Hydrocracking vegetable oil on borate-containing catalysts: Effect of nature of support

Abstract

The structure, texture, and acid properties of platinum catalysts on oxide (Al₂O₃, ZrO₂, ZrO₂–Al₂O₃) and borate-containing supports (B₂O₃–Al₂O₃, B₂O₃–ZrO₂) are studied. The catalysts are tested in the process of hydrocracking sunflower-seed oil at 380°C, 4.0 MPa, and a weight stock feed rate of 1.0 h^–1. It has been found that aluminum oxide (A) contains the γ-Al₂O₃ phase, zirconium dioxide (Z) includes 85 and 15 rel. % of the monoclinic (M) and tetragonal (T) phases, respectively, while zirconium dioxide with the addition of 2.5 wt % Al₂O₃ (ZA) comprises 14 and 86 rel. % of the M–ZrO₂ and T–ZrO₂ phases, respectively. The B₂O₃–Al₂O₃ (BA) and B₂O₃–ZrO₂ (BZ) systems modified with boron oxide (20 wt %) are X-ray amorphous. A Pt/BA catalyst differs from a Pt/A catalyst, while a Pt/BZ catalyst has a larger specific surface area and acidity than Pt/Z and Pt/ZA catalysts and contains Bronsted acidic centers (BACs) along with Lewis acidic centers (LACs). Only LACs are present on the surface of Pt/A, Pt/Z, and Pt/ZA catalysts. The LAC/BAC ratio in Pt/BA and Pt/BZ catalysts is 0.3 and 1.0, respectively. All the catalysts provide complete oil conversion to give C₅₊ hydrocarbons with a yield of 81.7–87.3 wt %. Pt/A catalyzes mainly decarboxylation and hydrogenation–dehydration reactions, while Pt/Z and Pt/ZA provide decarboxylation. The yield of diesel fraction reaches 71.8–73.9 wt % with an n-alkane content of 94.0–95.9 wt %. One-stage oil hydrocracking with the prevalence of hydrodecarbonylation and hydrogenation–dehydration reactions occurs on Pt/BA and Pt/BZ catalysts for 20 h to give the yield of the diesel fraction of at least 81.4 and 74.4 wt % and the total content of iso-alkanes and cycloalkanes of at least 28.3 and 60.7 wt %, respectively.