A method for preparing bio-fuel by in-situ catalytic upgrading of sludge hydrothermal crude oil under hydrogen atmosphere

Abstract

The application discloses a method for preparing biofuel by in-situ hydrogen-catalytic upgrading of sludge hydrothermal crude oil, and relates to the field of sludge resource treatment. The method for preparing biofuel by in-situ hydrogen-catalytic upgrading of sludge hydrothermal crude oil provided by the application adds long-chain alkane into the sludge hydrothermal crude oil to adjust the viscosity, so that the sludge hydrothermal crude oil can be fully mixed with liquid hydrogen-donor reagent and hydrogenation deoxidization upgrading reaction can be carried out. However, both the long-chain alkane and the liquid hydrogen-donor reagent can affect the viscosity of the biofuel obtained by upgrading the sludge hydrothermal crude oil and can affect the calorific value of the biofuel, so it is necessary to adjust the mass ratio between the sludge hydrothermal crude oil and the two reagents to be sludge hydrothermal crude oil: hydrogen-donor reagent: long-chain alkane = 1: (1-10): (1-20).

Description

Technical Field

[0001] This invention relates to the field of sludge resource utilization, specifically to a method for in-situ hydrothermal catalytic upgrading of sludge into biofuel. Background Technology

[0002] With the development of society, economy, and urbanization, the production of urban sewage sludge has been increasing year by year. Sludge contains organic matter, and recycling this organic matter can not only realize the resource utilization of sludge but also reduce environmental pollution. However, the current methods of treating urban sewage sludge are mainly incineration and landfill, and the means of resource utilization of the organic matter in sludge still need to be developed.

[0003] Sludge can be first hydrothermally treated to obtain sludge hydrothermal crude oil, the main component of which is a mixture of organic matter containing carbon, hydrogen, and oxygen. Under the catalysis of a catalyst, the sludge hydrothermal crude oil can undergo a hydrodeoxygenation reaction to achieve quality improvement, and then be transformed into biofuel with low oxygen content and high calorific value. However, existing production processes for producing biofuel from sludge hydrothermal crude oil often require the introduction of hydrogen gas into the reaction system and the maintenance of an initial hydrogen pressure of 1-3 MPa to ensure the smooth progress of the hydrodeoxygenation reaction. This reaction usually needs to be carried out at around 300°C. At this temperature, the pressure of the reaction system will increase to twice or more than the initial hydrogen pressure, which places very high demands on the pressure resistance of the production equipment, indirectly increasing the processing cost of sludge hydrothermal crude oil.

[0004] Existing technology discloses a method for preparing bio-oil from municipal sewage sludge through supercritical liquefaction with in-situ hydrogen supply. Methanol and ethanol are used simultaneously as solvents and hydrogen donors, directly hydrothermally liquefying the sludge to obtain bio-oil. The influence of the type of hydrogen donor on various properties of the bio-oil was investigated. However, the composition of the hydrothermal crude oil from sludge is complex and its viscosity is high. Using liquid instead of gas for hydrogen supply requires the addition of a large amount of liquid hydrogen donor to promote the smooth hydrodeoxygenation reaction of the hydrothermal crude oil from sludge. This leads to a decrease in the proportion of the upgraded hydrothermal crude oil from sludge in the reaction system, resulting in a decrease in the calorific value of the final biofuel, reaching a maximum of only 36.32 MJ / kg. Summary of the Invention

[0005] To address the problem that existing processes cannot utilize liquid hydrogen-donating reagents to produce high-calorific-value biofuels from hydrothermal crude oil in sludge, this invention provides a method for in-situ hydrogenation catalytic upgrading of hydrothermal crude oil in sludge to prepare biofuels. Long-chain alkanes are added to the system to adjust viscosity. By adjusting the mass ratio of the liquid hydrogen-donating reagent, hydrothermal crude oil in sludge, and long-chain alkanes, the viscosity of the reaction system is kept within a suitable range. Therefore, the hydrothermal crude oil in sludge and the hydrogen-donating reagent can fully contact each other, and the hydrothermal crude oil in sludge can extract hydrogen atoms from the liquid hydrogen-donating reagent to undergo a hydrodeoxygenation upgrading reaction, resulting in biofuels with excellent calorific value.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel includes the following steps:

[0008] The sludge hydrothermal crude oil, catalyst, hydrogen donor and long-chain alkanes are thoroughly mixed and the catalytic upgrading reaction of sludge hydrothermal crude oil is carried out at a reaction temperature of 200-350℃. After the reaction is completed, biofuel can be obtained.

[0009] The mass ratio of the sludge hydrothermal crude oil, hydrogen supply reagent and long-chain alkanes is 1:(1-10):(1-20);

[0010] The hydrogen-donating agent is a fatty alcohol and / or fatty acid with 1 to 12 carbon atoms;

[0011] The long-chain alkane is a straight-chain alkane with 10 to 20 carbon atoms.

[0012] In a specific embodiment of the present invention, the sludge hydrothermal crude oil can be prepared by sludge undergoing a hydrothermal reaction at 300-400°C for 0.5-2 hours.

[0013] In a specific embodiment of the present invention, the mass ratio of water to sludge in the above reaction system can be 10-15 mL / g.

[0014] In a specific embodiment of the present invention, the sludge can be any one or more of municipal sludge, pipeline sludge, and river and lake silt.

[0015] Conventional catalysts in this field are metal catalysts, all of which are applicable to this invention. In specific embodiments of this invention, the catalyst can be either an unsupported metal catalyst or a supported metal catalyst.

[0016] Specifically, the unsupported metal catalyst used in this invention can be any one or more of Fe, Ni, Co, Cu, Mo, and Zn.

[0017] The aforementioned unsupported metal catalyst can be prepared using conventional methods in the art. In a specific embodiment of the present invention, the unsupported metal catalyst is prepared by precipitation. The precipitant can be any one or more of sodium carbonate, ammonium carbonate, ammonia, and urea. Before the reaction, the catalyst is first reduced with hydrogen at a temperature of 200–600°C.

[0018] Specifically, the active metal component on the supported metal catalyst used in this invention is any one or more of Fe, Ni, Co, Cu, Mo, and Zn, and the catalyst support can be any one or more of Al2O3, SiO2, CeO2, and ZrO2.

[0019] The above-mentioned supported metal catalyst can be prepared using conventional methods in the art. In a specific embodiment of the present invention, the above-mentioned supported metal catalyst is prepared by impregnation.

[0020] It should be noted that using unsupported metal catalysts for catalytic reactions results in lower costs.

[0021] In a specific embodiment of the present invention, the catalytic upgrading reaction of sludge hydrothermal crude oil can be carried out in an air and / or nitrogen environment.

[0022] The hydrothermal crude oil obtained after hydrothermal treatment of sludge is a complex mixture. Its main components are organic matter containing carbon, hydrogen, and oxygen. More specifically, it is mainly long-chain fatty acids with 15 to 18 carbon atoms. Therefore, the hydrothermal crude oil has a very high viscosity.

[0023] The production of biofuel from hydrothermal sludge requires upgrading the crude oil. More specifically, it necessitates hydrodeoxygenation, which involves reducing the organic matter in the crude oil to yield long-chain fatty alcohols as fuel feedstock. Therefore, existing processes often require introducing hydrogen into the reaction system as a hydrogen source. However, introducing hydrogen requires equipment with excellent pressure resistance, which indirectly increases the processing cost of hydrothermal sludge. Furthermore, the high viscosity of sludge crude oil and the low solubility of hydrogen in it limit the catalyst's ability to fully contact and activate the hydrogen, restricting the efficiency of the hydrodeoxygenation reaction.

[0024] To address this issue, this invention employs fatty alcohols and fatty acids as liquid hydrogen-donating agents to replace hydrogen gas and supply hydrogen to the system in situ, thus reducing the pressure resistance requirements of the reaction equipment. However, using liquid hydrogen-donating agents to replace hydrogen gas still faces the problem of high viscosity of sludge hydrothermal crude oil, making it difficult for the hydrogen-donating agents to fully contact and react with it. Therefore, this invention also adds long-chain alkanes to the reaction system to adjust the viscosity. The reason for adding long-chain alkanes is to ensure the calorific value of the final biofuel while adjusting the viscosity: straight-chain alkanes with more than 10 carbon atoms are themselves the main components of fuels such as gasoline, diesel, and kerosene, and have a high calorific value. By using straight-chain alkanes with more than 10 carbon atoms to adjust the system viscosity, biofuel can be obtained without separation after the reaction.

[0025] Considering that long-chain alkanes themselves also have a certain viscosity, the number of carbon atoms in the long-chain alkanes selected in this invention should not be higher than 20, otherwise it will be difficult to play the role of adjusting viscosity.

[0026] Considering that sludge hydrothermal crude oil is a very viscous liquid, the liquid hydrogen donor should have a low viscosity. Furthermore, increasing the carbon number of fatty alcohols or acids reduces the hydrogen donation efficiency of the liquid hydrogen donor (resulting in more non-hydrogen gases such as CO2), thus limiting the reaction of sludge hydrothermal crude oil. Therefore, this invention selects fatty alcohols or acids with 12 or fewer carbon atoms as the hydrogen donor.

[0027] Optionally, the liquid hydrogen-donating reagent described above can be a straight-chain or branched fatty alcohol or acid.

[0028] Optionally, the above-mentioned liquid hydrogen-donating reagent may contain one or more hydroxyl or carboxyl groups.

[0029] It should be noted that fatty alcohols are used as liquid hydrogen donors in this field because they can generate hydrogen through steam reforming, oxidative steam reforming, and partial oxidation. Meanwhile, formic acid is generally used as a liquid hydrogen donor among fatty acids in this field, as other fatty acids are difficult to generate hydrogen through reforming or decomposition processes and are therefore generally not used as hydrogen donors.

[0030] The mass ratio of sludge hydrothermal crude oil, hydrogen donor, and long-chain alkanes is controlled at 1:(1-10):(1-20) to ensure that the final biofuel has both low viscosity and high calorific value. Insufficient hydrogen donor hinders the complete hydrodeoxygenation reaction of the sludge hydrothermal crude oil; excessive hydrogen donor leaves a large amount remaining in the system after sufficient reaction with the crude oil, and since the hydrogen donor itself has a low calorific value, this also affects the calorific value of the final biofuel. The introduction of long-chain alkanes is to adjust the system viscosity. Insufficient long-chain alkanes hinder the reaction between the sludge hydrothermal crude oil and the hydrogen donor, making it difficult to increase the calorific value of the resulting biofuel; however, excessive long-chain alkanes also reduce the calorific value of the final biofuel. This is because the primary source of calorific value for the biofuel in this invention is the upgraded sludge hydrothermal crude oil, while long-chain alkanes neither participate in the reaction nor have a higher calorific value than the upgraded sludge hydrothermal crude oil.

[0031] Preferably, the hydrogen-donating reagent has 1 to 5 carbon atoms.

[0032] Using fatty alcohols with 1 to 5 carbon atoms as hydrogen donors results in a reaction system with higher hydrogen donation efficiency and a more suitable viscosity.

[0033] More preferably, the hydrogen-donating agent is a fatty alcohol containing 1 to 2 hydroxyl groups.

[0034] Fatty alcohols are preferred as hydrogen donors because they can generate hydrogen through steam reforming, oxidative steam reforming, and partial oxidation. Further optimization is achieved by selecting fatty alcohols with 1 to 2 hydroxyl groups. This is because the hydroxyl oxygen in each alcohol molecule can form hydrogen bonds with the hydrogen atoms of other alcohol molecules. Therefore, increasing the number of hydroxyl groups per molecule leads to an increase in the viscosity of the liquid hydrogen donor itself. Although this improves hydrogen supply efficiency, it significantly increases the viscosity of the final biofuel, reducing its practicality.

[0035] Preferably, the long-chain alkane is a straight-chain alkane with 11 to 15 carbon atoms.

[0036] Adding straight-chain alkanes with 11-15 carbon atoms to the reaction system can reduce viscosity while maintaining the calorific value of the resulting biofuel. If the straight-chain alkanes have too many carbon atoms, the final biofuel will have a higher calorific value, but also a higher viscosity.

[0037] Preferably, the mass ratio of the sludge hydrothermal crude oil to the hydrogen-supplying reagent is 1:(2-6).

[0038] When the mass ratio of sludge hydrothermal crude oil to hydrogen-donating reagent is 1:(2-6), sufficient hydrogen-donating reagent can make the upgrading reaction of sludge hydrothermal crude oil more complete, so the resulting biofuel has a higher calorific value. And because the upgrading reaction is more complete, the final biofuel has a lower viscosity and is more practical.

[0039] More preferably, the mass ratio of the sludge hydrothermal crude oil to the catalyst is 1:(0.05~1).

[0040] The catalyst plays an important catalytic role in the hydrogen production reaction of the hydrogen-supplying reagent and the upgrading reaction of sludge hydrothermal crude oil. Therefore, it is necessary to control its addition amount. When the mass ratio of sludge hydrothermal crude oil to catalyst is 1:(0.05~1), the catalyst can enable both reactions involved in the reaction system to proceed more efficiently.

[0041] Preferably, the mass ratio of the sludge hydrothermal crude oil to long-chain alkanes is 1:(5-10).

[0042] When the mass ratio of sludge hydrothermal crude oil to long-chain alkanes is greater than 1:5, that is, there are too many long-chain alkanes, the viscosity of the reaction system decreases, but the calorific value of the bio-oil obtained by catalytic upgrading is also low. When the mass ratio of sludge hydrothermal crude oil to organic solvent is less than 1:10, that is, there are too few long-chain alkanes, the amount of sludge hydrothermal crude oil added is too low, and the calorific value of the biofuel produced is close to the calorific value of the long-chain alkanes themselves, making it difficult to reflect the contribution of upgraded sludge hydrothermal crude oil to the calorific value.

[0043] More preferably, the mass ratio of the hydrogen-donating reagent to the long-chain alkane is 1:(1.2 to 3.5).

[0044] By controlling the mass ratio of the long-chain alkanes and the hydrogen-donating reagents, the hydrothermal crude oil from sludge can undergo a more complete upgrading reaction at a lower viscosity, enabling the resulting biofuel to balance the relationship between calorific value and viscosity, thus possessing both high calorific value and low viscosity.

[0045] Preferably, the catalytic upgrading reaction of the sludge hydrothermal crude oil takes 1 to 12 hours.

[0046] The reaction time is controlled to be 1 to 12 hours in order to ensure that the upgrading reaction of sludge hydrothermal crude oil can proceed fully, while avoiding unnecessary energy waste.

[0047] Preferably, the catalytic upgrading reaction of the sludge hydrothermal crude oil is carried out at a reaction temperature of 250–330°C.

[0048] If the temperature is too high, the hydrogen-donating reagent is prone to escape from the reaction system, which leads to a decrease in the efficiency of the hydrothermal crude oil upgrading reaction and a decrease in the calorific value of biofuel; if the temperature is too low, the efficiency of the reaction will also decrease.

[0049] Preferably, the catalyst is a supported metal catalyst.

[0050] More preferably, the active components on the supported metal catalyst are Ni, Co and Zn.

[0051] By using the above three metals to construct the active components on the supported metal catalyst, the resulting biofuel has higher calorific value, lower viscosity, and higher density after the catalytic reaction is completed.

[0052] More preferably, the molar ratio of the active components on the supported metal catalyst is Ni:Co:Zn = 1:(0.2~1):(0.2~1).

[0053] More preferably, the loading of the active component on the supported metal catalyst is 5 to 30 wt%.

[0054] Compared with the prior art, the present invention has the following beneficial effects:

[0055] The method provided by this invention, which involves hydrothermal upgrading of sludge into crude oil, produces biofuel that possesses both high calorific value and low viscosity, meeting practical needs (lower viscosity results in better flowability and easier application). The biofuel provided by this invention has a calorific value above 36.5 MJ / kg and a viscosity below 3.02 mm. 2 Its density is as high as 0.71–0.93 g / cm³. 3 . Detailed Implementation

[0056] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0057] Example 1

[0058] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel includes the following steps:

[0059] The sludge hydrothermal crude oil, catalyst, hydrogen donor isopropanol and long-chain alkane n-dodecane are thoroughly mixed and the sludge hydrothermal crude oil is catalytically upgraded at a reaction temperature of 320℃ for 3 hours. After the reaction is completed, biofuel can be obtained.

[0060] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent and long-chain alkanes are 1g, 3g and 6g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent and long-chain alkanes is 1:3:6.

[0061] The mass ratio of the sludge hydrothermal crude oil to the catalyst is 1:0.1;

[0062] The catalyst is a supported metal catalyst, wherein the active components are Ni, Co and Zn, the molar ratio of the active components is Ni:Co:Zn = 1:0.5:0.5, the support is CeO2, and the loading of the active components on the catalyst is 20wt%.

[0063] The sludge hydrothermal crude oil is prepared by hydrothermal reaction of municipal sludge at 350℃ for 1 hour, and the mass ratio of water to sludge in the reaction system is 12 mL / g.

[0064] Example 2

[0065] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0066] The hydrogen-donating agent is methanol.

[0067] Example 3

[0068] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0069] The hydrogen-donating agent is dodecanol.

[0070] Example 4

[0071] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0072] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 1g, and 6g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:1:6.

[0073] Example 5

[0074] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0075] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 5g, and 6g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:5:6.

[0076] Example 6

[0077] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0078] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 10g, and 6g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:10:6.

[0079] Example 7

[0080] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0081] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 3g, and 1g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:3:1.

[0082] Example 8

[0083] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0084] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 3g, and 2g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:3:2.

[0085] Example 9

[0086] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0087] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 3g, and 8g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:3:8.

[0088] Example 10

[0089] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0090] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 3g, and 10g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:3:10.

[0091] Example 11

[0092] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0093] The masses of the sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes are 1g, 3g, and 20g respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen supply reagent, and long-chain alkanes is 1:3:20.

[0094] Example 12

[0095] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0096] The long-chain alkane is hexadecane.

[0097] Comparative Example 1

[0098] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0099] The hydrogen-donating agent is pentadecyl alcohol.

[0100] Comparative Example 2

[0101] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0102] The long-chain alkane is n-pentane.

[0103] Comparative Example 3

[0104] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0105] The hydrogen-donating reagent is n-dodecane.

[0106] Comparative Example 4

[0107] A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to produce biofuel, wherein the difference from Example 1 is:

[0108] The masses of the sludge hydrothermal crude oil, hydrogen-donating reagent, and long-chain alkanes are 1g, 0.05g, and 6g, respectively, that is, the mass ratio of sludge hydrothermal crude oil, hydrogen-donating reagent, and long-chain alkanes is 1:0.05:6.

[0109] Performance testing

[0110] The viscosity and density of the biofuels obtained in Examples 1-12 and Comparative Examples 1-4 were tested at 0°C using a viscometer and a density meter.

[0111] The theoretical calorific value of the biofuels obtained in Examples 1-12 and Comparative Examples 1-4 was calculated using the formula: HHV (MJ / kg) = 33800w. C +144153w H -18019w O +9412w S , where w C w represents the mass fraction of element C.H w represents the mass fraction of element H. O w represents the mass fraction of element O. S This represents the mass fraction of element S.

[0112] The specific implementation parameters and performance test data are shown in Tables 1-3 below:

[0113] Table 1. Parameter control in the preparation methods provided in Examples 1-12

[0114]

[0115] Table 2. Parameter control in the preparation methods provided in Comparative Examples 1–4

[0116]

[0117] Table 3. Performance test data of the examples and comparative examples

[0118] Calorific value (MJ / kg) <![CDATA[Viscosity at 0°C (mm 2 / s)]]> <![CDATA[Density (g / cm 3 )]]> Example 1 37.1442 2.79 0.7245 Example 2 36.8604 2.8 0.7213 Example 3 37.68 3.02 0.7634 Example 4 37.1232 2.92 0.7312 Example 5 37.1989 2.75 0.7211 Example 6 37.0322 2.70 0.7182 Example 7 37.6899 2.99 0.93 Example 8 37.5422 2.96 0.86 Example 9 37.3669 2.83 0.75 Example 10 36.9981 2.7 0.73 Example 11 36.6916 2.72 0.72 Example 12 39.8417 3.02 0.7188 Comparative Example 1 36.2203 2.97 0.7487 Comparative Example 2 36.6741 2.89 0.77 Comparative Example 3 36.6522 3.03 0.81 Comparative Example 4 36.8673 3.12 0.98

[0119] As can be seen from the data in Tables 1-3, when the hydrogen donor is methanol or isopropanol (Examples 1-2), since its carbon number is within the preferred range of 1-5 in this invention, it can achieve higher hydrogen supply efficiency and a more suitable viscosity, thus enabling the sludge hydrothermal crude oil to undergo a more complete upgrading reaction, resulting in biofuel with high calorific value and low viscosity. When the hydrogen donor is dodecanol (Example 3), the hydrogen supply efficiency decreases, therefore the efficiency of the sludge hydrothermal crude oil upgrading reaction decreases, and the calorific value of the resulting biofuel decreases accordingly, while the viscosity also increases (the viscosity of un-upgraded sludge hydrothermal crude oil is greater than that of the upgraded biofuel). Comparing the data from Examples 1 and 4-6, it can be seen that when the mass ratio of sludge hydrothermal crude oil to hydrogen donor is within the preferred range of 1:(2-6) in this invention (Examples 1 and 5), the upgrading reaction of the sludge hydrothermal crude oil can proceed more fully, thus resulting in biofuel with higher calorific value and lower viscosity. Comparing the data from Examples 1 and 7-11, it can be seen that when the mass ratio of sludge hydrothermal crude oil to long-chain alkanes is within the preferred range of 1:(5-10) in this invention (Examples 1, 9, and 10), the resulting biofuel can also have both higher calorific value and lower viscosity. This is because long-chain alkanes with fewer than 20 carbon atoms, as components of fuels such as diesel, have a high calorific value, but at the same time, they can adjust the viscosity of the reaction system of this invention through their own low viscosity.

[0120] The data from Comparative Example 1 show that when the carbon number of the alcohol is higher than 12, the hydrogen supply efficiency of the liquid hydrogen-donating reagent is significantly reduced, thus decreasing the calorific value of the resulting biofuel. The data from Comparative Examples 2 and 3 show that too many or too few carbons in long-chain alkanes also make it difficult to balance the viscosity and calorific value of the resulting biofuel. The data from Comparative Example 4 shows that insufficient addition of the hydrogen-donating reagent hinders the complete upgrading reaction of the sludge hydrothermal crude oil, also reducing the calorific value of the resulting biofuel.

[0121] The biofuel provided by this invention has a density of 0.71–0.93 g / cm³. 3 Within this range, the density is higher than most existing biofuels, indicating that the biofuel prepared by this invention has a higher energy density per unit volume.

[0122] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for in-situ hydrothermal catalytic upgrading of sludge and crude oil to prepare biofuel, characterized in that, Includes the following steps: Sludge is hydrothermally treated to obtain sludge hydrothermal crude oil. The sludge hydrothermal crude oil, catalyst, hydrogen donor and long-chain alkanes are thoroughly mixed and subjected to catalytic upgrading reaction at a reaction temperature of 200~350℃. After the reaction is completed, biofuel is obtained. The long-chain alkanes do not separate from the biofuel after the reaction is completed. The mass ratio of the sludge hydrothermal crude oil, hydrogen supply reagent and long-chain alkanes is 1:(3~5):6; The hydrogen-donating agent is isopropanol; The long-chain alkane is n-dodecane.

2. The method for preparing biofuel from sludge through hydrothermal crude oil in-situ hydrogenation catalytic upgrading as described in claim 1, characterized in that, The mass ratio of the sludge hydrothermal crude oil to the catalyst is 1:(0.05~1).

3. The method for preparing biofuel from sludge through hydrothermal crude oil in situ hydrogenation catalytic upgrading as described in claim 1, characterized in that, The catalytic upgrading reaction of the sludge hydrothermal crude oil takes 1 to 12 hours.

4. The method for preparing biofuel from sludge through hydrothermal crude oil in-situ hydrogenation catalytic upgrading as described in claim 1, characterized in that, The catalytic upgrading reaction of the sludge hydrothermal crude oil is carried out at a temperature of 250~330℃.

Images