US2760999A - Reforming of naphtha - Google Patents

Description

Unit rate r c lQe 2,760,999

REFORIVHNG F NAPI-ITHA Alex G. Oblad, Springfield, and Heinz Heinemann, Drexel Hill, Pm, assignors to Houdry Process Corporation, Wilmington, Del., a corporation of Delaware No Drawing. Application November 30, 1950, Serial No. 198,468

2 Claims. (Cl. 260668) an improved reforming process wherein high yields of gasoline of desired enhanced octane quality are obtained, while minimizing the occurrence or extent of such other accompanying reactions, such as cracking, which tend to produce coke and low molecular weight hydrocarbon gases, at the expense of desired gasoline yields.

In previous known processes for upgrading gasoline and naphtha fractions, involving treatment at superatmospheric pressure and in the presence of added hydrogen, catalysts have been employed having the property of promoting dehydrogenation reactions, the best known being molybdenum oxides on activated alumina. While under the conditions employed in these previous processes dehydrogenation of naphthenes present in the gasoline charged to reforming does take place, other simulta-' neous reactions occur to substantial extent, including cracking of parts of the charge, resulting in the formation of significant quantities of low molecular weight hydrocarbon gases accompanied by deposition of coke in sufficient amounts to limit the practical on-stream operating period to about 4-8 hours, followed by regeneration of the catalyst. The reported butane-free gasoline yields from such processes are in the order of about 70-80% by volume of the charge. In other related processes conditions were employed to dehydrogenate selected narrow cuts of naphthenic materials to aromatic hydrocarbons, operating under conditions obtaining lower conversion of the charge per pass, and generally at higher pressures (up to about 50-70 atmospheres) thanin the previously described process. In these processes operating at lower conversion levels longer on-stream periods of up to several days or more might be possible, requiring as much as about 20-24 hours for regeneration of the coke produced. Reformed products high in aromatic content are stated to be obtained, but the overall gasoline yields are not substantially better than those obtained in the previously described processes carried out at lower pressure;

In accordance with the present invention, naphthenes in gasoline and naphtha fractions, are selectively converted to aromatics under conditions disfavoring accompanying production of undesirable side products such as coke and gas.

out the reforming process under selected conditions and in the presence of catalysts Which selectively promote de- This desirable result is brought about by carrying hydrogenation reactions and have little or no initial or potential tendency to promote cracking or polymerization;

pounds per square inch, and liquid space rates (vol. oil/ hr./vo1. cat.) of 1 or more, preferably at least 2. The selected catalysts employed are characterized by the properties of being capable of dehydrogenating methylcyclohexane to aromatics under fixed operating conditions while being incapable of significantly converting normal heptane under the same conditions.

Among the catalysts that can be employed in the process of the invention there are included noble metals of the platinum-palladium group supported on nonacidic carriers having no significant cracking activity,

such as 0.1 to 2% Pt or Pd on MgO or on silica or titania gel; molybdenum oxides supported on inactive or inactivated carriers such as on silica gel, or on alumina specially treated to inactivate the cracking-promoting function thereof; 7.0 to 15.0% M003 by weight of the catalyst is generally satisfactory. The selectivity of various catalysts can be tested by their separate effects on con-- version of heptane and of methylcyclohexane under standarized conditions. In the following tabulation there are compared typical results obtained Withcatalysts of the invention as opposed to catalysts having significant cracking activity, such as 10% M003 on alumina, in the conversion of the stated hydrocarbons at a temperature of 950 F. under a pressure of 600 p. s. i. g., feeding the oil at a liquid space rate of 2 (vol./hr./vol.), 3 mols of hydrogenbeing added with the charge.

Since by the process of the invention cracking is minimized, the quantity of low molecular Weight gases produced is quite small and incremental coke deposition, if any, is so low that periodic regeneration of the catalyst is not necessary, or will be used only at infrequent intervals following an on-stream period going up to several weeks or more.

The reforming process of the invention is applicable to the treatment of various naphtha charge stocks containing naphthenes of the hydroaromatic type, including catalytically cracked distillates as well as straight run gasoline and naphthas and distillates from thermal cracking. An important application of the invention is in the treatment of gasoline and naphtha fractions derived from hydrogenative processes such as hydrogenative cracking and destructive hydrogenation, which fractions are'generally characterized by a high naphthene content and low octane rating.

' As pointed out in the copending application Serial No. 198,469, filed of even date herewith, and now abandoned, in the case of the noble metal catalyst, it is important that the support or carrier have a surface area adapted to extensive and uniform distribution of the active metal thereon and be free from components imparting acidity to the carrier; acidity can be measured by ability of the mass to chemisorb quinoline or other organic bases. Magnesium oxide is a preferred material for use as a carrier since it is relatively cheap and abundant, is slightly basic, and can be obtained or prepared in forms having the desired surface characteristics; both the light as well as the heavy forms of magnesia may be employed as well as the product obtained by simple precipitation by alkaline Patented Aug. 28, 1956 medium of" soluble magnesium salts, followed by drying.

The Ptor alternative metal component is employed generally in proportions of from about 0.1 to 2.0% by Weight of the carrier (water free basis), and preferably in: proportions of about 0.44% by weight thereof. Palladium andother' noble metals of the platinum and palladium group or combinations of these arealso suitable, but not necessarily with equal results. The hydrogenativemetal component can be deposited in or on the; carrier by impregnating the latter with an aqueous suspension of the metal oxide followed by reduction thereof to the free metal, orbydipping-the carrier in soluble salts or other soluble compoundsof the metals and v decomposing the the-same tofree metal or oxide. Thus, the-magnesia in the formof pellets or granules of desired size may be dipped in a solution of chloroplatinic acid or chloroplatinous acid of suitable concentration to provide the desired. quantity of Pt, then dried and decomposed by heating or reduction with hydrogen or by treatment with soda under reducing conditions. Palladium maybe depositedbyimpregnation of the magnesia carrier with PdClzsolution in suitable concentration followed by decomposition thereof directly to the metal, or to the oxide with subsequent reduction. Conversion of the oxides to free-metal, if necessary, can be readily efiected by reduction with hydrogen or other reducing agents in vapor form.

The deposition of the noble metal on silica or titania gel canbe carried out generally in the manner already described for deposition thereof onmagnesia carriers.

The molybdena-containing catalysts can be prepared by dipping the inactive or inactivated support in a solution of a soluble molybdenum salt, such as ammonium molybdate, and decomposing the salt to the oxide. Theinactivation of supports such as alumina, including socalled' activated and gamma alumina, is effected by treating the support with an alkaline earth compound, particularly with a magnesium or calcium salt in quantities effecting deposition of equivalent of 0.1 to 2% by weight of the alkaline earth oxide in the carrier. The deposition of the-alkaline earth oxide in the carrier is etfected prior to treatment with the molybdenum compound to obtain catalysts having the desired properties specified. It is also important that the alumina support, before or after deposition of the molybdenum compound be not heated to high temperatures or otherwise treated tocause transformation thereof to beta forms of alumina. Also suitable for deactivating the alumina support as to cracking function, but not necessarily with equal quantitative efiect, are alkali metal oxides particularly sodium oxide. These can be incorporated in the alumina in the same manner as the alkaline earth metal oxides described above, and in aboutthe same proportions.

Example I Heavy magnesia powder. (Merck #1478) was. hydrated by agitation; in water overnight then filtered. The filter cake was made. into an extrudable mix by adjustment of water content (mixing wet and dried, filter cake), a small mixture extruded through dies into strands and cut into cylindricalpellets. The wet pelletsweredried. at temperatures not in excess of 240 F., ground to powder and dipped in aqueous chloroplatinic acid containing 1.5 times the required amount of Pt, employing about 56 milliliters of liquid per grams of MgO. Excess liquid was filtered ofl and the powder oven dried, then heat treated in a muffle furnace for two hours at 1000 F. to drive off HCl. The powder was formed into pellets with addition of 5% corn oil and hardened by further heat treatment in air at 1056 F. for 2 hours.

A number of catalysts differing in Pt content were thus prepared including the following: 1.2% Pt on MgO by impregnating with an aqueous solution containing 54.5 grams HzPtClebI-IsO per liter, and 0.6% and 04% Pt on MgO using solutions containingrespectively 27 and 18 grams of HzPtClafil-IzO per liter.

The several catalysts were treated with a flowing stream of hydrogen before being contacted with the hydrocarbon charge.

The following table illustrates a number of runs carried outwith the above catalysts under the difierent operating conditions specified:

TABLE 2 [Catalyst 1.2% Pt on MgO.]

East Texas Naphtha East Texas Naph- Charge (B; R.190 tha (B. R. 240- 370 F., 352 F., 533 APT). 53.4 API) Parafiins, wt. percent 30 41 Clelins, wt. percent 0 0 Naphthenes, wt percent 43 45 Aromatics, Wt. percent 13 14 Octane N0s.:

GER-R Clear 51.2 57.6 +3 cc. TEL 7616 724 Operating Conditions: 7

Pressure, p. s. i. g 600 600 750 750 1111)., 950 r 950 950 1, 000 LSV, vol/hr lvol 2 2 2 2 HztOil ratio 3 6 5 5 Yields (percent of charge):

Gasoline (05+), vol. percent..... 94. 5 92. 8 94.1 74. 5 04, vol. percent"... 3. 9 3. 4 2. 5 16. 2 Dry Gas,,wt. percen 1. 4 3.0 1.9 9. 6 Coke, wt. percent... 0. 2 0.2 0. 1 1. 6 Octane-N0s.

CFR-M Clean. 61. 4v 60.8 74. 1 CFR-R Clear 72. 4 CFR-E-1-3 cc. TEL 87.5 Parafdns, wt. percent 37 42 43 29. Oleflns, wt. percent 3 2 2 3 Naphthenes, wt. percent- 23 22 19 21 Aromatics, wt. percent 37 34 36 47 It will be seen from the above table that at temperature of, 1000 F. as compared with the runs at 950 F. significant cracking has begun to take place as evidenced by considerably increased quantities of C4. and dry gas produced, comparatively high coke deposition, and reduction in paraflins by conversion.

The effect of change in space rate will be apparent from the runs in the following table showing results obtained charging the same naphtha feed. Also reported are amount of methyl cellulose, added as plasticizer, and, the 60 several runs with catalyst of lower Pt content.

TABLE 3 [Charge: East Texas Naphtha (B. R. 240-352 F., APP 53.3) .1

Catalyst-Percent Pt on MgO.---. 1.2 1.2. 0.6 0 4 Operating Conditions:

Pressure, p. s. i. g 750 600 600 600 600 600 Temp., F 950 950' 950 950 950 950 LSV, Vol./hr./vol- 0. 5, 4 6 2 2 2 H2; oil ratio 3 5 3 5 3 3 Period, Min 024() 0-30 -180 0-120 0-60 0-60 0-60 Yields (Percent Chg.),: p

Gaso (05+) vol. percent 94. 5 9. 41 93.4 92. 8 89. 7 95.5

C4, ,Vol. percent: 1. 6' 1. 8 2. 9 3. 4 5.1 3. 4

Dry gas, Wt. percent 4 2 2. 7 2. 9 2.0 3.0 2.6 1. 3

Coke, Wt. perc nt-.- 1 1 0.02 0.02 0. 1 0. 2 0.2 0. 2 Octane Nos.:

GER-R, CleaL-ag-a 82. 8 69. 4 71. 5 73.1 74. 0 'Z 7. 9. 69. 7

+3 cc. TEL 93. 7 85. 6 87. 8 87.8 88. l 89. 5 87. 3

From the foregoing results it appears that at space velocities below 1, cracking is commencing to take place to significant extent as evidenced by increase in dry gas and C4.s and notable coke depositions. At the preferred conditions of operation, it will also be observed, there is no significant change in catalyst properties, with in,- creasing time on stream the yields remaining substantially constant.

Example 11 Commercial activated-alumina tablets (Harshaw) were treated with 20% magnesium chloride (MgCl2) solution, using about 5 liters solution per kilogram of alumina, then washed free of chlorides and dried. The dried product was treated for thirty minutes with a solution of ammonium molybdate (calculated to deposit 10% MoOa on the alumina) containing about 270 grams M003 per liter of water, in the proportions of about 400 milliliters solution per kilo-gram of alumina. The treated product was drained, dried, and heat treated at 1050 F. for two hours. Before being placed on stream, hydrogen was passed over the catalyst to reduce the molybdena to lower valence forms. The final catalyst contained 0.28%

MgO.

The catalyst thus prepared was employed in reforming East Texas naphtha with the following results:

' TABLE 4 [Ohargez East Texas naphtha (B. R. 240352 F., API 53.3). Catalyst: M; on magnesia-treated alumina] Operating conditions:

Pressure, p. s. i. g 600 600 750 750 Temp 950 950 950 950 LSV 2 4 v 2 0. 5 Hz; oil ratio 3 5 3 3 Yields:

Gaso. (05+), vol. percent 86. 5 91. 3 88. 8 76. 4 04, vol. percent 8.1 4. 4 7. 2 17. 4 Dry Gas, wt. percent.. 4.1 3. 2 3. 8 6. 9 Coke, wt. percent 0.4 .007 0.6 0.7

Oetanes:

OFR-R clear 85.3 75. 0 79. 5 89. 8 +3 cc. TEL 95. 4 88. 4 93. 2 97. 4

It will be seen from the above table that at space rates' thenic hydrocarbons in a hydrocarbon fraction boiling approximately in the range of gasoline with concomitant formation of minimized quantities of normally gaseous hydrocarbons, coke and other cracked products which comprises contacting said hydrocarbon fraction with a nonacidic catalyst consisting essentially of 0.1 to 2% of noble metal from the group consisting of platinum and palladium deposited in a nonacidic dried gel carrier from the group consisting of silica gel and titania gel, said co-ntacting of the hydrocarbon fraction with the catalyst being in the presence of several mols of added hydrogen per mol of hydrocarbon at a temperature within the range from about 850 F. to about 975 F. at a pressure within the range of from about 400 lbs. per sq. in. to 1000 lbs. per sq. in. at a space velocity within the range from about 1 to about 6 liquid volumes of hydrocarbon per hour per volume of catalyst, whereby substantially all of the methylcyclohexane content of said hydrocarbon fraction is converted substantially completely to toluene and whereby the normal heptane content of said fraction is recovered substantially completely as normal heptane.

2. The method of selectively dehydrogenating naphthenic hydrocarbons in a hydrocarbon fraction boiling approximately in the range of gasoline with concomitant formation of minimized quantities of normally gaseous hydrocarbons, coke and other cracked products which comprises contacting said hydrocarbon fraction with a catalyst consisting of 0.1 to 2% platinum in a nonacidic titania gel in the presence of about 5 mols of added hydrogen at 'a temperature of about 950 F. at a pressure of about 600 lbs. per sq. in. at a space velocity of about 4 liquid volumes of hydrocarbon fraction per hr. per volume of catalyst whereby the methylcyclohexane content of said fraction is converted substantially completely to toluene and whereby the normal heptane content of said fraction is recovered substantially completely as normal heptane.

References Cited in the file of this patent UNITED STATES PATENTS 2,285,727 Komarewsky June 9, 1942 2,373,674 Crawford et al. Apr. 17, 1945 2,409,382 Peck Oct. 15, 1946 2,409,695 Laughlin Oct. 22, 1946 2,411,726 Holroyd et al. Nov. 26, 1946 2,479,110 Haensel Aug. 16, 1949 2,550,531 Ciapetta Apr. 24, 1951 OTHER REFERENCES Komarewsky et al.: Oil and Gas Journal, pages 90, 91, 92, 93 and 119 (5 pages), June 24, 1943.

Claims (1)

1. THE METHOD OF SELECTIVELY DEHYDROGENATING NAPHTHENIC HYDROCARBONS IN A HYDROCARBON FRACTION BOILING APPROXIMATELY IN THE RANGE OF GASOLINE WITH CONCOMITANT FORMATION OF MINIMIZED QUANTITIES OF NORMALLY GASEOUS HYDROCARBONS, COKE AND OTHER CRACKED PRODUCTS WHICH COMPRISES CONTACTING SAID HYDROCARBON FRACTION WITH A NONACIDIC CATALYST CONSISTING ESSENTIALLY OF 0.1 TO 2% OF NOBLE METAL FROM THE GROUP CONSISTING OF PLATINUM AND PALLADIUM DEPOSITED IN A NONACIDIC DRIED GEL CARRIER FROM THE GROUP CONSISTING OF SILICA GEL AND TITANIA GEL, SAID CONTACTING OF THE HYDROCARBON FRACTION WITH THE CATALYST BEING IN THE PRESENCE OF SEVERAL MOLS OF ADDED HYDROGEN PER MOLOF HYDROCARBON AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 850* F. TO ABOUT 975* F. AT A PRESSURE WITHING THE RANGE OF FROM ABOUT 400LBS. PER SQ. IN. TO 1000 LBS. PER SQ. IN. AT A SPACE VELOCITY WITHIN THE RANGE FROM ABOUT 1 TO ABOUT 6 LIQUID VOLUMES OF HYDROCARBON PER HOUR PER VOLUME OF CATALYST, WHEREBY SUBSTANTIALLY ALL OF THE METHYLCYCLOHEXANE CONTENT OF SAID HYDROCARBON FRACTION IS CONVERTED SUBSTANTIALLY COMPLETELY TO TOLUENE AND WHEREBY THE NORMAL HEPTANE CONTENT OF SAID FRACTION IS RECOVERED SUBSTANTIALLY COMPLETELY AS NORMAL HEPTANE.