Hydrotreating reactions of tall oils over commercial NiMo catalyst

Jinto M Anthonykutty,Juha Linnekoski,Juha Lehtonen,Ali Harlin

doi:10.1002/ese3.70

Jinto M Anthonykutty, Juha Linnekoski + Show 2 more

Open Access

https://doi.org/10.1002/ese3.70

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Abstract

AbstractCatalytic hydrotreating is an attractive method for upgrading bio‐derived oils into renewable feedstocks with less oxygen content, suitable for producing valuable hydrocarbons through various petro‐refinery processes. This study evaluates the catalytic activity of a commercial alumina (Al2O3) supported NiMo catalyst for hydrotreating tall oil feeds such as crude tall oil (CTO), distilled tall oil (DTO), and tall oil fatty acid (TOFA). Catalytic experiments carried out in a bench‐scale fixed bed reactor set‐up at different process conditions [space velocity (1–3 h−1), temperature (325–450°C), and H2 pressure (5 MPa)] produced a wide‐range of products from tall oil feeds. Hydrotreating of TOFA produced highest yield of n‐alkanes (>80 wt%) compared to DTO and CTO hydrotreating. A high conversion of fatty acids and resin acids was obtained in DTO hydrotreating. In CTO hydrotreating, a drop in conversion of fatty acids and resin acids was observed especially at the lowest temperature tested (325°C). The study revealed that there are various deoxygenation pathways preferential at different hydrotreating temperatures. As an example for TOFA, the decarboxylation route is dominant over the hydrodeoxygenation route at high temperatures (>400°C).

Highlights

Catalytic hydrotreating is an essential petro-refinery method to reduce the content of heteroatoms (S, N, and O) from raw materials, which has been widely employed to upgrade refinery feeds prior to such processes as catalytic reforming, catalytic cracking, and steam cracking [1]
Based on distribution of gaseous products obtained from tall oil hydrotreating experiments, it can be assumed that in tall oil fatty acid (TOFA) and distilled tall oil (DTO) hydrotreating at high temperatures (>400°C), mainly nonselective deoxygenation occurs with a sulfided NiMo catalyst by means of cracking [12, 28] which requires no hydrogen and produces short-chain oxygenates and CO2 as well as hydrocarbons [30]
The activity of a commercial alumina supported NiMo catalyst was evaluated for hydrotreating of different tall oil feedstocks

Summary

Introduction

Catalytic hydrotreating is an essential petro-refinery method to reduce the content of heteroatoms (S, N, and O) from raw materials, which has been widely employed to upgrade refinery feeds prior to such processes as catalytic reforming, catalytic cracking, and steam cracking [1]. In petro-refineries that use sulfur-rich fossil-fuel-based feeds, the catalytic hydrotreating technology is fully developed for the hydrodesulfurization (HDS) of petroleum products and naphtha streams [2,3,4]. The recent research developments prompted by the increasing demand of bio-based fuels and chemicals reinvent the importance of developing optimal hydrotreating (hydrodeoxygenation, HDO) methods for reducing the amount of oxygenates from complex bio-derived feeds before the thermochemical conversion process into fuels or chemicals. The amount of oxygenates in bio-derived oils vary depending on the origin of raw materials.

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