Method and apparatus for producing a hydrocarbon fraction and a hydrocarbon fraction and its use

Abstract

Provided is a method and apparatus for producing a hydrocarbon fraction. The hydrocarbon fraction is formed from biomass based synthesis gas, the synthesis gas is fed through at least two catalyst layer, the first catalyst layer includes Fe-based catalyst, the second catalyst layer includes Co-based catalyst, and the synthesis gas is treated by supplying the synthesis gas through the first and second catalyst layers in order to form a hydrocarbon composition including the hydrocarbon fraction. Further, provided is a hydrocarbon fraction and its use.

Claims

1. A method for producing a hydrocarbon fraction, wherein the hydrocarbon fraction is formed from biomass based synthesis gas, the method comprising: feeding the biomass based synthesis gas through at least two catalyst layers to form a hydrocarbon composition comprising the hydrocarbon fraction, wherein a first catalyst layer includes Fe-based catalyst for producing hydrocarbons and removing sulphur, and a second catalyst layer includes Co-based catalyst for modifying the hydrocarbons; and separating the hydrocarbon fraction from the hydrocarbon composition, wherein temperatures and pressures are controlled independently in both catalyst layers, and reaction pressure is between 3 to 10 bar in the first catalyst layer and reaction pressure is between 3 to 10 bar in the second catalyst layer, wherein the biomass based synthesis gas comprises an H.sub.2:CO molar ratio of about 1.1,and feeding the biomass based synthesis gas through the first catalyst layer increases the H.sub.2:CO molar ratio to about 1.5:1-2.5:1, and wherein the first catalyst layer is included in a first fixed bed reactor, and a temperature in the first catalyst layer is between 270 to 350 C.

2. The method according to claim 1, wherein the first catalyst layer and the second catalyst layer have been arranged sequentially so that the synthesis gas is first fed through the first catalyst layer and then through the second catalyst layer.

3. The method according to claim 1, wherein the reaction pressure is between 4 to 8 bar.

4. The method according to claim 1, wherein a temperature in the first catalyst layer is between 220 to 350 C.

5. The method according to claim 1, wherein a temperature in the second catalyst layer is between 180 to 250 C.

6. The method according to claim 1, wherein the hydrocarbon fraction is separated from the hydrocarbon composition.

7. The method according to claim 1, wherein the hydrocarbon fraction includes C.sub.5-C.sub.12 hydrocarbons.

8. The method according to claim 1, wherein the hydrocarbon fraction is a gasoline fraction.

9. The method according to claim 1, wherein at least one promoter is added to modify at least one catalyst.

Description

BRIEF DESCRIPTION OF THE DRAWING(S)

(1) In the following section, the invention will be described with the aid of detailed exemplary embodiments, referring to the accompanying FIGURE wherein

(2) FIG. 1 presents one embodiment of the apparatus according to the invention.

DETAILED DESCRIPTION

(3) FIG. 1 presents the apparatus according to the invention for producing a hydrocarbon fraction.

EXAMPLE 1

(4) The apparatus of FIG. 1 comprises two fixed bed reactors 2, 4 and a distillation device 6 in order to form a hydrocarbon fraction 7 from a biomass based synthesis gas 1. The first reactor 2 and the second reactor 4 are arranged in series and are joined together. The distillation device 6 is connected to the second reactor 4.

(5) The synthesis gas 1 is fed into the first reactor 2 which comprises the first catalyst bed 3 containing Fe-based catalyst, and from the first reactor the treated synthesis gas product is fed into the second reactor 4 which comprises the second catalyst bed 5 containing Co-based catalyst in order to form a hydrocarbon composition 9. From the second reactor 4 the hydrocarbon composition 9 is fed into the distillation device 6 in which the hydrocarbon fraction 7 is separated by distillating from the hydrobarbon composition. Preferably, the hydrocarbon fraction has a distillate area of 30-200 C. and the hydrocarbon fraction contains, preferably over 60% by weight, gasoline fraction hydrocarbons.

(6) The apparatus comprises a first temperature controlling device and a first pressure controlling device to control the temperature and pressure in the first catalyst layer 3. Further, the apparatus comprises a second temperature controlling device and a second pressure controlling device to control the temperature and pressure in the second catalyst layer 5. The first temperature controlling device and the first pressure controlling device are arranged in connection with the first reactor 2. The second temperature controlling device and the second pressure controlling device are arranged in connection with the second reactor 4. Then the temperatures and pressures can be controlled independently in the both reactors 2, 4.

(7) Further, the apparatus may comprise a gasification and synthesis process step 10 in which biomass material 11 is gasified to form the synthesis gas 1. Alternatively, the synthesis gas 1 is fed into the first reactor of the invention from outside of the process.

(8) Sulphur is mainly removed from the synthesis gas in the first reactor 2 in which the catalyst layer 3 acts as a guard bed. Further, by means of catalyst layer 3 H.sub.2:CO molar ratio can be increased at low pressure.

(9) The parts and devices of the apparatus used in this invention are known per se in the art, and therefore they are not described in any more detail in this context.

EXAMPLE 2

(10) In this example a hydrocarbon fraction is formed from biomass based synthesis gas. The hydrocarbon fraction is formed by means of the apparatus according to Example 1.

(11) The hydrocarbon fraction 7 is formed by using of combination of two catalyst layers, Fe-based catalyst layer 3 and Co-based catalyst layer 5. Typical properties of catalysts have been summarized in table 1.

(12) TABLE-US-00001 TABLE 1 Catalyst Property Co Fe Chain Growth Probability High Low Activity High Low Olefin Selectivity Low High H.sub.2/CO Ratio for Feed >2 0.5 to 2.5 Water-Gas-Shift Activity and Very Low High CO.sub.2 Selectivity Methane Selectivity High Low Suitable Operation temperature Only Low Low to High Temperature Sensitivity, Very Slight Activation Energy Sensitive Temperature Sensitivity, Sensitive Slight Product Distribution Pressure Sensitivity, Very Slight Product Distribution Sulfur Tolerance Very Little Little to intermediate Stability, Life Time Long Short Cost Expensive Cheap Separation from Wax Easy Difficult Robustness Excelllent Poor

(13) In the first reaction step 2 a synthesis gas product rich in alpha olefins is formed at a low pressure, about 6 bar, by means of an iron catalyst. Temperature is about 230 C. In addition to olefins, the product contains also paraffins, small amount of other olefins and about 5-8% by weight of oxygen containing products, mainly n-alcohols, such as oxygenates. Due to the natural water-gas-shift activity of iron catalysts the hydrogen to carbon-ratio of the synthesis can be low and a separate water-gas-shift (WGS) unit is not needed. H.sub.2:CO molar ratio is low, typically about 1:1, in biomass based synthesis gas. In the first reaction step 2 H.sub.2:CO molar ratio is increased to the level, preferably about 2:1, which is suitable for the Co-based catalyst. In this example the resulting synthesis gas product contains 18.8% by weight dry gas, 25.0% by weight liquid petroleum gas, 27.3% by weight C.sub.5-C.sub.12 hydrocarbons and 7.5% by weight oxygenates. An amount of C.sub.5-C.sub.12 olefins is 20.0% by weight.

(14) In the second reaction step 4 the synthesis gas product from the first reaction step 2 becomes in contact with a cobalt catalyst wherein the olefins and unreacted synthesis gas react further to hydrocarbons. Pressure is about 6 bar, and temperature is about 230 C. The resulting product is remarkably richer in paraffins and the yield of gasoline range, C.sub.5-C.sub.12, is much higher than after the first reaction step. In the hydrocarbon composition product 9 there are still oxygen containing products remaining most of which are dissolved in the water phase. In this example the resulting product contains 12.4% by weight dry gas, 17.0% by weight liquid petroleum gas, 52.3% by weight C.sub.5-C.sub.12 hydrocarbons and 7.2% by weight oxygenates. An amount of C.sub.5-C.sub.12 olefins is 4.1% by weight.

(15) Both of the reaction steps are highly exothermic and the excess heat can be utilized in the concentration of the water phase and the separation of the oxygen containing products.

(16) The hydrobarbon fraction 7 is separated from the hydrocarbon composition 9.

(17) Iron catalyst layer acts both as the first catalyst and as a guard bed for the cobalt catalyst. Further, iron catalyst increases H.sub.2:CO molar ratio for feed of cobalt catalyst layer. The iron catalyst layer produces olefins and other hydrocarbons from the synthesis gas with low H.sub.2:CO molar ratio at a low pressure. Reaction to gasoline can be carried out at a low pressure in the cobalt catalyst layer. There is no need for a separate water-gas-shift reactor, catalyst guard bed, hydrocracking after the reactor or adjusting stage of H.sub.2:CO molar ratio in the process of the present invention. The temperature control of the reactors according to the invention is not as strict as with a separate cobalt catalyst bed which is used alone in a process.

(18) The method and apparatus according to the invention is suitable in different embodiments for forming different kinds of hydrocarbon fractions.

(19) The invention is not limited merely to the examples referred to above; instead many variations are possible within the scope of the inventive idea defined by the claims.