Development of Coal-to-Olefins Technology

Coal-to-olefins is one of the important technologies for the production of olefins in my country. It uses coal as raw material to produce methanol through gasification, conversion, purification, synthesis and other processes, and then uses methanol to produce olefins (ethylene + propylene), and then produces polyolefins. (polyethylene, polypropylene) and other downstream products.

Among them, coal-to-methanol and olefin polymerization to polyolefin are traditional mature technologies, while methanol-to-olefin is a new technology successfully developed in recent years, and it is also the core technology link of coal-to-olefin.

The basic reaction process of methanol to olefins is that methanol is first dehydrated to dimethyl ether (DME), and then dehydrated to generate low-carbon olefins (ethylene, propylene, butene), and a small amount of low-carbon olefins are polycondensed, cyclized, and alkylated. , hydrogen transfer and other reactions to generate saturated hydrocarbons, aromatics and higher olefins.

At present, there are mainly two types of methanol-to-olefins technologies: MTO technology and MTP technology. MTO technology is a process for converting methanol into a mixture of ethylene and propylene. In addition to ethylene and propylene, there are by-products such as butene; MTP technology is a process for converting methanol into propylene. In addition to propylene, there are also ethylene, propylene, etc. Liquefied petroleum gas (LPG), naphtha and other products.

Among these two technologies, enterprises with coal resources can use coal as raw material to produce methanol through synthesis gas, and then use methanol to produce olefins; enterprises without coal resources (such as enterprises in coastal areas) can use purchased methanol (such as imported methanol) to produce olefins directly.

Currently representative methanol-to-olefins technologies mainly include: UOP/HydroMTO process jointly developed by UOP (US company) and Hydro (Norwegian company), MTP process of German Lurgi company, DMTO process of Dalian Institute of Chemical Physics, Chinese Academy of Sciences, China SMTO process of Petrochemical Shanghai Petrochemical Research Institute, SHMTO process of Shenhua Group, circulating fluidized bed methanol to propylene (FMTP) process of Tsinghua University, etc.

①UOP/HydroMTO process

This process uses crude methanol or product grade methanol as raw material to produce polymer grade ethylene/propylene. The reaction adopts fluidized bed reactor, the reaction temperature is 400~500℃, the pressure is 0.1~0.3MPa, and the selectivity of ethylene+propylene can reach 80%. , the molar ratio of ethylene and propylene can be 0.75~1.50.

In order to increase the yield of ethylene and propylene in the product gas, UOP has developed a technology that couples the methanol-to-olefins process with the C4, C5 olefins catalytic cracking process (olefinscracking process, OCP), and its diene (ethylene + propylene) selectivity can be Up to 85%~90%, and the ratio of ethylene/propylene can be adjusted in a wide range.

②Lurgi MTP process

The German company Lurgi began to develop the MTP process in 1996, using the zeolite-based modified ZSM-5 catalyst from Sudchemie, which has a high selectivity for low-carbon olefins.

Usually in the production process, the target product of the LurgiMTP process is propylene. First, methanol is dehydrated and converted into dimethyl ether, then dimethyl ether, methanol and water enter the first MTP reactor, and the reaction is at 400~450℃, 0.13~0.16MPa The conversion rate of methanol and dimethyl ether is over 98.99%. Propylene is the main product, and some ethylene, LPG and gasoline products are also by-products.

③ DMTO process of Dalian Institute of Chemical Physics, Chinese Academy of Sciences

The process consists of two stages of reaction: the first stage reaction is the high selectivity conversion of synthesis gas to dimethyl ether on the metal zeolite bifunctional catalyst; the second stage reaction is the high selectivity of dimethyl ether on the SAPO-34 molecular sieve catalyst It can be permanently converted into low-carbon olefins such as ethylene and propylene, and then simplified into syngas through methanol to directly produce olefins through technical research.

The catalytic conversion of methanol to olefins was realized in a dense-bed circulating fluidized bed reactor using SAPO-34 molecular sieve catalyst.

④ Sinopec SMTO process

The technology adopts the self-developed SMTO-1 catalyst, the conversion rate of methanol is greater than 99.5%, the selectivity of ethylene + propylene is greater than 81%, and the selectivity of ethylene + propylene + butene is greater than 91%.

The industrial application results of SMTO technology show that its ethylene selectivity is 42.10%, propylene selectivity is 37.93%, C2~C4 selectivity is 89.87%, methanol conversion rate is 99.91%, methanol unit consumption is 2.92t/t, coke formation rate is 1.74% .

⑤ Shenhua Group SHMTO technology

After the world's first large-scale industrialized methanol-to-olefins plant (using DMTO technology) was successfully put into trial operation in Shenhua Baotou, Shenhua Group carried out the development of a large number of new processes and technologies based on the rich experience accumulated in the industrial operation of the demonstration plant, including The development of new MTO catalyst (SMC-1) and the development of new MTO process. In 2012, the new methanol-to-olefins catalyst SMC-1 was successfully developed and used in Baotou MTO plant.

In the same year, Shenhua Group applied for the patent of the device and method for converting methanol into low-carbon olefins, and completed the development of a new 1.8 million tons/year methanol-to-olefins (SHMTO) process package. In September 2012, the Shenhua Xinjiang Ganquanbao 1.8 million tons/year methanol-to-680,000 tons/year olefins project using the SHMTO process was successfully put into trial operation. The industrial operation effect of the device shows that its ethylene selectivity is 40.98%, and the propylene selectivity is 39.38%, C2~C4 selectivity 90.58%, methanol conversion rate 99.70%, coke formation rate 2.15%.

⑥FMTP process of Tsinghua University

Using SAPO-18/34 molecular sieve catalyst and fluidized bed reactor, the methanol feed rate is 4250kg/h, the methanol conversion rate is 99.9%, the propylene/ethylene ratio in the product is 1.18:1, and the ethylene+propylene selectivity reaches 70.6%.

The FMTP process is generally an improvement on the MTP process, which can adjust the propylene/ethylene ratio from 1.2:1 to 1:0 (full propylene output). Using this technology to produce olefin products mainly propylene, the total yield of diene (ethylene + propylene) can reach 88%, and the raw material methanol consumption is 2.62t/t diene. Using FMTP technology, Gansu Pingliang Huating Coal Industry Group is building my country's first fluidized bed methanol to propylene plant. The project consumes 600,000 tons of methanol annually, produces 160,000 tons of polypropylene, 19,000 tons of liquefied gas, and 21,000 propane tons, 14,000 tons of gasoline, 8,000 tons of fuel gas, and 28,000 tons of methyl tert-butyl ether (MTBE). It is expected to be completed and put into operation in 2021.