CATALYTIC DECARBOXYLATION OF NAPHTHENIC ACIDS OVER PROTONIC ZEOLITE CATALYST: CASE STUDY AL-FULA CRUDE OIL

Abstract

In this thesis, experiments were conducted to investigate using HZSM-5 zeolite catalyst to reduce the TAN of a typical acidic crude oil obtained from Al-Fula blocks in Western Sudan. A full factorial design of experiment (DOE) framework enabled a better understanding of the efficacy of the catalyst at three parametric levels (reaction temperature: 250, 270, and 300 oC; reaction time: 2, 3, and 4 hr; and oil: catalyst weight ratio: 20, 22, and 25 g/g). The results demonstrate that the HZSM-5 zeolite catalyst provides up to 99% removal of NAs via the decarboxylation route. Also, the removal efficiency increases with increased temperature and residence time. The crude oil's acidity decreased after treatment with the catalyst for 4 hrs from 6.5 mg KOH/g crude to 1.24, 0.39, and 0.17 mg KOH/g at 250, 270, and 300 oC, respectively. A sharp decrease of TAN was observed at the oil: catalyst mass ratio of 20 g/g at 250 oC, and almost complete conversion of acids was achieved after 4 hrs. Another experiment at 270 oC showed a converse relationship between the oil: catalyst ratio and acid removal, suggesting the activation of side reactions at higher temperatures catalyzed by excess acid. Finally, a Langmuir Hinshelwood (LH) kinetic model has been developed to rapidly predict the performance of the HZSM-5 zeolite catalyst for the decarboxylation reaction. This thesis represents a detailed techno-economic analysis of a typical commercial-scale catalytic decarboxylation process of naphthenic acids over HZSM-5 zeolite. The process has been simulated using ASPEN Plus. The simulation findings showed that the volume of the three fixed bed reactors in semi regenerative process was 628 m3, and the fluidized bed reactor was 2392 m3. The weight of the catalyst required by the three fixed bed reactors was 0.5, 2, and 1 kg, respectively. The weight of the catalyst required by the fluidized bed reactor was 18 kg.The outcome of the economic analysis of the two proposed commercial scale reactors of a decarboxylation process of a capacity of 11,000 bbl /day showed that the CAPEX, including the total equipment cost for the fluidized bed reactor plant and semi-regenerative process plant, was $ 44,319,362 and $ 4,447,919, respectively. The annual operating cost for the Fluidized bed plant and semi-regenerative process plant was $ 45,269,180 and $1,771,839, respectively. This study demonstrates that catalytic decarboxylation over HZSM-5 zeolite is economically feasible and promising for removing NAs using a semi-regenerative process. The insight obtained from this work can be used as a basis for more comprehensive future financial and risk modeling of the process.