Impact of MTO process improvements on methanol consumption per unit
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In 1984, researchers at Union Carbonic Company developed a new class of silicoaluminophosphoric (SAPO) molecular sieve structures. One of these, SAPO-34 with a CHA structure, exhibited excellent catalytic performance in the methanol-to-olefins (MTO) reaction due to its appropriate acidity and pore size, which made it possible to introduce this MTO technology on an industrial scale. The world’s first facility capable of converting 1.8 million tons of methanol into 600,000 tons of olefins was successfully commissioned in August 2010; to date, the olefins production capacity of such facilities has exceeded 10 million tons. MTO technology has thus become an important method for producing ethylene and propylene. The essence of both the MTO reaction and the FCC reaction is acid-catalyzed reactions on molecular sieves combined with product selection; during these reactions, molecular sieve catalysts suffer from rapid coking, which leads to catalyst deactivation. The MTO process flow draws on the mature circulating fluidized bed production technology of FCC, addressing the issue of rapid catalyst deactivation. Compared with the FCC process, the MTO process technology shares many similarities as well as significant differences. In 1936, the world’s first catalytic cracking unit with a capacity of 100,000 tons per year was successfully put into trial production in Paulsboro. Over the more than 80 years that have passed since then, the FCC process has evolved through technologies such as fixed-bed, moving-bed, circulating fluidized-bed, and lift tube systems, and it is now highly mature. After nearly 10 years of development in MTO process technology, the DMTO process has also seen the introduction of the DMTO-II process package technology, which incorporates C4 cracking technology; as a result, the overall methanol consumption per unit of product is reduced to 2.67. UOP’s MTO process, when combined with OCP cracking technology, achieves an overall methanol consumption of around 2.65. In recent years, Sinopec Luoyang Engineering Co., Ltd. and the Institute of Catalysis of the Chinese Academy of Sciences have, by drawing on the mature FCC technology, improved and optimized the DMTO process technology. They carried out process modifications to the second-phase DMTO unit of Ningxia Baofeng Energy Group Co., Ltd., with the main improvements being as follows: (1) A rapid separation device was added to the reactor to enable quick separation of the catalyst from the product gas, thereby reducing the occurrence of secondary side reactions ； (2) A cooler is installed in the gas lift section of the regenerator to lower the temperature of the regenerated catalyst returning to the reactor, reduce catalyst coking, and increase the olefin yield ； (3) Optimize the methanol feeding process by adopting gas-phase methanol feeding, thereby completely eliminating the issue of liquid carried in the methanol feed, which facilitates the progress of the MTO reaction. The above three process improvements can effectively increase the olefin yield of the plant. Compared with the first-phase DMTO unit of Ningxia Baofeng Energy Group Co., Ltd., when using the same type of MTO catalyst, the methanol consumption per ton of olefin is approximately 2.98 (based on inventory data); using the calculation method applicable to the second-phase unit, this value is around 2.95. In the second-phase DMTO unit that employs the improved DMTO process, the optimal methanol consumption per ton of olefin is 2.87, representing a reduction of about 0.08. Apart from the contribution of these process improvements, another possible reason for this difference is that the second-phase DMTO unit was put into operation in October 2019, and as of now it has been running for only 4 months; therefore, the performance of the catalyst has not yet shown significant degradation, and its hydrothermal stability still needs to be verified through long-term operation in an industrial setting.
I’ve learned that fluidized bed process design isn’t easy at all. Refer to the FCC technical upgrade – the results are excellent
With the use of the same catalyst, the optimization of the MTO process improved the yield of the resulting dienes, which is worth emulating and learning from.
I am grateful to my fellow authors for sharing their insights. The widespread adoption of MTO technology in our country is thanks to the development of SAPO-34 molecular sieves; over the years, the advantages of catalysts have been fully utilized. It is truly encouraging that the methanol consumption per unit can reach another new low this time. We all hope that the stability of the catalyst will remain as consistent as before under the new process. We thank the engineers at Baofeng Phase II for their innovative approaches in optimizing the process, which provide valuable guidance for our future work.
Process improvements boost yield – key advancements in the MTO industry
Thanks to UOP’s development of the SAPO-34 molecular sieve back then, the advantages of MTO catalysts have been brought to near their maximum over the years. In the future, the development of the MTO process will be the decisive factor in reducing the methanol consumption per unit of product; objectivity and respect for facts are the key factors driving technological progress
In catalytic reactions, the reaction process is just as important as the performance of the catalyst. At present, we have focused too much on improving catalyst performance while neglecting the optimized design of process conditions. The industrial achievements resulting from the collaboration between Baofeng and the Institute of Chemistry, Chinese Academy of Sciences, serve as a valuable lesson for those of us working in the field of catalysts, and are worth learning from.
In fact, accelerating the rapid separation of reaction products from the catalyst can also be achieved by reducing the particle size of the molecular sieve, for example by using molecular sieves with nanocrystalline sizes. However, nano SAPO-34 molecular sieve crystals are often incomplete and contain many defects, which affects the selectivity for olefins. The improvement technique discussed in this article leverages the wisdom of China’s skilled craftsmen throughout history, even when the performance of existing SAPO-34 molecular sieves is already optimized. By employing process methods other than catalysts to accelerate the separation of reaction products from the catalyst, it represents a novel approach that not only reduces catalyst costs but also extends their useful life – excellent!
Research and engineering have their own perspectives; if they can work well together, success is much closer.
Thank you for sharing. In recent years, there have been constant good news reports about the reduction in methanol consumption per unit of MTO technology. A few years ago, it was mainly due to advances in catalyst technology; now, improvements in process technology are starting to have a significant impact. Looking forward to better news