DE2151572C2 - Use of carbon partially encapsulated with polytetrafluoroethylene as a contact agent - Google Patents

Description

The invention relates to the use of carbon specially encapsulated with polytetrafluoroethylene as a contact agent when carrying out a thermodynamically spontaneous redox reaction.

The US-PS 35 07 773 describes an electrode for use in the electrochemical reduction of Oxygen to peroxides. This consists of a one-piece carbon molding, that of polytetrafluoroethylene is interspersed. The term thermodynamically spontaneous redox reaction includes electrochemical ones Redox reactions do not. The US-PS 22 75 281 and 20 00 815 relate in whole or in part Carbon electrodes coated with a hydrophobic substance for electrochemical processes.

The US · PS 32 97 482 relates to a fuel cell in which the electrodes consist of carbon plates which on their side facing the hydrogen-containing or oxygen-containing space with a contiguous Polytetrafluoroethylene layer are coated. The two reaction gases do not meet here in one Reaction space to each other.

'The US-PS 24 59 907 relates to a method for converting gaseous or liquid reactants by putting them together through a mass conducts of porous carbon, the particles of which are bonded together with carbon, which comes from pitch are. The use of granulated coal as a catalyst is described in US Pat. No. 1,146,363 and 2,365,729 described.

DE-OS 15 42 450 describes the use of porous metal bodies as contact agents for chemical or electrochemical processes.

The US-PS 33 96 123 describes the preparation of a catalyst by mixing a particulate inorganic carrier, such as coal, with a powdery thermoplastic, heating the mixture until Softening point, cooling to a cake and breaking it into particles, whereupon this carrier material is impregnated with a catalytic substance. The catalyst support obtained in this way is not through the Thermoplastics partially encapsulated but interspersed

Finally, DE-AS 21 04 019 proposes the use of one coated with polytetrafluoroethylene Carrier, such as charcoal, to enrich liquid water with hydrogen isotopes from hydrogen gas before.

The object on which the invention is based now consisted in a thermodynamically spontaneous Redox reaction between a reducing agent and an oxidizing agent that are in contact with each other form an interface and at least one of which is in the liquid phase, the reaction rate and / or to increase the yield.

According to the invention, this object is achieved by using carbon as a contact agent with a Particle size from 9 nm to 2.5 cm used by partial encapsulation with 0.1 to 100% of its weight of polytetrafluoroethylene in places only is wetted by one reaction partner and in places only by the other reaction partner.

According to the invention, various oxidation and reduction products can be obtained by a redox process produce. The oxidizing agent is, for example, oxygen, air or a mixture of oxygen with other gases, an aqueous solution of an oxidizing agent such as a permanganate, or a organic material, such as nitrobenzene, while the reducing agent does not match the oxidizing agent is miscible and, for example, an aqueous solution, an organic liquid or a gas such as hydrogen gas, is. The contact broker probably has the function that he gets electrons from those in contact with him standing reducing agent molecules or ions to the oxidizing agent molecules in contact with it or conducts ions and thus promotes the electron transfer required in the reaction. In contrast to electrochemical systems, such as electrolysis or fuel elements, in where the anode and cathode are separated from one another by partition walls or by membranes and wherein the oxidation takes place on one electrode and the reduction takes place on the other electrode, closes the use according to the invention of adjacent oxidation and reduction reactions on the contact mediator in the same reaction rum and does not require the use of membranes or Partitions. Electrochemical processes are not considered to be under the term thermodynamic spontaneous redox reaction is viewed as falling.

With the help of the contact agent according to the invention, the rate and amount of product formation increases and the relative speed of product formation, i.e. H. the selectivity, affects where multiple products can be formed by oxidation or reduction. A typical example of the The latter system is the oxidation of aqueous sulfide solution with the formation of either sulfur or Thiosulfate.

An important aspect of the invention is that the contact agent is prevented from being exclusive is in contact with one of the reactants, i.e. the reducing agent or the oxidizing agent. When the term "flooded" is used in the description, it means that the contact agent is only in contact with either the oxidizing agent or the reducing agent. If it is flooded, there will be an increase in the

15th

Speed of product formation not achieved

Regardless of how the reaction mechanism in contact mediation is theoretically to be explained, the results give the following general rules applicable to the invention:

a) The redox reaction must be thermodynamically spontaneous in the sense that the change in the free energy is negative

b) The oxidizing agent and the reducing agent must be able to form an interface form.

c) Flooding of the electrically conductive material must be avoided.

d) Oxidizing agents and reducing agents must be in contact with each other and with the electrically conductive material.

In those cases where certain products should be formed preferentially x or selectively, the following additional rules are also applicable:

e) Mixing the oxidizing agent and reducing agent outside the reaction ^{space with 2:>} the contact dissector should be avoided.

0 Any other reaction between the reducing agent and oxidizing agent than that in the »redox zone«, as it is referred to below, should be kept to a minimum and ^{Jo should} preferably be switched off completely.

Since the reaction zone is a gas, a liquid and the contact agent or two liquids and Includes the contact maker, the latter must either be in contact with the gas and from the Liquid be wetted without being flooded by both, or it must be in contact with both Liquids stand and must not be flooded by either of them. If the term "wetted" here is used, it means that the contact angle between the contact transmitter and the one liquid low, d. H. is less than 90 ° and approximately 0. When the contact angle is large, d. H. greater than 90 ° and approximately 180 °, then tilts the one liquid to pull away from the surface of the contact agent, and the surface the contact agent is then essentially only in contact with the gas or the other liquid, d. i.e., in this case it is flooded with the gas or the other liquid. If on the other hand the surface the contact agent is slightly wetted by the; · a liquid, d. H. when the contact angle between the contact-making surface and the one liquid approaching the value 0, one tends to Liquid to cover the entire surface of the contact agent or to wet it, so that this is flooded. According to the invention, both should be avoided.

The contact mediator can for example be in the form of floating layers or flows through There are embankments, columns or towers. The floating layer is for the sake of simplicity often preferred and is hereinafter referred to in detail as b5 described. The contact broker can be stationary or mobile. It should have a large surface so porous carbon is preferred.

The possibility of increasing the speed in a redox reaction according to the invention can be demonstrate by the following examples of redox reactions:

a) Oxidation of ammonium, potassium, sodium or Strontium sulfide with air to the corresponding Polysulphides or thiosulphates,

b) oxidation of sodium thiosulphate with air to sodium sulphate,

c) Oxidation of iron (II) sulfate or iron (II) ammonium sulfate with air to iron (II I) sulfate,

dj oxidation of hydrogen sulfide, dissolved in alkali salts with air,

e) oxidation of sodium or potassium iodide with air to iodine,

f) Oxidation of hydroquinone with air to quinhydrone,

g) oxidation of phenols with air,

h) oxidation of sodium stannite with air to sodium stannate,

i) Oxidation of benzidine with air to benzidine blue,

j) Oxidation of leuco indigo with air to indigo blue,

k) oxidation of succinaldehyde with air,

1) Reduction of silver nitrate with hydrogen gas to silver,

m) Reduction of cerium (IV) sulfate to cerium (III) sulfate with Hydrogen gas,

n) Oxidation of benzaldehyde with air to benzoic acid,

o) oxidation of aniline with air,

p) reduction of potassium permanganate with hydrogen,

q) Reduction of chlorine with water and

r) Reduction of nitrobenzene with aqueous sodium sulfide.

■ The oxidizing agent and the reducing agent can be organic or inorganic materials in be in the form of gases, liquids or liquid solutions.

In the case of using porous materials as Kuntaktvermiuler should understandably neither the oxidizing agent nor the reducing agent through the pores of the contact agent in that sense be forced that a porous part as a diffuser with the formation of small bubbles of one of the reactants is used, the vesicles being mixed with the other reactant.

For the contact broker, carbon and activated carbon is optimal, as there is a relatively large ratio of Surface can gain weight and there are inclusions of metals and metal compounds in the Material can be easily introduced and coal can be finely divided. It is also about a readily available material that comes in a wide variety of particle sizes and with varying Surface sizes can be obtained. Coal types or carbon types from different sources often lead to different reaction rates. These differences can be easily identified by simple Determine procedure. Typical of the coal or carbon species used in the invention are soot, furnace soot, sewer soot or types of coal, which are obtained from sources such as wood, Corn on the cob, beans, nutshells, bagasse, lignin, coal, tar, petroleum residues, bones, pitch and

other carbonaceous materials can be obtained.

Usually the carbon or charcoal is used as a mixture of different particle sizes. The surface area of the carbonaceous material can vary from 3 m-7 ^{g to over 950 m 2} / g as determined by gas absorption using the BET method.

The carbon can in the way with polytetrafluoroethylene partially encapsulated and made moisture repellent by using polytetrafluoroethylene (PTFE) in emulsion form with finely divided carbon in an amount between 0.1 and 100%, based on on the solid carbon, mixed. The mixture is heated to the carrier and the dispersant for to remove the PTFE. Inclusions of nickel sulfate, silver nitrate and chloroplatinic acid can slow down the reaction rate further increase the redox reaction.

In the drawing means

F i g. 1 a schematic representation of a reactor according to the invention,

F i g. 2 is a schematic representation of another reactor according to the invention, in which two product-producing Zones are provided,

F i g. 3 shows a simplified representation of a reactor according to the invention, in which the contact broker on the Surface of the reducing agent floats.

Fig.4 is a schematic representation of a continuous Reactor according to the invention, in which the contact agent at the interface between the Oxidizing agent and the reducing agent is kept,

FIG. 5 is a schematic representation of another form of continuous reactor according to FIG Invention by using several troughs and in which the contact agent on the surface the reducing agent floats,

F i g. 6 shows a section along the line 6-6 in FIG. 5,

F i g. 7 shows a section through a reactor according to the invention in column form with a bed or Pack of the contact agent.

Fi g. 8 is a schematic representation of a closed Tower reactor according to the invention with parts broken away to show the internal components,

F i g. 9 is an enlarged partial section along the line 9-9 in FIG

FIG. 10 shows an enlarged section along the line 10-10 in FIG. 8.

Fig. 1 explains an application of the invention on Example of a reactor design. Inside is a container 10 made of polypropylene, stainless steel or the like with flow lines 12 and 14 for the introduction of a first flowable reactant and for the removal of the Reactant and the reaction products fitted in the container and a wall of the same Forming there is a contact mediator fill 15. The container 10 is also provided with second flow lines 16 and 17 for the introduction of a second flowable reactant and for the removal of unused Reaction partner equipped.

In operation, the reactants are introduced through introduction lines 12 and 16 and form one Interface at the mediator 15. The one reactant passing through an inlet conduit 12 has been introduced, a liquid reducing agent, which is from a reservoir, not shown through the space 19 with the aid of a pump, not shown, and then back to the same or one another reservoir is pumped. The oxidizing agent can be a liquid or a gas that is left in the space 20, and in the case of gas this is under slight pressure.

As can be seen, the in F i g. 1 shown apparatus can also be aligned so that the contact broker 15 lies horizontally over space 19 by rotating the entire apparatus by 90 °. With such a Alignment there may be no need to use a pressure system ίο for the fluid that is in the room 20 is located.

In the in F i g. 2, in which corresponding Reference symbols as in FIG. 1 is used, a variant is explained in which two separate beds ! ■ 5 of contact brokers 15 and 15a in container 10 be used. The space 19 receives one of the flowable reactants, which through line 12 is introduced, the reaction product being removed through the discharge line 14. The second flowable Reactant is introduced through introduction lines 16 and 16a, and unreacted material and Product can be withdrawn through the discharge lines 17 and 17a.

A simple arrangement for carrying out the invention in the form of single approaches and for Evaluation of contact agents is shown in Fig. 3, in which a container 25 liquid reactants 26 contains. The contacting agent 29 is in the form of particles lying on the surface swim and at the same time are in contact with the other reaction partner, which is a liquid or can be a gas.

In Fig. 4, a container 30 is provided with an inlet 31 for introducing a flowable reactant 32 and with an outlet 33 for the removal of reaction products and unreacted flowable reactant. In the container 30 there is a sieve element 34 at the level of the liquid level of the reaction partner 32 in the container 30, so that the underside of the sieve 34 is in contact with this reaction partner. The thickness of the contact mediator layer 35 is dimensioned such that the height is greater than the capillary slope of the reactant, so that the contact mediator is prevented from flooding the contact mediator. The free surface portion 36 of the contacting agent is contiguously exposed to a second reactant and operates in essentially the same way as a floating layer.
Another form of apparatus is shown in FIGS. 5 and 5, in which the reactor 45 is particularly suitable for continuous systems using a liquid reactant and a gaseous reactant. The embodiment shown contains four troughs, although the number of troughs used can of course be larger or smaller. Each trough is provided with a plurality of spaced apart dividers 48 which extend from a wall 49 of the trough. The partitions 48 terminate just before the opposite wall 51. Extending from the opposite wall 51 are several other partitions 53, and these terminate just before the wall 49. Liquid reactant is introduced into the trough through an inlet 55, and due to the arrangement of the Separation elements, nte 48 and 53

the liquid migrates in a serpentine manner to the trough outlet 56 which allows the liquid reactant material flows into the next trough below. In this way the liquid migrates Reactant from one trough to the next and is finally withdrawn through an exit line 57.

The contact mediator practically shines on the surface of the liquid reactant in the same manner as was described in connection with FIG. The apparatus of FIGS. 5 and 6 provides a continuous system in which fresh liquid reactant is introduced into inlet 55 and removed at outlet 57. The contact mediator, which is in finely divided form, is made up of impact elements 60 is prevented from migrating through the reactor and so these baffles are in the way of the liquid reactant that it passes under them, while the contact mediator is stationary is held. The other reactant is a gas that circulates between the troughs.

Another shape of reactor is in Fig. 7 in the form a column 65 of cylindrical shape. Reducing agent is introduced through an inlet, which can be 66 or 67, and unreacted reducing agent and product is from an outlet subtracted, which can be 67 or 66 depending on whether the liquid is flowing downwards or upwards. Oxidizer can be introduced through line 68 or 69 depending on whether it is a direct current flow or countercurrent flow is desired. In the column, the contact broker 70 is through screens 71 and 73 held. The column can be arranged vertically or horizontally or at an angle.

8 to 10 is a closed tower reactor 75 and has a plurality of vertically layered trough members 76, four of which are shown, although can optionally also be used more or less. In this construction, everyone contains Trough made of polypropylene, stainless steel or other suitable material several of each other spaced dividers 77 extending from one end wall 78 and just in front of the other End wall 79 ends. Extending from wall 79 is a second row of spaced partitions 80 that end just before wall 78. The separating elements 77 and 80 form flow channels for the reducing agent and oxidizing agents. The gaseous reactant is introduced through inlet 81 in ceiling 82, while the liquid reactant is introduced through inlet 84 into the blanket as well. One Inlet chamber 85 for liquid reactants is formed by baffles 86 and 87, which the space span between the adjacent side wall and the adjacent partition element 80. the Baffles end just below the ceiling 82, so that they have a space for the passage of gaseous reactants while the baffle 87 is spaced from the bottom of the trough so that it can flow therethrough of the liquid reactant under the baffle allows proximity of the inlet chamber for liquid For reactants, a gas inlet chamber 88 is provided through baffle 86 and end wall 79 is limited

Unreacted liquid reactants and product and somewhat gaseous reactants become withdrawn from an outlet 89 in chamber 85a, and that chamber is defined by baffles 86a and 87a, which correspond to the baffle plates 86 and 87 in construction. The top of the Outlet 89 extends over the lower end of the baffle 87a, as can be seen in FIG. 10, around the To increase the level of the liquid reactant in such a way that the contact agent 90 is prevented from doing so will flow from one trough to the next. Gaseous reactant flows over the top Edges of baffles 86a and 87a to an outlet chamber 88a and through outlet 91 to the next trough below. For the sake of simplicity, each trough is essentially the same Construction with passages 89a and 91a sealed at the inlet end of the trough, as in Figure 9 is shown. When the reactants flow into the next lower trough, they migrate in one the opposite direction in the trough above and exit through chambers in the The position and construction correspond to the chambers 85a and 88a. Ah the last trough will be gaseous Reactants, if such is still present, and the remaining gases withdrawn from the tower outlet 92, while unused liquid reactants and products are withdrawn from trough outlet 93 will.

The ceiling 82 is so tightly connected to the top trough by sealing elements that a forms a continuous flow channel through the partitions and walls, as shown in FIG. The floor of the top trough forms the ceiling for the trough below, with only the top trough is provided with a separate ceiling. The troughs are sealed with sealing elements 95, the various Can have shapes. In the form illustrated in FIGS. 8 to 10, the sealing elements are in the Form elastic parts in front of which on the upper end of the separators 77 and 80 and on the upper end of the Side and end walls of each trough adhere. In this way one can check the gas deposition rate control well and keep the system under pressure if desired.

example 1

Hydrogen sulfide gas was bubbled through an aqueous solution containing 20% tripotassium phosphut, KjPO «, contained. The resulting solution was divided into 90 g portions, each in 250 ml glass beakers of approximately the same dimensions and then referred to as belonging together will. On one portion, 2 g of activated carbon containing 2% PTFE (based on the carbon weight) had been made water-repellent, made to swim, while the other portion without coal was left. The above procedure was also repeated except that an aqueous solution was used with a content of 40% tripotassium phosphate was used instead of the 20% solution. The cups that the .Solution components were exposed to the ambient atmosphere for certain times after which equal parts are deducted and analyzed with regard to the sulfide sulfur and the zero-valent sulfur , which latter apparently appears as potassium polysulfide in the solution. The results are in the following table compiled in the - the analytical values found in grams per liter as Expressed sulfur are:

Time on Air in hours

20% K ₃ PO ₄ ,

sulfide

no money

sulfur

Carbon with 2% PTFE Sulphide sulfur

Time at 40% K ₃ PO ₄ air in

Hours of sulfide

no money

sulfur

Carbon with 2% PTFE sulfide sulfur

2.8
2.4
1.7

none
none
none

2.8 0.8 0.4

none

1.5

1.1

Example 2

Time in air no money activated Coal with in hours 2% PTFE Na ₂ S ₂ O ₃ SO ₄ Na ₂ S ₂ O ₃ SO ₄

68.3
67.0
64.5

0.7
0.6

68.3 63.4 52.5

0.7 1.8

5.2
4.5
3.0

none
none
none

5.1 1.6 0.7

none

2.4

2.8

The contact agent of the invention clearly increased the rate of occurrence of sulfur in the form of sulfide and increased the rate of occurrence of zero valent sulfur in comparison with the oxidation rates that were found without the carbon under otherwise identical conditions.

20th

Sodium thiosulfate, Na ₂ S ₂ O ₃ · 5 H ₂ O, in an amount of 100 g was dissolved in water to obtain 1000 g of solution, and 60 g of sodium bicarbonate was added and dissolved in an alkaline buffer to prevent precipitation to get free sulfur. Portions of the solution of 200 ml each, ie 215 g, were placed in paired glass beakers of 250 ml. On the surface of one portion, 2 g of activated carbon made water-repellent with 2% PTFE was made to float. Identical samples were withdrawn from each beaker after certain time intervals and analyzed for residual thiosulfate and sulfate using standard methods. The compositions are expressed in grams per liter of the formula given. The results obtained are summarized in the following table:

40

The presence of floating, water repellent made charcoal clearly increased the rate of occurrence of sodium sulfate

Example 3

Aqueous phosphoric acid at pH 4.0 was used as the solvent to make 50 g of hydroquinone dissolve and get 1 1 solution. Portions of this solution of 200 g each were divided into two Pairs of glass beakers of 250 ml and a glass beaker of 1000 ml. On the surface of one of the Portions in a beaker of 250 ml were 2 g of activated charcoal, the water-repellent with 2% PTFE After standing for 48 hours, equal samples were taken from each The proportion was decreased and the remaining hydroquinone was determined by a standard method by titration analyzed with potassium dichromate to a potentiometric endpoint. From the initial 10 g Hydroquinone in each cup, the rest was as follows:

no money

250 mi-Bcchei

1000 ml beaker

activated carbon with 2% PTFE

250 ml beaker

Surface, 32
cm ²

Hydroquinone, 9.5
G

81 9.5

32 8.6

The larger available surface area is obviously without any noticeable effect, while the The presence of floating contact agents accelerates the oxidative removal of hydroquinone.

The above procedure was repeated except that the solution contained 11.5 g of hydroquinone and 1 g of Sodium sulfate, dissolved in aqueous sodium hydroxide solution with a pH of 9.5. to get 1 I solution, contained. The bonding agent consisted of the same activated carbon but was made with 20% PTFE Made moisture-absorbent. The same samples were taken after a certain time interval. Of the initial 2.3 g of hydroquinone in each beaker, the remainder was as follows:

Time in air in hours

no money

250 ml cup

1000 ml beaker

activated carbon with 20% PTFE

250 ml beaker

45

20 2.0 2.1 1.9

44 2.0 1.8 1.7

68 1.8 1.7 1.5

92 1.7 1.6 1.4

116 - - 1.1

The larger exposed surface in the larger one

Becher appears to increase the rate of oxidation, but has the presence of the contacting agent on the solution in a smaller beaker has a greater effect than the enlarged surface.

B e i s ρ i e 1 4

A solution was made by adding 1 g of 2,6-dimethylphenol was dissolved in 20 ml of a 1 η sodium hydroxide solution. Half of the resulting solution was each in given two pairs of glass beakers of 50 ml. 0.5 g of activated was applied to the surface of one of the portions Charcoal made moisture repellant with 2% PTFE was made to float Solutions in the beakers were initially at 85 ° C. for 3 hours, then at room temperature overnight. the

Solution under the floating charcoal initially showed a yellow color, then darkened to brownish in less than an hour, while the solution without charcoal was yellowish for the entire duration of the experiment stayed. After the above standing, both solutions were neutralized with hydrochloric acid, with ethyl ether extracted, and the ether extracts were evaporated in watch glasses at room temperature. The first residues were a yellow oil from the portion without coal and a rubbery brown paste from the portion with floating coal. After a further 5 days the yellow oil had evaporated and left a tiny trace brown solid residue. The gummy brown paste became clear, brittle, reddish-brown Solid.

The above procedure was repeated except that the starting material was 2,6-diisopropylphenol was. Evaporation of the ether extracts left a mass of yellow crystals on the portion without charcoal and a mass of reddish-brown crystals from the portion with floating charcoal. After a few more days in a warm place the yellow crystals were sublimated and left only a brown trace, while the reddish brown crystals remained.

The final brown residues showed no coloration with crystal violet lactone. that's a sensitive reagent for phenols is. It can be seen that the contact promoter accelerated oxidative polymerization via the phenolic groups, possibly with the formation of polyphenoxyethers.

Example 5

A solution made by dissolving 0.2 g of indigo carmine (Cl. 1180) and from 1 g of sodium carbonate in 500 g of water was prepared with sodium dithionite (Na ^ SiOj) until the blue color disappears titrated. 150 g portions of this solution were placed in 250 ml glass beakers in pairs. on one share 5 g of polyethylene beads were made to swim. On another stake 5 g of activated carbon which had been made water-repellent with 2% PTFE. to swim brought. On a third portion were 5 g of activated carbon, the water-repellent with 10% PTFE was made to swim. After a few minutes the solution showed below that with 2% PTFE made water-repellent carbon radiates blue color that extends from the top to near the top Bottom of the beaker extended while at the same time the solution was under the moisture repellent with 10% PTFE made coal has fewer rays of blue color from the upper part and not as far as the clearing showed and the solution under the polyethylene beads showed only a thin blue film at the interface. After about 30 minutes, both solutions under the floating charcoal were deep blue while the solution was not significantly bluer than before under the polyethylene beads.

Examples

60

A solution was made by adding 0.2 g of indigo carmine and 1 g of sodium carbonate were dissolved in 500 g of water, and the blue solution was replaced by additional Dissolve 03 g of sodium dithionite, which is a Represented excess of reducing agent, made yellow 150 g portions of this solution were placed in 250 ml glass beakers in pairs. on one portion was 5 g of activated carbon, which had been made moisture-repellent with 2% PTFE, floated, and other portions were left without a floating intermediary. To about 15 minutes, rays of blue color were visible in the solution under the floating coal, which extended to the ground, while the parts without intermediaries are only very pale and incoherent Blue stains showed. The oxidation progressed in such a way that after about 2 hours the Solution under the floating charcoal was completely dark blue, while the solution without charcoal was still was yellow, with the exception of the pale and disjointed patches of blue tint that were already above were observed.

Example 7

Portions of 100 ml of aqueous silver nitrate solutions were placed in six paired glass Erlenmeyer flasks of 250 ml and, by connecting them in series, an equal gas atmosphere exposed. Each flask was closed with a rubber stopper, with openings in these two curved glass tubes were inserted. One tube served as access for the gas flow, the other Tube as a gas outlet. In four of the flasks, the inlet tube and the exhaust tube only went through the Stopper, but do not extend as far as the contained solution, while in two of the flasks the Insertion tubes were long enough that they went below the surface of the contained solution and in Glass frit diffusers ended. The exit tubes were the same as the other flasks.

Two solutions of silver nitrate were prepared, both of which were made from a silver nitrate storage solution started out in water with a concentration of 10% by weight. The first solution was through slow Add 40 ml of concentrated ammonia with stirring to 800 ml of storage solution, resulting in a brown Precipitate formed, and then adding ammonia dropwise until the precipitate regained was dissolved, prepared. The second solution consisted of the unchanged storage solution. The two solutions were designated as ammoniacal and watery to distinguish them. Proportions of ammoniacal Solution was added to three of the flasks and portions of the aqueous solution to the other three flasks.

Each row of three flasks contained one with 4 g of polyethylene (PE) beads floating on the surface, one in which 4 g of activated carbon made moisture-repellent with PTFE on the surface swam, and one that was closed with the stopper with the diffuser, Di? Flasks were in series connected one behind the other with plastic hoses, each of the output tubes of a piston with the The next feed tube was connected, in the order shown in the table below indicated. A hydrogen gas container was connected to the inlet tube of the first flask. Of the Hydrogen flow was started at a rate of 100 ml / min to the first flask and continued for 7 hours, then interrupted overnight for 16/2 hours, then again and recorded with the same flow rate the next day for another 7> / 2 Hours continued. The appearance of scale and precipitate in the flask was noted By filtering off all insoluble materials, burning the filter paper and other combustibles

Analysis of the constituents and weighing of the remaining ash was carried out FiUrat was left behind as silver nitrate determined by titration. The proportion of insoluble compounds and silver nitrate in solution, expressed as silver, is as a percentage of the total amount of silver found in the analysis specified.

Flask no solution

Distinguishing factor insoluble soluble pH value

Silver, silver

watering PE beads 2.5 aqueous Contact broker 22.3 ammonia
akalic PE beads 1.5 ammonia
akalic Contact broker 24.8 aqueous Diffuser 6.3 ammonia
akalic Diffuser 2.4

It was observed that Flask # 1 above contained a somewhat lackluster precipitate during Flask # 2 contained large amounts of shiny precipitate at the bottom of the flask. Flask # 3 contained a light brown precipitate, while flask No. 4 deposited amounts of silver on the charcoal contained. Both flasks with the diffusers showed black deposits on the walls of the flasks and dark precipitates under clear solutions floating on top.

Examination of these results reveals that the floating coal is the reduction of silver nitrate accelerated to metallic silver, even in comparison with the process in which made by the solution hydrogen was bubbled through a diffuser. Simultaneously with the formation of silver, acid was formed, and the last column with the pH value also shows that the greatest decrease in pH value, i. H. most of the acidification, occurred in the flasks which contained the contact agent according to the invention. Apparently the Reaction rate only slightly influenced by the presence or absence of ammonia.

Example 8

100 ml portions of an aqueous potassium permanganate solution were placed in four paired 250 ml glass Erlenmeyer flasks and exposed to the same gas atmosphere by connecting them in series. Each flask was closed with a rubber stopper, through the holes of which two curved glass tubes were inserted. One glass tube served as an inlet for the gas flow, the other as a gas outlet. In three of the flasks, the entry and exit tubes passed only through the flasks but did not extend to the contained solution, while in one of the flasks the entry tube was long enough to go below the surface of the contained solution and ended in a fritted glass diffuser . The exit tube in this case was the same as that of the other flasks. The solution was prepared by dissolving 1% by weight of potassium permanganate in water, and 100 ml portions were added to each flask. Four grams of polyethylene beads were floated on the surface of a solution in one of the flasks. On the surface of a solution in another flask 97.5 77.7 98.5

75.2

93.7 97.6

6.3

3.6

11.5

10.0

9.4 10.6

4 g of activated carbon made water-repellent with PTFE was used for swimming brought. A third flask was with the stopper

sealed, which contained the diffuser. The pistons were connected in series with plastic hoses, where the exit tube of one piston led to the entry tube of the next piston, the sequence is listed in the table below. A

A container of hydrogen gas was connected to the inlet tube of the first flask. A stream of hydrogen was introduced to the first flask at a rate of 100 ml / min and this became 6 Hours continued. This was followed by interruption overnight and then for 7½ hours Passing through continued. The contents of the flask were anaKsed by first filtering, then the The filtrate was titrated for residual permanganate. The results are summarized in the following table:

35

40

Piston Under- Remaining Percentage

No. divorce KMnO ₄ - des KMnO ₄ -

factor concentration, consumption

normality

1 2

50 PE beads empty

Contact broker Diffuser

0.282 0.256 0.000

0.121

5.7

14.1

100.00

58.7

The initial normal of the potassium permanganate solution was 0.299. At the final observation, all showed Samples a dark brown precipitate at the bottom of the flask, with flasks 3 and 4 longer Precipitation than the others contained. The rate of reaction in the flask with the contact agent was much faster than the reaction rate in the flask with the diffuser. the assumed reaction is the reduction of potassium permanganate to an insoluble brown manganese oxide, possibly manganese dioxide. Such a reaction is represented by the following reaction equation:

2KMnO ₄ + 3H ₂ -> 2MnO ₂ + 2KOH + 2 ₂ HO

Example 9

1 1 portions of deionized water prepared by distillation and Hindurchieiten through an ion exchange resin, "vurden ^{in v 'he} pairs 2-1 glass bottles was added and chlorine gas from a conventional bomb exposed Each bottle was sealed with a Gumniistopfen led through the two curved glass tubes . One of these glass tubes served as an inlet, the other as an outlet for the gas flow. In both bottles the inlet and outlet tubes only went through the stoppers but did not extend to the water they contained, while in the other two bottles the inlet tube was long enough to go below the surface of the water they contained, and in a fritted glass diffuser ended. The exit tubes were the same on all bottles and open to the atmosphere of a fume cupboard. 20 g of activated carbon, which had been made water-repellent with PTFE, floated on the surface of the water in two of the bottles. One of the bottles containing the floating coal was sealed with one of the stoppers with a diffuser. The inlet tubes of the four bottles, all of which had a stopcock, were connected to the chlorine bomb by plastic cord hoses, and the flow of chlorine to the bottles was adjusted so that it was about the same and maintained some pressure to force air out of the bottles and exclude. The water portions were kept in this way under chlorine for 22 hours at room temperature. Samples of the water in each bottle were then immediately analyzed for dissolved chlorine (1) by titration with sodium thiosulfate, and the pH (2) was also measured.

For better comparison, the pH values were converted into the apparent hydrogen ion concentration (3). The results are compiled in the following table, in which all values with the exception of pH values expressed as concentrations in equivalents per liter are:

Distinguishing factors

Immediate analysis 1. Cl ₂ 2. pH 3. (H ⁺ )

empty, dormant resting 0.17 2.1 0.008 Contact broker, Diffuser 0.01 1.3 0.050 Contact broker, 0.10 1.2 0.063 empty, diffuser 0.17 2.1 0.008

It is generally believed that chlorine can dissolve in contact with water and thereby the Solution of a green color given or with water to form hydrochloric and non-chlorous acids can react, the latter being indicated by a different color. The hypochlorous acid can decompose with formation of hydrochloric acid and oxygen. Hydrochloric acid is the source of hydrogen ions, which can be measured by the pH, while the hypochlorous acid in comparison a lot less is ionized. The sequence of reactions can be represented by the following equation:

Cl, + H, O

H ⁺

HCl + HClO

2HCl + 1 / 2Ο

The table above shows that in those bottles in which contact agent was not present, more dissolved chlorine (Cl ₂ ) occurred, while in the presence of contact agent higher hydrogen ion concentrations (H ⁺ ) were formed, as calculated from the pH. These hydrogen ions can only be due to the reaction of chlorine with water under the circumstances of this example. Obviously the contact broker accelerated them

ίο reaction of chlorine with water and causes that relatively little dissolved, unreacted chlorine remains

Example 10

Portions of 100 ml each of the aqueous cerium (IV) hydrogen sulfate solution were placed in four paired glass Erlenmeyer flasks of 250 ml and exposed to a similar hydrogen atmosphere by connecting them in series. Each flask was closed with a rubber stopper, through the openings of which two curved glass tubes passed. One tube served as the inlet for the gas flow, the other tube for the outlet of the gas flow. In three of the flasks the entry and exit tubes only passed through the stoppers but did not extend to the contained solution, while in one of the flasks the entry tube was long enough. to go under the surface of the contained solution, and ended up in a fritted glass diffuser. The exit tube was the same as in the other flasks. The solution was prepared by dissolving 40 g of cerium (IV) hydrogen sulfate [Ce (HSOi) ₄ ] in 960 g of distilled water and adding 20 g of concentrated sulfuric acid. Four grams of polyethylene beads floated on the surface of a solution in one of the flasks. On the surface of a solution in another flask floated 4 g of activated carbon which had been made water-repellent with PTFE. A third flask was closed with the stopper, which contained a diffuser. The flasks were connected in series with plastic tubing, with the outlet tube of one flask connected to the inlet tube of the next flask. The sequence is shown in the table below. A hydrogen gas container was connected to the inlet tube of the first flask. The hydrogen flow was commenced to the first flask at a rate of about 100 ml / min and continued for about 4 hours while the flasks were closely observed. The results are compiled in the following table:

Pistons

No.

Under-

shameful

factor

Observations

+ cr

2H ⁺ + 2CP

empty The solution remained unchanged clear yellow PE series Solution remained unchanged clear yellow Contact· yellowish-white precipitate Intermediary within 15 minutes, Accumulation during 2 1/2 hours Diffuser Turbidity within 1 hour, Intensification and accumulation very slowly

from

In contrast to the high solubility of cerium (IV) sulfate or acidic cerium (IV) sulfate in water Cerium (HI) sulfate has a low solubility although the exact composition of the precipitate Can be doubtful, it is believed that the occurrence of an insoluble material in the acidic Sulphate solution proves the formation of a cerium compound in which the valence is 3, namely by reducing the Value 4 of the starting material. For the cerium sulfate, the essential reduction can be caused by the occurrence of a precipitate can be represented by the following equation:

10

2Ce (HSO ₄ X, + H

Ce ₂ (SO ₄ ) J + 5H ₂ SO ₄

15th

Obviously, the contact agent accelerated the reaction between hydrogen gas and the cerium (! V) solution essential even if the floating contact maker is on a stationary surface found. Bubbling hydrogen gas through the cerium (IV) solution with a diffuser accelerated the process Reaction in comparison with a stationary surface without a contact mediator. The visual analysis regarding the occurrence of precipitations showed that the implementation was several times faster with the contact broker than went with the diffuser.

Example 11

An apparatus according to FIG. 7 constructed and consisted of a column 65 made of a glass tube of 5 cm Inside diameter. Reducing agent was introduced through inlet 66 at the top, and the product was withdrawn from an outlet 67. Air was introduced through line 69 and came from a Pump that gave a steady flow rate. The air was introduced using the countercurrent principle The contact mediator 70 consisted of a layer 40 cm deep, as described below. The layer was on a sieve in the bottom of tube 65 above inlet 66 and outlet 67 supported The activated carbon was made moisture-repellent by treatment with 2.5 and 10% PTFE made to deliver a liaison agent, and these three liaison agents became one another and in a row with the same activated carbon without any moisture repellant treatment compared by experiments. The reducing agent consisted of an aqueous solution of sodium sulfide of about two molar concentration. The residence time of the reducing agent solution in the layer became out the dimensions and the throughput and was calculated by changing the throughput rate of the reducing agent changed. Outflow samples were taken for analysis, if constant Conditions after each change were reached and they were based on standard procedures Sulphide, elemental sulfur, dissolved as polysulphide, and analyzed for thiosulphate. The analytical values of this Experimental series are compiled in the following table, in which the concentration for each type of product in Grams per liter, expressed as sulfur equivalent.

Dwell time (minutes) 33 47 53

64

72

77

102

Activated charcoal without moisture repellency

sulfide 50.6 with 2% PTFE 32.3 with 5% PTFE 25.9 with 10% PTFE 18.6 53.1 11.8 sulfur 2.9 24.3 28.2 27.2 34.6 1.6 27.5 Thiosulfate 0.0 2.6 9.0 29.1 7.7 1.3 35.8 Activated charcoal 0.0 sulfide 40.6 18.2 sulfur 14.1 25.9 Thiosulfate 1.3 10.2 Activated charcoal sulfide 35.2 17.9 sulfur 21.4 32.6 Thiosulfate 2.6 15.6 Activated charcoal sulfide 32.6 sulfur 24.6 Thiosulfate 0.0

Initially, the "sulfide" concentration of the reducing agent was about 64 g / l and the concentration the oxidation products "sulfur" and "thiosulfate" were practically 0. It can be seen that with increasing Residence time the "sulfide" decreases and the "sulfur" and the "thiosulfate" increase. It is also find that the oxidation is slow to proceed if the activated carbon is not moisture-repellent was made even when the oxidizing agent air and finely divided activated carbon are present.

Example 12

Another apparatus according to FIG. 7 constructed and worked as in Example 11, but with the Exception that the glass tubes that formed the column 65, only 2.5 cm in diameter and the layer in one

Depth of 70 cm was filled. Also was in this column the liquid outlet is connected to a riser pipe, the overflow of which is at the level of the upper boundary of the bed lay. Liquid introduced above flowed downward through the bed in countercurrent to that upward rising air, but the riser pipe outside the column maintained hydrostatic pressure and prevented that liquid ran out inside the column, with the exception of that caused by the inflowing liquid was replaced via the riser. 1 ο

Experiments were carried out with two reducing agent solutions, one of which was an aqueous solution of Sodium sulfide with about a two-molar concentration and the other an about one-molar iron (II) sulfate solution was. Each of the reducing agent solutions was each with two finely divided types of activated charcoal, which in

Sodium sulfide solution
Untreated activated carbon

of the tube were contained in a layer 70 cm high, tested in separate experiments, one of the finely divided activated carbons being untreated and the other of the two carbons being the same product but made moisture repellent with 10 weight PTFE. In each case, the reducing agent solution was passed through a column at a constant rate as indicated above, and when the operation of the column was constant, samples were taken for analysis. In all cases, air was passed through the column upward cm at room temperature and at a rate of 250 per minute, passed ³ The results of these four experiments are summarized in the following tables:

Flow rate (g / hr) 312 308 192 48 391 63.1 58.9 57.4 Sulfide (g / l as sulfur) 63.3 0.5 0.5 1.0 Sulfur (g / l as sulfur) 1.0 none 2.5 2.5 Thiosulfate (g / l as sulfur) none made Activated carbon, with 10% PTFE moisture repellent Flow rate (g / hr) 54 26 444 226 140

Sulfide (g / l as sulfur) 3.7 1.9 36.6 31.08 25.4 9.9 Sulfur (g / l as sulfur) 11.8 8.5 17.9 26.6 32.8 31.8 Thiosulfet (g / l as sulfur) 42.9 50.6 3.2 none none 21.8

The "sulfide" reducing agent had an initial concentration of about 64 g / L as sulfur and contained initially practically no "sulfur" and no "thiosulfate". The concentration of the "sulfide" reducing agent remains high in the case of the untreated activated carbon, indicating that there is only relatively little oxidation occurred compared with the case where the activated carbon was made moisture repellent. The lower flow rate values lead to a longer residence time of the reducing agent solution in the activated carbon layer, so that the reaction proceeds accordingly more completely.

Example 13

An apparatus was as shown in FIG. 8 and 10 conjugated and contained six stacked troughs in a closed tower, each trough 120 cm long, 60 cm wide and 5 cm deep. The troughs contained partitions so that liquid reaction partners could get through each trough flowed in a serpentine path about 180 cm long. Air as the oxidizing agent was in an amount of 44 l / min, while the reducing agent in an amount of 400 cmVMin. was fed. The reducing agent was an aqueous solution of sodium sulfide with about two molar concentration. Activated carbon made moisture repellent with 1% PTFE, was used as a contact agent and floated on the surface of the aqueous sodium sulfide solution in each of the troughs. At the flow rate of the reducing agent, the mean residence time was Reducing agent in the apparatus for a total of about 90 minutes or about 15 minutes in each trough. the Apparatus operated continuously for about 6 hours, at the end of which time the effluent from each Trough samples taken and analyzed. The products were elemental sulfur, known as sodium polysulfide was dissolved, as well as sodium thiosulfate. The analytical results are given as grams per liter of sulfur in each of the three forms, the sulfide form, the sulfur form and the thiosulfate form. Typical results of this Test are compiled in the following table:

Trough no .: 1

Sulfide (g / l as Sulfur) 62.1 60.5 57.4 52.5 45.1 28.2 Sulfur (g / l as sulfur) none none 1.6 3.6 11.2 28.5

21
continuation 21 51 sheet 572 3 22nd 4th 5 6th trough
I. No.: 2 3.0
64 6.5
84 20.0
91 60.2
89 Thiosulfate (g / l as sulfur)
Temperature (° C) none
59 none
58 For this 2 drawings

Claims (2)

Patent claims: 1. Use of carbon with a particle size of 9 nm to 2.5 cm passing through partial encapsulation with 0.1 to 100% of its weight of polytetrafluoroethylene in places only wetted by one reaction partner and in places only by the other reaction partner is used as a contact agent when carrying out a thermodynamically spontaneous redox reaction between a reducing agent and an oxidizing agent, which in contact with each other a Form interface and at least one of which is in the liquid phase. 2. Use of the contact agent according to claim 1 in the form of one on the reducing agent or oxidizer floating layer