Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8668—Removing organic compounds not provided for in B01D53/8603 - B01D53/8665
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
  • B01D53/86—Catalytic processes
  • B01D53/8659—Removing halogens or halogen compounds
  • B01D53/8662—Organic halogen compounds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/06—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04
  • B01J20/08—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising oxides or hydroxides of metals not provided for in group B01J20/04 comprising aluminium oxide or hydroxide; comprising bauxite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
  • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/3416—Regenerating or reactivating of sorbents or filter aids comprising free carbon, e.g. activated carbon
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/3433—Regenerating or reactivating of sorbents or filter aids other than those covered by B01J20/3408 - B01J20/3425
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
  • B01J20/30—Processes for preparing, regenerating, or reactivating
  • B01J20/34—Regenerating or reactivating
  • B01J20/345—Regenerating or reactivating using a particular desorbing compound or mixture
  • B01J20/3458—Regenerating or reactivating using a particular desorbing compound or mixture in the gas phase
  • B01J20/3466—Regenerating or reactivating using a particular desorbing compound or mixture in the gas phase with steam

Definitions

• the invention relates to a method for the regeneration of an adsorption filter which contains (halogeno)hydrocarbons.
• Halogenated hydrocarbons in particular chlorinated hydrocarbons, are used on a large scale. In agriculture, they are used intensively in the control of weeds and microorganisms. In the chemical industry they find many applications, for example as raw materials for the production of, inter alia, polymers and pesticides.
• HHCs are always toxic to a greater or lesser extent. Some HHC compounds are many times more toxic than, for example, potassium cyanide. In contrast to other substances which pollute the environment, such as NO x , SO 2 and NH 3 , HHCs are not included in the ecological cycle. They are not, or are very sparingly, microbiologically degradable and they are also not chemically reactive under normal conditions.
• HHCs Insofar as HHCs pass into the air, they are converted in the higher layers of the air into other substances which pollute the environment; the attack on the ozone layer is a consequence of this. If they pass into the soil, they then accumulate in ground and water and threaten, inter alia, the drinking water supply. The number of projects for cleaning up soil and ground water is increasing hand over fist and frequently it is mainly HHC pollution which is concerned here. In all of these cases, the HHCs constitute an unwarrantable pollution of the environment.
• HHC combustion also has the great disadvantage that, with the current state of technology, it constitutes pollution of the environment; there is an appreciable emission of CO 2 and NO x , while it is still not possible to prevent the emission of dioxin.
• a spent adsorption filter which contains ((halogeno)hydrocarbons can be regenerated by introducing the adsorption filter into a desorption apparatus, passing steam through the filter in this apparatus in a ratio such that the molar ratio of steam/carbon is greater than 1, passing the resulting mixture into a catalytic reactor and bringing it into contact, in this reactor, with a catalyst consisting of one or more transition metals and reacting it thereon.
• a steam to carbon molar ratio of 1:(2-4), preferably 1:(2.5-4) is used in this process.
• dichloroethane (DCE) this ratio is preferably 5 to 7.
• the catalyst used is preferably applied to a porous ceramic support.
• the catalyst is expediently made up on the basis of Pt, Rh, Ir, Pd, Ru, Ni, Fe and/or Co.
• the invention also provides a method for the removal of (halogeno)hydrocarbons from gases, which method is characterised in that
• the products obtained on desorption can subsequently be destroyed directly, that is to say converted into substances appreciably less harmful to the environment, or can be re-used.
• the steam added is used not only for the desorption but also for the conversion reaction, which leads to an appreciable saving in energy and costs.
• process control is excellent and as a result of the recycling a saving in raw material (active charcoal) is achieved and a waste stream is not formed, while fully automated operation is possible and contaminants can be removed down to extremely low levels.
• the first equation represents a reaction which must be regarded as kinetically controlled and the other two are equilibria.
• Reaction i) is endothermic and the other two are exothermic. If the conditions are selected well, the process can proceed autothermically.
• This system can be used for HHCs, which are then converted to, for example, hydrogen, carbon dioxide, methane and hydrogen halide.
• the method according to the invention has the advantage that large streams of air can be treated without these having to be heated. As a result of the central regeneration of the adsorber, the heat to be supplied is therefore used much more efficiently. A high efficiency is achieved by treatment with the aid of steam-reforming.
• adsorption filters which can be collected, a large regeneration installation can expediently be built at a central location and it is possible to use inexpensive standard adsorbers.
• the spent and regenerated adsorbers can be returned for re-use after regeneration.
• Particularly suitable adsorbent materials in the adsorbers for the method according to the invention are active charcoal, coconut charcoal and aluminium oxide. However, other absorbent materials can also be used.
• an adsorber can, depending on the precise application, be regenerated at least 100 times without the adsorption declining too much. Of course, all of this is dependent on the type of contamination on the active absorbent substance. If poisoning of the absorbent material takes place, fewer regeneration cycles will, of course, be possible. All of this is, however, well known to those skilled in the art.
• the amount of steam used in steam reforming also serves to prevent the deposition of carbon on the cataly ⁇ t.
• the steam has a two-fold function. On the one hand, the steam serves as desorption agent and at the same time the steam serves as agent for forming the reaction mixture with halogenohydrocarbons which has to be passed over the catalyst.
• the method according to the invention is suitable for the treatment of off-gases from, for example, spray installations and paint factories, for the treatment of stripper air in the clean-up treatment of ground water and for the destruction or conversion of substances from oil and paint residues, treatment of chemical waste, treatment of raw materials in the chemical industry and the like.
• the applicability of the treatment method according to the invention is illustrated with the aid of a number of simple tests using dichloroethane (DCE) and nickel and platinum catalysts. Both catalysts are applied to an aluminium oxide support.
• DCE dichloroethane
• Both catalysts are applied to an aluminium oxide support.
• the majority of tests were carried out at low temperature, on the one hand in order to keep the energy consumption as low as possible and on the other hand to avoid problems with the possible poisoning of the catalyst by hydrogen halide.
• the tests were carried out with short contact times in a flowthrough tubular reactor and with long contact times in a batchwise reactor, which also served for tests under high pressure.
• the content of converted DCE which together with the total reaction time gives a measure of the rate of reaction and the amount of DCE converted, is calculated via 6LC analysis from the product spectrum obtained via the GLC analysis.
• Total DCE converted from increase in the weight of lime when hydrochloric acid is formed this is chemically bound by the slaked lime. During this operation, hydroxyl groups are replaced by chloride, which is appreciably heavier. From the increase in weight it is possible to calculate back how much chloride was present and ultimately how much DCE was converted.
• Total DCE converted from the reduction in the N 2 content when DCE is converted into a number of products, the nitrogen content declines proportionately and an impression of the conversion is obtained. This method is sensible only if the DCE content in the vapour phase remains constant as a result of refluxing.
• the flask was provided with a reflux condenser, the outlet of which was connected to a wash bottle containing water.
• a glass capillary which was connected to a nitrogen cylinder fitted with a pressure relief valve was inserted through one of the necks, so that the reaction was carried out in an inert nitrogen environment and a turbulent gas flow was produced through the capillary, so that the vapour was able to come into contact with the catalyst.
• 50 ml gas samples were removed from the centre of the flask by means of a plastic tube through the condenser.
• the wash bottle contained 250 ml of demineralised water, in which the hydrochloric acid formed was collected. It was possible to heat the flask by means of a fitted heating jacket.
• tests were also carried out under elevated pressure in an autoclave.
• the catalyst was mixed with slaked lime and placed together with DCE and water in a glass insert in a 250 ml autoclave.
• the vapour was circulated by means of a vertical stirrer mechanism so that good contact with the catalyst could be achieved.
• the autoclave was flushed with nitrogen by three times in succession placing the autoclave under a nitrogen pressure of 10 bar and then letting down the pressure again. Using a pre-pressure of 2 bar, the autoclave was then heated to the desired temperature and finally brought to the desired operating temperature using nitrogen. Gas samples were collected via a sample tap in 50 ml Teflon gas syringes and then analysed by gas chromatography.
• Example VII In the experiment using Ni under 60 bar (Example VII) a large amount of a substance which was possibly propane was initially formed. In the relevant gas chromatograms the presence can be seen of a component which could not be defined but on the basis of retention time data was possibly methanol but more probably propane. For these experiments it was not important to investigate the identity of this substance in more detail and it was provisionally assumed that it was propane. Products such as, for example, monochloroethene were not present. In addition to propane, ethene was to be seen as the second product, while ethane, CO 2 and higher hydrocarbons later also came into the picture.
• Example V In the tests using Pt at 30 bar (Example V), mainly ethane and some ethene and CO 2 were to be seen initially, when the DCE conversion was still not complete. Subsequently, methane and higher hydrocarbons were also detected. Under a higher pressure of 130 bar (Example VII), the initial product was not ethane, but CO 2 and ethene were found in a ratio of 2 to 1. This implies that the amount of DCE converted to CO 2 is identical to the amount converted to ethene. In addition, just as in the experiment using Ni, a large amount of undefined substance, possibly propane, was present. There is no clear explanation for this. At a temperature of 440°C methane and higher hydrocarbons were also formed immediately under both pressures (Examples V and VI), while ethane is far and away the most important product.
• converted - Cl analys is in lime: ⁇ 0.8 g DCE;
• the experiments were carried out in a quartz tubular reactor fitted with a concentric preheater.
• the reactant stream consisted of nitrogen mixed with steam and DCE.
• nitrogen was passed in two parallel streams through a rotameter for flow control and then through a wash bottle filled with water or, respectively, DCE, after which the two streams were combined in a one-way vessel.
• the combined stream was then passed to the preheater and the reactor, after which the off-gas is vented via a wash bottle containing 250 ml of demineralised water to the ambient air. This latter bottle serves as a visible indication of the gas flow through the reactor, as a water lock in order to prevent oxygen flowing back to the reactor and also as a trap for acid product components.
• the reactor was first flushed for at least one hour at room temperature with the reaction mixture, after which a sample of the reaction mixture was taken from the off-air from the water lock. The analysis of this sample was used to calculate the composition of the reaction mixture, which is needed for conversion calculations.
• Example VIII An appreciable conversion of DCE was found both in the case of Pt (Example VIII) and in the case of Ni (Examples IX and X).
• cyclohexane was added to the reaction mixture in Example IX, but no great differences were found compared with the results of Comparative Example IX where no cyclohexane was used. For this reason only samples 42 and 45 (see Appendix) were calculated. In all cases no to very little CO was detected.
• Example VIII An appreciable conversion of DCE was found both in the case of Pt (Example VIII) and in the case of Ni (Examples IX and X).
• Catalyst Ni (not pretreated CRG, 0.10 g,
• wash water average conversion is about 39 %
• Catalyst Ni (not pretreated CRG, 0.10 g,
• wash water average conversion is about 40 %

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• Chemical & Material Sciences (AREA)
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Cited By (4)

Citations (6)

• 1990
  • 1990-07-26 NL NL9001697A patent/NL9001697A/nl not_active Application Discontinuation
• 1991
  • 1991-07-25 WO PCT/NL1991/000138 patent/WO1992001502A1/en unknown

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