n-Heptane isomerization over platinum and phosphorus supported on modified molybdenum oxide-mesoporous silica

Catalytic isomerization of n-alkanes into the corresponding branched isomers is an important reaction to produce clean fuel with high quality. Therefore, continuing studies on efficient catalysts for isomerization have been conducted in recent years. In this study, mesostructured silica nanoparticles (MSN) were mixed physically with platinum (Pt) and molybdenum oxide (MoO3) to prepare Pt/MSN and MoO3/MSN for n-heptane isomerization. Besides, the effect of support was studied by employing the bicontinuous concentric lamellar silica (KCC-1) which was prepared by microwaveassisted microemulsion, as MoO3 support (MoO3/KCC-1). In order to improve the catalytic activity, the effect of phosphorus (P) loading was carried out by impregnation of MoO3/KCC-1 with phosphoric acid to form P/MoO3/KCC-1. The catalysts were characterized using x-ray diffraction, surface area analysis, scanning electron microscopy, hydrogen-temperature programmed reduction, nuclear magnetic resonance, ultraviolet-visible, Fourier transform infrared (FTIR) and electron spin resonance (ESR) spectroscopies. High activity of n-heptane isomerization was observed on MoO3/MSN compared to the Pt/MSN in the presence of hydrogen at 350 °C, with yield of mono- and di-branched iso-heptane reaching 36.6% and 6.8%, respectively. ESR and FTIR studies indicated that the high activity and stability of MoO3/MSN could be attributed to the dissociative-adsorption of molecular hydrogen to form atomic hydrogen, which subsequently formed active (MoOx)-(Hy)+. The interaction of Pt/MSN and molecular hydrogen formed Pt-H, which was not active in n-heptane isomerization. In comparison, the MoO3/KCC-1 possessed low activation energy (28.1 kJ/mol), as well as gave higher yield of isomers (42.2%) compared to MoO3/MSN (35.8%). The result was related to the unique morphology of silica KCC- 1, which allowed high accessibility of bulky mass reactant to the active sites. The P/MoO3/KCC-1 showed a decrease in the Brønsted acid while new Lewis acidic centers were formed at 1624 cm-1 and 1587 cm-1, as observed by 2,6-lutidine adsorbed infrared. High yield of isomers obtained by P/MoO3/KCC-1 was related to the participation of the acidic centers at 1624 cm-1 and 1587 cm-1, in the formation of protons by trapping electrons, as well as high accessibility to active (MoOx)-(Hy)+. The ANOVA analysis indicated that the reaction temperature was the prominent significant variable in the production of isomers. Based on the optimization experiment, 44.9% yield of isomers was obtained at the optimum condition of 311 °C, treated at 464 °C for 6 h. This study highlighted the potential of modified mesoporous silica in the catalysis research, especially for linear alkane isomerization

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

Optimization of boron dispersion on fibrous-silica-nickel catalyst for enhanced CO2 hydrogenation to methane

There are numerous reports regarding boron-containing catalysts for hydrogen-related reactions from CO2 including dry reforming of methane and methanation. Besides enhancing the productivity, boron also improved nickel activity and stability. However, the detailed mechanistic study, particularly in explaining the starring role of boron in the enhanced reactions, is still lacking. Thus, herein we loaded boron on fibrous-silica-nickel and investigated their physicochemical properties and mechanistic route by means of in-situ FTIR for enhanced CO2 methanation. It was found that the appropriate dispersion of boron surrounds the nickel particles is an important factor to improve the adsorption of CO2 before interacting with split hydrogen atom from the nickel sides to form intermediates which are subsequently dehydrated, and then serial hydrogenation gave the final product of methane. Boron also accelerated the methanation and restricted coke formation. A hybrid approach on optimization via a face-centered central composite design and a response surface methodology showed that reaction using H2/CO2 ratio of 6, GHSV of 10,500 mL g−1 h−1, at 500 °C gave the highest percentage of CH4 of 84.3%. To indicate the error, the predicted values were compared to the experimental values, yielding an accurately minimal error ranging from 0 to 11%. As a result, the empirical models generated for CO2 hydrogenation to methane were reasonably accurate, with all actual values for the confirmation runs fitting within the 94% prediction interval

Platinum and molybdenum oxide supported on mesostructured silica nanoparticles for n-pentane and cyclohexane isomerization

Alkane isomerization into its equivalent branched isomers has gained numerous attention as a reaction to obtain high quality fuel. In this study, platinum and molybdenum oxide supported on mesostructured silica nanoparticles (Pt/MoO3/MSN) was prepared via impregnation method and tested for n-pentane and cyclohexane isomerization. The catalyst was characterized by using X-ray diffraction (XRD), nitrogen (N2) physisorption, and pyridine Fourier-transform infrared (pyridine-FTIR) spectroscopy. The IR result revealed that the addition of Pt and MoO3 into MSN formed different strength of Lewis and Brönsted acid sites. It was observed that the catalyst possessed strong acid sites and several numbers of relatively weak Lewis and Brönsted acid sites. Pt/MoO3/MSN was catalytically active towards n-pentane and cyclohexane isomerization with conversion of 63 and 87%, respectively, at 300 °C. It was proposed that the addition of Pt might assist the generation of active protonic acid sites from molecular hydrogen via the mechanism of hydrogen spillover and hence improve isomerization reaction

Utilization of a cost effective Lapindo mud catalyst derived from eruption waste for transesterification of waste oils

The most remarkable property of heterogeneous-catalyzed transesterification is its recyclability which surpass the issue by homogenous catalyst. Lapindo mud (LM), an eruption waste from Indonesia, was treated into an active catalyst for transesterification. LM is reasonably tolerant to FFA, as no visible soap layer was observed during transesterification of high acid value WCO (20.723 mgKOH/g) and POME (120.48 mgKOH/g) with FAME yield of 96.6% and 91.69%, respectively. The reaction conditions obtained for both reaction are mild and comparable to currently reported conditions except LM effectively accelerated the transesterification process of WCO. Reusability test showed that LM exhibited a stable performance with less than 10% declined in FAME after the seventh run with 95% catalyst recovery. Kinetic analysis showed that both WCO and POME transesterification fitted well with Langmuir-Hishelwood first order reaction. The activation energy for WCO and POME transesterification were 55.7 and 59.75 kJ/mol. This findings shows the possibility of LM as a catalyst in general heterogeneous reaction and particularly for transesterification to produce FAME

Exploration of reaction mechanisms on the plastic waste polyethylene terephthalate (PET) dissolved in phenol steam reforming reaction to produce hydrogen and valuable liquid fuels

The recycling of plastic waste is a good idea for countries which concern air pollution, CO2 emission, and public health. In this research article, PET, as one of the significant plastic waste, was selected to dissolve in phenol for value‐added liquid fuels and hydrogen gas production. This research aims to provide insight into the mechanism of PET waste and phenol steam reforming reaction. The catalytic steam reforming of PET dissolved in phenol employing Ni-Pt/Al-Ti catalyst was conducted in a fixed bed reactor. The reaction test illustrated that Ni-Pt/Al-Ti catalyst possesses high activity and stability in a long time on stream experiment. It was found that valuable liquid fuels such as styrene, acetic acid, benzoic, benzene, and many other components successfully produced from the PET-phenol steam reforming reaction. It was found that during the catalytic reforming of PET, several types of reactions such as dehydrogenation reaction, thermal cracking, steam reforming, water gas shift reaction, carbenium ion reaction, free radical reaction, dihydroxylation reaction, and coke formation occurred

Enhanced CO2 methanation at mild temperature on Ni/zeolite from kaolin: effect of metal–support interface

Catalytic CO2 hydrogenation to CH4 offers a viable route for CO2 conversion into carbon feedstock. The research aimed to enhance CO2 conversion at low temperature and to increase the stability of Ni catalysts using zeolite as a support. NaZSM-5 (MFI), NaA (LTA), NaY (FAU), and NaBEA (BEA) synthesized from kaolin were impregnated with 15% Ni nanoparticles in order to elucidate the effect of surface area, porosity and basicity of the zeolite in increasing Ni activity at mild temperature of ~200 °C. A highly dispersed Ni catalyst was produced on high surface area NaY meanwhile the mesoporosity of ZSM-5 has no significant effect in improving Ni dispersion. However, the important role of zeolite mesoporosity was observed on the stability of the catalyst. Premature deactivation of Ni/NaA within 10 h was due to the relatively small micropore size that restricted the CO2 diffusion, meanwhile Ni/NaZSM-5 with a large mesopore size exhibited catalytic stability for 40 h of reaction. Zeolite NaY enhanced Ni activity at 200 °C to give 21% conversion with 100% CH4 selectivity. In situ FTIR analysis showed the formation of hydrogen carbonate species and formate intermediates at low temperatures on Ni/NaY, which implied the efficiency of electron transfer from the basic sites of NaY during CO2 reduction. The combination of Ni/NaY interfacial interaction and NaY surface basicity promoted CO2 methanation reaction at low temperature

Strategies for introducing titania onto mesostructured silica nanoparticles targeting enhanced photocatalytic activity of visible-light-responsive Ti-MSN catalysts

Titanium-mesostructured silica nanoparticles (Ti-MSN) catalysts which are excellent photocatalytic materials for the environment were prepared by supporting mesostructured silica nanoparticles (MSNs) with titanium species synthesized by three different approaches: microwave and in situ and ex situ electrochemical methods, denoted as Ti-MSN-M, Ti-MSN-I, and Ti-MSN-E, respectively. The physicochemical properties of the catalysts were investigated via XRD, 29Si NMR, N2 adsorption-desorption, FTIR, ESR, and UV-DRS analyses. Characterization results revealed that the introduction of mesoporous titania nanoparticles (MTNs) prepared by the microwave method onto MSNs (Ti-MSN-M) did not significantly affect the silica framework. However, the silica network in the Ti-MSN-I and Ti-MSN-E was rather disrupted, particularly for the former catalyst, due to the desilication accompanied by isomorphous substitution of Ti in the MSN framework to form Si[sbnd]O[sbnd]Ti bonds. Ti was also found to be exchanged with the terminal hydroxyl groups of all catalysts to form the Si[sbnd]O[sbnd]Ti bonds. The addition of Ti species onto MSNs also increased the number of oxygen vacancies (Vo) and metal defect sites. Photocatalytic testing on the decolorization of Congo red (CR) resulted in the following order: Ti-MSN-I (94%) > Ti-MSN-M (90%) > Ti-MSN-E (34%). The Vo and metal defect sites were responsible in lowering the band gap of catalysts and decreasing the electron–hole recombination, while the great numbers of Si[sbnd]O[sbnd]Ti bonds as well as large surface area and pore volume increased the active sites and offered a good surface contact with light to enhance the activity of catalysts. A kinetic study demonstrated that the photodegradation followed the pseudo-first-order Langmuir-Hinshelwood model. Ti-MSN-I and Ti-MSN-M maintained their activities for up to five runs without serious catalyst deactivation, indicating their potential for the degradation of dye in wastewater. Mineralization measurements of CR by TOC and BOD5 analyses after 3 h of contact time were 85.7% and 87.6% using Ti-MSN-M, while 83.7% and 80.3% using Ti-MSN-I, respectively. Optimization by response surface methodology showed that the catalyst dosage, pH, and TiO2 loading were the significant factors in the decolorization of CR. This study demonstrated that these two green technologies; electrochemical and MW have a great potential to be used in synthesis of various advanced materials for greener and more sustainable processes