IE42277B1 - Pyrolyzed polymer particles - Google Patents

Description

This invention concerns partially pyrolyzed particles of resinous polymers and methods for their preparation. Application of these particles in the removal of impurities such as sulfur compounds, monomers, and other industrial con5 taminants or pollutants from gases and purifying pollutantcontaining liquid streams such as phenolics from waste streams and barbiturates from blood are claimed in Patent Specification No. The partially pyrolyzed macroreticular materials of this invention are particularly useful as adsorbents for vinyl chloride removal, blood purification, recovery of phenolic substances and, when metals are incorporated, particularly as catalytic agents for industrial and laboratory processes.

The most commonly used adsorbent today is activated carbon. The production of activated carbon for industrial purposes employs a wide variety of carbonaceous starting materials such as anthracite and bituminous coal, coke, carbonized shells, peat, etc. Suitability of such materials depends on a low ash content and availability in a uniform and unchanging quality.

Methods of activation can be considered in two categories. The first category includes chemical activation processes, in which the carbonaceous materials or sometimes the chars are impregnated with one or more activating agents such as zinc chloride, alkali carbonates, sulphates, bisulphates, sulfuric or phosphoric acid and then pyrolyzed (carbonized).

The action of these materials appears to be one of dehydration with high yields of carbon unaccompanied by tarry materials. The second category includes processes known as heat treatment in which chars are heated to temperatures between 350 and l,000°C. in the presence of C02< N2, 02, HCl, cl2, H20 and other gases. A portion of the char is burned as the surface area and activity of the carbon increases. Via careful control of activation parameters, manufacturers are today able to produce high surface area products (800—2,000 2 M /g) in a wide range of uniform particle sizes.

Production of activated carbon by the above processes gives materials with the highest available carbon capacities for a wide variety of adsorbates in both the liquid and gas phases. However, these materials possess the following disadvantages : a) difficult and expensive thermal regeneration b) high regeneration losses of 10%/cycle) c) friability of active carbon particles d) lack of control of starting materials.

Adsorbents produced according to the invention via pyrolysis of synthetic organic polymers are preferably spheres which possess a great deal of structural integrity which do not easily break apart or slough dust particles as is the case for active carbon. Because of this lack of friability, the regenerative losses are frequently lower than is common for active carbon.

Pyrolysis of synthetic organic polymers further allows a much greater degree of control of the starting materials and hence of the final product than is possible with naturally occurring raw materials used for production of activated carbons.

Incorporation of desirable elements and functional - 4 groups to enhance adsorbency for specific adsorbates is easily achieved. Control of the average pore size and pore size distribution is much more easily achieved with well defined synthetic starting materials. This increased control allows the production of adsorbents designed for specific adsorbates with adsorbent capacities far greater than is possible with activated carbons.

The present invention provides partially pyrolyzed particles, preferably in the form of beads or spheres, produced by the controlled thermal decomposition of synthetic polymer of the initial macro-porosity which may be found in macrorecticular polymer particles. In a preferred embodiment, the pyrolyzed particles are derived from the thermal decomposition of macrorecticulat ion exchange resins which contain a macroporous structure.

In one aspect of the invention there is provided a process for the preparation of partially pyrolyzed particles which comprises providing macroreticular resin particles made by polymerisation of one or more ethylenically unsaturated monomers and having imparted therto ion exchange functional groups which will help to maintain their macroreticular structure during pyrolysis, and subjecting the particles to thermal degradation in an inert atmosphere, optionally containing activating gas, while removing the volatile products produced, so that the resulting particles have multimodal pore distribution with macropores in their size range 50 S to 100,000 § in average critical dimension.

In another aspect the invention comprises a process for producing partially pyrolyzed particles of macroporoUs synthetic polymer which comprises thermally degrading at a temperature between 300° and 900°C and in an inert gaseous atmosphere optionally containing an activating gas, macro43277 - 5 porous synthetic polymer containing a carbon fixing moiety and derived from one or more ethylenically unsaturated monomers or monomers which may be condensation polymerised to yield macroporous polymers or mixtures thereof, for a time sufficient to drive off sufficient volatile components of the synthetic polymer to yield particles having (a) at least 85% by weight carbon, (b) multimodal pore distribution with macropores in the size range from 50 fi to 100,000 S in average critical dimension and (c) a carbon to hydrogen atom ratio of between 1.5:1 and 20:1,· and thereafter cooling said particles under said inert atmosphere to a temperature below that which would cause oxidation in air.

The invention also provides therefore partially pyrolyzed particles of a macroporous synthetic polymer having properties suitable for use in adsorption, molecular screening and/or catalysis and high resistance to crushing and particle sloughage comprising the product of controlled thermal degradation of a macroporous synthetic polymer containing a carbonfixing moiety and derived from one or more ethylenically unsaturated monomers or monomers which may be condensed to yield macroporous polymers, or mixtures thereof which partially pyrolyzed particles have: (a) at least 85% by weight of carbon, (b) multimodal pore distribution with macropores in the size range 5dS to 100,000$ in average critical dimension and (c) a carbon to hydrogen atom ratio of between 1.5:1 and 20:1, or, in another aspect, particles of macroporous synthetic polymer which have been subjected to heat treatment and which contain at least one carbonfixing moiety, said heat treated particles having (a) at least 85% by weight of carbon (b) multimodal pore distribution with at least one peak frequency of pore average critical dimension, preferably average pore diameter, in the range 50 $ 2 2 7 7 - 6 to 100,000 8 and (c) carbon to hydrogen atom ratio from 1.5:1 to 20:1.

In general pyrolysis comprises subjecting the starting polymer to controlled temperatures for controlled periods of time under certain ambient conditions. The primary purpose of pyrolysis is thermal degradation while efficiently removing the volatile products produced.

The maximum temperatures may range from 300°C to up to 900°C., depending on the polymer to be treated and the desired composition of the final pyrolyzed particles. High temperature e.g., about 700°C and higher result in extensive degradation of the polymer with the formation of molecular sieve sized pores in the product.

Most desirably, thermal decomposition (alternatively denoted pyrolysis or heat treatment is conducted in an inert atmosphere comprised of, for example, argon, neon, helium or nitrogen, using beads of macroreticular synthetic polymer substituted with a carbon-fixing moiety which permits the polymer to char without fusing in order to retain the macro20 reticular structure and give a high yield of carbon. Among the suitable carbon-fixing moieties are sulfonate, carboxyl, amine, halogen, oxygen, sulfonate salts, carboxylate salts and quaternary amine salts. These groups are introduced into the starting polymer by well-known conventional techniques, such as those reactions used to functionalize polymers for production of ion exchange resins. Carbon-fixing moieties may also be produced by imbibing a reactive precursor thereof into the pores of a macroreticular polymer which thereupon, or during heating, chemically binds carbon-fixing moieties onto the polymer. Examples of these latter reactive precursors include sulfuric acid, oxidizing agents, nitric acid, Lewis acids and acrylic acid. 2 2 7 7 - 7 Suitable temperatures for practicing the process of ' this invention are generally within the range of 300°C. to about 900°C., although higher temperatures may be suitable depending upon the polymer to be treated and the desired composition of the final pyrolyzed product. At temperatures above about 700°C, the starting polymer degrades extensively with the formation of molecular sieve sized pores in the product, i.e., 4—6 £ average critical dimension, yielding a preferred class of adsorbents according to this invention.

At lower temperatures the thermally-formed pores usually range from 6 £ to as high as 50 £ in average critical size. A preferred range of pyrolysis temperatures is between 400°C. and 800°C. As will be explained more fully hereinafter, temperature control is essential to yield a partially pyrolyzed material having the composition, surface area, pore structures and other physical characteristics of the desired product. The duration of thermal treatment is relatively unimportant, providing a minimum exposure time to the elevated temperature is allowed.

By controlling the conditions of thermal decomposition, in particular the temperature, the elemental composition, and most importantly the carbon to hydrogen atom ratio (C/H), of the final product particles is fixed at the desired composition. Controlled heat treatment yields particles intermediate in C/H ratio composition between activated carbon and the known polymeric adsorbents.

The following table illustrates the effect of maximum pyrolysis temperature on the C/H ratio of the final product, utilizing macroreticular functionalized polymers as the starting materials. 2 2 7 7 J Starting Material Composition TABLE X Maximum Pyrolysis Temperature C/H Ratio of Product (1) Styrene/Divinylbenzene copolymer adsorbent (control) 1 (2) Styrene/Divinylbenzene ion exchange resin with sulfonic acjj_d functionality (H form) 400°C. 1.66 (3) Same as (2) 500°C. 2.20 (4) Same as (2) 600°C. 2.85 (5) Same as (2) 800°C. 9.00 (6) Activated carbon (negligible hydrogen) A wide range of pyrolyzed resins may be produced by varying the porosity and/or chemical composition of the starting polymer and also by varying the conditions of thermal decomposition, in general, the pyrolyzed resins of the invention have a carbon to hydrogen ratio of 1.5:1 to 20:1, preferably 2.0:1 to 10:1, whereas activated carbon normally has a c/H ratio much higher, at least greater than 30:1 (Carbon and Graphite Handbook, Charles L. Mantell, Interscience Publishers, IO N.Y. 1968, p. 198). In general, the product particles contain at least 85% by weight of carbon with the remainder being principally hydrogen, alkali metals, alkaline earth metals, nitrogen, oxygen, sulfur, chlorine, etc., derived from the polymer or the functional group (carbon-fixing moiety) con15 tained thereon and hydrogen, oxygen, sulfur, nitrogen, alkali metals, transition metals, alkaline earth metals and other elements introduced into the polymer pores as components of a filler (may serve as a catalyst and/or carbon-fixing moiety or have some other functional purpose). - 9 The pore structure of the final product must contain at least two distinct sets of pores of differing average size, i.e., multimodal pore distribution. The larger pores originate from the macroporous resinous starting material which preferably contain macropores in the size range 50 to 100,000 Angstroms in average critical dimension. The smaller pores, as mentioned previously, generally range in size from 4 to 50 fi,depending largely upon the maximum temperature during pyrolysis. Such multimodal pore distribution is considered a novel and essenlo tial characteristic of the composition of the invention.

The pyrolyzed polymers of the invention have relatively large surface area resulting from the macroporosity of the starting material and the smaller pores developed during pyrolysis. In general the overall surface area as measured 2 by N adsorption ranges between 50 and 1500 M /gram. Of this, 2 2 the macropores will normally contribute 6 to 700 M /gram, pre2 ferably 6—200 M /g, as determined by mercury adsorption techniques, with the remainder contributed by the thermal treatment. Pore-free polymers, such as gel type resins which have been subjected to thermal treatment in the prior art (see, e.g.. East German Patent No. 27,022, February 12, 1964 No. 63,768, September 20, 1968) do not contribute the large pores essential to the adsorbents of the invention nor do they perform with the efficiency of the pyrolyzed poly25 mere described herein. The following table illustrates the effect of macroporosity on product composition: 43277 - 10 TABLE II Adsorbents from sulfonated styrene/divinylbenzene copolymers with varying macroporosity After Before Pyrolysis Pyrolysis Sample No. Polymer type % DVB Aver, pore size A Surface area (M2/g) Surface area 1 non-porous 8 0 0 32 2 macroporous 20 300 45 338 3 II 50 approx. 100 130 267 4 ' 80 50 570 570 5 6 20,000 6 360 All copolymers were sulfonated to at least 90% of theoretical maximum and heated in inert atmosphere to 800°C.

It may be noted from the data of Table II that the final surface area is not always directly related to the porosity of the starting material. The starting surface areas of the macro porous polymers span a factor of nearly 100 while the heat treated resins only differ by a factor of about 2. The nonporous gel resin has surface area well below the range of the starting materials of the invention and yielded a product with surface area substantially below the heat treated macro10 porous resin.

The preferred duration of pyrolysis depends upon the time needed to remove the volatiles from the particular polymer and the heat transfer characteristics of the method selected.

In general, the pyrolysis is very rapid when the heat transfer is rapid, e.g., in an oven where a shallow bed of material is pyrolyzed, or in a fluidized bed. To prevent burning of the pyrolyzed polymer, normally the temperature of the polymer is reduced to not more than 400°C., preferably not more than 22 7 7 - 11 300°C., before the pyrolyzed material is exposed to air. The most desirable method of operation involves rapid heating to the maximum temperature, holding the temperature at the maximum for a short period of time (in the order of 0—20 minutes) and thereafter quickly reducing the temperature to room temperature before exposing the sample. Products according to the invention have been produced by this preferred method by heating to 800°C. and cooling in a period of 20—30 minutes. Longer holding periods at the elevated temperatures are also satisfactory, since no additional decomposition appears to occur unless the temperature is increased.

Activating gases such as COj, SOy C^, or combinations thereof in small amounts tend to react with the polymer during pyrolysis and thereby increase the surface area of the final material. Such gases are optional and may be used to obtain special characteristics of the adsorbents.

The starting polymers which may be used to produce the pyrolyzed resins of the invention include macroreticular homopolymers or copolymers of one or more monoethylenically or polyethylenically unsaturated monomers or monomers which may be reacted by condensation to yield macroreticular polymers and copolymers. The macroreticular resins used as precursors in the formation of macroreticular heat treated polymers are not claimed as new compositions of matter in themselves. Any of the known materials of this type with an appropriate carbonfixing moiety is suitable. The preferred monomers are those aliphatic and aromatic materials which are ethylenically unsaturated.

Examples of suitable monoethylenically unsaturated monomers that may be used in making the granular macroreticular , 42277 - 12 resin include: styrene, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, tertbutyl acrylate, ethylhexyl acrylate, cyclohexyl acrylate, isobornyl acrylate, benzyl acrylate, phenyl acrylate, alkyl5 phenyl acrylate, ethoxymethyl acrylate, ethoxyethyl acrylate, ethoxypropyl acrylate, propoxymethyl acrylate, propoxyethyl acrylate, propoxypropyl acrylate, ethoxyphenyl acrylate, ethoxybenzyl acrylate, ethoxycyclohexyl acrylate, and the corresponding esters of methacrylic acid, ethylene,propylene, isobutylene, diisobutylene, styrene, vinyltoluene, vinyl chloride, vinyl acetate, vinylidene chloride, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, diacetone acrylamide, vinyl esters, including vinyl acetate, vinyl propionate vinyl butyrate, vinyl laurate, vinyl ketones including vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropyl ketone, vinyl n-butyl ketone, vinyl hexyl ketone, vinyl octyl ketone, methyl isopropenyl ketone, vinyl aldehydes including acrolein, methacrolein, crotonaldehyde vinyl ethers including vinyl methyl ether, vinyl ethyl ether, vinyl propyl ether, vinyl isobutyl ether, vinylidene compounds including vinylidene chloride, bromide, or bromochloride, esters of acrylic acid and methacrylic acid such as the methyl, ethyl, 2-chloroethyl, propyl, isopropyl, n-butyl, isobutyl, t-butyl, secbutyl, amyl, hexyl, glycidyl, ethoxyethyl, cyclohexyl, octyl, 2-ethylhexyl, decyl, dodecyl, hexadecyl and octadecyl esters of these acids, hydroxyalkyl methacrylates and acrylates such as hydroxyethyl methacrylate and hydroxypropyl methacrylate, also the corresponding neutral or half-acid half-esters of the unsaturated dicarboxylic acids including itaconic, citra30 conic, aconitic, fumaric and maleic acids, substituted acrylamides, such as N-monoalkyl, -Ν,Ν-dialkyl-, and N-dialkylaminoalkylacrylamides or methacrylamides where the alkyl groups may have from one to eighteen carbon atoms, such as - 13 42277 methyl, ethyl, isopropyl, butyl, hexyl, cyclohexyl, octyl, dodecyl, hexadecyl and octadecyl amonoalkyl esters of acrylic or methacrylic acid, such as β-dimethylaminoethyl, β-diethylaminoethyl or 6-dimethylaminohexyl acrylates and methacrylates, alkylthioethyl methacrylates and acrylates such as ethylthioethyl methacrylate, vinylpyridines, such as 2-vinyl pyridine, 4-vinylpyridine, 2-methyl-5-vinylpyridine. There may also be copolymerized with the polyfunctional methacrylates hereinbefore mentioned a difunctional methacrylate such as ethylene glycol dimethacrylate or trimethylolpropane dimethacrylate.

In the case of copolymers containing ethylthioethyl methacrylate, the products can be oxidized to, if desired, the corresponding sulfoxide or sulfone.

Polyethylenically unsaturated monomers which ordinarily act as though they have only one such unsaturated group, such as isoprene, butadiene, and chloroprene, may be used as part of the monoethylenically unsaturated category.

Examples of polyethylenically unsaturated compounds include: divinylbenzene, divinylpyridine, divinylnaphthalenes, diallyl phthalate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, divinylsulfone, polyvinyl or polyallyl ethers of glycol. Of glycerol, of pentaerythritol, of monothio or dithioderivatives of glycols, and of resorcinol, divinylketone, divinylsulfide, allyl acrylate, diallyl maleate, diallyl fumarate, diallyl succinate, diallyl carbonate, diallyl malonate, diallyl oxalate, diallyl adipate, diallyl sebacate, divinyl sebacate, diallyl tartrate, diallyl silicate, triallyl tricarballylate, triallyl aconitate, triallyl citrate, triallyl phosphate, N,N'-methylenediacrylamide, Ν,Ν'-methylenedimethacrylamide, Ν,Ν'-ethylenediacrylamide, trivinylnaphthalenes, and polyvinylanthracenes. 2 2 7 I A preferred class of monomers of this type are aromatic ethylenically unsaturated molecules such as styrene, vinyl pyridine, vinyl naphthalene, vinyl toluene, phenyl acrylate, vinyl xylenes.

Examples of preferred polyethylenically unsaturated compounds include divinyl pyridine, divinyl naphthalene, divinylbenzene, trivinylbenzene, alkyldivinylbenzenes having from 1 to 4 alkyl groups of 1 to 2 carbon atoms substituted in the benzene nucleus, and alkyltrivinylbenzenes having 1 to 3 alkyl groups of 1 to 2 carbon atoms substituted in the benzene nucleus. Besides the homopolymers and copolymers of these poly (vinyl)-benzene monomers, one or more of them may be copolymerized with up to 98% (by weight of the total monomer mixture) of (1) monoethylenically unsaturated monomers, or (2) polyethylenically unsaturated monomers other than the poly(vinyl)benzenes just defined, or (3) a mixture of (1) and (2). Examples of the alkyl-substituted di- and tri-vinylbenzenes are the various vinyltoluenes, divinylethylbenzene, 1,4- divinyl - 2,3,5,6 - tetramethylbenzene, 1,3,5 - trivinyl 2,4,6 - trimethylbenzene, 1,4 - divinyl - 2,3,6 - triethylbenzene, 1,2,4 - trivinyl - 3,5 - diethylbenzene, 1,3,5 - trivinyl - 2 - methylbenzene.

Most preferred are copolymers of styrene, divinylbenzene and ethylvinylbenzene.

Examples of suitable condensation monomers include* (a) aliphatic dibasic acids such as maleic acid, fumaric acid, itaconic acid, 1,1-cyclobutanedicarboxylic acid, etc.; (b) aliphatic diamines such as piperazine, 2-methylpiperazine, cis, cis-bis (4-aminocyclohexyl) methane, metaxylylenediamine, etc.; (c) glycols such as diethylene glycol, triethylene glycol, 1,2-butanediol, neopentyl glycol; (d) bischlorformates 2 2 7 7 such as cis and trans-1,4-cyclohexy1 bischloroformate, 2,2,2,4tetramethyl -13 - cyclobutyl bischloroformate and bischloroformates, other glycols ftientioned above; (e) hydroxy acids such as salicylic acid, m- and p-hydroxy-benzoic acid and lactones, derived therefrom such as the propiolactones, valerolactones, caprolactones; (f) diisocyanates such as cis and trans-cyclo-propane-1,2-diisocyanate, cis and trans cyclobutane-1,2-diisocyanate; (g) aromatic diacids and their derivatives (the esters, anhydrides and acid chlorides) such as phthalic acid, phthalic anhydride, terephthalic acid, isophthalic acid, dimethylphthalate; (h) aromatic diamines such as benzidine, 4,4'-methylenediamine, bis (4-aminophenyl) ether; (i) bisphenols such as bisphenol A, bisphenol C, bisphenol F, phenolphthalein resorcinol; (j) bisphenol bis (chloroformates) such as bisphenol A bis(chloroformate) 4, 4-dihydroxybenzophenone bis(chloroformate); (k) carbonyl and thiocarbonyl compounds such as formaldehyde, acetaldehyde, thioacetone acetone; (1) phenol and derivatives such as phenol, alkylphenols; and other condensation monomers and mixtures of the foregoing.

Ion exchange resins produced from aromatic and/or aliphatic monomers provide a preferred class of starting polymers for production of porous adsorbents. The ion exchange resin may also contain a functional group selected from cation, anion, strong base, weak base, sulfonic acid, carboxylic acid, oxygen containing, halogen and mixtures of the same. Further, such ion exchange resins may optionally contain an oxidizing agent, a reactive substance, sulfuric acid, nitric acid, acrylic acid, or the like at least partially filling the macropores of the polymer before heat treatment.

The synthetic polymer may be impregnated with a filler such as carbon black, charcoal, bonechar, sawdust or other carbonaceous material prior to pyrolysis. Such fillers provide 2 2 7 7 - 16 an economical source of carbon which may be added in amounts up to about 90% by weight of the polymer.

The starting polymers, when ion exchange resins,may optionally contain a variety of metals in their atomically dispersed form at the ionic sites. These metals may include iron, copper, silver, nickel, manganese, palladium, cobalt, titanium, zirconium, sodium, potassium, calcium, 2inc, cadmium, ruthenium and uranium. By utilizing the ion exchange mechanism it is possible for the skilled technician to control the amount of metal that is to be incorporated as well as the distribution.

Although the incorporation of metals onto the resins is primarily to aid their ability to serve as catalytic agents, useful adsorbents may also contain metal.

Synthetic polymers, ion exchange resins whether in the 15 acid, base or metal salt form are commercially available.

Adsorption processes for separating components from a gaseous or liquid medium which comprises contacting the medium with particles of a pyrolyzed synthetic polymer of this invention are the subject of Patent Specification No. //2/6 and fche whole contents of the disclosure and 20 claims of this copending Application as published for grant as herein incorporated by reference.

The adsorbents of the invention are particularly useful in the air pollution abatement field.

For example it has been discovered that a styrenedivinyl25 benzene based strongly acidic exchange resin pyrolyzed from any of the forms of Hydrogen, Iron (III), Copper (II), Silver (I) or Calcium (II) can decrease the concentration of vinylchloride In air preferably dry air from initial concentration of 2 ppm—300,000 ppm to a level of less than 1 ppm at flow rates of 1 bedvolume/hour to 600 bedvolume/min. preferably 2 2 7 7 - 17 10—200 bedvolume/minute.

The adsorbents when exhausted may be regenerated. The particular regenerant most suitable will depend on the nature of the adsorbed particle, but in general will include brine, solvents, hot water, acids and steam. The thermal regenerability of the adsorbents constitutes a distinct advantage.

Superior adsorbents may be produced according to this invention without the necessity of activation common to many carbonaceous adsorbents generally known as active carbon.

Adsorbents with properties both superior to and different from all other adsorbents may be produced directly in one step by heat treating polymers as described above. Activation with reactive gases is an optional process sometimes desirable for the modification of adsorbent properties but is not a necessary part of the invention. As shown in Tables III and IV below, the adsorption properties are markedly influenced by the maximum temperature to which the resin is exposed. As shown in Table III a temperature of 500°C produces an adsorbent which is optimum for chloroform removal from water. 2 277 - 18 TABLE XII Equilibrium Aqueous Chloroform Capacities for Various Adsorbents All adsorbents in equilibrium with 2 ppm CHC13 in deionized water at room temperature.

No. Sample Equilibrium Capacity at 2 ppm *S/DVB polymeric adsorbent Pittsburg Granular Activated Carbon 6.0 mg/g dry adsorbent .2 Sulfonated S/DVB resin pyrolyzed to 800°C 21 Same as No. 3 but oxygen etched 28 Same as No. 3 pyrolyzed to 500°C 45 S/DVB = Copolymer of styrene and divinylbenzene TABLE IV Molecular Screening Determination via Equilibrium Vapor Uptake Capacity (μ,Ι/g) No. SampleCC1/ Hexane2 1 Sulfonated S/DVB pyrolyzed to 500°C 12.1 15.6 2 Same as No. 1 pyrolyzed to 800°C 3.4 15.7 3 Pittsburgh Activated Carbon 41.0 40.9 4 Same as No. 2 oxygen etched 17.6 22.7 5 Carbon molecular sieve from Takede Chemical Industries 0.50 12.1 ^Effective minimum size 6.1 & Effective minimum size 4.3 S The following examples serve to illustrate but not limit the invention. In the examples the product pyrolyzed polymers all had pore sizes carbon contents and carbon to 2 2 7 7 - 19 hydrogen ratios according to the invention. Calgon and Amberlite·' are Registered Trademarks.

Example 1.

A 40 g sample of Amberlite 200, a Rohm and Haas Company styrene/DVB sulfonic acid ion exchange resin in the Na+ form, (49.15% solids) was placed in a filter tube and washed with 200 cc of deionised water 20 g of FeCl^ 6^0 were dissolved in about 1 1 of deionised water and passed through the resin sample in a columnar manner over a period of about four hours. Uniform and complete loading could be observed visually. The sample was then washed with 1 1 of deionised water, aspirated for 5 minutes and air dried for 18 hours. grams of this sample was then pyrolyzed together with several other samples in a furnace equipped for input of 7 1 of argon gas per minute. The sample was raised to a temperature of 706° C over a period of 6 hrs. with step increase of about 11O°C each hour. The sample was held at the maximum temperature for 1/2 hour. The power to the furnance was shut off and the furnace and contents were allowed to cool undisturbed to room temperature with the argon flowing continuously over the next 16 hours. The yield of solid material was 43% after pyrolysis. The physical characteristics of this sample are listed in Table V along with the data for Samples B through G, and I through K which were prepared in the same manner.

Example 2(a).

The technique of example I is modified in that 250 gm of Amberlite 200 in hydrogen form (obtained by converting the sodium form with hydrochloric acid) is pyrolyzed by raising the temperature continuously over siz hours to 76O°C. The sample is then allowed to cool over the next twelve hours 2 after which it shows a surface area of 390 m /g. +) •Η to c φ Q P o fi 0 Φ \ ri tp «ί fe fe nJ Φ ri Φ tn o \ fiCM m g ri fi W (0 Φ •ri ri to fi rri φ Ο ϋ ri O £? έ! to -ri x: to IP >i •iri rri a) o tP fe c •ri Φ •ri ri ri 0 fi ή *P Φ CO fe fi •ri •ri to ε* o □ φ t—! ε1 nj ω SD CM ID O N* in cn CM rO CM SD CO O (P N1 >cn O σ» cn SD CD fe a O’ fi Φ I—I fe ε fi O rri £ ε g1 ε e ε έ ε ε έ tP tn EP tP σ> tP & tn tn & O O O o o o o in rri o rri rri rri rH iri rri ra Γ- CM CM CM ΙΟ in o o CM Φ -P •ri rri ri φ N4 CO CM Φ •ri rri ri Φ fi H H H H fri H O O CM Φ -P •ri rri ri Φ I fi H H fi υ Φ •rl g fi c tP rt ra o o CM Φ •ri rri ri Φ o CM rri I CH H Φ •ri rri ri Φ ε ri O Sri fi ϋ O O CM •ri rri ri Φ o o CM Φ •ri iri ri Φ fi •ri o o CM fe •ri rH ri φ ra ra 4227? β • 0 co ft ft ft (0 ft >1 Ό to ft β rt 0 0 ft to □ β >1 a Pl Φ •η ft ft 0 ft to ft rt to Ol to Φ 0 β ft β H to 3 Pi Ό . to Φ CM ft Nt O rt >1 w ft β 0 ft ft to 0 >1 '0 04 β Φ 0 co •rl ft ft Ό CM Ο ω * β o ft ft rt to Φ β Φ Oi Φ ft £,1 +j ft rt Pi rt υ β ο •η ft rt to β ft rt w o o o rt ft ft rt dP dP dP O m o oo r* cm Cp tn bi \ X Φ Φ Φ ft ft ft 0 Q 0 £ S β β β β o ro ο CM CM CD 6 o 6 & Pi o § 0) V N (0 β Φ Λ ft iX β ft > ft U β Φ Φ Φ ft Μ Η Ο >ι ft Μ ft Cn β Μ ft Ο > Md Φ Λ C0 Φ co sample of polyacrylonitrile crosslinked with 15% •rl ft ft to Φ 0 Οι ft Ο α Φ ίχ ft Ο ft Ό Φ Ν >1 ft Ο Μ >d ft Φ β Φ Ν β Φ ft ft ίχ β ‘Η > ft Ω Cn CM S cn Μ Οι rd α ft φ β CM ο φ ω co β Μ Ο φ ft >ι +1 ft ϋ rt Οι 'ΰ Φ ο ft β β ο ft η § Ρ Η Φ rd < ft ft β Ο ft Φ Η ft tn > ο ft Μ ίχ ft ft ft ft § ‘3 * Ed rt cu *d rt Φ U Λί β ft ft β ft Φ co Λ w to O O to co O dP dP dP rt CM CD rt ft in cn β ft ft rt to ft β Φ β ο ϋ φ ft rt ft to o co Ό rt ft β Pl β ft CM dP in co co ft co >1 ft O to S Pl Φ to ft Φ ft TJ ft to Φ P. to β ft CM X Ο Φ ft Ed Φ · e * ft rt Ed a co to to to ϋ ft β +> cu ft 0 (0 E to to to Cn QJ β 3 β Φ to 0) Eh 0 0 0 > β · ft ft ft rt •Η X ft β EH 10 ft ft ft ft S 0 ft co β 0 • ft & § ft β 0 ft • • · ft »3 EH υ υ υ β 0 0 0 co 0 • o o 2 rt υ X r- CM O £ (0 m cn cd co s % ft CQ Φ >· ¢) de ft ft ft de Pi 0 & A £ 3 £ to 2 rt ro w cul W in O ft CM O o CM ffi dP O ft ft £ o rft rt to Φ > O a o o rt cn O ft to •rd rt β ft Ό Φ s >1 ft ft Ό rt Φ ft co φ ϋ co ft O rt rt Q £ to ft ft CM Φ ft Oi rt £ •rl β o1 cm ω w 3 * de de de in ft - 22 42377 Example 2(c).

Crush Resistance The physical integrity of beads of pyrolyzed polymers is greater than that of other spherical adsorbents and granular activated carbon as indicated in Table XIV.

Superior resistance to fragmentation is expected to result in a greatly extended useful life compared to granular carbon for which attrition losses can be large. Also the lack of sloughage of particulate matter by the pyrolyzed polymers allows their use in applications for which activated carbon is unacceptable such as blood treatment.

TABLE VII Crush Strength of Macroreticular Pyrolyzed Polymers and other Adsorbents Description No. Type Crush Strength^ (Kg) Sulfonated S/DVB heat 1 treated under inert atmosphere to indicated 2 temperature Spherical Activated 6 Carbon 400°C 2.3 500°c ^3.12 600°C ^3.42 800°C >3.42 1000°C 7>3.6 Kureha 0.93 Sample of unknown 0.51 Granular Activated 8 Carbon Japanese origin used for blood treatment experiments .

Pittsburgh BPL ^0.90 Mass which must be placed on upper of two parallel plates to fragment particle between plates-average of at least 10 trials. 2 2 7 7 - 23 2 Lower limit because at least one particle was not broken at maximum setting of 3.6 Kg.

^No beads were broken at maximum setting.

. Since particles are irregularly shaped, experiment was halted when a corner was knocked off. i) Carbon Fixing Moieties A wide variety of moieties have been shown to cause carbon fixation during pyrolysis. A partial list of moieties and the effectiveness of each is given in Table VIII. The exact chemical nature of the moiety is unimportant since any group which serves to prevent volatilization of the carbon during pyrolysis is satisfactory for the process. ii) Imbibed Carbon-Fixing Agents Filling the pores of a macroreticular copolymer with a reactive substance prior to pyrolysis serves to prevent volatilization of the carbon in the copolymer. In the case of sulfuric acid the material has been shown to go through a sulfonation reaction during heating which produces a substance similar to the starting material of sample I in Table VIII.

The greater carbon yield obtained via imbibing rather than presulfonation is unexpected indicating the process may be superior to other techniques of carbon fixation. iii) Impregnated Polymers Impregnation is exemplified in No. 4 of Table IX for which the pores of a carbon black containing S/DVB copolymer were filled with H2S0^ an^ Pyrolyzed. The carbon yield is higher than the corresponding experiment (sample 1) performed without the presence of the carbon black. - 24 TABLE VIII Carbon Fixing Moieties Resin Moiety Apparent Yieldl Carbon Yield2 Shape Retention S/DVB Sulfonate 37.0% 66% Yes S/DVB Carboxylate 47.3% 59% Yes S/DVB Chloromethyl 34% 48% Fair AN/DVB Nitrile 33% 73% Yes S/DVB Amine 20.2% 30% Fair 4-Vinyl Pyridine/DVB8 21% 26% Fair S/DVB 3 Carboxylate Pe +Salt 51% 59% Yes S/DVB 3 Sulfonate Fe +Salt 51% 77% Yes S/DVB Gas Phase Chlorinated 38.4% 76% Yes s/dvb Quaternary Ammo- 24% 46% Yes nium Salt '"Initial wt./final wt. x 100 after heating to at least 600°C. 2 Percent of carbon in copolymer which remains after heating.

Moiety is nitrogen contained in pyridine group.

TABLE IX Carbon Fixation Imbibing Agents Sample No. Copolymer Imbibed Material Apparent Carbon Shape Retention Yield Yield 1 S/DVB 98% H2SO4 66.7 86% Excellent 2 S/DVB Polyacrylic Acid Ni2+ Form 42.4 91% * Excellent 3 S/DVB AgN03 32 41% Excellent 4 S/DVB + 98% H»SO - 94% Excellent Carbohblack =£ *Assuming all residual carbon comes from S/DVB and all the polyacrylic acid volatilizes. impregnated during polymerization with 20% by weight of carbon black. - 25 Example 3.

The following experiment produced sample No. 1 in Table IX.

A sample of 30.79 g of the macroreticular copolymer (20% DVB/S) was placed in a 30 mm outside diameter quartz tube suitable for subsequent heat treatment. One end of the tube was blocked with quartz wool and the copolymer was piled on top of the quartz wool with the tube held vertically. Isopropanol, D.I. water and 98% H2S04 ·*· eac^1 were passed in sequence through the resin over a 1.5 hr. period. Excess H2S0^ was drained during a 10 min. hold. Approximately 5.5 g of acid remained in the pores of the resin. The tube was placed horizontally in a tube furnace and N2 passed through the tube at 4,800 cc/min. During heating white smoke and then a reddish, pungent smelling oil were emitted from the sample. The final product was black, shiny, free flowing beads roughly the same size as the starting resin.

Example 4.

The following experiment produced sample 2 of Table IX.

A benzoic acid copolymer was prepared from a chloromethylated resin (20% DVB/S) by nitric acid oxidation. A charge of 20.21 g of the solvent swelled and vacuum dried resin was placed in a quartz tube plugged at one end with quartz wool. The tube was held horizontally inside a Glascol heating mantle and heated gradually to 800°C. over a period of 200 mins. The sample was cooled to room temperature within about 120 min. Nitrogen flowed through the tube during heating at a rate of 4800 cc/min. White smoke was emitted by the sample during heating. The final product consisted of shiny metallic black beads.

Typical multimodal pore size distribution of the pyrolyzed polymer particles is illustrated hereinbelow in

Claims (27)

1. CLAIMS:1. Partially pyrolyzed particles of macroporous synthetic polymer having properties suitable for use in adsorption, molecular screening and/or catalysis and high resistance to crushing and particle sloughage comprising the product of controlled thermal degradation of macroporous synthetic polymer containing at least one carbon-fixing moiety and derived from one or more ethylenically unsaturated monomers, or monomers which may be condensed to yield macroporous polymers, or mixtures thereof, which partially pyrolyzed particles have: (a) at least 85% by weight of carbon, (fa) multimodal pore distribution with macropores in the size range 50 £ to 100,000 £ in average critical dimension and (c) a carbon to hydrogen atom ratio of between 1.5:1 and 20:1.

2. Partially pyrolyzed particles as claimed in claim 1 wherein the particles are beads or spheres of approximately the same dimensions as ion exchange resins.

3. Partially pyrolyzed particles as claimed in claim 1 or 2 wherein the particles contain micropores of molecular sieve size in the size range 4 £ to 6 £ in average critical dimension.

4. Partially pyrolyzed particles as claimed in any preceding claim wherein the surface area of the particles 2 measured by N adsorption is from 50 to 1500M /gram, of which 2 2 the macropores contribute 6 to 700M /gram as determined by mercury adsorption techniques.

5. Partially pyrolyzed particles as claimed in any preceding claim wherein the pores of the particles are bimodal with micropores in the size range 4 £ to 50 £ and macropores in the size range 50 £ to 100,000 £. 4 2 3 7 7 - 28

6. Partially pyrolyzed particles as claimed in any preceding claim wherein the carbon to hydrogen atom ratio is between 2.0:1 and 10:1.

7. Partially pyrolyzed particles as claimed in any preceding claim wherein the carbon-fixing moiety is selected from sulfonate,. carboxy, amine, halogen, oxygen, sulfonate salts, carboxylate salts and quaternary amine salts.

8. Partially pyrolyzed particles as claimed in any preceding claim wherein the carbon to hydrogen atom ratio of the particles is at least 9.0.

9. Particles of macroporous synthetic polymer which have been subjected to partial pyrolysis and which contain at least one carbon-fixing moiety, said heat treated particles having (a) at least 85% by weight of carbon (b) multimodal pore distribution with at least one peak frequency of pore average critical dimension, preferably average pore diameter, in the range 50 £ to 100,000 £ and (c) carbon to hydrogen atom ratio from 1.5:1 to 20:1.

10. Particles according to claim 9 having at least one peak frequency of pore average critical dimension in the range 50 £ to 100,000 £ and at least one other such peak in the range 2 £ to 50 £.

11. Particles as claimed in any preceding claim, wherein the particles contain up to 15% by weight of metal.

12. Particles as claimed in any preceding claim which contain up to 15% by weight of one or more of the following: alkali metal, alkaline earth metal, nitrogen, oxygen, sulfur, chlorine, transition metal.

13. Particles as claimed in claim 11 which contain up to 15% by weight of one or more of the metals: iron, copper. 4 2 2 7 7 - 29 silver, nickel, manganese, palladium, cobalt, titanium, zirconium, sodium, potassium, calcium, zinc, cadmium, ruthenium and uranium.

14. Partially pyrolyzed particles as claimed in claim 1 or 9 substantially as described in any one of the foregoing Examples.

15. A process for producing partially pyrolyzed particles of macroporous synthetic polymer which comprises thermally degrading at a temperature between 300°C and 900°C and in an inert gaseous atmosphere optionally containing an activating gas, macroporous synthetic polymer containing at least one carbon-fixing moiety and derived from one or more ethylenically unsaturated monomers, or monomers which may be condensation polymerized to yield macroporous polymers, or mixtures thereof, for a time sufficient to drive off sufficient volatile components of the synthetic polymer to yield particles having: (a) at least 85% by weight of carbon, (b) multimodal pore distribution with macropores in the size range from 50 § to 100,000 S in average critical dimension and (c) a carbon to hydrogen atom ratio of between 1.5:1 and 20:1, and thereafter cooling said particles under said inert atmosphere to a temperature below that which would cause oxidation in air.

16. A process as claimed in claim 15 wherein the thermal degradation is conducted at a temperature between 400°C and 800°C.

17. A process as claimed in claim 15 substantially as described in any one of the foregoing Examples.

18. A process for the preparation of partially pyrolyzed particles which comprises providing macroreticular resin particles made by polymerization of one or more ethylenically unsaturated monomers and having imparted 4 2377 r 30 thereto ion exchange functional groups which will help to maintain their macroreticular structure during pyrolysis, and subjecting the particles to thermal degradation in an inert atmosphere, optionally containing activating gas, while removing the volatile products produced, so that the resulting particles have multimodal pore distribution with macropores in the size range 50 £ to 100,000 £ in average critical dimension.

19. A process as claimed in claim 18 wherein the atmosphere in which thermal degradation is conducted is totally inert.

20. A process as claimed in claim 18 or 19 wherein the ion exchange functional groups are strong acid functional groups.

21. A process as claimed in claim 20 wherein the ion exchange functional groups are sulfonic acid groups.

22. A process as claimed in claim 18 or 19 wherein the particles subjected to thermal degradation are particles of sulfonated styrene/divinylbenzene copolymer.

23. A process as claimed in any one of claims 18 to 22 wherein the inert atmosphere is nitrogen.

24. A process as claimed in any of claims 18 to 23 wherein the thermal degradation is carried out at a temperature of 400 to 800°C.

25. A process as claimed in claim 18 whenever carried out substantially as described in foregoing Example 1 or 2(a).

26. Partially pyrolyzed particles whenever prepared by a process as claimed in any one of claims 15 to 17.

27. Porous carbonaceous material whenever prepared by a process as claimed in any one of claims 18 to 25.