METHOD FOR REGENERATING A CATALYST FOR PROCESSING REACTIVE FEEDSTOCK

Abstract

A process for regeneration of a process enclosure and a catalyst comprising precipitated ammonium salts, and a process and a process plant for continuous hydrotreating a feedstock comprising nitrogen and halides.

Claims

1. A process for regeneration of a process enclosure in which precipitation of ammonium salts has occurred on a catalyst, comprising the steps of directing a flow of a flushing stream comprising a flushing gas at a pressure from 0.5 MPag to 25 MPag, at a regeneration temperature above a sublimation temperature and below an activation temperature for stripping deposited carbon and hydrocarbons, to provide a flow of enriched gas and after the regeneration, the process enclosure comprising a reduced amount of ammonium salts, wherein precipitation of ammonium salts has occurred on the catalyst to an extent such that a continuous volume of at least 1 liter of catalyst is found inside the process enclosure which contains at least 10 wt % ammonium salts.

2. A process according to claim 1 in which the process of regeneration is carried out for a period of at least 100 hours.

3. A process according to claim 1, wherein said regeneration temperature is above 150 C.

4. A process according to claim 1, wherein said regeneration temperature is below 320 C.

5. A process according to claim 1, wherein said regeneration temperature is maintained below 210 C., for an initial period of mild regeneration before increasing the regeneration temperature.

6. A process according to claim 1, wherein a control system is configured to control one or more of the flow of the flushing stream and the regeneration temperature in dependence of a rate of release of ammonium salts, to keep the concentration in the enriched gas below a defined limit.

7. A process according to claim 1, wherein the enriched gas, optionally after combination with other gases is directed to contact an aqueous liquid, for transferring water soluble compounds to the aqueous liquid.

8. A process according to claim 6, wherein the regeneration rate is monitored by one or more of the following, analysis of gas composition of the flushing gas and the enriched gas or analysis of the composition of the aqueous liquid.

9. A process according to claim 1, wherein the flushing gas comprises at least 70 vol % hydrogen and optionally at least 10 ppm.sub.vol such as 50 ppm.sub.vol sulfide.

10. A process for hydrotreating a liquid oil stream comprising a reactive feedstock involving at least two reactors; wherein the liquid oil stream comprises at least 1 ppm wt halides in combination and at least 1 ppm wt N; the process comprising: (i) directing said stream comprising a reactive feedstock and a first hydrogen rich gas to a stabilization hydrotreatment step comprising hydrotreating the liquid oil stream, having a liquid oil flow rate, in a fixed bed reactor at a stabilization temperature of less than 250 C., wherein the fixed bed reactor comprises a hydrotreatment catalyst and said step providing a hydrotreated multiphase stream; and (ii) in an in-situ catalyst regeneration step comprising flushing the hydrotreatment catalyst at a regeneration temperature at or above said stabilization temperature and below a maximum regeneration temperature with a flushing gas having a flushing gas flow rate, providing an enriched gas, wherein the ratio of flushing gas flow rate to liquid oil flow rate is at least 0.5 Nm.sup.3/m.sup.3 and less than 5000 Nm.sup.3/m.sup.3.

11. A process according to claim 10 wherein said hydrotreatment step (i) is carried out in a first reactor and said in-situ catalyst regeneration step (ii) is carried out in a second reactor, and the hydrotreated two-phase stream is optionally in combination with said enriched gas separated in an off-gas gas stream and a liquid hydrotreated product, and said off-gas gas stream and said enriched gas are directed to be combined with an aqueous stream to provide a contaminated aqueous stream and a purified off-gas, and wherein the process configuration may be reconfigured such that step (i) is carried out in the second reactor and step (ii) is carried out in the first reactor.

12. A process according to claim 11, wherein at least an amount of the off-gas stream is comprised in said flushing gas.

13. A process according to claim 12, wherein said contaminated aqueous stream contains less than 5000 ppm.sub.wt halides.

14. A process according to claim 10, wherein an amount of said purified off-gas is comprised in said hydrogen rich gas.

15. A process plant comprising two reactors, and means of flow control, configured for enabling a process according to claim 10.

16. A process according to claim 5, wherein said initial period of mild regeneration has a duration of at least 5 hr.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0133] Embodiments of the present invention are explained by way of examples and with reference to the accompanying drawings. The appended drawings illustrate only examples of embodiments of the present invention, and they are therefore not to be considered limiting of its scope, as the invention may admit to other alternative embodiments.

[0134] FIG. 1. shows a process layout according to the present invention.

[0135] FIG. 2. shows the reactor loading scheme employed in Example 1.

[0136] FIG. 1 shows a process layout according to the present disclosure. In this Figure, heat exchangers (HX), coolers (COOL), pumps (PUMP), compressors (CMP) and separators (SEP) are designated by their label but only singled out when relevant. In FIG. 1 which water is separated from a reactive feedstock (100) in a feed separator and heated before being combined with an amount of hydrogen rich gas (102) and directed as feed stream (104) to a stabilization section (STAB) comprising a first stabilizer (STA), with related valves (VAF, VAG) and a similar second stabilizer (STB) and valves (VBF, VBG). The stabilization section is configured for having one stabilizer operating in a stabilization hydrotreatment mode while the other may operate in a regeneration mode. When the first stabilizer (STA) operates in stabilization hydrotreatment mode, feed valve A (VAF) is open, while gas valve A (VAG) is closed. At the same time, the second stabilizer (STB) operates in regeneration mode, with feed valve B (VBF) closed and gas valve B (VBG) open. Thereby the feed stream (104) is directed to stabilizer A in a first inlet line (108A), while a flushing gas stream (106) is directed to stabilizer B in a second inlet line (108B). The outlet stream (110A) from the first stabilization reactor (STA) is a two-phase stream comprising stabilized liquid and gases. The outlet stream (110B) from the second stabilization reactor (STB) may be a gas stream comprising the flushing gas and flushed ammonium halides, or alternatively a two-phase stream, if the system was configured for the flushing stream to comprise liquid, which may be beneficial for the stability of the catalyst. The two outlet streams and an amount of recycled product stream (112) are combined to a single stream (114) which is heated by process heat and directed to a guard reactor (GRD) in which metals and other heteroatoms forming solids compounds are removed, forming a purified hydrocarbon stream (116) which is directed to a hydrotreatment reactor (HDT) to provide a two-phase hydrocarbon rich stream (120).

[0137] The two-phase hydrocarbon rich stream (120) is separated into a gas phase product stream (124) and a first liquid product stream (122) of which an amount may be directed as recycled product stream (112). The gas phase product stream (124) is combined with an amount of wash water (126) in a water injector. This stream is cooled, such that the effluent stream may be separated in three phases, light product (132), sour water (133) and hydrogen rich gas (130) from which liquid is removed in a knock-out drum (DRUM). An amount of the first liquid product stream (134) and the light product (132) are combined and directed as a stripper feed (136) to a product stripper (STRP), which receives a stripping medium (138), commonly hydrogen. Water (142) is withdrawn from the stripped product (144). The stripper overhead (145) is washed with water, cooled and separated in sour water (151) and reflux (148).

[0138] The process gas loop as illustrated, involves directing make up hydrogen gas (152) to be combined with the hydrogen rich washed gas (154) and directed as recycle gas (156) which is split in the flushing gas (158) and the hydrogen rich recycle gas (102). To maintain catalyst activity, a sulfiding stream (152) is added to the flushing, unless the feedstock or recycle gas contains sufficient amounts of sulfur for maintaining sulfidation. This may be dimethyl disulfide or another sulfide containing stream.

[0139] The temperature of the warm flushing gas (158) controls the rate of sublimation in the stabilization reactor being regenerated. The temperature of this stream and the stream to stabilization hydrotreatment (104) is in this embodiment controlled by the heat integration considering temperatures and flows of the recycle gas (156), hot liquid recycle (112), hydrogen rich gas (102), feedstock (100) in connection with a steam circuit controlled by valve (V1) and involving boiler feed water (160), steam (162) and added hot high pressure steam (164), but other heat integration schemes may also be designed.

EXAMPLES

[0140] The invention will now be described with reference to the following non-limiting examples.

[0141] The following example illustrates the ability of thermal stripping of ammonium salts, by a simulation of rapid regeneration of catalysts containing a moderate amount of ammonium chloride.

[0142] The precipitation and sublimation of ammonium salts is described by the following reversible reaction (only the reaction for NH.sub.4Cl is shown)

##STR00001##

[0143] The equilibrium is governed by a equilibrium constant Kp, defined as:

[00001]$Kp=P_{{\mathrm{NH}}_3}*P_{\mathrm{HCl}}$

where P.sub.NH.sub.3 is the partial pressure of NH3 and P.sub.HCl is the partial pressure of HCl. Kp is dependent on temperature. The relation between Kp and temperature can be found in API Recommended Practice 932-B, Third Edition, June 2019. Kp is large at high temperature. Kp defines a maximum product of P.sub.NH3 With P.sub.HCl (P.sub.NH3*P.sub.HCl) in the gas phase at a given temperature. If the product of partial pressures of NH.sub.3 and HCl is at maximum, we consider the gas saturated.

[0144] The regeneration rates of solid ammonium chloride from a catalyst via sublimation were tested using NH.sub.4Cl-loaded 1/20 trilobe alumina-based catalyst support extrudates (surface area: 240 m.sup.2/g, pore volume: 1.0 ml/g). The NH.sub.4Cl-loaded extrudates were prepared with NH.sub.4Cl loadings of ca. 9 wt % and a NH4+:Cl.sup. molar ratio of 1.04-1.11 as measured by ion chromatography for NH.sub.4.sup.+ (ASTM D6919) and Cl.sup. (ASTM D4327)

[0145] Baseline experiments accounting for effects of the loading and unloading procedure of the NH.sub.4Cl-loaded extrudates in and out of the reactor, and any fast initial phenomena, were carried out under experimental conditions where 2.5% of the initial NH.sub.4Cl could be removed on the basis of a NH.sub.3 and HCl-saturated reactor exit gas from NH.sub.4Cl(s) decomposition. The baseline experiments were carried out in H.sub.2, and in H.sub.2+oil (hydrodesulfurized heavy naphtha, petroleum, white spirit type 1), at temperatures of 200 C. and 5 MPag for a duration of 3 hrs, 250 C. and 5 MPag for a duration of 2 hrs, and 300 C. and 16 MPag for a duration of 0.5 hrs. This resulted in NH4.sup.+ mass balances (after/before) of 0.79 (within 4%) and Cl.sup. mass balance of 0.95 (within 5%), and resulting NH.sub.4.sup.+:Cl.sup. molar ratios of 0.93 (within 6%). The fast initial step of some NH.sub.3-loss from the NH.sub.4Cl-loaded extrudates is assigned to a combination of desorption of superfluous NH.sub.3 from the sample preparation (NH.sub.4.sup.+:Cl.sup. molar ratio of 1.04-1.11) and a fast partial NH.sub.4Cl decomposition step to form chlorine chemical bonds with the alumina surfaces and a resulting NH.sub.3 desorption at 200-300 C. The latter is well-known and is evident in Example 1 on the basis of the NH.sub.4.sup.+:Cl.sup. molar ratios (<<1) after that test.

[0146] These experiments were carried out with a gas flow of 42.4 Nl/hr over 3 beds of catalyst support comprising NH.sub.4Cl having a total volume of 120 ml, resulting in a GHSV of 353 Nm.sup.3m.sup.3hr.sup.1 for all three beds to be regenerated.

[0147] Experiments designed to remove significant amounts of NH.sub.4Cl in a matter of a few days were also carried out, and the results are provided below. For this example, the reactor loading scheme is shown in FIG. 2 was employed, wherein the reference numerals for the reactor layers are as follows. [0148] 1. 3 mm acid-washed glass beads [0149] 2. Glass wool wad [0150] 3. NH.sub.4Cl-loadedi alumina-based support [0151] 4. Glass wool wad [0152] 5. NH.sub.4Cl-loaded alumina-based support [0153] 6. Glass wool wad [0154] 7. NH.sub.4Cl-loaded alumina-based support [0155] 8. Glass wool wad [0156] 9. Alumina-based support [0157] 10. Glass wool wad [0158] 11. Alkali-loaded alumina

Example 1

[0159] Flow: H.sub.2 42.4 Nl/hr, GHSV 353 Nm.sup.3m.sup.3hr.sup.1, Pressure: 5 MPag, Temperature: 250 C., Duration: 30 hrs

TABLE-US-00001 Final Initial Initial Final Final NH4/Cl Layer NH4+/g Cl/g NH4+/g Cl/g molar ratio 3 0.55 1.04 0.10 0.50 0.37 5 0.55 1.04 0.15 0.60 0.42 7 0.55 1.04 0.21 0.73 0.45 9 0.00 0.00 0.08 0.33 0.39 11 0.00 0.00 0.07 0.42 0.09 2 + 4 + 6 0.00 0.00 0.00 0.05 0.02 8 + 10 0.00 0.00 0.03 0.18 0.32 Reactor exit 0.00 0.00 0.07 0.15 0.96 Mass balance 0.44 0.95

[0160] As can be seen, salt removal from the reactor bed was observed upon treatment with the hydrogen gas stream at the temperatures, pressures and times used.

[0161] Various modifications and variations of the present invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in chemistry, chemical engineering or related fields are intended to be within the scope of the following claims.