CN106336919A - Novel desulfurization method of biodiesel - Google Patents

Abstract

The invention relates to a novel desulfurization method of biodiesel. The method comprises the steps that sulfur-containing compounds in the biodiesel are removed through two stages of high vacuum distillation, crude biodiesel is pumped into a first-stage desulfurization tower for first-stage high vacuum distillation, the tower top of the first-stage desulfurization tower is rich in light components of the sulfur-containing compounds; desulfurized biodiesel at the kettle bottom of the first-stage desulfurization tower is pumped into a second-stage desulfurization tower through a pump for second-stage high vacuum distillation, biodiesel reaching the standard is steamed out from the tower top of the second-stage desulfurization tower, the content of sulfur in the biodiesel reaching the standard is lower than 10 ppm, biological asphalt heavy components are obtained in a tower kettle of the second-stage desulfurization tower, the absolute operation pressure of the desulfurization towers ranges from 10 Pa to 1,000 Pa, and the tower kettle heating temperature ranges from 200 DEG C to 300 DEG C. The method is simple in technological process, low in equipment investment cost and capable of obtaining the biodiesel meeting the standard stably; compared with a traditional petrochemical oil product desulfurization method, a high-temperature catalytic reaction is not related, new substances are not introduced, therefore, the process is safer, the oil product structure is not destroyed, and it is guaranteed that the oil quality is stable.

Description

A new method for biodiesel desulfurization

technical field

The invention belongs to the technical field of biodiesel refining, and in particular relates to a new biodiesel desulfurization method, which is especially suitable for removing sulfur compounds in biodiesel.

Background technique

With the increasing shortage of petrochemical resources, the development of renewable bio-energy is a hot topic today, and biodiesel is one of the most typical ones. All countries in the world are developing different raw material resources to produce biodiesel according to their own advantages. my country's catering industry is developed, and there is a large amount of waste oil. At present, waste oil (such as gutter oil) is mainly used to produce biodiesel. Due to its low cost, it has become a promising biodiesel raw material. But one major problem is that it contains certain sulfur compounds (mainly organic matter in sulfur-containing wastewater from restaurants, homes, and other facilities). When biodiesel is burned, the sulfur is released into the atmosphere as sulfur dioxide, causing environmental and health problems. In view of the hazards of sulfur in oil, major countries and regions in the world have promulgated more and more stringent standards for sulfur in oil. For example, GBT 20828-2015 clearly states that, according to the different sulfur content, biodiesel is divided into two categories, S50 and S10, which mean that the sulfur content does not exceed 50 ppm and 10 ppm respectively. With the improvement of sulfur standards in clean diesel in the world, reducing the sulfur content in diesel has become the focus of global attention.

As one of the important processes of oil cleaning, desulfurization technology has been widely studied, and some new technologies with good application prospects have been developed, mainly including hydrogenation and non-hydrogenation. Hydrodesulfurization refers to the removal of organic sulfur-containing compounds in diesel by converting them into hydrogen sulfide through catalyst action in the presence of hydrogen. Non-hydrogenation desulfurization technologies mainly include adsorption desulfurization, extraction desulfurization, complexation desulfurization, catalytic desulfurization, oxidation desulfurization and so on. However, due to the low sulfur content in biodiesel (fatty acid methyl ester), further deepening desulfurization using hydrogenation or non-hydrogenation technology is not only costly, but also destroys the chemical structure of biodiesel.

Sulfur-containing compounds in biodiesel mainly include low-boiling active sulfur (hydrogen sulfide, mercaptan, disulfide and polysulfide) and high-boiling inactive sulfur (sulfide, thiophene, benzothiophene, dibenzothiophene) Among them, thiophene sulfur-containing compounds account for more than 85% of the total sulfur content of diesel oil. At present, there are few reports on the removal of sulfur compounds in biodiesel.

Contents of the invention

In view of the current difficulty in biodiesel desulfurization, the present invention provides a new simple and efficient biodiesel desulfurization method, which is especially suitable for the removal of sulfur compounds in biodiesel.

The new biodiesel desulfurization method is to remove sulfur compounds in biodiesel through two-stage high-vacuum rectification, which is characterized in that crude biodiesel is injected into a first-stage desulfurization tower for one-stage high-vacuum rectification, and one-stage The light components of sulfur-containing compounds are enriched at the top of the desulfurization tower; the light-removed biodiesel at the bottom of the primary desulfurization tower is pumped into the secondary desulfurization tower for secondary high-vacuum rectification, and steamed out at the top of the secondary desulfurization tower Standard biodiesel, the sulfur content in the standard biodiesel is less than 10ppm, and the heavy component of bio-asphalt is obtained from the bottom of the secondary desulfurization tower.

The novel method for biodiesel desulfurization is characterized in that both the primary desulfurization tower and the secondary desulfurization tower are packed towers with high efficiency and low pressure drop.

The novel method for biodiesel desulfurization is characterized in that the operating absolute pressure of the primary desulfurization tower and the secondary desulfurization tower is between 10-1000 Pa, and the heating temperature of the tower bottom is between 200-300°C.

The novel method for biodiesel desulfurization is characterized in that the light components enriched in sulfur compounds are C10-14 light components and sulfur compounds.

The novel method for biodiesel desulfurization is characterized in that the primary desulfurization tower is at least one tower.

The new biodiesel desulfurization method is characterized in that the heating medium of the first-stage desulfurization tower and the second-stage desulfurization tower is high-temperature heat-conducting oil.

The novel method for biodiesel desulfurization is characterized in that the crude biodiesel raw material is waste oil, including gutter oil, waste animal and vegetable oil or acidified oil.

By adopting above-mentioned technology, compared with prior art, the beneficial effect of the present invention is as follows:

The present invention utilizes the difference between the boiling point of the main components of biodiesel (carbon 16 and carbon 18 methyl esters) and the boiling range of sulfur-containing compounds, and enriches the sulfur-containing compounds in the light components and the heavy components of bio-asphalt through two-stage high-vacuum rectification and cutting the light and heavy components to obtain biodiesel meeting the S10 standard, the sulfur content is less than 10ppm, the process is simple, the equipment investment is small, and the low-sulfur biodiesel meeting the standard can be stably obtained, which is comparable to traditional petrochemical oil desulfurization Compared with the method, it does not involve high-temperature catalytic reaction and does not introduce new substances, so that the desulfurization process is safer, the structure of the oil product is not damaged, and the quality of the oil product is guaranteed to be stable.

Description of drawings

Fig. 1 is a schematic flow chart of an embodiment of the present invention;

Fig. 2 is the gas chromatogram of light components at the top of the primary desulfurization tower of the present invention;

Fig. 3 is a gas chromatogram of heavy components of bio-asphalt at the bottom of the secondary desulfurization tower of the present invention.

In the picture: 1-first-level desulfurization tower, 2-second-level desulfurization tower.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited thereto.

Example 1 The crude biodiesel raw material used is waste grease gutter oil, its sulfur content is about 50ppm (detected by ultraviolet fluorescence method), and its fatty acid methyl ester content distribution is shown in Table 1, wherein C14-0 is methyl myristate, C16 -0 is methyl palmitate, C18-0 is methyl stearate, C18-1 is methyl oleate, C18-2 is methyl linoleate, C18-3 is methyl linolenate:

Table 1 Contents of fatty acid methyl esters in waste oil

As shown in Figure 1, the crude biodiesel produced from gutter oil is pumped into the first-stage desulfurization tower 1, the heating temperature of the first-stage desulfurization tower 1 is controlled at 200°C, the operating absolute pressure is 50Pa, and the reflux ratio is 20. Light components are obtained from the top of desulfurization tower 1, and the liquid in the first desulfurization tower 1 is poured into the second desulfurization tower 2. The heating temperature of the second desulfurization tower 2 is controlled at 220°C, the operating absolute pressure is 30 Pa, and the reflux ratio is 1. The standard low-sulfur biodiesel is obtained at the top of the second-stage desulfurization tower 2, which meets the S10 standard in GBT 20828-2015, and the heavy component of bio-asphalt is obtained from the bottom of the tower. The inner diameter of the first-stage desulfurization tower is 20mm, and the packing is stainless steel metal spring packing , the packing height is 1000mm; the inner diameter of the secondary desulfurization tower is 20 mm, the packing is stainless steel metal spring packing, and the packing height is 500mm.

After the crude biodiesel is desulfurized by two-stage high-vacuum rectification, the results of the quality and sulfur content of each stream are shown in Table 2:

Table 2 The results of the quality and sulfur content of each stream in the product after two-stage high-vacuum rectification and desulfurization

Figure 2 is a gas chromatogram of sulfur-containing compounds in light components. It can be seen from the figure that sulfur-containing compounds in light components mainly exist in three forms: mercaptans and thioethers, alkylthiophenes and alkylbenzothiophenes. , the boiling range of this kind of sulfur-containing compounds is about 166-332 ° C, which is equivalent to the boiling range of light component low-carbon methyl esters (carbon number ≤ 14) in biodiesel. Figure 3 is a gas chromatogram of sulfur compounds in the heavy fraction. The sulfur-containing compounds in the heavy component are composed of three types: alkylthiophenes, alkylbenzothiophenes and alkyldibenzothiophenes. There are no mercaptans and thioethers, but there are high-boiling alkyl Dibenzothiophene sulfur-containing compounds. Because the boiling range of alkyldibenzothiophene sulfur-containing compounds is above 350°C, which is close to the boiling range of methyl ester components above C18, such sulfur-containing compounds are enriched in the bottom of the secondary desulfurization tower without being evaporated. out. The main components of crude biodiesel are C16 and C18 methyl esters, so through two-stage high-vacuum rectification, the sulfur-containing compounds are enriched in the light components at the top of the first-stage desulfurization tower and the bio-asphalt in the bottom of the second-stage desulfurization tower Among the heavy components, the biodiesel meeting the S10 standard is obtained at the top of the secondary desulfurization tower. Through this process, the total yield of crude biodiesel from waste oil is about 90%, and the yield of biodiesel meeting the S10 standard is about 85%.

The above-mentioned embodiments are only used to explain the present invention, but do not limit the protection scope of the present invention. Except for the above-mentioned embodiments, all technical solutions formed by equivalent replacement or equivalent transformation all fall within the protection scope of the present invention.

Claims (7)

1. a kind of biodiesel desulfurization new method, removes sulfur-containing compound in biodiesel by two-stage high vacuum rectification, and it is special Levy and be that coarse biodiesel is squeezed into first grade desulfurizing tower (1) carries out one-level high vacuum rectification, the enrichment of first grade desulfurizing tower (1) tower top contains The light component of sulphur compound；The de- light biodiesel of first grade desulfurizing tower (1) bottom is squeezed into two-grade desulfurizing tower (2) by pump and is carried out two Level high vacuum rectification, steams biodiesel up to standard in two-grade desulfurizing tower (2) tower top, in this biodiesel up to standard, sulfur content is low In 10ppm, two-grade desulfurizing tower (2) tower reactor obtains Biological asphalt heavy constituent.

2. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that first grade desulfurizing tower (1) and two grades Desulfurizing tower (2) is the packed tower of high efficiency low pressure drop.

3. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that first grade desulfurizing tower (1) and two grades , between 10-1000 pa, tower reactor heating-up temperature is between 200-300 DEG C for the operation absolute pressure of desulfurizing tower (2).

4. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that be enriched with the light of sulfur-containing compound Group is divided into c10-14 light component and sulfur-containing compound.

5. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that first grade desulfurizing tower (1) is at least One tower.

6. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that first grade desulfurizing tower and two grades are de- The heating medium of sulfur tower is high temperature heat conductive oil.

7. a kind of biodiesel desulfurization new method according to claim 1 is it is characterised in that coarse biodiesel raw material is useless Abandon oils and fatss.