MXPA01002053A - Process for the simultaneous treatment and fractionation of light naphtha hydrocarbon streams - Google Patents

Abstract

A flow diagram of one embodiment of the invention having one catalyst bed (14A) in a distillation column/naphtha splitter (14).

Description

PROCESS FOR THE SIMULTANEOUS TREATMENT AND FRACTIONATION OF LIGHT NAFTA HYDROCARBON STREAMS BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention is concerned with a process for concurrently fractionating and hydrotreating a stream of full-range naphtha. More particularly, the full-range naphtha stream is put into hydrodesulphurisation and simultaneous separation to a light boiling range naphtha and a heavy boiling range naphtha. The two boiling range naphthas are treated separately according to the amount of sulfur in each cut and the final use of each fraction.

RELATED INFORMATION Oil distillate streams contain a variety of organic chemical components. In general, currents are defined by their boiling ranges that determine the compositions. The processing of the currents also affects the composition. For example, products either of catalytic pyrolysis (cracking) or technical catalytic pyrolysis (cracking) processes contain high concentrations of olefinic materials as well as saturated materials (alkanes) and polyunsaturated materials (diolefins). Additionally, these components can be any of the various isomers of the compounds. The composition of the untreated naphtha, as it comes from the raw separation or direct run stream, is mainly influenced by the crude source. Naphthas from crude paraffin sources have more straight chain saturated or cyclic compounds. As a general rule the matter of the "sweet" crude (low sulfur content) and naphthas are paraffinic. Naphthenic crudes contain more unsaturated and cyclic and polycyclic compounds. Higher sulfur content crudes tend to be naphthenic. The treatment of the different direct run naphthas may be slightly different depending on their composition due to the source of the crude oil. Reformed or reformed naphtha in general does not require additional treatment, except perhaps distillation or solvent extraction for a valuable aromatic product separation. Reformed naphtha has essentially no sulfur contaminants due to the severity of its pretreatment for the process and the process itself. The naphtha subjected to catalytic pyrolysis as it comes from the catalytic pyrolysis apparatus has a relatively high octane number as a result of the olefinic and aromatic compounds contained therein. In some cases this fraction can contribute as much as half of the gasoline in the refinery source along with a significant portion of the octane. The boiling range material of naphtha gasoline subjected to catalytic pyrolysis concurrently forms a significant part («1/3) of the inventory of the gasoline product cluster in the United States of America and provides the largest portion of the sulfur. Sulfur impurities may require separation, usually by hydrotreating in order to comply with product specifications or to ensure compliance with environmental regulations. The most common method of removal of the sulfur compounds is by hydrodesulfurization (HDS) in which the petroleum distillate is passed over a solid particulate catalyst comprising a hydrogenation metal supported on an alumina base. Additionally copious amounts of hydrogen are included in the feed. The following equations illustrate the reactions in a typical HDS unit; (1) RSH + H2 RH + H2S (2) RC1 + H2 RH + HCl (3) 2RN + 4H2 RH + NH3 (4) ROOH + 2H2 _.:__ RH + H20 The typical operating conditions for HDS reactions They are: Temperature, ° C (° F) 315.5-415.5 (600-780) Pressure, Kg / cm2 (psig) 42.2-211 (600-3000) Recycling speed H2 SCF / bbl 1500-3000 Compensation of new H2, SCF / bbl 700/1000 After that hydrotreating is complete the product can be fractionated or simply subjected to flash vaporization to release the hydrogen sulfide and collect the now desulfurized naphtha. In addition to providing high octane number mix components, naphthas subjected to catalytic pyrolysis are frequently used as sources of olefins in other processes such as etherifications. The hydrotreating conditions of the naphtha fraction to separate the sulfur will also saturate some of the olefinic compounds in the fraction reducing octane and causing a loss of the source olefins. Several proposals have been made to separate the sulfur while retaining the most desirable olefins. Since the olefins in the naphtha subjected to catalytic pyrolysis are mainly in the fraction below the boiling point of these naphthas and the impurities containing sulfur tend to be concentrated in the high boiling fraction., the most common solution has been pre-fractionation before hydrotreating. Pre-fractionation produces a light-boiling range naphtha that boils in the range of 5 carbon atoms to about 121 ° C (250 ° F) and a high-boiling naphtha that boils in the range of about 121-246 ° C (250-475 ° F). The predominantly light or lower boiling sulfur compounds are mercaptans whereas heavy or higher boiling compounds are thiophenes and other heterocyclic compounds. Separation by fractionation alone will not separate the mercaptans. However, in the past mercaptans have been separated by oxidation processes involving caustic washing. A combination of oxidizing separation of mercaptans followed by fractionation and hydrotreating of the heavier reaction is described in U.S. Patent 5,32,742. In the oxidizing separation of the mercaptans the mercaptans are converted to the corresponding disulfides. In addition to treating the lighter portion of the naphtha to separate the mercaptans, a catalytic reformer unit has traditionally been used as feed to increase the octane number if necessary. Also, the lighter fraction can be subjected to further separation to remove the olefins of 5 valuable carbon atoms (amylenes) which are useful in the preparation of ethers.

It is an advantage of the present invention that the sulfur can be separated from the light olefin portion of the stream to a heavier portion of the stream without any substantial loss of olefins. Substantially all of the sulfur in the heavier portion is converted to H2S by hydrodesulfurization and is more easily distilled from the hydrocarbons.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the present invention uses a naphtha splitter as a distillation column reactor to treat a portion or all of the naphtha to separate the organic sulfur compounds contained therein. The catalyst is placed in the distillation column reactor, such that the selected portion of the naphtha is contacted with the catalyst and treated. The catalyst can be placed in the rectification section to treat the lightest boiling range compounds, only, in the separation section to treat the heavier boiling range components only or in the whole column to treat widely naphtha. In addition, the distillation column reactor can be combined with standard one-step fixed-bed reactors or another distillation column reactor to finely adjust the treatment.

As used herein, the term "distillation column reactor" means a distillation column that also contains catalyst such that the reaction and distillation proceed concurrently in the column. In a preferred embodiment, the catalyst is prepared as a distillation structure and serves as both the catalyst and the distillation structure.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a simplified flow diagram of one embodiment of the invention having a catalytic bed in a distillation / naphtha splitter column that is used to treat the heavier components only. Fig. 2 is a simplified flow diagram of a variation of the embodiment of Fig. 1 having two catalytic beds in a distillation / naphtha splitter column which is used to treat the full boiling range of naphtha. Figure 3 is a simplified flow diagram of a variation of Figure 2 having two catalytic beds in a distillation / naphtha splitter column which is used to treat full boiling naphtha and the heavy naphtha is removed directly underneath of the catalytic bed, lower.

Figure 4 is a simplified flow diagram of a variation of the embodiment of Figure 3 having a continuous catalytic bed in a diagonal distillation column / naphtha splitter which is used to treat full boiling naphtha and naphtha is removed at a higher point in the column than Figure 3. Figure 5 is a simplified flow chart of an embodiment of the invention wherein there is a single catalytic bed in the rectification section of a distillation / divider column. of naphtha which is used to treat light naphtha only and heavy naphtha is treated in a conventional reactor. Fig. 6 is a simplified flow diagram of another embodiment of the invention wherein a conventional front end reactor is used as a safety bed or protection bed for the distillation column / naphtha splitter which is used to treat the naphtha full boiling range. Fig. 7 is a simplified flow diagram of a mode similar to that of Fig. 5 where the naphtha distillation / splitter column is used to treat light naphtha only and the heavy naphtha is treated in a distillation column reactor separated. Fig. 8 is a simplified flow chart of a mode similar to Fig. 5 where the naphtha distillation / splitter column is used to treat light naphtha only and the heavy naphtha is treated in a conventional reactor . Fig. 9 is a simplified flow diagram of a variation of the embodiment of Fig. 8 in which the naphtha distillation / splitter column is used to treat light naphtha only and the heavy naphtha is treated in a gasoline reactor. Separate distillation column having a conventional safety or protection bed with the reactor bottoms of the separated distillation column being recycled through the protection bed. Fig. 10 is a simplified flow chart of an alternative embodiment of the invention similar to that of Fig. 9 where the naphtha distillation / splitter column is used to treat light naphtha only and heavy naphtha is first treated in a protective bed reactor and then finished in a distillation column reactor, separated. Figure 11 is a simplified flow chart of another embodiment of the invention wherein the distillation / splitter column of naphtha is used to treat light naphtha alone and the heavy naphtha is treated in a separate distillation column reactor with the Steam outlets from the separate distillation column being finished in a standard single pass reactor.

DETAILED DESCRIPTION OF THE INVENTION The process feed comprises a sulfur-containing petroleum fraction that boils in the boiling range of gasoline. Feeds of this type include light naphthas having a boiling range of about 5 carbon atoms to 165.5 ° C (330 ° F) and full-range naphthas having a 5 carbon atom division range of 215.5 ° C ( 420 ° F). In general, the process is useful in the boiling range material of the naphtha of the catalytic pyrolysis products because they contain the desired olefins and undesirable sulfur compounds. Direct-run naphthas have very little olefinic material and unless the source of oil is "acidic", very little sulfur. The sulfur content of the fractions subjected to catalytic pyrolysis will depend on the sulfur content of the feed to the catalytic pyrolysis apparatus, as well as the boiling range of the selected fraction used as feed to the process. The lighter fractions will have lower sulfur contents than the higher boiling fractions. The front end of naphtha contains most olefins with high octane content but relatively little sulfur. The sulfur components at the front end are mainly mercaptans and typical of these compounds are: methyl mercaptan (boiling point 6.1 ° C (43 ° F)), ethyl mercaptan (boiling point 37.2 ° C (99 ° F)), n-propyl mercaptan (boiling point 67.8 ° C (154 ° F)), iso-propyl mercaptan (boiling point 57.2-60 ° C (135-140 ° F)), isobutyl mercaptan (boiling point 87.8 ° C ( 190 ° F)), tert-butyl mercaptan (boiling point 63.9 ° C (147 ° F)), n-butyl mercaptan (boiling point 97.8 ° C (208 ° F)), sec-butyl mercaptan (boiling point d) 95 ° C (203 ° F)), iso-amyl mercaptan (boiling point 121 ° C (250 ° F)), n-amyl mercaptan (boiling point 126.1 ° C (259 ° F)), alpha-methylbutyl mercaptan (boiling point 122.2 ° C (234 ° F)), alpha-ethylpropyl mercaptan (boiling point 145 ° C (293 ° F)), n-hexyl mercaptan (boiling point 151.1 ° C (304 ° F)), 2-mercapto hexane (d boiling point 140 ° C (284 ° F)) and 3-mercapto he xano (d boiling point 57.2 ° C (135 ° F)). Typical sulfur compounds found in the heaviest boiling fraction include the heavier mercaptans, sulphides, and thiophene disulfides. The reaction of organic sulfur compounds in a refinery stream with hydrogen on a catalyst to form H 2 S is commonly called hydrodesulfurization. Hydrotreating is a broad term that includes the saturation of olefins and aromatics and the reaction of organic nitrogen compounds to form ammonia. However, hydrodesulfurization is included and is sometimes referred to in the same hydrotreatment.

Catalysts that are useful for the hydrodesulfurization reaction include Group VIII metals such as cobalt, nickel, palladium, alone 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, metals are provided as the oxides of metals supported on extruded products or spheres and as such are not generally useful as distillation structures. The catalysts contain metal components of Group V, VIB, VIII of the periodic table of the elements and mixtures thereof. The use of the distillation system reduces deactivation and provides longer runs than the fixed bed hydrogenation units of the prior art. Group VIII metal provides increased overall average activity. Catalysts containing a Group VIII metal such as molybdenum and a Group VIII metal such as cobalt or nickel are preferred. Suitable catalysts for the hydrodesulfurization reaction include cobalt-molybdenum, nickel-molybdenum and nickel-tungsten. The metals are generally present as supported oxides on a neutral base such as alumina, silica-alumina or the like. The metals are reduced to sulfur either in use or before use by exposure to the currents containing the sulfur compound. The catalyst can also catalyze the hydrogenation of the olefins and polyolefins contained within the light catalytic pyrolysis naphtha and to a lesser degree the isomerization of some of the mono-olefins. Hydrogenation, especially of the mono-olefins in the lighter fraction may be undesirable. The properties of a typical hydrodesulfurization catalyst are shown in Table I below: TABLE I Manufacturing Criterion Catalyst Co. Design C-448 Form Extruded product tri-lobal Nominal size Diameter 1.2 mm Metal,% by weight Cobalt 2-5% Molybdenum 5-20 Alumina support The catalyst is usually in the form of extruded products having a diameter of 0.3175 cm (1/8"), 0.1587 cm (1 / 16") or 0.0794 cm (1/32 inch) and an L / D of 1.5 to 10. The catalyst can also be in the form of spheres having the same diameters. They can be directly charged to standard single-step fixed-bed reactors that include supports and reagent distribution structures. However, in their regular form they form a mass too compact and must be prepared in the form of a catalytic distillation structure. The catalytic distribution structure must be able to function as a catalyst and as a means of mass transfer. The catalyst must be properly supported and spaced within the column to act as a catalytic distillation structure. In a preferred embodiment the catalyst is contained in a woven wire mesh structure as described in U.S. Patent No. 5,266,546, which is incorporated herein by reference. More preferably, the catalyst is contained in a plurality of closed wire mesh tubes either at one end or the other and laid through a sheet of wire mesh fabric such as a mist separator wire. Then the sheet and tubes are laminated to a bale or bale for loading to the reactor of the distillation column. This embodiment is described in U.S. Patent 5,431,890 which is incorporated herein by reference. Other catalytic distillation structures useful for this purpose are described in U.S. Patents 4,731,229, 5,073,236, 5,431,890 and 5,730,843 which are also incorporated by reference. Reaction conditions for sulfur separation only in a standard single-stage fixed-bed reactor are in the range of 260-371.1 ° C (500-700 ° F) at pressures between 28.1-70.3 Kg / cm2 (400 -1000 psig). The residence times expressed as the space velocity per hour of liquid are in general commonly between 1.0 and 10. The naphtha in the fixed-bed reaction of a single step may be in the liquid phase or in the gas phase depending on the temperature and pressure, the Total pressure and hydrogen gas velocity adjusted to obtain partial pressures of hydrogen in the range of 7.03 - 49.2 Kg / cm2 (100-700 psia). The operation of the hydrodesulphurization in fixed bed of a single step is otherwise well known in the art. The appropriate conditions for desulfurization of naphtha in a distillation column reactor are very different from those in a standard drip bed reactor, especially with respect to the total pressure and partial pressure of hydrogen. Typical conditions in a reaction distillation zone of a naphtha hydrodesulfurization distillation column reactor are: Temperature 232-371.1 ° C (450-700 ° F) Total pressure 5.3-21.1 Kg / cm2 (75-300 psig) Pressure partial H2 0.42-5.27 Kg / cm2 (6-75 psia) LHSV naphtha approximately 1-5 H2 speed 10-1000 SCFB Operation of the distillation column reactor results in a liquid phase and a vapor phase between the Distillation reaction zone. A considerable portion of vapor is hydrogen while a portion is hydrocarbon in vapor of the petroleum fraction. The actual separation may only be a secondary consideration. Without limiting the scope of the invention it is proposed that the mechanism that produces the effectiveness of the present process is the condensation of a portion of the vapors in the reaction system, which prevents sufficient hydrogen in the condensed liquid to obtain the required intimate contact between the hydrogen and the sulfur compounds in the presence of the catalyst to result in their hydrogenation. In particular, the sulfur species are concentrated in the liquid while the olefins and H2S are concentrated in the vapor allowing a high conversion of the sulfur compounds with a low conversion of the olefin species. The result of the operation of the process in the distillation column reactor is that lower partial hydrogen pressures (and thus lower total pressures) can be used. As in any distillation there is a temperature gradient between the distillation column reactor. The temperature at the lower end of the column contains higher boiling material and thus a higher temperature than at the upper end of the column. The lower boiling fraction, which contains more easily separable sulfur compound, is subjected to lower temperatures at the top of the column which provides higher selectivity, that is less hydrocracking or saturation of the desirable olefinic compounds. The higher boiling portion is subjected to higher temperatures at the lower end of the distillation column reactor to subject the sulfur-containing ring compounds to open catalytic pyrolysis and to hydrogenate the sulfur. It is believed that the present distillation column reaction is a benefit first, because the reaction occurs concurrently with the distillation, the initial reaction products and other current components are separated from the reaction zone as soon as possible by reducing the probability of secondary reactions. Secondly, because all the components boil at the reaction temperature is controlled by the boiling point of the mixture at system pressure. The heat of reaction simply creates more boiling, but does not increase in temperature at a given pressure. As a result, more control over the rate of reaction and product distribution can be obtained by regulating system pressure. An additional benefit that this reaction can gain from the distillation column reactions is the washing effect that the internal reflux provides to the catalyst thereby reducing the accumulation and coking of the polymer. Finally, the hydrogen that flows upwards acts as a separation agent to help separate the H2S that is produced in the distillation reaction zone. The attached figures show several processing schemes to obtain particular results. The same elements have been given the same designations in the figures. It should be noted that the rearrangement of the elements in the various modalities are all directed to the separation of naphthas and the reduction in organic sulfur compounds. In Figure 1 the catalyst 12a is charged only to the separation section 12 of a naphtha divider 10 configured as a distillation column reactor. The naphtha feed is to the distillation column reactor 10 above the separation section via the flow line 1 and combined with hydrogen from the flow line 2. The rectification section 14 is left devoid of the catalyst to prevent the lighter components are subjected to the hydrodesulfurization catalyst and prevent undesirable saturation of the olefins. The light naphtha is boiled in the rectification section 14 and is separated together with the unreacted hydrogen and H2S as vapor outlet via the flow line 3. The light naphtha is condensed in the condenser 20 and separated from the hydrogen and H2S and other light components in the receiver / separator 30. The uncondensed liquids are separated from the separator 30 via the flow line 19 and taken to the trap 50 where any liquid (entrained or subsequently condensed) is separated via the flow line 8. and combined with the light naphtha product in the flow line 7. The separator liquid is separated via the line of the flow 5 with a portion being returned to the reactor of the distillation column as reflux via the flow line 6. The naphtha product is separated via the flow line 7. The heavy naphtha fraction is subjected to hydrodesulfurization by the catalyst 12a in the separation section and is separated as a bottom via the flow line 13. A portion of the bottoms is circulated through the heater reboiler 40 heated via the flow lines 21 and 17. The product of the heavy naphtha is separated via the line flow 15. Most of the gas in the trap 50 is recompressed and recycled to the heated reboiler 40 via the flow line 11. A vent can be provided to prevent the accumulation of the inert hydrocarbons normally present in the hydrogen streams. of refinery and to separate some of the H2S. The preferred operating conditions and results for the reactor of the distillation column of Figure 1 are as follows: pressure 7.03-21.09 Kg / cm2 (100-300 psig) H2 speed 30-1000 scfh partial pressure H2 0.07-4.22 Kg / cm2 (1-60 psi) LHSV 0.2-5.0% of HDS 98 A second embodiment is shown in Figure 2. This embodiment differs from that of Figure 1 only by including a catalytic bed 14A in the rectification section 14. The remaining description is identical to Figure 1. The catalyst in the upper bed can be selected such that it is less active such that the monoolefins are not hydrogenated or can be the same as the bottom and used to hydrogenate those olefins if they are present Preferred operating conditions and results for the distillation column reactor of Figure 2 are as follows: pressure 7.03-21.09 Kg / cm2 (100-300 psig) H2 speed 30-1000 scfh partial pressure of H2 0.07-4.22 Kg / cm2 (1-60 psi)% of HDS 50-97 WHSV 0.2-5.0 A third mode is shown in figure 3, which differs only slightly from that shown in Figure 2. The lower section 16 of the separation section is left devoid of catalyst and the heavy naphtha product is withdrawn in a lateral extraction via the flow line 19. Most of the bottom is made to recirculate through the reboiler 40 through the flow line 21. A tail, which is boiling higher than the desired heavy fraction is otherwise taken as the bottom via the flow line 13 to prevent the accumulation of heavy in the system. The advantage of this process is that the higher boiling material containing refractory sulfur compounds is separated in the glue. With reference to figure 4 a process similar to that of figure 3 is shown. Here, the catalytic bed 12 is now continuous between the separation section 12 and the rectification section 14. The heavy naphtha is withdrawn as a lateral extraction via the flow line 23 slightly below the rectification section. As Figure 3, a tail is removed as a bottom via the flow line 13 to prevent the accumulation of heavy and separate the refractory sulfur compounds. Figure 5 shows a useful modality when the sulfur content of the heavy fraction is such that it needs treatment under significantly different conditions than those available in the divider. The catalytic bed 14A is placed in the rectification section 14 with the separation section 12 left devoid. The feed is directly below the rectification section 14. The bottom product of the heater 40 not recirculated to the column is fed to a single-stage fixed bed reactor 60 containing a catalytic hydrodesulfurization bed 62. The effluent is made pass to a high pressure separator 70 where the heavy naphtha is withdrawn via the flow line 23. The steam from the high pressure separator is recycled to the separation section 12 via the flow line 25. In Figure 6 the reactor 60 single-step fixed bed containing catalyst bed 62 is placed upstream of reactor 10 of the distillation column. In this case, the reactor 10 of the distillation column acts as the polishing reactor and the fixed bed reactor 60 can act as a safety bed. The reactor of the safety bed can be recharged more easily than the hydrodesulfurization or regenerated catalyst than the distillation column reactor. Figure 7 describes a process similar to that shown in Figure 5 except that the finishing reactor 60 for the bottom heavy naphtha stream is a second distillation column reactor 60 with 2 catalyst beds 62 and 64. The bottom of the heavy naphtha of the first reactor 10 of the distillation column is fed to the second reactor 60 of the distillation column below the bed 62 of the rectification section and above the bed 64 of the separation section via the flow line 15. Hydrogen for the second reactor of the distillation column 60 is added to the recycle gas stream 29 via the flow line 41 to compose a combined stream in the flow line 43. The second reactor of the distillation column 60 includes all the auxiliary equipment that the first distillation column reactor 10 has included a condenser 50, a receiver / separator 70, a trap at 90 and a heated reboiler 80. The product of naphtha p This is taken as leaving steam via the flow line 17 to the condenser, from here to the receiver / separator 70, via the flow line 47 and separated from the receiver / separator via the flow line 23 and combined with the liquid from the trap from the flow line 31 to the product line 33. The gas from the receiver / separator 70 is taken via the flow line 49 to the trap 90 where any liquid is separated via the flow line 31 before its recompression and recycling via the flow lines 25 and 29. A small vent hole 27 is taken to prevent inert accumulation in the system. Most of the bottom is combined with the recycled hydrogen in the flow line 37 and recirculated again from the heated reboiler 80. A bottom product is separated via the flow line 35 and 39 to prevent the accumulation of heavy loads in the system. The preferred operating conditions for the two distillation column reactors of Figure 7 are as follows: Tower 1 (10) Tower 2 (60) Pressure 1.76-8.79 Kg / cm2 25-125 psig 7.03-21.09 Kg / cm2 100-300 psig H2 speed 30-300 scfb 30-1000 scfh H2 partial pressure 0.03-0.70 Kg / cm2 0.5-10 psi 0.07-4.22 Kg / cm2 1-60 psi% HDS 85-95 (OH) 50-98 WHSV 0.2- 5.0 0.2-5.0 The process shown in Fig. 8 is also similar to that of Fig. 5 except that the feed to the single-pass fixed-bed reactor is heated in its own heated heater 80. The effluent from the reactor 60 is taken via the flow line 33 to the condenser 50 and from here to the receiver / separator 70 when the liquid is withdrawn via the flow line 23. The gas from the receiver / separator is taken via the flow line 35 and further cooled in the cooler 100 before it passes through. the trap 90. The trap vapor is taken via the flow line 25 and most of it is recycled via the flow line 29. The nitrogen is added to the recycle as necessary via the flow line 41 and the combined stream is fed to the heated heater via the flow line 43. The liquid of the trap is taken via the flow line 31 and combined with the heavy naphtha product in the flow line 23 and separated via the flow line 33. Figure 9 shows a a variation in the process of Figure 8 which includes a fixed bed reactor 100 which acts as a protection bed in the front of the second reactor 60 of the distillation column having all the necessary auxiliary equipment including the condenser 50 of the steam outlet, receiver / separator 70 and trap 90. The heated heater 80 for the reactor 100 of the single-stage fixed bed acts as the reboiler for the distillation column reactor by taking a portion of the bottom in the flow line. and circulate via the flow line 37. A queue is taken via the flow line 39 to prevent the accumulation of heavy loads in the system. The heavy naphtha product is taken as vapor outlet from the second reactor 60 of the distillation column via the flow line 17 and condensed in the condenser 50 and collected in the receiver / separator 70. The gas from the receiver / separator is taken via the flow line 49 to the trap 90 to separate any liquids contained therein. Most of the gas in the trap on line 25 is recycled via flow line 29. A small portion is vented via flow line 27 to prevent inert accumulation. A portion of the heavy naphtha product is returned as reflux via the flow line 45. The liquid is taken from the trap 900 via the flow line 31 and combined with the heavy naphtha product in the flow line 23 and separated via the flow line 33. Compensating hydrogen is added as necessary via the flow line 41 and combined with the recycle in the flow line 43 and fed to the heater 80. Referring now to Figure 10 a similar process is shown that shown in Figure 9. However, there is no recycling of any of the vapor output vapors. The second distillation column reactor 60 has its catalyst bed 62 located only in the separation zone to treat only the heavier naphtha. A final embodiment is shown in Figure 11 which is also similar to that shown in Figure 7, except that the steam outlet of the second reactor of the distillation column is further treated in a reactor 100 of a fixed one-step bed. standard containing a catalyst bed 112 that now serves as a finishing reactor. In many of the modes hydrogen is recycled back to the reactors. Ventilation holes may be sufficient to keep H2S levels sufficiently low for the reaction. However, if desired, the recycling site can be cleaned using conventional methods to separate the H2S.

The invention presents a flexible arrangement for treating various naphthas using a distillation column / naphtha splitter reactor and auxiliary reactors.

Claims (14)

1. CLAIMS 1. A process for the hydrodesulfurization of naphtha in a distillation column reactor having a separation section and a rectification section, characterized in that it comprises the steps of: (a) feeding a hydrocarbon stream of boiling point range of naphtha containing organic sulfur compounds and hydrogen to a distillation column reactor above the separation section, (b) concurrently in the distillation column reactor: (i) separating the naphtha to a light boiling range naphtha and a heavy boiling naphtha, (ii) contacting the heavy boiling range naphtha and hydrogen with a hydrodesulfurization catalyst in the separation section to selectively react the heavier organic sulfur compounds with the hydrogen to form H 2 S; (c) separating the light boiling range naphtha, H2S and unreacted hydrogen from the reactor of the distillation column as steam outlet, (d) separating the heavy boiling range naphtha from the distillation column reactor as a bottom.
2. 2. The process according to claim 1, characterized in that it further comprises the steps of: (e) cooling the steam outlet to condense the light boiling range naphtha and separating it from hydrogen and H2S, (f) returning a portion of the light boiling range naphtha condensed to the distillation column reactor as reflux; (g) recirculating a portion of the bottom through a reboiler and (h) feeding the unreacted hydrogen from the vapor outlet to the reboiler for circulation to the distillation column reactor at a point below the separation section.
3. 3. The process in accordance with the claim 1, characterized in that it further comprises the steps of: (b) contacting the light boiling naphtha and hydrogen with a hydrodesulfurization catalyst in the rectification section to selectively react the lighter organic sulfur compounds with the hydrogen for form H2S; (i) recirculating a portion of the bottom through a reboiler and (j) feeding the unreacted hydrogen from the vapor outlet to the reboiler for recirculation to the distillation column reactor to a point below the separation section.
4. 4. The process in accordance with the claim 3, characterized in that it further comprises the steps of: (g) cooling the vapor output to condense the light boiling range naphtha and separating it from the hydrogen and H2S and (h) returning a portion of the light boiling range naphtha. condensed to the distillation column as reflux.
5. 5. The process according to claim 3, characterized in that the lower portion of the separation is devoid of the hydrodesulfurization catalyst and a side stream is taken from the separation section at a point just below the hydrodesulfurization catalyst located in the separation.
6. 6. The process in accordance with the claim 4, characterized in that the lower portion of the separation is devoid of the hydrodesulfurization catalyst and a sidestream is taken from the reactor of the distillation column at a point just below the rectification section.
7. 7. A process for the hydrodesulfurization of naphtha in a distillation column reactor having a separation section and a rectification section, characterized in that it comprises the steps of: (a) feeding a hydrocarbon stream of boiling point range naphtha containing organic sulfur compounds and hydrogen to a distillation column reactor above the separation section, (b) concurrently in the distillation column reactor: (i) separating the naphtha to a light boiling range naphtha and a heavy boiling range naphtha, (ii) contact the boiling range naphtha. heavy and hydrogen with a hydrodesulfurization catalyst in the separation section to selectively react the heavier organic sulfur compounds with the hydrogen to form H2S; (c) separating the light boiling range naphtha, H2S and unreacted hydrogen from the distillation column reactor as steam outlet, (d) separating the heavy boiling naphtha from the distillation column reactor as a bottom, ( e) feeding the unreacted hydrogen to a reboiler for recirculation back to the distillation column reactor at a point below the separation section and (f) feeding a portion of the reboiler effluent to a fixed bed reactor of a single step containing a hydrodesulfurization catalyst to react a portion of the heavy organic sulfur compounds with hydrogen to form H2S.
8. 8. The process according to claim 7, characterized in that it further comprises the steps of: (g) cooling the steam outlet to condense the light boiling naphtha and separating it from hydrogen and H2S, (h) returning a portion of the light boiling range naphtha condensed to the distillation column reactor as reflux and (i) recirculating a portion of the bottom through a reboiler.
9. 9. The process according to claim 7, characterized in that the effluent from the single-stage fixed bed reactor is separated into a gaseous portion containing unreacted hydrogen and the H2S and a liquid portion containing the boiling range naphtha. and the gaseous portion is recycled to the distillation column reactor below the separation section.
10. 10. The process in accordance with the claim 7, characterized in that it further comprises the steps of: (f) feeding the remainder of the bottom and additional hydrogen to a one-step fixed bed reactor containing a hydrodesulfurization catalyst to react a portion of the heavy organic sulfur compounds with hydrogen to form H2S, (g) cool the vapor output to condense the light boiling range naphtha and separate it from hydrogen and H2S; (h) returning a portion of the light boiling range naphtha condensed to the distillation column as reflux and (i) recirculating a portion of the bottom through a reboiler. The process according to claim 10, characterized in that it further comprises the steps of: (j) feeding the effluent from the single-stage fixed-bed reactor to a second distillation column reactor; (k) concurrently in the second distillation column reactor, (i) contacting the heavy boiling range naphtha and hydrogen with a hydrodesulfurization catalyst to further react the additional organic sulfur compounds with the hydrogen to form HS and (ii) separating the heavy boiling range naphtha to a stream of heavy naphtha and a tail stream; (1) separating the stream of heavy naphtha, H2S and unreacted hydrogen from the second distillation column reactor as steam outlet; (m) separating the bottom stream from the second distillation column reactor as bottoms; (n) cooling the steam outlet to condense the heavy naphtha stream and separate it from hydrogen and H2S; (o) returning a portion of the condensed heavy naphtha stream to the second distillation column as reflux; (p) recirculating a portion of the heavier boiling range naphtha through the one-step fixed bed reactor; (q) recycle the unreacted hydrogen from the steam outlet to the one-step fixed bed reactor with the naphtha feed. The process according to claim 10, characterized in that it further comprises the steps of: (j) feeding the effluent from the single-stage fixed-bed reactor to a second distillation column reactor; (k) concurrently in the second distillation column reactor: (i) separating the heavy boiling range naphtha to a stream of heavy naphtha and a tail stream and (ii) contacting the boiling point range naphtha heavy and hydrogen with a hydrodesulfurization catalyst in the rectification section of the second distillation column reactor to further react the additional organic sulfur compounds with hydrogen to form HS and (1) separate the stream of heavy naphtha, H2S and hydrogen unreacted from the second distillation column reactor as a vapor outlet; (m) separating the tail stream from the second distillation column reactor as bottoms; (n) cooling the steam outlet to condense the heavy naphtha stream and separate it from hydrogen and H2S; (o) returning a portion of the condensed heavy naphtha stream to the second distillation column as reflux; (p) recirculating a portion of the heavier boiling range naphtha through the one-step fixed bed reactor; (q) recycle the unreacted hydrogen from the steam outlet to the one-step fixed bed reactor with the naphtha feed. 13. A process for the hydrodesulfurization of naphtha, characterized in that it comprises: (a) feeding hydrogen and naphtha to a single-stage fixed bed reactor containing a hydrodesulfurization catalyst to thereby react a portion of the organic sulfur compounds contained therein with hydrogen to form H2S; (b) feeding the effluent from the one-step fixed bed reactor to a distillation column reactor; (c) concurrently in the distillation column reactor: (i) contacting the full-range naphtha of boiling point and hydrogen with a hydrodesulfurization catalyst to further react the additional organic sulfur compounds with the hydrogen to form H2S and (ii) separating naphtha in a light boiling range naphtha and a heavy boiling range naphtha; (d) separating the light boiling naphtha, H2S and unreacted hydrogen from the distillation column reactor as a vapor outlet, (e) separating the heavier boiling range naphtha from the distillation column reactor as a bottom, (f) cooling the vapor output to condense the light boiling range naphtha and separating it from hydrogen and H2S, (g) returning a portion of the condensed light boiling naphtha to the distillation column reactor as reflux; (h) recirculating a portion of the heavier boiling range naphtha through the one-step fixed bed reactor; (i) recycle the unreacted hydrogen from the steam outlet to the one-step fixed bed reactor with the naphtha feed. 14. A process for the hydrodesulfurization of naphtha in a distillation column reactor having a separation section and a rectification section, characterized in that it comprises the steps of: (a) feeding a hydrocarbon stream of boiling point range naphtha containing organic sulfur compounds and hydrogen to the distillation column reactor above the separation section, (b) concurrently in the distillation column reactor: (i) separating the naphtha to a light boiling range naphtha and a heavy boiling range naphtha, (ii) contacting the light boiling range naphtha and hydrogen with a hydrodesulfurization catalyst in the rectification section to make the lighter organic sulfur compounds selectively react with hydrogen to form H2S; (c) separating the light boiling range naphtha, H2S and unreacted hydrogen from the distillation column reactor as a vapor outlet, (d) separating the heavier boiling range naphtha from the distillation column reactor as a bottom, (e) cooling the vapor output to condense the light boiling range naphtha and separate it from the hydrogen and H2S; (f) returning a portion of the light boiled range naphtha condensed to the distillation column reactor as reflux; (g) recirculating a portion of the heavier boiling range naphtha through a reboiler; (h) recycle the unreacted hydrogen from the steam outlet to the distillation column reactor with the naphtha feed and (1) feed the rest of the heavier boiling range naphtha and additional hydrogen to a second distillation column; (j) concurrently in the second distillation column reactor: (i) separating the heavier boiling point naphtha in a stream of heavy naphtha and a tail stream and (ii) contacting the naphtha in the range of heavy boiling point and hydrogen with a catalytic hydrodesulfurization section to react the heavier organic sulfur compounds with the hydrogen to form H2S; (k) separating the stream of heavy naphtha, H2S and unreacted hydrogen from the second distillation column reactor as steam outlet and (1) separating the bottom stream from the second distillation column reactor as bottom.