Atthapon Srifa

Production of bio-hydrogenated diesel by catalytic hydrotreating of palm oil over NiMoS2/γ-Al2O3 catalyst.

Catalytic hydrotreating of palm oil (refined palm olein type) to produce bio-hydrogenated diesel (BHD) was carried out in a continuous-flow fixed-bed reactor over NiMoS2/γ-Al2O3 catalyst. Effects of dominant hydrotreating parameters: temperature: 270-420°C; H2 pressure: 15-80 bar; LHSV: 0.25-5.0 h(-1); and H2/oil ratio: 250-2000 N(cm(3)/cm(3)) on the conversion, product yield, and a contribution of hydrodeoxygenation (HDO) and decarbonylation/decarboxylation (DCO/DCO2) were investigated to find the optimal hydrotreating conditions. All calculations including product yield and the contribution of HDO and DCO/DCO2 were extremely estimated based on mole balance corresponding to the fatty acid composition in feed to fully understand deoxygenation behaviors at different conditions. These analyses demonstrated that HDO, DCO, and DCO2 reactions competitively occurred at each condition, and had different optimal and limiting conditions. The differences in the hydrotreating reactions, liquid product compositions, and gas product composition were also discussed.

Catalytic behaviors of Ni/γ-Al2O3 and Co/γ-Al2O3 during the hydrodeoxygenation of palm oil

The deactivation and regeneration behaviors of Ni/γ-Al2O3 and Co/γ-Al2O3 catalysts in the hydrodeoxygenation (HDO) of palm oil were investigated at 573 K and 5 MPa in a trickle bed reactor. The catalysts were prereduced at 773 K for 3 h before the HDO experiments. The catalysts exhibited good catalytic activity (>90% yield) and remained stable for 100 h on-stream. Nevertheless, after 150 h on-stream, the product yield gradually decreased from 92.2 to 76.2% over the Ni catalyst and dramatically declined from 88.6% to ca. 56.6% over the Co catalyst. The combined decarbonylation and/or decarboxylation (DCOx) reactions were dominant over the HDO reaction when the reaction was catalyzed by the Ni catalyst. Meanwhile, the contribution of DCOx and HDO reactions was nearly comparable over the Co catalyst. The XRD and XANES analyses confirmed the partial formation of metallic nickel or cobalt after prereduction and the further in situ reduction during the HDO experiments, suggesting the coexistence of the metal and metal oxides on the catalyst surfaces. The XRD and TEM analyses revealed some sintering of the nickel and cobalt particles during the time course of reaction. Based on the TPO analysis, the carbon deposition rate on the cobalt catalyst was faster than that on the nickel catalyst and would be the major reason for the catalyst deactivation, and the sintering was the minor one. Additionally, the regeneration under air at 773 K followed by reduction in H2 at 773 K can completely restore the catalytic activity.

COx-free hydrogen production via ammonia decomposition over molybdenum nitride-based catalysts

COx-free hydrogen generation via ammonia decomposition has received much attention as an important process for fuel cell applications. In the present study, non-precious Mo nitride-based catalysts with Co, Ni, and Fe additives were synthesized by temperature-programmed reaction of the corresponding oxide precursors with NH3. N2 adsorption, X-ray diffraction (XRD), NH3-temperature programmed surface reaction (NH3-TPSR), NH3 pulse reaction, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were carried out to gain better insight into the chemical and textural properties of the catalysts. The XRD analysis confirmed the formation of the Mo2N, Co3Mo3N, Ni3Mo3N, and Fe3Mo3N phases, which act as active species for ammonia decomposition reaction. The Co3Mo3N, Ni3Mo3N, and Fe3Mo3N catalysts were more active for ammonia decomposition than the Mo2N catalysts, indicating that the Co, Ni, and Fe species promoted the reaction. The increase in particle size and the decrease in surface area by the Co, Ni, and Fe addition did not negatively affect the ammonia decomposition activity. Interestingly, the Co, Ni, and Fe addition facilitated the recombinative desorption of N atoms from the active components, resulting in the enhancement in the activity. In addition, kinetic analysis was also conducted in detail to investigate the effects of the NH3 and H2 partial pressures. The Co, Ni, and Fe addition alleviated the negative effect of the H2 poisoning on the active sites.

Heterogeneous Catalysts for Advanced Biofuel Production

The triglyceride-based feedstocks and biomass derivatives have been considered promising resources for production of advanced biofuels, namely, green diesel and biojet fuels. Among the series of deoxygenation reactions, hydrodeoxygenation is a majority in the green diesel production when utilizing the group of metal sulfides catalysts, namely, MoS2 with various doping elements. Moreover, decarbonylation is predominant over sulfur-free catalysts including noble metals, e.g., Pd and Pt, and non-precious transition metal, e.g., Ni. The decarboxylation is an interesting pathway due to unconsumed H2 reaction mechanism. As for biojet fuels, the composite of metal/metal sulfides with strong solid acids are promising approaches to catalyze hydroisomerization and cracking reactions of the straight-chain alkanes into the branch ones with proper carbon atoms. Alternatively, the alumina- and zeolite-supported metal catalysts have been extensively developed for the conversion of biomass derivatives into biojet fuels, fuel additives, and biochemical platforms. The research, development, and engineering of novel heterogeneous catalysts could be a key factor for commercialization and strong establishment of the biorefinery and biofuel industries.

Photocatalytic Hydrogen-Generation of Polyoxotungstate Nano-Clusters from Biomass

The photocatalytic reaction of polyoxotungstate, [BW12O40]5- and [SiW12O40]4-, led to the generation of hydrogen gas from biomass such as a sugarcane juice and tapioca starch under irradiation of UV light. These photoreactions were investigated in the pH dependence. The results showed that hydrogen was obtained at 2<pH<4. The photolysis of [BW12O40]5- and [SiW12O40]4- in presence of 60 ml of sugarcane juice at pH 2 level were obtained 0.15 ml and 0.51 ml of hydrogen, respectively. Especially, it was observed that the photolysis of the starch evolved oxygen without any catalysts. The oxygen contents affected to the reduced species of polyoxotungstates. Each photoreaction exhibited a different behaviour for the dependence of the amounts of catalyst. Lowering amounts of [SiW12O40]4- produced much hydrogen at pH 2 level. In contrast, lowering amounts of [BW12O40]5- could not evolve much hydrogen due to the domination of reoxidation of the reduced species by oxygen.