Hydrodeoxygenation of guaiacol on noble metal catalysts

Hydrodeoxygenation (HDO) performed at high temperatures and pressures is one alternative for upgrading of pyrolysis oils from biomass. Studies on zirconia-supported mono- and bimetallic noble metal (Rh, Pd, Pt) catalysts showed these catalysts to be active and selective in the hydrogenation of guaiacol (GUA) at 100 °C and in the HDO of GUA at 300 °C. GUA was used as model compound for wood-based pyrolysis oil. At the temperatures tested, the performance of the noble metal catalysts, especially the Rh-containing catalysts was similar or better than that of the conventional sulfided CoMo/Al₂O₃ catalyst. The carbon deposition on the noble metal catalysts was lower than that on the sulfided CoMo/Al₂O₃ catalyst. The performance of the Rh-containing catalysts in the reactions of GUA at the tested conditions demonstrates their potential in the upgrading of wood-based pyrolysis oils.     

Kinetic behavior of hydrogenation of aromatics in diesel fuel over silica–alumina-supported bimetallic Pt–Pd catalyst

The kinetics and long-term stability test of the aromatic hydrogenation of diesel fuel were studied on SiO₂–Al₂O₃ supported bimetallic Pt–Pd catalyst. The tests on the influence of operating parameters and kinetics studies were carried out using Pt (0.5 wt.%)–Pd (1.0 wt.%)/SiO₂–Al₂O₃, which provided the highest catalytic activity in a previous paper [Applied Catalysis A: General, 192 (2000) 253] with hydrotreated light cycle oil (LCO)/straight-run light gas oil (SRLGO) feedstocks containing 30 vol.% aromatics/100 wppm sulfur and 34 vol.% aromatics/420 wppm sulfur under numerous conditions. The results on this catalyst obtained at different LHSV showed an excellent fit to first-order kinetics. The apparent activation energy was determined to be 92 kJ/mol. Long-term stability test demonstrated the excellent stability of this catalyst. The products during the long-term stability test are of good quality, with the upgraded color, the increased cetane index, and sufficiently decreased sulfur content.     

Preparation of core-shell structured Ni2P/Al2O3@TiO2 and its hydrodeoxygenation performance for benzofuran

Highly active Ni₂P catalyst supported on core-shell structured Al₂O₃@TiO₂ for hydrodeoxygenation (HDO) of benzofuran (BF) was prepared and the effect of water on the performance for BF HDO over as-prepared catalyst was studied. The hydrophobic TiO₂ shell can enhance the catalytic activity, water resistance and HDO stability of the Ni₂P/Al₂O₃ catalyst. The Ni₂P/A@T exhibited the highest HDO activity of 95% with O-free products yield of 87%, which is an increase of 40% when compared with that found for Ni₂P/Al₂O₃ (47%).     

Synergetic effect of combined use of Cu–ZnO–Al2O3 and Pt–Al2O3 for the steam reforming of methanol

Commercial Cu–ZnO–Al₂O₃ catalysts are used widely for steam reforming of methanol. However, the reforming reactions should be modified to avoid fuel cell catalyst poisoning originated from carbon monoxide. The modification was implemented by mixing the Cu–ZnO–Al₂O₃ catalyst with Pt–Al₂O₃ catalyst. The Pt–Al₂O₃ and Cu–ZnO–Al₂O₃ catalyst mixture created a synergetic effect because the methanol decomposition and the water–gas shift reactions occurred simultaneously over nearby Pt–Al₂O₃ and Cu–ZnO–Al₂O₃ catalysts in the mixture. A methanol conversion of 96.4% was obtained and carbon monoxide was not detected from the reforming reaction when the Pt–Al₂O₃ and Cu–ZnO–Al₂O₃ catalyst mixture was used.     

Novel inexpensive transition metal phosphide catalysts for upgrading of pyrolysis oil via hydrodeoxygenation

Supported molybdenum/molybdenum‐phosphides as inexpensive catalysts for bio‐oil hydrodeoxygenation (HDO) were in‐house prepared using different support materials, i.e., Al₂O₃, activated carbon (AC), MgAl₂O₄, and Mg₆Al₂(CO₃)(OH)₁₆. The HDO activity of these catalysts were investigated using a 100 mL bench‐scale reactor operating at 300°C with an initial hydrogen pressure of 50 bar for 3 h with a pyrolysis oil (PO). The catalytic efficiencies for bio‐oil HDO for the catalysts were compared with the expensive but commercially available Ru/C catalyst. Addition of small amount of P to the Mo catalysts supported on either AC and Al₂O₃ led to increased degree of deoxygenation (DOD) and oil yield compared with those without P. MoP supported on AC (MoP/AC) demonstrated bio‐oil HDO activity comparable to the Ru/C catalyst. Furthermore, three AC‐supported metal phosphides for PO HDO were compared under the same conditions, and they were found to follow the order of NiP/AC > CoP/AC > MoP/AC. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3664–3672, 2016     

Mesoporous silica–alumina as support for Pt and Pt–Mo sulfide catalysts: Effect of Pt loading on activity and selectivity in HDS and HDN of model compounds

The potential of mesoporous silica–alumina (MSA) material as support for the preparation of sulfided Pt and Pt–Mo catalysts of varying Pt loadings was studied. The catalysts were characterized by their texture, hydrogen adsorption, transmission electron microscopy, temperature programmed reduction (TPR) and by activity in simultaneous hydrodesulfurization (HDS) of thiophene and hydrodenitrogenation (HDN) of pyridine. Sulfided Pt/MSA catalysts with 1.3 and 2 wt.% Pt showed almost the same HDS and higher HDN activities per weight amounts as conventional CoMo and NiMo/Al₂O₃, respectively. The addition of Pt to sulfided Mo/MSA led to promotion in HDS and HDN with an optimal promoter content close to 0.5 wt.%. The results of TPR showed strong positive effect of Pt on reducibility of the MoS₂ phase which obviously reflects in higher activity of the promoted catalysts. The activity of the MSA-supported Pt–Mo catalyst containing 0.5 wt.% Pt was significantly higher than the activity of alumina-supported Pt–Mo catalyst. Generally, Pt–Mo/MSA catalysts promoted by 0.3–2.3 wt.% Pt showed lower HDS and much higher HDN activities as compared to weight amounts of CoMo and NiMo/Al₂O₃. It is proposed that thiophene HDS and pyridine hydrogenation proceed over Pt/MSA and the majority of Pt–Mo/MSA catalysts on the same type of catalytic sites, which are associated with sulfided Pt and MoS₂ phases. On the contrary, piperidine hydrogenolysis takes place on different sites, most likely on metallic Pt fraction or sites created by abstraction of sulfur from MoS₂ in the presence of Pt.     

Hydrogenation of vegetable oil using highly dispersed Pt/γ-Al2O3 catalyst: Effects of key operating parameters and deactivation study

In the present work, Pt/γ-Al₂O₃ catalysts with high metal dispersion were prepared and characterized using chloroplatinic acid and platinum acetylacetonate as metal precursors. The activity and selectivity of the catalysts were evaluated in the hydrogenation of sunflower oil. A comprehensive analysis of the effects of key operational parameters on catalytic performance was carried out. The experimental variables were hydrogen pressure (275.8–551.6 kPa), temperature (160–200°C), and catalyst loading (0.005–0.015 kg Pt_exp/m³_oil). Platinum catalysts were active, with a double bond conversion of 28% at 2 h. The metal precursor affected catalyst selectivity. The catalyst prepared with chloroplatinic acid exhibited a lower formation of trans-isomers compared with Pt acetylacetonate. The γ-Al₂O₃ supported platinum catalyst with a metal loading of 0.51 wt.% and a metal dispersion of 98% maintained its initial catalyst activity and selectivity after 10 consecutive uses (1200 min accumulate operation time), without changes in its catalytic properties. The obtained results suggested that Pt catalysts are an attractive alternative to conventional nickel catalysts for the hydrogenation of vegetable oil.     

Hydroconversion of n-paraffins in light naphtha using Pt/Al2O3 catalysts promoted with noble metals and/or chlorine

The effect of combining 0.35 wt.% Pt with 0.35 wt.% of either Ir, Rh, Re or U on γ-Al₂O₃ support was investigated for the hydroconversion of n-pentane and n-hexane in a pulsed micro-reactor system at a temperature range of 300–500°C, except for Rh/Al₂O₃ (150–500°C). The dispersion of the metals in the catalysts under study was determined by H₂ chemisorption. The effect of chlorine addition between 1.0 and 6.0 wt.% was investigated and a content of 3.0 wt.% Cl being of optimum promotion. Highest activities for hydroisomerization, hydrocracking and hydrogenolysis were exhibited by Pt, Ir and Rh/Al₂O₃ catalysts, respectively, whether the catalysts were Cl-free or containing 3% Cl. However, Re and U catalysts were inactive. Maximum hydroisomerization selectivities using chlorinated bimetallic catalysts could be arranged in the following order: PtU/Al₂O₃>PtRe/Al₂O₃>PtIr/Al₂O₃>PtRh/Al₂O₃. However, PtRh/Al₂O₃, before and after chlorination, was the most active catalyst for hydrogenolysis. The apparent reaction rate constants as well as the apparent activation energies (E_a) for the hydroconversion of n-pentane and n-hexane were calculated and the compensation effect relationship between E_a and logarithm of the pre-exponential factor was estimated. n-hexane reaction on PtRh/Al₂O₃ catalysts deviates from this relationship for mechanistic variation.     

The Synergy of the Support Acid Function and the Metal Function in the Catalytic Hydrodeoxygenation of m-Cresol

The hydrodeoxygenation (HDO) of m-cresol is investigated as a model for the HDO of phenolic compounds from lignin pyrolysis. Pt catalysts supported on ??-Al₂O₃ and SiO₂ are effective for the conversion of m-cresol to toluene and methylcyclohexane at 533?K and 0.5?atm H₂. Experiments using Pt/??-Al₂O₃ show that the reaction proceeds by a combination of Pt-catalyzed hydrogenation and acid-catalyzed dehydration reactions. Dehydration of a partially hydrogenated oxygenate intermediate is most likely the dominant reaction pathway to toluene. The acidity of the ??-Al₂O₃ support was modified by base (K₂CO₃) and acid (NH₄F) treatments, and increasing the number and strength of acid sites was found to increase the rate of HDO. Pt/SiO₂ was more active for m-cresol HDO than Pt/Al₂O₃. The reaction rate on Pt/Al₂O₃ and Pt/SiO₂ decreased after 5?h on stream, but Pt/Al₂O₃ regained initial reactivity after reductive treatment in H₂.     

Transformation of α-olefins over Pt–M (M = Re,Sn, Ge) supported chlorinated alumina

Three bimetallic catalysts, consisting of platinum and a second metal supported on chlorinated alumina, i.e. Pt–Re/Al₂O₃, Pt–Sn/Al₂O₃, and Pt–Ge/Al₂O₃, have been used in the transformation of two α-olefins, 1-pentene and 1-hexene. Their conversion to internal and branched olefins is highly interesting for their use in reformulated gasolines and as intermediate chemicals. The catalysts characterization has been accomplished by different techniques, such as elemental and XRD analysis, N₂ adsorption, TPD of ammonia and hydrogen chemisorption. Among the three catalysts, Pt–Sn/Al₂O₃ showed the highest hydrogenation activity, whereas Pt–Ge/Al₂O₃ was the less active towards the hydrogenation of the olefins, according to their H₂ adsorption abilities. The bimetallic catalysts were compared to the monometallic one (Pt/Al₂O₃), as well as to the support. The catalyst and reaction conditions significantly influenced the products distribution. Hydrogenation was dominant at low temperatures (up to 350–400 °C) while skeletal isomerization and double bond shift prevailed at higher temperatures.     

Al2O3–Ce:YAG composite phosphor ceramics for white laser lighting: Novel preparation and regulatable properties

In this work, a series of Al₂O₃–Ce:YAG phosphor powders were synthesized by regulating the excess Al³⁺ of (Y,Ce)₃Al₅O₁₂ via coprecipitation method for the first time, where Al³⁺, Ce³⁺, and Y³⁺ elements were uniformly distributed. With the increase of Al³⁺ content, the morphology of the powders changed from wormlike shapes to flaky shapes, and Y₃Al₅O₁₂ phases had a tendency to convert to YAlO₃ phases. The x wt.% Al₂O₃–(Y_0.999Ce_0.001)₃Al₅O₁₂ (x = 20, 30, 40, 50, 60, and 70) composite phosphor ceramics (CPCs) were obtained by vacuum sintering (1775°C × 10 h), where Al₂O₃ and Ce:YAG phases were also well-distributed. When the Al₂O₃ content was 30–40 wt.%, the average grain size of Al₂O₃ was close to that of Ce:YAG. A solid-state laser lighting device was constructed by a 450 nm laser source and CPCs in a reflection mode. By adjusting the laser power, the correlated color temperature (CCT) values of white laser diodes (LDs) were achieved close to the standard white light of 6500 K. Impressively, the white LDs equipped with the 40 wt.% Al₂O₃-containing CPCs showed the optimum CCT of 6498 K (color coordinates: 0.31 and 0.38), as well as a high luminous flux of 1169 lm and efficiency of 166 lm/W at the LD power of 7.05 W. This work has provided a potential idea to optimize the composition uniformity of Al₂O₃–Ce:YAG CPCs as also to explore their excellent performance in the application of white laser lighting.     

Pt/BEA–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalysts for the isomerization of benzene/heptane mixtures. I: Optimizing the support’s composition

Pt/BEA–Al₂O₃ catalysts for the hydroisomerization of benzene-containing gasoline fractions are studied using a model feedstock (20% benzene and 80% n-heptane). The catalysts are prepared by varying the zeolite content from 5 to 70 wt % at a constant Pt loading of 0.3 wt % in all samples, with an aqueous H₂PtCl₆ solution being used as the Pt precursor. The acid properties of the samples are studied by means of temperature-programmed desorption (TPD). The effect of the support’s zeolite/binder ratio on the activity of the catalysts is determined: an increase in the zeolite content raises the system’s acidity and shifts the range of the reaction toward lower temperatures. The optimum zeolite/binder ratio is found to be 30% BEA/70% Al₂O₃. Changing the SiO₂/Al₂O₃ ratio of the zeolite from 25 to 40 is shown to have no noticeable effect on catalyst activity. The use of the catalysts supported on 30% BEA/70% Al₂O₃ in the hydroisomerization of benzenecontaining gasoline fractions can be recommended for improving environmental performance.     

NiFe/γ-Al2O3: A universal catalyst for the hydrodeoxygenation of bio-oil and its model compounds

NiFe bimetallic catalyst shows an excellent activity and selectivity for the hydrodeoxygenation (HDO) of three typical model compounds of bio-oil. The conversion of furfuryl alcohol, benzene alcohol and ethyl oenanthate is 100, 95.48 and 97.89% at 400 °C and the yield to 2-methylfuran, toluene and heptane is 98.85, 93.49 and 96.11% at 0.1 ml/min flow speed and atmospheric pressure. It indicates that the major reaction pathway is the cleavage of C–O rather than C–C. After the catalytic HDO of bio-oil over NiFe/Al₂O₃ catalyst, the heating value changes from 37.8 to 43.9 MJ/kg, the pH changes from 6.65 to 7.50.     

Influence of the storage material on the storage of NO x at low temperatures

The NO _x storage performance at low temperature (100–200 °C) has been studied for model NO _x storage catalysts. The catalysts were prepared by sequentially depositing support, metal oxide and platinum on ceramic monoliths. The support material consisted of acidic aluminium silicate, alumina or basic aluminium magnesium oxide, and the added metal oxide was either ceria or barium oxide. The NO _x conversion was evaluated under net-oxidising conditions with transients between lean and rich gas composition and the NO _x storage performance was studied by isothermal adsorption of NO₂ followed by temperature programmed desorption of adsorbed species. The maximum in NO _x storage capacity was observed at 100 °C for all samples studied. The Pt/BaO/Al₂O₃ catalyst stored about twice the amount of NO _x compared with the Pt/Al₂O₃ and Pt/CeO₂/Al₂O₃ samples. The storage capacity increased with increasing basicity of the support material, i.e. Pt/Al₂O₃ · SiO₂ < Pt/Al₂O₃ < Pt/Al₂O₃ · MgO. Water did not significantly affect the NO _x storage performance for Pt/Al₂O₃ or Pt/BaO/Al₂O₃.

     

Fabrication of supported Pd–Ir/Al2O3 bimetallic catalysts for 2‐ethylanthraquinone hydrogenation

A series of χ wt % Pd‐(1‐χ) wt % Ir (χ = 0.75, 0.50, and 0.25) catalysts supported on γ‐Al₂O₃ have been prepared by co‐impregnation and calcination‐reduction, and subsequently employed in the hydrogenation of 2‐ethylanthraquinone—a key step in the manufacture of hydrogen peroxide. Detailed studies showed that the size and structure of the bimetallic Pd–Ir particles vary as a function of Pd/Ir ratio. By virtue of its small metal particle size and the strong interaction between Pd and Ir, the 0.75 wt % Pd–0.25 wt % Ir/Al₂O₃ catalyst afforded the highest yield of H₂O₂, some 25.4% higher than that obtained with the monometallic 1 wt % Pd catalyst. Moreover, the concentration of the undesired byproduct 2‐ethyl‐5,6,7,8‐tetrahydroanthraquinone (H₄eAQ) formed using the Pd–Ir bimetallic catalysts was much lower than that observed with the pure Pd catalyst, which can be assigned to the geometric and electronic effects caused by the introduction of Ir. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3955–3965, 2017     

Effective combination of non-thermal plasma and catalyst for removal of volatile organic compounds and NOx

A plasma/catalyst hybrid reactor was designed to overcome the limits of plasma and catalyst technologies. A two-plasma/catalyst hybrid system was used to decompose VOCs (toluene) and NOx at temperature lower than 150 °C. The single-stage type (Plasma-driven catalyst process) is the system in which catalysts are installed in a non-thermal plasma reactor. And the two-stage type (Plasma-enhanced process) is the system in which a plasma and a catalyst reactor are connected in series. The catalysts prepared in this experiment were Pt/TiO₂ and Pt/Al₂O₃ of powder type and Pd/ZrO₂, Pt/ZrO₂ and Pt/Al₂O₃ which were catalysts of honeycomb type. When a plasma-driven catalyst reactor with Pt/Al₂O₃ decomposed only toluene, it removed just more 20% than the only plasma reactor but the selectivity of CO₂ was remarkably elevated as compared with only the plasma reactor. In case of decomposing VOCs (toluene) and NOx using plasma-enhanced catalyst reactor with Pt/ZrO₂ or Pt/Al₂O₃, the conversion of toluene to CO₂ was nearly 100% and about 80% of NOx was removed. This work was presented at the 6 ^th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006.     

Benzene hydroisomerization over Pt/MOR/Al2O3 catalysts

Benzene hydroisomerization is among the promising processes converting benzene into methylcyclopentane (MCP), which is an environmentally friendlier, octane boosting component of motor fuels. Benzene hydroisomerization into MCP over the Pt/MOR/Al₂O₃ (MOR = mordenite) catalytic system is reported here. The dependence of the yield of the target product on the acidic properties of the support and platinum precursor ([Pt(NH₃)₄]Cl₂ or H₂PtCl₆) have been investigated in order to optimize the catalyst composition. The acidic properties of the surface have been altered by introducing 30–95 wt % alumina into the support. Catalytic activity has been measured in the hydroisomerization of cyclohexane and a benzene (20 wt %) + n-heptane (80 wt %) mixture in a flow reactor at 250–350°C, 1.5 MPa, H₂: CH = 3: 1, a cyclohexane LHSV of 6 h^?1, a mixed feedstock LHSV of 2 h^?1, a catalyst bed volume of 2 cm³, and catalyst pellet sizes of 0.25–0.75 mm. The most efficient catalyst for cyclohexane and n-heptane isomerization and benzene hydroisomerization is the platinum-containing catalyst (0.3 wt % Pt) whose support consists of 30 wt % MOR and 70 wt % Al2O3. The highest yield of the target products of isomerization in the presence of this catalyst is attained in the temperature range from 280 to 310°C, which is thermodynamically favorable for MCP formation from benzene. This indicates that this catalyst is promising for the hydroisomerization of benzene-containing gasoline fractions. Use of H₂PtCl₆, a readily available chemical, as the platinum precursor is favorable for commercialization of the catalyst and ensures price attractiveness in its industrial-scale manufacturing.     

Highly selective and stable multimetallic catalysts for propane dehydrogenation

Different mono (Pt), bi (Pt–Sn, Pt–Pb, Pt–Ga) and trimetallic (Pt–Sn–Ga) catalysts based on Pt and supported on different materials (Al₂O₃, Al₂O₃–K and ZnAl₂O₄) were tested under severe process conditions in the propane dehydrogenation reaction (both in continuous and in pulse reactors). Results show that the Pt–Sn–Ga/ZnAl₂O₄ catalyst has a better and more stable performance in propane dehydrogenation (high yield to propene and low coke deposition), than the other bi‐ and trimetallic systems and a commercial catalyst. Thus, the use of an adequate support (ZnAl₂O₄) in combination with the addition of Ga to the Pt–Sn bimetallic system enhances the catalytic performance. © 2000 Society of Chemical Industry     

Impact of support oxide and Ba loading on the NOx storage properties of Pt/Ba/support catalysts: CO2 and H2O effects

A series of 1 wt.%Pt/_xBa/Support (Support = Al₂O₃, SiO₂, Al₂O₃-5.5 wt.%SiO₂ and Ce_0.7Zr_0.3O₂, x = 5–30 wt.% BaO) catalysts was investigated regarding the influence of the support oxide on Ba properties for the rapid NO_x trapping (100 s). Catalysts were treated at 700 °C under wet oxidizing atmosphere. The nature of the support oxide and the Ba loading influenced the Pt–Ba proximity, the Ba dispersion and then the surface basicity of the catalysts estimated by CO₂-TPD. At high temperature (400 °C) in the absence of CO₂ and H₂O, the NO_x storage capacity increased with the catalyst basicity: Pt/20Ba/Si < Pt/20Ba/Al5.5Si < Pt/10Ba/Al < Pt/5Ba/CeZr < Pt/30Ba/Al5.5Si < Pt/20Ba/Al < Pt/10BaCeZr. Addition of CO₂ decreased catalyst performances. The inhibiting effect of CO₂ on the NO_x uptake increased generally with both the catalyst basicity and the storage temperature. Water negatively affected the NO_x storage capacity, this effect being higher on alumina containing catalysts than on ceria–zirconia samples. When both CO₂ and H₂O were present in the inlet gas, a cumulative effect was observed at low temperatures (200 °C and 300 °C) whereas mainly CO₂ was responsible for the loss of NO_x storage capacity at 400 °C. Finally, under realistic conditions (H₂O and CO₂) the Pt/20Ba/Al5.5Si catalyst showed the best performances for the rapid NO_x uptake in the 200–400 °C temperature range. It resulted mainly from: (i) enhanced dispersions of platinum and barium on the alumina–silica support, (ii) a high Pt–Ba proximity and (iii) a low basicity of the catalyst which limits the CO₂ competition for the storage sites.     

La–Ni modified S2O82−/ZrO2-Al2O3 catalyst in n-pentane hydroisomerization

The La –Ni–S₂O₈²⁻/ZrO₂ –Al₂O₃ (La–Ni–SZA) was prepared and the effect of La and Ni on the structure and isomerization performance of catalyst was investigated. The addition of La could lead to a higher dispersion of metal and more acid sites. The addition of Ni can promote redox performance of catalyst and formation of Lewis acid sites. The highest isopentane yield of 66.5% at a lower reaction temperature of La–Ni–SZA can be attributed to the synergistic interaction between La and Ni.