DE102021110700B3 - Filter for sulphurous gases - Google Patents

Abstract

The present invention relates to a filter for a gas sensor for filtering gases containing sulfur, comprising a first filter material and a second filter material, the first filter material being a transition metal compound and the second filter material being a manganese compound. In addition, the present invention relates to a method for filtering gases containing sulfur and the use of a filter according to the invention for filtering gases containing sulfur, in particular hydrogen sulfide. The present invention also includes sensors for determining the concentration of analyte gases, in particular of hydrocyanic acid and/or thiophene or their derivatives.

Description

The present invention relates to a filter for a gas sensor for filtering gases containing sulfur, having a first filter material, a second filter material and a third and/or a fourth filter material, the first filter material being a transition metal compound and the second filter material being a manganese compound. In addition, the present invention relates to a method for filtering gases containing sulfur and the use of a filter according to the invention for filtering gases containing sulfur, in particular hydrogen sulfide. The present invention also includes sensors for determining the concentration of analyte gases, in particular of hydrocyanic acid and/or thiophene or their derivatives.

State of the art

Filters for gas sensors are generally known from the prior art. They are used, for example, to intercept substances that can falsify or negatively affect the measurement result of the gas sensor. Such substances can be removed by means of a filter from a gas mixture that includes an analyte gas that is to be analyzed by the gas sensor. Gases containing sulfur in particular, in particular hydrogen sulfide, are such a substance that frequently occurs as a harmful substance, particularly when determining the concentration of certain analyte gases such as hydrocyanic acid or thiophene or their derivatives, and can thus adversely affect the sensitivity of many different gas sensors.

Filters are therefore already known which are designed to filter hydrogen sulphide from a gas mixture to be examined. Conventionally, lead compounds in particular are used as filter materials for this purpose. It is generally known in this context, for example, that lead acetate can be used to detect—and thus to bind and retain—hydrogen sulfide. However, a negative aspect of such filters known from the prior art is that lead compounds and in particular lead acetate can have a toxic effect and are mostly harmful to the environment and are therefore undesirable.

In addition, various other types of filters are also known, as disclosed DE 4481363 C2 a filter agent containing activated carbon fibers as a carrier for an MnO type chemical agent for removing hydrogen sulfide. DE 198 42 528 A1 also discloses impregnated fibrous materials containing manganese compounds useful for removing hydrogen sulfide. DE 695 25 066 T2 discloses the use of manganese and indium together as an electrically conductive coating on a filter medium and U.S. 2001/0016184 A1 discloses the use of indium oxide as a substance to prevent the formation of hydrogen sulfide. US2004/0063578 A1 discloses the use of a gas desulfurization composition containing indium oxide and a promoter which may be a manganese compound. DE 102015001591 A1 discloses a filter for a gas sensor which has a first and a second filter material, the first filter material being an indium compound and the second filter material being a manganese compound.

The disadvantage of the filters known from the prior art is that the service life of the filter and/or the filter performance, in particular when filtering gases containing sulfur such as hydrogen sulfide, is only short or insufficient. There is therefore still an increased need for filters for gas sensors, which in particular filter out sulphur-containing gases from a gas mixture and have an improved or increased service life compared to the filters known from the prior art without the addition of toxic lead compounds.

object of the invention

The object of the present invention is therefore to provide a filter which avoids the problems known from the prior art and which is suitable for filtering sulphur-containing gases, in particular hydrogen sulfide, and whose service life is increased or reduced compared to the filters known from the prior art .is improved.

Summary of the Invention

These and other objects are achieved according to the invention by the content of the independent patent claims. Preferred configurations are contained in the dependent claims and are described in more detail below.

Surprisingly, it was found that the service life of conventional filters for gas sensors known from the prior art can be significantly improved if at least one transition metal compound and one manganese compound are used as filter materials.

According to the invention, a filter for a gas sensor for filtering sulfur-containing gases is proposed for this, which has at least a first filter material, a second filter material and a third and/or a fourth filter material, the first filter material having a transition metal compound and the second filter material is a manganese compound.

Surprisingly, it has been shown that a filter according to the invention can filter sulphur-containing gases, in particular hydrogen sulfide, and has an improved or longer service life compared to the filters previously known from the prior art. At the same time, it has been shown that, for example, hydrocyanic acid or thiophene compounds, such as tetrahydrothiophene, can pass through such a filter unhindered. Such a filter can thus be used, for example, as a filter for a hydrocyanic acid sensor or for a thiophene sensor.

Detailed description of the invention

The filter according to the invention for filtering gases containing sulfur comprises at least a first and a second filter material. According to the invention, a filter material is understood to mean an active material which reacts chemically and/or physically on contact with a specific gas or substances contained in the gas and in this way retains, absorbs or changes the gas to be filtered or the substances to be filtered in such a way that they components downstream of the filter become harmless, while allowing other gases or substances contained in the gas to pass through unhindered. Such filter materials can, for example, be in the form of particles, with the gas or the substances contained in the gas flowing around the particles, so that the gas or its substances can react, for example, on the surface of the particles. The filter material can also be in the form of a mat through which the gas or fluid flows, with the gas likewise flowing along the surface—for example along a meshwork or along pores or the like—and being able to react there.

In one embodiment, the filter material or the filter materials comprises a carrier material as an auxiliary substance (additive). A carrier material can be designed, for example, so that the active filter material, which causes the binding of the gas or the fluid, for example hydrogen sulfide and/or the by-products formed during the binding of H ₂ S, is optimally surrounded and penetrated by the gas stream to be examined can. At the same time, it enables the handling and assembly of the filter material in a corresponding filter. For example, it is conceivable that such a carrier material is coated or impregnated with the active component of the filter material.

According to the invention, the first filter material is a transition metal compound. In a preferred embodiment, the transition metal compound is a transition metal halide, more preferably a Group 11 and 12 transition metal halide (copper, silver, gold (Group 11); zinc, cadmium, mercury (Group 12)), even more preferably a Group 12 transition metal halide and particularly preferred is zinc chloride (ZnCl ₂ ).

According to the invention, the second filter material is a manganese compound. The simultaneous use of a first filter material containing a transition metal compound in a filter together with a second filter material containing a manganese compound has proven to be particularly advantageous for filtering hydrogen sulfide. It is conceivable that the gas mixture to be examined first flows through the first filter material, which contains the transition metal compound, and then through the second filter material, which contains the manganese compound. The manganese compound is preferably a Mn(II), Mn(III) or Mn(IV) compound. It is also conceivable that the manganese compound is a permanganate, manganate or hypomanganate compound, ie an Mn(VII), Mn(VI) or Mn(V) compound. The manganese compound is preferably selected from Mn(II), Mn(III), Mn(IV), Mn(V); Mn(VI) and Mn(VII) compounds. More preferably, the manganese compound is selected from Mn(III), Mn(IV) and Mn(V) compounds. A conceivable Mn(IV) compound is, for example, manganese dioxide (MnO ₂ ). A conceivable Mn(VII) compound could be potassium permanganate, for example. Potassium manganate would also be conceivable as an Mn(VI) compound.

The manganese compound of the second filter material is preferably a manganese oxide or a manganese carbonate, in particular manganese dioxide (manganese dioxide). If the reaction of H ₂ S with the aid of the first filter material (such as ZnCl ₂ ) releases hydrogen chloride and the second filter material contains a manganese oxide, the released hydrogen chloride can react with the manganese oxide to form manganese chloride and water. The manganese oxide is preferably α-manganese dioxide (α-MnO _{2 )} . It is also possible to use potassium permanganate as the manganese compound, with the manganese compound being reduced to manganese dioxide in a subsequent step. This can be done, for example, in a reducing atmosphere known to those skilled in the art, for example by means of gassing with an alcohol such as ethanol and/or isopropanol, or by gassing with hydrogen peroxide and/or ammonia reduce ammonia-filled atmosphere.

Surprisingly, it has turned out to be particularly advantageous if the transition metal compound of the first filter material is zinc chloride. Hydrogen sulfide flowing into the filter can then, for example, be bound very effectively in the form of zinc sulfide (ZnS), releasing hydrogen chloride. This can then be converted into manganese chloride (MnCl ₂ ) and water by the manganese compound located in the second filter material, in particular manganese dioxide.

In one embodiment, the filter according to the invention comprises a third filter material. The third filter material is an indium compound, and in particular indium(III) chloride (inCl ₃ ). The inventors have found that when a first filter material and a third filter material are used simultaneously, which are preferably a metal halide and a transition metal halide, respectively, the absorption of gas flowing into the filter, such as hydrogen sulfide, can be improved . Without being bound by theory, the inventors suspect that when hydrogen sulfide flows into the filter, it is mixed with the transition metal compound of the first filter material and the indium compound of the third filter material, with zinc chloride being particularly preferred as the first filter material and indium(III) chloride as the third Filter material are used to zinc sulfide (ZnS) and / or indium sulfide (In ₂ S ₃ ) can react.

According to a further embodiment, the filter according to the invention comprises a fourth filter material. The use of a fourth filter material is independent of the use of an optionally used third filter material. This means that a possible fourth filter material can be used in addition to the first and the second filter material, optionally and preferably used with a first, a second and a third filter material.

The fourth filter material is selected from one or more members of the group consisting of alkali metal chlorites, alkaline earth metal chlorites, alkali metal chlorates, alkaline earth metal chlorates, alkali metal perchlorates, alkaline earth metal perchlorates, alkali metal bromites, alkaline earth metal bromites, alkali metal bromates, alkaline earth metal bromates, alkali metal perbromates, alkaline earth metal perbromates, alkali metal iodates, alkaline earth metal iodates, alkali metal periodates, alkaline earth metal periodates. The fourth filter material is preferably an alkali metal perchlorate or an alkaline earth metal perchlorate, more preferably an alkaline earth metal perchlorate, and the fourth filter material is particularly preferably calcium perchlorate Ca(ClO ₄ ) ₂ .

The inventors have surprisingly found that with the simultaneous use of a second filter material (the manganese compound, particularly preferably manganese dioxide) and a third filter material, particularly indium chloride, and/or a fourth filter material, particularly calcium perchlorate, the filter performance of the filter according to the invention can be further improved. Without being bound to theory, the inventors assume that the use of calcium perchlorate is preferred because the use of a fourth filter material can improve or increase the effect of the second filter material (manganese compound, particularly preferably manganese dioxide).

In addition to the first filter material and the second filter material, a filter according to the invention contains a third and/or a fourth filter material. In addition to the first filter material and the second filter material, a filter according to the invention preferably contains both a third filter material and a fourth filter material. It is particularly preferred to use zinc chloride as the first filter material, indium(III) chloride as the third filter material, manganese dioxide as the second filter material and calcium perchlorate as the fourth filter material.

As already mentioned above, the individual filter materials can each independently have further auxiliary substances such as, for example, carrier materials. In a first embodiment, only the first filter material and/or the second filter material has a carrier material as a further component. In another embodiment, all of the filter materials arranged in the filter have a carrier material as a further component. So it is possible that the filter materials, i. H. the active substances are supported, for example, on a carrier body such as aluminum oxide, activated carbon, hollow microspheres or kieselguhr and nonwoven materials such as glass nonwovens or polymer nonwovens. It can be preferred if the individual filter materials additionally comprise carrier materials and/or are applied to the carrier materials. Carrier materials can improve the effect of the active material by allowing the gas flow to be examined to flow better around and penetrate the filter material. Furthermore, it enables the handling and assembly of the filter material in a corresponding filter. For example, it is conceivable that such a carrier material is coated or impregnated with the active component of the filter material.

In another embodiment, the filter materials include additives that can improve the stability of the filter materials over a long period of time. So it is conceivable that at least one other component of the first and / or the second filter material and / or the third filter material and / or the fourth filter material buffer substance is. In particular, an acidic buffer substance can be advantageous as a component of the second filter material and/or the fourth filter material. Acetate buffers, citrate buffers or the like can be used as possible buffer substances. In one embodiment, the second filter material comprises or consists of acid-buffered manganese dioxide, eg acetate-buffered manganese dioxide.

The arrangement of the filter materials in the filter can vary or be configured differently. In one embodiment, it is conceivable that the filter materials are designed as a loose bed. The carrier material can consist of porous carrier particles which are each impregnated with the first and/or the second filter material. For example, a first quantity of support particles may be treated with the first filter material, i.e., a material containing a transition metal compound, preferably a Group 11 and 12 transition metal halide, more preferably a Group 12 transition metal halide, and most preferably zinc chloride.

A second quantity of support material may be treated with the second filter material, i.e. a material comprising a manganese compound, preferably manganese dioxide. The carrier particles of the first and the second quantity can then be mixed together and introduced into a filter housing as a loose bed.

It is also possible for the first filter material and the second filter material to be arranged in layers one above the other in the filter. In this embodiment it is preferred that initially the first filter material is arranged in one layer in the filter and that the second filter material is arranged in a second layer above the first filter material. The arrangement is preferably such that the first filter material, ie the filter material which is a transition metal compound, in particular zinc chloride, first comes into contact with the sulphur-containing gas along the diffusion path as it flows through the filter. In this configuration, it is particularly conceivable that the sulfur-containing gas, which is in particular hydrogen sulfide, can first react with the transition metal compound, which is preferably a transition metal halide and particularly preferably zinc chloride, when flowing through with the hydrogen sulfide to form a transition metal sulfide. The substance released during this reaction, for example hydrogen chloride (HCl), can then be converted into manganese chloride and water in the overlying layer with the second filter material.

As already mentioned, it is possible to mix both the first and the second filter material and to introduce this mixture into the filter. It is also possible to arrange the individual filter materials in layers one above the other. In this configuration, it is particularly advantageous if the first filter material and optionally the third filter material, either in layers one above the other or mixed, first come into contact with the sulfur-containing gas along the diffusion path, and that the second filter material and optionally the fourth filter material subsequently Flowing through the sulfur-containing gas through the first filter material and optionally come into contact with the third filter material. In other words, in a preferred embodiment the filter materials are arranged such that the sulphur-containing gas, in particular hydrogen sulfide, when flowing through the filter first comes into contact with the filter materials which are suitable for converting the hydrogen sulfide into hydrogen chloride. This is followed by the layers with the filter materials, which are suitable for reacting with the hydrogen chloride. In this case, the filter materials which are suitable for reacting with the sulfur-containing gas are arranged at the lower end, whereas the filter materials which are suitable for reacting with hydrogen chloride are arranged at the upper end of the filter.

In this context, the lower end means the end at which the sulphur-containing gas enters the filter. Upper end means the end facing the gas sensor. It is clear to a person skilled in the art what is meant by lower and upper end.

• - Filtermaterial 1 / Filtermaterial 3 / Filtermaterial 2;
• - Filtermaterial 3 / Filtermaterial 1 / Filtermaterial 2;
• - Filtermaterial 1 / Filtermaterial 2 / Filtermaterial 4;
• - Filtermaterial 1 / Filtermaterial 4 / Filtermaterial 2;
• - Filtermaterial 1 / Filtermaterial 3 / Filtermaterial 2 / Filtermaterial 4;
• - Filtermaterial 1 / Filtermaterial 3 / Filtermaterial 4 / Filtermaterial 2;
• - Filtermaterial 3 / Filtermaterial 1 / Filtermaterial 4 / Filtermaterial 2;
• - Filtermaterial 3 / Filtermaterial 1 / Filtermaterial 2 / Filtermaterial 4;

Arrangements of the filter materials in the filter according to the invention are as follows:

• - Filter material 1 / filter material 3 / filter material 2;
• - Filter material 3 / filter material 1 / filter material 2;
• - Filter material 1 / filter material 2 / filter material 4;
• - Filter material 1 / filter material 4 / filter material 2;
• - Filter material 1 / filter material 3 / filter material 2 / filter material 4;
• - Filter material 1 / filter material 3 / filter material 4 / filter material 2;
• - Filter material 3 / filter material 1 / filter material 4 / filter material 2;
• - Filter material 3 / filter material 1 / filter material 2 / filter material 4;

The specified arrangements of the filter materials relate to the layers of the individual filter materials. The individual filter materials can each be present independently of one another either in powder or granular form or they can be applied or supported independently of one another on carrier materials. The filter materials 1 and 3 are designed in such a way that they can react with the sulphur-containing gas, in particular with hydrogen sulfide, to form a metal sulfide and also to form hydrogen chloride. The filter materials 2 and 4 are designed in such a way that they can react with the hydrogen chloride. Metal chlorides and water, for example, can form here. Gas-permeable separating layers, such as glass fleece (glass fiber fleece) or polymer fleece, can be arranged between the respective individual layers of the respective filter materials.

In one embodiment, the filter according to the invention comprises a third filter material. In this configuration, it is also possible for the third filter material, the indium compound, in particular indium(III) chloride, to also be applied to a carrier material. In this configuration it is possible for the third filter material to be mixed together with the first filter material and the second filter material, both the first filter material and the second filter material also being applied to a carrier material.

In yet another embodiment, the filter according to the invention comprises a fourth filter material. In particular, it is possible for the filter according to the invention to comprise a first filter material, a second filter material and a fourth filter material. It is therefore expressly not necessary to use the fourth filter material (particularly preferably alkaline earth metal perchlorate, even more preferably calcium perchlorate) exclusively in connection with the third filter material (indium compound, preferably indium(III) chloride). The filter according to the invention preferably comprises a first filter material, a second filter material and a fourth filter material. A filter according to the invention particularly preferably comprises a first filter material, a second filter material, a third filter material and a fourth filter material. More preferably, at least one of the aforementioned filter materials is applied to a carrier material, preferably at least two filter materials, more preferably three filter materials and particularly preferably all filter materials.

In another embodiment, the filter materials, that is to say the active materials directly, can be in the form of a loose bed, that is to say without additional carrier material. In this embodiment, the filter materials, ie at least the first filter material and the second filter material, are arranged in the filter, for example in powder form or as granules. In this embodiment, as in the previously described embodiment including the carrier material, it is possible for the first and the second filter material and optionally the third and/or the fourth filter material to be mixed with one another and thus arranged in the filter. In another embodiment, it is possible that initially the first filter material is arranged in a layer in the filter and above that a second layer with the second filter material. The arrangement of the individual filter materials, if they are arranged in layers, is preferably always chosen so that first the first filter material and optionally the third filter material first come into contact with the sulphur-containing gas along the diffusion path of the sulphur-containing gas, and that the second filter material and optionally the fourth filter material is positioned over the layer of first filter material and optionally third filter material.

In this configuration, it may be desirable for a gas-permeable separating layer to be located between the first layer with the first filter material and the second layer with the second filter material. This separating layer can, for example, be a paper layer or a fleece layer or the like.

In a further embodiment, the filter according to the invention comprises at least one third filter material, the third filter material being an indium compound and in particular indium(III) chloride. In this embodiment, it is also possible to use the third filter material in powder form or as granules and/or to apply the third filter material to a carrier material and to arrange this in the filter. In this embodiment it is preferred if the first filter material is mixed together with the third filter material and this mixture is arranged at the bottom of the filter. The bottom of the filter means the opening in the direction of the environment, while the top of the filter means the opening in the direction of the sensor. In other words, this means that the mixture of the first and third filter material (ie the transition metal compound and the indium compound) first comes into contact with the sulfur-containing gas along the diffusion path of the sulfur-containing gas, which is in particular hydrogen sulfide.

In a further embodiment, both the first filter material and the second filter material are supported on a fleece, in particular a glass fleece (also glass fiber fleece). In one embodiment, it is advantageous if a fleece is first soaked in a solution of the second filter material, ie the manganese compound, and then dried net will. A solution of the first filter material is then placed on the glass fleece previously supported with the first filter material. Furthermore, it can be preferred to support a glass fleece supported in this way optionally with a third and/or fourth filter material. It is particularly favorable to initially support the fleece with the second filter material, ie to soak and dry it, and then to support it with the first filter material. Optionally, such a supported fleece can also be supported with a third and/or fourth filter material. The carriers with the first and optionally the third and fourth filter material can be carried out in any order. It is also possible to produce a solution comprising the first and optionally the third and fourth solvent and to support the fleece with this solution.

In yet another embodiment, the first filter material and the second filter material are each supported independently of one another on a fleece and the fleeces are arranged one above the other in the filter. In this configuration, too, it is possible to additionally arrange a third and/or fourth filter material in the filter, which can also be supported independently of one another on separate fleeces. As already described above, the mats are preferably arranged such that first the first and optionally the third filter material come into contact with the sulfur-containing gas along the diffusion path of the sulfur-containing gas and then the mats comprising the second and optionally the fourth filter material.

The nonwovens or the filter materials, both supported and in powder form or as granules, are preferably arranged in such a way that along the diffusion path of the sulphur-containing gas first the first and optionally the third filter material or the third and the first filter material and then the second and optionally the fourth filter material or the fourth and the second filter material can be flowed through. Along the diffusion path of the gas means a lower end into which the gas flows or diffuses into the filter, and an upper end facing the sensor.

In yet another embodiment, the first filter material can be in the form of granules and/or powder and the second filter material can be supported on a fleece. It can thus be expressly desired to combine some of the filter materials in powder or granular form with other filter materials which are supported on a fleece.

• - 5 bis 95 Gew.% des ersten Filtermaterials, bevorzugt 10 bis 90 Gew.%, weiter bevorzugt 10 bis 80 Gew.% und insbesondere bevorzugt 15 bis 75 Gew.% und
• - 5 bis 95 Gew.% des zweiten Filtermaterials, bevorzugt 10 bis 90 Gew.%, weiter bevorzugt 10 bis 80 Gew.% und insbesondere bevorzugt 15 bis 75 Gew.%

sowie

• - bis zu 70 Gew. % des dritten Filtermaterials, und/oder
• - bis zu 30 Gew. % des vierten Filtermaterials,

jeweils bezogen auf die Gesamtmenge des Filtermaterials, wobei die Gesamtmenge des ersten und zweiten und des dritten und/oder vierten Filtermaterials 100 Gew.% ergeben, auf.The filters according to the invention have at least:

• - 5 to 95% by weight of the first filter material, preferably 10 to 90% by weight, more preferably 10 to 80% by weight and particularly preferably 15 to 75% by weight and
• - 5 to 95% by weight of the second filter material, preferably 10 to 90% by weight, more preferably 10 to 80% by weight and particularly preferably 15 to 75% by weight

such as

• - up to 70% by weight of the third filter material, and/or
• - up to 30% by weight of the fourth filter material,

in each case based on the total amount of the filter material, the total amount of the first and second and the third and/or fourth filter material being 100% by weight.

• - 10 bis 50 Gew.% des ersten Filtermaterials, insbesondere Zinkchlorid, bevorzugt 20 bis 40 Gew.%, weiter bevorzugt 25 bis 35 Gew.%, sowie
• - 10 bis 30 Gew.% des zweiten Filtermaterials, insbesondere Mangandioxid, bevorzugt 10 bis 25 Gew.%, weiter bevorzugt 15 bis 25 Gew.%, sowie
• - 20 bis 70 Gew.% des dritten Filtermaterials, insbesondere Indium(III)-chlorid, bevorzugt 30 bis 65 Gew.%, weiter bevorzugt 40 bis 60 Gew.%,

jeweils bezogen auf die Gesamtmenge des Filtermaterials, wobei die Gesamtmenge des ersten und zweiten und dritten Filtermaterials 100 Gew.% ergeben, auf.A preferred filter according to the present invention comprises:

• - 10 to 50% by weight of the first filter material, in particular zinc chloride, preferably 20 to 40% by weight, more preferably 25 to 35% by weight, and
• - 10 to 30% by weight of the second filter material, in particular manganese dioxide, preferably 10 to 25% by weight, more preferably 15 to 25% by weight, and
• - 20 to 70% by weight of the third filter material, in particular indium(III) chloride, preferably 30 to 65% by weight, more preferably 40 to 60% by weight,

in each case based on the total amount of the filter material, the total amount of the first and second and third filter material being 100% by weight.

• - 10 bis 80 Gew.% des ersten Filtermaterials, insbesondere Zinkchlorid, bevorzugt 20 bis 70 Gew.%, weiter bevorzugt 30 bis 60 Gew.%, sowie
• - 10 bis 40 Gew.% des zweiten Filtermaterials, insbesondere Mangandioxid, bevorzugt 15 bis 35 Gew.%, weiter bevorzugt 20 bis 35 Gew.%, sowie
• - 10 bis 30 Gew.% des vierten Filtermaterials, insbesondere Calciumperchlorat, bevorzugt 10 bis 25 Gew.%, weiter bevorzugt 10 bis 20 Gew.%,

jeweils bezogen auf die Gesamtmenge des Filtermaterials, wobei die Gesamtmenge des ersten und zweiten und vierten Filtermaterials 100 Gew.% ergeben, auf.Another preferred filter according to the present invention includes:

• - 10 to 80% by weight of the first filter material, in particular zinc chloride, preferably 20 to 70% by weight, more preferably 30 to 60% by weight, and
• - 10 to 40% by weight of the second filter material, in particular manganese dioxide, preferably 15 to 35% by weight, more preferably 20 to 35% by weight, and
• - 10 to 30% by weight of the fourth filter material, in particular calcium perchlorate, preferably 10 to 25% by weight, more preferably 10 to 20% by weight,

in each case based on the total amount of the filter material, the total amount of the first and second and fourth filter material being 100% by weight.

• - 10 bis 40 Gew.% des ersten Filtermaterials, insbesondere Zinkchlorid, bevorzugt 10 bis 35 Gew.%, weiter bevorzugt 15 bis 35 Gew.%, sowie
• - 10 bis 30 Gew.% des zweiten Filtermaterials, insbesondere Mangandioxid, bevorzugt 10 bis 25 Gew.%, weiter bevorzugt 15 bis 25 Gew.%, sowie
• - 20 bis 70 Gew.% des dritten Filtermaterials, insbesondere Indium(III)-chlorid, bevorzugt 30 bis 60 Gew.%, weiter bevorzugt 40 bis 55 Gew.%, sowie
• - 5 bis 30 Gew.% des vierten Filtermaterials, insbesondere Calciumperchlorat, bevorzugt 5 bis 25 Gew.%, weiter bevorzugt 5 bis 20 Gew.%,

jeweils bezogen auf die Gesamtmenge des Filtermaterials, wobei die Gesamtmenge des ersten und zweiten und dritten und vierten Filtermaterials 100 Gew.% ergeben, auf.Another preferred filter according to the present invention comprises:

• - 10 to 40% by weight of the first filter material, in particular zinc chloride, preferably 10 to 35% by weight, more preferably 15 to 35% by weight, and
• - 10 to 30% by weight of the second filter material, in particular manganese dioxide, preferably 10 to 25% by weight, more preferably 15 to 25% by weight, and
• - 20 to 70% by weight of the third filter material, in particular indium(III) chloride, preferably 30 to 60% by weight, more preferably 40 to 55% by weight, and
• - 5 to 30% by weight of the fourth filter material, in particular calcium perchlorate, preferably 5 to 25% by weight, more preferably 5 to 20% by weight,

in each case based on the total amount of the filter material, the total amount of the first and second and third and fourth filter material being 100% by weight.

Furthermore, the invention includes an electrochemical gas sensor for an analyte gas. The analyte gas is the gas that is applied to the electrochemical gas sensor. The analyte gas usually diffuses together with air and other components from the ambient atmosphere through the filter to the gas sensor according to the invention, or the electrochemical gas sensor according to the invention is acted upon with it. The gas sensor of the present invention is in particular a hydrogen cyanide sensor or a thiophene sensor. It is known that thiophene and hydrocyanic acid are often contaminated with hydrogen sulfide or sulfur dioxide. However, hydrogen sulfide in particular has a negative effect on an electrochemical gas sensor, so that it is desirable to filter it out of the gas mixture comprising analyte gas and other components.

• 1: einen Querschnitt durch einen nicht-erfindungsgemäßen Filter mit einem schichtförmigen ersten Filtermaterial und einem schichtförmigen zweiten Filtermaterial;
• 2: einen Querschnitt durch eine alternative Ausführungsform des nicht-erfindungsgemäßen Filters wobei die Filtermaterialien durch eine poröse Trennschicht voneinander getrennt sind;
• 3: einen Querschnitt durch eine weitere alternative Ausführungsform des nicht-erfindungsgemäßen Filters, wobei die Filtermaterialien als lose Schüttung von Partikeln im Gehäuse des Filters angeordnet sind;
• 4: einen Querschnitt durch eine bevorzugte Ausführungsform des erfindungsgemäßen Filters, aufweisend insgesamt vier auf Glasvliese geträgerte Filtermaterialien;
• 5: einen Querschnitt durch eine weitere alternative Ausführungsform eines erfindungsgemäßen Filters aufweisend insgesamt vier Filtermaterialien, wobei die Filtermaterialien als lose Schüttung von Partikeln im Gehäuse des Filters angeordnet sind;
• 6: einen Vergleich der Begasungsfestigkeit zwischen einem erfindungsgemäßen und einem aus dem Stand der Technik bekannten Filter.

Further configurations of the filter according to the invention and its possible structure are presented below with reference to the following figures. Show it:

• 1 : a cross section through a filter not according to the invention with a layered first filter material and a layered second filter material;
• 2 : a cross section through an alternative embodiment of the filter not according to the invention, the filter materials being separated from one another by a porous separating layer;
• 3 1: a cross section through a further alternative embodiment of the filter not according to the invention, the filter materials being arranged as a loose bed of particles in the housing of the filter;
• 4 : a cross section through a preferred embodiment of the filter according to the invention, having a total of four filter materials supported on glass fleece;
• 5 : a cross section through a further alternative embodiment of a filter according to the invention having a total of four filter materials, the filter materials being arranged as a loose bed of particles in the housing of the filter;
• 6 : a comparison of the fumigation resistance between a filter according to the invention and a filter known from the prior art.

1 shows a filter 10 which has a carrier disc 1 and a housing 2 . The carrier disk 1 comprises porous PTFE and is permeable to a gas mixture to be examined. The housing 2 has the shape of a hollow cylinder and is connected to the carrier disc 1 . The housing 2 has a projection at the upper end of the filter, ie in the direction of the gas sensor. A first filter material 3 and a second filter material 4 are arranged between the projection of the housing 2 and the carrier disk 1 . In this embodiment, the first filter material 3 comprises a glass fleece which is impregnated with a transition metal compound, zinc chloride in the illustrated case. In the embodiment shown, the second filter material 4 also comprises a glass fleece which is impregnated with a manganese compound. In the example shown, the manganese compound is manganese dioxide (manganese dioxide).

A gas to be examined flows through the filter 10 from the lower end of the filter 10 toward the upper end of the filter 10 (diffusion path of the gas). The upper end of the filter means the end pointing towards the gas sensor. The gas first flows through the carrier disc 1, then through the first filter material 3 and finally through the second filter material 4. In this way, the hydrogen sulfide contained in the gas to be examined can first react with the zinc chloride and be bound in the form of zinc sulfide. The hydrogen chloride released during this reaction can then react with the manganese dioxide of the second filter material to form manganese chloride and water.

2 shows an alternative filter not according to the invention. The gas to be examined flows through the filter 20 as in 1 from the bottom to the top. The filter 20 also has a carrier disk 1 and a housing 2. The housing 2 has two housing sections 2, 5 and a separating layer 6 in the form of a separating disk 6. FIG. the Cutting disk 6 comprises a porous PTFE material and is gas permeable.

The carrier disc 1 is a porous PTFE disc through which the gas to be examined can flow. The second housing section 5 has the same shape as the housing 2 of the exemplary embodiment 1 a head start. A first filter material 3 and a second filter material 4 are also arranged in the housing 2 here. The first filter material 3 in turn comprises a glass fleece which is coated with a transition metal compound, namely with zinc chloride. The second filter material 4 also includes a glass mat coated with manganese dioxide. The fleece for the first filter material 3 is preferably coated by soaking the fleece with an aqueous solution of the first filter material. The glass fleece is preferably supported with the second filter material 4 by soaking the glass fleece with an aqueous potassium permanganate solution (aq. KMnO ₄ solution), with potassium permanganate being at least partially reduced to manganese dioxide in a subsequent step. This can be done, for example, in a reducing atmosphere known to those skilled in the art, for example by gassing with an alcohol such as ethanol and/or isopropanol or also by gassing with hydrogen peroxide and/or ammonia or by storage in an atmosphere with an alcohol and/or hydrogen peroxide and/or or ammonia-filled atmosphere.

The filter not according to the invention in 2 is built up in layers. In this case, the carrier disc 1 forms a first layer. The first filter material 3 , which is surrounded by the first housing section 2 , is arranged on the carrier disk 1 . The first housing section 2 and the first filter material 3 are covered by the separating disk 6 . The second filter material 4 is arranged on the cutting disk 6 . The second filter material 4 is in turn surrounded by the second housing section 5 . In this case, the second filter material 4 is held by the projection of the housing section 5 . The separating disk 6 is arranged between the first housing section 2 and the second housing section 5 and between the first filter material 3 and the second filter material 4 .

the inside 3 The filter 30 shown has a housing 2 which is mounted on a carrier disc 1 . The carrier disk comprises a porous, gas-permeable PTFE plate. The porous housing 2 here has the shape of a pot. The pot is filled with the filter material 3 and the filter material 4 . The filter materials 3 and 4 are in the form of aluminum oxide particles and activated carbon particles, respectively, which are each impregnated with either zinc chloride or MnO ₂ . The particles with the first filter material 3 and the second filter material 4 are filled into the housing 2 in a loose heap. A gas stream to be examined flows through the filter 30 from the lower end to the upper end.

In an exemplary embodiment (not shown) not according to the invention, it is provided that the filter 10 has a carrier disc 1 and a housing 2 . The housing 2 has a shape that corresponds to that in 1 shown housing shape corresponds. In this exemplary embodiment, the first filter material 3 and the second filter material 4 are present in a common layer. In this case, this layer has a carrier material in the form of a porous fleece material which is coated with the two filter materials 3 , 4 . In a particularly preferred embodiment, the porous fleece material is a glass fleece.

The inventive in 4 The filter 40 shown has a housing 2 which is mounted on a carrier disk 1 . The carrier disk comprises a porous, gas-permeable PTFE plate. The porous housing 2 has the shape of a hollow cylinder and is connected to the carrier disc 1 . The housing 2 has a projection at the upper end of the filter, ie in the direction of the gas sensor. A first filter material 3 , a third filter material 9 , a second filter material 4 and a fourth filter material 8 are arranged between the projection of the housing 2 and the carrier disk 1 . In this configuration, all four filter materials 3 , 4 , 8 , 9 each comprise a glass fleece which is impregnated with the respective filter materials 3 , 4 , 8 , 9 . The first filter material 3 comprises a glass mat which is impregnated with an aqueous zinc chloride solution. The third filter material 9 comprises a glass mat which is impregnated with an aqueous indium(III) chloride solution. In the embodiment shown, the second filter material 4 comprises a glass mat which is impregnated with a manganese dioxide solution. In the embodiment shown, the fourth filter material 8 comprises a glass mat which is impregnated with an aqueous solution of calcium perchlorate. A gas to be examined flows through the filter 40 from the lower end of the filter 40 toward the upper end of the filter 40 (diffusion path of the gas). The upper end of the filter means the end pointing towards the gas sensor. The gas first flows through the carrier disc 1, then the first filter material 3, then the third filter material 9, then the second filter material 4 and finally the fourth filter material 8.

In an embodiment that is not shown, the arrangement of the first and third filter material 3, 9 and/or the second and fourth filter material 4, 8 can be reversed, so that the gas flowing through the filter according to the invention, for example, first passes through the carrier disk 1, then through the third filter material 9, subsequently through the first filter material 3, and/or thereafter through the fourth filter material 8 and finally the second filter material 4.

the inside 5 The filter 50 according to the invention shown has a housing 2 which is mounted on a carrier disk 1 . The carrier disk comprises a porous, gas-permeable PTFE plate. The porous housing 2 here has the shape of a pot. The pot is filled with the filter materials 3, 4, 8 and 9. All filter materials 3, 4, 8 and 9 are in the form of aluminum oxide particles or activated carbon particles, which are each impregnated with either zinc chloride, indium(III) chloride, MnO ₂ and calcium perchlorate. The particles of the respective filter materials are filled into the housing 2 in a loose bed. A gas stream to be examined flows through the filter 50 from the lower end to the upper end.

The in the 1 , 2 , 3 , 4 and 5 The filters 10, 20, 30, 40 and 50 shown are all filters for, inter alia, electrochemical gas sensors.

In 6 is the gas resistance of a filter according to the invention (dashed line, designation F1586) with the gas resistance of a filter known from the prior art ( DE 102015001591 A1 ; solid line, designation F648). The filters were gassed with 20 ppm hydrogen sulfide. The filter according to the invention has a total of four filter materials, with the first filter material zinc chloride (contains 28% by weight), the second filter material manganese dioxide (contains 17% by weight), the third filter material indium(III) chloride (contains 45% by weight .%) and the fourth filter material is calcium perchlorate (contained at 10% by weight).

A glass mat was first soaked in a 0.25 molar aqueous potassium permanganate solution and then reduced in a desiccator for 72 hours. Thereafter, the glass fleece was successively impregnated with a 0.25 molar aqueous zinc chloride solution, with a 0.25 molar aqueous indium(III) chloride solution and with a 0.05 molar aqueous calcium perchlorate solution, with the glass fleece between the respective steps with gaseous nitrogen has been dried.

Reference List

1

carrier disc

2

Housing

3

first filter material

4

second filter material

5

housing section

6

release layer

8th

fourth filter material

9

third filter material

10

filter

20

filter

30

filter

40

filter

50

filter

Claims (16)

Filter for a gas sensor for filtering gases containing sulfur, comprising at least a first filter material and a second filter material, the second filter material being a manganese compound, the first filter material being a transition metal compound, characterized in that - the filter comprises at least a third filter material which is a is an indium compound, or - the filter comprises at least a fourth filter material, which is selected from one or more members of the group consisting of: alkali metal chlorites, alkaline earth metal chlorites, alkali metal chlorates, alkaline earth metal chlorates, alkali metal perchlorates, alkaline earth metal perchlorates, alkali metal bromites, alkaline earth metal bromites, alkali metal bromates, alkaline earth metal bromates, alkali perbromates, alkaline earth metal perbromates, Alkali iodate, alkaline earth iodate, alkali periodate, alkaline earth periodate, or - both. filter by claim 1 wherein the transition metal compound is a transition metal halide, preferably a Group 11 and 12 transition metal halide, more preferably a Group 12 transition metal halide, and most preferably zinc chloride. Filter according to any one of the preceding claims, wherein the manganese compound is a manganese oxide or a manganese carbonate, preferably manganese dioxide. A filter according to any one of the preceding claims, wherein the indium compound is indium chloride. Filter according to any one of the preceding claims, wherein the fourth filter material is selected from one or more members of the group consisting of: Alkali metal perchlorates and/or alkaline earth metal perchlorates, preferably alkaline earth metal perchlorates and in particular calcium perchlorate. Filter according to one of the preceding claims, wherein the filter materials are designed as a loose bed. Filter according to any one of the preceding claims, wherein the first filter material and/or the second filter material and/or the third filter material and/or the fourth filter material are in the form of one or more layers. Filter according to one of the preceding claims, wherein the first filter material and/or the second filter material and optionally the third filter material and/or the fourth filter material are supported on at least one carrier material. filter by claim 8 , wherein the carrier material is a fleece material, preferably a glass fleece, wherein the fleece material is preferably impregnated and/or coated with at least one filter material, more preferably with at least two filter materials and in particular with all filter materials comprising the filter. Filter according to one of the preceding claims, wherein a separating layer is arranged at least between the first and the second filter material, preferably between all the filter materials comprising the filter. Filter according to one of the preceding claims, wherein the filter has at least one buffer substance. Filter according to one of the preceding claims, wherein the filter comprises at least one support disk and a housing. Filter according to one of the preceding claims, wherein the filter materials are arranged such that along the diffusion path of the sulfur-containing gas first the first and optionally the third filter material or the third and the first filter material and then the second and optionally the fourth filter material or the fourth and flows through the second filter material. Filter according to one of the preceding claims, wherein the filter comprises at least: - 5 to 95% by weight of the first filter material, preferably 10 to 90% by weight, more preferably 10 to 80% by weight and particularly preferably 15 to 75% by weight, and - 5 to 95% by weight of the second filter material, preferably 10 to 90% by weight, more preferably 10 to 80% by weight and particularly preferably 15 to 75% by weight, and - up to 70% by weight of the third filter material, and/or - Up to 30% by weight of the fourth filter material, in each case based on the total amount of the filter material, the total amount of the first and second and the third and/or fourth filter material being 100% by weight. Gas sensor for determining the concentration of an analyte gas, in particular hydrocyanic acid and/or thiophene or derivatives thereof, comprising a filter according to one of Claims 1 until 14 . Using a filter according to one of the Claims 1 until 14 for filtering gases containing sulfur, in particular hydrogen sulfide, preferably in a gas sensor claim 15 .

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