Applied Petrochemical Research (v.2, #3-4)
Direct oxidation of cyclohexane to adipic acid using nano-gold catalysts by A. Alshammari; A. Köckritz; V. N. Kalevaru; A. Bagabas; A. Martin (61-67).
Adipic acid (AA) is one of the most important commercially available aliphatic dicarboxylic acids, which has a large industrial application in the manufacture of Nylon-6 and Nylon-66. The present work demonstrated a green chemistry route for the direct oxidation of cyclohexane (CH) to AA using supported nano-gold catalyst in one-step reaction. The catalysts were prepared in two steps and were then characterized by different methods such as ICP, BET surface area, XRD, SEM, TEM, etc. Catalytic tests were carried out using Parr autoclave in the temperature range of 100–170 °C, and the products were analyzed by gas chromatograph. Among all investigated catalysts, TiO2 supported nano-gold exhibited the superior activity compared to all other tested catalysts. The conversion of CH and the selectivity of AA obtained over TiO2 supported catalyst were 16.4 % and ca. 21.6 %, respectively, without a noticeable change in the catalyst stability. In summary, it is possible to produce AA with ca. 8 % yield using nano-gold supported on TiO2.
Keywords: Adipic acid; Cyclohexane; Nano-gold; Titanium dioxide
Framework flexibility and rational design of new zeolites for catalysis by Asel Sartbaeva; Stephen A. Wells (69-72).
Zeolite materials have proved very useful as chemical catalysts and the search for new zeolite structures with novel channel and pore shapes is ongoing. We discuss a geometric feature of zeolite frameworks, the flexibility window, which may provide a criterion to identify hypothetical structures which can be synthesised as zeolites. In recent research using data on zeolite frameworks under compression, we show strong links between this geometric feature and the physics of zeolite frameworks.
Keywords: Zeolite; Framework; Flexibility window; Geometric simulation
Selective zeolite catalyst for alkylation of benzene with ethylene to produce ethylbenzene by Mohammed C. Al-Kinany; Hamid A. Al-Megren; Eyad A. Al-Ghilan; Peter P. Edwards; Tiancun Xiao; Ahmad. S. Al-Shammari; Saud A. Al-Drees (73-83).
In this work, a selective catalyst of BXE ALKCAT zeolite has been developed with about 30 % of ZSM-5 balanced with kaolinite, and applied for gas-phase alkylation of benzene (BZ) with ethylene (E). The catalyst has been tested in a fixed-bed down-pass flow reactor under different conditions of temperatures ranging between 300 and 450 °C with BZ to E mole ratios ranging between 1:1, 3:1 and 6:1 under atmospheric pressure and space velocity ranges between 0.1 and 150 h−1. The BXE ALKCAT zeolite catalyst has been characterized using: scanning electron microscope, X-ray diffraction, specific surface area, pore volumes, pore size distributions, X-ray photoelectron spectroscopy, and differential thermal analysis, and thermo-gravimetric analyses. Ethylbenzene was the main product of alkylation, and diethylbenzene isomers (ortho-, meta-, and para-) were the minor products. In the case of 1:1 mol ratio of BZ to E, the selectivity of EB about 85.5 % at highest conversion of BZ was obtained after 1 h of reaction on stream at 450 °C. A decrease in the temperature to 300 °C (with 1:1 mol ratio) caused the selectivity of EB to decrease to 73.0 %. EB and DEBs yields were found to increase with increasing the reaction temperature and decreasing the mole ratio of BZ to E. The conversion of BZ appeared to be depending strongly on mole ratio of BZ to E at a given temperature. The study has shown that the BXE ALKCAT zeolite is active as a catalyst for the alkylation reaction and selective to EB compared with other zeolite catalysts.
Keywords: Alkylation; Ethylation; Ethylbenzene; Zeolite
Transformation of ethylene to higher hydrocarbons on silica-supported Ir catalysts: the nature of carbonaceous deposits by Hongwei Yang; Shik Chi Edman Tsang (85-91).
The first stage of ethylene decomposition followed by second stage of temperature-programmed surface reduction (H2-TPSR) to produce higher hydrocarbons at different temperatures over silica-supported iridium catalysts has been investigated. The catalysts for the two stepwise reactions are characterized by X-ray diffraction, Raman and Fourier transformed infrared spectroscopies, temperature-programmed reduction, and mass spectroscopy. These studies reveal that ethylene decomposition at low temperatures (≤673 K) in the first stage produces mainly C1 hydrocarbon moieties on the Ir surface via dissociative adsorption, the sequential hydrogenation in the second stage will give arise to CH4. The surface polymerization of C1 to higher hydrocarbon species and metathesis reactions under these temperatures are also clearly evident. When ethylene is decomposed at 773–973 K, stable graphitic carbon deposits with poor propensity for hydrogenation are obtained. Interestingly, water formed from surface dehydroxylation on silica can produce a significant quantity of CO/H2 with these carbons during the H2-TPSR at elevated temperature.
Keywords: Ethylene homologation; Iridium catalysts; Hydrocarbon species; Propylene metathesis; Mass spectroscopy
The environmental feasibility of algae biodiesel production by Tara Shirvani (93-95).
Microalgae can grow in waste or seawater, have vastly superior biomass yields per hectare and, most importantly, the CO2 removed from the atmosphere during photosynthetic growth of the plant offsets CO2 released during fuel combustion. Algae-based fuel products are more promising than first-generation biofuels, as they exclude land use and food security issues, but require a mass production breakthrough to be viable. Through a life cycle approach, we evaluate whether algal biodiesel production can be a viable fuel source once the energy and carbon intensity of the process are managed accordingly. Currently, algae biodiesel production is 2.5 times as energy intensive as conventional diesel. Biodiesel from advanced biomass can only realize its inherent environmental advantages of GHG emissions reduction once every step of the production chain is fully optimized and decarbonized. In the case of Saudi Arabia which operates on a 100 % fossil-based electricity and heat grid, the inherent environmental advantages of producing algae biodiesel would be heavily overshadowed by the nation’s carbon-intensive energy and power sector.
Keywords: Algae biodiesel; Lifecycle analysis; Carbon footprint; Cumulative energy demand; Energy security; Renewable energy
Neutron scattering studies of catalyst systems at the ISIS neutron spallation source by Martin O. Jones; Andrew D. Taylor; Stewart F. Parker (97-104).
The ISIS neutron spallation facility is a world-leading centre for neutron scattering and has a formidable selection of elastic and inelastic neutron scattering instruments to study the physical properties of solids and liquids by a number of techniques that include diffraction, total scattering and molecular spectroscopy. In addition, complex sample environment apparatus may be utilized with these instruments that allows materials to be studied under controlled gas environments as a function of temperature, pressure and gas flow. Here, we discuss the application of these instruments and various sample environments to materials challenges within the field of catalysis, describe some of the more recent catalysis and catalysis-related experiments and highlight the capabilities of the ISIS facility in tackling catalytic challenges.
Keywords: Neutron; Neutron diffraction; Inelastic neutron scattering; Catalysis