Deoxygenation Of Methyl Laurate Research Articles

Deoxygenation of methyl laurate: influence of cation and mesoporosity in fau zeolites

Catalytic activity of materials prepared by means of sodium ion-exchange by potassium and cesium in NaY zeolite, was studied in the deoxygenation of methyl laurate, as biodiesel model compound. The increase of the Ion-exchange produced a basicity increase that leads to a lower deactivation in the deoxygenation of methyl laurate, reaching a steady conversion of about 92% for 4 h (time on stream, TOS) with the CsKY zeolite. However, the potassium ion exchange leaded to higher production of bio-hydrocarbons, especially unsaturated (96% of the C10, C11 and C12 production), with higher production of C11 by means of decarbonylation. Furthermore, mesoporosity on the KY zeolite was generated, using SDBS (sodium dodecylbenzene sulphonate) during the synthesis, with the aim of increasing its capacity to process bulky molecules. The presence of mesoporosity in the potassium zeolite allowed a higher tolerance to deactivation maintaining a steady conversion of about 90% for 4 h TOS. The yield to desirable products (C10 to C12 hydrocarbons) was about 37%. Therefore, biofuel upgrading can be carried out using potassium Y zeolite with mesoporosity.

Synergistic effects between Cu and Ni species in NiCu/γ-Al2O3 catalysts for hydrodeoxygenation of methyl laurate

Cu was introduced into Ni/γ-Al2O3 to prepare mesoporous NixCuy/γ-Al2O3 catalysts with different Ni and Cu contents. H2-TPR, XRD, BET, H2-TPD, and in-situ XPS were used to study the physicochemical properties of the prepared NixCuy/γ-Al2O3 catalysts. The catalytic performances of NixCuy/γ-Al2O3 catalysts were evaluated by methyl laurate catalytic hydrodeoxygenation (HDO) reaction. The NixCuyO/γ-Al2O3 precursors can be reduced to Ni0, Cu0, and NiCu alloy active species by H2 at 420°C. Formed NiCu alloy can effectively promote the electronic effect between Ni and Cu, and enhance the adsorption and activation abilities of the corresponding catalyst for the reactant molecules. The Ni active sites preferentially catalyzes the decarbonylation/carboxyl (DCO) reaction in the deoxygenation of methyl laurate, while the HDO pathway is predominant on the Cu active sites. The deoxygenation pathway obviously changes from DCO to HDO at the mole ratio of Ni/Cu lower than 3/7, and the main deoxygenation products change from C11 to C12 alkane. At the H2/Oil ratio of 500N, the space velocity (SV) of 1.5 h−1, H2 pressure(P) of 2 MPa, and the reaction temperature of 380°C, the Ni3Cu7/γ-Al2O3 catalyst shows the best methyl laurate DCO properties. And methyl laurate conversion and the main deoxygenation products C11 alkane selectivity can reach 98.3 and 87.4%, respectively. Moreover, Ni3Cu7/γ-Al2O3 catalyst also exhibits good stability.

Remarkably reducing carbon loss and H2 consumption on Ni–Ga intermetallic compounds in deoxygenation of methyl esters to hydrocarbons

Abstract Ni–Ga alloy (Ni/Ga atomic ratio of 8), Ni3Ga and Ni5Ga3 intermetallic compounds (IMCs) catalysts were prepared from Ni–Mg-Al-Ga layered double hydroxides (LDHs) for the deoxygenation of methyl esters to hydrocarbons. In the alloy and IMCs, the presence of Ga reduced the surface Ni atom density, and the charge transfer from Ga to Ni increased the electron density of Ni. In the deoxygenation of methyl laurate, the Ni catalyst gave a complete hydrogenolysis of methyl laurate to CH4 at 330 °C and 3.0 MPa, while the presence of Ga promoted the HDO pathway and suppressed C C bond hydrogenolysis and methanation. The Ni5Ga3 catalyst exhibited the best desired performance. Even at 400 °C, it gave the yield of C11 and C12 hydrocarbons of ∼99%, and the selectivity to CH4 (SCH4) was only 2.4%. In the deoxygenation of methyl octanoate and methyl palmitate, the Ni5Ga3 catalyst also gave the yield of hydrocarbons above 95%. Reactivity evaluation and methyl propionate-TPD and TPSR results indicate that the C OCH3 bond instead of the O CH3 one was cleaved on both Ni and bimetallic Ni–Ga catalysts. It is highlighted that methanol, derived from the C OCH3 bond hydrogenolysis, mainly decomposed to CO and H2 on IMCs, while it was converted to methane on metallic Ni and alloy. It is of great significance that H2 could be yielded from the methyl ester itself. In short, the utilization of Ni–Ga IMCs can effectively reduce carbon loss and H2 consumption, all of which are ascribed to the geometric and electronic effects of Ga.

Deoxygenation of methyl laurate as a model compound on Ni-Zn alloy and intermetallic compound catalysts: Geometric and electronic effects of oxophilic Zn

A series of Ni-Zn bimetallic catalysts with different Ni/Zn atomic ratios were prepared from layered double hydroxides (LDHs) with an atomic ratio of 3 between divalent (Ni2+ and Zn2+) and trivalent ions (Al3+). After the mixed oxides derived from calcined LDHs were reduced with H2 at 650°C, Ni-rich alloy with a fcc structure was synthesized at Ni/Zn ratios≥2, while an Ni-Zn intermetallic compound (IMC) with a tetragonal L10 structure was generated at Ni/Zn atomic ratios of 1 and 1/2, and an Ni-Zn IMC was generated with a cubic structure at Ni/Zn ratio of 1/8. HAADF-STEM-EDS, H2 chemisorption and magnetic measurements showed that Ni and Zn atoms were uniformly distributed in catalysts, and the ensembles of Ni atoms decreased with decreasing Ni/Zn ratios. XPS and CO-TPD characterizations revealed a charge transfer from Ni to Zn. In the deoxygenation of methyl laurate as a model compound to diesel-like hydrocarbons, although the addition of Zn reduced the conversion of methyl laurate, mostly due to the decrease in Ni content, a synergetic effect between Ni and Zn was suggested to enhance turnover frequency (TOF), and higher TOFs were obtained on the catalysts with Ni/Zn ratios of 1/1 and 1/2. Because of the high oxophilicity of Zn, this synergetic effect also promoted the hydrodeoxygenation pathway. With decreasing Ni/Zn ratios, the molar ratio between C11 hydrocarbons and both C12 hydrocarbons and oxygenates decreased. Particularly, it was smaller than 0.2 on Ni-Zn IMC when the reaction temperature was 330°C, and much lower than that of 60.5 on the metallic Ni catalyst. Compared with metallic Ni, Ni-rich alloys and IMCs (especially IMCs) showed lower reactivity for CC bond hydrogenolysis and CO/CO2 methanation, which was more remarkable with decreasing Ni/Zn atomic ratios and increasing reaction temperatures. Particularly, when the conversion of methyl laurate was close to 100% at 400°C, the metallic Ni catalyst dominatingly gave methane, which was derived from CC bond hydrogenolysis as well as complete methanation of CO/CO2, and the total selectivity to C11 and C12 (i.e., SC11+C12) was only 1.1%. However, when the Ni/Zn atomic ratio was≤2/1, SC11+C12 reached as high as 96.2%, and the molar ratio between (CO+CO2) and C11 hydrocarbons was still larger than 1.0, i.e., CC bond hydrogenolysis and methanation were remarkably suppressed on Ni-Zn IMC catalysts. We suggest that the role of Zn is ascribed to its geometric and electronic modification of Ni in the alloy and IMC.

Deoxygenation of Methyl Laurate as a Model Compound to Hydrocarbons on Ni2P/SiO2, Ni2P/MCM-41, and Ni2P/SBA-15 Catalysts with Different Dispersions

The deoxygenation of methyl laurate as a model compound to diesel-like hydrocarbons was performed on Ni2P/SiO2, Ni2P/MCM-41, and Ni2P/SBA-15 catalysts. The effect of Ni2P dispersion on the catalyst structure and performance was investigated. The average Ni2P crystallite sizes varying from 3 to 12 nm were obtained. In correlation with the Ni/P ratio, the catalyst acid amount was mainly determined by the surplus P species. The deoxygenation was tested at 300–340 °C, 2.0 MPa, weight hourly space velocity of 10 h–1, and H2/methyl laurate ratio of 50. For different catalysts, the conversion of methyl laurate followed the different sequence from the turnover frequency (TOF). The TOF increased with the Ni2P crystallite size. The lower TOF on smaller crystallites can be attributed to the stronger interaction between Ni and P. Both hydrodeoxygenation and decarbonylation pathways occurred on the Ni2P catalysts. As indicated by the ratio between n-undecane (n-C11) and n-dodecane (n-C12) being larger than 1.0, the ma...