Conversion Of M-cresol Research Articles

Co doping induces CoxP-Ni2P bimetallic site and acid synergistic effect to achieve efficient hydrodeoxidation

The development of highly efficient hydrodeoxidation (HDO) catalyst is the key to upgrade the quality of bio-oil. CoxP-Ni2P/SiO2-y catalysts (y is the initial P/(Ni+Co) molar ratio) comprised of CoxP-Ni2P bimetallic sites and acidic site were prepared by doping Co into Ni2P active phase using mesoporous SiO2 as the support. The structure and chemical properties of the catalyst were characterized by XRD, BET, XPS, H2-TPR, NH3-TPD, Py-FTIR and TEM methods. The effects of Co doping and P/M molar ratio on the HDO performance of Ni2P/SiO2 catalyst were investigated taking m-cresol as the model compound. The results show that Co doping not only creates new CoxP active sites, but also optimizes the electronic structure of Ni2P, thus improving the HDO activity of the catalyst. Among the CoxP-Ni2P/SiO2-y catalysts, CoxP-Ni2P/SiO2-0.5 with P/M molar ratio of 0.5 exhibits the best catalytic performance, with the m-cresol conversion of 98.7% and selectivity to the deoxidized product methylcyclohexane (MCH) of 95.6% at 275 °C, 2 MPa and 1 h. The HDO of m-cresol over the CoxP-Ni2P/SiO2-y catalyst mainly proceeded through hydrogenation-deoxygenation (HYD) pathway.

Enhanced Hydrodeoxygenation performance through novel Al-Doped radial channel Silica-Supported Carbon-Encapsulated nickel catalysts

Hydrodeoxygenation (HDO) plays a crucial role in upgrading pyrolysis-oil derived from biomass. Here we describe a method for fabricating a carbon-encapsulated nickel metal–acid bifunctional catalyst (Ni@C/RCS-Al) supported on aluminum-doped radial channel silica (RCS-Al). This catalyst exhibits a large surface area and highly dispersed accessible active sites, achieved through a combination of salicylate- and MOF-assisted strategies. The RCS-Al was prepared by a one-pot salicylate-assisted hydrothermal method in an aqueous phase containing an Al source, which is simple, has a high yield, and saves time. The results show that Ni@C/RCS-Al displays a well-defined radial channel pore structure with a mesopore diameter of 31.1 nm, which can significantly increase the number of accessible active sites and accelerate mass transfer. The MOF-assisted strategy leads to the formation of highly dispersed smaller carbon-encapsulated nickel nanoparticle active sites, and Al doping contributes to the adjustable acid sites, demonstrating that Ni@C/RCS-Al is a metal–acid bifunctional catalyst. Importantly, the kinetics study revealed a high reaction constant for the constructed Ni@C/RCS-Al catalyst. Ni@C/RCS-Al demonstrates remarkable performance in HDO, achieving complete m-cresol conversion and 100 % selectivity to the target product methylcyclohexane within a brief period of 75 min (T = 250 °C p = 2 MPa, m-cresol/catalyst (g) = 7.5). This exceptional performance stems from its radial channel pore structure and optimization of metal–acid sites. The thin carbon layer on the Ni surface contributes to its superior stability and water resistance, as verified by an experimental study and DFT calculations. This work opens up a new idea for the application of radial channel silica-supported catalysts in various reactions.

Melt infiltration for the preparation of finely dispersed Ni-FeOx nanoparticles on SBA-15 for the hydrodeoxygenation of m-cresol

The polymer-assisted melting infiltration method was used to finely disperse Ni, Fe and bimetallic Ni-Fe precursors in ordered mesoporous SBA-15 support. This approach allowed to obtain small Ni nanoparticles, in the order of 2 nm in size, with finely dispersed iron oxide surrounding metallic Ni, without evidence of Ni-Fe alloy formation. The catalysts were used in the HDO reaction of m-cresol at 300 °C and atmospheric pressure. The conversion of m-cresol was found to be dependent on Ni content, with the total reaction rate decreasing when Ni is partially replaced by iron. Toluene was the main product obtained for both, mono Ni and bimetallic Ni-Fe catalysts, thus suggesting that nickel nanoparticles when in the form of small sized particles, are the active sites for deoxygenation, independent on the presence of oxophilic iron site in their proximity. Such findings will serve for the further design of effective catalysts for the upgrading of lignin-derived bio-oil.

Enhancing direct deoxygenation of m-cresol to toluene through inhibiting C-C hydrogenolysis via alloying Ni with Cu

Selective hydrodeoxygenation (HDO) of biomass lignin derived phenolics to aromatics is an attractive approach for utilization of biomass lignin, since minimal H2 is consumed. Herein, bimetallic Ni-Cu/SiO2 catalysts with varying Cu/Ni molar ratios were synthesized by a modified homogeneous precipitation-deposition method and tested for HDO of m-cresol at 350 °C and atmospheric pressure. Characterizations indicate the formation of Ni-Cu alloys with an enrichment of Cu on the surface, which breaks the contiguous surface Ni atoms and reduces the Ni ensemble size. Despite bare Ni/SiO2 favors both C-C hydrogenolysis to CH4 and direct deoxygenation (DDO) to toluene, Ni-Cu/SiO2 makes DDO the dominant pathway (yield of 7.6% at conversion of 9.6% and yield of 90.4% at conversion of 95.2%) while suppresses the C-C hydrogenolysis to a very minor one. Ni-Cu/SiO2 with an optimal Cu/Ni molar ratio of 0.5 produced a turnover frequency (TOF) of 3.09 min−1 for m-cresol conversion. The TOF for toluene formation on Ni-Cu/SiO2 increases by ∼3 times to 2.24 min−1 from that on bare Ni/SiO2 whereas the TOF of CH4 formation is reduced by ∼10 times to 0.16 min−1. This study demonstrates that dilution of Ni by an inert metal such as Cu can effectively enhance DDO through inhibiting C-C hydrogenolysis during HDO of phenolics at atmospheric pressure.

Highly Stable and Selective Catalysts for m-Cresol Hydrogenolysis to Aromatics

Deoxygenation is an essential link for upgrading bio-based low-value phenolics to aromatics, which is achieved through the catalytic hydrogenation way. Herein, we designed and synthesized kinds of Ni-confined catalysts via tailoring the preparation procedures. The highest hydroxyl hydrogenolysis performance (r[garomatics·gNi–1·h–1] = 103.5 at 290 °C) in vapor m-cresol conversion so far was obtained over Ni@Silicalite-1 prepared via the in situ encapsulation method due to the average 2.5 nm Ni nanoparticles uniformly encapsulated within silicalite-1 crystals for improving the shape selectivity with the vertical adsorption mode of phenolics. The appropriate porosities are proven to play a crucial role in shape-selective catalysis for hydroxyl hydrogenolysis of m-cresol. In addition, Ni@Silicalite-1 showed outstanding stability in 200 h long run with 95.5% conversion and 74.2% aromatics yield without obvious deactivation. This work provided a novel insight into tuning hydroxyl hydrogenolysis of phenolics by designing metal@zeolite catalysts with different microenvironments and ultrasmall metal nanoparticles.

Production of thymol from alkylation of m-cresol with isopropanol over ZSM-5 catalysts: Artificial Neural Network (ANN) modelling

Thymol is one of the most widely used chemicals in the cosmetic and health industries and a known antioxidant. There are different methods for the preparation of thymol. One of the efficient methods for the synthesis of thymol is the alkylation of m-cresol using isopropanol as the alkylating agent and ZSM-5 acid catalysts. Different parameters such as SiO2/Al2O3 ratio, temperature and Weight Hourly Space Velocity (WHSV) can affect the conversion and selectivity of m-cresol alkylation. The application of tools to predict the effect of each of the effective factors and, thus, the proposition of a strong model of reaction conditions will lead to maximum conversion and selectivity. A connectionist tool has been used to evaluate the conversion and selectivity in thymol synthesis. The model simultaneously correlates the thymol selectivity and m-cresol conversion to independent variables. An appropriate statistical analysis has been carried out in order to guarantee the generalization and strength of the deterministic model. The developed network leads to coefficient of determination (R2) of 0.9890 and 0.9889 for the thymol selectivity and m-cresol conversion, respectively. Furthermore, the error analysis shows mean squared error (MSE) values of 2.2060 and 1.8126 for the thymol selectivity and m-cresol conversion, respectively.

Sn-assisted nickel synergistically catalyzes the direct cleavage of CAr[sbnd]O bond in lignin-derived m-cresol: Theoretical and experimental analysis

Refining lignin for aromatic hydrocarbons was crucial in the development of clean energy. The most effective way to enhance the carbon efficiency of the raw materials was to reduce the hydrogen consumption and maximize the retention of aromatic ring by directly breaking the CArO bond. In this regard, Sn was introduced to regulate the selectivity of Ni/SiO2 for m-cresol hydrodeoxygenation (HDO) products at low hydrogen consumption. Thanks to the formation of the Ni-Sn alloy in the system, the bimetallic sites synergistically catalyze the CArO bond scission through lowering the reaction energy barrier. Further from charge analysis, it was concluded that the charge transfer from Sn to Ni promotes the hydrogenolysis, and the charge transfer between the slab and the adsorbate provides the possibility for the occurrence of direct deoxygenation reaction. The COHP analysis resulted that the introduction of Sn accelerated the CArO bond cleavage. Interestingly, another deoxygenation pathway was proposed from the isomerization conversion of m-cresol to dienone intermediate (3-methyl-3,5-cyclohexadienone) in the calculation of transition state. Further HDO can form toluene effortlessly due to the presence of the oxyphilic metal Sn. This also explains the high selectivity of Ni-Sn to toluene. Moreover, the introduction of the Sn promoter effectively prolongs the lifetime of the catalyst by enhancing the tolerance to carbon deactivation.

Encapsulated Ni Nanoparticles within Silicalite-1 Crystals for Upgrading Phenolic Compounds to Arenes

About 3–5 nm Ni nanoparticles were significantly encapsulated within different crystal sizes of a silicalite-1 matrix through tailoring the hydrothermal synthesis conditions and ratios of feeding materials, which were applied in the upgrading of phenolic compounds to arenes via the hydrogenolysis route. The smaller the sizes of Ni@silicalite-1 crystals with similar Ni contents and nanoparticles, the more obvious the active centers could be characterized. The enhancement in both phenol/m-cresol conversion and benzene/toluene selectivity was obtained with the decrease in crystal sizes of Ni@silicalite-1, which originated from the selective elimination of the hydroxyl group, hindrance of further hydrogenation of aromatics, and the formation of methane. Furthermore, Ni@silicalite-1 was first reported for its superior stability for more than 300 h during m-cresol conversion, which maintained a high conversion from 78.4% at 8 h to 76.2% at 334 h and aromatics yield from 73.1% at 8 h to 72.6% at 334 h. Therefore, Ni@silicalite-1 provided an alternative methodology for terminal priority to achieve selectivity control different from hydrogenation on phenyl rings via a thermodynamically favorable flat mode. Ni nanoparticles encapsulated within zeolites provided a new method to regulate the adsorption mode of reactants to modify aromatic selectivity steric effects originating from shape selectivity of the silicalite-1 matrix, which also contributed to much better stability of Ni nanoparticles.

Developing Fe/zeolite catalysts for efficient catalytic wet peroxidation of three isomeric cresols.

Five Fe/zeolite (i.e., Fe/ZSM-5-1, Fe/ZSM-5-2, Fe/ZSM-5-3, Fe/MCM-22, and Fe/MOR) were prepared and tested as catalysts in the catalytic wet peroxide oxidation process (CWPO). Their adsorption and catalytic effects on the removal of three isomeric cresols were systematically explored. Sufficient characterizations were carried out to illuminate the iron species dispersed on the catalysts' surface porous channels. Other properties of the catalysts such as the Si/Al ratio, crystalline structures, and morphologies were systematically studied. After loaded with iron, the catalysts maintained zeolite's framework, which possessed specific porous structures and surface areas. Interestingly, the Si/Al ratio seemed to be an important issue influencing the adsorption and catalytic degradation of cresols due to n-π interaction and the acceleration of HO• generation, respectively. The amount of framework-Fe and Fe3+Al-Si in Fe/ZSM-5-3 was the most, which was crucial for its better catalytic ability than the other Fe/ZSM-5 catalysts (71.19% for m-cresol conversion). In conclusion, the catalytic activities of all the Fe/zeolites followed the sequence: Fe/ZSM-5-3> Fe/ZSM-5-2> Fe/ZSM-5-1> Fe/MCM-22>Fe/MOR. For three cresols, m-cresol was more susceptible to the attack of HO• than p- and o-cresol because more positions of m-cresol could be easy to be approached by the oxidizing agent. Considering the mild reaction condition in this study, such as 30 °C, pH=4.0, and catalyst dosage=1.0 g/L, the Fe/ZSM-5-3 was a promising zeolite catalyst for the degradation of refractory contaminants in practical wastewater.

A study on the alkylation of m-cresol with 1-decene over mesoporous silica supported tungstophosphoric acid (HPW)

Linear alkylcresols were synthesized in high yield by the alkylation of m-cresols with 1-decene in the presence of 25%HPW/SBA-15 catalyst. The physicochemical properties of the catalyst were investigated by means of N2 adsorption/desorption measurements (textural properties: surface area, pore volume and average pore diameter) and thermal desorption of diethyl-amine (acidity and the acid strength distribution). HPW-loaded acid as well as the SBA-15 support displayed a mesoporous structure. The effects of the reaction time and the catalyst amount on the reaction were studied. The main monitored parameters were the conversion of m-cresol, yield of decylcresol isomers (ortho- and para-) and yield of polyakylated cresol. The results indicates that 25%HPW/SBA-15 catalyst has high catalytic activity, with the m-cresol conversion of 93.8% , at 160 °C with a reaction time of 150 min and a catalyst loading of 0.5 wt% m-Cresol was alkylated preferably in the para-position, the yield of 4-(decan-2yl)-3-methylphenol, after 150 min reaction time was 54.5%.

Hydrocarbons Production from m-Cresol as a Lignin Model Compound Over Nickel Silicate Catalysts

Hydrodeoxygenation (HDO) reactions under low/atmospheric pressure of hydrogen should be studied to solve the problem of the economics of the high-pressure hydrogen upgrading process. Therefore, in this study, the catalytic HDO reaction of m-cresol in atmospheric hydrogen pressure was evaluated using Ni/silica and Nickel silicate (Ni-MCM-41) catalysts. The Ni-MCM-41 catalyst exhibited higher conversion of m-cresol than Ni/silica. The high activity of the Ni-MCM-41 catalyst was due to the large specific surface area and the high nickel loading.

Fabrication of boron-doped diamond films electrode for efficient electrocatalytic degradation of cresols.

The choice of anode materials has a significant influence on the electrocatalytic degradation of organics. Accordingly, the electrocatalytic activity of several active anodes (Ti/Ru-Ir, Ti/Ir-Ta, Ti/Pt) and non-active anodes (Ti/PbO2, Ti/SnO2, Si/BDD (boron-doped diamond)) was compared by electrocatalytic degradation of m-cresol. The results indicated Si/BDD electrode had the strongest mineralization ability and the lowest energy consumption. And the order of the activity of m-cresol degradation was as follows: Si/BDD>Ti/SnO2>Ti/PbO2>Ti/Pt>Ti/Ir-Ta>Ti/Ru-Ir. Also their intermediate products were compared. The effects of experimental parameters on electrocatalytic degradation of m-cresol with Si/BDD electrode showed m-cresol conversion was affected slightly by the electrode spacing and electrolyte concentration, but affected greatly by the temperature and current density. And smaller electrode spacing and current density, higher electrolyte concentration and temperature were beneficial to reduce energy consumption. Their degradation processes were all accord with the pseudo-first-order reaction kinetics completely. In addition, the results of electrocatalytic degradation of m, o, p-cresol indicated there was almost no significant difference on conversion rate between cresols isomers with the current density of 30mAcm-2. However, the influence of group position was shown when the current density was reduced to 10mAcm-2 and cresols conversion followed the sequence of m-cresol≈o-cresol>p-cresol.

Iron-loaded carbon nanotube-microfibrous composite for catalytic wet peroxide oxidation of m-cresol in a fixed bed reactor.

A kind of novel iron-loaded carbon nanotube-microfibrous composite (Fe2O3-CNT-MF) catalyst is prepared and tested for fixed bed m-cresol catalytic wet peroxide oxidation (CWPO) reaction. Results show that the Fe2O3-CNT-MF can significantly decline the pressure drop of the fixed bed. Higher temperature, lower feed flow rate, higher catalyst bed height, and higher H2O2 dosage are beneficial to m-cresol degradation. Lower pH can also improve m-cresol degradation, but it will cause severe iron leaching. The highest m-cresol removal (over 99.5%) and total organic carbon (TOC) removal (53.6%) can be observed under condition of 2cm bed height, flow rate of 2mL/min, reaction temperature of 70°C, 6g/L H2O2, and initial pH = 1. Meanwhile, the Fe2O3-CNT-MF catalyst shows good stability with less than 10% decrease in m-cresol conversion and 7% decrease in TOC conversion after 24-h reaction and less than 2mg/L iron leaching is observed in all conditions except for strong acid condition. Two probable pathways of m-cresol degradation process are presented. Under most conditions, m-cresol will first be turned into methylhydroquinone, followed by oxidation to p-toluquinone. In basic condition, some m-cresol will first be changed into 4-methylpyrocatechol. These aromatic intermediates will then be oxidized into some small molecular acids and finally be mineralized to CO2 and H2O.

Biomass-derived phenolics conversion to C10–C13 range fuel precursors over metal ion-exchanged zeolites: Physicochemical characterization of catalysts and process parameter optimization

Selective formation of C10–C13 range fuel precursors by gas-phase alkylation of m-cresol (a bio-oil product from lignin/lignocellulosic biomass) with iso-propanol (light oxygenates) over highly efficient metal ion-exchanged zeolite catalysts is reported. Zn-HY zeolite exhibited higher catalytic activity as compared to Zn-HZSM5, Zn-HBEA, Zn-HMCM22, and other metal ion-exchanged HY zeolites. The catalytic activity was observed to increase with zinc content in HY, which is attributed to its high Lewis acidity. A comprehensive investigation of important process parameters like reaction temperature (200–300 °C), WHSV (1.68–3.92 h−1), iso-propanol:m-cresol mole ratio (1:1–3:1), and catalyst loading (0.5–1.5 g) is reported and optimized using Design of Experiment (DoE) through Response Surface Methodology (RSM). Experimental data was fitted to a second-order polynomial equation using multiple regression analysis with high determination coefficient (R2) value of 98.65% for conversion of m-cresol and 98.37% for selectivity to thymol. An m-cresol conversion of ∼92% with ∼71% selectivity to thymol was obtained over Zn-HY-III containing 0.99 mmol g−1 zinc at optimal conditions of 250 °C temperature, 2.8 h−1 WHSV, 2:1 reactant mole ratio, and 1 g catalyst loading. This work demonstrates the prevention of carbon fraction loss during hydrodeoxygenation by efficient alkylation of phenolics with oxygenates obtained as major fractions in bio-oil.

Hydrodeoxygenation of m-Cresol over Ru based catalysts: Influence of catalyst support on m-Cresol conversion and methylcyclohexane selectivity

The hydrodeoxygenation (HDO) of m-Cresol (a representative of lignin bio-oil) has enormous potential for the production of valuable compounds. The products obtained from HDO of m-Cresol (m-Cr) are blendable into conventional fuels and essential for chemical industries such as plastic, fiber, rubber, resin, film, and coating industry. Ruthenium loaded acidic supports (ZSM-5, β-zeolite, y-zeolite, mordenite, COK12, ZrO2, TiO2) were used for the selective hydrodeoxygenation of m-Cresol into methylcyclohexane (MCXane). The effects of acid sites, as well as the pore size of the different supports on the hydrodeoxygenation activity and selectivity towards methylcyclohexane were addressed. The methylcyclohexane yield increased with increasing number of acid sites up to optimum acidity (532 μmol/gm) along with pore size (5.9 Ao). The experiments were carried out at 225–325 °C and 1–40 bar hydrogen pressure in a fixed bed reactor and observed that reaction temperature, and hydrogen pressure promoted the hydrodeoxygenation. The Ru/ZSM-5 is a stable (240 h) catalyst and displayed excellent behavior in both hydrodeoxygenation activity (100%) and methylcyclohexane selectivity (100%) for m-Cresol.

Oxidative degradation of cresol isomers using ozone in the presence of SiO2-supported nickel, iron, manganese and vanadium catalysts

We report the catalytic ozonation as a viable tool in the oxidative degradation of cresol isomers. SiO2-supported metal catalysts with 2.5 and 7.5 wt.% (Ni, Fe, Mn, V) were employed in this ozone initiated oxidation reactions. All catalysts were characterized using various analytical techniques such as XRD, FT-IR, SEM-EDX, TEM, ICP-OES, and BET-surface area analyses. XRD studies revealed the existence of Fe as Fe2O3 and Mn as Mn3O4 on the supports’ surface. EDX results displayed a dispersion homogeneity of the metals over the surface of SiO2 support, and the ICP-OES analysis confirm the concentration of a loaded metal. The degradation of cresols (m-, o-, p-cresol) was investigated by aerating each substrate with ozone (0.123 mg/L) in a glass reactor from 6 to 24 h of reaction time at ambient reaction conditions. The catalytic activities of various metal loaded SiO2 catalysts in terms of conversion and selectivity were studied. The reaction products of various cresol isomers were identified using GC–MS analysis. m-Tolyl acetate (m-TA), 2,3-dihydroxytoluene (2,3-DT), diethyl maleate (DM) and diethyl oxalate (DO) were the identified products in the oxidative degradation of m-Cresol. Whereas, o-cresol yielded o-tolyl acetate (o-TA), 2,5-dihydroxytoluene (2,5-DT), DM and DO as products. p-Cresol produced p-tolyl acetate (p-TA), 3,4-dihydroxytoluene (3,4-DT), DM and DO as reaction products. The Ni(2.5%)/SiO2 catalyst possess excellent activity towards the conversion of m-cresol (85.0%), whereas, Fe(2.5%)/SiO2 led to highest conversion for both o-cresol (76.3%) and p-cresol (87.0%).

In-situ hydrogenation of bio-oil/bio-oil phenolic compounds with secondary alcohols over a synthesized mesoporous Ni/CeO2 catalyst

Mesoporous ceria, which was synthesized under supercritical conditions, was found to be an effective support material of Ni catalyst for the in-situ hydrogenation of m-cresol (a representative compound of bio-oil) using secondary alcohols of 2-propanol (2-PrOH) and 2-butanol (2-BuOH) as a hydrogen source (H-donor) to produce 3-methylcyclohexanol, 3-methylcyclohexene, and methylcyclohexane under a H2 gas-free atmosphere. The activities of different metal catalysts (Ni, Cu, and Co) for the in-situ hydrogenation of m-cresol were examined using 2-PrOH as a H-donor. Total and effective conversion of m-cresol achieved only over Ni/CeO2 because of its fair catalytic properties, as determined by N2 adsorption-desorption, hydrogen temperature-programmed reduction, ammonia temperature-programmed desorption, X-ray diffraction, and transmission electron microscopy. The dependence of Ni/CeO2 performance on the reaction time (4–6 h) and Ni loading (3–9 wt%) was examined from the in-situ hydrogenation of m-cresol with 2-PrOH. The deactivation test of Ni/CeO2 was performed by reusing the spent catalyst, which was then regenerated through successive oxidation and reduction, several times in the m-cresol transformation employing 2-PrOH as a H-donor. In addition to m-cresol, other phenolic model compounds of bio-oil, such as anisole, phenol, and guaiacol, were also treated by in-situ hydrogenation with 2-PrOH over Ni/CeO2. Although this catalyst was effective for phenol and guaiacol transformation, it was relatively ineffective for anisole conversion. The in-situ hydrogenation of crude bio-oil with 2-PrOH and 2-BuOH was accomplished over the Ni/CeO2 catalyst, resulting in a refined bio-oil with a 37.5–38.9% lower oxygen content and a high heating value (HHV) of up to 25 MJ/kg.

Preparation of novel iron-loaded microfibers entrapped carbon-nanotube composites for catalytic wet peroxide oxidation of m-cresol in a fixed bed reactor

A novel microfibers entrapped carbon-nanotube composite catalyst with iron loaded (MF-CNT-Fe2O3) was develop followed by fixed bed catalytic wet peroxide oxidation (CWPO) of m-cresol. Firstly, the microfibers entrapped carbon-nanotube composite (MF-CNT) support was prepared by wet lay-up papermaking process and sintering process and the entrapment ratio of support was evaluated. Then active components were loaded on support by metal organic chemical vapor deposition (MOCVD) method. Characterizations were carried out including Field-Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive Spectroscopy (EDS), N2 adsorption–desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-Temperature-Programmed Reduction (H2-TPR) and Thermogravimetric Analysis (TG), respectively. At last, catalytic activity was tested. Results showed that the best entrapment ratio (72.5%) occurred when stirring time was 9.5 min and the mass ratio of CNTs to stainless steel fibers was 6:3. Characterization results illustrated that advanced three-dimensional network was formed in the microfibers composites and catalysts performed high thermal stability. CNTs were successfully entrapped in the fibers and iron components were uniformly dispersed on supports. CWPO results showed that MF-CNT-Fe2O3 catalysts prepared by MOCVD performed better than by impregnation method. Additionally, MF-CNT-Fe2O3 catalysts could perform high CWPO activity (m-cresol conversion highest at 99% and TOC conversion highest at 42%, respectively). Little iron loss was observed in all treated effluents.

Influence of Re addition to Ni/SiO2 catalyst on the reaction network and deactivation during hydrodeoxygenation of m-cresol

The reaction network of hydrodeoxygenation of m-cresol was investigated over Ni/SiO2 and Ni-Re/SiO2 catalysts at 300 °C and 1 atm H2. m-Cresol conversion proceeds through three major primary pathways: phenyl ring hydrogenation to 3-methylcyclohexanone and 3-methylcyclohexanol, CC hydrogenolysis to CH4 and phenol, and deoxygenation to toluene. Re addition promotes dehydrogenation of the initially formed methylcyclohexanone and methylcyclohexanol to surface intermediates followed by deoxygenation toward formation of toluene. CC hydrogenolysis happens on unsaturated compounds with phenyl ring, instead of saturated compounds, since dehydrogenation is requested prior to CC cleavage. The turnover frequency (TOF) for CH4 formation follows the order of m-cresol < toluene << benzene, indicating that CC hydrogenolysis is accelerated after deoxygenation and/or demethylation. Increasing reaction temperature promotes both deoxygenation and hydrogenolysis. The toluene selectivity keeps low even at higher temperature of 340 °C on monometallic Ni catalyst due to successive CC hydrogenolysis to CH4. Re addition not only promotes deoxygenation to toluene by providing active Ni-Re neighboring sites, but also inhibits the aromatics hydrogenolysis to CH4, resulting in high toluene selectivity on bimetallic catalyst. Both catalysts show a similar deactivation trend and coke is speculated to be the major reason for deactivation.

Ozone Initiated Oxidation of Cresol Isomers Using γ-Al2O3 and SiO2 as Adsorbents

Ozone initiated oxidation of environmentally unfriendly organic compounds is one of the powerful tools that is utilized to convert and/or completely mineralize these substances. Here we have adopted the adsorption phenomenon in combination with ozonation (0.123 mg/L) of the hazardous cresol isomers mounted in a glass column. An oxide of aluminum (γ-Al2O3) or silicon (SiO2) was used as an adsorbent material. These materials were characterized using XRD, SEM and TEM techniques. Various cresols (m-, o-, p-cresol) were oxidized for different time intervals, viz. 1, 3 and 5 h. The γ-Al2O3 adsorbent was found to have a relatively high catalytic effect towards conversion of m-cresol (52%) into oxidation products, whereas SiO2 promoted the conversion of o-cresol (57%) and p-cresol (62%) the most. The resultant oxidation products that were identified using GC–MS were dominantly isomeric from all three cresols. Oxidation of m-cresol produced m-tolyl acetate (m-TA), 2,3-dihydroxytoluene (2,3-DT) and diethyl maleate (DM) whereas o-cresol produced o-tolyl acetate (o-TA), 2,5-dihydroxytoluene (2,5-DT) and DM. Finally, the oxidation of p-cresol produced p-tolyl acetate (p-TA), 3,4-dihydroxytoluene (3,4-DT) and DM. Amongst all identified oxidation products, tolyl acetates recorded highest percentage selectivities from all adsorbates especially in 1 h reactions. The ozone initiated oxidation of various cresol isomers was explored using various metal oxide (γ-Al2O3 or SiO2) material as adsorbents. The metal oxide adsorbent materials were characterized using XRD, SEM and TEM techniques. The effect of adsorption and ozonation time on percentage conversion and selectivity towards reaction products upon ozonation of various cresols is emphasised. The positively identified oxidation products contains various tolyl acetates, dihydroxytoluenes and diethyl maleates that are isomeric to the cresol isomer used. The ethanol mediated esterification of carboxylic acid to produce tolyl acetate as product is reported.