Process trial on hydrogenation reactors for sugar syrups treatment, to produce polyols with low ethylene glycol content

In the last years the pharmaceutical world had to fight against intoxications linked to the presence of ethylene glycol in cough syrups, which led a lot of children to experience kidney failure and eventually also death. It is known that the ethylene glycol is an unwanted side product of the sugars’ hydrogenation, performed to produce reduced sugars (also named as “polyols”) which are used in food and pharma industry as low-calories sweeteners alternative of the conventional sugars. In particular, the objective of this thesis work is to figure out how to produce both maltitol and Non Crystallizable (NC) sorbitol syrups with a low ethylene glycol content, more precisely below 50ppm and 75ppm on commercial basis (so @70% of dry substance). To do so, it has firstly been performed a baseline study on both products, to understand which is the average ethylene glycol formation during the production of the two syrups; it has been found that the maltitol syrup always shows an ethylene glycol content below the maximum limit set by the customers, while the NC sorbitol has always a too high ethylene glycol concentration. The very high ethylene glycol content of NC sorbitol is due to the presence of mannitol greens, a stream coming from the crystalline mannitol channel, which is very high in ethylene glycol, used to ensure the minimum mannitol content in the NC sorbitol syrup. After trying to reduce the ethylene glycol concentration of the mannitol greens by acting on the mannose hydrogenation, it has been found that the only way to produce NC sorbitol with low ethylene glycol content, at the moment, is to avoid the usage of mannitol greens. In conclusion, NC sorbitol with low ethylene glycol content can be obtained by means of either polyols’ syrups blend or via sugars’ blend hydrogenation.