Effect of support on molybdenum oxide acidity for n-heptane isomerization

Skeletal isomerization of alkanes into the corresponding branched isomers has attracted many attentions as a reaction to produce clean fuel with high octane quality. In this study, molybdenum oxide (MoO3) catalyst supported on mesostructured silica nanoparticles (MSN), HZSM-5 and MCM-41 activity were being tested towards n-heptane isomerization at 623 K. The catalyst acidity was characterized by using FTIR pre-adsorb pyridine. The results showed that MoO3-MSN possesses highest Lewis acid and lowest Brönsted acid concentrations. The catalytic testing towards n-heptane isomerization showed that MoO3-MSN exhibited the highest n-heptane conversion of 18.7 % at 623 K. It was suggested that the high Lewis acid in the MoO3-MSN may facilitate the formation of active protonic acid sites from molecular hydrogen through hydrogen spillover mechanism and hence improves the n-heptane conversion

n-Heptane isomerization over molybdenum oxide supported catalysts

Concern over the negative effects of fuel and oil usage on the environment has caused changes in regulations with severe impacts on gasoline, other jet fuels and lubricating oils. In order to improve the octane quality of a gasoline fraction, the refinery industry uses some high-octane rating components that are paraffinic in nature. The octane index is improved by increasing the degree of iso-alkane branching. Since the highly branched isomers have a relatively low environmental impact, the skeletal isomerization of n-alkane can be a key technology for production of high quality gasoline [1]. However, the practical application of this process has only been confined to short chain alkanes, because the isomerization of long-chain alkanes is usually accompanied by undesirable cracking. Thus, catalysts with a sufficiently good balance of metal and acid functions under suitable reaction conditions are generally needed to suppress cracking in order to achieve high isomerization selectivity for long-chain alkanes [2]. Molybdenum oxide (MoO3) supported catalysts have been extensively studied in recent years due to their possible potential to catalyze the isomerization of linear alkanes [3]. Based on previous study, catalyst support is one of the crucial factors that influence the catalyst acidity [4]. Therefore, in this study, a series of MoO3 catalyst supported by HZSM-5, MCM-41, SiO2and ZrO2was prepared by impregnation method. Their structural property was characterized using nitrogen physisorption analysis and the acidic property was determined by pyridine adsorbed IR spectroscopy. The catalytic property of all catalyst was evaluated over n-heptane isomerization at 623 K. The result showed that MoO3-ZrO2catalyst exhibits the highest catalytic activity with 33.9 % conversion. The result was attributed from the Lewis acid property of the catalyst which was crucial in the n-heptane isomerization. Comparison between all the catalyst acidic property and their catalytic activity is discussed

Kinetic analysis of 2-chlorophenol photodegradation over alpha-feooh nanoparticles prepared in cationic surfactant electrolyte

2-Chlorophenol (2-CP) which widely used in various chemical processes such as in agriculture, paper, cosmetic, biocide, and public health industries, presents serious threats to the surrounding ecosystem. In recent years, photocatalytic treatment system was found to be the most promising alternative for the abatement of this recalcitrant pollutant1. a–FeOOH as a semiconductor catalyst, has been widely used in the degradation of many chlorinated compounds due to its unique electrical, optical and photoluminescence properties2. Owing to the advantages of using electrochemical as a catalyst preparation method3, this study reports the electrosynthesis of a– FeOOH nanoparticles in a cationic surfactant, IS (IS-FeOOH). IS that acts as an only electrolyte is capable in producing IS-FeOOH nanoparticles without any agglomeration4. Its crystallinity and morphology were analyzed using an X–ray diffractometer and a transmission electron microscope, respectively. The characterization results verified that IS plays an important role in the miniaturization of the a–FeOOH nanoparticles, with a diameter range of 5–10 nm (Figure 1). The activity of IS–FeOOH was tested on a photodegradation of 2– chlorophenol (2–CP). Results showed that at nearly neutral condition of pH 5 was able to completely degrade 2–CP within 180 min of reaction at 50°C, using 0.03 g L-1 of catalyst dosage and 50 mg L-1 of 2–CP initial concentration. Kinetic analysis indicates that the apparent rate constant, kapp increased with increasing initial concentration of 2–CP up to 50 mg L-1 and then reduced as the initial concentration increased to 70 mg L-1. The calculated kr and KLH were 8.3 mg L–1 min–1 and 2.8 × 10-4 L mg–1, respectively, suggesting a surface reaction was the controlling step of the process. The results provide strong evidence to support the potential use of IS as an alternative electrolyte to synthesize nanosized photocatalyst that can be used to treat organic pollutants

Metal-promoted mesoporous ZSM5 for CO methanation to produce synthetic natural gas (SNG)

In recent years, enormous emissions of carbon oxide (CO and CO2) by combustion of fossil and fuel have contributed to the increase in global temperatures and climate changes due to the ‘greenhouse effect’ [1]. In order to solve this problem, production of synthetic natural gas (SNG) from synthetic gas (CO and H2) via methanation process is one of the essential alternatives [2]. Therefore, developing an efficient catalyst formethanation reaction is indispensable. Mesoporous zeolites have been reported to have superiorcatalytic performance with respect to their conventional (purely microporous) zeolites due to the combination features of intrinsic microporosity with an auxiliary mesopore network of inter- or intracrystalline nature [3, 4]. In this study, mesoporous ZSM5 (mZSM5) and a series of metal-promoted mZSM5 for CO methanation were prepared by dual templating and impregnation methods, respectively. The physical properties of the catalysts were characterized with X-ray diffraction (XRD), nitrogen physisorption and Field Emission Scanning Electron Microscopy (FESEM). The catalytic CO methanation was performed on metal-promoted mZSM5 at 423-723 K under atmospheric pressure in the presence of H2. The result showed that the catalytic performance of CO methanation followed the order: Rh/mZSM5 >Co/mZSM5 > Pd/mZSM5 > Zn/mZSM5 at 723 K. The highest activity was observed on Rh/mZSM5 with conversion and selectivity of 94.7% and 86.6%, respectively. This study showed that the addition of metal on mZSM5 can significantly improve the catalytic activity on CO methanation

Isomerization of C5-C7 linear alkanes over WO<inf>3</inf>-ZRO<inf>2</inf> under helium atmosphere

The effect of WO3 on the properties and catalytic isomerization of C5-C7 linear alkanes over ZrO2 was studied under helium atmosphere. The WO3-ZrO2 was prepared by impregnation of Zr(OH)4 with an aqueous (NH4)6[H2W12O40], followed by calcination at 1093 K for 3 h in air. The amount WO3 was 10 wt%. XRD and BET studies showed that the introduction of WO3 stabilizes the tetragonal phase of ZrO2, leading to larger surface area and stronger acidity of ZrO2. Pyridine FTIR study verified the interaction of WO3 with ZrO2 formed strong Lewis and Bronsted acid sites. The presence of WO3 increased the catalytic isomerization of C5-C7 linear alkanes. The conversion of C5, C6 and C7 reached 1.3, 2.6 and 5.1 %, respectively. While the selectivity of isopentane, isohexane and isoheptane reached 15.6, 20.5 and 19.5 %, respectively. The high activity of WO3-ZrO2 was due to the ability of WO3 to adsorb and dissociate linear alkane to form hydrogen and alkane radical in which the atomic hydrogen underwent to the formation of protonic acid sites and hydride. The presence of protonic acid sites and hydride determined the activity of WO3-ZrO

Mercury(II) and arsenic(V) biosorption onto low cost biosorbent

Mercury and arsenic are the two most toxic pollutants which pose a great threat to both human health and organism security. A great deal of research over recent decades has been motivated by the requirement to lower the concentration of these heavy metals in water and the need to develop low cost techniques which can be widely applied for heavy metals remediation. In recent years, biosorption appears to be the most promising method because of its cost effective, easy regeneration of biosorbents, and possibility of metal recovery1. Inexpensive naturally occurring lignocellulosic materials such as coconut coir pith, rice straw, rice husk ash and sugarcane bagasse have been studied for heavy metal removal by several researchers2-4. These lignocellulosic biomass waste materials mainly composed of cellulose, hemicellulose and lignin. Various chemical groups exist including hydroxyl group play a critical role in the biosorption processes by cation exchange phenomena. In this work, stem fibers extracted from Musaceae family (Figure 1) as a low cost biosorbent for Hg(II) and As(V) removal was evaluated. A simple pretreatment by HCl and NaOH on the biosorbent show a great potential for sequestering both cationic and anionic heavy metal ions from aqueous solution. The performance of the biosorbent was tested by the biosorption of Hg(II) and As(V) in a batch system under varying pH, biosorbent dosage, and initial metal concentration. Biosorption of Hg(II) and As(V) ions reached equilibrium in 90 min. It was observed that the adsorption yield for both metal ions was found to be pH dependent. The maximum adsorption capacity of Hg(II) takes place at pH 7 while As(V) at pH 5. Their adsorption behaviour can be described as Langmuir isotherm with maximum adsorption capacities of 15.7 and 2.2 mg/g for Hg(II) and As(V) ions, respectively. The adsorption kinetics was best described by the pseudo-second order model. The results show that this biosorbent which belongs to the Musaceae family could be used as a low-cost material for the biosorption of Hg(II) and As(V) in water treatment

Multi-walled carbon nanotubes improve the physicochemical properties of mesostructured silica nanoparticles for efficient adsorption of methylene blue

Carbon nanotubes (CNTs) have attracted great attention in nanoscale science and technology due to their unique optical, electronic a nd mechanical properties 1 . Besides, mesostructured silica nanoparticles (MSN) have become effective adsorbents owe to its high surface area and pore size which is essential to adsorb wide range of organic pollutant 2-4 . Modification of CNT with MSN may enhance the dispersion properties and adsorption capacities from their singles. In this study, a series of carbon nanotubes–mesostructured silica nanoparticles (CNT–MSN) composites were prepared by a simple sol-gel method with 1, 3 and 5 wt.% loading of CNT. The composites then calcined to remove surfactants (Scheme 1). Their surface properties were characterized by XRD, N 2 physisorption, TEM and FTIR, while the adsorption performance of the CNT–MSN composites were evaluated on the adsorption of methylene blue (MB) under varying pH (2–11), adsorbent dosage (0.05–0.5 g L - 1 ), initial MB concentration (5–100 mg L -1 ) and temperature (303-323 K). The increasing CNT loading into MSN were found to improve the physicochemical properties of the material and led to an enhanced adsorptivity for MB. N 2 physisorption measurements revealed the developmen t of a bimodal pore structure that increased the pore size, pore volume and surface area. The best conditions were achieved at pH 8, 0.05 g L -1 CNT–MSN dosage, 100 mg L -1 MB concentration and 303 K. The maximum adsorption capacity re ached for 5 wt.% CNT- MSN was 524 mg g -1 . The equilibrium data were evaluated using the Langmuir and Freundlich isotherm models, with the Langmuir model affording the best fit to the adsorption data. The adsorption kinetics was best described by the pseudo-first order model. Thermodynamic studies showed that the adsorption process was spontaneous, exothermic and occur through physisorption mechanism. Therefore, CNT-MSN is believed to be a promising adsorbent for dye removal as well as removal of wide range wastewater

Study on anti-quorum sensing potentials and phytochemical constituents of Euphorbia hirta

Euphorbia hirta is an annual broad-leaved herb and widely used as traditional medicine to treat various ailments. This herb was tested on the anti quorum sensing (anti-QS) potentials in fresh (edible or macerated) forms and acetone extracts via biomonitor strain Chromabacterium violaceum (ATCC 12472). The biomonitor strain has an ability to produce purple pigment (violacein) under QS-control. The different parts of E. hirta extracts were then subjected to preliminary phytochemical screening using standard procedures and finally analyzed by Gas Chromatography-Mass Spectrometry (GC-MS). Preliminary screening on fresh parts of this herb revealed that leaves exhibited the highest anti-QS activities towards C. violaceum. The results also exhibited the wide variation in the anti-QS activities on whole plants, flowers, stems, leaves and roots of E. hirta from acetone extraction. The highest anti-QS activities were recorded by leaves and flowers extracts as the lowest of minimum QS inhibition concentration values (1.8906 mg/ml) were indicated by both extracts respectively. Phytochemical screening of E. hirta extracts revealed the presence of carbohydrates, lipids, protein, flavonoids, alkaloids, saponins, resins, steroids, acidic compounds, tannins, glycosides, phenols and terpenoids. The quantitave phytochemical assays via GC-MS indicated that this herb rich with fatty acids, terpenoids and phenolic compounds. Keywords: Euphorbia hirta, Chromabacterium violaceum, anti-quorum sensing, phytochemical assays

Heterogeneous catalyst application in biodiesel production: Needs to focus on cost effective and reusable catalysts

Uses of heterogeneous catalyst in bio-energy production also refer to as green energy has been in existence and well researched. Majority of recent heterogeneous catalysts produced focus on optimizing yield of biodiesel from a single feedstock without concerted efforts been made to consider the cost of production. They are mostly developed and produced from synthetic chemicals with their attendants high cost of production. The present review summarizes the needs to produce heterogeneous solid catalyst from wastes and natural resources like clay which is available in all parts of the world

Heterogeneous catalyst screening for biodiesel production from Moringa oil

The production of biodiesel as an alternative to fossil fuels has gained world interest nowadays due to global energy crisis and environmental awareness. Biodiesel is the preferred choice because it is environmental friendly as it decreases the possibility of acid rain and greenhouse effect by reducing the emission amount of COx, SOx and hydrocarbons that are incompletely burned during fuel combustion compared to diesel1. The strict regulations made by the environmental protection agency (EPA) to reduce the noxious emissions and the governmental legislations have motivated the biodiesel industry to formulate the new makeup diesel/biodiesel blends (B10 and B20)2. According to research by US Geological Oil and Gas Journal (1995-2000), Malaysia petroleum resources only can last for less than 50 more years3. Despite new oil reservoir discoveries in areas such as the Gulf of Mexico and the Tupi and Guara fields off South-East Brazil, Sudan, the Caspian Sea, Sakhalin, and in the Artic4, fossil fuels is no longer reliable as it is expensive and depleting sources. Biodiesel sources are renewable as it can be produced from vegetable oil, tallow, lard and waste cooking oil5. Vegetable oil can be categorized into two, edible and non-edible. Numerous research of biodiesel has been made using edible feedstock like palm, soybean, and sunflower oils. However, considering that edible vegetable oils are expensive, researchers has prompted to establish a cheap feedstock for biodiesel from non-edible crops. This study reports a catalyst screening process for biodiesel production from Moringa oil via transesterification process using various heterogeneous catalysts with methanol. The reaction condition is fixed throughout the process which are 3wt.% catalyst loading, 9:1 methanol to oil ratio, reaction temperature of 60oC and 60 min reaction duration to determine the best catalyst for the biodiesel conversion from Moringa oil