TREATMENT OF FLUIDS

Abstract: Fluids are treated to remove undesirable chemical species such as sulphur by bringing the fluid into contact with an adsorbent (10) having a crystal structure, such as an SbSn intermetallic; neucleophilic polar heads (13) are attracted to defect sites (12) in the adsorbent surface.

Description: "Treatment of Fluids" INTRODUCTION Field ofthe Invention The invention relates to treatment of fluids to remove undesirable constituents, more particularly chemical species. Prior Art Discussion Such fluid treatment arises to a large extent in the hydrocarbon fuel processing industry, for example, reduction of sulphur in an oil refinery. One approach to such treatment is generally referred to as a hydrotteating process in which the feedstock is subjected to high temperatures and pressures. This approach involves a large energy input and equipment is expensive. A different approach is proposed in EP 254781 (Chevron) which involves contacting the feedstock with a sorbent having a metal such as sodium, potassium, barium or calcium. EP 332324 (ICI) proposes removal of hydrogen sulphide by passing the feedstock through a zinc oxide-containing absorbent. The absorbent may be regenerated using a water-containing gas stream. It appears that absorption as a treatment method suffers from the problems of being effective only for gaseous feedstreams, and of allowing a limited feedstream throughput. Therefore, the invention is directed towards achieving treatment of fluids in a simpler manner. SUMMARY OF THE INVENTION According to the invention, there is provided a method of treating a fluid having an undesirable chemical species, the method comprising the step of bringing the fluid into contact with a filter having a surface crystal structure to facihtate adsorption of undesireable chemical species ofthe fluid onto the filter. In one embodiment, the filter comprises defect sites on the surface adjacent electron- deficient atoms. This provides a very effective adsorption mechanism. In one embodiment, the filter comprises an intermetallic, and the intermetallic may contain Sb and Sn. In one embodiment, the fluid contains water. In one embodiment, the fluid is a liquid and is an emulsion, and preferably one of the emulsion phases is an electrolyte. Preferably the emulsifying agent is a surfactant. In one embodiment, the surfactant the surfactant is of the type which acts to reverse micelles contøining heterocyclic - containing groups so that these groups are orientated towards the outside. Preferably, the surfactant is of the type in which the hydrophobic group is the long chain and the hydrophihc group is a carboxylate. In another embodiment, a magnetic field is applied to the fluid as it is brought into contact with the filter. In the latter embodiment, an electrical potential may be applied to the filter. In one embodiment, the method comprises the further steps of rejuvenating the filter by washing with a water solution. In one embodiment, the fluid is a hydrocarbon oil feedstock. In one embodiment, viscosity is reduced. In one embodiment, turbidity is increased. The invention also provides a method of treating an emulsion in which one phase is an electrolyte, by bringing the emulsion into contact with an adsorbent having a surface crystal structure. Preferably, the adsorbent is an intermetaUic. In one embodiment the emulsifying agent is a surfactant. Preferably, the surfactant is of a type which acts to reverse micelles so that adsorbate species face outwardly. Preferably, the surfactant contains calcium. Preferably, the surfactant contains sodium. In one embodiment, the surfactant is of the type in which the hydrophobic group is the long chain and the hydrophilic group is a carboxylate. In one embodiment, electrical energy is applied to the adsorbent and the emulsion. The energy may be applied as a magnetic filed around the adsorbent. The energy may be applied as a direct voltage applied to the adsorbent. The applied voltage may be in me range 0.8 V to 2.0 V. According to another aspect, me invention provides a method of treating a liquid comprising the steps of forming an emulsion in which one phase is an electrolyte and the emulsifying agent is a surfactant which acts to reverse micelles so that heterocyclic-containing functions are oriented towards the outside, and bringing the emulsion into contact with an adsorbent. Preferably the adsorbent has a crystal structure. In one embodiment, the adsorbent comprises defect sites on its surface adjacent electron-deficient atoms. The invention also provides a method of desulphurising a hydrocarbon feedstream comprising the steps of bringing the feedstream into contact with an adsorbent having a surface crystal structure until sulphur species adsorb onto the adsorbent surface. Preferably, the adsorbent comprises defect sites on its surface adjacent electron- deficient atoms. In one embodiment, the adsorbent is an intermetallic. In another embodiment, the adsorbent is an SbSn intermetaUic. The invention also provides a fluid filter comprising having comprising having an adsorbent with surface crystal structure to facilitate adsorption of undesireable chemical species onto the filter when the fluid containing the adsorbate comes into contact with it. In one embodiment, the absorbent comprises defect sites on the surface at adjacent electron-deficient atoms. Preferably, the adsorbent is an intermetaUic. In another embodiment, the intermetallic is an SbSn intermetaUic. Preferably, the filter filter comprises means for applying electrical energy to enhance adsorption. DETAILED DESCRIPTION OF THE INVENTION Brief Description ofthe Drawings The invention wiU be more clearly understood from the foUowing description of some embodiments thereof, given by way of example only with reference to the accompanying drawings, in which: - Fig. 1 is a diagram showing reversal of an asphaltene miceUe in an adsorbate fluid; Fig. 2 is a diagram iUustrating sulphur adsorption; Fig. 3 shows scanning electron micrographs of SbSn filter samples sintered in 100% hydrogen atmospheres; Fig. 4 is an X-ray diffraction pattern of sintered SbSn powder; Fig. 5 is an optical micrograph ofthe surface of SbSn filters; Figs. 6 and 7 are cyclic voltammogram plots indicating reactions of a fluid with a filter; Fig. 8 is a diagram showing an experimental set-up for treatment of hydrocarbon liquids; and Figs. 9, 10, and 11 are plots indicating adsorption of inorganic Sulphur on an intermetaUic filter. Detailed Description ofthe Invention The invention provides filtration of fluids by adsorption of undesirable species of fluids onto a filter surface. The filtration medium material has a weU defined crystalline structure with surface cavities and defects generaUy in the nano-scale, 2nm to lOOnm. It has been found that, to be effectively treated, the fluid preferably has the foUowing properties:- (a) if a liquid, it is preferably an emulsion in which one phase is an electrolyte such as water containing smaU quantities of ionic salts for ionic conduction, or (b) if a gas, it preferably contains moisture. For an emulsion, the emulsifying agents are preferably surfactants which form layers containing vesicles and miceUes. The general types of surfactant found to be suitable are anionic, ionic and Zwitterionic surfactants. Preferably, in die surfactant the hydrophobic group is the long chain (e.g. fatty acid) and the hydrophuic group is a carboxylate . Na and Ca are preferably present as salts. Such surfactants are naturaUy-occurring in petroleum resin and asphaltene fractions. Such surfactants act! to reverse miceUes containing undesirable species. An example is given in Fig. 1 in which the asphaltene in native petroleum is reversed. The miceUe reversal arises by membrane mimetic chemistry action in which the heterocycUc containing functions (S,N,O) are orientated towards the outside from the miceUes. Consequentiy, chemical reactions such as destructive adsorption are facilitated. Where the fluid is a gas, it must contain moisture and the molecules preferably have low molecular weights, below 200. An example is natural gas in which the Sulphur species may be H2S, R2S, or RSH. AU of these have low molecular weights and are volatile, and may therefore undergo surface adsorption. For filtration, a liquid feedstock containing adsorbate species is brought into contact with the filter. An electrical potential arises in the fluid causing electrokinetic (or "zeta") potential. Alternatively a potential may be caused by an externaUy-induced electrical field. This potential, in an environment in which the miceUes are reversed by the surfactants, causes the polar adsorbtate species to interact with the filter surface. This action is a type of destructive adsorption in which bonds with the fluid are broken, for example an S-C bond. The nucleophuic atoms attack electron deficient cavities in the filter. In the case of asphaltenes, adsorbent destruction cracks the asphaltene into resins or aromatics. The diagram of Fig. 2 gives an iUustrative example. Referring to Fig. 2, the SbSn intermetaUic structure is identified as 10. The Sb atoms form me electron deficient cavities 12 in the filter surface, and these attract nucleophuic polar sulphur heads 13 . By this action, the long chain taU part 14 ofthe fluid molecule is broken by vibrational and rotational forces, and thus elemental sulphur is removed from the liquid. The foUowing sets out one example of how an SbSn filter is produced. Words which are used in headings of subsequent parts ofthe description are underlined. InitiaUy, there is melt preparation in which an equiatomic composition of tin and antimony is melted in a graphite crucible using an induction heater. True atomic mterrnixing occurs in the molten state. The melt is held for 10 minutes at 500°C with a hydrogen gas cover to avoid oxidation. The melt is bottom poured into an atomisation nozzle operated with high pressure nitrogen at a plenum pressure of 2.5 MPa for gas atomisation. Nitrogen escapes ti rough an annular gap surrounding the melt stream, causing formation of droplets. The adiabatic expansion of the gas rapidly cools the droplets and accelerates them away from d e melt source. During the subsequent flight, d e droplets freeze into SbSn intermetaUic crystalline particles with an average size of lOμm. The particles are coUected in a container containing nitrogen gas. These particles may be directiy used because the microscopic size of the particles provides a high surface area for contact with the fuel. For example, the particles may be loose packed in a column. The particles may also be used when bonded to a substrate. Further, it is envisaged that a substrate having a porous structure may be used onto which the composition is coated, instead of providing an integral porous structure. In this case, a ceramic or metaUic substrate may be used, and the composition may be coated by chemical or physical vapour deposition techniques, of by plasma spray coating. Alternatively, me powder may be used as foUows to produce a porous structure through which fuel passes for surface contact. The powder is loose packed into a machined graphite mould to form a disc witi me addition of approximately 2% by weight stearic acid as a pore former. The graphite is heated in a hydrogen sintering atmosphere to bond the particles at 370°C for 30 minutes. By sintering in this manner, a porous filter having an optimal balance between bonding and porosity is formed. The filter thus produced has the foUowing properties:- Porosity: 40-50% Permeability: 10 "π m 2 Pore size: 25μm The foUowing description sets out alternative ways of implementing steps of the process. Melt Preparation The materials used could in addition include other metals such as platinum, gold or paUadium. The formulation need not be equiatomic. The end-product intermetaUic preferably has a tin atomic percentage in the range of 39.5 to 57%. The melt may be at any temperature at which it does not absorb and/ or react with oxygen. It is envisaged that the materials need not necessarily be melted. For example, separate powders could be mechanicaUy aUoyed with sufficient energy such that me metals physicaUy combine into a single powder. Gas Atomisation The gas atomisation pressure is dependent on the desired particle size, whUe being sufficient to provide the necessary high cooling rate. It is estimated that this is at least 10 3 o C/s. For example, a lower pressure of 0.7 MPa may be used, providing a larger particle size of 20 μm. The atomisation gas may alternatively be hydrogen, argon, helium or any other inert gas or any mixture of such gases. Sintering Atmosphere It is not essential that a hydrogen atmosphere be used. Due to the problems associated with using a lower temperature hydrogen furnace, sintering behaviour has been studied in nitrogen and nitrogen-hydrogen atmospheres. It was found that sintering of filters in either complete nitrogen or a combination of hydrogen and nitrogen atmospheres resulted in a black coating on the surface. This was due to the deposition of carbon on the surface of the filter. Stearic acid is a hydrocarbon consisting of several C-H bonds and was used as a pore-forming additive. Burn out of stearic acid is facilitated by the breaking of carbon-hydrogen and the formation of simple gases using a reducing atmosphere. Hydrogen is a reducing atmosphere and helps in the burnout of stearic acid as weU as in the sintering ofthe powders. The use of a nitrogen atmosphere does not cause these two processes because of its non- reducing behaviour. The carbon deposition on the surface also hampered the sinterabUity of the powders. The samples sintered using the hydrogen/nitrogen combination were black on me surface and were very frag e. The carbon coating was found only on the surface and not on die other sides of die filter. The discoloration may also be due to carbon deposition. An interesting phenomenon noticed was tiiat carbon deposition was prevented when die powder samples were covered by a graphite plate over d e mould. Also, the powders covered by the graphite plate and sintered in a nitrogen atmosphere showed the same sintering behaviour as die powders sintered in hydrogen atmospheres. The covering plate (which was made of graphite) would have caused the formation of carbon monoxide which is a reducing atmosphere. It is envisaged that a plate oti er man graphite could be used, provided some part ofthe mould is carbon when using a nitrogen atmosphere. Figure 3 shows fractographs of samples sintered in fuU hydrogen and fuU nitrogen atmospheres. They have a siπύlar pore structure. The permeabUity, density and shrinkage of me filters sintered in 100% nitrogen and 100% hydrogen atmosphere are shown in Table 1. Table 1 Atmosphere Permeability Densi y % Shrinkage % Shrinkage % Mass Loss (m 2 ) (%) in ht. in dia. 100% H 2 lxlO 11 58 20 11 3.3 100% N 2 7xl0 12 61 17 9.5 3.1 The X-ray diffraction patterns of the samples also show that the filters sintered using the nitrogen and hydrogen atmosphere form the same intermetaUic phase SbSn (refer to Fig. 4). In conclusion, powders mixed with 2 wt. % stearic acid showed the maximum permeabUity and pore size. The powders can be sintered in both 100% hydrogen as weU as 100% nitrogen atmospheres, but for sintering in 100% nitrogen, the samples are covered at the top by a graphite boat to provide a reducing atmosphere. The samples sintered in 100% nitrogen atmosphere also formed d e same intermetaUic SbSn phase. Sintering may be carried out by heating graphite to 370°C in a graphite boat arrangement. In this case, oxygen reacts with the graphite to form CO gas, further oxidation reactions leading to formation of C0 2 . Both reactions remove oxygen or oxides from the sintering environment. There is a continual consumption of graphite as it is transformed into a vapour over time. Any suitable reducing atmosphere could be used. Examples are use of methane, CO, H 2 , N 2 - H 2 mixes, NH 3 , and dissociated ammonia. Suitable combinations of the above gases could be used by endothermic or exothermic burning processes. In particular, the use of H 2 -N 2 is attractive because at low H 2 levels of a few percent, the atmosphere is non-explosive, yet stiU reducing. Additional Step - Sintering Additives The process may have the additional step of adding an additive to the intermetaUic powder to dUate the pores during sintering to provide a larger catalyst surface area. This is briefly referred to above and is described in more detaU in this section. In one example, stearic acid was chosen as a binder to be added to the powder to increase the permeabUity. The stearic acid used was Industrene 5016 manufactured by Witco. The reason for choosing stearic acid was that it completely burns out before reaching the sintering temperature of 370°C. Stearic acid and d e powder were mixed in a grinder to form a uniform blend of the powder and me binder. The total time of grinding was approximately 2 minutes. The grinding was done in short time intervals of 20 seconds so as to prevent melting of stearic acid caused by heat generated in the grinder. The sintering experiments were carried out in a retort in both nitrogen and hydrogen atmospheres. The permeabUity experiments were conducted using permeabUity measuring equipment using air as the flow medium and mercury as the reference liquid in a column. The Archimedes method was used to measure the final density. Table 2 below compares the % density and permeabUity of filters sintered by mixing powders with different weight percentages of stearic acid at 370°C in H 2 atmosphere. Table 2 Wt. % binder PermeabUity (m 2 ) Pore diameter (μm) Density (%) 0 5xl0 13 20 61 0.5 9xl0 12 37 65 1 9xl0 12 35 65 1.5 7xl0 12 50 62 2 2xl0 n 53 58 In Table 2, aU of the measurements were made for powders sintered in a cavity made of graphite boat, 19 mm in diameter and 4.3 mm in height and were not of the size of me actual filter. The powder mixed with 2 wt.% stearic acid gave a maximum permeability of 2x10 " m 2 and was approximately 50 times more permeable than the powders mixed with 1.5 and 1 wt.% binder showed an increase in density whUe the powders mixed with 1.5 and 2 wt.% showed a decrease in density. Powders mixed with stearic acid showed better sintering behaviour than the powders that were not mixed with binders. The initial increase in density could be attributed to diis behaviour. The decrease in density for powders mixed witii more than 1 wt.% was due to the excessive pores created by me burnout of stearic acid. The powder mixed witii 2 wt.% stearic acid and sintered had a maximum pore size of 52 μm and die highest porosity. Figure 5 shows optical micrographs of the surface of filters sintered from powders with 0 and 2 wt.% stearic acid. In general, any suitable agent which occupies space during heating but burns our during sintering may be used. Clean burnout at relatively low temperatures is desired. Stearic acid in powder form has been found to be suitable at a particle size of lOOμm or less. The powder may be added upon vibration of the intermetaUic powder to aUow a lower packing density, giving a dUated structure with a higher permeabUity after sintering. Any suitable pore forming agent which has these general properties could be used, for example, ammonium carbonate, camphor, naphtfia, ice, monostearates, and also low molecular weight waxes and organic gels. It is also envisaged that a pore foπning agent which acts to provide a reducing atmosphere could be used, for example paraffin wax, which forms methane on burnout. It is also envisaged that the filter could be formed from one or a number of layers so that the desired properties are obtained using me layers as "standard parts". The filter could have physical properties which are different from those oudined above. The foUowing are desirable parameter value ranges:- Porosity: 30 to 50% PermeabUity: 1 to 400 x 10 13 m 2 Pore size: 2 to 300 μm The above is a description of one method of producing an SbSn intermetaUic. However, such an intermetaUic may be produced by alternative techniques such as by physical vapour deposition. This depends on the structure of me filter, which in turn depends on d e particular operating conditions and type of feedstream being treated. It has been found that an SbSn intermetaUic is particularly effective. It is expected mat other materials having simUar crystal structures would also be effective. For example, CuZn and CuZr have close lattice parameter matches and an identical Pearson space group. Operation of FUter Irrespective of the physical arrangement of the filter, it is used to treat a fluid by bringing the fluid into contact with it, causing undesirable chemical species to be adsorbed onto its surface. The filter acts as an adsorbent, the fluid species which is removed being the adsorbate. The adsorption depends on die nature of die fluid being treated and on the fUtration process employed. Many different fluids may be treated, including many polymeric and hydrocarbon fluids. The filtration may be enhanced by use of a magnetic field in the fluid. Alternatively, or in addition, an electrical potential may be applied to the filter itself. Such electrical and /or magnetic fields provide an attraction gradient towards the filter. Such a field may also aUow selectivity ofthe species adsorbed. The filtration action provides beneficial effects for some fluids in addition to removal of undesirable species. One such effect is reduction of viscosity of fluids such as non- Newtonian fluids including crude oU or condensate. Anomer such effect is very quick destabilisation of an emulsion by virtue of a reaction with surfactants. This action is particularly effective if the emulsifying agents are surfactants including Na and/or Ca ions. If water is to be introduced to die fluid to improve the filtration effect, the artificial surfactants should include Na and/or Ca ions. A further effect is an increase in turbidity. When the filter ceases to be effective, a clean filter is substituted and the original is cleaned. Cleaning involves application of an electric field to the filter, possibly with a wash using a strongly alkaline cleaning fluid. However, in some instances the filter may be cleaned witii a wash only. Regarding the SbSn intermetaUic filter, in more detaU, cyclic voltammagram tests carried out witii electrodes of tin only, antimony only, and the intermetaUic (LM) indicate tiiat the intermetaU c action is not simply a sum of the actions of tin and antimony separately. Also, these tests demonstrate that more than one reaction occurs as die voltage is varied. This indicates tiiat if a voltage is apphed, filtration may be tuned for selectivity. Referring to Fig. 6, cyclic voltammogram plots are shown for an infiltrated intermetaUic filter in an equal crude oU/water mixture. The scan rate was lOmV/s, although this parameter is of littie importance because response was found to be independent of the scan rate. As is clear from these plots, there are peaks at c. -1.2 to -1.3 V. This indicates drat a specific reaction occurs involving adsorption of a species onto the filter at a particular voltage bias. It also indicates that the process is not reversible because of lack of activity for forward bias. A subsequent set of tests carried out with the water portion of die above mixture revealed d e plots shown in Fig. 7. There are again reaction peaks at c. -1.2 to -1.3 V, but also two other less pronounced reaction peaks, including one at a forward bias. This confirms that die reaction is irreversible and tiierefore a solvent wash would be required for filter cleaning. They also indicate tiiat presence of water is important, and that the active adsorbates are preferably water soluble such as inorganic salts. These latter conclusions were borne out by further tests with the oU portion alone which resulted in lower significant reactions. The foUowing examples lustrate the filtration method. Tests were carried out to analyse effectiveness of the filter in various adsorbate fluids. The tests were also carried out with a filter of another material - stainless steel. Tests With Fuel Oils The invention finds particular application in treatment of combustible fuels such as oU and natural gas because of die major impact these fuels have on the environment. In such fluids on undesirable constituent is Sulphur, which is usuaUy present in the range of 100 to 1000 ppm. Sulphur not only poUutes the atmosphere itself, but it also poisons conventional catalysts for cleaning exhaust gases. Sulphur also damages engine parts such as turbine blades - causing major design and maintenance problems in the avionics field for example. Sulphur takes different forms, for example, thiophene, benzorhiophene or dibenzothiophene. In d e existing art, hydrotreating processes are used for removal of Sulphur and diese are effective for reduction to below 50 ppm. These processes are based on high pressure and temperature treatment with hydrogen to remove H 2 S. The coUected streams of H 2 S at the refinery are then further treated to remove and recover elemental Sulphur. However, these processes involve not only very expensive and complex plant and control methods, but also a high energy input - again adversely affecting d e environment. These processes also reduce some of the unsaturated organic compounds present, consuming more Hydrogen than needed to treat the Sulphur. Various tests have been carried out which indicate the beneficial effect of oU fUtration according to die invention. Tests involved pumping the oU in a dynamic rig through a housing containing SbSn intermetaUic, providing a contact time of 1 to 5 seconds. Other tests were static - the filter being introduced into d e oU in powder form. For crude oU, an effect is de-emulsification by removal of natural surfactants. This effect depends on the stability of the emulsion and/or the total energy input into me emulsion. The foUowing improvements were observed:- (i) SubstantiaUy high levels of inorganic sulphide species were removed from the water phase. (n) The pH value in the water considerably improved. (iii) SARA analyses demonstrated decreases in asphaltene and resin content, and increases in aromatic content. (iv) In d e oU phase, die viscosity was gready reduced. It was found tiiat if a magnetic field was applied to die Uquid emulsion, separation was delayed. In this case, high levels of organic S were removed and selectivity of the adsorbed species was achieved by adjusting the magnetic field. A simUar effect was observed if an electrical potential was applied to die filter. Referring to Fig. 8 an experimental apparatus 10 is illustrated. The apparatus comprises a feed flask 11 from which the feedstock is drawn by a pump 12 through a powder bed 13 containing SbSn intermetaUic. Valves 14 aUow direction of the feedstock eitiier (a) in a single-pass flow to a sampling bottie 15 or (b) in a re-cycling flow. A power supply 16 feeding a coU 17 provide an induced magnetic field in die powder bed 13, when activated. Tests were carried out with a crude oU having a sulphur concentration as set out in Table 3 below, as determined by GC spectra. Table 3. In a first stage, the crude oU was pumped in die recycling circuit for 30 minutes. The sample size was 600ml and it had a ratio of 3 parts oU to 2 parts water by volume. The flow rate was 20 - 25 nU/min. the quantity of SnSb intermetaUic powder was 40% ofthe weight of d e sample feedstock. In a second stage a voltage of 1.2 V was apphed to create a magnetic field and the emulsified effluent from the first stage (about 300ml) was pumped through the powder bed (adjusted to remain at 40% of sample weight) in a single pass to die sampling bottle 15. The voltage level should be in die range 0.8 V to 2.0 V and is preferably approximately 1.2 V. For sampling after both stages, the effluent was aUowed to de-emulsify and d e samples were analysed by the modified Eschka method (ASTM 3177-89) for total sulphur determination and by die Thin Layer Chromatography (TLC) Method for SARA analysis. The foUowing are the results for removal of total sulphur. Table 4 Table 5 below sets out the SARA analysis. Table 5 Notes:- (a) Figures to left of / are % of original and to die right are die % change. (b) Figures to left of / are % of sample relative to die first stage, and to right are die % change, (c) The figures in parendieses are total % change relative to die original sample. These results demonstrate that the composition of the crude oU has been changed by die intermetaUic. Regarding the SARA composition, d e objective is to increase saturates and aromatics and to reduce resins and asphaltenes. This benefits downstream processing in the refinery. The results indicate tiiat if the sequence is changed to incorporate an applied voltage initiaUy and tiien subsequentiy repeating without a voltage, die resin and asphaltenes would be significandy reduced. Regarding elemental sulphur. Eleven organo species were identified. Desulphurisation by die filter, with and without an apphed voltage occurred uniformly across the species. The level reached 67.6%. It is anticipated that by incorporating multiple filter units and by increasing surface area of the intermetaUic, levels of sulphur reduction wiU exceed tiiose achieved in diese experiments. The foUowing test were also carried out with die crude oU of Table 3, as foUows: A Continuous flow with a flowrate of 20 - 25 ml/min in a recycling circuit and witiiout apphed voltage, as for the first stage above. B Continuous flow with a flowrate of 20 - 25 rrU/min without recycling and witii an apphed voltage. This is sirriilar to d e second stage above, except die sample is fresh and not the effluent from test A. A SARA analysis demonstrated: (i) For test-type A, - asphaltene content reduced by 27%, resin content reduced by 30%, aromatics content increased by 40% and saturates content decreased slighdy. (ii) For test type B, - asphaltene content increased by 18%, resin content increased by 8%, aromatics content decreased by 20% and saturates content increased by 6%. Other tests were carried out using the apparatus 10 and the crude oU as set out in Table 3. The total S content of emulsified samples before and after reactions were measured in the oU phase, which was separated from the re-emulsified samples by a modified Eschka method, and in the water phase by the Titrimetric Method and die Turbidimetric Metiiod. These methods were also used for analysis of the separate phases after treatment. The foUowing are die results. Table 6 Table 7 OU Phase Tests With Model Solutions Tests were carried out using an Sb/Sn intermetaUic filter as a powder in 40 ml distiUed water having a fixed concentration of sodium sulphide (Na 2 S) of 348 mg- S/l. Adsorption was measured for different concentrations of intermetaUic and a fixed contact time of 30 hrs. To avoid interference from dissolved oxygen, d e distiUed water was stripped for 3 hrs. There was a controUed pH of 3 ± 0.5. The result is shown in Fig. 9, from which it wiU be seen that the inorganic Sulphur concentration decreased by about 11% for 5g of intermetaUic. Tests were then carried out witii different initial Na 2 S concentrations, a fixed contact time of 30 hours, a fixed amount of intermetaUic (15% w/w), and a controUed pH of 3 ± 0.5. The deionised water was again stripped for 3 hours. The results are shown in Figs. 10 and 11. Fig. 10 indicates tiiat with increasing concentration of sulphide, the adsorption capacity of the intermetaUic increases. Fig. 11 indicates mat die adsorption behaviour of inorganic sulphide can be described weU by using d e Freundlich equation. Further tests carried out both with and widiout HCl in solution indicated a higher Sulphur adsorption efficiency with HCl. This indicates tiiat there may be selective adsorption of Na prior to S, and tiiat diere is much better adsorption in an acidic solution (pH = 3.0). In anodier test die fluid was dibenzodiiophene emulsified witii distiUed water (40% by vol.) by addition of surfactant (Span 20). The results were as foUows:- Table 8 These results are very significant because dibenzodiiophene is particularly difficult to remove. Tests with partly refined fuels. Tests were also carried out with partiy-refined oU, naphtha, in which d e predominant S-containing compounds were substituted thiophenes, benzothiophenes, and a smaU fraction of dibenzothiophenes. The tests were dynamic - the oU being pumped through a housing containing polymer Raschig rings coated witii Sb/Sn intermetaUic. It was found tiiat die presence of water was necessary to obtain significant Sulphur reduction with optimum results being obtained when the fuU naphtha was emulsified witii water and dien filtered. Water washing prior to treatment gave reductions between 10% and 30%. Emulsification ofthe fuU naphtha with water using an added surfactant gave an improved performance. Tests have demonstrated a reduction from 1700 ppm to 700 ppm Sulphur. Tests with diesel fuel have shown a reduction in the Sulphur levels by 40% without water treatment. Gasoline has shown significant improvements when treated witiiout water treatment. These tests indicate tiiat a possible strategy for fUtration is in several stages, first to treat the crude on arrival at a refinery, intermediate treatment during d e refiriing process (naphtha), and finaUy a last stage treatment ofthe final product. It is known that the organic Sulphur species in lighter petroleum (gasoline, diesel and naphtha) are different from those in heavy petroleum (high Sulphur containing crude oU and heavy oU). The lighter petroleum contains mostly polar and polarizable Sulphur compounds such as mercaptans and hydrogen sulphide, but heavy oUs contain polarizable Sulphur compounds such as dibenzotiiiophenes. There is more effective removal of polar or polarizable sulphide compounds from petroleum products tiian from crude petroleum. It has been observed in die naphtha tests that die presence of water was in many instances essential for the intermetaUic to effectively either remove the natural or artificial surfactants and completely separate the two liquids from an emulsified state or efficientiy remove Sulphur species, other than in crude oU. Further it has been shown that the water portion of natural emulsions is an active component in the reaction. Furthermore, these reactions appear to occur at specific voltages and current densities. By replicating these conditions it has been shown tiiat by fine tuning d e voltage, specific elements can be removed from the crude oU widiout affecting d e emulsified state of die liquid. Rejuvenation of Filter For commercial application of the invention, it is important that the filter can be cleaned repeatedly for re-use. A filtration system would comprise a control system which moves filters out ofthe flow conduit, cleans the filters and subsequendy moves them back into the flow conduit. It has been found tiiat die surface of the filter is cleaned by immersion in a cleaning hquid and application of a voltage. In one example, cyclic voltammogramms were carried out with a scan range of -1.5 V vs. SCE to 1.5 V vs. SCE. The cleaning liquids were water, Alconox detergent, and again water. It was observed that current levels returned to d e same range as for the initial water test, indicating tiiat die detergent was removing significant quantities of Sulphur. An XPS analysis of one filter demonstrated a reduction of 6 atomic % S to approximately zero. Filtration of Other Fluids The filtration method of die invention may be used with other fluids. For example gases such as natural gas, combustion products or contaminated gases may be treated. In one example, it is envisaged tiiat blood may be treated, in which case undesirable polar molecules may be removed. More generaUy, food or medical products may be treated to remove undesirable constituents. Also it is envisaged that contaminated waste water and sea water may be effectively treated.

Claims: CLALMS 1. A method of treating a fluid having an undesirable chemical species, the method comprising the step of bringing the fluid into contact with a filter having a surface crystal structure to facihtate adsorption of undesirable chemical species ofthe fluid onto the filter. 2. A method as claimed in claim 1, wherein the filter comprises defect sites on the surface adjacent electron-deficient atoms. 3. A method as claimed in claims 1 or 2, wherein the filter comprises an intermetaUic. 4. A method as claimed in claim 3, wherein the intermetaUic metals are Sb and Sn. 5. A method as claimed in any preceding claim, wherein the fluid contains water. 6. A method as claimed in claim 5, wherein the fluid is a liquid and is an emulsion. 7. A method as claimed in claim 6, wherein one of the emulsion phases is an electrolyte. 8. A method as claimed in claim 7, wherein the emulsifying agent is a surfactant. 9. A method as claimed in claim 8, wherein the surfactant is of the type which acts to reverse miceUes containing heterocyclic - containing groups so that these groups are orientated towards die outside. 10. A method as claimed in claim 9, wherein the surfactant is of the type in which the hydrophobic group is die long chain and the hydrophUic group is a carboxylate. 11. A method as claimed in any preceding claim, wherein a magnetic field is applied to the fluid as it is brought into contact with the filter. 12. A method as claimed in any preceding claim, wherein an electrical potential is apphed to the filter. 13. A method as claimed in any preceding claim, wherein the method comprises the further steps of rejuvenating the filter by washing with a water solution. 14. A method as claimed in any preceding claim, wherein the fluid is a hydrocarbon oU feedstock. 15. A metiiod as claimed in 14, wherein viscosity is reduced. 16. A method as claimed in claims 14 or 15, wherein turbidity is increased. 17. A method of treating an emulsion in which one phase is an electrolyte, by bringing the emulsion into contact with an adsorbent having a surface crystal structure. 18. A method as claimed in claim 17, wherein the adsorbent is an intermetaUic. 19. A method as claimed in claim 17, wherein the emulsifying agent is a surfactant. 20. A method as claimed in claim 19 wherein the surfactant is of a type which acts to reverse miceUes so that adsorbate species face outwardly. 21. A method as claimed in claim 20 wherein the surfactant contains calcium. 22. A method as claimed in claims 20 or 21 wherein the surfactant contains sodium. 23. A method as claimed in any of claims 20 to 22 wherein the surfactant is ofthe type in which the hydrophobic group is the long chain and the hydrophilic group is a carboxylate. 24. A method as claimed in any of claims 17 to 23 wherein electrical energy is apphed to the adsorbent and the emulsion. 25. A method as claimed in claim 24, wherein the energy is applied as a magnetic field around the adsorbent. 26. A method as claimed in claim 24 wherein the energy is apphed as a direct voltage apphed to die adsorbent. 27. A metiiod as claimed in claim 26, wherein the apphed voltage is in the range 0.8 V to 2.0 V. 28. A method of treating a hquid comprising the steps of foπning an emulsion in which one phase is an electrolyte and die emulsifying agent is a surfactant which acts to reverse miceUes so that heterocydic-containing functions are oriented towards the outside, and bringing the emulsion into contact with an adsorbent. 29. A method as claimed in claim 28, wherein the adsorbent has a crystal structure. 30. A method as claimed in claim 29, wherein the adsorbent comprises defect sites on its surface adjacent electron-deficient atoms. 31. A metiiod of desulphurising a hydrocarbon feedstream comprising the steps of bringing the feedstream into contact with an adsorbent having a surface crystal structure until sulphur species adsorb onto the adsorbent surface. 32. A method as claimed in claim 31, wherein the adsorbent comprises defect sites on its surface adjacent electron-deficient atoms. 33. A method as claimed in claim 32, wherein the adsorbent is an intermetaUic. 34. A method as claimed in claim 33, wherein the adsorbent is an SbSn intermetaUic. 35. A fluid filter comprising having an adsorbent with surface crystal structure to facilitate adsorption of undesireable chemical species onto the filter when the fluid containing the adsorbate comes into contact with it. 36. A filter as claimed in claim 35, wherein the adsorbent comprises defect sites on die surface at adjacent electron-deficient atoms. 37. A filter as claimed in claims 35 or 36, wherein the adsorbent is an intermetaUic. 38. A filter as claimed in claim 37, wherein the intermetaUic is an SbSn intermetaUic. 39. A filter as claimed in any of claims 35 to 38, further comprising means for applying electrical energy to enhance adsorption.

Inventors: DUFFIELD ROGER, RANDALL GERMAN, RONALD IACOCCA, TEH FU YEN, DUFFIELD, ROGER, RANDALL, GERMAN, RONALD, IACOCCA, TEH, FU, YEN
Applicants: DUFFIELD ROGER, KLINAIR ENVIRONMENTAL TECHNOLO, RANDALL GERMAN, RONALD IACOCCA, TEH FU YEN, DUFFIELD, ROGER, KLINAIR ENVIRONMENTAL TECHNOLOGIES (IRELAND) LIMITED, RANDALL, GERMAN, RONALD, IACOCCA, TEH, FU, YEN
Application year: 1998
Main classification: B01J20
IPC codes: B01D15, B01J20, C10G25, C10G31