Which is more economical currently: the route for directly producing low-carbon olefins from syngas, or the route for producing olefins via methanol (MTO, MTP)?

If the direct synthesis of low-carbon olefins from syngas can be scaled up industrially, it would certainly be more competitive than MTO/MTP. However, the biggest problem is that this approach can currently only be explored in the laboratory; there are many issues related to both catalytic performance and selectivity, so industrial application is still a long way off. It is unrealistic to expect the results reported in existing literature to be applied in industry in the short term. So, do you think there is any comparability between a technology that is still in the laboratory stage and one that is already ready for industrial application?

One process that could be considered at present is the high-temperature direct synthesis of low-carbon olefins using iron catalysts; however, selectivity is the biggest issue. Combining the selective properties of molecular sieves with the high catalytic activity of iron might represent a viable path for industrial application in the future.

The properties of molecular sieves are also important, as they affect the secondary reactions of olefins. I’m not sure what kind of carrier is suitable for such reactions

This post was last edited by fossil-zhang on 2010-4-16 at 20:10. In fact, this reaction is the Fischer-Tropsch synthesis; the goal is to have the products be low-carbon-chain alkenes. Using an iron catalyst at high temperatures (320–350 degrees) yields the closest result, as it increases the selectivity for low-carbon-chain alkenes significantly. However, with conventional iron catalysts, carbon chain elongation is inevitable, and the selectivity for C5+ compounds remains relatively high. Moreover, iron catalysts also exhibit high selectivity for carbon dioxide at high temperatures. One approach that can be considered is to load iron into ZSM-5 or SAPO-34 molecular sieves at a high dispersion and high loading level (within the molecular sieve cages), and use the pore size selection and acidity of the molecular sieves to control product selectivity. But the problem is what the strength and stability of such catalysts are like; the loading amount may not be very high either, as the pore sizes and cage dimensions of these molecular sieves are quite small (around 0.5 nm). It is difficult to load a large amount of iron into these pores, and this could even lead to the pores being blocked. As a result, the catalytic performance might be low. If iron cannot be loaded into the pores, then the selective function of the molecular sieves is greatly reduced. Some people have considered doping these molecular sieves with iron, but the amount of doping that can be used is limited (too much doping prevents the formation of molecular sieves); as a result, the catalytic activity of iron is relatively low, and the material tends to exhibit acidic properties. This is similar to MTO/MTP catalysts, which in industrial use are generally based on ZSM-5 or SAPO-34 series materials doped with iron. So, after going back and forth, it ended up at MTO/MTP. This is also why the direct production of low-carbon olefins from syngas has not been feasible to date; it is difficult to implement on an industrial scale, though it is possible to conduct research and publish articles on the topic. Apart from this approach, I really can’t think of any other way. After all, the direct synthesis of low-carbon olefins from carbon monoxide and hydrogen follows the Fischer-Tropsch route, and it is well known that Fischer-Tropsch has poor selectivity; this issue has not been resolved fundamentally over the years. Recently, some Japanese researchers came up with an idea: they wrapped molecular sieves around the catalyst to form a membrane, thereby enabling the synthesis of gasoline with high selectivity. However, this method is merely a workaround that allows the Fischer-Tropsch products to be cracked on this molecular sieve membrane, without actually changing the selectivity of the Fischer-Tropsch process. I suggest using this method to coat the molecular sieve membrane over the iron catalyst and carrying out a reaction at high temperatures to see what the selectivity for low-carbon olefins is like; there might be some useful results. Hehe, I myself want to give it a try, but I don’t have the time, and the lab students aren’t interested in exploring this either. If anyone is interested, they can give it a shot – publishing a paper on the results would also be good, and if it works well, it could be a viable approach.

One of the biggest disadvantages of producing olefins from methanol is that the reaction generates large amounts of water that is of no value; this water must be treated in order to meet environmental emission standards. If it were possible to produce olefins from syngas, the economic advantages would be obvious, but at present there is no practical solution available.

When producing olefins from syngas, the selectivity is not expected to be very high, as the syngas contains a large amount of hydrogen; the olefins formed will rapidly convert into alkanes in the presence of the catalyst and hydrogen.

This post was last edited by *aojungnft on 2010-4-16 at 22:40. At present, it is definitely more cost-effective to produce olefins from methanol; producing olefins from syngas alone cannot yet be considered an alternative. Using syngas to directly produce olefins, with a focus solely on olefins, is a very complicated task; it may even be more complicated than the direct production of dimethyl ether from syngas, which has been the goal of many efforts. This is determined by the reaction pathways, that is, the number of successive reactions involved. sun0225: As long as it is a final product prepared from syngas and contains only C and H, regardless of what the intermediate products are, water will be generated in the end, thereby pushing out the oxygen. To achieve profitability, the shorter the process route, the better. When the target product does not have to be diesel per se, high-temperature Fischer-Tropsch synthesis is an option worth considering; this was also discussed in previous posts. Currently, there are companies building synthetic oil plants, companies constructing methanol plants to convert methanol into olefins, and even companies building synthetic methane plants. In terms of scale, for oil production, it ranges from several million tons to over 3 million tons; for olefin production, it is generally around 60 wt%. So let’s take a look at the approximate composition of the products obtained through high-temperature Fischer-Tropsch synthesis (excluding oxides): 20% methane, 55% compounds with 5 carbon atoms or more, and 25% compounds with 2–4 carbon atoms. Among those compounds with 2–4 carbon atoms, alkenes predominate, with propylene being the most abundant. Such a product composition can well meet the proportions of synthetic oil and synthetic olefin products currently under production, and methane is also available. The products are separated: the oils are kept as oils, the olefins are taken apart separately, and the C2-C4 alkanes are mixed with methane. The calorific value of the gas per unit volume is higher than that of pure methane – what a advantage. Furthermore, it is also desirable that the processing capacity of high-temperature Fischer-Tropsch reactors be higher than that of slurry bed reactors. Go for high-temperature Fischer-Tropsch; you can get everything you want! Hehe.

The direct production of low-carbon olefins from syngas is still in the laboratory research phase, while the latter is in the industrial demonstration stage. They cannot be compared. Theoretically, however, the former would be a route with a simpler production process, lower material and energy consumption, as well as reduced investment and operating costs. However, we need to continue conducting in-depth research; only once breakthroughs are achieved in industrial demonstration can the former truly gain an advantage.

This is mainly a catalyst issue; if catalyst development progresses well domestically, it will inevitably make the production of olefins from syngas more economical, as the methanol intermediate is no longer needed, which also reduces energy consumption. This issue will have to be determined based on the development of catalysts. As for the claim that methanol is used as an intermediate, it’s completely unnecessary. Since there is an overcapacity in methanol production at present, there is a significant shortage of olefins as an important chemical raw material. Moreover, considering the downstream products of methanol, the olefin route appears to be the more appropriate choice.

It’s a bit early to talk about cost-effectiveness now. What catalytic technologies and catalysts should be used by the relevant research institutions to continue conducting experiments on the conversion of syngas into olefins, in order to improve yield and selectivity, is something that needs to be discussed at present. The methanol-to-olefins technology has been successful; **it is possible to establish several pilot plants to fully assess the consumption levels in an industrial setting, thereby providing the necessary data for future improvements. Hehe