US2938855A - Production of middle distillate - Google Patents

Description

M15' 31, 1960 R. B. MASON ETAL 2,938,855

PRODUCTIGN OF MIDDLE DISTILLATE Filed Aug. 29, 1956 3 Sheets-Sheet 1 William F. Arey, Jr. Inventors Charles N. Kimberlin, Jr.

By Qui-Q du--L( Attorney May 3l, 196() R. a. MASON ETAI- PRODUCTICN OF MIDDLE DISTILLATE 3 Sheets-Sheet 2 Filed Aug. 29, 3.956

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Chorles N. Kimberlin, Jr

By M Attorney May 31, 1960 R. B. MASON ETAL. 2,938,855

PRODUCTION OF MIDDLE DISTILLATE Filed Aug. 29, 1956 3 Sheets-Sheet. 3

ne, j "6 w'ATER AnnlrloN FIG-III MIXING AND HYDROLYZING SECTION `e Ralph B. Mason William F. Arey, Jr. Inventors Charles N. Kimberlin, Jr.

BY Wd! Attorney PRODUCTION or Mronnn nrsrlLLATE Ralph Burgess Mason, Livingston, William Floyd Arey, Jr., and Charles Newton Kimberlin, Jr., Baton Rouge, La., assignors to Esso Research and Engineering Cornpany, a corporation of Delaware Filed Aug. 29, 1956, Ser. No. 606,823

5 Claims. (Cl. 20S- 71) The present invention relates to distillate fuel manufacture and it pertains more specically to the manufacture of high quality distillate fuels such as heating oils, diesel fuel, jet fuels and the like from naphthas boiling in the gasoline boiling range.

The principal object of the present invention is to provide a process for converting low octane and/ or unstable naphthas into materials of higher value and higher boiling range.

Hitherto, oil refineries have been generally operated to maximize naphtha production for use as gasoline motor fuel. Some naphthas are of substantially lower octane value than others, but could be blended with high anti-knock constituents to produce gasoline blends of acceptable quality. However, with the introduction of `high compression ratio automobile engines, the octane requirements of gasoline have been steadily increasing, thus severely narrowing the choice of constituents suitable as gasoline blending agents. Thus, much virgin naphtha and naphthas resulting from catalytic cracking of gas oil, hitherto used as gasoline blends for engines of moderate compression ratio, can no longer be used for this purpose. Similarly, refinery processes such as iiuidized coking of residua, and visbreaking operations produce naphthas that are unstable and sludge forming, and are of too high sulfur content for satisfactory use as fuels.

Concomitant with the increasing accummulation of these relatively low value naphthas in the refineries, there has grown up in recent years substantial demands for hydrocarbons boiling in the middle distillate range of about 300 to 750 F. The rapid growth of heating oil installations both here and abroad, and the rapid dieselization of transportation equipment has caused the supply of middle distillate to be out of balance with that of motor gasolines. However, operating crude oil and distillate refinery processes to maximize middle distillates would seriously interfere with the production of high quality naphthas. An object of the present invention is to provide middle distillate fuels without interfering with maximum high quality and octane gasoline production.

Thus, heretofore middle distillate fuels have been produced as by-products in the manufacture of gasoline, and such fuels of relatively high quality could be obtained directly from fractions of the virgin crude oil or from the cracking of virgin crudes. The phenomenal increase in demand for middle distillate fuels has presented a serious problem to the oil refining industry.

Middle distillates, or distillate fuels, generally boil in the range of about 350 to 750 F., the so-called heater oils boiling in the range of 350 to 550 F., while diesel fuels boil at about 400 to 650 F.

In accordance with the present invention, renery imbalance between gasoline and heating oil demands and stocks are restored by catalytic conversion of low quality naphtha fractions into middle distillates. In a sense nited States Patent o this is the reverse of the hitherto trend of petroleum refining where the gasoline fraction was the desired product, and where low grade gasoline fractions were upgraded to high anti-knock material by such processes as reforming or isomerization. The present invention involves principally conversion of the naphtha into middle distillate by catalytic condensation reaction involving formation and reaction of an oleinic intermediate, if a completely saturated naphtha, such as casinghead or virgin naphtha is initially fed into the process. In brief compass, it has been found that excellent yields of high quality low gravity middle distillates may be obtained by the catalytic conversion, in the presence of a boron fluoride-water catalyst, of low quality naphthas containing at least some unsaturation. In one embodiment of the present invention naphtha is thermally, catalytically, or steam cracked to a relatively low degree of conversion, forming substantial quantities of olefins which are then passed to the catalytic conversion zone. In another embodiment, low grade catalytic or coker naphtha is fed directly into the catalytic conversion zone or is mixed with virgin or casinghead naphtha prior to conversion. Though the presence of oleiins is a necessary intermediate, there is a net disappearance of naphtha over and n above the olefins, and it is probable that under the reaction conditions, polymerization is accompanied by substantial alkylation.

The catalyst employed in the present invention consists of a liquid comprising EP3 and Water. In general, it is preferred to use a composition in which the amount of water present varies from 2 to l mois per mol of B123.

it is readily prepared by bubbling BF3 gas into water while keeping the mixture cool.

Several critical conditions must be maintained in accordance with the present invention to obtain good yields of middle distillate. Temperatures must be in the range such that middle distillates rather than lubricating oil boiling range material is formed. Secondary, exceptionally intimate contacting of the mutually insoluble catalyst and hydrocarbon phases must be achieved to maintain an economical process. Thirdly, it is essential to obtain the highest degree of recovery and reuse of the catalyst.

The objects of the invention and its advantages will be more readily apparent from the more detailed description hereinafter when read in conjunction with the accompanying drawings showing preferred embodiments thereof.

Figure I is a diagrammatic representation of a preferred system employing a multi-stage oper-ation wherein the catalyst ow is countercurrent to the feed so that the most active catalyst is employed in the nal stages to convert the more non-reactive oleiins.

Figure ll is a diagrammatic representation of a preferred system employing a multi-stage operation with concurrent ow of feed and catalyst but with increasing reaction condition severity in the stages.

Turning now to Figure I, a naphtha feed comprising low quality octane constituents, such as virgin naphtha, is passed via line 2 to cracking zone 4 where, under carefully controlled conditions of 50 to 400 p.s.i.g. and temperatures in the range of 950 to 1l00 F. at feed rates in the range of 0.2 to 6 v./v./hr. to insure relatively low conversion of about 10% to 30% but high olefin selectivity, the naphtha is partially converted to an oletinic product of substantially similar boiling range but of higher olefinicity, of the order of 5% to 20%. The eiuent from cracking zone 4 is now passed, after light gas separation, via lines 6 and 8 into rst stage naphtha conversion reactor 10. If desired, low quality oleinic naphtha, such as coker naphtha, may also be passed to reactor via lines 7 and 8. If olenic naphtha is the only feed, cracking Zone 4 may be by-passed completely. It is absolutely essential that an intimate mixing of feed and catalyst take place within reactor 10. Though mechanical agitation may be employed, it is far preferable to achieve this by dispersion of the reactants in a jet to form an emulsion. This emulsion, with recycle, permits control of the Vaverage residence time, which is about 0.25 to 4 hours. It is preferred to employ hydrocarbon to catalyst ratios in the range of 4/l to 8/1, although higher ratios containing less B133 may be employed. The contacting is carried out at pressures in the range of atmospheric to 50 p.s.i.g., preferably atmospheric, and at temperatures in the range of 50 to 150 F., preferably 75 to 120 F. In accordance with this embodiment of the present invention, along with the fresh feed land recycle emulsion vfrom the first stage, there is injected into the lower portion vof reactor 10 catalyst from the first stage settler- 22 and catalyst from the second stage, as will be shown more Vclearly hereinafter. Both of these catalysts are at least partially spent. ln the naphtha polymerizationalkylation process, some of the oleiins are far more reactive than others. Thus, at conditions of maximum conversion this leads to sludge formation and catalyst degradation so that the catalyst is not performing at maximum ethciency. Partially spent catalyst, however,

has been found to have sufficient activity to condense Y the more reactive oleiins. Thus, in accordance with this embodiment, rapid catalyst degradation is prevented by the most reactive oleiins in theV fresh feed to reactor 10 by employing the fresh or restored catalyst to condense the less reactive oleiins in a second stage, and condensing the more reactive oleiins with the partially spent catalyst from the second condensation stage.

The emulisiied reaction product, comprising unconverted naphtha and oleiins, BFS-H2O catalyst, and higher boiling hydrocarbons produced in the reactor, is withdrawn from reactor 10 via line 12 and a portion of the emulsion, from 50% to 90%, is recycled to the reactor via lines 14 and 8. The balance of the emulsion is passed to first stage settling zone 22. The lower catalyst layer may be withdrawn through line 18 and in part recycled, or it may be in part or completely drawn off -via line 24 for regeneration in a manner known per se, as by passage to a catalyst concentration section, not forming a part of this invention.

The hydrocarbon layer, containing in solution some of the catalyst, is withdrawn from an upper portion of settler 22 through line 26 and is injected through line 28 into the lower portion of second stage reactor k30. Fresh or restored EP3-H2O catalyst is passed into zone 30 through line 36, and, as inthe case of rst stage reactor 10, a portion of the emulsion withdrawn from the upper portion of reactor 30, is recycled to control contact time. Reaction conditions in reactor 30 are generally the same order of magnitude as in the first stage in terms of contact time and rates.

In zone 30 the fresh or restored catalyst contacts the i less reactive olens, and conversion of the olefinic material is substantially complete.

The emulsiiied efliuent from the second stage withdrawn through line 32 is in part recycled through line 34 to reactor 30, and the balance passed to settling zone 40. The lower aqueous catalyst phase is Withdrawn through line 42 and in part recycled to reactor 30; the major portion, however, is passed via lines 16 and 8 to first stage reactor l@ wherein it contacts fresh feed as set forth above.

The upper, hydrocarbon layer containing some Vdissolved catalyst is now passed to fractionation section 50. Though the hydrocarbon layer may be Waterwashed to recover dissolved catalyst, this would require a concentration step and reduced pressures which impose additional operation problems. In the preferred embodiment shown here, the hydrocarbon product is passed to distillation zone 50 where the desired middle distillate fraction boiling in the range of 350 .to 750 F. is segregated and withdrawn through line 56. During the distillation, B133 in solution, the dissolved BFS-H2O complexes, and some BFS-hydrocarbon complexes Vare withdrawn in the lower boiling fractions. These fractions are preferably recycled via lines 52 and 58 to reactor 30. Make up water may be added to prepare the desired Elsa-H2O ratio catalyst.

Y The EP3-free naphtha is withdrawn as a side stream :through line 53 and is advantageously recycled at least in part through line 54 to the olefin producing section of the system, here cracking unit 4. Similarly, heavy bottorns boiling above the middle distillate range may be passed via line 60 to cracking unit 4.

Turning now to Figure II, there is described an embodiment of staged reaction with concurrent dow. As previously pointed out, under conditions normally empioyed, catalyst is deactivated by polymer build-up with the more reactive olens. This'loss in activity and yield frequently renders the operation unprotable. These difficulties are avoided in the present embodiment by conducting the condensation in stages of increasing severity as the operation proceeds. For this purpose, four methods vmay be employed.

Save for the concurrent ow of catalyst and feed, the ow of streams in Figure li is substantially the same as in Figure I. For this reason, and in the interest of simplicity, only those portions of Figure II are numbered that function differently from Figure I.

Turning now to Figure II, first stage reactor 70 receives fresh olefin feed through line 72 and fresh recycle and reconstituted BF3-H2O catalyst through line 74. To second stage vreactor S0 there is fed partially reacted hydrocarbon stream through line 86, and partially spent catalyst through lines S4 and 82. One method of achieving increased severity in reactor over reactor 70 is to maintain the vtemperature in the latter at 30 to 50 F. while that in the former is at 250? 'to 300 F. Concomitantly with, or instead of this temperature differential, there is maintained in first stage 70 a more dilute BFS-H2O solution. Thus in reactor 70 there may be maintained a BF3 concentration of 40% to 65%, based on BF3+H2O, while in reactor 80, a concentration of 66% to 79% obtains. The latter is the saturation value at atmospheric pressure.

Instead of, or along with increasing the temperature, the pressure may be progressively increased. The initial stage 70 thus may be maintained at atmospheric pressure while stage 80 may be at 500 to 600 psig., or higher.

Unreacted olens separated from the final reaction product in the distillation zone are preferably recycled to the Zone of increased severity.

The process of the present invention is further illustrated by the following specific examples.

Example 1 l An example of the excellent performance of the boron fluoride-water catalyst has been shown experimentally. To 44.8 grams of water, boron uoride was added to the near saturation point at a temperature of about 50-75 F. To 206.5 grams of this solution 777.4 grams of a naphtha from commercial catalytic cracking operations was added slowly'and with vigorousstirring at a temperature of about 50 F. and atmospheric pressure. Following the completeV naphtha addition agitation was continued for 4 hours at ambient temperature approximately 80" F.) The total product Vwas transferred to a separatory funnel and the lower layer was drawn oi. The upper layer was water-washed and was submitted for analysis. The following analytical data demonstrate the eectiveness of the operation. in the lproduction of` middle distillate (350-650 F. hydrocarbons).

assente This yield of 46% of middle distillate is near the ultimate for this feed.

Example 2 Catalyst HzSOs BFa-Hzo HaPO4 Conc. of active component,

Wt. Percent 96 80 80 79 79 B5 Total v./v 44 54 108 43 159 65 Temp., F 120 115 115 120 120 S0 Pressure (l) (l) (l) (l) (l) (l) Vol. Percent 350 F.+Prod- 13 S 6 20 18 0 l Atmospheric.

These data show the marked superiority of the BFS-H2O catalyst. Not shown by the data were the diiculties experienced in sludge formation and acid re- -covery with H2SO4.

Example 3 In another experiment a catalytic naphtha of higher yolefin content than used in the preceding experiments (Bromine No. 150 vs. 90) was treated as in Example 1. The yield of 350 F. plus product was 60%. A separate portion of this total product was distilled to 300 F. cut point and under these conditions a 65 vol. percent yield of product useful as heating oil, etc. resulted.

Example 4 In another experiment a visbreaker naphtha of lower olefin content (Bromine No. 61 vs. 90 and 150) was treated as in Example l. The yield of 350 F. plus product was 22%. lt is observed that conditions employed during commercial visbreaking are similar to those for the cracking step in the previous disclosures.

Example 5 A highly selective production of middle distillate with the boron fluoride-water catalyst is shown by the Engler distillation data on the total product from each of the feeds employed in the previous examples. In each case the end point is 650 F. and less. The data are:

Feed Catalytic Visbrealrer Naphtha Naphtha Bromlne No 90 150 61 IBP, F 113 123 138 138 141 164 150 201 160 262 170 358 172 410 182 454 200 507 234 80% 560 384 632 510 95% 640 594 Example 6 In another set of experiments the advantages of staged operation are demonstrated. The operation as described in Example 1 was repeated with fresh feed but with the same catalyst with a marked decline in catalyst activity. The composited product from the second and third cycles, which was incompletely converted, was contacted with fresh catalyst with the same yield as obtained initially and with less catalyst degradation. The data are:

Experiment 1 2 (Feed) Batch Operation B D Feed Catalytic Naphtha Comp. Prod.

from B and C 60/40 Blend.

Vol. Ratio, Feed/Cat., 9

An important feature of the present invention involves a novel means of catalyst recovery. In the` preparation of middle distillate by reaction of oletinic naphthas with boron uoride-water catalyst considerable polymer is formed which remains with the catalyst. This decreases the activity of the catalyst and necessitates catalyst replacement. For such processes to' be economical a catalyst regeneration technique is required.

A11 excellent method of catalyst recovery consists in (1) separation and drawing oli the lower or catalyst layer containing the deactivating polymer, (2) hydrolysis of the catalyst, (3) separation of the polymer, and (4) distillation of the water layer to recover the boron iiuoride. The feasibility of the process is demonstrated in an experiment in which 4258 grams of a catalytic naphtha was contacted with 1187 grams of a boron fluoride-water preparation containing about 79% kboron liuoridc. From this operation 3456 grams of hydrocarbon and 1895 grams of a separated lower layer were recovered. Of this lower layer 564 grams were added to 1265 grams of water and the charge was heated in an autoclave with agitation for 4 hours at 400 F. The discharged product was separated into layers and the oil product was washed with Water to remove all traces of residual boron fluoride from the hydrolysis. The hydrocarbon layer was analyzed and was found to contain 87.5% carbon and 12.5% hydrogen. A separate analysis showed the complete absence of fluoride which demonstrates the complete removal of boron uoride catalyst and also demonstrates the hydrocarbon purity of the polymer.

Furthermore, by this technique the yield of high boiling hydrocarbons is increased. Thus the 300 F. plus product from the original condensation and distillation was 56.2 weight percent of the original feed. Upon recovery of the polymer this yield is increased to 72.7 percent.

The catalyst recovery process is shown in Figure Ill. Spent catalyst withdrawn through line 24 (Figure I) for regeneration is passed into hydrolyzing-mixing zone 104l where, after hydrolysis and settling (10S), the hydrolizer water is passed to an atmospheric distillation section 114. The polymer settling out is scrubbed in water scrubber 122 and recovered. ln 114 the aqueous BF3 is distilled at atmospheric pressure, gaseous BF3 and water going overhead and withdrawn through lines 146 and 14S and 152.. The Water is limited to an amount less than that required to yield BFa-HZO. The two streams are combined to yield a catalyst containing about 79% BFS. The water is returned via lines 134 and 120 to the hydrolysis section.

Alternatively, the hydrolizer water may be distilled under reduced pressure in section 132, taking water overhead and leaving EP3-21120 asa bottoms product.

The boron fluoride recovery from the hydrolyzer water may be done by either of two 'distillation procedures or by a combination of both. in method A the aqueous boron lluori'de is distilled' at atmospheric pressure taking.

gaseous BF?, and' water overhead. The latter is limited to a `quantity somewhat less than that requiredto yield BF3H2O. The two overhead streams are combined, to yeild the catalyst containing about 79% boron uoride. The water is returned to the hydrolysis section.

Method B consists in distilling the bydrolyzer water under reduced pressure wherein water is taken overhead leaving as bottoms boron fluoride with two Waters of hydration. This can be fortitied with fresh BPB, or can be concentrated as in method A. In cases where atmospheric pressure concentration is employed the bottoms are usually returned to the reduced pressure distillation section to minimize boron liuoride losses. The use of reduced pressure prior to the iinal concentration aiords a recycle stream to the hydrolyzer of less boron tiuoride content.

The two concentrators may be used in combination with the hydrolyzer solution split with part going to each concentrator or the two may be used intermittently.

IThe process as described anords a more economical production of middle distillate from olelinic materials because a greater yield of highboiling polymer ofY high purity is achieved and because the catalyst isl recovered for conY tinuous use.

What is claimed is:

1. An improved processr for converting paranic low octane naphthas into middle distillates boiling inthe range of from about 350". to 750 F., which comprises passing said naphthas to a cracking Zone, maintaining ya temperature of from about 950 to 1100 F., pressure of from about 50 to 400 p.s.i.g. and space velocity of from about 0.2 to 6 v./v./hr. in said cracking zone, converting said naphthas in said `Zone to an ellluent containing about to 20% oletins, passing said eliiuent to a tworeactor olefin conversion system, maintaining pressures of from about 15 to 50 psig., temperatures of from about 50 to 150 F. and a hydrocarbon to catalyst ratio in the range of from about-4:1 to 8:1 in each of said recators, jetting said effluent into the rst reactor to form an emulsion with partially spent BF3H2O catalyst from the second reactor, withdrawing the emulsion from said tirst reactor, separating a portion oisaid emulsion into an aqueous spent catalyst fraction'and'a'hydrocarbon fraction, jetting said hydrocarbon fraction into the second reactor to form a second yemulsion with fresh BF3H2O catalyst having a mol ratio of water to BF3 in the range of about 1:1 to 2:1, withdrawing saidl second emulsion from the second reactor, separating a portion or" said second emulsion into a partially spent catalyst fraction and a second hydrocarbon fraction, passing said partially spent catalyst fraction to the rst reactor, passing said second hydrocarbon fraction to a fractionation zone and recovering a middle distillate fraction from said fractionation zone.

2. The process of claim l wherein said spent catalyst fraction is regenerated in a process comprising passing said spent catalyst traction to a hydrolysis zone, separating perature of from about 950 to` 1l00 F., pressure of' from about 50 to 400 p.s.i.g. and space velocity of from about 0.2 to 6 v./v./hr. in said zone, converting said naphthas in said zone tov an euent containing; about 5 to 20% olelins, jetting effluent Yfrom` said zoneconcurfv rently withV fresh BFS'HgO catalystv havingk a mol ratio of water to B133 in the range of about 1:1 to 2:-1 to form an emulsion in the first reactor of a two-reactor olen conversion system, maintaining a temperature of` from about 30 to 50 F. and low pressure in said rst reactor, with-v drawing the emulsion from said first reactonseparating a portion of said emulsion into an aqueous partially spent catalyst fraction and a hydrocarbon fraction, jetting a portion of said aqueous partially spent catalyst fraction and said hydrocarbon fraction in the secand reactor totorm a second emulsion, maintaining a temperature of about 250 to 300 F. in said second reactor and recovering from said second reactor good yields of middle distillate.

5. An improved process for converting parafinic low octane naphthas into middle distillates boiling in the range from about 350 to 750 F., which comprises passing said naphthas to a cracking zone, maintaining Ia temperature of from about 950L7 to 1l00 'F., pressure of from about 50 to 400 p.s.i.g. andjspace velocityofV from about 0.2 to 6 v./v./hr. in said zone, converting said naphthas in said zone to an eiiuent containing about 5 to 20% oleiins, jetting etlluent from said zone with a BFS-H2O catalyst containing about 40 to 65% EP3 to forman emulsion in the first reactor of a two-reactor olefin conversion System, maintaining a temperature of frornraborut 30 to 50 F. and low pressure in said firstn reactor, withdrawing theV emulsion from said first reactor, separating a portion of said emulsion into an aqueous partially spent catalyst vfraction and a hydrocarbon fraction, jetting a portion of said hydrocarbon fraction with a BF3lH2O catalyst containing about 66 to 79% BF3 in the second reactor to form a second emulsion, maintaining a temperature of about'250 to 300 F. in said second reactor and recovering from said second reactor good yields of middle distillate.

References Cited in the le of this .patent UNlTED STATES PATENTS ...a New x

Claims (1)

1. AN IMPROVED PROCESS FOR CONVERTING PARAFFINIC LOW OCTANE NAPHTHAS INTO MIDDLE DISTILLATES BOILING IN THE RANGE OF FROM ABOUT 350* TO 750*F., WHICH COMPRISES PASSING SAID NAPHTHAS TO A CRACKING ZONE, MAINTAINING A TEMPERATURE OF FROM ABOUT 950* TO 1100*F., PRESSURE OF FROM ABOUT 50 TO 400 P.S.I.G. AND SPACE VELOCITY OF FROM ABOUT 0.2 TO 6 V./V./HR. IN SAID CRACKING ZONE,CONVERTING SAID NAPHTHAS IN SAID ZONE TO AN EFFLUENT CONTAINING ABOUT 5 TO 20% OLEFINS, PASSING SAID EFFLUENT TO A TWO-REACTOR OLEFINS CONVERSION SYSTEM, MAINTAINING PRESSURES OF FROM ABOUT 15 TO 50 P.S.I.G., TEMPERATURES OF FROM ABOUT 50* TO 150*F. AND A HYDROCARBON TO CATALYST RATIO IN THE RANGE OF FROM ABOUT 4:1 TO 8:1 IN EACH OF SAID REACTORS, JETTING SAID EFFLUENT INTO THE FIRST REACTOR TO FORM AN EMULSION WITH PARTIALLY SPENT BF3.H2O CATALYST FROM THE SECOND REACTOR, WITHDRAWING THE EMULSION FROM SAID FRIST REACTOR SEPARATING A PORTION OF SAID EMULSION INTO AN AQUEOUS

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