Noor Asmawati Mohd Zabidi

Catalytic conversion of palm oil over mesoporous aluminosilicate MCM-41 for the production of liquid hydrocarbon fuels

The catalytic cracking of palm oil to liquid hydrocarbon fuels was studied in a fixed bed micro-reactor operated at atmospheric pressure, reaction temperature of 723 K and weight hourly space velocity (WHSV) of 2.5 h−1 over the synthesized mesoporous molecular sieve MCM-41 materials. Mesoporous aluminosilicate with Si/Al ratio of 50 was synthesized using the hydrothermal method. Different pore sizes were obtained by changing the type of template and organic directing agent (ODA) used. The synthesized materials were characterized using various analytical methods such as X-ray powder diffraction (XRD), BET surface area, inductive coupled plasma (ICP), MAS NMR, FTIR and temperature-programmed desorption (TPD). The materials exhibit a crystalline structure of MCM-41 mesoporous molecular sieves with surface area varyng from 550 to 1200 m2/g and an average pore size (APS) ranging from 1.8 to 2.8 nm. The synthesized MCM-41 catalysts show high activity for palm oil cracking. The conversion of palm kernel oil, lower-molecular-weight oil, was higher as compared to higher-molecular-weight, palm olein oil. MCM-41 materials were selective for the formation of linear hydrocarbons, particularly, C13 when palm kernel oil was used and C17 when palm olein oil was fed. The yield of liquid product decreased with the increase of surface area of the catalyst. The gasoline selectivity increased whereas diesel selectivity decreased with the conversion of palm oil.

Correlation between Fischer-Tropsch catalytic activity and composition of catalysts

This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on alumina. The catalysts were prepared by a wet impregnation method. Samples were characterized using temperature-programmed reduction (TPR), temperature-programmed oxidation (TPO), CO-chemisorption, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM-EDX) and N2-adsorption analysis. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K and 1 atm, with H2/CO = 2 v/v and space velocity, SV = 12L/g.h. The physicochemical properties and the FTS activity of the bimetallic catalysts were analyzed and compared with those of monometallic cobalt and iron catalysts at similar operating conditions.H2-TPR analysis of cobalt catalyst indicated three temperature regions at 506°C (low), 650°C (medium) and 731°C (high). The incorporation of iron up to 30% into cobalt catalysts increased the reduction, CO chemisorption and number of cobalt active sites of the catalyst while an opposite trend was observed for the iron-riched bimetallic catalysts. The CO conversion was 6.3% and 4.6%, over the monometallic cobalt and iron catalysts, respectively. Bimetallic catalysts enhanced the CO conversion. Amongst the catalysts studied, bimetallic catalyst with the composition of 70Co30Fe showed the highest CO conversion (8.1%) while exhibiting the same product selectivity as that of monometallic Co catalyst. Monometallic iron catalyst showed the lowest selectivity for C5+ hydrocarbons (1.6%).

Development of niobium-promoted cobalt catalysts on carbon nanotubes for Fischer-Tropsch synthesis

Abstract Cobalt-based catalysts were prepared by a wet impregnation method on carbon nanotubes (CNTs) support and promoted with niobium. Samples were characterized by nitrogen adsorption, TEM, XRD, TPR, TPO and H2-TPD. Addition of niobium increased the dispersion of cobalt but decreased the catalysts reducibility. Fischer-Tropsch synthesis (FTS) was carried out in a fixed-bed microreactor at 543 K, 1 atm and H2/CO = 2 for 5 h. Addition of niobium enhanced the C5+ hydrocarbons selectivity by 39% and reduced methane selectivity by 59%. These effects were more pronounced for 0.04%Nb/Co/CNTs catalyst, compared with those observed for other niobium compositions.

Effect of niobium promoters on iron-based catalysts for Fischer-Tropsch reaction

Abstract Niobium-promoted Fe/CNT catalysts were prepared using the wet impregnation method. The samples were characterized by nitrogen adsorption, H 2 -TPR, TPD, XRD and TEM. The Fischer-Tropsch Synthesis (FTS) was carried out in a fixed-bed microreactor at 220°C, 1 atm and H 2 /CO=2 for 5 h. Addition of niobium into Fe/CNTs increased the dispersion, decreased the average size of the iron oxide nanoparticles and the catalyst reducibility. The niobium-promoted Fe catalyst resulted in appreciable increase in the selectivity of C 5+ hydrocarbons and suppressed methane formation. These effects were more pronounced for the 0.04%Nb/Fe/CNT catalyst, compared to those observed from other niobium compositions. The 0.04%Nb/Fe/CNT catalyst enhanced the C 5+ hydrocarbons selectivity by a factor of 67.5% and reduced the methane selectivity by a factor of 59.2%.

Synthesis of Cobalt Nano Particles on Silica Support Using the Strong Electrostatic Adsorption (SEA) Method

Supported cobalt is one of the common catalysts used in Fischer-Tropsch synthesis (FTS). Strong electrostatic adsorption (SEA) was employed to synthesize cobalt nano particles supported on silica. Cobalt nitrate was used as the catalyst precursor and non-porous silica spheres, which were synthesized using the modified Stöber method, were used as a catalyst support. Point of zero charge (PZC) for silica was determined using equilibrium pH at high oxide loading (EpHL) method. The optimum pH was determined by measuring cobalt uptake versus pH. High cobalt uptake at basic pH and low cobalt uptake at acidic pH indicates electrostatic interaction between the cobalt complexes in the precursor solution and the hydroxyl group on the support’s surface. Catalysts prepared at optimum pH were characterized using TPR, XPS and TEM. TPR shows reduction peak at high temperature (587°C) indicating strong interaction between cobalt and silica support. XPS shows presence of Co2+ species on the surface. TEM images of the Co/SiO2 at 5 wt% and 10 wt% cobalt loadings show fairly well-dispersed cobalt oxide nano particles on the spherical silica support with narrow particle size distribution. The findings suggest that SEA was deemed a suitable method to prepare supported cobalt catalysts.

Effects of Nb Promoter on the Properties of Cu/ZnO/SBA-15 Catalyst and Performance in Methanol Production

Hydrogenation of CO2 provides an alternative route for methanol production and attractive option for CO2 utilization. The present work investigates the synthesis of Cu-based catalyst on mesoporous silica (SBA-15) and promotion of the Cu-based catalyst with niobium (Nb). The addition of Nb promoter enhanced the reducibility and dispersion of the active sites as well as increased the BET and Cu surface areas. The performance of the synthesized catalyst in the hydrogenation of CO2 was evaluated in a fixed-bed microreactor at 523K, 22.5bar and H2/CO2 of 3. The CO2 conversion using the Cu/ZnO/SBA-15 catalyst was 14.2 % and increased to 17.1% on the Nb-promoted catalyst. The yield of methanol obtained using the un-promoted Cu-based catalyst was 51.4 g/h.gcat and it increased to 143 g/h.gcat over the Nb-promoted catalyst.

The role of support morphology on the performance of Cu/ZnO-catalyst for hydrogenation of CO2 to methanol

The effects of SBA-15 support morphology on the activity of Cu/ZnO catalyst in the hydrogenation of CO2 to methanol was investigated. In the hydrogenation of CO2 to methanol at 210°C, 2.25 MPa, H2/CO2 ratio of three remarkable difference was obtained using Cu/ZnO catalyst supported on SBA-15 with different morphology. The catalysts were characterized using N2-adsorption, field emission scanning microscopy (FESEM/EDX), transmission electron microscopy (HRTEM), and temperature-programmed reduction (TPR). Characterization of the catalyst showed that support morphology, surface area, metals dispersion, and reducibility influenced the catalytic performance. On the fiber-shaped SBA-15, copper dispersion was 29 % whereas on the spherical-shaped SBA-15, the dispersion was 20 %. The experimental results showed that the catalyst supported over fiber-shaped SBA-15 exhibit higher CO2 conversion (13.96 %) and methanol selectivity (91.32 %) compare to catalyst supported over spherical-shaped SBA-15.

Influence of Acid and Thermal Treatments on Properties of Carbon Nanotubes

The application of carbon nanotubes as a catalyst support has received considerable attention recently. The influence of acid and thermal treatments on the properties of multi-walled carbon nanotubes (MWCNTs) is presented in this paper. MWCNTs were treated with 65 wt% HNO3 at the 120 °C for 14 h in order to open the caps and introduce functional groups on the MWCNTs. Then thermal treatment was carried out at 600, 700, 800, 900 °C for 3 h in flowing Ar gas in a tubular furnace. The MWCNTs were characterized by N2- adsorption, FESEM and Raman spectroscopy. The thermal treatment resulted in slight morphological changes of the MWCNTs. The acid and thermal treatments also increased the BET surface areas and pore volumes of the MWCNTs.

Synthesis and Characterization of Bimetallic Fe/Co Nanocatalyst on CNTs for Fischer-Tropsch Reaction

Cobalt and iron are common catalysts used in the Fischer-Tropsch (FT) reaction. This paper presents the synthesis and characterization of monometallic and bimetallic cobalt and iron nanoparticles supported on carbon nanotubes (CNTs). The CNTs-supported nanocatalysts were synthesized by a wet impregnation method at various ratios of Fe:Co. The physicochemical properties of the samples were analyzed by H2-temperature programmed reduction (TPR), CO and H2-chemisorption analyses, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis. The effects of incorporation of Fe into Co on the physicochemical properties of Co/CNTs in terms of degree of reduction, CO and H2 chemisorptions and morphologies were investigated. TEM showed that metal nanoparticles were well dispersed on the external surface and inside the CNTs. For monometallic Co/CNTs and Fe/CNTs, the average metal particle size was 5±1 nm and 6±1 nm, respectively. For the bimetallic 70Co30Fe/CNTs nanocatalysts, the average particle size was found to be 4±1 nm. Metal particles attached to the outer walls were bigger than the ones inside the CNTs. H2-TPR analysis of Co/CNTs indicated two temperature regions at 330°C (low temperature) and 491°C (high temperature). The incorporation of iron into cobalt nanocatalysts of up to 30 % of the total metal loading enhanced the catalyst’s H2 and CO chemisorptions capacities and reducibility.

The influence of catalyst factors for sustainable production of hydrocarbons via Fischer-Tropsch synthesis

Abstract Fischer-Tropsch synthesis (FTS) is a process which catalytically converts syngas (H2 and CO) into clean hydrocarbon fuels. Syngas can be derived from non-petroleum feed stocks such as coal, natural gas or biomass. Increasing the quality of products by development of novel catalysts with high activity and selectivity is desirable in FTS reaction. This article reviews and summarizes recent developments in FTS catalysts and the effects of key factors such as active metals, catalyst supports and promoters on feedstock conversion and product selectivities.