Effect of Hydrohalogenation of Metal/Zeolite Catalysts for Cyclohexene Hydroconversion ‐Part 3‐ Pd/H‐ZSM‐5 Catalysts

Abstract

Cyclohexene (CHE) hydroconversion was performed in a flow reactor at atmospheric pressure and temperatures of 50–400 °C using: Pd/H‐ZSM‐5, Pd/H‐ZSM‐5(HCl), and Pd/H‐ZSM‐5(HF) catalysts. These catalysts were characterized for acid site strength distribution via NH3 TPD, Pd dispersion via H2 chemisorption, TPR via reduction of the metal oxide in the catalysts and XRD for tracing crystallinity The hydroconversion steps proceeded as follows: CHE → Cyclohexane (CHA); CHE → Methylcyclopentenes (MCPEs) → Methylcyclopentane (MCPA); CHE → Cyclohexadienes (CHDEs) → Benzene → Alkylbenzenes; CHE and others → Hydrocrackedproducts. The overall hydroconversion of CHE was achieved in the catalyst order: Pd/H‐ZSM‐5 > Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl). CHE hydrogenation step was the major reaction at low temperatures which significantly inhibited via HCl treatment, but slightly enhanced via HF treatment. At medium temperatures, on all catalysts, isomerisation to MCPEs and MCPA increase to a maximum then a decline with a further increase of temperature. The overall isomerisation of CHE was highest on the untreated catalyst. During the higher temperature range, dehydrogenation, alkylation and hydrocracking were increased with temperature. Dehydrogenation of CHE always yielded larger amounts of 1,3‐CHDE than 1,4‐CHDE. These cyclohexadienes were produced in the catalyst order: Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl) > Pd/H‐ZSM‐5. In general, benzene alkylation to toluene exceeded that of xylenes, indicating that the second methylation is more difficult than the first. However, the catalytic activities for benzene and toluene production were in the order: Pd/H‐ZSM‐5 » Pd/H‐ZSM‐5(HCl) > Pd/H‐ZSM‐5(HF), whereas for xylenes production, Pd/H‐ZSM‐5 » Pd/H‐ZSM‐5(HF) > Pd/H‐ZSM‐5(HCl). Intrapore diffusion plays an important role during the dehydrogenation reactions as well as during the interconversion of individual aromatic hydrocarbons.

Produce Low Aromatic Contents with Enhanced Cold Properties of Hydrotreated Renewable Diesel Using Pt/Alumina-Beta-Zeolite: Reaction Path Studied via Monoaromatic Model Compound

“…However, the addition of alumina binder suppresses Lewis acid site number, and further increases the Brønsted acid site number to have moderated acidic strength on the surface [9]. Thepublications observed on protonation of Brønstedacid sites induce hydrogen ions for rebranching and isomerisation processes in high Si/Al zeolites [10][11][12][13][14][15][16][17][18]. The previous study revealed that zeolite makes the transition metal more electrophilic, thus helps the reoxidation of metal during the reaction [19].…”

“…Hydrotreated FAME in Gas Oil ( In recent decades, hydro-isomerisation of ULSD by noble metals on acidic solid catalyst like zeolites or silica aluminates in micro-or mesopore structure was used in refineries [6][7][8][9]. Zeolite synthesis with different crystalline structure and characteristics had widely studied and, its performance was investigate using hydro-isomerisation and hydrocracking on ZSM, Y-type, H-β, SAPO and MCM for branching the high molecular weight straight-chain hydrocarbons [6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Product shape selectivity mainly achieved through the crystalline pore structure and molecule size in pore diffusive diameter, but the acidity of catalyst play the main role in product distribution [13][14][15].The tuning of the acidic property of zeolite and extrudate was achieved by varying SiO 2 /Al 2 O 3 (or Si/Al) and the operating temperature.…”

“…Also, Cl acts as a catalytic poison if it substitutes through feed in the form of HCl [19];whereas investigating with F doping shows a low acid site number and low hydrogenation activity as compared to Cl [10,11]. Skeletal isomerisation and conversion increases if Cl ions introduced into alumina to form Brønsted acid sites [11,12]. The reaction has to perform at low temperatures to improve equilibrium yield and lower chlorine elution.…”

“…Apart from acidity, large or medium pore size was required to avoid secondary cracking [23]. Similarly, large diameter pore zeolite can increases monobranch isomers with low hydrocracking at higher isomerisation selectivity [9][10][11][12][13][14][15].…”

“…Traditionally, hydrogenation of aromatic compounds in diesel was carried using noble metal on alumina. Hydrogenation of ring mainly initiated between 150 and 200 • C, further increase in temperature substantially enhance dehydrogenation [11][12][13]. Hence, the required hydro-dearomatisation after hydro-isomerisation can examine, if both hydrogenation and dehydrogenation function were performed in a single-stage over a zeolite at an operating temperature from 200 to 300 • C, with hydrogenation of aromatic compounds depends on moderate temperature [13,22].…”