The presented invention relates to a method of obtaining paraffinic hydrocarbons from natural fat, specifically, from waste vegetable oils, animal fat or algal oils.
The high cost involved in the mining and processing of fossil fuels, their depleting resources, and the limited global reserves of crude oil has caused greater interest in renewable resources. Most commonly, the fuels obtained from renewable resources are ethanol from maize and sugar, as well as vegetable oils used as diesel fuel. In the area of diesel fuel obtained from renewable sources, there are two sub-areas: bio-diesel (fatty acid methyl esters), described for instance in:
Taking into consideration the above-mentioned limitations in the use of biodiesel, alternative fuels are being sought. There is a potential for making green diesel (II and III generation biofuels) from renewable raw materials by converting fatty acids from triglycerides and/or free fatty acids originating from natural fat, especially waste vegetable oils, animal fat or algal oils to obtain linear aliphatic saturated hydrocarbons (paraffins). Green diesel has a high cetane number, which is necessary in maintaining the good performance of diesel engines (
Recently, various types of waste materials are regarded as a source of raw materials for making other higher-value products. Vegetable oils, animal fat and various kinds of waste edible fat are part of the waste classified in the Waste Catalogue (Polish Journal of Laws Dz.U No. 112 of 2001, Item 1206), principally, in Group 2. Such waste must be disposed of properly so as not to create any environmental hazard. Algae with a high lipid content will be especially valuable (oil content in certain species is as high as above 80% of dry algal biomass) for it will constitute a raw material for third generation biofuels. The use of algae as energy plants has a huge potential because they quickly adapt to growth conditions, may be grown both in fresh and sea water, and also because land is not required for its production. Furthermore, due to the fact that two-thirds of the earth's surface is covered with water, algae will be a renewable source with a huge potential for the global energy needs.
A higher share of biocomponents in the market for liquid fuels and liquid biofuels for use in transport is an important element of sustainable development, leading to an improved energy security by diversifying fuel supply sources and reducing dependence on petroleum imports while, in addition, having a positive impact on natural environment through appropriate waste management. According to forecasts, a dynamic growth of the market for synthetic hydrocarbons obtained from biomass will be observed, as they will constitute a substitute of petroleum in the future.
Two methods of obtaining paraffins from fatty acids are described predominantly in the literature: hydrodeoxygenation, HDO (R-COOH + 3H2 →- R-CH3 + 2H2O), and decarboxylation (R-COOH → R-H + CO2), for example in
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It was found that synthetic saturated aliphatic hydrocarbons (paraffins) may be obtained with high efficiency from natural fat and/or waste fat, by conducting the process according to the method of the invention under atmospheric pressure conditions in a continuous manner in the presence of heterogeneous catalysts.
In the method of the invention to obtain paraffinic hydrocarbons from natural fat and/or waste fat, in a coupled flow system, under atmospheric pressure, at an elevated temperature, in the presence of an inert gas, in the presence of heterogeneous catalysts a double-stage process is carried out whereby raw waste fat, or any other natural fat, is thermally transformed under strictly defined conditions (Fraction 1 is formed) in the first stage, and then the product obtained in the first stage is treated, in order to hydrogenate its olefin content, with hydrogen or with a mixture of hydrogen and carbon monoxide obtained in the selective decomposition of methanol (Fraction 2 is formed).
The fraction obtained in Stage I by the method of the invention (Fraction 1) may not be used directly as a biocomponent of fuels or as a biofuel because its hydrocarbons have a high degree of unsaturation, therefore, it requires further treatment by hydrogenation of its olefins (Fraction 2).
The thermodynamic conditions of the process of hydrogenation of Fraction 1, conducted with the use of methanol as a hydrogen donor, are much milder, compared with direct reduction with the use of hydrogen. It was found that the presence of carbon monoxide has a favorable effect on the hydrogenation of unsaturated compounds under atmospheric pressure, especially in reactions where the hydrogenation of compounds with a carbon chain length of more than C20 does not occur.
In the method of the invention to obtain paraffinic hydrocarbons from natural fat, specifically from waste vegetable oils, animal fat or algal oils, the process is performed in two stages, in a coupled flow-type system, in atmospheric pressure conditions, in the presence of heterogeneous catalysts following their thermal activation, preferably at a temperature of 450°C in a stream of air for 1 hour, so that in Stage I the fat and/or waste fat is heated at a temperature of 100-500°C, in the presence of an inert gas, in the presence of a catalyst in the form of a metal oxide on an oxide support or in the form of a mixture of at least two metal oxides on an oxide support, whereafter the product obtained in Stage I is treated, in the presence of an inert gas, at a temperature of 100-500°C, in the presence of a metallic catalyst on an oxide support, with hydrogen gas or with a mixture of hydrogen and carbon monoxide, obtained by the selective decomposition of methanol.
Preferably, the catalyst used in Stage I is CoO, NiO, FeO, MoO3, and the oxide support used is SiO2, Al2O3, TiO2, MgO, the aluminosilicate halloysite.
Preferably, the catalyst used in Stage I is a mixture of metal oxides, preferably two or three metal oxides, selected from the group comprising CoO, NiO, FeO, MoO3, and the oxide support used is SiO2, Al2O3, TiO2, MgO, the aluminosilicate halloysite.
Stage I of the process is preferably carried out at a catalyst load of 0.5-20 hr-1.
Preferably, the inert gas used in Stage I is argon or nitrogen.
Preferably, in Stage II of the process, which is performed with the use of hydrogen gas, the catalyst used is Pd, Ru, Pt, Rh, Co/Mo, Ni/Mo, Mo, W, Fe, and the oxide support used is SiO2, Al2O3, TiO2, MgO, ZrO2.
Preferably, in Stage II of the process, which is performed with the use of a mixture of hydrogen and carbon monoxide, the catalyst used is Pd, Ru, Pt, Rh, Co/Mo, Ni/Mo, Mo, W, Fe, most preferably Zr, and the oxide support used is SiO2, Al2O3, TiO2, MgO, ZrO2.
Stage II of the process is preferably carried out at a catalyst load of 0.5-20 hr-1.
Preferably, the inert gas used in Stage II is argon or nitrogen.
Preferably, the selective decomposition of methanol is carried out by subjecting the anhydrous methanol to a reduction reaction in a coupled flow-type system, in atmospheric pressure conditions, at a temperature of 80-350°C, in the presence of an inert gas, over a heterogeneous catalyst in the form of a metal oxide on an oxide support.
Preferably, the catalyst used for the selective decomposition of methanol is CoO, NiO, CuO, ZnO, FeO, MoO3 while the oxide support is SiO2, Al2O3, TiO2, MgO, the aluminosilicate halloysite.
Preferably, the inert gas used in methanol decomposition is argon.
Preferably, methanol decomposition is carried out at a catalyst load of 0.5-20 hr-1.
Preferably, the methanol decomposition catalyst is activated at a temperature of 450°C in a stream of air for 1 hour.
Preferably, the mixture of hydrogen and carbon monoxide from methanol decomposition is used for reducing the reaction catalyst, in Stage II of the process, from its starting form to a metallic form. It was found that the presence of carbon monoxide prevents agglomeration of the active phase of the catalyst during its reduction.
In the process conducted according to the method of the invention, the starting raw material may be any kind of natural fat, including waste vegetable oils and waste animal fat from food processing as well as algal oils containing triglycerides and/or fatty free acids C6-C22, of which the sources may include rapeseed, palm, coconut, sunflower, soy, linseed, maize, or peanut oils, animal fat, poultry fat, marine fat, prehydrolyzed fats, i.e., rendering fat, oils from various species of algae, or combinations of two or more fats.
In the process conducted according to the method of the invention, a mixture of saturated and unsaturated aliphatic hydrocarbons, mainly C6-C18 (Fraction 1), is obtained in Stage I while in Stage II (hydrogenation stage) the hydrogenation of the olefins contained in Fraction 1 takes place, as a result, a mixture of synthetic hydrocarbons which is enriched with saturated hydrocarbons (Fraction 2) is formed, mainly C6-C18 and contains the particularly desirable C12-C17 fraction. The obtained mixture of paraffinic hydrocarbons (Fraction 2 without olefins) may be used as an independent fuel or as a component of liquid fuels, mainly diesel, thus becoming an alternative fuel source. In Stage I of the process conducted by the method of the invention, products are formed mainly as the result of decarboxylation involving the fatty acids and/or triglycerides contained in the starting raw material. Other probable mechanisms of the formation of Fraction 1 include hydrodeoxygenation with hydrogen being formed in situ as well as catalytic cracking.
In the event of insufficient amount of paraffins obtained in Fraction 2, Stage II may be repeated by refluxing Fraction 2 to the reactor in Stage II of the process, thereby further enriching the hydrocarbon fraction in saturated hydrocarbons.
The green diesel formed in the process of the invention (Fraction 2 without olefins) has the properties required for it to be used as diesel fuel or for mixing with petrochemical products, for instance those with lower cetane numbers. The cetane number may be controlled by selecting the appropriate heterogeneous catalyst and process conditions. Green diesel has the desirable lubricity, viscosity and density, and is useful in the diesel engines currently in use.
The method of the invention is illustrated in the Examples. A feasible way to carry out illustrated in Examples VIII-X, while Examples XI-XV illustrate a combination of the two stages of the process conducted by the method of the invention.
The process was conducted in a flow-type catalytic system, as shown in the figure,
The catalyst used was 5%NiO+10%MoO3/SiO2 in the amount of 1 g obtained from a single solution of precursors. The raw material used was Category III rendering fat (a hydrolyzed waste animal fat, whose composition is given in wt % in Table 1 - Sample I). The composition of the rendering fat depends on the season of the year.
Sample II was used in the examples that follow.
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 2.
The process was conducted as in Example I. The catalyst used was 10%NiO+10%MoO3/SiO2 in the amount of 1 g obtained from a single solution of precursors, and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample II).
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 3.
The process was conducted as in Example I. The catalyst used was 10%NiO/SiO2 in the amount of 1 g and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample I).
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 4.
The process was conducted as in Example I, at a temperature of 400°C. The catalyst used was 5%MoO3/5%CoO/SiO2 in the amount of 1 g obtained by impregnation, and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample II).
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 5.
The process was conducted as in Example I, at a process temperature of 400°C. The catalyst used was 5%MoO3/10%CoO/SiO2 in the amount of 1 g obtained by impregnation, and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample II.
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 6.
The process was conducted as in Example I at a temperature of 440°C. The catalyst used was 5%MoO3/10%CoO/SiO2 obtained by impregnation, in the amount of 6 g, and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample II). The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 7.
The process was conducted as in Example I, at a temperature of 400°C. The catalyst used was 5%CoO/5%MoO3/SiO2 in the amount of 1 g obtained by dry impregnation, and the raw material was Category III rendering fat, whose composition in wt % is given in Table 1 - sample II).
The compositions of the raw material [wt %] and fraction 1 [wt %] are given in Table 8.
The process of reduction of the olefins contained in Fraction 1 from Stage 1 is illustrated in the examples.
The process was conducted in a flow-type, coupled catalytic system, composed of a methanol decomposition system and a Fraction 1 hydrogenation system, as shown in the figure,
The compositions of fraction 1 [wt %] and fraction 2 [wt %] are given in Table 9.
The process was conducted as in Example VIII, at a temperature of 400°C. The catalyst used for Stage II was H2PtCl6/Al2O3 in the amount of 0.5 g, and the product from Example VI was used as Fraction 1.
The compositions of fraction 1 [wt %] and fraction 2 [wt %] are given in Table 10.
The process was conducted in a single-stage flow-type catalytic system, composed of a glass reactor, as shown in the figure,
The compositions of fraction 1 [wt %] and fraction 2 [wt %] are given in Table 11.
A double-stage process composed of Stages I and II is illustrated in the Examples.
The process was conducted in a flow-type catalytic system shown in the figure.
In Fraction 2 (at a 99% conversion), only saturated hydrocarbons C6-C17 (including C12-C17) in the amount of 85% (80%), respectively, and esters in the amount of 15% were obtained.
The process was conducted as in Example XI, the temperature used in Stage II was 400°C. The raw material used was a waste refined rapeseed oil of the following composition: C16:0 (10%), C18:0 (1.1%), C18:1 (46%), C18:2 (13%), C18:3 (4.5%), other (25.4%). The catalyst in Stage II was 10%Pd/Al2O3. In Fraction 2 (at a 100% conversion) the following hydrocarbons were obtained: saturated C6-C18 (including C12-C17) 85% (66%) respectively, unsaturated C6-C18 (including C12-C17), 7.2% (6%) respectively, and other products - 7.8% (mainly esters and alcohols).
The process was conducted as in Example XI, the temperature in Stage II was 500°C. The raw material used was waste animal fat (pork lard) of the following composition: C14:0 (3%), C16:0 (30%), C18:0 (15%), C18:1 (45%), C18:2 (5%), other (2%). The catalyst in Stage II was 10%Pd/Al2O3. In fraction 2 (at a 100% conversion) the following hydrocarbons were obtained: saturated C6-C18 (including C12-C17) 80% (63%) respectively, unsaturated C6-C18 (including C12-C17) 8% (3%) respectively, and other products - 12% (mainly esters and alcohols).
The process was conducted as in Example XI. The raw material used was a mixture of palmitic acid C16:0 and stearic acid C18:0 as a composition model of an algal oil after pyrolysis (Chlorella sp.) at a molar ratio of C16:0 to C18:0 of 1:0.7, respectively. The catalyst in Stage II was 10%Pd/Al2O3. In fraction 2, saturated C15 and C17 hydrocarbons were obtained with a yield of 75%.
The process was conducted as in Example XI. The catalyst used in Stage II was 10%Pd/Al2O3. The raw material used was a waste hydrolyzed poultry fat of the following composition: C14:0 (1%), C16:0 (24%), C16:1 (6%), C18:0 (8%), C18:1 (29%), C18:2 (22%), other (10%). The catalyst used in Stage II was 10%Pd/Al2O3. In fraction 2 (at a 100% conversion) the following hydrocarbons were obtained: saturated C6-C17 (including C12-C17) 85% (65%) respectively, unsaturated C6-C17 (including C12-C17) 5% (2%) respectively, and other products - 10% (mainly esters).
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