FP07-0005-00 DESCRIPTION PROCESS FOR HYDROGENATION OF WAX AND PROCESS FOR PRODUCTION OF FUEL BASE TECHNICAL FIELD 5 [0001] The present invention relates to a wax hydrotreating process and to a process for manufacturing a fuel base material. BACKGROUND ART [0002] Recent years have seen a rapid tightening of restrictions on the sulfur contents of liquid fuels such as gasoline or light oil, with an eye 10 toward protecting the environment. This has helped lead to the development of cleaner liquid fuels with low sulfur and aromatic hydrocarbon contents. One production process for such clean fuels is Fischer-Tropsch (FT) synthesis which uses as starting materials hydrogen and carbon monoxide obtained from gasification of asphalt or 15 coal, or refining of natural gas. FT synthesis allows production of liquid fuel bases rich in paraffins and containing no sulfur, while simultaneously allowing production of waxes (FT waxes) as well. FT waxes are further converted to middle distillate fractions (kerosene or light oil bases) by hydrocracking. 20 [0003] When a middle distillate fraction produced by hydrocracking of wax or by FT synthesis is used as a fuel base material, it is important to achieve a high yield from the viewpoint of economy of the process, but from the viewpoint of fuel properties, the normal paraffin content is preferably low while the isoparaffin content is instead preferably high. 25 In the case of light oil, for example, a high normal paraffin content impairs the low-temperature flow properties, sometimes restricting its FP07-0005-00 use as a commercial product in extreme cases. Since light oil produced by FT synthesis consists almost entirely of normal paraffins, it cannot easily be used in that form. [0004] Techniques for manufacturing fuel base materials by 5 hydrocracking of waxes have already been investigated, and for example, hydrocracking processes using FT waxes are described in the following Patent documents 1 to 3. [Patent document 1] International Patent Publication No. 2004/028688 [Patent document 2] Japanese Unexamined Patent Publication No. 10 2004-255241 [Patent document 3] Japanese Unexamined Patent Publication No. 2004-255242 DISCLOSURE OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION 15 [0005] However, when wax is hydrocracked for extended periods by the wax hydrocracking processes described in Patent documents 1 to 3 mentioned above, the catalytic activity of the catalyst deteriorates with time and the normal paraffin content of the obtained fuel base material increases, or the fuel base material yield may be reduced. 20 [0006] Conventionally, development of high-performance wax hydrocracking catalysts has been the major goal, whereas virtually no reports exist of improving catalyst activity during operation, i.e. prolonging catalyst life. A typical process for manufacturing middle distillate fractions in the field of petroleum refining involves 25 hydrocracking of vacuum light oil, and low-sulfur light oil can be manufactured by this process. In cases where catalyst deterioration 2 C:\NRPotnbDCC\REC\38009)_ DOC.I10M/201 1 -3 during the process is greater than expected, measures commonly taken include reducing the amount of raw material supplied for the planned period of operation, and lowering the cracking severity. However, such measures are not preferred because they lower the operating efficiency. It is therefore a highly desirable goal 5 to develop a catalyst reactivating process that can be applied to inhibit catalyst deterioration, i.e. catalyst deterioration that exceeds expectations. [0007] The present invention has been accomplished in light of the aforementioned problems of the prior art, and seeks to provide a wax hydrotreating process and a process for manufacturing a fuel base material, whereby the catalytic 10 activity that deteriorates with time during hydrocracking of wax for long periods is improved and a fuel base material with an adequately reduced normal paraffin content can be obtained at a satisfactory yield. MEANS SOLVING THE PROBLEMS [0008] In a first aspect, the invention provides a wax hydrotreating process 15 characterized by comprising a first step wherein a wax with a C16 or greater normal paraffin content of 70 mass% or greater is used as the starting material and the wax is contacted with a catalyst in the presence of hydrogen for hydrocracking, the catalyst consisting of a metal of Group VIII of the Periodic Table supported on a carrier containing an amorphous solid acid, a second step wherein the starting 20 material is temporarily switched from the wax to a light paraffin with a C9-21 paraffin content of 60 mass% or greater, and the light paraffin is contacted with the catalyst in the presence of hydrogen for hydrocracking, and a third step FP07-0005-00 wherein the starting material is switched from the light paraffin to the wax and the wax is contacted with the catalyst in the presence of hydrogen for hydrocracking. [0009] According to this wax hydrotreating process, when wax is 5 hydrocracked using a catalyst consisting of a metal of Group VIII of the Periodic Table supported on a carrier containing an amorphous solid acid, the starting material is temporarily switched to a light paraffin and the light paraffin is hydrocracked by the catalyst, thereby allowing improvement in the catalytic activity of the catalyst that has 10 deteriorated with time during the previous hydrocracking of the wax, after which the starting material is switched back to the wax, so that a fuel base material with an adequately reduced normal paraffin content can be obtained at a satisfactory yield for prolonged periods. [0010] In the wax hydrotreating process of the invention, the wax is 15 preferably FT wax, produced by Fischer-Tropsch synthesis (FT synthesis). Using FT wax as the starting material will tend to increase the middle distillate fraction yield. [0011] The light paraffin used in the wax hydrotreating process of the invention is also preferably produced by Fischer-Tropsch synthesis. 20 Using such a light paraffin will allow the reaction temperature in the third step to be reduced to a more satisfactory level. [0012] Also, the second step of the wax hydrotreating process of the invention is preferably carried out at a reaction temperature of 150 320'C. By conducting the light paraffin hydrotreating at a reaction 25 temperature of 150-320'C, it is possible to more satisfactorily improve the catalytic activity of the catalyst that has deteriorated with time, and 4 FP07-0005-00 obtain a higher yield of a fuel base material with a more adequately reduced normal paraffin content for prolonged periods. [0013] The invention further provides a process for manufacturing a fuel base material characterized by comprising a first step wherein a 5 wax with a C16 or greater normal paraffin content of 70 mass% or greater is used as the starting material and the wax is contacted with a catalyst in the presence of hydrogen for hydrocracking, the catalyst consisting of a metal of Group VIII of the Periodic Table supported on a carrier containing an amorphous solid acid, a second step wherein the 10 starting material is temporarily switched from the wax to a light paraffin with a C9-21 paraffin content of 60 mass% or greater, and the light paraffin is contacted with the catalyst in the presence of hydrogen for hydrocracking, a third step wherein the starting material is switched from the light paraffin to the wax and the wax is contacted with the 15 catalyst in the presence of hydrogen for hydrocracking, and a fourth step wherein a middle distillate fraction is obtained from the treated product obtained in the first to third steps. According to this manufacturing process, it is possible to improve the catalytic activity of the catalyst that deteriorates with time during hydrocracking of wax for 20 long periods, and to obtain a fuel base material with an adequately reduced normal paraffin content at a satisfactory yield. EFFECTS OF THE INVENTION [0014] According to the present invention, it is possible to provide a wax hydrotreating process and a process for manufacturing a fuel base 25 material, which can improve the catalytic activity of the catalyst that deteriorates with time during hydrocracking of wax for long periods, 5 C.\NRfonDC\REC18(098_ LDOC-iM O 20 -6 and can produce a satisfactory yield of a fuel base material with an adequately reduced normal paraffin content. BRIEF DESCRIPTION OF THE DRAWINGS [001 5A] Embodiments of the invention will be described with reference to the 5 following non-limiting drawings. [0015B] Fig. 1 is a flow chart showing an example of a preferred fuel base material manufacturing apparatus for carrying out the fuel base material manufacturing process of the invention. DESCRIPTION OF THE REFERENCE SYMBOLS 10 [0016] 10: reaction column, 12: hydrocracking catalyst layer, 20: distillation column, 100: fuel base material manufacturing apparatus. BEST MODE FOR CARRYING OUT THE INVENTION [0017] Preferred embodiments of the invention will now be described in detail. [0018] The wax hydrotreating process of the invention is a process 15 characterized by comprising a first step wherein a wax with a Cl 6 or greater normal paraffin content of 70 mass% or greater is used as the starting material and the wax is contacted with a catalyst consisting of a metal of Group VIll of the Periodic Table supported on a carrier containing an amorphous solid acid, a second step wherein the starting material is temporarily switched from the wax to a light 20 paraffin with a C9-21 paraffin content of 60 mass% or greater, and the light paraffin is contacted with the catalyst in the presence of hydrogen for hydrocracking, and a third step wherein the starting material is switched from the light paraffin to the wax and the wax is contacted with the catalyst in the presence of hydrogen for hydrocracking. 25 [0019] The wax hydrotreating of the invention may be carried out FP07-0005-00 using, for example, a catalyst-packed fixed bed reactor. The wax starting material is introduced into the fixed bed reactor and contacted with the catalyst in a hydrogen atmosphere for hydrocracking to obtain a product oil. 5 [0020] The catalyst for hydrocracking which is packed in the reactor for use may be one consisting of a metal of Group VIII of the Periodic Table supported on a carrier containing an amorphous solid acid. The carrier is preferably an amorphous solid acid that has been molded into pellets using a binder. 10 [0021] As examples of amorphous solid acids there may be mentioned silica-alumina, silica-zirconia, alumina-boria and silica magnesia, among which silica-alumina and alumina-boria are preferred. These may be used alone or in combinations of two or more. The amorphous solid acid content in the catalyst is preferably 15 20-100 mass% and more preferably 50-100 mass% based on the total catalyst mass. [0022] The binder may be, for example, silica, alumina or the like, and alumina is preferred. The binder content in the catalyst is preferably 0-80 mass% and more preferably 0-50 mass% based on the 20 total catalyst mass. [0023] The metal of Group VIII of the Periodic Table which is supported on the carrier may be, for example, nickel, rhodium, palladium, iridium, platinum or the like, among which palladium and platinum are preferred. These may be used alone or in combinations 25 of two or more. When slack wax containing an oil component is used as the starting material, it is particularly preferred to support a 7 FP07-0005-00 combination of palladium and platinum on the carrier. The Group VIII metal content in the catalyst is preferably 0.01-2.0 mass% and more preferably 0.1-1.0 mass% based on the total catalyst mass. [0024] The wax used as the starting material in the first step and third 5 step of the wax hydrotreating process of the invention is a petroleum based or synthetic wax containing at least 70 mass% of C16 or greater, preferably C20 or greater and more preferably C21 or greater normal paraffins. As examples of petroleum-based waxes there may be mentioned slack wax and microwax, and as examples of synthetic 10 waxes there may be mentioned "FT waxes" which are manufactured by FT synthesis. FT waxes are most preferred. [0025] The light paraffin used as the starting material in the second step of the wax hydrotreating process of the invention is a fuel base material with a C9-21 paraffin content of 60 mass% or greater, 15 preferably a fuel base material with a C9-20 paraffin content of 60 mass% or greater, even more preferably a fuel base material with a C9 20 paraffin of 70 mass% or greater, and most preferably a C9-20 FT synthesis product oil. [0026] As the reaction conditions in the first and third steps, for most 20 purposes the reaction temperature will be preferably 270-360'C and more preferably 300-350'C. If the reaction temperature is below 270'C, the normal paraffin content of the produced middle distillate fraction will tend to be high, and if it is above 360'C, the middle distillate fraction yield will tend to be low. In particular, a reaction 25 temperature of above 370'C results in more production of aromatic compounds than when the reaction temperature is within the range 8 FP07-0005-00 specified above, and therefore is not preferred from the viewpoint of obtaining a clean fuel base material. [0027] In the first and third steps, the liquid space velocity (LHSV) of the wax with respect to the catalyst in the fixed bed reactor is 5 preferably 0.1-5.0 h-1 and more preferably 0.3-3.0 h- 1 . If the liquid space velocity is below 0.1 h~1, the normal paraffin content of the produced middle distillate fraction will tend to be high, and if it is above 5.0 h-1, the middle distillate fraction yield will tend to be low. [0028] Also, the pressure for the reaction in the first and third steps 10 affects the cracking activity and is therefore in a range of preferably 1.0-10.0 MPa and more preferably 2.0-7.0 MPa. A pressure below 1.0 MPa will tend to promote deterioration of the catalyst, while a pressure above 10.0 MPa will tend to reduce the middle distillate fraction yield. 15 [0029] The hydrogen/oil ratio in the first and third steps is not particularly restricted, but normally it is preferred to be 50 NL/L or greater. A hydrogen/oil ratio of less than 50 NL/L will tend to lead to more olefins in the produced middle distillate fraction, thereby lowering the oxidation stability of the fuel. 20 [0030] As the reaction conditions for the second step, the reaction temperature is preferably 150-320'C and more preferably 180-310'C. If the reaction temperature is below 150*C, the light paraffins may be resistant to isomerization, improvement in the catalytic activity may be insufficient and the normal paraffin content of the fuel base material 25 obtained in the third step will tend to be increased, while if it is above 320'C, the crude light paraffins will be lightened, tending to result in a 9 FP07-0005-00 lower yield of the final fuel base material. [0031] The liquid space velocity (LHSV) of the light paraffins with respect to the catalyst in the fixed bed reactor during the second step is preferably 0.1 h- 1 or greater and more preferably 0.5 h-' or greater. 5 The liquid space velocity is preferably not less than 0.1 h-1 because more time will be necessary to sufficiently improve the catalytic activity. [0032] There are no particular restrictions on the pressure during the reaction of the second step, but it is preferably in the same pressure 10 range as in the first step, and in terms of operational management, it is more preferably kept at the same pressure as in the first step. There are also no particular restrictions on the hydrogen/oil ratio for the second step, but it is preferably in the same hydrogen/oil ratio range as in the first step, and in terms of operational management, it is more 15 preferably kept at the same hydrogen/oil ratio as in the first step. [0033] By carrying out hydrotreating of wax by the first to third steps described above, it is possible via the second step to improve the catalytic activity of the catalyst that deteriorates with time, and a fuel base material with an adequately reduced normal paraffin content can 20 thus be obtained at a high yield for prolonged periods. [0034] The fuel base material manufacturing process of the invention will now be explained. The process for manufacturing a fuel base material according to the invention is characterized by comprising a first step wherein a wax with a C16 or greater normal paraffin content 25 of 70 mass% or greater is used as the starting material and the wax is contacted with a catalyst in the presence of hydrogen for 10 FP07-0005-00 hydrocracking, the catalyst consisting of a metal of Group VIII of the Periodic Table supported on a carrier containing an amorphous solid acid, a second step wherein the starting material is temporarily switched from the wax to a light paraffin with a C9-21 paraffin content 5 of 60 mass% or greater, and the light paraffin is contacted with the catalyst in the presence of hydrogen for hydrocracking, a third step wherein the starting material is switched from the light paraffin to the wax and the wax is contacted with the catalyst in the presence of hydrogen for hydrocracking, and a fourth step wherein a middle 10 distillate fraction is obtained from the treated product obtained in the first to third steps. [0035] The first to third steps for hydrocracking of the starting material are preferably carried out according to the same process as the wax hydrotreating process of the invention. 15 [0036] The middle distillate fraction obtained in the fourth step may be a fraction with a boiling point in the range of 145-360'C. [0037] A fuel base material manufacturing apparatus used to carry out the fuel base material manufacturing process of the invention will now be explained. Fig. 1 is a flow chart showing an example of a 20 preferred fuel base material manufacturing apparatus for carrying out the fuel base material manufacturing process of the invention. The fuel base material manufacturing apparatus 100 shown in Fig. 1 is constructed with a reaction column 10 and a distillation column 20 for distillation of the reaction product obtained from the reaction column 25 10 (the treated product obtained by hydrocracking of the starting material). The reaction column 10 is a fixed bed-type reaction 11 FP07-0005-00 column, including within it a hydrocracking catalyst layer 12 containing the catalyst consisting of a metal of Group VIII of the Periodic Table supported on a carrier comprising an amorphous solid acid as explained above. In the reaction column 10, the starting 5 material is subjected to hydrocracking by the hydrotreating process of the invention as described above. At the top of the reaction column 10 there is connected a line Li for supply of the starting material into the reaction column 10, while a line L2 for supply of hydrogen is connected upstream from the connection of the line Li with the 10 reaction column 10. At the bottom of the reaction column 10 there is connected a line L3 for removal of reaction product from the reaction column 10, with the other end of the line L3 being connected to an ordinary pressure distillation column 20. [0038] The distillation column 20 is used for fractionation of the 15 reaction product obtained by reaction in the reaction column 10 into separate fractions with specific boiling point ranges. The reaction product from the distillation column 20 may be subjected to fractional distillation into a gas fraction (C4 and lower light hydrocarbons), a heavy naphtha fraction (fraction with boiling point of 80-145'C), a 20 kerosene fraction (fraction with boiling point of 145-260'C), a light oil fraction (fraction with boiling point of 260-360'C) and a bottom oil fraction (fraction with boiling point of 360 0 C and higher), to obtain the desired fuel base material. The distilled fractions obtained from the distillation column 20 are each transported to later stage processes 25 through lines (L4-L8) connected to the distillation column 20. EXAMPLES 12 FP07-0005-00 [0039] The present invention will now be explained in greater detail by examples and comparative examples, with the understanding that the invention is not limited to the examples. [0040] (Example 1) 5 FT wax (C20-80, C21 or greater normal paraffin content: 95 mass%) was prepared as the starting material for hydrocracking. Separately, silica-alumina (alumina content: 0.16 mol%) and an alumina binder were combined in a mass ratio of 80:20, and after molding into a cylinder form with a diameter of about 1.5 mm and a length of about 3 10 mm, it was fired at 500'C for 1 hour to obtain a catalyst carrier. The obtained catalyst carrier was impregnated with a mixed aqueous solution containing chloroplatinic acid and tetraammine dichloropalladium and dried at 120'C for 3 hours, after which it was fired at 500'C for 1 hour to produce a hydrocracking catalyst 15 comprising platinum and palladium in a mass ratio of 90:10 at a content of 0.8 mass% with respect to the total catalyst mass, supported on a catalyst carrier. [0041] Next, 200 ml of the catalyst was packed into a fixed bed reactor and the metals (platinum and palladium) were subjected to 20 reduction treatment at 345'C for 4 hours under a hydrogen stream prior to reaction. The starting material was then hydrotreated continuously for 30 days under conditions with a liquid space velocity of 1.5 h' for the starting material with respect to the catalyst (300 ml/h in terms of liquid flow rate), a pressure of 2.8 MPa and a hydrogen/oil ratio of 570 25 NL/L, while constantly adjusting the reaction temperature for a starting material cracking severity of 80 mass% (first step). The product oil 13 FP07-0005-00 obtained during this procedure was collected and distilled to obtain a C 10-20 light paraffin A (paraffin content: 99 mass%). [0042] At 30 days after initiating the hydrotreating, the starting material was switched from the FT wax to light paraffin A, and the 5 light paraffin A was hydrotreated for 24 hours (second step). The reaction conditions for this treatment were a reaction temperature of 310 C, a liquid space velocity of 2.5 h-, a pressure of 2.8 MPa and a hydrogen/oil ratio of 350 NL/L. [0043] After hydrotreating of the light paraffin A, the starting 10 material was switched back to the FT wax and was hydrotreated under the original conditions (conditions for a cracking severity of 80 mass% as in the first step) (third step). [0044] Table 1 shows the reaction temperatures for this series of hydrotreating steps, as the temperature at the start of the reaction 15 (reaction start temperature), the temperature immediately before switching the starting material from the FT wax to the light paraffin A (pre-light oil treatment temperature) and the temperature immediately after switching the starting material from the light paraffin back to the FT wax (post-light oil treatment temperature). The reaction 20 temperature is an index of the catalytic activity, with a lower reaction temperature representing more satisfactory catalytic activity. Table 1 also shows the normal paraffin content (indicating isomerization) and yield for the product oil with a boiling point of 145-360'C, of the product oil obtained by hydrotreating after switching the starting 25 material from the light paraffin back to the FT wax. [0045] (Example 2) 14 FP07-0005-00 The hydrotreating of the first to third steps described above was conducted in the same manner as Example 1, except that a C9-22 middle distillate fraction (C9-20 paraffin content: 89 mass%) produced by FT synthesis was used instead of the light paraffin A as the starting 5 material for the second step. Table 1 shows the reaction temperatures for this series of hydrotreating steps, the normal paraffin content of the product oil with a boiling point of 145-360'C (indicating isomerization) and the yield. [0046] (Example 3) 10 The hydrotreating of the first to third steps described above was conducted in the same manner as Example 1, except that the reaction temperature for hydrotreating of the light paraffin A in the second step was 335'C. Table 1 shows the reaction temperatures for this series of hydrotreating steps, the normal paraffin content of the product oil with 15 a boiling point of 145-360'C (indicating isomerization) and the yield. [0047] (Example 4) The hydrotreating of the first to third steps described above was conducted in the same manner as Example 1, except that the reaction temperature for hydrotreating of the light paraffin A in the second step 20 was 120'C. Table 1 shows the reaction temperatures for this series of hydrotreating steps, the normal paraffin content of the product oil with a boiling point of 145-360'C (indicating isomerization) and the yield. [0048] (Comparative Example 1) Hydrotreating of FT wax was conducted in the same manner as 25 Example 1, except that the first step was carried out continuously without the second step. Table 1 shows the reaction temperature after 15 FP07-0005-00 30 days from the start of operation for hydrotreating of the FT wax as "pre-light oil treatment temperature", and the reaction temperature after an additional 24 hours as "post-light oil treatment temperature". Table 1 also shows the normal paraffin content of the product oil with a 5 boiling point of 145-360C (indicating isomerization) and the yield, obtained after 31 days from the start of operation. [0049] [Table 1] Reaction Pre-light oil Post-light oil Normal Yield start treatment treatment paraffin (mass%) temperature temperature temperature content ( 0 C) (OC (C) (mass%) Example 1 323 336 326 10 55 Example 2 323 336 327 12 55 Example 3 323 336 326 10 54 Example 4 323 336 330 14 54 Comp. 323 336 338 16 53 Example I I [0050] As clearly seen by the results shown in Table 1, it was confirmed that temporarily supplying alight paraffin during operation 10 for the hydrocracking of wax for a prolonged period can improve the activity of the catalyst that deteriorates with time, and can produce an isoparaffin-rich (low normal paraffin) fuel base material at a satisfactory yield. INDUSTRIAL APPLICABILITY 15 [0051] As explained above, the present invention can provide a wax hydrotreating process and a process for manufacturing a fuel base material, which can improve the catalytic activity of the catalyst that deteriorates with time during hydrocracking of wax for long periods, and can produce a satisfactory yield of the fuel base material with an 20 adequately reduced normal paraffin content. M6 C:\NRfonbnDCC\REC\3xx)98_.DOClWN21n1 II - 16A [0052] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgment or any form of suggestion that that prior art forms part of the common general knowledge. [0053] Throughout this specification and the claims which follow, unless the 5 context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.