CERTIFICATE OF VERIFICATION I, Shiro TERASAKI Japanese Patent Attorney Registered No. 9265 of SOEI PATENT & LAW FIRM Ginza First Bldg., 10-6, Ginza 1-chome, Chuo-ku, Tokyo 104-0061 Japan states that the attached document is a true and complete translation to the best of my knowledge of International Patent Application No. PCT/JP2007/053931 Dated this 12th day of August, 2008 Signature of translator: Shiro TERASAKI AU-verification(PCT) FPO7-0092-00 DESCRIPTION METHOD OF WAX HYDROCRACKING Technical Field [0001] The present invention relates to a wax hydrocracking method. 5 Background Art [0002] In recent years, regulations on the sulfur content of liquid fuels, such as gasoline and gas oil, is becoming more severe in view of environmental protection. Therefore, there are growing expectations for a clean liquid fuel with low sulfur or aromatic hydrocarbon content. 10 [0003] In this regard, two methods of manufacturing a clean fuel are now in the spotlight, i.e., the Fischer-Tropsch (FT) synthesis which uses carbon monoxide and hydrogen obtained from reforming of natural gas, and the gas to liquid (GTL) synthesis which subjects the wax (FT wax) produced by FT synthesis to further hydrocracking. The fuel 15 substrate obtained by FT synthesis has normal paraffin as a principal component, so there is a limitation on using it as gasoline or gas oil, but the fuel substrate obtained by hydrocracking of FT wax has the characteristic that it is rich in isoparaffins. In GTL, the aim is usually to manufacture a middle fraction (fuel substrate such as kerosene and 20 gas oil). [0004] Techniques for hydrocracking wax to manufacture a fuel substrate have already been explored, e.g., in Patent Documents 1-3, a hydrocracking method using a specific hydrocracking catalyst is mentioned. 25 Patent document 1: International publication No. 2004/028688 pamphlet FPO7-0092-00 Patent document 2: JP-A 2004-255241 Patent document 3: JP-A 2004-255242 Disclosure of the Invention [0005] However, in prior art wax hydrocracking methods, as disclosed 5 in the aforesaid patent documents 1-3, development of a highly efficient hydrocracking catalyst was the focus, and there were effectively no reports of an improvement in the yield of the fuel substrate by improvement of the process. Although it is important to reduce the hydrogen consumption amount used for hydrocracking from the 10 viewpoint of economic efficiency, it cannot be said that sufficient studies have been performed in this regard. [0006] It is therefore an object of the invention, which was conceived in view of this situation, to provide a wax hydrocracking method which can 15 substantially raise the yield of a middle fraction, and can substantially reduce the hydrogen consumption amount. [0007] In order to solve the aforesaid problem, according to the wax hydrocracking method of the invention, a first hydrocracking catalyst layer is provided upstream of a fixed bed reactor and a second 20 hydrocracking catalyst layer is provided downstream of the fixed bed reactor, respectively, so that the condition expressed by Equation (1) below is satisfied; hydrogen and wax are made to flow through the first hydrocracking catalyst layer, and hydrogen is re-added to the decomposition product 25 from the first hydrocracking catalyst layer further upstream than the upstream end the second hydrocracking catalyst layer; 2 FPO7-0092-00 and a mixture containing the decomposition product and re-added hydrogen is made to flow through the second hydrocracking catalyst layer. dl/(dl+d 2 ) _> 1/3 (1) 5 In Equation (1), di is the distance from the upstream end to the downstream end of the first hydrocracking catalyst layer, and d 2 is the distance from the upstream end to the downstream end of the second hydrocracking catalyst layer. [0008] According to the wax hydrocracking method of the invention, 10 first and second hydrocracking catalyst layers are provided so that the distances from their upstream ends to their downstream ends (i.e., the thickness in the flow direction) di, d 2 satisfy the above equation, and in addition to supply of hydrogen to the first hydrocracking catalyst layer, the yield of the middle fraction in the decomposition product from the 15 second hydrocracking catalyst layer can be considerably increased by re-adding hydrogen to the decomposition product from the first hydrocracking catalyst layer in the aforesaid specific position. Moreover, compared with the case where hydrogen is supplied to only the first hydrocracking catalyst layer, the hydrogen consumption amount 20 in the first and second hydrocracking catalyst layers can be considerably reduced. [0009] Although unreacted hydrogen may be contained in the decomposition product from the first hydrocracking catalyst layer, the hydrogen which is re-added to the decomposition product further 25 upstream than the upstream end of the second hydrocracking catalyst layer is different from the aforesaid unreacted hydrogen. 3 FPO7-0092-00 [0010] In the present invention, it is preferred that the hydrogen amount re-added to the decomposition product from the first hydrocracking catalyst layer further upstream than the upstream end of the second hydrocracking catalyst layer, is more than 5 % by volume relative to the 5 hydrogen amount supplied to the first hydrocracking catalyst layer. [0011] In the present invention, it is preferred that the wax used as material is a wax obtained by a Fischer-Tropsch synthesis. [0012] In the invention, it is preferred that the first and second hydrocracking catalyst layers contain ultra-stabilised Y type zeolite 10 (USY zeolite), respectively. Brief Description of the Drawings [0013] Fig. 1 is a diagram showing an example of a fixed bed reactor according to the invention. Fig. 2 is a diagram showing another example of the fixed bed reactor 15 according to the invention. Best Modes for Carrying Out the Invention [0014] Hereafter, some embodiments of the invention will be described in detail. [0015] Fig. 1 is a diagram showing a preferred example of a fixed bed 20 reactor used for the first embodiment of the invention. In the fixed bed reactor shown in Fig. 1, two reactors la, lb are connected in series through a transport line L3. Hydrocracking catalyst layers 2a, 2b are provided in the reactors 1 a, 1 b respectively so that the condition expressed by the following Equation 25 (1) is satisfied. When the reactors la, lb have the same configuration, d j , d 2 can be 4 FPO7-0092-00 adjusted by adjusting the fill ratio of each hydrocracking catalyst which constitutes the hydrocracking catalyst layers 2a, 2b: di/(dl+d 2 ) > 1/3 (1) In Equation (1), d, is the distance from the upstream end to the 5 downstream end, of the hydrocracking catalyst layer 2a, and d 2 is the distance from the upstream end to the downstream end of the hydrocracking catalyst layer 2b. [0016] Moreover, since it gives an even better improvement in the yield of the middle fraction and decrease of hydrogen consumption amount, it 10 is preferred that dl/(dl+d 2 ) in the aforesaid Equation (1) is 1/3-5/6, and more preferred that it is 7/12-9/12. [0017] The hydrocracking catalyst which constitutes the hydrocracking catalyst layer 2a, and the catalyst which constitutes hydrocracking catalyst layer 2b may be identical or different. 15 [0018] The hydrocracking catalysts which constitute the hydrocracking catalyst layers 2a, 2b, are not particularly limited provided that they have hydrocracking capability, but the carrier preferably contains an amorphous solid acid such as silica alumina, silica zirconia, alumina boria or silica magnesia, or a crystalline-solid acid, such as USY zeolite, 20 mordenite, beta zeolite, ZSM-22, or SAPO-1 1, and USY zeolite is particularly preferred. [0019] When the carrier of the hydrocracking catalyst includes USY zeolite, the proportion of the USY zeolite relative to the carrier is not particularly limited, but from the viewpoint of suppressing lighter mass 25 of the fuel substrate, it is preferably 15 wt % or less, or more preferably 5 wt % or less. 5 FPO7-0092-00 [0020] The molar ratio of the silica/alumina in the USY zeolite is not particularly limited, but it is preferably 30-200, more preferably 30-100 and most preferably 30-60. The average particle size of the USY zeolite is preferably 1.0pm or less, but more preferably 0.5pm or less. 5 If the average particle diameter of USY zeolite is larger than this upper limit, the fuel substrate tends to lighter mass. [0021] The hydrocracking catalyst may further contain a binder for carrier casting. The binder is not particularly limited, but a preferred binder is alumina 10 or silica. The form of the carrier is not particularly limited, and it may have any form such as particulate or cylindrical (pellets). [0022] The hydrocracking catalyst is preferably a Group VIII metal of the Periodic Table supported on this carrier. Specific examples of the 15 Group VIII metal are cobalt, nickel, rhodium, palladium, iridium and platinum. Among these, one or more metals selected from palladium and platinum is preferred, and in particular, when using slack wax containing oil as the raw material, both palladium and platinum are preferably supported on the carrier. The metal amount supported on 20 the carrier is not particularly limited, but is preferably 0.01 to 2 wt % relative to the carrier. [0023] The line L1 for supplying hydrogen inside the reactor la is connected with the apex of the reactor la, and the line L2 for supplying wax is connected further upstream than the connection part with the 25 reactor of the line LI. Hence, wax and hydrogen can be introduced together to the reactor la, and made to flow through the hydrocracking 6 FPO7-0092-00 catalyst layer 2 to perform hydrocracking. [0024] The wax used for hydrocracking may be for example a petroleum or synthetic wax containing 30 % by mass or more of a normal paraffin having 16 or more carbon atoms, but preferably 20 or 5 more carbon atoms. The petroleum wax may be a slack wax or a microwax, and the synthetic wax may be a FT wax manufactured by FT synthesis. [0025] An example of a reactor wherein the hydrogen supply line L 1 and the wax supply line L2 were joined together was shown in Fig. 1, 10 but the hydrogen supply line L1 and the wax supply line L2 may be separately connected with the reactor la, respectively. As for the circulation direction of the wax, this is preferably the direction from the apex to the base of the reactor la as shown in Fig. 1. [0026] The conditions under which wax hydrocracking in the reactor la 15 is performed are not particularly limited, but the reaction temperature is preferably 250-370 0 C. If the reaction temperature exceeds 370 0 C, aromatic compounds are easily produced, which is not preferred from the viewpoint of obtaining a clean fuel substrate. The reaction pressure (hydrogen partial pressure) is preferably 1-12 MPa, but more preferably 20 2-6 Mpa. If the reaction pressure is less than the lower limit, the hydrocracking catalyst tends to deteriorate, and if the upper limit is exceeded, the reaction temperature required to obtain an identical decomposition rate tends to increase, which are both undesirable outcomes. The liquid spatial velocity is not particularly limited, but it 25 is preferably 0.1-3.0h-1. The ratio (hydrogen/oil ratio) of fthie total hydrogen amount and oil supplied is preferably 100-850NL/L, but more 7 FPO7-0092-00 preferably 200-650 NL/L. [0027] The decomposition product from hydrocracking in the reactor la is sent to the reactor lb via the transporting line L3. At this time, hydrogen from the hydrogen supply line L4 connected with the 5 transporting line L3 is re-added to the decomposition product. [0028] Since the amount of hydrogen re-added to the decomposition product from the hydrogen supply line L4 can further improve the yield of the middle fraction obtained after hydrocracking in the reactor lb, it is preferably 5 % by volume or more relative to the hydrogen amount 10 supplied from the hydrogen supply line L1 to the reactor la. [0029] In Fig. 1, an example of a device wherein the hydrogen supply line L4 was connected with the transporting line L3 was shown, but the connection position of the hydrogen supply line L4 need only be between the downstream end of the hydrocracking catalyst layer 2a, and 15 the upstream end of the hydrocracking catalyst layer 2b. For example, the hydrogen supply line L4 may be connected to the apex of the reactor 1 b to perform hydrogen re-addition. [0030] In this way, further hydrocracking is performed by circulating the decomposition product to which hydrogen was re-added over the 20 hydrocracking catalyst layer 2b of the reactor lb. Since the hydrocracking conditions in the reactor lb are the same as the hydrocracking conditions in the reactor l a, overlapping parts of the description are omitted. The hydrogenation conditions in the reactor la and reactor l b may be identical, or different. 25 [0031] According to the first embodiment, the hydrocracking catalyst layers 2a, 2b are respectively provided so that the distances di, d 2 from 8 FPO7-0092-00 the upstream ends to the downstream ends thereof (i.e., the thickness in the flow direction) satisfy the condition expressed in (1), and in addition to hydrogen supply from the hydrogen supply line L1 to the hydrocracking catalyst layer 2a, hydrogen is re-added from the 5 hydrogen supply line L4 to the decomposition product from the first hydrocracking catalyst layer. Hence, the yield of the middle fraction in the decomposition product from the hydrocracking catalyst layer 2b can be considerably increased. Moreover, the sum total of the hydrogen consumption amounts in the hydrocracking catalyst layer 2a, 10 2b is considerably reduced compared with the case where hydrogen was supplied to the-hydrocracking catalyst layer 2a only from the hydrogen supply line L1. The obtained decomposition product, in addition to the middle fraction, generally contains naphtha (fraction having a boiling point less than 145 0 C) and wax (fraction exceeding a boiling point of 15 360oC). By sampling the decomposition product from the line L5 connected with the base of the reactor lb, and performing distillation etc., the aforesaid fraction can be separated and substrates can be obtained for various applications. [0032] Fig. 2 is a diagram showing a preferred example of the fixed bed 20 reactor relating to a second embodiment of the invention. In the fixed bed reactor shown in Fig. 2, in the reactor I c, the hydrocracking catalyst layers 2a, 2b are provided so that they satisfy the condition expressed by the aforesaid Equation (1). [0033] The line L1 for supplying hydrogen to the reactor ic is 25 connected to the apex of the reactor lc, and the line L2 for supplying wax is connected further upstream than the connecting part with the 9 FPO7-0092-00 reactor of the line Ll. Hence, wax and hydrogen can be introduced together into the reactor 1 c, and made to flow through the hydrocracking catalyst layer 2a, 2b sequentially to perform hydrocracking. 5 [0034] A gap is provided between the lower end of the hydrocracking catalyst layer 2a and hydrocracking catalyst layer 2b, and the hydrogen supply line L4 is connected to a position corresponding to this gap on the side of the reactor Ic. In this way, hydrogen can be re-added from the hydrocracking catalyst layer 2a to the decomposition product, and 10 the mixture of decomposition product and re-added hydrogen made to flow through the hydrocracking catalyst layer 2b to perform hydrocracking. [0035] In this embodiment, since the hydrocracking catalyst which constitutes the hydrocracking catalyst layers 2a, 2b is the same as the 15 hydrocracking catalyst in the first embodiment, overlapping parts of the description are omitted. If the reactor Ic has a fixed shape (e.g., cylindrical shape) regardless of how the cross-sectional surface area is obtained when the catalyst filling area is cut by a plane perpendicular to the flow direction, dl, d 2 can be adjusted by adjusting the filling amount 20 of hydrocracking catalyst forming the hydrocracking catalyst layers 2a, 2b. [0036] Moreover, the hydrocracking conditions in the reactor Ic can be made identical to the hydrocracking conditions in the reactors I a, l b in the first embodiment. 25 [0037] According to the second embodiment, the hydrocracking catalyst layers 2a, 2b are respectively provided so that the distances 10 FPO7-0092-00 from the upstream ends to the downstream ends thereof (i.e., the thickness in the flow direction) d 1 , d 2 satisfy the condition expressed in (1), and in addition to hydrogen supply from the hydrogen supply line L 1 to the hydrocracking catalyst layer 2a, hydrogen is re-added from the 5 hydrogen supply line L4 to the decomposition product from the first hydrocracking catalyst layer. Hence, the yield of the middle fraction in the decomposition product from the hydrocracking catalyst layer 2b can be considerably increased. Moreover, the sum total of the hydrogen consumption amounts in the hydrocracking catalyst layers 2a, 2b is 10 considerably reduced compared with the case where hydrogen is supplied to the hydrocracking catalyst layer 2a only from the hydrogen supply line LI. The obtained decomposition product, in addition to the middle fraction, generally contains naphtha (fraction having a boiling point less than 145 0 C) and wax (fraction exceeding a boiling point of 15 360 0 C). By sampling the decomposition product from the line L5 connected with the base of the reactor lb, and performing distillation etc., the aforesaid fraction can be separated and substrates can be obtained for various applications. EXAMPLES 20 [0038] Hereafter, the invention will be described still more concretely based on an example and a comparative example, but the invention is in no way limited to the following examples. [0039] (Example 1) Using silica alumina (molar ratio of silica/alumina: 6.2), and an alumina 25 binder, a cylindrical carrier having (p about 1.5mm and a length of 3rmm was cast (silica alumina/alumina binder =80:20 (mass ratio)). This jI FPO7-0092-00 carrier was impregnated with a solution of chloroplatinic acid, and 0.8 wt % of platinum was supported on the carrier. The hydrocracking catalyst was obtained by drying and calcinating this. [0040] Next, the reactors la, lb of the fixed bed reactor having the 5 construction shown in Fig. 1 were filled with the obtained hydrocracking catalyst, and the hydrocracking catalyst layers 2a, 2b were thereby formed. In this example, the reactors la, lb had an identical shape wherein the catalyst filling area was cylindrical, and by arranging the hydrocracking catalyst filling amount to be 60ml in the 10 reactor la and 90ml in the reactor lb, dl/(dl+d 2 ) in Equation (1) was set to 1/3. For the hydrocracking catalysts forming the hydrocracking catalyst layers 2a, 2b of the reactors la, lb, reduction treatment was performed in a hydrogen gas current prior to hydrocracking, at 345 0 C for 4 hours, and the catalyst was thereby activated. 15 [0041] Next, wax hydrocracking was performed using the aforesaid fixed bed reactor. The starting material wax was FT wax (carbon number: 21-80 and normal paraffin content 95 % by mass). During wax hydrocracking, the flow rate of the hydrogen supplied to the reactor l a from the 20 hydrogen supply line L1 was 200NL/h, and the flow rate of hydrogen from the hydrogen supply line L4 re-added from the reactor la to the decomposition product was 50NL/h. Moreover, in the reactors la, lb, the liquid spatial velocity of the starting material is 2.0h-1 (300 ml/h as a solution flow rate), the hydrogen partial pressure was 3.5M Pa, and 25 the reaction temperature (same temperature in both the reactors la, lb) was adjusted so that the mass of the light fraction having a boiling point 12 FPO7-0092-00 of 360C relative to the mass of starting material wax was 80 % by mass. The reaction temperature in this example was 355oC. [0042] Gas chromatography analysis was conducted on the decomposition product obtained by hydrocracking, and the yield of the 5 middle fraction (145-360oC fraction) was calculated. Hydrogen consumption amount was computed by quantifying the hydrogen in the off-gas, and from the difference with the supply amount. The obtained result is shown in TABLE 1. [0043] (Example 2) 10 Wax hydrocracking was performed, and the yield of the middle fraction and hydrogen consumption amount were calculated in an identical manner to that of Example 2, except the flow rate of hydrogen supplied from the hydrogen supply line L1 to the reactor la was 20NL/h. The obtained result is shown in TABLE 1. 15 In this example, when the reaction temperature (same temperature in both the reactors la, lb) was adjusted so that the mass of the light fraction having a boiling point of 360'C relative to the mass of starting material wax was 80 % by mass as in Example 1, the reaction temperature was 358oC. 20 [0044] (Comparative Example 1) Wax hydrocracking was performed, and the yield of the middle fraction and hydrogen consumption amount were calculated in an identical manner to that of Example 1, except that hydrogen was not re-added from the hydrogen supply line L4 to the decomposition product from 25 the reactor la. TABLE 1 shows the obtained result. In this comparative example, when the reaction temperature (same temperature 13 FPO7-0092-00 in both the reactors la, lb) was adjusted so that the mass of the light fraction having a boiling point of 360oC relative to the mass of starting material wax was 80 % by mass as in Example 1, the reaction temperature was 360 0 C. 5 [0045] (Comparative Example 2) Wax hydrocracking was performed, and the yield of the middle fraction and hydrogen consumption amount were calculated in an identical manner to that of Example 1, except the catalyst filling amount was 30ml in the reactor la and 120ml in the reactor lb. TABLE 1 shows 10 the obtained result. In this comparative example, when the reaction temperature (same temperature in both the reactors l a, 1 b) was adjusted so that the mass of the light fraction having a boiling point of 360oC relative to the mass of starting material wax was 80 % by mass as in Example 1, the reaction temperature was 356oC. 15 [0046] (Example 3) Using USY zeolite (Si 2 /Al 2 0 3 =40mol/mol) and silica zirconia (silica/zirconia: 1.Smol/mol), and an alumina binder, a cylindrical carrier having p about 1.5mm and a length of 3mm was cast (USY zeolite/silica zirconia/alumina binder =37:90 (mass ratio)). This 20 carrier was impregnated with a solution of chloroplatinic acid, and 0.8 wt % of platinum was supported on the carrier. The hydrocracking catalyst was obtained by drying and calcinating this. [0047] Wax hydrocracking was performed, and the yield of the middle fraction and hydrogen consumption amount were calculated in an 25 identical manner to that of Example 1, except that a hydrocracking catalyst obtained as described in this way was used. TABLE 1 shows 14 FPO7-0092-00 the obtained result. In this example, when the reaction temperature (same temperature in both the reactors la, lb) was adjusted so that the mass of the light fraction having a boiling point of 360 0 C relative to the mass of starting material wax was 80 % by mass as in Example 1, the 5 reaction temperature was 311 0 C. [0048] (Comparative Example 3) Wax hydrocracking was performed, and the yield of the middle fraction and hydrogen consumption amount were calculated in an identical manner to that of Example 3, except that hydrogen was not supplied 10 from the supply port 3b of the the reactor 1 a. TABLE 1 shows the obtained result. In this comparative example, when the reaction temperature (reactors 1 a, lb both the same temperature) was adjusted so that the weight of the light fraction of 360 0 C or less boiling point to the weight of material wax was 80 wt % as in Example 1, the reaction 15 temperature was 313'C. [0049] 15 FPO7-0092-00 TABLE 1 Hydrogen re- Yield of middle Hydrogen d,(dl+d 2 ) addition fraction consumption (yes/no) (% by mass) amount (SCF/B) Ex. 1 1/3 yes 57.4 520 Ex. 2 1/3 yes 56.1 530 Comp. CompEx.1 1/3 no 54.6 570 Ex.1 _ _ _ _ _ _ _ _ _ _ _ _ Comp. Ex.2 1/5 yes 55.2 570 Ex.3 1/3 yes 60.4 510 Comp. CompEx.3 1/3 no 55.6 580 Ex.3 [0050] As shown in TABLE 1, in Examples 1-3, the hydrocracking 5 catalyst layers 2a, 2b are respectively provided so that the distances d 1 , d 2 from the upstream ends to the downstream ends thereof satisfy the condition expressed in (1), and in addition to hydrogen supply to the hydrocracking catalyst layer 2a, hydrogen is re-added to the decomposition product from the hydrocracking catalyst layer 2a 10 between the first hydrocracking catalyst layer and second hydrocracking catalyst layer 2b. Hence, the yield of the middle fraction can be considerably increased, and the hydrogen consumption amount can be considerably reduced. Industrial Applicability 15 [0051] As described above, according to the wax hydrocracking method of the invention, the yield of the middle fraction can be considerably 16 FPO7-0092-00 increased and hydrogen consumption amount can be considerably reduced. 17