Hydrotreating catalyst for removal of contaminants from hydroprocessing feeds

Abstract

A hydroprocessing catalyst is provided that is made with an organic acid, such as tartaric acid, that provides for an improved capacity for removal of silicon from hydrocarbon feeds. The catalyst has more available hydroxyl sites than catalysts made using other impregnation liquids besides tartaric acid.

Description

[0001]HYDROTREATING CATALYST FOR REMOVAL OF CONTAMINANTS FROM HYDROPROCESSING FEEDS Background Petroleum feeds need to be treated for the removal of impurities that tend to inactivate catalysts. In particular, it has been found that nickel and vanadium are poisons to the operation of catalysts. In addition, silicon is a frequently found catalyst poison in hydroprocessing units. Silicon species adsorb on the catalyst surface by forming a strong bond with the alumina (hydroxyl sites) on the catalyst. These bonds reduce the active sites which impacts the hydrotreating activity and leads to deactivation of the downstream catalysts. Summary It has been found that a hydroprocessing catalyst made by a process comprising impregnating a composition comprising about 1-20 wt% Group VIB metal oxide, 1-10 wt% Group VIIIB metal oxide, and 1-10 wt% a Group Va oxide with an impregnating solution containing at least one organic acid is effective in remove of silicon from hydrocarbon feeds. In particular, when the organic acid has at least two carboxylic groups, it is effective in removing silicon which is a catalyst poison. Tartaric acid is a preferred organic acid to be used in preparation of the catalysts. Detailed Description Specifically, it has been found that the use of certain organic acids during the impregnation of metals onto the catalyst support produces a catalyst more capable of removing silicon from petroleum feeds. In particular, it has been found that the use of tartaric acid (TA) during the metal (Ni and Mo) impregnation on the alumina support is advantageous in the removal of silicon. Citric acid (CA) and phosphorus can also be utilized. Phosphorous also adsorbs onto the hydroxyl sites on the alumina surface consuming sites that could be utilized for silicon adsorption. Organic acids such as citric acid and tartaric acid are assumed to be vaporized during either the catalyst finishing or sulfiding process, leaving hydroxyl sites available for silicon pickup. Based on this hypothesis, citric acid and tartaric acid were tried but only tartaric acid provided increased silicon pickup. It may be that tartaric acid evaporates “cleanly” while citric acid evaporates into carbon species that may have formed coke on the hydroxyl sites. This was corroborated by FTIR analysis of calcined forms using tartaric acid and citric acid versions. Oxide forms have similar hydroxyl population while after calcination tartaric acid provided higher hydroxyl sites than citric acid. CHN analysis shows calcined tartaric acid version has <0.05 wt% carbon (below the detection limit) while calcined citric acid version has 0.2 wt% carbon left on the catalyst. To dissolve metals in the impregnation solution, acids are required. Phosphoric acid can be utilized, which also improves hydrotreating activity. In the application of the catalyst as a silicon trap, hydroxyl sites need to be free for the pickup of silicon species. If the phosphorus impregnated catalyst with metal levels Ni / Mo 2.7 / 8 is considered as base case. Silicon pickup can be increased by either decreasing the metal and phosphorus levels or replacing phosphorus by organic acids as attenuation of hydroxyl sites decreases through these two pathways. The disadvantages of decreasing metal level are there is a debit on the hydrotreating activity, and the overall catalyst density decreases due to this improvement in Si pickup per volume basis as compared to base case is not much. Thus, using tartaric acid provides an alternate pathway to dissolve molybdenum in the impregnation solution and improves the silicon pickup both on weight and volume basis, since the same metal levels can be maintained. Note that a minimum phosphorus level is necessary to ensure molybdenum solubility. The catalyst sampled prepared through tartaric acid impregnation pathway shows a shoulder at ~996 cm-1in a Raman spectrum which is unique to the tartaric acid impregnation route and has not been observed for other samples. Origin of this peak may be due to the tartaric acid version catalyst having a better silicon pickup performance than the citric acid version. The catalyst has a Raman spectrum with a shoulder at ~996 cm-1. Raman spectra were collected on a Horiba LabRam HREvolution spectrometer in backscatter configuration equipped with a 532nm laser, 600 grooves / mm diffraction grating, 10x objective lens, and confocal microscope. Spectra were collected of multiple spots in the 100-1200 cm-1Raman shift range. To allow for quantitative analysis, ~0.5wt% of anatase titania was physically mixed with the samples to create an internal standard for spectral normalization. Spectra were collected using the Horiba software LabSpec 6. All data analysis, including averaging, smoothing, and normalization, were performed in OriginPro 2022. Preparation Process According to the Invention More precisely the subject of the invention is a process for the preparation of a catalyst from a catalytic precursor comprising a support based on alumina and / or silica-alumina and / or zeolite and comprising at least one element of group VIB and optionally at least one element of group VIII, said process comprising impregnation of said precursor with a solution of an organic acid such as tartaric acid, characterized in that it comprises the Impregnation of a dried, calcined or regenerated precursor with at least one solution containing at least one carboxylic acid, then maturing and drying at a temperature lower than 200° C., possibly followed by a heat treatment at a temperature lower than 350° C., preferably lower than 300° C., the catalytic precursor solution usually contains phosphorus. A method is provided of preparing a hydrotreating catalyst comprising 1-20 wt% and preferably 5-15 wt% of a Group VIB metal oxide, 1-10 wt%, preferably 1-5 wt% of a Group VIIIB metal oxide, 1-10 wt%, preferably 1-5 wt% of a Group Va oxide, where an impregnating solution is used which contains at least one organic acid that is generally a carboxylic acid comprising at least one carboxyl group and 1-20 carbon atoms (carbon atoms in the carboxyl group included). Other similar molecules besides organic acids may be used such as aldehydes and ketones, but they are much less preferable. Suitable organic acids include acetic acid, citric acid, malic acid, maleic acid, formic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyhexanoic acid, tartaric acid, glyceric acid, gluconic acid, oxalic acid, malonic acid, and ascorbic acid, etc. Within this group of acids, organic acids such as tartaric acid comprising at least two carboxylic groups are preferred. The preferred organic acids that burn off cleanly from the catalyst are preferred as this has been found to be enabling higher hydroxyl sites on catalyst surface leading to higher contaminant pickup. This is measured from the FTIR spectra of dried vs calcined sample where tartaric acid version retains higher hydroxyl sites than citric acid version. Hydroxyl groups are quantified based on integration of spectra in the region 3825-3200 cm-1. The FTIR spectra were collected on a Thermo Nicolet iS50 instrument. The powdered samples were pressed into 13 mm diameter self-supporting pellets of ~10 mg for transmission FTIR experiments. Spectra were collected using 512 scans, 2 cm-1resolution, moderate attenuation, in the 700-5000 cm-1range. All spectral analysis was carried out in GRAMS AI software. All FTIR spectra were normalized to the pellet weight, truncated, baseline corrected, then truncated to the hydroxyl region and baseline corrected again in the hydroxyl region. To obtain the available hydroxyl concentrations, the FTIR spectra were integrated in the hydroxyl region (3825-3200 cm-1). To calculate the hydroxyl content consumed by metals deposition in the finished catalyst, the FTIR spectrum of the finished catalyst was subtracted from the FTIR spectrum of the related base with no metals present. The subtracted FTIR spectrum was integrated in the hydroxyl region (3825-3200 cm-1). A preferred amount of organic acid is adjusted to solubilize metals in the impregnation solution, such as molar ratio organic acid / Group VIIIB metal oxide, is at least 0.5. The finished catalyst is obtained by drying the catalyst after metal impregnation. The drying temperature is selected to minimize organic acid decomposition. The silica species will be attracted to available hydroxyl sites on the alumina surface of the catalyst used in this disclosure. This invention involves using tartaric acid in the metal impregnation solution with tartaric acid / Ni molar ratio being 1. Metal impregnation was done through incipient wetness. With molybdenum source as molybdenum trioxide and nickel as nickel carbonate. Target metal content on the catalyst is Mo 8 wt% nickel 2.7 wt% and phosphorus 0.5 wt%. In terms of oxides: MoO3 12 wt% NiO 3.44 wt% and P2O51.14 wt%. To achieve this, impregnation solution was prepared by adding the desired amount of tartaric acid to deionized water followed by the addition of nickel carbonate. Then phosphoric acid (H3PO4) was added until all solids were dissolved in the solution. Solution temperature was raised to 85⁰C. After bubbling subsided, molybdenum trioxide was added. The slurry was mixed at 120 RPM until foaming subsided. The solution was further heated for 3 hours at 93⁰C. Table 1. The table shows the hydrotreating activity (hydrodenitrogenation (HDN) and hydrodesulfurization (HDS) and silicon pickup of different version of Si trap catalysts. The tartaric acid version shows higher Si pickup (on wt. and vol basis) while maintaining hydrotreating activity. Median Si pickup Si pickup (vol Surface Catalyst versionMetals (wt%)pore HDN HDS (wt% of fresh of fresh area a diameter RVAcRVAccatalyst catalyst loaded (m2 / g) (Å)bloaded basis)cbasis)cBase case Ni / Mo / P 2.7 / 8 / 2 200 89 100 100 9.2 58.0Low metal60% of base (Ni / Mo / P1.6 / 4.8 / 1.2) 214 87 79 95 10.3 57.1Tartaric Ni & Mo same as acidbase; P 0.5221 85 88 102 10.0 62.4a: From SURFACE AREA U964 b: From MERCURY POROSIMETRY U578 c: From pilot plant tests performed at 2000 psig, 3000 SCFB, 710⁰F. For HDN and HDS, LHSV is 3.8 hr-1. Si pickup is measured at LHSV 10-30 hr-1. Feed is VGO blended with silicon dopant. TGA-MS studies showed that samples that are impregnated using tartaric acid solution show only carbon dioxide and water being evolved during calcination. This contrasts to samples that are impregnated with citric acid showing some other species besides carbon dioxide and water being evolved. Analysis was done on a TA Discovery TGA with a MKS MS attached. Approximately 40mg of as received catalyst was used for analysis. The test method consisted of a temperature ramp of 50 °C / min to 400°C under a flow of 45 mL / min of 20% O2 / He. The surface area and median pore diameter analysis shown in the above table is for determining the surface area (SA), total pore volume (PV), average pore diameter (PD), and pore size distribution from 2 to approximately 60 nm (20 to 600 angstroms) of porous materials. The method describes the standard procedure for analysis, data collection and reporting using a commercially available instrument. Outline of Method: The sample is degassed using heat and vacuum. After weighing, it is cooled in liquid nitrogen. The amount of nitrogen gas adsorbed on the sample is measured at various predetermined pressures. The instrument computer processes the data and calculates surface area, total pore volume, average pore diameter, and pore size distribution based on the isotherm. The results are printed and / or plotted as desired.

Claims

Claims 1. A method of preparing a hydroprocessing catalyst comprising impregnating a composition comprising about 1-20 wt% Group VIB metal oxide, 1-10 wt% Group VIIIB metal oxide, and 1-10 wt% a Group Va oxide with an impregnating solution containing at least one organic acid.

2. The method of claim 1 wherein said organic acid is selected from the group consisting of acetic acid, citric acid, malic acid, maleic acid, formic acid, glycolic acid, hydroxypropionic acid, hydroxybutyric acid, hydroxyhexanoic acid, tartaric acid, glyceric acid, gluconic acid, oxalic acid, malonic acid, and ascorbic acid.

3. The method of claim 1 wherein said organic acid comprises at least two carboxylic groups.

4. The method of claim 1 wherein said organic acid is tartaric acid.

5. The method of claim 1 wherein said composition comprises 5-15 wt% Group VIB metal oxide.

6. The method of claim 1 wherein said composition comprises 1-5 wt% Group VIIIB metal oxide.

7. The method of claim 1 wherein said composition comprises 1-5 wt% Group Va oxide.

8. The method of claim 1 wherein said organic acid burns off cleanly from an impregnated catalyst.

9. The method of claim 1 wherein a molar ratio of said organic acid to said Group VIIIB metal oxide is at least about 0.

5.

10. The method of claim 1 wherein said hydroprocessing catalyst is dried after said impregnation at a temperature selected to minimize organic acid decomposition.

11. A process of removing silicon from a hydrocarbon composition comprising contacting said hydrocarbon composition with a hydroprocessing catalyst made by impregnating a composition comprising about 1-20 wt% Group VIB metal oxide, 1-10 wt% Group VIIIB metal oxide, and 1-10 wt% a Group Va oxide with an impregnating solution containing at least one organic acid followed by drying said hydroprocessing catalyst.

12. The process of claim 11 wherein said organic acid is tartaric acid.