Relationship between the deterioration of bleachability index (DOBI) value and hydrogenation performance for the hydrogenation of split-crude palm oil (s-CPO) in the oleochemical industry

Abstract

A major cause of premature catalyst deactivation in the catalytic hydrogenation of fatty acids is the presence of impurities in the feedstock. With more oleochemical plants shifting to opportunistic crude palm oil (CPO) as their feedstock, the feedstock quality becomes an important factor in their procurement process. For CPO, the impurities level can be coarsely estimated by the deterioration of bleaching index (DOBI). A high DOBI value (e.g. DOBI > 2.99) indicates good quality CPO and ease in processing, while low DOBI value implies low level of carotene and/or high level of oxidised sludge oil, both of which could be detrimental to the processing of CPO. In our work, unsplit CPO feedstocks with varying DOBI value were directly hydrogenated in a laboratory-scale pressure reactor with the presence of commercial nickel catalysts. Experimental results showed that catalyst deactivation was linked to DOBI value, where decreasing DOBI led to faster catalyst deactivation. For example, iodine value (IV) < 1.0 can be achieved for CPO with high DOBI value (2.97) after 150 min, and IV of 5–7 and IV > 20 were achieved for medium DOBI value (2.57–2.68) and low DOBI value (2.24), respectively. For CPO with low DOBI value (2.24), doubling the catalyst dosage ensured that the hydrogenated product met the low IV specification. This work showed that identifying the CPO with DOBI value presents an indicator to the manufacturer to find the right CPO tailored to the existing processes to maximise profitability.