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The activity and S-tolerance of monometallic and bimetallic Ir–Pd catalysts with different atomic ratio (Ir/Pd = 0.5, 1 and 2) and the same total metal content (1 wt%) supported on SiO2–Al2O3 were studied in the hydroconversion of decalin. In the absence of sulfur, bimetallic catalysts showed less activity and selectivity to decalin ring opening products compared to the iridium monometallic catalyst. However they exhibited a greater tolerance to thiophene poisoning (S = 10 ppm). The catalysts with Ir/Pd = 1 and 2 (atomic ratio), with similar metal dispersion, had better resistance to sulfur. The optimal ratio found, Ir/Pd = 1, could be related to the formation of bimetallic particles and an adequate acidity. The total acidity of the catalysts decreased with an increasing Ir/Pd atomic ratio. The addition of sulfur did not significantly modify the selectivity to ring opening products but reduced the formation of dehydrogenated (undesirable) and cracking products. The distribution of the cracking products confirmed that in the absence of S the metallic function controls the decalin ring opening mechanism, except with the monometallic Pd catalyst. With the addition of S the acid function predominates because the activity results correlate with the acidity of the catalysts. [ABSTRACT FROM AUTHOR]

The influence of Ir content on sulphur tolerance for the selective ring opening of decalin was investigated. Ir/SiO2‐Al2O3 catalysts (70 wt% and 80 wt% SiO2) were used. In the absence of sulphur, slight differences were observed on the yields according to the metallic content regardless of the support used. Although the results of cyclopentane hydrogenolysis showed that the metallic function acquires importance as the metal content increases, for these metal percentages the acid function limits the rate of decalin opening reaction. Products distribution are strongly modified using decalin with S content compared to pure decalin. The formation of dehydrogenated products is virtually null due to S adsorbed on the metal sites. The support has low influence on the thiotolerance. The results, related to the amount of S per Ir surface atom, showed that for a moderate S content (S/Irsurf ∼ 0.30), 1.5 Ir/Sy appears to be less poisoned than 1Ir/Sy and 2Ir/Sy. [ABSTRACT FROM AUTHOR]

In this work, the deactivation of the Ru‐Sn‐B/Al2O3 catalyst prepared by the incipient wetness method in the selective hydrogenation reaction of methyl oleate to fatty alcohol was studied. There was a decrease in both the activity and selectivity of fatty alcohol during successive reaction experiments. The fresh and deactivated catalysts were evaluated by different techniques such as TPR, XPS, TGA, Raman, and FTIR to determine the deactivation causes. Lower Ru and Sn content were found in the deactivated catalyst due to the loss of the active material during hydrogenation reaction. As the metal loss was more important for Ru than for Sn, the Ru/Sn ratio was changed, leading to a decrease of the selectivity. Moreover, the analysis of the XPS peak by the deconvolution of Sn species suggests the more active (SnOx) species for selective hydrogenation are more affected than the less selective (SnOy). Coke deposition was not observed by Raman and FTIR. [ABSTRACT FROM AUTHOR]

BACKGROUND: Fatty alcohols are produced commercially by selective hydrogenation of fatty acid esters using copper‐chromium catalysts. To reduce drastic reaction conditions, ruthenium‐tin (Ru‐Sn) catalysts reduced with sodium borohydride (NaBH4) have been proposed. Chlorine (Cl) negatively affects the selectivity and activity of this catalytic system. To get further information on why Cl influences the selectivity negatively, this study investigated the influence of the preparation method on titania (TiO2)‐supported catalysts, which leads to catalysts with different Cl contents. RESULTS: The activity and selectivity were greatly affected by the Cl content, which depends on the metal impregnation method (co‐impregnation in excess of solution or co‐impregnation by incipient wetness) and the support pre‐calcination. Chlorine affects the Ru–Sn metal interaction, modifying the activity and selectivity. Catalysts with high Ru–Sn interaction are more selective to oleyl alcohol. Catalysts prepared by the co‐impregnation method exhibit bigger particles than catalysts prepared by the incipient wetness method, with agglomerated Ru3Sn7 cubic phase of 50 nm surrounded by amorphous Ru‐Sn. CONCLUSION: High interaction between Ru and Sn is preferred because segregated Ru species are not selective for the formation of oleyl alcohol. The electronic state of Ru0 is very important because small variations in the electron density lead to a decrease in the adsorption of hydrogen, or because Ru0‐H species do not have the adequate binding energy to produce the necessary 'hydride form'. The Ru electronic state is modified by the Cl that surrounds it, decreasing its ability to adsorb hydrogen. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

In this paper, a review is presented of the evolution of different catalytic systems and operating conditions used in the selective hydrogenation of acids and esters of fatty acids to obtain fatty alcohols, which have broad industrial applications in the oleochemical industry. In addition, the current status of the different technologies used industrially (Lurgi, Davy and Henkel) for obtaining fatty alcohols, as well as major global sources of raw materials for the oleochemical industry are put forward. Finally, the reaction mechanisms of the selective hydrogenation process of oleic acid and methyl oleate to obtain the corresponding unsaturated alcohol as well as the new catalysts proposed by researchers are described. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The influence of indium on the properties of Pt–Re/Al2O3 catalysts used in naphtha reforming is studied. The addition of indium to the Pt–Re/Al2O3 catalyst produces a big decrease of acidity. It also produces an inhibition of the metal function, i.e., dehydrogenation and hydrogenolysis activity. The reaction of n-C5 isomerization shows that indium addition decreases the total activity of the Pt–Re catalyst but increases the selectivity to the i-C5 isomers. The selectivity to low cost light gases (C1–C3) is particularly decreased. The reaction of n-C7 reforming showed that addition of indium increases the stability of the catalyst and the selectivity to aromatics, and decreases the production of light gases. [ABSTRACT FROM AUTHOR]

The catalytic properties of V–Sb/ZrO2 and bulk Sb/V catalysts for the oxidative dehydrogenation of propane were studied. Samples were characterized by nitrogen adsorption, temperature-programmed reduction, temperature-programmed pyridine desorption and photoelectron spectroscopic techniques. Vanadia promotes the transition of tetragonal to monoclinic zirconia and the formation of ZrV2O7. Surface V and Sb oxide species do not appear to interact among them below monolayer coverage, but SbVO4 forms above monolayer. Simultaneously the excess of antimony forms α-Sb2O4. Activity and selectivity show no dependence on the acidity of the catalysts. However, there is a strong dependence of activity/selectivity on composition; surface vanadium species are active for propane oxidative dehydrogenation and the presence of Sb, affording rutile VSbO4 phase makes the system selective to C3H6, this is believed to be related to the redox cycle involving dispersed V5+ species and lattice reduced vanadium site in the rutile VSbO4 phase. [ABSTRACT FROM AUTHOR]

Pt–Sn/γ-Al2O3 catalysts with different Sn loadings were prepared by incipient wetness coimpregnation of γ-Al2O3 with H2PtCl6 and SnCl2. The Pt–Sn interaction was tested by temperature-programmed reduction and the catalytic activity was measured by cyclohexane dehydrogenation. The catalysts were coked by cyclopentane at 500 °C and totally or partially decoked with O2 at 450 °C or O3 at 125 °C. Coke deposits were studied by TPO and the catalytic activity of coked catalysts, partially or totally regenerated, by cyclohexane dehydrogenation.The TPO with O3 shows that coke combustion with O3 starts at a low temperature and has a maximum at 150 °C, that is a compensation between the increase of the burning rate and the rate of O3 decomposition when increasing the temperature. Meanwhile O2 burns coke with a maximum at 500 °C. When performing partial decoking with O3 (125 °C) the remaining coke is more oxygenated and easier to burn than the coke that remains after decoking with O2 (450 °C).After burning with O3 the dehydrogenation activity of the fresh catalyst is recovered, while after burning with O2 the activity is higher than that of the fresh catalyst. The burning with O3 practically does not change the original Pt–Sn interaction while the burning with O2 produces a decrease in the interaction, producing free Pt sites with higher dehydrogenation capacity.The differences in coke combustion with O3 and O2 are due to the different form of generation of activated oxygen, the species that oxidizes the coke. O3 is activated by the γ-Al2O3 support at low temperatures firstly eliminating coke from the support while O2 is activated by Pt at temperatures higher than 450 °C and the coke removal starts on the metal. Then, the recovery of the Pt catalytic activity as a function of coke elimination is faster with O2 than with O3. [Copyright &y& Elsevier]

A study on the deactivation phenomena affecting the catalysts of small-scale natural gas catalytic combustors was undertaken in this work. The influence of simulated aging pretreatments on the activity of Pt-Pd catalysts supported over gamma alumina for the catalytic combustion of CH4 was assessed under atmospheric conditions and in the 50–950 °C temperature range. Accelerated deactivation tests consisted of steaming at temperatures between 500–800 °C.The results showed that the activity of the deactivated catalysts depended on two opposite phenomena. An enhancement of the activity was encountered for low aging temperatures and was addressed to chlorine (Cl) elimination (as detected by chemical analysis). Conversely, at higher temperatures the accelerated aging treatment produced a decrease in the activity, and this was allegedly linked to a decrease in the available metal surface area produced by sintering. During the catalyst lifespan and under real operation conditions, a first period is therefore expected where the catalytic activity improves due to the Cl elimination by the water (H2O) produced during combustion. Afterwards, the activity would decrease because of the sintering of the metal phase. Both processes, Cl elimination and sintering, occur simultaneously.Five different catalyst formulations with variable Pt and Pd contents were tried and 0.4%Pt-0.8%Pd was found to be the most active. The results found are discussed in terms of the activity of the monometallic catalysts, the degree of interaction of the Pt and Pd phases and the previously mentioned phenomena of sintering and Cl elimination. [Copyright &y& Elsevier]

The influence of the thermal treatments of Pt/SO42−-Zr(OH)4 catalysts on the activity for the metal-catalyzed reaction of cyclohexane dehydrogenation and the acid-catalyzed reaction of n-butane isomerization, were studied in this work. A mutual antagonism between the conditions for optimal activity of the acid and metal functions was found and was seemingly related to the crystallization of the support. In order to be able to isomerize n-butane, SO42−-Zr(OH)4 had first to be calcined in air at Tcalc>400 °C. The onset of activity and strong acid properties coincided with the appearance of the tetragonal crystal phase. SO42−-Zr(OH)4 supported Pt, prepared from chloroplatinic acid, was tried to be converted to the metal state (Pt0) in order to have full catalytic capacity. When Pt/SO42−-Zr(OH)4 was first calcined in air at Tcalc>400 °C, Pt remained in a seemingly oxidized state, with no de/hydrogenation properties even after reduction in H2 at 300 °C. Under certain conditions, Pt metal properties were improved: (i) calcining Pt/SO42−-Zr(OH)4 in air at Tcalc<400 °C; (ii) calcining Zr(OH)4 at Tcalc>400 °C before sulfating the support; and (iii) calcining Pt/SO42−-Zr(OH)4 in N2 instead of air. In these cases, though Pt dehydrogenation activity increased, the activity of the acid function decreased (iii) or was practically null ((i) and (ii)). The support was amorphous in case (i) and mainly monoclinic in case (ii). Sulfate loss and conversion into the monoclinic phase occurred in case (iii). As compared to sulfate-free Pt/ZrO2, sulfur poisoning always decreased the metal activity of sulfated catalysts but the decrease was higher for mainly tetragonal sulfate-doped catalysts. The final conclusion is that the optimum activation conditions for the metal and acid functions in Pt/SO42−-Zr(OH)4 are mutually excluding. The deleterious effect of SO42−-ZrO2 (SZ) on Pt metal activity is closely related to the growth and/or the presence of the tetragonal phase and cannot be prevented if a high activity of the acid function is demanded by the reacting system. [Copyright &y& Elsevier]

The conversion of methanol to olefins (MTO, T = 400 and 450 °C, WHSV=4 h-1) was studied using ZSM5, SAPO34 and amorphous silica-aluminas (different percentages of SiO 2 , 40%, 60% and 70%) (commercial catalysts) treated or not by HCl. All the catalysts studied present type IV adsorption/desorption isotherms of N 2. The incorporation of HCl decreased the surface area, increased the pore size, the total acidity and the quantity and strength of Brønsted acid sites. The increase in the reaction temperature favors the yield of ethylene to a greater extent than that of propylene. The highest light olefins yield was obtained with catalysts containing 60% SiO 2 at 400ºC. Its good performance is attributed to the combination of adequate acidity, high specific surface area, and small pore size. Catalysts with 40% SiO 2 are not suitable for MTO. The addition of HCl to the aluminosilicates cause further deactivation. [Display omitted] • The SAPO34 and ZSM5 catalysts are used as benchmarks for develop new catalysts for metanol to olefins. • Amorphous aluminosilicates of different composition SiO 2 -Al 2 O 3 treated or not by HCl were studied. • Amorphous silica-alumina catalyst with 60% SiO 2 are promising, although they do not have shape selectivity. • The addition of HCl to the aluminosilicates cause further deactivation. [ABSTRACT FROM AUTHOR]

Abstract: The use of reflux aged zirconia gel in the synthesis of sulfated zirconia catalysts for isomerization of short paraffins and isomerization-cracking of long paraffins was assessed. It was found that reflux aging greatly improved zirconia textural properties. The growth of the monoclinic phase was greatly suppressed and the initial area and sintering resistance were increased. The specific surface area of reflux aged material with no sulfate was almost 75m2 g−1 after calcination at 800°C. Sulfate promotion of aged materials further increased the tetragonal/monoclinic ratio and the area of sulfated catalysts was 220m2 g−1 after calcination at 600°C. Impregnation of reflux aged materials with sulfate produced materials which had very low activity in isomerization of n-butane. The effect of aging was explained in terms of a dissolution-precipitation process that eliminated specific sites of the gel that were responsible for much of the activity of the final catalyst. In the case of the hydroisomerization-cracking of long paraffins the effect was less deletereous partly due to the higher reactivity of this feedstock. [Copyright &y& Elsevier]

Abstract: Pt-Re-Ge/γAl2O3 catalysts were prepared by the catalytic reduction method using different impregnation media (H2O, HCl and NH3) and different Ge contents (0.0, 0.1, 0.3, 1.0 and 2.0%). The influence of these preparation parameters on the activity for n-heptane conversion and the selectivity to toluene at atmospheric pressure was assessed. The catalysts were also characterized by ICP-AES, temperature programmed reduction, pyridine temperature programmed desorption and CO pulse chemisorption. The results show that as the pH is increased the Ge content increases and the catalysts present a lower hydrogenolytic activity and a lower toluene selectivity. Ge addition modifies both metal and acid functions. The catalyst with minimum Ge content prepared using water as impregnation medium has the best performance. [Copyright &y& Elsevier]

Abstract: Preparation of trimetallic Pt–Re–Ge/Al2O3 and Pt–Ir–Ge/Al2O3 naphtha reforming catalysts by means of a surface redox reaction (namely the catalytic reduction method), was studied by varying the concentration of Ge. The catalytic reduction method was chosen in order to favor the interaction of Ge with the active Pt–Re and Pt–Ir phases. The results shows that the deposition of Ge on the bimetallic catalysts does not seemingly depend on the nature of the metal phase (Pt–Ir or Pt–Re). The test reactions indicated that Ge addition modified the properties of both the metal and acid functions of the bimetallic catalysts. The modification of the acidity is due to the deposition of part of Ge on the support. The n-C7 reforming results show that Pt–Re–Ge/Al2O3 and Pt–Ir–Ge/Al2O3 catalysts with low Ge contents (≤0.3%) have similar catalytic performances (toluene yield, C1–C4 formation, coke deposit) as the presulfided bimetallic samples. This effect is attributed to an efficient passivation of hydrogenolytic activity at low Ge contents. At higher Ge contents a drastic decrease of the toluene yield is observed due to a strong poisoning of the metal phase and the formation of isolated Ge species. [Copyright &y& Elsevier]

Abstract: Pt–Re/Al2O3 and Pt–Ir/Al2O3 catalysts were modified by addition of an inactive metal, germanium, in order to suppress the strong hydrogenolytic activity of these types of catalysts. The influence of the addition method of germanium over Pt–Re and Pt–Ir catalysts was studied in order to find which one (catalytic reduction, successive impregnations and coimpregnation methods were used) produced the best trimetallic catalysts in terms of activity, selectivity and passivation of the hydrogenolytic activity of the metal function of the parent bimetallic catalyst. Ge addition produces a significant decrease of the activity of the metal function, affecting both non-demanding and demanding reactions and also the methane production during n-heptane reforming. It also produces an inhibition of the acid function but the resulting acid/metal activity ratio is higher than that of the bimetallic parent catalysts. Catalytic reduction was found to be the best method of Ge addition in the case of the Pt–Ir catalyst series, producing the most stable catalysts, with the lowest cracking and the highest toluene yield. The same was true for the Pt–Re catalysts prepared by coimpregnation. [Copyright &y& Elsevier]

• New heterogenous Rh-Sn-B/Al 2 O 3 catalysts for selective hydrogenation of oleic acid to fatty alcohol were studied. • Sn and Rh were found to be in interaction, activity of the metal function and TPR traces being modified by tin addition. • Higher yields to oleyl alcohol as compared to other reported catalysts were obtained. • Sn addition limits the Rh activity for hydrogenation of the C C double bond thus increasing the formation of oleyl alcohol. The influence of tin loading of Rh-Sn-B/γ-Al 2 O 3 catalysts on the selective hydrogenation of oleic acid to fatty alcohol was studied. The catalysts were characterized by N 2 sorptometry, temperature programmed reduction and X-ray photoelectron spectroscopy. Cyclohexane dehydrogenation and cyclopentane hydrogenolysis were also used to evaluate the metal function. Sn and Rh are in interaction since the conversion values of the cyclohexane, cyclopentane, and TPR profiles are modified by tin addition. Moreover, XPS analysis showed that Sn modifies the amount of Rh on the surface and its reduction state. The yield to oleyl alcohol was maximum for the Rh(1 wt%)-Sn(4 wt%)-B/γ-Al 2 O 3 and Rh(1 wt%)-Sn(5 wt%)-B/γ-Al 2 O 3 catalysts. This behavior could be explained considering that the Sn addition limits the Rh activity for hydrogenation of the C C double bond, thus increasing the formation of oleyl alcohol. At low Sn content, high selectivity to octadecane appears due to the total hydrogenation of the C C, C OH and C O bonds. [ABSTRACT FROM AUTHOR]