By Wang Yuying, Qu Yin, Research Institute of Jilin Petrochemical Co.
Syngas-to-methanol process remains as the most important technology adopted by global methanol producers. By the sources of synthesis gas, coal-based methanol is mainly produced in China, while natural gas-based methanol is mainly made abroad. Given the dual pressure posed by environmental protection and energy crisis, CO2 hydrogenation-to-methanol process, as a new green chemical technology, is drawing more and more attention in recent years.
Four synthesis technologies
CO2 hydrogenation-to-methanol technology consists of traditional direct hydrogenation, photocatalytic reduction, electrocatalytic reduction and biocatalytic reduction. Among them, direct hydrogenation method has been adopted for commercial methanol production.
The traditional fossil syngas-to-methanol process and the emerging CO2 synthesis process from renewable hydrogen are shown in Figure 1. The renewable hydrogen is derived from a variety of raw materials.
Figure 1 Traditional fossil syngas-based methanol (a) and emerging CO2-based methanol using renewable hydrogen from various sources (b)
R&D progress of catalysts for CO2 hydrogenation-to-methanol technology in China
Research on catalysts for CO2 hydrogenation-to-methanol technology has achieved great process so far, with highlights as below:
The researchers of Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences, modified Cu/ZnO/ZrO2 catalyst prepared by the traditional coprecipitation technology by using the vapor phase method and ultrasonic impregnation method so as to achieve highly selective methanol synthesis from CO2 hydrogenation, with the selectivity of methanol up to more than 97%.
The solid solution bimetallic oxide catalyst (ZnO-ZrO2) was independently developed by a team led by Li Can, a researcher at Dalian Institute of Chemical Physics, Chinese Academy of Sciences. It was successfully used in the world's first 1 000-ton solar fuel synthesis demonstration project undertaken by the Institute. The catalyst triggers the hydrogenation of CO2 to methanol with high selectivity and stability. The per pass methanol selectivity is more than 90%, and the energy attenuation rate is less than 2% when the catalyst is operated for 3 000h.
With independent intellectual property right, the new-type nano composite oxide efficient copper-based catalyst, was developed by a team of Shanghai Institute of Advanced Research, Chinese Academy of Sciences, led by Sun Yuhan and Wang Hui. It was successfully used in the 5 000 t/a CO2 hydrogenation-to-methanol industrial test unit of CNOOC Fudao Co., Ltd. The catalyst solves the problems of low CO2 conversion rate and catalyst deactivation. It has survived the 4 000h stability test and industrial single pipe verification. As a result, the industrial catalyst with independent intellectual property right and its scale-up production process have been developed.
In 2021, a team led by Deng Dehui, a researcher of Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and another team led by Wang Ye, a professor of Xiamen University, worked together to use a few layer MoS2 catalyst rich in sulfur vacancies to produce CO2 hydrogenation-to-methanol with low temperature, high efficiency and long-life span for the first time. The activity and selectivity of MoS2 catalyst are superior to those of metal oxide catalyst previously reported, and the stability of MoS2 catalyst outperforms, providing a new way for the conversion and utilization of CO2 with low energy consumption and high efficiency.
Domestic industrialization progress
Shanxi Institute of Coal Chemistry, Chinese Academy of Sciences completed the single pipe test of CO2 hydrogenation-to-methanol in 2016, and the test operation was stable.
Shanghai Institute of Advanced Research, Chinese Academy of Sciences, cooperated with Shanghai Huayi Group to complete the preparation of a 100 000-300 000 t/a CO2 hydrogenation-to-methanol process in 2006 based on the previous 1 200h single pipe test and research.
In July 2018, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, signed a cooperation agreement with Lanzhou Xinqu Petrochemical on a 1 000-ton CO2 hydrogenation-to-methanol (called as “liquid sunlight") technological development project, that is, to establish a 1 000 t/a industrial demonstration unit of methanol from hydrogen using renewable energy such as solar energy to electrolyze water and from CO2 hydrogenation. In January 2020, the 1 000-ton CO2 hydrogenation-based methanol unit was successfully started up. In October 2020, the demonstration project successfully passed the continuous 72h on-site assessment. It can produce 1 440 tons of methanol every year after reaching the design capacity.
In May 2019, Henan Shuncheng Group and CRI signed a cooperation agreement to introduce CRI’s technology to build a 100 000t/a CO2 hydrogenation-based methanol project, with CO2 consumption of 150 000 tonsevery year. The investment in the project is estimated at RMB600 million.
In September 2020, by adopting the new nanobase metal catalyst independently developed by Shanghai Institute of Advanced Research, CNOOC Fudao Co., Ltd. completed the engineering development of an industrial test unit and the engineering design of the unit, and built a 5 000 t/a industrial test unit for CO2 hydrogenation-to-methanol process. The unit ran for more than 600h in total, passed the 72h on-site assessment, and captured a series of technical data such as the startup, shutdown and operation control scheme of the industrial test unit.
In June 2021, Shenyang Blower Works Group Corporation (SBW)Engineering Complete Sets Co., Ltd. and Anyang Shunli Environmental Protection Technology Co., Ltd. signed a general equipment contract to build the first CO2 hydrogenation-to-green methanol industrial plant in China. The project adopts coke oven gas produced by Henan Shuncheng Group and CO2 of the industrial waste gas from Anyang Steel Charging Company as raw materials to produce 110 000 t/a methanol and 70 000 t/a LNG. Sources said that the project can directly reduce 160 000 tons of greenhouse gas CO2 and indirectly reduce 550 000 tons of CO2 each year by directly absorbing and digesting CO2, so it provides good social and ecological benefits.
In addition, with the technological upgrade and faster industrialization of CO2 hydrogenation-to-methanol, the National Technical Committee for Gas Standardization issued two national standards in September 2017 - CO2-to-Methanol Technological Guidelines (GB/T 34250-2017) and Safety Technical Procedures for CO2-to-Methanol Process (GB/T 34250-2017), which provide standard support for the future industrialization of CO2 hydrogenation-to-methanol.
Coal-based methanol and natural gas-based methanol industries are facing huge environmental pressure and energy crisis, while CO2 hydrogenation-to-methanol process, as a new green chemical technology, has drawn much attention in recent years. With the technology, CO2 can be widely used, which lends great support to the development of CCUS industrial chain.
Although some 1 000-ton pilot demonstration projects have been put into operation in the world, CO2 hydrogenation-to-methanol technology has not been widely used due to high prices of hydrogen. However, the fast-growing hydrogen energy industry will bring down the prices. This, coupled with the development of carbon trading market, leads to a bright future for the technology.