JPH07103377B2 - Method for removing mercury in liquid hydrocarbons - Google Patents

Description

Detailed Description of the Invention a. Purpose of the invention Industrial field Liquid hydrocarbons such as NGL (Natural Gas Condensate) recovered from natural gas, depending on the origin, may be several tens to several hundreds μ
It contains mercury up to g / l. When NGL is used as a chemical raw material, for example, as an ethylene raw material, corrosion of the heat exchanger in the cryogenic separation process and deterioration of the catalyst in the process of hydrogenating acetylene, diene, etc. pose problems.

For removing mercury in gaseous hydrocarbons such as natural gas,
Sulfur-supporting activated carbon was already used, but there is no industrialized process for liquid hydrocarbons.

2. Description of the Related Art The present inventors have characterized in that a liquid or gas containing mercury is brought into contact with an adsorbent containing a sulfide of one or more metals selected from the group consisting of molybdenum, tungsten and vanadium. Method for removing mercury as
-2873) was proposed. However, NGL contains mercury compounds such as ionic mercury and organic mercury that can be extracted with hydrochloric acid in addition to elemental mercury. As described above, the adsorbent composed of heavy metal sulfide is effective in removing elemental mercury, but not so effective in removing mercury compounds.

In order to remove ionic mercury and high molecular weight organic mercury, it is also effective to use a method of contacting with an aqueous solution such as sodium sulfide or sodium polysulfide to absorb it, but it is possible to avoid complication in the process. Absent.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention An object of the present invention is to provide a method for removing various forms of mercury in a liquid hydrocarbon by a simple operation.

B. Structure of the invention Means for solving the problem The method for removing mercury in a liquid hydrocarbon according to the present invention is a step of heating a liquid hydrocarbon containing mercury to 200 ° C. or higher, and heating the liquid hydrogen oxide to 200 ° C. or lower. And a step of contacting with an adsorbent containing a sulfide of molybdenum.

The heat treatment temperature may be 200 ° C. or higher. Below 200 ° C, the conversion of mercury compounds to elemental mercury is insufficient. Note that the heat treatment may be performed while also performing distillation for cutting heavy components, or simply by applying heat, but since there are cases where solid components are also contained in NGL, these may be adsorbed in an adsorption column. Distillation is preferable in that it cannot be put in

Naturally, the upper limit of the heat treatment temperature should be lower than the decomposition temperature of the target hydrocarbon, and the upper limit is around 370 ° C.

By heat treatment, ionic mercury and high-molecular-weight organic mercury are all converted to elemental mercury, so the mercury level can be reduced to less than 10 μg / l using the adsorbent alone.

Examples of the adsorbent include those containing a sulfide of molybdenum, or those containing a carrier such as silica, alumina, silica-alumina, zeolite, ceramic, glass, resin or activated carbon.

In the case of supporting on a carrier, the amount of metal supported on the adsorbent is sulfide, so 1 to 20 wt% of metal is suitable. Moreover, it does not matter even if other metal components or inorganic components are included.

It preferred because the carrier has a direction of having a large specific surface area the better the contact efficiency, 5~400m ² / g, particularly preferably those having a specific surface area of 100 to 250 m ² / g, but is not limited thereto.

As an adsorbent, a molybdenum-based (Mo) that is used for desulfurization treatment of kerosene and vacuum gas oil (VGO) as a water desulfurization catalyst
It is possible to use a sulfurized (Co, Ni-based) catalyst or a waste catalyst (sulfurized) that has deteriorated after being used for a certain period of time. Therefore, if the waste catalyst is used as an adsorbent, the manufacturing cost of the adsorbent can be significantly reduced, which is very advantageous.

When removing mercury from liquid hydrocarbons containing mercury,
The contact treatment temperature with the adsorbent is preferably 200 ° C. or lower. 200
If the temperature exceeds ℃, problems such as evaporation of hydrocarbons and cracking occur.

The method of contacting the liquid hydrocarbon containing mercury with the adsorbent is arbitrary, but the fixed bed flow system is particularly preferable. Continuous operation is possible by adopting the fixed bed distribution method.

The present invention will be specifically described below with reference to examples.

Example 1 N containing about 50 μg / l elemental mercury and about 200 μg / l ionic mercury
By distilling GL according to ASTM D86, it was separated into a distillate consisting of a fraction at 250 ° C or lower and a residue. At this time NGL
The liquid temperature was about 300 ° C. The distillate was about 80 vol% and the residue was about 20 vol%.

When the mercury contents of the distillate and the residue were measured, the mercury in the distillate was 205 μg / l and the mercury in the residue was 3 μg / l.
The reason why the amount of mercury recovered does not reach 100% is considered to be a loss due to part of the mercury adhering to the equipment and part of it being carried by the light gas and escaped to the outside of the system.

Next, the distillate was taken to 100 ml, and Co-Mo sulfide on alumina (metal component before sulfiding; Co: 0.94 wt%, Mo: 6.70 wt%) was added to this.
After adding 1 g and stirring for 30 minutes and filtering, the mercury content in the filtrate was 2.1 μg / l.

Comparative Example 1 0.1 g of the same adsorbent (Co-Mo sulfide on alumina) as that used in Example 1 was added to 100 ml of the same NGL used in Example 1 without heating, and the mixture was stirred for 30 minutes and filtered after filtration. When the mercury concentration in the liquid was measured, it was 190 μg / l. In addition, 1N-HC for the filtrate
1 μg of mercury in NGL after adding 100 ml and stirring for 10 minutes
It was less than / l. This means that the mercury remaining in the liquid after adsorption was all ionic mercury. That is, it is shown that the adsorbent can remove only part of ionic mercury in addition to elemental mercury.

Example 2 NGL containing about 5 mg / (as Hg) of organic mercury was distilled in the same manner as in Example 1 to separate a distillate consisting of a fraction at 200 ° C. or lower and a residue. At this time, the NGL liquid temperature was about 240 ° C.
The distillate was 82 vol% and the residue was about 16 vol%.

The mercury concentration in the distillate was 3.4 mg / immediately after distillation,
It became 1.3 mg / day, and there was no change thereafter. This is probably because the saturated solubility was included immediately after the distillation. The mercury concentration in the residue was 3.4 μg / l.

In this case as well, the recovery rate of mercury has not reached 100%,
It is considered that this is also due to the same reason as described in Example 1.

Next, 100 ml of the distillate was taken, to which 0.1 g of the same adsorbent (alumina-supported Co-Mo sulfide) used in Example 1 was added, and the mixture was stirred for 30 minutes and filtered to remove mercury in the filtrate. When the content was measured, it was 4.1 μg / l.

When the raw material NGL used in Example 2 was filtered with No. 5C filter paper to separate solids, the mercury concentration was 1.6 mg /. this
100 ml of NGL is the same adsorbent used in Example 1 (Co-Mo
0.1 g of sulfide) was added and the mixture was stirred for 30 minutes, and the concentration of mercury in the filtered solution after filtration was found to be almost unchanged. Next, 5 wt% of activated clay was added to this filtrate and the mixture was stirred for 30 minutes, and the concentration of mercury in the filtrate after filtration was measured and found to be 1 μg / l or less. The results indicate that the mercury in this NGL is organic mercury (high molecular weight).

Comparative Example 2 NGL containing about 5 mg / l (as Hg) of the same organic mercury as used in Example 2 was heated to 180 ° C., and fractionated into a fraction and a residue at 150 ° C. or lower. The distillate amount was 4 vol% and the mercury concentration was 23 μg / l. On the other hand, the mercury concentration in the residue was 10.4 mg / l.
This corresponds to 4 mg / l mercury in NGL before distillation. That is, it was found that almost no decomposition occurred at this temperature.

C. Effects of the Invention 1. The process can be simplified.

2. Equipment costs can be reduced.

3. No post-treatment required.

Claims (2)

[Claims] 1. A step of heating a liquid hydrocarbon containing mercury to 200 ° C. or higher, and a step of bringing the heated liquid hydrocarbon into contact with an adsorbent containing a sulfide of molybdenum at a temperature of 200 ° C. or lower. A method for removing mercury in liquid hydrocarbons, which is characterized in that 2. The method for removing mercury from liquid hydrocarbons according to claim 1, wherein the adsorbent is one in which Mo-Co sulfide or Mo-Ni sulfide is supported on a carrier.