Current situation of PX market and technology deve

2022-08-12
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Paraxylene (PX) market and technology development status in China and the world

paraxylene (PX) is an important organic chemical raw material, which can be used to produce purified terephthalic acid (PTA) or dimethyl terephthalate (DMT), and then PTA or DMT reacts with ethylene glycol to produce polyethylene terephthalate (PET), that is, polyester, which is further processed and spun to produce polyester fiber and tire industry. This is a landmark change for polyester cord

pet resin can also be made into polyester bottles, polyester films, plastic alloys and other industrial components. In addition, PX is also used in medicine

p-xylene is separated from mixed xylene, which is mainly composed of p-xylene, o-xylene and m-xylene. Mixed xylene used to come mainly from coking industry. Now it mainly comes from the petrochemical industry. The output of coking xylene is very small, accounting for less than 2% of the total output, and almost all of it is used directly as mixed xylene without separation. At present, the output of mixed xylene from petrochemicals in the United States has accounted for 99.9% of the total output. According to statistics, China's polyester production capacity has increased from 5.945 million T/A in 2000 to 20 million T/A in 2005, almost quadrupling. Driven by the polyester industry, the domestic PTA production capacity has also expanded rapidly. In 2001, the output was less than 2.2 million tons, and by 2005, it had reached about 5.5 million tons, with an average annual growth rate of more than 25%. Nevertheless, domestic PTA still cannot meet the strong demand. The import volume in 2005 was close to 6.5 million tons, which also made the apparent consumption in 2005 close to 12million tons. The huge demand for PTA has driven the development of PTA industry, which fundamentally created the rise of China's PX industry in the next five years

if the tensile strength is too large,

on the basis of digestion and absorption of imported technology, China's PX production technology has made considerable progress. Among them, hat series toluene disproportionation and transalkylation catalysts developed by Shanghai Petrochemical Research Institute are not only used in many imported units in China, but also export the complete set of toluene disproportionation and transalkylation technology to Iran for the construction of 870000 T/a toluene disproportionation unit. Ski series of xylene isomerization catalysts developed by Sinopec Research Institute of petrochemical industry have increased the unit load by more than 30% without changing the main equipment such as reactors and compressors, and have been used in seven domestic xylene isomerization units. The first industrial application of PX adsorbent rax-2000 developed by the Research Institute of petrochemical industry in the imported unit of Sinopec Qilu Branch has changed the long-term dependence on imports of PX adsorbents

according to statistics, China's PX production capacity reached 2.97 million T/A in 2005. In 2005, China's paraxylene output was about 2.3 million T, and the import volume reached 1.608 million T

in 2006, the national development and Reform Commission issued the PX 11th Five Year Plan for the layout of construction projects. This "plan" is a guiding document for the construction of PX projects during the Eleventh Five Year Plan period in China, and it is also the basis for the approval of relevant projects. The principles of project construction arrangement proposed in the plan are: (1) meet the requirements of industrial policies, have reasonable scale economy and advanced technology; (2) Give priority to relying on the old plant to tap the potential for transformation and expansion to improve competitiveness; (3) Encourage the use of domestically developed technologies and domestic equipment construction; (4) Raw materials mainly come from refineries and ethylene plants, and there are many by-products; Priority should be given to projects supporting large-scale refineries, and projects without large-scale refineries will not be considered temporarily; (5) The products are mainly used for PTA production, and the construction of PX device should try to match the distribution of PTA enterprises, although we have to clarify; (6) Encourage investment diversification and support joint ventures and cooperation between state-owned and private enterprises. According to this principle, during the "Eleventh Five Year Plan" period, Tianjin Petrochemical, Yangzi Petrochemical, Shanghai Petrochemical and Urumqi stone will be arranged to continuously attract the attention of foreign universal tensile testing machine enterprises in China's huge consumer market, and four reconstruction and expansion projects will be arranged, with an additional capacity of 1.83 million T/A; Jinling Petrochemical, Maoming Petrochemical, Fujian Refining and chemical integration project, Dahua Group relocation supporting project, CNOOC Hainan oil refining project, Xiamen Tenglong aromatics and other six new projects were arranged, with a new capacity of 4.15 million T/A. It is estimated that by 2010, the national PX capacity will reach 8.67 million t/a, with a new capacity of 5.98 million T/A, which can meet more than 85% of domestic demand, of which the capacity in East China is 4.32 million T/A, accounting for about 50% of the country. The plan also lists 4 projects that have been reported but not included in the 11th five year plan, with a total capacity of 2.45 million T/A

in 2005, the global PX capacity reached 25.89 million tons. At present, the world's paraxylene production is mainly concentrated in Asia, North America, South America and Europe. The top five production capacities are the United States, South Korea, Japan, China, India and Southeast Asia. The PX capacity of the United States is as high as 4.93 million tons, accounting for 18% of the global PX capacity. Asia accounts for 67% of the global PX capacity. In 2006, the current global PX production capacity was about 27.59 million T/A, of which 18.5 million T/A was in Asia (including the Middle East), accounting for 68.2%; 5.5 million T/A in North America, accounting for 20.2%; 2.87 million T/A in Europe, accounting for 10.6%; 270000 t/a in South America, accounting for 1.0%. In terms of demand, the demand for PX in the Asian market is as high as 17 million tons, and the production load of PX devices must be more than 90% to meet the demand. In 2005, the demand for PX increased by 1.2 million tons, and the production capacity increased by only 700000 tons/A. In 2006, with the expansion of many PTA units such as Xianglu group, Sinopec Yangzi branch and PetroChina Liaohua company, the demand for PX further expanded, which may increase by 1.5 ~ 2million tons. The tight supply situation of PX is likely to be fundamentally alleviated until the two 1.5 million T/a PX units of Iran and Taiwan, China chemical company in Taiwan Province are fully put into operation. It is estimated that the global PX production capacity and demand will increase at the rate of 1.9% and 2.6% annually from 2006 to 2011, mainly in Asia, especially China

due to the steady growth of demand, the global consumption of PX is mainly concentrated in the PTA field. At present, 80% - 90% of the global PX output is used to produce PTA. Recently, the development of DMT production is slow, and the consumption of PX will decline. As many newly invested PTA units in Asia are put into operation, the PX consumption in this region will further increase, and the proportion of consumption in the total output will further increase. New PX units in North America are mainly concentrated in the United States, and the PX used for PTA production will increase to 82.1%. Due to low production costs and sufficient supply of raw materials, investment in the petrochemical industry in the Middle East will grow steadily. More PTA and PX units will be built in this area, and the proportion of PX used to produce PTA will also further increase

from the perspective of Global trade, North America (mainly the United States) is the main exporter of PX. The PTA production of the United States is about 4million tons, and the PX consumption is 2.7 million tons, while the PX production capacity of the United States is as high as 4.93 million tons, and a large amount of surplus PX is exported to Asia and Mexico (in 2005, it is expected that Asia will import more than 1.3 million tons of PX. A considerable part of it is imported from the United States)

in the next few years, 96% of the new p-xylene production capacity in the world will be concentrated in Asia, about 40% in China, and the other 48% in the Middle East, Japan, Taiwan, India and the South Asian subcontinent

due to the increasing demand for PX, extracting and separating PX directly from reforming oil and pyrolysis gasoline is far from meeting the demand. One goal of the current Aromatics Complex is to increase the yield of xylene and reduce the yield of benzene at the same time

due to the limitation of thermodynamic equilibrium, the content of xylene (MP) is usually high in the middle of xylene mixture, while the content of PX, which is in great demand in industry, is low. Therefore, toluene disproportionation and alkyl transfer process, C8 aromatics isomerization process and toluene selective disproportionation process are often used in industry to increase px

toluene disproportionation and alkyl transfer process theoretically does not consume hydrogen, and the consumption of equipment and utilities is also small. Typical processes abroad mainly include: the "tatoraytm" process developed by UOP and Toray, Japan; "Mtdp-3" process of Mobil company; "Xylene plus" process developed by Arco; UOP's "PX plus" process. Except that "xylene plus" process uses Y-type molecular sieve d-8 silicon aluminum pellets as catalyst and moving bed process, other processes use fixed bed process and hydrogen mordenite or ZSM-5 zeolite catalyst

Sinopec Shanghai Petrochemical Research Institute has conducted research in this technology field for more than 30 years, and the s-tdt process developed has been industrialized in 1997. Compared with the tatoray process, the s-tdt process allows the raw material to contain C10 heavy aromatics, and uses the internationally leading hat series catalysts, which has low energy and material consumption, so that the process has excellent technical and economic indicators. From HAT-095 catalyst to hat-097 catalyst, the treatment capacity of the catalyst is greatly increased, but the hydrogen hydrocarbon ratio is getting lower and lower. Under the condition that the compressor is not replaced, the purpose of capacity expansion can be achieved only by replacing the catalyst

the traditional toluene disproportionation and alkyl transfer process to produce xylene is a thermodynamic equilibrium product. The typical composition is px:mx:ox (o-xylene) = 24:54:22. ExxonMobil has developed two generations of selective toluene disproportionation processes, namely "mstdp" process and "mtpx" process. The former uses ZSM-5 as catalyst, and the content of PX in the product can reach 82% - 90%. It was industrialized in 1988

the latter uses silicon modified HZSM-5 as catalyst, which was industrialized in 1997. When the toluene conversion is 20% - 30%, the PX selectivity can reach more than 90%. In addition, UOP's "PX plus" process uses modified zeolite as catalyst. When the toluene conversion is 30%, the PX content in xylene exceeds 90%. ExxonMobil has recently stopped the transfer of patented technology of mstdp process. In 2001, the company developed the "PX" process to maximize the production of PX. Its PX concentration is very high (more than 90%). If it is sent to the "crystpx" process for further purification, it can reach 99.5%. It is said that this process does not need high-temperature reaction and the operation process can be simplified. LG Caltex company of South Korea has adopted this technology in its 350000 T/a PX production unit and put it into operation in 2003. In addition, GTC recently obtained the franchise to market the selective toluene disproportionation process technology gs-stdp of Indian Petrochemical Corporation (IPCL)

the SD-01 toluene shape selective disproportionation catalyst developed by Shanghai Petrochemical Research Institute has been industrialized in SINOPEC Tianjin Branch in 2005. The catalyst adopts conventional hydrogenation process and adiabatic fixed bed reactor, which has the characteristics of high velocity, low hydrogen hydrocarbon ratio and high PX selectivity. The reaction conditions are pressure 1.2 ~ 4.5MPa, temperature 420 ~ 470 ℃, hydrogen hydrocarbon ratio 1.5 ~ 2.5, space velocity 3 ~ 5H-1, toluene conversion greater than 30%, selectivity greater than 93%, benzene/xylene molar ratio less than 1.4, and PX of condensate phase product after the reactor outlet is greater than 12.7wt%. The economic benefit of the process using this catalyst is obviously improved

c8 aromatics isomerization aims to improve PX yield. At present, UOP's "isomer" process and ExxonMobil's "mhai" process are widely used in industry. The main difference between the two is that the ethylbenzene treatment process is different. " Through dealkylation and disproportionation of ethylbenzene, the "mhai" process has a high conversion rate of ethylbenzene, but the loss of xylene is also large. The "XY" process developed by ExxonMobil to maximize the production of xylene with em4500 shape selective zeolite as catalyst has the following advantages: (1) high production capacity and PX quality; (2) 100% PX can reach the equilibrium value during the operation cycle; (3) High ethylbenzene conversion; (4) Low operation cost; (5) Less catalyst is used; (6) The operating cycle and catalyst life are long. It is said that the conversion rate of ethylbenzene can reach more than 80% and the loss of xylene can be reduced by more than 50% by using "XY" process. Mobil also developed the XY-2 process, which is more competitive than the XY process

in recent years, isomerization technology has developed to double-layer or multi-layer catalyst composite beds. Generally, the first layer of catalyst is ethylbenzene conversion catalyst, and the second layer is

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