US3377268A - Demetallization of petroleum fractions - Google Patents

Description

United States Patent C) 3,377,268 DEMETALLIZATION F PETROLEUM FRACTIONS Tao Ping Li, Texas City, Tex., and Robert John Rosscup, Valparaiso, lnd., 'assignors to Standard Oil Company,

Chicago, 11]., a corporation of Illinois No Drawing. Filed Dec. 27, 1965, Ser. No. 516,750 9 Claims. (Cl. 208-252) ABSTRACT OF THE DISCLOSURE Method for removing metal compounds from petroleum tractors utilizing an absorbent which has been treated with a member of the group consisting of nicotinic acid, isonicotinic acid, salts of said acids and mixtures thereof.

This invention pertains to removal of metal compounds from petroleum fractions. More particularly, the invention relates to a method for removing metal compounds from petroleum fractions utilizing an adsorbent selected for such compounds.

Metals in petroleum hydrocarbon fractions, particularly the heavier fractions boiling above about 700 F., have long been recognized as deleterious catalyst poisons during refining of these materials. The metals in these fractions, primarily nickel and vanadium, are deposited on the solid catalyst resulting in poisoning of desired catalytic activity and, in some cases, catalyzing undesirable side reactions. Refining ence of such metals is particularly harmful are catalytic cracking and hydrocracking.

Some metal compounds are volatile and are distilled overhead with heavy oils during vacuum distillation of crude oil to produce feedstocks for refining into more valuable products such as gasoline and jet fuel. The metals problem has become particularly serious in modern refineries employing vacuum distillation at a pressure of 50 mm. mercury absolute and lower in order to recover a maximum amount of feedstock for catalytic cracking. The distillate from such vacuum distillation units contains many useful hydrocarbons having boiling points well above 1,000" B, however such distillat usually also contains harmful volatile metal compounds such as porphyrins.

The present invention provides a method for removing metal compounds from a metal-containing petroleum fraction which method comprises contacting the petroleum fraction in the liquid phase with a solids selective adsorbent selective for metal compounds and recovering a treated fraction substantially free of metal, periodically discontinuing the contacting and regenerating the adsorbent by washing metal compounds therefrom with a substantially metal-free liquid solvent for the metal compounds and resuming contacting with additional metal-containing petroleum fraction for metal removal therefrom. The selected adsorbent for use in the present invention consists essentially of a solidadsorbent containing from about 5 to about 50% by weight of a compound selected from the class consisting of nicotinic acid, isonicotinic acid, salts of said acids, and mixtures thereof. The efliciency of contacting is improved by diluting the petroleum fraction with a paraffin hydrocarbon diluent prior to contacting the diluted fraction with the adsorbent. Suitable parafiinic hydrocarbon diluents include parafiins having 5 to 8 carbon atoms per molecule. Hexane is a preferred diluent.

The selected adsorbent is periodically withdrawn from the contacting with the petroleum fraction being demetallized and freed of metals by washing the adsorbent with a solvent selected from the class consisting of aroprocesses in which the presmatic hydrocarbons, pyridine and mixturesthereof. By proper choice of the solvents used for eluting the metal compounds from the selective adsorbent, nickel and vanadium compounds can be separately recovered for further processing to recover their metal values. To accomplish this the adsorbent loaded with metal compounds is first eluted with a liquid mixture of paraffin hydrocarbon and aromatic hydrocarbon to elute nickel porphyrin from the selective adsorbent for the recovery of nickel, and thereafter eluting from the selective adsorbent vanadium porphyrin by washing the adsorbent with a liquid mixture of aromatic hydrocarbon and pyridine followed by recovery of the vanadium values from the luent. Preferably the selective adsorbent is first washed free of oil with a liquid parafiin hydrocarbon, such as hexane, prior to eluting the nickel therefrom with the parafiin hydrocarbon-aromatic hydrocarbon mixture. The par'afiin hydrocarbon, component of the solvent for eluting nickel porphyrine preferably has 5 to 8 carbon atoms per molecule, hexane being a particularly preferred paraflin hydrocarbon. The aromatic hydrocarbon used for eluting vanadium porphyrin suitably has 6 to 8 carbon atoms per molecule, benzene being. a preferred aromatic solvent.

Following the selective elution of nickel porphyrin and vanadium porphyrin from the selective adsorbent, the adsorbent is regenerated by washing any adsorbed nonporphyrin metal therefrom using washes of pyridine, benzene and hexane to restore the adsorbent capacity of the selective adsorbent for further contacting with metalcontaining petroleum fraction. The regeneration becomes necessary where distillation bottoms fractions, such as deasphalted reduced crude, are being treated for metals removal.

In addition to its usefulness in providing substantially metal-free petroleum fractions for further refining, the invention also provides an analytical technique for separating and isolating nickel porphyrin and vanadium p01 phyrin from petroleum fractions. Such a separation has heretofore been impossible. j

The selective adsorbent is prepared by supporting a pyridine derivative on an adsorbent solid. Alumina and silica gel are preferred adsorbent solids, however other adsorbent materials may be used. Suitable pyridine derivatives are the carboxylic acids of pyridine such as nicotinic acid, isonicotinic acid, picolinic acid and the like and the salts of such acids. Isonicotinic acid is a preferred acid and ammonium isonicotinate is a preferred salt.

The adsorbent solid used to prepare the selective adsorbent may be in any desired shape or size such as cylindrical pellets, spheres, extrudates, etc. Any suitable method of contacting the petroleum fraction and the selective adsorbent may be used. For convenience, it is usually preferred to form a bed of selective adsorbent particles and percolate the petroleum fraction and eluting solvents therethrough.

The invention will be further illustrated by thefollowing examples which are preferred embodiments of the invention. It is to be understood that the examples are for the purpose of illustration and are not to be deemed as limiting the scope of the present invention.

In the following examples the vanadyl and nickel porphyrins were determined by a Beckman DB spectrophotometer. The principal peaks at 570 mg and 550 mg in the visible band were used for the calculation of vanadyl and nickel porphyrin concentrations, respectively. Bands at 412 my. and 396 ml for V and Ni respectively were used to monitor column efliuents.

EXAMPLE I To show the effectiveness of nicotinic acid on alumina, 14.6 grams of nicotinic acid was thoroughly mixed with 35 grams of adsorbent alumina in a glass jar. The mixture was placed in a Pyrex tube of one-inch diameter and 18 inches in length. Dry nitrogen was passed through the tube at a rate of about 20 liters per hour. The tube was heated by a tube furnace to 150 C. for hours. The temperature was controlled by a thermocouple placed at the center of the tube. During the heating period, water was found at the outlet of the tube and the nicotinic acid powder gradually disappeared. The acid was sublimed and apparently adsorbed on the surface of the alumina. An adsorbent of uniform appearance was obtained. No free acid was visible. The yield was 47.9 grams accounting for 96.6% of the weight of the materials charged. The weight loss is presumably due to the elimination of water generated by the reaction between the hydroxyl groups on the alumina surface and the nicotinic acid. This generation of water is about 79.5% of the theoretical. The adsorbent contained about 27 wt. percent of nicotinic acid.

A column was charged with the adsorbent saturated with n-hexane. A sample of molecular still distillate from Gulf Coast reduced crude containing 42 p.p.m. by wt. of vanadium and 11.5 p.p.m. by wt. of nickel was loaded on the column and fractions were then eluted with n-hexane and benzene, in sequence. The oil was recovered from the iirst fraction of the effluent. Its metal content was determined chemically. Porphyrins were eluted by the benzene. The separation was monitored by frequently taking the UV spectrum of the efiluent which showed the presence of nickel and vanadylporphyrin. Concentrations in the order of molar are detectable in the 400 m region.

The present separation is ditferent from ordinary liquid chromatography in which a chromatogram representing all components in the sample is developed with the solvent. In the present system, separation is achieved by eluting with different solvents. In other words, one solvent elutes off some specific components leaving the others still adsorbed on the column.

The treated distillate contained only 2.2 ppm. by weight of vanadium and 6.7 p.p.m. of nickel. Metals recovered and isolated as the porphyrins were 35.3 p.p.m. of vanadium and 1.95 p.p.m. of nickel, by weight based on distillate feed. Thus, 94.5% of the vanadium and 23.3% of the nickel were removed from the distillate by nicotinic acid on adsorbent alumina.

EXAMPLE II A selective adsorbent was prepared essentially according to the procedure used in Example I, except that isonicotinic acid was used in place of nicotinic acid and the mixture of acid and alumina was heated, under nitrogen, 3.5 hours at 150 C., 2 hours at 200 C.,and 1 hour at 250 C. At the end of heating, very litle sublimination of isonicotinic acid was observed. The yield was 68.1 grams from 21 grams of isonicotinic acid and 49 grams of alumina. The furnished adsorbent contained 26% isonicotinic acid.

Treating the same feed and in the same manner as in Example I, except for a final elution with methanol, using the isonicotinic acid-containing adsorbent, resulted in a treated oil having less than 2 p.p.m. of vanadium and less than 1 p.p.m. of nickel. Metal isolated as porphyrin complexes in this example were 36.73 p.p.m. vanadium and 6.99 p.p.m. nickel.

EXAMPLE III In this test conducted as in Example II, ammonium isonicotinate was supported on the alumina instead of the acidand dioxane was used instead of methanol as the final eluent. To prepare the selective adsorbent, twenty-one grams of isonicotinic acid was added slowly to a solution of 16.4 ml of ammonium hydroxide (15.3N) in 61.6 ml of water. The mixture was stirred with a glass rod until the acid completely dissolved. The final solution had a'pI-I value of five. Alumina (49 grams) was added cautiously to the solution. Water was evaporated from the mixture at low heat on a hot plate. The solid was then dried in an oven at C. for 2 hours. It was transferred into a Pyrex tube and heated at 200 C. in a nitrogen atmosphere for an hour. The adsorbent, containing 19.5% of ammonium isonicotinate, weighed 63 grams.

A good separation wasv obtained, resulting in the recovery of 8.07 p.p.m. of nickel as the porphyrin, based on feed. The vanadium porphyrin could not 'be determined due to its decomposition by peroxide present in the dioxane eluent.

EXAMPLE IV In this test, also conducted as in Example II, sodium isonicotinate was supported on the alumina instead of the acid and pyridine was used instead of methanol as the final eluent. To prepare this adsorbent, forty-nine grams of alumina was added slowly to a solution of 21 grams of isonicotinic acid in 62 ml. of 3 N sodium hydroxide. The mixture was evaporated to dryness and the solid obtained was dried at 105 C. for 3 hours. The adsorbent was then placed in a Pyrex tube and heated under nitrogen at a flow rate of 20 l./hr., for 2 hours at C., and one hour each at 200, 250, and 300 C. It weighed 73.4 grams and contained 33 wt. percent sodium isonicotinate.

Complete isolation of vanadium from nickel porphyrins was obtained in the amounts of 40.56 p.p.m. and 7.30 p.p.m., respectively. The treated distillate contained less than 0.05 p.p.m. of vanadium and 0.88 p.p.m. of nickel.

EXAMPLE V In this test, heavy gas oil from Gulf Coast crude oil was treated as in Example IV using the sodium isonicotinate on alumina selective adsorbent. The gas oil feed contained 0.45 p.p.m. vanadium and 0.08 p.p.m. nickel.

The treated oil contained only 0.002 p.p.m. vanadium and 0.017 p.p.m. nickel. Metals recovered as the porphyrins amounted to 0.3 p.p.m. and 0.016 p.p.m. vanadium and nickel, respectively.

EXAMPLE VI Deasphalted reduced crude vacuum distillation bottoms from Gulf Coast crude was demetallized by diluting it with n-hexane to reduce the viscosity and contacting the diluted feed with sodium isonicotinate on alumina selective adsorbent prepared as in Example IV. The undiluted de asphalted reduced crude feed contained 33 and 6 p.p.m. of vanadium and nickel, respectively. The general procedure for treating was as in Example I, but using nhexane, benzene, and pyridine in sequence as the eluents.

Metals remaining in the treated reduced crude were 0.19 p.p.m. vanadium and 4.5 p.p.m. nickel. Metals recovered and isolated as the porphyrins were 18.3 p.p.m. vanadium and 2.43 p.p.m. nickel, by wt. based on feed.

EXAMPLE VII In this example, sodium isonicotinate on silica gel was used to treat molecular distillate as in Example I. The procedure for preparing this adsorbent was the same as that described in Example I, except that instead of alumina, silica gel was used as support. Seventy-one grams of adsorbent, containing 26% of sodium isonicotinate, was obtained from 17.5 grams of isonicotinic acid and 52.5 grams of silica gel.

The molecular distillate described in Example Iwas treated using the general procedure described in Example I except that n-hexane, benzene, and pyridine were used in sequence as eluents.

The treated distillate contained less than 0.05 p.p.m. vanadium and less than 0.05 p.p.m. nickel. Metals recovered and isolated as the porphyrins were 40.2 p.p.m. vanadium and 7.29 p.p.m. nickel, each by weight based on distillate feed.

, Having thus describedthe invention, what is claimed 1. A method for removing metal compounds from a metal-containing petroleum fraction which method com prises contacting said fraction in the liquid phase with a 7 selective adsorbent selective for metal compounds and recovering a treated fraction substantially free of metal, periodically discontinuing said contacting and regenerat ing said adsorbent by washing metal compounds therefrom with a substantially metal-free liquid solvent for said compounds and resuming contacting with additional metalcontaining petroleum fraction for metal removal therefrom, said selective adsorbent consisting essentially of a solid adsorbent containing from about 5 to about 50 percent by weight of a compound selected from the class consisting of nicotinic acid, isonicotinic acid, salts of said acids, and mixtures thereof.

2. The method of claim 1 wherein said petroleum fraction is a crude oil fraction boiling above about 700 F.

3. The method of claim 1 wherein said fraction is diluted With a diluent consisting essentially of parafiin hydrocarbon prior to said contacting.

4. The method of claim 1 wherein said liquid solvent is selected from the class consisting of aromatic hydrocarbons, pyridine and mixtures thereof.

5. The method of claim 1 wherein nickel porphyrin compounds and vanadium-porpyhrin compounds are recovered separately from said selective adsorbent after contacting with said fraction has been discontinued by the steps of (1) eluting nickel porphyrin from said selective adsorbent with a liquid mixture of paraflin hydrocarbon and aromatic hydrocarbon and recovering eluted nickel porphyrin, and thereafter (2) eluting vanadium porphyrin from said selective adsorbent with a liquid mixture or aromatic hydrocarbon and pyridine and recovering eluted vanadium porphyrin.

6. The method of claim 5 wherein step (1) is preceded by washing oil from said selective adsorbent with liquid paraffin hydrocarbon.

7. The method of claim 5 wherein said paraflin hydrocarbon has 5 to 8 carbon atoms per molecule and said aromatic hydrocarbon has 6 to 8 carbon atoms per molecule.

8. The method of claim 7 wherein said parafiin hydrocarbon consists essentially of hexane and said aromatic hydrocarbon consists essentially of benzene.

9. The method of claim 5 wherein said step (2) is followed 'by washing said selective adsorbent with pyridine, benzene and hexane to remove adsorbed non-porphyrin metal therefrom and regenerate said adsorbent and restore adsorbent capacity thereof for further contacting with metal-containing petroleum fraction.

References Cited UNITED STATES PATENTS 2,925,375 2/1960 Fleck et a1. 208254 2,925,379 2/1960 Fleck et a1. 208-254 2,925,380 2/1960 Fleck et al. 208-254 2,925,381 2/1960 Fleck et al. 208-254 SAMUEL P. JONES, Primary Examiner.