Applied Petrochemical Research (v.6, #3)
On choosing the most appropriate catalysts for the conversion of carbon dioxide to fuels and other commodities, and on the environmentally benign processing of renewable and nonrenewable feedstocks by Sir John Meurig Thomas; Rowan K. Leary (167-182).
Until recently the drive to discover and utilize renewable feedstocks for the production of energy and for the manufacture of materials was exceptionally strong. Now, however, because of the realisation that nonrenewable (e.g. gas and oil) reserves are still superabundant, a different emphasis is appearing. This involves utilizing both nonrenewable and renewable feedstocks in an environmentally responsible manner. One important recent development involves the drive to utilize feedstocks, such as pyrolysis oil, microalgae and general bio-waste, like sawdust and other nonedible products from lignocellulose. Another is the aim to ensure that CO2 can be converted to fuels or useful materials, thereby diminishing its concentration in the atmosphere. This paper focuses on these themes; but it also addresses other important specific questions. Among these, the following are of particular interest: (i) How may catalytic cracking be made more environmentally acceptable? (ii) The emergence of single atom catalysts as means of effecting important chemical reactions.
Keywords: CO2 ; Catalyst; Photocatalyst; Environmentally benign; Fuel; Renewable and nonrenewable feedstocks; Bio-oil; Catalytic hydrothermal reactor; Microalgae
Methane dehydroaromatisation and methanol activation over zeolite catalysts: an overview by J. S. J. Hargreaves (183-190).
A brief overview of methane dehydroaromatisation over MoO3/H-ZSM-5 derived catalysts, the deposition of carbonaceous residues from methanol over H-mordenite and the role of binders in zeolite catalysed reactions is presented. The selective poisoning of methane cracking catalysts is proposed as a potential strategy for the development of methane dehydroaromatisation catalysts. In the case of methanol conversion over H-mordenite, evidence is presented for the formation of larger alkylated aromatics, such as methylnaphthalenes. Binders, ubiquitous components of technical catalysts, have been documented to have a number of important effects often outweighing laboratory based modifications, and therefore, consideration of their effects should be made at an early stage of catalyst development.
Keywords: Binder; Methane; Methanol; Mordenite; Zeolite; ZSM-5
Preparation of odour removal catalysts with self-regeneration capability by Yongxiang Zhao; Lili Zhao; Yu Huang; Haoyi Chen; Tiancun Xiao (191-199).
Odours remain at the top of air pollution complaints both indoor and outdoor, which can come from sewage, rotten food, and human digestions. Activated carbon has been used to absorb the odour materials, but its physical absorption can easily be saturated and could be a potential pollution source when less odour compounds exist in the surrounding environment. Here, for the first time, we have developed an activated carbon-alumina composite-supported ZnCu bimetallic metal oxide catalyst, which not only has very high capacity to absorb the strong smell sulfide, but also can convert sulfide into sulfur by the oxygen in air and the organic sulfur into sulfone, which removes the odour material in a chemical way and also endows the self-regeneration ability for the sorbent, leading to a longer and more efficient way to control odour in air. The ZnCu catalyst which contains 50 % of active carbon in the support has the highest sulfur capacity. The preparation parameters, such as calcination temperature, composition of the active components, and the test conditions, have a significant effect on the odour removal capability, and the conversion over the catalyst. The main structure of the bimetallic oxide catalysts does not change even after half-year industrial site use, which completely converts sulfur into sulfur powder and also convert CO into CO2. The surface morphology changes, while the main crystalline structure remains, which showed the self-regenerability of the catalyst.
Keywords: Odour removal; Composite support; Catalyst; Self-regeneration; Sulfur-containing compounds
Methane reforming over Ni-based pyrochlore catalyst: deactivation studies for different reactions by Nitin Kumar; Zi Wang; Swarom Kanitkar; J. J. Spivey (201-207).
A 1 wt% Ni-based La2Zr2O7 pyrochlore catalyst was synthesized using the modified Pechini method. The catalyst was characterized by H2-TPR, and pre- and post-reaction XRD, and tested for its methane-reforming activity under three different reaction conditions: (a) dry-reforming (CH4 + CO2), (b) oxy-CO2 reforming (CH4 + CO2 + O2), and (c) bi-reforming (CH4 + CO2 + H2O). The TPR results show that NiO in the fresh, calcined catalyst is completely reversible to Ni0. The XRD results show that the crystalline pyrochlore structure is stable under all three reaction conditions. Under dry-reforming conditions, the catalyst deactivated rapidly. In oxy-reforming, the catalyst activity also decreased, but far less rapidly than under dry-reforming conditions. However, under bi-reforming conditions, no deactivation was observed at comparable times-on-stream. TPO of the spent catalysts showed greatest carbon deposition for the dry-reforming, a significant portion of which was graphitic and difficult to remove. For oxy-reforming, there was much less carbon deposition as compared to the dry-reforming, and a major part of which was the amorphous, atomic carbon, which is relatively easy to remove. Unlike under bi-reforming, no significant carbon deposition was observed at the conditions tested here. This indicates that the presence of steam resists carbon deposition compared to dry-reforming or oxy-reforming.
Keywords: Reforming; Dry-reforming; Bi-reforming; Oxy-reforming; Pyrochlore; Syngas; Methane activation
Advances in the study of coke formation over zeolite catalysts in the methanol-to-hydrocarbon process by B. Liu; D. Slocombe; M. AlKinany; H. AlMegren; J. Wang; J. Arden; A. Vai; S. Gonzalez-Cortes; T. Xiao; V. Kuznetsov; P. P. Edwards (209-215).
Methanol-to-hydrocarbon (MTH) process over acidic zeolite catalysts has been widely utilised to yield many types of hydrocarbons, some of which are eventually converted into the highly dehydrogenated (graphitized) carbonaceous species (cokes). The coking process can be divided into two parallel pathways based on the accepted hydrocarbon pool theory. From extensive investigations, it is reasonable to conclude that inner zeollite cavity/channel reactions at acidic sites generate cokes. However, coke formation and accumulation over the zeolite external surfaces play a major role in reaction deactivation as they contribute a great portion to the total coke amount. Herein we have reviewed previous literatures and included some recent works from KOPRC in understanding the nature and mechanism of coke formation, particularly during an H-ZSM-5 catalysed MTH reaction. We specially conclude that rapid aromatics formation at the zeolite crystalite edges is the main reason for later stage coke accumulation on the zeolite external surfaces. Accordingly, the catalyst deactivation is in a great certain to arise at those edge areas due to having the earliest contact with the incoming methanol reactant. The final coke structure is therefore built up with layers of poly-aromatics, as the potential sp2 carbons leading to pre-graphite structure. We have proposed a coke formation model particularly for the acidic catalyst, which we believe will be of assistance in understanding—and hence minimising—the coke formation mechanisms.
Keywords: Zeolite catalyst; Methanol to hydrocarbons; Coking; Catalyst deactivation
Application of Ni–Al-hydrotalcite-derived catalyst modified with Fe or Mg in CO2 methanation by Xiaolong Wang; Tao Zhen; Changchun Yu (217-223).
In this work, Ni–Al-hydrotalcite-derived catalyst modified with Fe or Mg for CO2 methanation was investigated in an attempt to improve the reaction activity at low temperature. Through the characterization of XRD, H2-TPR, and N2-BET, 0.05Fe–Ni–Al2O3-HT catalyst can be found with a better reducing property, higher surface area, better Ni dispersion, and smaller pore size. The CO2 conversion using this catalyst was tested in a fixed-bed reactor in laboratory. The result showed better reaction activity at low temperature. At 219 °C, the CO2 conversion could reach 80.8 %. Meanwhile, the highest CO2 conversion of 96.0 % was achieved at 350 °C.
Keywords: CO2 methanation; Ni–Al hydrotalcite; Activity; Reducibility; Larger/smaller pore size
Surface engineering and self-cleaning properties of the novel TiO2/PAA/PTFE ultrafiltration membranes by Lina Chi; Yingjia Qian; Boyu Zhang; Zhenjia Zhang; Zheng Jiang (225-233).
Immobilization of nano-scaled TiO2 onto polymeric ultrafiltration (UF) membrane offers desirable antifouling and self-cleaning properties to the membrane, which is practical in wastewater purification only if the mechanical strength and long-term self-cleaning durability are realized. This paper reported the surface roughness, mechanical properties, thermal stability, and recycling self-cleaning performance of the novel TiO2/PAA/PTFE UF membranes, which were coated via an innovative plasma-intensified coating strategy. Through careful characterizations, the enhanced engineering properties and the self-cleaning performance were correlated with the surface chemical composition and the creative coating technique. In the recycling photocatalytic self-cleaning tests in photodegradation of methylene blue (MB) solution, about 90 % MB photocatalytic capability of TiO2/PAA/PTFE composite membranes could be recovered with simple hydraulic cleaning combined with UV irradiation. The mechanical properties and thermal stability of TiO2/PAA/PTFE also satisfy the practical application in water and wastewater treatments, despite that the original engineering properties were slightly influenced by PAA grafting and TiO2 coating. The changed properties of the composite UF membrane relative to PTFE are reasonably attributed to the variation of the surface chemical species and chemical bonding, as well as the thickness and evenness of the surface functional layers.
Keywords: PTFE; TiO2 ; Ultrofiltration membrane; Ultrafiltration; Self-cleaning
Perfomances of different additives on NiO/γ-Al2O3 catalyst in CO methanation by Zhong He; Xiaolong Wang; Rong Liu; Shiwang Gao; Tiancun Xiao (235-241).
In this work, NiO/γ-Al2O3 catalyst with different additives prepared by excessive dipping method, was investigated in CO methanation in an attempt to improve the reaction activity and enhance the anti-coking property. The influences of additives, such as Zr, Co, Ce, Zn and La, on catalysts in performance of CO methanation were studied in a fixed-bed reactor. The catalysts were characterized by XRD, H2-TPR, H2-TPD and CO-TPD. The results showed that the addition of the additives could promote the dispersion of nickle species on support and decrease the crystallite size of Nickel species. The reduction temperatures of catalysts were all reduced except the one with Mg. The catalytic results showed that additives improved the reaction activity of CO methanation. Especially, the addition of La gave the best catalytic performance of 100 % CO conversion and 99.61 % CH4 selectivity, respectively. The space–time yield of CH4 was achieved as high as 2134.5 g kg−1 h−1.
Keywords: CO methanation; Nickel-based catalysts; Additives; Fixed-bed reactor
Heterogeneously catalyzed lignin depolymerization by Antonio Pineda; Adam F. Lee (243-256).
Biomass offers a unique resource for the sustainable production of bio-derived chemical and fuels as drop-in replacements for the current fossil fuel products. Lignin represents a major component of lignocellulosic biomass, but is particularly recalcitrant for valorization by existing chemical technologies due to its complex cross-linking polymeric network. Here, we highlight a range of catalytic approaches to lignin depolymerisation for the production of aromatic bio-oil and monomeric oxygenates.
Keywords: Biomass; Lignin; Heterogeneous catalysis; Solid acid
Impact of carbon nanotubes addition on electrical, thermal, morphological, and tensile properties of poly (ethylene terephthalate) by Basheer A. Alshammari; Arthur Wilkinson (257-267).
In this study, multi-walled carbon nanotubes (MWCNTs) were incorporated into poly (ethylene terephthalate) (PET) matrix in their as-received (A-MWCNTs) and treated (T-MWCNTs) forms. Melt-compounding method was used for the preparation of these carbon nanotubes (CNTs)-reinforced PET composites. The electrical conductivity, thermal stability, morphological, and tensile properties were investigated. For testing and characterization, impedance spectroscopy, thermo-gravimetric analysis, scanning electron microscopy, transmission electron microscopy, Fourier-transform infrared spectroscopy and tensile testing were utilized. The results demonstrates that an incorporation of ~0.25 wt% A-MWCNTs, an electrically conductive polymer nanocomposite (~0.2 S/m), was formed with a low percolation threshold (~0.33 wt%). In contrast, at the same loading of T-MWCNTs or even up 2 wt% did not yield conductive polymer. Presumably, such behavior is attributed to the acid treatment that disrupted the inherent electrical conductivity of the CNTs and also reduced their aspect ratio. Nevertheless, T-MWCNTs showed a better dispersion and distribution into the PET matrix than that of A-MWCNTs counterpart. Moreover, an improved tensile behavior was observed for T-MWCNTs incorporated composites than that of A-MWCNTs counterpart. Improved thermal stability was observed for PET/A-MWCNTs in both the air and nitrogen atmospheres. Whereas, PET/T-MWCNTs exhibited the highest thermal stability in all samples in nitrogen atmosphere. However, poor thermal response was seen in air atmosphere.
Keywords: Carbon nanotubes; PET; Nanocomposites; Modifications and properties
Catalytic decomposition of carbon-based liquid-phase chemical hydrogen storage materials for hydrogen generation under mild conditions by Felipe Sánchez; Davide Motta; Nikolaos Dimitratos (269-277).
The increasing demand of energy requires the development of sufficient and sustainable energy sources. However, the upcoming hydrogen economy is suffering from challenges which need to be solved. In this context, the search for liquid hydrogen storage materials and successful utilisation is crucial due to the high gravimetric and volumetric hydrogen densities, easy recharging, low capital investment, and low potential risks. In this review, we survey the progress made in hydrogen generation from carbon-based liquid-phase chemical hydrogen storage materials, focusing mainly on the catalytic decomposition of formic acid for hydrogen production.
Keywords: Formic acid decomposition; Hydrogen generation; Supported metal nanoparticles; Colloidal methods
Capture and recycle of industrial CO2 emissions using microalgae by Michael H. Wilson; Daniel T. Mohler; John G. Groppo; Thomas Grubbs; Stephanie Kesner; E. Molly Frazar; Aubrey Shea; Czarena Crofcheck; Mark Crocker (279-293).
A novel cyclic flow photobioreactor (PBR) for the capture and recycle of CO2 using microalgae was designed and deployed at a coal-fired power plant (Duke Energy’s East Bend Station). The PBR was operated continuously during the period May–September 2015, during which algae productivity of typically 0.1–0.2 g/(L day) was obtained. Maximum CO2 capture efficiency was achieved during peak sunlight hours, the largest recorded CO2 emission reduction corresponding to a value of 81 % (using a sparge time of 5 s/min). On average, CO2 capture efficiency during daylight hours was 44 %. The PBR at East Bend Station also served as a secondary scrubber for NO x and SO x , removing on average 41.5 % of the NO x and 100 % of the SO x from the flue gas. The effect of solar availability and self-shading on a rudimentary digital model of the cyclic flow PBR was examined using Autodesk Ecotect Analysis software. Initial results suggest that this is a promising tool for the optimization of PBR layout with respect to the utilization of available solar radiation.
Keywords: Algae; Carbon dioxide; Photobioreactor; Flue gas; Power plant; Utilization
New in situ solid-state NMR strategies for exploring materials formation and adsorption processes: prospects in heterogenous catalysis by Kenneth D. M. Harris (295-306).
Solid-state NMR spectroscopy is a powerful technique for studying structural and dynamic properties of solids and has considerable potential to be exploited for in situ studies of chemical processes. However, adapting solid-state NMR techniques and instrumentation for in situ applications are often associated with technical challenges, and for this reason, the opportunities remain underexploited. This paper highlights two experimental strategies that we have developed in recent years for in situ solid-state NMR investigations of solid-state processes. One technique is focused on probing details of the time evolution of materials formation processes, and the other technique is focused on understanding the time evolution of adsorption processes in microporous and mesoporous solid host materials. Each of these in situ solid-state NMR techniques has significant prospects for applications in areas relating to heterogeneous catalysis.
Keywords: Solid-state NMR; In situ techniques; Adsorption processes; Materials formation processes; Crystallization