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by crystallization during aging of a film may be demonstrated by x-ray examination of films failing upon aging. It is shown by film 74 that when an iron soap already prepared is added to linseed oil in an amount equivalent to the usual amount of ferric oxide in other films a much larger increase in density occurs than in the films with oxide drier. .This is partly an effect of hastening a change which later ensues in the oxide films. The soap separates and causes difficulty only in extreme aging. If, then, aging or oxidation could be inhibited, such failures might be prevented. EFFECTOF ImmITOEts-This is shown in a preliminary way in sample 55. After 32 hours’ sunning the increase in density is nearly the same with the two inhibitors, but after an additional 3 months’ aging an appreciable difference is apparent. For while the film without inhibitor increases 3.28 per cent in density, the further increases with inhibitors are smaller. A suitable inhibitor should act in just this way -enable thorough drying and setting of the film and stop excessive overaging and oxidation. The effects are very evidently manifested by the simple density measurements. l\IECHASIShX O F FAILi:RE--Without recourse to Complex chemical changes occurring in the drying of linseed oil films, the foregoing measurements point to a mechanism, already suggested by previous experimental work, of failure in such films upon aging: stresses and strains are set up throughout the film as a result of unequal contraction of surface and inner layers and also the non-homogeneity of the film, which is caused by the formation of metallic soaps which subsequently crystallize in layers producing still larger stresses. Certainly density changes continue with natural aging after both sunning and ultra-violet treatment, and there is an important time factor for reaching equilibrium independent of methods of accelerating those chemical and physical changes which take place. From these preliminary studies it may be concluded that density measurements may be considered a valuable research and control method in problems of the drying oils. Summary of Results
Accurate density measurements are made by the flotation method on a large number of thin films of linseed oil after a
627
constant preliminary baking treatment which permits solidification. These films and the characteristic density changes, which are usually increased, illustrate the effects of presence, amount, and type of drier; the effect of sunning and weathering, of ultra-violet aging, of ozonization, and of natural aging in darkness; the influence of thickness on density and volume change; the effect of superposing two thin films as compared with a single film; the effect of addition of metallic soaps; and of the effect of inhibitors. Of interest are the great sensitiveness of thickness, since the thinner the film the greater the density increase in a given time; the large change of the upper as compared with the lower of the superposed films during sunning, and the equal change in ultraviolet irradiation; the large increases after more than 3 months’ exposure t o weathering accompanying failure. -4mechanism of failure of linseed oil films independent of complex chemical changes is indicated by the density data: stresses and strains are set up throughout the film as a result of unequal contraction of surface and inner layers (except with ultra-violet aging), and also because of the non-homogeneity caused by the formation of metallic soaps which in extreme aging may crystallize with disastrous results. Linseed Oil Research Reported in Industrial and Engineering Chemistry since 1911 Brier and Wagner, 20, 759 (1928). Chataway. 19, 639 (1927). Eastman and Taylor, 19, 896 (1927). Evans, Marling, and Lower, 18, 1229 (1926). Evans, Marling, and Lower, 19, 640 (1927). Larsen and Young, 17, 277 (1925). Long and Amer, 18, 1252 (1926). Long and Egge, 20,809 (1928). Long, Egge, and Wetterau, 19, 903 (1927). Long, Knauss, and Smull, 19, 62 (1927). Long and Moore, 19, 901 (1927). Long and Wentz, 17,905 (1926). Long and Wentz, 18,1245 (1926). Long,Zimmermann, and Nevins, 20, 806 (1928). Rhodes and Cooper, 17, 1255 (1925) Rhodes and Goldsmith, 18, 566 (1926). Rhodes and Mathes, 18, 30 (1926). Stutz, 19, 897 (1927). Stutz, Nelson, and Schmutz, 17, 1138 (1925). Thurman and Crandall, 20, 1390 (1928).
A New Contact Sulfuric Acid Process‘ A. 0. Jaeger THESELKIEX COMPANY, PITTSBURGH. PA.
An ideal temperature control, both in vertical temperature gradient and uniformity of temperature in horizontal sections, is for the first time obtained by the new converter system. The new contact masses are more efficient from a standpoint of catalytic activity and overload capacity than the best commercial platinum catalysts and are completely immune to poisoning by gaseous poisons for platinum. The new process is peculiarly suited for the solution of the difficult problems encountered in plants using smelter gases. For the first time in the history of sulfuric acid in the United States a contact sulfuric acid plant is able to produce acid so cheaply that when diluted to chamber acid strength it is cheaper than acid produced by the chamber process. This opens up a new field for contact sulfuric 1
Received X a y 13, 1929.
acid plants and the new process is in a position to replace the chamber process more and more, as shown by the fact that a large plant has been built using the new process to produce acid to be diluted to chamber strength. Not only is it possible for the first time in the United States to produce acid of chamber acid strength more cheaply from a contact plant installation, but the acid manufacturer is thereby given a flexibility never hitherto possessed. History of Contact Process
HE contact process for the manufacture of sulfuric acid has developed through four distinct periods. The first period is represented by Phillips’ discovery, in 1831, of the fundamental reaction-the conversion of sulfur dioxide into sulfur trioxide when mixed with air and passed at an elevated temperature through tubes containing platinum. The discovery that substances other than platinum, such as
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oxides of trivalent iron, copper, and chromium, were capable of acting as catalysts marked the second period. The third period saw the beginning of the commercial operation of the process through the patents of Winkler in Germany and Squire and Messel in England, and was brought into being by the demand for strong sulfuric acid and oleum in the synthetic production of alizarin and other dyestuffs (1868 to 1872). However, it was not until the fourth period, ushered in by Knietsch’s famous lecture in 1901, that a successful commercialization of the process was attained as a result of the application of the law of mass action and the realization of the part played by temperature in the reaction velocity
\
\ Figure I-Automatic
’ Heat Exchange Converter
and conversion. Upon reaching the conclusion that contact masses must be cooled instead of heated to assure the proper course of the reaction, Knietsch introduced a number of converters possessing effective cooling but of complex design and susceptible to leakage. Knietsch’s investigations on catalyst poisoning and catalyst behavior under various conditions, physical properties of fuming sulfuric acids and sulfur trioxide and their action on iron and steel, and technical problems in the way of using gases from pyrites burners finally brought the process using platinum catalysts to a commercial success. Other investigators also made contributions. The ;\ramiheim process consisted of two-stage conversion-first m-ith ferric oxide and then with platinum as the catalyst. Schroeder and Grillo made improvements in converter design and introduced the magnesium sulfate carrier for platinum. The Tentelew process used a different design of converter and cooling system and accomplished thorough purification of the burner gases. The contact sulfuric acid process --as introduced into the United States in 1898, when the General Chemical Company of S e w Pork acquired from German concerns American patents corresponding to the German patents of Knietsch and others. This fourth period was based, first, on processes requiring a commercial purification of the reaction gases to avoid poisoning of the platinum catalysts, and second, on an accurate and skilled supervision of the process by trained chemists. I n attempts to avoid the difficulties caused by the extreme sensitiveness of the platinum catalysts t o poison-
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ing experiments were made with various contact masses containing vanadium compounds, but none of them really challenged the supremacy of platinum (8).* Improvements Embodied in New Process
It was thought that the fourth period had practically brought the contact sulfuric acid process to a finished state and no further basic improvements were considered likely. However, the developments of a few investigators in the last five years, including the inventions in converter systems, contact masses, and reaction control by the present writer, culminating in The Selden Company’s contact sulfuric acid process, have made such far-reaching improvements possible that one might almost speak of the opening of a fifth period. These improvements include, first, the provision of a temperature gradient, which is automatically maintained irrespective of fluctuations in flow, and which permits the carrying out of the contact sulfuric acid reaction in complete accordance with its kinetic and thermodynamic requirements. The second improvement lies in the use of non-platinum contact masses which are not affected by the gaseous poisons for platinum and which in their conversion efficiency and durability equal or exceed the best platinum contact masses commercially available. The third improvement might almost be said to flow from the second-namely, the elimination of the costly purification process applied to the reaction gases for the elimination of gaseous poisons, a necessity in a plant using platinum catalysts. These three improvements put the contact sulfuric acid process in its commercial developments on a new and more efficient basis. It is no longer necessary to provide for the constant attendance of skilled chemical supervisors in the running of commercial plants of various sizes, and the control of temperature in the reaction, in so far as it could be controlled in the processes hitherto known, no longer depends only on skilful manipulation and constant close watching. These improvements hare so greatly reduced the cost of contact acid that it has been possible for the first time in the United States to produce contact acid and then dilute it to chamber acid strength more cheaply than acid of the same strength can be produced by the chamber process. By reason of the economies thus made possible the contact sulfuric acid process is enabled t o enter a new field which had been considered closed to it by reason of the cost of the process. S o t only has it proved to be cheaper to produce acid of chamber strength by diluting contact acid made by the new process, but such a plant gives the acid manufacturer a flexibility impossible hitherto, either with chamber plants or contact plants, since he can a t will, and in accordance with the demands of the acid market, sell his whole production as strong acid or oleum or as acid of chamber strength, or he can market part of his acid in one form and part in the other, and the proportion can be varied from day to day n-ithout affecting the running of the plant. This new contact process is therefore destined to replace more and more the chamber process in the United States, and this movement has already begun, as the largest plant yet built using the new process is diluting its contact acid to chamber strength and was built with this purpose in mind. The first two improvements which are the basic causes of the enhanced efficiency of the modern processes and which are about t o be described, may be taken up, first, from the angle of temperature control and converter design, and second, from the standpoint of contact mass efficiency. Temperature Control and Converter Design
The catalytic oxidation of suIfur dioxide to sulfur trioxide is an equilibrium reaction. As the temperature increases,
* Italic numbers in parenthesis refer to literature cited at end of article.
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the conversion equilibrium is a maximum a t about 400" C. shown in Figure 1. I n this converter double countercurrent for practical gas velocities, but a t this temperature the reac- heat-exchange elements are used instead of the single tubes tion velocity is very low, too low for commercial production. used by Audianne. The result is a much more effective heat As the temperature increases above 400 O C. the reaction veloc- transfer because of the greater velocity of gas flow in the ity increases very rapidly, far more rapidly than does the narrow annulus between the two tubes. The tubes are temperature, so that, for example, a t 500" C. the reaction embedded in the catalyst so that the latter can be readily velocity is about forty times as great as a t 400" (2. At the filled in; and it is not necessary to provide for gas-tight consame time, however, the percentage of conversion, as deter- nections in the heat-exchange elements, as any slight leakages through the tube sheet supporting the heat-exchange elemined by the reaction equilibrium, drops. ,4n ideal converter system. in accordance with the kinetics ments are unimportant since all the gases must pass through of the reaction, requires high temperature in the contact the contact mass. This at once removes all maintenance mass first encountering the reaction gases so as to provide for troubles incident to maintaining tight joints in tube sheets, high reaction velocity, and the temperature should gradually which is so serious a factor in the complicated tubular conand continuously fall as the gases pass through the contact verters of Knietsch and also to a lesser extent in the Audianne mass, the last portions of the contact mass being maintained converter. The heat transfer efficiency of the double countera t about 400" C. In the ordinary arrangement of converters current elements is so high that the cooling capacity within in which the gases pass in a vertical direction, this means working limits increases in exact proportion to the flow of that there must be a smooth, vertical temperature gradient; reaction gases through the elements, which would only be but in any horizontal cross section of the contact mass the possible in an Audianne converter with excessively long tubes temperature should be uniform, otherwise there will be a and a corresponding increase in back pressure. The Jaegernon-uniform utilization of the contact mass and an inade- Bertsch converter, described above, despite its marked adquate reaction velocity in the portions which are not main- vantages over the Audianne converter, does not give any more uniform temperature throughout a horizontal cross sectained a t the proper temperature. Various attempts were made to obtain a good temperature tion of contact mass than does the Audianne converter, as distribution. One method which is used extensively in plants no compensation is provided for the unavoidable cooling in the United States (consists of a converter system using effect of the converter shell. It should be noted that in both the Audianne and the two Grillo type converters in series with heat exchangers between them, the first Grillo being operated a t a high tem- Jaeger-Bertsch converters the reaction gases themselves are perature to obtain high reaction velocity and the second Grillo used as temperature-controlling medium and are therefore a t a temperature more favorable for maximum conversion preheated to reaction temperature in direct contact with the equilibrium. This system helped in obtaining a vertical catalyst, thus eliminating or minimizing the use of external heat temperature gradient, though in two sharp steps instead of exchangers where relatively cold sulfur dioxide gases are used. The next advance is a converter (6) in which the problem the ideal smooth curve; but there was no uniformity of temperature in horizontal (cross sections, since the main cooling of uniform temperature in any horizontal cross section of of the Grillo type converter is by the radiation from the shell the catalyst is solved, both for converters having double and a hotter center portion always results. The control countercurrent heat-exchange elements and for converters of temperature in horizontal cross sections was obtained having single tubes of the Audianne type. The spacing or to some extent in the Knietsch type of converter, at, hon-ever, design or amount of reaction gases flowing through the cooling a serious cost in complexity and maintenance difficulties. tubes or elements is varied from the periphery t o the center, Audianne (1) took a step forward and provided tubes running through the catalyst layer of a Grillo type con4-R I verter through which tho incoming reaction gases pass before flowing through the contact mass. Helical stoppers are placed in the tubes to create sufficient back pressure to insure that the reaction gases pass in uniform quantity through each tube. Audianne achieved a much "* 2 better temperature control than in a Grillo, since the cooling gases reached the catalyst in the center of the t converter as effectively as a t the periphery, and to a certain extent the temperatxre control is automatic, as the cooling effect increases almost in proportion to the flow of reaction gases through them and, of course, the heat 3 evolved in the reaction increases in direct proportion to the amount of gases flowing through. The Audianne converter, however, shares some of the disadvantages of 6 the Knietsch converter because the tubes have t o be tight and the replacement of catalyst is very difficult. The ?MPE.eGTPtE 4cf Y GPRDCDEGeFE5 300 00 300 COO principal disadvantages of the Audianne converter, h o w 1 ever, lie in the fact that it does not compensate for unFigure 2-Temperature Curve of C o m p o u n d A u t o m a t i c H e a t Exchange avoidable cooling due to the converter shell, for the dis- Converter S y s t e m Consisting of A u t o m a t i c Heat-Exchange Converter i n Series with Two-Layer Grillo Converter Using 7 t o 8 Per Cent Sulfur Ditribution of cooling gas is deliberately made uniform and, oxide Gas of course, near the IseriIsherv the catalvst is cooled both by the cooling tubks &id 6y radiatioh from the converter so that the central portions of the catalyst are cooled more shell, whereas the central portions of the catalyst are cooled strongly than the peripheral portions, this non-uniform coolonly by the cooling tubes Therefore, the peripheral portions ing being equal and opposite in sign to the non-uniform coolwill be cooler in the Audianne converter than the central ing due to converter-shell radiation, thereby completely or portions, though the difference is not so great as in a Grillo. substantially compensating for the latter. The next step forward is an invention by the writer and Although a fully compensated converter of the double J. A. Bertsch (U. S. patent application pending) and is countercurrent heat-exchange type completely satisfies one I
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factor of the ideal converter system-namely, uniform temperature in any horizontal cross section of catalyst-it does not provide for an adequately smooth vertical temperature gradient, since the cooling of the heat-exchange elements must be sufficient to care for the very rapid evolution of heat in the portions of the contact mass maintained a t relatively high temperature for high reaction velocity and, therefore, are not perfectly adjusted for the later portions of the contact mass where the temperature for best conversion equilibrium is obtained and where, owing to the low reaction velocity, the contact mass volume and the time of contact of the partly reacted gases with the contact mass must be relatively much greater than in the hotter portion.
Figure 3-Compound
Annular Heat-Exchange Converter S y s t e m
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sign of converter system is very economical to conshruct, but because of the lack of positive cooling in the Grillo type converters it is limited in output by the capacity of the Grillo layers to maintain a satisfactory temperature for maximum equilibrium. This design of converter is used commercially in a large installation where the system units are run a t 121/2 to 15 tons sulfuric acid equivalent per day, allowing a factor of safety of more than two. Figure 3 is of the same general design as Figure 2 , but illustrates a very economical design of heat-exchange elements in the form of concentric annuli, a new type of heat-exchange element permitting the complete elimination of tube sheets and also a very rapid assembly. The principle of gas flow is, of course, identical with that in Figure 1. It will be noted that the systems illustrated in Figures 2 and 3 can be applied to an ordinary Grillo plant without difficulty, as it is only necessary to install the automatic heat-exchange converter in place of some of the Grillo layers, making this type of system very attractive for the remodeling of existing Grillo plants with a great increase of output and the advantages inherent in this new system. Figures 4 illustrates a system in which the automatically cooled converter reverses the position of catalyst and heatexchange elements shown in Figures 2 and 3. Here the catalyst is in tubes, and closed-end perforated tubes are slipped over them to form the double countercurrent heatexchange elements, an extraordinarily effective automatic heat exchange being thereby obtained. A careful study of this modification of the system shows that it can be built by slipping the perforated closed-end tubes over the catalyst tubes of an ordinary Tentelew converter and connecting i t in series with a Grillo converter, a most attractive method of redesigning existing Tentelew plants for greatly increased outputs and easy and automatic reaction control. Figures 5 and 6 show the preferred embodiment and performance curves of the new system used in The Selden Company's most modern design of large converter systems. The gases pass from the bottom to the top, first through a converter provided with double countercurrent heat-exchange elements and then, without intercooling, through a converter
The final step is taken in the converter system invented by the writer (S), diagrammatic sketches of typical commercial applications being shown in Figures 2 , 3, 4, and 5. A preferred modification of this system provides one contact mass layer or converter cooled with a double countercurrent heat-exchange system fully compensated for converter shell cooling (for simplicity the compensation is not shown in the drawings), in which the portion of the reaction carried out a t high temperature and high reaction velocity takes place followed in series by one or more converters which are maintained a t lower temperatures, the last being maintained a t the temperature for maximum conversion equilibrium. Provision is also made to bring these temperature variations in the later converters, either by intercooling or by cooling elements, in contact with the catalyst itself. Thissystem for the first time provides for a practically ideal, smooth, vertical temperature gradient in installations whose size and output are almost unlimited, and all the advantages of compensated automatic heat exchange with resultant uniform temperature in horizontal cross sections of the catalyst are retained. Figure 2 shows the simplest type of converter system in which only the first converter is provided with internal cooling, the reaction gases being brought t o a lower temperature c zone before passing through each uncooled layer by means of the baffles which throw the gases against a portion of the Figure 4-Tentelew Converter Transformed i n t o Compound converter shell provided with little or no insulation. For Automatic Heat-Exchange Converter S y s t e m economy in installation space, of course, the different converters are arranged one above another, as is common prac- provided with double countercurrent cooling elements operatice in the art. The curve taken from temperatures registered ated by an external gaseous cooling medium, which in inby the numbered thermocouples indicated on the drawing stallations using hot sulfur dioxide gases is normally air. shows a smooth vertical temperature gradient in each con- Where cold sulfur dioxide gases are furnished to the system verter, though there is a slight heating up in the Grillo type they may be used as a cooling medium with a concomitant converters which are not provided with internal heat ex- preheating to the desired temperature for entering into the change; but this heating is small, as only a small percentage automatic heat-exchange converter. The spacing of the of the reaction takes place in these converters and the heat is heating elements in the second converter is, of course, nowhere adequately taken care of by this type of cooling. This de- near so close as in the first converter, as the amount of heat
A
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being about 1900, when vanadium pentoxide was investigated as a catalyst but did not show sufficient efficiencyto be of any commercial interest. Further work was done in preparing non-platinum cont,act masses in which vanadium oxide or salts of vanadic acid, such as iron vanadate and silver vanadate, were impregnated into various carriers, such as kieselguhr, pumice, and the like. I n 1914 the British Patent 8462 was filed covering a contact mass obtained by introducing vanadium as an ereliangeable base in an ordirrary zeolite. This contwt mass did not achieve any comniercial importance, owing primarily to the fact that vanadium oxide so looscly combined t,ended t o agglomerate wider reaction temperatures because of its relatively low melting point. For many years no further attempts were made t o prepare contact masses in tlie form of complex compounds, such as zeolites. I n 1924 tlie writer used a different type of zeolite contact mass in which vanadic pentoxide forms a part of the nonexchangeable nucleus of the zeolite. This contact mass, particularly when diluent bodies vere embedded in the framework of the zeolite to form a homogeneous whole, proved to be Forty-Ton Converters. Assembled a more effective catalyst. than any hitherto described in the t o be taken out in the second coriverter is much less and it literature, arid did riot lose its activity by agglomeration since the v a n a d i u m is desirable to increase oxide w a s i n suffithe contact-mass cross ciently strong chemical section so that t.he time combination to resist of contact of the partly t,he temperatures enreacted gases with the couutered in bhe ree a r i t a c t m a s s is inaction. T h i s new creased in accordance catalyst, together with with theslower reaction ininor modi E i ca t i oiis velocity a t t.he lower ( 2 ) was sold to and intemperature. In this design a practically perstalled in the plant of the Xonsanto Chcmifect control of the gas temperature is had in cnl Works in East Si. h i i s , Ill. (n). both converters, as is s h o w n by the curve, Further work with complex vanadiiini which, in the contactc o m p o u n d s of t h e m a s portion of the two type of base-exchange converters, is p r a c t i bodies, siliceous and cally a srnooth, vertical non-siliceous and their temperature gradieii t derivatives, resulted in (see Figure 8) closely the iiiverition of s t i l l approximating the Plant i o Constructfon Using The Seiden COmDanY’* Converter System i d e a l . Since the secmore complex, highly ond convorter is cooled by elements embedded in the efficient contact masses (6, 6, 7). The perSected contact catalyst, its effectiveness is not clianged by an increase in size, and this type OS system can therefore he used in a single converter system having an output OS 40 to 80 tons sulfuric acid equivalent or more with better tliaii a 2 to 1 safety factor, giving a conversion efficiency of 98 to 98.4 per cent using 7 to 8 per cent sulfur dioxide gases and t.lie new non-platinum coniact, masses dencribed below. Large BS is tlie output of a single converter system, as shown in Fiwre 5, in plants of great capacit.y it has been practicable to operate three or more of these illlit systems i n parallel from a single source of sulfur dioxide gnses and feeding into a siirgle ahsorption systein-a very economic:id and compact design. Plants built or building within tlie last year rising these convorter systems have a total capacity of more thsn 300,000 tons of sulfuric acid per ~mtium. New Nan-Platinum Contact Masses
The attempts to develop a saiisfactory non-platinum contact mass began early in the history of the contact sulfuric acid process, the first work with vanadium contact masses
ConPoi Room of Confact Sullurlc Acid Plant of I20 Tons Daily CIlDSCllY
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masses used in The Selden Company’s new contact sulfuric acid process contain as their active ingredients non-siliceous base-exchange bodies in which vanadium oxide is present in the non-exchangeable nucleus. These contact masses exceed in efficiency the best platinum catalysts in commercial use, while possessing extraordinary resistance to high temperatures, long life, and a complete indifference to gaseous poisons for platinum. In fact, a test was made by representatives of
The effectiveness of the contact mass in large-scale operation fully confirms the results in the laboratory test converter, as is shown by the conversion curve in Figure 6 taken from a 40-ton converter system unit. The first 10 per cent, of the contact mass, in which the temperature rises to its maximum, converts 80 per cent of the sulfur dioxide to trioxide, which is considerably in excess of the best commercial results with platinum catalysts. The first converter provided with automatic temperature control converts 96 per cent of the sulfur dioxide, thus greatly simplifying the control of temperature in the second converter, which has t o handle only 2 per cent of the reaction. Constant skilled chemical supervision of this part of the system is thus rendered unnecessary. The conversion efficiencies with the different percentages of gas described above are fully borne out and even exceeded by large-scale commercial operation, where the temperature conditions are even more favorable. Thus in a 50-ton plant which was operated for a time with 5 per cent gases, an analysis showed a conversion of more than 99.9 per cent, the analysis requiring 55 minutes to an hour:
1
Patents JOO
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600
In addition to the Cnited States patents covering the contact masses and the converter systems described above, there are many pending applications for United States patents, and corresponding applications and patents are on file or issued in the principal foreign countries.
Figure 5-Temperature Curve of Compound A u t o m a t i c Heat-Exchange Converter S y s t e m Consisting of A u t o m a t i c Heat-Exchange Converter i n Series w i t h Air-Cooled Converter using 7 t o 8 Per C e n t Sulfur Dioxide Gas
a prominent sulfuric acid company in the United States in which the contact mass was subjected to the action of excessive amounts of catalyst poisons, such as compounds 100 of arsenic, selenium, antimony, hydrofluoric acid, and 540 hydrochloric acid, the total weight of the poison being 1 90 about two-thirds of the total weight of the contact 1 mass. Despite this extraordinarily drastic treatment, $30 1 do the contact masses showed no diminution in activity 1 7 To 8 f SO, GPI 9 and in the case of some of the poisons actually showed 1$ .: 70 a slight increase in activity, this being noticeably the case after the addition of arsenic compounds to the -8 2 reaction gas. It is thus clear that the contact mass m-5 60 3 is ideally suited for installations operating with smelter $: 50 gases of various types where the problem of catalyst 13 poisoning is most acute, and in fact the operation of L6 a contact sulfuric acid plant on smelter gases was a 40 complete success and strikingly demonstrated the uo: 18 advantages of the process for this type of installaI& 30 tion. 20 The efficiency of the contact mass used in the new 1 PCPCPNT CATRLYJT process was tested under the standard testing condi1 10 tions for olatinum and also in full-scale commercial 1 .a I I I I 1 I I I I 1 I I I I 1 1 1 operation. When using a loading of 135 liters of 7 Figure 6 per cent burner gases per hour per 200 cc. of conThe author wishes t o acknowledge the generous help and tact mass (the standard test conditions for platinum contact masses) in a standard laboratory test converter, con- facilities which were given without stint by The Selden versions from 97 to 98.8 per cent were obtained. An in- Company and which made possible the development, percrease of loading to 150 liters per hour showed no drop fection, and commercialization of this new process. in conversion and even a t 200 liters’ loading the drop was scarcely noticeable. At 300 liters’ loading the drop was less Patents and Literature Cited than 1 per cent, showing the enormous catalytic power of the contact mass. A second series of tests in a standard laboraAudianne, U. S. Patent 1,450,661 (April 3, 1923). tory converter using a loading of 150 liters per 200 cc. conJaeger and Bertsch, U. S. Patent 1,657,754 (January 31, 1928). Jaeger, U. S. Patent 1,660,511 (February 28, 1928). tact mass was run to show the changes with changing concenJaeger, U. S. Patent 1,675,308 (June 24, 1928). trations of sulfur dioxide in the reaction gases. With 5 Jaeger, U.S. Patent 1,675,309 (June 26, 1928). per cent sulfur dioxide gases the conversion is 99.5 per Jaeger, U. S. Patent 1,685,672 (September 25, 1928). cent; with 6 per cent the conversion is 98.8 per cent; with Jaeger, U. S. Patent 1,694,123 (December 4, 1928). 7 per cent, 98.5 per cent; with 8 per cent, 98 per cent; Lunge, “Manufacture of Acids and Alkalies,” Vol. IV by Miles, and with 9 per cent the conversion is still above 97 per p . 122 (1925). Nickell, Chem. Met. Eng., 36, 153 (1928). cent.
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