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Removing H2S from Oil

1、INTRODUCTION
Sulfur compounds exist in various light oils made from petroleum. Such as mercaptan, hydrogen sulfide, which cause foul odors and deteriorate the finished products. In addition, due to their acidity, they are corrosive to metals, which is harmful for storage and usage of oil products. Therefore, it is necessary to remove them.
In the refining industry, an aqueous base such as sodium hydroxide or ammonia is employed fulfilling the purpose. Although its effectiveness and the low cost of fresh caustic are the reasons for its widespread use, the aqueous base especially sodium hydroxide always causes some problems. Such as spending many caustic materials, and discarding lots of hazardous waste. So environmental agencies around the world have tightened the regulations aimed at controlling its disposal. Solid bases merge as an ideal alternative to the aqueous bases to overcome the environmental and economic problems. The report concerning solid base is mostly concentrate in mercaptan oxidation, these solid bases selected from the group consisting of magnesium, nickel, zinc, copper, aluminum, iron oxides and mixtures thereof. However the report concerning solid base on removal of hydrogen sulfide was hardly consulted.
This paper reports the effect of factors of preparation for the solid base on removal of hydrogen sulfide at ambient temperature.
Thus selecting the optimum factor of preparation for the solid base on the removal of hydrogen sulfide in light oil.
2. EXPERIMENTAL
2.1 Preparation of solid base
Activated carbon marked by DV-01was used as supporter in this study. The activated carbon was calcined at high temperature for 6h, then impregnated with a aqueous solution of some alkalic materials at ambient temperature. The saturated activated carbon was filtrated in vacuum for period of time, then dried period of time at special
temperature.
Experimental Oil
Petroleum ether(boiling point 90—120℃) was used as experimental oil with 800—1000μg/g hydrogen sulfide
concentration.
Capability test of solid base for the removal of hydrogen sulfide
1g solid base was loaded in a 200ml flask, to this flask 100ml experimental oil was added, then the solution was electromagnetism stirred at ambient temperature with protection of nitrogen, the stirred speed was 350rpm. The hydrogen sulfide concentration in light oil was analyzed with period by the method of GB/T1792-88.

Materials calculation
The adsorption quantity of solid base for hydrogen sulfide as follows: Xg = (C0-Ct)•ρV•10-3/M
where
Xg: the adsorption quantity of the solid base for hydrogen sulfide mg/g
C0: Preliminary concentration of hydrogen sulfide μg/g
Ct: concentration of hydrogen sulfide at t hour μg/g
ρ、V: density, vol. of oil g/ml, ml
M: the quality of the used solid base g

The effect of different chemical components of solid base on the removal of H2S
With different alkalic materials, six kinds of solid base were prepared and the removal capacities for H2S were tested. , the SB15 solid base for absorption of hydrogen sulfide has the highest capacity.
The solid base adsorption for hydrogen sulfide has a competitive between physical adsorption and chemical adsorption.
The removal capacity for hydrogen sulfide of the solid base was the sum of physical adsorption and chemical adsorption. Different solid base has different surface area and chemical center, so the capacity for hydrogen sulfide removal is alternatively. SB15 has the best chemical components.

The effect of solid base vacuum filtration time on the removal of H2S
Experiments examine the effect of time of vacuum filtration during preparation of the solid base for the removal of hydrogen sulfide. The activated carbon was impregnated with the optimum concentration of aqueous, then the loaded activated carbon was vacuum filtrated by different time, thereby making A series of solid bases.

the adsorption capacity of the solid base for hydrogen sulfide firstly increased and then decreased with the increase of the vacuum filtration time during the preparation of the solid base. As a result, the time of vacuum filtration is a major factor for the solid base on removal of hydrogen sulfide, the optimum time of vacuum filtration should be 60 min.

The effect of solid base drying time on the removal of H2S
A series of solid bases were made with different time of drying from short to long. And the removal of hydrogen sulfide of these solid bases were examined.

the adsorption quantity of the solid base for hydrogen sulfide firstly increased then decreased with the time of
drying prolonged in the preparation of the solid base. The shorter the time of drying is, the higher the water content of the solid base is, the higher water content of the solid base reduced the physical adsorption of the solid base for hydrogen sulfide. With the further drying, the water is so less in the solid base that can not provide the polar
environment for the chemical adsorption. consequently the chemical adsorption quantity of hydrogen sulfide in the solid base was decreased greatly.
It was found that the optimum time of drying for the solid base with good properties should be 2 hr.

The effect of additive on the removal of H2S
It is believed that the function of polar compound is to serve as a proton transfer medium in the chemical reaction. Specially the compounds are selected from the group consisting of water, alcohols, esters, ketones, diols and mixtures thereof. A group of polar compounds was chosen as the additive for the solid base for removal
of H2S. Experiments were carried out for measuring the adsorption capacity of the solid base with different quantity of the additive.

the additive was added, thus the adsorption of the solid base for hydrogen sulfide has greatly increased.

CONCLUSIONS
1.Preparation factors of the solid base play an important role for the solid base on removal of hydrogen sulfide. The preparation factors include the components of solid base, the time of vacuum filtration and the time of drying.
2. The adsorption capacity of the solid base for hydrogen sulfide was the sum of physical adsorption and chemical adsorption.
3. Adding a group of polar compounds can promote significantly the removal of hydrogen sulfide by the solid base. The optimum quantity of the additive is 6000 μg/g.