SOLVENTS FROM PINE R. C. Palmer,
NEWPORT INDUSTRIES, INC, PENSACOLA, FLA.
vents and chemicals. It is of interest to note that in the last decade alone some 1O,OOO,OOO tons of forest waste have been reclaimed by a dozen or more plants using the extraction process. The fundamental process of extraction is a two-stage operation. After being ground into small chips, the stumps ol; other dead wood are placed in metal vessels or retorts and extracted with a petroleum or coal tar solvent. The terpene oils dissolved in the solvent are then separated by fractional distillation; the solvent is re-used and the terpenes are further refined into turpentine and other terpenes which occur only in old wood. The nonvolatile residue from the extract METHODS O F PRODUCTION is the rosin. The st?cond phase of the operation is pressure steaming of the chips for additional solvent recovery for reFour different processes are used in this country in prouse. The chips are used principally as fuel, although a t one ducing solvents from the pine tree. Until recently, the operation extracted wood is conveyed to an adjacent plant method that was first in volume was the time-honored collecfor conversion to a building and insulating board. tion of oleoresin from the living tree. The gum is gathered Sulfate pulp cooking of southern pine has long been conperiodically during the spring, summer, and early fall months sidered a potential source of terpenes and related by-products, from containers fastened onto the tree. Until recent years the resin was refined in equipment near the forest. The and ranks third in volume of production. The recovery of these materials from the paper industry in the southern apparatus was a simple still, heated by direct fire to vaporize Atlantic and Gulf Coast states has not kept pace with the the oil and connected to a cooling worm and receiver to conexpansion in the kraft paper production, but in the last three dense and collect the turpentine. This method has been reor four years there has been a notable increase in the separaplaced lately to an appreciable extent by more modern ention of these by-products. The primary process involves gineering methods in large central refineries. Here the the condensation of volatile terpene oils in the blowoff of the oleoresin is first treated in various ways to remove foreign digesters, and the separation of crude fatty acid oils by gravity matter, and the volatile oil is then separated from the resinous portion by steam and fractional distillation. after acidification of the alkaline black liquors. A number of methods have been devised for refining these materials since Another method, now first in the quantity produced, is the solvent extraction of the wood. they are not very useful in This industry had its beginthe crude state. Sulfate turning about thirty years ago; it pentine, as the terpene oil from was based largely on the pfemthis process is known commerFor the production of primary materials from the ise, since proved erroneous, cially, requires considerably pine tree, useful as solvents, four important that the living tree would more than simple refining to methods are employed, The collection of oleosoon cease to be a commerfree it completely of the charresin from the living tree still produces a subcial source of terpenes. It was acteristic odor associated with stantial quantity of turpentine oil; this system is recognized that the enormous the sulfate pulping process. tonnage of pine stumps and This has been largely solved, now adopting modern methods in large central other waste from lumbering however, and the best quality refineries. First in volume of initial products is operations contained a potensulfate turpentine is now bethe solvent extraction of dead wood; this branch tially great quantity of turing used for most purposes has grown rapidly in recent years and made pentine and rosin. This informerly employing only fresh progress in developing derivatives which have imdustry has become well estabnatural turpentine or the highlished within the last fifteen est quality steam-distilled wood portant chemical uses. A large potential source years. The method of extractturpentine. of terpenes is the pine pulp and paper indusing the products was necesThe fourth method is the a large quantity of fatty acids and rosin try; sarily based on a central oldest of all-the destructive and other by-products should be available from chemical plant and an e5cient d i s t i l l a t ion industry. The this origin. The destructive distillation of pine process, both as to engineermanufacture of pine tar from ing and chemistry, in order fat pine wood for use in treating wood is an old process and i s the fourth important to survive. It was therefore cordage a n d i n caulking method of yielding solvents as well as cheminatural that, after fundawooden ships was one of the cal by-products, Alpha-pinene is the only submental problems were solved, earliest industries established stance common to the four methods and is the attention was turned to dein continental America, and the starting chemical for many possible derivatives. veloping many secondary solpresent naval stores industry
P
RODUCTS from the pine tree rival those from petroleum as the oldest solvents known to the arts. The ancient Egyptians and even earlier civilizations undoubtedly employed crude turpentine or oleoresin as we know it today. The use of this material as a vehicle for the natural earth colors in decorating and perhaps as a binder for various constructional purposes constitute the early counterparts for the use of terpenes and related products in the modern paint, varnish, and plastic industries.
1023
1024
INDUSTRIAL A N D ENGINEERING CHEMISTRY
acquired its niinie from these uses. Tlre modern version of the process consists in heating the piiie wood, botlr stumps and other forest rraste, in closed retorts :at a siiffiriently liigh temperature t o bring about destructive distillation. The more volatile terpene oils distill off witliout muelr change, but tlie rosin and wood fiber are largely broken down by the process. NRPENllNE
Vol. 35, No. 10
oil in the manufacture of shelf goods mid industrial paints has led to the 8e:ir~bfor and discovery of other uses. Many of these new applications, however, like c o d tar and many petroleum solvents, are more properly considered clremical as sell its sulvent uses. For instmee, the large clrcruical use for a-pinene LW the raw material for thc synthesis of camphor is indirectly a solvent applicntion, since the camphor is largely employed :is a plasticizing solvent for nitrocellulose in the manufaetore of celluloid and many related products. The entire requirements of cimphor in this country, including the expanded war purposes as well m other uses, are being supplied by synthetic camphor. a-Pinene derived from oil of turpentine is the principal raw material employed, although a portion of the synthetic camphor, chiefly U. 8. 1’. made, is obtained from another terpene source. Other uses include conversion to phsrinaeeutieals, suoh as tetpin hydrate. A recent development which many believe will eventurrlly rank %?a leading chemical use for turpentine is the mnnufzcture of neutral resins from @-pineneby catalytic polymrrizstion. The latest data on the consumption of turpentine in tlie United States showed that more than half was used under the heeding “chemicals a n d phsrmneenticels”, an indication of how this old industry is turning to new fields.
Each of these uinjnr S O U ~ P ~ yields Y m u e ~xoduetsd i e tinetive to the process. The most widely distributed of all the terpenes, a-pinene, is the only solvent coininon to the four methods and is the priiicipal constituent of oil of turpentine recovered from the living tree. a-Pinene is also the predominating constituent Of tile oils obtained in the extrilction process. &Pinene, tlie other biryclie terpene which eomposes between 30 and 35 per cent of nsturnl turpentine oil, is not preserit. i n wood turpentine, but the lattcr. curitsins a number of other t.erpenes not found in the u:itur:d nil. Chemically the pulp by-product turpentine contains both a- and &pinene in about the same retio as the oil obtained from gum oleoresin. Tlie use of turpeutioc as a solrent in the paint snd varnish indiistry is so ~ o i n n i ~ that ii it is generally believed to be t h e prinripal use. Statistical infomntion published by the 11. S. Department of Agrirulture does not confirm this idee. It was probably true, however, at the beginning of the last deeade, but tlie use of turpentine as a thinner by paint and varnish manufacturers has been largelyreplaced by petroleum solvents. Recent data compiled by the Government in iiiea t e s tliut at present not more than 30 to 40 per cent of the tntd turpentine produced is coiisunied i n this country as 3 solvent in the manufacture of paint, varnish, nnri l a c q u e r . Fortunately, the true worth of this oil in painting and deeornting is still recognized and substantial qunntities iire still being used for this purpose; this use will no doubt continue for many years. I n d u s t r i a l , furniture, floor, nnd shoe polishes and creams consume B good deal of turpentine, shich are also solvent uses. CEEMICALUBEs. The Thirty-Plate Vacuum Columns Used for Soparatio decline in the use of this Solvent, Pinme, Dlpmkne. and Pine Oi?
DIPENTENE ZERPENEE
Petroleum
Much attention has been given the other oils besides a-pinene recovered from the dead pine wood. These oils are properly grouped into two elrsses: (1) monncyclic terpenes, prineipally dipentene together with the isomeric terpinenes irnd terpinolene, and (2) a group of oils called “pine oil”. The latter is principally a mixture of tertiary and secondary alcohols and a small amount of a terpene oxide and it phenol e t h e r , methylchwicol. Tlie hydrocarbons of the first group are difficult to separate by distillntion and are sold cornm e r e i a l l y u n d e r the n s m e “dipentene”, as well its numerous trade names. One of the more recent chemical applications of the monocyclic terpene hydrocarbons is the conversion to the corresponding aromatic dehydrogenation- hydrogenation products. One commercial process subj e c t s d i p e n t e n e , terpinene, or terpinolene
October, 1943
INDUSTRIAL A N D ENGINEERING CHEMISTRY
to a liquid-phase catalytic disproportionation to obtain pcymene and p-menthane. The cymene is further treated by liquid-phase oxidation to yield a krt-tolyl-carbinol which is then dehydrated to the cy-methyl-p-methyl-styrene. During this step a portion of the alcohol is dehydrated to the styrene which is oxidized in the process to p-methylacetophenone. An interesting by-product of this process is cumic acid (iopropylbenzoic acid). It was expected that if acids were produced they would be by the oxidation of the is@propyl group rather than the attack on the p-methyl position. Cumic acid is, however, not yet available commercially. These dipentene oils are finding many uses in connection with the war. Besides providing the necessary solvents for a number of Army, Navy, and other specification paints and varnishes, this type of terpene is of special value as a penetrating and softening solvent in rubber reclaiming. They are also the base for the manufacture of terpene ethers which are finding an important application as insecticides. When these monocyclic terpenes were first made, there was no market for them, and the development of uses was the subject of intensive chemical research. As indicated above, that work has been attended by considerable success; it may even be necessary to convert a-pinene to the monocyclic hydrocarbon by isomerization in order to supply the demand. PINE OIL
The pine oil recovered from dead wood, composed primarily of tertiary and secondary alcohols, was in much the same position when this industry was established as were the dipentene oils, One of the earliest uses developed for pine oil waa as a frothing solvent in the then new flotation process for reclaiming low grade copper-, lead-, and zinc-bearing ores. The mining industry is still probably the largest single user of this oil. The high solvent properties of pine oil, together with the polar character of the tertiary alcohols, has resulted in the large use of this material as a solvent and wetting agent in a variety of textile manufacturing and also as solvent lubricant in synthetic fiber production. The pine oils are also widely used as an important ingredient of many disinfectants, insecticides, and deodorants. The natural constituents are recovered by chemical separation and have many important uses. Considerable pine oil is thus processed to produce the “0-terpineol” of commerce which is used not only as solvent but as a perfume base principally for soaps. The process includes the step of dehydrogenating the secondary alcohols, fenchol and borneol, to obtain their corresponding isomeric ketones, fenchone and camphor, Liquid fenchone is a powerful plasticiaing solvent just as is the familiar solid, camphor. The phenol ether, methylohavicol, present in the natural oil is converted to its isomer, anethole, which is largely used because of its licorice flavor. The pine oil manufactured at the present time by the extraction of pine wood has not been sufficient to meet the demand, and in recent years a synthetic pine oil has been produced from turpentine. Chemical pine oil resembles natural oil closely in composition; so here also because of the growing demand the basic terpene oil, a-pinene, is finding a chemical market as the raw material for pine oil. FATTY ACIDS
The other by-products obtained from southern pine kraft consist principally of fatty acids comprising both oleic acids and small amounts of other, more unsaturated vegetable acids, such as linolenic and linoleic, and also rosin acids. These crude vegetable fatty acids and rosin are available in the wood in considerably larger quantity than the terpenes and, with the growing demand for all fats, could make a sub-
1025
stantial contribution to the much needed supplies of fatty oils. This product is sold commercially under the name “tall oil”; that being manufactured at present is, for the most part, only partially refined. A large amount of these crude fatty acids was produced by the paper mills last year, including the rosin acids which make up about 40 per cent of the total; if they had all been refined and separated from the rosin acids, a huge quantity of liquid fat would have become available for use as soaps and possibly as paint and varnish vehicles and many other uses. Edible fats now being used solely for industrial purposes would thus have been released. DESTRUCTIVEDISTILLATION PRODUCTS
I n the destructive distillation process the natural oils and decomposition products of the rosin acids, cellulose, and lignin are recovered as a crude oil. This tar oil is then separated by chemical treatment and fractional distillation into several light solvent oils and light and heavy pine tars. The 1 solvent oils are further refined into various fractions, such as toluene and xylene containing solvents, as well as turpentine, dipentene, and finally pine oils. These terpene oils have certain characteristics which usually identify them with this process. All of the oils have a large number of uses as solvents in a number of industries, including paint, varnish, lacquer, and rubber jeclaiming. The pine oils and lighter pine tar oils were among the first to be employed in the solvent ore-flotation development, and ti considerable amount is still ueed for that purpose. These oils are also widely used because of their medicinal, disinfectant, and deodorant properties. Pine tars occupy an important position in the rubber industry where they have been used for many years as a plasticizing antioxidant component of natural as well as reclaimed rubber goods. ROSIN OILS
The resin base, rosin, from which the solvent turpentine oil has been separated, cannot be disregarded when solvents from the pine tree are being considered. An old and important use for rosin is in the manufacture of rosin spirits and oils by destructive distillation; these oils have a wide variety of application as solvents and lubricants and for special paints and other compounds of particular importance now in shipbuilding. Recent figures on the production of these oils in this country show the quantity produced annually as nearly equal to the amount of turpentine consumed industrially in paint and varnish. ISOPRENE
Any discussion of the role of terpenes in solving important chemical problems of the war would hardly be complete without a t least mention of the fact that substantial amounts of isoprene are being produced from terpenes. The extent of this development is not available as public information. The importance of isoprene to the chemical rubber program has been described elsewhere and need not be re-emphasized here. Incidentally, some unsaturated solvents which largely boil in the toluene-xylene range, as well as some film-forming solvent materials, will probably be available as by-products from the isoprene operation. It has been possible to give only a limited survey of the production and uses of solvents from the pine tree. The total quantity of the primary products discussed is relatively small compared to the total volume of solvents produced by the petroleum, coal tar, and fermentation industries, but the wide variety of applications has indicated the importance of the contributions being made by this industry to the over-all prosecution of the war.
