WO2011116788A1

WO2011116788A1 - Layered titanates

Info

Publication number: WO2011116788A1
Application number: PCT/EP2010/001864
Authority: WO
Inventors: Sergey Britvin; Sergey Krivovichev; Oleg Sidra; Andrey Zolotarev; Vladislav Gurzhiy; Daria Spiridonova; Wulf Depmeier
Original assignee: Saint Petersburg State University; Christiab-Albrechts Universität Zu Kiel
Priority date: 2010-03-25
Filing date: 2010-03-25
Publication date: 2011-09-29
Also published as: RU2564339C2; WO2011116788A8; EP2550238A1; RU2012141707A

Abstract

Layered titanate with the chemical formula KN₂H₄.mA_1-2O.(Ti_1-qM_q)(O_2-wOH_xF_y)2-z.nH₂O wherein k,m,q,w,x,y and z are coefficients ranging from 0.01 to 0.5; n is an integer, wherein 0 ≤ n ≤ 5; A is at least one cation having a valence of 1 to 3; M is at least one metall having a valence of 1 to 7; comprising chemically bound anion-free hydrazine intercalated in the interlayer space of the titanate layers.

Description

LAYERED TITANATES

The invention relates to a new family of layered titanates, a method for producing these titanates, and using these new titanates for extraction of noble metals (Au, Rh, Pd, Ir, Pt, Ag) from solutions and as precursors for the preparation of Ti0₂-based nano-materials, including Ti0₂/Se nano-composites for mercury vapour scavenging and doped Ti0₂ nano-materials.

BACKGROUND OF THE INVENTION

Micro- and nanocristalline layered titanates have attracted considerable interest in industry due to specific chemical and physical properties. Principal building blocks of their crystal structures are layers (slabs) composed of [Mi_-x(0_1-yOH_y)6] octahedra. The octahedrally coordinated cation M is preferably titanium, with possible subordinate substitutions by other cations. The layers possess negative charge which is compensated by intercalation of different cations into the interlayer space. Intercalated cations could be protons (H⁺), hydronium (¾0⁺), ammonium (NH ⁺) or other cations of uni- or divalent metals. Due to the similarity of their crystal structures, layered titanates have similar X-ray powder diffraction patterns characterized by the presence of a principal reflection at d = 9.5 ± 1.5 A (0.95 ± 1.5 nm) corresponding to the interlayer spacing. Variations of c/-value are dependent on the diameter of the intercalated cation and the hydration stage of the interlayer. In general, layered titanates are used as precursors for the production of nanocristalline Ti0₂ polymorphs: anatase, rutile and Ti0₂(B). Recently, a new, orthorhombic, polymorph of Ti0₂ was reported and claimed by patent EP 1748033. This polymorph, Ti0₂(JT), can only be synthesized starting from layered titanates. Besides their use as Ti0₂ precursors, layered titanates have their own technical usages. Layered titanates of Li, Mg and K are patented as heat-resistant friction materials (EP1440940, EP1081206, EP1329421, US7307047, US7078009, EP1170257). Patent EP1419994 claims the method for producing lamellar titanic acid (i.e. protonated layered titanate) and lamellar titanium dioxide by acid treatment of layered titanates. Lamellar titanic acid and lamellar titanium dioxide can be used as fillers for paints and resins, cosmetic materials, pigments and catalysts, cation exchange materials. Patent US6838160 discloses a method for producing ultrathin coating films composed of titanium dioxide obtained from layered titanates. The produced coating is an effective filter absorbing ultraviolet radiation. Patent WO2006033069 discloses energy storage devices, hydrogen storage devices and lithium-ion pseudo-capacitive devices based on the Ti0₂(B) polymorph produced from layered titanates. Protonated layered titanates are disclosed in patents JP1966650, JP 1936988 and JP2671949. Patent US6908598 claims layered sodium titanate as selective ⁸²Sr sorbent.

Recovery of noble metals from different types of industrial solutions and waste-waters has a long history. Hydrazine itself is an excellent reductant which can be used for recovery of noble metals. Hydrazine or its salts, in case of direct reduction of noble metals from solutions, possess the following disadvantages: high over dosage of hydrazine needed for complete reduction; high level of environmental pollution; low recovery of metals from diluted solutions, due to formation of non-precipitated colloidal solutions of noble metals. Mercury vapour pollution is a well known environmental problem. Most of mercury is released in the atmosphere with industrial combustion gases, especially with coal combustion gases, the estimated amount of mercury pollution is ~48 metric tons per year (Johnson et al. 2008). According to recent decisions of EU, strict regulations in mercury release should be applied (Commission of the European Communities: "Community Strategy Concerning Mercury", Brussels, 28.01.2005 COM(2005) 20 final). A series of industrial mercury vapour scavengers are claimed in several inventions: US20060198774, US20060198775, US20060198776, US20060198777, US20070092419, US20080254979, US20080274877, US20080279739, US20080295689, US20080300132, US20080305949. It has been shown that selenium is an excellent sorbent for mercury vapours. Disadvantage of using pure nano- and microcrystalline selenium as industrial Hg scavenger is its instability to oxidation at high temperature in atmospheric conditions. Yet another and markedly growing source of mercury pollution is compact fluorescent lamps (CFL). It is known that pure selenium is a highly toxic substance which raises problems with its long-time storage under household conditions. Thus stable selenium-bearing composite sorbents would be highly appreciated for the above mentioned applications.

Hydrazine, H₂N-NH₂, and its derivatives have an extremely wide field for technical usages. This is derived from the specific chemical properties of hydrazine: strong reductive properties;

presence of =N-N= bond;

presence of amine function -N¾ considerably more active than the amine function of aliphatic and aromatic amines;

- easy catalytic decomposition of hydrazine followed by formation of nitrogen, hydrogen and/or ammonia;

easy formation of azides by reaction of hydrazine and nitrites;

Hydrazine is used for the synthesis of various organic compounds and a wide variety of other industrial applications is also related to hydrazine and its derivatives.

Direct hydrazine fuel cells (DHFC) are known as effective source of electrical power [Asazawa, K., Yamada, K., Tanaka, H., Oka, A., Taniguchi, M., Kobayashi, T. (2007) A Platinum-Free Zero-Carbon-Emission Easy Fuelling Direct Hydrazine Fuel Cell for Vehicles. Angew. Chem. 119, 8170-8173]. Recently, a new group of resin-based composites is claimed as intermediates for hydrazine storage (patent WO08007650), which are, in turn, used as hydrazine sources in a new generation of fuel cells [WO03056649, WO06095840, WO08007651, WO09034913].

A great disadvantage in using hydrazine is the problem that hydrazine is highly toxic and dangerously unstable, especially in the anhydrous form. According to the U.S. Environmental Protection Agency: Symptoms of acute (short-term) exposure to high levels of hydrazine may include irritation of the eyes, nose, and throat, dizziness, headache, nausea, pulmonary edema, seizures, coma in humans. Acute exposure can also damage the liver, kidneys, and central nervous system. The liquid is corrosive. Limit tests for hydrazine in pharmaceuticals suggest that it should be in the low ppm range. On February 21 , 2008, the United States government destroyed the disabled spy satellite USA 193 with a sea-launched missile, purportedly due to the potential danger of a hydrazine release if it re-entered the Earth's atmosphere intact.

Ti0₂-based nano-materials, including Ti0₂-based catalysts and photocatalysts, is a markedly growing family of materials which can be used in different fields of chemical industry. The influence of dopant elements on catalytic and photocatalytic activity of titania is presently extensively studied (X. Chen and S.S. Mao: Titanium Dioxide Nano-materials: Synthesis, Properties, Modifications and Applicatioins. Chem. Rev. 2007, v. 107, p. 2891-2959). It is shown in the present invention that layered hydrazine titanates can be used as effective precursors for the preparation of Ti0₂-based nano-materials.

The objective of the invention is thus to provide new titanate-based compounds which can be used as solid state source_for chemically bound hydrazine. They can be used in industrial applications similar to pure hydrazine but with the great advantage of having much higher stability. It is another objective of the invention to provide improved materials for the extraction of noble metals from waste solutions. It is another objective of the invention is to provide improved Ti0₂/Se nano-composite materials for effective mercury vapour scavenging. It is another objective of the invention to provide improved precursors for the preparation of Ti0₂-based nano-materials.

The solutions for the above-mentioned technical problems are achieved by the embodiments characterized in this claim.

SHORT DESCRIPTION OF THE FIGURES

Fig. 1 shows the typical morphology of LHT-9 particles in HRTEM images.

Fig. 2 shows typical XRD patterns of LHT-9 recorded on (1) a conventional scanning diffractometer (Bragg-Brentano geometry) and (2) a image- plate diffractometer (transmission geometry).

Fig. 3 shows the IR spectra of typical LHT-9 and pure hydrazine hydrate.

Fig. 4 shows TG and Gram-Schmidt curves of typical sample of LHT-9.

Fig. 5 shows FTIR spectra of gases evolved by thermal decomposition of

LHT-9 in Pt crucible.

Fig. 6 shows Ti0₂-Se nano-composite obtained from LHT-9 (Example 6).

High-resolution energy-filtered TEM image (HR EFTEM) and energy- filtered element distribution maps for Ti and Se.

Fig. 7 shows X-ray powder patterns (CuKa) of Ti0₂/Se/HgSe composites obtained by treatment of Ti0₂-Se nano-composite in Hg vapour

(Example 7). DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to a family of hydrazine titanates (hydrazinium titanates) with layered crystal structure, the members of which being conjointly designated LHT-9 hereinafter (Layered Hydrazinium Titanate - 9A). LHT-9 combine the following properties:

1) Layered titanate structure;

2) Nanometer-sized particles;

3) Chemically bound anion-free hydrazine. LHT-9 contain chemically bound hydrazine (hydrazinium ion) intercalated into the interlayer space of the layered titanate. The chemical composition of LHT-9 can be identified in terms of mole ratios of constituents as follows:

A:N₂H4-wA₁.₂0-(Tii_-qM_q)(0_2-H,OH_iF ,)_2-z'«H₂0

In the present formula, k,m,q,w,x,y,z are coefficients ranging from 0.01 to 0.5; 0<«<5. Cation A is at least one cation of valence 1 to 3, preferably from the group: H, Li, Na, K, Rb, Cs, Tl, /?4 (ammonium or its organic derivatives), NR₃Oi? (hydroxylammonium or its organic derivatives), N₂.#₄ (hydrazinium or its organic derivatives), H₃0 (hydronium), Ag, Au, Mg, n, Fe, Co, Ni, Cu, Zn, Cd, Hg, Hg, Sn, Pb, Ca, Sr, Ba. A may also represent any organic or elementoorganic cation. Metal M is at least one element having valence 1 to 7 substituting for titanium, preferably from the group: Li, Mg, Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Sn, Sb, Hf, Ta, W, Ru, Rh, Pd, Os, Ir, Pt. Hydrazine (as molecular hydrazine - N₂H_t, or hydrazinium ions - (N₂H₅)⁺, (N₂H₆)²⁺), titanium and oxygen are essential constituents of the LHT-9 composition.

LHT-9 contains 1-15 wt.%, preferably 6-10 wt.% of hydrazine, and the Ti0₂ content ranges from 50-95 wt.%, preferably 85-95 wt.%. Fig. 1 (a,b) shows the typical platy habit of LHT-9 leaflets. LHT-9 has particle size in between 5 and 500 nm, depending on thermal and chemical conditions of the synthesis. In case of the platy particles shown in Figs. 1 a,b, typical width of the leaflets is 30-100 nm and the typical thickness is 3-20 nm. LHT-9 may have platy, lamellar (nano-plates, nano-sheets, nano-lamella, nano-flakes), tubular (nano-tubes, nano-scrolls), fibrous (nano-rods, nano- needles, nano-whiskers) or isometric morphology. The habit of LHT-9 particles depends on the thermal and chemical conditions of their synthesis.

X-ray powder diffraction patterns of LHT-9 are characterized by the presence of a significant reflection at d = 9.5 ± 1.5 A corresponding to the interlayer spacing of LHT-9. (Table 1, Fig. 2). The relative intensities of the X-ray reflections may change to a certain degree with changing morphology of the LHT-9 particles.

Table 1

Main XRD reflections of LHT-9

d, A I Io*

9.5±1.5 vs-s

3.5±0.2 M

3.2±0.2 S

2.3±0.2 M

1.9±0.1 M

* VS - very strong reflection, S - strong, M - medium

The infrared absorption spectrum of LHT-9 (Fig. 3 a,b) contains strong bands at 470±20, 670±20 and 900±20 cm^'1 assigned to stretching vibrations of Ti-0 bonds in the (Ti0₆) octahedra. Characteristic vibrations of hydrazinium appear at 955±20 (stretching ( N-N)), 1100±20 cm^"1 (wagging -NH₃ ⁺), 1415±20 and 1520±20 cm^"1 (scissor H-N-H). The band at 1620±20 cm^"1 is assigned both to scissor H-N-H vibrations in hydrazine and scissor H-O-H vibrations in molecular water. Note the substantial differences between the IR-spectra of LHT-9 and of pure hydrazine hydrate (Fig. 3 a,b), namely the absence of twist H-N-H vibrations (1280 and 1340) in the spectrum of LHT-9; the absence of the scissor vibration H- N-H (1415 and 1520) in the spectrum of hydrazine hydrate; significant difference in the frequencies of stretching (N-N) modes around ~ 1000 cm^"1. This clearly indicates that Hydrazine is chemically bound to the titanate and that there is no free hydrazine in LHT-9

The thermal decomposition of LHT-9 (Pt crucible, Ar flow) was studied by means of thermogravimetry and evolved gas FTIR spectroscopy (Fig. 4 and 5). There are two steps of gases evolution. The first step occurs between 40 and 150 °C and corresponds to dehydration of LHT-9. The second step between 180 and 225 °C corresponds to evolution of gaseous hydrazine and its thermal decomposition into NH₃ and N₂.

The method for the preparation of LHT-9 disclosed in the present invention comprises mixing, in any sequence, of solutions having the following general composition:

Solution A

The solution contains water and the following essential constituents:

a. Any compound of titanium or titanyl (TiO)²⁺ as source of titanium, preferably halogenides T1X4 (X=F,Cl,Br,I); titanyl salts TiOX_2/n (X is any anion of valence n); salts or complexes of trivalent titanium Ti³⁺; halogenotitanic acids and their salts A_2/mTi[Xi._n(OH)_n]₆ (A is any cation of valence m, X=F,Cl,Br,I, 0<w<l); any complex compounds of titanium; any titanoorganic compounds, preferably aryloxides or alkoxides of titanium Ti(OR)4_-nX_n, where R is any organic or metalloorganic radical, preferably methyl (CH₃), ethyl (C2H5), propyl isomers (C₃H₇), butyl isomers (C₄H9), X=F,Cl,Br,I. Concentration of titanium in solution A is varying in between 0.01 and 6 mole per liter, preferably 0.1-1 mole per liter. b. Any ion forming stable complex ions with titanium, preferably from the group: fluoride ion in form of any compound, preferably as HF (hydrofluoric acid); fluorides Aⁿ⁺F„ (A is any cation of valence n); hexafluorotitanic acid H₂TiF₆; hexahalogenotitanates A_2/mTi(Fi_-nX_n)₆ (A - any cation of valence m, X=F,Cl,Br,I,OH, 0<«<1); hydrofluorides Aⁿ⁺F_n /«HF (A is any cation of valence n, 0</M<4); oxycarboxylic acids or their salts, preferably oxalic, citric, malic, tartaric, tartronic acid or their salts. Concentration of complexing ion in solution A is varying in between 0.01 and 30 mole per liter, preferably 0.1-1 mole per liter. Mole ratio of complexing ion to titanium in solution A ranges between 0.1 and 100, preferably 0.5-10. Complexing ion is an essential modifying constituent in the synthesis of LHT-9. Synthesis without complexing ion yields either amorphous titanium hydroxide or the anatase polymorph of titanium dioxide as it is disclosed in patent WO2005/051847. Solution B

Hydrazine (>½¾), hydrazine hydrate (N₂H4-H₂0) or an aqueous solution containing hydrazine or salts of hydrazine in any soluble form. The hydrazine concentration in solution B varies in between 0.1 and 30.5 mole per liter, preferably 1-15 mole per liter. Solution B is alkaline (pH>7). The necessary level of alkalinity is achieved by the presence of free hydrazine or by adding of any alkali, preferably of aqueous solution of NaOH, OH or NH₃.

Solutions A and B are mixed together in any sequence under following required conditions: - the resultant reaction mixture should have alkaline reaction (pH>7);

- reaction temperature ranging between -10 and 130°C, preferably at room temperature;

- in an atmosphere of any gas, preferably in air;

- under vacuum or gas pressure of 0-100 bar, preferably under atmospheric pressure. The resultant reaction mixture is thermally treated by one of the following methods:

Method A. Reaction mixture is heated to boiling temperature followed by boiling for between

0.1 minutes and 30 days, preferably 10-30 minutes. Method B. Reaction mixture is placed into an autoclave and treated under hydrothermal conditions (1 10-300°C) for between 1 minute and 30 days, preferably 2-24 hours.

Post-reaction thermal treatment (boiling or hydrothermal treatment) of the resultant mixture is the essential required condition for synthesis of LHT-9, otherwise the synthesis results in formation of either amorphous titanium hydroxide or in the anatase polymorph of titanium dioxide, as disclosed in patent WO2005051847.

LHT-9 can be used for many technical purposes including:

1. Carrier substances (chemical containers) containing chemically bound hydrazine and thus allowing to retrieve hydrazine and its compounds, including as possible sources of hydrazine for direct hydrazine fuel cells;

2. Matrices for carrying out inorganic, organic and bioorganic syntheses. Chemically bound hydrazine is used as active constituent;

3. Ion-exchange materials;

4. Reductive sorbents for recovery of noble metals (Rh, Pd, Pt, Au, Ir, Ag) from different industrial solutions;

5. Reductants for reduction of U, Pu, Np and Tc in spent nuclear fuel;

6. Precursors for synthesis of other nanocristalline titanates; 7. Catalysts, including photocatalysts, and precursors for producing catalysts and photocatalysts;

8. Precursors for preparation of titanium dioxide, including doped titanium dioxide;

9. Precursors for preparation of friction materials based on layered titanates.

10. Precursors for preparation of composite nano-materials, including Ti0₂-Se nano- composites for Hg vapour scavenging.

The applications above are listed as typical examples. However, the present invention is not limited to above mentioned examples; layered hydrazine titanates may also be used in other industrial or scientific applications.

As it has been noted above, LHT-9 may be used in a wide range of industrial applications. Below is an application of LHT-9 for effective recovery of noble metals (Au, Rh, Pd, Ir, Pt, Ag) from solutions. A model solution was used containing all above listed metals in concentration of 50 ppm of each metal. It was prepared by dissolution of appropriate amounts of the salts (KAuCl₄, (NH₄)₃RhCl₆, Na₂PdCl₄, K₂IrCl₆, K₂PtCl₆) in 1 litre of distilled water. The model solution of silver has been prepared separately from AgN0₃ dissolved in water. 20 mL of solution of platinum group metals, and separately 20 mL of solution of AgN0₃ were mixed each with 100 mg of air-dried LHT-9, and the suspensions were left for 12 hours under occasional shaking. After that, aliquots (10 mL) of clear depleted solutions have been taken for subsequent metal determination. The concentrations of noble metals in initial and depleted supernatant solutions were determined by means of inductive-coupled plasma spectrometry (ICP). Effectiveness of recovery of each metal was then determined by calculation of distribution coefficients Kj, mL/g), according to standard formula:

K, c.

in which:

C, - initial concentration of metal in supernatant (g/mL);

Cf - residual concentration of metal in depleted supernatant (g/mL);

V- volume of initial solution (mL);

m - mass of sorbent (g) The K_d values for individual metals are listed in Table 2.

Table 2.

Initial concentrations (C„ ppm), residual concentrations (C/, ppm) and distribution coefficients (K_d, mL/g) for noble metals recovered on LHT-9 sorbent

It can be seen that LHT-9 provides nearly full recovery of noble metals from the solution. The by-products of recovery process are diluted (<0.01%) solution of hydrochloric acid and gaseous nitrogen. The maximum noble metal loading of LHT-9 sorbent depends on different factors, such as valence of the noble metal in the solution, type of the anion or complex of metal, and varies in between 5 and 35 mg of noble metal per 100 mg of air-dry sorbent.

Subsequent processing of the metal-loaded sorbent may include, as an example, the following stages:

1. Removal of excess water (filtering, centrifugation or decantation);

2. In case of high metal loading, sorbent may be directly remelted for precious metals;

3. In case of low metal loading, the loaded sorbent is dissolved in hydrofluoric acid (HF) or in solution of alkali metal or ammonium hydrofluoride (NaF-nHF, KF-nHF, NH F «HF. The residual precipitate of precious metals is separated by any appropriate method (filtering, centrifugation or decantation) or directly dried by evaporation.

4. Residual solution, containing hexafluorotitanic acid H₂TiF , may be used for recycling of LHT-9 sorbent. Yet another embodiment of LHT-9 is its usage as effective reducing agent for selenium allowing preparation of Ti0₂-selenium nano-composite materials, by reduction of selenium from solutions containing Se⁴⁺, Se⁶⁺ in any soluble form. The following example illustrates the preparation of a Ti0₂-Se nano-composite. A batch of LHT-9 is immersed into a solution containing selenite anion (Se0₃)2^" or (HSe0₃)^" in any form. A direct reduction of selenium is observed yielding nano-composite containing hydrated titanium dioxide and red selenium. Reaction schemes (just for illustration, not for quantitative calculation) may be represented as:

N₂H₆ ²⁺ + Se0₃ ^2"→ Sej + N₂† + 3H₂0

N₂H₅ ⁺ + Se0₃ ^2"→ Se| + N₂† + OH^" + 2H₂0

Ν₂Η₆Τΐ₄θ₉ + H₂Se0₃→ Se| + 4Ti0₂j + N₂† + 4H₂0

Ti0₂-Se nano-composites formed from LHT-9 and H₂Se0₃ can be used as effective scavengers for mercury vapour, irreversibly absorbing up to ~13 wt. % of Hg during 10 hours exposure under hot air conditions, simulating industrial combustion gases. The resulting product, Ti0₂/Se/HgSe composite, may be used as raw material for recycling of mercury.

Yet another embodiment of LHT-9 is its usage as a convenient precursor for the preparation of metal-doped Ti0₂ nano-materials which can be exploited as possible catalysts and/or photocatalysts.

Materials and methods

The present invention is illustrated below by way of typical examples. However, the present invention is not limited to concentrations, compositions and synthesis conditions described in the examples.

Example 1. Preparation of LHT-9

Solution A - 100 mL of 0.3 aqueous solution of hexafluorotitanic acid, H₂TiF₆. Preparation: 2.4 g (0.03 mole) of commercial titanium dioxide is dissolved at room temperature in 10 mL of 40% hydrofluoric acid HF. The volume of solution is adjusted to 100 mL by adding water.

Solution B - 100 mL of 6.7M aqueous hydrazine solution. Preparation: 33 mL (0.67 mole) of commercial hydrazine hydrate, Ν₂Η₄Ή₂0, is dissolved in water and volume is adjusted to 100 mL by adding water. Solution B is added to solution A with stirring under ambient conditions. Resultant reaction mixture is heated to boiling temperature and boiled for 20 minutes. Precipitate of LHT-9 is filtered, washed and dried in air at room temperature. Chemical composition of LHT-9, in terms of mole ratios of constituents, is N₂H4-4Ti0₂ l-4H₂0. Water content is dependent on post-reaction thermal treatment. XRD pattern of LHT-9 is similar to that presented in Table 1.

Example 2. Preparation of LHT-9

Solution A - 100 mL of 0.1 aqueous solution of potassium hexafluorotitanate, K₂TiF₆. Preparation: 2.4 g (0.01 mole) of commercial K₂TiF₆ is dissolved in 90 mL of hot water ( t = 80°C). The volume of solution is adjusted to 100 mL by adding of hot water.

Solution B - 50 mL (1.0 mole) of commercial hydrazine hydrate, Ν₂Η₄Ή₂0.

Solution B is added to hot solution A with stirring. Resultant reaction mixture is heated to boiling temperature and boiled for 15 minutes. Precipitate of LHT-9 is filtered, washed and dried in air at room temperature. Chemical composition of LHT-9, in terms of mole ratios of constituents, is 0.9Ν₂Η4·0.1Κ₂Ο·4ΉΟ₂·1-4Η₂Ο. Water content is dependent on post-reaction thermal treatment. XRD pattern of LHT-9 is similar to that presented in Table 1.

Example 3. Preparation of LHT-9

Solution A - 9.5 g (0.05 mole) of commercial titanium tetrachloride TiCl₄ is dissolved at room temperature in 10 mL of 36% hydrochloric acid HC1. The solution is mixed with 10 mL of 40% hydrofluoric acid HF. Total volume is adjusted by water to 100 mL. Solution B - 100 of 5M aqueous hydrazine solution. Preparation: 25 mL (0.5 mole) of commercial hydrazine hydrate, N₂H₄ H₂0, is adjusted by adding water to 100 mL.

Solution B is added to solution A with stirring under ambient conditions. Resultant reaction mixture is heated to boiling temperature and boiled for 20 minutes. Precipitate of LHT-9 is filtered, washed and dried in air at room temperature. Chemical composition of LHT-9, in terms of mole ratios of constituents, is 1.3N₂H₄-3Ti0₂ l-4H₂0. Water content is dependent on post-reaction thermal treatment. XRD pattern of LHT-9 is similar to that presented in Table 1. Examples 4 and 5 illustrate conditions of synthesis out of range resulting in the formation of either amorphous titanium hydroxide or anatase-form titanium dioxide, , instead of LHT-9.

Example 4.

Solution A - 100 mL of 0.3M aqueous solution of hexafluorotitanic acid, H₂TiF₆. Preparation: 2.4 g (0.03 mole) of commercial titanium dioxide is dissolved at room temperature in 10 mL of 40% hydrofluoric acid HF. The volume of solution is adjusted to 100 mL by adding water. Solution B - 100 mL of 6.7 aqueous hydrazine solution. Preparation: 33 mL (0.67 mole) of commercial hydrazine hydrate, Ν₂Η4·Η₂0, is dissolved in water and volume is adjusted to 100 mL by adding water.

Solution B is added to solution A with stirring under ambient conditions. Resultant reaction mixture is filtered, washed and dried in air at room temperature. The chemical composition of the thus obtained product corresponds to the formula Ti0₂-2.4H₂0. The XRD pattern shows that the substance is amorphous.

Example 4 differs from example 1 by the lack of a required condition, thermal treatment (boiling). The resultant product is thus amorphous titanium hydroxide.

Example 5.

Solution A - 9.5 g (0.05 mole) of commercial titanium tetrachloride TiCl₄ is dissolved at room temperature in 10 mL of 36% hydrochloric acid HC1. The volume is adjusted by water to 100 mL.

Solution B - 100 of 5M aqueous hydrazine solution. Preparation: 25 mL (0.5 mole) of commercial hydrazine hydrate, >½¾·¾(), is adjusted by adding water to 100 mL.

Solution B is added to solution A with stirring under ambient conditions. The resultant reaction mixture is heated to boiling temperature and boiled for 20 minutes. The precipitate is filtered, washed and dried in air at room temperature. The chemical composition of LHT-9 corresponds to the formula Ti0₂. The XRD pattern of the product shows that it is titanium dioxide with anatase structure.

Example 5 differs from example 3 by lack of the required reaction component, fluoride ion. The resultant product is thus anatase titanium dioxide.

Example 6 - Preparation of Ti0₂-Se nano-composite from LHT-9

200 mg of air-dried LHT-9 is immersed in 10 mL of 1 (~12 wt. %) solution of H₂Se0₃ and left to stay for 12 hours with occasional shaking. During this period, the white powder of LHT-9 becomes of brownish-red colour due to the formation of elemental amorphous red selenium. The resulting nano-composite powder is filtered, washed and dried in air at room temperature. The chemical composition of the resulting substance is in the range: Ti0₂ 45-55 wt. %, Se 25-30 wt. %, H₂0 15-25 wt. %. Thermal studies reveal that Ti0₂-Se nano- composite is air-stable and resistant to heating in air atmosphere up to at least 300 °C. An investigation using energy-filtered high-resolution TEM mapping (EFTEM mapping, Fig. 6) reveals that the obtained nano-composite possesses flake-like morphology inherited from LHT-9, and selenium is homogeneously distributed in Ti0₂ matrix. The thus obtained Ti0₂- Se nano-composite can be used as effective scavenger for Hg vapour. Example 7 - Using Ti0₂-Se nano-composite (prepared from LHT-9) for mercury vapour scavenging

Three batches of Ti0₂-Se nano-composite, 100 mg each batch, were placed in Teflon-lined autoclaves. In each of three autoclaves, 100 mg of metallic mercury was placed in open glass vials. The autoclaves were closed and then heated for 10 hours under the following temperatures: 60°C, 80°C and 95°C. After cooling to room temperature, the autoclaves were opened. It was immediately observed that batches of Ti0₂-Se nano-composite had changed their color from initial brownish-red to grey-black. Chemical analysis revealed that the Ti0₂- Se nano-composite became mercury-containing, The following Hg contents were determined (wt.%): 3% (60°C), 12% (80°C), 13% (95°C). X-ray powder diffraction data (Fig. 7) reveal that the mercury is chemically bound in form of mercury selenide (tiemannite) HgSe. Thus it can be concluded that mercury is irreversibly chemically bound by Ti0₂-Se nano-composite. The resulting product, Ti0₂/Se HgSe composite, may be used as convenient raw material for recycling of LHT-9, mercury and selenium.

Example 8 - Using LHT-9 for the preparation of metal-doped Ti0₂ nano-materials

100 mg of as-prepared LHT-9 is immersed in 20 ml of HCl-acidified (pH 1.2) 1% aqueous solution of stannous chloride, SnCl₂. It is immediately observed that the white powder of LHT-9 becomes egg-yolk coloured. The composition of the resultant product determined by ICP and TGA analysis is as follows (wt. %): Ti0₂ 52.9; SnO 30.9; Cl < 0.1. Thus, the egg- yolk coloured product is a Ti0₂/SnO H₂0 composite which can be used for the production of Sn-doped titania nano-materials.

Claims

1. Layered titanate with the chemical formula

A:N₂H₄- wA_1-20 (Ti_{1 -tl}M_q)(0_2-wO¾F )_2-,-«H₂0 wherein

- k,m,q,w,x,y and z are coefficients ranging from 0.01 to 0.5;

- n is an integer, wherein 0 < n < 5;

- A is at least one cation having a valence of 1 to 3;

- Mis at least one metal having a valence of 1 to 7; comprising chemically bound anion-free hydrazine intercalated in the interlayer space of the titanate layers.

2. Layered titanate according to claim 1 , characterized in that A is selected from the group consisting of H, Li, Na, K, Rb, Cs, Tl, Nii₄ (ammonium or its organic derivatives), NR^OR (hydroxylammonium or its organic derivatives), N₂&»

(hydrazinium or its organic derivatives), H₃0 (hydronium), Ag, Au, Mg, Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg, Hg, Sn, Pb, Ca, Sr, Ba.

3. Layered titanate according to one of the preceding claims, characterized in that M is selected from the group consisting of Li, Mg, Al, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Nb, Mo, Sn, Sb, Hf, Ta, W, Ru, Rh, Pd, Os, Ir and Pt.

4. Layered titanate according to one of the preceding claims, characterized in that the interlaying spacing is in the range of 0.8 nm to 1.1 nm.

Layered titanate according to one of the preceding claims, characterized in that the layered titanate is formed as platelets with a size in the range of 5 to 1,000 nm.

Method for the production of layered titanate according to one of the claims 1 to 6, comprising the steps of:

- preparing an aqueous solution comprising

a. a compound comprising titanium or titanyl [(TiO)²⁺] as a source of titanium, wherein in the titanium concentration of the aqueous solution is in the range of 0.01 to 6 mole per liter,

b. a complex forming ion forming stable complex ions with titanium;

- preparing a alkaline solution comprising Hydrazine (N₂H₄), hydrazine hydrate (Ν₂Η₄Ή₂0) or an aqueous solution containing hydrazine or salts of hydrazine in any soluble form, wherein the hydrazine concentration of the alkaline solution is in the range of 0.1 and 30.5 mole per liter;

- mixing the aqueous solution with the alkaline solution; and

- heating the mixture to boiling temperature followed by boiling for between 0.1 minutes and 30 days

or

placing the mixture into an autoclave and perform treatment under hydrothermal conditions with a temperature in the range of 110 to 300 °C for between 1 minute and 30 days.

Method according to claim 7, characterized in that the compound comprising titanium or titanyl [(TiO)²⁺] is selected from the group consisting of halogenides T1X4, wherein X = F, CI, Br and I; titanyl salts TiOX2/_n, wherein X is any anion of valence n; salts or complexes of trivalent titanium Ti³⁺; halogenotitanic acids and their salts Α2_/ΓηΤι[Χι- n(OH)_n]6,wherein A is any cation of the valence m and X = F, CI, Br, I, 0<«<1, any complex compounds of titanium, any titanoorganic compounds, preferably aryloxides or alkoxides of titanium Ti(OR)4_-nX_n, wherein R is any organic or metalloorganic radical, preferably methyl (CH₃), ethyl (C₂H₅), propyl isomers (C₃H₇), butyl isomers (C₄H9), and wherein X - F, CI, Br, I.

8. Method according to any one of claims 7 and 8, characterized in that the titanium

concentration of the aqueous solution comprising titanium or titanyl [(TiO)²⁺] as a source of titanium is in the range of 0.1 to 1 mole per liter.

9. Method according to any one of claims 7 to 9, characterized in that the complex

forming ion is selected from the group fluoride ions in form of any compound, preferably as HF (hydrofluoric acid); fluorides Aⁿ⁺F_n, wherein A is any cation of the valence n hexafluorotitanic acid H₂TiF₆; hexahalogenotitanates A₂/_mTi(Fi_-nX_n)6, wherein A is any cation of valence m, and X = F, CI, Br, I, OH, 0<«<1 ; hydrofluorides Aⁿ⁺F_n /wFfF, wherein A is any cation of valence n, and 0<m<4; oxycarboxylic acids or their salts, preferably oxalic, citric, malic, tartaric, tartronic acid or their salts.

10. Method according to any one of claims 7 to 10, characterized in that the hydrazine concentration of the alkaline solution is in the range of 1 and 15 mole per liter.

1 1. Method according to any one of claims 7 to 11, characterized in that the alkalinity is achieved by the presence of free hydrazine or by adding of any alkali, preferably of aqueous solution of NaOH, KOH or NH₃.

12. Method according to any one of claims 7 to 12, characterized in that the mixture is boiled for between 10 to 30 min.

13. Method according to any one of claims 7 to 12, characterized in that the mixture is treated in the autoclave for between 2 and 24 hours.

14. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a carrier for supplying hydrazine in direct hydrazine fuel cells.

15. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as matrices for carrying out inorganic, organic and bioorganic syntheses, wherein bound hydrazine is used as an active constituent.

16. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as an ion-exchange material.

17. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a reductive sorbent for the recovery of noble metals from industrial solutions.

18. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a reductant for the reduction of U, Pu, Np and Tc in spent nuclear fuel.

19. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a precursor for the synthesis of nanocristalline titanates.

20. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a catalyst, including a photocatalyst, and/or as a precursor for producing a catalyst.

21. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a precursor for the preparation of titanium dioxide, including doped titanium dioxide.

22. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a precursor for the preparation of friction materials based on layered titanates.

23. Use of layered titanates according to one of claims 1 to 6 and/or layered titanates obtained by the method of any one of claims 7 to 14 as a precursor for the preparation of composite nano-materials, including Ti0₂-Se nano-composites for Hg vapour scavenging.