阅读说明：本技术 一种酸化油制低硫生物柴油的方法 (Method for preparing low-sulfur biodiesel from acidized oil ) 是由 罗萍 许建 王义永 平原 于 2019-10-12 设计创作，主要内容包括：本发明涉及生物柴油生产,具体提供了一种酸化油制低硫生物柴油的方法,包括以下步骤：步骤一,酸化油预处理,加入磷酸,除去水胶杂质；步骤二,酯化,进行三次酯化反应；步骤三,酯交换,加入甲醇与催化剂,高温高压反应后离心处理；步骤四,粗甲酯后处理,加入纯甘油,高温高压反应后离心处理；步骤五,将粗甲酯后处理中的甘油采用甘油精制工艺进行精制；步骤六,蒸馏,通过蒸馏获得生物柴油；本发明在酯化的过程中,酸性催化剂与水分离,不存在大量含酸出水的处理,酯化废水处理成本低；且酯化反应、酯交换反应均采用高温高压法,反应时间短,生产效率高；采用用甘油萃取粗甲酯中的皂和硫化物,使硫含量与游离甘油含量都大大降低。(The invention relates to biodiesel production, and particularly provides a method for preparing low-sulfur biodiesel from acidified oil, which comprises the following steps: step one, acidifying oil pretreatment, adding phosphoric acid, and removing water gel impurities; esterification, namely carrying out esterification reaction for three times; step three, ester exchange, adding methanol and a catalyst, reacting at high temperature and high pressure, and then centrifuging; step four, after-treatment of the crude methyl ester, adding pure glycerol, and after high-temperature and high-pressure reaction, carrying out centrifugal treatment; step five, refining the glycerol in the post-treatment of the crude methyl ester by adopting a glycerol refining process; step six, distilling to obtain biodiesel; in the esterification process, the acid catalyst is separated from water, so that a large amount of acid-containing effluent is not treated, and the treatment cost of the esterification wastewater is low; the esterification reaction and the ester exchange reaction adopt a high-temperature high-pressure method, the reaction time is short, and the production efficiency is high; the soap and sulfide in the crude methyl ester are extracted by glycerol, so that the sulfur content and the free glycerol content are greatly reduced.)

1. The method for preparing the low-sulfur biodiesel from the acidified oil is characterized by comprising the following steps of:

step one, acidic oil pretreatment, namely adding 2 percent of water and 0.03 percent of phosphoric acid into the acidic oil, stirring at a low speed for 20min at a temperature of 80-90 ℃, centrifuging the acidic oil at a temperature of 80-90 ℃ by using a centrifugal machine, and removing water heterocolloid;

step two, esterification, namely, proportioning the pretreated acidified oil and a certain mass of methanol, carrying out three times of esterification reactions in a high-temperature and high-pressure environment, and carrying out methanol removal treatment after each esterification reaction;

step three, ester exchange, namely adding methanol and an alkaline catalyst into an ester exchange pressure reaction kettle, carrying out ester exchange reaction at high temperature and high pressure, directly decompressing and removing the methanol after the reaction is finished, feeding the material into a centrifugal machine to separate soap-containing glycerol, and transferring crude methyl ester of supernatant into a post-treatment process;

step four, after-treatment of the crude methyl ester, adding the crude methyl ester in the step three into a glycerin extraction kettle, adding pure glycerin, then stirring uniformly at a high speed, putting into a centrifuge for centrifugal treatment, and obtaining supernatant and lower glycerin after treatment, wherein the supernatant after treatment is low-sulfur crude methyl ester, and transferring the low-sulfur crude methyl ester into a distillation tower;

step five, refining the glycerol in the post-treatment of the crude methyl ester by adopting a glycerol refining process, and recycling the refined glycerol;

and step six, distilling, namely distilling the low-sulfur crude methyl ester at high temperature and high pressure to obtain the biodiesel.

2. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the second step, the specific process of the first esterification reaction is that the pretreated acidified oil and methanol are mixed according to the mass ratio of 1: 0.15 to 0.20, adding the mixture into a pressure reaction kettle, adding 0.3 to 0.5 percent of phosphoric acid as a catalyst, carrying out esterification reaction under the reaction conditions of the temperature of 140 ℃ and the temperature of 160 ℃ and the pressure of 0.8 to 1.0MPa for 10 minutes, directly relieving the pressure, and separating water generated by the deacidification reaction from a reaction system along with methanol in the pressure relief process.

3. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the second step, the specific process of the second esterification reaction is that the mass ratio of the materials after the first esterification to the methanol is 1: 0.15-0.2, carrying out esterification reaction under the reaction conditions of temperature of 140-.

4. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the second step, the specific process of the second esterification reaction is that the mass ratio of the materials after the second esterification to the methanol is 1: 0.1-0.15, carrying out esterification reaction at the temperature of 140 ℃ and 160 ℃ and under the reaction condition of 0.8-1.0MPa for 5 minutes, directly decompressing to remove methanol, treating the esterified material by a centrifuge to separate impurities from the esterified material in the reaction process, detecting the acid value of the esterified material to be less than 1, and transferring the esterified material to an ester exchange reaction kettle.

5. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the third step, the ester exchange temperature is controlled at 120-130 ℃, the pressure is controlled at 0.6MPa, and the reaction time is 15 min.

6. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the fourth step, the mass ratio of the added pure glycerol to the crude methyl ester is 1: 10, the stirring temperature is controlled to be 40-70 ℃, and the stirring time is controlled to be 10 min.

7. The method for preparing low-sulfur biodiesel from acidized oil according to claim 1, which is characterized in that: in the sixth step, the distillation temperature is controlled at 220-280 ℃, and the distillation pressure is controlled at-0.1 MPa.

Technical Field

The invention relates to the technical field of biodiesel production, in particular to a method for preparing low-sulfur biodiesel from acidified oil.

Background

China is the country advocating the production of biodiesel by taking waste oil as a raw material all over the world, but in a historical period, the use of the waste oil is still the mainstream, and the process characteristics and relevant policy starting points of the biodiesel in China are determined by taking the waste oil as the raw material. From the composition, waste oil can be divided into four types, namely acidified oil, waste kitchen oil, animal oil and the like, and vegetable oil, animal oil and animal and plant mixed oil are obtained at a different angle. In order to improve the utilization rate of the waste oil, the waste oil can be used for preparing biodiesel, so that the waste biological oil is changed into valuable, but the following disadvantages exist in the actual production:

1. the existing acid-base two-step method for producing biodiesel by acidifying oil selects phosphoric acid as a catalyst for acidification, and has the disadvantages of large acid wastewater amount, high salt content and large treatment difficulty;

2. the production of the existing production process is carried out at low pressure and normal temperature, so that the time consumption is long and the production efficiency is low;

3. the biodiesel produced by the existing production process has high sulfur content and much free glycerin.

Disclosure of Invention

The invention aims to provide a method for preparing low-sulfur biodiesel from acidized oil, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme: a method for preparing low-sulfur biodiesel from acidized oil specifically comprises the following steps:

step one, acidic oil pretreatment, namely adding 2 percent of water and 0.03 percent of phosphoric acid into the acidic oil, stirring at a low speed for 20min at a temperature of 80-90 ℃, centrifuging the acidic oil at a temperature of 80-90 ℃ by using a centrifugal machine, and removing water heterocolloid;

step two, esterification, namely, proportioning the pretreated acidified oil and a certain mass of methanol, carrying out three times of esterification reactions in a high-temperature and high-pressure environment, and carrying out methanol removal treatment after each esterification reaction;

step three, ester exchange, namely adding methanol and an alkaline catalyst into an ester exchange pressure reaction kettle, carrying out ester exchange reaction at high temperature and high pressure, directly decompressing and removing the methanol after the reaction is finished, feeding the material into a centrifugal machine to separate soap-containing glycerol, and transferring crude methyl ester of supernatant into a post-treatment process;

step four, after-treatment of the crude methyl ester, adding the crude methyl ester in the step three into a glycerin extraction kettle, adding pure glycerin, then stirring uniformly at a high speed, putting into a centrifuge for centrifugal treatment, and obtaining supernatant and lower glycerin after treatment, wherein the supernatant after treatment is low-sulfur crude methyl ester, and transferring the low-sulfur crude methyl ester into a distillation tower;

step five, refining the glycerol in the post-treatment of the crude methyl ester by adopting a glycerol refining process, and recycling the refined glycerol;

and step six, distilling, namely distilling the low-sulfur crude methyl ester at high temperature and high pressure to obtain the biodiesel.

Preferably, in the second step, the specific process of the first esterification reaction is to mix the pretreated acidified oil and methanol in a mass ratio of 1: 0.15 to 0.20, adding the mixture into a pressure reaction kettle, adding 0.3 to 0.5 percent of phosphoric acid as a catalyst, carrying out esterification reaction under the reaction conditions of the temperature of 140 ℃ and the temperature of 160 ℃ and the pressure of 0.8 to 1.0MPa for 10 minutes, directly relieving the pressure, and separating water generated by the deacidification reaction from a reaction system along with methanol in the pressure relief process.

Preferably, in the second step, the specific process of the second esterification reaction is that the mass ratio of the material after the first esterification to methanol is 1: 0.15-0.2, carrying out esterification reaction under the reaction conditions of temperature of 140-.

Preferably, in the second step, the specific process of the second esterification reaction is that the mass ratio of the material after the second esterification to methanol is 1: 0.1-0.15, carrying out esterification reaction under the reaction conditions of temperature of 140-.

Preferably, in the third step, the transesterification temperature is controlled at 120-130 ℃, the pressure is controlled at 0.6MPa, and the reaction time is 15 min.

Preferably, in the fourth step, the mass ratio of the added pure glycerol to the crude methyl ester is 1: 10, the stirring temperature is controlled to be 40-70 ℃, and the stirring time is controlled to be 10 min.

Preferably, in the sixth step, the distillation temperature is controlled at 220 ℃ and 280 ℃, and the distillation pressure is controlled at-0.1 MPa.

Compared with the prior art, the invention has the beneficial effects that:

1. in the esterification process, the acid catalyst is separated from water, so that a large amount of acid-containing effluent is not treated, and the treatment cost of the esterification wastewater is low;

2. the esterification reaction and the ester exchange reaction both adopt a high-temperature high-pressure method, and the reaction time is short;

3. and a crude methyl ester post-treatment step of extracting soaps and sulfides in the crude methyl ester with glycerin so that the soap content of the crude methyl ester before entering the tower is below 0.05%, the sulfur content is below 30ppm, and the free glycerin content is below 0.02%.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example one

The invention provides a technical scheme that: a method for preparing low-sulfur biodiesel from acidized oil comprises the following steps:

step one, pretreating acidified oil, taking 500g of acidified oil, measuring that the water impurity content in the acidified oil is 3% and the sulfur content is 350ppm, adding 10g of water and 0.15g of phosphoric acid, stirring at a low speed of 80-90 ℃ for 20min, putting the materials into a centrifuge for centrifugal treatment at the temperature of 80-90 ℃, obtaining 482g of acidified oil after treatment, taking 20g of material detection indexes, and measuring: water content 0.05%, impurity content 0.08%, acid value 150mgKOH/L, sulfur content 200 ppm;

step two, esterification and first esterification reaction, namely 462g of pretreated acidified oil is taken, 92.4g of 20 percent methanol and 1.4g of phosphoric acid are added into an esterification reaction kettle, the temperature is kept for 10min under the reaction conditions of the temperature of 140-: the water content was 0.15%, and the acid value was 14.5 mgKOH/L; and (2) performing a second esterification reaction, namely adding 90g of 20% methanol into 450g of the material subjected to the first esterification, putting the mixture into a second esterification reaction kettle, performing the esterification reaction under the reaction conditions of the temperature of 140-: the water content was 0.05%, the acid value was 1.9mgKOH/L, and the sulfur content was 98 ppm; and (3) carrying out esterification reaction for the third time, namely taking 430g of the material subjected to esterification for the second time, adding 43g of 10% methanol, putting the material into a third esterification reaction kettle, carrying out esterification reaction under the reaction conditions of the temperature of 140-: the water content is 0.03%, the acid value is 0.85mgKOH/L, the sulfur content is 82ppm, wherein, 1.8g of acid catalyst is collected after the second esterification centrifugation;

step three, ester exchange, namely putting 400g of esterified material into an ester exchange reaction kettle, adding 80g of 20% methanol and 0.25% KOH1g, carrying out ester exchange reaction under the reaction conditions of temperature of 120-: the soap content was 0.6%, the sulfur content was 60 ppm;

step four, performing post-treatment on the crude methyl ester, namely adding 350g of the crude methyl ester into a glycerol extraction kettle, adding 35g of pure glycerol, stirring at a high speed for 10min, controlling the temperature to be 40-70 ℃, putting the mixed material into a centrifugal machine for centrifugal treatment, separating lower-layer glycerol and upper-layer clear liquid after treatment, taking the upper-layer clear liquid for distillation, repeatedly using the lower-layer glycerol after refining, taking 10g of the treated crude methyl ester as a detection index, and measuring: the acid value is 0.5gKOH/L, and the sulfur content is 31 ppm;

step five, refining the glycerin after the post-treatment of the crude methyl ester by a glycerin refining process to obtain 38g of pure glycerin;

step six, distilling the low-sulfur crude methyl ester, taking 300g of the treated crude methyl ester, and distilling under the conditions of pressure of-0.1 MPa and temperature of 220-280 ℃ to obtain 262.5g of biodiesel.

Example two

The invention provides a technical scheme that: a method for preparing low-sulfur biodiesel from acidized oil comprises the following steps:

step one, acidic oil pretreatment, wherein 600g of acidic oil is taken and measured: 2.5 percent of water impurity and 410ppm of sulfur, adding 12g of water and 0.18g of phosphoric acid, stirring at a low speed of 80-90 ℃ for 20min, keeping the temperature of the materials at 80-90 ℃, putting the materials into a centrifugal machine for centrifugal treatment to obtain 582g of acidified oil after treatment, taking 20g of material detection indexes, and measuring: the water content is 0.04 percent, the impurity content is 0.06 percent, the acid value is 139mgKOH/L, and the sulfur content is 280 ppm;

step two, esterification and first esterification reaction, namely, 560g of pretreated acidified oil is taken, 112g of 20% methanol and 1.68g of phosphoric acid are added into an esterification reaction kettle, the temperature is kept for 10min under the reaction conditions of the temperature of 140-: the water content was 0.13%, the acid value was 11.4mgKOH/L, and the sulfur content was 170 ppm; and (2) carrying out a second esterification reaction, namely taking 540g of the material subjected to the first esterification, adding 108g of 20% methanol, putting the material into a second esterification reaction kettle, keeping the temperature for 10min under the reaction conditions of the temperature of 140-: the water content was 0.05%, the acid value was 1.6mgKOH/L, and the sulfur content was 120 ppm; and (3) performing esterification reaction for the third time, namely adding 52g of 10% methanol into 520g of the material subjected to secondary esterification, putting the material into a third esterification reaction kettle, preserving the temperature for 10min under the reaction conditions of the temperature of 140-: the water content was 0.03%, the acid value was 0.78mgKOH/L, the sulfur content was 95ppm, wherein, 2.05g of the acid catalyst collected after the second esterification centrifugation;

step three, ester exchange, namely putting 500g of esterified material into an ester exchange reaction kettle, adding 100g of 20% methanol and 0.2% KOH1g, preserving the temperature for 15min under the reaction conditions of temperature of 120-: the soap content was 0.5%, the sulfur content was 65 ppm;

step four, carrying out post-treatment on the crude methyl ester, namely adding 480g of the crude methyl ester into a glycerol extraction kettle, adding 48g of 10% pure glycerol, stirring at a high speed for 10min, controlling the temperature to be 40-70 ℃, putting the mixed material into a centrifuge for centrifugal treatment, separating lower-layer glycerol and upper-layer clear liquid after treatment, taking the upper-layer clear liquid for distillation, reusing the lower-layer glycerol after refining, taking 10g of the treated crude methyl ester as a detection index, and measuring: the acid value is 0.45mgKOH/L, and the sulfur content is 35 ppm;

step five, refining the glycerin after the post-treatment of the crude methyl ester by a glycerin refining process to obtain 54g of pure glycerin;

step six, distilling the low-sulfur crude methyl ester, taking 400g of the treated crude methyl ester, and distilling under the conditions of pressure of-0.1 MPa and temperature of 220 ℃ and 280 ℃ to obtain 352.4g of biodiesel.

EXAMPLE III

The invention provides a technical scheme that: a method for preparing low-sulfur biodiesel from acidized oil comprises the following steps:

step one, carrying out acidification oil pretreatment, taking 400g of acidification oil, and measuring: 3.2 percent of water impurity and 290ppm of sulfur content, adding 8g of water and 0.12g of phosphoric acid, stirring at a low speed for 20min at the temperature of 80-90 ℃, keeping the materials at the temperature of 80-90 ℃, putting the materials into a centrifuge for centrifugal treatment to obtain 385g of acidified oil after treatment, and taking 20g of material detection indexes to obtain: the water content is 0.05 percent, the impurity content is 0.08 percent, the acid value is 144mgKOH/L, and the sulfur content is 310 ppm;

step two, esterification and primary esterification reaction, namely taking 350g of pretreated acidified oil, adding 70g of 20% methanol and 2g of recycled phosphoric acid (the phosphoric acid in the experiments 1 and 2 is collected and detected to have a content of 55%), putting the mixture into an esterification reaction kettle, preserving the temperature for 10min under the reaction conditions of the temperature of 140 ℃ and the pressure of 0.8-1.0MPa, directly relieving the pressure after the reaction is finished, so that low-boiling sulfide, water generated by the reaction and the methanol are flashed and separated from the reaction system together, adopting nitrogen protection in the pressure relief process, taking 10g of primary esterified material detection indexes, and measuring: the water content was 0.18%, the acid value was 14.8mgKOH/L, and the sulfur content was 195 ppm; and (2) performing a second esterification reaction, namely adding 66g of 20% methanol into 330g of the material subjected to the first esterification, putting the mixture into a second esterification reaction kettle, performing the esterification reaction under the reaction conditions of the temperature of 140-: the water content was 0.04%, the acid value was 2.0mgKOH/L, and the sulfur content was 145 ppm; and (3) performing esterification reaction for the third time, namely taking 310g of the material subjected to esterification for the second time, adding 31g of 10% methanol, putting the material into a third esterification reaction kettle, performing esterification reaction under the reaction conditions of the temperature of 145-160 ℃ and the pressure of 0.8-1.0MPa, directly relieving pressure after the reaction is finished, flashing a small amount of residual low-boiling sulfide and water generated by the reaction together with the methanol to separate from a reaction system, adopting nitrogen protection in the pressure relief process, transferring the material subjected to esterification for the third time into an ester exchange reaction kettle, taking 10g of the detection indexes of the material subjected to esterification for the second time, and measuring: the water content is 0.05%, the acid value is 0.95 mgKOH/L, the sulfur content is 105ppm, wherein, the acid catalyst collected after the second esterification is 2.3 g;

step three, ester exchange, namely putting 290g of esterified material into an ester exchange reaction kettle, adding 58g of 20% methanol and 0.25% KOH0.73g, preserving heat for 15min under the reaction conditions of temperature of 120-: the soap content was 0.65%, the sulfur content was 70 ppm;

step four, performing after-treatment on the crude methyl ester, namely adding 270g of the crude methyl ester into a glycerol extraction kettle, adding 27g of recovered refined glycerol (the content of the refined glycerol in the after-treatment of the crude methyl ester in experiments 1 and 2 is 98.5%), stirring at a high speed for 10min, controlling the temperature to be 40-70 ℃, putting the mixed material into a centrifuge for centrifugal treatment, separating out lower-layer glycerol and upper-layer clear liquid after treatment, taking the upper-layer clear liquid for distillation, reusing the lower-layer glycerol after refining, taking 10g of the treated crude methyl ester as a detection index, and measuring: the acid value is 0.52mgKOH/L, and the sulfur content is 40 ppm;

step five, refining the glycerol after the post-treatment of the crude methyl ester by a glycerol refining process to obtain 33g of pure glycerol;

step six, distilling the low-sulfur crude methyl ester, taking 250g of the treated crude methyl ester, and distilling under the conditions of pressure of-0.1 MPa and temperature of 220 ℃ and 280 ℃ to obtain 220.5g of biodiesel.

The results of the tests and comparisons of the biodiesel produced by the above three groups of examples are shown in the following table:

the biodiesel prepared by the three groups of embodiments meets the national standard of the biodiesel, wherein the yield of the biodiesel prepared by the third embodiment is the highest and reaches 88.2 percent, so the biodiesel has better market popularization value.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.