refining india 2024
Studies on methanol dehydration over beta zeolite catalyst
Arundhathi Racha, Chanchal Samanta, Mahesh W Kasture, Rakesh Vankayala and Chiranjeevi Thota Bharat Petroleum Corporation Ltd, Corporate R&D centre
• Methanol synthesis: Synthesis gas (syngas), composed mainly of carbon mon- oxide (CO) and hydrogen (H₂), is produced from feedstocks such as natural gas or coal. The syngas is then converted into methanol through catalytic reactions. • Dehydration of methanol: The pro- duced methanol is subsequently dehy- drated to form DME. This step is typically conducted over solid acid catalysts, such as zeolites, which facilitate the removal of water and promote the formation of DME. The overall reactions can be summarised as follows:
Production of fuels and chemicals with a lower carbon footprint is emerging to reduce the environmental impact of petroleum-derived fuels and chemicals. Dimethyl ether (DME) stands out as a via- ble option because of its favourable com- bustion characteristics, emitting lower levels of nitrogen oxides (NOx) and par- ticulate matter (PM) compared to conven- tional fossil fuels. For instance, DME can be blended with liquefied petroleum gas (LPG) or used directly in diesel engines, making it an attractive alternative in both transportation and domestic applications. DME has the potential to reduce emis- sions by up to 85% compared to fossil fuels.¹ DME can be produced from dehydration of renewable methanol, which in turn can be produced from biomass or hydrogena- tion of captured CO₂.² , ³ However, metha- nol dehydration is not straightforward, and depending on the catalyst system, metha- nol conversion can lead to the production of different kinds of products, such as ole- fins, gasoline, aromatics or DME. Some alternative on-purpose production routes, such as methanol-to-gasoline (MTG), methanol-to-olefins (MTO), and metha- nol-to-aromatics (MTA), are commercially developed and under various stages of development.⁴ Selective production of DME from meth- anol necessitates the selection of active and selective catalysts that would be non- selective towards undesired side reactions. With this objective, at Bharat Petroleum (BPCL) R&D studies have been conducted to identify a suitable catalyst system for selective conversion to methanol to DME. In India, the urgency to enhance energy security is paramount, given its heavy reli- ance on imported fossil fuels. The Indian government is actively promoting the pro- duction of methanol and DME from domes- tic resources, such as coal and biomass, to reduce import dependency and foster self-reliance. This initiative aligns with India’s com- mitment to the Paris Agreement and its goal of achieving carbon neutrality by 2070.⁵ The Methanol Economy Research Programme (MERP) highlights the poten- tial of methanol and DME to mitigate rising import costs and improve energy security, as they can be produced from locally avail- able resources, including high-ash coal and captured CO₂ from industrial processes. The production of DME and light hydro- carbons (olefins) from methanol is crucial for several reasons. Firstly, these com- pounds can be synthesised from renew- able feedstocks, contributing to a circular economy and promoting sustainable devel- opment. Secondly, the ability to convert methanol into DME and light hydrocarbons provides flexibility in meeting the diverse needs of the petrochemical industry, which is essential for economic growth. For exam-
The Indian government has
Methanol (MeOH)
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ple, ethylene, propylene, and butylene are key components in the manufacture of plastics and synthetic rubber. The Indian government has initiated projects to establish methanol and DME production facilities, recognising their potential to support domestic energy needs and reduce reliance on imports. The National Coal Gasification Mission aims to gasify substantial amounts of coal by 2030, facilitating the production of syngas, which can be converted into meth- anol and subsequently into DME and light hydrocarbons. initiated projects to establish methanol and DME production facilities, recognising their potential to support domestic energy needs and reduce reliance on imports
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Indirect synthesis
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Figure 1 Dimethyl ether production route
This strategic approach not only addresses energy security but also con- tributes to pollution reduction, as DME combustion results in lower emissions com- pared to traditional fossil fuels.
2CH₃OH → CH₃OCH₃ + H₂O
v Direct route: In this method, DME is synthesised directly from syngas in a sin- gle reactor, which simplifies the process and can enhance efficiency. This approach allows for the simultaneous production of methanol and DME, potentially reducing capital and operational costs compared to the indirect method. The direct synthe- sis of DME from syngas is an area of active research, particularly for improving yield and reaction conditions.
Production routes for DME and light hydrocarbons
The production of DME and light hydrocar- bons (C₂ to C₄) can be achieved through various routes, primarily categorised into direct and indirect methods ( Figure 1 ). These processes utilise different feed- stocks, including natural gas, coal, bio- mass, and organic waste, to produce these valuable compounds. Main production routes for DME Indirect route: This is the conven- tional method for DME production, which involves two main steps:
Main production routes for light hydrocarbon production
There are two main routes for producing light hydrocarbons (C₂ to C₄) from metha- nol ( Figure 2 ): Methanol to olefins (MTO) process: • Methanol is first synthesised from syn- gas (CO + H₂), which can be derived from natural gas, coal, biomass, or other carbo- naceous feedstocks. • The methanol is then converted to light hydrocarbons (ethylene, propylene) over zeolite catalysts like SAPO-34 or ZSM-5 at elevated temperatures (400-500°C). • The light olefins can be further pro- cessed into gasoline-range hydrocarbons or other valuable chemicals. v Methanol dehydration to DME fol- lowed by DME conversion: • Methanol is dehydrated to DME over solid acid catalysts like zeolites or alumina at 250-400°C. • The DME is then converted to light ole- fins and paraffins in a second reactor using the same zeolite catalysts as in the MTO process. • The light hydrocarbons can be separated and further processed as needed. Key considerations in these processes include: • Catalyst design and optimisation to tune product selectivity towards desired light hydrocarbons. • Efficient heat integration and process configuration to improve energy efficiency and economics. • Effective separation and purification of the light hydrocarbon products.
DTO or MTO ?
Light ole ns Ethylene & Propylene
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SAPO-34 Catalyst
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Figure 2 Light hydrocarbon production route
Tubular reactor
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Figure 3 Experimental setup for DME and light hydrocarbon production
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