|Doing It Differently|
MD, UOP India Pvt Ltd
| Methanol-to-Olefins technology opens new, economical routes to light olefins from low cost feedstocks
Amongst the largest volume petrochemicals in the world, olefins are building blocks for everything from packaging materials, home ware, piping and insulation, to synthetic rubbers and antifreeze. Honeywell’s UOP now has a revolutionary solution that produces olefins more economically than many traditional sources. The solution is MTO, writes Steve Gimre, Managing Director, UOP India Private Limited, A Honeywell Company.
By June of this year, China’s Wison (Nanjing) Clean Energy Co Ltd, has successfully produced more than 360 million pounds of light olefins at a plant in Nanjing, China, using UOP’s breakthrough Methanol-to-Olefins (MTO) process technology. The plant, the first commercial-scale facility to use the UOP/Hydro MTO process technology, has been operating since September 2013 and is successfully meeting both quality and quantity expectations for light olefins.
The Wison facility uses UOP’s Advanced MTO process that combines the UOP/Hydro MTO process and the Total/UOP olefin cracking process. The combination significantly increases yields and feedstock efficiency. The process converts methanol, which can be derived from low-cost raw materials such as coal or natural gas, into ethylene and propylene. MTO also offers flexibility in the ratio of propylene to ethylene produced, so operators can adjust plant operations to most effectively address market demands.
Ethylene and propylene are two of the largest volume petrochemicals in the world. Ethylene is used in a variety of products including polyethylene (food packaging, house wares), polyvinylchloride (piping, construction materials), polyethylene terephthalate (bottles, films), and polystyrene (insulation, cups). Likewise, propylene is used in a variety of applications including polypropylene (films, packaging, automotive components), acrylonitrile (synthetic rubbers), propylene oxide (antifreeze, polyurethane foams) and many others.
Current Status of Olefin Manufacturing
Nearly all of the world’s ethylene is produced via steam cracking technology. Steam cracking uses high temperatures (8000C - 9000C) and steam to crack and dehydrogenate hydrocarbons into ethylene and other valuable by-products. Propylene is one of the most important by-products from steam cracking of propane and higher hydrocarbons. Approximately 55 per cent of the world’s supply of propylene comes from steam cracking. Propylene is also supplied as a by-product from fluid catalytic cracking (~35%) and propane dehydrogenation (~5%).
Over the past several decades, the manufacturing capacities for these chemicals have undergone remarkable transitions, with impressive growth in some regions and flat production in others (Figure 1). Two of the most important factors shaping the development of most chemical markets are regional demand and feedstock cost and availability.
Driven mainly by the availability of low cost ethane, ethylene production capacity in the Middle East (ME) has grown significantly over the past 10 - 15 years. Similarly, after more than a decade of minimal growth, ethylene capacity in the Americas is increasing due to the availability of low cost ethane from shale gas and enhanced gas recovery technologies. The availability of low cost feeds can be an important driver for investments into new production capacity.
The Asia Pacific region has also experienced tremendous growth in ethylene production capacity. However, unlike ME, this region does not possess an abundance of cheap ethane. With no other options available until recently, naphtha has been the predominant feedstock even though it has been up to more than five times more expensive than the ethane used in other regions. New technologies such as advanced MTO have the potential for changing the game by opening up new routes based on alternative, low cost feed stocks.
The MTO Promise
UOP’s MTO process is a path-breaking innovation for producing ethylene and propylene from methanol. Since methanol can be made using a variety of different feedstock, MTO opens up an entirely new direction for the production of ethylene and propylene starting from low cost, alternative raw materials such as coal or natural gas.
Methanol is widely produced from natural gas or coal at locations with abundant reserves. By utilising methanol derived from these cost-advantaged raw materials, MTO enables low costs of production for olefins in regions that do not have large reserves of ethane. MTO can also help to fill the gap between propylene demand and supply from steam crackers and refineries by producing olefins at high ratios of propylene to ethylene.
The conversion of methanol to olefins and other hydrocarbons products has been widely studied. Initial work in the 1970s and early 1980s focused on conversion of methanol to gasoline range products and employed ZSM-5 type zeolites. Selectivity of methanol to ethylene and propylene over ZSM-5 was generally low, with selectivities favouring heavier more highly-branched hydrocarbons and aromatics. This catalyst technology was utilised in the commercial development of the Mobil MTG Process. During the 1980s, a group of scientists at Union Carbide (which later became part of UOP LLC) discovered a new class of materials, Silicoaluminumphosphates (SAPO) molecular sieves. Of these, the discovery of SAPO-34 provided a technology breakthrough.
SAPO-34’s unique pore size, geometry and acidity created a more selective route for methanol conversion to ethylene and propylene with reduced heavy by-products.
A More Advanced Process
In the early 1990s, UOP and Norsk Hydro A S formed an alliance to develop MTO technology. This collaboration with Norsk Hydro led to the development of the UOP/HYDRO MTO process. In developing the process, UOP built on its in-house Fluid Catalytic Cracking (FCC) experience for fluidised reactor and regenerator and known steam cracker art.
Unrelated to MTO at the time, ATOFINA was at work in the 1990s developing an olefin cracking technology. Shortly after, in 2000, ATOFINA (which later became part of Total Petrochemicals and today of TOTAL Refining and Chemicals) and UOP formed a joint alliance to further develop olefin cracking technology. This collaboration led to the development of the Total Petrochemicals/UOP olefin cracking process.
The Total Petrochemicals/UOP olefin cracking process has been integrated with the UOP/HYDRO MTO process. This combination of processes is the basis for Advanced MTO.
A major milestone for MTO commercialisation was the start up in 2009 of the semi-commercial, fully integrated MTO demonstration unit (Figure 2) in Belgium, which successfully demonstrated the performance of the integrated UOP/Hydro MTO process with the Total Petrochemicals/UOP olefin cracking process.
How It Works
The UOP/Hydro MTO process utilises a fluidised reactor and regenerator system to convert methanol to olefins using a proprietary SAPO-34 type catalyst.
The process can be operated on crude or un-distilled methanol, as well as with pure (Grade AA) methanol. The choice of feedstock quality generally depends on project-specific situations because there can be advantages in either case. Figure 3 (on previous page) illustrates a simple flow diagram for the UOP Advanced MTO process.
The methanol feed is preheated and then introduced into the reactor. The conversion of methanol to olefins requires a selective catalyst that operates at moderate to high temperatures. The reaction is exothermic so heat can be recovered from the reaction. Carbon or coke accumulates on the catalyst and requires removal to maintain catalyst activity. The coke is removed by combustion with air in a catalyst regenerator system. A fluidised bed reactor and regenerator system is ideally suited for the MTO process because it allows for heat removal and continuous catalyst regeneration. The reactor operates in the vapour phase at temperatures between 650 to 1000°F and pressures between 15 and 45 psig. A slipstream of catalyst is circulated to the fluidised bed regenerator to maintain high activity.
The reactor effluent is cooled and quenched to separate water from the product gas stream. The product gas is compressed and then unconverted oxygenates are recovered and returned to the reactor. The reactor provides very high conversion so there is no need for a large recycle stream. After the oxygenate recovery section, the effluent is further processed in the fractionation and purification section to remove contaminants and separate the key products from the by-product components. Ethylene and propylene are produced as polymer-grade products and sent to storage. The C4 - C6 fraction can be sent to the OCP reactor where it is selectively converted to light olefins, the majority of which is propylene. Typically the propylene to ethylene ratio in OCP reactor effluent is about 4:1. The OCP product is separated by fractionation, with the C3 and lighter fraction sent to the MTO product recovery section and the residual C4 plus fraction used as a by-product fuel.
MTO in Numbers
In most regions of the world, either methane or coal is readily available at prices that make UOP’s advanced MTO process a better economic choice than naphtha cracking. Investment in MTO can be staged by first constructing and operating the MTO unit based on purchased methanol and then later constructing the gasification and methanol synthesis sections. Likewise, existing methanol producers can use MTO integrate downstream and move into the light olefins market.
To date, UOP has licensed four MTO units, the first of which to come online was the Wison plant. All of these units are located in China and are based on either purchased methanol or coal. In total, more than 10 million tpy of combined ethlyene plus propylene production capacity from MTO technologies is planned to come on-stream in China by 2015. Shandong Yangmei Hengtong Chemicals Co Ltd, expected to start up later this year, will use the technology to produce 295,000 metric tons per year of ethylene and propylene, and Jiutai Energy (Zhungeer) Co., expected to start up in 2015, will use it to produce 600,000 metric tons per year of ethylene and propylene. Jiangsu Sailboat Petrochemical Chemicals is also building what is expected to be the largest single-train MTO unit in the world, producing 833,000 metric tons of ethylene and propylene per year.
India – What MTO Can Do
For India, MTO can help the country meet its growing demand for olefins by using methanol derived from cheaper and more abundant coal, maximizing yields of high-value petrochemicals and reducing operating costs. Figures 4 and 5 depict the growth curves for the polyethylene and polypropylene industries in India. As is evident, the olefins market is propelled by domestic demand, and is expected to grow at a CAGR of ~10.5 per cent (till 2018).
On the feedstock end, India has plentiful coal reserves, while the country’s natural gas and oil reserves are limited. Of India’s fossil fuel reserves, 93 per cent is coal, with crude oil and natural gas representing only 3 and 4 per cent, respectively. To utilise coal as a petrochemical feed stock, the first step is gasification of coal to synthesis gas. By using MTO technology, this synthesis gas can be converted into petrochemicals. This approach can help channel valuable crude oil imports toward fuels while supporting petrochemicals growth in India
Olefin production would imperatively use either methanol or naptha as feedstock. Methanol however, has a distinct cost advantage over naptha:
At a methanol price of 400 USD/MT, an MTO-based light olefins plant will have a feedstock cost advantage of 560 USD/MT of light olefins production. This advantage increases to 820 USD/MT of light olefins at a methanol price of 300 USD/MT. An MTO-based ethylene plant also produces twice as much propylene as a naphtha-based ethylene plant. Propylene traded at USD 1,396/MT (in April 2014) as against ethylene that traded at USD 1,254/MT (figures from PGPI). The growth rate of the price of propylene is also significantly higher than ethylene’s.
Regional demand and the regional availability and cost of key raw materials are some of the most important factors shaping the development of petrochemical markets. Clearly, for regions with vast resources of coal such as India, MTO could provide long-term raw material security. The UOP/Hydro MTO process provides an economically-attractive route to convert cost-advantaged raw materials such as coal to high value-added olefins. MTO could work here as a potential game changer.
This year UOP celebrates a century of innovation in the refining and petrochemical industries, with 80 years influencing India’s oil and gas sector.
UOP entered the Indian market in the 1930s with its licensing of the Dubbs Thermal Cracking process to produce gasoline at the Digboi refinery in Assam, which operated in until 1999. Since then, UOP’s technology solutions have continued to drive developments in the industry to give customers the means to economically produce materials that are in high demand.