DEVICES AND METHODS FOR IMPROVED GENERATION OF HYDROGEN

TECHNICAL FIELD

[0001] The present invention generally relates to compositions and methods for generation of hydrogen using silicon based compounds. More particularly, the invention discloses a composition of matter, processes and devices for generating hydrogen using such compounds as siloxene, organosilanes or polysilanes, and catalysts which result in generating hydrogen as needed safely and efficiently.

BACKGROUND INFORMATION

[0002] The ability to store hydrogen efficiently, economically and safely is one of the challenges to be overcome to make hydrogen an economic source of energy. US Patent Application Serial No. 60/705,331 and PCT/US08/52127 describe the limitations in the current commercialization of fuel cells, internal combustion engines fueled with hydrogen and engine exhaust after-treatment systems utilizing hydrogen. These patent applications also disclose technology and processes that utilize certain silicon based compounds to generate hydrogen safely and efficiently on an "as needed" basis, thus eliminating the hazards of storing hydrogen in bulk as part of a fuel cell system or coupled with an internal combustion engine.

[0003] There remains a need for further improvements which enhance efficiency, performance and cost; for clean sources of energy for portable and stationary fuels cells, and for internal combustion engines; for technology that can reduce harmful exhaust gas by products of combustion from an internal combustion engine. The present invention addresses these needs.

SUMMARY

(0004] This invention disclosure describes compositions and processes for use in generation of hydrogen using silicon-based compounds as a starting material. This disclosure also describes devices that can be used to generate hydrogen as needed from silicon-based compounds.

[0005] This invention provides a method for generating hydrogen on an as needed basis in a controlled manner, by contacting an article, such as a tablet, a bar or a sphere comprising siloxene with water and a catalyst. The catalyst may be an organic amine or a strong base such as sodium hydroxide, potassium hydroxide or calcium hydroxide which may be incorporated into the tablet, bar or sphere. The tablet may further include a high molecular mass polymer such as carbopol which acts as a binder.

[0006] The invention also provides methods and devices for generating hydrogen on an as needed basis in a safe and controlled manner, by contacting the siloxene powder or tablet or an organosilane or polysilane gel with an organic amine catalyst or a strong base and the condensate from the exhaust stream of an internal combustion engine, thus providing a highly efficient NO _x reducing agent .

[0007] The invention also provides methods for generating hydrogen directly by contacting water and a starting material comprising a metal suicide (e.g., calcium suicide), with a catalyst, such as KOH or NaOH, wherein hydrogen is produced as needed by altering the reaction conditions, such as conducting the reaction at a temperature of greater than 13O ⁰ F to enhance gravimetric efficiency.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a flow diagram of the overall hydrogen generation process where a siloxene tablet or organosilane or polysilane gel is used as a fuel.

[0009] Figure 2 is a schematic representation of a cartridge-type hydrogen generator for light duty diesel applications using siloxene tablets applications.

[0010] Figure 3 is a schematic representation of an exhaust gas condensate unit for use with internal combustion engines.

DETAILED DESCRIPTION

[0011] U.S. Patent Application Serial No. 60/705,331, the entire contents of which are incorporated herein by reference, describes in detail a process using silicon-based chemistry to generate hydrogen safely, as needed, eliminating the need for storage of large amounts of hydrogen in pressure vessels. PCT patent application US 08/52127, the entire contents of

which are also incorporated herein by reference, further describes the processes and catalysts that further maximize the production of hydrogen beyond that which can be typically obtained by uncontrolled mixing of silicon-based compounds with water and a catalyst.

[0012] The present invention describes that the silicon-based compounds in the above referenced patent applications can be made into an article (such as a tablet, a bar, or a sphere) or a gel, providing higher levels of efficiency, control and safety. The tablet format increases the volumetric density of the materials, eliminates the need for space-occupying and energy- consuming pumps required to move powders. The tablet also provides the option of incorporating a catalyst for certain applications, for example, where a separate catalyst storage vessel would have functional or cost limitations. The tablet format also eliminates the need for a powder cartridge and facilitates the re-fueling process.

[0013] The longest dimension of a tablet can range in size from less than one quarter inch to more than two inches. In some cases, a larger bar or sphere with a size of greater than five inches may be used in place of a tablet, further minimizing the need to move materials and further improving the economics based on volumetrics of an integrated unit. According to embodiments of the invention, tablets or bars having high aspect ratios of may be used, because the higher the surface area, the quicker and more complete the reaction. A catalyst may be incorporated directly within the article eliminating the need for separate mixing devices while providing an increase in the rate of reaction.

[0014] Methods and devices described in the present invention may also provide hydrogen as needed by mixing the water condensate from the exhaust of an internal combustion engine with the siloxene, organosilane or polysilane-based tablets and a catalyst. This method reduces the volume, mass and cost of materials required and also provides the opportunity to improve engine combustion efficiency by lowering the temperature of the exhaust gases returned to the combustion chamber and also providing the opportunity for the addition of a small amount of hydrogen which has been shown to be effective in improving combustion and lowering harmful exhaust emissions.

|0015] In some embodiments, calcium suicide may be utilized (optionally, in combination with a catalyst such as KOH or NaOH) as a direct hydrogen source, in particular at higher temperatures, to generate hydrogen as shown in the general reaction scheme

CaSi ₂ + 6H ₂ O → SiO ₂ + Ca(OH) ₂ + 5 H ₂ .

[0016] The following terms and definitions are used in the present application.

[0017] Throughout the description and claims of this specification the word "comprise" and other forms of the word, such as "comprising" and "comprises," means including but not limited to, and is not intended to exclude, for example, other additives, components, integers, or steps.

[0018] As used in the description and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a composition" includes mixtures of two or more such compositions, reference to "an organosilane" includes mixtures of two or more such organosilanes, reference to "the silane" includes mixtures of two or more such silanes, and the like.

[0019] "Optional" or "optionally" means that the subsequently described event or circumstance can or cannot occur, and that the description includes instances where the event or circumstance occurs and instances where it does not. For example, statements about a device that optionally contains a check valve refers to devices that have a check valve and devices that do not have a check valve.

[0020] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as "about" that particular value in addition to the value itself. For example, if the value "10" is disclosed, then "about 10" is also disclosed. It is also understood that when a value is disclosed that "less than or equal to" the value,

"greater than or equal to the value" and possible ranges between values are also disclosed, as appropriately understood by the skilled artisan. For example, if the value "10" is disclosed, then "less than or equal to 10" as well as "greater than or equal to 10" is also disclosed. It is also understood that throughout the application data are provided in a number of different formats and that this data represent endpoints and starting points and ranges for any combination of the data points. For example, if a particular data point "10" and a particular data point "15" are disclosed, it is understood that greater than, greater than or equal to, less than, less than or equal to, and equal to 10 and 15 are considered disclosed as well as between 10 and 15. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0021] References in the specification and concluding claims to parts by mass of a particular element or component in a composition denotes the mass relationship between the element or component and any other elements or components in the composition or article for which a part by mass is expressed. Thus, in a compound containing 2 parts by mass of component X and 5 parts by mass component Y, X and Y are present at a mass ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.

(0022] A mass percent (mass %) of a component, unless specifically stated to the contrary, is based on the total mass of the formulation or composition in which the component is included. As used herein the term "gravimetric efficiency" means the yield of hydrogen per unit mass of starting material. A high gravimetric efficiency is achieved by optimization of starting materials, catalysts, and processes.

[0023] As used herein the term "aspect ratio" refers to a ratio between the longest and the shortest dimension of an article; for example, for tablets it means the ratio between the diameter and the thickness of the tablet, and for bars - a ratio between the length and the thickness.

[0024] As used herein the term "as needed basis" used interchangeably with the term "on demand" refers to the ability to control the reaction conditions wherein the amount of hydrogen produced is controlled.

|0025] As used herein the term "in a controlled manner" means the amount of hydrogen produced can be varied in a predictable manner by alteration of the reaction conditions.

[0026] As used herein the term "reaction conditions" includes, but is not limited to, temperature, feed rate, stoichiometry and back pressure.

[0027] As used herein, the term "substituted" is contemplated to include all permissible substituents of organic or inorganic compounds. In one example, the permissible substituents can include acyclic and cyclic, branched and unbranched, carbocyclic and heterocyclic, and aromatic and nonaromatic substituents of compounds. Illustrative substituents include, for example, those described below. The permissible substituents can be one or more and the same or different for appropriate compounds. For purposes of this disclosure, the heteroatoms, such as nitrogen, can have hydrogen substituents and/or any permissible substituents _. of organic or inorganic compounds described herein which satisfy the valences of the heteroatoms. This disclosure is not intended to be limited in any manner by the permissible substituents of compounds.

[0028] "A ¹ ," "A ² ," "A ³ ," and "A ⁴ " are used herein as generic symbols to represent various specific substituents. These symbols can be any substituent, not limited to those disclosed herein, and when they are defined to be certain substituents in one instance, they can, in another instance, be defined as some other substituents.

[0029] The term "alkyl" refers to substituted and unsubstituted C ₁ -C ₃₀ straight chain or branched saturated aliphatic hydrocarbon groups, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, isopropyl, isobutyl, tert-buty\, sec-butyl, and the like.

[0030] The term "alkylene" is defined as compounds containing at least one carbon-carbon double bond (C=C), and as used refers to a hydrocarbon group of from 2 to 40 carbon atoms with a structural formula containing at least one carbon-carbon double bond.

[0031] The term "aryl" as used herein is a group that contains any carbon-based aromatic group including, but not limited to, benzene, naphthalene, phenyl, biphenyl, phenoxybenzene, and the like.

[0032] The term "silane" as used herein is represented by the formula H-SiA ¹ A ² A ³ , where A ¹ , A ² , and A ³ can be, independently, hydrogen, or a substituted or unsubstituted alkyl, alkoxy, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, or cycloalkenyl. Generally, the term "silane" means a silicon analogue of an alkane, alkoxyl, alkene, alkyne, or aryl where one, more than one, or all carbon atoms in those structures are replaced by a silicon atom and at least one of the silicon atoms is covalently bonded to a hydrogen atom. The term "organosilane" refers to the same basic structure and is generally used interchangeably with the term "silane," with the proviso that in an organosilane at least one of A ¹ , A ² , and A ³ is not hydrogen.

[0033] In some examples, a silane can be analog of an unsubstituted alkane and have the general formula of Si _n H _2n + ₂ . Such structures are typically named according to regular nomenclature where the word "silane" is preceded by a numerical prefix (di, tri, tetra, etc.) for the number of silicon atoms in the molecule. Thus, Si ₂ H ₆ is disilane, Si ₃ H ₈ is trisilane, and so forth. There is usually no prefix for one, as SiH ₄ is referred to as simply "silane." Silanes can also be named like any other inorganic compound; for example, silane can be named silicon tetrahydride, disilane can be named disilicon hexahydride, and so forth. Silanes that are substituted with a hydroxyl group are called silanols.

[0034] In other examples disclosed herein, a silane can be substituted with one or more organic groups such as an alkane, alkene, alkyne, or aryl. Such structures, which contain a silicon-carbon bond, are typically referred to as organosilanes. Examples of some well known organosilanes include te/t-butyldimethylsilane, trimethylsilane, phenylsilane, and the like. Silanes with more than one silicon atom can also be referred to as polysilanes.

[0035] Throughout this disclosure and the appended claims, the term "silane" is intended to include organosilanes, polysilanes, branched silanes, cyclic silanes, substituted silanes (e.g., silanols), and unsubstituted silanes, though in some instances these structures can be referred to specifically herein. Further, a radical of such a silane can be specifically referred to as a "silyl," but throughout the disclosure silyls are also intended to be included within the meaning of silanes.

[0036] The terms "amine" or "amino" as used herein are represented by the formula NA ¹ A ² A ³ , where A ¹ , A ² , and A ³ can be, independently, hydrogen, an alkyl, halogenated

alkyl, alkenyl, alkynyl, aryl, heteroaryl, cycloalkyl, cycloalkenyl, heterocycloalkyl, or heterocycloalkenyl group described above.

[0037] The term "a catalyst" is defined as substance that changes the speed or yield of a chemical reaction without being itself substantially consumed or otherwise chemically changed in the process.

[0038] The term "polymer" is defined as being inclusive of homopolymers and copolymers. The term "homopolymer" is defined as a polymer derived from a single species of monomer. The term "copolymer" is defined as a polymer derived from more than one species of monomer, and includes terpolymers, and quaterpolymers.

[0039] Reference will now be made in detail to specific aspects of the disclosed materials, compounds, compositions, articles, and methods, examples of which are illustrated in the accompanying examples and figures. The specific starting materials, catalysts and processes are generally disclosed in U.S. Patent Application Serial No. 60/705,331 and PCT Application PCT/US08/52127.

[0040] Disclosed herein are compositions, methods, and devices that improve the overall system efficiency and hydrogen yield when using organosilanes, polysilanes and siloxene as fuel. According to embodiments of the invention, hydrogen generating articles are provided. For illustrative purposes only, in a non-limiting way, the shape of articles that can be used include cuboidal or discal (i.e., shaped as tablets), spherical, elliptical or lenticular. There are no limitations on the shape of the hydrogen generating articles, and additional shapes into which the hydrogen generating articles can be shaped include also oblate spherical, prolate spherical, cylindrical (including right circular cylindrical), convex (including plano-convex), pyramidal (including truncated pyramidal), conical (including frustoconical), and ogival shape. Those having ordinary skill in the art can determine the required shape and can devise a method of shaping the hydrogen generating articles in any other desired way.

[0041] In several examples disclosed herein, the hydrogen generating articles are shaped as tablets or bars having the ranges of dimensions as discussed above. According to embodiments of the invention, tablets or bars having high aspect ratios, such as between about 3: 1 and about 20: 1 , may be used. Tablet compositions comprising siloxene can be used to generate hydrogen, which in turn can be used in (e.g., supplied to) a fuel cell or an internal

combustion engine or exhaust after treatment catalyst. The siloxene is produced from suicides or from rice straw and has the basic formula SIeH ₃ ^O _3-O (such as Si ₆ H ₆ Os) with a varying amount of repeating units and layers. The size of the siloxene aggregates can range from under one micron to over sixty microns in addition to higher amounts of oxygen.

[0042] The siloxene powder is typically mixed with an organic solvent, such as methanol or isopropanol, a polymer which acts as the binder, and an amine activator, i.e., a base which acts to crosslink active sites on the polymer. A catalyst can be also optionally incorporated to facilitate the hydrogen liberation reactions when contacted with water. The polymer is a high molecular mass hydrocarbon that unfolds at temperatures higher than ambient. The polymer comprises carbonyl functionalities along the length of the chain. In some embodiments, one or more synthetic polymeric thickeners from a family known under the trade name Carbopol ^® (available from Lubrizol Corp. of Wickliffe, Ohio) may find particular utility in this composition.

[0043] An amino activator that is used to crosslink with the active sites on the polymer can be at least one organic amine that ranges from a C ₃ amines to an amine with 50 or more carbons (C50), such as C3 to Ci ₆ amines.

[0044] If a catalyst is used in the siloxene-based hydrogen generating articles, the amino activator used to crosslink the polymer may also serve as a catalyst. For example, propylamine may be utilized as such a catalyst. Examples of other suitable catalysts include NaOH, KOH, Ca(OH) ₂ and CaH ₂ . If propylamine is used as a catalyst, the quantity of propylamine catalyst may be between about 0.1 % and about 5 % by mass.

[0045] The above-described compositions are compressed at high pressures (500 to 20,000 psi) (i.e., approximately 3.4 MPa to 137.9 MPa) to form an article in the desired shape described above, e.g., a tablet, a bar or a sphere. The materials are then dried to remove the organic solvent. The so formed tablet, bar or sphere can liberate hydrogen when combined with water, in the mass ratio of water to siloxene that is between about 1 : 1 and about 10: 1 , in the presence of a catalyst at temperatures ranging from 3O ⁰ F to 212 ⁰ F (i.e., approximately from -I ⁰ C to 100 ⁰ C), as long as the water is a liquid. Water from many sources can be utilized, including the fuel cell effluent, exhaust gas condensate, seawater and wastewater.

[0046] In the above described articles for generating hydrogen, such as tablets, the embodiments of the present invention provide for the ratio of the binder polymer to siloxene that may be between about 0.1 % and about 1.0 % by mass of the siloxene, and for the ratio of the amine activator to siloxene that is between about 0.1 % and about 1.0 % by mass of the siloxene. An amount of the amine greater than about 0.5 % may cause the release of hydrogen prematurely, due to the initiation of the reaction generating hydrogen using only trace amount of water that is contained in the solvents used, i.e., methanol or isopropanol. An amount of either the amine or the binder lower than 0.1% may not be sufficient to ensure effective binding of the siloxene tablet.

[0047] According to other embodiments, a gel may also be utilized when a liquid organosilane or polysilane is selected for a given application. Carbopol or similar compounds may be used as a cross-linking agent to thicken the organosilane or polysilane. No additional organic solvent is required. A small amount of water may be useful in initiating the thickening reaction. The gel lowers the volatility of the organosilane and polysilane thus improving its safety and efficiency through reduced evaporative losses. In such a gel, organosilane may be any of trisilane, tetrasilane, hexasilane, pentasilane, cyclopentasilane, substituted cyclopentasilane, cyclohexasilane, substituted cyclohexasilane; a short chain hydrocarbon with at least one terminal silane group(s), disilabutane, disilapropane, phenylsilane, disilylbenzene, trisilylbenzene, hexasilylbenzene , or combinations thereof.

[0048] A strong base catalyst may be incorporated in the above-described organosilane or polysilane gel, such as organosilane or polysilane. Again, the gel may be shaped in any of the above-described forms, including a tablet, a bar, or a sphere. To generate hydrogen, the so formed gel-based article may be combined with water, wherein the quantity of the catalyst is between about 0.1 % and about 5 % by mass of the water, and the mass ratio of water to the starting material is between about 1 : 1 and about 1 :4.

[0049] Devices or cartridges that can be used to convert silanes into hydrogen can be designed specific to each application, whether it be for a portable or stationary device, and whether mass or volume is more important. In some embodiments, the devices may include an exhaust gas cooler for condensing out water vapor; a mixing chamber for mixing the exhaust gas condensate and a catalyst; a mixing chamber for mixing an organosilane,

polysilane or a siloxene starting material, the exhaust gas condensate, and a catalyst; a reaction chamber comprising a hydrogen outlet; a hydrogen outlet comprising a hydrogen permeable membrane; and a silicate by-product precipitate collector.

[0050] More specifically, the devices or cartridges may be connected to a fuel cell, to the intake air of an engine, to a vehicle exhaust after-treatment system or to any other device that needs hydrogen as a fuel. As shown by Fig. 1, generally devices feed the reactants and catalyst as needed to a reaction zone. The call for the reactants to the reaction chamber can be controlled simply by a check valve responding to a pressure increase in the reaction zone or can be controlled by electronic activation of valves and pumps. The devices blend the reactants in the desired concentrations, segregate the resulting hydrogen gas, and deliver the gas to the fuel cell, engine, engine exhaust after-treatment system or other hydrogen consuming device. The devices can also contain a means for segregating and collecting the silicate precipitate, refluxing clean water, and preventing backflow of reaction products into the reactant streams.

[0051] An example of a particularly useful device is a system that functions in the exhaust stream of an internal combustion engine. The device/system first cools the exhaust stream to collect a water vapor condensate. The exhaust gas cooler also solubulizes nitrogen dioxide in the condensed water to form nitric acid, particularly after an oxidation catalyst which converts nitrogen oxide which is non-soluble in water, to nitrogen dioxide which is highly soluble in water. Condensing the nitrogen dioxide out of the exhaust stream reduces the amount OfNO _x that must be treated by the exhaust after treatment system.

[0052] In this embodiment, a siloxene or a calcium suicide starting material may be combined with the condensate from an internal combustion engine and a catalyst, thus generating hydrogen. The solubulized NO ₂ being present in the condensate may be further sequestered into a harmless nitrate precipitate, allowing to achieve the reduction of nitrogen oxides by between about 1 % and about 99 %. The catalyst that may be used in such an embodiment may be a dilute strong base, e.g., NaOH, KOH, Ca(OH) ₂ , an alkylamine, an arylamine, CaH ₂ , UV light, or combinations thereof.

[0053] If an alkylamine is used as such a catalyst, the alkylamine may include a substituted or unsubstituted mono-, di-, and tri-alkyl amine, hydroxyalkylamine, and a substituted or

unsubstituted mono-, di-, tri-alkenylamine, for example, any of methylamine, ethylamine, propylamine, isopropylamine, butylamine, tert-butylamine, pentylamine, hexylamine, heptylamine, octylamine, nonylamine, decylamine, undecylamine, dodecylamine, tridecylamine, tetradecylamine, pentadecylamine, hexadecylamine, heptadecylamine, octadecylamine, nonadecylamine, icosylamine, henicosylamine, doicosylamine, triicosylamine, tetraicosylamine, and combinations thereof.

[0054] The exhaust gas water condensate is then mixed with a catalyst as described in PCT US08/52127 and then mixed with the siloxene tablet to produce hydrogen. Alternatively, the water condensate can be mixed directly with a tablet comprised of the siloxene and a catalyst, such as calcium hydride. The hydrogen produced is directed to a Lean NO _x Trap (LNT) as a reducing agent for nitrogen oxides not condensed out of the exhaust stream.

[0055] Alternatively or additionally, the hydrogen can be routed directly to the combustion chamber through the exhaust gas recirculation (EGR) stream as a supplementary fuel and combustion enhancer. Depending on the application set-up, the reduction OfNO _x in the exhaust by trapping the NO ₂ fraction in the condensed exhaust water vapor can range from 1 to 99 %. The hydrogen then not needed by the LNT could be routed to the combustion chamber. The exhaust gas cooler provides additional benefit by improving the volumetric efficiency of the engine through the reduction in temperature of the EGR stream.

[0056] In one example, the device can be as shown by Fig. 2. The device comprises a mixing chamber for mixing a polysilane or organosilane, water and catalyst(s). The mixing chamber can comprise an inlet for the polysilane or organosilane with check valve to regulate the amount of fuel introduced into the reaction zone to minimize pressure build up, and a water inlet also with a check valve.

[0057] The reaction chamber can also comprise a silicate collector such as absorbed glass mat, which can be used to contain and/or remove the silicate by-product of the reaction. When a polysilane is used the reaction zone may also contain a source of UV light to catalyze the reaction.

[0058] In another example, a device for automobiles or light duty vehicles can be as shown by Fig. 3. The device comprises a metal housing with separated storage for the organosilane, polysilane or silicide-based fuel, and a reaction chamber. Water vapor is condensed from the

engine exhaust and directed to the device where it is first mixed with the catalyst and then mixed with the fuel. The liberated hydrogen is directed to the intake air system of the engine, or is directed to the exhaust gas after-treatment system or is directed to an on-board fuel cell. The precipitate is collected in the cartridge.

[0059] Some features of the present invention may be further illustrated by the following non-limiting example.

EXAMPLE 1. A Hydrogen Generating Article As a Tablet

[0060] A siloxene tablet as described above was added to a reaction flask. A rubber stopper was then used to seal the neck of the flask. The flask was then connected by tubing to a graduated cylinder that was filled with water and then inverted and placed in a reservoir of water. A solution of 0.5 M sodium hydroxide in water was then injected using a syringe into the reaction vial. The gas generated during the reaction was collected in the top portion of the graduated cylinder displacing the water. The calculated gravimetric efficiency which is the mass of the hydrogen generated divided by the mass of the siloxene is shown in the table.

[0061] In a second example a saturated solution of calcium hydroxide replaced the sodium hydroxide. In a third example, a solution of water with 5 (w) % n-propylamine replaces the sodium hydroxide. Table 1, below, summarizes the results.

Table 1. Tablet Study Results

Tablet Material Reactant Catalyst Volume H ₂ MaSs H ₂ Gravimetric mass, g liberated ml liberated, g efficiency, %

Siloxene 0.73 NaOH 400 0.032800 4.49

Siloxene 0.68 Ca(OH) ₂ 300 0.024600 3.62 n-propyl Siloxene 1.5 amine 920 0.0492 5.03

[0062] It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. AU publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety for all purposes.