Salt formation issue in the alkylation purification of ionic liquids

Salt deposition on the heat exchanger tube side of the tower fed by the alkali wash water after the high-efficiency separation tank

This post was last edited by Someone on 2019-6-30 at 19:20. I spent some time previously thinking about the applications of ionic liquids in alkylation reactions; rather than focusing on specific issues, I’ll just share my own thoughts. The biggest problem with ion liquids to date is the lack of large-scale applications. In the field of chemistry, no matter how advanced the techniques in your laboratory are, if they can’t be scaled up, then it’s as good as nothing! The few key players in the domestic ion liquid industry must have considered boosting the industrial application of ion liquids. Ionic liquids do show good results in tetraalkylation reactions in the laboratory; after all, petroleum universities have been researching this area for many years and have published numerous papers on it. Naturally, I thought about industrializing this product. But it’s simple to conduct a small-scale test in the laboratory; however, scaling up the process to make the entire production line functional is difficult, and producing products that meet quality standards is even more challenging! The laboratory doesn’t take these issues into account! The laboratory doesn’t even consider the economic costs! It’s not like I’m spending my own money anyway. Let’s talk about the issue of alkylation of ionic liquids. Alkylation is an acid-catalyzed reaction that requires an appropriate acid strength; concentrated sulfuric acid is used in industry. And what are ionic liquids? The essence of ionic liquids is salts! However, ionic liquids can also catalyze alkylation reactions. This indicates that such ionic liquids are salts composed of a strong acid and a weak base. Therefore, one must use an acid stronger than concentrated sulfuric acid, along with a bit of base, in order to synthesize an ionic liquid suitable for alkylation reactions. So if you look at the literature, there are basically two types of ion liquids that can be alkylated: one type is chloroaluminate ion liquids, and the other type is the so-called B-acid ion liquids. What is this B-acid ionic liquid? It’s just superacid plus some base; stir it around, and the acidity of the original superacid is reduced, allowing it to be used for alkylation! The key point is that superacidic substances are definitely more expensive than concentrated sulfuric acid! So this B-acid ionic liquid can only be used to publish papers; in industrial applications, it’s nothing but a waste of effort. As for another category, which involves adding a small amount of ionic liquid to concentrated sulfuric acid, it is said that this can also have a promoting effect, but I won’t say anything more on that. I’d like to complain once again about many professors and researchers in China – I’ve found that many of them don’t even consider solving real industrial problems; they only think about how to publish papers, build relationships, secure projects, and obtain academic titles. . . Guiding students in conducting experiments means having them add this or that substance; there will always be changes. The data obtained needs to be carefully analyzed to identify a pattern. To put it bluntly, even adding dog shit to a catalyst can cause changes! As for chloroaluminate ionic liquids, an important reason why it is these ones that are used for industrial applications rather than B-acid ionic liquids is that they are much cheaper! It’s quite rare to find a substance with an acidity level higher than that of concentrated sulfuric acid, yet at a price that isn’t too high; chloroaluminate might be one of the few options available. What is chloroaluminate? It is aluminum chloride. Do you know what catalyst was used initially for alkylation? Aluminum chloride is what is used–including in the early alkylation of benzene, aluminum chloride was often utilized as well. The acidity of this stuff is indeed very high; the problem is that the corrosion it causes is quite severe! Not only that, but due to the high acidity, there are also quite a number of by-products from the alkylation reaction. To this end, Yves Chauvin from the French Institute of Petroleum Research thought of adding an organic base to reduce the acidity of aluminum chloride. It was the year 1988 when this idea was first presented in a patent; in 1994, another paper on molecular catalysis was published. Up to that time, this gentleman referred to these substances as “molten salts”, which are what we now call ionic liquids. By the way, Yves Chauvin is that elderly gentleman who won the Nobel Prize in Chemistry in 2005 for his research on olefin metathesis. Well, now we know that chloroaluminate ionic liquids are aluminum chloride combined with an organic base. According to the article published by the Petroleum University, it is a triethylammonium hydrochloride-aluminate ionic liquid combined with copper(I) chloride – this is their \"composite ionic liquid\". It’s not clear whether this is the same formula used in industry as described in their article. So the question is, how much is this stuff per ton? I don’t know, but the price of the finished product is definitely higher than that of the raw materials. Friends who are interested can calculate the cost per ton of the raw materials for this product based on the ratios given in the relevant literature. Anyway, I think it’s definitely much more expensive than concentrated sulfuric acid. Moreover, ionic liquids cannot be regenerated. Their literature states that it can be regenerated by adding some hydrogen chloride, but in industry, I am quite skeptical about this. By the way, ionic liquids are claimed to be green, environmentally friendly, non-corrosive, and non-polluting – do you believe that? Anyway, I don’t believe it. Another major advantage of ionic liquids is their low acid consumption; according to their reports, the acid consumption per ton of alkylated oleic acid is 5 kg. But the key issue isn’t whether the acid consumption is high or low; it’s the cost. If the cost of reprocessing spent concentrated sulfuric acid drops to 10 yuan per ton, which is cheaper than purchasing concentrated sulfuric acid itself, then is acid consumption still a problem? So how should we view this acid consumption of 5 kg/t? We should consider what its cost is. How much is 5kg of ionic liquid? Even if the acid consumption of concentrated sulfuric acid is 100 kg, which is more expensive: 5 kg of ionic liquid or 100 kg of concentrated sulfuric acid? Even if we add the cost of regenerating the waste acid, which one is more expensive? I think, from this perspective, ionic liquids may not necessarily be competitive; of course, this is just my own doubt, and it’s very likely that I’m wrong. As for the waste acid from ionic liquids, ionic liquids inevitably become deactivated. What should be done with deactivated ionic liquids? Regeneration is out of the question; was it burned? I believe that the treatment of waste acid from ionic liquids might also be a problem. I’m not sure how they handle this in industry; could the original poster share some insights? Overall, aside from its good results in the laboratory, I think there are many issues with using ionic liquids for alkylation on an industrial scale. Of course, it’s also possible that they have already solved it, but haven’t made it public. As for the other chemical applications of ionic liquids, to be honest, I’m not optimistic about them. I think that ionic liquids are more suitable for laboratory research – for writing a few articles, and for researchers to use them to secure funding or obtain academic titles; after all, there aren’t many people who specialize in this area. But industrial applications are really dubious and unreliable. Due to their high viscosity and cost, many people are now working on supported ionic liquids or polymeric ionic liquids. It seems that there are industrial applications for these as well, but I’m not sure whether there is an issue of ionic liquid loss; if so, can it be resolved? How to solve it? If it can’t be solved, how can ionic liquids be regenerated? Should we just replace the catalyst? What about the cost then? A few years ago, I attended a presentation by a Taiwanese professor; he also worked on supported ionic liquids, using the method of chemical grafting. This involves relatively strong intermolecular forces. Even so, he said that only laboratory research can be conducted; the loss of ionic liquids is inevitable, and after a few cycles it becomes unusable. To be honest, I’m not very optimistic about the industrial application prospects of ionic liquids. Of course, this is just my personal opinion; after all, I don’t work with ionic liquids and have only paid casual attention to this field, so there are bound to be some misunderstandings. I welcome everyone’s discussions on this topic.

To correct one point: ionic liquids are Lewis acids. Additionally, ionic liquids with reduced activity can definitely be regenerated! The octane number of the oil we produce ranges from 96 to 97, and this value remains quite stable. Similarly, the dry point stays within the range of 170–180. As for what you mentioned regarding “making hats” or something similar, I don’t really understand it. I’m speaking only in terms of this technology. Naturally, there will be many drawbacks at the initial stage of industrialization; time is needed for optimization! Very little solid residue is produced when it is actually in operation. As long as you keep the impurities in the raw materials under control, the long-term prospects are very promising! We succeeded on the first attempt at driving it. After a little over 7 months, it coincided perfectly with the plant-wide maintenance period; when we opened the equipment, there was hardly any corrosion at all! So this technology can still be promoted!

This post was last edited by So-and-so on 2019-8-30 at 16:37. Butyl alkylation is a reaction catalyzed by Brønsted acids; whether it’s concentrated sulfuric acid, hydrofluoric acid, or molecular sieves, they all utilize Brønsted acid sites. The main component of the complex ionic liquids developed by the Petroleum University is aluminum chloride. Aluminum chloride is a strong L-type acid; however, in the presence of water, it transforms into a B-type acid, which is a well-established fact. Liu Zhichang and others have also published articles on the origin of acidity in ionic liquids – those interested can take a look at those articles. In fact, if both the catalyst and the raw materials are completely anhydrous, the catalytic efficiency will certainly be poor. As for the recyclability of ionic liquids, Liu Zhichang and his colleagues have also written articles on this topic; hydrogen chloride can be used for that purpose, but industry certainly requires some other measures as well. However, this regeneration cannot go on indefinitely; at a certain point, it will be necessary to dispose of the waste acid and replenish it with fresh acid, just like in the case of concentrated sulfuric acid. So, how should the waste ionic liquid that is produced be dealt with? Do you have any relevant treatment methods in your processes? The official website of the Petroleum University states that 5 kg of ionic liquid is required per ton of alkylated oleic acid. I’m not sure whether this 5 kg of ionic liquid can be regenerated If it cannot be regenerated, then these 5 kg of ionic liquid must be more expensive than 100 kg of concentrated sulfuric acid, right? If these 5 kg of ionic liquid can be regenerated, then overall, how much acid is consumed? How much lower is the overall cost compared to the concentrated sulfuric acid process?

You should get in touch with those in Deyang to see if they can work with you; so-and-so is a doctor specializing in alkylation. The specialty is alkylation technology

As for what you said about the low corrosiveness, you can put your hand in to give it a try; the formation of salt is caused by acids and alkalis present in the subsequent system. This situation tends to occur if the airspeed issue is not handled properly, just like in the DuPont version. The Rumas version can contain acid at most; its low corrosivity is simply ridiculous. The sulfuric acid device doesn’t cause severe corrosion right away either. If alkylation of ionic liquids were truly effective, Deyang wouldn’t have gone bankrupt. When Lanlian tried to use this approach in the past, why wasn’t it used again later on? Lanlian also has methods for pre-treatment, and quite a few of them at that

The ion liquid alkylation process at the Golmud refinery has been restarted recently, but the results are not good; the octane rating is only around 93-94, and the product contains chlorine····

It’s a crap product; it’s practically deadly. Its corrosion rate can reach 10 mm/year