Environment-friendly biomass liquid fuel and preparation method thereof

Abstract

The invention relates to an environment-friendly biomass liquid fuel and a preparation method thereof in the field of biomass fuel preparation, the environment-friendly biomass liquid fuel comprises alcohols, ethers and biomass oil, the alcohols are low-carbon alcohols, the ethers are ethers obtained by performing catalytic dehydration on the low-carbon alcohols, and ethers obtained by condensing the alcohols and aldehydes, the biomass oil is biodiesel, and the biomass oil is a mixture of the biodiesel and the ethers. The biomass liquid fuel is high in oxygen content and cetane number, combustion of the fuel in an engine is more sufficient, particulate matter and black smoke are greatly reduced, the fuel does not contain sulfur, sulfur oxide cannot be generated after combustion, the fuel is more friendly to a three-way catalyst and an aftertreatment device, the service life of the three-way catalyst and the aftertreatment device is prolonged, finally, the main component of the fuel comes from biomass, and the fuel is environmentally friendly. The carbon emission in the life cycle is lower, and the growth of greenhouse gases can be slowed down. For popularization and application of public transportation and urban logistics vehicles, the fuel can improve the urban air quality and relieve the pressure of oil resource shortage, and has great social and environmental benefits.

Description

Technical Field

[0001] The present invention relates to biomass liquid fuels, and particularly to an environment-friendly biomass liquid fuel and a preparation method thereof applied to the field of biomass fuel preparation. Background Art

[0002] Currently, the common vehicle liquid fuels are mainly gasoline and diesel, both of which are derived from fossil resources. During their combustion process, traditional fuels have many environmental problems: they emit pollutants such as carbon monoxide (CO), hydrocarbons (HC), nitrogen oxides (NOx), and particulate matter. In addition, the combustion of fossil fuels will produce a large amount of carbon dioxide (CO2) greenhouse gas.

[0003] To reduce the dependence on petroleum resources and lower emissions, various alternative fuels have been developed in recent years, such as alcohol fuels and biodiesel.

[0004] The specification of invention patent CN201210137813.6 discloses an apparatus and method for continuously preparing biodiesel under medium temperature and medium pressure conditions. The apparatus and method disclosed in this application can achieve continuous atomization feeding and continuous extraction. Under medium temperature and medium pressure conditions, a very small amount of catalyst is used for esterification reaction to obtain biodiesel, with short reaction time, high product quality, high working efficiency, less capital investment, low equipment corrosion degree, and long service life.

[0005] However, there are still technical bottlenecks in the actual application of alternative fuels: (1) The calorific value of single alcohol fuels (such as methanol and ethanol) is relatively low, only about half of that of gasoline, resulting in a decline in engine power, difficult cold start at low temperatures, and strong material corrosion, requiring engine modification; (2) Biodiesel (fatty acid methyl ester) can directly replace part of diesel, but it has poor low-temperature fluidity (easy to solidify), high oxygen content, which is likely to cause an increase in nitrogen oxide emissions, and the raw material supply of pure biodiesel is limited; (3) Ether fuels such as dimethyl ether have the advantages of high cetane number and clean combustion, but dimethyl ether is gaseous at room temperature and requires high-pressure storage. A single alternative fuel is difficult to simultaneously achieve high calorific value and clean emissions. There is an urgent need to develop a new type of liquid fuel that combines the advantages of alcohol fuels, ether fuels, and biomass fuels to overcome the existing technical bottlenecks. Summary of the Invention

[0006] Aiming at the above-mentioned prior art, the technical problem to be solved by the present invention is that a single alternative fuel is difficult to simultaneously achieve high calorific value and clean emissions, and there is an urgent need to develop a new type of liquid fuel that combines the advantages of alcohol fuels, ether fuels, and biomass fuels.

[0007] To solve the above problems, the present invention provides an environment-friendly biomass liquid fuel, which includes alcohols, ethers and biomass oil. The alcohols are low-carbon alcohols, the ethers are ethers obtained by catalytic dehydration of low-carbon alcohols and ethers obtained by condensation of alcohols and aldehydes. The component of the biomass oil is biodiesel, that is, fatty acid esters prepared from animal and vegetable oils. The mass ratio of alcohols, ethers and biomass oil is: 5-20%, 10-30%, 50-85%.

[0008] In the above environment-friendly biomass liquid fuel and its preparation method, alcohols, ethers and biomass oil are organically combined, with the advantages of high calorific value, low emission and renewable, etc., and can be used as automobile engine fuel, thus effectively reducing tail gas pollution and alleviating the pressure of fossil energy.

[0009] The preparation method of the environment-friendly biomass liquid fuel mainly includes the following steps:

[0010] S1. Raw material pretreatment: Take plant oil as the raw material of biomass oil, and pretreat the plant oil, filter to remove impurities and moisture, so that the water content of the plant oil is reduced to less than 0.1%. The alcohol raw material is anhydrous methanol with a purity of ≥99.5%. The pretreated plant oil and alcohol raw material are respectively stored in the raw material tank for later use;

[0011] S2. Transesterification reaction: Put the pretreated plant oil and alcohol raw material into the transesterification reaction kettle according to the molar ratio of oil to alcohol of 1:6-1:8, add the alkaline catalyst KOH, and the dosage of the catalyst is 0.5%-1% of the mass of the plant oil. Start stirring in the reaction kettle, raise the temperature to 55°C-65°C, pressurize the reaction kettle to 0.3 Mpa, and keep the constant temperature reaction for 1-2 hours, so that the triglycerides in the oil and methanol fully undergo transesterification reaction to generate fatty acid methyl ester and by-product glycerol. After the transesterification is completed, turn off the heating and let it stand to obtain the reaction mixture;

[0012] S3. Product separation and purification: The reaction mixture obtained in step S2 is subjected to sedimentation and stratification. The bottom precipitation phase is the glycerol phase, and the upper layer is the crude biodiesel phase. Slowly release the glycerol by-product. The crude biodiesel is washed several times with warm water, and then the excess methanol is recovered by vacuum distillation to obtain the biodiesel intermediate. Then the biodiesel intermediate is vacuum dried at 110°C to obtain a pure biodiesel product with a water content of <0.05%. The obtained biodiesel is a light yellow transparent liquid with a density of 0.88 g / cm 3 , and the kinematic viscosity is 4.5 mm 2 / s;

[0013] S4. Ether production by catalytic dehydration of alcohol: Feed the anhydrous methanol stored in step S1 into a fixed-bed etherification reactor through a metering pump, and fill the fixed-bed etherification reactor with a solid acid catalyst. The solid acid catalyst is selected from γ-alumina or HZSM-5 zeolite molecular sieve. Heat the reactor to 250 - 300 °C and maintain the pressure at 0.5 - 1.5 MPa. The methanol undergoes a dehydration coupling reaction on the catalyst surface:

[0014] 2CH3OH → CH3OCH3 + H2O;

[0015] Obtain the product dimethyl ether and water. Cool the mixed gas generated by the reaction to room temperature in a condenser, condense out the liquid dimethyl ether and the water phase, and separate the dimethyl ether from the water using a gas-liquid separator: Discharge the water phase for treatment, and the gaseous dimethyl ether enters a refrigerated storage tank to obtain the liquefied dimethyl ether;

[0016] S5. Mixing and blending: Mix the biodiesel obtained in step S3 and the liquefied dimethyl ether obtained in step S4 in a pressure-resistant sealed mixing tank at a mass ratio of 4:1, and stir for 20 minutes. Control the temperature at about 30 °C during the mixing process and keep the pressure in the tank not lower than 0.6 MPa to obtain the finished product of the alcohol-ether-based biomass liquid fuel.

[0017] As a further improvement of the present application, step S2 and step S4 are carried out synchronously without priority to improve the production efficiency of the biomass liquid fuel.

[0018] As a further improvement of the present application, in step S4, the catalyst HZSM-5 belongs to a ten-ring zeolite molecular sieve and has two sets of mutually intersecting pores (pore diameter of about 0.51×0.55 nm), and its microporous specific surface area can be as high as 395 m 2 / g. Under a scanning electron microscope, HZSM-5 usually presents regular micron-sized crystal particles, and the average grain size is about 1 - 2 μm.

[0019] As another improvement of the present application, in step S4, the catalyst γ-Al2O3 is a transition alumina, showing a mesoporous structure, a porous network structure composed of nanoparticles, having a very high porosity, and its internal surface area can reach 200 - 400 m 2 / g.

[0020] As a supplementary improvement of the present application, in step S5, add a stabilizer or a cosolvent accounting for less than 1% of the total mass to the finished product of the biomass liquid fuel to further improve the low-temperature miscibility of the finished product of the biomass liquid fuel. The final product is a single homogeneous liquid, which does not separate layers at room temperature and has good storage stability.

[0021] In summary, the biomass liquid fuel of the present application has a high oxygen content and a high cetane number. The fuel burns more fully in the engine, significantly reducing particulate matter and black smoke. The fuel does not contain sulfur and will not produce sulfur oxides after combustion, which is more friendly to the three-way catalytic converter and the aftertreatment device and extends their service life. Finally, the main components of this fuel come from biomass, are renewable, and have lower carbon emissions in the life cycle, which is conducive to slowing down the growth of greenhouse gases. For the popularization and application of public transportation and urban logistics vehicles, the fuel of the present invention can improve urban air quality and relieve the pressure of tight oil resources, having significant social and environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the preparation method of the environment-friendly biomass liquid fuel according to the first embodiment of the present application;

[0023] Figure 2 Microscopic pore structure model diagram of HZSM-5 molecular sieve in the alcohol catalytic dehydration to ether step according to the first embodiment of the present application;

[0024] Figure 3 Comparison diagram of the combustion emissions of the biomass liquid fuel and traditional diesel according to the second embodiment of the present application;

[0025] Figure 4 Gas chromatogram (FID) of the biomass liquid fuel according to the second embodiment of the present application;

[0026] Figure 5 Fourier transform infrared (FTIR) spectrum of the biomass liquid fuel according to the second embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following provides a detailed description of the two embodiments of the present application with reference to the accompanying drawings.

[0028] The first embodiment:

[0029] Figure 1 An environment-friendly biomass liquid is shown, including alcohols, ethers, and biomass oil. The alcohols are preferably lower alcohols, such as methanol or ethanol and their mixtures; the ethers are ethers obtained by catalytic dehydration of lower alcohols, such as dimethyl ether (DME) and diethyl ether, and ethers obtained by condensation of alcohols and aldehydes, such as polyoxymethylene dimethyl ether, etc. The biomass oil component is preferably biodiesel, that is, fatty acid esters prepared from animal and vegetable oils, such as fatty acid methyl ester. The mass ratio of alcohols, ethers, and biomass oil is: 5-20%, 10-30%, 50-85%. Among them, the optimal ratio is that the total content of alcohols and ethers accounts for about 20% and the biomass oil content is about 80%, which can ensure the stability and high calorific value of the fuel.

[0030] Its preparation method mainly includes the following steps:

[0031] S1. Pretreatment of raw materials: Take vegetable oil as the raw material for bio-oil, such as waste cooking oil or wild oil crop oil (such as palm oil, rapeseed oil, etc.), and pretreat the vegetable oil. Filter to remove impurities and moisture, and reduce the water content of the vegetable oil to less than 0.1% to avoid saponification in the subsequent transesterification reaction. The alcohol raw material is anhydrous methanol (or ethanol) with a purity of ≥99.5%. The pretreated vegetable oil and alcohol raw materials are stored in raw material tanks for later use;

[0032] S2. Transesterification reaction: Put the pretreated vegetable oil and alcohol raw materials into the transesterification reactor according to the molar ratio of oil to alcohol of 1:8, add the alkaline catalyst KOH, and the catalyst dosage is 1% of the mass of the vegetable oil. Start stirring in the reactor, raise the temperature to 65°C, pressurize the reactor to 0.3 Mpa, and keep the temperature constant for 2 hours to fully carry out the transesterification reaction between the triglycerides in the oil and methanol, generating fatty acid methyl ester (biodiesel) and the by-product glycerol. The high-pressure environment increases the solubility of methanol and thus speeds up the reaction rate. After the transesterification is completed, turn off the heating and let it stand to obtain the reaction mixture;

[0033] S3. Product separation and purification: The reaction mixture obtained in step S2 is subjected to sedimentation and stratification. The bottom precipitated phase is the glycerol phase, and the upper layer is the crude biodiesel phase. Slowly release the glycerol by-product. The crude biodiesel is washed several times with warm water to remove the residual catalyst and soap, and then the excess methanol is recovered by vacuum distillation to obtain the biodiesel intermediate. Then the biodiesel intermediate is vacuum dried at 110°C to obtain a pure biodiesel product with a water content of <0.05%. The obtained biodiesel is a light yellow transparent liquid, with a density of 0.88 g / cm 3 (at an ambient temperature of 20°C), and a kinematic viscosity of 4.5 mm 2 / s (at an ambient temperature of 40°C), which can be directly used as diesel fuel or stored for standby. The by-product glycerol can be further refined for the preparation of glycerol ether fuel additives or other uses to improve the resource utilization rate;

[0034] S4. Alcohol catalytic dehydration to ether: Feed the anhydrous methanol stored in step S1 into the fixed-bed etherification reactor through a metering pump, and fill the fixed-bed etherification reactor with a solid acid catalyst. The solid acid catalyst is selected from γ-aluminum oxide or HZSM-5 molecular sieve. Heat the reactor to 280°C and maintain the pressure at 1 MPa. Methanol undergoes a dehydration coupling reaction on the surface of the catalyst:

[0035] 2CH3OH → CH3OCH3 + H2O;

[0036] The products obtained are dimethyl ether (DME) and water. The mixed gas generated by the reaction is cooled to room temperature by a condenser, and the liquid dimethyl ether and the aqueous phase are condensed out. A gas-liquid separator is used to separate dimethyl ether from water: the aqueous phase is discharged for treatment, and the gaseous dimethyl ether enters a refrigerated storage tank (maintaining an appropriate pressure to liquefy it). The obtained liquefied dimethyl ether has a product purity of over 99%. A small amount of unreacted methanol is removed with the aqueous phase or recycled back to the etherification reactor to improve the raw material utilization rate;

[0037] S5. Mixing and blending: The biodiesel obtained in step S3 and the liquefied dimethyl ether obtained in step S4 are mixed in a pressure-resistant and sealed mixing tank at a mass ratio of 4:1 and stirred for 20 minutes. During the mixing process, the temperature is controlled at about 30 °C, and the pressure in the tank is maintained not lower than 0.6 MPa to prevent the gasification loss of dimethyl ether and ensure that dimethyl ether is fully dissolved and dispersed in the biodiesel, obtaining the finished product of the alcohol-ether-based biomass liquid fuel.

[0038] Step S2 and step S4 are carried out simultaneously without a specific sequence, increasing the production efficiency of the biomass liquid fuel.

[0039] Please refer to Figure 2 , in step S4, the catalyst HZSM-5 belongs to a ten-ring zeolite molecular sieve, where the shaded color is oxygen and the bright color is silicon-aluminum. It has two sets of intersecting pore channels (pore diameter of about 0.51×0.55 nm), and its microporous specific surface area can be as high as 395 m 2 / g. Under a scanning electron microscope (SEM), HZSM-5 usually presents regular micron-sized crystal particles with an average grain size of about 1–2 μm.

[0040] In step S4, the catalyst γ-Al2O3 is transition alumina, showing a mesoporous structure, a porous network structure composed of nanoparticles, with a very high porosity, and its internal surface area can reach 200–400 m 2 / g.

[0041] The high specific surface area and unique pore channels of these catalysts help to improve the cracking and esterification efficiency of macromolecules (such as oils and fats) in biomass, thus promoting the preparation of environmentally friendly fuels.

[0042] In step S5, a stabilizer or cosolvent (such as n-propanol, n-butanol) accounting for less than 1% of the total mass is added to the finished product of the biomass liquid fuel to further improve the low-temperature miscibility of the finished product of the biomass liquid fuel. The final product is a single homogeneous liquid that does not separate into layers at room temperature and has good storage stability.

[0043] The biomass liquid fuel prepared through the above steps can be directly transported to the vehicle fuel tank through a fuel filling system. The operating conditions and parameters of each unit can be slightly adjusted according to the specific scale and actual production environment. The process conditions of the method of the present invention are mild, and the equipment used includes a reaction kettle, a settling tank, a fixed bed reactor, a pressurized mixing tank, etc., all of which are mature industrial devices and have good prospects for industrial application.

[0044] Due to the high oxygen content and high cetane number of the biomass liquid fuel in this embodiment, the fuel burns more fully in the engine, and the particulate matter and black smoke are greatly reduced, which helps diesel vehicles meet more stringent emission standards (such as the "National VI" standard);

[0045] Secondly, the fuel does not contain sulfur and will not produce sulfur oxides after combustion, which is more friendly to the three-way catalytic converter and the aftertreatment device and prolongs its service life;

[0046] Finally, the main components of this fuel come from biomass, which is renewable and has lower carbon emissions in the life cycle, contributing to slowing down the growth of greenhouse gases. For the popularization and application of public transportation and urban logistics vehicles, the fuel of the present invention can improve urban air quality and relieve the pressure of tight oil resources, with significant social and environmental benefits.

[0047] Particularly, in certain application scenarios, the fuel of the present invention can also be mixed with conventional diesel in any proportion to form a blended fuel to improve adaptability. For example, in cold regions, a certain proportion of petrochemical diesel can be added to improve the low-temperature fluidity; in high-load working conditions, a small amount of high-carbon alcohol ethers can be incorporated to further increase the calorific value and power.

[0048] The second embodiment:

[0049] Using waste cooking oil as raw material to prepare an environmentally friendly biomass liquid fuel, take 5 kg of waste rapeseed oil (free fatty acid content < 1%) treated through step S1, add 1.0 kg of anhydrous methanol (the molar ratio of oil to alcohol is 1:6) and 40 g of KOH (accounting for 0.8% of the oil quality) into a 5 L stainless steel reaction kettle, heat to 60 °C and stir for 1 hour.

[0050] After the reaction is completed, let it stand for 30 minutes, and release about 0.5 kg of glycerol layer to obtain crude biodiesel. Wash the crude biodiesel 3 times with 60 °C hot water until the washing liquid is neutral, and then recover 0.1 kg of unreacted methanol by vacuum distillation at 90 °C. Finally, 4.4 kg of pure biodiesel is produced, and the ester yield is about 88%.

[0051] The main components of the obtained biodiesel are C16 - C18 fatty acid methyl esters, with a cetane number of about 52, an initial boiling point of 350 °C, and a flash point of 170 °C, meeting the main indicators of the Chinese national biodiesel standard.

[0052] Add 100 g of catalyst HZSM-5 to a fixed-bed etherification reactor, and introduce 0.5 kg of methanol. Continuously react under the conditions of a temperature of 270 °C and a pressure of 1.0 MPa to prepare dimethyl ether.

[0053] Mix 2.0 kg of the above-prepared biodiesel with 0.3 kg of liquefied dimethyl ether (mass ratio is approximately 87:13) in an autoclave. Control the temperature at 25 - 30 °C and the pressure at 0.8 MPa, and mechanically stir for 15 minutes to obtain 2.3 kg of a homogeneous and transparent biomass liquid fuel.

[0054] Test the key performance indicators of the biomass liquid fuel: density 0.82 g / cm 3 (at an ambient temperature of 20 °C), kinematic viscosity 3.8 mm 2 / s (at an ambient temperature of 40 °C), the closed-cup flash point is not detected (due to the presence of volatile dimethyl ether, the flash point does not appear under normal pressure, but it is safe and controllable under pressurized conditions), lower heating value 36.5 MJ / kg, and oxygen mass fraction is approximately 15%.

[0055] The evaluation results of the engine combustion performance show that the cetane number of this fuel is approximately 54, close to that of high-quality diesel, and the combustion is rapid and stable. This fuel was tested on a modified single-cylinder direct injection diesel engine, comparing with the conditions of petrochemical diesel.

[0056] Please refer to Figure 3 , the simulated comparison of the combustion emissions of biomass liquid fuel and traditional diesel in a compression ignition engine (taking the emissions of diesel as 100). The dark columns are alcohol-ether biofuels, and the light columns are diesel.

[0057] Compared with diesel, the PM, CO, and HC emissions of the biomass liquid fuel are significantly reduced (only approximately 20%, 50%, and 30% of diesel respectively), and the NO x emissions decrease slightly (approximately 90% of diesel).

[0058] This change trend is consistent with the emission characteristics of biodiesel and fuels added with oxides: biomass fuels with a high oxygen content burn more fully, thus significantly reducing PM, CO, and HC. Research shows that for every 1% increase in the oxygen content of the fuel, the PM emissions of the diesel engine can be reduced by an average of 7 - 10%. Alcohol-ether-based fuels contain a relatively high proportion of oxygen (from alcohols and ethers), and the soot significantly decreases during combustion.

[0059] At the same time, alcohol / ether fuels have a relatively high latent heat of vaporization and a relatively low in-cylinder combustion temperature, which helps to inhibit the formation of NO x . Generally speaking, the environmentally friendly biomass liquid fuel significantly reduces the main harmful emissions while maintaining the power performance, which is beneficial to reducing air pollution.

[0060] Please refer toFigure 4 , the gas chromatogram (FID) of the biomass liquid fuel, with the X-axis being the retention time (min). The peak area reflects the content of each component. There are small molecule peaks of alcohols / ethers at low retention times, and peaks of fatty acid methyl esters at high retention times.

[0061] The fuel sample shows a multi-component mixture chromatogram after gas chromatography analysis. The early eluate peaks with retention times of 1 - 3 minutes mainly correspond to low-boiling small molecule alcohols and ethers, such as alcohols (e.g., the ethanol peak is approximately at 2.0 min) and ethers (e.g., the diethyl ether peak is at 3.5 min), etc.

[0062] Subsequently, a series of peaks with relatively large intensities appear at longer retention times of 7 - 9 minutes. These peaks correspond to the fatty acid methyl ester (FAME) components in biodiesel, such as methyl ester derivatives of C16 - C18 long-chain fatty acids. Typically, a series of peaks such as methyl palmitate (C16:0), methyl stearate (C18:0), methyl oleate (C18:1), methyl linoleate (C18:2), etc. will appear in the GC chromatogram of biodiesel (fatty acid methyl ester). The areas of multiple retention peaks in the above chromatogram indicate that the fuel contains a certain proportion of alcohols / ethers (for improving combustion performance and cold start) and traditional biodiesel components. By separating each component through gas chromatography and quantifying with the peak area, it can be confirmed that the biomass liquid fuel contains a mixture of components such as alcohols, ethers, and fatty acid methyl esters, verifying that its formulation composition is consistent with the patent formulation design.

[0063] After gas chromatography analysis, the single-pass conversion rate of methanol reaches 80%, and the selectivity of dimethyl ether > 98%. The reaction products are separated by condensation, and 0.28 kg (about 0.35 L) of liquefied dimethyl ether with a purity of 97% is collected.

[0064] Please refer to Figure 5 , which is the Fourier transform infrared (FTIR) spectrogram of the fuel sample. The horizontal axis is the wave number (cm -1 ). The positions of the main functional group absorption peaks (3400, 2925, 1740, 1170 cm -1 ) are marked with gray dotted lines in the figure.

[0065] The FTIR spectrum can be used to characterize the functional group structure in the alcohol-ether-based fuel. Several typical absorption peaks can be identified from the spectrum:

[0066] The C-H stretching vibration appears as strong peaks at ~2920 cm -1 and ~2850 cm -1 , corresponding to the asymmetric and symmetric CH2 stretching vibrations of the long alkyl chains in the fuel. These strong peaks indicate that the fuel contains long-chain alkyl groups (saturated fatty acid esters have obvious C-H absorption).

[0067] The stretching vibration of D-C=O appears at ~1740 cm -1 with a sharp and strong absorption peak, which is attributed to the carbonyl group of esters. The ester carbonyl of fatty acid methyl esters usually absorbs in the range of 1750–1735 cm -1 , which is consistent with Figure 5 , proving the presence of ester bonding in the sample.

[0068] The stretching of the C-O bond shows an absorption band near 1170–1100 cm -1 , which is the characteristic absorption region of the C-O single bond in esters and ethers. The strong absorption peak at 1160–1170 cm -1 corroborates the existence of the ester bond in fatty acid methyl esters.

[0069] The O-H vibration (if there is free alcohol) may appear as a broad absorption peak at ~3400 cm -1 (this peak is relatively weak in this example, indicating that the alcohol has been mainly converted or has a low proportion). These infrared characteristic peaks are consistent with those reported in the literature for biodiesel and alcohol ether functional groups. For example, saturated fatty esters have absorptions at 2923 / 2854 cm -1 (C–H), 1740 cm -1 (C=O), and around 1170 cm -1 (C–O). Thus, the FTIR spectrum provides a fingerprint verification of the fuel molecular structure, supporting that the biomass liquid fuel in this embodiment indeed contains functional groups such as ester groups, ether bonds, and alkyl groups, realizing the molecular characteristics of the formulation.

[0070] Compared with traditional diesel, the biomass liquid fuel of this application has the following advantages:

[0071] Improved combustion efficiency: By optimizing the ratios of various fuels and the production and preparation processes, the fuel burns more fully, not only reducing energy waste but also effectively improving the thermal energy utilization rate during fuel combustion.

[0072] Significantly reduced pollution emissions: Compared with traditional fuels, this patented technology significantly reduces the emissions of harmful gases and further reduces the pollution to the air environment.

[0073] Further enhanced fuel stability: By adopting specific formulations and treatment processes, the fuel is more stable during storage and use, and is not prone to stratification, volatilization, or deterioration.

[0074] Wider application range: It can be applied to a variety of industrial and civil combustion equipment without significant modification, facilitating popularization and application and improving market adaptability.

[0075] Combined with the current actual requirements, the above-mentioned implementation manner adopted in this application, the protection scope is not limited thereto. Within the scope of knowledge possessed by those skilled in the art, various changes made without departing from the concept of this application still fall within the protection scope of the present invention.

Claims

1. An environment-friendly biomass liquid fuel, comprising alcohols, ethers and biomass oil, characterized in that: The alcohols are lower alcohols, the ethers are ethers obtained by catalytic dehydration of lower alcohols, and ethers obtained by condensation of alcohols and aldehydes. The biodiesel component of the bio-oil is fatty acid esters prepared from animal and vegetable oils. The mass ratio of the alcohols, ethers and bio-oil is: 5-20%, 10-30%, 50-85%.

2. A preparation method of an environment-friendly biomass liquid fuel, characterized in that: It includes the following steps: S1. Raw material pretreatment: Take vegetable oil as the raw material for bio-oil, and pretreat the vegetable oil, filter to remove impurities and moisture, so that the water content of the vegetable oil is reduced to less than 0.1%. The alcohol raw material is anhydrous methanol with a purity of ≥99.5%. The pretreated vegetable oil and alcohol raw material are stored in the raw material tanks for later use; S2. Transesterification reaction: Put the pretreated vegetable oil and alcohol raw material into the transesterification reactor according to the molar ratio of oil to alcohol of 1:6-1:8, add the alkaline catalyst KOH, and the dosage of the catalyst is 0.5%-1% of the mass of the vegetable oil. Start stirring in the reactor, raise the temperature to 55°C-65°C, pressurize the reactor to 0.3 Mpa, and keep the constant temperature reaction for 1-2 hours to make the triglycerides in the oil fully transesterify with methanol to generate fatty acid methyl ester and by-product glycerol. After the transesterification is completed, turn off the heating and let it stand to obtain the reaction mixture; S3. Product separation and purification: The reaction mixture obtained in step S2 is subjected to sedimentation and layering. The bottom precipitated phase is the glycerol phase, and the upper layer is the crude biodiesel phase. The glycerol by-product is slowly released. The crude biodiesel is washed several times with warm water, and then the excess methanol is recovered by vacuum distillation to obtain a biodiesel intermediate. Then, the biodiesel intermediate is dried under vacuum at 110 °C to obtain a pure biodiesel product with a water content of <0.05%. The obtained biodiesel is a pale yellow transparent liquid with a density of 0.88 g / cm 3 , and a kinematic viscosity of 4.5 mm 2 / s; S4. Catalytic dehydration of alcohol to ether: Feed the anhydrous methanol stored in step S1 into the fixed-bed etherification reactor through a metering pump, and fill the fixed-bed etherification reactor with a solid acid catalyst. The solid acid catalyst is γ-aluminum oxide or HZSM-5 molecular sieve. Heat the reactor to 250-300°C, and maintain the pressure at 0.5-1.5 MPa. Methanol undergoes dehydration coupling reaction on the surface of the catalyst: 2CH3OH→CH3OCH3+H2O; To obtain the product dimethyl ether and water, the mixed gas generated by the reaction is cooled to room temperature by a condenser, and the liquid dimethyl ether and the water phase are condensed out. The dimethyl ether and water are separated by a gas-liquid separator: the water phase is discharged for treatment, and the gaseous dimethyl ether enters a refrigerated storage tank to obtain the liquefied dimethyl ether; S5. Mixing and blending: Put the biodiesel prepared in step S3 and the liquefied dimethyl ether prepared in step S4 into a pressure-resistant and sealed mixing tank according to a mass ratio of 4:1, and stir for 20 minutes. Control the temperature at about 20-30°C during the mixing process, and keep the pressure in the tank not less than 0.6 MPa to obtain the finished product of the alcohol-ether-based biomass liquid fuel.

3. The preparation method of an environment-friendly biomass liquid fuel according to claim 2, characterized in that: Step S2 and step S4 are carried out synchronously without priority.

4. The preparation method of an environment-friendly biomass liquid fuel according to claim 2, characterized in that: In the step S4, the catalyst HZSM-5 belongs to a ten-ring zeolite molecular sieve, having two sets of mutually intersecting pores (pore diameter is about 0.51×0.55 nm), and its microporous specific surface area can be as high as 395 m 2 / g. Under a scanning electron microscope, HZSM-5 usually presents regular micron-sized crystal particles, and the average grain size is about 1–2 μm.

5. The preparation method of an environment-friendly biomass liquid fuel according to claim 2, characterized in that: In the step S4, the catalyst γ-Al2O3 is transitional alumina, with a mesoporous structure, a porous network structure composed of nanoparticles, and an extremely high porosity. Its internal surface area can reach 200–400 m 2 / g.

6. The preparation method of an environment-friendly biomass liquid fuel according to claim 2, characterized in that: In step S5, a stabilizer or cosolvent accounting for less than 1% of the total mass is added to the finished product of the biomass liquid fuel.

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