Fatty Acid Hydrogenation

The fatty acid hydrogenation is a key process for many industrial applications. Fatty acids are fundamental intermediate products for various type of industries such as pharmaceuticals, cosmetics, chemicals and detergents, through to vertical sectors such as tyre manufacturing, but most of these applications require the hydrogenation of fatty acids (with the notable exception of paint and textile industry).

Generally, given the high cost of hydrogen, manufacturers tend to choose palm oil or tallow, which have a low IV (Iodine Value), as raw materials. Since the IV measures the degree of unsaturation of a fat or oil, it follows that the lower the IV, the less hydrogen will be needed to complete the process.

Focusing on the final result, it’s important to specify that when we talk about hydrogenation, we’re always referring to full hydrogenation. In fact, theoretically there is also a selective process aimed at reducing the amount of polyunsaturated fatty acids, but selective hydrogenation leads to the formation of trans fatty acids (only the “cis” form exists in nature) with substantially different chemical characteristics.

The industrial use of fatty acids mainly concerns products with a  high melting point. Historically, before hydrogenation became feasible, high melting point products were obtained by pressing, separating a solid part from a liquid.

It should be noted that the term melting point is not chemically correct as it should only apply to pure components, whereas normally the hardened product is a mixture of various fatty acids.

Hydrogenated Fatty Acid are often referred to  as single, double or triple pressed. The reason is once again historical because, as mentioned, before the appearance of the hydrogenation process, hardened fatty acids were produced by separating the more liquid ones through a mechanical process.

The pressing steps could be repeated to obtain more solid products, hence the names.

Obviously, modern hydrogenation allows to achieve a much higher degree of saturation, with Iodine Values well below 0.5 (residual unsaturation is measured by the amount of iodine required for complete saturation).

Today the “hardening” stages performed by saturating the double bonds with hydrogen gas, which is bubbled through the oil in the presence of a metal catalyst at high temperatures and pressures. The catalyst is almost exclusively Nickel- based.

TECHNOLOGY ADVANTAGES

The hydrogenation of fats results in more stable products with a longer shelf life and a lower cost. . Furthermore, by varying the level of hydrogenation, fats of different consistency can be obtained, depending on their melting point.

As already mentioned, almost all technologies involve the use of Nickel as a catalyst. It must be said that Platinum can also be used as a catalyst, with advantages and disadvantages.

The main advantage is that there is no actual consumption of Platinum because the only recovery is due to mechanical losses during cleaning. The main disadvantages relate to the initial cost, which is so high that only very few units working with Platinum are operational.

The most common design for Nickel catalyst- based plants is a batch reactor, which offers the best control possibilities. The plant can be converted to continuous operation, to increase the heat recovery with feed/product heat exchangers. The plant can also be designed and constructed for fully continuous operation, with two fixed-bed reactors. However, this is a lesser used technology due to its difficulty in adapting to different feedstocks. The final stage of hydrogenation is filtration, performed to remove the catalyst.

Due to the huge range of quality of raw materials and the wide variety of products to be obtained, there is no single process scheme for the production of hydrogenated fatty acids, but there are several possible routes with different steps:

• Oil hydrogenation -> splitting -> fatty acids distillation: this route has the lowest overall consumption of utilities and catalysts. Investment costs are also lower, as the hydrogenation of oil requires much lower pressure. Moreover, since oil does not react with the catalyst, the distillation residue can be used as chicken feed. The downside is that this route only yields hydrogenated products. It is also necessary to have raw materials free of metallic impurities that could poison the catalyst (not suitable for most tallows).
• Splitting -> fatty acids hydrogenation -> distillation: suitable for almost all raw materials. The downsides are the higher investment cost (high pressure hydrogenation is needed for fatty acids) and the higher consumption of catalyst compared to oil hydrogenation. The distillation residue cannot be used as animal feed (and it is not easy to dispose of) due to the presence of Nickel soaps.
• Splitting -> distillation -> hydrogenation -> distillation or post bleaching: post bleaching is a process of splitting Nickel soap with an acid and absorbing it on filter aid. This route is only used with extremely low-grade materials.

FURTHER ADVANTAGES OF CMB TECHNOLOGY

One of CMB’s greatest strengths is its ability to continuously develop its R&D capabilities, drawing on a combination of engineering expertise and scientific knowledge. System design and development take place seamlessly, with constant comparison and complete compliance in terms of material quality and construction procedures. The end result is an optimised, efficient, and highly reliable product.

In particular, the design of CMB hydrogenation units is optimised to achieve the Client’s desired objectives, both in terms of production costs and quality of the final products. On the other hand, CMB plants can also help Clients minimise consumption of catalyst, hydrogen and other utilities.

• Optimisation of catalyst consumption: The reactors designed and built by CMB allow a high recirculation rate with a very efficient jet mixer in the reactor. In this way can be granted an optimum contact between catalyst, hydrogen and fatty acids allowing the reaction to proceed even with a very low amount of catalyst.
• Smart hydrogen consumption: The amount of hydrogen required for the reaction is stoichiometric, but the loss occurs when the hydrogenated product is discharged and the residual gas is vented. The system designed by CMB provides that venting is not carried out on all batches, but only when a build-up of inert gas occurs.
• Streamlined utilities consumption: CMB’s technology allows to recover latent heat by feeding the effluent heat exchangers. In case of high IV raw materials, the reaction heat is recovered, generating low pressure steam.

CMB constantly supports its Clients, from the initial briefing to delivery and start-up. Contact our professionals now for a consultation and discover the difference, relying on experts. Contact us now: info@cmb.it