US2012062A - Process for the preparation of monochromates and dichromates - Google Patents

Description

Y dium, .the quantity ofthe alkaline agent employed' Ybeing such thatA for thercase of the formationriof f dihromates it remains below that required for Patented ug. 20 1935 PROCESS lion 2,012,062 j THE .PREPARATION 0F MONOCHROMATES AND DICHROMATES Jules Emilel Dezinant, CuiseLamotte,1Franoe, aS'- 'signor to Bezel-Malena, Socit Industrielle dev Produits ChimiquesgjP tion yof France chromates and diohromates, f;

I have..` already vproposed, inmy Pate-nt Nol,A 1,955,326dated YAprilr 17, 1934,1a process` forthe manufacture of monochromates .andY dichromates consistingl in subjectingat temperatures above 10020., metallic chromium or substances .con.

tainingV the same orv chromium alloys to an oxidizingl reaction in the presence cfgalkaline-.oi1

alkaline earth hydroxides,carbonates, onbicarbonates or of Y monochromates an aqueousmethe iormation; of monochromates.Y i I l M Inacoordance With u the Ypresent invention it Vhas been found that for lthe formation of mono'- chnomates or dichromates Vthelpresence of` alka.- t

lineeor-` alkalineearth .hydroxides carloonateav or bicagrbonatesY or offmonochromates is not abso-Y lutjely nece ss.ary. Y .Inaocordanoe with theinventionfit isV possiblerfifo employ;` instead of or gtogiherfwith alkaline-oLalkaline earth agents and, in the case of the preparationof .dici-1romates, instead ofor together with alkaline-or alkaline .eartl1 :agents-,orof Vmonochromates, in

general allcompoundslcapahle of giving up Ytheir] alkaline principle linden-the oxidizing actionl in.

the course of the 'DIOCssi i By suchfoxidizing conditionsl itis Vto be .un-V derstoodas disclosed by the examples given inj this speciication later on, that the reaction takes place with a current-,of oxygen Aor airunder arti;-

Aiicial pressure. or W-ith oxygen developed during the reaction throughgithe initial introduction Vof an oxygen-yielding, reagent like potassium* chlorateL f "Ilie tendency of chromium to beconverted in-to hexayalentchrornium is so Vmarked that in the course of the oxidizing processgzthe added sub'- stances undergo va-decomposition which causes i them .to give .up theirn alkalineprinciple tothe `.chron-iiurrl;according to the quantity of the alkaline piinciple entering into reaction it is'rpossible to obtain either monochromatesor dichromates ormixtures of these twocompounds. Y

.In order' to properly.y distinguish between, an falkaline agentperse .and a substance which in v.thisLeaseunderproper oxidizing conditions will give up its falkaline principle to the chromium, it -iswell to remember that: i'.

A Solution LofY anacidcontains -catonwH and Y*non-metall-ic ions (anions) Va sol lotion .of a .base contains hydroxylions V(an-ions)v and metallic ions (.c'aticms);V and a solution of a hydrogen `ions Y arisg-France, a. corpora,-

s clanes; l' (c1: 23.-5s1) saItcOntanS non-.metallic (anions) and 1011s atioiis). t I v l VIn an .acid the anionsare'the .active elements Whichcombine with the' attacked metal, forming chlorides, sulphatesphcsphates, nitrates, ete,

freeing the lfiydrogeri.` In .a base .01T alkaline agent, it is the oationfwhioh -ifs'the.:actiye.ellesA ment, While in asalt solution'the anions and i cations' `lflirili'arid neutralize .leach other, as long `asnodecomposition takesplace, .Only l.

after .suon decomposition is effected under .special I-cireumstances, tree` acting cations are .liberatori and-a chemical reaction isjrealized Thus asap stance `vviiricli .normallyY cannot be' f classified .as base, .can becomean alkaline' agent.

While an alkaline agent contains itsationjn Ldo not .claim .as nari .of my inv.antiontheV .use of..oxides,.hydroxides .oi :alkali .or .alkali earth metals'per senfNor `.dojrI Lclz'tim't'hz-e use yo`:f2..cnl2+ bonates oi alkali .oi-alkali .earth metals per se.'

Ido not claim as part ofmy presentinvention aireerstatathe substances, employed according to fthe present invention Vare kthose capable .of 1 liberating their `cations...generally under th.. #i dizing :action .of the reaction.'

Vthe yuse .of monochromates, taken alone, sub-1 stances capable of givin'gfupfree acting' cations to the 4chromium under the' influence of fthe' .oxi-

' dizing reaction,

As compounds Whichv i in themselves are-" base Vbut in the presence of ari-oxidizing reaction are capable of giving up their alkaline princi-ple',

'tl-ierecan vloe employed the most'varied salts of vstrong or Weak inorganic or'orga-nic acid'sor-also oxygen compounds of a salt like CharacteLQOr i chlorides, phosphates, monochromatesgvaoetates, silicates, aluminates, nitrates, chlorates, nthefper salts, manganates, permanganates o r-t'he like@ It may be remarked that theselat-ter compounds can actbothas oxidizing Vagents and when decomposed jas alkaline agents, :They can even be utilized oniyias oxidizing .agents together with true alkalinagents'or other agents" capable 'of Agiving 'up their; alkaline principle. As alkaline agents are` usedlalkaline `0r alkaline earthhysiroxidea .Carbonates' or .bicarbonates or monochromates..

-uptneir cations under the action .of the' 'oxidizing reaction.4 Said characteristic is clearly exem- Plifled by ihefollowing Examples 1; 2,',and 43.. N

lffor example organic derivativeslarevveme ployed, ithe onganic. principleis in general oxidized As amatter .of fact, Y.the s311135 just .bOV indicati@ are Vnormally not bases biliare .Capable .of sitting lowing examples are given and it may be remarked that Example 5 illustrates the splitting up of potassium sulphate under the oxidizing -decomposition action of trivalent chromium.

Examples (l) 16 parts of finely pulverized errochrome-y containing 65% Cr and 9.5% C, :14.2 parts of anhydrous sodium sulphate, 10 parts of calcium carbonate, 200 parts of Water are heated in an autoclave With good agitation at Zim-290 C.; a current of oxygen or air is passed through under pressure. The progress of the reaction is controlled by means of the content'of carbonic acid which is determined in the gas leaving the apparatus.

` The reaction product is filtered. The liquid contains pureV sodium dichromate.

V`iZield97%. f 1 -(2) 16 parts of nely pulverizedV ferrochrome containing 65% Cr and 9.5% C, 28.4 parts of anhydrous sodium sulphate, 20 partsof calcium Vcarbonate, 200 parts of Water are treated as indicated in Examplel.

v After filtration of the reaction product a-liquid lis obtained containing sodiumjmonochromate. 4Yield quantitative. f o f y `(3) 16 parts of finely pulverized ferrochrome 200 parts of water, are heated in an autoclave for some-hoursto`290-300 C. VvTowards the end of' the'reaction alittle oxygenV under pressure is passed through in order tofacilitatethe elimination of 'carbonic acid formed and to support the oxidation.`` l

There are easily obtained yields of potassium dichromateexceeding '70%. 1 n y.

. (4) 16 ,parts of finely pulverized ferrochrome containing 65% Cr and 9.5% C, 139 parts of trisodium phosphate l Aq, 200 parts of Water, are heated in an autoclave with good agitation for some hours to 280-1300o C. and a Acurrent of air or oxygen is passed through Withathepractically complete elimination of` the carbonio acid produced-.fromrthe ferrochrome. There is obtained afteriltration a monochromatic liquor together with disodiumphosphate which is separatedby crystallization. Yield about 80%.

p (5) y17.3 parts of ferrochrome of 60% Cr, 35 parts of potassium sulphate, 200 parts of vvvater are heated for some hours in a current of oxygen at 280-300 C. in an autoclave with gooda'gitation. The reaction product is iiltered and there is obtained an acid liquid containing potassium dichromato. phate has produced alkali which is absorbed by the hexavalent chromium on one hand and the =:free sulphuric acid on the other'hand.

` Thefree acid present prevents the reaction from progressing beyonda content of free acid of rabout 0.5% H2504.'

The yield obtained is 16-20% for the above example. n By Working in a more dilute medium in such a The splitting up of the potassium sulmanner as to remain below a content of free acid of 0.5% H2SO4 the yield can be considerably increased. In this case it is desirable to increase the content of potassium sulphate.

This'method of working presents the inconvenience of producing acid dichromate liquors of loW contentand by reason ofV this fact it is to be recommended to neutralize the free acid formed during the reaction preferably by adding f1. Process for Ythe manufacture of monochromates or dichromates consisting in subjecting a substance containing metallic chromium to oxidizing decomposition at temperatures above 100 C., underpressure and in an aqueous medium, in the presence of a compound being not normally classiied as a base but other than a monochromate and capable of giving up free acting cations to the chromium under the influence of the oxidizing reaction. v v2. Process for the manufacture of monochromatesor dichromates consisting in subjecting a substance containing metallic chromium to oxidizingdecomposition at temperatures above 100 C., under pressure and in an aqueous medium, in the presence of a compound being not normally classied as a base but other than a monochromate and-capable of giving up free Aacting cations to the chromium under the influence of the oxidizing reaction, and in the presence of an alkaline agent. o

l3.'Prooess for the manufacture of- Vmonochromates or dichromates consisting in subjecting a substance containingmetallic chromium to oxidizing decomposition at tenriperatures above `100" C., under pressure and in an aqueous medium, in the presence of a compound being not normally classied as a base but other than a mono- Ychromate and ycapable of giving up free acting cations to the chromium under the iniluence of the oxidizing reaction, and acting at the same time as an oxidizing agent. Y

4'. Process Vfor the manufacture' of monoohromates or dichromates consisting in subject- Y ing a substance containingvmetallic chromium to oxidizing decomposition at 'temperatures' above 100 C., under pressure and in an aqueous medium, in the presence of `a compound rbeing not normally classied as a base but other than a monochromate'and'capable of giving up free acting cations tothe chromium under the influence of the oxidizing reaction, and acting at the same time as an oxidizing agent and in the presence of an alkaline agent. Y v I 5. Process for the manufacture of `monochromates ordichromatesconsisting in subjecting ferrochrome to oxidizing decomposition at temperatures above 100 C., under pressure and in an aqueous medium in the presence of a compound being not normally classied as a base but other than a'monochromate and capable of giving up free acting cations to the chromium under the lin- `iiuence of the oxidizing reaction. f 6. Process Afor the manufacture of mono chromates or dichromates consisting in subjecting ferrochrome to oxidizing decomposition at temperatures above 100 C., under pressure and inv 'an aqueous medium,`in the presence of a coman aqueous medium, in the presence of Y a compound being not normaliy'classiiied as a base but other than a monochromate and capable of giv-v ing up free acting cations to the chromium under the inuence of the. oxidizing reaction, and acting at the same time as an oxidizing agent. l

8. Process for the manufacture of monochromates or 'dichromates consisting in .subjecting ferrochrome to oxidizing decomposition at temperatures above 100 C., under pressure and inA f an aqueous medium, inthe presence of a compound being not normallyclassied as a base but other than a monochromate and capable Aof giving up free vacting catior'lsr to the chromium under the influence of the oxidizing reaction, and act- K ing at the saine time as'an oxidizing agent and in the presence of ran alkaline agent.

JULES EmLE DEMANT.