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NGV.' 25,- 1945'- " " K.. D. ASHLEY; AL 2,411,320 MÃNUFACTURE OF ('ÈÀ‘TÍU'JYSTS> Filed sept. 22, A1942 NJ@ \Q . 2,411,820 Patentedy Nov. 26, 1946 UNITED _v ‘MANUFAcTUnE _ _ 2,411,320l oF cA'rALY's'rs _ I Á . ' _if e _'Kenneth D. Ashley, Noroton,_a_nd ‘Alphons v0. Jaeger, Greenwich, Conn., a‘ssìg‘nors’to' Ameri- < can 'Cyanam'id Company, >New York, N. Y.,- a Corporation-@Maine 'Y ’ ’ .i _' ~ 'e .t x applicati@ september 22„1942', serial No; `459,262 ,_ _ ' 201mm.l (c1.‘252-'250`) f ' y ' - ‘catalysts in the quantities commensurate _with This invention relates 'to- the manufacture of f catalysts, and more particularly tothe manufac- _ _ the _extent of the~petroleumiridi1stry.'1; Ordinary silica gel is` preciuitated by ture of gel-type catalysts containing oxides or ` - acìdifylng 'relatively strong solutions _of alkali metal Aisili catès with relatively .conc_entrate'df- mineral 4acids _ hydrous oxides of'metals of .the third and fourth v _ groups of the periodic system. While the princi# ples of the invention may be >applied _to- the pro~ __ t to _produce a colloidalsolu'tion of silicic’aCid. and duction of gel-type catalysts for> any `_’purpose, _ ` . the'same procedure is employedf for the'man'ufac "tureof aluminagel and other'hydrousoxide gels , they are particularly useful in themanufacture "used as adsorberits.V `In _all _cases _theconçentra of cracking catalysts, dehydration catalysts and dehydrogenation catalysts of any desired parti Ations are such'thatthe entire reaction" mixture soonj sets'to ,a'hydrogeL and _this'hydrogel is cle size, such as those employed for the catalytic ` washed with hot ’water to'removejthe' _free acid dehydrogenation or cracking of petroleum >frac- n _and mostof the waterf-fsolublè salts, _Howeven it. tions fory the production of butadiene or of high is impossible to reinovethë'augaii metal "sans from octane gasoline and those used for dehydrating 'ahydrogel by _this method to‘_`_„the extent neces glycols such as 1,4-,_2,4- or_2,3-butylene glycols to saryjfor catalytic purposes, and >therefore these butadiene. ' y , 'A _ __ _ An important class of gel-type catalystsin wide commercial use for dehydrogenation and-crack ing reactions are silica catalystsprepared by pre cipitating hydrated silica from waterglass solu tions.- Alumina-silica, aluminaètitanium-'oxide " . salts `have been* _removed ji‘rfo'rn- the freshly precipl- ‘ tated silic'ic_'__acidfg€l _by repeated filtration and washingl" This filas 'provento be avtedious and _expensive procedure, _for the'iiltration rate of aqueous suspensions of ordinary gelatinous silica _isy extremely slow. "Moreoventhe alkallmetal ionsare adsorbed so 4'strongly vbythe continuous > silica and alumina-zirconium. oxide-silica cata- 1 lystsare produced by precipitating solutions con coating of gelatinous silica on afllter that large taining aluminum or mixtures of 'alumina' with 25 quantities of Wash Water are necessary for their zirconium or titanium on a precipitated silica hy removal, and the slow rate of penetration of the drogel. Representative catalysts of the first class ‘ _ vvash 'Waterthrough alilter cloth coated with a are described in U. S. Patents Nos. 2,285,314 and ' layer of'gelatin‘ous silica has increased still fur 2,287,917. It is a principal object ofthe present "f . therthedifliculties encountered inA operating this f invention to provide -an improved-method’for the _process ona largev scale. ' ' ' We have’discovered that an aqueous suspension _of hydr'ou's oxides consisting oforcontainlng ge manufacture of catalysts of these _classes,«which yprocess is especially adapted to the large scale ' manufacture ofv gel-type catalysts of'high efli l latinous'jhydrat'ed silica can be pretreated in such ciency. In their broader aspects, however, some of the features of the present invention are ap _ ‘f a manner as to'iacilitate the _filtration and wash ing' thereof without impairing vthe, activity of. gels plicable to the `manufacture of any gel-'type cata- _' 'v produced when the hydrated silica is dried and " calcined. The most important feature of our'pre _ treatment is referred to _hereinafter as a fioccu -` _ lation step _and the silica sc_treated is referred lyst consisting'of cr comprising active silica.' Gel-type catalysts containing .active vsilica should be substantially free from alkaliv metal to' a‘s _floccul'ated _s_i1ica,'but it should> beunder "stood that these terms referto the condition and position. Such catalysts should also be of'rela _ _'behavio'rÍ'of A' the silica __or'_.other _hydrated metal compounds and >other Water-soluble salts that might act as a flux in the iinishedcatalyst com _ tively uniforml particle size, with a ¿minimum _ " _'oxide' duringjthe._dewatering'and Washing thereof amount ofñnesnThe'present invention 1s rpar- ` which catalysts are substantially free from corn- _ ' pounds ofalkali metals and are of relatively uni- ’ ject"r the vaqueous _suspensionsr containing' gelat inou's hydrated silica to -a conditioning procedure which does not materially change the density. appearance or degree of dispersion rof the hy form particle size. A principal advantage of the invention resides in the fact’thatgel-type lcata lysts having these desirable properties can vbe pre pared from such cheap and readily available -rna- " terials> as sodium> and iwtassiurn> silicates by the method thereof, which "method is especially adapted for large scale manufacture of cracking ratlher than to' any noticeable'ch'ange in the aque ous suspensions‘afterthe 'ñocculating agent has `_ been added._ I__lrlpl‘acticing our- invention wer sub ticularly directed to methods forthe preparation of gel-type catalysts containing `active silica, ‘Ídrated vsilica particle‘sin'the aqueous slurry, but ,'which _'so modiñes these „particles“ that they >form _' a relatively thick',_porous‘iilter‘cake'of good me " chanical strength' instead ofthe 'ordinary thin, 55 slushy filter ’cakes- that are obtained when ordi 2,411,820 3 4 nary gelatinous silica suspensions are filtered. We believe that the water-dispersible adhesive point it may be stated that except where other wise noted all the tanks subsequent to tank I colloids hereinafter referred to as fiocculating agents operate to modify in some way the electric charge on the hydrated silica particles in sus or redisperse gels that have settled or been fioc pension, but the advantages 0f our invention are culated. are equipped with agitators which move very slowly, so that there is no tendency to break up not limited by this theory of operation and the suflicient additional water to reduce the SiO: to other causes. The flocculating agents which modify the ge latinous silica particles in the manner described In the tank 3 sufficient additional acid « is added to bring the pH to about 'LOZ-’7.8 and results obtained may be due partly or even wholly 10 content to 3.8%. After suitable retention in the correction tank 3 the gelatinous hydrated silica slurry resulting are preferably added to the aqueous gelatinous ' from the acid addition and dilution is passed to a silica suspension after the suspension has been blending and aging tank 4, wherein it may be aged for a period of time, although definite im aged under slow agitation for any suitable time. provements are noted when the aging step has 15 Aging of the slurry appears to increase the aver been omitted. We have found that aging ap age particle size of the silica suspension either by pears to aid materially in obtaining a relatively agglomeration of the smaller particles or by their thick and porous filter cake; in fact, we have adhesion to larger sized particles. It will be noted some improvements in the filtration and noted that tanks 3 and 4 are both provided with washing of slurries of gelatinous hydrated silica 20 side outlets, which permit the retention of about which had been aged for 1-2 hours, but to which 25% of the aged suspension from a preceding no ñocculating agentwas added. Our invention batch to function as a nucleus for particle size in its broader aspects therefore includes the com growth. bined steps of aging followed by filtration as one The aged slurry is vpassed t0 tank 5, which is a of its important features. 25 flocculating apparatus in which the silica is fioc A number,` of important advantages are ob culated to a condition in which it is ready Afor tained by preconditioning pulps or slurries of ge _ filtering and washing to remove the water-soluble latinous hydrated silica in the manner described alkali metal salts.> The slurry in tank 5 is first above, prior to the dewatering thereof. We have brought to a pH of 5-6 by the addition of suitable found that inorganic salts such as sodium sul 30 amounts of sulfuric acid or other mineral acid fate, sodium nitrate, sodium chloride and the aftell which a flocculating agent is added. . Rep like can be more rapidly and completely removed resentative adhesive colloids that we have used from a ñocculated silica slurry by washing as with success for this purpose are glue, gelatin, well as by filtration, and the silica can therefore gluten and gluten-containing materials such as be dewatered by any suitable procedure; More wheatv flour 'and the like. These and similar over, flocculation of the hydrated silica also re flocculating agents are preferably added as solu suits in a final dried product of much greater tions or suspensions in water and are employed uniformity in partidle size, as compared with the inv amounts of 0.001% to 0.1%. based on the irregular size of the particles obtained by drying weight of the slurry. hydro'gels of silica or silica and alumina obtained 40 The flocculating agent is distributed uniformly ~by the ordinary methods heretofore employed. Our invention in its broader aspects therefore in cludes the dewatering and washing of ilocculated silica by any suitable method including filtra tion, settling and decantation, thickening and the like. ' The application of these discoveries to an im proved method for the manufacture of gel-type catalysts suitable for use in hydrocarbon crack ing and conversion reactions will be illustrated by the following description of a preferred method of catalyst manufacture with reference to the accompanying drawing. This drawing is a flow sheet in which the details of our preferred process are diagrammatically illustrated by tanks, Afilters and flow lines, but it should be understood that the invention in its broader aspects is not> limited thereto. In carrying out Àthe process illustrated in the ' throughout the hydrated silica suspension in tank ,5 by means of slow agitation, The resulting floc culated suspension is then pumped to the distrib `utor box B, which is a wooden box of relatively large cross-sectional? area provided with one or more vertical partitions ‘I and adapted to main tain the silica in a fiocculated condition while supplying a steady fiowof slurry to the filter Il. This may be an ordinary filter press or any other known type of filter, but is preferably a rotary -filter of the vacuum drum type provided with fine Water sprays for continuous washing of the fil ter cake, in order to aid in the separation of salts of alkali metals and other undesirable ma terials‘from the silica. ` . On the `filter 8 the silica can be Washed free from the major part of its Water-soluble impur ities by wash water which may be acidified with a little sulfuric or hydrochloric acid, the filtra drawing wefirst prepare a dilute solution of so 60 tion and washing being greatly aided by the floc dium or potassium silicate in a mixing tank I, culation of the silica in the tank 5. In large scale which is provided with a suitable high-speed >im» operation the wash water from this and other pelÀlor-type or turbine type agitator 2 to obtain , similar washing steps of the process is preferably uniform mixing of the charge. The diluted regenerated for reuse by contact with a cation water glass solution is neutralized with sulfuric, exchange resin such as sulfonated coal, which re hydrochloric, nitric or other mineral acid to a pH moves the sodium ions and regenerates free sul of about 7.4-7.8, after which the agitation is con-furic acid or hydrochloric acid in the solution. tinued for about 1/2 hour. The amounts and The washed ñlter cake is then discharged into a strength of the reagents are such that the solu repulper 9, which is an enamel-lined vessel ñt tion contains about 5% S102. 70 ted with a horizontal agitator I0 which may be After the preliminary acidification the con a relatively high speed agitator. In the repulper tents of tank I are discharged into tank 3, which the filter cake is again dispersed in water to form is a correction tank equipped with a suitable a uniform slurry for further treatment. agitator and of a size suillcient to permit a reten In the preparation of catalysts or catalyst car tion of the charge for about '75 minutes. At this 75 riers consisting essentially of silica the slurry 6 5 ' lsuitable type, such as a-hotair or steam heated Il to a fiocculating and adjusting tank'IZ where- ' ` drier. ' By this means-we'may remove `rasfmuch ' from the repulper >9 may be passed Vthro'ughlline ~ * as 40 to 60% ofthe water inthe filter cake, _after in the silica may be aged and flocculated >by the ‘which Lthe dryingïof the partially- dried gel may. addition of a flocculating agent if` desired." In - be completed‘iin a ycalcinerhof the rotary kiln preparing mixed catalysts containing'the active type. Alternatively, the` drying maybe carried silica together with , other >catalytically, active " vout in one or more rotary' kilns, and such a cal ciner is illustrated on the drawing. « metal oxides and/or hydrogels the silica-slurry is ñrstpassed to one of the two tanks*I3,an`d,I4.„~ A T_he’calciner is preferably direct-'firedin a fire solution ofaluminum sulfate or ‘other salt of the 7 desired metal'is then added tothe slurry suspen 10 box 25 and sufficient capacity is provídedvto 'heat the catalyst to'temperatures of `1500o F. before it sion after which sufficient ammonia is added as ` is discharged.' The dried' material is then ground - in a. grinder 26 to «io-mesh size and is obtained ammonium hydroxide to precipitate the hydrated metal oxide from its salts. Thus, for‘example, as a product containing >not more'than’0105% ' in the preparation o'f a silica-'alumina’catalyst of ~ the type described in U. S. Patent No. 2,285,314 al A1`5` fNaz'O and little or> n_o FezOa'orother undesirable solution of aluminum sulfate `in kwater 'is added to ' the slurry of silica in the tank I3 under continu-`rv ' materials, v ` > The' following'specific examples are given to Íshow the 'results obtained by the process of ourv ous agitation during one-halfïhour after which invention and also tovlllustrate the importance 8%r aqua ammonia‘is added during 10-20 min ' utes to bring the'pI'li'to’4.5-5.7.y In the prepara- „ r20 of certain features of .thisprocesa' ` tion of modified catalysts a small amount of zir ^ conium or titanium sulfate may also ‘be added . ‘ ' " remplie-ir Inpracticing the foregoing process. according and precipitated. By'employing thel tanks I3 and I4 in parallel it is possible, of course, tohan .gto oneembodiment’thereof, 4.36 tons ofsodium die a second batch of the semi-purified silica `25' silicate in the form- 4ofvv commercial‘waterglass f `was added to .thevmix'ingtank I, together with while the alumina or >other polyvalent metal is 18.54 tons of water, and ,after completing- the being added‘to and precipitated in the first batch, dilutionl 2.2 tons 'of `24.9% sulfuric acid were added. After agitatlng for one-half hour the and any number of tanks may be employed in'thls vmanner in large scale operation.- ~ _ » y After the addition and precipitation of alumina4 -30 'resulting slurry was passedthrough the correc tion‘and aging tanks 3 and"l,"as=previously de . -or other metal salts in`v the tanks I3 or Iloth‘e're- " scribed, and 0.015% ‘of’ glue was added in the >sulting slurry is introduced intol the aging- and ñocculation tank I5, Glue, gelatin or other` suit able flocculating agent may be> added in approx imately the rsame quantities that were used inthe -fiocculating tank 5l' After suitable >floccul'ation ,the solids were then filteredioff on the filter 8 ’ and washed ‘with‘30.9 tons ofwaterïcontaining". sufficient sulfuric acid toïreduce'the pH of 4the wash water to 2.8. The washed filter’ _cake was repulped with 9.6 tons of water` in therepulper “land run into tank I3, where a solution-*of 0.8 Vtank 5 if desired, but'this'is- 'not usually neces- _‘; , sary since the hydrated aluminum oxide makesv the slurry much easier tolñlter. In the tankflä »the slurry is preferably adjusted to ‘L5-6% sol ton of> aluminum sulfatedin "1.16y tons of >water ids by the addition of water -if' necessary,"andv lwas added. y ' kept under slow .agitationuntil the hydrated The alum K‘was' then precipitated by the addition of 1.87` tons of k8,%’§l\I_IH4.OH solu washing. It is thenpassed' to the -ñlter I6, which , ' tion and the resulting> slurry wasr flocculated in vthe tank I5 by the addition oit-0.015%v of‘glu'eas is a rotary filter similar to the'filter `8,~ and the flocculated solids are separatedfrom the accom 45 before., AAfter the following'filtrationstep the alumina-silica mixture is ready for filtration and -cake on the'filter I6 was washed- with 25.5 tons 'panying salt solution and washed with acidifled . water ' as before. ' : . vof water containing sufficient sulfuric acid to reduce its pH to 2.5-¿3 and repulped in 12.9 tons The same quantities kof dilute lacid ofwater. V V y In order to reduce still further‘the content ofl alkali metal salts, ammonium salts, and otherl ' undesirable water-soluble material from the sil 50 and waterwere used ony the filter I8 and re ica-alumina mixture, the filter cake is‘again' pref, . "Apulper 20, but 21.9`tons ofl'purewater were used erably reslurried in water-,in 'a second Vrepulper ` " to Wash the filter cake onj'the filter [22. YAfter ' 1 thei'calci’nation 1.26 tons of an oil-cracking cat I'I and again filtered on la rotary filter I8, with or alyst were `obtained which contained 90% SiOz >and"10% A1203 in a highly active condition'. , `> Example 2f. .. without reflocculation and aging in tank I9 de pending on the condition of the solids .at this -> point. rI‘he filter cake »from 'the' filter I8 may then be reslurried once more in the repulper 20 .if desired, brought to a vsolids content of 5%.and a pI-I of. 4.3-5.0 in’ the tank 2I kand filtered on the - v52.5 pounds of water and 12.5pounds lof 41° ~ Bé.- commercial` sodium silicate containing- 28.5% rotary filter 22 which is washed with water to 60 remove the remaining water-Soluble impurities. The filter cake is then removed at approximate ly 10% solids onto a belt conveyor 23, which dis charges it into a calciner 24. x Because of the 'large quantities of water `re tained by gelatinous hydrated silica or silica-alu mina mixtures a relatively large drier or calciner is necessary. In some cases, however, we havev SiO:y and 8.9% of NazO are run into a mixing tank> f corresponding to the mixing tank I _on the draw . ing. 6.5 pounds of 25% sulfuric acid were addedv wlth the agitator 2 vat sufficiently high speed to keep the material moving away from the edges of the tankwhen the mixture became thick. After 30 minutes the resulting mixture was transferred to a tank corresponding to the floc culating tank 5 provided‘with a slow-moving,>v gate-typeV agitator. v24 pounds ofv waterwere found that the purified gelatinous filter cake can be advantageously dried and calcined by a plu 70 added along with 0.1-0.3 pounds-of 25% sulfurick acid .to reduce the pH to 6.8-'7.8. The mixture y drying stages. Thus„` for example, we was allowedïto age for 2 hours, the pH was re’ may-subject the wet filter cake to hot air or other duced to 5.5'by the addition of further quantities drying ~’gases by vsupporting iton- a belt or other of sulfuric acid and a water-solution of glue was conveying mechanism which is passed continu ously or vintermittently through a drier of any 75 added equivalent -to 0.015% of glue on the weight f y 2,411,820 8 of the slurry. After completing the fiocculation , a rotary filter such as an Oliver filter. vAbout but a .three hour period was necessary to filter the resulting suspension and only a small amount of wash water could be passed through the filter 20 minutes were required for the filtration and cake. oí the hydrated silica the fioc was dewatered on the filter cake Was 0.75 inch thick. ` The filter - cake was washed with water containing a small VExample 5 amount of hydrochloric acid by means of fine sprays at the rate of 2.5-3 gallons of water per pound of SiOz in the slurry. A sample of the 8.5% of 'NazO and 28.5% of SiOz was diluted with 12.5 lbs. of 41° Bé. sodium silicate containing 52.5 lbs. of pure water lin a mixer of the turbine filter cake was then found to contain about 0.2% 10 type (see Chemical , Engineering Handbook, p. 1288). 6.5 lbs. of 25% sulfuric acid were added of sodium on the weight of the SiOz. ~ with vigorous agitation .during 20-30 minutes, Enough Water was added to the filter cake to afterlwhich the mixer was emptied and Washed make 70 pounds of slurry. To this slurry was added 2.3 pounds of aluminum sulfate contain with 24 lbs. of Water containing 0.3-0.4 lb. of of A1203 in the form of 5` pounds of an 15' 25% sulfuric acid. The Wash water was added to the precipitated silica slurry and the mixture solution. Ammonium hydroxide con was aged for 1.5-2 hours at a pH of 7.0-7.3. A 15% of NH3 was then addedto bring A Water solution of glue was then added in amounts to 4.2-5.5. The mixture was ñltered, the filter. cake was washed as before andvslurried " ' of (ml-0.02% of glue and the flocculated hydrous silica was dewatered by filtration. A dried sample with enough Water to bring the solids content of the filter cake contained 0.22% sodium. ~ ' (SiOz plus A1203) to 4-6% and the mixture was The filter cake was washed on the filter with again filtered and washed. This filter cake was an amount of wash water equal to the original again reslurried in water and filtered land the weight of the slurry, sludged up with a little . filter cake was washed and thoroughly dewat ered. It was then found to contain NazO equiva 25 water and aged for 12 hours. It was then diluted with water to 4-6% solids, 5% being the preferred lent to only 0.01% of the weight of solids in the ing 17% aqueous taining the pH sample. figure, 0.015% of glue was again added. and the silica slurry was again filtered and the filter cake washed with acidified water. The sodium con« ' Example 3 A gelatinous hydrated silica slurry was >pre 30 tent of a dried sample of the filter cake was 0.02%. pared exactly as described in Example 2, but was The aging, fiocculation,A filtration and washing filtered Without the addition of glue. The filter was repeated a third time,rbut in this case no cake was very wet and soft and fell away from acid was used inl the Wash Water. This re the filter cloth when the Wash water .was ap-> duced the sodium content to 0.01%. The filter plied. For this reason it was difficult to wash 35 cake was then calcined as described in Example l the filter cake on a filter of .the Oliver type. and the resulting pure *silica catalyst Was ground to 4-6 mesh.` Escdmple 4 It was well suited for use as a dehydration catalystvfor the production of buta 720 parts by weight of 41° Bé. sodium silicate diene from butylene glycols. solution was dissolved in 2600 parts by weight `of 40 -What we claim is: ' water and the solution was placed in a kettle 1. A method of preparing a silica-containing equipped with an agitator having three paddles catalyst which comprises the steps of neutralizing ank aqueous alkali metal silicate solution by the which was rotated at 100 R. P. M. Acid was addedin 40 minutesto bring the pH to 3, after addition of an vacid to form an aqueous slurry of which the pH slowly rose to 5.0. gelatinous'silica containing alkali metal salts, aging the slurry, adding glue to flocculate the silica, and separating the alkali metal salts by dewatering and washing.- It Was neces sary to add sufficient acid to lower the pH to about 3 in order to neutralize the sodium in the grains of the hydrous SiOz, since these grains _vary in size from a .few microns to 1/8" in diame ter. 2. A method of preparing a silica-containing This slurry would not filter until the pH 50 catalyst which comprises the steps of neutralizing was increased to 6.5. It then formed a %” cake on the filter but very litle Wash water could be an aqueous alkali metal silicate solution by the Aaddition of an acid to.form an aqueous slurry of passed through the cake. gelatinous silicaV containing alkali metal salts, After repeated at tempted washings a sample analyzed 1.3% of NazO, based on the SiOz content. After reslur rying the filter cake in Water a second attempted filtration on the Oliver type filter gave a filter cake only 1/8” thick. The aluminum salt was added to a slurry of this filter cake in water and precipitated with ammonia in the usual manner, aging the slurry, adding glue to flocculate the silica, and. separating the alkali metal salts by filtering off the fiocculated silica and washing the ñlter cake. - ` KENNETH D. ASHLEY. ALPHONS O. JAEGER.