MXPA00001433A - Process for reducing total acid number of crude oil - Google Patents

Abstract

The invention comprises a method for reducing the amount of carboxylic acids in petroleum feeds comprising the steps of (a) adding to said petroleum feed a catalytic agent comprising an oil soluble or oil dispersible compound of a metal selected from the group consisting of Group VB, VIB, VIIB and VIII metals, wherein the amount of metal in said petroleum feed is at least about 5 wppm, (b) heating said petroleum feed with said catalytic agent in a reator at a temperature of about 400 to about 800°F (about 204.44 to about 426.67°C) and a pressure of about atmospheric to about 1000 psig (about 6996.33 kPa) in the substantial absence of hydrogen, and (c) sweeping the reactor containing said petroleum feed and said catalytic agent with an inert gas to maintain the combined water and carbon dioxide partial pressure below about 50 psia (344.75 kPa).

Description

PROCESS TO REDUCE THE TOTAL ACID NUMBER OF CRUDE OIL FIELD OF THE INVENTION The present invention is directed to a method for reducing the Total Acid Number (TAN) of crude oils, a number which is based on the amount of carboxylic acids, especially naphthenic acids, which are present in the petroleum.

BACKGROUND OF THE INVENTION The presence of relatively high levels of petroleum acids, e.g., naphthenic acids, in crude oils or fractions thereof is a problem for petroleum refiners and "more recently also for producers. , these acids, which are found to a greater or lesser degree in virtually all crude oils, are corrosive, tend to cause equipment failures, and lead to high maintenance costs, more frequent general inspections than would otherwise be necessary. , reduce the quality of the product and cause environmental waste problems There is a very significant amount of literature, both patents and publications, dealing with the removal of naphthenic acid through conversion or absorption, for example, many aqueous materials they can be added to crude or fractions of crude to convert naphthenic acids into some other mater ial, eg, salts, which can be eliminated or are less corrosive. Other methods for removal of naphthonic acid are also well known including absorption, on zeolites, for example, Additionally, a common practice for overcoming the problems of naphthonic acid is the use of expensive, corrosion-resistant alloy materials in refinery equipment or producer, who will find relatively high concentrations of naphthonic acid. Another common practice involves mixing the raw with high TAN with lower TAN crude, the latter, however, being significantly more expensive than the former. . A reference. Lazar, et al. (US 1,953,353). teaches the decomposition of naphthenic acid from primary distillate crudes or distillates, carried out at atmospheric pressure between 315.6 to 398.9SC. However, it only recognizes C02 as the only decomposition product of naphthenic, non-hydrocarbon, gaseous acid, and makes no provision to avoid the accumulation of reaction inhibitors. Additionally, the Patenté of E.U.A. Do not.

No. 2,921,023 describes the removal of naphthenic acids from heavy petroleum fractions by hydrogenation with a molrbdene oxide catalyst on silica / alumina. More specifically, the preference process hydrogenates the oxo compounds and / or olefinic compounds, for example, naphthenic acids, - in the presence of sulfur compounds contained in organic mixtures without affecting the sulfur compounds. This is achieved by subjecting the organic mixture to the action of hydrogen at temperatures between about 232.2 to 315.6SC, in the presence of a molybdenum oxide containing catalyst having a reversible water content of less than about 1.0% by weight. The life of the catalyst is extended by regeneration. WO 96/06899 describes a process for essentially removing naphthonic acids from a hydrocarbon oil. The process includes hydrogenation at 1 to 50 bar (100 to 5000 kPa) and 100 to 300SC of a crude oil that has not been previously distilled or from which a naphtha fraction has been distilled using a catalyst consisting of Ni-Mo or Co-Mo on an alumina carrier. The specification describes the pumping of hydrogen into the reaction zone. There is no mention of controlling the water and the partial pressure of carbon dioxide.

The U.S. Patent A. 3,617,501 describes an integrated process to refine whole crude, but does not dispute the reduction of TAN. The first step of the process includes hydrotreating a feed, which may be a whole crude oil fraction, using a catalyst comprising one or more metals supported on a carrier material. Preferably, the metals are metal oxides or sulphides, such as molybdenum, tungsten, cobalt, nickel and iron supported on an appropriate carrier material such as alumina or alumina which contains a small amount of silica. The catalyst can be used in the form of a fixed bed, a suspension or a fluidized bed reactor. With respect to the suspension operation, mention is not made of catalyst particle size, the concentration of catalyst in the feed or the use of unsupported catalysts (ie, without carrier), British Patent, 236,230 describes a process for the removal of naphthenic acids from distilled petroleum fractions by processing on hydrotreating catalysts supported without the addition of gaseous hydrogen. There is no mention of controlling the partial pressure of water and carbon dioxide. The Patents of E.U.A. Nos. 4,134,825; 4,740,295; 5,039,392; and 5,620,591, all of which are incorporated herein by reference, teach the preparation of unsupported, highly dispersed catalysts of nominal micrometer particle size, from soluble petroleum or oil dispersible compounds of metals selected from groups IVB, VB, VIB, VIIB and VIII of. the periodic table of elements and application of the catalyst for hydroconversion that improves heavy feeds, including whole oil crudes or with primary distillation. Hydroconversion is defined in these patents as a catalytic process conducted in the presence. of hydrogen wherein at least a portion of the heavy constituents and coke precursors (ie, Conradson Carbon) are converted to lower boiling compounds. The broader scales cited in these references with respect to process conditions include temperatures in the range of 339.9 to 4809C, partial pressures of hydrogen ranging from 3.52-351.50 kg / cm2 gauge (446.08 to 34576.33 kPa) and 10 -2000 wppm of catalyst metal based on the weight of the feed material. These references are directed to the conversion that improves heavy feeds and do not recognize that the catalysts can be used to selectively destroy carboxylic acids, e.g., naphthenic acids, Another method for removal of such acids includes treatment at temperatures of at least about 204.44SC, preferably at least about 315.56aC while sweeping the reaction zone with an inert gas to remove innate inhibitors to or formed during the treatment. However, this approach is loaded by the volatilization of naphthenic acids, which are found in distilled or light petroleum fractions that evaporate instantaneously during the thermal treatment. In addition, the treatment temperatures may be too high for this method to be used in downstream applications where it is desirable to destroy the acids before the stationary pipe furnaces, ie at temperatures of about 287.78aC or below, Thus, there is a need to eliminate or at least substantially reduce the concentration of petroleum acid in crude or fractions thereof which is low cost and friendly to the refinery. This technology would be particularly appropriate for crude or fractions where the TAN value is approximately 2 or higher. The TAN, determined by the ASTM method D-664, is milligrams of KOH required to • neutralize the organic acids contained in 1.0 gram of oil.

COMPENDIUM OF THE INVENTION The present invention is directed to a method for destroying carboxylic acids in whole crudes and crude fractions. The invention comprises a method for reducing the amount of carboxylic acids in petroleum feeds comprising the steps of (a) adding to the petroleum feedstock a catalytic agent comprising a petroleum soluble or petroleum dispersible compound of a selected metal. from the group consisting of Group VB, VIB, VIIB and VIII metals, where the amount of metal in the petroleum feed is at least about 5 wppm, J b) heating the oil feed with the catalytic agent in a reactor at a temperature of from about 204.44 to about 426.67SC, and a pressure from about atmospheric to about 70.30 kg / cm2 gauge (about 6996.33 kPa) in the substantial absence of hydrogen and (c) sweeping the reactor containing the oil feed and the catalytic agent with an inert gas to maintain the combined partial pressure of water and carbon dioxide less than about of 3.52 kg / cm2 absolute (approximately 344.75 kPa). TAN is defined as the weight in milligrams of base required to neutralize all the acidic constituents in petroleum. Vacuum waste conversion is defined as the conversion of boiling material above 551.671C to boiling material less than 551.67aC.

BRIEF DESCRIPTION OF THE FIGURE Figure 1 is the partial pressure calculated for water as a function of the reactor pressure and inert gas scavenging regime for the process of the present invention. '- DETAILED DESCRIPTION OF THE INVENTION The present invention eliminates or destroys carboxylic acids (e.g., naphthenic acids) from petroleum feeds such as whole crude oils (including heavy crudes) and fractions thereof such as petroleum fractions of Vacuum gas, crude primary distillation, atmospheric residues, vacuum residues, and vacuum gas oil. . The present method reduces the TAN by at least about 40% in the oil feed, • The process is carried out at temperatures from about 204.44 to about 426.67BC, more preferably from about 232.22 to about 398.89aC, and from most preferably from about 260.00 to about 343.33aC. The pressures vary from about atmospheric to about 70_.30 kg / cm2 gauge (approximately atmospheric at 6996.33 kPa), preferably about 1.05 to about 35.14 kg / cm2 gauge (about 204.75 to about 3548.83 kPa), and so more preferably from about 2.11 to about 21.09 kg / cm2 manomotive (about 308.18 to about 2169.83 kPa). The amount of catalyst, calculated as metal or catalyst metals, used in the process varies from at least about 5, preferably about 10 to about 1000 parts per million by weight (wppm) of the oil feed. trying. Conveniently, during the process of the present invention, less than about 30% waste conversion occurs, and conveniently, less than about 20% where the vacuum residues are defined as boiling hydrocarbon material above 551.67. BC The catalyst particle size ranges from about 0.5 to about 10 micrometers, preferably about 0.5 to 5 micrometers, and more preferably about 0.5 to 2.0 micrometers. The catalysts are prepared from precursors, also referred to herein as catalytic agents, such as petroleum-soluble or oil-dispersible compounds of Group metals. VB, V.IB, VIIB, or VIII and mixtures thereof. Suitable metal catalysts and metal compounds are described in the U.S. Patent. No. 4,134,825 incorporated herein by reference. An example of a petroleum-soluble compound is the metal salt of a naphthenic acid such as molybdenum naphthenate. Examples of petroleum dispersible compounds are phosphomolybdic acid and ammonium heptamolybdate, the materials that first dissolve in water and then disperse - in the oil as a mixture of water in oil, where the droplet size of the phase of water is less than about 10 microns. Ideally, a catalyst precursor concentrate is prepared first, wherein the petroleum soluble or petroleum dispersible metal compound (s) is mixed with a portion of the process feed to form a concentrate containing at least about 20% by weight. 0.2% by weight of catalyst metal, de. preferably about 0.2 to 2.05 by weight of catalyst metal. See, for example, the patents of E.U.A. Nos. 5,039,392 or 4,740,295, incorporated herein by reference. The resulting precursor-concentrate can be used directly in the process or first converted into a metal sulphide concentrate or an activated catalyst concentrate before use. The catalyst precursor concentrate can be converted to a metal sulphide concentrate by treating with elemental sulfur (added to the feed portion used to prepare the concentrate) or with hydrogen sulfide at 148.89 to 204.44SC for 10-15 minutes (v .gr., see US Patent 5,039,392; 4,479,295 and 5,620,591 incorporated herein by reference). The metal sulfide concentrate can be converted to catalyst concentrate by heating at from 315.56 to 398.89aC for a sufficient time to form the catalyst (e.g., see U.S. Patent Nos. 5,039,392, 4,740,295, and 5,620,592) . The concentrate catalyst consists of nanoscale metal sulfide sites distributed in a hydrocarbonaceous matrix that is derived from the petroleum component of the concentrate. The total particle size can be varied, but fails within the range of 0.5 to 10 micrometers, preferably in the range of about 0.5 to 5.0 micrometers, and more preferably 0.5 to 2.0 micrometers. For the present process, ST can employ the precursor concentrate, the metal sulphide concentrate, or the catalyst concentrate. In each case, the oil feed is mixed with the concentrate to obtain the desired concentration of metal in the feed, that is, at least about 5 wppm, preferably about 10 to 1000 wppm, when the concentrates d? precursor or metal sulfide- are used, the catalyst that has a particle size d? about 0.5 to 10 microns, preferably 0.5 to 5 microns and more preferably 0.5 to 2.0 microns are formed in the process heating step in the TAN conversion reactor. Preferred metals include molybdenum, tungsten, vanadium, iron, nickel, cobalt and chromium. For example, heteropolyacids of metals can be used. Molybdenum is particularly well suited to the process of the present invention. Preferred molybdenum compounds are molybdenum naphthenates, molybdenum dithiocarbamate complexes (see, US Patent No. 4,561,964 incorporated herein by reference), phosphomolybdic acid, and molybdenum phosphorodithioate complexes. (e.g., MOLYVANÍR) -l, molybdenum di (2-ethylhexyl) phosphorodithioate, supplied by R. T, Vanderbilt Company, Other small particle catalysts that are useful for the practice of the present process include metal-rich ash. from controlled combustion of petroleum coke (see, see US Patents Nos. 4,169,038, 4,178,277 and 4,204,943 incorporated herein by reference). Finely divided iron based materials, which satisfy the particle size restrictions noted herein, such as red mud from alumina processing can also be used. The present process to decrease the amount of organic acids in petroleum feeds, is conducted without the addition of hydrogen. The water vapor and carbon dioxide, which result from the decomposition of carboxylic acids, act as inhibitors for the decomposition of the remaining carboxylic acids. Water is a particularly strong inhibitor. In this way, if the feed to the process contains water, a previous instantaneous evaporation step can be used to remove substantially all of the water. Additionally, the. vestigial amounts of water entering the process with the feed, as well as the water and carbon dioxide formed in the course of the destruction of carboxylic acids, must be purged from the process so that the partial pressure of water and carbon dioxide in the reaction zone is maintained below about 3.52 kg / cm2 absolute (about 344.75 kPa), preferably less than about 2.11 kg / cm2 absolute (about 206.85 kPa), more preferably less than about 1.41 kg / cm2 absolute (approximately 137.9 kPa), more preferably less than about 0.703 kg / cm2 absolute (about 68.95 kPa), and particularly less than about 0.35 kg / cm2 absolute (about 34..48 kPa). Substantially all water as used herein means as much water as can be removed by methods known to those skilled in the art. Although it is not desired to be limited by theory, it seems that most of the water formed in the destruction of carboxylic acids under conditions of the present process involves the formation of anhydride in intermediary (a reversible reaction with water), therefore , the effect of water inhibition on the decomposition of acid.

Equation A RCO 2RCOOH H20 + O RCD RCO RCO '- > R- + CO O RCO RCO '- > R- + CO, As will be illustrated in the examples that follow, water can have a strong inhibiting effect on the rate of destruction d? carboxylic acid. Carbon dioxide is also an inhibitor, but to a much lesser degree. To illustrate the potential for water pressure buildup resulting from the destruction of carboxylic acids under the conditions claimed for the process of the present invention, a hypothetical case was assumed where the TAN of the whole crude is reduced from 5.3 to 0.3. by heat treatment within the temperature scale set forth in this invention, and that 0.5 moles of water are produced for each mole of acid that is destroyed. The partial pressures calculated for water are shown in Figure 1 as a function .d? the reactor pressure and the rate at which a gas d is used? inert sweep (e.g., nitrogen, helium, argon, methane). Note that partial water pressures as high as 3.16 kg / cm2 absolute (310.28 kPa) can be obtained from decomposition d? acid alone when operating within the scale of pressures claimed for this process, thus emphasizing the preference to start the process with a dry feed and maintain the sweep gas regime to maintain the water pressure within the specified levels . From a process point of view, the catalyst can be left in the treated crude (depending on the type of metal and concentration) or be removed by conventional means "-such as filtration.The following examples illustrate the invention, but it is not intended that be limited in any way.The feed material used in this study was a mixture of Ko and Bolobo crudes from CHAD.The mixture was desalted and heated to 110aC with nitrogen purge to remove bulk water. in Table 1.

TABLE 1 TAN (mg KOH / g crude) 5.3 Sulfur,% by weight 0.2 Vacuum residues,% by weight 49 Gravity API 18 Viscosity, cSt @ 40aC 1100 Example 1: This example was carried out in a stirred 300 cc autoclave reactor (300 ml). The reactor was operated in a batch mode with respect to the crude that was charged. The gas was flowed through the autoclave to control the concentration of inhibitors in the reaction zone. '-. The reactor was charged with 100 g of Kome / Bolobo mixture, flooded with helium and then heated to 329.44 ° C with stirring during the treatment. 60 minutes at 329.44aC. The helium was flowed through the reactor at a rate of 0.1 liters per minute during the test. During cooling, the reactor liquid was discharged and measured to determine the content of TAN (ASTM D664 where TAN = mg KOH per gram of crude oil or product oil).

Example 2: Example 1 was repeated, except what? the reactor was charged with 100 g of mixture d? Komo / Bolobo and 0.62 g of MOLYVAN (R) -L (an amount sufficient to provide 500 wppm of Mo in the reactor feed). This compound, supplied by R.T. Vanderbilt Company, is di (2-ethylhexyl) phosphorodithioate molybdenum containing 8.1% Mo.

Example 3 Example 2 was repeated, except that the reactor product was filtered to recover catalyst solids before testing the liquid.

Example 4. -. Example 2 was repeated, except that water was fed to the reactor to reflect the operation with feed containing i. or% by weight of water ..

Table 2 Summary of Examples Examples 1 2 3 4 ' Mo wppm 0 500 500 500 Temp. (aC) 329.44 329.44 329.44 329.44 Time (minutes) 60 6p 60 '60 • Reactor pressure 3.16 3.16 3.16 - 3.16 kg / cm2 absolute (kPa) 310.28 310.28 310.2 310.28 Water (absolute kg / cm2) < 0.70 < 0.70 < 0.70 < 0.70 Filtered (yes / no) no No yes no TAN 3.43 2.71 2.60 3.21 Conversion "of Vacuum Residues,% 0 0 0 The examples in Table 2 illustrate that 'the rate of destruction of TAN under relatively mild thermal conditions can be accelerated by, the addition of trace amounts of molybdenum, provided as a petroleum-soluble molybdenum compound, without addition of hydrogen (compare Examples 2). and '3 with Example 1). Additionally, it is shown that the water has an inhibiting effect on the conversion of TAN (Compare Examples 2 and 3 with Example 4).

Claims (8)

1. A method for reducing the amount of carboxylic acids in petroleum feeds comprising the steps of: (a) adding to the petroleum feedstock a catalytic agent comprising a petroleum-soluble or oil-dispersible compound of a metal selected from from the group consisting of Group VB, VIB, VIIB and VIII metals, wherein the amount of metal in the petroleum feed is at least about 5 wppm; (b) heating the petroleum feed with the catalytic agent in a reactor at a temperature of about 204.44 to about 426.67SC, and a pressure from about atmospheric to about 70.30 kg / cm2 manomotically (about 6996.33 kPa) in the substantial absence of hydrogen; and (C) sweeping the reactor containing the oil feed and the catalytic agent with an inert gas to maintain the combined partial pressure of water and carbon dioxide less than about 3.52 kg / cm2 absolute (about 344.75 kPa).

2. The method according to "claim 1, wherein the catalytic agent comprises 31- a catalyst precursor concentrate of a petroleum-soluble or oil-dispersible metal compound prepared in a petroleum feed selected from the group consisting of crude, primary, primary distillate crude, atmospheric residue, vacuum residue, petroleum Vacuum gas, and mixtures thereof

3. The method according to claim 1, wherein the catalytic agent comprises a metal sulphide concentrate of a petroleum soluble or dispersible petroleum metal compound prepared in a petroleum feed selected from the group consisting of whole crudes, crude primary distillation, atmospheric waste, vacuum residue, vacuum gas oil and mixtures thereof. "

4. The method of compliance • with claim 3, wherein the concentrate of. The sulfide of m? tal is heated at a temperature and for a time sufficient to form a dispersion of catalyst particles of 0.5 to 10 micrometers comprising a metal sulfide component in association with a carbonaceous solid derived from the petroleum feed. in which the metal sulfide is dispersed.

5. The method according to claim 1, wherein the catalytic agent is a dispersion of catalyst particles of 0.5 to 10 micrometers comprising a metal sulfide component in association with a carbonaceous solid derived from the feed.

6. The method according to claim 1, wherein the metal is selected from the group consisting of molybdenum, tungsten, vanadium, iron, nickel, cobalt, chromium, and mixtures thereof. The method according to claim 1, wherein the petroleum-soluble or oil-dispersible metal compound is a heteropoly acid of tungsten or molybdenum 8. The method according to claim 1, wherein the metal compound oil-soluble or oil-dispersible is selected from the group consisting of phosphomolybdic acid, molybdenum naphthenate, and molybdenum dialkyl-p-phorodithioate. according to claim 1, wherein the combined partial pressure of water and carbon oxides is less than about 0.35 kg / cm2 absolute (34.48 kPa). 10. The method according to claim 1, wherein the water is substantially removed from the oil feed before the heating step.