Application of Domestic Catalyst in PP Production of Loop Process

China Petroleum and Chemical Corporation (Sinopec) Jinan Branch's polypropylene (PP) plant uses a domestic single-loop reactor process. After the plant was put into production in 1998, the domestically-produced high-efficiency PP catalyst N-II has been used. In 2002, DQ series catalysts first produced T30S in PP equipment industry, and also produced V30S, Z30S, H30S, biaxially oriented PP (BOPP) special resin T36F and high-grade non-woven special material JNW28. By using the catalyst, the device runs smoothly, the product quality is excellent, the catalyst consumption is at a low level, and the production cost is effectively reduced.

1 Characteristics of DQ Catalyst DQ catalyst is a new generation of PP spherical rescue catalyst developed by Sinopec Beijing Research Institute of Chemical Industry. It can be applied to homopolymerization, random copolymerization and block copolymerization for the preparation of PP with high ethylene content. Widely used in various polymerization processes. The technical characteristics of the catalyst mainly include: (1) high activity, activity greater than or equal to 50 kg / g (liquid phase bulk polymerization, 70 ° C, 2 h), long active life center (greater than 6 h); (2) catalyst and its preparation The polymer is spherical, the particle size of the catalyst can be adjusted according to the process requirements; (3) the hydrogen sensitivity is good, and the polymer melt flow rate (MFR) can be adjusted widely (the homopolymer is 0.2-150.0g/10min) (4) The polymer product has a high isotactic index and good adjustability; (5) a high apparent density of the polymer (greater than or equal to 0.47 kg/m3); (6) excellent performance of the polymer product.

2 Application of DQ catalyst on PP device 2.1 Production of traditional PP grade DQ series catalyst was used in PP plant in early 2002, first producing T30S and Z30S products. According to the characteristics of the D0 catalyst, the hydrogen concentration was adjusted from 400 μL/L to 500 μL/L, and the catalyst injection amount was lowered by 20%, and other parameters remained unchanged. During the transformation process, the operation of the device was stable, the opening of the loop discharge valve and the fluctuation of the material level of the high-pressure propylene flash tank (D-301) were significantly reduced, but the axial pump power increased slightly by 2-3 kW. The first batch of PP products produced using the new catalyst was analyzed and tested, the powder ash was reduced by 30 μg/g, and the other quality indexes were the same as those produced by using the N-II catalyst. Since then, the production of the Z30S using the DQ series of catalysts has been successful.

According to the technical data obtained during the production of T30S and Z30S and the good operating conditions of the device, the use of DQ catalyst to produce H30S has been successful.

2.2 Production of BOPP special resin T36F In 2004, the BOPP production line of PP downstream equipment of Sinopec Jinan Branch was started, and the raw material T36F used by it was provided by the device. The isotactic index of the product is required to be stable at 95.5%-96.5%, MFR at 2.6-3.0 g/10 min, and ash not higher than 150 μg/g. The production of high quality PP resin by single loop reactor process is very difficult to operate, and the fluctuation of production process parameters must be strictly controlled.

Due to the low PP isotactic index produced by DQ catalyst, its hydrogen regulation performance is slightly worse than that of N-II catalyst, and the MFR of the product is more stable. In addition, its fluidity is better, and it is not easy to produce a low-equivalent index product. The key parts such as material and D-301 are blocked, so DQ catalyst is selected for the production of film T36F.

In August 2004, the first batch of T36F trial production was carried out. The parameters were adjusted according to the performance index of DQ catalyst. The test was carried out until 12h, the product isotactic index reached 95.8%, the MFR was stable at 2.9g/10min, the product quality was controllable, and the device continued to operate stably. After analyzing the products, the performance indicators have fully met the T36F quality requirements.

The T36F products produced have been tested by BOPP manufacturers, and the film drawing speed has reached 370m/min or more, and other performance indexes are excellent.
2.3 Product quality of PP Since August 2004, the device has been able to produce various grades of PP with MFR of 2-40g/10min and isotactic index of 94%-98% using DQ catalyst. The catalyst can be adjusted only by adjusting the amount of hydrogen added. The whole production process is stable and the product quality is stable. More than 85% of the products such as T30S, T36F, V30S, Z30S, JNW28 and H30S are produced to the first grade, and the pass rate of the transition material is 100%. After product analysis and testing, all performance indicators have reached the quality requirements of the products, and some product quality is shown in Table 1.

Table 1 Performance of PP products produced using DQ catalyst
Tab.1 Properties of the PP resin prepared with DQ catalyst
PP grade T30S T36F V30S Z30S JNW28 H30S
Hydrogen addition amount / (μL·L-1) 450 440 1500 2450 1500 2900
MFR/[g·(10min)-1] 2.56 2.88 17.10 26.32 35.14 32.10
Isotactic index,% 96.2 95.8 96.3 96.2 97.6 96.8
Powder ash / (μg · g - 1) 126 126 123 123 122 134
Yield tensile strength / MPa 33.16 34.42 35.95 35.62 35.57 38.45
Elongation at break, % 501
"Fisheye" number (0.2-0.7mm) / (pieces · m-2) 160 164 168 164 180
Note: The quality grades are all excellent grades.
3 Factors Affecting the Activity of DQ Catalyst 3.1 Effect of Hydroxy Sulfur (COS) Content on Catalyst Activity According to the change of catalyst activity, it was found that the activity of the catalyst was related to the quality of propylene. The COS content in propylene varies greatly, which has a significant effect on the activity of the catalyst. When the COS content is high, the content of impurities such as CO2 and methyl sulfide is changed. Therefore, the factor affecting propylene quality is the COS content. The activity of each batch of the main catalyst in 2006 was measured according to the production grade. It can be seen from Table 2 that the larger the COS content in propylene, the lower the catalyst activity. When the COS content in the raw material propylene is less than 10 μg/g, the effect on the catalyst is not large.

3.2 Measures to improve the activity of the main catalyst 3.2.1 The relevant process of the improved device is finally determined by analyzing the process flow of the upstream and downstream related devices.

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