CN1335361A - Method and Catalyst for Selective Hydrodesulfurization of Cracked Gasoline - Google Patents

Abstract

Preparation of a process and catalyst for selective hydrodesulfurization of cracked gasoline, the catalyst and hydrogenation process have significantly higher hydrodesulfurization selectivity than traditional hydrodesulfurization catalysts and hydrogenation technologies, namely: stronger High hydrodesulfurization capacity (hydrodesulfurization rate 75-95%) and lower olefin saturation (olefin saturation 5-20%), desulfurized gasoline has less octane loss (RON loss 2-3 units ). The pressure in the reaction process is 1-4MPa, the temperature is 250-350°C, the liquid phase space velocity is 1-10h ^-1 , and the hydrogen-oil volume ratio is 100-500.

Description

Method and Catalyst for Selective Hydrodesulfurization of Cracked Gasoline

The invention relates to a method for selective hydrodesulfurization of cracked gasoline (naphtha) and a method for preparing a catalyst, which belongs to the improvement and innovation of the refining process of light oil products in the petrochemical industry. Selective hydrodesulfurization process of cracked gasoline (naphtha) in the presence.

It is well known that cracked gasoline (naphtha), especially catalytically cracked gasoline (naphtha) or heavy oil catalytically cracked gasoline (naphtha), contains a large amount of sulfur. Methods for reducing sulfur content include: 1) hydrofinishing of whole-fraction feedstocks for cracking or coking units, and 2) hydrogenation of products from these units. The first option is costly because of the need for a huge hydrotreating unit and the consumption of a large amount of hydrogen. The second option is a shortcut but results in saturation of olefins (typically 20-80v% of the feedstock), which also lowers the octane number ((RON+MON)/2) of the gasoline product by 10-20 units. The octane loss associated with desulfurization has a large impact on the octane of the refinery's finished gasoline. Typical technologies for hydrodesulfurization of cracked gasoline (naphtha) previously disclosed include:

1. US Pat. No. 4,140,626 (Bertolacini and Sue-A-Quan) describes a selective hydrodesulfurization technology, using metals from Group VIB and Group VIII supported on a carrier with at least 70 wt% MgO. More specifically, the Group VIB metal is Mo and the Group VIII metal is Co. The catalyst contains 3 wt% CoO and about 16 wt% _MoO3 supported on pure MgO support. When the hydrodesulfurization rate is 75-85%, the olefin saturation is quite low (≤40wt%), and the loss of octane number is small (≤2 units).

2. USPat.No.4,132,632 (Yu and Myers) is very similar to the above-mentioned patents except that the metal loading is limited to 4-6 wt% of VIB metals and 0.5-2 wt% of VIII metals. And more specifically, Group VIB metal Mo and Group VIII metal Co are used. Catalyst I contains about 1 wt% CoO and about 5 wt% _MoO3 , supported on a pure MgO support. Catalyst II contains about 3 wt% of CoO and about 17 wt% of MoO ₃ , and the support contains 80 wt% of MgO (catalysts such as the aforementioned USPat. At the same hydrodesulfurization level (about 82-84%), catalyst I can obtain lower olefin saturation and higher octane number than catalyst II, and the loss of octane number is very small (about 1.6 units). In addition, for both catalysts, the olefin saturation is rather low (≤40 wt%) and the loss of octane is small (≤2.6 units) in the range of hydrodesulfurization studied.

3. At the 1978 NPRA Annual Meeting (San Antonio, Texas), Coates, Myers, and Sue-A-Quan presented a paper titled "Hydrodesulfurization of Cracked Naphtha with Minimal Octane Loss," illustrating what Amoco calls For the bright future of "selective ultra-refining process". The paper was published about a year before the aforementioned patent was issued. The paper mentions two catalysts (probably derived from the above two patents), in which selective desulfurization is the technical feature of the process. The new catalyst exhibits lower deactivation rates in hydrodesulfurization than conventional hydrotreating catalysts. The loss of octane number when the hydrodesulfurization rate is 90% is said to be 4 MON or 4.5 RON. The octane loss mentioned in this document is much higher than Amoco's subsequent patent.

4. GB2,225,731 promulgated a hydrogenation catalyst containing VIB and VIII group metal hydrogenation components homogeneously loaded on a carrier containing MgO and Al ₂ O ₃ . Mg/Al molar ratio is 3-10/1. The catalyst is said to have comparable hydrodesulfurization activity to similar _catalysts supported on _Al2O3 .

The object of the present invention is to avoid the disadvantages of the above-mentioned prior art and provide a method for selective hydrodesulfurization of cracked gasoline (naphtha) and a preparation method of the catalyst. Its main technical feature is to prepare a special hydrodesulfurization catalyst in advance, and then pass the raw material oil to be treated through the reactor where the catalyst forms a bed.

The main components of this catalyst are CoO+MoO, K ₂ O, CuO, MgAlO composite oxide with hydrotalcite as precursor and Al ₂ O ₃ , and the weight ratio of each component is: CoO+MoO: 6-20%; K ₂ O: 0-5%; CuO: 0-5%; MgAlO composite oxide with hydrotalcite as precursor: 30-95%; Al ₂ O ₃ : 0-80%.

The selective hydrodesulfurization of cracked gasoline adopts the gas-phase hydrogenation process, that is, the above-mentioned special catalyst is used. The reaction pressure of the process is 1-4MPa, the reaction temperature is 250-350℃, and the liquid phase space velocity is 1-10h ^-1 . The volume ratio of hydrogen to oil is 100-500. Wherever possible, use a fluidized or ebullating bed, preferably a fixed bed.

The technical characteristics of the present invention will be described in detail below in conjunction with embodiment:

(1). In the preparation of the catalyst, its main steps are as follows:

① Preparation of carrier: After mixing and grinding hydrotalcite Mg _a Al _b CO ₃ (OH) _c .nH ₂ O, alumina Al ₂ O ₃ , water and acid, the mixture is forged or extruded according to the size required by the design to The formed strips are dried at 80-150°C for 10-30 hours, and then fired at 400-600°C for 2-8 hours;

②It is prepared by immersion in metal salt solution, the metal salt used is nitrate or carbonate, and the immersion time is 6-12 hours

③Roasting treatment: the roasting temperature is 300-600°C, and the time is 2-8 hours; the best roasting temperature is 400-500°C, and the time is 4-6 hours.

④Vulcanization treatment: The vulcanization temperature is 260-350°C, the vulcanization time is 8-48 hours, and the hydrogen-oil volume ratio is 100-50

(2). The choice of raw material oil is mainly cracked gasoline (naphtha), which can be thermally cracked gasoline or naphtha, catalytic cracked gasoline or naphtha, coker gasoline or naphtha, steam cracking in ethylene production process Gasoline or naphtha, usually full-range cracked gasoline (naphtha) obtained from cracking and coking unit operations. It can contain 3-80% alkanes, 1-80% alkenes, 3-80% naphthenes, 3-80% aromatics and a small amount of sulfur- and nitrogen-containing compounds. It can be any fraction cut within the above range. Wherein, the sulfur content may be 100-20000 ppm, and the nitrogen content may be 20-2000 ppm.

(3). The use of the reactor is mainly a fixed bed, although it is possible to use a fluidized bed or an ebullating bed.

According to above three principles, the present invention is carried out operation, obtains following result:

Example 1

Weigh 30g of SB powder (γ-Al ₂ O ₃ produced by Condea, Germany) or hydrotalcite or a mixture of the two, mix evenly with 30ml of water and 0.9g of HNO ₃ , and extrude it into a diameter of 1.6mm on a catalyst extrusion molding machine The strips were dried under infrared lamp for 5 hours, dried in an oven at 120°C for 10 hours, calcined in a muffle furnace at 500°C for 5 hours, and finally ground and sieved to obtain 20-40 mesh catalyst carrier particles.

Example 2

Weigh 12g of the γ-Al ₂ O ₃ carrier prepared by the method of Example 1, weigh 1.2g of Co(NO ₃ ) ₂ .7H ₂ O and dissolve it with 8g of deionized water, pour the carrier into the solution, and soak for 12h , dried at 120°C for 10 hours, and then fired at 500°C for 5h. Catalyst I was prepared by loading 12% MoO ₃ with ammonium molybdate according to the above steps. Example 3

The preparation steps are the same as in Example 2, except that 2% K ₂ O is also loaded on the catalyst, which is Catalyst II.

Example 4

The catalyst carrier of SB powder/hydrotalcite=1/3 was prepared by the method in Example 1, and CoO, MoO ₃ and K ₂ O were respectively impregnated according to the method in Example 2 to obtain Catalyst III.

Example 5

The catalyst supported by pure hydrotalcite was prepared by the method in Example 1, and CoO, MoO ₃ and K ₂ O were respectively impregnated according to the method in Example 2 to obtain Catalyst IV.

The approximate composition of various catalysts is listed in Table 1.

The composition of table 1 catalyst catalyst carrier active ingredient load capacity I γ-Al ₂ O ₃ Co,Mo CoO+MoO ₃ =16%K ₂ O=2%, Co:Mo=1:3 II γ-Al ₂ O ₃ Co, Mo, K III Hydrotalcite/γ-Al ₂ O ₃ =3/1 Co, Mo, K IV Hydrotalcite Co, Mo, K

The properties of the typical cracked gasoline raw materials used in hydrotreating can be described by Table 2. The properties of the raw material FCC gasoline in Table 2 sample FCC raw material n-alkanes (%) 4.29 Isoparaffin (%) 20.29 Olefin (%) 39.72 Naphthenic(%) 6.68 Aromatics (%) 22.41 RON 94.28 MON 87.52 (RON＋MON)/2 90.90 Sulfur content (ppm) 1203

Each of the catalyst systems in Examples 2 to 5 was tested for hydrodesulfurization on a high-pressure micro-reactor. The catalyst was ground into a size of 20-40 mesh, and 16ml of the catalyst was loaded into the reactor, and presulfurized with straight-run gasoline containing 3v% CS ₂ for 12 hours at 260°C, 280°C, and 300°C respectively. Fuel FCC gasoline at test temperature. The reaction was carried out for 10 hours and a sample was taken for analysis. Typical reaction conditions are: temperature 260-300°C, pressure 2.0Mpa, liquid space velocity 3.75h ^-1 , hydrogen-oil volume ratio 180.

In each example, 1) hydrodesulfurization percentage (this is related to the mass percentage of feed sulfur removal); 2) olefin saturation (showing the mass percentage of saturated olefins in the feedstock); 3) selection Factor (expressed in log(1-HDS%)/Log(1-HYD%)); 4) antiknock index (RON+MON)/2 and loss of octane number, the results are shown in Table 3. Table 3 FCC gasoline selective hydrodesulfurization test results serial number temperature °C Desulfurization rate HDS% Olefin saturation HYD% selectivity factor (RON＋MON)/2 (RON＋MON)/2 loss I 280 97.8 98.7 0.8 75.8 13.5 II 260280300 64.261.999.0 43.574.980.6 1.80.72.8 84.180.679.8 5.28.89.5 III 260280300320 42.556.062.487.9 11.330.522.943.4 4.62.33.83.7 88.083.186.783.8 2.97.84.27.1 IV 280300320 24.059.174.6 3.07.016.1 8.912.37.8 87.987.286.5 1.42.12.9 IV-1 320 90.1 39.8 4.6 83.7 5.6 The properties of FCC gasoline, a typical product obtained by hydrotreating, are listed in Table 4.

Table 4 Composition properties of product FCC gasoline sample Product 1 Product 2 n-alkanes (%) 6.31 7.70 Isoparaffin (%) 23.30 24.82 Olefin (%) 36.81 33.21 Naphthenic(%) 7.67 8.62 Aromatics (%) 22.63 22.28 RON 90.33 89.55 MON 84.03 83.34 (RON＋MON)/2 87.18 86.45 Sulfur content (ppm) 431 340

In summary, the following conclusions can be drawn:

1. In the range of temperature and pressure tested, the technology of the present invention shows higher hydrodesulfurization selectivity by substantial factors.

2. When the hydrogenation operation is carried out within the conventional liquid space velocity (LHSV) range, the technology of the present invention promises to achieve the goal of hydrodesulfurization ≥ 60%.

3. The selectivity of HDS catalyst can be improved by adding metal K promoter.

4. The catalysts supported by Mg-Al-O composite oxide and modified γ-Al ₂ O ₃ have higher HDS activity and lower HYD rate.

5. When the hydrodesulfurization rate is 70%, the olefin saturation rate is about 16%, and the octane number loss is 2.9 units.

Claims (4)

1. A catalyst for selective hydrodesulfurization of cracked gasoline, whose main components are CoO+MoO, K ₂ O, CuO, MgAlO composite oxide and Al ₂ O ₃ with hydrotalcite as a precursor, characterized in that, The weight ratio of each component is: CoO+MoO: 6-20%; K _{2 O} : 0-5%; CuO: 0-5%; MgAlO composite oxide with hydrotalcite as precursor: 30-95%; O ₃ : 0 to 80%. 2. A method for selective hydrodesulfurization of cracked gasoline, characterized in that the catalyst according to claim 1 is used, and a gas phase hydrogenation process is adopted, the reaction pressure of the process is 1 to 4MPa, and the reaction temperature is 250 to 350°C , the liquid phase space velocity is 1-10h ^-1 , and the hydrogen-oil volume ratio is 100-500. 3. The method for selective hydrodesulfurization of cracked gasoline according to claim 2, characterized in that the gas-phase hydrogenation process should use a fluidized bed, ebullating bed or fixed bed. 4. the catalyst of hydrodesulfurization according to claim 1, is characterized in that following steps should be adopted to realize in preparation: ① Preparation of carrier: After mixing and grinding hydrotalcite Mg _a AlbCO ₃ (OH)c.nH ₂ O, alumina Al ₂ O ₃ , water and acid, the mixture is forged or extruded according to the size required by the design to form Strips, dried at 80-150°C for 10-30 hours, then roasted at 400-600°C for 2-8 hours; ②It is prepared by immersion in metal salt solution, the metal salt used is nitrate or carbonate, and the immersion time is 6-12 hours ③Roasting treatment: the roasting temperature is 300-600°C, and the time is 2-8 hours; the best roasting temperature is 400-500°C, and the time is 4-6 hours. ④Vulcanization treatment: The vulcanization temperature is 260-350°C, the vulcanization time is 8-48 hours, and the hydrogen-oil volume ratio is 100-500.