industrial and Engineering Chemistry under the caption Comparative efficiencies of the components of creosote oil as preservatives for timber.

Example 2.-Using as a starting material soft. intermediate or hard pitches, they are subjected to hydrogenation at necessary pressures, temperatures and for the desired time as above described until a new oil has been formed that will not distil more than up to 210 C., and such` that when distillation is carried to a point of 355 C. the residue will not be greater than permitted bythe trade standard. The thus par= tially hydrogenated material is then simple distilled at a maximum temperature of 500 C. preferably to an upper limit of substantially 400C. to remove a distillate comprising the desired product for use as a wood preservative.

The residual matter resulting from said simple distillation is then again charged back to the hydrogenationvessel, compensation being made if desired by new material for the distillate removed `and hydrogenating conditions again repeated as above stated. Economic and commercial operations dictate the advisability of the addition of fresh compensating'jgmaterial', however f this is not necessary to the success of the process inasmuch as total conversion of the residual matter4 into a desired oil can be effected Without compensation of new material for the distillate removed by simple distillation.

Instead of operating intermittently as described in the foregoingfit falls within the scope of the invention to operate the process continuously. For example, material in the hydrogena `tion vessel may be continuously withdrawn at a controlled rate preferably with pressure reducing means in its path, and delivered to a conventional still where the' newly formed fracthe liquid charge in the simple still stripped of the newly induced fractions is then continuously withdrawn and returned to the hydrogenating vessel for Yfurther hydrogenation. Means must 4be provided to continuously or at intervals restore the volume of the material to the reaction chamber.

The conventional use of heat exchangers and the like may be incorporated if and when desired.

tions are removed by distillation. A portion of r Example 3.-This process is also especially ap- .plicable to the treating of high residue oils from a conventional direct recovery still. Those versed in the art will immediately know what is meant by the direct recovery still and no explanation here is thought necessary. I

` The direct recovery still maybe set so as to recover all possible volatile -matter with the sending of the resultant vapors into a fractlonating column whereby permissible oil is thrown into one channel and non-permissible oil is thrown into another channel, the non-permissible oil being then subjected to hydrogenating conditions as above described to produce an acceptable and desired oil in regards its float test, coke test, and insolubility in'benzol., I have repeatedly found that hydrogenation as practiced and described by me has the effect-of lowering insolubility in benzol.

It is'well to note that when'practicing my special form of hydrogenation for the production of acceptable and desired creosote from coal tar or the like, I do not desire cracking conditions.

f Whatever the usual definition of cracking may be, I refer to cracking as at'condition wherein polymerization has the effect of salting out carbon. This salting outofcarbon I do not desire because it would make more or less impossible the total volumetric conversion of coal tar or the like my hydrogenation is carried only to thepointy where a new oil is synthesized that will distil not more than 5% up to 210 C. However inasmuch as future creosote specifications may be changed, that is, a larger percentage of low boiling fractions may be made permissible, it necessarily falls within the scope of this invention to hydrogenate the aforementioned residual matter untilan oil is produced which will distil in its lowerboiling range in accordance with creosote specifications.

It is also important to again note that the neutral fractions of coal tar are equally as toxic as the phenolic `compoundsof similar distillation range. Therefore my invention does4 not, presuppose a condition wherein a starting material must have phenolic compounds or the like. Attention is directed to the fact that he lowering of the boiling point of neutral fractions has the effect of increasing their toxicity. In other words, using as starting material neutral fractions notacceptable as wood preservatives I can l transform theminto acceptable and toxic irac-v tions of a desired wood preservative.

I consider as pioneer in the art my process for the total volumetric conversion of coal tar or thelike into a permissible and acceptable and desired creosote.`

In the procedure of the process hydrogen is conveniently secured by dissociation of methane.

The hydrogen is placed under pressure, preheated and delivered to the reaction chamber. AA portion l of the gas from the reaction chamber may be 5 withdrawn, purified, restored as to volume by addition of fresh hydrogen and again introduced as at first. The material kis desirably agitated while bubbling the gas therethrough. However any procedure may be adopted whereby intimate contact between gas and material is secured. I t is a well known fact that the hydrogenation of coaltar or the' like necessarily at times produces undesirable amounts of methane and hydrogen sulphide.

For the sake of economy it may be desirable tol remove undesirable amounts of methane and hydrogen sulphide from the hydrogen or hydrogen-containing gases. This procedure is necessaryand advisable for economic reasons that/are immediately apparent to those skilled in the art.

Hydrogenation in liquid phase is preferred but it also falls within the scope of the invention to hydro'genate in vapor phase if and when advisable and such operating conditions may be incorporated in any of the above examples.

The above description is silent as to the presence or absence of catalysts. It is well known that the material of the wall of the reaction chamber may have a catalytic action. For commercial reasons it is preferred to carry out the invention without an added or apparent catalyst, assuming any. such effect of the material of the apparatus itself as not an iapparent catalyst.

To reduce the required pressure or temperature or to shorten the process, catalysts may be used.

Many catalysts are possible of use, such as Luxmasse (the residual material after alumina has been removed from bauxite), all oxides, halides. and sulphates of common metallic elements under proper conditions known to the art.

It necessarily follows that a preferred catalyst is one partially or entirely immune to the poison- -ing eiect of sulphur.k I therefore in practice if and when a catalyst 1s desired use such a catalyst. Examples of catalysts somewhat immune to 4,-, sulphur poisoning are molybdenum oxide and chromium oxide.'

Well known methods, either batch or contin- `urous, of revivifying catalysts may be practiced.

Purifying the gases has been referred to.. It is 50 found that a considerable quantity of nitrogen compounds are found in the system as a result of the operation. The, purification of the gases may include--the removal of these compounds as lao by scrubbing with sulphuric acid with recovery 1. The. method of producing a preservative wood impregnant which comprises: subjecting a pitch obtained from a material in the groupA consisting of coal tars and rosin pitch to hydrogena- Vtion with the temperature, pressure, and time socontrolled that when the hydrogenated product,

distillate has no greater percentage of ends boiling above 355 C. than is permitted by said specifications.

2. The method of claim 1 wherein the said hydrogenation and distillation steps are repeated in cycles upon the residue of each preceding dis- 4tillation step.

3. The method of producing Va. preservative wood impregnant which comprises: subjecting a. pitch obtained from a material in the group consisting of coal tars and rosn pitch to a hydrogenation with the temperature, pressure, and

time controlled so that less than 10% of the hydrogenated fractions recoverable as the wood pres'ervative'distills upto 210 C. and not less than 50% of the distillate boils below 355 C.

when the product is distilled;.distllling the hy-l drogenation product until the distillate has a no greater percentage of ends boiling below 210 C.

and above 355 C. than is permitted in specifica-v tions accepted in the trade for a wood preservative creosote directly recovered by distillation of coal tar.

4. The method of claim 1 performed as a con,- tinuous operation by substantially continuous circulation of hydrogenated material from the Y hydrogenatlon chamber to the still and of residue from the still to said chamber at a rate to properly control the extent ofthe hydrogenation.

5. The method of producing a preservative wood impregnant which comprises: subjecting a pitch obtained from a material in the group consisting of coal tars and rosin pitch to hydrogenation with the temperature, pressure, and time so controlled that if the hydrogenated product is distilled up to a temperature to recover the desired product-asa distillate said distillate will have no greater percentage of ends boiling below 210 C. than is permitted in specifications accepted in the trade for a wood preservative creosote directly recovered by distillation of coal tar andso controlled that the percentage of materials in said distillate boiling between 210 C. and 355 C. required by said sp eciflcation is produced. JACQUELIN E. HARVEY, JR.

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