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Deactivation of HDS catalysts in deoxygenation of vegetable oils

Paper ID Volume ID Publish Year Pages File Format Full-Text
41457 45890 2011 9 PDF Available
Title
Deactivation of HDS catalysts in deoxygenation of vegetable oils
Abstract

Several rapeseed oils with different degree of upgrading were used as feedstocks for deoxygenation over sulfided CoMo/γ-Al2O3 catalyst. The rapeseed oil samples differed in the concentration of inorganic impurities, water, free fatty acids and phospholipids. The catalytic experiments were carried out in a fixed bed reactor at constant reaction conditions (310 °C, WHSV = 2 h−1, hydrogen pressure 3.5 MPa). Refined rapeseed oils were converted to hydrocarbons more efficiently than neat rapeseed oil, trap grease and waste oil. The high concentration of phospholipids in trap grease was the most likely cause of catalyst deactivation by coking. Decomposition of phospholipids as well as oligomerization of rapeseed oil by phosphoric acid at 310 °C was confirmed by separate laboratory experiments. The high concentration of alkalis in waste rapeseed oil was the main reason for increased deactivation in comparison with neat rapeseed oil. Sulfur removal from catalyst active sites affected adversely the deoxygenation of triglycerides. The catalyst deoxygenation activity was partially restored by pulse addition of dimethyldisulfide (DMDS) to the feedstock, however the degradation of active sites by loss of sulfur was not fully reversible. In contrast, continually added sulfur agent (DMDS) ensured significantly slower catalyst deactivation. Moreover, presence of H2S lowered considerably hydrodeoxygenation/decarboxylation ratio.

Graphical abstractFigure optionsDownload full-size imageDownload high-quality image (137 K)Download as PowerPoint slideResearch highlights▶ Impurities in vegetable oils, such as alkalis and phosphorus, cause deactivation of deoxygenation catalysts. ▶ Phospholipids yield phosphoric acid that promotes quick formation of carbonaceous deposits. ▶ H2S prevents catalyst deactivation and affects the deoxygenation pathway. ▶ Decarboxylation is promoted at the expense of hydrodeoxygenation due to H2S.

Keywords
Deoxygenation; Deactivation; Hydrotreating catalysts; Biofuels; Vegetable oils
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 394, Issues 1–2, 28 February 2011, Pages 9–17
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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Any Questions? feel free to contact us