TECHNICAL FIELD

The invention relates to an alkaline electrolyzer used in the production of the green hydrogen.

The invention particularly relates to an alkaline electrolyzer separator membrane which is configured to provide the use of the environmentally friendly and long-lasting alkaline electrolyzer with low cost, high thermal resistance and low carbon emission in the hydrogen production by electrolysis from the renewable and non-renewable sources;

- which is provided with high mechanical strength, resistance to high alkaline medium and flexibility with the use of kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66), as well as which is obtained by applying the mixture/slurry respectively comprising PSU (Polysulfone), PVDF (Polyvinylidene Fluoride), PTrFE (polyvinylidene fluoridetrifluoroethylene), Aloe vera (aloe emodin, aloin/barbaloin, aloesin, emodin) as binders onto the base made of PPS (Polyphenylene sulfide) with an open mesh structure, high alkaline resistance, and woven or non-woven structure, polyester or any of the derivatives thereof, and which is used to produce the green hydrogen by electrolysis with low cost, high thermal resistance and low carbon emission and in an environmentally friendly and long-lasting way.

BACKGROUND OF THE INVENTION

As the fossil fuels and the climate change caused by them reach the sensible levels, the serious environmental problems have begun to be experienced in the world. The amount of the greenhouse gases that cause the climate change continues to increase day by day. In 2015, the studies were started to be performed to bring the global temperature increase in this century to the pre-industrial levels.

Many countries pledge to achieve the net zero carbon dioxide (CO2) emission by midcentury to limit the temperature increase to 1 .5‘C. Achieving full decarbonization will require the concerted and far-reaching actions across all economic sectors. It is estimated that 8.8% less CO2 was emitted in the first six months of 2020 compared to the same period in 2019 (Liu et aL, 2020). However, for sustained long-term reduction, the need for structural and transformational changes in global energy production and consumption and underlying socio-economic systems cannot be underestimated.

The energy transformation constitutes a major shift in electricity generation from fossil fuels to the renewable sources such as solar and wind. However, all sectors or industries cannot easily switch from the fossil fuels to the electricity. The sectors in which the electrification is difficult (which have difficulty in transition to decarbonization) include steel, cement and chemical industry, long-haul road transport, maritime transport, and aviation (IRENA, 2020b).

The green hydrogen also provides a link between the growing and sustainable renewable electricity generation and the sectors that have difficulty in electrification (IRENA, 2018). Hydrogen is a suitable energy carrier for the intermittent renewable energy systems such as solar and wind in line with the decarbonization targets. Hydrogen is also an important raw material for the production of ammonia which is used in the production of petrochemical and fertilizer. Approximately 95% of the hydrogen used globally is produced from natural gas and 5% from coal by electrolysis. Currently, the hydrogen production from renewable sources is limited, but the projects for green hydrogen production are increasing (IRENA, 2019).

The low costs and technological developments in variable renewable energy reduce the production costs of green hydrogen. Therefore, there is an increasing interest in green hydrogen obtained from the water electrolysis. By mid-2020, seven countries have adopted net zero greenhouse gas emissions targets in legislation, while another 15 countries have proposed similar legislation or policy documents. In total, more than 120 countries have announced net zero emissions targets (WEF, 2020).

It is aimed that the green hydrogen produced from the renewable electricity sources will become an important part of this transformation in the coming years. The production of green hydrogen is a very important field in the world, but the main problem is the need to reduce the cost. As long as the capacity factors are below 50%, the cost of hydrogen will be very high. The big opportunity in the green hydrogen production is how to reduce the cost of electrolysis technologies and make them competitive.

The green hydrogen production by electrolysis from renewable sources will become widespread in parallel with the increase in the renewable energy sources. This will make the electrolysis systems cheaper. Considering the strategic plans of the countries for the installation of the large-scale electrolyzers around the world, it is important to develop and expand this technology with the available resources. In particular, the alkaline electrolyzers are widely used due to the absence of the need for the noble metal catalysts and their known technology.

While the asbestos diaphragms were used in the alkaline electrolyzers in the past, today, due to the damages and prohibition of asbestos, the fibrous polymeric materials have been replaced and constitute the most expensive component in the electrolyzer. Therefore, there is a search for a separator membrane for the alkaline electrolyzers, which is affordable in terms of price performance and can be integrated into the sustainable production.

The object of the invention is to provide an alkaline electrolyzer separator membrane to be used in the production of green hydrogen by electrolysis from the renewable and nonrenewable sources.

The invention particularly relates to an alkaline electrolyzer separator membrane which is configured to provide the use of the environmentally friendly and long-lasting alkaline electrolyzer with low cost, high thermal resistance and low carbon emission in the green hydrogen production by electrolysis from the renewable and non-renewable sources;

- which is provided with high mechanical strength, resistance to high alkaline medium and flexibility with the use of kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66), as well as which is obtained by applying the mixture/slurry respectively comprising PSU (Polysulfone), PVDF (Polyvinylidene Fluoride), PTrFE (polyvinylidene fluoridetrifluoroethylene), Aloe vera (aloe emodin, aloin/barbaloin, aloesin, emodin) as binders onto the base made of PPS (Polyphenylene sulfide) with an open mesh structure, high alkaline resistance, and woven or non-woven structure, pPolyester or any of the derivatives thereof, and which is used to produce the green hydrogen by electrolysis with low cost, high thermal resistance and low carbon emission and in an environmentally friendly and long-lasting way.

SUMMARY OF THE INVENTION

The invention describes a mineral coated/f illed alkaline electrolyzer separator membrane used in the production of the green hydrogen by electrolysis by coating kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66) onto the polymer.

Although the kaolin clay is one of the mineral-rich underground resources, it contains more than one inorganic component. The kaolin clay comprises silicon and its oxides in different crystal structures, as well as many other inorganic agents such as alumina, zirconium, etc.

Here, the mineral oxides with different crystal structures are formed by burning mineral nitrates, etc. obtained by dissolving the kaolin clay in nitric acid, etc. at different rates. The contribution of the obtained mineral oxides with different crystal structures to the ionic conductivity in the separator membrane is investigated.

Resistance, porosity and wettability of the separator membrane in an alkaline medium are important for the ionic conductivity. PPS (Polyphenylene sulfide) and polyester fiber as separator membrane are covered with the mineral oxide filled slurry onto the underlay prepared in mesh, fabric or felt forms. Primarily, the alkaline medium resistance of PPS (Polyphenylene sulfide) is increased with the mineral oxides. In the alkaline electrolyzer, the coating is performed with the mineral oxide filled slurry to provide the ion conductivity, to prevent the passing of gas between the anode and cathode, and to provide the membrane with the mechanical strength. The porosity varies depending on the mineral structure. Another important parameter, wettability, is provided by the mineral oxides since there is an aqueous medium. The mineral oxide content contains a large amount of alumina, which distinguishes the invention from the existing separator membranes.

In the discovery of the invention, it is the object to develop an alkaline electrolyzer separator membrane, and the polymeric separator membranes made of PPS (Polyphenylene sulfide) and polyester filled with kaolin clay (alumina, zirconium, etc.) with different mineral content show higher ionic conductivity and better gas barrier properties compared to the existing separator membranes. In addition, one of the most important advantages of the resulting separator membrane is that it has a high thermal resistance and good mechanical properties, and is environmentally friendly.

DETAILED DESCRIPTION OF THE INVENTION

The invention describes an alkaline electrolyzer separator membrane which is used in the production of the green hydrogen by electrolysis and which is obtained by coating kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66) onto PPS (Polyphenylene sulfide) or polyester.

Kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66) are used in the alkaline electrolyzer separator membrane according to the invention. In addition, PSU (Polysulfone), PVDF (Polyvinylidene Fluoride), PTrFE (polyvinylidene fluoride-trifluoroethylene), Aloe vera (aloe emodin, aloin/barbaloin, aloesin, emodin) are used as binders respectively.

Preperation of the Alkaline Electrolyzer Separator Membrane

In the preparation of the alkaline electrolyzer separator membrane according to the invention, the usage percentages of the chemicals in the content and the solution composition are given in the table below. The chemical percentages and reaction medium conditions used in the preparation of the alkaline electrolyzer separator membrane according to the invention are given above. The alkaline electrolyzer separator membrane is prepared by three different methods. These are:

I. Method:

Firstly, kaolin/kaolinite clay and AI2O3 in the composition of mullite are ground with a 3- dimensional mechanical grinder until the particle size is 1 nm-500 pm. In the next stage, N-Methyl-2-Pyrrolidone and its derivatives as a solvent and PSU (Polysulfone) and its derivatives as a binder (or PVDF and its derivatives, Aloe vera and its derivatives) are added in certain proportions, and thoroughly homogenized together with the powder mixture with a vacuum mixer at minimum 500 rpm, maximum 2500 rpm. In the next stage, the resulting slurry is applied homogeneously onto PPS (Polyphenylene sulfide) or polyester (felt, mesh, fabric) with a thickness of 200-600 pm by means of a film coating device. The resulting separator membrane is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried in a vacuum oven at 0-60°C or in an oven at 30-120X3, is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried at 25°C under the room conditions, is dried at 25°C under the room conditions without being immersed in water,

- is dried in a vacuum oven at 0-60°C or in an oven at 30-120X without being immersed in water, leading to an alkaline electrolyzer separator membrane according to the invention.

II. Method:

Firstly, kaolin/kaolinite clay and AI2O3 in the composition of mullite are ground with a 3- dimensional mechanical grinder until the particle size is 1 nm-500 pm. In the next step, they are mixed with N-Methyl-2-Pyrrolidone and its derivatives as a solvent, containing 1 -50% of PSU (Polysulfone) and its derivatives (or PVDF and its derivatives, Aloe vera and its derivatives) in certain proportions until it becomes homogeneous. The ground clay is added to the homogeneous mixture at a rate of 5-97% and it is turned into a slurry. For the prepared slurry; kaolin/kaolinite clay or AI2O3 is homogenized thoroughly with a mechanical mixer at different speeds (50-2000 rpm) and at different temperatures (25-50°C), the slurry is homogenized thoroughly with a vacuum mixer at minimum 500 rpm, maximum 2500 rpm.

- The slurry is thoroughly homogenized in an ultrasonic bath at the frequencies of 35-53 kHz, at the temperatures of 25-60X3.

In the next stage, the resulting slurry is applied homogeneously onto PPS (Polyphenylene sulfide) or polyester (mesh, felt, fabric) in an amount of 200-600 pm by means of a film coating device. The resulting separator membrane

- is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried in a vacuum oven at 0-60°C or in an oven at 30 - 120X ,

- is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried at 25°C under the room conditions,

- is dried at 25°C under the room conditions without being immersed in water,

- is dried in a vacuum oven at 0- 60 or in an oven at 30-120X3 without being immersed in water, leading to a local alkaline electrolyzer separator membrane according to the invention.

III. Method:

Firstly, kaolin/kaolinite clay and AI2O3 in the composition of mullite are ground with a 3- dimensional mechanical grinder until the particle size is 1 nm-500 pm. In the next step, they are inserted into a reaction vessel with N-Methyl-2-Pyrrolidone and its derivatives as a solvent, containing 1 -50% of PSU (Polysulfone) and its derivatives (or PVDF and its derivatives, Aloe vera and its derivatives) in certain proportions and mixed in open/closed (Reflux etc.) system under nitrogen atmosphere/normal atmosphere at 25- 60°C until it becomes homogeneous. The ground clay is added to the homogeneous mixture at a rate of 5-97% and it is turned into a slurry. For the prepared slurry;

- kaolin clay and AI2O3 are homogenized thoroughly with a mechanical mixer at different speeds (50-2000 rpm) and at different temperatures (25-50°C), the slurry homogenized thoroughly with a vacuum mixer at minimum 500 rpm, maximum 2500 rpm,

- the slurry is thoroughly homogenized in an ultrasonic bath at the frequencies of 35-53 kHz, at the temperatures of 25-60 3.

In the next stage, the resulting slurry is applied homogeneously onto PPS (Polyphenylene sulfide) and polyester (mesh, felt, fabric) in an amount of 200-600 pm by means of a film coating device. The resulting separator membrane

- is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried in a vacuum oven at 0-60°C or in an oven at 30 - 120X ,

- is immersed in water, and is kept in water for 1 -60 minutes to remove N-Methyl- 2-Pyrrolidone from the separator membrane surface, and then is dried at 25°C under the room conditions,

- is dried at 25°C under the room conditions without being immersed in water,

- is dried in a vacuum oven at 0-60°C or in an oven at 30 - 120X3 without being immersed in water, leading to an alkaline electrolyzer separator membrane according to the invention.

The alkaline electrolyzer separator according to the invention has been produced with 3 different methods as stated above, and it can be produced with different methods in an alternative structure. The invention is based on the use of kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66) used in the content of the alkaline electrolyzer separator membrane according to the invention, as well as is based on obtaining said membrane by applying the mixture/slurry obtained by using respectively PSU (Polysulfone), PVDF (Polyvinylidene Fluoride), PTrFE (polyvinylidene fluoride-trifluoroethylene), Aloe vera (aloe emodin, aloin/barbaloin, aloesin, emodin) as binders onto the base of PPS (Polyphenylene sulfide) with an open mesh structure, high alkaline resistance, and woven or non-woven structure, Polyester or any of the derivatives thereof.

In use; in the alkaline electrolyzer, the coating is performed with the mineral oxide filled slurry to ensure the ion conductivity, to prevent gas passage between the anode and cathode, and to provide the membrane with the mechanical strength.

The base made of PPS (Polyphenylene sulfide) or polyester (felt, mesh, fabric) is coated with the mineral oxides to increase the resistance to high alkaline medium during the electrolyzer operation in the alkaline medium. The base coated with the specified mineral oxides has an open mesh structure, high alkaline resistance, woven or non-woven structure, and PPS (Polyphenylene sulfide), Polyester or any of the derivatives thereof can be used.

The porosity, which is an important parameter for the ionic conductivity, has been changed depending on the mineral structure used.

The membrane wettability is a mandatory property for the ionic conductivity. Since the alkaline electrolyzer works in an aqueous medium, the wettability is provided by the mineral oxides.

In the production of green hydrogen by electrolysis, the difference of the environmentally friendly and long-lasting alkaline electrolyzer separator membrane according to the invention with low cost, high thermal resistance and low carbon emission from the existing separator membranes is the kaolin/kaolinite clay and alumina (AI2O3) in the used composition of mullite aluminum silicate (AI2.34O4.83Sio.66).

In the alkaline electrolyzer separator membrane according to the invention, the wettability, another important parameter, is provided with the use of kaolin/kaolinite clay and alumina (AI2O3) in the composition of mullite aluminum silicate (AI2.34O4.83Sio.66); the alkaline electrolyzer separator membrane according to the invention is provided with high mechanical strength, resistance to high alkaline medium and flexibility with a large amount of alumina in the mineral oxide content.