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2014, Vol. 23, No. 4　Online: 2014-07-24


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Xiong and coworkers in their article on pages 414–419 reported the hydrogen storage over alkali metal hydride and alkali metal hydroxide composites. They proposed that alkali metal hydroxide and hydride composite systems contain both protonic (H bonded with O) and hydridic hydrogen and their interaction results in the production of hydrogen. NaOH-NaH is only the reversible hydrogen storage system among the tested three composites. The enthalpy of dehydrogenation reaction increased with the increase of atomic number of alkali metals. The results of thermodynamic calculation are in well consistence with the experimental results.

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Design of two-stage membrane reactor for the conversion ofcoke-oven gas to H2 and CO Zhibin Yang, Yuwen Zhang, Xueguang Wang, Weizhong Ding 2014, 23(4): 411-413.  DOI: 10.1016/S2095-4956(14)60165-0 摘要 ( 6117 )   The catalyst function was achieved in two regions in an oxygen permeation membrane reactor: H2 dissociated and reacted with lattice oxygen or oxygen ions to form H2O near the membrane surface. The H2O formed could react with the residual CH4 away from the membrane surface area.

ARTICLES

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Hydrogen storage over alkali metal hydride and alkali metal hydroxide composites Pei Yu, Yong Shen Chua, Hujun Cao, Zhitao Xiong, Guotao Wu, Ping Chen 2014, 23(4): 414-419.  DOI: 10.1016/S2095-4956(14)60166-2 摘要 ( 6492 )   Alkali metal hydroxide and hydride composite systems contain both protic (H bonded with O) and hydridic hydrogen. The interaction of these two types of hydrides produces hydrogen. The enthalpy of dehydrogenation increased with the increase of atomic number of alkali metals, i.e., -23 kJ/molH2 for LiOH-LiH, 55.34 kJ/molH2 for NaOH-NaH and 222 kJ/molH2 for KOH-KH. These thermodynamic calculation results were consistent with our experimental results. H2 was released from LiOH-LiH system during ball milling. The dehydrogenation temperature of NaOH-NaH system was about 150℃; whereas KOH and KH did not interact with each other during the heating process. Instead, KH decomposed by itself. In these three systems, NaOH-NaH was the only reversible hydrogen storage system, the enthalpy of dehydrogenation was about 55.65 kJ/molH2, and the corresponding entropy was ca. 101.23 J/(molH2·K), so the temperature for releasing 1.0 bar H2 was as high as 518℃, showing unfavorable thermodynamic properties. The activation energy for hydrogen desorption of NaOH-NaH was found to be 57.87 kJ/mol, showing good kinetic properties.

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A Novel Sr2CuInO3S p-type semiconductor photocatalyst for hydrogen production under visible light irradiation Yushuai Jia, Jingxiu Yang, Dan Zhao, Hongxian Han, Can Li 2014, 23(4): 420-426.  DOI: 10.1016/S2095-4956(14)60167-4 摘要 ( 7725 )   A novel Sr2CuInO3S oxysulfide p-type semiconductor photocatalyst has been prepared by solid state reaction method and it exhibits intriguing visible light absorption properties with a bandgap of 2.3 eV. The p-type semiconductor character of the synthesized Sr2CuInO3S was confirmed by Hall efficient measurement and Mott-Schottky plot analysis. First-principles density functional theory calculations (DFT) and electrochemical measurements were performed to elucidate the electronic structure and the energy band locations. It was found that the as-synthesized Sr2CuInO3S photocatalyst has appreciate conduction and valence band positions for hydrogen and oxygen evolution, respectively. Photocatalytic hydrogen production experiments under a visible light irradiation (λ>420 nm) were carried out by loading different metal and metal-like cocatalysts on Sr2CuInO3S and Rh was found to be the best one among the tested ones.

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Chemoselective hydrogenolysis of tetrahydrofurfuryl alcohol to 1,5-pentanediol over Ir-MoOx/SiO2 catalyst Zhiqiang Wang, Boonrat Pholjaroen, Mengxia Li, Wenjun Dong, Ning Li, Aiqin Wang, Xiaodong Wang, Yu Cong, Tao Zhang 2014, 23(4): 427-434.  DOI: 10.1016/S2095-4956(14)60168-6 摘要 ( 6821 )   In this work, MoOx promoted Ir/SiO2 catalysts were prepared and used for the selective hydrogenolysis of tetrahydrofurfuryl alcohol (THFA) to 1,5-pentanediol in a continuous flow reactor. The effects of different noble metals (Ir, Pt, Pd, Ru, Rh), supports and Ir contents were screened. Among the investigated catalysts, 4 wt%Ir-MoOx/SiO2 with a Mo/Ir atomic ratio of 0.13 exhibited the best catalytic performance. The synergy between Ir particles and the partially reduced isolated MoOx species attached on them is essential for the excellent catalytic performance of Ir-MoOx/SiO2. The catalyst exhibited a better hydrogenolysis efficiency of THFA with the selectivity of 1,5-pentanediol of 65%-74% at a conversion of THFA of 70%-75% when the initial THFA concentration is ranging from 20 wt% and 40 wt%. And higher system pressure was also in favor of the conversion of THFA. During a stability test, the conversion of THFA and 1,5-pentanediol yield over Ir-MoOx/SiO2 decreased with reaction time, which can be explained by the leaching of Mo species during the reaction.

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CH4 reforming with CO2 for syngas production over La2O3 promoted Ni catalysts supported on mesoporous nanostructured γ-Al2O3 Narges Habibi, Mehran Rezaei, Nasrollah Majidian, Mahmood Andache 2014, 23(4): 435-442.  DOI: 10.1016/S2095-4956(14)60169-8 摘要 ( 6808 )   Nanostructured γ-Al2O3 with high surface area and mesoporous structure was synthesized by sol-gel method and employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide. The prepared samples were characterized by XRD, N2 adsorption-desorption, TPR, TPO, TPH, NH3-TPD and SEM techniques. The BET analysis showed a high surface area of 204 m2·g-1 and a narrow pore-size distribution centered at a diameter of 5.5 nm for catalyst support. The BET results revealed that addition of lanthanum oxide to aluminum oxide decreased the specific surface area. In addition, TPR results showed that addition of lanthanum oxide increased the reducibility of nickel catalyst. The catalytic evaluation results showed an increase in methane conversion with increasing lanthanum oxide to 3 mol% and further increase in lanthanum content decreased the catalytic activity. TPO analysis revealed that the coke deposition decreased with increasing lanthanum oxide to 3 mol%. SEM and TPH analyses confirmed the formation of whisker type carbon over the spent catalysts. Addition of steam and O2 to dry reforming feed increased the methane conversion and led to carbon free operation in combined processes.

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Effect of the graphitic degree of carbon supports on the catalytic performance of ammonia synthesis over Ba-Ru-K/HSGC catalyst Wei Jiang, Ying Li, Wenfeng Han, Yaping Zhou, Haodong Tang, Huazhang Liu 2014, 23(4): 443-452.  DOI: 10.1016/S2095-4956(14)60170-4 摘要 ( 7243 )   A series of high surface area graphitic carbon materials (HSGCs) were prepared by ball-milling method. Effect of the graphitic degree of HSGCs on the catalytic performance of Ba-Ru-K/HSGC-x (x is the ball-milling time in hour) catalysts was studied using ammonia synthesis as a probe reaction. The graphitic degree and pore structure of HSGC-x supports could be successfully tuned via the variation of ball-milling time. Ru nanoparticles of different Ba-Ru-K/HSGC-x catalysts are homogeneously distributed on the supports with the particle sizes ranging from 1.6 to 2.0 nm. The graphitic degree of the support is closely related to its facile electron transfer capability and so plays an important role in improving the intrinsic catalytic performance of Ba-Ru-K/HSGC-x catalyst.

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Separation of CO2/CH4 and CH4/N2 mixtures using MOF-5 and Cu3(BTC)2 Junmin Li, Jiangfeng Yang, Libo Li, Jinping Li 2014, 23(4): 453-460.  DOI: 10.1016/S2095-4956(14)60171-6 摘要 ( 9006 )   In this paper we used MOF-5 and Cu3(BTC)2 to separate CO2/CH4 and CH4/N2 mixtures under dynamic conditions. Both materials were synthesized and pelletized, thus allowing for a meaningful characterization in view of process scale-up. The materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). By performing breakthrough experiments, we found that Cu3(BTC)2 separated CO2/CH4 slightly better than MOF-5. Because the crystal structure of Cu3(BTC)2 includes unsaturated accessible metal sites formed via dehydration, it predominantly interacted with CO2 molecules and more easily captured them. Conversely, MOF-5 with a suitable pore size separated CH4/N2 more efficiently in our breakthrough test.

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Excellent complete conversion activity for methane and CO of Pd/TiO2-Zr0.5Al0.5O1.75 catalyst used in lean-burn natural gas vehicles Yun Wang, Haidi Xu, Hongyan Shang, Maochu Gong, Yaoqiang Chen 2014, 23(4): 461-467.  DOI: 10.1016/S2095-4956(14)60172-8 摘要 ( 7409 )   Palladium catalysts are supported on TiO2, ZrO2, Al2O3, Zr0.5Al0.5O1.75 and TiO2-Zr0.5Al0.5O1.75 prepared by co-precipitation method, respectively. Catalytic activities for methane and CO oxidation are evaluated in a gas mixture that simulated the exhaust from lean-burn natural gas vehicles (NGVs). Pd/TiO2-Zr0.5Al0.5O1.75 performs the best catalytic activity among the tested five catalysts. For CH4, the light-off temperature (T50) is 254℃, and the complete conversion temperature (T90) is 280℃; for CO, T50 is 84℃, and T90 was 96℃. Various techniques, including N2 adsorption-desorption, X-ray diffraction (XRD), H2-temperature-programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) are employed to characterize the effect of supports on the physicochemical properties of prepared catalysts. N2 adsorption-desorption and SEM show that TiO2-Zr0.5Al0.5O1.75 expresses uniform nano-particles and large meso-pore diameters of 26 nm. H2-TPR and XRD indicate that PdO is well dispersed on the supports and strongly interacted with each other. The results of XPS show that the electron density around PdO and the proportion of active oxygen on TiO2-Zr0.5Al0.5O1.75 are maxima among the five supports.

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Alkali metal cation doping of metal-organic framework for enhancing carbon dioxide adsorption capacity Yan Cao, Yunxia Zhao, Fujiao Song, Qin Zhong 2014, 23(4): 468-474.  DOI: 10.1016/S2095-4956(14)60173-X 摘要 ( 6295 )   Metal-organic frameworks (MOFs) have attracted much attention as adsorbents for the separation of CO2 from flue gas or natural gas. Here, a typical metal-organic framework HKUST-1(also named Cu-BTC or MOF-199) was chemically reduced by doping it with alkali metals (Li, Na and K) and they were further used to investigate their CO2 adsorption capacities. The structural information, surface chemistry and thermal behavior of the prepared adsorbent samples were characterized by X-ray powder diffraction (XRD), thermo-gravimetric analysis (TGA) and nitrogen adsorption-desorption isotherm analysis. The results showed that the CO2 storage capacity of HKUST-1 doped with moderate quantities of Li+, Na+ and K+, individually, was greater than that of unmodified HKUST-1. The highest CO2 adsorption uptake of 8.64 mmol/g was obtained with 1K-HKUST-1, and it was ca. 11% increase in adsorption capacity at 298 K and 18 bar as compared with HKUST-1. Moreover, adsorption tests showed that HKUST-1 and 1K-HKUST-1 displayed much higher adsorption capacities of CO2 than those of N2. Finally, the adsorption/desorption cycle experiment revealed that the adsorption performance of 1K-HKUST-1 was fairly stable, without obvious deterioration in the adsorption capacity of CO2 after 10 cycles.

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Preferential oxidation of CO in excess H2 over the CeO2/CuO catalyst：Effect of initial support Zhiming Gao, Yuanyuan Gong, Qiang Zhang, Hao Deng, Yong Yue 2014, 23(4): 475-482.  DOI: 10.1016/S2095-4956(14)60174-1 摘要 ( 8292 )   Three series of CeO2/CuO samples were prepared by impregnation method and characterized by XRD, N2 adsorption-desorption, temperature-programmed reduction (TPR), XPS and TEM techniques. In comparison with the samples prepared with CuO as initial support, the samples with Cu(OH)2 as initial support have higher reducibilities and smaller relative TPR peak areas, and also larger specific surface areas at calcination temperatures of 400℃-600℃. As a result, Cu(OH)2 is better than CuO as initial support for preferential oxidation of CO in excess H2 (CO-PROX). The best catalytic performance was achieved on the sample calcined at 600℃ and with an atomic ratio of Ce/Cu at 40%. XPS analyses indicate that more interface linkages Ce-O-Cu could be formed when it was calcined at 600℃. And the atomic ratio of Ce/Cu at 40% led to a proper reducibility for the sample as illustrated by the TPR measurements.

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Synthesis of Pt and Pt-Fe nanoparticles supported on MWCNTs used as electrocatalysts in the methanol oxidation reaction J. R. Rodriguez, R. M. Félix, E. A. Reynoso, Y. Gochi-Ponce, Y. Verde Gómez, S. Fuentes Moyado, G. Alonso-Núñez 2014, 23(4): 483-490.  DOI: 10.1016/S2095-4956(14)60175-3 摘要 ( 6285 )   This work reports a feasible synthesis of highly-dispersed Pt and Pt-Fe nanoparticles supported on multiwall carbon nanotubes (MWCNTs) without Fe and multiwall carbon nanotubes with iron (MWCNTs-Fe) which applied as electrocatalysts for methanol electrooxidation. A Pt coordination complex salt was synthesized in an aqueous solution and it was used as precursor to prepare Pt/MWCNTs, Pt/MWCNTs-Fe, and Pt-Fe/MWCNTs using FeCl2·4H2O as iron source which were named S1, S2 and S3, respectively. The coordination complex of platinum (TOA)2PtCl6 was obtained by the chemical reaction between (NH4)2PtCl6 with tetraoctylammonium bromide (TOAB) and it was characterized by FT-IR and TGA. The materials were characterized by Raman spectroscopy, SEM, EDS, XRD, TEM and TGA. The electrocatalytic activity of Pt-based supported on MWCNTs in the methanol oxidation was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Pt-Fe/MWCNTs electrocatalysts showed the highest electrocatalytic activity and stability among the tested electrocatalysts due to that the addition of "Fe" promotes the OH species adsorption on the electrocatalyst surface at low potentials, thus, enhancing the activity toward the methanol oxidation reaction (MOR).

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Effect of ZSM-5 zeolite morphology on the catalytic performance of the alkylation of toluene with methanol Hongyu Wu, Min Liu, Wei Tan, Keke Hou, Anfeng Zhang, Yiren Wang, Xinwen Guo 2014, 23(4): 491-497.  DOI: 10.1016/S2095-4956(14)60176-5 摘要 ( 6394 )   A series of ZSM-5 zeolites, with the morphologies of sphere, sphere with cubic particles on the surface, and cubic particles, were synthesized by hydrothermal method using n-butylamine as the template, assisted by the addition of NaCl and crystal seed. X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray fluorescence (XRF) and temperature-programmed desorption of ammonia (NH3-TPD) were used to characterize these samples. The samples were tested with toluene methylation reaction. The modified sample composed of spherical particles with 3 μm crystal particles on the surface had a para-xylene selectivity of 95% and maintained 79% of the initial conversion after running the reaction for 50 h. This modified sample showed the best stability among the tested three modified samples.

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Synthesis of dual-doped non-precious metal electrocatalysts and their electrocatalytic activity for oxygen reduction reaction Li Xu, Guoshun Pan, Xiaolu Liang, Guihai Luo, Chunli Zou, Gaopan Chen 2014, 23(4): 498-506.  DOI: 10.1016/S2095-4956(14)60177-7 摘要 ( 8019 )   The pyrolyzed carbon supported ferrum polypyrrole (Fe-N/C) catalysts are synthesized with or without selected dopants, p-toluenesulfonic acid (TsOH), by a facile thermal annealing approach at desired temperature for optimizing their activity for the oxygen reduction reaction (ORR) in O2-saturated 0.1 mol/L KOH solution. The electrochemical techniques such as cyclic voltammetry (CV) and rotating disk electrode (RDE) are employed with the Koutecky-Levich theory to quantitatively obtain the ORR kinetic constants and the reaction mechanisms. It is found that catalysts doped with TsOH show significantly improved ORR activity relative to the TsOH-free one. The average electron transfer numbers for the catalyzed ORR are determined to be 3.899 and 3.098, respectively, for the catalysts with and without TsOH-doping. The heat-treatment is found to be a necessary step for catalyst activity improvement, and the catalyst pyrolyzed at 600℃ gives the best ORR activity. An onset potential and the potential at the current density of -1.5 mA/cm2 for TsOH-doped catalyst after pyrolysis are 30 mV and 170 mV, which are more positive than those without pyrolized. Furthermore, the catalyst doped with TsOH shows higher tolerance to methanol compared with commercial Pt/C catalyst in 0.1 mol/L KOH. To understand this TsOH doping and pyrolyzed effect, X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) are used to characterize these catalysts in terms of their structure and composition. XPS results indicate that the pyrrolic-N groups are the most active sites, a finding that is supported by the correspondence between changes in pyridinic-N content and ORR activity that occur with changing temperature. Sulfur species are also structurally bound to carbon in the forms of C-Sn-C, an additional beneficial factor for the ORR.

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Co(Ⅱ)-salen complex encapsulated into MIL-100(Cr) for electrocatalytic reduction of oxygen Panpan Miao, Gang Li, Guoquan Zhang, Hong Lu 2014, 23(4): 507-512.  DOI: 10.1016/S2095-4956(14)60178-9 摘要 ( 7255 )   Co(Ⅱ)-salen was encapsulated in MIL-100(Cr) metal organic framework by "ship in a bottle" to synthesize a new electrocatalyst, Cosalen@MIL-100(Cr). The material was characterized by XRD, FT-IR, UV-Vis and N2-adsorption. The Cosalen@MIL-100(Cr) modified glassy carbon electrode exhibits a well-defined reduction peak at the potential of -0.21 V toward the oxygen reduction reaction (ORR) by cyclic voltammetry (CV) in pH = 6.84 phosphate buffer. Almost 400 mV positive shift of potential at Cosalen@MIL-100(Cr) modified electrode for ORR compared with that at bare glassy carbon, indicates that Cosalen@MIL-100(Cr) possesses excellent electrocatalytic activity. The transferred number of electrons for ORR was determined by chronocoulometry. The result suggests that the introduction of Co(Ⅱ)-salen complex into MOF increases the electrocatalytic activity via a four-electron reduction pathway. Furthermore, this electrocatalyst exhibits good stability and reproducibility.

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Nano-crystalline FeOOH mixed with SWNT matrix as a superior anode material for lithium batteries Mingzhong Zou, Weiwei Wen, Jiaxin Li, Yingbin Lin, Heng Lai, Zhigao Huang 2014, 23(4): 513-518.  DOI: 10.1016/S2095-4956(14)60179-0 摘要 ( 5805 )   Nano-crystalline FeOOH particles (5～10 nm) have been uniformly mixed with electric matrix of single-walled carbon nanotubes (SWNTs) for forming FeOOH/SWNT composite via a facile ultrasonication method. Directly using the FeOOH/SWNT composite (containing 15 wt% SWNTs) as anode material for lithium battery enhances kinetics of the Li+ insertion/extraction processes, thereby effectively improving reversible capacity and cycle performance, which delivers a high reversible capacity of 758 mAh·g-1 under a current density of 400 mA·g-1 even after 180 cycles, being comparable with previous reports in terms of electrochemical performance for FeOOH anode. The good electrochemical performance should be ascribed to the small particle size and nano-crystalline of FeOOH, as well as the good electronic conductivity of SWNT matrix.

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Synergistic effect of W and P on ZSM-5 and its catalytic performance in the cracking of heavy oil Dongmin Han, Nannan Sun, Jianwei Liu, Chunyi Li, Honghong Shan, Chaohe Yang 2014, 23(4): 519-526.  DOI: 10.1016/S2095-4956(14)60180-7 摘要 ( 7003 )   In order to develop the conversion of heavy oil with a high yield of propylene in the catalytic cracking process, ZSM-5 zeolite was modified by tungsten and phosphorus, which was proved to be an effective method. Characterization results show that the improvement of catalytic performance could be correlated to the interaction of phosphorus and tungsten species on ZSM-5. P inhibited the aggregation of tungsten species on ZSM-5 and was conductive to convert the tungsten species with octahedral coordination into tetrahedral coordination. And this ultimately led to that more acid sites were reserved after hydrothermal treatment in the tungsten and phosphorus co-modified ZSM-5 catalyst. Phosphorus species played an important role to restrain the dehydrogenation activity of tungsten. In addition, a model reflecting the interaction between tungsten species and ZSM-5 framework was proposed.

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Cu-Co bi-metal catalyst prepared by perovskite CuO/LaCoO3 used for higher alcohol synthesis from syngas Yuzhen Fang, Yuan Liu, Wei Deng, Junhai Liu 2014, 23(4): 527-534.  DOI: 10.1016/S2095-4956(14)60181-9 摘要 ( 8003 )   Cu-Co bi-metal catalysts derived from CuO/LaCoO3 perovskite structure were prepared by one-step citrate complexing method, and the structure evolution reaction from CuO/LaCoO3 to Cu-Co2C/La2O2CO3 under H2 pretreatment was investigated by techniques of XRD, TPR and TEM. The results suggest that a much higher dispersion of copper significantly enhanced the reduction of cobalt, and a stronger interaction between copper and cobalt ions in LaCoO3 particles led to the formation of bi-metallic Cu-Co particles in the reduced catalysts and the enrichment of Co on the surface of bimetallic particles. The prepared catalysts were highly active and selective for the alcohol synthesis from syngas due to the presence of copper-modified Co2C species.

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Production of octyl levulinate biolubricant over modified H-ZSM-5：Optimization by response surface methodology Kakasaheb Y. Nandiwale, Sunil K. Yadava, Vijay V. Bokade 2014, 23(4): 535-541.  DOI: 10.1016/S2095-4956(14)60182-0 摘要 ( 9870 )   The present study highlighted the use of modified H-ZSM-5 (Meso-HZ-5) as heterogeneous catalyst for the synthesis of octyl levulinate biolubricant by catalytic esterification of biomass derived renewable levulinic acid (LA) with n-octanol. The process variables such as catalyst loading (X1), n-octanol to LA molar ratio (X2) and reaction temperature (X3) were optimized through response surface methodology (RSM), using Box-Behnken model. Analysis of variance was performed to determine the adequacy and significance of the quadratic model. The yield of octyl levulinate was obtained to be 99% at optimum process parameters. The developed quadratic model was found to be adequate and statistically accurate with correlation value (R2) of 0.9971 to predict the yield of octyl levulinate biolubricant. The study was also extended on the validation of theoretical and experimental data, including catalyst reusability.