High Metal–Acid Balance and Selective Hydrogenation Activity Catalysts for Hydrocracking of 1-Methylnaphthalene to Benzene, Toluene, and Xylene

Abstract

Hydrocracking of 1-methylnaphthalene to benzene (B), toluene (T), and xylene (X) was performed over a series of bi-functional catalysts (W/Beta) at 420 °C and 6 MPa. The reaction results and kinetic study indicated that metal–acid balance (metal–acid interaction and metal–acid ratio) and metal dispersion had a great impact on the cracking, hydrogenation, and selective hydrogenation activity, which directly determine the BTX yield. An inappropriate metal–acid ratio would lead to producing plenty of intermediates or by-products, and poor metal dispersion would result in low hydrogenation activity. However, good metal dispersion usually accompanies the strong metal–acid interaction, which reduces the sulfidation of metal. In this work, a new tungsten precursor, W-complex, was used to prepare the catalysts with good dispersion of metal oxides and high hydrogenation activity. The external surface acidity of zeolite was modified to regulate the metal–acid interaction by forming a layer of SiO2 on acid sites through chemical liquid deposition.

Effect of the catalyst in the BTX production by hydrocracking of light cycle oil

“…Figure 5 shows a summary of the total BTX yield from naphthalene derivatives from the principal results [27][28][29][30][31][32][33]. The highest total BTX yield was 55% using a hydrocracking catalyst composed of 5 W(l)/Beta-0.15 (TEOS) [33] remarkably like the maximum yield attained when BTX was obtained from tetralin hydrocracking (53%).…”

“…Figure 5 shows a summary of the total BTX yield from naphthalene derivatives from the principal results [27][28][29][30][31][32][33]. The highest total BTX yield was 55% using a hydrocracking catalyst composed of 5 W(l)/Beta-0.15 (TEOS) [33] remarkably like the maximum yield attained when BTX was obtained from tetralin hydrocracking (53%). The 65% theoretical conversion was never reached because not only BTX can be obtained, but also some hydrogenated hydrocarbons and other higher molecular weight alkylbenzenes, besides, with these model molecules (naphthalene and naphthalene derivatives) more hydrogenation and isomerization reactions may compete with the hydrocracking process [12].…”

“…Wu et al [33] studied in detail the hydrocracking catalysis for BTX production from naphthalene type compounds. To make the catalysis manufacture cheaper, it was prepared via the WO 2 (C 6 H 6 NO) 2 complex, following the next procedure: 15 mL methanol and 0.4 g 2-methoxypyridine were added to a solution of 0.3 g tungsten hexachloride in 15 mL of acetonitrile and then stirring at room temperature for 15 min.…”

“…It seemed that to reach the best hydrocracking performance a balance between Brønsted and Lewis sites is required. According to Wu et al [33] after carrying out kinetic studies of the 1-methylnaphthalene hydrocracking, they found out that the strong acidity resulted in a strong interaction between acid centers and metal centers, which can decrease the hydrogenation activity of the catalyst. On the other hand, low acidity resulted in high hydrogenation activity (high hydrogenation reaction rates) but low selective-hydrogenation activity, meaning that hydrogenation of the first and second aromatic rings can occur without giving place to hydrocracking by consecutive hydrogenation reactions.…”

Effect of Zn Contents of W/Zn-Beta Catalysts on Their Catalytic Performance in the Selective Hydrocracking of Tetrahydronaphthalene into Benzene, Toluene, and Xylene

“…The nine-lump kinetic model, shown in Figure , for THN HDC reaction was established in this work based on our previous work, , and the reaction rate constants were calculated by the following equations normald Y 1 M 1 · normald τ = r 1 = prefix− ( k 1 + k 6 + k 7 ) C 1 = C normalT 0 · [ − false( k 1 + k 6 + k 7 false) Y 1 ] Y normalH 2 + ∑ i = 1 8 Y i normald Y 2 M 1 · normald τ = r 2 = k 1 …”