Technical Field

[0001] The present invention relates to porous liquids containing one or more oligomers wherein the oligomers contain a plurality of interconnected aromatic groups. The invention also relates to the use of porous liquids in processes involving the separation or purification of fluids, especially the separation or purification of gases. The invention also relates to processes for the preparation of porous liquids of the invention.

Background of Invention

[0002] Many of the important industrial processes carried out throughout the world involve fluid purification as a step in the process. For example the purification of industrial gases prior to sale or natural gas typically involves removal of a number of unwanted materials such as water, carbon dioxide, carbon monoxide or other unwanted gases that may interfere with the end use of the purified gas. Industrial gases that need to be purified before use include air, nitrogen, helium, argon, hydrogen, oxygen and hydrocarbons.

[0003] In addition industrial flue gas produced by industry requires purification before being released into the atmosphere. Flue gas is the gas exiting an industrial plant to the atmosphere via a flue, which is a pipe or channel for conveying exhaust gases from a fireplace, oven, furnace, boiler or steam generator. An example of a well-known flue gas is the combustion exhaust gas produced by a power plant. The most common contaminants present in these industrial gases are carbon monoxide, carbon dioxide, sulfur dioxide and trioxide, nitrogen oxides, hydrogen sulfide and small organic molecules. Removal of these impurities is important to reduce environmental pollution and minimize climate change.

[0004] The most commonly used processes to purify gases on an industrial scale are liquid scrubbers (where a basic or acidic solution is used to absorb an acidic or basic gas, respectively), exchange resins (where immobilized bases or acids are used to absorb an acidic or basic gas, respectively), membranes (which separate gases based on competitive adsorption, differences in diffusion rates, molecular discrimination and/or sieving) or complicated distillation apparatus. Whilst all these processes are useful there is still a need for improved processes for fluid separation/purification.

[0005] One potential solution may involve the use of novel porous materials. There has been an explosion of interest in porous materials over the last few decades, due to our ability to investigate materials at the nanoscale and the broad application potential of nanotechnology across a wide variety of applications. Accordingly readily available synthetic porous materials are expected to play a fundamental role in future advances across the biological and chemical sciences, including the industrial separations due to the possibility of controlled surface interactions, fast molecular transport and molecular selectivity. Examples of porous solids include metal -organic Frameworks (MOFs), porous aromatic frameworks (PAF’s) and covalent organic frameworks (COF’s).

[0006] Despite the exceptional uptake and selectivity offered by MOFs, COFs, PAFs, activated carbons and other advanced porous materials in separations, their other properties are in certain instances incompatible for use on an industrial scale. For example, porous solids of this type are difficult to transport through a factory (pumping), exhibit poor thermal conductivity and generally may have long regeneration times making them undesirable for industrial scale applications.

[0007] As process considerations, continuous operation of packed bed systems can require multiple streams due to differences in the time required for adsorbent exhaustion and regeneration. Fleat recovery from packed-bed systems is also non trivial, as considerable energy losses are incurred by the necessary changes to a plant’s thermal mass during cycling. Alternative processes, such as fluidized beds can also be challenging from an engineering perspective and pose major risks to process reliability, especially at larger scales. In addition with space a premium, especially in off-shore plants, low adsorbent densities and bulky multi-bed systems put considerable pressure on a plant footprint.

[0008] As a result of the difficulty in using porous solids many industrial processes still utilise distillation and liquid-scrubber processes which rely on phase changes or chemical bonding to separate chemical species. [0009] While modern plants are designed to accommodate the kinetics of each process, minimize changes in vessel thermal mass and to recover waste energy, poor sorbent solubilities and high intrinsic enthalpy requirements (vaporization and /or solvent regeneration) limit the achievable efficiency of these processes. Other problems faced, in particular, by amine based solvents for CO2 capture include plant corrosion, product saturation with water, as well as emissions issues related to human and environmental toxicity.

[00103 While porous adsorbents offer better separation fundamentals, advanced fluid sorbents offer a less capital intensive solution to process inefficiencies through retrofitting of existing plant equipment. Conceptually, combining the separation efficacy of porous solids with the process applicably of liquids may offer a step-wise change to the enormous quantity of energy used by separations worldwide.

[0011] Recently, the held belief that porosity was restricted to solid materials has been disproven by reports of liquids with porosity. Amongst a broad range of potential uses, Porous Liquids (PLs) have the potential to see the adsorption and functional characteristics of porous materials applied in chemical industries as a direct replacement of process fluids in existing solvent scrubbers. Although extrinsic porosity (inter-molecular space) is well established phenomena in liquids, ‘Porous liquids’ are defined by the presence of intrinsic (intra-molecular) porosity and/or cavities within the liquid state material.

[00123 PLs are classified as one of three categories, Type I, Type II and Type III based on their composition, however stringent validity conditions are not yet defined. Type I are true porous liquids: a single component that is both liquid and porous. Type II & Type III are multi-component systems combining a normally solid porogen in a non-pore penetrating solvent and arguably only differ by the scale of the included porogen (molecular or nanoparticle). Accordingly, porous liquids have promise as materials for use in separation technology although to date the available porous liquids for use in applications of this type is quite limited.

[00133 Accordingly it would be desirable to provide alternative porous liquids that may find application in the separation or purification of fluids such as gases or contaminated liquids. As a result of significant work in the area the present applicants have now identified a process for the production of a porous liquid which shows potential in this area.

Summary of Invention

[0014] The present applicants have now developed a controlled process for the formation of relatively low molecular weight liquid oligomers comprising aromatic residues that are connected via a bond or linking group that are able to function as porous liquids. This has allowed the applicants to produce certain liquid oligomers that can act as Type I porous liquids.

[0015] The present invention therefore provides a porous liquid comprising one or more oligomers, each oligomer containing from 4 to 35 aromatic residues; the aromatic residues in each oligomer being connected via a bond or a linking group, wherein the linking group is a methylene (-CH2-) group; and further wherein each aromatic residue in the oligomer is independently a residue of the formula:

[0016] wherein each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group;

[0017] each B represents a bond to another aromatic moiety within the compound or a bond to a linking group;

[0018] n is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5; [0019] m is an integer selected from the group consisting of 0,1 , 2, 3, 4, and 5;

[0020] 0 is an integer selected from the group consisting of 1 , 2, 3, 4 and 5;

[0021] wherein the sum of n+m+o is 6. [0022] In certain embodiments the porous liquid contains a single oligomer species. In other embodiments the porous liquid contains a number of oligomer species.

[0023] As stated above the porous liquid may contain one or more oligomers with each oligomer containing from 4 to 35 aromatic residues. In one embodiment each oligomer contains from 8 to 35 aromatic residues. In one embodiment each oligomer contains from 4 to 15 aromatic residues. In one embodiment each oligomer contains from 4 to 8 aromatic residues.

[0024] In yet a further aspect the present invention provides a method of preparing a porous liquid comprising one or more oligomers, each oligomer containing from 4 to 35 aromatic residues; the aromatic residues in each oligomer being connected via a bond or a linking group, wherein the linking group is a methylene (-CH2-) group; and further wherein each aromatic residue in the oligomer is independently a residue of the formula:

[0025] wherein each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group;

[0026] each B represents a bond to another aromatic moiety within the compound or a bond to a linking group; [0027] n is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5;

[0028] m is an integer selected from the group consisting of 0,1 , 2, 3, 4, and 5;

[0029] 0 is an integer selected from the group consisting of 1 , 2, 3, 4 and 5; [0030] wherein the sum of n+m+o is 6;

[0031] the method comprising reacting an aromatic compound of the formula:

[0032] wherein each R is independently selected from the group consisting of alkyl, alkenyl, and alkynyl;

[0033] p is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5; [0034] q is an integer selected from the group consisting of 1 , 2, 3, 4, 5 and 6; [0035] wherein the sum of p+q is 6;

[0036] with an oxygen containing linking agent in the presence of a lewis acid; wherein the mole ratio of oxygen containing linking agent to aromatic compound is less than 10.

[0037] The applicants have found that control of the amount of linking agent and/or synthetic conditions and or the substitution pattern on the aromatic residue leads to the reaction terminating whilst the compound is still relatively small leading to formation of a liquid oligomer.

[0038] Many porous liquids currently published contain ordered caged structures. The oligomers of the present invention are not ordered to form a specific caged structure or any particular structural shape. They can be described as optionally substituted phenyl moieties linked via methylene linking groups to form oligomers containing a total of 4-35 aromatic rings.

[0039] The porous liquids of the present invention have been found to be useful in the purification and/or separation of fluids as it has been found that certain materials preferentially bind to the liquid allowing the liquid to be used in purification and separation applications.

[0040] In yet a further aspect the present invention provides a method of removing a contaminant from a fluid, the method comprising: (a) contacting a fluid containing a contaminant with a porous liquid of the invention under conditions to allow the liquid to absorb the contaminant; and

(b) separating the fluid from the porous liquid to produce a liquid with enriched contaminant levels and a fluid with depleted contaminant levels.

[0041] In certain embodiments the fluid is a liquid. In certain embodiments the fluid is a gas.

[0042] In principle the method can be used to remove any contaminant from a fluid where the contaminant has a greater affinity for the porous liquid than the fluid does. In certain embodiments the contaminant is selected from the group consisting of carbon dioxide, sulfur dioxide and trioxide, nitrogen oxides, hydrogen sulphide or an organic species. In one preferred embodiment the contaminant is carbon dioxide.

[0043] In yet a further aspect the present invention provides a method of of removing CO2 from a fluid, the method comprising:

(a) contacting a fluid containing CO2 with a porous liquid of the invention under conditions to allow the porous liquid to absorb the CO2; and (b) separating the fluid from the porous liquid to produce a liquid with enriched CO2 levels and a fluid with depleted CO2 levels.

Brief Description of Drawings

[0044] The present invention will now be described with reference to the figures of the accompanying drawings, which illustrate particular preferred embodiments of the present invention, wherein:

[0045] Figure 1 shows the change in infrared adsorption spectra for a porous liquid of the invention, pDCX and polystyrene and toluene after exposure to supercritical CO2. Identified peak is characteristic of adsorbed CO2. [0046] Figure 2 shows differential Scanning Calorimetry (DSC) results showing (2a) the cooling and (2b) heating temperature cycles of 1 , 1 A, 1 B, 1 C and pDCX, as well as two polystyrene standards as a melt-able polymer control, whilst (2c) shows Thermal Gravimetric Analysis (TGA) of 1 , 1 A, 1 B, 1 C, 1 D, 1 E, 1 F. [0047] Figure 3 shows molecular weights of 1 , 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, and pDCX by Gel Permeation Chromatography. Molecular weights presented are based on THF-soluble fraction of products after filtration (0.2 pm); except for 1 F and pDCX, which are insoluble in THF.

[0048] Figure 4 shows Nitrogen adsorption isotherms of (4a) pDCx, 1 E and 1 F, (4b) 1 B, 1 C, 1 D and 1 E and (4c) 1 , 1 A and 1 B. The three graphs were shown to highlight the similar isotherm shapes of, 1 A, 1 B, 1 C, 1 D, 1 E, 1 F, albeit at greatly reduced scales.

[0049] Figure 5 shows Carbon dioxide adsorption isotherms for 1 , 1 A, 1 B, 1 C, 1 D, 1 E, 1 F and pDCX at (5a) 273K and (5b) 298K. 1 , and V1 A-C show negligible CO2 uptake at atmospheric pressure.

[0050] Figure 6 shows High pressure carbon dioxide isotherms at 0 °C, 25 °C, 50 °C, 80°C, and 100 °C for 1 (6a) and high pressure methane isotherms at 25 °C, and 50 °C for 1 (6b). High pressure carbon dioxide isotherms at 0 °C, 25 °C, 50 °C, 80°C, and 100 °C for pDCX (6c) and high pressure methane isotherms at 25 °C, and 50 °C for pDCX (6d).

[0051] Figure 7 shows High pressure isotherms CO2/CH4 for (7A) 1 and (7b) pDCX at 25 °C and 50 °C.

[0052] Figure 8 shows Calculated composition of aromatic ring functional groups)from ¹ H NMR spectra of 1 , 1 A, 1 B, 1 C, 1 D, 1 E, Ratios were determined from peak integral ratios after normalizing to the toluene monomer’s Ar-CH3) peak; which is excluded from crosslinking calculations in the above plot. 1 E is highlighted red as an outlier as NMR peak integrals indicate the 1 E was incompletely dissolved in tetrachloroethane(d2). 1 F and pDCX did not dissolve in tetrachloroethane(d2). [0053] Figure 9 shows a process flow drawing of a preferred embodiment of the method of the invention.

Detailed Description

[0054] In this specification a number of terms are used that are well known to a skilled addressee. Nevertheless, for the purposes of clarity, a number of terms will be defined.

[0055] Throughout the description and the claims of this specification the word “comprise” and variations of the word, such as“comprising” and“comprises” is not intended to exclude other additives, components, integers or steps. [0056] The term“oligomer” refers to a compound that is intermediate between a monomer and a polymer normally having a specified number of units derived from the same base compound or compounds typically having between 4 and a hundred units.

[0057] The term“porous liquid” refers to a liquid which contains intrinsic (intra molecular) porosity and/or cavities within the liquid state material. The term includes those liquids where the intrinsic porosity only occurs under certain conditions and therefore includes liquids that exhibit induced intrinsic porosity.

[0058] The term“aromatic” is generally used to describe molecules that contain a cyclic (ring shaped) planar (flat) portion that contains a ring of resonance bonds that exhibits more stability than other geometric or connective arrangements with the same set of atoms.

[0059] An aromatic compound contains a set of covalently bound atoms with the following specific characteristics: (1 ) A delocalised conjugated p system, most commonly an arrangement of alternating single and double bonds, (2) a coplanar structure, with all the contributing atoms in the same plane, (3) the contributing atoms arranged in one or more rings and (4) the structure having a number of p delocalized electrons that is even but not a multiple of 4. That is, the structure contains 4n+2 TT- electrons, where n is an integer (Huckels rule).

[0060] The term fluid is used herein to refer to substances that continually deform under applied shear and include liquids and gases. Fluid separation includes separation of two gases, separation of two liquids, separation of a liquid and a gas and separation of a fluid from a solid.

[0061] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

Porous Liquids of the invention

[0062] As stated above the applicants of the present invention have developed a class of porous liquid materials that may be classified as porous liquids as they exhibit induced porosity under pressure. The porous liquid materials of the present invention comprise a porous liquid comprising one or more oligomers, each oligomer containing from 4 to 35 aromatic residues; the aromatic residues in each oligomer being connected via a bond or a linking group, wherein the linking group is a methylene (- CH2-) group; and further wherein each aromatic residue in the oligomer is independently a residue of the formula:

[0063] wherein each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group; [0064] each B represents a bond to another aromatic moiety within the compound or a bond to a linking group;

[0065] n is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5;

[0066] m is an integer selected from the group consisting of 0,1 , 2, 3, 4, and 5; [0067] o is an integer selected from the group consisting of 1 , 2, 3, 4 and 5;

[0068] wherein the sum of n+m+o is 6.

[0069] The porous liquid materials of the invention may contain a single oligomer, or they may contain a number of oligomers as components of the liquid material. In one embodiment the porous liquid contains a single oligomer. In one embodiment the liquid contains at least two oligomers. In one embodiment the liquid contains at least three oligomers. In one embodiment the liquid contains at least four oligomers. In one embodiment the liquid contains at least 5 oligomers. In one embodiment the liquid contains at least six oligomers. In one embodiment the liquid contains at least seven oligomers. As will be appreciated by a skilled worker in the art the number of oligomers present in the porous liquid material will be determined, at least in part by the process of synthesis of the liquid.

[0070] As stated previously the oligomer(s) contained in the porous liquid of the present invention contrast to many porous liquids currently published which contain ordered caged structures. In contrast the oligomers of the present invention are not ordered to form a specific caged structure or any particular structural shape. They can be described as optionally substituted phenyl moieties linked via methylene linking groups to form oligomers containing a total of 4-35 aromatic rings. The optionally substituted phenyl groups in any given oligomer may be the same or different depending upon the starting materials used in the reaction to produce the oligomer. In circumstances where the porous liquid contains more than one oligomer it is likely that they may be very different in gross structure.

[0071] The porous liquids of the invention contain one or more oligomers, each oligomer containing from 4 to 35 aromatic residues. In each oligomer each aromatic residue is connected to at least one other aromatic residue either directly via a bond or through a linking group. As will be readily appreciate in each oligomer it is likely that certain of the aromatic residues will only be connected to one other aromatic residue within the oligomer whereas other aromatic residues will be connected to more than one other aromatic residue within the oligomer. In addition as would be appreciated an aromatic residue may make multiple connections to another aromatic residue. [0072] In describing the oligomer therefore it is the average number of connections that each aromatic residue in the oligomer makes that is more meaningful than the number of aromatic residues that any individual aromatic residue is connected to. In one embodiment each aromatic residue in the oligomer has on average between 1.1 and 3 connections to other aromatic residues in the oligomer. In one embodiment each aromatic residue in the oligomer has on average between 1.2 and 2.5 connections to other aromatic residues in the oligomer. In one embodiment each aromatic residue in the oligomer has on average between 1.2 and 2 connections to other aromatic residues in the oligomer. In one embodiment each aromatic residue in the oligomer has on average between 1.4 and 1.8 connections to other aromatic residues in the oligomer.

[0073] In the oligomers contained in the porous liquids of the present invention each oligomer contains from 4 to 35 residues. In some embodiments each oligomer contains from 4 to 15 aromatic residues. In another embodiment each oligomer contains from 4 to 10 residues. In yet an even further embodiment each oligomer contains from 4 to 8 aromatic residues. In yet an even further embodiment each oligomer contains from 4 to 6 aromatic residues.

[0074] In some embodiments each oligomer contains from 8 to 35 residues. In some embodiments each oligomer contains from 8 to 15 aromatic residues. [0075] The nature of the aromatic residues in the oligomers contained in the porous liquids of the invention will vary depending upon the synthetic methodology used to produce the liquids. In some embodiments all aromatic residues within an oligomer will be derived from the same base material and as such all aromatic residues within the oligomer will have the same base structure (although the substituent pattern may vary). In some embodiments the aromatic residues in an oligomer may be derived from more than one base material and as such the aromatic residues in an oligomer may be different.

[0076] Each aromatic residue in the oligomer is independently a residue of the formula (1 ):

Formula (1 )

[0077] wherein each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group;

[0078] each B represents a bond to another aromatic moiety within the oligomer or a bond to a linking group;

[0079] n is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5; [0080] m is an integer selected from the group consisting of 0,1 , 2, 3, 4, and 5; [0081] o is an integer selected from the group consisting of 1 , 2, 3, 4 and 5;

[0082] wherein the sum of n+m+o is 6.

[0083] In another embodiment each aromatic residue in the oligomer is independently a residue of the formula (2):

Formula (2) [0084] wherein R is selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group;

[0085] each B represents a bond to another aromatic moiety within the oligomer or a bond to a linking group; [0086] ma is an integer selected from the group consisting of 0, 1 , 2, 3, and 4;

[0087] oa is an integer selected from the group consisting of 1 , 2, 3, 4 and 5;

[0088] wherein the sum of ma + oa is 5.

[0089] In the compounds of formula 1 and 2 each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group. In one embodiment each R is an alkyl group. In one embodiment each R is an alkenyl group. In one embodiment each R is an alkynyl group.

[0090] In one embodiment each R is an alkyl group. In one embodiment each R is Ci to Ci2 alkyl. In one embodiment R is methyl. In one embodiment R is ethyl. In one embodiment R is n-propyl. In one embodiment R is 2-propyl. In one embodiment R is n-butyl. In one embodiment R is sec-butyl. In one embodiment R is t-butyl. In one embodiment R is pentyl. In one embodiment R is hexyl. In one embodiment R is dodecyl.

[0091] In one embodiment R is selected from the group consisting of -CH3, - C(CH ₃ )3, -CH2CH3, -(CH )2CH ₃ , -(CH2) ₃ CH3, -(CH2) ₃ CH3, -(CH2) ₅ CH3, -(CH2) ₆ CH3, - (CH )7CH ₃ , -(CH )8CH3, -(CH )9CH3, -(CH )IOCH3, and -(OH )iiOH ₃ . It is preferred that

R is -CHs.

[0092] The aromatic residues in the oligomers are connected to each other either via a bond or by a methylene linking group.

[0093] In one embodiment the oligomer comprises from 4 to 35 optionally substituted phenyl residues, each phenyl residue being covalently bonded to one or more optionally substituted phenyl residues in the oligomer by at least one methylene linking group. [0094] In these embodiments each optionally substituted phenyl is covalently linked to one or more optionally substituted phenyl by bridging methylene groups between adjacent optionally substituted phenyl. In one set of embodiments the methylene bridging groups form covalent links between two adjacent phenyl groups to form a six membered carbocyclic ring that is attached to the phenyl rings. The methylene bridge may provide a six membered ring between adjacent aryl groups to provide, for example, 9,10-dihydroanthracene structures.

[0095] The oligomers contained in the porous liquid of the present invention may vary widely in their weight depending upon the number and nature of the aromatic groups. In general the oligomers have a molecular weight in the range of from 300 to 6000. In one embodiment the oligomers have a molecular weight of from 350 to 4000. In one embodiment the oligomers have a molecular weight of from 400 to 2000.

Synthesis of Porous liquids of the invention

[0096] As would be readily apparent to a skilled worker in the art from the structure of the oligomers contained in the porous liquids of the present invention may at least in theory be produced using a wide variety of synthetic techniques.

[0097] Nevertheless, in one embodiment the method involves the use of a Friedel Crafts alkylation reaction to insert the linking group between the aromatic groups.

[0098] Accordingly the present invention provides a method of preparing a porous liquid of the invention the method comprising, A method of preparing a porous liquid comprising one or more oligomers, each oligomer containing from 4 to 35 aromatic residues; the aromatic residues in each oligomer being connected via a bond or a linking group, wherein the linking group is a methylene (-CH2-) group; and further wherein each aromatic residue in the oligomer is independently a residue of the formula:

[0099] wherein each R is independently selected from the group consisting of an alkyl group, an alkenyl group, and an alkynyl group;

[0100] each B represents a bond to another aromatic moiety within the compound or a bond to a linking group;

[0101] n is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5; [0102] m is an integer selected from the group consisting of 0,1 , 2, 3, 4, and 5; [0103] o is an integer selected from the group consisting of 1 , 2, 3, 4 and 5;

[0104] wherein the sum of n+m+o is 6;

[0105] the method comprising reacting an aromatic compound of the formula:

[0106] wherein each R is independently selected from the group consisting of alkyl, alkenyl, and alkynyl;

[0107] p is an integer selected from the group consisting of 0, 1 , 2, 3, 4, and 5; [0108] q is an integer selected from the group consisting of 1 , 2, 3, 4, 5 and 6; [0109] wherein the sum of p+q is 6;

[0110] with an oxygen containing linking agent in the presence of a lewis acid; wherein the mole ratio of oxygen containing linking agent to aromatic compound is less than 10. [0111] The applicants have found that if the ratio of linking agent to aromatic compound exceeds this ratio then the reaction tends to continue and rather than stopping at the stage where a liquid is produced the reaction tends to continue and form polymeric solids which will useful in other applications are not desired as they are solids rather than liquids. As the ratio reduces there is greater control of the reaction and higher levels of liquids are produced.

[0112] There are a wide range of aromatic compounds that may be used in the synthetic method of the present invention.

[0113] In one embodiment the aromatic compound is a compound of the formula 4:

Formula 4.

[0114] wherein R is selected from the group consisting of alkyl, alkenyl, and alkynyl.

[0115] Examples of particularly suitable aromatic compounds for use in the methods of the present invention include the following: [0116] Whilst in general a single aromatic chemical is used in the formation of the porous liquid of the invention, in principle there is no reason why more than one could not be used. [0117] The reaction may utilize a number of an oxygen containing linking agents with the only requirement being that the oxygen containing linking agent is suitable for linking two aromatic compounds in a linking reaction. Examples of suitable linking agents include dimethoxy methane, chloromethoxy methane, trimethoxy methane, and trisopropyloxy methane.

[0118] In one embodiment the linking agent is dimethoxy methane. In one embodiment the linking agent is chloromethoxy methane. In one embodiment the linking agent is trimethoxy methane. In one embodiment the linking agent is trisopropyl methane.

[0119] The amount of oxygen containing linking agent may vary although as stated previously the applicants have found that in order to ensure that the reaction terminates (to produce a liquid) rather than propagating (to produce a solid) it is necessary that the ratio of oxygen containing linking agent to aromatic compound be less than 10.0 on a mol/mol basis. In one embodiment the mole ratio of oxygen containing linking agent to aromatic compound is less than 5. In one embodiment the mole ratio of oxygen containing linking agent to aromatic compound is less than 4. In one embodiment the mole ratio of oxygen containing linking agent to aromatic compound is less than 3. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 3:1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 2.8:1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 2.6:1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 2.4:1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 2.2:1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is from 1 :1 to 2.1 :1 on a mol/mol basis. In one embodiment the ratio of oxygen containing linking agent to aromatic compound is about 2:1 on a mol/mol basis.

[0120] The reaction is carried out in the presence of a Lewis acid. In one embodiment the Lewis acid may be selected from the group consisting of AIBr3, AlC , GaCb, FeCb, SbCIs, ZrC , SnCL, BCb, BF3 and SbC .Examples of particularly suitable Lewis acids include AICI3 and FeCb. In one embodiment the Lewis acid is AICI3. In one embodiment the Lewis acid is FeCb. The amount of Lewis acid used may vary considerably as would be well appreciated by a skilled addressee but is typically from 0.001 mol % to 0.6 mol %.

[0121] The reaction may be carried out in any non-interfering solvent as would be appreciated by a skilled worker in the art. In order to be considered non-interfering a solvent has to be anhydrous (as water will quench the reactive intermediate) and not react with the reagents under the reaction conditions utilized for the reaction. [0122] The reaction may be carried out at any suitable temperature at which the solvent is a liquid. In practice, however, the reaction is carried out at a temperature of from 20°C to 100°C depending upon the solvent system used. In general a suitable temperature is from 20°C to 40°C. In one embodiment the reaction is carried out at from 18°C to 25°C. In one embodiment the reaction is carried out at 25°C. [0123] The time taken for the reaction may vary greatly and will depend upon the nature of the reagents, the catalyst used and the temperature of the reaction. Nevertheless the reaction typically takes from 10 mins to 24 hours, more commonly from 1 hour to 12 hours. A skilled worker in the field will readily be able to determine a suitable time of reaction once the other process parameters have been determined. [0124] Upon completion of the reaction the reaction medium is quenched and excess Lewis acid removed. This may be achieved in a number of ways but is generally done by addition of methanol and/or water followed by extraction until all aqueous extracts are clear indicating that all Lewis acid has been removed. Once Lewis acid has been removed the material is further purified by removal of solvent and any unreacted starting materials typically using vacuum distillation.

Applications of the Porous liquids

[0125] The porous liquids of the present invention have been found to be useful in the purification and/or separation of fluids as it has been found that certain materials preferentially bind or have an affinity for the liquid allowing the liquid to be used in purification and separation applications.

[0126] Accordingly, the porous liquids of the present invention may be used in a range of separation processes including separation of fluids such as a mixture of gases, a liquid/gas mixture, a mixture of liquids, a mixture of a liquid and solute (which may be dissolved in the liquid), mixture of liquid and particulate solid dispersed in the liquid, a mixture of gas and particulate solid dispersed in the gas. All these applications rely on the materials to be separated having different affinities for the porous liquid of the invention thus allowing for the liquid to be used in their separation.

[0127] Apart from fluids in general, the porous liquid of the present invention can also advantageously find applications in various industrial gas separation processes. For example a porous liquid according to the invention can find application in processes for the pre-combustion capture of CO2 and N2, and they show potential applicability for the separation of CO2 from other gases particularly from flue gases. In a further example, a porous liquid according to the invention can find application in purification of natural gases.

[0128] Accordingly, the present invention provides a method of removing a contaminant from a fluid, the method comprising:

(a) contacting a fluid containing a contaminant with a porous liquid of the invention under conditions to allow the liquid to absorb the contaminant; and

(b) separating the fluid from the porous liquid to produce a liquid with enriched contaminant levels and a fluid with depleted contaminant levels.

[0129] As stated above the method of the present invention can be used to remove a contaminant from any fluid including liquids and gases. In certain embodiments the fluid is a liquid. In certain embodiments the fluid is a gas. In certain embodiments the fluid is a flue gas. In certain embodiments the fluid is natural gas.

[0130] In principle the method can be used to remove any contaminant from a fluid where the contaminant has a greater affinity for the porous liquid than the fluid does. In certain embodiments the contaminant is selected from the group consisting of carbon dioxide, sulfur dioxide and trioxide, nitrogen oxides, hydrogen sulfide. In one preferred embodiment the contaminant is carbon dioxide.

[0131] As stated above in order for the method of the invention to be practiced all that is required is that the contaminant has a greater affinity for the porous liquid than the fluid. This allows the contaminant to be preferentially taken into the porous liquid of the invention from the fluid and leads to the fluid having depleted contaminant levels.

[0132] The first step in the method of the present invention is to contact a fluid containing a contaminant with a porous liquid of the invention under conditions to allow the liquid to absorb the contaminant. This can be done in any way well known in the art and the exact method chosen will depend upon the nature of the fluid to be treated. In one embodiment the contacting occurs at elevated pressure. In one embodiment the pressure is greater than 10 bar. In one embodiment the pressure is greater than 20 bar. In one embodiment the pressure is greater than 30 bar. In one embodiment the pressure is greater than 40 bar.

[0133] For example in circumstances where the fluid to be treated is a gas it is typical that the gas is passed through the porous liquid to allow the contaminant to pass from the fluid to the liquid. This can be done on a quiet rudimentary basis by such simple means as bubbling a gas through a stirred or agitated batch of the porous liquid of the invention which will allow the contaminant to pass from the fluid to the liquid.

[0134] As will be appreciated, however on an industrial scale such processes are typically carried out using counter current separation technology. In processes of this type are typically carried out using an absorption column with a gas containing the contaminant entering the absorption column at the bottom and a porous liquid of the invention being introduced at the top of the column. The process may be carried out using absorption columns well known in the art with parameters such as column length, column size and the like being readily determined by a skilled process engineer. [0135] A schematic diagram of the process is shown in figure 9. As can be seen the gas to be treated enters the bottom of the absorber column and a porous liquid of the invention enters the absorber column at the top of the column. The two materials run counter current to each other and as they pass the contaminant passes from the gas to the porous liquid of the invention. As will be appreciated the ability of the contaminant to completely pass from the gas to the porous liquid will depend upon a number of factors.

[0136] The absorber column has an outlet for the treated gas (the fluid with depleted contaminant levels) at the top of the absorber column and an outlet for the porous liquid (the liquid with enriched contaminant levels) at the bottom of the column. As will be appreciated in this embodiment the treated gas and the porous liquid are separated based on their relative densities. As will also be appreciated a similar principle may be used where the fluid to be treated is a liquid as long as the liquid containing the contaminant has a different density to the porous liquid of the invention.

[0137] The porous liquid of the invention that is enriched with contaminant is then typically transported to a desorber column whereby contaminant may be removed from the liquid. This may be carried out in a number of ways but is typically achieved by the application of heat as the absorbed contaminant has greater volatility than the porous liquid of the invention. The contaminant will thereby exit the desorber column as a gas (at the top of the column and the stripped porous liquid then exits the desorption column at the base. The regenerated porous liquid may then be recycled to the absorber column.

[0138] Accordingly in a preferred embodiment the invention provides a process for treating a feed gas stream comprising a contaminant, the process comprising the steps of (a) providing a feed gas stream containing a contaminant; (b) providing an absorption column and a supply of substantially pure porous liquid of the invention; (c) introducing porous liquid of the invention from said supply thereof and feed gas stream into said absorption column (d) contacting said feed gas stream in said absorption column with a counter-current flow of porous liquid of the invention in an amount sufficient to absorb and entrain substantially all of said contaminant present in the feed gas stream (e) withdrawing from said absorption column a substantially contaminant free residual gas stream and (f) withdrawing from said absorption column a porous liquid of the invention containing the absorbed contaminant.

[0139] In one preferred form of this embodiment the porous liquid containing the absorbed contaminant withdrawn in step (f) is subjected to a regeneration step to remove contaminant and produce regenerated porous liquid. In one embodiment the regenerated porous liquid is recycled to the absorber column.

[0140] The methods of the invention have been found to be particularly suitable for the removal of carbon dioxide from fluids such as from liquids and gases and in particular from gases such as flue gases or natural gas.

[0141] In yet a further aspect the present invention provides a method of removing CO2 from a fluid, the method comprising:

(a) contacting a fluid containing CO2 with a porous liquid of the invention under conditions to allow the liquid to absorb the CO2; and (b) separating the fluid from the porous liquid to produce a liquid with enriched CO2 levels and a fluid with depleted CO2 levels.

[0142] The invention will now be illustrated by way of examples; however, the examples are not to be construed as being limitations thereto. Additional compounds, other than those described below, may be prepared using methods and synthetic protocols or appropriate variations or modifications thereof, as described herein.

Examples

[0143] All raw materials were purchased from commercial sources as follows: Toluene, Merck, analysis; xylene (mixed), Alfa Aesar, 97 %; mesitylene, Sigma Aldrich, 98 %; ethyl benzene, UniLab, 95 %; propyl-benzene, Sigma Aldrich, 98 %; butyl-benzene, Sigma Aldrich, 99 %; pentyl-benzene, Sigma Aldrich, 99 %; hexyl- benzene, TCI, 98 %; dodecyl-benzene, TCI, 98 %; tert-bytl-benzene, Sigma Aldrich, 99 %; and a,a’-dichloro-para-xylene, Sigma Aldrich, 99 % were used as received. [0144] Reagents (dimethoxymethane or formyl-dialdehyde (FDA), 99+ %; and anhydrous Iron chloride (Fe ^m Cl3), 97 %) were purchased from Sigma Alridch and used as received. Solvents dichloromethane, dichloroethane, methanol, and diethyl ether (dried) were purchased from Merck and used as received. All water used was sourced from the building’s installed RO water supply.

[0145] pDCX was prepared by the iron chloride catalyzed hyper-crosslinking of a,a’-dichloro-para-xylene in dichloroethane as described by Wood and co-workers (C. H. Lau, X. Mulet, K. Konstas, C. M. Doherty, M.-A. Sani, F. Separovic, M. R. Hill and C. D. Wood, Angew. Chem. Int. Ed, 2016, 55, 1998-2001.) Polystyrene Standards (1 kDa - narrow distribution, Scientific Polymer Products; and 35 kDa, Sigma Aldrich) were used as received.

Example 1 - General Synthetic Procedure

[0146] The general synthetic procedure is illustrated with reference to the figure below using a substituted phenyl group as the aromatic group, and dimethoxy methane as the linking agent.

o vent

[0147] In general the required amount of aromatic compound (30 mmol), Lewis acid (iron chloride (2.4 g)), and dimethoxy methane (5.3 ml) were dissolved in a Schott Bottle of solvent (dichloromethane (90 ml)) and left to react overnight. After forming a burgundy/brown solution, unreacted Lewis acid was removed by successive additions of methanol and water, until the decanted aqueous layer became colourless. Solvent and any unreacted starting materials were then removed by gradual heating under vacuum to produce the liquid composition.

Example 2 - Synthesis of liquids of the invention

[0148] Following the general procedure outlined in example 1 using a variety of starting material organic compounds the liquid products shown in table 1 were produced. Table 1 - Liquids of the invention

Note: Mn, Mw and PDI were determined by GPC

Example 3 - Uptake of CO2 by the liquid of the invention

[0149] In order to demonstrate the ability of compounds of the invention to absorb gases such as C02 a comparison test was carried out to determine the ability of a sample liquid of the invention to the known absorbent pDCX. The tested liquid was liquid 1 from example 2.

[0150] Qualitative uptake of carbon dioxide can be compared between liquids by the characteristic infrared adsorption of CO2 at -2335 cnr ¹ , as described by Greenway and co-workers. (R. L. Greenaway, D. Holden, E. G. B. Eden, A. Stephenson, C. W. Yong, M. J. Bennison, T. Hasell, M. E. Briggs, S. L. James and A. I. Cooper, Chem. Sci., 2017). In this work, infrared spectral analysis of carbon dioxide uptake was measured after exposure to supercritical CO2 to ensure saturation. Samples of 1 , pDCX, and polystyrene controls were loaded into small vials, transferred to a high pressure cell (with a sapphire window), and then left overnight under supercritical carbon dioxide (35°C, 70-80 Bar). Toluene was saturated with carbon dioxide bubbled through a sintered frit for 1 hr. After saturation, all samples were sealed and immediately analyzed using a Thermo Scientific NICOLET 6700 FT- IR under atmospheric conditions. The results are shown in figure 1.

[0151] As can be seen liquid 1 was found to retain carbon dioxide, whereas adsorbed gas was lost from the highly porous pDCX after pressure release. Solid polystyrene (PS) controls of similar and higher MW to 1 also contained significant CO2 after saturation, as gas becomes trapped in the solid polymer’s interstitial voids after partial dissolution in SCO2.

Example 4 - Comparison of liquid 1 to products exposed to forcing linking conditions

[0152] Further crosslinked analogs or derivatives of 1 were prepared by reacting 10mmol (~1 g) of 1 with increasing quantities of Catalyst and dimethoxy methane in DCM (9 ml), and washing as described above as shown in table 2.

Table 2 - Reaction conditions and comparative products

[0153] The resulting series of materials (1 , 1A, 1 B, 1C, 1 D 1 E and 1 F) in order of additional crosslinking by FDA-knitting), transited from a liquid to continuous solid, fine powder, and finally, to insoluble granules; similar in appearance to pDCX. [0154] Differential Scanning Calorimetry (DSC) was undertaken using a Mettler

Toledo Differential Scanning Calorimeter. Samples were encapsulated in pierced aluminium pans, and cycled between -60 °C and 160 °C three times at 10 °C/min under nitrogen. Thermal Gravimetric Analysis (TGA) was undertaken using a Mettler Toledo TGA 2 STARe System thermogravimetric analyzer from 25 °C to 1000 °C at 5 °C/min under 50 ml/min nitrogen.

[0155] As can be seen for figures 2a, 2b and 2c Solid to liquid phase transitions were observed for 1 (T _c - 42 °C) and the three variants with the least additional crosslinking; 1 A (Tc, onset! 16 °C ) ,1 B (Tc onset! 28 °C) and 1 C (Tc onset! 75 °C).

[0156] Compared to short and medium chain polystyrene, these materials displayed very broad (20-30 °C range) melting transitions. Like pDCX, the higher molecular weight 1 D, 1 -E, and 1 -F did not undergo a phase change below 160°C. 1 has a molecular weight of 570 Da, roughly equivalent to ~6 monomer units) that increased exponentially with additional crosslinking. NMR ( ¹ H) spectra show a gradual increase methylene bridges (Ar-Chte-Ar) with crosslinking, replacing the monomer’s aromatic protons (Ar-H). [0157] The steady increase in thermal stability confirms that secondary cross- linking reaction increased both the molecular weight and the degree of crosslinking of 1.

Example 5 - Determination of molecular weight of linked products [0158] The products produced in example 4 were subjected to gel permeation chromatography. Gel Permeation Chromatography (GPC) was performed by a Waters Alliance e2695 liquid chromatograph equipped with three mixed C and one mixed E PLgel columns (Polymer Laboratories) and a Waters 2414 differential refractometer using a tetrahydrofuran (THF) eluent at 30 °C (flow rate: 1 mL min ^-1 ). Number (Mn) and weight-average (Mw) molar masses were evaluated using Waters Empower Pro software. Molar masses are reported as PSt equivalents, after calibrating GPC columns with low dispersity polystyrene (PSt) standards (Polymer Laboratories). A third order polynomial was used to fit the log Mp vs time calibration curve, which was linear across the molar mass range 2 x 10 ² to 2 x 10 ⁶ gmol ¹ . Samples were filtered using a 0.47 pm and 0.2 pm cartridge filters before analysis. The results are shown in Table 3.

Table 3 - Summary of GPC results for products of example 4.

[0159] As can be seen with reference to figure 3 the molecular weight increases relatively rapidly in this series.

Example 6 - Low Pressure Gas sorption [0160] After careful testing to confirm the prepared materials in example 4 (ie 1 and 1 A to 1 F) would not vaporize under high temperature and vacuum conditions, carbon dioxide (273 K, 298 K) and nitrogen (77 K, 273 K) adsorption isotherms were measured using an Micromeritics ASAP 2420. Samples were activated under vacuum at 130 °C overnight prior to analysis. Langmuir and BET surface areas were calculated using Micromeritics instrument software from collected nitrogen (77 K) isotherms. The BET and Langmuir surface areas were calculated and shown in Table 4.

Table 4 - BET and Langmuir surface areas of products of example 4 and pDCX.

[0161] As can be seen in figure 4a to 4c the materials had negligible nitrogen uptake.

[0162] The carbon dioxide adsorption isotherms for 1 and 1 A to 1 F and pDCX at (i) 273K and (ii) 298K. 1 , and 1 A-C show negligible CO2 uptake at atmospheric pressure. Despite the large apparent uptake of carbon dioxide at high pressure, 1 displayed relatively poor CO2 capacity at low pressure. However, unlike nitrogen adsorption, CO2 capacity increased rapidly with degree of crosslinking; with 1 F showing 40% of pDCX’s CO2 capacity from only 5% of the surface area. Example 7 - Carbon dioxide and methane isotherms of 1

[0163] Despite significant retention after exposure to supercritical CO2, 1 showed little uptake during low pressure experiments. Ts unusual sorption behavior was thus further investigated by comparing carbon dioxide and methane high pressure isotherms, representative of high pressure natural gas purification. [0164] High pressure isotherms were recorded using a Setaram PCTPro.

Samples were analyzed in the order: CO2 (298 K), CO2 (323 K), CO2 (353 K), CO2 (373 K), CO2 (273 K), CH (298 K) and CH ₄ (323 K), with free volume (He) recalculated between each test. The CO2 (298K) isotherm was then repeated to confirm samples were not affected by the isotherm regime. Temperature was controlled using an ice/oil bath as appropriate. Negative uptakes at high pressure and temperature were investigated by comparing to glass beads and empty samples.

[0165] After running a number of high pressure isotherms on glass beads (1 mm) and with an empty vessel, it was determined that negative uptakes are an artifact of the instrument analysis methods, occurring in cases of negligible absorbance, where vessel temperature differs significantly from that of the and instrument reservoir (298 K). the results are shown in figures 6 and 7. [0166] Although adsorbents are normally reported in specific uptake per unit mass (mmol/g); here we report high pressure adsorption on a volume (STP) basis, due to the effect the considerable difference adsorbent density (1 1.05 g/cm ³ vs. pDCX 0.21 g/cm ³ ) would have on the column size, a crucial factor for this separation process.

[0167] High pressure gas isotherms of 1 and pDCX displayed a large deviation for the gases tested, particularly in terms of absolute capacity and isotherm shape (Figure 7). Characteristic of microporosity, pDCX exhibits a type I isotherm that plateaus at high pressure. On the other hand, 1 showed a Type III isotherm, a shape usually associated to poor guest-surface interaction, and an unusual observation given Ts near-identical chemical structure to pDCX. As expected, pDCX showed good uptakes for both gases, with a greater capacity for carbon dioxide than for methane at 298K. At higher temperatures, adsorption of both gases in pDCX decreased, but considerably more so for CO2 (Figure 7b) .By comparison, volumetric adsorption of carbon dioxide (298 K) in 1 increased exponentially with pressure, reaching 35% of the capacity of pDCX at 46 Bar (1.08 mmol/cm ³ vs. 3.18 mmol/cm ³ , respectively.). At higher temperatures for CO2, and methane at both temperatures, gas adsorption by 1 was effectively at all measured pressures.

[0168] Importantly, this represents an almost infinite selectivity for CO2 over CH4 for 1 , a stark improvement over pDCX (CC>2:CH4 = 2.7) and other microporous carbon materials (C02:CH4 = 1.4 - 2.6) at 30 Bar. It should also be highlighted that these results indicate 1 can be almost completely regenerated at 50 °C; a temperature change of just 22 °C, and a significant reduction to the temperature (100-150 °C), and heating duty, required for aqueous amine regeneration.

Example 8 - Determination of molecular interconnectivity

[0169] In order to determine the degree of interconnectivity of the materials in example 4 proton Nuclear Magnetic Resonance ( ¹ H NMR) spectra were collected using a Bruker Av400X NMR, using tetrachloroethane(d2) (TCE). Deuterated chloroform and dichloromethane could not be used due to solvent peak overlap. NMR results from 1 F are not plotted due to the misleading data trends caused poor solubility. pDCX was not attempted due its insolubility in TCE. Peak integrations for each sample are normalized to the monomer’s three aromatic methyl protons (Ar- CH3) which are unchanged by the crosslinking reaction. The degree of crosslinking is thus the decrease in aromatic protons (Ar-H) and increase in methylene bridges (Ar- CH 2-Ar) per monomer unit. Chemical shifts between 1.84 and 2.73 were assigned to the methyl protons, chemical shifts between 3.5 and 4.21 were assigned to the bridging methylene group protons and chemical shifts between 6.49 and 7.49 were assigned to the aromatic protons. The results are shown in table 5.

Table 5 - Relative intensities of different samples

[0170] The results of the nmr studies are displayed graphically in figure 8. Ratios were determined from peak integral ratios after normalizing to the toluene monomer’s Ar-CH3) peak; which is excluded from crosslinking calculations in the above plot. As can be seen from figure 8 NMR ( ¹ H) spectra show a gradual increase in methylene bridges (Ar-Chte-Ar) with crosslinking, replacing the monomer’s aromatic protons (Ar- H). Interestingly, after normalizing to Ar-CH3 intensity, the sum of aromatic ring substituents decrease over the series. This additional degree of crosslinking is attributed to the Scholl coupling of phenyl groups; a reaction also catalyzed by the Friedel-Crafts catalyst.

Example 9 - Positron Annihilation Lifetime Spectroscopy (PALS)

[0171] PALS is a well-known characterisation technique used to investigate the free volume within condensed matter. The lifetime of the positrons has been shown to correlate with the average size and relative number of pores or free volume elements within the sample.

[0172] The porous liquid was degassed prior to analysis and run under the flow of different gas atmospheres (CO2 and N2). The positron source ( ²² NaCI) was sealed in a Mylar envelope and placed in the centre of the liquid sample. A minimum of five files with 1 x 10 ⁶ integrated counts per file was collected. The spectra was analysed using LT_v9 software and fitted to three lifetimes and a source component (1.677 ns and 2.6%). The first component was fixed to 125 ps due to para-positronium annihilation of a bound state between the positron and an electron of opposite spin. The second component was attributed to free annihilation with electrons (-380 ps) and the third lifetime was attributed to ortho-positronium formation with the positron forming a bound state with an electron of the same spin. This long lifetime (up to 142 ns) was used to further calculate the average free-volume diameter within the sample using the Tao-Eldrup equation. The results are shown in Table 6.

Table 6 - Positron Annihilation Lifetime Spectroscopy (PALS) analysis of 1 under various environmental conditions.

[0173] These results demonstrate that 1 does not contain significant permanent porosity under atmospheric nitrogen or carbon dioxide.

[0174] Finally, it will be appreciated that various modifications and variations of the methods and compositions of the invention described herein would be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention that is apparent to those skilled in the art are intended to be within the scope of the present invention.