CN115678629A - A method for producing ultra-low sulfur content liquefied gas - Google Patents

Abstract

The invention discloses a method for producing liquefied gas with ultra-low sulfur content, which comprises contacting a desulfurization adsorbent with a sulfur-containing liquefied gas raw material, and the contact conditions include: the temperature is normal temperature to 200°C, and the volume space velocity is 500-20000h ^‑1 ; wherein, the desulfurization adsorbent contains a carrier and an active component, the carrier is a manganese oxide molecular sieve, and the active component is an iron oxide. The method of the present invention can remove sulfur-containing substances in sulfur-containing liquefied gas at normal temperature or at a lower temperature, and realize the purification of sulfur-containing substances by using the special crystal structure of the active phase through adsorption combined with catalytic conversion to obtain ultra-low sulfur content of liquefied gas. The desulfurization adsorbent used in the invention has low cost, high desulfurization precision, high sulfur capacity, and high single-pass conversion rate. The production method is convenient in operation and simple in process, which is beneficial to industrialization promotion.

Description

A method for producing ultra-low sulfur content liquefied gas

technical field

The invention relates to the field of industrial gas treatment, in particular to a method for producing liquefied gas with ultra-low sulfur content.

Background technique

With the increase in the processing volume of imported high-sulfur crude oil and the increase in the proportion of residual oil blending, the sulfur content of the liquefied gas produced by the catalytic cracking unit of the refinery also increases. The liquefied gas usually contains H ₂ S, COS, CS _2. Toxic and harmful components such as mercaptans, sulfides and disulfides have a great impact on subsequent industrial processing and civil fuels, so liquefied gas must be deeply desulfurized. The demercaptanization in liquefied petroleum gas mostly adopts the Merox extraction and oxidation demercaptanization technology, fiber membrane technology, fixed bed non-alkali sweetening technology or adsorption method developed by UOP Company of the United States. Among them, the alkaline washing process consumes a lot of lye, which is easy to cause environmental pollution; the catalyst in the Merox extraction and oxidation process is easy to aggregate and deactivate, and the total desulfurization rate is not high; the fiber membrane sweetening process has a large investment and is easy to be blocked by impurities; fixed bed adsorption process High operating temperature and high energy consumption.

U.S. patents such as US4705620 and US2921020 and domestic patents such as CN1990828A use new technologies to improve the separation technology of disulfide mixture and lye, reduce the content of disulfide in lye, and improve the desulfurization rate of liquefied petroleum gas. The traditional Melox method still has the following problems: (1) the cobalt phthalocyanine catalyst used is in the alkali phase, which is easy to aggregate and deactivate, resulting in frequent replacement of the catalyst and the cost of the catalyst is quite high; (2) the desulfurization rate is not stable enough, The main reason is that the concentration of disulfide in the regenerated lye is difficult to control, and the lye will reintroduce the disulfide into the liquefied petroleum gas, resulting in a decrease in the total desulfurization rate; coming devastation. Merichem Company in the United States has adopted a fiber membrane contactor technology to greatly increase the mass transfer rate between the alkali liquid phase and the hydrocarbon flow phase, thereby improving the utilization rate of the alkali liquid, reducing the consumption of the alkali liquid, and reducing the alkali residue emissions (USP4124494, USP4159964). However, the removal rate of mercaptan by the fiber membrane desulfurization process is still affected by the quality of alkali liquor regeneration, and the improvement of the total sulfur removal rate is not obvious; and this method will still produce a certain amount of alkali residue, which will pollute the environment; finally , the process has high requirements on the purity of various media, and corresponding filters need to be installed, and regular cleaning is required, which increases maintenance costs.

Adsorption desulfurization technology is another commonly used method for removing organic sulfur in liquefied petroleum gas. This method utilizes the effects of physical adsorption, van der Waals force, chemical adsorption, and complex adsorption between adsorbents and sulfides to remove sulfides from It is separated from liquefied petroleum gas and has the characteristics of simple and convenient operation, low investment and no pollution. Compared with the pure hydrodesulfurization method, it will not cause the loss of octane number.

Contents of the invention

The purpose of the present invention is to provide a method for producing ultra-low sulfur content liquefied gas at normal temperature and low temperature by using a high-precision, high-sulfur-capacity desulfurization adsorbent. To achieve the above object, the present invention specifically includes the following content:

The invention provides a method for producing liquefied gas with ultra-low sulfur content, which includes contacting a desulfurization adsorbent with a sulfur-containing liquefied gas raw material, and the contact conditions include: the temperature is normal temperature to 200°C, and the volumetric space velocity is 500-20000h ^{- 1} ; wherein, the desulfurization adsorbent contains a carrier and an active component, the carrier is a manganese oxide molecular sieve, and the active component is an iron oxide.

The method of the present invention can remove sulfur-containing substances in sulfur-containing liquefied gas at normal temperature or at a lower temperature, and realize the purification of sulfur-containing substances by using the special crystal structure of the active phase through adsorption combined with catalytic conversion to obtain ultra-low sulfur content of liquefied gas. The desulfurization adsorbent used in the invention has low cost, high desulfurization precision, high sulfur capacity, and high single-pass conversion rate. The production method is convenient in operation and simple in process, which is beneficial to industrialization promotion.

Detailed ways

The technical solutions of the present invention will be further described below according to specific embodiments. The protection scope of the present invention is not limited to the following examples, which are listed for illustrative purposes only and do not limit the present invention in any way. Unless defined otherwise, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the present specification's definitions will control.

The sulfur content in the present invention generally adopts the mass content in terms of sulfur element, and generally adopts mass percentage or ppm as the unit of measurement. The ultra-low sulfur content liquefied gas refers to the sulfur content in the finally obtained liquefied gas is far lower than The sulfur content required by the subsequent use or process, generally, the sulfur content in the ultra-low sulfur content liquefied gas obtained by the method of the present invention is 1 ppm.

The invention provides a method for producing liquefied gas with ultra-low sulfur content. The method includes contacting a desulfurization adsorbent with a sulfur-containing liquefied gas raw material. The contact conditions include: the temperature is normal temperature to 200°C, and the volume space velocity is 500 -20000h ^-1 ; the contact conditions are preferably: the temperature is normal temperature to 150°C, and the volume space velocity is 800-10000h ^-1 ; wherein, the desulfurization adsorbent contains a carrier and an active component, and the carrier is a manganese oxide molecular sieve, The active component is iron oxide. The normal temperature in the present invention refers to the ambient temperature that does not need to be heated, generally 13-35°C, that is to say, the temperature range of the contact condition in the present invention can be 15-200°C, 20-200°C, etc. depending on the ambient temperature.

The present invention has no special limitations on the source of the sulfur-containing liquefied gas raw material oil, the type of sulfur-containing substances, and the sulfur content. One or more of hydrogen sulfide, mercaptan, disulfide, carbonyl sulfide, and sulfide, the content of which is generally 10-200ppm.

According to the present invention, the place where the desulfurization adsorbent contacts the sulfur-containing liquefied gas raw material is not particularly limited, and may be various reactors well known to those skilled in the art, preferably a fixed-bed reactor, so that the sulfur-containing liquefied gas raw material gas is continuously pass. During the contact process, various conventional methods can be used to increase the contact efficiency and improve the adsorption reaction effect.

The carrier in the desulfurization adsorbent of the present invention is manganese oxide molecular sieve, and the active component is iron oxide. Wherein the manganese oxide molecular sieve can be selected from one or more of birnessite, Buserite, hydroxymanganite, spessenbergite, manganese potassium ore, and calcium manganese ore, and the active component of the iron oxide can be One or more forms of ferrous oxide (FeO), iron oxide (Fe ₂ O ₃ ), and ferric oxide (Fe ₃ O ₄ ). Based on the dry basis weight of the desulfurization adsorbent, the content of each component in _the desulfurization adsorbent in the present invention is preferably: the content of the carrier is 80 to 99.5% by weight, and the iron oxide calculated as _Fe2O3 The content is 0.5 to 20% by weight.

The specific surface and pore volume of the desulfurization adsorbent of the present invention are not particularly limited, generally, the specific surface area can be 50-300m ² /g, and the pore volume can be 0.2-1.2m ³ /g.

The source of the desulfurization adsorbent used in the present invention is not particularly limited, and it can be a commercial reagent, or can be prepared by itself from raw materials, as long as the composition and content meet the corresponding requirements of the present invention. In order to better realize the method of the present invention, the present invention provides two preparation methods for obtaining the desulfurization adsorbent, namely the doping method and the loading method, which are respectively described as follows:

Method a is a doping method, which is to mix the reduced manganese compound with the iron metal salt first, and then mix it with the oxidized manganese compound for hydrothermal reaction, so as to avoid the formation of undesired complexes between the iron metal salt and the oxidized manganese compound. Changing the crystal structure mainly includes the following steps:

(a-1) dissolving the reduced manganese compound and the iron metal salt in water to obtain a mixed solution;

(a-2) mixing the oxidized manganese compound with the mixed solution described in step (a-1), performing a hydrothermal reaction, and collecting the precipitate;

(a-3) Drying and roasting the precipitate in step (a-2) to obtain the desulfurization adsorbent.

In the present invention, oxidized manganese compounds and reduced manganese compounds are relative; oxidized manganese compounds generally refer to compounds containing relatively high-valence manganese (such as Mn7+, Mn6+, etc.), and reduced manganese compounds generally refer to compounds containing relatively Low-valence manganese (such as Mn2+, etc.) compounds. For example, the oxidized manganese compound is selected from one or more of potassium permanganate, potassium manganate, and sodium permanganate, and the iron metal salt is selected from ferric nitrate, ferric sulfide, ferric chloride, citric acid One or more of iron and iron acetate, and the manganese compound in the reduced state is selected from one or more of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; preferably, the manganese compound in the oxidized state, The molar ratio of the reduced manganese compound to the iron metal salt is (0.2-3):1:(0.01-1).

The precipitate obtained in step (a-2) can be washed as required. Washing refers to washing the collected solid product with deionized water until the washing liquid is neutral (for example, the pH value is 6.5-7.5).

Drying and roasting in step (a-3) are common operations in this field, and there are no special restrictions on relevant conditions. For example, the drying temperature in step (a-3) is 80-350°C, preferably 100-300°C, and the time is 1-24h, preferably 2-12h; the temperature of calcination is 200-900°C, preferably 250-800°C, and the time is 0.5-12h, preferably 2-6h. Calcination can be carried out under air atmosphere or under inert gas atmosphere, preferably under _N2 atmosphere.

In order to further improve the performance of the desulfurization adsorbent, between step (a-2) and step (a-2), it also includes the step of adding acid to the mixed solution to adjust the pH value of the mixed solution to 0.2-3 The acid can be common inorganic acids such as nitric acid, hydrochloric acid, sulfuric acid, or organic acids such as acetic acid that can achieve the above-mentioned purpose.

Method b is a loading method, first preparing manganese oxide molecular sieves from oxidized manganese compounds and reduced manganese compounds, and then loading iron metal salts on it, specifically including the following steps:

(b-1) subjecting an aqueous solution containing an oxidized manganese compound and a reduced manganese compound to a hydrothermal reaction, collecting a solid product and performing first drying and first roasting to obtain a manganese oxide molecular sieve;

(b-2) loading iron metal salt on the manganese oxide molecular sieve, and obtaining the desulfurization adsorbent after second drying and second calcination.

Wherein the selection and content of oxidized manganese compound, reduced manganese compound and iron metal salt can refer to method a, before carrying out the hydrothermal reaction, preferably including the step of adding acid to the aqueous solution, adjusting the pH value of the aqueous solution to 0.2～ 3. The choice of acid can also refer to method a.

The method provided by the invention can directly obtain liquefied gas with ultra-low sulfur content at a relatively low temperature. The desulfurization adsorbent has low cost, high desulfurization precision, high sulfur capacity, and high single-pass conversion rate. The desulfurization method is convenient in process and simple in operation, which is beneficial to Industrialization promotion.

The present invention will be further described below through specific examples, and these examples have described preferred embodiment, but are not construed as limiting the present invention, and any skilled person who is familiar with this specialty may utilize the content of the invention that above-mentioned relates to be changed into equivalent change An equivalent embodiment of .

Reagents, Instruments and Tests

Unless otherwise specified, the reagents used in the present invention are analytically pure, and all reagents used are commercially available.

The model of XRD diffractometer adopted in the present invention is XRD-6000 type X-ray powder diffractometer (Shimadzu, Japan), and XRD test condition is: Cu target, Kα ray (wavelength λ=0.154nm), tube voltage is 40kV, tube current It is 200mA, and the scanning speed is 10°(2θ)/min.

The content of active component adopts X-ray fluorescence spectroscopic analysis method RIPP 132-90 (petrochemical analysis method (RIPP experimental method), edited by Yang Cuiding, Gu Kanying, Wu Wenhui, the first edition in September, 1990, page 371-379 of Science Press ) measured.

The H ₂ S analysis instrument used in the present invention is a German SICK GMS810 hydrogen sulfide analyzer.

Preparation Example 1

Dissolve 3.17g potassium permanganate in 40.55g deionized water, heat and stir to dissolve it to form potassium permanganate solution, mix 50% by weight manganese sulfate solution of 5.78g with 1.56g ferric nitrate and stir evenly, mix the above two Mix the two solutions, add 6ml of nitric acid and stir evenly, adjust the pH value to less than 3, and react at 130°C for 24h. Filter the resulting brown precipitate and wash it with deionized water several times until the pH of the washing solution is 7, then dry the solid product at 120°C overnight and roast it in air at 500°C for 4 hours to obtain the desulfurization adsorbent A1: 10% Fe ₂ O ₃ -OMS-2.

Preparation example 2

The desulfurization adsorbent A2 was prepared in the same steps as in the preparation example 1, except that the content of the active component Fe ₂ O ₃ was different, and the composition of A2 was 15% Fe ₂ O ₃ -OMS-2.

Preparation example 3

The desulfurization adsorbent A3 was prepared in the same steps as Preparation Example 1, except that the solid product was roasted in a nitrogen atmosphere instead of the same roasting atmosphere to obtain desulfurization adsorbent A3: 15% Fe ₂ O ₃ -OMS-2N.

Preparation Example 4

Mix potassium permanganate solution, manganese sulfate solution, ferric nitrate, and nitric acid and transfer to a flask equipped with a condenser tube, and reflux at 120°C for 24 hours. Other steps are the same as in Example 1 to obtain desulfurization adsorbent A4: 10% Fe ₂ O ₃ -OMS-2-Ref.

Preparation Example 5

First, the manganese molecular sieve OMS-2 carrier was prepared by hydrothermal synthesis, 3.17g potassium permanganate was dissolved in 40.55g deionized water, heated and stirred to dissolve it to form a potassium permanganate solution, and then mixed with 5.78g of 50 wt. % manganese sulfate solution, and added 6ml of nitric acid to adjust the pH value of the solution to 1.0, stirred evenly, and reacted at 130°C for 24h. The resulting brown precipitate was filtered and washed with deionized water several times until the pH of the washing solution was 7, and then the solid product was dried at 120°C overnight, and then calcined at 400°C for 4 hours in an air atmosphere to prepare the manganese oxide molecular sieve OMS -2.

Afterwards, ferric nitrate was loaded onto the OMS-2 carrier, and the solid product was dried at 120° C. overnight and calcined at 500° C. in air for 4 hours to prepare desulfurization adsorbent A5: 15% Fe ₂ O ₃ -OMS-2.

Prepare comparative example 1:

A commercial iron oxide desulfurizer (Shandong Maojia Environmental Protection HT506 iron oxide desulfurizer, hereinafter referred to as D1) was selected as the desulfurization adsorbent.

XRD analysis was carried out on the desulfurization adsorbents of the preparation example and the comparison example. The preparation example only showed the characteristic peak of OMS-2, indicating that it had the OMS-2 molecular sieve structure, and the active metal iron was uniformly doped. When the calcination atmosphere was changed to N ₂ , Mn ₃ O ₄ was found in the crystals of the desulfurization adsorbent A3, and more oxygen vacancies would be generated in the crystals of the desulfurization adsorbent, which was beneficial to increase the sulfur capacity of the adsorbent.

Example

It is used to specify the scheme and effect of the present invention and the prior art, specifically: 1.5g of desulfurization adsorbent (or contrast agent) taken by weighing is placed in a fixed-bed reactor, and the sulfur-containing liquefied gas raw material (see Table 1 for specific composition) ) pass through the mass flow meter together with the carrier gas (usually N ₂ ) into the fixed bed reactor, and carry out the contact reaction at 40°C, the volume space velocity of the reaction is 2000h ^-1 , analyze the sulfur content in the liquefied gas after the reaction, The results are shown in Table 2.

Table 1

composition content/% C1～C2 5.8 C3H8 38.6 C3H6 36.5 C4H10 19.0 H₂S 50ppm CH₃SH 50ppm

Table 2

As can be seen from the data in the table, when the desulfurization adsorbent provided by the present invention is used for desulfurization of liquefied gas, the effect is far better than that of commercial iron oxide desulfurizer, and the sulfur content in the liquefied gas obtained by the method of the present invention is lower than 1ppm, far It is better than the liquefied gas obtained by using the comparative example, and has remarkable effects.

According to the physical and chemical properties of the manganese oxide molecular sieve, the present invention fully utilizes the special crystal structure of the iron-manganese oxide molecular sieve to give full play to its advantages in the field of liquefied gas desulfurization, so that it can have commercial products at a relatively low temperature (60°C). nearly six times the sulfur capacity of ferric oxide. At the same time, the preparation method of the desulfurization adsorbent is simple and repeatable, which is beneficial to industrial promotion.

The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention. These simple modifications All belong to the protection scope of the present invention.

In addition, various combinations of different embodiments of the present invention can also be combined arbitrarily, as long as they do not violate the idea of the present invention, they should also be regarded as the disclosed content of the present invention.

Certainly, the present invention also can have other multiple embodiments, without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should belong to the scope of protection of the appended claims of the present invention.

Claims (10)

1. A method for producing liquefied gas with ultra-low sulfur content, comprising contacting a desulfurization adsorbent with a sulfur-containing liquefied gas raw material, and the contact conditions include: the temperature is normal temperature to 200°C, and the volumetric space velocity is 500-20000h ^-1 ; Wherein, the desulfurization adsorbent contains a carrier and an active component, the carrier is a manganese oxide molecular sieve, and the active component is an iron oxide. 2. The method according to claim 1, wherein the manganese oxide molecules are screened from one or more of birnessite, Buserite, hydroxydangite, spessnerite, manganite, and calcium manganese The iron oxide is selected from one or more of ferrous oxide (FeO), iron oxide (Fe ₂ O ₃ ), and ferric oxide (Fe ₃ O ₄ ). 3. The method according to claim 1, wherein, based on the dry basis weight of the _{desulfurization} adsorbent, the content of the carrier is 80 to 99.5% by weight, and the iron oxide in _Fe2O3 The content is 0.5 to 20% by weight. 4 . The method according to claim 1 , wherein the contact conditions include: the temperature is normal temperature to 150° C., and the volume space velocity is 800-10000 h ⁻¹ . 5. The method according to claim 1, wherein the sulfur-containing substance in the sulfur-containing liquefied gas raw material is one or more selected from hydrogen sulfide, mercaptan, disulfide, carbonyl sulfide, and sulfide. One species, based on the total mass of sulfur-containing liquefied gas raw materials, the sulfur content calculated as sulfur element is 20-200ppm. 6. The method according to claim 1, wherein the desulfurization adsorbent is prepared by method a or method b, Method a includes the following steps: (a-1) dissolving the reduced manganese compound and the iron metal salt in water to obtain a mixed solution; (a-2) mixing the oxidized manganese compound with the mixed solution described in step (a-1), performing a hydrothermal reaction, and collecting the precipitate; (a-3) drying and roasting the precipitate described in step (a-2) to obtain the desulfurization adsorbent; Method b includes the following steps: (b-1) subjecting an aqueous solution containing an oxidized manganese compound and a reduced manganese compound to a hydrothermal reaction, collecting a solid product and performing first drying and first roasting to obtain a manganese oxide molecular sieve; (b-2) loading iron metal salt on the manganese oxide molecular sieve, and obtaining the desulfurization adsorbent after second drying and second calcination. 7. The method according to claim 6, wherein, in method a and method b, the oxidized manganese compound is independently selected from one or more of potassium permanganate, potassium manganate, sodium permanganate The iron metal salts are independently selected from one or more of ferric nitrate, ferric sulfide, ferric chloride, ferric citrate, and ferric acetate, and the reduced manganese compounds are independently selected from manganese sulfate, One or more of manganese nitrate, manganese acetate, manganese chloride; Preferably, the molar ratio of the oxidized manganese compound, the reduced manganese compound and the iron metal salt is (0.2-3):1:(0.01-1). 8. The method according to claim 6, characterized in that, the drying temperature in step (a-3) of the method a is 80-350°C, the time is 1-24h, and the roasting temperature is 200-900°C, The time is 0.5-12h; the temperature of the first drying in the method b is 80-350°C, the time is 1-24h, the temperature of the first roasting is 200-900°C, the time is 0.5-12h, the temperature of the second drying The temperature of the second calcination is 80-350° C., and the time is 1-24 hours. The temperature of the second calcination is 200-900° C., and the time is 0.5-12 hours. 9. method according to claim 6, is characterized in that, between described step (a-2) and step (a-2), also comprise the step of adding acid in described mixing solution, adjust described mixing The pH value of the solution is 0.2-3. 10. The method according to claim 6, characterized in that, before the hydrothermal reaction in the method b, it further comprises the step of adding acid to the aqueous solution to adjust the pH value of the aqueous solution to 0.2-3.