Патент USA US2102863код для вставки
Dec. 21, ‘1937. 2,102,863 a. w. TALBERT ET AL MANUFACTURE OF PAVI‘RTIAL OXIDATION PRODUCTDS Filed Nov. 6. 1935 ._i .. i .F9LY.;: I - m // Patented Dec. 21, 1937 - I ‘ 2,102,863 ‘UNITED STATES‘ PATENT OFFICE . 2,102,863 MANUFACTURE - 0F PARTIAL OXIDATION PRODUCTS ' 4 Guy W. Talbert, Summit, N. J., and John D. Kerr, Forest Hills, N. Y., assignors to National Aniline & Chemical Company, Inc., New York, N.-Y,, a corporation of New York Application November s, 1933, Serial No. 696,802 ' 8 Claims. (01. 260-123) This invention relates to ‘improvements in the manufacture of partial oxidation products of organic chemical substances, and especially of normally solid organic chemical substances, by 5 a. process which involves passing a 'vaporous re action mixture containing the organic chemical substance in the vapor phase and an oxidizing. , gas in contact with an oxidation catalyst main tained at-a suitable reaction temperature. H. It O relates generally to an improved process and ap paratus for forming the vaporous'r'eaction mix ture, and more especially to an improved process and apparatus for forming a mixture of va porized naphthalene and air for use in the cat 15 alytic formation of phthalic anhydride; » "The present invention has for an object im provements in the manufacture of ‘partial oxi dation products of organic chemical substances by catalytic processes of the type hereinbefore the material employed‘ and the sensitivity of the reaction to changes in the composition of the reaction mixture and in the reaction conditions. Thus, mixtures of naphthalene and air within certain ranges of proportions are likely to ex- 5 plode; it is therefore desirable for e?icient and safe operation that the concentration of naph thalene in the air-naphthalene mixture supplied to the catalyst be known and/or controlled sub stantially at all‘ times. To avoid operating with- 10 in the explosive range of naphthalene-air mix times while securing ef?cient utilization of the ' - naphthalene, it is generally the practice to em ploy a relatively high ratio of air to naphthalene, as for'example 25 parts to 30 parts by weight of 15 airper part by weight of naphthalene. The re action between naphthalene and air is more-' over, highly exothermic, and is preferably car- _ ried out at a relatively high temperature (for ex ample, in the neighborhood of 350° C. to 550° 0.). 20 20 referred to, whereby uniform mixtures of nor mally solid vaporizable organic chemical sub-» In view of the relatively small size of the pas stances and oxidizing gases may be obtained and sages through which the vaporous reaction mix consequently high yields and uniformity of the desired product may be secured. 25 A further object of the-present invention is to provide a satisfactory and efficient apparatus for carrying out such improved processes. Other objects of the invention will in part be obvious and will in part appear hereinafter. 30 The invention will be describedas applied to the vapor phase catalytic oxidation of naphtha lene with air for the production of phthalic an hydride. It is to be understood, however, that the invention is not limited thereto and that 35 changes may be made in the details'of the process and apparatus as well as in the mate ' rials treated, proportions of ingredients, order of steps, etc. within the scope of the appended , patent claims. 40 ' ' ture travels in contact with the catalyst and the consequent high speed ,of passage, and further owing to the relatively high reaction tempera- 25 ture employed and the relatively small amount of naphthalene present at any instant, changes in the composition of the vaporous reaction mix ture produce far reaching effects upon the cata lytic reaction and consequently upon the quality 30 ' and yield of the product _(phthalic anhydride) obtained. ' It has heretofore been proposed to provide a naphthalene vapor-air mixture, for use in the cat. alytic formation of phthalic anhydride, by provid- 35 ing a relatively large, shallow body of molten naphthalene and passing a stream of air over the surface thereof, whereby naphthalene vapors are sublimed and mixed with the air. This pro In the vapor phase catalytic oxidation of cedure has the disadvantage that,_uniformity of 40 naphthalene with air‘ for the production of “operation is di?icult to'secure. Unless a very phthalic anhydride in accordance with one well pure naphthalene is employed, the composition of the vapor changes as the vaporization pro known method, a mixture of air. and naphtha lene vapors is passed in contact with a catalyst 45 maintained at a suitable reaction temperature; as for example, vanadium oxide‘associated with a suitable carrier and contained in tubes of ' small cross sectional area which are in indirect heat contact with a temperature controlling bath 50 that is adapted to boil at a temperature suitable. for maintaining the desired reaction tempera ture. ' ‘ ' The proper formation of the vaporous reac tion mixture employed in the oxidation entails 55 considerable diiliculty, owing to the nature of gresses, due to initialv sublimation of the more volatile fractions of the body of molten material, 45 l with consequent change in the composition of ‘ the air-vapor mixture. The passage,; further more, of such large quantities of air as are re quired for the production of vaporous-mixtures of the desired concentration over a large surface 50 of molten naphthalene renders exceedingly vdif ?cult maintenance of a uniform concentration 'of the air-vapor mixture. It has also heretofore been proposed to form the naphthalene vapor mixture by passing a 65 2,102,863 2 . stream of heated air through a body of molten naphthalene under such conditions, that the air is substantially saturated with naphthalene va por at a known temperature, forming a primary varying with and regulated by the pressure in said high pressure zone. In accordance with a jfurther feature of the present invention, the stream of air is passed through a conduit under air-naphthalene mixture, and then diluting the‘ suitable pressure to provide the desired ?ow through the system (which will be referred to saturated air-naphthalene mixture with addi tional air. While this procedure is much su perior to the above-mentioned procedure, in that only a part of the large quantity of air employed 10 in the oxidation reaction is passed in contact herein as the “normal” gas pressure), a reduc tion in pressure of said air stream is produced ina zone of said conduit by the ?ow of said air stream therethrough, and liquid naphthalene‘ is 10 with the molten naphthalene, so that more ac drawn into the air stream by the reduction in curate control is obtainable, it has the disad pressure thereby produced. vantage of requiring regulation and/or control - In the practice of the present invention in ac cordance with a preferred method of procedure, a stream of air, heated to a temperature above of the temperature of the molten naphthalene, 15 of the concentration of the primary air-naphtha lene mixture, and of the amount of auxiliary air employed for producing the ?nal vaporous re action mixture. In addition, variations in the pressure in the system, as for example changes 20 in the resistance of the catalyst mass to the flow of gas mixture therethrough, which vari ations are not transmitted to the primary air the melting point of naphthalene, is passed through ‘a conduit leading to a catalytic convert er containing a catalyst adapted to bring about the oxidation of naphthalene to phthalic anhy dride, which conduit contains a‘ Venturi con— 20 striction or other suitable means for producing, a reduction in pressure by the ?ow of the air vapor mixture and the auxiliary air stream in stream through said conduit, and naphthalene the proper ratio, cause variation in the concen in molten condition is drawn into said air stream through ‘a calibrated ori?ce by the reduction in 25 25 tration of the air-vapor mixture and consequent pressure resulting from the ?ow of said air stream ' ly in the quality and yield of the. product. ' According to the present invention, regulation of the concentration of naphthalene in the naph thalene-air mixture is obtained by utilizing the 30 ?ow of the air stream through the apparatus to control the introduction of the naphthalene into the mixture. ’ We have found, according to the present invention, that many of the objections to the prior methods of forming the vaporous 35 reaction mixture may be overcome and other through said Venturi constriction. It will ac cordingly be understood that where a conduit having a Venturi pipe therein is referred to in the appended claims it is intended to include 30 any conduit having a restricted cross-section in a zone thereof whereby on passing a stream of gas through the conduit a Venturi effect in the gas stream is produced. In order to renderthe highly desirable advantages may be secured by supply of naphthalene substantially independent of external conditions, the naphthalene is main employing the so-called “Venturi” or similar ef tained under a pressure substantially the same 35 fect, for example that which results from the ,as that prevailing in the conduit leading from flow of a ?uid through a graduated constriction of the Venturi to the catalytic converter inlet; as the “Venturi” type in a conduit, to supply the naphthalene to the air stream. Inasmuch as the reduction in pressure which ,occurs at the throat of a Venturi pipe varies in, accordance with variations in the speed of ?ow of the air stream through said pipe, it is possible, in ac cordance with the present invention, to main tain a substantially uniform ratio of naphthalene to air in the vaporous reaction mixture, notwith standing variations in the rate of ?ow of the for example, by maintaining a body of molten 40. naphthalene in a closed vessel at a relatively constant surface level and controlling the pres sure on the surface of said body of naphthalene so as to have it correspond substantially with the pressure prevailing in the conduit between 45 the‘ Venturi and the catalytic converter inlet (herein referred to as the pressure of the result ing gaseous reaction mixture). The surface level of the body of molten naphthalene is pref erably maintained at a point below that at which 50 50 air stream through the system. The invention accordingly comprises the steps ‘ the naphthalene is introduced into the-Venturi, and their relation, and the apparatus, having the so that the naphthalene is drawn into the air features of construction and combination and arrangement of parts adapted to carry out said 55 steps, which will be illustrated in the process and apparatus hereinafter disclosed. The scope of ‘the invention will be indicated in the appended stream substantially solely by the reduction in pressure produced by‘ the ?ow of, the air stream patent claims. . . . . > In the conversion of naphthalene to phthalic anhydride by catalytic oxidation in the vapor phase with air, in accordance with one feature of thepresent invention, the vaporous or gaseous reaction mixture is produced by passing a stream through the Venturi zone of the conduit. ' . The invention will be further described in con 5a nection with the accompanying drawing in which , Fig. 1_ diagrammatically represents one form of apparatus for carrying out'the invention; Fig-2 illustrates a somewhat different appara 60 tus for carrying out the invention; and Fig. 3 is a vertical section of a Venturi tube employed in the practice of the'invention, show of air through a zone of high velocity in such a ing details of its construction. _ The apparatus illustrated in Fig. 1 comprise a 65 65 manner as to create a suction in said zone, which suction is sensitive to pressure variations in said jpreheater I, a Venturi tube 2, a supply tank 3, air stream, ‘and liquid naphthalene is introduced into said zone in a quantity proportionate to the a separator l, and a catalytic converter 5. The preheater l shown in the drawing is pro quantity of gas passing through said zone. In vided with a suitable gas inlet 6 and vis'aglapted to 70 accordance with another feature of the present Y effect the heating of thej_=gas by indirect heat 70 invention, the stream of air is passed. ?rst ; exchange with steam, .is'uitable means such as, through a zone of high velocityand low pressure, and second through a zone of low velocity and high pressure, and liquid naphthalene is intro 75 duced into the low pressure zone under a pressure steam inlet 1 being provided for the introduction’ of steam; A dr'awo?' 8 is shown for'withdraw ing steam and/or condensate. A gas conduit 9 75 ' leads from the preheater l to the Venturi tube 2. 2,192,883 This conduit may be lagged or jacketed, if desired. , , ‘ The Venturi tube 2 is provided with a gas pas 3 . The Venturi tube 22 is provided with a gas passage therethrough from the conduit 30 to a conduit 3| leading to the inlet of‘ the separator sage therethrough from the inlet conduit 9 to a "24, and has intermediate of these conduits a vconduit [0 leading to the separator 4, and has throat 32. Conduits 33 and 33' are adapted to intermediate of these conduits a throat ||. Con conduct liquid from the supply tank 23 to suit- . duits I2 and I2’ provide communication from the able inlets or ori?ces in the venturi at or near the throat 32 thereof. liquid supply tank 3 to the interior of the Ven The liquid supply tank 23 is provided with a turi tube‘ at a point at or near the throat || I liquid inlet 34 as well as outlet conduits 33 10' thereof. The liquid supply tank 3 is shown as a closed and 33'. Suitable devices, such as test cocks 35a, 35b and 350 permit the determination of the vessel provided with a suitable inlet M for supply liquid level in the supply tank. A valved vent 39 ing liquid naphthalene. The inlet I4 may be con nected with any suitable source of liquid and the may also be provided to open the tank to the level of liquid in the tank may be regulated in atmosphere if desired. A steam jacket 237' may any suitable manner, as by manual control of the be employed for maintaining the liquid in the ' valve i412. The inlet i4 -is preferably connected supply tank in a heated condition. ‘ The separator 24 may be of any suitable con- " with a suitably heated constant-level liquid‘feed of the well-known type adapted to maintain the 20 liquid in the tank 3 at a substantially constant surface level. If desired, an auxiliary liquid sup ply l3 may be provided. A steam jacket 37' or other-suitable heating or insulating means may . be supplied for maintaining'the liquid in the supN? in ply tank in a heated condition where such‘is de sirable. A valved vent l8 to the atmosphere may also be provided for opening the tank '3 to the at mosphere if desired. gases or gas and vapor enter through conduit 3| and leave through a conduit 31. A steam'jacket 247‘ having a suitable steam inlet and a drawoff is provided for avoiding a temperature drop in the 25 separator. ‘ or gas and ‘vapors enter through conduit l0 and leave through a conduit It. A steam jacket 47'_ vails in conduit 31 and variations of pressure in . struction for removing suspended matter from the gases or gas and vapor passingtherethrough. A centrifugal separator or electrical precipitator, for‘ example, may be used for this purpose. In the separator illustrated in the drawing the gases having a suitable steam inlet and a drawoff is provided for avoiding heat losses or a‘ tempera ture drop in this unit of equipment. 40 In the separator illustrated in the drawing, the Conduit 31 leads to the settling chamber or ‘separator 25 wherein further removal of "sus pended matter .may be e?ected. This separator is likewise provided with a suitable steam jacket. 30 257'. The conduit 31 is connected by means of an equalizer pipe 36 to the supply tank 23 at a point above the liquid level in said tank. In this way the liquid in the supply tank may be maintained under substantially the same pressure that pre 35 . The separator 4 may be of any suitable con '30 structionfor removing suspended matter from the gases or gas and vapor passing therethrough. 20 Conduit i6, which leads from the separator 4 to the catalytic converter 5, ,is connected by means of an equalizer pipe I5 to the supply tank 3 at a point above the‘liquid level in said tank. By this means the liquid in the supply tank may be maintained at substantially the same pres~ sure as prevails in conduit l6, and variations in pressure in the latter immediately‘ transmitted td the liquid in the supply tank. Both the equal izer pipe l5 and the conduit l6 have been illus— trated as being suitably lagged with insulation I52‘ and I62‘. If desired, these pipes may be jack eted or, where maintenance of high temperatures either is not necessary or'may be obtained in another manner the lagging may be dispensed ‘ with. - Converter 5, of well known construction, is adapted to contain a suitable catalyst for carry ing' out ‘the. oxidation process and is provided with a valved outlet |9_ for the withdrawal of 60 reaction products while maintaining desired pres sure conditions in the catalytic converter. . The apparatus illustrated in Fig. 2 comprises a preheater 2|,_a Venturi tube 22, a supply tank v23, separators 24 and 25, and converter 26. ' ,The preheater 2| is provided with a gas inlet 21. As illustrated the preheater may employ steam as a heating medium, suitable means being ‘ provided for'bringing the steam into-heat‘ex change relation with the gas in its passage through the preheater. For this purpose a steam ' inlet 28 and drawoi‘l 29 are shown for introducing steam ‘and for withdrawing steam and/or con densate. Agasv conduit 30 leads from the pre heater 2| to the Venturi tube 22. This conduit may be lagged or jacketed, if desired. this conduit immediately transmitted to the liquid in the supply tank. ‘ A condut 38 connected with the separator 25 by an annular passage 38' leads to the converter 26. The conduits 31 and 38 as well as the equalizer pipe 36 have been shown as being provided with suitable steam jackets 317', 337', and 367.. It will be understood, of course, that under certain con ditions these may be dispensed with if so desired 45 or suitable lagging may be substituted. The converter 26 is-of well-known construction and contains a suitable oxidation catalyst. . It is provided with suitable valved-outlet means 40 for ' withdrawal of the reaction products of the cata lytic conversion. ' - Fig. 3 illustrates a preferred type of Venturi tube, for use in the preferred process of this in-‘ vention, having a tapered inlet portion 4| and a tapered outlet portion 42 which are provided with ?anges 43 and 44 cooperating to form a union between these two portions of the Venturi tube. ' The ?anges may be suitably drilled and secured by stud bolts 45 or other suitable securing means. Internally of the tubesyat the intersection of the 60 tapered walls, a portion is cut away to admit an annular sleeve 46. , The sleeve 46 is designed to ?t smoothly into the Venturi so that no appreciable roughness of the walls occurs. This sleeve 46 also serves to properly alignv the two tapered mem~ bers 4| and 42. l ’ Adjacent the constricted portion of the Ven turi tube, the member 42 is providedwith two wells or chambers 41 and 48. The wells are pro vided with pipes 49 and '53 adapted tqconnectv them with the supply tank‘. The wells‘ are also; provided with ori?ce plates 5| ‘and 52 having ori--[-_-v ?ces 5|’ and 52' communicating with the interior of the Venturi passage at a point slightly toward the outlet side thereof from the maximum con 2,102,868 4 passed in contact with the catalyst which is suit striction of the throat. The or?ce plates‘ are ad vantageously separate members which may be ably heated to cause the oxidation of naphtha screwed into the walls of the Venturi tube and lene and its conversion to phthalic anhydride. constitute replaceable units. The wells 41 and - The reaction product is withdrawn at outlet I9. The quantity of naphthalene drawn in and 48 are provided with plugs 53 and 54 ‘to provide access to the ori?ce plates 5| and 52', for cleaning, mixed with-the air will vary, of course, depend ing on the design of the apparatus, the pres replacement, etc. The pipes 49 and 50 are provid sure conditions existing" in the system, etc. As ed with screens 49s and 50s to remove solid mate rial which might plug the ori?ces. The screens an example, we may consider a Venturi tube 10 may be of any suitable type, as for example,v standard removable suction and pressure strain ers of about 100 mesh, such as are ordinarily used let and outlet portions being 25 inches and 55% in pipes to remove sediment. A needle valve 55 threaded into the plug 54 and 15 having an adjusting knob 56 is provided to control the ?ow of liquid through the ori?ce 52’. The valve stem 51 of the needle valve is suitably packed by the gland 58 to prevent leakage during operation. The ori?ce 52' is preferably some 20 what larger in diameter than the ori?ce 5|’ so that the ?ow of liquid into the venturi is con-' trollable within wide limits. having‘ a diameter of Bile-inches at the ends, a 10 diameter at the throat of 131; inches, a length of 801/4 inches (the lengths of the tapered in- . - The venturi is preferably constructed of brass, while the sleeve 46 and the ori?ce plates 5| and 52 may avantageously be stainless steel. The in terior walls of the venturi may be ?nished smooth after assembly so that no roughness occurs at the points where these ?ttings are inserted. ' In the operation of the apparatus shown in Fig. 1, as applied to the catalytic oxidation of naph thalene to phthalic anhydride in accordance with inches respectively)‘ and provided with a naph thalene inlet ori?ce 5|’ of 1*; inch diameter at a distance of 1%}, inches below the-maximum constriction. Under the conditions above set forth (that is an air supply at about 30 pounds gauge pressure and a catalytic converter op erating at a gauge pressure of about 22 pounds 20 at the exit thereof) about 3,000 pounds of air ' may be- passed through the system per hour. Under these conditions, the gauge pressure on the discharge side of the venturi, or in conduit IE, will be about 28 to 28.5 pounds. Thus there 25 willbe a pressure differential of about 1.5 to about 2 pounds between the intake side and the discharge side of the venturi. Such an appa ratus operating under the speci?ed conditions will maintain a supply of 100 pounds of mol- ' ten naphthalene through the ori?ce 5|’ solely one method of operation, air under suitable pres- . by the suction created by the air in passing sure for passing the vaporous reaction mixture through the venturi, giving a weight ratio of through the system, including the catalytic con 30 to 1 of air to naphthalene. By maintaining the surface level of molten 35 verter (for example, air at a gauge pressure ofv about 30 pounds per square inch for use in con naphthalene in supply tank 3 at a substantially nection with a converter operating at a gauge constant level not substantially above the ori?ce 5|’, a substantially constant ratio of naphtha lene togair is secured; notwithstanding the ?uc~ tuations in the operation, temperature, speed pressure at the exit thereof of about 22 pounds) ‘is admitted from a suitable source to the inlet of 40 preheater I in which it is heated to “a suitable temperature adapted to provide vaporization of naphthalene, as for example, about 150° to about 160°‘ C. Naphthalene in a molten condition is supplied to the tank 3 in such quantities as to 45 maintain a. substantially constant level of liquid in said tank. . of gas ?ow, pressure and the like which ordi narily occur in the manufacture of phthalic anyhydride by. vapor phase catalytic oxidation of naphthalene. The equalizer l5 automatically and rapidly maintains the naphthalene in supply tank ‘3 at substantially the pressure prevailing in conduit .|6, so that the effect of ordinary pressure varia tions occurring in the system on the naphtha lene supply is substantially eliminated; and by The preheated air enters the Venturi tube and, ‘passing through the throat || thereof, creates a suction which draws naphthalene through the 50 conduits l2 and I2’ from the supply tank 3. The turbulence resulting from the ?ow of the air . maintaining a constant surface level of naphtha stream through the Venturi throat results in lene in the tank 3 at or below the level of the rapid and efficient mixing of the naphthalene ori?ce 5|’, the naphthalene is drawn into the and heated air as well as assisting in rapid venturi 2 solely by the venturi effect produced by the ?ow of air through it. If desired, the 55 vaporization of the naphthalene. In the usual operation, the flow of naphthalene naphthalene in the tank 3 may be maintained through tube I2’ is regulated by a suitable valve, at a constant level at or above the ori?ce 5|’; such as needle valve 55. Ordinarily this valve but in that event the hydrostatic head of liquid is closed except at the beginning of the process naphthalene becomes a factor in its supply, and naphthalene may be introduced into the system 60 when a. reaction mixture‘ rich in naphthalene is desired in order to get the temperature in the , even if no air is‘?owing through the venturi 2. converter 5 up to the desired point. After the To avoid such a result, which may lead to dan process is well started, the naphthalene is ordi-‘ gerous operating conditions, the naphthalene is narily fed to the'Venturi tube solely through preferably maintained in tank 3 at a surface supply pipe l2, the quantity being regulated by -‘ level about 2 inches below the level of ori?ce 5|’. 65 65 ' the ori?ce 5|’. Preferably the level of naphtha For delivery of the same weight of air per lene. in tank 3 is maintained substantially con hour through the venturi, it is evident that the stant- at a point about 2 to about 8 inches below converter may be operated at other‘i pressures the ori?ces 5|’ and 52'. ' - 70 ' The air-naphthalene'mixture passes from the Venturi tube into the separator or tar extractor l where suspended matter is removed. It then passes throughthezconduitJli to'the converter ' 5, preferably without substantial reduction 'in‘ temperature. In- the converter 5 the mixture is within the- limits‘ of the air supply.~pressure; , since a lowering of the pressure in the converter, merely eifectsa reduction of the pressure on'. the discharge side of the venturi and a conse quent reduction of pressure on the intake side of the venturi, which change is transmitted to’ the naphthalene in the tank 3 by the equalizer 75 5 2,102,863 ii. If the converter 5 is operatedat such a low pressure that the pressure on the discharge side of‘ the venturi is say 12 to ‘14 pounds per ‘ square inch (or about atmospheric pressure), the equalizer I 5 may be eliminated and the vent l3 may be opened to the atmosphere. Even un der the latter conditions, naphthalene will be drawn into the air stream by the suction pro-' duced in the venturi, although of course not 10 necessarily at the same ratio of air to naphtha lene as in the above example. However, in the catalytic conversion of naphthalene to phthalic anhydride, operation at such relatively low pres sure is not ordinarily desirable since it diminishes. the output of theconverter and otherwise affects » formity in the quality and yield of phthalic an hydride are obtained. While the invention has been speci?cally de scribed in connection with the production of phthalic anhydride by the catalytic oxidation of naphthalene in the vapor phase, as has been noted, the invention is not limited thereto but may be generally applied to other processes for ' the manufacture of partial oxidation products of organic chemical substances by catalytic oxi 10 dation in the vapor phase. Thus, the. process and apparatus of the present invention may be employed for the production of partial oxidation products by employing molten anthracene, phe nanthrene, acenaphthene, acenaphthalene, ?uo-v the process.v Discharge pressures in the venturi -rene or other vaporizable normally solid organic greater than about 12 to about 14 pounds per chemical substances instead of naphthalene. Other oxygen-containing and/or oxidizing gases square inch generally require the use ‘of the equal izer l5,.or other suitable means for maintain , may be employed instead of air. Suitable temperature and pressure gauges 20 ing pressure on the naphthalene supply during may, of course, be provided for the apparatus of 20 ,the operation of the apparatus shown, and pref erably at substantially the pressure prevailingv our invention in order to ascertain the conditions in various portions of the apparatus. We have in the conduit IS. The operation of the apparatus shown in Fig. found it desirable, for example, to provide pres sure gauges 59 and 60 at the inlet and near the 2 is carried out in a similar manner. Thus, pre heated air is passed from the preheater 2|, at outlet of the Venturi ~tube in order to assure a temperature .for example, of about 150° to proper regulation of the pressure conditions in about 160° C., through the Venturi pipe 22.’ The reduction in pressure cause by the passage of 30 the preheated air through t 'e Venturi pipe 22_ serves to draw molten naphthalene from the sup ply tank 23 into the preheated air through the conduit 33 or conduits 33 and 33'. The result ing vaporous reaction mixture is, passed through separator 24 and then through conduit 31 tov settling chamber 25, wherein more complete re moval of tar and other suspended matter is ef-v fected. The resulting cleaned vaporous- reac tion mixture containing naphthalene vapor and 40 air then passes into catalytic converter 26 where it is contacted with a suitable catalyst (as for, example vanadium oxide associated with a car this unit'of the apparatus. - In the above description of one method of operating the process and apparatus of our in vention, the prevailing pressures have been set forth in terms-oi gauge pressure. However, the pressures existing in the various zones or" the system need not always be maintained at a posi tive gauge pressure to come within the purview of our invention. Reference to pressures as high pressures and low pressures is purely relative and pressure as used in the appended claims refers not to gauge pressure but to absolute pressure. As is. well known the pressure and velocity head 40 of a ?uid undergoes wide variation in passing from the inlet to the throat of a Venturi and rier) under reaction conditions adapted for the - from the throat to the outlet thereof. The fluid in the zones in proximity to the inlet and outlet ‘ production of phthalic anhydride ‘and the result is ‘at comparatively high pressure and corre ing reaction mixture is withdrawn from the con 45 spondingly low velocity while in the restricted verter through the outlet 40. As in the case of the apparatus shown- in Fig. 1, the pressure on area at or near the throat there is created a low the naphthalene contained in supply tank 23 is prmsure zone in which the ?uid travels at high maintained at substantially the same pressure velocity.v In the claims these zones have ac cordingly been referred to for convenience as 50 50 as prevails in the conduit 31 by the equalizer 36. zones of low velocity and high pressure, and a The process and apparatus of the‘ present in vention possess manifold advantages as com- » zone of high velocity and low pressure, respec pared with those heretofore employed. Inas much as the introduction of naphthalene in the preferred practice of the invention depends sole ly upon the quantity of air passing through the system a de?nite ratio of naphthalene to air may tively. ' 4 We claim: 1. In the conversion of a normally solid or 55 ganic vaporizable substance to partialoxidation products by catalytic oxidation in the vapor phase with an oxygen-containing gas, the method of forming a vaporous reaction mixture of the oxy gen-containing gas and vapors of said substance 60 Since the quantity of liquid naphthalene intro duced into the gas stream depends on the pres‘ which comprises passing a'stream of the oxygen sure at the point of introduction and the pres containing gas through a Venturi pipe, maintain sure applied to the liquid, variations in pressure ing a.‘ body of said substance in molten condi of the gas stream result in a corresponding vari~ tion, drawing said substance from said body into 65 said stream of oxygen-containing gas by the suc- be maintained notwithstanding. fluctuations in the operation and conditions of the process. ation in they rate of introductionof the naph thalen'e. Consequently the adverse e?ect, of such variations is in large part' compensated and a tion created by said stream in passing through said Venturi pipe and forming a vaporous reac tion mixture, maintaining the surface level of greater uniformity of composition of ,the result- ‘ said body substantially constant, and maintain ant gas mixture is obtainable than byprevious ing a substantially constant pressure on said body 70 70 methods of operation. vThe process and appa of said substance. ratus, moreover, are simpler to control, less trou blesome to operate, and are more certain in their maintenance of the desired ratio than those 75 heretofore. employed. As a result, greater uni ~ \ 2. In the conversion of anormally solid or ganic vaporizable substance to partial oxidation products by catalytic oxidation in the vapor phase with an oxygen-containing gas, the method of 75. 6 2,102,863 forming a vaporous reaction mixture of the oxy gen-containing gas and vapors of said substance which comprises passing a stream of the oxygen containing gas through a Venturi pipe, maintain ing body of said substance in molten condition, dra ‘ ng said substance from said body into said stream of oxygen-containing gas by the suction created by said stream in passing'through said Venturi pipe and forming a, vaporous reaction 10 mixture, maintaining the surface level of said body substantially constant at a point not sub stantially above the point at which said sub stance is introduced into said stream of oxygen containing gas and maintaining a substantially 15 constant pressure on said body of said substance. 3. In the conversion of a normally solid or ganic vaporizable substance to partial oxidation products by catalytic oxidation in the vapor phase ‘with an oxygen-containing gas, the method of tion mixture, maintaining the surface level of said body substantially constant at a point not substantially above the point at which said naph thalene is introduced into said stream of oxygen containing gas, and maintaining a pressure on said body of naphthalene substantially corre sponding with the pressure of the resulting va porous reaction mixture. 6. In the conversion of a normally solid organic vaporizable substance ‘to partial oxidation prod 10 ucts by catalytic oxidation in the vapor phase with air, the method of forming a vaporous re action mixture of air and vapors ofsaid substance which comprises passing 'a stream of air through a Venturi pipe, maintaining a body of said sub stance- in molten condition, drawing said sub 15 stance from said body into said stream of airby the suction created by said stream in passing through said Venturi pipe and supplying heat to the resulting mixture, thereby forming a vaporous 20 20 forming a vaporous reaction mixture of the oxy gen-containing gas and vapors of said substance ‘ reaction mixture, maintaining the surface level which comprises passing a stream of the oxygen of said body substantially constant at a "point containing gas through a Venturi pipe, maintain ing a body of said substance in molten condition, drawing said substance from said body into said stream of oxygen-containing gas by the suction created by said stream in passing through said Venturi pipe and forming a vaporous reaction not substantially above the point at which said material is introduced into said stream of air, and maintaining said substance at substantially the pressure of the resulting vaporous reaction mixture. ' . 7. In the conversion of naphthalene to phthalic mixture, maintaining the surface level of said ‘anhydride by catalytic oxidation with air, the not substantially above the point at method of forming a.vaporous reaction mixture which said substance is introduced into said of naphthalene vapor and air which comprises stream of oxygen-containing-gas, and maintain passing a stream of heated air through a Ven 80 body turi pipe, drawing molten naphthalene “from a stantially corresponding with the pressure of the ' body thereof into said air stream by the suction 85 resulting vaporous reaction mixture. created by said air stream in passing through said 4. In the conversion of naphthalene to phthalic Venturi pipe, thereby forming a vaporous reaction anhydride by catalytic oxidation in the vapor mixture, maintaining the surface level of said phase with an oxygen-containing gas, the method body of molten naphthalene substantially conof forming a vaporous reaction mixture of ‘the stant at a point not substantially above the point oxygen-containing gas and vapors of naphtha at which said naphthalene is introduced into said lene which comprises'passing a streamof the air ‘stream, and maintaining a pressure on said oxygen-containing gas through a Venturi pipe, body of naphthalene substantially corresponding maintaining a body of naphthalene in molten with the pressure of the resulting vaporous reac ing a pressure on said body of said substance sub condition, drawing naphthalene from said body 45 into said stream of oxygen-containing gas by the tion mixture. 35 ' ' 40 ' suction created by said stream in passing through 8. In the conversion of naphthalene to phthalic anhydride by catalytic oxidation with air, the said Venturi pipe and forming a vaporous reac-' method of forming a vaporous reaction mixture ' tion mixture, maintaining the surface level of of naphthalene vapor and air which comprises said body substantially constant, and maintaining passing a stream of air at a temperature of about a pressure on said body of naphthalene substan tially corresponding with the pressure of the re viding a body of molten naphthalene at a tem sulting vaporous reaction mixture.. ' , ' 5. In the conversion of naphthalene to phthalic anhydride by catalytic oxidation in the vapor 55 phase with an oxygen-containing gas, the method of forming a vaporous reaction mixture of/ the oxygen-containing gas and vapors of naphthalene which comprises passing a stream of the oxygen containing gas through a Venturi pipe, main taining a body of naphthalene in molten condi tion, drawing- naphthalene from said body into said stream of oxygen-containing gas by the suc tion created by said stream in passing through said Venturi pipe and forming a vaporous reac 150° to about 160° 0. through a Venturi pipe, pro v50 perature of about 130° C., introducing naphtha lene from said body into the throat of said Ven turi pipe, thereby forming a vaporous reaction mixture, maintaining the surface level, of said body of naphthalene at substantially the level of said point of- introduction of naphthalene'into said Venturi pipe, and maintaining a pressure on vthe surface'of said body of naphthalene substan- , tially corresponding with the pressure of the re 60 sulting vaporous reaction mixture. . GUY w. TAIIBER'I‘. JOHN D. KERR.