Process and catalyst for upgrading gasoline

Abstract

Process and catalyst for upgrading gasoline comprising durene (1,2,4,5-tetramethylbenzene) and pseudodocumene, the process comprises hydroisomerization of durene (1,2,4,5-tetramethylbenzene) and pseudocumene (1,2,4-trimethylbenzene) contained in the gasoline in presence of a catalyst comprising a sulfided base metal supported on an acidic carrier, thereby converting durene (1,2,4,5-tetramethylbenzene) to isodurene (1,2,4,5-tetramethylbenzene) and prehnitene (1,2,3,4-tetramethylbenzene) and converting pseudocumene (1,2,4-trimethylbenzene) to mesitylene (1,3,5-trimethylbenzene).

Claims

1. A process for upgrading a synthetic gasoline comprising durene (1, 2, 4, 5-tetramethylbenzene) and pseudocumene (1, 2, 4-trimethylbenzene) derived from catalytic conversion of methanol or a methanol-dimethylether mixture, the process comprising hydroisomerization of durene and pseudocumene contained in the synthetic gasoline in presence of hydrogen, a catalyst comprising sulfided nickel supported on an acidic carrier, and a sulfur dopant to produce an upgraded synthetic gasoline, wherein durene (1, 2, 4, 5-tetramethylbenzene) is converted to isodurene (1, 2, 3, 5-tetramethylbenzene) and prehnitene (1, 2, 3, 4-tetramethylbenzene) and pseudocumene (1, 2, 4-trimethylbenzene) is converted to mesitylene (1, 3, 5-trimethylbenzene), said upgraded synthetic gasoline has a reduced durene and pseudocumene content and an increased combined isodurene and prehnitene content relative to said synthetic gasoline, and the upgraded synthetic gasoline has at least the same octane rating as the synthetic gasoline.

2. The process of claim 1, wherein the catalyst has a nickel content of 0.5 to 20 wt %.

3. The process of claim 1, wherein the acidic carrier comprises a zeolite.

4. The process of claim 3, wherein the zeolite has a SiO.sub.2/Al.sub.2O.sub.3 ratio in the range of 15 to 300.

5. The process of claim 3, wherein the zeolite comprises ZSM-5.

6. The process of claim 1, wherein the acidic carrier comprises alumina.

7. The process of claim 1, wherein the catalyst is supported on a mixture of ZSM-5 and alumina.

8. The process of claim 7, wherein the catalyst comprises 1-5 wt % nickel, and an acidic carrier comprising the ZSM-5 and alumina in a ratio between 50:50 and 70:30.

9. The process of claim 1, further comprising a step of separating a light fraction from the synthetic gasoline and by-passing the light fraction around the hydroisomerization.

10. The process according to claim 1, wherein hydroisomerization conditions include a temperature of between 250 and 400 C.

11. The process of claim 1, wherein the synthetic gasoline includes more pseudocumene than durene.

Description

EXAMPLE 1

(1) The catalyst was prepared by impregnating cylindrical extrudates comprising ZSM-5 and alumina with aqueous Ni nitrate, followed by calcination in air. A 100 ml fixed bed of the catalyst was loaded in an isothermal fixed-bed reactor (1.5 cm approximate internal diameter) and sulfidation of the catalyst was carried out by hydrotreating a sulfur-containing naphtha fraction.

(2) After sulfidation was completed, a model heavy gasoline with the composition shown in Table 1 was treated by mixing the model feed with pure hydrogen, heating to reaction temperature and carrying out the isomerization reactions in the presence of the sulfided catalyst. The reactor product was separated in a high pressure and low pressure separators. Total liquid product samples from the low pressure separator were taken and analyzed.

(3) Table 2 shows the test conditions, measured hydrogen consumption and product yield whilst the composition, calculated RON (by Detailed Hydrocarbon Analysis), pour and cloud points are shown in Table 3.

(4) TABLE-US-00001 TABLE 1 Model heavy gasoline Compound wt % A9 Pseudocumene (1,2,4-trimethylbenzene) 46.2% A10 Durene (1,2,4,5-tetramethylbenzene) 25.3% A10 diethylbenzene 15.4% N8 1,2-dimethylcyclohexane 1.1% A8 xylenes 8.8% A11 pentamethylbenzene 1.0% A10 naphthalene 2.2%

(5) TABLE-US-00002 TABLE 2 Conditions, H2 consumption, product yields. Time on stream 0 211 453 522 Condition h FEED Cond#1 cond#2 cond#3 Pressure barg 16 16 16 Temperature C. 325 305 345 LHSV 1/h 0.98 0.50 0.50 H2/liquid feed Nl/l 156 305 303 H2 consumption Nl/l 8 5 18 Yields C1-C4 wt. % FF 0.00 1.81 1.19 4.41 C5-140 C. wt. % FF 7.60 15.40 12.55 21.17 140-150 C. wt. % FF 1.80 1.96 1.58 3.44 150-160 C. wt. % FF 0.00 0.88 0.49 1.24 160-170 C. wt. % FF 19.50 20.22 18.16 25.01 170 C.+ wt. % FF 71.1 59.77 66.04 44.87 C5+ wt. % FF 100.00 98.24 98.83 95.73 C4+ wt. % FF 100.00 98.69 99.20 96.58 FF = fresh feed

(6) TABLE-US-00003 TABLE 3 Conditions, composition and selected properties. Time on stream 0 211 453 522 Condition h FEED cond#1 cond#2 cond#3 Pressure, barg barg 16 16 16 Temperature C. 325 305 345 LHSV 1/h 0.98 0.50 0.50 H2/liquid feed N1/1 156 305 303 Liquid Recovery wt. % FF 100.0 98.15 98.71 95.47 COMPOSITION Durene(1,2,4,5- Tetramethylbenzene) wt % TLP 25.54 19.6 21.2 12.9 Pseudocumene (1,2,4- Trimethylbenzene) wt % TLP 45.4 37.3 40.4 26.2 Mesitylene (1,3,5- Trimethylbenzene) wt % TLP 0.1 2.5 1.9 5.6 CONVERSION Durene(1,2,4,5- Tetramethylbenzene) Wt % 0% 23% 17% 49% Pseudocumene (1,2,4- Trimethylbenzene) Wt % 0% 18% 11% 42% SUBTOTALS Sum tetramethyl- wt % TLP 26 26 26 26 benzenes Sum trimethyl- wt % TLP 46 41 43 34 benzenes Sum xylenes + wt % TLP 8 15 13 18 ethylbenzenes Sum diethylbenzenes wt % TLP 15 7 9 4 Toluene wt % TLP 0 1 1 4 Benzene wt % TLP 0 1 0 3 Ratio of mesitylene 0.3% 6% 4% 16% (1,3,5-Trimethyl- benzene) to sum of trimethyl- benzenes Calculated RON 94 97 96 100 Pour Point C. 14 1 5 23 Cloud Point C. 16 2 8 22 FF = fresh feed TLP = total liquid product

(7) Pour point can be improved by 20 degrees at 30 wt % durene (1,2,4,5-tetramethylbenzene) conversion and by 37 degrees at 50 wt % conversion. At 30 and 50 wt % durene conversion, the respective gain in (calculated) RON is 4 and 6. Hydrogen consumption is less than 18 Nl/l (0.11 mol/mol)

EXAMPLE 2

(8) The catalyst was prepared by impregnating cylindrical extrudates comprising ZSM-5 and alumina with aqueous Ni nitrate, followed by calcination in air. 3.8 g of the catalyst was loaded in the reactor.

(9) A full range synthetic gasoline produced by converting methanol over H-ZSM-5 at 340-400 C. and a pressure of 1.5 MPa was fractionated into a light and heavy gasoline with a sulfur content of less than 10 wppm. Properties of the heavy gasoline are shown in Table 4. A portion of the heavy gasoline fraction was then doped with dimethyldisulfide (DMDS) to give a final sulfur content of 138 wt ppm.

(10) TABLE-US-00004 TABLE 4 Properties of the heavy gasolines Heavy gasoline Sulfur, wt % <0.0010 Hydrogen, wt % 10.61 Specific Gravity 60/60 F. 0.8672 Cloud Point, C. 1.4 Pour Point, C. 2 Durene (1,2,4,5-tetramethylbenzene) content, wt % 19.7 Calculated RON 87.3 Boiling point distribution 0.5 wt % (IBP), C. 97 5 wt %, C. 137 10 wt %, C. 139 15 wt %, C. 144 20 wt %, C. 160 30 wt %, C. 168 40 wt %, C. 170 50 wt %, C. 171 60 wt %, C. 180 70 wt %, C. 196 80 wt %, C. 198 85 wt %, C. 198 90 wt %, C. 199 95 wt %. C. 221 99.5 wt % (FBP), C. 299

(11) In test A, the sulfidation was carried out by heating the reactor up to 150 C. @ 5 C./min (H2 flow=250 Nml/min, P=50 barg). Then feeding the 138 wt ppm S-doped heavy gasoline at a rate of 0.1 ml/min (equivalent to WHSV=1.36 h-1). H2 flow is then set to 30 Nml/min (H2/oil=300 Nml/ml), and subsequently heating up again to 325 C. @ 2 C./min. After 4 hours at 350 C., the sulfidation mixture is switched to the <10 wt ppm heavy gasoline.

(12) In test B, the catalyst was sulfided with a mixture of 2.5 wt % DMDS in n-C7. All of the DMDS is thermally decomposed in the preheater to H2S. The sulfidation was carried out by heating the reactor up to 150 C. @ 5 C./min (H2 flow=250 Nml/min, P=50 barg). Then feeding the sulfidation mixture at a rate of 0.3 ml/min (equivalent to LHSV=3.3 h-1 and H2/oil=833 Nml/ml), and subsequently heating up again to 350 C. @ 2 C./min. After 4 hours at 350 C., the sulfidation mixture is switched to the 138 wt ppm S-doped heavy gasoline.

(13) In test C, the reactor is heated up to 150 C. @ 5 C./min (H2 flow=250 Nml/min, P=50 barg). Then feeding the less than 10 wt ppm S heavy gasoline at a rate of 0.1 ml/min (equivalent to WHSV=1.36 h-1). H2 flow is then set to 30 Nml/min (H2/oil=300 Nml/ml), and subsequently heating up again to 325 C. @ 2 C./min.

(14) In tests A-C, the heavy gasoline was treated by mixing it with pure hydrogen, at a WHSV=1.4 h-1 and H2/oil=300 Nl/l (approx 1.9 mol/mol) and testing at two different conditions. In cond#1 temperature was set at T=324 C., whilst cond#2 was at T=344 C. and each condition ran for about 25 hours.

(15) The reactor product was separated in a system comprising a high pressure and low pressure separators. The composition of the liquid phase in the high pressure separator was analysed by gas chromatography.

(16) After each test, the spent catalyst was characterized and the measured sulfur content of the spent catalyst of tests A-C is used as an indicative parameter of the degree of sulfidation of the metal in the catalyst.

(17) FIG. 1 in the drawings shows that, as the upgrading takes place in the presence of hydrogen, it is necessary to add sulfur to the metallic nickel in order to reduce the rapid hydrogenolysis/cracking that forms light hydrocarbons.

(18) FIG. 2 in the drawings shows that in the transformation of 1,2,4-trimethylbenzene (pseudocumene), the selectivity to isomerization products, i.e., 1,3,5-trimethylbenzene (mesitylene) and 1,2,3-trimethylbenzene (hemimellitene), increases by having added small quantities of sulfur, particularly at 345 C.