Production of BHD (Bio Hydrofined Diesel) with Improved Cold Flow ...

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Decarbonation Selectivity,% 50 40 30 20 10 0 3MPa 6MPa 100 200 300 400 Reaction Temperature,℃ Fig. 3 Reaction temperature and decarbonation selectivity From Fig. 2, it can be seen that the decarbonation reaction requires less hydrogen than the dehydration reaction, for the same amount of deoxygenation. Also, decarbonation is less of an exothermal reaction than dehydration. Therefore, reaction conditions of high decarbonation selectivity are better from the standpoint of the suppression of hydrogen consumption and exothermicity. However, when decarbonation selectivity increases, the carbon number of the produced hydrocarbon decreases and gas oil yields decrease, and carbon dioxide emissions increase; these are disadvantages. When designing a process of BHD production, we should consider all of these aspects. 2.3 Test run using BHD We conducted a field test using an actual vehicle, whose fuel contained BHD produced by the method stated above. The test was conducted from October 2007 to March 2008 in collaboration with the Tokyo government, Toyota and Hino. The field test was completed with no problems. The details of the test are described in the paper; "Verification Test of Bio Hydrofined Diesel by Tokyo City Hybrid Bus" JSAE 20085928. 2.4 Comparison between BHD and FAME The accelerated oxidation test results for BHD and FAME are shown in Table 4. Oxygen was bubbled through the oil for 16 hours at 115°C. Acid numbers were measured before and after the test. Compared to FAME, BHD showed a much smaller acid number increase in the accelerated oxidization test, confirming its superior oxidation stability. This is because the oil’s unsaturated bonds have been hydrogenated, and we can say that this allays concerns currently held about problems with FAME use. Table 4 Oxidation Stability of BHD and FAME
Acid Number (before test) Acid Number (after test) Palm BHD Palm FAME Conventional Diesel Oil mgKOH/g 0.00 0.26 0.00 mgKOH/g 0.03 10.40 0.07 The cold flow properties of the BHD are shown in Table 5. The cloud point of the BHD is about 20°C, slightly worse than FAME. Cloud point is the temperature at which wax (paraffin) begins to separate when and oil is chilled to a low temperature, and it serves as an important indicator of practical performance in automotive applications in low temperatures. The cloud point of BHD (20°C) is much higher than the value prescribed in the JIS (Japan Industrial Standard) standard, and thus BHD cannot be used by itself in winter. Table 5 Cold Flow Properties of BHD Palm BHD Palm FAME Conventional Diesel Oil Cloud Point ℃ 20 15 -6 Pour Point ℃ 20.0 12.5 -30.0 CFPP ℃ 22 11 -9 This poor low-temperature performance is due to the fact that hydrogenated oil is a straight chain hydrocarbon (normal paraffin). In the field test, the fuel contained only 10% BHD, and its cold flow properties were acceptable. However, the poor cold flow properties of BHD are an issue when we increase the BHD content or use the BHD-blended diesel in very cold areas. In order to improve the cold flow properties of BHD, we isomerized BHD (normal paraffin) into iso-paraffin, which has branched chains in its molecular structure. In the next section, we discuss the examinations. 3. ISOMERIZATION OF BHD 3.1 Isomerization conditions We conducted reaction experiments involving BHD isomerization using our pilot plants. The feed BHD was made using the method described in the second section. Two kinds of noble metal catalysts (amorphous type and zeolite type) were used. Reaction temperature: 300°–340°C; reaction pressure: 3-10 MPa; LHSV: 1 h -1 . 3.2 Compositions of isomerization products Typical compositions of isomerization products are shown in Fig. 5. Feed BHD is isomerized into iso-paraffin and simultaneously cracked into light fractions whose carbon numbers are lower than C14. This means that the gas oil fraction will decrease as we proceed with the isomerization reaction, which is necessary to improve cold flow properties. Therefore, when we design the process of BHD
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Production of BHD (Bio Hydrofined Diesel) with Improved Cold Flow ...

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