Applied Petrochemical Research (v.8, #2)
Autoxidation of aromatics by Natalia Montoya Sánchez; Arno de Klerk (55-78).
Autoxidation is a conversion pathway that has the potential to add value to multinuclear aromatic-rich coal liquids, heavy oils and bitumens, which are typically considered low-value liquids. In particular, autoxidation of these heavy materials could lead to products that may have petrochemical values, e.g., lubricity improvers and emulsifiers. Proper assessment of an oxidative transformation to ring-open the multinuclear aromatics present in heavy feeds relies on the understanding of the fundamentals of aromatic oxidation. This work reviews the selective oxidation chemistry of atoms that form part of an aromatic ring structure using oxygen (O2) as oxidant, i.e., the oxidation of aromatic carbons as well as heteroatoms contained in an aromatic ring. Examples of industrially relevant oxidations of aromatic and heterocyclic aromatic hydrocarbons are provided. The requirements to produce oxygenates involving the selective cleavage of the ring C–C bonds, as well as competing non-selective oxidation reactions are discussed. On the other hand, the Clar formalism, i.e., a rule that describes the stability of polycyclic systems, assists the interpretation of the reactivity of multinuclear aromatics towards oxidation. Two aspects are developed. First, since the interaction of oxygen with aromatic hydrocarbons depends on their structure, oxidation chemistries which are fundamentally different are possible, namely, transannular oxygen addition, oxygen addition to a carbon–carbon double bond, or free radical chemistry. Second, hydrogen abstraction is not necessary for the initiation of the oxidation of aromatics compared to that of aliphatics.
Keywords: Autoxidation; Catalytic oxidation; Multinuclear aromatics; PAHs; Heterocyclic aromatics; Clar formalism
Maximization of propylene in an industrial FCC unit by Yakubu M. John; Raj Patel; Iqbal M. Mujtaba (79-95).
The FCC riser cracks gas oil into useful fuels such as gasoline, diesel and some lighter products such as ethylene and propylene, which are major building blocks for the polyethylene and polypropylene production. The production objective of the riser is usually the maximization of gasoline and diesel, but it can also be to maximize propylene. The optimization and parameter estimation of a six-lumped catalytic cracking reaction of gas oil in FCC is carried out to maximize the yield of propylene using an optimisation framework developed in gPROMS software 5.0 by optimizing mass flow rates and temperatures of catalyst and gas oil. The optimal values of 290.8 kg/s mass flow rate of catalyst and 53.4 kg/s mass flow rate of gas oil were obtained as propylene yield is maximized to give 8.95 wt%. When compared with the base case simulation value of 4.59 wt% propylene yield, the maximized propylene yield is increased by 95%.
Keywords: FCC riser; Maximization; Propylene; Optimization; Parameter estimation
Preparation of a new, green and recyclable catalyst, silica-supported 1-(2-sulfooxy)ethyl)1H-pyridine-1-ium-chloride, and a solvent- and metal-free protocol for the synthesis of 14-aryl-14H-dibenzo[a,j]xanthene derivatives by Sami Sajjadifar; Maryam Pornuroz (97-105).
A cost-effective and convenient procedure for the synthesis of silica-supported 1-(2-sulfooxy)ethyl)1H-pyridine-1-ium-chloride SiO2/[SEP]Cl as a recoverable heterogeneous and Brønsted acid catalyst is described, and was used for the one-pot synthesis of aryl-14H-dibenzo[a,j]xanthenes under solvent- and metal-free conditions at 110 °C in short reaction time with a yield of up to 95%. The present method offers several advantages such as simplicity in operation, ease of preparation and recycling of Brønsted acidic ionic liquid (BAIL), solvent-free reaction conditions, and no hazardous organic solvents are used in the entire procedure including workup and purification.
Keywords: 1-(2-Sulfooxy)ethyl)1H-pyridine-1-ium-chloride; One-pot reaction; 14-Aryl-14H-dibenzo[a,j]xanthene; Solvent- and metal-free conditions; Brønsted acidic ionic liquid
Acetalization of glycerol with acetone over various metal-modified SBA-15 catalysts by Sarthani Ammaji; G. Srinivasa Rao; Komandur V. R. Chary (107-118).
Several catalysts containing metals such as Al, Zr, Ti and Nb were incorporated in SBA-15 with Si/M ratio = 20 using the hydrothermal process. These catalysts were evaluated for their reactivity during acid-catalyzed condensation of glycerol with acetone to yield a mixture of branched compounds, namely (2,2-dimethyl- [1,3] dioxane-4-yl)-methanol (solketal) and 2,2-dimethyl- [1,3] dioxane-5-ol, which are being used as fuel additives. The synthesised catalyst samples were characterized by ICP-AES analysis, N2 adsorption–desorption measurements, X-ray diffraction, FT-IR, SEM–EDX, UV–visible diffuse reflectance spectroscopy, TPD of ammonia and ex situ pyridine-adsorbed FT-IR spectroscopy. The various characterization results confirm that metal oxides were incorporated in the pore wall of the SBA-15 matrices. The results of NH3-TPD and ex situ adsorbed pyridine FT-IR analyses showed that the acidity of the samples increased after incorporation of metal into the pure SBA-15 samples. Among various metals incorporated into the SBA-15, the Nb–SBA-15 (Si/Nb = 20) showed higher catalytic activity toward the acetalization of glycerol in liquid phase compared to that of other samples investigated. Under the optimal reaction conditions, the Nb–SBA-15 (Si/Nb = 20) exhibited 95% glycerol conversion with 100% solketal selectivity. The catalyst reusability studies indicated that the Nb–SBA-15 sample is regenerable and highly stable in the acetalization of glycerol.
Keywords: Glycerol; Acetalization; Solketal; SBA-15; Metal-incorporated SBA-15
Catalytic cracking of naphtha: The effect of Fe and Cr impregnated ZSM-5 on olefin selectivity by Ebrahim Mohiuddin; Masikana M. Mdleleni; David Key (119-129).
This study focuses on the modification of ZSM-5 in order to enhance the catalytic cracking of refinery naphtha to produce light olefins. ZSM-5 was metal modified using different loadings (0.5–5 wt%) of Fe and Cr via the impregnation method. The metal modified ZSM-5 samples are compared and the effect of metal loading on the physicochemical properties and catalytic performance is investigated. Fe and Cr modification had an effect on both the physicochemical properties of the catalysts as well as catalytic activity and selectivity. Metal loading caused a decrease in the specific surface area which decreased further with increased metal loading. Fe had a greater effect on the total acidity in particular strong acid sites when compared to Cr. The optimum Fe loading was established which promoted selectivity to olefins, in particular propylene. Fe also had a dominant effect on the P/E ratio of which a remarkable ratio of five was achieved as well as enhanced the stability of the catalyst. Cr was found to be a good promoter for selectivity to BTX products with a two-fold increase observed when compared to Fe-modified catalysts.
Keywords: ZSM-5; Metal-modified; Catalytic cracking; Naphtha; Olefins