CA1127104A - Combination process for upgrading naphtha - Google Patents
Combination process for upgrading naphthaInfo
- Publication number
- CA1127104A CA1127104A CA332,899A CA332899A CA1127104A CA 1127104 A CA1127104 A CA 1127104A CA 332899 A CA332899 A CA 332899A CA 1127104 A CA1127104 A CA 1127104A
- Authority
- CA
- Canada
- Prior art keywords
- fraction
- zsm
- reformate
- naphtha
- boiling
- 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.)
- Expired
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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
- C10G59/00—Treatment of naphtha by two or more reforming processes only or by at least one reforming process and at least one process which does not substantially change the boiling range of the naphtha
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J29/00—Catalysts comprising molecular sieves
- B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
- B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
- B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
- B01J29/42—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing iron group metals, noble metals or copper
- B01J29/44—Noble metals
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/10—After treatment, characterised by the effect to be obtained
- B01J2229/26—After treatment, characterised by the effect to be obtained to stabilize the total catalyst structure
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
- B01J2229/30—After treatment, characterised by the means used
- B01J2229/42—Addition of matrix or binder particles
-
- 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
- C10G2400/00—Products obtained by processes covered by groups C10G9/00 - C10G69/14
- C10G2400/02—Gasoline
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
COMBINATION PROCESS FOR UPGRADING NAPHTHA
ABSTRACT OF THE DISCLOSURE
A straight-run naphtha is fractionated at about 66 which is just below the boiling point of methylcyclopentane. The 66°C+ fraction is reformed, and at least a portion of the reformate reacted in the presence of a ZSM-5-type catalyst.
ABSTRACT OF THE DISCLOSURE
A straight-run naphtha is fractionated at about 66 which is just below the boiling point of methylcyclopentane. The 66°C+ fraction is reformed, and at least a portion of the reformate reacted in the presence of a ZSM-5-type catalyst.
Description
~ ~ ~ 7 001 -1~
002 BACKGROUND,AND SUMMARY OF THE INVENTION
003 This invention relates to a combination process for 004 upgrading a naphtha fraction. In one aspect, the invention 005 relates to a process combining reforming and aromatization over 006 a ZSM-5-type zeolite, to produce a product useful as a high-007 octane gasoline blending stock or a source from which benzene, 008 toluene and xylene can be recovered. In another aspect, the 009 invention relates to a process combining reforming, isomeri-010 zation and hydrocracking in the presence of a ZSM-5-type 011 zeolite to produce a product useful as a high-octane gasoline 012 blending stock and as a source for recovering benzene, toluene 013 and xylene.
014 In view of the current concern over air pollution and 015 environmental control, processes which will increase the octane 016 number of gasoline while minimizing or eliminating the need for 017 additives are being sought.
018 One traditional way of increasing the octane of a 019 naphtha fraction has been to subject it to catalytic reforming, 020 usually over a platinum-containing or bimetallic catalyst. In 021 the reformer, naphthenes and paraffins are converted to aro-022 matics, both reactions which substantially increase the octane 023 number of the hydrocarbons involved. Naphthenes are reformed 024 to aromatics with high selectivity. ~owever, the selectivity 025 with which paraffins are converted to aromatics decreases with 026 the number of carbon atoms per paraffin molecule. Only a minor 027 fraction of C6 paraffins is converted to benzene. Other reac-028 tions which occur in the reformer are isomerization and crack-029 ing of paraffins. The cracking to C3- hydrocarbons represents 030 an irreversible yield loss, and the isomerization of paraffins 031 mainly to singly branched paraffins is a reversible reaction in 032 which a relatively high concentration of low-octane n-paraffins 033 remain in thermal equiIibrium with the branched isomers. Thus, U34 inclusion of C6 paraffinic hydrocarbons in a reformer feed is a 035 less efficient use of the catalyst and reactor facilities than 036 the inclusion of C6 naphthenes.
037 Another way of improving the octane number of hydro-038 carbon fractions is by contacting them with a ZSM-5 type of ~7~Q~
002 aluminosilicate zeolite catalyst to produce new aromatic rings 003 from aliphatic compounds. For example, U.S. Patent 3,761,389 004 teaches aromatization of a hydrocarbon fraction boiling within 005 the range of C2 to 400F with a ZSM-5 type of synthetic alumino-006 silicate zeolite catalyst, and U.S. Patent 3,756,942 teaches 007 aromatization of a feed consisting essentially of C5+ paraf-008 fins, olefins and/or naphthenes over a ZSM-5-type catalyst to 009 produce a predominantly aromatic liquid and a light hydrocarbon 010 gas. If the aromatization is performed at high temperature 011 (e.g., about 538C) and low pressure (e.g., about 1 atmosphere) 012 without added H2~ the light gas includes C2-C4 olefins as well 013 as Cl-C4 paraffins.
014 The art discloses several combinations of reacting a 015 hydrocarbon stream over a reforming catalyst and over a ZSM-5-016 type catalyst. For example: in U.S. Patent 3,729,409 there is 017 described a process for upgrading a reformate by contacting the 018 reformate and hydrogen with a ZSM-5-type zeolite, to selec-019 tively crack the normal paraffins and to form and alkylate aro-020 matic compounds. In U.S. Patent 3,849,290 there is described a 021 process for reforming a naphtha and then removing normal and 022 singly branched hydrocarbons by selective cracking to leave an 023 aromatics-enriched product. In these two processes, some 024 cracking of the alkyl side chain on the aromatic ring occurs, 025 resulting in production of unwanted light ends. In U.S. Patent 026 3l770,614 there is disclosed a process in which a reformate is 027 fractionated and the light reformate fraction (C6 to 116 or 028 127C) passed over a ZSM-5-type zeolite to alkylate mono-029 aromatics. In U.S. Patent 3,950,241 there is disclosed a 030 process for upgrading naphtha by separating it into low- and û31 high-boiling fractions, reforming the low-boiling fraction, and 032 combining the high-boiling naphtha with the reformate for 033 contact with a ZSM-5-type catalyst to crack the paraffins.
034 Reacting heavy naphthas over ZSM-5-type catalysts in 035 the absence of H2 and at high temperatures leads to rapid cata-036 lyst deactivation, while processing naphthenes over them leads 037 primarily to cracking, which reduces liquid yields.
J.~;Z71`~9L
002 ~e have found it advantageous to separate a naphtha 003 into a light fraction and a heavy fraction, reform the heavy 004 fraction, and pass at least a portion of the reformate over 005 ZSM-5-type catalyst to produce a C5+ product fraction enriched 006 in aromatic hydrocarbons.
007 In particular, we have provided a process for 008 upgrading a l.apntha-boiling-range hydrocarbon to useful 009 products which comprises:
010 ~1) separating said naphtha into a light naphtha fraction 011 boiling below methylcyclopentane and containing C6 aliphatics 012 and lower-boiling hydrocarbons, and a heavy naphtha fraction 013 containing methylcyclopentane and higher-boiling hydrocarbons;
014 (2) reforming said heavy naphtha fraction under reforming 015 conditions to produce a reformate stream enriched in aromatics 016 compared with said heavy naphtha fraction;
017 (3) passing at least a portion of said reforma~e in 018 contact with a ZSM-5-type catalyst at an elevated temperature 019 and recovering from the ZSM-5 contacting operation a 020 hydrocarbon effluent enriched in aromatic hydrocarbons; and 021 (4) separating said effluent into a C4- stream and a C5+
022 product stream.
024 Figures 1 and 2 are schematic block-type flow diagram 025 of preferred embodiments of the present invention in which each 026 block represents one particular step or zone oE the process.
027 Conventional items such as pumps, compressors, miscellaneous 028 valving, etc., are believed to be well within the skill in the 02~ art and have been omitted from the drawing. Likewise, with 030 respect to the piping throughout the process system, only the 031 major streams required to illustrate the relationships between 032 the various stages are presented. Accordingly, various recycle 033 lines and vent gas streams, etc., have also been omitted.
035 Referring to the flow diagram depicted in Figure 1, a 036 C5 to C8 straight-run naphtha obtained from an Alaskan North 037 Slope crude oil is charged through line 20 into fractionator 'Z7~
002 21. The naphtha has an approximate composition of 55 volume 003 percent paraffins, 35 volume percent naphthenes and 10 volume 004 percent aromatics. In the fractionator, the naphtha is sepa-005 rated into a light fraction comprising C5 and C6 hydrocarbons 006 boiling under about 66C tl50F) and a heavy fraction including 007 methylcyclopentane boiling above about 66C ~150F). The light 008 naphtha frac~ion, about 20 volume percent of the feed, is 009 removed from fractionator 21 via line 25. The heavy naphtha 010 fraction, about 80 volume percent of the feed, is charged via 011 line 26 to reformer 27 in which it is reformed under conven-012 tional mild reforming conditions with a platinum-rhenium-013 chloride reforming catalyst (see, for example, U~S. Patent 014 3,415,737, inoorpor~t~ heroin by rcfer~ncc~ to increase the 015 aromatics content and octane number of the naphtha. The refor-016 mate, in a yield of approximately 90 LV% and substantially 017 depleted of naphthenes, is passed to separation zone 30 via 018 line 28. In separation zone 30, which may comprise one or more 019 stages, hydrogen is recovered for recycle to the reformer (not 020 shown), light gases are removed and one or more reformate frac-021 tions are recovered.
022 In one embodiment of the present invention, for maxi-023 mizing BTX production, the naphtha feed is preferably a C5 to 024 C8 straight-run naphtha, and all of the C3+ reformate is passed OZ5 via line 31, combined with the light naphtha fraction in line 026 25 and passed into ZSM reaction zone 38. In the ZSM reaction 027 zone, the normal and lightly branched paraffins undergo aromati-028 zation, and aromatics, particularly xylenes, are isomerized.
029 The ZSM reaction zone is operated at reaction conditions 030 including a temperature of 538C (1000F), no added hydrogen, 031 and an LHSV of 2 V/V/Hr. The effluent from ZSM reaction zone 032 38 is passed via line 39 to separation zone 40 wherein a C5+
033 product stream in an amount of about 70 weight percent of the 034 combined feed in line 25 and rich in aromatics is separated and 035 sent via line 48 for recovery of benzene, toluene and xylene 036 values therefrom. The C4- component of the effluent is prefer-037 ably separated into an H2/Cl/C2 fraction which is removed via ~Z71~
002 line 42 and a C3/C4 fraction, in an amount of about 18 weight 003 percent of the combined feed, which may be removed from the 004 process via line 47 but which is preferably recycled via line 005 46 to ZSM reaction zone 38. The C3/C4 fraction may contain 006 propylene and butenes in addition to propane and butane.
007 In another embodiment of the present invention, the 008 naphtha feed is preferably a C5 to C8 straight-run naphtha, and 009 the reformer effluent is separated in separation zone 30 into a 010 C3 to 135C - (275F-) fraction which is sent via line 31 to the 011 ZSM reaction zone operated at conditions to form and isomerize 012 aromatics, and a 135C+ t275F+) fraction rich in xylenes which 013 may be passed via line 32 to a conventional xylene isomeri-014 zation zone, such as that described in U.S. Patent 3,948,758 015 ir;aorpor~ted horein by rcfcrcnc~. When the feed is a fu]l-016 boiling-range naphtha, a Cg+ fraction may be removed from sepa-017 ration zone 30 via line 33 and used as a high-octane (research 018 octane number of about 116 Clear) gasoline blending stock.
019 Advantages of this embodiment include a longer ZSM catalyst 020 life because higher-end-point hydrocarbons which tend to coke 021 the ZSM catalyst are not passed over it and a more efficient 022 use of the ZSM catalyst and reactor because feeding the C8+ aro-023 matics to the ZSM reaction zone would not contribute to higher 024 aromatics yields and would reduce catalyst life.
025 In yet another embodiment of the present invention, 026 particularly useful for the production of high-octane gasoline, 027 a full-boiling-range straight-run naphtha is the feedstock, the 028 reformer effluent is separated in separation zone 30 into a 029 light reformate fraction tc3 to 104C or 220F), usually about 030 70 volume percent of the reformate, which is passed via line 31 031 to the ZSM reaction zone, and a heavy reformate fraction (lOC+
032 or 220F+), usually having a research octane number of about 033 106 (Clear), which is sent to a gasoline pool (not shown) via 034 line 32. The light reformate fraction in line 31 is combined 035 with the light naphtha fraction in line 25 and preferably also 036 with a recycle C3/C4 stream, and passed in contact with a ZSM-5-037 type zeolite catalyst at reaction conditions previously men-038 tioned. The effluent from zone 38 is passed via line 39 to 1~271~9L
002 separation zone 40, from which a C5+ fraction having a research 003 octane number of about 116 (Clear) is removed via line 48 and 004 combined with the heavy reformate fraction in line 32 to form a 005 high-octane gasoline blendin~ stock having a research octane 006 number of at least 90 (Clear), and preferably 95 and still more 007 preferably at least 100 or more.
008 An advantage of this embodiment is that in splitting 009 the reformate at 104C (220F), C7 paraffins having a low 010 octane number are included in the feedstock to the ZSM reaction 011 zone in which they will undergo aromatization, but must of the 012 toluene fraction is excluded since feeding it to the ZSM reac-013 tion zone would not increase aromatics yield~. Another 014 advantage of this embodiment is that the reformer is used for 015 what it does efficiently and in high yield: dehydrocyclization 016 of naphthenes, while C6- paraffins are aromaticized over the 017 ZSM catalyt to form high-octane aromatic compounds rather than 018 cracked to C4- in the reformer, with the attendant yield loss.
019 Referring to the flow diagram depicted in Figure 2, 020 an Arabian straight-run naphtha fraction boiling in the range 021 of C5-193C (380F) is charged through line 121 into fractiona-022 tor 122. The naphtha has an approximate composition of 66 023 volume percent paraffins, 2] volume percent naphthenes and 13 024 volume percent aromatics. In the fractionator, the naphtha is 025 separated at about 66C (150F) into a light naphtha fraction 026 comprising C5 and C6 hydrocarbons boiling under about 66C
027 (150F) and a heavy naphtha fraction boiling above about 66C
028 (1505F) which includes most of the methylcyclopentane. The 029 light naphtha fraction, about ]0 volume percent of the feed, is 030 remo~ed from fractionator 122 via line 124. The heavy naphtha 031 fraction, about 90 volume percent of the feed, is charged via 032 line 126 into reformer 127 in which it is reformed under conven-033 tional reforming conditions with a platinum-rhenium-chloride 034 reforming catalyst (see, for examplel U.S. Patent 3,415,737, 035 inco~por~Qd ~cre~ eefcrcncc). The reformer acts to 036 increase the aromatics content and octane number of the 037 naphtha. The reformate, having a research octane number of 71~
001 ~7~
002 about 98, in a yield of approximately 83 liquid volume percent 003 and substantially depleted of naphthenes, is passed to sepa-004 ration zone 129 via line 128. In separation zone 129, which 005 may comprise one or more stages, hydrogen is recovered for 006 recycle to the reformer (not shown), C4- light gases are 007 removed and the C5+ reformate is split into two fractions. The 008 first fraction is a C5-77C (170F) light reformate which is 009 removed from the separator via line 134. The light reformate 010 has a research octane number of about 71 and is about 10 liquid 011 volume percent of the total reformate.
012 The light reformate in line 134 is combined with the 013 light straight-run naphtha fraction having a research octane 014 number of about 65 in line 124 and passed as a composite stream 015 via line 124 into isomerization zone 150, where it is contacted 016 in the presence of hydrogen (supply line not shown) with a 017 hydrocarbon isomerization catalyst. The isomerization condi-018 tions in zone 140 include a temperature of approximately 150C
019 (302F), a pressure of 15 atmospheres, a liquid hourly space 020 velocity of 1.5 V/V/Hr and a hydrogen to hydrocarbon mol ratio 021 of 3 . The resulting isomerizate is withdrawn in line 15] and 022 passed to separator 152 wherein it is separated into a C4- frac-023 tion and a liquid hydrocarbon fraction in about a 95 liquid 024 volume percent yield and having a research octane number of 025 about 79. The C4- fraction is withdrawn from separator 152 via 026 line 153 and the hydrogen component therein may be separated 027 and recycled to isomerization zone 150, if desired. The C5+
028 fraction from separator 152 is withdrawn via line 156 and 029 passed to a gasoline pool as a high-octane gasoline blending 030 stock.
031 Referring again to separator 129, the portion of the 032 reformate boiling above 77C (170F) is passed via line 133 to 033 ZSM conversion zone 134. About 90 liquid volume percent of the 034 reformate leaves separator 129 via line 133 and this heavy 035 reformate fraction has a research octane number of approxi-036 mately 100. In the ZSM reaction zone, the heavy reformate is 037 contacted with an H-ZSM-5 catalyst comprising 50% zeolite and l~.Z7~
002 50% Catapal matrix. ZSM reaction conditions include a tempera-003 ture of 343C (650F), a pressure of 28 atmospher~s (400 psig), 004 a hydrogen to hydrocarbon mol ratio of 5, and a liquid hourly 005 space velocity of 2 V/~/Hr. The ZSM reactor is operated at 006 reaction conditions to crack out paraffins, leaving mainly aro-007 matics in the effluent, and to isomerize the xylenes as well as 008 generally upgrade the octane of the effluent. The effluent 009 from the ZSM reactor is withdrawn via line 35 and is charged to 010 separator 136. A C4- fraction is withdrawn from the top of the 011 separator via line 137 and a C5+ fraction is removed from sepa-012 rator 136 via line 138. The C5+ fraction has a research octane 013 number of approximately 113, contains approximately 45 volume 014 percent BTX and represents about 85 volume percent of the feed 015 to the ZSM reaction zone. The C5+ fraction in line 138 may be 016 sent via line 140 to form a part of the high-octane gasoline 017 pool, or some or all of it may be sent via line 139 to a BTX
018 separation step, and if desired the BTX-depleted stream may be 019 returned to the gasoline pool.
020 The advantage to this flow scheme of the present 021 invention is that it allows the isomerization zone, the reform-022 ing zone and the ZSM reaction zone each to be operated with the 023 feedstocks that are converted most effectively therein. The 024 CS-66C portion of the straight-run naphtha is more advan-025 tageously isomerized than reformed, because the lower tempera-026 tures in the isomerization zone favor production of more highly 027 branched paraffins with a resulting higher octane. In the 028 reformer, C5 and C6 paraffins would suffer a yield loss due to 029 cracking as well as having a relatively high equilibrium amount 030 of low-octane normal and slightly branched paraffins. Thus, 031 the process of the present invention provides for sending the 032 portion of the naphtha containing C6+ naphthenes (such as 033 methylcyclopentane) and higher-boiling hydrocarbons to the 034 reforming zone where the naphthenes are efficiently converted 035 to aromatics, while the light naphtha containing C5 and most of 036 the C6 paraffins is sent to the isomerization zone.
037 The advantage of splitting the reformate into a light ~1271~
002 fraction (boiling.from C5 to 77C) is that this fraction may be 003 isomerized to further increase the octane number with little 004 decrease in yield. The heavy reformate containing benzene and 005 higher-boiling hydrocarbons is advantageously contacted with 006 the ZSM catalyst at cracking conditions to remove any C7~ paraf-007 fins and leave a product stream concentrated in aromatics such 008 as benzene, toluene and xylene.
009 Process Feeds 010 Feedstocks suitable for use in the process of the 011 present invention include full-boiling-range na~htha hydro-012 carbon materials boiling in the range of C5 hydrocarbons up to 013 about 175C (347F) or 200C (392F) which contain low-octane 014 paraffinic C5 and C6 components and preferably are C5 to C8 015 straight-run naphthas. The C6 naphthenes in these naphthas are 016 excellent reformer feedstock components, for they are 017 efficiently converted to aromatics. The paraffins are undesir-018 able as components of a gasoline pool because of their low 019 research octane numbers, usually under about 70 (Clear, ASTM
020 Method). The C7+ paraffins are suitable reformer feed compo-021 nents, but the C6- paraffins are marginal because of the yield 022 loss when they are cracked and the e~uilibrium amount of rela-023 tively low-octane normal and singly branched paraffins which 024 remain after isomerization.
025 Reforming Sta~e 026 The reformer of the present invention is a conven-027 tional one in which the feedstock is contacted with a platinum-028 containing reforming catalyst, preferably a bimetallic catalyst 029 such as platinum-rhenium-chloride on alumina, under reaction 030 conditions such as a temperature from 427 to 552C (800-031 1025F), preferably from 454-538C (850-1000F), a pressure 032 from atmospheric to 50 atmospheres or higher, preferably from 033 6.8 to 40 atmospheres, a liquid hourly space velocity from Q.l 034 to 10, preferably from 0.5 to 5, and a hydrogen to hydrocarbon 035 mol ratio from 0.5 to 20, and preferably from 1 to 10. During 036 reforming a multitude of reactions takes place, including ~ 271Q~
dehydrogenation, isomerization, dehydrocyclization, hydrocracking, and com-binations thereof to yield a product having an increased content of aro-matics and branched-chain hydrocarbons. The reformer is especially efficient when used to convert naphthenes to aromatics.
ZSM Reaction Zone At least a portion of the reformate is passed over a ZSM-5-type catalyst in a ZSM reaction zone operated at conditions including an elevated temperature. Broadly; the temperature will be from 343 to 649C (650 to 1200F) and the pressure will be from 0.5 to 55 atmospheres and a liquid hourly space velocity from 0.1 to 20 and preferably 1 to 5.
In the preferred embodiment in which the ZSM reaction zone is op-erated at conditions to crack paraffins and isomerize C8 aromatics in the feed, the preferred reaction conditions include a temperature from 371-482C
(700-900F), a hydrogen pressure from 1.7 to 55 atmospheres, and a hydrogen to hydrocarbon mol ratio from 1 to 10 and preferably 3 to 8.
In the preferred embodiment in which the light naphtha fraction is combined with at least a portion of the reformate and optionally a recycle or externally supplied C3/C4 stream, the reaction zone is preferably main-tained under reaction conditions promoting aromatization of paraffinic com-poundsJ such as a temperature from 454 to 566C (850 to 1050F) and more preferably from 500 to 540C (932 to 1004F), a pressure from 0.5 to 35 atmospheres or higher, more preferably from 1 to 10 atmospheres and still more preferably 1 to 5 atmospheres, and preferably in the absence of added hydrogen.
The ZSM-5-type zeolite itself is known in the art per se, and is exemplified by ZSM-5, ZSM-8, ZSM-ll and ZSM-35 and other similar materials.
ZSM-5-type zeolites, described in United States Patents 3,702,886, 3,729,409 and 3,770,614, describe the ZSM-5 preparation, composition and use as well as related information. The H-ZSM-5 or Zn-H-ZSM-5 forms of the ZSM-5-type zeolites are ,. . .
2t7~
002 preferred for use herein and may be obtained by conventional 003 base and/or ion-exchange methods well known to the art. It is 004 especially beneficial with respect to the catalyst life and 005 coke formation for the ZSM-5 zeolite to have a silica-to-006 alumina mol ratio from 40 to 160, and preferably from 60 to 007 120.
008 The catalyst of the ZSM reaction zone may be in any 009 convenient form, that is, as required for conventional fixed, 010 fluid or slurry usage. Preferably, the ZSM-5-type is a fixed-011 bed type with the zeolite being composited with an inorganic 012 binder or matrix such as alumina, silica, silica-alumina mix-013 tures, naturally occurring and conventionally processed clays, 014 e.g., kaolin and the like, as well as silica-magnesia, silica-015 zirconia, etc., and mixtures of any of them. ~he composite is 016 preferably prepared by mixing the binder or matrix in the form 017 of a gel or a cogel with the zeolite, followed by shaping or ex-018 truding to the desired form and size customary for the intended 019 use. The relative proportions of zeolite and binder may vary 020 widely, from 5% to 95% by weight, with preferably 35% to 80%
021 and more preferably about 65% of the composition being zeolite.
022 The preferred binder is alumina.
023 Isomerization Zone 024 The isomerization zone is used to isomerize C5 and C6 025 paraffins in the light naphtha and light reformate fractions.
026 Any suitable light paraffinic hydrocarbon isomerization cata-027 lyst and method may be used and numerous suitable methods have 028 been described in the prior art and descriptions of representa-029 tive methods are given in an article entitled "Advances in 030 Isomerization" by P. A. Lawrence et al, Proceedings of the 031 Seventh World Petroleum Congress, Volume IV, pp. 135-145, 032 Elsevier Publishing Company (1967). Other examples of isomer-033 ization processes for paraffins appear in the following U.S.
034 Patents: 2,834,823, 3,190,939, 3,527,835, 3,577,479, 3,578,725, 035 and 3,789,082.
036 In a preferred embodiment, the isomerization is 037 carried out using as the catalyst a chlorided composite of l~Z7~
002 platinum dispersed upon porous alumina (e.g., see U.S. Patent 003 3,789,082, Example 1). In another preferred embodiment, the 004 catalyst employed is a composite of palladium and ultra-stable 005 Y crystalline aluminosilicate molecular sieve in the H form 006 (see, for example, U.S. Patent 3,293,192). This catalyst is 007 prepared by any suitable method. For example an aqueous 008 solution of the palladium salt is admixed with acid-peptized 009 alumina hydrogel and, thereafter, the palladium is 010 gravimetrically precipitated in a finely divided form by ad-011 mixing a minor amount of 1,2,3-benzotriazole in hydrogel (see 012 for example U.S. Patent 3,978,001). Next, the H-Y sieve is 013 ad-mixed with the hydrogel and the resulting composite is 014 shaped, dried and calcined for use. Sufficient amounts of the 015 components are used to provide on a dry basis for each 100 016 parts by weight a composite containing alumina, ultra-stable 017 Y-sieve and palladium in an amount of 35, 65 and 0.3 parts, 018 respectively. The relative amounts of these components may be 019 varied widely as in the conventional practice, and yet the 020 catalyst will be effective for isomerizing the feed herein.
021 The isomerization of the C5-C6 paraffinic hydrocarbon feed 022 under hydrocarbon isomerizing conditions per se is not 023 considered as inventive.
002 BACKGROUND,AND SUMMARY OF THE INVENTION
003 This invention relates to a combination process for 004 upgrading a naphtha fraction. In one aspect, the invention 005 relates to a process combining reforming and aromatization over 006 a ZSM-5-type zeolite, to produce a product useful as a high-007 octane gasoline blending stock or a source from which benzene, 008 toluene and xylene can be recovered. In another aspect, the 009 invention relates to a process combining reforming, isomeri-010 zation and hydrocracking in the presence of a ZSM-5-type 011 zeolite to produce a product useful as a high-octane gasoline 012 blending stock and as a source for recovering benzene, toluene 013 and xylene.
014 In view of the current concern over air pollution and 015 environmental control, processes which will increase the octane 016 number of gasoline while minimizing or eliminating the need for 017 additives are being sought.
018 One traditional way of increasing the octane of a 019 naphtha fraction has been to subject it to catalytic reforming, 020 usually over a platinum-containing or bimetallic catalyst. In 021 the reformer, naphthenes and paraffins are converted to aro-022 matics, both reactions which substantially increase the octane 023 number of the hydrocarbons involved. Naphthenes are reformed 024 to aromatics with high selectivity. ~owever, the selectivity 025 with which paraffins are converted to aromatics decreases with 026 the number of carbon atoms per paraffin molecule. Only a minor 027 fraction of C6 paraffins is converted to benzene. Other reac-028 tions which occur in the reformer are isomerization and crack-029 ing of paraffins. The cracking to C3- hydrocarbons represents 030 an irreversible yield loss, and the isomerization of paraffins 031 mainly to singly branched paraffins is a reversible reaction in 032 which a relatively high concentration of low-octane n-paraffins 033 remain in thermal equiIibrium with the branched isomers. Thus, U34 inclusion of C6 paraffinic hydrocarbons in a reformer feed is a 035 less efficient use of the catalyst and reactor facilities than 036 the inclusion of C6 naphthenes.
037 Another way of improving the octane number of hydro-038 carbon fractions is by contacting them with a ZSM-5 type of ~7~Q~
002 aluminosilicate zeolite catalyst to produce new aromatic rings 003 from aliphatic compounds. For example, U.S. Patent 3,761,389 004 teaches aromatization of a hydrocarbon fraction boiling within 005 the range of C2 to 400F with a ZSM-5 type of synthetic alumino-006 silicate zeolite catalyst, and U.S. Patent 3,756,942 teaches 007 aromatization of a feed consisting essentially of C5+ paraf-008 fins, olefins and/or naphthenes over a ZSM-5-type catalyst to 009 produce a predominantly aromatic liquid and a light hydrocarbon 010 gas. If the aromatization is performed at high temperature 011 (e.g., about 538C) and low pressure (e.g., about 1 atmosphere) 012 without added H2~ the light gas includes C2-C4 olefins as well 013 as Cl-C4 paraffins.
014 The art discloses several combinations of reacting a 015 hydrocarbon stream over a reforming catalyst and over a ZSM-5-016 type catalyst. For example: in U.S. Patent 3,729,409 there is 017 described a process for upgrading a reformate by contacting the 018 reformate and hydrogen with a ZSM-5-type zeolite, to selec-019 tively crack the normal paraffins and to form and alkylate aro-020 matic compounds. In U.S. Patent 3,849,290 there is described a 021 process for reforming a naphtha and then removing normal and 022 singly branched hydrocarbons by selective cracking to leave an 023 aromatics-enriched product. In these two processes, some 024 cracking of the alkyl side chain on the aromatic ring occurs, 025 resulting in production of unwanted light ends. In U.S. Patent 026 3l770,614 there is disclosed a process in which a reformate is 027 fractionated and the light reformate fraction (C6 to 116 or 028 127C) passed over a ZSM-5-type zeolite to alkylate mono-029 aromatics. In U.S. Patent 3,950,241 there is disclosed a 030 process for upgrading naphtha by separating it into low- and û31 high-boiling fractions, reforming the low-boiling fraction, and 032 combining the high-boiling naphtha with the reformate for 033 contact with a ZSM-5-type catalyst to crack the paraffins.
034 Reacting heavy naphthas over ZSM-5-type catalysts in 035 the absence of H2 and at high temperatures leads to rapid cata-036 lyst deactivation, while processing naphthenes over them leads 037 primarily to cracking, which reduces liquid yields.
J.~;Z71`~9L
002 ~e have found it advantageous to separate a naphtha 003 into a light fraction and a heavy fraction, reform the heavy 004 fraction, and pass at least a portion of the reformate over 005 ZSM-5-type catalyst to produce a C5+ product fraction enriched 006 in aromatic hydrocarbons.
007 In particular, we have provided a process for 008 upgrading a l.apntha-boiling-range hydrocarbon to useful 009 products which comprises:
010 ~1) separating said naphtha into a light naphtha fraction 011 boiling below methylcyclopentane and containing C6 aliphatics 012 and lower-boiling hydrocarbons, and a heavy naphtha fraction 013 containing methylcyclopentane and higher-boiling hydrocarbons;
014 (2) reforming said heavy naphtha fraction under reforming 015 conditions to produce a reformate stream enriched in aromatics 016 compared with said heavy naphtha fraction;
017 (3) passing at least a portion of said reforma~e in 018 contact with a ZSM-5-type catalyst at an elevated temperature 019 and recovering from the ZSM-5 contacting operation a 020 hydrocarbon effluent enriched in aromatic hydrocarbons; and 021 (4) separating said effluent into a C4- stream and a C5+
022 product stream.
024 Figures 1 and 2 are schematic block-type flow diagram 025 of preferred embodiments of the present invention in which each 026 block represents one particular step or zone oE the process.
027 Conventional items such as pumps, compressors, miscellaneous 028 valving, etc., are believed to be well within the skill in the 02~ art and have been omitted from the drawing. Likewise, with 030 respect to the piping throughout the process system, only the 031 major streams required to illustrate the relationships between 032 the various stages are presented. Accordingly, various recycle 033 lines and vent gas streams, etc., have also been omitted.
035 Referring to the flow diagram depicted in Figure 1, a 036 C5 to C8 straight-run naphtha obtained from an Alaskan North 037 Slope crude oil is charged through line 20 into fractionator 'Z7~
002 21. The naphtha has an approximate composition of 55 volume 003 percent paraffins, 35 volume percent naphthenes and 10 volume 004 percent aromatics. In the fractionator, the naphtha is sepa-005 rated into a light fraction comprising C5 and C6 hydrocarbons 006 boiling under about 66C tl50F) and a heavy fraction including 007 methylcyclopentane boiling above about 66C ~150F). The light 008 naphtha frac~ion, about 20 volume percent of the feed, is 009 removed from fractionator 21 via line 25. The heavy naphtha 010 fraction, about 80 volume percent of the feed, is charged via 011 line 26 to reformer 27 in which it is reformed under conven-012 tional mild reforming conditions with a platinum-rhenium-013 chloride reforming catalyst (see, for example, U~S. Patent 014 3,415,737, inoorpor~t~ heroin by rcfer~ncc~ to increase the 015 aromatics content and octane number of the naphtha. The refor-016 mate, in a yield of approximately 90 LV% and substantially 017 depleted of naphthenes, is passed to separation zone 30 via 018 line 28. In separation zone 30, which may comprise one or more 019 stages, hydrogen is recovered for recycle to the reformer (not 020 shown), light gases are removed and one or more reformate frac-021 tions are recovered.
022 In one embodiment of the present invention, for maxi-023 mizing BTX production, the naphtha feed is preferably a C5 to 024 C8 straight-run naphtha, and all of the C3+ reformate is passed OZ5 via line 31, combined with the light naphtha fraction in line 026 25 and passed into ZSM reaction zone 38. In the ZSM reaction 027 zone, the normal and lightly branched paraffins undergo aromati-028 zation, and aromatics, particularly xylenes, are isomerized.
029 The ZSM reaction zone is operated at reaction conditions 030 including a temperature of 538C (1000F), no added hydrogen, 031 and an LHSV of 2 V/V/Hr. The effluent from ZSM reaction zone 032 38 is passed via line 39 to separation zone 40 wherein a C5+
033 product stream in an amount of about 70 weight percent of the 034 combined feed in line 25 and rich in aromatics is separated and 035 sent via line 48 for recovery of benzene, toluene and xylene 036 values therefrom. The C4- component of the effluent is prefer-037 ably separated into an H2/Cl/C2 fraction which is removed via ~Z71~
002 line 42 and a C3/C4 fraction, in an amount of about 18 weight 003 percent of the combined feed, which may be removed from the 004 process via line 47 but which is preferably recycled via line 005 46 to ZSM reaction zone 38. The C3/C4 fraction may contain 006 propylene and butenes in addition to propane and butane.
007 In another embodiment of the present invention, the 008 naphtha feed is preferably a C5 to C8 straight-run naphtha, and 009 the reformer effluent is separated in separation zone 30 into a 010 C3 to 135C - (275F-) fraction which is sent via line 31 to the 011 ZSM reaction zone operated at conditions to form and isomerize 012 aromatics, and a 135C+ t275F+) fraction rich in xylenes which 013 may be passed via line 32 to a conventional xylene isomeri-014 zation zone, such as that described in U.S. Patent 3,948,758 015 ir;aorpor~ted horein by rcfcrcnc~. When the feed is a fu]l-016 boiling-range naphtha, a Cg+ fraction may be removed from sepa-017 ration zone 30 via line 33 and used as a high-octane (research 018 octane number of about 116 Clear) gasoline blending stock.
019 Advantages of this embodiment include a longer ZSM catalyst 020 life because higher-end-point hydrocarbons which tend to coke 021 the ZSM catalyst are not passed over it and a more efficient 022 use of the ZSM catalyst and reactor because feeding the C8+ aro-023 matics to the ZSM reaction zone would not contribute to higher 024 aromatics yields and would reduce catalyst life.
025 In yet another embodiment of the present invention, 026 particularly useful for the production of high-octane gasoline, 027 a full-boiling-range straight-run naphtha is the feedstock, the 028 reformer effluent is separated in separation zone 30 into a 029 light reformate fraction tc3 to 104C or 220F), usually about 030 70 volume percent of the reformate, which is passed via line 31 031 to the ZSM reaction zone, and a heavy reformate fraction (lOC+
032 or 220F+), usually having a research octane number of about 033 106 (Clear), which is sent to a gasoline pool (not shown) via 034 line 32. The light reformate fraction in line 31 is combined 035 with the light naphtha fraction in line 25 and preferably also 036 with a recycle C3/C4 stream, and passed in contact with a ZSM-5-037 type zeolite catalyst at reaction conditions previously men-038 tioned. The effluent from zone 38 is passed via line 39 to 1~271~9L
002 separation zone 40, from which a C5+ fraction having a research 003 octane number of about 116 (Clear) is removed via line 48 and 004 combined with the heavy reformate fraction in line 32 to form a 005 high-octane gasoline blendin~ stock having a research octane 006 number of at least 90 (Clear), and preferably 95 and still more 007 preferably at least 100 or more.
008 An advantage of this embodiment is that in splitting 009 the reformate at 104C (220F), C7 paraffins having a low 010 octane number are included in the feedstock to the ZSM reaction 011 zone in which they will undergo aromatization, but must of the 012 toluene fraction is excluded since feeding it to the ZSM reac-013 tion zone would not increase aromatics yield~. Another 014 advantage of this embodiment is that the reformer is used for 015 what it does efficiently and in high yield: dehydrocyclization 016 of naphthenes, while C6- paraffins are aromaticized over the 017 ZSM catalyt to form high-octane aromatic compounds rather than 018 cracked to C4- in the reformer, with the attendant yield loss.
019 Referring to the flow diagram depicted in Figure 2, 020 an Arabian straight-run naphtha fraction boiling in the range 021 of C5-193C (380F) is charged through line 121 into fractiona-022 tor 122. The naphtha has an approximate composition of 66 023 volume percent paraffins, 2] volume percent naphthenes and 13 024 volume percent aromatics. In the fractionator, the naphtha is 025 separated at about 66C (150F) into a light naphtha fraction 026 comprising C5 and C6 hydrocarbons boiling under about 66C
027 (150F) and a heavy naphtha fraction boiling above about 66C
028 (1505F) which includes most of the methylcyclopentane. The 029 light naphtha fraction, about ]0 volume percent of the feed, is 030 remo~ed from fractionator 122 via line 124. The heavy naphtha 031 fraction, about 90 volume percent of the feed, is charged via 032 line 126 into reformer 127 in which it is reformed under conven-033 tional reforming conditions with a platinum-rhenium-chloride 034 reforming catalyst (see, for examplel U.S. Patent 3,415,737, 035 inco~por~Qd ~cre~ eefcrcncc). The reformer acts to 036 increase the aromatics content and octane number of the 037 naphtha. The reformate, having a research octane number of 71~
001 ~7~
002 about 98, in a yield of approximately 83 liquid volume percent 003 and substantially depleted of naphthenes, is passed to sepa-004 ration zone 129 via line 128. In separation zone 129, which 005 may comprise one or more stages, hydrogen is recovered for 006 recycle to the reformer (not shown), C4- light gases are 007 removed and the C5+ reformate is split into two fractions. The 008 first fraction is a C5-77C (170F) light reformate which is 009 removed from the separator via line 134. The light reformate 010 has a research octane number of about 71 and is about 10 liquid 011 volume percent of the total reformate.
012 The light reformate in line 134 is combined with the 013 light straight-run naphtha fraction having a research octane 014 number of about 65 in line 124 and passed as a composite stream 015 via line 124 into isomerization zone 150, where it is contacted 016 in the presence of hydrogen (supply line not shown) with a 017 hydrocarbon isomerization catalyst. The isomerization condi-018 tions in zone 140 include a temperature of approximately 150C
019 (302F), a pressure of 15 atmospheres, a liquid hourly space 020 velocity of 1.5 V/V/Hr and a hydrogen to hydrocarbon mol ratio 021 of 3 . The resulting isomerizate is withdrawn in line 15] and 022 passed to separator 152 wherein it is separated into a C4- frac-023 tion and a liquid hydrocarbon fraction in about a 95 liquid 024 volume percent yield and having a research octane number of 025 about 79. The C4- fraction is withdrawn from separator 152 via 026 line 153 and the hydrogen component therein may be separated 027 and recycled to isomerization zone 150, if desired. The C5+
028 fraction from separator 152 is withdrawn via line 156 and 029 passed to a gasoline pool as a high-octane gasoline blending 030 stock.
031 Referring again to separator 129, the portion of the 032 reformate boiling above 77C (170F) is passed via line 133 to 033 ZSM conversion zone 134. About 90 liquid volume percent of the 034 reformate leaves separator 129 via line 133 and this heavy 035 reformate fraction has a research octane number of approxi-036 mately 100. In the ZSM reaction zone, the heavy reformate is 037 contacted with an H-ZSM-5 catalyst comprising 50% zeolite and l~.Z7~
002 50% Catapal matrix. ZSM reaction conditions include a tempera-003 ture of 343C (650F), a pressure of 28 atmospher~s (400 psig), 004 a hydrogen to hydrocarbon mol ratio of 5, and a liquid hourly 005 space velocity of 2 V/~/Hr. The ZSM reactor is operated at 006 reaction conditions to crack out paraffins, leaving mainly aro-007 matics in the effluent, and to isomerize the xylenes as well as 008 generally upgrade the octane of the effluent. The effluent 009 from the ZSM reactor is withdrawn via line 35 and is charged to 010 separator 136. A C4- fraction is withdrawn from the top of the 011 separator via line 137 and a C5+ fraction is removed from sepa-012 rator 136 via line 138. The C5+ fraction has a research octane 013 number of approximately 113, contains approximately 45 volume 014 percent BTX and represents about 85 volume percent of the feed 015 to the ZSM reaction zone. The C5+ fraction in line 138 may be 016 sent via line 140 to form a part of the high-octane gasoline 017 pool, or some or all of it may be sent via line 139 to a BTX
018 separation step, and if desired the BTX-depleted stream may be 019 returned to the gasoline pool.
020 The advantage to this flow scheme of the present 021 invention is that it allows the isomerization zone, the reform-022 ing zone and the ZSM reaction zone each to be operated with the 023 feedstocks that are converted most effectively therein. The 024 CS-66C portion of the straight-run naphtha is more advan-025 tageously isomerized than reformed, because the lower tempera-026 tures in the isomerization zone favor production of more highly 027 branched paraffins with a resulting higher octane. In the 028 reformer, C5 and C6 paraffins would suffer a yield loss due to 029 cracking as well as having a relatively high equilibrium amount 030 of low-octane normal and slightly branched paraffins. Thus, 031 the process of the present invention provides for sending the 032 portion of the naphtha containing C6+ naphthenes (such as 033 methylcyclopentane) and higher-boiling hydrocarbons to the 034 reforming zone where the naphthenes are efficiently converted 035 to aromatics, while the light naphtha containing C5 and most of 036 the C6 paraffins is sent to the isomerization zone.
037 The advantage of splitting the reformate into a light ~1271~
002 fraction (boiling.from C5 to 77C) is that this fraction may be 003 isomerized to further increase the octane number with little 004 decrease in yield. The heavy reformate containing benzene and 005 higher-boiling hydrocarbons is advantageously contacted with 006 the ZSM catalyst at cracking conditions to remove any C7~ paraf-007 fins and leave a product stream concentrated in aromatics such 008 as benzene, toluene and xylene.
009 Process Feeds 010 Feedstocks suitable for use in the process of the 011 present invention include full-boiling-range na~htha hydro-012 carbon materials boiling in the range of C5 hydrocarbons up to 013 about 175C (347F) or 200C (392F) which contain low-octane 014 paraffinic C5 and C6 components and preferably are C5 to C8 015 straight-run naphthas. The C6 naphthenes in these naphthas are 016 excellent reformer feedstock components, for they are 017 efficiently converted to aromatics. The paraffins are undesir-018 able as components of a gasoline pool because of their low 019 research octane numbers, usually under about 70 (Clear, ASTM
020 Method). The C7+ paraffins are suitable reformer feed compo-021 nents, but the C6- paraffins are marginal because of the yield 022 loss when they are cracked and the e~uilibrium amount of rela-023 tively low-octane normal and singly branched paraffins which 024 remain after isomerization.
025 Reforming Sta~e 026 The reformer of the present invention is a conven-027 tional one in which the feedstock is contacted with a platinum-028 containing reforming catalyst, preferably a bimetallic catalyst 029 such as platinum-rhenium-chloride on alumina, under reaction 030 conditions such as a temperature from 427 to 552C (800-031 1025F), preferably from 454-538C (850-1000F), a pressure 032 from atmospheric to 50 atmospheres or higher, preferably from 033 6.8 to 40 atmospheres, a liquid hourly space velocity from Q.l 034 to 10, preferably from 0.5 to 5, and a hydrogen to hydrocarbon 035 mol ratio from 0.5 to 20, and preferably from 1 to 10. During 036 reforming a multitude of reactions takes place, including ~ 271Q~
dehydrogenation, isomerization, dehydrocyclization, hydrocracking, and com-binations thereof to yield a product having an increased content of aro-matics and branched-chain hydrocarbons. The reformer is especially efficient when used to convert naphthenes to aromatics.
ZSM Reaction Zone At least a portion of the reformate is passed over a ZSM-5-type catalyst in a ZSM reaction zone operated at conditions including an elevated temperature. Broadly; the temperature will be from 343 to 649C (650 to 1200F) and the pressure will be from 0.5 to 55 atmospheres and a liquid hourly space velocity from 0.1 to 20 and preferably 1 to 5.
In the preferred embodiment in which the ZSM reaction zone is op-erated at conditions to crack paraffins and isomerize C8 aromatics in the feed, the preferred reaction conditions include a temperature from 371-482C
(700-900F), a hydrogen pressure from 1.7 to 55 atmospheres, and a hydrogen to hydrocarbon mol ratio from 1 to 10 and preferably 3 to 8.
In the preferred embodiment in which the light naphtha fraction is combined with at least a portion of the reformate and optionally a recycle or externally supplied C3/C4 stream, the reaction zone is preferably main-tained under reaction conditions promoting aromatization of paraffinic com-poundsJ such as a temperature from 454 to 566C (850 to 1050F) and more preferably from 500 to 540C (932 to 1004F), a pressure from 0.5 to 35 atmospheres or higher, more preferably from 1 to 10 atmospheres and still more preferably 1 to 5 atmospheres, and preferably in the absence of added hydrogen.
The ZSM-5-type zeolite itself is known in the art per se, and is exemplified by ZSM-5, ZSM-8, ZSM-ll and ZSM-35 and other similar materials.
ZSM-5-type zeolites, described in United States Patents 3,702,886, 3,729,409 and 3,770,614, describe the ZSM-5 preparation, composition and use as well as related information. The H-ZSM-5 or Zn-H-ZSM-5 forms of the ZSM-5-type zeolites are ,. . .
2t7~
002 preferred for use herein and may be obtained by conventional 003 base and/or ion-exchange methods well known to the art. It is 004 especially beneficial with respect to the catalyst life and 005 coke formation for the ZSM-5 zeolite to have a silica-to-006 alumina mol ratio from 40 to 160, and preferably from 60 to 007 120.
008 The catalyst of the ZSM reaction zone may be in any 009 convenient form, that is, as required for conventional fixed, 010 fluid or slurry usage. Preferably, the ZSM-5-type is a fixed-011 bed type with the zeolite being composited with an inorganic 012 binder or matrix such as alumina, silica, silica-alumina mix-013 tures, naturally occurring and conventionally processed clays, 014 e.g., kaolin and the like, as well as silica-magnesia, silica-015 zirconia, etc., and mixtures of any of them. ~he composite is 016 preferably prepared by mixing the binder or matrix in the form 017 of a gel or a cogel with the zeolite, followed by shaping or ex-018 truding to the desired form and size customary for the intended 019 use. The relative proportions of zeolite and binder may vary 020 widely, from 5% to 95% by weight, with preferably 35% to 80%
021 and more preferably about 65% of the composition being zeolite.
022 The preferred binder is alumina.
023 Isomerization Zone 024 The isomerization zone is used to isomerize C5 and C6 025 paraffins in the light naphtha and light reformate fractions.
026 Any suitable light paraffinic hydrocarbon isomerization cata-027 lyst and method may be used and numerous suitable methods have 028 been described in the prior art and descriptions of representa-029 tive methods are given in an article entitled "Advances in 030 Isomerization" by P. A. Lawrence et al, Proceedings of the 031 Seventh World Petroleum Congress, Volume IV, pp. 135-145, 032 Elsevier Publishing Company (1967). Other examples of isomer-033 ization processes for paraffins appear in the following U.S.
034 Patents: 2,834,823, 3,190,939, 3,527,835, 3,577,479, 3,578,725, 035 and 3,789,082.
036 In a preferred embodiment, the isomerization is 037 carried out using as the catalyst a chlorided composite of l~Z7~
002 platinum dispersed upon porous alumina (e.g., see U.S. Patent 003 3,789,082, Example 1). In another preferred embodiment, the 004 catalyst employed is a composite of palladium and ultra-stable 005 Y crystalline aluminosilicate molecular sieve in the H form 006 (see, for example, U.S. Patent 3,293,192). This catalyst is 007 prepared by any suitable method. For example an aqueous 008 solution of the palladium salt is admixed with acid-peptized 009 alumina hydrogel and, thereafter, the palladium is 010 gravimetrically precipitated in a finely divided form by ad-011 mixing a minor amount of 1,2,3-benzotriazole in hydrogel (see 012 for example U.S. Patent 3,978,001). Next, the H-Y sieve is 013 ad-mixed with the hydrogel and the resulting composite is 014 shaped, dried and calcined for use. Sufficient amounts of the 015 components are used to provide on a dry basis for each 100 016 parts by weight a composite containing alumina, ultra-stable 017 Y-sieve and palladium in an amount of 35, 65 and 0.3 parts, 018 respectively. The relative amounts of these components may be 019 varied widely as in the conventional practice, and yet the 020 catalyst will be effective for isomerizing the feed herein.
021 The isomerization of the C5-C6 paraffinic hydrocarbon feed 022 under hydrocarbon isomerizing conditions per se is not 023 considered as inventive.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A process for upgrading a naphtha-boiling range hydrocarbon to useful products, which comprises:
(1) separating said naphtha into a light naphtha fraction boiling below methylcyclopentane and containing C6 aliphatics and lower-boiling hydrocarbons, and a heavy naphtha fraction containing methylcyclopentane and higher-boiling hydrocarbons;
(2) reforming said heavy naphtha fraction under reforming conditions to produce a reformate stream enriched in aromatics compared with said heavy naphtha fraction;
(3) passing at least a portion of said reformate in contact with a ZSM-5-type catalyst at an elevated temperature and recovering from the ZSM-5 contacting operation a hydrocarbon effluent enriched in aromatic hydrocarbons; and (4) separating said effluent into a C4- stream and a C5+
product stream.
(1) separating said naphtha into a light naphtha fraction boiling below methylcyclopentane and containing C6 aliphatics and lower-boiling hydrocarbons, and a heavy naphtha fraction containing methylcyclopentane and higher-boiling hydrocarbons;
(2) reforming said heavy naphtha fraction under reforming conditions to produce a reformate stream enriched in aromatics compared with said heavy naphtha fraction;
(3) passing at least a portion of said reformate in contact with a ZSM-5-type catalyst at an elevated temperature and recovering from the ZSM-5 contacting operation a hydrocarbon effluent enriched in aromatic hydrocarbons; and (4) separating said effluent into a C4- stream and a C5+
product stream.
2. The process of Claim 1 wherein step (3) further comprises separating said reformate into a light reformate fraction containing C5 and C6 paraffinic hydrocarbons and a heavy reformate fraction containing benzene and higher-boiling hydrocarbons which heavy reformate fraction is said portion of the reformate passed into contact with the ZSM-5-type zeolite catalyst at conditions selected to effect cracking of normal and lightly branched hydrocarbons as well as isomerization of xylenes, including a temperature from 371° to 482°C, a pressure from 1.5 to 55 atmosphere, and a hydrogen-to-hydrocarbon mol ratio from 1 to 15, and further comprising (5) passing said light reformate fraction together with said light naphtha fraction into contact with a hydrocarbon isomerization catalyst under isomerization conditions including a temperature from 50 to 300°C and a pressure from 0.5 to 100 atmospheres and recovering the resultant isomerized product comprising C5+ hydrocarbons having a higher proportion of multi-branched paraffins than the feed to the isomerizing operation.
3. The process of Claim 2 wherein at least a portion of said C5+ product stream from said ZSM contacting operation is combined with said isomerized hydrocarbon product to form a gasoline blend having a research octane number above about 95 (Clear).
4. The process of Claim 2 wherein benzene, toluene and xylene values are recovered from at least a portion of said C5+
product stream from said ZSM contacting operation and the resulting benzene, toluene and xylene-deficient stream is combined with the C5+ portion of said isomerized hydrocarbon product to form a hydrocarbon blend having a research octane number above about 95 (Clear).
product stream from said ZSM contacting operation and the resulting benzene, toluene and xylene-deficient stream is combined with the C5+ portion of said isomerized hydrocarbon product to form a hydrocarbon blend having a research octane number above about 95 (Clear).
5. The process of Claim 1 wherein in step (3) said reformate portion is combined with said light naphtha fraction and the ZSM contact conditions include a temperature from 343 to 649°C and a pressure from 0.5 to 68 atmospheres.
6. The process of Claim 5 wherein the naphtha is a C5 to C8 straight-run naphtha and all of said reformate is passed in contact with said ZSM-5-type catalyst, and said product is sent for recovery of the benzene, toluene and xylene components therein.
7. The process of Claim 5 wherein said reformate is sepa-rated into a first fraction boiling just below xylene and a second fraction containing xylene and higher-boiling compo-nents, said first fraction is said portion which is passed in contact with said ZSM-5-type catalyst, said product is sent for recovery of the benzene, toluene and xylene components thereof, and said second fraction is isomerized to optimize the xylene content thereof.
8. The process of Claim 5 further comprising separating a C3/C4 fraction from said aromatics-enriched effluent, and recycling said C3/C4 fraction in contact with said ZSM-5-type catalyst.
9. The process of Claim 5 wherein said ZSM-5-type cata-lyst is the Zn-H-ZSM-5 form.
10. The process of Claim 5 wherein said aromatization conditions include a temperature from 500° to 540°C and a pressure from 1 to 5 atmospheres, and no added hydrogen.
11. The process of Claim 1 wherein said ZSM-5-type cata-lyst is the H-ZSM-5 form.
12. A process for upgrading a naphtha-boiling-range hydro-carbon to useful products, including a high-octane gasoline having a research octane number of at least 90 (Clear), which comprises:
(1) separating said naphtha just below the boiling point of methylcyclopentane into a light naphtha fraction containing C6 paraffins and lower-boiling hydrocarbons and a heavy naphtha fraction containing methylcyclopentane and higher-boiling hydro-carbons;
(2) reforming said heavy naphtha fraction under reforming conditions selected to increase the octane rating of the gasoline-boiling-range product;
(3) fractionating the product of the reforming operation into a light reformate which contains a substantial amount of C7- paraffins and a heavy reformate fraction which contains most of the toluene and the remaining high-boiling hydrocarbons;
(4) forming aromatics from said paraffins by passing said light reformate together with said light naphtha fraction in contact with a ZSM-5-type zeolite catalyst under aromatization conditions including a pressure from 0.5 to 35 atmospheres, a temperature from 454° to 556°C and no added hydrogen and recovering an aromatics-enriched effluent from said aromati-zation operation;
(5) separating said aromatics-enriched effluent into a C4- fraction and a C5+ fraction; and (6) combining said C5+ fraction with said heavy reformate to produce said high-octane gasoline.
(1) separating said naphtha just below the boiling point of methylcyclopentane into a light naphtha fraction containing C6 paraffins and lower-boiling hydrocarbons and a heavy naphtha fraction containing methylcyclopentane and higher-boiling hydro-carbons;
(2) reforming said heavy naphtha fraction under reforming conditions selected to increase the octane rating of the gasoline-boiling-range product;
(3) fractionating the product of the reforming operation into a light reformate which contains a substantial amount of C7- paraffins and a heavy reformate fraction which contains most of the toluene and the remaining high-boiling hydrocarbons;
(4) forming aromatics from said paraffins by passing said light reformate together with said light naphtha fraction in contact with a ZSM-5-type zeolite catalyst under aromatization conditions including a pressure from 0.5 to 35 atmospheres, a temperature from 454° to 556°C and no added hydrogen and recovering an aromatics-enriched effluent from said aromati-zation operation;
(5) separating said aromatics-enriched effluent into a C4- fraction and a C5+ fraction; and (6) combining said C5+ fraction with said heavy reformate to produce said high-octane gasoline.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US954,061 | 1978-10-23 | ||
| US05/954,064 US4190519A (en) | 1978-10-23 | 1978-10-23 | Combination process for upgrading naphtha |
| US954,064 | 1978-10-23 | ||
| US05/954,061 US4181599A (en) | 1978-10-23 | 1978-10-23 | Naphtha processing including reforming, isomerization and cracking over a ZSM-5-type catalyst |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1127104A true CA1127104A (en) | 1982-07-06 |
Family
ID=27130344
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA332,899A Expired CA1127104A (en) | 1978-10-23 | 1979-07-31 | Combination process for upgrading naphtha |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1127104A (en) |
| DE (2) | DE2954499C2 (en) |
| GB (1) | GB2034351B (en) |
| NL (1) | NL7907411A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4837114B2 (en) * | 2010-03-26 | 2011-12-14 | 千代田化工建設株式会社 | Aromatic hydrocarbon production method and aromatic hydrocarbon production plant |
| CN104321412B (en) | 2012-05-02 | 2016-08-17 | 沙特阿拉伯石油公司 | Farthest produce aromatic hydrocarbons from hydrocracked naphtha |
| US10093873B2 (en) | 2016-09-06 | 2018-10-09 | Saudi Arabian Oil Company | Process to recover gasoline and diesel from aromatic complex bottoms |
| US11066344B2 (en) | 2017-02-16 | 2021-07-20 | Saudi Arabian Oil Company | Methods and systems of upgrading heavy aromatics stream to petrochemical feedstock |
| US11591526B1 (en) | 2022-01-31 | 2023-02-28 | Saudi Arabian Oil Company | Methods of operating fluid catalytic cracking processes to increase coke production |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3729409A (en) * | 1970-12-24 | 1973-04-24 | Mobil Oil Corp | Hydrocarbon conversion |
| US3770614A (en) * | 1971-01-15 | 1973-11-06 | Mobil Oil Corp | Split feed reforming and n-paraffin elimination from low boiling reformate |
| US3785955A (en) * | 1971-12-01 | 1974-01-15 | Universal Oil Prod Co | Gasoline production process |
-
1979
- 1979-07-31 CA CA332,899A patent/CA1127104A/en not_active Expired
- 1979-09-15 DE DE19792954499 patent/DE2954499C2/de not_active Expired
- 1979-09-15 DE DE19792937376 patent/DE2937376A1/en active Granted
- 1979-10-05 NL NL7907411A patent/NL7907411A/en not_active Application Discontinuation
- 1979-10-11 GB GB7935288A patent/GB2034351B/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| NL7907411A (en) | 1980-04-25 |
| GB2034351B (en) | 1982-12-01 |
| GB2034351A (en) | 1980-06-04 |
| DE2937376A1 (en) | 1980-04-30 |
| DE2937376C2 (en) | 1988-05-26 |
| DE2954499C2 (en) | 1988-06-01 |
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