BRPI0621540B1 - Process for reducing the total acid number (tan) of a liquid hydrocarbon feedstock - Google Patents

Description

Field of the Invention The present invention relates to a process for the reduction of the total acid number (TAN) of a hydrocarbonaceous feed filler (TAN) of a total hydrocarbon feedstock liquid, in particular crude oil.

Background of the Invention Crude oil and other liquid hydrocarbon streams with a large amount of acids are difficult to refine. Especially in the distillation unit of a crude oil refinery, a large amount of acids leads to corrosion problems. Acids are known to be removed by hydrotreating, that is, the same process in which other heteroatoms such as sulfur and nitrogen are removed from liquid hydrocarbon feedstocks. Hydrotreating, however, is a process that is performed downstream of the distillation unit in a refinery.

To avoid corrosion problems resulting from the acid content of the crude oil, different crude oil streams are typically mixed to obtain a crude oil feedstock with an acceptable amount of acids. The acid content of a crude oil or other hydrocarbonaceous liquids is generally expressed as the total acid number (TAN) of such a liquid. TAN represents milligrams of KOH per gram of liquid required to neutralize acid according to a procedure described in ASTMD664. There is a need in the art for a process that is capable of reducing the TAN of liquid hydrocarbon streams such as crude oil that are used as feedstock in refineries, with minimal conversion of sulfur and nitrogen containing compounds and unsaturated hydrocarbons. By such a process, an acceptable refinery feedstock would be obtained with minimal hydrogen consumption. SUMMARY OF THE INVENTION It has been found that catalysts which are essentially free of hydrogenating components that are typically used for hydroconversion reactions such as hydrodesulfurization, hydrodesionitrogen, and hydrocracking, i.e. metal compounds of any of Columns 5 to 10 of the Periodic Table. Elements may be used for the selective hydrogenation of acids in liquid hydrocarbon streams, in particular in crude oil.

Accordingly, the present invention provides a process for reducing the total acid number (TAN) of a liquid hydrocarbon feedstock, wherein the feedstock is contacted, in the presence of a hydrogen-containing gas and at a temperature in the range. from 200 to 400 ° C and at elevated pressure with a catalyst comprising a column 3 or 4 metal oxide from the Periodic Table of Elements or a lanthanide whose catalyst is essentially free of column 5 to 10 metals or compounds thereof to obtain a liquid hydrocarbon product with a reduced total acid number.

An advantage of the process according to the invention is that the total acid number of the feedstock is reduced by hydrogenation whereas other hydrogenation reactions such as hydrodesulphurization, hydrodesionitation and saturation of unsaturated hydrocarbons are minimized.

DETAILED DESCRIPTION OF THE INVENTION In the process according to the invention a liquid hydrocarbon feedstock is contacted in the presence of a hydrogen containing gas at a temperature in the range of from 200 to 400 ° C and at elevated pressure with a catalyst comprising an oxide of a column 3 or 4 metal or a lanthanide, the catalyst of which is essentially free of column 5 to 10 metals or compounds thereof. The feedstock may be any liquid hydrocarbon stream comprising carboxylic acids, that is, organic acids. The process is particularly suitable for feed loads comprising naphthenic acids. Preferably, the feedstock is a crude oil, a distillate stream such as naphtha or diesel, a residual fraction from an atmospheric distillation of crude oil or a distilled hydrocarbonaceous product that does not meet TAN product specifications such as heating oil. The process according to the invention is particularly suitable for reducing the total acid number of the crude oil. The hydrogen containing gas is preferably hydrogen or synthesis gas. The use of synthesis gas as hydrogen-containing gas is particularly advantageous in a situation where hydrogen gas is not available, for example, in remote locations such as offshore platforms. The temperature and pressure at which the feedstock is in contact with the catalyst is such that hydrogenation of the carboxylic acids, i.e. at least 200 ° C, occurs. The temperature is below the temperature at which thermal decomposition of carboxylic acids occurs, ie below 400 ° C. Preferably, the temperature is in the range of from 250 to 390 ° C, more preferably from 300 to 380 ° C. The process is carried out at a high pressure, ie above atmospheric pressure. Preferably, the pressure is in the range of from 2 to 200 bar gauge, more preferably from 10 to 150 bar gauge, even more preferably from 25 to 120 bar gauge. The catalyst comprises a metal oxide from Column 3 or 4 of the Periodic Table of Elements (most recent IUPAC notation) or a lanthanide. The oxide may also be a mixed oxide of two or more such metals. The catalyst may also comprise a mixture of two or more such oxides. The catalyst is essentially free of metals from Columns 5 to 10 of the Periodic Table of Elements (most recent IUPAC notation) or compounds thereof. Reference in this case to a catalyst essentially free of certain compounds is to a catalyst that is free of such compounds except for minimal amounts, typically in the range of ppm or less, which may be present as unintended contaminants or as remnants of a process. ore refining to obtain Column 3 or 4 metal oxide or lanthanide.

Preferably, the catalyst comprises a column 4 metal oxide or a lanthanide. Preferred metal oxides from Group 4 metal are titanium oxide and zirconium oxide, a preferred oxide of a lanthanide is ceria. More preferably, the catalyst consists of titanium oxide and / or zirconium oxide, most preferably the same as zirconium oxide. The catalyst may be prepared by any preparation method known in the art. Preferably, the catalyst is prepared such that its specific surface area is at least 10 m / g, more preferably at least 30 m / g. The feedstock for the process according to the invention preferably has a total acid number of at least 0.2 mg KOH / g feedstock, preferably at least 0.5 mg KOH / g feed loading, more preferably at least 1.0 mg KOH / g feed loading. The reference in this case to the total acid number is the amount of KOH (in mg) per gram of feedstock as determined by ASTM D664. The liquid hydrocarbonaceous product preferably has a TAN of at most 0.2 mg KOH / g feed rate, more preferably at most 0.1 mg KOH / g feed rate, most preferably at most 0.05 mg KOH / g feed rate. The TAN is preferably reduced to such an extent that the liquid hydrocarbon product with a reduced total acid number has a maximum of 50% of the feedstock TAN, more preferably a maximum of 30%.

Example Hydrogenation Process In a Microflow reactor, crude oil was contacted with an inert solid material (0.1mm silicon carbide particles) or one of the catalysts described below (catalyst particles diluted with silicon carbide particles). : 1/1 volume / volume) in the presence of a gas containing hydrogen or nitrogen for at least 100 hours. Two different crude oils were used. For experiments 1 to 8 and 13 to 16, a West African crude oil (crude 1) was used; For experiments 9 to 12, a crude oil from the Middle East (crude 2) was used. The specifications of both crude oils are given in table 1. The exact conditions for each experiment are given in table 2. The total acid number (TAN) of the liquid effluent from each experiment was determined according to ASTM D664. The hydrogen sulfide concentration in the vapor effluent was determined by gas chromatography. The TAN of the liquid effluent and the hydrogen sulfide concentration in the vapor phase effluent are also presented in table 2.

Experiments 3, 4, 6, 7, 9, 10, 12 and 14 to 16 are experiments according to the invention. Experiments 1,2, 5, 8, 11 and 13 are comparison experiments.

Catalysts The following catalysts were used in the hydrogenation experiments.

Titania Catalyst 1 A titania catalyst named titania 1 was prepared as follows. An amount of 3192 grams of titania powder (P25 from Degussa; ignition loss: 4.4 wt% at 540 ° C) was mixed with 100 grams of dihydrated oxalic acid in a mixing mill kneader (Simpson). After 4 minutes of milling the mixture, 981 grams of deionized water and 100 grams of polyethylene glycol were added and the milling of the mixture continued for a further 12 minutes. Then 100 grams of methyl cellulose was added and the milling of the mixture continued for a further 20 minutes. The mixture thus formed was extruded molded through a 1.7 mm diameter trilobulated shape matrix plate. The three lobes were dried for 2 hours at 120 ° C and calcined for 2 hours at 500 ° C.

The resulting titania trilobules have a surface area of 52 m2 / g as measured by nitrogen adsorption (BET method) and a pore volume of 0.31 ml / g as measured by mercury introduction. Titania Catalyst 2 Titanium particles commercially available as X096 (from CRI Catalyst Company) were used as a titania catalyst (also known as titania 2). These titania particles have a surface area of 120 m2 / g as measured by nitrogen adsorption (BET method) and a pore volume of 0.32 ml / g as measured by mercury introduction.

Zirconia Catalyst A zirconia catalyst was prepared as follows. An amount of 264 grams of zirconia powder (RC100 from Daiichi; ignition loss: 5.3 wt.% At 540 ° C) was mixed with 90 grams of a 5 wt.% Solution of polyvinyl alcohol in deionized water. in a kneader (Wemer & Pfeider Sigma LUK 0.75 kneader). After 7 minutes of kneading action, 2.5 grams of a cationic amide polyacryl (Superfloc from Cytec) were added and after being kneaded for 20 minutes, 8 grams of deionized water was added. The mixture was kneaded for a further 22 minutes. The mixture thus formed was extruded into 1.7 mm diameter trilobules. The extrudates were dried for 2 hours at 120 ° C and calcined for 2 hours at 550 ° C.

The resulting zirconia trilobules have a surface area of 54 m2 / g as measured by nitrogen adsorption (BET method) and a pore volume of 0.35 ml / g as measured by mercury introduction.

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Claims (10)

Process for reducing the total acid number (TAN) of a liquid hydrocarbon feedstock, characterized in that the feedstock is contacted in the presence of a hydrogen-containing gas and at a temperature in the range of from 200 at 400 ° C and at elevated pressure with a catalyst comprising a metal oxide of a Column 3 or 4 of the Periodic Table of Elements or a lanthanide whose catalyst is essentially free of column 5 to 10 metals or compounds thereof , to obtain a liquid hydrocarbon product with a reduced total acid number. Process according to Claim 1, characterized in that the oxide is a column 4 metal oxide or a lanthanide, preferably titanium oxide or zirconium oxide, more preferably zirconium oxide. Process according to Claim 2, characterized in that the catalyst consists essentially of titanium oxide and / or zirconium oxide. Process according to any one of the preceding claims, characterized in that the pressure is in the range from 2 to 200 bar gauge, preferably from 10 to 150 bar gauge, more preferably 25 to 120 bar gauge. Process according to any one of the preceding claims, characterized in that the temperature is in the range from 250 to 390 ° C, preferably from 300 to 380 ° C. Process according to any one of the preceding claims, characterized in that the hydrogen-containing gas is synthesis gas or hydrogen. Process according to any one of the preceding claims, characterized in that the feedstock has a TAN of at least 0.2 mg KOH / g feedstock, preferably at least 0.5 mg KOH. / g feedstock, preferably at least 1.00 mg KOH / g feedload. Process according to any one of the preceding claims, characterized in that the liquid hydrocarbonaceous product has a TAN of at most 0.2 mg KOH / g feedstock, preferably at most 0.1 mg KOH. / g feed load, more preferably at most 0.05 mg KOH / g feed load. Process according to any one of the preceding claims, characterized in that the liquid hydrocarbon product with a reduced total acid number has a TAN of at most 50% of the TAN of the crude oil product, preferably at most 30%. . Process according to any one of the preceding claims, characterized in that the liquid hydrocarbon feedstock is crude oil.