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[process technology] methanol olefin technology (MTO/MTP)

Ethylene, propylene and other low carbon olefins is an important basic chemical raw materials, with the development of the national economy, especially the development of modern chemical industry is rising demand for low carbon olefin, will increasingly prominent contradiction between supply and demand.
MTP process of methanol ethylene, propylene and methanol propylene is an important chemical technology.
It is the core technology of developing non-petroleum resources to produce ethylene and propylene products by using methanol synthesized from coal or natural gas as raw materials and producing low carbon olefins.
Technology introduction

Methanol to Olefins (Methanol to Olefins, MTO) and Methanol to Propylene (Methanol to Propylene) is a new technology, the two important C1 chemical synthesis refers to coal or natural gas of Methanol as raw materials, with the help of a similar form of catalytic cracking unit of fluidized bed, chemical technology of producing low carbon olefin.
In the 1970s, American Mobil discovered Methanol to Gasoline (MTG) reaction when studying Methanol using zsm-5 catalyst for other oxygen-containing compounds.
In 1979, the government used natural gas to build the first MTG device in the world, with capacity of 750,000 tons per year, which was put into operation in 1985 and then stopped for economic reasons.
From the analysis of MTG reaction mechanism, low carbon alkene is the intermediate product of MTG reaction, so the development of MTG process has promoted the development of MTO process.
Some well-known international petrochemical companies, such as Mobil, BASF, UOP and Norsk Hydro, have invested heavily in technology development.
Mobil company in the development of ZSM - 5 catalyst as the foundation, the earliest research methanol into ethylene and other low carbon olefin work, however, is a breakthrough of UOP and Norsk veidekke two companies cooperation developed by UOP MTO - 100 as catalyst of UOP/veidekke MTO process.
Domestic scientific research institutions, such as the dalian institute of science and technology of the Chinese academy of sciences, the university of petroleum, and the China petrochemical and petrochemical research institute have also carried out similar work.
One of syngas by dimethyl ether system developed by dalian compound low carbon olefin process route (SDTO) original, and the traditional syngas via methanol to low carbon olefin, in comparison with the MTO of CO conversion rate is high, above 90%, and the construction investment and operation cost saving 50% ~ 80%.
When using D0123 catalyst, the product is mainly ethylene. When using D0300 catalyst, the product is mainly propylene.
Catalytic reaction mechanism

The main reaction of MTO and MTG is:
2 ch3oh and C2H4 + 2 h2o
3 ch3oh and C3H6 + 3 h2o
Methanol dehydration to dimethyl ether (DME) first, the formation of the equilibrium mixture including methanol, dimethyl ether and water, and then into low carbon olefin, low carbon olefins through hydrogen transfer, alkylation and condensation reaction alkanes, aromatic hydrocarbons, cyclanes and higher olefins.
Methanol is dehydrated to form dimethyl ether under the action of solid acid catalyst, and its intermediate is a protonated surface methoxide.
Low carbon olefin is converted to alkanes, aromatics, cycloalkanes and higher alkenes. The process is a typical positive carbon ion mechanism with hydrogen transfer reaction.
The conversion of dimethyl ether into low carbon olefin has many mechanisms and has not been recognized.
The original MTO catalyst developed by Mobil was zsm-5 and its ethylene yield was only 5%.
The improved process name MTE, that is, methanol converted to ethylene, was originally fixed bed reactor, then changed to fluidized bed reactor, and the selectivity of ethylene and propylene was 45% and 25% respectively.
UOP developed the m-to-100 catalyst with sapo-34 as the active component, and its ethylene selectivity was significantly better than that of zsm-5, making the MTO process breakthrough.
The selectivity of ethylene and propylene was 43% ~ 61.1% and 27.4% ~ 41.8%.
According to patents published abroad, the focus of MTO research and development is still the improvement of catalysts to improve the selectivity of low-carbon olefin.
The introduction of various metal elements into the sapo-34 skeleton, which is called a molecular sieve called MAPSO or ELPSO, is one of the important means of catalyst modification.
The introduction of the metal ions can cause the changes of molecular sieve acid and orifice size, smaller orifice limits the diffusion of large molecules, beneficial to the improvement of the small molecule olefins selectivity, forming moderate acid center, also will be beneficial to the production of olefins.
Technology introduction

The representative MTO technology in foreign countries is mainly: UOP/Hydro, ExxonMobil technology, and Lurgi MTP technology.
The technological processes of ExxonMobil and UOP/Hydro are not very different. They are all in fluidized bed reactor. Methanol is reacted in the reactor, and the produced products are separated and purified to obtain ethylene, propylene and light fuel.
The UOP/Hydro process has been carried out on the methanol unit of statoil national petroleum company, which has achieved 99.8% conversion rate of methanol, 45% propylene yield, 34% ethylene yield and 13% butene yield.
Lurgi company focused by making a propylene, the new technology of methanol using middle cooling adiabatic fixed bed reactor, using the south chemical company providing special zeolite catalyst, high propylene selectivity.
According to the company, the cost of investing $180 million in the production of 1,600 tons of propylene production.
It is reported that luqi's methanol propylene technology will be produced for the first time, and it will be installed in Iran for 100,000 tons/year. It is expected to start production in 2009.
From the patents published abroad, MTO has made some new improvements.
1. MTO intermediate step with dimethyl ether (DME).
Water or water vapor has certain harm to the catalyst, can reduce water saving investment and production cost, to produce the same amount of light olefins produced by water, methanol, dimethyl ether is twice as much, so devices size can be reduced, the production cost can be decreased.
2. Flexible production of olefins through olefin disproportionation.
By changing the reaction temperature can adjust the proportion of ethylene propylene, but higher temperature would affect the service life of catalyst, and through the disproportionation reaction of ethylene and available butene disproportionation to produce propylene, also can make ethylene and propylene disproportionation for butene, will not affect the service life of catalyst, so as to make the product distribution is more flexible.
3. Use methane as a reaction diluent.
The use of methane as thinner than water or water vapor can reduce the damage to the catalyst.
Technology development status

The dalian compound of the Chinese academy of sciences is the earliest research unit in China engaged in the development of MTO technology.
Since the 1980s, it has been working on olefins from methanol.
During the "six or five" period, the laboratory test was completed and 300 tons/year (methanol treatment capacity) was completed during the "seven-five" period.
The mesoporous zsm-5 zeolite catalyst reached the international advanced level at that time.
In the early 1990s, the new process method for the production of low carbon olefin by dimethyl ether (SDTO) was first established in the world, which was listed as the key technology of the national "85" key technology.
The new process is made up of two pieces of reaction, the first reaction is the syngas in to a metal - zeolite bifunctional catalysts with high selectively into dimethyl ether, the second period of reaction of dimethyl ether in the SAPO - 34 high molecular sieve catalyst in selective transformation of low carbon olefins such as ethylene, propylene.
SDTO new process has the following characteristics:
1. The synthesis gas dimethyl ether breaks the thermodynamic limit of the methanol system of syngas, and the CO conversion rate can be close to 100%, which can save 5 ~ 8% of the investment compared with the methanol produced by methanol.
2. The catalyst with small hole phosphorous silica (sapo-34) was used as the molecular sieve catalyst, which was significantly higher than that of the zsm-5 catalyst.
3. In the second paragraph, the reaction heat can be effectively derived from the fluidized bed reactor to realize the reaction-regeneration continuous operation;
4. The new process is flexible, and the two-stage reaction process that it contains can be combined into the whole process of making olefins, and can be used separately.
In particular, the sapo-34 molecular sieve catalyst can be directly used as MTO process.
Flow in the synthesis of SAPO - 34 catalyst, has successfully developed in domestic cheap by triethylamine or diamine synthesis methods of SAPO - 34 molecular sieve as the template agent, its production costs than tetraethyl ammonium hydroxide as the template agent widely used at home and abroad will be reduced by more than 85% of SAPO - 34.
Dalian institute of chemical physics and luoyang petrochemical engineering company and the new coal chemical industry in Shanxi Province science and technology development co., LTD., after consultation, formally signed the "methanol to low carbon olefins industrialization pilot project" cooperation agreement, agreed to construction equipment of demonstration, first, fully understand and verify the MTO process problems in scientific research and pilot phase has not yet been confirmed, for the construction of the equipment of large-scale industrialization of MTO, laying a solid and reliable technical basis, common open up China's oil resources in the production of low carbon olefin coal chemical new course.
It is reported that the total investment of this project is 60 million yuan, the test equipment construction period is 12 months, the trial operation period is 6 months.
Planned to complete the construction, installation and commissioning of the test equipment, and formally put the experiment into operation and complete all the test work.
For the project to the selection of MTO process technology, the design of the key equipment, key equipment selection, catalyst industrialization application performance problems, such as engineering verification and testing, for MTO industrialization provide valuable engineering experiences.
Not only in scientific research, but also in the construction of large MTO factories, in addition to the olefin project of our company baotou coal, the major coal provinces in China also have substantive actions.
Shaanxi province has launched three large-scale coal chemical projects for foreign investment. The three major projects are the MTP project with annual output of 2 million tons of methanol and 600,000 tons of propylene in yushen coal field in northern shaanxi.
With an annual output of 2.4 million tons of methanol, 800,000 tons of olefin, MTO projects in the MTO project, and a production capacity of 1.5 million tons of methanol, 27.30 million tons of ethylene and 227 thousand tons of propylene in the northwest of guanzhong.
The main technology used in the project of yushen coal field is Texaco coal syngas technology, luqi company's methanol synthesis technology and methanol propylene technology, total investment is about 9671 million yuan;
Yulin-hengshan coalfield, adopted technology of the project has been preliminary recommended using UOP/provincial company of MTO process technology, project recommend adopt Texaco coal to syngas technology, pidec in methanol synthesis technology, UOP/provincial company MTO process technology, with a total investment of 8.388 billion yuan.
And methanol to propylene anhui huaibei coal mine project in our country, it is alleged that the project will use the coal conversion of syngas production 2 million tons/year methanol (first to build a 500000 tons/year methanol plant, plan 3 years to build).
Luqi company will provide methanol production technology and methanol production of propylene (MTP) technology, propylene production capacity 350,000 tons/year.
At present, the naphtha and light diesel oil and other raw materials resources shortage, if it's to them as the only source of raw materials, low carbon olefin production to meet demand for low carbon olefin production every year in our country obviously doesn't work, must come out a new way.
If area rich in coal resources in our country, to speed up the industrial development of the coal base MTO process, implementation to ethylene, propylene, represented by low carbon olefin production diversified raw material, do not break is to resolve our country petroleum resources nervous, promote the fast development of low carbon olefins industry in China is the most effective way, but also to realize the coal-rich province in mainland China to realize the coal resource advantage transformation.
On the other hand, in recent years, our country methanol market remain high for a long period of time, make the society a large number of investment enthusiasm of methanol, methanol product in the next few years people have concerns about the market problems.
The MTO technology also provides guarantee for the solution of methanol market.