Processes for upgrading biooils

Abstract

The present relates to a process for upgrading a biooil, comprising the steps of - providing a biooil feed - in a heating stage heating the biooil to T 200 – 350 C - in a reaction stage reacting the biooil feed with an alcohol at T 200 – 350 C, for t 2 – 120 min obtaining an upgraded biooil, - wherein alcohol is added to the biooil before the biooil is heated.

Description

[0001]Processes for upgrading biooils Field of the invention The present invention relates to processes for upgrading biooils. Background A global energy and sustainability transition is currently one of few internationally acknowledged urgent needs. A major part of this transition is focused on substituting fossil fuels for transportation wherein utilization of biomass is expected to play a major role. However, even though biomass utilization as a base for production of fuels has been pursued over the last 20+ years only limited large scale success has been achieved. One issue continues to be the quality of the produced oil on important parameters such as stability and total acid number. Objects of the invention An object of the present invention is to provide a method for upgrading sub spec biooil. Summary of the invention This and other advantages are provided by a process for upgrading a biooil, comprising the steps of: - providing a biooil feed - in a heating stage heating the biooil to T 200 – 350 C - in a reaction stage reacting the biooil feed with an alcohol at T 200 – 350 C, for t 2 – 120 min obtaining an upgraded biooil, - wherein the alcohol is added to the biooil before the heating stage. The applicant has shown that the quality of a biooil on important parameters may be improved by reaction with alcohol at the specific temperatures. Biooils are complex often with 1000+ components in various concentrations. The components of the oil may react with each other as well as with the alcohol. This means that if alcohol is added to the biooil feed prior to the heating such as prior to heating in the heating stage where the temperature reaches the reaction temperature 150 – 400 C, such as 200 – 350C less unwanted reactions take place and the quality of upgraded oil is better. It has further been realized that addition of the alcohol to the biooil feed before heating such as heating above 60C such as above 75 - 100C compared to allowing the biooil to reach a higher temperature before adding the alcohol may limit undesired reactions as well as enabling advantageous reactions. The reactions achieved may include depolymerization by cleavage of ether linkages and other oxygen containing bonds, deoxygenation by decarboxylation, deoxygenation by hydrogen donation from alcohol. Many biooils have a high viscosity which may be lowered by increasing the temperature. However, applicant has realized the importance of adding alcohol to the biooil before the temperature is raised to above 60C or in some embodiments before the temperature is raised above a temperature in the interval between 75 and 100C in order to avoid destabilization of the oil and / or the formation of unwanted byproducts. This means that it may be advantageous the ensure that the biooil feed has a temperature which provides a lowered viscosity but in order avoid destabilization of the oil and / or the formation of unwanted byproducts alcohol is preferably added before the temperature of the biooil is above 60C such as before the biooil feed has a temperature between 75 – 100C. The biooil and alcohol is preferably heated to a reaction temperature up to 350C and preferably above 180C, such as up to or between 200C, 220, 240, 260, 280, 300, 310, 320 or 330C. In some preferred embodiments the biooil and alcohol is heated to and reacted at temperatures around or below 300C, such as 150 – 320C, such as 180C - 320, such as 200 – 300C. At temperatures T 200 – 350C the pressure may for example be 2 – 250 bar, such as 5 – 150 bar. Preferably the heating time in the heating stage is below 90 minutes such as below 60 minutes such as below or between 30, 20, 15, 10, 8, 5 or 2 minutes, such as 90 – 2 minutes, such as 30 – 2 minutes, such as 20 – 2 minutes. By comparing experiments wherein heating time to reach a reaction temperature of 240 – 280C is below 10 min (pipe exp) and approximately 90min (autoclave) it has been shown that a shorter heating time may be preferred to avoid formation of heavy molecules. In some embodiments further alcohol is added after the heating stage. This may have a positive effect of the reactions by ensuring that sufficient alcohol is present to promote advantageous products and minimize undesired reactions of components of the oil. Preferably, the process is a continuous flow through process. The applicant has realized that it may be beneficial if the alcohol is forced in contact with the biooil in the reaction stage. This may be achieved by different means such as stirring, alcohol injection etc. The forced contact may be advantageous by ensuring sufficient time for effective contact between alcohol and the reacting biooil components. In some embodiments the total amount of alcohol added is at least 5wt%, such as 10 – 150wt% such as 10, 15, 20, 30, 50 , 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 wt% or in ranges there between relative to the biooil feed. Large surplus of alcohol does not appear to have negative effects on the upgraded process however limiting the wt% of alcohol may be relevant from a cost efficiency perspective. The biooil may e.g. be a product from a pyrolysis, Hydrothermal liquefaction or an oil based thermal liquefaction process. I.e. the bio–oil can be the product of conventional pyrolysis, fast pyrolysis, hydro pyrolysis or any type of oil by a pyrolysis reaction. The oil can be a product of hydrothermal liquefaction with the liquefaction solvent was water or an aqueous phase. The oil can be a product of base catalyzed depolymerization carried out in organic as well as aqueous solvent medium. The oil can be a product of gasification and would commonly be known as gasification tar. The oil can be a product of solvent liquefaction in which the solvent is organic and where the organic solvent can be recycled product oil. In general the oil can be any biooil that contains molecules with double bound oxygen like ketones, aldehydes and organic acids. The oil can also or in addition be a fraction of any of these oil products and a mixture of these. The present also relates to a plant for carrying out the process. The plant may comprise means for feeding in the biooil feed, means for adding alcohol, a heating source for heating source for heating the biooil+ alcohol mix, means for providing the heated biooil+alcohol mix to a reaction stage and means for allowing the upgraded biooil to be obtained from the reaction stage. The plant may also comprise means for pressurizing and pressure regulating the heating stage and / or the reaction stage as well as it may comprise means for alcohol recovery. In some embodiments the alcohol is a short chain and / or primary alcohol such as methanol and / or ethanol. Experiments and examples In a first series of experiments pyrolysis oil with a water content between 10 – 12 wt% was treated in alcohol in a 600 mL stirred HT 4545 Parr batch in the presence of alcohol. The experiment was carried out at 280°C. The pyrolysis oil and alcohol (here methanol) were premixed in a 50:50 ratio, and the total feed charged in the reactor was approximately 150 g. The atmosphere inside the vessel was flushed three times with nitrogen to create an inert overhead environment prior to heating. Heating was applied through an electric heating jacket. Constant stirring was applied during heat-up and maintained throughout the experiment. When the desired set point for the internal temperature of the vessel was reached, the reaction period was defined to begin. After a period of 20 min, the vessel was let cool down. The contents of the batch autoclave were recovered with THF and filtered on a pre-weighed glass fiber filter (1.6 μm pore size). The filter cake comprising the solid product of the reaction was washed with THF and subsequently dried at 60 °C until stable weight. The filtrate was rotary evaporated (50 °C, 10 mbar) for 30 min or until stable weight of the heavy liquid fraction. The heavy evaporation residue fraction is denoted as the oil product. To facilitate a fair comparison between the upgraded oil and the feed, the as-received pyrolysis oils were mixed with THF, filtered and evaporated similarly to the procedure described above for product from the upgrading. All oil was subjected to analytical characterization. The results showed that TAN of the pyrolysis oil was significantly improved while other parameters such as oil yield was not significantly reduced and solids were not significantly produced. Untreated After oil treatment TAN mg 57.3 7.5 KOH / g In a second series of experiments 1:1 (by weight) pre-mixed solution of pyrolysis oil and methanol was added to the reactors prior to sealing. The interior atmosphere was flushed three times with nitrogen to create a non-pressurized, inert atmosphere prior to experimentation in the sand bath. The filled, flushed pipe reactors were dipped into a preheated sand bath for 20 minutes. After the reaction time, the pipe reactors were taken out immediately and quenched in a water bath for fast cool-down. Pressure was monitored throughout the process and the final gas pressure was recorded at ambient temperature. The contents of pipe reactors were extracted using THF and filtered on a pre-weighed glass fiber filter (Whatman GF / A). The filter cake was dried overnight, and the mass was recorded. The filtrate was rotary evaporated (50℃, 10 mbar) to remove water, methanol and THF for 30 minutes or until stable weight of the recovered heavy liquid fraction. The recovered heavy liquid and is defined as the oil product, assumed to be free of water and methanol. The oil yield was calculated as the mass of heavy liquid relative to the mass of the initial pyrolysis oil. Solid yields were calculated from the dried solid product (filter cake) relative to the mass of the initial pyrolysis oil. For both oil yields and solids yields it important to note that the initial pyrolysis oil contain water and solids, whereas the recovered oil product is solids and water free. Some of the results are summaries in the Plots below showing Solid Yield (plot 1), Oil yield (plot 2) and TAN (plot3 ),. In can be seen that the methanol treatment study with pyrolysis oil has shown promising potential to significantly reduce TAN of the pyrolysis oil with minimal solids yield and with high oil yields. It was shown that a treatment with methanol at 300 ℃ and 350 ℃ are the most suitable conditions for reduction of TAN as it produces and oil product with a TAN of 15 mg KOH / mg however a significant reduction is observed from 200C which is the lowest tested temperature indicating that a reduction in TAN may be archived already from 180C or even from 150C. Other important performance parameters are oil and solids yields. Solids formation is at its lowest at 300 ℃ and increased noticeably at 350 ℃. Similarly, product oil yields were higher at 300°C that at 350°C. Overall it was shown that treatment in methanol from 200C from 350°C with 300C as an indicated optimal temperature has a significant effect on reduction of TAN while conserving the oil yield and with minimal solids yield. Plot 1 Plot 3 In a third series of experiments, experiments were performed in tube reactors immersed in a fluidized sandbath. The volume of the reactors is approximately 10 cm3, and they are attached to a capillary with a digital pressure sensor, a relief valve and a needle valve. The volume of the capillary is estimated to be 4 cm3. The temperature of the fluidized sandbath is monitored in the middle of the sandbath with a K-type thermocouple and is assumed to be the reaction temperature. Preliminary tests with a non-pressurized tube reactor filled with model oil and with a thermocouple immersed in the oil, were performed to determine the heating rate up to 350 °C. It was observed that the temperature was reached after a 2.5 min. A set of experiments without ethanol were performed as a benchmark. For easier handling and due to the high viscosity of the bio-oil (from an oil based thermal liquefaction process), small pellets of solid bio-oil have been produced and stored at – 18 °C. For the experiments with ethanol, accurately weighed oil was charged in a flask and was manually mixed with ethanol under heating (approximately 50 °C) until a homogeneous liquid was achieved. The total weight was carefully monitored during the mixing and the mass losses were assumed to be evaporated ethanol, which was considered for calculating the final composition of the mixture. Consequently, a syringe was used to transfer approximately 3 g of the feed mixture in a tube reactor. The tube reactor and the capillary assembly were connected, and the overhead volume was purged with nitrogen three times to remove atmospheric oxygen. Finally, the reactor was pressurized to approximately 10 barg with nitrogen and was immersed in the fluidized sandbath. When the reaction time has elapsed, the reactors were removed from the sandbath and were cooled to ambient temperature in a water bath. After the final pressure at ambient temperature was recorded the reactor system was carefully depressurized via the needle valve and the reactor was separated from the capillary assembly. To recover the products of the reaction, the capillary was separated from the reactor pipe and the reactor was immersed in THF and sonicated. In addition, the capillary was washed with THF to recover potential condensate overhead. The mixture of THF and reaction product was filtered on a glass fiber filter (1.6 μm) under vacuum, and the filter cake was dried at 60 °C overnight to determine the THF insoluble fraction. The filtrate was then evaporated at 50 °C and 10 mbar, until the mass was stable. The evaporation residue (biooil) was characterized by the analytical methods reported in Section 3.3. The solid yield is determined based on the measured mass of solids from the solvent assisted filtration and the loaded mass of biomass as (mass_solids / mass_biomass)*100%. Sample ID Ethanol Overall Solid yield TAN mass (wt%) (mg balance KOH / g) (wt%) Untreated - - 0.0 20.2 biooil 249 °C Pipe 80 No 116.4 16.0 Pipe 82 No 81.1 15.7 Pipe 81 Yes 111.4 2.6 5.9 Pipe 83 Yes 108.5 4.0 5.2 299 °C Pipe 84 No 109.4 13.5 Pipe 85 No 103.7 12.8 Pipe 86 Yes 108.4 3.4 2.2 Pipe 87 Yes 105.9 5.3 2.0 341°C Pipe 88 No 99.6 11.8 Pipe 89 No 95.2 13.5 Pipe 90 Yes 101.7 6.9 2.3 Pipe 91 Yes 87.8 4.2 2.1 412 °C Pipe 93 No 79.0 28.3 Pipe 94 No 94.6 25.0 Pipe 95 Yes 76.9 10.9 22.6 Pipe 96 Yes 96.9 23.8 24.7 It was concluded that the treatment of the biooil at high temperature yielded in all cases some solid fraction (THF insolubles), which clearly is increasing with temperature from, 1-4 wt% at 259 °C up to 24 wt% at 412 °C. Considering the total acid number, the results show a very clear reduction of TAN with the thermal treatment. Importantly the processing with ethanol contributes to a reduction between 76 % and 91 %, which suggests that the presence of ethanol at high temperature render the biooil less corrosive. Considering that the reduction of TAN at 299 °C and 241 °C is almost identical, in conjunction with the on average slightly lower THF insoluble yield at 299 °C, it is suggested that from the temperatures tested in this work, 300 °C is adequate for a massive improvement of the biooil TAN, and no significant loss to solids / char. In summary results have shown that both ethanol and methanol provide a significant reduction in TAN of the tested biooils. Similar experiments show that 2-propanol also provides a reduction of TAN of the biooils however the reduction isn’t as significant as observed for both methanol and ethanol indicating that not only short chained alcohols may be preferred but also primary alcohols. Description of the drawings Fig 1 shows a schematic view of aspects of the invention Detailed description of the invention Fig 1 shows a schematic diagram of some embodiments of the process 1 according to the invention. A biooil is fed to the process. Alcohol may be added to the biooil at a first point A1 before a heating step 2. Alcohol may optionally be added at a second point A2 prior to a reaction stage S1 and / or at a third point A3 to the reaction stage. The biooil + alcohol is reacted in the reaction stage S1 at a reaction temperature T1 for a specified residence time Res1. As indicated with arrows and connecting lines the process in Fig 1 is a process where a biooil feed is fed into the system and moves through stages with alcohol addition, heating, in to a reaction stage wherefrom upgraded biooil is expelled.

Claims

CLAIMS 1. A process for upgrading a biooil, comprising the steps of- providing a biooil feed - in a heating stage heating the biooil to T 200 – 350 C - in a reaction stage reacting the biooil feed with an alcohol at T 200 – 350 C, for t 2 – 120 min obtaining an upgraded biooil, - wherein alcohol is added to the biooil before the heating stage.

2. Process according to claim 1, wherein further alcohol is added after the heatingstage.

3. Process according to any of claim 1 or 2, wherein the alcohol is forced in contact withthe biooil in the reaction stage.

4. Process according to any of the preceding claims, wherein the total amount ofalcohol added is 5 – 150wt% relative to the biooil feed.

5. Process according to any of the preceding claims, wherein the alcohol is ethanoland / or methanol.

6. Process according to any of the preceding claims, wherein the time in the heatingstage is below 90 minutes such as below 30 minutes, such as 30 – 2 minutes.

7. Process according to any of the preceding claims, wherein the time in the heatingstage is below 20 minutes.

8. Process according to any of the preceding claims, wherein the alcohol is addedbefore heating the biooil feed above 60C such, as above 75 - 100C.

9. Process according to any of the preceding claims, wherein the biooil is a productfrom a pyrolysis, Hydrothermal liquefaction or an oil based thermal liquefaction process.

10. Process according to any of the preceding claims, wherein the process is acontinuous flow through process11. A plant for carrying out the process according to any of the claims 1 – 10.

12. The plant according to claim 11, comprising means for feeding in the biooil feed,means for adding alcohol, a heating source for heating the biooil+ alcohol mix, means for providing the heated biooil+alcohol mix to a reaction stage and means for allowing the upgraded biooil to be obtained from the reaction stage.

13. The plant according to claim 10 or 11, comprising means for pressurizing and / orpressure regulating the heating stage and / or the reaction stage.

14. The plant according to any of the claims 10 - 12, comprising means for alcoholrecovery.

Images