Selection of methanol synthesis catalysts

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Selection of methanol synthesis catalysts: Alcohol synthesis can be carried out at high or low pressures, and different catalysts are used under different pressure levels. Operating conditions for methanol production via high, medium, and low pressure methods: Synthesis method – High-pressure method, Medium-pressure method, Low-pressure method. Pressure: Around 30 MPa, 10.0–15.0 MPa, 4.0–5.0 MPa respectively. Temperature: 360–400°C, 250–280°C, 200–300°C respectively. Catalysts: Zn-Cr, Cu-Zn-Cr, Cu-Zn-Al. Compared with the high-pressure process, the medium and low pressure processes use Cu-Zn-Al catalysts, which reduces side reactions during the reaction process, improves the quality of crude methanol, lowers raw material consumption, requires less investment, and results in lower costs. The manufacturers and models of copper-based catalysts used in the widely adopted methanol synthesis processes both domestically and internationally are as follows: abroad, there is the ICI51-7 copper-based catalyst from ICI Company, as well as the KM-101 low-pressure methanol catalyst from Topsoe Company; companies in Southern Germany and several chemical manufacturers in the United States also produce such catalysts. The main domestic manufacturers include C302, an early low-pressure synthesis catalyst produced by Sichuan Tianyi Technology (Southwest Institute of Chemical Engineering); the newer model XNC-98, also produced by this company; as well as the new low-pressure methanol catalysts C306 and C307 manufactured by Nanhua Institute. Here is a comparison between the XNC-98 catalyst produced by Sichuan Tianyi Technology and the ICI51-7 catalyst manufactured by ICI: Table showing the relative space-time yield and the rate of activity decline. Catalyst model, Relative space-time yield, Rate of activity decline after 5 hours at 350°C (×102), Relative activity (per unit weight) at 210°C, 230°C, 250°C, 270°C, 250°C, 230°C: XNC-98 – 1.00, 1.00, 1.00, 1.00, 13.9, 18.9, 1.03; ICI-51-7 – 0.86, 0.96, 0.98, 1.00, 13.6, 26.2, 1.20. C306/C307 have the same activity as XNC-98. The methanol synthesis process in this project utilizes patented technology from East China University of Science and Technology; therefore, copper-based catalysts such as XNC-98 or C306 were chosen, as they possess low-temperature activity and stability similar to those of foreign catalysts, thereby reducing costs compared to foreign catalysts. The catalyst becomes active only after reduction; therefore, it must be reduced before use. In catalyst reduction, it is mainly copper oxide that is reduced. The reduction reaction is carried out using H2 or a mixture of (H2+CO), in an environment of inert gases such as N2 or natural gas. Furthermore, the reducing gas must not contain substances such as CL, S, and heavy metals that can poison the catalyst. During the reduction process, it is necessary to closely monitor changes in the bed temperature (exit temperature). When the bed temperature rises sharply, immediate actions must be taken such as stopping or reducing the flow rate of H2 or (H2+CO), increasing the gas circulation rate, or implementing replacement systems to address the situation. Since the reduction of copper oxide is an exothermic reaction, the principle of \"adding hydrogen without raising temperature, and raising temperature without adding hydrogen\" should be followed during the reduction process. Moreover, each addition should be done in small amounts, multiple times.