CA2040764A1 - Hydrodewaxing method - Google Patents
Hydrodewaxing methodInfo
- Publication number
- CA2040764A1 CA2040764A1 CA002040764A CA2040764A CA2040764A1 CA 2040764 A1 CA2040764 A1 CA 2040764A1 CA 002040764 A CA002040764 A CA 002040764A CA 2040764 A CA2040764 A CA 2040764A CA 2040764 A1 CA2040764 A1 CA 2040764A1
- Authority
- CA
- Canada
- Prior art keywords
- dewaxing
- olefinic
- effluent
- fraction
- hydrogen
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Abstract
HYDRODEWAXING METHOD
ABSTRACT
Hydrocarbon feeds are dewaxed (14) and hydrotreated (24) in a two-stage dewaxing-hydrotreating reactor system with interstage separation of olefinic and naphtha and light olefins. Separation of the naphtha and olefins is carried out by stripping (78) the effluent from the dewaxing reactor (14) with a stripping medium such as make-up hydrogen or vapor from the hydrotreater effluent. Hydrogen recycle for the dewaxer (14) and the hydrotreater (24) is taken from the stripper/separator (78) after removal of the olefinic naphtha and removal of contaminants.
ABSTRACT
Hydrocarbon feeds are dewaxed (14) and hydrotreated (24) in a two-stage dewaxing-hydrotreating reactor system with interstage separation of olefinic and naphtha and light olefins. Separation of the naphtha and olefins is carried out by stripping (78) the effluent from the dewaxing reactor (14) with a stripping medium such as make-up hydrogen or vapor from the hydrotreater effluent. Hydrogen recycle for the dewaxer (14) and the hydrotreater (24) is taken from the stripper/separator (78) after removal of the olefinic naphtha and removal of contaminants.
Description
2~764 ,.
HYDRODEWAXING METHOD
This invention relates to a method for hydrodewaxing a hydrocarbon feed, such as a middle distillate or a lubricant hydrocarbon fraction.
The dewaxing of hydrocarbons to produce liquid products of lower pour point is a process of great commercial significance. Although alternatives exist, the use of shape-selective catalysts, such as the intermediate pore size æeolite catalysts, and in particular, ZSM-5, to selectively convert those paraffins that contribute the most to high pour point has many advantages over other methods.
Catalytic dewaxing over intermediate pore size zeolites and in particular, over ZSM-5, is a known process and is described in, for example, U.S. Patent No. Reissue 28,398. Such a dewaxing process produces significant quantities of olefins, including C3 and C4 olefins as well as C5+ olefins in the gasoline boiling range, as a result of which a relatively high octane olefinic naphtha is one of the by-products of the process.
Catalytic dewaxing is typically effected in the presence of hydrogen to retard catalyst aging.
However, the conditions employed are not conducive to olefin saturation so that significant quantities of gasoline range and lighter olefins are produced in the process. Moreover, in the dewaxing of lube boiling range hydrocarbons, the effluent from the dewaxing reactor may be cascaded directly into a hydrotreating reactor in order to saturate and stabilize lube range olefins in the dewaxing products. Similarly, in distillate dewaxing, a hydrotreater may be provided in order to remove unsaturation unless the dewaxed distillate is combined with virgin distillate and the combined distillate treated in the refinery CHD
(catalytic hydrodesulfurization) unit. In both of 2~7~
these cases, the hydrogen consumption of the hydrotreating step is needlessly increased by the saturation of olefinic components outside the boiling range of the desired products, principally of C5- and gasoline range olefins. To reduce hydrogen consumption it would be possible to arrange for separation between the dewaxing reactor and the hydrotreater but this may still leave lower olefins to be carried out over into the hydrotreater.
It has now been found that improved separation of the lower olefinic materials may be provided by stripping the dewaxed products prior to hydrotreating, preferably using an oil solvent such as naphtha which is fed into the top of a stripper/separator so that the recycle gas is essentially free of wet gas and heavier fractions. Operation in this manner confers several benefits. One is a significant reduction in the hydrogen consumption in the hydrotreating reactor since the majority of the light olefins are no longer hydrotreated in the hydrotreating reactor. In addition, the hydrogen circulation rate for the hydrotreating reactor can be better controlled so as to reduce the pressure drop across the hydrotreating reactor.
Alternatively, the hydrotreating reactor can be operated at a higher pressure level than the hydrodewaxing reactor; this affords the opportunity to modify the pour point of dewaxed lube products.
Accordingly, the invention resides in a process for dewaxing a hydrocarbon feed comprising:
1. dewaxing the feed by contacting the feed in the presence of hydrogen with a dewaxing catalyst;
2. obtaining a dewaxed effluent;
HYDRODEWAXING METHOD
This invention relates to a method for hydrodewaxing a hydrocarbon feed, such as a middle distillate or a lubricant hydrocarbon fraction.
The dewaxing of hydrocarbons to produce liquid products of lower pour point is a process of great commercial significance. Although alternatives exist, the use of shape-selective catalysts, such as the intermediate pore size æeolite catalysts, and in particular, ZSM-5, to selectively convert those paraffins that contribute the most to high pour point has many advantages over other methods.
Catalytic dewaxing over intermediate pore size zeolites and in particular, over ZSM-5, is a known process and is described in, for example, U.S. Patent No. Reissue 28,398. Such a dewaxing process produces significant quantities of olefins, including C3 and C4 olefins as well as C5+ olefins in the gasoline boiling range, as a result of which a relatively high octane olefinic naphtha is one of the by-products of the process.
Catalytic dewaxing is typically effected in the presence of hydrogen to retard catalyst aging.
However, the conditions employed are not conducive to olefin saturation so that significant quantities of gasoline range and lighter olefins are produced in the process. Moreover, in the dewaxing of lube boiling range hydrocarbons, the effluent from the dewaxing reactor may be cascaded directly into a hydrotreating reactor in order to saturate and stabilize lube range olefins in the dewaxing products. Similarly, in distillate dewaxing, a hydrotreater may be provided in order to remove unsaturation unless the dewaxed distillate is combined with virgin distillate and the combined distillate treated in the refinery CHD
(catalytic hydrodesulfurization) unit. In both of 2~7~
these cases, the hydrogen consumption of the hydrotreating step is needlessly increased by the saturation of olefinic components outside the boiling range of the desired products, principally of C5- and gasoline range olefins. To reduce hydrogen consumption it would be possible to arrange for separation between the dewaxing reactor and the hydrotreater but this may still leave lower olefins to be carried out over into the hydrotreater.
It has now been found that improved separation of the lower olefinic materials may be provided by stripping the dewaxed products prior to hydrotreating, preferably using an oil solvent such as naphtha which is fed into the top of a stripper/separator so that the recycle gas is essentially free of wet gas and heavier fractions. Operation in this manner confers several benefits. One is a significant reduction in the hydrogen consumption in the hydrotreating reactor since the majority of the light olefins are no longer hydrotreated in the hydrotreating reactor. In addition, the hydrogen circulation rate for the hydrotreating reactor can be better controlled so as to reduce the pressure drop across the hydrotreating reactor.
Alternatively, the hydrotreating reactor can be operated at a higher pressure level than the hydrodewaxing reactor; this affords the opportunity to modify the pour point of dewaxed lube products.
Accordingly, the invention resides in a process for dewaxing a hydrocarbon feed comprising:
1. dewaxing the feed by contacting the feed in the presence of hydrogen with a dewaxing catalyst;
2. obtaining a dewaxed effluent;
3. stripping the dewaxed effluent with a gaseous stripping medium to form a dewaxed fraction, a light olefinic gas fraction and an olefinic gasoline fraction;
2~7~
F-52~7 ~3~
2~7~
F-52~7 ~3~
4. separating the dewaxed fraction from the olefinic gasoline fraction and the light olefinic gas fraction, and;
5. hydrotreating the dewaxed fraction in the presence of hydrogen with a hydrotreating catalyst.
The separation of the light hydrodewaxing products may be enhanced by stripping with effluent vapor from the hydrotreating reactor, hydrogen make-up and/or hydrogen recycle. Overall hydrogen make-up requirements are reduced in that the light hydrodewaxing products including the light C5- olefins and olefinic gasoline, are not subject to hydrotreating in the hydrotreating reactor. Recoveries up to about 90% of the C5+ gasoline, as well as up to 20% C3 and up to 45% C4 upstream of the hydrotreating reactor can be attained by the present invention.
The lower boiling components of the dewaxer effluent can be further treated to upgrade the naphtha fraction to high octane olefinic naphtha having an octane number of 90RON + 0. The resulting olefinic gasoline can be directly blended into the existing gasoline pool. The recovered C3/C4 olefins can be utilized as alkylation unit feed, or as a feedstock to an oligomerization unit such as that described in U.S.
Patent No. 4,695,364.
The present olefin separation/stripping technique may be employed either with lube boiling range feeds or to produce middle distillate fuels, e.g., kerosene and jet fuel. Thus, the feed may be a neutral or residual lube feed, e.g., light neutral, heavy neutral or bright stock, or an atmospheric or vacuum gas oil feed for distillate fuel production.
The invention will now be more particularly described with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a conventional hydrodewaxing process.
-` 2 0 ~
Figure 2 is a schematic representation of a hydrodewaxing process according to a first example of the invention.
Figure 3 is a schematic representation of a hydrodewaxing process according to a second example of the invention.
Figure 4 is a schematic representation of a hydrodewaxing process according to a third example.
Figure 5 is a schematic representation of a fractionator for achieving a higher olefinic C3/C4 recovery.
Referring to the drawings, Figure 1 shows a simplified schematic of a conventional lube hydrodewaxing process in which a hydrocarbon fraction such as a lube range raffinate feed is fed via conduit lO through heat exchanger 12 to a hydrodewaxing reactor 14 containing a ZSM-5 catalyst. A source of hydrogen (not shown) is fed through conduit 16, to the hydrodewaxing reactor 14 with make-up hydrogen supplied through line 18. The dewaxed reactor effluent exits the reactor 14 through conduit 20 and passes through heat exchanger 22 and conduit 26 into hydrotreating reactor 24. The hydrotreater reactor effluent exits through conduit 28 and then passes through heat exchanger 30 and conduit 32 to separator 34. The bottoms from separator 34 are fed by conduit 36 to naphtha stripper 38 which operates in a conventional manner with steam introduced through conduit 40 into the lower portion of the stripper to separate naphtha and light gases from the lube oil and kerosene which leave the stripper 38 as the bottoms fraction through conduit 56. The overhead from the stripper 38 is fed through conduit 44 to a heat exchanger 46 and then through conduit 49 to a settling tank 50. Unstabilized naphtha is withdrawn from the settling tank 50 through conduit 52 while lighter gases are withdrawn through conduit 54 for use as fuel or as a feed to an - 2 ~ 6 ~
oligomerization unit as noted above. The bottoms effluent from stripper 38 comprising lube oil and kerosene, is conveyed in conduit 56, to downstream processing units, such as a vacuum stripper (not shown).
The lighter effluent leaving separator 34 through conduit 56 passes through heat exchanger 60 and conduit 62 to separator 64. The bottoms from separator 64 are fed through conduit 66 to an intermediate level in the naphtha stripper 38. Contaminants such as hydrogen sulfide plus nitrogen are removed from the effluent leaving separator 64 through conduit 68 in scrubber 70.
The hydrogen leaving scrubber 70 via line 72 is partly recycled through conduit 74 and recycle compressor 75 to hydrodewaxing reactor 14 and partly removed through conduit 76.
Figure 2 illustrates a dewaxing process similar to that shown in Figure 1 but with intermediate separation and stripping, according to a first example of the present invention. The same references as those in Figure 1 are used to indicate like elements in Figure 2 and the remaining drawings. The intermediate separation and stripping section of the first example is indicated by the dotted line DL of Figure 2 and comprises an olefin fractionator 78 to which is fed the effluent from hydrodewaxing reactor 14. A source of make-up hydrogen is introduced through inlet 80 to fractionator 78 to strip the lighter olefinic dewaxing products from the hydrodewaxer effluent. These olefins leave the fractionator 78 as overhead and are conveyed through outlet 82, heat exchanger 84, and conduit 88 to a gas/liquid phase separator 86. The bottoms from the separator 86, comprising Unstabilized olefinic naphtha, are removed through conduit 90 and partially withdrawn through conduit 92. Fractionator reflux is provided by pump 93 and conduit 94 which return part of the olefinic naphtha to olefinic fractionator 78. Light 2~7~
gases from separator 86 are removed via conduit 96 and are partially fed through conduit 98 and heat exchanger 99 to provide a source of feed hydrotreating reactor 24. The remainder of the light gases pass through conduit 100, flow control valve 102, and conduit 104 to a scrubber 70 so as to provide a source of high purity recycle hydrogen to the hydrodewaxing reactor 14, conveyed through conduits 74 and 18.
Variable flow control valve 106 is used to control the flow of dewaxed effluent through heat exchanger 22 to fractionator 78. For increased fractionation efficiency, heat exchanger 22 may be by-passed by controller 106 so that the flow may be sent directly to the fractionator 78, preferably to a tray below the mainfeed tray where stream 26 from heat exchanger 22 is fed to the fractionator. Variable flow control valve 106 is actuated in response to a signal from temperature sensor 108 on line 118 via communication line 110. An additional flow control valve 112 is connected by communication line 116 to sensor 114 at the bottom of fractionator 78 to control the flow of the stripped, dewaxed effluent through conduit 118 form fractionator 78 to hydrotreater 24.
As can be appreciated from the process schematically illustrated in Figure 2 the effluent of hydrodewaxing reactor 14 is stripped in fractionator 78 to remove olefins and the light product leaving fractionator 78 through outlet 82 primarily comprised C3/C4 olefins and C5+ gasoline. The light products recovered from the fractionator overhead can be sent to the unsaturated gas plant of an FCC unit for further separation onto C3, C4 and C5+ components. The removal of the olefinic fraction also permits better control of the hydrogen circulation rate for the hydrotreating reactor by feeding hydrogen-containing overhead streams through conduit 98 to hydrotreater 24 thereby permitting a reduction in the pressure in the 2~4~
hydrotreating reactor and its associated separation system pressure drop.
Unrecovered olefinic C3/C4 components plus ethene leaving the fractionator section through conduit 104 are recycled with the hydrogen, through conduit 18, to hydrodewaxing reactor 14 and may undergo conversion to olefinic gasoline over the ZSM-5 catalyst used in hydrodewaxing reactor 14 by olefin-to-gasoline oligomerization. This is not possible in the conventional process illustrated in Figure 1 since the entire dewaxer effluent is processed in the hydrotreating reactor and this converts all the olefins in the effluent to paraffins.
Additional advantages may be achieved by the alternative embodiment in Figure 3, in which the dotted line DL2 illustrates separation and stripping section of this second example. In Figure 3, the hydrotreating reactor 24 can be operated at a pressure higher than that of the hydrodewaxing reactor 14 by providing a pump 120 to increase the pressure of the stripped hydrodewaxing effluent leaving fractionator 78 through variable flow control valve 112 and conduit 118. High purity hydrogen for the hydrotreater 24 is provided at an appropriate pressure from recycle compressor via conduit 128. Moreover, effluent vapor from the hydrotreater 24 after passage through the separators 34 and 64 is recycled to the hydrodewaxing reactor 14 via conduit 68.
In the third example shown in Figure 4, the hydrotreating reactor effluent vapor is used as a stripping medium in the fractionator 78 and is fed from separator 34 through conduit 122 to the bottom of fractionator 78. This is especially beneficial if severe stripping of the hydrodewaxing reactor effluent is desired in olefinic fractionator 78 since the quantity of effluent vapor from separator 34 will usually exceed the quantity of make-up hydrogen.
-` 2~7~
As noted, with regard to the embodiments described in Figures 2-4, the light overhead fractions (C3, C4) from the fractionator are mostly carried into the gaseous phase. Higher C3/C4 recoveries can be obtained by employing the fractionator illustrated in Figure 5.
Thus, referring to Figure 5, the fractionator 278 has input conduits 222 for introducing the effluent from a hydrodewaxing reactor (not shown) as well as a stripping medium conduit 280 for introducing a stripping gas, such as hydrogen or hydrotreating reactant effluent vapor. A lean oil is also introduced through conduit 282 to the top of fractionator 278 to dissolve the C3/C4 hydrocarbons and the unstabilized olefinic naphtha plus rich oil is withdrawn from fractionator 278 through conduit 284. A portion of the unstabilized olefinic naphtha plus rich oil may be returned as reflux through pump 286, cooler 290 and conduit 292, while the remainder is withdrawn via conduit 294 to further downstream treatment sections (not shown). The bottoms from fractionator 278 comprise an effluent including lube oil and kerosene which leave through conduit 296 while the top of olefin fractionator 278 produces an overhead comprising treat gas withdrawn through conduit 298. The hydrogen purity of the treat gas is significantly improved as compared with the conventional fractionators.
It is possible to upgrade about 90% (based on Figure 2 configuration) of the hydrodewaxing reactor effluent naphtha to high octane olefinic naphtha with an octane number of 90 (R+O). This is an improvement of approximately 15 to 20 octane numbers over that obtainable by hydrotreating the naphtha. The olefinic gasoline so produced can be directly blended into the gasoline pool after treating which reduces the load on the hydrotreater, which permits processing more hydrocarbons per catalyst (weight basis).
2 ~ 7 6 ~
The present invention permits the recovery of approximately 20% of olefinic C3 and up to about 45~ of the C4 produced in the hydrodewaxing reactor (based on Figure 2 configuration). By removing these olefins from the dewaxing effluent before introduction into the hydrotreating reactor, hydrogen consumption is significantly reduced because hydrogen is not consumed in saturating the olefins in the hydrotreater 24.
Significant advantage also results from the fact that by-products of the present invention include recycle gas of higher hydrogen purity than previously obtainable. In addition, hydrogen circulation rate and overall operating pressures may be selected so that hydrotreating may be accomplished at a higher pressure than the hydrodewaxing step. Moreover, stripping steam requirements and stripper size for the naphtha stripper can be significantly reduced as a result of the removal of the olefinic fraction at an earlier stage in the unit.
By effecting olefin separation between the dewaxer and the hydrotreater the naphtha stripper diameter can be reduced although the treat gas compressor size will need to be increased to handle the increased gas volume at this stage. The olefins recovery does not affect the lube recovery or lube quality. All the lube components leave the olefin fractionator as bottoms and are mixed with the required volume of hydrogen before entering the hydrotreating reactor. The naphtha end point can be controlled by use of reflux as previously described.
In a similar way to that described above for lube protection, the interstage separation of the olefinic cracking products produced by the dewaxing reactions may also be effected in distillate dewaxing.
Application of the present olefin separation-stripping technique to distillate dewaxing will follow the same lines as described in detail above, except that a 2~76~
F-S21~ -10-relatively taller fractionator tower will be required in order to achieve the desired degree of product separation in view of the relative closeness of boiling points with distillate products and feeds. A higher reflux ratio, with a consequent effect on tower size may also be needed to separate products adequately although the light olefins will be removed in the C4 olefin fractionator in the manner described above.
The separation of the light hydrodewaxing products may be enhanced by stripping with effluent vapor from the hydrotreating reactor, hydrogen make-up and/or hydrogen recycle. Overall hydrogen make-up requirements are reduced in that the light hydrodewaxing products including the light C5- olefins and olefinic gasoline, are not subject to hydrotreating in the hydrotreating reactor. Recoveries up to about 90% of the C5+ gasoline, as well as up to 20% C3 and up to 45% C4 upstream of the hydrotreating reactor can be attained by the present invention.
The lower boiling components of the dewaxer effluent can be further treated to upgrade the naphtha fraction to high octane olefinic naphtha having an octane number of 90RON + 0. The resulting olefinic gasoline can be directly blended into the existing gasoline pool. The recovered C3/C4 olefins can be utilized as alkylation unit feed, or as a feedstock to an oligomerization unit such as that described in U.S.
Patent No. 4,695,364.
The present olefin separation/stripping technique may be employed either with lube boiling range feeds or to produce middle distillate fuels, e.g., kerosene and jet fuel. Thus, the feed may be a neutral or residual lube feed, e.g., light neutral, heavy neutral or bright stock, or an atmospheric or vacuum gas oil feed for distillate fuel production.
The invention will now be more particularly described with reference to the accompanying drawings, in which:
Figure 1 is a schematic representation of a conventional hydrodewaxing process.
-` 2 0 ~
Figure 2 is a schematic representation of a hydrodewaxing process according to a first example of the invention.
Figure 3 is a schematic representation of a hydrodewaxing process according to a second example of the invention.
Figure 4 is a schematic representation of a hydrodewaxing process according to a third example.
Figure 5 is a schematic representation of a fractionator for achieving a higher olefinic C3/C4 recovery.
Referring to the drawings, Figure 1 shows a simplified schematic of a conventional lube hydrodewaxing process in which a hydrocarbon fraction such as a lube range raffinate feed is fed via conduit lO through heat exchanger 12 to a hydrodewaxing reactor 14 containing a ZSM-5 catalyst. A source of hydrogen (not shown) is fed through conduit 16, to the hydrodewaxing reactor 14 with make-up hydrogen supplied through line 18. The dewaxed reactor effluent exits the reactor 14 through conduit 20 and passes through heat exchanger 22 and conduit 26 into hydrotreating reactor 24. The hydrotreater reactor effluent exits through conduit 28 and then passes through heat exchanger 30 and conduit 32 to separator 34. The bottoms from separator 34 are fed by conduit 36 to naphtha stripper 38 which operates in a conventional manner with steam introduced through conduit 40 into the lower portion of the stripper to separate naphtha and light gases from the lube oil and kerosene which leave the stripper 38 as the bottoms fraction through conduit 56. The overhead from the stripper 38 is fed through conduit 44 to a heat exchanger 46 and then through conduit 49 to a settling tank 50. Unstabilized naphtha is withdrawn from the settling tank 50 through conduit 52 while lighter gases are withdrawn through conduit 54 for use as fuel or as a feed to an - 2 ~ 6 ~
oligomerization unit as noted above. The bottoms effluent from stripper 38 comprising lube oil and kerosene, is conveyed in conduit 56, to downstream processing units, such as a vacuum stripper (not shown).
The lighter effluent leaving separator 34 through conduit 56 passes through heat exchanger 60 and conduit 62 to separator 64. The bottoms from separator 64 are fed through conduit 66 to an intermediate level in the naphtha stripper 38. Contaminants such as hydrogen sulfide plus nitrogen are removed from the effluent leaving separator 64 through conduit 68 in scrubber 70.
The hydrogen leaving scrubber 70 via line 72 is partly recycled through conduit 74 and recycle compressor 75 to hydrodewaxing reactor 14 and partly removed through conduit 76.
Figure 2 illustrates a dewaxing process similar to that shown in Figure 1 but with intermediate separation and stripping, according to a first example of the present invention. The same references as those in Figure 1 are used to indicate like elements in Figure 2 and the remaining drawings. The intermediate separation and stripping section of the first example is indicated by the dotted line DL of Figure 2 and comprises an olefin fractionator 78 to which is fed the effluent from hydrodewaxing reactor 14. A source of make-up hydrogen is introduced through inlet 80 to fractionator 78 to strip the lighter olefinic dewaxing products from the hydrodewaxer effluent. These olefins leave the fractionator 78 as overhead and are conveyed through outlet 82, heat exchanger 84, and conduit 88 to a gas/liquid phase separator 86. The bottoms from the separator 86, comprising Unstabilized olefinic naphtha, are removed through conduit 90 and partially withdrawn through conduit 92. Fractionator reflux is provided by pump 93 and conduit 94 which return part of the olefinic naphtha to olefinic fractionator 78. Light 2~7~
gases from separator 86 are removed via conduit 96 and are partially fed through conduit 98 and heat exchanger 99 to provide a source of feed hydrotreating reactor 24. The remainder of the light gases pass through conduit 100, flow control valve 102, and conduit 104 to a scrubber 70 so as to provide a source of high purity recycle hydrogen to the hydrodewaxing reactor 14, conveyed through conduits 74 and 18.
Variable flow control valve 106 is used to control the flow of dewaxed effluent through heat exchanger 22 to fractionator 78. For increased fractionation efficiency, heat exchanger 22 may be by-passed by controller 106 so that the flow may be sent directly to the fractionator 78, preferably to a tray below the mainfeed tray where stream 26 from heat exchanger 22 is fed to the fractionator. Variable flow control valve 106 is actuated in response to a signal from temperature sensor 108 on line 118 via communication line 110. An additional flow control valve 112 is connected by communication line 116 to sensor 114 at the bottom of fractionator 78 to control the flow of the stripped, dewaxed effluent through conduit 118 form fractionator 78 to hydrotreater 24.
As can be appreciated from the process schematically illustrated in Figure 2 the effluent of hydrodewaxing reactor 14 is stripped in fractionator 78 to remove olefins and the light product leaving fractionator 78 through outlet 82 primarily comprised C3/C4 olefins and C5+ gasoline. The light products recovered from the fractionator overhead can be sent to the unsaturated gas plant of an FCC unit for further separation onto C3, C4 and C5+ components. The removal of the olefinic fraction also permits better control of the hydrogen circulation rate for the hydrotreating reactor by feeding hydrogen-containing overhead streams through conduit 98 to hydrotreater 24 thereby permitting a reduction in the pressure in the 2~4~
hydrotreating reactor and its associated separation system pressure drop.
Unrecovered olefinic C3/C4 components plus ethene leaving the fractionator section through conduit 104 are recycled with the hydrogen, through conduit 18, to hydrodewaxing reactor 14 and may undergo conversion to olefinic gasoline over the ZSM-5 catalyst used in hydrodewaxing reactor 14 by olefin-to-gasoline oligomerization. This is not possible in the conventional process illustrated in Figure 1 since the entire dewaxer effluent is processed in the hydrotreating reactor and this converts all the olefins in the effluent to paraffins.
Additional advantages may be achieved by the alternative embodiment in Figure 3, in which the dotted line DL2 illustrates separation and stripping section of this second example. In Figure 3, the hydrotreating reactor 24 can be operated at a pressure higher than that of the hydrodewaxing reactor 14 by providing a pump 120 to increase the pressure of the stripped hydrodewaxing effluent leaving fractionator 78 through variable flow control valve 112 and conduit 118. High purity hydrogen for the hydrotreater 24 is provided at an appropriate pressure from recycle compressor via conduit 128. Moreover, effluent vapor from the hydrotreater 24 after passage through the separators 34 and 64 is recycled to the hydrodewaxing reactor 14 via conduit 68.
In the third example shown in Figure 4, the hydrotreating reactor effluent vapor is used as a stripping medium in the fractionator 78 and is fed from separator 34 through conduit 122 to the bottom of fractionator 78. This is especially beneficial if severe stripping of the hydrodewaxing reactor effluent is desired in olefinic fractionator 78 since the quantity of effluent vapor from separator 34 will usually exceed the quantity of make-up hydrogen.
-` 2~7~
As noted, with regard to the embodiments described in Figures 2-4, the light overhead fractions (C3, C4) from the fractionator are mostly carried into the gaseous phase. Higher C3/C4 recoveries can be obtained by employing the fractionator illustrated in Figure 5.
Thus, referring to Figure 5, the fractionator 278 has input conduits 222 for introducing the effluent from a hydrodewaxing reactor (not shown) as well as a stripping medium conduit 280 for introducing a stripping gas, such as hydrogen or hydrotreating reactant effluent vapor. A lean oil is also introduced through conduit 282 to the top of fractionator 278 to dissolve the C3/C4 hydrocarbons and the unstabilized olefinic naphtha plus rich oil is withdrawn from fractionator 278 through conduit 284. A portion of the unstabilized olefinic naphtha plus rich oil may be returned as reflux through pump 286, cooler 290 and conduit 292, while the remainder is withdrawn via conduit 294 to further downstream treatment sections (not shown). The bottoms from fractionator 278 comprise an effluent including lube oil and kerosene which leave through conduit 296 while the top of olefin fractionator 278 produces an overhead comprising treat gas withdrawn through conduit 298. The hydrogen purity of the treat gas is significantly improved as compared with the conventional fractionators.
It is possible to upgrade about 90% (based on Figure 2 configuration) of the hydrodewaxing reactor effluent naphtha to high octane olefinic naphtha with an octane number of 90 (R+O). This is an improvement of approximately 15 to 20 octane numbers over that obtainable by hydrotreating the naphtha. The olefinic gasoline so produced can be directly blended into the gasoline pool after treating which reduces the load on the hydrotreater, which permits processing more hydrocarbons per catalyst (weight basis).
2 ~ 7 6 ~
The present invention permits the recovery of approximately 20% of olefinic C3 and up to about 45~ of the C4 produced in the hydrodewaxing reactor (based on Figure 2 configuration). By removing these olefins from the dewaxing effluent before introduction into the hydrotreating reactor, hydrogen consumption is significantly reduced because hydrogen is not consumed in saturating the olefins in the hydrotreater 24.
Significant advantage also results from the fact that by-products of the present invention include recycle gas of higher hydrogen purity than previously obtainable. In addition, hydrogen circulation rate and overall operating pressures may be selected so that hydrotreating may be accomplished at a higher pressure than the hydrodewaxing step. Moreover, stripping steam requirements and stripper size for the naphtha stripper can be significantly reduced as a result of the removal of the olefinic fraction at an earlier stage in the unit.
By effecting olefin separation between the dewaxer and the hydrotreater the naphtha stripper diameter can be reduced although the treat gas compressor size will need to be increased to handle the increased gas volume at this stage. The olefins recovery does not affect the lube recovery or lube quality. All the lube components leave the olefin fractionator as bottoms and are mixed with the required volume of hydrogen before entering the hydrotreating reactor. The naphtha end point can be controlled by use of reflux as previously described.
In a similar way to that described above for lube protection, the interstage separation of the olefinic cracking products produced by the dewaxing reactions may also be effected in distillate dewaxing.
Application of the present olefin separation-stripping technique to distillate dewaxing will follow the same lines as described in detail above, except that a 2~76~
F-S21~ -10-relatively taller fractionator tower will be required in order to achieve the desired degree of product separation in view of the relative closeness of boiling points with distillate products and feeds. A higher reflux ratio, with a consequent effect on tower size may also be needed to separate products adequately although the light olefins will be removed in the C4 olefin fractionator in the manner described above.
Claims (9)
1. A process for dewaxing a hydrocarbon feed comprising:
a. dewaxing the feed by contacting the feed in the presence of hydrogen with a dewaxing catalyst;
b. obtaining a dewaxed effluent;
c. stripping the dewaxed effluent with a gaseous stripping medium to form a dewaxed fraction, a light olefinic gas fraction and an olefinic gasoline fraction;
d. separating the dewaxed fraction from the olefinic gasoline fraction and the light olefinic gas fraction, and;
e. hydrotreating the dewaxed fraction in the presence of hydrogen with a hydrotreating catalyst.
a. dewaxing the feed by contacting the feed in the presence of hydrogen with a dewaxing catalyst;
b. obtaining a dewaxed effluent;
c. stripping the dewaxed effluent with a gaseous stripping medium to form a dewaxed fraction, a light olefinic gas fraction and an olefinic gasoline fraction;
d. separating the dewaxed fraction from the olefinic gasoline fraction and the light olefinic gas fraction, and;
e. hydrotreating the dewaxed fraction in the presence of hydrogen with a hydrotreating catalyst.
2. A process according to Claim 1 in which the dewaxing catalyst comprises ZSM-5.
3. A process according to Claim 1 or Claim 2 in which the stripping medium comprises make-up hydrogen for the dewaxing process.
4. A process according to Claim 1 of Claim 2 in which the stripping medium comprises effluent vapor from the hydrotreating step.
5. A process according to any preceding Claim which includes separating the light olefinic gas fraction from the olefinic gasoline fraction.
6. A process according to Claim 5 in which at least part of the light olefinic gas fraction is recycled to the dewaxing step.
7. A process according to Claim 5 in which the hydrotreating step is operated at a higher pressure than the dewaxing step and in which the light olefinic gas fraction is passed to the hydrotreating step at the pressure of the hydrotreating step.
8. A process according to Claim 7 in which effluent vapor from the hydrotreating step is passed to the dewaxing step.
9. A process according to any preceding Claim in which the dewaxed effluent is stripped in the presence of an oil solvent for light hydrocarbons boiling below the gasoline boiling range to dissolve the light hydrocarbons in the oil solvent.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/301,700 US5015359A (en) | 1986-06-30 | 1989-01-25 | Hydrodewaxing method with interstate recovery of olefin |
| CA002040764A CA2040764A1 (en) | 1986-06-30 | 1991-04-18 | Hydrodewaxing method |
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US12543586A | 1986-06-30 | 1986-06-30 | |
| CA002040764A CA2040764A1 (en) | 1986-06-30 | 1991-04-18 | Hydrodewaxing method |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2040764A1 true CA2040764A1 (en) | 1992-10-19 |
Family
ID=25674562
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002040764A Abandoned CA2040764A1 (en) | 1986-06-30 | 1991-04-18 | Hydrodewaxing method |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2040764A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2563886B1 (en) * | 2010-04-30 | 2022-09-21 | SK Innovation Co., Ltd. | Method of manufacturing high quality lube base oil using unconverted oil |
-
1991
- 1991-04-18 CA CA002040764A patent/CA2040764A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2563886B1 (en) * | 2010-04-30 | 2022-09-21 | SK Innovation Co., Ltd. | Method of manufacturing high quality lube base oil using unconverted oil |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100452253B1 (en) | Two stage hydroprocessing process with series recycle gas flow | |
| KR102243952B1 (en) | Process for recovering gasoline and diesel from the aromatic complex bottom | |
| EP0664827B1 (en) | Gasoline upgrading process | |
| EP1288277B1 (en) | Hydrocracking process product recovery method | |
| WO1994026848A1 (en) | Method for producing feedstocks of high quality lube base oil from unconverted oil of fuels hydrocracker operating in recycle mode | |
| CA2029426C (en) | Production of gasoline and distillate fuels from light cycle oil | |
| US4935120A (en) | Multi-stage wax hydrocracking | |
| US5015359A (en) | Hydrodewaxing method with interstate recovery of olefin | |
| EP0067020B1 (en) | Hydrostripping process of crude oil | |
| US3941680A (en) | Lube oil hydrotreating process | |
| US2983669A (en) | Hydrodesulfurization of selected gasoline fractions | |
| US5925234A (en) | Process for the production of an internal combustion engine fuel base by hydrotreatment and extraction, and the product therefrom | |
| US5262044A (en) | Process for upgrading a hydrocarbonaceous feedstock and apparatus for use therein | |
| US4973396A (en) | Method of producing sweet feed in low pressure hydrotreaters | |
| CA2040764A1 (en) | Hydrodewaxing method | |
| US20050011811A1 (en) | Desulfurization of a naphtha gasoline stream derived from a fluid catalytic cracking unit | |
| US20050035026A1 (en) | Catalytic distillation hydroprocessing | |
| CA1300067C (en) | Process for the flexible production of high-quality gas oil | |
| WO2020076504A1 (en) | Multi-stage fractionation of fcc naphtha with post treatment and recovery of aromatics and gasoline fractions | |
| EP0554945B1 (en) | Process for upgrading a hydrocarbonaceous feedstock | |
| EP0629683B1 (en) | Process for upgrading a hydrocarbonaceous feedstock | |
| SU1086007A1 (en) | Method for hydraulic purification of fuels | |
| AU785312B2 (en) | Hydrocracking process product recovery method | |
| KR20220168993A (en) | Hydrocracking process | |
| CN114901374A (en) | Process for preparing a feed for a catalytic cracking unit for the production of olefins using a divided wall column and/or a conventional column |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |