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
  • B01D53/02—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
  • B01D53/04—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 with stationary adsorbents
  • B01D53/047—Pressure swing adsorption
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/20—Organic adsorbents
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/20—Organic adsorbents
  • B01D2253/204—Metal organic frameworks (MOF's)
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/30—Physical properties of adsorbents
  • B01D2253/302—Dimensions
  • B01D2253/306—Surface area, e.g. BET-specific surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2253/00—Adsorbents used in seperation treatment of gases and vapours
  • B01D2253/30—Physical properties of adsorbents
  • B01D2253/302—Dimensions
  • B01D2253/308—Pore size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2256/00—Main component in the product gas stream after treatment
  • B01D2256/24—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2256/00—Main component in the product gas stream after treatment
  • B01D2256/24—Hydrocarbons
  • B01D2256/245—Methane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2257/00—Components to be removed
  • B01D2257/50—Carbon oxides
  • B01D2257/504—Carbon dioxide
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2259/00—Type of treatment
  • B01D2259/40—Further details for adsorption processes and devices
  • B01D2259/40011—Methods relating to the process cycle in pressure or temperature swing adsorption
  • B01D2259/40077—Direction of flow
  • B01D2259/40081—Counter-current
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
  • Y02C20/00—Capture or disposal of greenhouse gases
  • Y02C20/40—Capture or disposal of greenhouse gases of CO2

Definitions

• the present invention relates to adsorption processes, and more particularly to pressure swing adsorption processes.
• the process employs metal-organic framework materials having a high porosity and high surface areas, and are useful in the separation of carbon dioxide from hydrocarbon streams.
• One technique for separation of one component in a gas from a mixture uses adsorption of one or more components from the mixture onto an adsorbent. This process is further enhanced through pressure swing adsorption (PSA). Pressure swing adsorption entails passing a feedstream over an adsorbent where one, or more, components of the feedstream are selectively adsorbed onto the adsorbent, and where the process of adsorption is performed at a relatively high pressure.
• PSA pressure swing adsorption
• the adsorbent is regenerated by reducing the pressure over the adsorbent, and a process of desorption is performed at the relatively low pressure.
• the desorption process can also be accompanied by the passing of a purge gas having a low concentration of the adsorbate to enhance desorption.
• the separation of gases from a gas mixture through adsorption in a pressure swing adsorption process is controlled by the pressures used in the process and the capacity of the adsorbent for one, or more, of the components in the gas mixture.
• the process usually entails a tradeoff between the range in pressure, and the load capacity of the adsorbent for many of the materials used. It is desirable to be able to use materials that can overcome some of these tradeoffs.
• the invention is a pressure swing adsorption process for removing carbon dioxide from a hydrocarbon stream.
• the process passes the hydrocarbon stream over a metal organic framework material at a high adsorption pressure, generating an effluent stream with a reduced carbon dioxide content.
• the process then reduces the pressure over the metal organic framework material and releases the carbon dioxide from the material, and generates a stream having carbon dioxide.
• the process steps are then repeated.
• the process uses multiple adsorption beds comprising the metal organic framework material and cycles the pressures sequentially through the beds to produce a continuous process.
• Figure 1 is the comparison of CO2 adsorption on different materials
• Figure 2 is the comparison of CH4 adsorption on carbon and MOF-5
• Figure 3 is a comparison of CO2 adsorption isotherms for a variety of MOFs and IRMOFs.
• the separation of gases from a gas mixture through adsorption in a pressure swing adsorption process is controlled by the difference between adsorption and desorption pressures and capacity of one of the components in the gas mixture.
• the process usually entails a tradeoff between the pressure differences and the capacity for many of the materials used.
• the capacity is the amount of material adsorbed by the adsorbent. It is desirable to be able to use materials that can overcome some of these tradeoffs.
• pressure swing adsorption a gas made up of at least two constituents, is separated using the differences in selectivity of one of the constituents. Usually, the gas is purified by selectively removing an undesired constituent of the gas.
• the gas is typically fed into an adsorption unit at an elevated pressure, where one of the constituents is preferentially adsorbed onto an adsorbent. While one constituent is preferentially adsorbed, other constituents are also adsorbed, and it is desired to use adsorbents that have significant differences in the adsorption of the desired constituents.
• the adsorbent is regenerated through reversing the adsorption process to desorb the constituents. This is done by changing the conditions of the adsorbent environment through reducing the pressure. At a defined time or conditions, the gas feed to the adsorption unit is stopped, and the adsorption unit is depressurized.
• the gas feed is stopped when the adsorption unit is near or at capacity for the adsorbent with the desired constituent.
• the adsorption unit is depressurized to a specified level where the adsorbed constituents desorb generating a desorbent stream that is relatively rich in the constituent that is more strongly adsorbed onto the adsorbent.
• the desorption process can use an inert gas, or a non- hydrocarbon gas to facilitate the desorption process.
• the desorption gas is passed over the adsorbent to remove the adsorbed constituents as they desorb from the adsorbent.
• the desorption gas is passed over the adsorbent in a direction opposite the direction of the feed gas to regenerate the adsorbent.
• An aspect of a pressure swing adsorption system is the isotherm for adsorbing a component in a gas dictates the operating pressures and loading onto the adsorbent. Most materials have an isotherm, wherein the saturation limit is rapidly approached, and then there is a small incremental improvement in adsorption for a relatively large increase in pressure.
• the working capacity of an adsorbent is defined as difference in the amount of the adsorbed components on the adsorbent between the adsorption pressure and the desorption, or regeneration, pressure. Lowering the regeneration pressure can increase the capacity of the adsorbent for selectively removing a component from a gas, but the effluent stream from the regeneration step may need to be recompressed. However, a lower regeneration pressure increases the recompression costs.
• adsorbents In pressure swing adsorption, there are many classes of adsorbents that are suitable. The selection is dependent upon the feed gas constituents and other factors generally known to those skilled in the art. In general, suitable adsorbents include molecular sieves, silica gels, activated carbons, activated aluminas, and other porous metal oxides. When purifying methane containing streams, the methane is often adsorbed along with the impurities that one wishes to remove. The choice of adsorbent presents problems in selecting an adsorbent that has the greatest differential in adsorption between methane and selected impurities.
• the search is for a high permeability material that also has a high capacity for use in a pressure swing adsorber.
• One embodiment of the invention is a process using pressure swing adsorption for the removal of carbon dioxide from a hydrocarbon rich feedstream.
• the process comprises passing the hydrocarbon feedstream having carbon dioxide over an adsorbent in an adsorption zone, and at a temperature and pressure sufficient to adsorb a portion of the carbon dioxide.
• the remaining gases in the feedstream become an effluent stream having a reduced carbon dioxide content.
• the adsorbent in the process is one of a series of materials known as metal organic framework (MOF) materials, and has a high surface area and high porosity. The surface area of the material is greater than 1500 m 2 /gm.
• the pressure in the adsorption zone is then reduced to a pressure for desorbing the carbon dioxide, and generates a desorption effluent stream having an enriched carbon dioxide content.
• the process during desorption can include passing a carbon dioxide lean purge gas over the adsorbent.
• the process can be carried out by either passing the adsorbent bed through a high pressure adsorption zone, and then moving the adsorbent bed to a low pressure desorption zone, such as occurs with an adsorbent wheel in a rotating drum adsorber.
• the process can also be carried out by alternately pressurizing the adsorbent bed and passing the feedstream over the bed, and depressurizing the adsorbent bed and passing a purge gas over the bed.
• the feedstream is passed over the adsorbent, in a first adsorbent zone, at the highest pressure of the process, with the carbon dioxide and some of the other constituents adsorbed, generating a carbon dioxide depleted methane stream.
• the carbon dioxide depleted methane discharges from the adsorption zone so that carbon dioxide adsorption fronts are formed in the zone at the methane feedstream inlet end and progressively move toward the outlet.
• the adsorption zone is sized to produce a hydrocarbon gas product primarily comprising methane with a carbon dioxide concentration less than 1% by volume and preferably less than 0.1% by volume.
• the feedstream to the adsorbent unit is terminated when either the carbon dioxide adsorption front is at a predetermined point in the adsorption unit, or when there is an increase in the carbon dioxide in the CO 2 depleted methane stream to above a predetermined value.
• the feedstream is then terminated to the first adsorption zone, and directed to a second adsorption zone.
• the first adsorption zone is depressurized and a purge gas is passed through the first adsorption zone to regenerate the adsorbent in the first adsorption zone.
• the purge gas preferably flows in a counter current direction relative to the flow of the feedstream in the adsorption zones to remove the carbon dioxide in the reverse direction that it was adsorbed.
• the operating conditions for the pressure swing adsorption process include adsorption pressures from 2 MPa (20 atms.) to 5 MPa (50 atms.).
• the desorption pressure is in a range from 1 kPa (1 atm) to 1.5 MPa (15 atms.), with a preferred range from 500 kPa (5 atm) to 1 MPa (10 atms.).
• the desorption step is preferably operated at a pressure sufficient to minimize recompressing the desorption effluent stream.
• the adsorbent needs to be thermally stable for a range of temperatures, and operation is at temperatures between O 0 C to 400 0 C.
• MOFs metal-organic framework materials.
• MOFs have very high surface areas per unit volumes, and have very high porosities.
• MOFs are a new generation of porous materials which have a crystalline structure comprising repeated units having a metal or metal oxide with a charge and organic units having a balancing counter charge.
• MOFs provide for pore sizes that can be controlled with the choice of organic structural unit, where larger organic structural units can provide for larger pore sizes.
• the capacity and adsorption characteristics for a given gas is dependent on the materials in the MOF, as well as the size of the pores created. Structures and building units for MOFs can be found in US 2005/0192175 published on September 1, 2005 and PCT publication no. WO 2002/088148 published on November 7, 2002, both of which are incorporated by reference in their entireties.
• the materials of use for this process include MOFs with a plurality of metal, metal oxide, metal cluster or metal oxide cluster building units, hereinafter referred to as metal building units, where the metal is selected from the transition metals in the periodic table, and beryllium.
• metal building units where the metal is selected from the transition metals in the periodic table, and beryllium.
• Preferred metals include zinc (Zn), cadmium (Cd), mercury (Hg), and beryllium (Be).
• the metal building units are linked by organic compounds to form a porous structure, where the organic compounds for linking the adjacent metal building units include 1,3,5- benzenetribenzoate (BTB); 1 ,4-benzenedicarboxylate (BDC); cyclobutyl 1,4- benzenedicarboxylate (CB BDC); 2-amino 1,4 benzenedicarboxylate (H2N BDC); tetrahydropyrene 2,7-dicarboxylate (HPDC); terphenyl dicarboxylate (TPDC); 2,6 naphthalene dicarboxylate (2,6-NDC); pyrene 2,7-dicarboxylate (PDC); biphenyl dicarboxylate (BDC); or any dicarboxylate having phenyl compounds.
• BTB 1,3,5- benzenetribenzoate
• BDC 1 ,4-benzenedicarboxylate
• CB BDC cyclobutyl 1,4- benzenedi
• Specific materials that show improvement in adsorption properties have a three- dimensional extended porous structure and include: MOF- 177, a material having a general formula of Zn 4 O(1, 3, 5-benzenetribenzoate) 2 ; MOF-5, also known as IRMOF-I, a material having a general formula of Zn 4 O(1, 4-benzenedicarboxylate) 3 ; IRMOF-6, a material having a general formula of ZruO ⁇ yclobutyl 1,4-benzenedicarboxylate); IRMOF-3, a material having a general formula of Zn 4 O(2-amino 1,4 benzenedicarboxylate) 3 ; and IRMOF-11, a material having a general formula of ZruO ⁇ erphenyl dicarboxylate) 3 ,or Zn 4 O(tetrahydropyrene 2,7- dicarboxylate) 3 ; and IRMOF-8, a material having a general formula of Zn 4 O
• the capacities for 13X, activated carbon, and MOF-5 are 1.4, 3.5 and 9.8 lbs CO 2 /ft 3 , (or 22.4, 56.1 and 157 kg CO 2 /m 3 ) respectively.
• the capacity can be increased by lowering the desorption pressure, and for activated carbon, with a desorption pressure at 1 atm, the capacity increases from 3.5 to 8.3 lbs CO 2 /ft (133 kg C0 2 /m ).
• methane When removing carbon dioxide from a methane rich stream, methane is also adsorbed onto the adsorbent.
• the methane is a co-adsorbate, and it is desirable to remove more carbon dioxide relative to the methane removed from the feedstream.
• the methane adsorption isotherm is shown in Figure 2 for MOF-5 and for activated carbon.
• the loadings for methane are 2.15 IbS-CH 4 VfB and 1.05 lbs-CH 4 /ft3 respectively.
• the ratio of CO 2 to methane for MOF-5 is 4.56 and the ratio for activated carbon is 3.33.
• a MOF-5 is a preferred material having zinc oxide cluster building units with the building units linked by a 1 ,4-benzenedicarboxylate organic compound.
• Another preferred material that is suitable for use in pressure swing adsorbers with high waste gas pressure include MOF- 177, a material having zinc oxide cluster building units with the building units linked by a 1,3,5-benzenetribenzoate organic compound. Additional MOFs, as listed above, are also useful adsorbents for CO 2 removal.
• One aspect of the invention is to have a material, or combination of materials, that changes the shape of the isotherm, such that the capacity-pressure curve does not taper off as pressure increases, but still retains significant capacity increases as the pressure is increased, as can be seen in Figures 1 and 2 with these materials for the normal pressure ranges for PSA.

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• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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• 2006
  • 2006-12-13 CA CA002633652A patent/CA2633652A1/en not_active Abandoned
  • 2006-12-13 RU RU2008129692/15A patent/RU2008129692A/ru unknown
  • 2006-12-13 JP JP2008547688A patent/JP2009521320A/ja not_active Withdrawn
  • 2006-12-13 EP EP06850286A patent/EP1963766A2/en not_active Withdrawn
  • 2006-12-13 WO PCT/US2006/062038 patent/WO2007111738A2/en active Application Filing
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