JP2796754B2 - Mercury removal from liquid hydrocarbons - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Object of the Invention [Industrial Application Field] Natural gas condensate, which is a liquid hydrocarbon, has recently begun to be used as a raw material for ethylene. Natural gas condensate contains up to several ppm of mercury, depending on the region of origin. Mercury must be removed because it causes corrosion of the low-temperature heat exchanger, poisoning of the catalyst, and deterioration of the working environment.

[Prior art] [Prior art] Natural gas condensate contains elemental mercury, ionic mercury, organic mercury (reactive reactive mercury), etc., and the amount varies depending on the place of production. Elemental mercury is an adsorbent, ionic mercury can be removed with an aqueous Na ₂ S solution, and organic mercury can be removed with a solid acid.However, in the case of organic mercury removal with a solid acid, polar compounds coexisting in condensate are also adsorbed. The amount of mercury adsorbed was small and had some practical problems.

[Problems to be Solved by the Invention] The present invention was discovered while studying an economically excellent method for removing organic mercury, and simultaneously decomposes mercury compounds and adsorbs mercury to greatly improve the process. It is an object of the present invention to provide a method for removing mercury in liquid hydrocarbons, which has advantages such as simplification and not producing liquid waste containing mercury.

B. Constitution of the Invention [Means for Solving the Problems] The method for removing mercury in a liquid hydrocarbon according to the present invention comprises heating a liquid hydrocarbon containing a mercury compound under heating at 170 to 300 ° C.
The method is characterized in that the liquid hydrocarbon is brought into contact with an adsorbent mainly composed of molybdenum sulfide at a pressure higher than the vapor pressure of the liquid hydrocarbon to simultaneously decompose the mercury compound and adsorb and remove the mercury.

According to the present invention, it is possible to remove mercury and mercury compounds from various liquid hydrocarbons, particularly liquid hydrocarbons obtained from natural gas condensate or petroleum accompanying gas.

In carrying out the present invention, it is desirable to wash the liquid hydrocarbon with water in advance. Some liquid hydrocarbons contain polar nitrogen compounds and oxygen compounds, as well as solid fine particles. These substances have an adverse effect on adsorbents mainly composed of molybdenum sulfide, and are removed by washing with water. It is desirable to do.

As the adsorbent, a sulfide of molybdenum or a composite sulfide obtained by adding cobalt or nickel to molybdenum is used. The addition amount of these cobalt and / or nickel is preferably 0.05 to 0.9, particularly preferably 0.1 to 0.8 in terms of atomic ratio to molybdenum. Although these sulfides can be used as they are as an adsorbent, they are preferably used by being supported on silica, alumina, or another suitable carrier.

At room temperature, molybdenum-based adsorbents adsorb only elemental mercury and low-molecular-weight mercury compounds such as CH ₃ HgCl and (C ₂ H ₅ ) ₂ Hg. Liquid hydrocarbons contain ionic mercury and organic mercury that cannot be treated with an adsorbent, and heating is an operation necessary to decompose these ionic mercury and organic mercury into simple substances. It takes tens of minutes to several hours at 200 to 300 ° C. only by thermal decomposition, but the temperature can be lowered on the adsorbent, and the time can be shortened at the same temperature.

The catalytic cracking temperature is 170-300 ° C, the pressure is more than the vapor pressure of liquid hydrocarbon, usually 5-30 kg / cm ² G,
The contact is preferably performed for about 10 minutes or less, preferably for about 10 minutes or less. If the temperature is lower than 170 ° C., the decomposition takes too much time and is uneconomical. On the other hand, when the temperature exceeds 300 ° C, the decomposition of liquid hydrocarbons,
The decrease in the adsorption capacity due to the formation of carbonaceous material on the adsorbent becomes remarkable, which is not preferable.

Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to the following examples.

Example 1 A Co-Mo-based adsorbent (Mo: 7%, Co: 0.9%, carrier: Al) previously sulfided into a stainless steel reaction tube having an inner diameter of 14 mm and a length of 500 mm
10 g of ₂ O ₃ ) was charged, and natural gas condensate containing 1300 ppb as mercury was supplied at a predetermined temperature and flow rate, and the mercury concentration at the outlet was measured. The measurement was based on a gold amalgam-flameless atomic absorption method.

Table 1 shows the measurement results of the temperature, flow rate and outlet mercury concentration.

Table 1 shows that almost all mercury can be removed under the conditions of 250 ° C. and 50 ml / h.

This adsorbent has a flow rate at room temperature as shown in Comparative Example 2.
At 50 ml / h, it only adsorbs up to the outlet mercury concentration of 124 ppb,
The results in the table show that the mercury compounds in the natural gas condensate were decomposed to form a simple substance and adsorbed. At higher flow rates, the residual mercury is also higher, which means that decomposition and adsorption are insufficient.

Comparative Example 1 The reaction tube used in Example 1 was filled with the same volume of glass beads as the catalyst used in Example 1, and a predetermined flow rate of natural gas condensate was supplied at 250 ° C. to perform thermal decomposition. The natural gas condensate after decomposition is further converted to Co-Mo sulfide 10
After supplying the column filled with g at room temperature, the mercury concentration was measured. The results are shown in Table 2.

As shown in Table 2, it was not possible to sufficiently decompose only by heating.

Further, even when the thermal decomposition temperature was 290 ° C. and the flow rate was 56 ml / h, only 167 ppb could be removed.

[Comparative Example 2] An adsorption experiment was performed using the same natural gas condensate as in Example 1 at 10 g of the Co-Mo sulfide used in Example 1, at a temperature of 16 ° C, and at a flow rate of 50 ml / h. Is 124ppb
Met. This cannot be removed any more even at a flow rate of 25 ml / h.

[Comparative Example 3] With the apparatus used in Example 1, temperature: 150 ° C, flow rate: 210 ml / h
An adsorption experiment was performed using the same natural gas condensate as in Example 1 under the conditions described above, and the mercury concentration at the outlet was 253 ppb. These results indicated that at 150 ° C, adsorption and removal of mercury was insufficient.

C. Advantages of the Invention 1) Organic mercury can be removed simultaneously with simple mercury and ionic mercury.

2) The process is simple.

3) Since no liquid waste containing mercury is produced, it is easy to take measures against waste.

4) The operation management of the device is easy.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toru Matsuzawa 2110 Saki-cho, Handa-shi, Aichi Prefecture, Niigata Institute of Technology, Japan (56) References JP-A-1-315489 (JP, A) JP-A-2 −2873 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C10G 25/06

Claims (1)

(57) [Claims] 1. A liquid hydrocarbon containing a mercury compound is added in an amount of 170 to 300.
Decomposition of a mercury compound and adsorption and removal of mercury are simultaneously performed by contacting an adsorbent containing molybdenum sulfide as a main component under a pressure of not less than the vapor pressure of the liquid hydrocarbon under heating at a temperature of ° C. A method for removing mercury in liquid hydrocarbons.