DE2742370A1 - Coupled photochemical synthesis of hydrazine and hydrogen peroxide - by reacting nitrogen and water with sodium and sodium peroxide formed photochemically - Google Patents

Abstract

Synthetis is effected by (a) converting Na2O, dissolved in molten NaOH, to Na and Na2O2 by a photochemical reaction; (b) reacting the Na in part directly with the NaOH, forming H2 and Na2O, and in part with the H2 formed and with N2, forming NaNH2; (c) oxiding the NaNH2 with part of the Na2O2, forming N2H4 and Na2O, and hydrolysing part of the Na2O2 with H2O forming H2O2 and NaOH; and (d) recycling the soln. of Na2O in NaOH formed to stage (a). The process allows solar energy to be stored in the form of metastable chemical cpds., which can be used directly as fuels. They can be stored and transported easily as liquids (stabilised by mixing with water), can be used in normal technical systems without major modification and do not upset the ecological balance.

Description

Photochemical method for coupled synthesis

of hydrazine and hydrogen peroxide we go at the bottom considerations on the assumption that the liquid energy carrier petroleum in a few decades will no longer be available. Our goal is to improve our work on technical Photosynthesis to contribute to the development of a new technology that enables To store solar energy in fora metastatic chemical compounds. These connections should be used as an energy source to replace petroleum and its products as well as plant-produced oxygen. It is urgent, mostly such high-energy cheiischen compounds to produce, which are used as energy sources in conventional technical systems can be used without major modifications, which as Liquids are easy to store and transport and which do not affect have on the ecological balance. Vir see a more secondary condition than important to, nailich the requirement that these energy sources are as easy as possible in fuel cells without the detour via a theriodynaiischen cycle process in electrical The field on which a technical photosynthesis takes place should be able to convert energy for the use of solar energy is limited on two sides: the one borderline case is the even heated Daipf power plant to provide electrical power Energy for already known electrochemical synthesis processes the Energy carrier, the other borderline case is the plant. A closer look at the biological model shows the following: all plants - as far as we know today - initially produce the same internal energy carrier ATP (adenosine triphosphate) in the course of the lithium reaction ii chlorophyll, which is then used in subsequent reactions will produce plant-specific carbohydrates and oxygen.

In zoological organisms, too, ATP is the universal internal energy carrier, which is necessary for the maintenance of all life processes, but which is now formed using the energy of the carbohydrates and oxygen. As an energy carrier that is only effective internally, ATP does not appear in the gross equation Biol photosynthesis (1-) 6 C02 + 6 H20 C6Hl206 02 breathing It was our idea (as stated in P 24 05 134 of January 30, 1974) to take over this principle and, with an essential modification, to transfer it to technology in a greatly simplified manner: in the solar systems for technical photosynthesis, an energy carrier is produced that is directly can be used universally in technical systems (e.g. fuel cells or heat engines) and consists of two liquid components. These two components can be separated from one another, but transferred directly to the technical systems. (This is not possible in the case of the plants' ATP). We have proposed the two liquid metastable compounds hydrazine (N2H4) and hydrogen peroxide (H2O2) as components of the technical energy carrier. The easiest way to stabilize them is to add water, they can be mixed with water and react with each other when they come into contact; the stored energy is released in the process.

The common reaction products are water and nitrogen. which both belong to the natural components of the atmosphere and are in turn starting materials for technical photosynthesis. The gross equation is: Techn. Photosynthesis (lb) N2 C H20 N2114 + 211202 combustion No biologically formed oxygen in the air is required for combustion. In fuel cells, hydrazine is able to release 4 electrons during the anode reaction: The two components, which we have chosen for technical reasons, show a striking similarity in their chemical structure: both hydrazine and hydrogen peroxide consist of two identical groups; Hydrazine is made up of two amide groups, (NH2) 2 = N2H4, hydrogen peroxide consists of two OH groups, (OH) 2 = H2O2. from alkali hydroxides. The amides of the alkali series are salt-like compounds. They mainly consist of alkali cations and amide anions (have ion lattices analogous to NaOH). Two negatively charged NH2 groups become radicals after they have given up their electrons and couple with the release of energy to form the hydrazine molecule: (hG is the free enthalpy of reaction). We were guided by the ideas that had already been developed around the turn of the century for the formation of hydrogen peroxide through the electrolysis of aqueous potassium hydroxide solutions. Two negatively charged OH ions are discharged at the anode; the resulting radicals couple to hydrogen peroxide: In both cases, however, the difficulty has to be overcome - which has not yet been achieved satisfactorily - to protect the newly formed hydrazine or hydrogen peroxide molecules from disintegrating on the electrodes or from reacting with the starting materials. Sodium oxide reacts violently with hydrazine to form sodium hydrazide and ammonia; our experiments indicate that it is also catalytically active in the conversion of hydrazine into ammonia. (Nevertheless, this route is possible; if calcium amide is chosen instead of sodium amide and it is dissolved in formamide, then hydrazine is obtained electrolytically in much greater yield.) We have in one. next step (see P 26 54 514 vol 29.11.76) the two reaction sequences (3) and (4) are carried out with sodium peroxide (Na2O2) as a common electron acceptor: The associated electron donor is metallic sodium (Na): The donor-acceptor pair is generated electrolytically from a sodium oxide melt in the reverse reaction to (5a) and (Sb): As known from the historical process for the production of hydrogen peroxide, sodium peroxide is able to split every two water molecules in the course of hydrolysis: The resulting sodium hydroxide (NaOH) serves as a carrier for hydrogen, which is released in the melt by metallic sodium in a weakly endergonic reaction: The hydrogen is bound with the nitrogen from the air to form the azide group (NH) z, with the sodium providing an electron for stabilization (in the form of the negative amide ion): The oxidation according to Eq. (3) to hydrazine is carried out with Na2O2.

What is important here is the function of brackets, which is sodium peroxide, (NaO) 2 = Na2O2, which is composed of two NaO radicals. Has. It enables two neighboring NH2 ions to be coupled to hydrazine by releasing their two electrons. The reaction formed from (3) and (5) is thus The actual electron acceptor is the NaO radical. Experiments we laughed about with the oxidation of sodium amide melts with oxygen confirm this idea. The oxygen was attached to metallic sodium in the melt, with hydrazine directly being formed. The problem here is the possibility that hydrazine reacts with excess oxygen, which is noticeable in the form of deflagration.

The consideration of the NaO radical is described for the following photochemical process of importance Originally we saw no other way than to use solar energy via control room and further via electrical energy to go and electrolytically generate the electron donor acceptor pair. Included was not thought of the borderline case of the solar power plant, and the electrical one Provide energy, but to a solar-heated magnetohydrodynamic (MHD) -Systei (P 24 oS 134 from 01/30/74). This energy converter, which is also a Alkali metal used, namely as thermodynamic and magnetohydrodynamic Working equipment, can convert heat into electrical heat without going through the turbine and generator To convert energy.

From today's point of view, it is much more advantageous to follow the direct photographic path. By this we mean that the energy input into the alkali oxide-alkali amide system is not carried out by electrical energy, but directly by light energy. The best-known example of an application is the alkali oxide photocell, preferably with potassium as the alkali metal. The radiation required to release electrons in photocathodes as a function of the wavelength # is known for alkali metals. The measurements of the photocurrent in FIG. 1 relate to an arrangement, typical of a photocathode, of carrier metal (Ag) for the alkali oxide layer, of the oxide layer and the alkali metal layer in the state at ambient temperature. Curve 1 relates to Na, 2 to potassium, 3 to Rb and 4 to Cs. Curve 5 is the spectrum of solar radiation at sea level. In our case, however, according to the invention, we do not work with solids (at ambient temperature) but with alkali melts (in a much higher temperature range) which also contain oxide. We will replace the electrolytic reaction (5c) described in an earlier application (P 26 54 S14 of 11/29/76) for generating the donor-acceptor pair with the following light reaction with sodium: The spectral ranges shown in FIG. 1 for the sensitivity of photocathodes with various alkali metals and oxides represent upper limit values for our processes, since no free electrons are required here and the ranges are shifted to the region of longer wavelengths because of the recovered temperatures of the melts. This is a very important fact. The free enthalpy of reaction (lo) decreases with increasing temperature, it is zero in the temperature range around 2300 C.

The higher the temperature, the lower the required Quantum energy. In this way (within the limits set by practice) the reaction (lo) in an optimal range of the spectrum of solar radiation also drain with the cheap alkali metals K and Na; on the other hand will The IR region of the spectrum is used by the fact that this radiation is in the form of heat used to form the melt and to achieve the desired temperature level will.

Less well known are lithium compounds such as lithium hydride (LiH) and imide (LiNH), in which the hydrogen is split off by incident light or exchanges place with lithium. We will also make use of the following reaction with lithium, in which lithium nitride and lithium amide are formed: Example 1 for a technical photosynthesis system Sodium oxide is introduced into molten NaOH. If this melt is irradiated with visible light hv, sodium oxide is first split into sodium and NaO radicals; In a secondary reaction, two NaO radicals combine to form one molecule of sodium peroxide (1.1) °). The metallic sodium reacts with sodium hydroxide, releasing hydrogen to form sodium oxide (1.2). One can think of using this hydrogen in statu nascendi (before it combines to form molecules and escapes from the melt) in order to mix it with nitrogen Add sodium atoms in the form of sodium amide (1.3). It is to be expected that the melt will have a retarding effect on the recombination speed. The figures in round brackets stand for the correspondingly numbered reaction equations to which reference is made in the text.

atomic to molecular hydrogen. In the case of the direct sodium aside production indicated here, hydrazine formation is now achieved in a tertiary subsequent reaction by the pure oxidation of two sodium amide molecules each by a sodium peroxide (1.4). If it is possible to produce sodium amide stoichiometrically in accordance with the reaction equations, then the risk of hydrazide formation is considerably reduced compared with the previously mentioned processes. Each newly formed aeid molecule is processed further directly to hydrazine, so that there are no excess amide molecules available for the subsequent reaction with hydrazine. In this process, which does not provide for direct photochemical hydrolysis, the splitting of water is pre-established by sodium peroxide (1.5). This produces hydrogen peroxide and sodium hydroxide, which serves as a carrier of hydrogen for the formation according to (1.2) and (1.3) - in addition to its function as a solvent for sodium oxide at a relatively low temperature. 6hu (1.1) 6 Na20 6hv b 3 (Nau) + 6 Na enstpr. (Lo) 2 (1.2) 4 NaOH * 4 Na to 4 Na, + 4 H (7) (1.3) 4 H + N2 * 2 Na - b 2 Na (NH2) (8) (1.4) 2 Na (NH2) + (NaO) 2, 2 Na, O + (NH?), (9) (1.5) 4 H20 + 2 (NaO) 2 ----- 4 NaOH + 2 (OH) 2 (6) Total 4 H20 + N2 6hu (NH2) 2 + 2 (OH) 2 (lbs Example 2 for a technical photosynthesis system In Example 1 just described, the entire photochemical process is based on the alkali metal sodium, which serves as a base material in conjunction with potassium or as a substitute for potassium. As elegant as it seems to attempt the synthesis of the two components of the energy carriers in a single photosystem, the difficulty lies in the fact that several reactions have to be coordinated with one another based on sodium (potassium) in a second photosystem based on lithium. The starting point is lithium imide, which, when irradiated with light quanta hv, changes into lithium nitride and lithium amide due to a partial change of position between lithium and hydrogen within the lithium imide (2.7). Lithium amide can easily be broken down thermally into ammonia and lithium imide (2.6).

Ammonia is now the compound that is gaseous from the second photosystem escapes and the desired NH2 group is transported into the first photosystem. There the ammonia can either come from metallic sodium or (as in our example) be absorbed by sodium oxide (2.3), in the latter case sodium amide is formed; the excess hydrogen atom becomes sodium hydroxide in the form of our hydrogen carrier bound. (The process then continues as in Example 1). Lithium nitride that is apart from (2.7) also forms (2.8) directly from lithium and nitrogen, becomes in the present process reacted with hydrogen to lithium amide (2.9).

The lithium released in the process can in turn absorb nitrogen according to (2.8) in a next step. It is the ability of the lithium atom to easily split and store molecular nitrogen that makes the route via ammonia attractive; In our experience, sodium is hardly able to form nitride quickly, which is ultimately the reason for the slow formation of sodium amide from the elements. 6hv (2.1) 6 pa 0 --3 (NaO) 2 + 6 Na ntapr (lo) 2 2 (2.2) 6 NaOH * 6 Na ~ 6 Na20 + 3 H2 ff (7) (2.3) ,, 2 N113 * 2 Na20 ------ * 2 NaOH * 2 Na (2.6) 1 2 NaNH2 * (NaO) 2 -2 NoaO * 2 Na20Na20 22 (9) (2.3) 1 4 H20 + 2 (NaO) 2 4 N-OH * 2 (OH) 2 (6) 2 2 I. (2.6) 6 LINH j i2 Li2N11 T 2 NH3 (2.7) 2 Li2N11> Li N LiNH2 1 (11) 3 (2.8) 6 Li * 2 ~ v2 Li 3N (2.9> 6 112 + 3 Li3 (2.9) Li H, 3 LiN112 ¼ Total 4 11 ° + N2 6hv + 2hv (NH2) 2 + 2 (OH) 2 (lb) 2 i (N1122 2

Claims (3)

"Photochemical Decay in the Coupled Synthesis of Hydrazine and hydrogen peroxide Hydrazine and hydrogen peroxide from nitrogen and water, characterized in that sodium dioxide dissolved in molten sodium hydroxide, in a light reaction is converted into sodium and sodium peroxide, some of which the sodium is directly with the sodium hydroxide with the release of hydrogen to sodium oxide in part reacts with the hydrogen formed in this way and with nitrogen to form sodium amide, and of which the sodium peroxide partially oxidizes the sodium amides to hydrazine and sodium oxide, partly for the hydrolytic cleavage of water to hydrogen peroxide and sodium hydroxide is consumed, which is produced in these reactions Sodium oxide dissolved in the likewise formed sodium hydroxide in turn Light reaction is supplied. 2. The method according to claim 1, characterized in that potassium takes the place of sodium. 3. Process according to Claims 1 and 2, characterized in that the formation of sodium amide is carried out with the help of a second photosystem, by removing ammonia in the second photosystem from nitrogen and from that in the first photosystem hydrogen formed as a result of the reaction of light with sodium oxide is formed, and adding this ammonia to the first Photosystem broadcast there reacted with sodium oxide to form amide and sodium hydroxide is, whereby the ammonia formation in the second photosystem by the addition of the dem first photosystem originating hydrogen on lithium nitride with the formation of Lithium and lithium amide is going on, the lithium of which is used to form nitrogen of lithium nitride, and of which the lithium amide by thermal cleavage is decomposed into ammonia and lithium imide, and eventually the lithium imide is converted back into lithium nitride and lithium amide by a reaction of light.