Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G45/00—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds
  • C10G45/02—Refining of hydrocarbon oils using hydrogen or hydrogen-generating compounds to eliminate hetero atoms without changing the skeleton of the hydrocarbon involved and without cracking into lower boiling hydrocarbons; Hydrofinishing

Definitions

• the present invention relates to the hydrodesulfurization of petroleum streams in a distillation column reactor. More particularly the invention relates to a process wherein a petroleum fraction is fed to a distillation column reactor containing a hydrodesulfurization catalyst in the form of a catalytic distillation structure where the organic sulfur compounds contained in the petroleum fraction are reacted with hydrogen to form H 2 S which can be stripped from the overhead product.
• Petroleum distillate streams contain a variety of organic chemical components. Generally the streams are defined by their boiling ranges which determine the compositions. The processing of the streams also affects the composition. For instance, products from either catalytic cracking or thermal cracking processes contain high concentrations of olefinic materials as well as saturated (alkanes) materials and polyunsaturated materials (diolefins). Additionally, these components may be any of the various isomers of the compounds.
• sulfur Organic sulfur compounds present in these petroleum fractions are denoted as, "sulfur".
• the amount of sulfur is generally dependent upon the crude source. For instance the Saudi Arabian crudes are generally high in sulfur as are certain domestic crudes. Kuwaiti, Cambodian and Louisiana crudes are generally low in sulfur.
• the type of sulfur compounds will also depend on the boiling range of a given stream. Generally the lower boiling fractions contain mercaptans while the heavier boiling fractions contain thiophenic and heterocyclic sulfur compounds.
• the organic sulfur compounds are almost always considered to be contaminants. They hinder in downstream processing and at the very least make obnoxious SO 2 gas when burned. For these reasons it is very desirable to remove these compounds. The degree of removal is dependent upon the use of the fraction. For instance, feed streams to catalytic reforming require extremely low sulfur concentrations (less than 1 wppm). Current EPA regulations call for combustible motor fuels such as gasoline, kerosene or diesel to have no more than about 500 wppm sulfur. It is expected that in the future the sulfur specification will be lowered to about 50 wppm, especially for gasoline.
• HDS hydrodesulfurization
• the catalyst used for hydrodesulfurization necessarily is a hydrogenation catalyst and the support sometimes is acidic in nature. The latter characteristics provide for some hydrocracking and hydrogenation of unsaturated compounds.
• the hydrocracking results in a higher volume of a less dense (lower specific gravity) material than the feed.
• Typical operating conditions for the prior art HDS reactions are: Temperature °C (°F) 316 - 416 (600-780) Pressure, kPa above atmospheric (psig) 4137-20685 (600-3000) H 2 recycle rate, m 3 /0.16m 3 (SCF/bbl) 40 - 90 (1500-3000) Fresh H 2 makeup, m 3 /0.16m 3 (SCF/bbl) 20 - 30 (700-1000)
• the product is fractionated or simply flashed to release the hydrogen sulfide and collect the now sweetened fraction.
• a method of carrying out catalytic reactions has been developed wherein the components of the reaction system are concurrently separable by distillation using the catalyst structures as the distillation structures.
• Such systems are described variously in U.S. Pat. Nos. 4,215,011; 4,232,177; 4,242,530; 4,250,052; 4,302,356 and 4,307,254 commonly assigned herewith.
• commonly assigned U.S. Patent 4,443,559; 5,057,468; 5,262,012; 5,266,546 and 5,348,710 disclose a variety of catalyst structures for this use and are incorporated by reference herein.
• a distillation column reactor has been utilized wherein a solid particulate catalyst has been placed within a distillation column so as to act as a distillation structure.
• the distillation column reactor has been found to be particularly useful in equilibrium limited reactions because the reaction products have been removed from the reaction zone almost immediately. Additionally the distillation column reactor has been found to be useful to prevent unwanted side reactions.
• the present invention uses catalytic distillation in hydrodesulfurization at low total pressures below about 1999 kPa above atmospheric (290 psig) and more preferably in the range of 0 to 1379 kPa above atomospheric (0 to 200 psig) low hydrogen partial pressure in the range of 0.7 kPa to 482 kPa (0.1 to 70 psi) and temperatures in the range of 204°C to 427°C (400 to 800°F).
• the invention may be said to comprise:
• distillation column reactor results in both a liquid and vapor phase within the distillation reaction zone.
• a considerable portion of the vapor is hydrogen while a portion is vaporous hydrocarbon from the petroleum fraction. Actual separation may only be a secondary consideration.
• Within the distillation reaction zone there is an internal reflux and liquid from an external reflux which cool the rising vaporous hydrocarbon condensing a portion within the bed.
• the mechanism that produces the effectiveness of the present process is the condensation of a portion of the vapors in the reaction system, which occludes sufficient hydrogen in the condensed liquid to obtain the requisite intimate contact between the hydrogen and the sulfur compounds in the presence of the catalyst to result in their hydrogenation.
• the result of the operation of the process in the catalytic distillation mode is that lower hydrogen partial pressures (and thus lower total pressures) may be used.
• any distillation there is a temperature gradient within the distillation column reactor.
• the temperature at the lower end of the column contains higher boiling material and thus is at a higher temperature than the upper end of the column.
• the lower boiling fraction which contains more easily removable sulfur compounds, is subjected to lower temperatures at the top of the column which provides for greater selectivity, that is, less hydrocracking or saturation of desirable olefinic compounds.
• the higher boiling portion is subjected to higher temperatures in the lower end of the distillation column reactor to crack open the sulfur containing ring compounds and hydrogenate the sulfur.
• the upward flowing hydrogen acts as a stripping agent to help remove the H 2 S which is produced in the distillation reaction zone.
• Petroleum fractions which may be treated to remove sulfur by the instant process are naphthas, kerosene and diesel.
• the fractions may be straight run material direct from a crude fractionation unit or may be the result of downstream processing, such as fluid catalytic cracking, pyrolysis or delayed cooking.
• the hydrogen rate to the reactor must be sufficient to maintain the reaction, but kept below that which would cause flooding of the column which is understood to be the "effectuating amount of hydrogen" as that term is used herein.
• the mole ratio of hydrogen to sulfur compound in the feed varies according to the type of compound and the amount of hydrogen expected to be consumed by side reactions such as double or triple bond saturation.
• Hydrogen flow rates are typically calculated as m 3 /0.16m 3 (standard cubic feet per barrel of feed (SCFB)) and are in the range of 9 to 90 m 3 /0.16m 3 (300 to 3000 SCFB).
• a low total pressure below about 1999 kPa above atmospheric (290 psig), for example in the range of 0 to 1379 kPa above atmospheric (0 to 200 psig) is required for the hydrodesulfurization and hydrogen partial pressure of less than 482 kPa above atmospheric (70 psi) down to 0.7 kPa above atmospheric (0.1 psig) can be employed, e.g. 0.7 to 482 kPa above atmospheric (0.1 to 70 psig) preferably about 3.5 to 70 above atmospheric (0.5 to 10 psig).
• the preferred hydrogen partial pressure is less than 450 kPa above atmospheric (50 psig). This preferably is a hydrogen partial pressure in the range of about 0.7 to 70 kPa (0.
• typical conditions are overhead temperature in the range of 177 to 288°C (350 to 550°F), the bottoms temperature in the range of 260 to 427°C (500 to 800 °F), and the pressure in the range of 172 kPa to less than 2068 kPa above atmospheric (25 to less than 300 psig).
• typical conditions are overhead temperature in range of 177 to 343°C (350 to 650°F), the bottoms temperature in the range of 260°C to 427° C (500 to 800°F), and the pressure in the range of 0 to 1379 kPa above atmospheric (0 to 200 psig).
• typical conditions are overhead temperature in the range of 177°C to 343°C (350 to 650°F), the bottoms temperature in the range of 300 to 500°C (500 to 850°F), and the pressure in the range 0 to 1034 kPa above atomospheric (0 to 150 psig).
• Catalyst which are useful for the hydrodesulfurization reaction include metals Group VIII such as cobalt, nickel, palladium, alone or in combination with other metals such as molybdenum or tungsten on a suitable support which may be alumina, silica-alumina, titania-zirconia or the like. Normally the metals are provided as the oxides of the metals supported on extrudates or spheres and as such are not generally useful as distillation structures.
• the catalysts contain components from Group V, VIB, VIII metals of the Periodic Table or mixtures thereof.
• the use of the distillation system reduces the deactivation and provides for longer runs than the fixed bed hydrogenation units of the prior art.
• the Group VIII metal provides increased overall average activity.
• Catalysts containing a Group VIB metal such as molybdenum and a Group VIII such as cobalt or nickel are preferred.
• Catalysts suitable for the hydrodesulfurization reaction include cobalt-molybdenum, nickel-molybdenum and nickel-tungsten.
• the metals are generally present as oxides supported on a neutral base such as alumina, silica-alumina or the like.
• the metals are reduced to the sulfide either in use or prior to use by exposure to sulfur compound containing streams.
• the catalytic material is a component of a distillation system functioning as both a catalyst and distillation packing, i.e., a packing for a distillation column having both a distillation function and a catalytic function.
• reaction system can be described as heterogenous since the catalyst remains a distinct entity.
• a preferred catalyst structure for the present hydrogenation reaction comprises flexible, semi-rigid open mesh tubular material, such as stainless steel wire mesh, filled with a particulate catalytic material in one of several embodiments recently developed in conjunction with the present process.
• the new catalyst structure is a catalytic distillation structure comprising flexible, semi-rigid open mesh tubular material, such as stainless steel wire mesh, filled with a particulate catalytic material said tubular material having two ends and having a length in the range of from about one-half to twice the diameter of said tubular material, a first end being sealed together along a first axis to form a first seam and a second end being sealed together along a second axis to form a second seam wherein the plane of the first seam along the axis of said tubular material and the plane of the second seam along the axis of said tubular material bisect each other at an angle of about 15 to 90°.
• U.S. Patent No. 4,242,530 and U.S. Pat. No. 4,443,559 disclose supported catalyst in a plurality of pockets in a cloth belt or wire mesh tubular structures, which is supported in the distillation column reactor by open mesh knitted stainless steel wire by twisting the two together into a helix.
• U.S. Pat. No. 5,348,710 describes several other suitable structures in the prior art and discloses new structures suitable for this process.
• Other catalytic distillation structures useful for this purpose are disclosed in U.S. Patents 4,731,229 and 5,073,236.
• the particulate catalyst material may be a powder, small irregular chunks or fragments, small beads and the like.
• the particular form of the catalytic material in the structure is not critical, so long as sufficient surface area is provided to allow a reasonable reaction rate.
• the sizing of catalyst particles can be best determined for each catalytic material (since the porosity or available internal surface area will vary for different material and of course affect the activity of the catalytic material).
• the preferred catalyst structures for the packing are those employing the more open structure of permeable plates or screen wire.
• a catalyst structure was prepared as disclosed in U.S. Pat No. 5,431,890, containing 0.430 kgs (0.947 pounds) of the catalytic material described in Table I and placed in the middle 6 m (nineteen feet) of a 6m (20 foot) tall 25 mm (1 inch) diameter distillation column reactor. There were 150 mm (1 ⁇ 2 foot) of inert packing in a rectifying section above the catalyst and 100 mm (1/3 foot) of inert packing in a stripping section below the catalyst. Liquid feed was fed to the distillation column reactor at either at about the mid point or below the catalyst bed and hydrogen was fed at the bottom of the catalyst bed. In each of the examples there is a showing of a substantial reduction in the amount of organic sulfur in both the overheads and bottoms, the removed organic sulfur that has been converted to H 2 S and separated overhead by partial condensation of the overheads.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)

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• 1996
  • 1996-06-27 WO PCT/US1996/010971 patent/WO1997003149A1/en active IP Right Grant
  • 1996-06-27 CA CA002226632A patent/CA2226632C/en not_active Expired - Fee Related
  • 1996-06-27 KR KR1019970709884A patent/KR100437965B1/ko not_active IP Right Cessation
  • 1996-06-27 JP JP50584697A patent/JP3819030B2/ja not_active Expired - Fee Related
  • 1996-06-27 EP EP96923485A patent/EP0842242B1/en not_active Expired - Lifetime
  • 1996-06-27 CN CN96195011A patent/CN1074038C/zh not_active Expired - Lifetime
  • 1996-06-27 ES ES96923485T patent/ES2214544T3/es not_active Expired - Lifetime
  • 1996-06-27 DE DE69632135T patent/DE69632135T2/de not_active Expired - Fee Related
  • 1996-06-27 AU AU63984/96A patent/AU6398496A/en not_active Abandoned
  • 1996-06-27 RU RU98102136/04A patent/RU2157399C2/ru active
• 1998
  • 1998-01-09 MX MX9800298A patent/MX9800298A/es active IP Right Grant

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