Purification process

Abstract

A process is described for removing halogen compounds, particularly chlorine compounds, from a contaminated liquid hydrocarbon cut from a refinery, comprising the steps of (i) passing the contaminated liquid hydrocarbon over a first sorbent to remove organic halide compounds therefrom, and then (ii) optionally passing the contaminated liquid hydrocarbon over a second sorbent to remove hydrogen halide, wherein the contaminated liquid hydrocarbon at least during the step (i) is at a temperature of 150°C or higher.

Description

[0001] P102515

[0002] 1

[0003] Purification process

[0004] This invention relates to purification processes and in particular to the removal of halogen compounds, particularly chlorine compounds, from liquid hydrocarbons.

[0005] 5

[0006] Halogen compounds such as hydrogen chloride and organic chloride compounds may be present as contaminants in various process fluids, but are a particular problem in processing hydrocarbon-containing gases and liquids, where they can cause corrosive damage to equipment and poison catalysts used in hydrocarbon processing. Typically it is desired to have a process fluid containing less than about 2 ppm, and preferably less than about 0.1 ppm, by volume of such contaminants.

[0007] WO2013045883 (A1) describes a process for removing halogen compounds from a process fluid, comprising the steps of (i) passing a process fluid containing hydrogen halide over a first

[0008] 15 sorbent to remove hydrogen halide and generate a hydrogen halide depleted process fluid and then, (ii) passing the hydrogen halide depleted process fluid over a second sorbent to remove organic halide compounds therefrom.

[0009] The conventionally, such processes are operated at temperatures below 100°C so that

[0010] 20 desorption of the halogen compounds from the sorbents is minimised. The Applicants have found surprisingly that at elevated temperatures the removal of organo-halogen compounds from liquid hydrocarbons is enhanced.

[0011] Accordingly, the invention provides a process for removing halogen compounds from a contaminated liquid hydrocarbon cut from a refinery, comprising the steps of (i) passing the contaminated liquid hydrocarbon over a first sorbent to remove organic halide compounds therefrom, and then (ii) optionally passing the contaminated liquid hydrocarbon over a second sorbent to remove hydrogen halide, wherein the contaminated liquid hydrocarbon at least during the step (i) is at a temperature of 150°C or higher.

[0012] By “sorbent” we hereby include adsorbent and absorbent.

[0013] The contaminated liquid hydrocarbon is a liquid hydrocarbon cut from a refinery. Such liquid hydrocarbon streams may comprise primarily C5, or C6, or C7 or preferably C8 hydrocarbons. In a particularly preferred arrangement, the contaminated liquid hydrocarbon is a reformate recovered from a reforming unit in a refinery, which comprises one or more C8 hydrocarbons.

[0014] 30 The reformate may be treated before or after distillation to stabilise the reformate.

[0015] The present invention has been found to be of particular use in treating unstabilised reformates, i.e. reformate recovered from a catalytic reforming unit in a refinery prior to P102515

[0016] 2 distillation to remove light components, because the contaminated liquid hydrocarbon may usefully be heated using distillation preheat to achieve temperature. Such treatment also removes a need to have additional hydrogen halide sorbent beds.

[0017] The halogen compounds are typically bromine compounds and / or chlorine compounds but more commonly are chlorine compounds. Thus by “organic halide compounds” we include in particular haloalkanes such as chloromethanes, chloroethanes, chloropropanes and

[0018] 5 chlorobutanes, as well as other longer chain chloroalkanes

[0019] The amount of halogen compounds may be in the range 0.1-20 ppm (vol).

[0020] In the present invention, without upstream treatment to remove halide compounds, the contaminated liquid hydrocarbon is passed over a first sorbent to remove organic halide compounds therefrom, wherein the contaminated liquid hydrocarbon at least during this step is at a temperature of 150°C or higher.

[0021] The first sorbent may comprise an alkalised alumina or an alkalised zinc-alumina or a zeolite,

[0022] 15 preferably zeolite Y or zeolite 13X.

[0023] In a first preferred arrangement, the first sorbent comprises an alkalised zinc-alumina composition. More preferably, the first sorbent is made from a mixture of hydrated alumina, sodium bicarbonate, zinc oxide or basic zinc carbonate, and a clay binder in which the alkali

[0024] 20 metal to zinc atomic ratio is above 0.8. It is especially preferred that the alkali metal to zinc atomic ratio is in the range from about 0.8 to 2.2. Particularly preferred first sorbent is produced by granulating ZnO, NaHCOs, and alumina trihydrate powders with a clay binder. The granulated material is preferably calcined to convert the carbonate to oxide. Such sorbents are described in in WO 99 / 39819 (A1).

[0025] 25

[0026] In another preferred arrangement, the first sorbent comprises zeolite 13X. Such materials are commercially available,

[0027] In another preferred arrangement, the first sorbent comprises a coated transition alumina extrudate, wherein the coating is selected from sodium oxide or potassium oxide.

[0028] The second sorbent, where used, may be any suitable hydrogen halide sorbent. The second sorbent may comprise a carbon, an alumina, or an alkalised metal oxide such as alkalised alumina, alkalised silica and alkalised aluminosilicate, preferably an alkalised alumina or an

[0029] 35 alkalised zinc-alumina. Preferred second sorbent materials include alkalised alumina and zin- P102515

[0030] 3 alumina materials. Most preferably, the second sorbent comprises an alkalised alumina, for example as described in EP1053053 A1 ,

[0031] The second sorbent may be the same or different from the first sorbent.

[0032] 5

[0033] The first and second sorbents preferably have an average particle size in the range 1-10 mm, and preferably 1-5 mm, in order to obtain the optimum balance of surface area versus pressure drop.

[0034] A preferred purification system comprises a first sorbent comprising an alkalised alumina or alkalised zinc alumina sorbent in the form of granules, and / or a zeolite granule or extrudate, especially comprising zeolite 13X, or a coated transition alumina extrudate, wherein the coating is selected from sodium oxide or potassium oxide. The second sorbent, where used, comprises an alkalised alumina or alkalised zinc alumina sorbent in the form of granules.

[0035] 15

[0036] According to one embodiment of the process, a process fluid containing one or more organic halide compounds is passed through a fixed bed of a particulate first sorbent disposed in a vessel, producing an organic halide depleted process fluid. The organic halide depleted process fluid recovered from the first sorbent is then passed through the second sorbent bed,

[0037] 20 which may be in the same vessel or a different vessel, that adsorbs the hydrogen halide compounds.

[0038] In addition to removing hydrogen halide compounds, the second sorbent may also remove organo-halide compounds that slip through the first sorbent or are formed on the surface of

[0039] 25 the first sorbent.

[0040] The contaminated liquid hydrocarbon, at least when it is contacted with the first sorbent is at a temperature of 150°C or higher, preferably 160°C or higher. The maximum temperature is preferably below 260 °C or more-preferably 220°C. A particularly preferred operating temperature range is in the range 180-200 °C. The temperature over the second sorbent may be the same or different, but is preferably the same or lower than in the first step. The pressure may be in the range 1 to 100 bar abs, preferably 1 to 40 bar abs.

[0041] The invention will now be further described by reference to the following examples.

[0042] 35

[0043] Example 1

[0044] Two sorbent materials were tested to determine their effectiveness for organochloride compound removal at elevated temperature. Sorbent 1 was PURASPEC™2255, a granulated hydrogen chloride sorbent material comprising alkalised zinc and alumina as described in P102515

[0045] WO99 / 39819 A1 . It is commercially available from Johnson Matthey. Sorbent 2 was a zeolite molecular sieve product, 13X supplied by ETIC.

[0046] The organochloride removal performance of Sorbent 1 and Sorbent 2 was tested on a fixed

[0047] 5 bed reactor using the following conditions:

[0048] A 50ml bed of the sorbent was charged to a reactor of 150mm diameter.

[0049] A pressure of 15barg N2 was applied to the reactor which was then heated to the desired test temperature (see table).

[0050] A liquid feed of iso-octane containing the following organochlorides, each at 56ppm (as Cl) was fed through the sorbent bed at a flow rate of 200ml / h.

[0051] • 1 -chlorobutane

[0052] • 1 -chloropentane

[0053] • 1 ,5-dichloropentane

[0054] • Chlorocyclopentane

[0055] 15 • 2-chloropentane

[0056] • 1 -chlorooctane

[0057] • 2-chloroethylbenzene

[0058] • 1 -chlorodecane

[0059] • 1-chloro-4-phenylbutane

[0060] • 1- / 2-chloronaphthalene

[0061] The liquid exiting the reactor was routinely analysed, using a GC-XSD analyser. The total chloride exiting the reactor for each test is shown in the following tables.

[0062] The length of the test varied depending on how quickly chloride was observed in the exit liquid.

[0063] 25 Comparative Example - Sorbent 1 , 69°C test

[0064] Comparative Example - Sorbent 1 , 128°C test

[0065] Example 1 (a) Sorbent 1 , 189°C test P102515

[0066] 5

[0067] Example 1 (b) Sorbent 1 , 220°C test

[0068] Example 1 (c) - Sorbent 1 , 250°C test

[0069] Comparative Example - Sorbent 2, 69°C test

[0070] Comparative Example - Sorbent 2, 128°C test P102515

[0071] 6

[0072] Example 1 (d) - Sorbent 2, 189°C test

[0073] Example 1 (e) - Sorbent 2, 220°C test

[0074] Example 1 (f) - Sorbent 2, 250°C test

[0075] It was found that for both Sorbent 1 and Sorbent 2 increasing the temperature resulted in increased overall organochloride removal. At 220-250°C, Sorbent 1 was found to outperform

[0076] 10 Sorbent 2 for organochloride removal. At 189°C, Sorbent 1 and Sorbent 2 achieved equal levels of organochloride removal.

Claims

P1025157Claims.1 . A process for removing halogen compounds from a contaminated liquid hydrocarbon cut from a refinery, comprising the steps of (i) passing the contaminated liquid hydrocarbon over a first sorbent to remove organic halide compounds therefrom, and then (ii) optionally passing the contaminated liquid hydrocarbon over a second sorbent to remove hydrogen halide, wherein the contaminated liquid hydrocarbon at least during the step (i) is at a temperature of 150°C or higher.

2. A process according to claim 1 , wherein the contaminated liquid hydrocarbon comprises primarily C5, or C6, or C7 or preferably C8 hydrocarbons.

3. A process according to claim 1 or claim 2, wherein the contaminated liquid hydrocarbon is a reformate recovered from a catalytic reforming unit in a refinery, preferably an unstabilised reformate.

4. A process according to any one of claims 1 to 3, wherein the halogen compounds are bromine compounds or chlorine compounds, preferably chlorine compounds.

5. A process according to any one of claims 1 to 4, wherein the halide content of the contaminated liquid hydrocarbon is in the range 0.1-20 ppm (vol).

6. A process according to any one of claims 1 to 5, wherein the first sorbent comprises an alkalised alumina or an alkalised zinc-alumina or a zeolite, preferably zeolite Y or zeolite 13X.

7. A process according to any one of claims 1 to 5, wherein the second sorbent comprises a carbon, an alumina, or an alkalised metal oxide such as alkalised alumina, alkalised silica and alkalised aluminosilicate, preferably an alkalised alumina or an alkalised zinc-alumina.

8. A process according to any one of claims 1 to 7, operated at least during step (i) at a temperature in the range 160 to 260°C, preferably 180 to 200°C.

9. A process according to any one of claims 1 to 8, operated at a pressure in the range 1 to 100 bar abs, preferably 1 to 40 bar abs.

10. A process according to any one of claims 1 to 9 wherein the first and second sorbents are placed in the same vessel.P102515811. A process according to any one of claims 1 to 10, wherein the contaminated liquid hydrocarbon is heated upstream of the second sorbent in heat exchange with a distillation product in a refinery.

Images