US1905719A - Catalytic apparatus - Google Patents

Description

April 25, 1933. A. o. JAEGER 1,905,719 v CATALYTI C APPARATUS Filed June 10, 1929 2 Sheets-Sheet l INVENTOR; flp/va/vs 0. Wi'ff,

ATTORNEY.

April 25, 1933- A. o. JAEGER 1,905,719

CATALYTI C APPARATUS 7 Filed June 10, 1929 2 Sheets-Sheet 2 INVENTOR. fiz PHO/YJ 0. C/A'GZA ATTORNEY. I

Patented Apr. 25, 1933 "UNITED STATES PATENT OFFICE ALPHONS O. J'AEGER, OF MOUNT LEBANON, PENNSYLVANIA, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE SELDEN RESEARCH ENGINEERING CORPORATION, OF PITTSBURGH, PENNSYLVANIA, A CORPORATION OF DELAWABE CATALYTIC APPARATUS Application filed June 10, 1929. Serial No. 369,544.

This invention relates to catalytic apparatus and more particularly to bath cooled converters for carrying out vapor phase catalyses. v

Bath cooled converters of the so-called tubular type in which catalyst compartments in theshape of tubes or other shapes such as rectangles, squares, etc. have in the past fallen into two general types, namely,

those cooled by a non-boiling bath surrounding the tubes or catalyst compartments and those cooled by a boiling bath surroundlng the tubes. The former have the advantage that the bath changes in temperature as 1t passes over the tubes and that, therefore, a

temperature gradient is possible, a very 1mportant factor in most catalytic reactions which usually require much higher temperatures in the portion of the catalyst encountering fresh reaction gases than in later portions'. Converters provided with a non-boiling bath-also have the advantage that only a single'liquid-tight tube sheet is necessary, namely, a bottom tube sheet. The bath materials may be relatively cheap, such as molten, low priced metals, as lead or even more economical baths, such as eutectic mixtures of salts, for examplein the case of salts used for organic oxidations a eutectic mixture of sodium nitrate and sodium nitrite. Despite the advantages of low priced .bath

' material, relatively cheap construction, simple maintenance problems and the all-important possibility of an adequate tempera- V '3 ture gradient in the catalyst tubes, simple non-boiling bath converters have been sup planted in many cases, especially with strong exothermic reactions such as the oxidation of certain organic compounds, for example 7 40 naphthalene to phthalic anhydride, by tubular converters with a boiling bath surrounding the tubes, using in the case of organic oxidations boiling mercury under various pressures or alloys of mercury which boil at the desired temperature. Boiling sulfur bath passes up over the catalyst tubes, then out of the zone of catalytic reaction where it is cooled, (preferably by a gaseous medium, and returne to the lower portion of the catalyst tubes, this circulationbeing described and claimed in the patent toJ. M. Selden, No. 1,647,317 dated Nov. 1,1927. This con verter type has achieved large commercial success, particularly in the oxidation of naphthalene to phthalic anhydride, and is superior to the best boiling bath converters from the standpoint of catalytic efiiciency, lowcost and long life. The circulation, however, is not strictly defined and, therefore,

the size of converter which can be built is limited to a certain extent since it is not possible to adequately cool central tubes in converters cxceedingthe normal dimensions because of the tendency of the bath circulatmg by 'thermosiphon 'efiect totake the easiest path.

An improvement on the non-boiling bath converter, especially those embodying the circulating principle ofthe Selden patent, is described and claimed in my co-pending application'Serial No. 256,189, filed Feb. 23, 1928. In this application a non-boiling bath is combinedwith cooling elements contain- 1 'ing boiling liquids, preferably located in' a zone separated from the catalytic zone and in, some modifications provided with the circulation principles of the Selden patent either by thermosiphon or mechanical circulation. This type of converter combines automatic temperature control, which is the only advantage of a boiling bath, with the advantages of a non-boiling bath converter of the ordinary type, and the disadvantages of the boiling bath are minimized since only a small amount is used with a correspondingly low cost and the boiling bath can be disposed in closed-end tubes suitably mani folded, a construction which is both cheap and durable and is not subject to the serious leakage troubles which are such a menace to any plant using an ordinary boiling bath converter. Even the converter described in my co-pending application above referred to, improvement, though it is over the simple circulating non-boiling bath converter and the ordinary boiling bath converter, still possesses certain disadvantages in that the size of the converter is subyect to the same limitation as is the circulated nonboiling bath converter of the Selden patent. It is impossible to bring about a uniform circulation over peripheral and central tubes alike with converters that exceed a certain size, although with eflicient mechanical circulation much larger converters may he satisfactorily built than those using the simple circulation of the Selden patent.

The present invention eliminates all of the disadvantages of the circulating non boiling bath converters of the Selden patent and of my co-pending application, applicable to converters of any size, the cooling efficiency, particularly in the preferred embodiments, being unaffected by the temperature of the converters, and in the preferred embodiments all the advantages of automatic temperature control inherent ,in boiling bath converters are obtained. At

the same time the present invention permits an ideal temperature gradient in the catalyst compartments, something which has not been possible with hitherto used, and which to their fullest extent the mostm'odern and efficient contact masses, at the same time permitting high loadings with great smoothness of operation.

According to thepresent invention a nonboiling bath is circulated longitudinally along catalyst tubes instead of across them. in the ordinary non-boiling bath converter of the circulating type. a The heated bath is then removed from the, zone of catalytic action and is subjected to cooling. In the preferred embodiments there is a plurality of zones of catalyst tubes with alternating zones of closed-end tubes containing a suitable boiling liquid, the flow being regulated by bafiles in zigzag manner, first up over the catalyst tubes in one zone, down over the cooling tubes in the first cooling zone, then permits utilizing and is any of the converters up along the catalyst tubes in the next zone, and so on until the cooled bath from the last cooling zone is finally returned to the bottom of the tubes in the first catalyst zone. The number of cooling zones and catalyst zones, which are preferably arranged concentrically, for example in the form of concentric polygons, (hexagons are illustrated in the drawings) may consist wholly of catalyst tubes and tubes containing a boiling liquid, or in the preferred embodiments the last cooling zone is the converter shell which is subjected to temperature regulation by the passage of a gaseous medium thereover, a cooling method similar to that shown in the Selden patent above referred to. In this manner converters of great size can be built, all the advantages of automatic temperature control of the boiling bath are retained, a very small amount of expensive boiling bath is used, and it is housed in a construction which is both cheap and free from serious maintenance problems and the relatively cheaply constructed and highly efiicient converter shell cooling effect of the Selden atent is utilized to the fullest.

All of these advantages are combined with the essential feature of the present invention, namely, the circulation of the bath longitudinally along the catalyst tubes or compartments instead of transversely thereto or partly transversely and partly longitudinally as in the modern commercial converters built under the Selden patent in which large numbers of small vertical tubes take the place of larger catalyst compartments shown in the Selden patent and which represented commercial practice in 1920, the date patent. The perof the filing of the Selden feet counterflow of the non-boiling bath with respect to the catalyst tubes where the heat is evolved and the cooling zones where the bath is cooled permits an ideal temperature gradient without any sacrifice in output, capacity, or in ease and reliability of operation. It is a significant advantage of the present invention that the flow is the same at high speed as at low, which is not the case with convection circulation undirected by baflles. It is alsosignificant to note that the zigzag counterflow, which is typical of the converters of the present invention, is achieved in a direction which is always parallel with that induced action. In other words, the natural ten ency of the bath heated by the catalyst tubes is to rise along the tubes and this is precisely the direction in which it flows. Normally, the portion of bath being cooled in the cooling zones tends to flow downwardly and this is again parallel to the direction of fiow in the converter. Thus, mechanical circulation may be used with thermosiphon bath circulation, assisting each other and effecting a notable saving in power and in the case of by the thermosi honsmaller converters or where the exotlierm of the reaction is not excessive mechanical circulation may even be dispensedwith,'although for most reactions it is distinctly preferable to provide a positive mechanical circulation; the greater smoothness of control and surety more than counterbalances the slight complication 'ofapparatus and the small amount of power used. However, the invention is not limited in its broader aspects to converters in which mechanical circulation is provided. V

The present invention is applicable to all exothermic catalyses. Itis'particularly effieient in strongly exothermicreactions such as the oxidation of organic compounds and in this field presents many attractive features. The invention, however, is not limited to the oxidation of organic compounds,

but is generally applicable to exothermic.

vapor phase catalyses. A few representative catalyses are:

1. Reactions n which an intermediate oxidation product isproduced. The oxidation of benzol, toluol, phenol, tar phenols or furfural and other compounds containing the group CH CH=CHCH to maleic acid and fumaric acid or mesotartaric acid; cresol to salicylaldehyde and salicylic acid; tuluol and the various halogen and nitro substituted toluols to the corresponding aldehydes .and acids; xylenes, pseudocumene, mesitylene, paracymene and other derivatives to the corresponding aldehydes and acids; naphthalene to naphthaquinone, phthalic anhydride and maleic acid; phthalic anhydride to maleic acid and fumaric acid; anthracene to anthraquinone; phenanthrene to phenanthraquinone, diphenie acid, phthalic anhydride and maleic acid, acenaphthene to acenaphthylene, acenaphthaquinone, bisacenaphthylidenedione, n a p h th a l dehydie acid, naphthalic anhydride and hemimellitic acid; fluorene to fluorenone; eugenol and isoeugenol to vanillin and vanillic acid; methyl alcohol and methane to formaldehyde; ethyl alcohol to acetic acid; ethylene chlorhydrine to chloracetic acid and the like.

2. Reactions in which an undesired im purity is burned out, such as the purification of crude anthracenes of various degrees'of impurity with total combustion of carbazole, dead oils and in some cases phenanthrene; purification of crud naphthalenes and crude mononuclear hydrocarbons, such. as benzols and the like; purification of ammonia from coal tar with the burning out of the organic impurities such as phenolic bodies present, etc. v

3. Oxidation of mixtures of organic compounds to desired intermediate products with removal of impurities such as the oxidation of crude anthracenes, phenanthrenes,

and the like to intermediate products such as anthraquinone, phenanthraquinone, di-

with concomitant removal of carbazole and dead oils by total combustion; the oxidation,

of crude tar acids to maleic and fumaric acids with the combustion of certain impurities, etc. v

Reductions and hydrogenations, such as, reducing nitro compounds, for example nitrobenzene, dinitrobenzenc, nitrophenol, nitronaphthalene and their homologues to the correspondin amines or the corresponding hydrogenate amines, the reduction of aldehydes and ketones toalcohols, such as benzaldehyde to benzyl alcohol, acetaldehyde to ethyl alcohol, crotonaldehyde to the corresponding butyl alcohol, and the like, the reduction of oxides of carbon to methanol, methane, higher alcohols and ketones or petroleum-like products, the hydrogenation of aromatic compounds to alicyclic com ounds such as benzene to cyclohexane, nap thalene to tetra'line or decaline, anthracene to hydrogenated anthracenes, phenol to cyclohexanol, acetylene to ethylene and ethane, and the like, polybasic acids to inner esters, such as phthalic anhydride to phthalid, camphoric acid to campholid, and the like, reduction of nitrogen containing heterocyclic compounds to aliphatic amines such as phridine to amylamine are also of importance.

In addition to reactions in which a more or less homogeneous raw material is reduced, certain mixtures of raw materials may be effectively reduced with or without the pres ence of additional reducing gases. Thus, for example, oxides of carbon may be reduced'in the presence of-the vapors of many organic compounds. For example, they may be reduced in the presence of aliphatic hydrocarbons, such, as paraflins, olefines,

acetylenes, hydrocarbons having the formuthe desired direction with great effectiveness by the incorporation of suitable stabilizer promoters or stabilizers in the contact masses.

- Another class of combined reaction consists ,in the reduction of oxides of carbon with or without hydrogen in the presence of vapors of aliphatic alcohols, such as parafiin alcohols having the formula C H OH, or unsaturated alcohols having the formula 0m OH, or C Hg OH, etc; Pol alent alcohols such as glycol, glycerol an the like, may be reduced in combination with carbonyl compounds.

oxides of carbon with or without hydrogen.

Oxidation products of alcohols, such as, for example, saturated or unsaturated aldehydes and ketones, or oxidation products of polyvalent alcohols, such as glycolaldehydes, glyoxal, glyoxylic acid, oxalic acid, and the like, may be used for vapor hase reductions in thepresence of oxides of carbon and hydrogen. Oxidation alcohols and divalent isomeric alcohols may also be used, of course only where it is possible to obtain the vapors of the compounds without undesired decomposition.

Aliphatic acids form another important class of compounds which can be reduced in combination with oxides of carbon. The

acids include fatty acids, oxyacids, lactones,

polybasic acids, ketone acids, and the like. Other miscellaneous aliphatic carbonyl compounds such as aldehyde alcohols, diketones, triketones, oxymethylene ketones, ketone aldehydes, ketone alcohols and the like, may also be combined with oxides of carbon and reduced in the presence of the contact mass described above to form many valuable products.

In addition to compounds of the aliphatic series which may be reduced together with oxides of carbon, various compounds of the alicyclic series, such as, for example, alicyclic compounds, for instance, cycloparafiins, cyclodiolefines, may be combined with oxides of carbon and reduced. Examples of specific members of this class are cyclohexane, c clopentadiene, dicyclopentadiene, and the li e. Of course alicyclic carbonyl compounds, such as cyclohexanol, cyclohexanone, etc., may be used, it being understood in this connection and throughout the specification that'any compound containing the CO group, irrespective of whether the oxygen is united to carbon with a single or a double bond, are included under the term Aromatic compounds, drocarbons, naphthalenes, a n t h r a c e n e s, phenanthrenes, phenols, aromatic alcohols, aldehydes, ketonesand acids may be reduced in the presence of oxides of carbon and hydrogen, of course only insofar as the products are capable of volatilization without undesired decomposition.

Heterocyclic compounds, such as products containing the furane nucleus, pyrrole bodies, pyrrolidines and the like, may be reduced together with oxides of carbon.

In the inorganic field exothermic catalytic reactions such as the synthesis of ammonia and the oxidation of ammonia to oxides of nitrogen are well suited for the converters of the present invention, which can also be used for the contact sulfuric acid process as .it is possible to obtain a temperature gradicut which is so necessary-for the high reaction velocities, combined with satisfactory products of trivalent,

such as benzene tion of naphthalene conversion and which makes a boiling bath converter so hopelessly unsuited for the con tact sulfuric acld process.

The invention will be described in greater detail in connection with the drawings which are diagrammatic representations of a typical commercial design of converter suitable for the oxidation of organic compounds. The operation of the converter will be described in connection with the oxidation of naphthalene to. phthalic anhydride, a reaction which brings out the features of control of the invention in ,a very striking manner. It should be understood, of course, that this description-is merely of a typical embodiment, and the invention is equally applicable to the other reactions set forth above, and modifieddesigns of converters are also included.

In the drawings:

Fig. 1 is a vertical section through a converter embodying the principles of the present invention; and

Fig. 2 is a horizontal cross section through the converter of Fig. 1 along the line of 2-2.

The converter consists of a shell 1 with bottom and top pieces and lower and upper tube sheets 3 and 4. This shell is provided with reaction gas inlet 20 and outlet 21 and is surrounded. by an air cooling jacket 2, which is provided with gas burners 22 around the circumference of the converter to heat up the bath when starting up. The air jacket is further provided with fiues 23 controlled by dampers 24. Within the shell 1, supported by the tube sheets, are arranged series of catalyst tubes 6, 7 and 8. Between these is suspended a baflle structure which may be of any shape, but which is shown as hexagonal in cross-section. These bafiies consist of side walls 10 and 12 and bottom walls 25 and are suspended from the upper tube sheet 4. Within the baflies are mounted rows of tubes 14 and 15 which are closed at the lower ends and are designed to contain a liquid which boils below the reaction temperature. At the upper ends these tubes are connected to manifolds 16 and 17 which lead to condensers 18. Any number of halffie structures may be arranged concentrically, two being shown on the present drawings. The mechanical circulation of the bath is effected by the propeller 19'which fits sufiiciently closely in the bafile 13 to provide for satisfactory circulation.

When the converter is used for the oxidato phthalic anhydride, the catalyst tubes 6, 7 and 8 are filled partly or wholly with a phthalic anhydride catalyst, this being supported at the bottom by means of a screen which is in turn supported by the screen supporter 5: A vaporized mixture of air and naphthalene, having, for example, a ratio of 18 liters of air per gram of naphthalene, enters through the inlet 20 at a temperature of about 150-160" C. The reaction ases passing through the upper portion 0% the catalyst tubes 6, 7 and 8 are preheated to reaction temperature by the heat of the bath. The heat generated in the catalyst tubes is transferred to this liquid and causes it to rise in the spaces surrounding the tubes. This action is supplemented by the propeller 19 situated at the center of the converter. The rising liquid over-flows the baflles 12 and 10 and comes in contact with the tubes 14 and 15 which contain the liquid adapted to boil below reaction temperatures. The excess heat contained in the circulating liquid is taken up by the boiling liquid in these tubes as latent heat of vaporization and the circulating liquid so cooled descends between the hexagonal baffies and escapes under thewalls 11 and 9, thereby coming into contact with other sets of catalyst tubes. Here it absorbs more reaction heat and once more rises. When the rising liquid overflows the outer baflle 27, it comes into contact with the shell of the converter which is air cooled as has been described. It, thereafter, descends between the bafile 27 and the converter shell and passes beneath the bottoms 25 of the bafiles and again comes in contact with the central catalyst tubes. This cycle is repeated and an extremely efiicient cooling of the catalyst tubes results since the flow of liquid is al ways along the tubes instead of across them and a maximum efiiciency of heat transfer is thereby made possible.

It is preferable to pass the gases from the top to the bottom of the catalyst tubes, as normally the highest reaction temperature is in the portions of the catalyst which encounter the fresh reaction gases and, therefore, the fiow from the top to the bottom gives the most effective heat gradient and permits absorption of heat by the bath.

However, so efficient is the cooling of the bath in converters of the present invention that it is feasible to pass the gases from the bottom to the top of the catalyst tubes. This is of advantage in some reactions which are extremely sensitive as the greatest heat head and correspondingly the most vigorous cooling is encountered in the portion of the catalyst which is struck'by the fresh gases. Preheating is, however, by no means as effective when the gases are circulated from the bottom to the top as the lower portions of,

the bath are, of course, below the temperature at which the end of the reactionltakes place. In most catalyses, however, this is not serious as the catalyses will usually begin at temperatures considerably below those for maximum conversion and the heat evolved in the catalyst rapidly brings the latter up to reaction temperature, for the catalyst is at all'points where vigorous reaction takes the bath.

In the drawings the cooling tubes containplace considerably hotter than ing the boiling bath are shown as provided.

This application is in part a continuation of my co-pending application Serial No. 256,189 filed February 23, 1928.

What is claimed as new is:

1. An apparatus for carrying out vapor phase catalyses, comprising in combination a converter shell a plurality of zones of vertical catalyst tubes arranged concentrically therein, zones of tubes containing a cooling medium arranged between the zones of catalyst. tubes and a baflle structure consisting in a baflle surrounding the central zone of catalyst tubes and extending from a point below the upper level of the bath to a point slightly above the bottom of the converter, a second bafile surrounding the first zone of cooling tubes and extending from above the upper surface of the bath to a point slightly above the lowest point of the first baflle, a third bafile surrounding the second zone of catalyst tubes and extending from a point slightly above the bottom of the converter to a point slightly below the upper surface of the bath, the first and third baflies being joined at their bottom edge by a horizontal baflle. The baflling structure being repeated for each additional zone of cooling tubes and catalyst tubes whereby the bath is caused to flow upwardly along the catalyst tubes of the central zone, downwardly along the cooling tubes of the first cooling tube zone, upwardly over the catalyst tubes of the second catalyst tube-zone and so on until the bath flows over the top of the bafile surrounding the last zone of catalyst tubes, whereupon it flows downwardly between the converter shell and the last baflle, underneath the horizontal. baflle joining the bottoms of the odd numbered bafiles and into the bottom of the central zone of catalyst tubes.

2. An apparatus according to claim 1, in

which mechanical bath circulation is pro-- which the cooling medium in the cooling tubesis a liquid having a boiling point lower than the lowest temperature at which the non-boiling bath is used.

5. An apparatus according to claim 1, in which the cooling tubes contain a liquid having a boiling point slightly below the lowest temperature at which the non-boiling bath is used.

Signed at Pittsburgh, Pennsylvania, this 3rd day of June, 1929. Y

ALPHONS O. JAEGER.

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