A patent issued last week that describes a PTC-cyanide reaction to form a cyanohydrin and reminded us of a few common misconceptions that we have seen over the years that have resulted in nuisance plant operability problems in mild cases and cost companies tens of millions of dollars per year in lost yield in severe cases! We will teach how to overcome these three misconceptions in our 2-day course “Industrial Phase-Transfer Catalysis” to be conducted in Prague next month (now register here for public PTC course in Prague). We will highlight these issues in the free PTC webinar to be conducted later this week on September 11, 2019 (now register here for free PTC webinar on Sep 11, 2019).
The first myth believed by some is that it is necessary to dissolve all of the alkali metal cyanide salt in water in order to carry out a PTC-cyanide reaction. In 2001, we visited a plant to identify opportunities to improve the performance of several large volume processes that used PTC or should use PTC. One of the large scale processes used cyanide as an aqueous solution. We pointed out that there may be a cause-and-effect relationship between the long and costly reaction time and the use of too much water in the system that hydrates the cyanide anion and reduces its nucleophilicity. The plant operators explained that they needed to dissolve the cyanide in water to facilitate the reaction.
We then explained that a phase-transfer catalyst is able to extract the cyanide anion from the surface of solid NaCN or KCN if it has a thin film of saturated cyanide salt, called “the omega phase” (discovered by Prof. Charles Liotta), that can be formed and optimized using small amounts of water. When we optimize the amount of water, usually at relatively low levels and using solid-liquid PTC conditions, reactivity greatly increases and we can achieve an increase in plant capacity, of an EXISTING plant, without capital investment!
Be sure to register for the free PTC webinar that will be conducted on September 11, 2019, in which we will discuss the effect of hydration in PTC systems.
A second misconception is that cyanide can only act as a nucleophile.
In the late 1990’s we received a non-confidential inquiry from a company that was suffering from a 35% yield loss (!!!) in a process that produced several hundred tons per year of a secondary nitrile from a secondary alkyl halide. I spoke with the plant chemist and said that I speculate that the yield loss is due to the cyanide anion partially acting as a base in addition to its predominant activity as a nucleophile. He confirmed that indeed the major side reaction was dehydrohalogenation. I told him that the solution is very simple and that he should submit a request for a PTC Process Consulting Agreement to his management so we could work together and recover the wasted value of about 100 metric tons per year of product!
The company did not engage us and used the poor excuse that they were not very profitable and did not want to invest in consulting! I replied that they would be a lot more profitable if they produced an extra 100 tons per year with no additional cost. That is when we learned that the real reason for declining our offer was organizational resistance to change. That was my incentive to write the article “5 Reasons that Companies Miss Process Improvement and Profit Opportunities using Phase-Transfer Catalysis.” Unfortunately, the content of the article is still true today and is waiting for a champion (maybe YOU?!) in each company to take the initiative to stop wasting money on inefficient processes. If you want to contact us, please use THIS form and not the outdated Email address shown in the article.
We learned that several years later, the company figured out how to reduce the dehydrohalogenation in the cyanide-halide displacement using phase-transfer catalysis. They literally wasted millions of dollars of lost profit (!!!) because they didn’t want to admit that the relatively inexpensive PTC Process Consulting could show them technology that their technical team did not know. Is your company wasting lost profit right now due to resistance to change?!
The third misperception is that cyanide reactions are best performed using polar solvents.
As we show on page 109 of our 2-day PTC course manual, the product literature of one of the DMSO producers writes “DMSO is the best solvent for reactions involving cyanide and azide nucleophiles”. On page 215 of our PTC course manual, we compare 8 crucial process performance parameters for using PTC versus using PTC for reactions such as cyanide and azide reactions.
As always, the bottom line is that expert choice of PTC process conditions for cyanide reactions, can result in millions of dollars of added profit, which also saves a lot of jobs (maybe even YOUR job). Now register for the 2-day PTC course in Prague to be held on October 15-16, 2019 or bring the 2-day PTC course in-house to your company site to save millions of dollars, euros, etc.
