Hydrotreating of bottoms fractions resulting from conversion of methanol to gasoline in order to decrease durene and produce distillate

BACKGROUND OF THE INVENTION
This invention relates generally to the conversion of methanol so as to produce gasoline and, more particularly, to the treatment of a bottoms obtained from said conversion process in order to decrease durene and to produce distillate.
The conversion of methanol to gasoline is an important area of technology which has the potential of becoming even more important as the supply of crude oil is diminished and/or increased in price. Particularly advantageous catalysts which are utilized in the conversion of methanol to gasoline are a special class of crystalline aluminosilicate zeolite catalysts of which H-ZSM-5 is the most preferred member. There are many patents and publications which describe the conversion of methanol to gasoline over said special zeolites, including U.S. Pat. Nos. 3,931,349; 3,969,426; 3,899,544; 3,894,104; 3,904,916; 3,894,102; the disclosures of which are incorporated by reference.
One particular problem residing in the conversion of methanol to gasoline over ZSM-5 type zeolites is that durene is produced in amounts higher than that expected from C.sub.10 aromatic equilibrium distributions. Once an aromatic ring is formed in the presence of unreacted methanol, alkylation to tetramethylbenzenes occurs rapidly, but the smaller higher melting durene molecule (1,2,4,5-tetramethylbenzene, melting point 175.degree. F.) diffuses out of the ZSM-5 pore much more rapidly than isodurene (1,2,3,5-tetramethylbenzene) or prehnitene (1,2,3,4-tetramethylbenzene). There have been various proposals advanced in order to control or minimize the amount of durene which is produced in the catalytic conversion of methanol to gasoline. One unpublished proposal heretofore suggested by coworkers of the instant inventors includes isomerization of the bottoms fraction of a methanol to gasoline process in order to decrease the durene content.
The instant invention is directed towards an improvement over the aforementioned isomerization process in that it is directed towards hydrotreating of a bottoms fraction with hydrogenation metals on both acidic and non-acidic supports in order to enhance the conversion of durene and to produce petroleum distillates.
In one specific embodiment, the novel process of this invention is directed towards processing over an acidic oxide supported metal catalyst in an H.sub.2 atmosphere, as opposed to an isomerizaton process and distinct advantages are obtained, not only with respect to catalyst life, but also with respect to product distribution and the efficiency of converting durene.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A durene-containing bottoms fraction from a methanol to gasoline process, obtained from the total gasoline fraction by topping off at least the light olefinic fraction, is hydrotreated over supported metal catalysts under conditions to reduce durene by either conversion of the durene to other compounds with preservation of the aromatic ring or hydrogenation. In general, conversion with preservation of the aromatic ring is favored by use of acidic supports and low pressure, whereas hydrogenation to make a naphthenic distillate is favored by use of strong hydrogenation metal, high pressure, and a low acidity support.
As can be seen, the first step in the novel process of this invention resides in subjecting the total gasoline derived from the conversion of methanol to a distillation process or fractionation process in order to remove at least the light olefinic fractions. It is not advantageous to treat the total gasoline fraction since the light olefins contained therein would hydrogenate to less valuable paraffins in the various hydrotreating steps. The exact point at which the total gasoline is cut is not narrowly critical and a dividing point can be at a temperature ranging from about 200.degree. to about 400.degree. F. A more preferred cut point range is from 300.degree. to 400.degree. F., and more particularly preferred being at about 350.degree. F. This invention will be described in detail with respect to making an initial separation at 350.degree. F., although it is to be understood that higher or lower temperatures can be used as above set forth. The 350.degree. F.+ bottoms obtained from a conventional methanol to gasoline operation obtained by fractionating the hydrocarbon product from said process is then hydrotreated over a supported metal catalyst under conditions to reduce durene at temperatures ranging from about 450.degree.-800.degree. F. at hydrogen pressures of from 50-3000 psig. When operating under the aromatic ring preservation mode of this invention, the 350.degree..sup.+ bottoms fraction is preferably contacted with hydrogen at a pressure ranging from about 200 to 400 psig, a temperature of about 500.degree.-700.degree. F., utilizing as a conversion catalyst, a hydrogenation metal, or a compound thereof supported on an acidic support. Acidic supports are well known in the art and include such materials as silica-alumina, silica-magnesia, silica-titania, as well as crystalline aluminosilicate zeolites which have been base exchanged so as to replace at least part of the alkali metal cations originally associated therewith with cations having an acidic function, e.g. hydrogen, ammonium, rare earth, etc. Specific examples of operable hydrogenation components, include metals, oxides and sulfides of metals of the Periodic Table which fall into Group VIB, including chromium, molybdenum and the like; Group IIB including zinc, cadmium and Group VIII, including cobalt, nickel, platinum, palladium, rhenium, rhodium and the like and combinations of metal sulfides and oxides of metals of Group VIB, such as nickel-tungsten sulfide, cobalt oxide, molybdenum oxide and the like. If the acidic support is a crystalline aluminosilicate zeolite such as faujasite, either natural or synthetic, i.e. zeolite X or Y, then the hydrogenation component can be associated with the zeolite by techniques well known in the art, including base exchange, impregnation, electrodeposition, etc.
When operating under the hydrogenation mode, in accordance with the novel process of this invention, it is preferred that the hydrogenation be carried out in the presence of a strong hydrogenation component, i.e. platinum, palladium, etc. on a support which has little or no acidity. Such supports are well known in the art, the most common example being alumina. A preferred catalyst for operation in the hydrogenation mode of the novel process of this invention would be platinum on aluminum. It is to be noted, however, that any non-acidic support can be utilized such as silica, charcoal, as well as crystalline aluminosilicate zeolites which have had their acidity reduced or eliminated by steaming, base exchange with alkali metal cations or being synthesized so as to contain substantially no alumina in the framework lattice.
Typical operating conditions for the hydrogenation mode include temperatures of 450.degree. to 900.degree. F., and more preferably, from 500.degree. to 800.degree. F. and pressures ranging from 500 to 3000 psig and more preferably from 1000 to 2000 psig.
From a practical point of view, operations within this temperature and pressure range require the use of a rather strong hydrogenation function which can be obtained either by using strong hydrogenation components, such as platinum, in moderate amounts, or larger amounts of less strong hydrogenation components, such as cobalt molybdenum. It is to be noted, however, that certain commercial cobalt molybdenum catalysts, such as one supplied by American Cyanamid and identified as HDS-20A does not have sufficient hydrogenation activity to be operable within the conditions set forth. This catalyst would, indeed, reduce durene if operated under more severe conditions of temperature and pressure but, quite obviously, such is not economically attractive.

BRIEF DESCRIPTION OF DRAWING
FIG. 1 is a plot of tetramethylbenzene isomer distribution versus temperature.
FIG. 2 is a plot which shows the effect of temperatures on aromatics by carbon number.
FIG. 3 is a plot of boiling point versus percent overhead.
FIG. 4 is a plot of total aromatics versus pressure.
FIG. 5 is a plot of percent reduction in durene versus days on stream with and without hydrogen.

The following examples will illustrate the novel process of this invention.
EXAMPLE 1
Charge Stock
The charge stock used in all of the examples which follow was obtained by distilling the liquid hydrocarbon product obtained by converting methanol to gasoline over a fixed bed of H-ZSM-5 at an inlet temperature of 680.degree. F., outlet temperature of 770.degree. F., a pressure of 300 psig and an WHSV of 1.6. The distillation was carried out to a cut point of 350.degree. F. in order to obtain two fractions. The tetramethylbenzenes were distributed as follows:
______________________________________ Total IBP-350.degree. F. 350.degree. F.+ Bottoms______________________________________Wt. % of cut 100 89 11TetramethylbenzeneContents, Wt. %1,2,4,5 (Durene) 6.8 2.6 43.81,2,3,5 (Isodurene) 0.2 0.1 1.61,2,3,4 (Prehnitene) 0.1 <0.1 1.1Octane No., R+O 94.1 91.9 Solid*______________________________________ *Calculated by difference, 111
The 350.degree. F.+ bottoms were solid at room temperature. The detailed composition is shown in Table 4.
EXAMPLE 2
Catalysts
Four different catalysts were used in carrying out experimental studies which are identified as follows:
(A) Pt/Al
This platinum on alumina catalyst was prepared by impregnating gamma alumina with chloroplatinic acid to 0.6 weight percent platinum. The chlorine content of the dried catalyst was 0.7 weight percent. The catalyst was reduced in situ with hydrogen at 900.degree. F. prior to use.
(B) Co/Mo/Al
This is a cobalt-molybdenum on alumina catalyst sold by the American Cyanamid Company under their designation HDS-20A which was precoked and presulfided.
Ni/W/Ti/Si/Al
This is nickel-tungsten-titanium deposited on silica-alumina and is a commercially available hydrocracking catalyst supplied by the Chevron Chemical Company under their designation ICR-106. It contained 19.7 weight percent tungsten, 6.5 weight percent nickel, 4.5 weight percent titanium, 0.04 weight percent cobalt oxide, and 0.03 weight percent molybdenum oxide. Prior to use, this catalyst was sulfided by treatment with 2% H.sub.2 S in H.sub.2 S at 750.degree. F.
(D) Ni/W/Si/Al/REHX
This is a nickel-tungsten deposited on a 50/50 parts by weight composite of a rare earth ammonium ion exchanged zeolite X in a silica-alumina matrix. It contained 10.1 wt. % tungsten and 3.8 wt. % nickel. The catalyst was sulfided prior to use by treatment with 2% H.sub.2 S at 750.degree. F.
EXAMPLE 3
A series of runs were made with the Ni/W/Ti/Si/Al catalyst at various temperatures and pressures. All runs were made with 10 cc of catalyst in a microunit equipped with heated charge and product lines. Overnight material balances were made. Light and heavy gas (from weathering of dry ice trap) compositions were determined by mass spec, and liquid product compositions by gas chromatography. Hydrogen consumptions were calculated from the hydrogen content of charge and products. Octane numbers (R+O) were obtained on both total liquid product (where liquid at room temperature) and 330.degree. F.- distillation overheads. Pour point, aniline no., and H/C ratio determinations were made on the 350.degree. F.+ distillation bottoms. Hydrogen circulation and LHSV were kept constant at 5000 SCF/bbl and 0.5, respectively.
The actual runs and the results are shown in Table I.
TABLE 1__________________________________________________________________________RUN DATACatalyst - ICR 106, Ni/W/Ti/Si/AlCharge-350.degree. F.+MTG Bottoms Conditions-0.5 LHSV, 5000 SCF H.sub.2 /bbl__________________________________________________________________________Pressure, psig CHARGE 200 .rarw. .rarw. 400 .fwdarw. .fwdarw. 700 875.sup.(1) .rarw. 1500 .fwdarw.Temp. .degree.F. Average 550 450 501 552 650 699 650 650 550 600 651Max. 554 452 505 556 653 703 653 652 553 601 652Mat. Bal. Time. Hrs. 19 181/2 23 23 19 221/2 22 19 221/2 23 23Accumulative Time, 5.0 4.2 3.4 2.4 6.2 7.1 4.6 5.4 1.8 2.8 3.7DaysLiquid Product Gravity, 29.5 31.5 29.9 31.3 35.4 38.7 40.0 44.4 41.3 36.9 42.5 49.8.degree.APIPour Point, .degree.F. +85 -5 +70 -15 -60 <-70 -70 <-70 <-70 +5 <-70 <-70O. N., R + O -- 100.0 101.4 99.9 95.7 95.3 97.2 87.4 88.6 88.3 80.5 80.2Tetramethyl Benzenes,wt %1,2,4,5-TetraMe 43.8 12.9 29.0 15.8 8.7 6.3 6.3 3.7 5.6 12.5 4.9 1.1(Durene)1,2,3,5-TetraMe 1.6 15.7 10.3 18.0 10.9 8.2 8.3 4.0 7.2 10.3 5.0 0.9(Durene)1,2,3,4-TetraMe 1.1 2.8 2.7 3.2 1.9 1.6 1.8 0.9 1.5 2.5 1.2 0.3(Durene)Mat. Bal, Wt % 1 98.0 96.6 97.7 96.2 96.9 97.4 95.1 98.8 96.1 95.1 94.5Yields, Wt % (NLB)C.sub.1 + C.sub.2 <0.1 <0.1 <0.1 <0.1 0.3 0.8 0.3 1.7 <0.1 <0.1 0.1C.sub.3 0.5 0.1 0.3 1.0 2.1 2.6 1.6 2.4 0.2 0.7 1.4C.sub.4 0.8 0.1 0.4 1.7 5.1 6.2 5.9 6.4 0.9 2.4 5.6C.sub.5 -330.degree. F. 12.0 7.4 25.0 39.4 39.7 54.1 41.2 22.6 38.4 64.3 100.2330.degree. F.+ 87.2 92.5 73.9 54.7 52.1 41.4 51.2 78.0 61.6 32.6 100.5 100.4 100.6 101.6 101.6 101.4 103.3 102.9 101.7 103.1 104.0H.sub.2 Consumption, 315 215 360 900 980 840 1940 1710 970 1785 2375SCF/bblC.sub.5 -330.degree. F. GasolineGravity, .degree.API 41.1 39.8 44.5 47.7 48.1 51.5 50.3 44.6 49.0 52.8Specific 0.8198 0.8261 0.8038 0.7895 0.7879 0.7731 .7785 0.8035 0.7838 0.7676O.N. R + O -- -- 92.0 89.6 92.7 81.1 84.2 82.3 81.2 77.5Boiling Range .degree.F.(D-2887)10% 239 270 232 135 97 157 139 196 194 16450 343 350 339 282 279 279 279 294 294 28890 390 392 386 336 336 333 334 341 336 332330.degree. F.+ DistillateGravity .degree.API 29.5 29.9 29.8 31.8 31.6 30.2 35.4 33.5 34.0 38.2 42..2Specific 0.8789 0.8769 0.8774 0.8665 0.8677 0.8748 0.8476 .8577 0.8551 0.8338 0.8145Pour Point .degree.F. +85 -- +15 -25 -20 -15 -70 -25 +20 <-70 <-70Aniline No. -- <20 <20 <20 <20 <20 <20 40.0 40.0 83.9 117.1Diesel Index -- <10 <10 <10 <10 <10 <10 13.4 13.6 32.0 49.4Hydrogen Wt % 10.43 10.60 10.72 11.05 10.88 10.48 11.40 11.86 12.06 12.80 13.14Carbon Wt % 88.6 88.38 88.52 88.10 86.63 88.10 87.87 87.64 86.46 87.05 84.97H/C Ratio 1.40 1.43 1.44 1.49 1.49 1.42 1.55 1.61 1.66 1.75 1.84Boiling Range .degree.F.(D-2887)10% 322 365 365 363 317 317 314 314 313 307 30950 395 425 433 411 359 356 359 355 371 352 34290 537 496 497 492 424 422 426 423 441 429 42095 737 504 508 500 445 444 446 440 460 449 43898 861 517 526 512 460 450 462 457 491 476 459__________________________________________________________________________ .sup.(1) 80% H.sub.2, 20% CO
EXAMPLE 4
The procedure of Example 3 was repeated using the Co/MO/Al catalyst. The operating conditions are shown in Table 2.
TABLE 2______________________________________RUN DATACatalyst HDS-20A, Co/Mo/Al ConditionsCharge - 350.degree. F.+ MTG Bottoms 0.5 LHSV, 5000 SCF H.sub.2 /bbl______________________________________Pressure, psig CHARGE .rarw. 400 .fwdarw. .rarw. 2000 .fwdarw.Temp., .degree.F., Average 600 651 650 751Max. 603 655 653 754Mat. Bal, Time, Hrs. 181/2 231/2 161/2 .22Accumulative Time,Days 0.8 1.8 2.4 3.3Liquid ProductGravity, .degree.API 29.5 30.5 29.8 31.3 34.7Pour Point, .degree.F. +85 +85 +85 +85 +65O.N., R + O -- -- -- -- 91.4Tetramethyl Benzeneswt. %1,2,4,5-TetraMe(Durene) 43.8 28.11,2,3,5-TetraMe 1.6 2.01,2,3,4-TetraMe 1.1 0.7Mat. Bal. Wt. % 102.2Yields, NLBC.sub.1 + C.sub.2 <0.1C.sub.3 0.1C.sub.4 0.1C.sub.5 -330.degree. F. 100.8350.degree. F.+H.sub.2 Consumption,SCF/bbl 580______________________________________
EXAMPLE 5
The procedure of Example 3 was repeated using the Pt/Al catalyst. The operating conditions are shown in Table 3.
TABLE 3__________________________________________________________________________RUN DATACATALYST - R F - 1009, 0.6% Pt on Alumina Conditions-Charge - 350.degree. F.+ MTG Bottoms 0.5 LHSV, 5000 SCF H.sub.2 bbl.__________________________________________________________________________Pressure, psig CHARGE 400 .rarw. 700 .fwdarw. 1500Temp., .degree.F. Average 656 650 700 752Max. 656 657 704 758Mat, Bal. Time Hours 221/2 6 161/2 18Accumulative Time, Days 0.9 1.2 1.8 2.5Liquid Product Gravity, API 29.5 32.2 -- 34.7 44.2Pour Point, .degree.F. .+-.85 +80 +80 +75 <-70O.N., R + O -- -- -- -- 77.2Tetramethyl Benzenes, wt. %1,2,4,5-TetraMe (Durene) 43.8 5.01,2,3,5-TetraMe 1.6 1.21,2,3,4-TetraMe 1.1 0.2Mat. Bal. Wt % 100.2 96.4Yields, Wt % (NLB)C.sub.1 + C.sub.2 <0.1 <0.1C.sub.3 0.2 0.1C.sub.4 0.2 0.3C.sub.5 -330.degree. F. 55.3 101.9330.degree. F.+ 48.8 102.3 104.4H.sub.2 Consumption, SCF/bbl. 1340 2560C.sub.5 330.degree. F. GasolineGravity, .degree.API 48.2Specific 0.7876O.N., R + O 76.0Boiling Range, .degree.F. (D-2887)10% 27750 31490 341330.degree. F.+ DistillateGravity, .degree.API 29.5 39.4Specific 0.8789 0.8280Pour Point, .degree.F. +85 <-70Aniline No. -- 118.2Diesel Index -- 46.6Hydrogen, Wt % 10.43 13.60Carbon, Wt % 88.6 86.41H/C Ratio 1.40 1.87Boiling Range, .degree.F. (D-2887)10% 322 31550 395 37390 537 45595 737 50698 861 628__________________________________________________________________________
Complete product compositions were determined for some of the runs from Examples 3-5 and said compositions are set forth in Table 4.
TABLE 4__________________________________________________________________________PRODUCT COMPOSITIONS Co/Mo/Al Pt/AlCATALYST .rarw. .rarw. Ni/W/Ti/Si/Al, ICR-106 .fwdarw. .fwdarw. HDS-20A RF-1009__________________________________________________________________________Pressure, psig CHARGE 200 .rarw. .rarw. .rarw. 400 .fwdarw. 700 875.sup.(1) .rarw. 1500 .fwdarw. 2000 1500Temp., .degree.F. Average 550 450 501 552 650 699 650 550 600 651 751 752Liquid Product 29.5 31.9 29.9 31.3 35.4 38.7 40.0 44.4 41.3 36.9 42.5 49.8 34.7 44.2GRAVITY, .degree.APIFour Point, .degree.F. +85 -5 +70 -15 -60 -- -70 -- -- +5 <-70 <-70 +65 <-70O. N., R + O 100.0 99.9 95.7 95.3 97.2 87.4 88.6 88.3 80.5 80.2 94.1 77.2Product Composition,Wt %C.sub.1 -- -- -- -- 0.1 0.3 0.1 1.1 -- -- 0.1 -- --C.sub.2 -- -- -- -- 0.2 0.5 0.2 0.6 -- -- -- --C.sub.3 0.3 0.1 0.3 1.0 2.1 2.6 1.6 2.4 0.2 0.7 1.4 0.1 0.1C.sub.4 0.8 0.1 0.4 1.7 5.1 6.2 5.9 6.4 0.9 2.4 5.6 0.1 0.3C.sub.5 0.5 0.1 0.3 0.9 2.6 3.3 2.7 2.6 0.2 0.7 2.2 -- 0.3C.sub.6 Total 0.5 -- 0.2 1.3 3.4 3.9 5.9 4.0 0.8 2.3 5.6 0.2 0.6P 0.3 -- 0.1 0.6 1.4 1.7 2.0 1.5 0.2 0.6 1.7 0.1 0.3O -- -- -- -- -- -- -- -- -- -- -- -- --N 0.2 -- 0.1 0.7 1.9 2.1 3.9 2.5 0.6 1.7 3.9 0.1 0.3A -- -- -- -- 0.1 0.1 -- -- -- -- -- -- --C.sub.7 Total 0.9 0.1 0.7 2.1 4.1 4.4 5.1 4.4 0.8 1.7 3.6 0.5 0.4P 0.1 -- 0.1 0.2 0.6 0.4 0.6 0.7 0.1 0.2 0.5 0.1 0.1O -- -- -- -- -- 0.1 0.1 0.1 -- -- 0.2 -- --N 0.3 -- 0.2 1.1 2.3 2.1 3.6 2.8 0.5 1.3 2.8 0.3 0.3A 0.5 0.1 0.4 0.8 1.2 1.8 0.8 0.8 0.2 0.2 0.1 0.1 --C.sub.8 Total 2.3 3.2 2.6 3.6 6.7 8.8 10.8 5.6 6.1 2.1 2.9 1.4 2.2 0.9P -- 0.1 -- 0.1 0.2 0.3 0.3 0.6 0.4 0.1 0.2 0.6 0.1 0.2O -- -- -- -- -- -- -- 0.1 -- 0.1 1.4 -- -- 0.1A 2.3 3.1 2.6 3.5 6.5 8.5 10.5 4.9 5.7 1.9 1.3 0.8 2.1 0.6C.sub.9 Total 23.4 33.3 27.4 27.5 34.7 35.1 37.1 26.4 30.5 21.1 17.4 17.3 21.5 23.8P 0.2 0.5 0.6 0.5 1.6 2.3 1.4 6.1 3.7 3.4 6.0 9.4 1.6 9.1O -- 0.1 0.1 -- 0.4 0.9 1.8 2.0 2.7 0.8 1.8 4.8 0.5 10.0A 23.2 32.7 26.7 27.0 32.7 31.9 33.9 18.3 24.1 16.9 9.6 3.1 19.4 4.7C.sub.10 Total 59.8 43.4 52.6 48.4 29.5 20.8 20.5 14.2 18.4 35.8 17.8 43 36.2 10.9P -- -- 0.1 -- 0.2 0.1 0.1 0.3 0.2 0.2 1.5 0.6 0.2 1.7O -- -- -- -- -- -- -- -- -- -- -- -- -- --A 59.8 43.4 52.5 48.4 29.3 20.7 20.4 13.9 18.2 35.6 16.3 3.7 36.0 9.2C.sub.11 Aromatics 10.7 10.1 12.9 11.3 8.4 5.0 4.4 4.2 4.7 9.4 5.9 0.9 13.2 3.2Unknown (C.sub.10 +) 3.8 7.3 4.5 7.9 15.3 14.3 7.4 31.4 21.7 30.6 51.2 61.6 27.0 63.9 100.0 100.5 100.4 100.6 101.6 101.6 101.4 103.3 102.9 101.9 103.0 104.0 100.8 104.4Total Aromatics, 96.0 89.7 94.8 90.6 77.7 67.4 71.1 42.1 53.5 64.0 33.5 7.8 70.8 18.0Wt %Durene, Wt % of 44 13 29 16 9 6 6 4 5 13 5 1 28 5Total ProductDurene, Wt % of 46 14 31 17 11 9 8 9 10 20 15 13 40 28Total AromaticsDurene, Wt % of 73 30 55 33 30 29 29 29 27 36 31 27 78 54C.sub.10 Aromatics__________________________________________________________________________
EXAMPLE 6
A series of runs were made with the Ni/W/Si/Al/REHX catalyst at various temperatures while maintaining a constant pressure of 400 psig. The runs were made as described in Example 3. Hydrogen circulation and LHSV were varied and in some runs no hydrogen was employed but nitrogen was substituted in its place.
The actual runs and the results are shown in Table 5:
TABLE 5__________________________________________________________________________Run Data__________________________________________________________________________Atomosphere Charge H.sub.2 N.sub.2 H.sub.2 N.sub.2LHSV 0.5 0.5 1H.sub.2 or N.sub.2, SCF/bbl 5000 5000 2500Temp., .degree.F. 499 500 500 525 549 550 550 550 550 699 800 901Mat. Bal. Time, Hrs. 22 23 23 23 23 23 23 20 17 20 20 23TOS, Days 0.9 1.9 3.8 4.7 5.7 6.7 7.6 8.4 9.1 9.9 10.7 11.7Liq. Prod. Gravity, .degree.API 30.0 33.0 32.6 30.8 31.1 32.5 32.1 31.6 29.4 29.3 29.1 29.3 29.0Pour Point, .degree.F. -10 -10 +10 +5 -5 0 +5 >75 +50 >75 75 >75O.N., R + O 102.9 103.1 102.0 102.7 103.0 102.1 102.2 -- 103.2 -- -- --Tetra Me Benzenes, Wt. %Durene 51.9 11.3 11.8 15.0 14.5 12.6 13.2 13.7 47.3 23.9 52.2 52.7 52.9Isodurene 3.0 13.5 14.0 17.2 17.2 15.7 16.4 17.1 8.1 21.6 4.9 4.9 4.0Prehnitine 0.7 2.3 2.4 3.0 3.1 2.8 3.0 3.1 3.7 3.0 1.6 1.6 1.4Total 55.6 28.1 28.2 35.2 34.8 31.1 32.6 33.9 59.5 48.5 58.7 59.2 58.3Mat. Bal, Wt. % 95.3 99.7 102.0 100.4 100.8 100.5 99.9 99.7 100.2 98.4 98.9 98.7Yields, Wt %C.sub.1 + C.sub.2 -- 0.1 <0.1 <0.1 <0.1 0.3 0.3 0.2 <0.1 <0.1 <0.1 <0.1 <0.1C.sub.3 -- 1.7 1.6 0.7 0.8 1.2 1.0 0.9 <0.1 0.4 <0.1 <0.1 <0.1C.sub.4 -- 1.7 1.3 0.7 0.7 1.7 1.4 1.2 <0.1 0.4 <0.1 <0.1 <0.1C.sub.5 -- 1.1 0.9 0.5 0.7 1.2 0.9 0.9 0.1 0.2 <0.1 <0.1 <0.1C.sub.6 + 100 95.7 96.3 98.0 97.7 95.9 96.4 96.8 99.9 98.8 99.9 100.0 100.00H.sub.2 Cons., SCF/bbl 150 80 -90 -50 210 30 0 -- 130 -- -- --Aromatics Dist., Wt. %C.sub.6 -- <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1C.sub.7 -- 0.7 0.6 0.4 0.4 0.6 0.8 0.5 <0.1 0.2 <0.1 <0.1 <0.1C.sub.8 0.3 8.1 7.7 5.0 5.1 6.5 6.2 5.6 0.9 2.1 0.5 0.3 0.4C.sub.9 18.9 35.9 35.5 30.4 29.5 29.8 29.4 30.9 20.9 22.0 19.3 19.2 19.5C.sub.10 66.7 34.1 35.2 45.5 46.1 38.7 44.4 43.8 60.3 62.2 70.1 70.4 69.2C.sub.11 + 9.3 7.4 8.4 11.1 10.6 11.8 8.1 9.1 6.3 9.4 8.6 8.5 9.3Total 95.2 86.2 87.4 92.4 91.7 87.4 88.9 89.9 98.4 95.5 98.5 98.4 98.4Durene DistributionWt. % of Total Product 52 11 12 15 15 13 13 14 48 24 52 53 53Wt. % of Tetramethylbenzene 93 40 42 43 42 41 40 40 80 49 89 89 91Wt. % of C.sub.10 Aromatics 79 35 34 33 31 33 30 31 68 38 74 75 76% Reduction in Durene -- 78 77 71 72 76 75 74 9 54 Nil Nil Nil__________________________________________________________________________
Discussion of Results
A. Ni/W/Ti/Si/Al
Effect of temperature
Durene conversion becomes significant at temperatures above about 450.degree. F. This is graphically illustrated in FIG. 1 which is a plot (based on Tables 1 and 4) of tetramethylbenzene isomer distribution versus temperature. Isodurene is the main product and is higher than durene at 500.degree.-700.degree. F., while prehnitene is essentially unchanged. These and other pertinent results are summarized in Table 6 below:
TABLE 6______________________________________Temperature Effect-Product Distribution of C.sub.10 Aromatics400 psig______________________________________Temperature, .degree.F. Charge 450 500 550 650 700Durene, wt. % 43.8 29.0 15.8 8.7 6.3 6.3Isodurene 1.6 10.3 18.0 10.9 8.2 8.3Prehnitene 1.1 2.7 3.2 1.9 1.6 1.8Total C.sub.10 Aromatics 59.8 52.5 48.4 24.3 20.7 20.4Total Aromatics 96.0 94.8 90.6 77.7 67.4 17.1Durene Dist., wt. % ofC.sub.10 Aromatics 73 55 33 30 30 30Total Aromatics 46 31 17 11 9 9______________________________________
The 30% concentration of durene in total C.sub.10 aromatics appears to be an equilibrium value at 500.degree. F. and higher.
Both total aromatics and C.sub.10 aromatics decrease with temperature. FIG. 2 shows the change in all the aromatics by carbon number. It can be seen that the C.sub.11 aromatics also decrease, but not as much as the C.sub.10. Both C.sub.9 and C.sub.8 aromatics increase significantly, and toluene, not present in the charge, also appears. This all indicates that, in addition to some isomerization, dealkylation is also occurring.
At the upper temperature range some lighter paraffins, mainly butanes appear. The dealkylation is thus not simple conversion to methane, but generates primarily C.sub.3 -C.sub.5 paraffins. Some hydrogenation of aromatic rings is also occurring, as indicated by hydrogen consumption and appearance of C.sub.10 + saturates (naphthenes). Octane No. (R+O), however, does not drop below 95 at this pressure.
TABLE 7______________________________________Temperature EffectC.sub.1 -C.sub.5 Yields, C.sub.5 + Octane No., H.sub.2 Consumption400 psig______________________________________Temperature, .degree.F. Charge 450 500 550 650 700C.sub.1, wt. % -- -- -- -- 0.1 0.3C.sub.2, wt. % -- -- -- -- 0.2 0.5C.sub.3, wt. % -- 0.1 0.3 1.0 2.1 2.6C.sub.4, wt. % -- 0.1 0.4 1.7 5.1 6.2C.sub.5, wt. % -- 0.1 0.3 0.9 2.6 3.3C.sub.10 + saturates 3.8 4.5 7.9 15.3 14.3 7.4H.sub.2 Cons., SCF/bbl -- 215 360 900 980 840C.sub.5 +O.N., R + O -- 101.4 99.9 95.7 95.3 97.2______________________________________
The run at 500.degree. F. represents the optimum for lowering durene while maintaining C.sub.5 yield (99.9 weight percent) and octane (99.9 R+O). The boiling point curve of this product is compared with that of the charge in FIG. 3. It is 10.degree.-50.degree. F. lower boiling throughout, and shows a desirable disappearance of a very high boiling "tail" in the charge.
A run was made at 875 psig, 650.degree. F. with a hydrogen stream containing 20% CO (Table 1) to demonstrate that the use of a purified H.sub.2 stream is not necessary. Methane make was 1.7 weight percent due to some hydrogenation of CO, but durene isomerization was satisfactory.
Effect of Pressure
Total aromatics were reduced to 8% by increasing pressure to 1500 psig, 650.degree. F. (FIG. 4). Hydrogenation was not as complete at 550.degree. F. Light paraffin make was not effected by pressure, and the octane no. of the saturated product was low, as expected. Also, as expected, the equilibrium concentration of durene of about 30% in the C.sub.10 aromatics was uneffected by pressure.
TABLE 8______________________________________Pressure Effect 550.degree. F. 650.degree. F.______________________________________Pressure, psig Charge 200 400 1500 400 700 1500C.sub.4 -, wt. % -- 1.3 2.7 1.1 7.5 7.8 7.1Total Aromatics,Wt. % 96.0 89.7 77.7 64.0 67.4 42.1 7.8H.sub.2 Cons.,SCF/bbl -- 315 900 970 900 1940 2375C.sub.5 + O.N.,R + O -- 100. 95.7 88.3 95.4 87.4 80.2Durene, wt. % 43.8 12.9 8.7 12.5 6.3 3.7 1.1Durene Dist.,wt. %of Total C.sub.10Aromatics 73 30 30 36 30 29 27______________________________________
The higher pressures are necessary for production of distillate with acceptable quality.
TABLE 9______________________________________330.degree. F. + Distillate Yield and Products______________________________________Pressure, psig Charge 400 700 1500Temperature.degree.F. 650 650 550 600 650330.degree. F. +Dist., wt. % -- 54.7 41.4 78.0 61.6 32.6Gravity,.degree.API 29.5 31.6 35.4 34.0 38.2 42.2Specific 0.8789 0.8677 0.8476 0.8551 0.8338 0.8145Pour Point.degree.F. +85 -20 -70 +20 <-70 <-70Aniline No. -- <20 <20 40.0 83.9 117.1Diesel Index -- <10 <10 14 32 49H/C Ratio 1.40 1.49 1.55 1.66 1.75 1.84______________________________________
The distillate made at 1500 psig, 650.degree. F. meets the minimum diesel index of 45. It is primarily naphthenic, as indicated by the low H/C ratio (FIG. 4). Yield based on the original MTG gasoline is 3.6 weight percent. The 7.4 weight percent IBP-330.degree. F. gasoline has an O.N. (R+O) of 77.5.
B. Co/Mo/Al Catalyst
Acidity and hydrogenation activity of this catalyst were too low for any significant conversion of durene with aromatic ring preservation or hydrogenation of aromatics except at severe conditions (Table 2). At 2000 psig, 750.degree. F., durene was lowered from 44 to 28 weight percent and total aromatics from 96 to 71 weight percent (Table 4).
C. Pt/Al Catalyst
This catalyst also exhibited little conversion of durene with aromatic ring preservation, but was more active for hydrogenation than Co/Mo/Al. At 1500 psig, 750.degree. F., durene was reduced to 5 weight percent, and total aromatics to 18 weight percent (Table 3). Results compare with the Ni/W/Ti/Si/Al catalyst as follows:
TABLE 10______________________________________Comparison of Pt/Al with Ni/W/Ti/Sa/Al1500 psig Pt/Al Ni/W/Ti/Si/Al______________________________________Temperature, .degree.F. 750 650Durene, wt. % 5.0 1.1Total Aromatics, wt. % 18.0 7.8C.sub.4 -, wt. % 0.4 7.1C.sub.5 -330.degree. F. Gasoline, wt. % 55.3 64.3O.N., R + O 76.0 77.5330.degree. F. + Distillate, wt. % 48.8 32.6Gravity, .degree.API 39.4 42.2Pour Point, .degree.F. <-70 <-70Aniline No., .degree.F. 118.2 117.1Diesel Index 47 49H/C Ratio 1.87 1.84______________________________________
The Pt/Al catalyst makes less light paraffins, less low octane gasoline, and about 50% more 330.degree. F.+ distillate of about the same quality as the Ni/W/Ti/Si/Al catalyst, and thus would be preferred for making distillate from methanol by this route.
D. Ni/W/Si/Al/REHY
The data in Table 5 shows that hydrogen is essential for durene reduction. When hydrogen is replaced with nitrogen, activity is lost and no durene reduction is obtained--even at temperatures as high as 900.degree. F. Activity is regained when hydrogen is introduced again. This is graphically demonstrated in FIG. 5 which is based on Table 5.
FIG. 5 is a plot of durene reduction versus days on stream with and without hydrogen. As can be seen, durene reduction was almost nil with nitrogen.
Catalyst D is superior to Catalyst C in durene reduction, octane number, and hydrogen consumption. This is shown in the following Table 11:
TABLE 11______________________________________Comparison of Catalyst C with Catalyst DCharge 350.degree. F.+ MTG Bottoms400 psig, 500.degree. F. Catalyst C Catalyst D______________________________________WHSV 0.5 0.5 1.0SCF H.sub.2 /BBL 5000 5000 2500TOS, Days 3.5 2 4Yields, Wt. %C.sub.1 + C.sub.2 <0.1 0.1 <0.1C.sub.3 0.3 1.6 0.7C.sub.4 0.4 1.3 0.7C.sub.5 99.9 97.5 98.7 100.6 100.4 100.1H.sub.2 Cons., SCF/BBL 360 210 40DureneCharge, Wt. % 43.8 51.9 51.9Product, Wt. % 15.8 12.2 15.2% Reduction 64 76 71C.sub.5 + O.N., R + O 99.9 103.1 102.0______________________________________

Number	Name	Date	Kind
3917737	Yoo	Nov 1975
4238631	Daviduk	Dec 1980

Hydrotreating of bottoms fractions resulting from conversion of methanol to gasoline in order to decrease durene and produce distillate

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