INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY Fieldner et al., Bur. Mines, Tech. Paper 479 (1930). Fiecher and Lessing, "Conversion of Coal into Oils," Van Nostrand, 1925. Fischer and Zerbe. Brennstoff-Chem.. 4. 853 (1923). Fleissner, Trans. Fuel Conf.; World Power Conf., London, 1928, 1, 328 (1929).
Francis and Morris, Bur. Mines, Bull. 340 (1931). Gauger and Iverson, Quart. J . Univ. N . Dak., 20, No. 4 (1930). Gauger and Salley, Proc. 2nd Intern. Conf. Bituminous Coal, 1 , 312 (1928).
Gauger, Taylor, and Ulmen, IND. ENG. CHEM.,24, 36 (1932). Gordon, Lavine, and Harrington, Ibid., 24, 928 (1932). Harris, Beloher, and Gauger, Ibid., 23, 199 (1931). Holmes, U. S. Geol. Survey, Bull. 290 (1905). Jeffrey, M e m . Am. Acad. Arts Sci., 15, No. 1 (1924). Kersrhbaum, Proc. 2nd Intern. Conf. Bituminous Coal, 1 , 284 (1928).
Koth and Lavine, IND.ESO.CHEM.,25, 328 (1933). Ibid., 25, 570 (1933). Lavine and Gauger, Ibid., 22, 1226 (1930). Lavine, Gauger, and Mann. Ihid., 22. 1347 (1930).
(40) (41) (42) (43) (44) (45) (46) (47) (48) (49) (50) (51) (52) (53) (54) (55) (56) (57) (58)
Vol. 26, No. 2
Lessing, J. Gas Lighting, 127, 570 (1914). Marson and Cobb, Gas J.,39, 171 (1925). Mumford, U. S. Patents 1,268,187 and 1,287,592 (1918). O'Keefe, Wesfern Can. C o d Rev., 15, No. 8, 4 (1932). Parr and Kreesman, Univ. Ill., Bull. 46 (1910). Parr and Wheeler, Ibid., 38 (1909). Phillips, Univ. Texas, Bull. 189 (1911). Phillips and Worrell, Ibid., 307 (1913). Porter and Ralston, Bur. Mines, Tech. Paper 113 (1916). Randall and Kreisinger, Bur. Mines, Bull. 2 (1912). Reits, M. S. Thesis, Univ. N. Dak., April, 1931. Schoch, U. S. Patents 1,508,617 (1924), 1,574,174 (1926). Thompson. Phil. Mag., 4, 42, 448 (1871). Tropsch, Chem. Rev., 6, 63 (1929). Tryon, Mann. Rogers, Bur. Mines, Mineral Resources of the u. s.,1930, Pt. 11, 599-773. White, Bur. Mines, Bull. 29 (1911). White and Thiessen, Ibid., 38 (1913). Wright, Ibid., 58 (1913). Zsigmondy, 2. anorg. allgem. Chem., 71, 356 (1911).
RECEIVEDAuguat 31. 1933.
The Hydrogenation of Coal C. C. WRIGHTAND A. W. GAUGER Mineral Industries Experiment Station, The Pennsylvania State College, State College, Pa.
T
During recent years the subject of coal hydrogenated or mineral oil dispergenation has aroused much interest in the ScientiJic sion medium, (2) hydrogenation mand for l i q u i d f u e l s d u r i n g r e c e n t years, u s i n g other dispersion media, world. The development of high temperaturecoupled with the dirth of natural and (3) hydrogenation in the petroleum resources in certain high Pressure hydrogenation and its application absence of dispersion media. industrial countries rich in coal to coal by Bergius has provided the chemist with r e s e r v e s , has resulted in exa new weapon for attacking the problem. THEORETICAL IXVESTIGATIONS research upon methods Of theoretical interest are the numerous inAs early as 1911, Bergius (31, for converting coal into oil. A vestigations dealing with the relationships bewhile investigating the thermal consideration of the u l t i m a t e composition of various typical tween the Physical and chemical Properties Of d e c o m p o s i t io n of heavy oils coal and its susceptibility io hydrogenation, the under hydrogen pressure, p!ofuels, both solid and liquid, indieffects of varying conditions upon hydrogenation, duced a petroleum spirit consistcates that the mature coals are partial hydrogenation and its effect upon coking ing essentially of saturated hyr i c h e r i n available hydrogen' than the younger fuels, and that drocarbons. Shortly thereafter properties, and hydrogenation as a means of inthe same process was applied gasoline is richer in available hydrogen than the heavy tars VeStigUting the Constitution Of Coal. to an artificial c o a l p r e p a r e d From the commercial standpoint, interest from cellulose, yielding a product and fuel oils. It should be centers around the &uelopment of the original similar to petroleum. The next possible, therefore, to produce step, hydrogenation of natural ~~~~i~patents to the stage of plant-scale operaliquid fuels from solid fuels by coal, soon followed. a d d i t i o n of hydrogen to the tion, the application of catalysts and promoters, I n August, 1914, Bergius (2) latter. the &VelOPment of the two-phase Process for patented a noncatalytic procThe first recorded attempt to producing lube oil and gasoline substitutes, and ess for the treatment of coal or hydrogenate coal was made some the economic s t a t u of the commercial process o t h e r carbonaceous residue to sixty years ago by Berthelot ( 5 ) , obtain oils, ammonia, and other who treated finely div.ided coal at the present time,both in ~~~~i~~ and abroad. with a saturated hydriodic acid products. Briefly, the process consisted of subjecting the coal solution a t 270" C. (518" F.) for several hours, and found that over 60 per cent of the or other substance, a t a temperature between 300" and 500" coal substance was converted into liquid hydrocarbons. The C. (572" to 932" F.) to the action of hydrogen a t pressures method was devoid of commercial significance and appears above 10 atmospheres. Later, more detailed descriptions of the process (4) into have aroused little or no scientific attention. Thus the matter stood, a scientific possibility but a commercial im- dicated the use of pressures of about 200 atmospheres, and probability until the discoveries of Bergius less than twenty- the mixing of the charged coal with a pasting oil or dispersion medium consisting of the heavier fractions from a previously five years ago. Some of the experimental investigations which, in part, hydrogenated oil or tar. A Luxmasse, consisting essentially have been responsible for this remarkable development, of ferric oxide, and claimed to be noncatalytic, was also are arbitrarily classified under three headings as follows: added, to facilitate removal of sulfur. The first hydrogena(1) berginization or destructive hydrogenation using a hydro- tions were carried out in a small stationary retort equipped with a stirring device, but later a rotary retort was used. 1 Available hydrogen = %H - % '' -3z%N (all figures on moisture- and The yield of petroleum-like products varied between 40 and 8 14 70 per cent by weight, depending upon the nature of the ash-free basis). HE greatly increased de-
I N D U S T R I A L A N D E N G I N E E R I N G CH E MI ST R Y
February, 1934
original coal, and hydrogen absorption varied between about 3 and 5 per cent. Numerous investigations have been conducted by other workers upon the physical conditions for the noncatalytic production of gasoline from coal using essentially the original Bergius methods. The following summary includes a few of the more significant. LAszl6 (29) found optimum conversions for Italian lignite a t 470" C. (878" F.) and with initial pressures of 140 to 150 atmospheres. T'arga (43) obtained maximum conversion of brown coal a t 470" C. and an initial pressure of 100 atmospheres. Oshima and Tashiro (35) studied both the quantity and the quality of the oils obtained from Japanese coals, and found that temperature,. pressure, time of reaction, nature of original coal, and purity of the hydrogen all played an important role in the character of the final product. Levi, Padovani, and blariotte (30) from their studies on Italian coals, conclude that the hydrogenation occurs in three stages: (1) Up t o 300" C. (572" F.): transformations without formation of gas or vapor, with only slight hydrogen absorption, and with high yelds of extractable compounds possessing a marked tendency toward polymerization. (2) 350" t o 400' C. (662" to 752" F.): hydrogenation principally in the liquid phase, corresponding somewhat to destructive distillation, and resulting in almost complete liquefaction of the coal. (3) 400" to 500" C. (752" to 932" F.): cracking of more resistant molecules with hydrogenation essentially in the vapor phase.
Hlayica (25) conducted a similar investigation on Bohemian brown coal and reached a somewhat similar conclusion, defining the three stages as follows: (1) 300" t o 400" C. (572" to 752" F.): production of an asphaltic-like mass with very rapid absorption of hydrogen and formation of water from the oxygenated molecules of the coal. (2) 400" to 450' C. (752" to 842" F.): moderate absorption of hydrogen by the originally formed asphaltic mass and complete liquefaction of the coal. (3) 450" to 500" C. (842' to 932" F.): severe cracking of the hydrogenated products with formation of gaseous and low-boiling products.
The isolation and identification of the products from the berginization of coal are problems that have attracted the attention of many investigators. Of these researches, the following are typical examples: Stadnikov (41) berginized boghead coal and obtained by distillation of the resulting oil a number of low-boiling fractions from which were isolated cyclic and bicyclic hydrocarbons, phenols, and neutral cyclic and polycyclic oxygenated compounds. Pertierra (34) obtained an oil consisting of 59.8 per cent neutral oils, 32.0 per cent phenols, and 8.2 per cent bases. The neutral oils contained 52.0 per cent aromatic, 28.7 per cent paraffinic, and 7.3 per cent unsaturated hydrocarbons. The phenols contained phenol, 0- and m-cresol, and pyrocatechol; in the bases, pyridine and dimethylpyridine predominated. Ormandy and Craven (32),investigating the oil from berginized bituminous coal, isolated over fifteen pure compounds, including benzene and its homologs; N - and isoheptanes, hexanes, pentanes, and butane ; and cycloparaffins. Von Makray (31) berginized brown coal and obtained an oil yield of 45.6 per cent. A material balance showed the following interesting relationships: C
In oil In gas In residue
In other forms
%
H
%
0
%
'h
%
S %
53.4 29.8 15 as phenols 31.4 as bases .... 21.7 21.8 46 as Cot .... 24.6 Remainder 36.6 as Hz0 Remainder .. .. a8 H20 Gaseous 41 a8 NHa 97.6 as FeS hydrocarbons and residue
..
....
165
Heyn and Dunkel ($4) berginized a low-rank coal with an ash content of 17.7 per cent and a volatile matter content of 28.5 per cent, and obtained 36.45 per cent oil. Investigation of the oil showed 75.5 per cent neutral oils, 2 per cent phenols, 3.5 per cent bases, small quantities of organic acids and resins, and the remainder residue. From these fractions about twenty pure compounds were isolated, of which the following predominated in each group: Bases: aniline, toluidine, and xylidine. Phenols: o- and m-cresol, xylenol, and phenol. Oils from stripped gases: benzene and homologs together with hexahydro- derivatives. Light neutral oil: essentially aromatics. Higher neutral oil fractions: naphthalene and hydro- derivatives. Solid residue : small percentage of paraffin hydrocarbons and remainder aromatics (phenanthrene, etc.). With regard to the application of catalysts to coal hydrogenation, reference should here be made to the comprehensive summaries of the patent literature which have been published by Ellis (24))Gall6 (I?'), Rosendahl (38), and Skinner (400). According to patent claims, it appears that virtually all the oxides, chlorides, sulfides, sulfates, and carbonates of the common metallic elements exert a catalytic influence upor1 the process. Aside from patents, however, the number of published investigations is relatively small. Experiments by the British Fuel Research Board have demonstrated that ferric oxide itself exerts a mild catalytic effect, while the Luxmasse of Bergius is quite an active catalyst. Since the Luxmasse was supposedly iron oxide, although obtained by extraction of alumina from bauxite, the investigators were led to the discovery that the active ingredient in the Luxmasse was titanium oxide which occurs in small percentages in the natural substance and appears to exert a promoter action. Studies by Bowen and Nash (7) showed nickel oxide to be superior to Luxmasse, and ammonium molybdate to be the most active catalyst tested. Hlavica (85) compared the effectiveness of zinc, nickel, cobalt, and copper compounds with that of iron oxide and found 30 to 100 per cent increases in yields, zinc chloride apparently producing the best results. Tashiro (42) studied the use of the oxides of nickel, zinc, iron, copper, manganese, and aluminum, and found that nickel oxide decreased the iodine number of the products to 12 per cent of the original value. Zinc oxide and ferric oxide to a lesser extent produced the same result. The oxides of copper and of manganese were without influence, while alumina furthered the decomposition. A similar investigation by Levi and co-workers (SO) showed that nickel oxide did not, as claimed, lower the effective reaction temperature but did lower markedly the required reaction time. Mixtures of nickel and iron oxides proved more effective than either catalyst individually. Because of the difficulties inherent in the separation of coal hydrogenation products from the pasting oil and its decomposition products, and because of the relative uncertainty of the role played by these oils in the reaction, a number of investigators have resorted to the use of other dispersion media. Usually some pure chemical compound was chosen which could be separated readily from the reaction products, and which was itself inert to the action of hydrogen under the conditions involved. As typical of this method of attack, the following may be cited: The investigators a t the Mines Research Laboratory, Birmingham, England (19), after encountering the aforementioned difficulties, decided upon the use of phenol and developed a product separation based upon solubility in phenol and chloroform, Twenty-nine coals varying in rank from lignite to anthracite were hydrogenated. Satisfactory conversions were obtained in all cases except for the anthracites. Contrary to the early views of Bergius, they obtained excellent yields with coals having a carbon
166
e
1 1 - D U S T R 1.4 L A N D E N GI N E E R I S G C H E ,M I S T R Y
content greater than 85 per cent. Attempts to correlate the hydrogenation yields with other known properties of the coal were, however, without success. Beuschlein and co-workers (6) used phenol, anthracene, and diphenyl as dispersion agents and concluded that the use of pure solvents followed by a product separation based on methods differing from those of commercial practice gives little or no indication of the industrial adaptability of a coal to berginization. A somewhat similar conclusion may be drawn from the research conducted by investigators of the Research Council of Alberta (86) who found that the conversion obtained by hydrogenation of various coals in phenol, tetralin, petrolatum, bitumen, etc., were largely functions of the dispersion agents used, tetralin proving the most effective. Despite the lack of commercial applicability attending this type of investigation, it is, nevertheless, a promising field for studies upon the constitution of coal and upon the mechanism of coal hydrogenation reactions. A number of workers, attempting to eliminate entirely the difficulties inherent in the use of dispersion media, have experimented in the absence of any such agent. Fischer and eo-workers (15) have conducted a long series of investigations in this field, some of which were begun even before the discoveries of Bergius became public. Modifying Berthelot's original experiments by the addition of red phosphorus to the reaction mixture of hydriodic acid and coal, Tropsch (16) obtained yields as high as 70 per cent and found that in general the geologically young coals were most susceptible to hydrogenation. Using mater gas, sodium formate, carbon monoxide-steam mixtures, and sodium carbonate with niolecular hydrogen, as sources of nascent hydrogen, these investigators succeeded in obtaining appreciable conversions of the coal. Experiments were conducted in many cases upon the separation and isolation of compounds from the products, and it is of interest to note that here again, as in investigations on direct berginization products, the compounds isolated were essentially aromatic in nature. The action of molecular hydrogen in the absence of dispersion media has been investigated by Shatwell and Kash (Sg), who reported unsatisfactory results when tried on bituminous coals. Varga (@), von hlakray (SI),and Fischer (15) working with brown coals, however, all report fairly satisfactory yields of oil products under berginization conditions. An important aspect of coal hydrogenation in the ab;'ence of dispersion media, which for many years escaped notice, is that of partial hydrogenation. It was not until 1923 that investigators of the British Fuel Research Board (12) discovered the remarkable effect this treatment had up011 the coking properties of a coal. While making a study of the intermediate products formed a t temperatures below 400" C., i t was observed that marked changes occurred in the nature of the coal, although little or no oil was produced. Suhsequent research on a series of coals ranging from peat to anthracite shoxed that the coking properties of all bituminous coals were greatly improved by this treatment. The process of partial hydrogenation consists of heating the coal, under about 200 atmospheres hydrogen pressure, to a temperature of 300" to 400" C. (520" to 752" F.), The exact temperature is a function of the original coal, and once attained the heating is discontinued. The product usually has a somewhat pitchlike appearance as though fusion had occurred. Water is produced in small quantities, together with traces of oil. The hydrogen absorption varies between 1.5 and 0.5 per cent by weight of the coal treated. A similar investigation by the Mines Research Laboratories, England (ZO), shows the same general results and indicates that the production of a coke from anthracite may be possible by treatment a t more elevated temperatures. An investiga-
Vol. 26, No. 2
tion of some American coals by Yancey and Wright (4) has shown that oxygen-free hydrogen, correct degree of agitation, and closely controlled rate of heating are essential in obtaining optimum results. Summarizing briefly the results of experimental investigation, we find that with the exception of Berthelot's original experiments, all advances in the field of coal hydrogenation have been accomplished in the past two decades. Using no catalyst other than the Bergius Luxmasse which was supposedly added for the sole purpose of sulfur removal, numerous investigators have successfully berginized coals varying in rank from lignite to semi-bituminous. Studies of the oils produced by berginization have proved them to be essentially aromatic, although under certain conditions relatively high yields of paraffinic compounds may be obtained. Catalytic studies seem to indicate that compounds of molybdenum, nickel, and zinc are the most effective for this process. Experiments, using dispersion media other than the commercially used hydrogenated oils and basing estimates of conversion upon the yields of various extractable fractions, appear to be of little or no assistance in predicting the adaptability of a coal to the industrial process. Although of marked scientific interest, the use of nascent hydrogen has led to no commercial developments. The discovery of partial hydrogenation and its effect upon the coking properties of coal is relatively new and no industrial applications have been made of the process.
INDCSTRIAL DEVELOPMENT Development from an experimental-scale batch process to a commercially feasible plant-scale operation was a problem of no mean dimensions. Industrial high pressure-high temperature processes were still in their infancy, and many of the problems confronting the pioneers of this process were unique. A few of the major factors involved include the following: (1) Conversion from batch to continuous operation. Development of construction materials to withstand
(2)
temperature, pressure, and corrosion. (3) Prevention of local heating and control of temperature. (4) Manufacture of cheap hydrogen. ( 5 ) Development of nonpoisoning catalyst and promoters. (6) Separation and treatment of products.
It is to the economic solution of these and related problems that we owe the commercial development of the process to its present status. Unfortunately, as is true with most technical processes, the actual details of commercial operation are either guarded as trade secrets or so camouflaged in patent specifications that accurate information on the process is unobtainable. I n a general way, however, a few of the major advances have been made public. CONVERsION FROM BATCH TO CONTINUOUS OPERATION. Early in the development of Bergius' work i t was found that a rotary retort was superior to the stationary type with stirrer, because, in addition to acting as a stirring device, it facilitated more uniform temperature control. Since Bergius had from the first used a pasting oil, the next step in th-e conversion to a continuous process was relatively simple. It involved only suitable devices for pumping the paste into the converter at reaction pressure and for removing the hydrogenated products still under pressure a t the exit. To facilitate handling and treatment of the pasty mass of oil and powdered coal, the charge passes through preheaters before being forced into the converter. The products of hydrogenation together with unconverted pasting oil and coal are cooled to increase the viscosity before passing through a valve giving access to a chamber a t atmospheric pressure. Hydrogen is supplied and the gaseous products are remored through separate valves.
February, 1934
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167
COSSTRUCTIOS UATEHIALS. Owing largely to the rapid use. This shortening of the effective life was traced to two growth of the synthetic ammonia process, high-pressure causes (21): first, preferential adsorption by the catalyst of the technic had already reached an advanced degree of perfection, heavier molecules present in the raw materials, resulting in but it was soon discovered t,hat berginization presented a new exclusion of other molecules from the catalytic reaction zone; problem. Instead of dealing with two highly purified gases and secondly, dehydrogenation and polymerization of the in a stationary system, the new process called for the treat- heavier molecules of the reaction products because of the ment of ?olid, liquid, and gaseous reactants in a moving high partial pressure of the hydrogenation products. To system. Research on alloy steels resulted in the develop- obviate these difficulties the process has been divided into ment of *everal products satisfactory for commercial opera- stages. I n Germany three stages are used while in Great tion (26, @), Those containing high percentages of one or Britain the tendency has been to employ only two. The niore of the metals chromium, cobalt, molybdenum, tungsten, stages of the German process (37) are, respectively: vanadium, manganese, or the metalloids horon, silicon, arsenic, and antimony, proved most satisfactory. illurninurn (1) Hydrogenation in the liquid phase of the oil-coal paste (716' to 860' F.) and alloys of the same metals have recently been patented by at temperatures between 380' and 460" C. at pressures of 200 to 250 atmospheres. The reaction is arrested I. G. Farbenintluqtrie (27) and are claimed to be superior to at a point where the h a 1 product is mainly heavy oil [boiling the alloy -teels. point, 325" C. (617" F.) or above]. HEATAPPLIc.4nos IND TEMPER ITURC CownoL. Closely (2) Hydrogenation in the liquid phase of the heavy oils t o related to the selection of satisfactory construction materials produce a middle oil [boiling point, 180" t o 325" C. (356" to 617" F.)]. A temperature of about 450" C. (842" F.) and a is the problem of applying heat and maintaining accurate pressure of about 250 atmospheres are maintained in this stage. temperature control. By jacketing the converter, and cir(3) oVapor-phase hydrogenation of the middle oil at 500' culating in the jacket hot inert gases such as nitrogen or to 520 C. (932" t o 968" F.) and a t the same pressures as before carbon dioxide a t a pressure slightly below that in the con- to produce light oils. verter, both problems were greatly simplified (14, @). The I n the British process (37) the two liquid-phase treatnients converter walls could then be made of alloys highly resistant are combined and the throughput so regulated that the prodto the corrosive action of the reactants a t the high temperature involved, while the jacket could be made of alloys selected uct is essentially middle oil with just sufficient production of for their pressure-resisting qualities a t high temperatures. heavy oil for pasting purposes. The final stage is the same in Moreover, this method of heating lends itself to very close both processes. Separation of the process into stages serves to eliminate tempsrature control. Early commercial plants of this design have succeeded in maintaining the temperature constant both of the aforementioned difficulties. I n the liquidwithin 5' C. (9" F.) for weeks of continuous operation, and phase treatment, hydrogen concentrations of 70 per cent can in recent inqtallations even better control is claimed. Local be satisfactorily maintained and the catalyst is not called heating, which was a major source of trouble in early work, upon to activate reactions producing light oils; in the vaporphase treatment, a hydrogen concentration of over 85 per is completely eliminated by this form of construction. MANUFACTURE OF CHEAPHYDROGEN. It is estimated cent can readily be maintained, and the dehydrogenation that approximately 40,000 cubic feet of hydrogen are required and polymerization of the reaction products are thus preper ton (1.24 cubic meters per kg.) of bituminous coal treated. vented. The catalysts used for the liquid-phase hydrogenation From an economic standpoint, therefore, the cheap production of this gas in large quantities is an all-important factor depend somewhat upon the nature of the raw materials and for industrial success. Fortunately coal hydrogenation, are usually added in admixture with the oil-coal paste. Imunlike the synthetic ammonia and methanol processes, does pregnation of the coal prior to pasting with the oil has proved not require highly purified hydrogen. A successful process satisfactory but offers no advantages over the usual method. has been developed which depends basically upon the follow- For the vapor-phase hydrogenation the catalyst is suspended ing chemical reactions in the presence of a catalyst (18): inside the converter, and the selection is based upon the nature of the final product desired. By careful control of temperaCHI HzO +3Hz CO at 1100' C. (2012' F.) (1) ture, pressure, catalyst, and time of reaction, it is possible CO H 2 0e Con H Pat 700' C. (1292" F.) (2) to produce light oil ranging from one that is completely aromatic to one essentially paraffinic in nature (18). Ethane reacts similarly. SEPARATION AND TREATMENT OF PRODUCTS. A brief Although minor modifications are in vogue, the process consists essentially of subjecting the stripped gaseous products of description of the present-day process for the production of berginization to the aforementioned reactions. Any de- motor fuels from coal serves as an excellent summary of ficiency of hydrogen is made up by addition of water gas. the progress made since the day of Bergius' laboratory-scale Since the unconverted solid residues from berginization are batch process: Powdered coal is mixed with the required used for steam raising, the production of hydrogen becomes weight of heavy oil from a previous hydrogenation, and the self-sufficient and utilizes the two major by-products from the suitable catalysts are incorporated. The pasty mixture is main process. then pumped into a preheater where the temperature of the CATALYSTS AND PROMOTERS. Because of the great secrecy paste is brought to that in the liquid-phase converter, usually which surrounds the actual catalysts and promoters com- about 425" C. (797" F.). In the preheater, care is taken to mercially used, little information on this score is available. prevent local overheating. The coal under this treatment It is known, however, that the development of nonpoisoning becomes highly swollen. The major portion disperses in the catalysts has resulted in the extensive use of metallic sulfides, oil, and the whole mass becomes fluid. The charge is then especially those of molybdenum, tungsten, and cobalt. More forced into the converter a t about 200 atmospheres pressure. recently the use of the metals and compounds of iron, nickel, Rotation of the converter serves to keep the mass well agicobalt, molybdenum, and tungsten in the presence of gaseous tated, thus preventing both local overheating and settling out hydrogen sulfide has been recommended ( I S ) . The advan- of catalysts and coal particles. tages claimed for this latter procedure are increased activity The nongaseous products from this stage are separated and life of the catalyst. by distillation, leaching, and centrifuging into light, middle, I n the industrial application of catalysts to berginization, and heavy oils, plus an unconverted residue. Light oils go i t was divoyered that their activity diminished rapidly with directly to the refinery, heavy oils are recycled as pasting oil,
++
++
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INDUSTRIAL AND ENGINEERING CHEMISTRY
and middle oils pass to the vapor-phase converter. The solid residues are used for steam raising, and the steam is employed for converting the stripped gaseous hydrocarbons to hydrogen. I n the second stage the middle oils are cracked and hydrogenated. By careful control of temperature and a judicious selection of catalysts, it is converted almost entirely into the desired product with very little formation of gas. The products are separated by distillation, and any unconverted oil is recycled. The light oil or gasoline fraction is combined with that from the first stage and undergoes a light chemical treatment, after which it is ready for marketing. This refined product is a high-grade, lorn-sulfur, water-white motor fuel of high octane rating. T o obtain products other than gasoline by berginization, modification of the conditions in the final stage of the process are required. It is claimed that lubricating oils have been manufactured successfully in Germany by hydrogenation of brown coal and brown-coal tars (11). For the production of Diesel and fuel oils, the process has not proved entirely satisfactory, owing largely to the fact that the middle oils produced by hydrogenation are not paraffinic. Recent reports from the Imperial Chemical Industries, Ltd., indicate that by the application of new catalysts this difficulty will soon be overcome (18). Commercial exploitation of the berginization process has, of course, been limited to those countries poor in petroleum resources. I n Germany and the central European countries where brown coals are abundant, the process is usually applied to low-temperature, brown-coal tars rather than to coal directly, These countries have only limited resources of high-rank coals, and as a result there is a ready market for semicoke. Moreover, low-temperature tars being richer in hydrogen content than the original coal are more easily and cheaply berginized. For economic reasons, therefore, i t has been the natural tendency to stress development of tar berginization. I n 1921 a 30-ton (27-metric ton) per day plant a t Rheinau, and in 1928 a 100-ton (90.7-metric ton) per day plant a t Duisberg were constructed for the direct berginixation of coal. The process was found uneconomical, however, and both plants were closed (37). I n 1932 three plants were in operation in Germany hydrogenating brown-coal tars, and about 1,000,000 barrels (159,000,000 liters) per year of gasoline were being produced from this source (37). Recent development of improved catalysts by I. G. Farbenindustrie has resulted in a return to the direct hydrogenation of brown coal. The large Leuna hydrogenation works and several small plants are now hydrogenating brown coal on a large scale (10, 11). More detailed information has recently been made available with respect to the situation in Great Britain. Because of the extensive deposits of high-rank coal in Britain, the production of semicoke is not so profitable an undertaking as on the continent, and, as a consequence, exploitation of the process has tended toward the direct conversion of bituminous coals into oil. Industrial development of berginization in Great Britain may be attributed largely to the early work of the Gas Light & Coke Company, the Fuel Research Board, and more recently to Imperial Chemical Industries, Ltd. The latter has carried the development to the stage of full-scale commercial operation. The Billingham plant of Imperial Chemical Industries has now been in operation for several years. I t is operating as a two-stage process and has a throughput of 15 tons (13.6 metric tons) of coal per day. It is claimed that between 80 and 93 kg. of refined gasoline are obtained from 100 kg.
Vol. 26, No. 2
of moisture- and ash-free coal (18). The hydrogen absorphion is between 4.5 and 7 per cent of the weight of coal, the overall coal consumption is 3.15 tons for each ton of gasoline, and thermal efficiency is between 40 and 43 per cent, all figures being on the ash-moisture-free basis (18). Based upon a figure of $3.10 per ton for the coal, the cost of gasoline production (including fixed charges, depreciation, etc.) amounts to 14 cents per Imperial gallon. For several years, motor fuel produced in Great Britain from coal (by carbonization processes) has enjoyed a preference of 16 cents per Imperial gallon in the form of an import duty on petroleum products (8). This preference, however, was fixed yearly by Parliament with no guarantee of its continuance. This year (1,22),largely with the hope of stimulating the production of motor fuel by berginization of coal and thus bolstering a waning coal industry, Parliament passed a bill which guarantees an 8 cent Imperial gallon preference for a period of ten years beginning April 1, 1934. With such a guarantee, Imperial Chemical Industries feel justified in carrying out their plans of a large commercial unit for direct coal berginization (1). The proposed plant, construction of which has already been authorized, is to cost approximately $11,000,000. The estimated annual coal consumption will be 1,000,000 tons (907,000 metric tons) and the actual throughput 350,000 tons (317,000 metric tons). The production of refined motor fuel is expected to be 30,000,000 Imperial gallons (136,000,000 liters) per year, which is equivalent to about 2.5 per cent of the total domestic consumption. Based on data obtained from the Billingham plant, the maximum cost of production should not exceed 14 cents per Imperial gallon (28). To an American such a production cost sounds prohibitive. I n Great Britain, however, where wholesale costs of gasoline, exclusive of the tax of 16 cents per Imperial gallon, have ranged from 56 cents per gallon during the war to about 8 cents a t the present time, and where the average during normal business conditions is about 25 cents per gallon, the project appears quite feasible. With respect to the possible exploitation of berginization in America, i t is necessary to consider several possible angles. As is well known, the Standard Oil Development Company (9,23) is at present engaged in the commercial hydrogenation of petroleum oils and residues, and there seems every liielihood of continued development in this field. The probability of direct coal hydrogenation becoming a competitor with natural petroleum production seems remote because present production costs far exceed the value of the petroleum substitutes obtained. It is unlikely that this production cost could be lowered sufficiently to make exploitation feasible. Hydrogenation of high-temperature tars has not to date proved successful even in Europe, mainly because of the nature of the tars, Hydrogenation of low-temperature tars, however, is fairly well established in Germany. Low-temperature carbonization processes in America have thus far proved to be rather unsuccessful ventures (35). Should the process ever attain a sound footing, however, it is not unlikely that hydrogenation of the tars will prove an important factor in the economic development. As a final possibility there is the application of berginization to coal or tars for the production of products other than motor fuels, such as solvents and fine chemicals. This field has been virtually neglected up to the present, despite the fact that i t would appear to be one of the most promising of the profitable phases of berginization. It is to be hoped that in the near future more extensive research will be conducted upon this phase of the process and will lead to the development of new industrial applications of intrinsic value to the coal industry of America.
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February, 1934
INDUSTRIAL AND ENGINE ERING CHEMISTRY
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END OF SSMPOSIWM
BLASTING ROI CK Ih’ BLACKCANI!Oh-,
PART OF THE WORKPRELIM .INARY TO THE CONSTR ~UCTION OF BOULDERDAM, A
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Courtesy, Dorr Cornpanu, Inc.
