US2227547A - Process for producing alkali metal sulphides - Google Patents

Description

Jan. 7, 1941. E. LANzl-:TTI

PROCESS FOR-PRODUCING ALKALI METAL SULPHIDES Filed April 15, 1956 N olENFZmUZoU mmmvIU @23000 INVENTOR. ENzo LANZETT/ zar-.3.6m m NM2 www:

ATTORNEYS.

lili

dit

dit

rid

iid

Patented Jau. 1', 1941 UNITED STATES PATENT OFFICE 2,227,547 PROCESS FOB PBODUUING ALKALI METAL SULPHIDES Enzo Lanzettl, Como, Italy, asslgnor to Luigi Achille, Milan, Italy Application April 15, 1936, Serial No. 74,592 In Italy June 15, 1935 5Claims.

lution of the corresponding alkalimetal polysul- According to this invention, the sodium sulphide, which usually is prepared by reduction o! the sodium sulphate with carbon, is produced by reaction of sodium amalgam with aqueous solu tion of sodium polysulphide or a solution oi sulphur in aqueous sodium sulphide.

The polysulphide may be prepared by reaction of sodium sulphide with sulphur and then reacted with the amalgam, or the solution of the sulphur in the sodium sulphide and the reaction with the amalgam are caused to take place at the same time,

The reaction forming the basis oi the process may be represented as iollows: l

uundamentally the invention thereiore resides in the synthesis ci the sodium sulphide from sodium in lthe amulgam and elemental sulphur.

it is obvious that when the amount ci allrall-l ncetal ci the amalgam does not correspond to that oi the polysulphide used, sulphides are obtained.

Example i @ne oi the Well-known electrolyaers provided with a porom diaphrauui may he employed, the electrolyte hein@ a concentrated solution oi common salt.. `lliurinu the electrolysis duely divided sulphur is brouuht to contact with the electrolyte consisting ol sodium amalgam iu the cathodic chamber only. The liquid in the cathodic chamher may be agitated by suitable means. During the operation the addition oi .the sulphur is controlled in auch a way that the total sulphur content (S :including Naas) in the electrolyte of the cathodic sone is maintained in such a. manner that for the electric conductivity substantially the NaCl is decisive. 'I'he apparatus may he heated or cooled by suitable means. When continuing the electrolysis Nage is formed in the cathodic zone by the combination of the nascent alkali metal with sulphur, for instance, in the iorm of NanSc. The electrolytic reaction may be represented by the following formula:

smell-sendmail mixtures ol allrali metal It may be assumed that ondary reaction takes place:

From. the solutions containing sodium sulphide 5 and sodium chloride or in some cases sodium sulphide, sodium chloride and sodium hydroxide, the sodium sulphide may be separate by one of the Well-known methods. The process as described may also be carried out continuously by 10 correspondingly controlling the current intensity as well as the supply of the electrolyte and the sulphur.

the following sec- Emamplc 2 The apparatus used may be an electrolyser l5 provided with bell or an electrolyzer provided With a liquid diaphm The electrolyte may he a concentrated solution ol potassium chloride. During the electrolysis the electrolyte is brought in. the cathodic zone to contact with Kelis dis- 2u solved, lor instance, in water. During the oporm ation the addition oi Kaus is controlled in such a way that the total sulphur concentration (S4-Else) in the electrolyte of the cathodie sone is kept within such limits, that the KCl is decisive 25 for the electric conductivity.

The apparatus may be heated or cooled. Un contiuuinc the electrolysis its@ ls obtained in the cathodlc zone by the combination of E 'with Kea..

The electrolytic reaction may loe eitpressed as mucus:

fenomenos-amapola llhe iollowlng secondary reaction is assumed to tolte place:

,The process may be carried throuph continuously as in Eixample l. The potassium sulphide :may be separated trom the resulting solutions t@ by one oi the well-known methods.

Esempio :i

liti

pended in a suitable medium, for instance, water, NazS is formed by the reaction between the amalgam and the sulphur according to the following formula:

2Hg'Na+s- Na2s+2ng The following secondary reaction may take place:

Hg+S=Hes Furthermore the following reaction might oc- The contact between the amalgam and the sulphur may take place in the state of static equilibrium or may be intensified by stirring. The apparatus may be heated or cooled as required. The sodium sulphide may be separated from the solution or suspension by well-known methods. The process may also be carried through continuously.

Example 4 The decomposition of the amalgam may be effected in a separate apparatus. The latter may be of different type or shape (tube, channel or chamber) and may consist of metal or other suitable material. It may be provided with agitating means or not, and may further be provided with means for heating or cooling. The amalgam which is introduced into the apparatus continuously or intermittently may be of different concentration, for instance, it may contain 5 grams Na per 1000 grams Hg. The amalgam is brought to contact in the reaction apparatus with an aqueous solution of NazSz, the operation being controlled in such a way that during the contact between Hg and NazSz also HgNa is continuously present. In other terms the reaction takes place in continuous presence of HgNa., for instance, 0.6 gram of Na being present per 1000 grams of mercury. Inthis way I may attain that not HgS but NazS is formed by the combination of the amalgam with the polysulphide. The reaction may also proceed according to the following formulae:

HgNax-i-NazSz-NaeS-l-HgNa-z or, as the case may be,

Hg Nas 2+2Hg-Na=3Hg+2Na2s The following secondary reaction may occur:

HgNax-i-HzOeNaOH-i-H-{FHgNai-i The resulting amalgam may be returned, either immediately or after the remaining sodium has been removed by well-known methods, to circulate again in the electrolytic apparatus.

The process may also be carried out continuously. The sodium sulphide may be separated from the solution by well-known methods.

Example 5 The same apparatus as mentioned sub 4 may be employed. The sodium amalgam is brought to contact in the reaction apparatus, for instance, with an aqueous alcoholic solution of NazSs, care being taken that during the contact between the amalgam and the solution always activated S(Na2S1) be continuously present. In this case I may avoid the formation of NaOH, only NazS being formed. The reaction may be expressed by the following equation:

As a secondary reaction the formation of HgS may take place according to the well-known formula. The process may be a continuous one.

Example 6 The same apparatus is employed as sub 4. In the reaction apparatus the sodium amalgam comes into contact, for instance, with an aqueous solution of Na2S4. The process is conducted in such a way that both the conditions of Examples 4 and 5 are realized, i. e. the contact between the amalgam and the Na2S4 is accomplished in such a. manner that sodium and activated sulphur are always present.

Furthermore the process is conducted in such a way that during the contact stoichiometric ratios exist between the amalgam and the Na2S4 to obtain a sodium sulphide of greatest purity.

By proceeding in this way the formation of NaOH and HgS may be avoided and a sodium sulphide of excellent purity may be obtained. This process too may be carried out continuously; the sodium sulphide may be separated by crystallisation or fusion. l

To avoid the formation of mercury sulphide during the reaction, the amalgam should be slightly in excess. 'Ihe mercury sulphide is soluble in solution of sodium sulphide with formation of Hg(NaS) 2, which, through the action of the amalgam, gives NazS and Hg, according to the equation:

In order to avoid the formation of sodium hydroxide, it is suitable to exclude materials tending to cause decomposition of the amalgam.

Generally the reaction between amalgam and polysulphide to form the sodium sulphide is aided by thorough contact among the reagents, by increase in the temperature, by increase of the quantity of sodium in the amalgam and by increase of the sulphur content in the polysulphide.

Upon the accompanying drawing is shown dlagrammatically, the apparatus which may be utilized. The electrolytic cell l may be used for the production of the amalgam while the sodium poly-sulphide may be produced in the chamber 5.

The sodium amalgam and sodium polysulphide are then caused to flow together into the reaction apparatus 2.

In the reaction chamber 2, the characteristic orange color of the polysulphide solution will be decolorized progressively as the polysulphide is converted to the sulphide.

A part of the sodium sulphide solution obtained is passed into the chamber 4 where sulphur is added to it and it is then passed into the chamber 5 for reintroduction into the chamber 2.

The remaining portion of the sodium sulphide may be passed into the cooler 6 for the preparation of crystals containing 32% NazS or into a concentrator 1 where sodium sulphide is provided having a concentration of 62% NazS.

The mercury from the reaction apparatus 2 is washed in the apparatus 3 and then returned to the electrolytic cell I.

I claim:

1. The process of producing alkali metal sulphides which comprises reacting an alkali metal amalgam with an aqueous solution of the corresponding alkali metal polysulphide.

2. The process of producing alkali metal sulphdes which comprises reacting an alkali metal amalgam with an aqueous solution of the corresponding alkali metal sulphide and sulphur.

5. In the manufacture of sodium sulphide, the improvement which comprises reacting sodium amalgam with the corresponding sulphide and sulphur in an aqueous medium to form additional sodium sulphide.

ENZO LANZETTI.

Images