In this study, a Pd-based catalytic model over a nitrogen enriched fibrous Porous-Organic-Polymer (POP) is established to execute hydrodeoxygenation of various vegetable oils in producing potential large-scale renewable diesel. Here we report a cost-effective synthesis strategy for a new microporous hypercrosslinked POP through the FeCl₃ assisted Friedel–Crafts alkylation reaction, followed by fabrication of Pd⁰-NPs (2–3 nm) using a solid gas phase hydrogenation route to deliver a novel catalytic system. This catalyst (called Pd@PPN) exhibits versatile catalytic performance for different types of vegetable oils including palm oil, soybean oil, sunflower oil and rapeseed oil to furnish long chain diesel range alkanes. The catalyst is comprehensively characterized using various spectroscopic tools and it shows high stability during five runs of recycling without leaching of Pd. Our results further reveal that a direct decarbonylation (DCN) pathway of fatty acids to produce alkanes with one fewer carbon is the dominant mechanism. Under optimized conditions, using stearic acid to represent the long linear carboxylic acids in the vegetable oils, up to 90% conversion with 83% selectivity of C17-alkane has been achieved on our fabricated catalyst. Density functional theory (DFT) calculations are performed to provide insights into the electronic properties of the catalyst, the mechanistic reaction pathway, the crucial role of the catalyst surface and the product selectivity trend. The strong interaction between the corrugated polymer-frame-structure and the Pd-NPs suggests the presence of high density step sites on the fabricated Pd-NP anchored within the cage of the polymer structure. DFT calculations also reveal the strong promotional effect of step sites and charge transfer in facilitating rate-limiting steps during the decarbonylation (DCN) pathway and removal of strongly bound intermediates formed during the process, therefore explaining the high activity of the fabricated Pd@PPN catayst for the hydrodeoxygenation (HDO) conversion to produce bio-based alkane diesel.

Tar is the undesired viscous black liquid produced during the gasification of biomass. Catalytic elimination of tar is feasible and is economically promising. In the present investigation, we performed first-principles calculations (i) to elucidate the decomposition mechanism of tar on the popular nickel (Ni) catalyst and (ii) to reveal the promotional effect of boron (B) in improving the activity and stability of the Ni catalyst for tar decomposition. Being the most abundant component of tar, toluene was chosen as a model compound. On the Ni(111) surface, toluene adsorbs strongly in a bridge configuration and the activation barrier for methyl C–H dissociation is 72 kJ mol⁻¹. Toluene can further decompose on the Ni(111) surface via stepwise dehydrogenation of the methyl group. The aromatic C–H bond at the ortho position could only be activated after the complete dehydrogenation of the methyl group, which is followed by subsequent ring opening (activation barriers are 112 and 84 kJ mol⁻¹, respectively) and C–C cleavages, to generate smaller hydrocarbons. The incorporation of subsurface B into the Ni catalyst (B–Ni) results in a corrugated Ni top surface and toluene adsorbs more strongly by 11 kJ mol⁻¹ on the B–Ni catalyst than on pure Ni. Although the mechanism of toluene decomposition remains unchanged after doping with boron, the decomposition of toluene is significantly promoted on B–Ni. The activation barrier for the first methyl C–H dissociation on B–Ni is reduced to 51 kJ mol⁻¹. Subsequent methyl C–H activations are also promoted on the B–Ni catalyst, but to a smaller extent. The aromatic C–H activation is also strongly promoted (89 kJ mol⁻¹vs. 112 kJ mol⁻¹ on pure Ni). Additional calculations on stepped surface models of Ni show that the activation barriers of toluene decomposition on the B–Ni surface are very close to those on B5 and F4 step sites of pure Ni, thus suggesting that the promotional effect of B on the catalytic activity of Ni could be mainly attributed to the creation of step-like corrugations on the Ni surface. These corrugations could also inhibit the formation of graphene-like structures on B–Ni.

The effects of different mixtures of organic structure-directing agents (OSDAs) on the formation of SAPO-34 structure have been investigated. Different OSDAs, namely, triethylamine (TEA), tetraethylammonium hydroxide (TEAOH), and morpholine (Mor) and their combinations were used to synthesize SAPO-34 by a hydrothermal method. The template concentration was optimized by eliminating the competing phases to obtain the purest form of SAPO-34 phase. The as-synthesized samples were analyzed by XRD, FE-SEM/EDS, FT-IR, surface area/pore volume measurements, NH3-TPD, TG/DTA, and 29Si NMR MAS. The selection of template notably impacts the crystal size and physicochemical characteristics of as-synthesized SAPO-34. The sample prepared with 3 Mor : 3 TEA : 1 TEAOH exhibited the highest total acidity, smallest crystal size below 3 µm, and high surface area up to 697 m²/g.

SAPO-34 was prepared with a mixture of three templates containing triethylamine, tetraethylammonium hydroxide, and morpholine, which leads to unique properties for support and production cost reduction. Meanwhile, Cu/SAPO-34, Fe/SAPO-34, and Cu-Fe/SAPO-34 were prepared through the ion-exchanged method in aqueous solution and used for selective catalytic reduction (SCR) of NO_x with NH₃. The physical structure and original crystal of SAPO-34 are maintained in the catalysts. Cu-Fe/SAPO-34 catalysts exhibit high NO_x conversion in a broad temperature window, even in the presence of H₂O. The physicochemical properties of synthesized samples were further characterized by various methods, including XRD, FE-SEM, EDS, N₂ adsorption-desorption isotherms, UV-Vis-DRS spectroscopy, NH₃-TPD, H₂-TPR, and EPR. The best catalyst, 3Cu-1Fe/SAPO-34 exhibited high NO_x conversion (> 90%) in a wide temperature window of 250–600 °C, even in the presence of H₂O. In comparison with mono-metallic samples, the 3Cu-1Fe/SAPO-34 catalyst had more isolated Cu²⁺ ions and additional oligomeric Fe³⁺ active sites, which mainly contributed to the higher capacity of NH₃ and NO_x adsorption by the enhancement of the number of acid sites as well as its greater reducibility. Therefore, this synergistic effect between iron and copper in the 3Cu-1Fe/SAPO-34 catalyst prompted higher catalytic performance in more extensive temperature as well as hydrothermal stability after iron incorporation.