Amount Of Acid Sites Research Articles

Development of a Ru catalyst supported on HY zeolite for the oxidative decomposition of NH3 triggered at room temperature

On-site hydrogen production from the oxidative decomposition of NH3 with a catalyst is highly required in the countryside where external heat is hardly supplied. In this study, Ru-based zeolite catalysts were prepared by impregnation and subsequent washing using RuCl3·3H2O and HY zeolite or H-MOR zeolite for the oxidative decomposition of NH3. The H-MOR-supported Ru catalyst could not be self-heated by feeding 80% NH3/20% O2 to the catalyst bed at room temperature. By contrast, the HY-supported Ru catalyst underwent self-heating to approximately 773 K upon feeding the reactants owing to the heat released by NH3 adsorption and oxidation, leading to excellent performance for the oxidative decomposition of NH3 during five cycles of start-up tests. Characterization results indicated that the Cl-free Ru/HY catalyst exhibited self-heating due to the presence of small well-dispersed Ru metal particles and a large amount of surface acidic sites.

Ethanol Coupling Reactions over MgO-Al2O3 Mixed Oxide-Based Catalysts for Producing Biofuel Additives.

Catalytic conversion of ethanol to 1-butanol was studied over MgO-Al2O3 mixed oxide-based catalysts. Relationships between acid-base and catalytic properties and the effect of active metal on the hydrogen transfer reaction steps were investigated. The acid-base properties were studied by temperature-programmed desorption of CO2 and NH3 and by the FT-IR spectroscopic examination of adsorbed pyridine. Dispersion of the metal promoter (Pd, Pt, Ru, Ni) was determined by CO pulse chemisorption. The ethanol coupling reaction was studied using a flow-through microreactor system, He or H2 carrier gas, WHSV = 1 gEtOH·gcat.-1·h-1, at 21 bar, and 200-350 °C. Formation and transformation of surface species under catalytic conditions were studied by DRIFT spectroscopy. The highest butanol selectivity and yield was observed when the MgO-Al2O3 catalyst contained a relatively high amount of strong-base and medium-strong Lewis acid sites. The presence of metal improved the activity both in He and H2; however, the butanol selectivity significantly decreased at temperatures ≥ 300 °C due to acceleration of undesired side reactions. DRIFT spectroscopic results showed that the active metal promoted H-transfer from H2 over the narrow temperature range of 200-250 °C, where the equilibrium allowed significant concentrations of both dehydrogenated and hydrogenated products.

Mechanistic studies of lower temperature isomerization of n-heptane over fibrous silica molybdenum catalyst

Platinum (Pt) inclusion on fibrous silica molybdenum (FSMO) and MoO3/KCC-1 catalysts has been prepared and utilized for the lower temperature (200–350 °C) catalytic isomerization of n-heptane. The impact of Pt inclusion towards the structure, morphology, and acid distribution of catalysts was characterized by XRD, FTIR, N2-physisorption, Py-IR, and H2-IR. Compared with MoO3/KCC-1, FSMO demonstrated superior MoO3 dispersion and amount of Lewis acid site associated with the in-situ synthesis technique. Although Pt inclusion slightly lessened acid sites due to inevitable partial coverage by the Pt cluster, the considerably higher amount of Lewis acid sites compared to Brønsted and conjugated sufficiently for generating protonic acid sites for enriching the isomerization activity. In contrast to Pt/MoO3/KCC-1 and undoped catalysts, Pt/FSMO achieved a superior conversion of 70.9% with 63.6% isomer yield at a low temperature of 250 °C. The 28-h stability tests demonstrated that Pt/FSMO recorded stable isomerization activity, with a superior isomer yield (∼48–52%) and inferior cracking yield (<3.0%) than Pt/MoO3/KCC-1.

The role of porosity and acidity in the catalytic upcycling of polyethylene

Plastics have become fundamental and widespread materials in our everyday life. Nowadays, the most demanded plastics are polyolefins, accounting for nearly half of the Global plastic production. However, the end-of-life disposal of these materials is an issue inevitably connected to their increased production. Among chemical recycling techniques, the most thoroughly investigated process is the catalytic pyrolysis, showing a vast panorama of different set-ups optimized for the major production of either gaseous or liquid compounds. In this contribution a series of mesoporous silica-based materials, either pure SiO2 or substituted with Zr and Al, were systematically synthetized varying both porous framework and surface acidity, in the attempt of rationalizing the effect of each parameter (deeply characterized by physico-chemical methods) on the catalytic pyrolysis of linear low-density polyethylene (LLDPE). The synthetized materials together with some zeolites and aluminas reference samples were tested towards LLDPE degradation in a batch reactor set-up optimized for the formation and accumulation of the gaseous compounds, coupled with IR spectroscopy for in situ monitoring the evolution of the most abundant species (mostly propylene and branched C4-C6 olefins, together with a minor fraction of ethylene and short hydrocarbons). This work points out the necessity of the presence of Brønsted acid sites for a good activity (in terms of both the yield of gaseous products and lowering of the process temperature), but it also reveals a non-negligible role of the Lewis acid sites and it warns about the importance of controlling not only the amount of acid sites but also their strength.

Superior adsorption and removal of toxic industrial dyes using cubic Pm3n aluminosilica form an aqueous solution, Isotherm, Kinetic, thermodynamic and mechanism of interaction

In the current work, a direct synthesis method was used to create an ordered mesocage cubic Pm3n aluminosilica nanoadsorbent with mesopores and a monolith-like shape. Rhodamine B (RB), a harmful dye for the environment, was successfully removed from wastewater using this aluminosilica nanoadsorbent. The aluminosilica nanoadsorbent's multi-directional pores (3D), mesostructural geometries, and loading amount of Bronsted acid sites were important in improving the coverage of the nanoadsorbent surfaces and intra-particle diffusion of adsorbate (RB) molecules onto the network surfaces and into the pore architectures of monoliths. The cubic Pm3n aluminosilica composite was characterized via XRD, EDX, XPS, FT-IR, HRSEM, BET, HRTEM, and pHzpc which was 4.05. The effect of pH on the adsorption process has been studied. In addition, the initial concentration approves that the reaction fitted to Langmuir. While, during the study, the effect of time the adsorption kinetic model was fitted to the pseudo-second order. On the other hand, the effect of temperature was proof that the reaction was spontaneous and endothermic. The RB was adsorbed at cubic Pm3n aluminosilica composite with high amount 1.75 mmLg−1. However, the reusability showed that the efficiency of the removal of RB using this adsorbent was more than 91 % after 6th cycle. The capability to design reversal RB adsorption systems with several reuse cycles is a key characteristic of the cubic Pm3n aluminosilica composite.

Synthesis of etheric ester based biofuel additive over bifunctional metal/zeolite catalysts comprising NiRe nanoparticles and Beta zeolite

Biomass derived etheric ester compounds show promising applications as renewable fuel additives and solvents. In this study, we reported the preparation of bifunctional transition metal/zeolite catalysts comprising Ni-Re bimetal nanoparticles and Beta zeolites prepared via conventional wet-impregnation method. The bifunctional nature makes it possible for the synthesis of ethyl-4-ethoxy pentanoate (EEP) as etheric ester starting from ethyl levulinate (EL) in presence of H2 with good performance. The textural properties and acidity of the catalysts were characterized by several techniques: XRD, TEM, STEM-Mapping, H2-TPR and XPS. The addition of ReOx increased the dispersion and reducibility of NiO·NH3-TPD and in-situ FT-IR of pyridine adsorption confirmed that the NiReOx/Beta catalyst affords large amount of Lewis acid sites and certain amount of Bronsted acid sites. The attained Bronsted acid sites in BEA topology may be the key sites contributing to the etherification. Under optimized reaction conditions, namely 160 °C, 1 MPa H2 and reaction time of 2 h, almost full conversion of EL with 83% yield of EEP could be achieved in ethanol.

Ni2P/Beta@SBA-16 core-shell catalyst with tunable shell thickness for the hydrodenitrogenation of quinoline

A series of core-shell structural hydrodenitrogenation (HDN) catalyst supports, using H-Beta zeolite nanoparticles as the core and tunable mesoporous materials SBA-16 thin film thickness as shell, were designed and controllably synthesized. The corresponding Ni2P catalyst were prepared, and their catalytic performances were tested for quinoline HDN. It was found that the high external surface area provided by the mesoporous shell layer of the core-shell catalyst favored the formation of Ni2P nanoparticles with more uniform particle size. The Py-IR result indicates that the SBA-16 shell thickness plays an important role in influencing the ratio of the amount of Bronsted and Lewis acid sites on the catalyst. The H2-TPR results indicates that the introduction of core-shell structure can adjust the metal-support interactions (MSI) of materials. The core-shell support with suitable shell thickness (70 nm) exhibits a wide pore structure, large surface area and sufficient amounts of Lewis and Bronsted acid sites. These properties contribute to the formation of tiny and size homogeneous (4.6 nm) Ni2P nanoparticles. Smaller Ni2P particles present more active sites, which increases catalytic activity. The Ni2P/H-Beta@SBA-16–2 catalyst with the most suitable shell thickness exhibited a higher reaction rate constant and TOF for HDN reaction of quinoline.

Enhanced Resistance to Pb Poisoning of the Co‐modified Mn/Fe‐pillared Clay Catalysts for NH3‐SCR at Low Temperatures

AbstractLead (Pb) is a heavy metal commonly found in industrial exhaust gases, which can reduce catalytic activity of a catalyst for the NH3‐SCR reaction. In this study, 4.0 wt% Mn‐loaded Fe‐pillared interlayer clay (4Mn/Fe‐PILC) and its Co‐modified catalyst (2Co‐4Mn/Fe‐PILC) were prepared, in the meanwhile the 4Mn/Fe‐PILC‐Pb and 2Co‐4Mn/Fe‐PILC‐Pb samples were also obtained using the impregnation method with a Pb(CH3COO)2 aqueous solution. It was found that the addition of 2.0 wt% cobalt could significantly enhance Pb resistance of the 4Mn/Fe‐PILC catalyst. The characterization results revealed that the doping of Co to Mn/Fe‐PILC increased the surface Mn4+ species concentration, reducibility, and acid site amount, thereby improving Pb resistance of the catalyst. Furthermore, the in situ DRIFTS results demonstrated that Co modification enhanced the adsorption capacity of NH3 or NO, especially influenced formation of the NH3 intermediates and bridging nitrate species, which were also conducive to the improvement in Pb resistance of the catalyst.

One-Pot Conversion of Furfural to γ-Valerolactone over Co- and Pt-Doped ZSM-5 Catalysts

γ-Valerolactone (GVL) is one of the useful biomass compounds produced via different reaction pathways from hemicellulose. In this study, Co- and Pt-doped/ZSM-5 catalysts with different Co loadings (0–10 wt.%) and Pt loadings (0.5–2 wt.%) were prepared by impregnation method and employed in a one-pot conversion of furfural to GVL. The yield of GVL increased with increasing reaction temperature from 100 to 140 °C. At the reaction temperature of 120 °C, higher amounts of secondary products such as AL and IPL can be converted to GVL, especially on the Co- and Pt-modified ZSM-5 catalysts. Compared to the non-modified H-ZSM-5 (GVL yield 35.4%), Co- and Pt-doped ZSM-5 catalysts exhibited much higher yield of GVL with the 1%Pt/ZSM-5 catalyst showing the highest yield of GVL at 85.4% at 120 °C and 1 bar N2 without the use of liquid acid or external H2 supply. The catalyst performances were correlated to the physicochemical properties of the catalysts such as the amount and type of acid sites. The NH3-TPD and in situ FTIR spectra of pyridine adsorption results revealed that Co- and Pt-loaded on ZSM-5 enhanced Lewis and weak acid sites, which are beneficial for the reaction. The results present a simple strategy to obtain high GVL yield under relatively mild conditions.

Impacts of support properties on the vacuum residue slurry-phase hydrocracking performance of Mo catalysts

To deeply understand the effects of support properties on the performance of Mo-based slurry-phase hydrocracking catalysts, four Mo-based catalysts supported on amorphous silica alumina (ASA), γ-Al2O3, ultra-stable Y (USY) zeolite and SiO2 were prepared by the incipient wetness impregnation method, respectively, and their catalytic performances were compared in the vacuum residue (VR) hydrocracking process. It is found that the Mo/ASA catalyst exhibits the highest VR conversion among the different catalysts, indicating that both the appropriate amount of acid sites, especially B acid sites and larger mesoporous volume of ASA can enhance the VR hydrocracking into light distillates. Furthermore, Mo catalysts supported on the different supports show quite different product distributions in VR hydrocracking. The Mo/ASA catalyst provides higher yields of naphtha and middle distillates and lower yields of gas and coke compared with other catalysts, it is attributed to the highest MoS2 slab dispersion, the highest sulfuration degree of Mo species, and the most Mo atoms located at the edge sites for the Mo/ASA catalyst, as observed by HRTEM and XPS analyses. These features of Mo/ASA are beneficial for the hydrogenation of intermediate products and polycyclic aromatic hydrocarbons to restrict the gas and coke formation.

Graphitic carbon nitride (g-C3N4) as a super support for Mn–Ce based NH3-SCR catalyst: Improvement of catalytic performance and H2O/SO2 tolerance for NOx removal

Low temperature NH3 selective catalytic reduction (NH3-SCR) technology is an efficient and economical strategy for NOx removal. In this study, Mn–Ce oxides supported on graphitic carbon nitride (g-C3N4) was applied to the NH3-SCR of NOx at low temperature compared with Mn–Ce oxides supported on commercial TiO2, γ-Al2O3, and montmorillonite (MNT). The NOx conversion and H2O/SO2 tolerance of 8% Mn–Ce/g–C3N4–300 were superior to those of 8% Mn–Ce/TiO2-300, 8% Mn–Ce/γ-Al2O3-300 and 8% Mn–Ce/MNT-300 in the temperature window of 100–300 °C, and more than 95% NOx conversion could be obtained within the whole temperature range. According to the experimental and characteriazation results, the superior low temperature NH3-SCR performance of 8% Mn–Ce/g–C3N4–300 could be attributed to the formation of Ce–O–Mn solid solution structure, the higher concentrations of the surface elements, the optimun low-temperature reduction behavior, the largest amount of total acid sites, the highest (Mn4++Mn3+)/(Mn4++Mn3++Mn2+) and (Ce3+)/(Ce3++Ce4+) ratios, and the modest Oα/(Oα+Oβ) ratio.

Unveiling geometric and electronic effects of Pt species on water-tolerant Pt/ZSM-5 catalyst for propane oxidation

Si/Al ratio of ZSM-5 affecting Pt/ZSM-5 catalyst water-tolerance has been investigated for propane oxidation. Under wet condition (5 % H2O), it is found that Pt/ZSM-5 (18) catalyst contains both irreversible and reversible deactivation Pt active sites; Pt/ZSM-5 (130) and Pt/ZSM-5 (500) catalysts have only reversible deactivation Pt active sites; all the Pt active sites in the Pt/ZSM-5 (1200) catalyst are water tolerant. It is further found that the Si/Al ratio of ZSM-5 determines the geometrical and electronic states of Pt particles, and amount of surface acid sites on catalysts, thereby affecting the water tolerance of Pt/ZSM-5 catalyst. Low Si/Al ratio of ZSM-5 benefits to anchor the Pt species and form small Pt particles, but Pt particle with small size and more oxidized state Pt species (Ptδ+) on Pt/ZSM-5 (18) is easily poisoned by H2O. More Pt0 species generating on large Pt particle during propane oxidation reaction and low surface acid sites on Pt/ZSM-5 (1200) catalyst are responsible for its high water tolerance.

Excellent operating temperature window and H2O/SO2 resistances of Fe-Ce catalyst modified by different sulfation strategies for NH3-SCR reaction.

Expecting to gain an excellent operating temperature window and superior catalytic activity of the catalyst in SCR reaction, the Fe-Ce bimetallic oxide catalyst was firstly prepared and sulfated with two different sulfation strategies by H2SO4. It is interestingly found that both the two sulfation strategies can significantly broaden the operating temperature window of the catalyst. In particular, the SFC and FCS both exhibit superior resistance to H2O + SO2, and the NOx conversion of the SFC even displays no changes in the coexistence of H2O and SO2. The characterization results show that different sulfation strategies can generate amorphous sulfate species rather than bulk sulfate species. Furthermore, more surface-adsorbed oxygen as well as higher contents of Ce3+ and Fe3+ can be obtained on the sulfated catalysts, especially for the SFC catalyst. Meanwhile, different sulfation strategies will progressively enhance the redox ability and amounts of strong acid sites, which will contribute to broadening the operating temperature window for the NH3-SCR reaction. Additionally, different sulfation methods do not change the reaction pathway of catalysts. However, the adsorption of ad-NH3 species and reactivity of ad-NOx species are significantly changed. These lead to the reaction pathway shifts to E-R direct over the SFC and the promotion of E-R and L-H mechanisms over the FCS catalyst.

Different alkali metals promoted Cr/Al2O3 catalysts for propane dehydrogenation

Unmodified Cr/Al2O3 and Cr/Al2O3 doping with different alkali metals (Li, Na, K) were prepared by the incipient wetness impregnation method. The surface elements of all the catalysts are evenly distributed and well loaded, and the addition of alkali metals does not change the crystal structure and surface texture. Both Cr6+ and Cr3+ species exist on all catalysts, and the addition of alkali metals can increase the amount of Cr6+ species, and Cr6+ species are basically converted into active Cr3+ species in the reaction thus increasing the initial propane conversion in the reaction. The addition of alkali metals reduced the amount of total acid sites and the strong acid sites of the catalyst, thus inhibiting the occurrence of side reactions and the formation of carbon deposition, and reducing the deactivation rate of the catalyst. Cr-0.5Na/Al2O3 exhibited the best catalytic performance and the lowest carbon deposition.

Graphite supported heteropolyacid as a regenerable catalyst in the dehydration of 1-butanol to butenes

1-butanol dehydration reaction has recently emerged as a sustainable route to produce butenes which can be further oligomerized to be applied as jet fuel. However, the high catalyst deactivation rates observed during this reaction due to coke deposition is still a pending matter. As promising catalysts for this reaction, we have supported two heteropolyacids (HPA), i.e. H4SiW12O40 (STA) and H3PW12O40 (TPA), on two commercial carbon materials: an activated carbon (AC) and a high surface area graphite (HSAG). Aiming to evaluate the role of HPA-support interactions, the STA was also dispersed over metallic oxides of different acidic nature, namely SiO2, Al2O3 and ZrO2. An exhaustive physicochemical characterization revealed that after the HPA dispersion thorough the support, the Keggin structure was maintained and an increase in the amount and strength of acid sites was provoked, but in different degree according to the HPA type and support’s nature. While the TPA-based catalysts developed less quantity of total acid sites, but higher strength than their STA-carbon counterparts, the STA/AC and TPA/AC samples exhibited a slight major amount of acid sites than STA/HSAG and TPA/HSAG. The HPA-support interactions have ultimately modulated to some extent the activity, selectivity, stability and regeneration ability of the synthesized catalysts, when applied in the gas phase butanol dehydration reaction at 275 °C. The higher STA decomposition temperature prompted by the graphitic support, among other factors, allowed the total regeneration of the highly active (39 mmolBuOH∙min−1∙ga.p) and n-butenes selective (>98 %) STA/HSAG catalyst by means of combustion of carbon deposits at 400 °C.

Copper Foam-Supported CuxO@Fe2O3 Core–Shell Nanotubes: An Efficient Ozonation Catalyst for Degradation of Organic Pollutants

Copper foam (CF)-supported CuxO@Fe2O3 core–shell nanotubes (CF/CuxO@Fe2O3 NTs) were synthesized as a hybrid catalyst for heterogeneous catalytic ozonation (HCO). The hybrid catalyst exhibits high activity and excellent stability for the HCO of organic pollutants. The total organic carbon removal rates of methyl orange, ibuprofen, and nitrobenzene via HCO were 89, 82, and 88%, respectively, which are over 2 times higher than the corresponding values obtained without the catalyst. The hybrid catalyst also displays wide pH operation range, low metal leaching, easy separation from treated water, and excellent recyclability. We prove that large amounts of Lewis acid sites with medium acidity are created at the CuxO/Fe2O3 interface due to the synergic effect of CuxO and Fe2O3. These medium acid sites are the main active centers for the production of free hydroxyl radicals (•OH) and superoxide radicals (O2•– or HO2•) in neutral solution. Moreover, the 3D porous framework of the catalyst enables easy dispersion in and separation from water. This work develops a new strategy to design HCO catalysts by combining strong and weak Lewis acid oxides and also opens a new avenue for developing HCO catalysts on a 3D porous framework.

Mesoporous zeolite Beta supported Ni nanoparticles for the catalytic hydroconversion of extraction portion from Jinjitan subbituminous coal to cycloalkanes

The catalytic hydroconversion (CHC) of heavy carbon organic species (HCOSs) to cycloalkanes represents an importantly used chemical industry process due to the wide applicability of the resulting products in energy and fine chemistry. Despite the existing conventional catalysts applied to the CHC of HCOSs, the development of highly active bifunctional Ni-based heterogeneous catalysts for this process is still a challenge. Therefore, we show that the modified deposition–precipitation of nickel (II) nitrate on hydrothermally synthesized mesoporous zeolite Beta (MZB) prepares a Ni/MZB catalyst with a through-crosslinking mesopore structure and uniformly disperse Ni nanoparticles (NPs) at rough MZB crystal surface. The 10%Ni/MZB (10% Ni loading), in the presence of exposing on amount of accessible Lewis acid sites (LASs) and attaching Ni NPs by chemical bonding from the silica matrix of MZB skeleton, exhibits excellent activity to promote the CHC of all kind of aromatic rings and heteroatom-containing species, including chain alkanes, arenes, oxygen-containing organic compounds (OCOCs), nitrogen-containing organic compounds (NCOCs), and sulfur-containing organic compounds (SCOCs), to produce cycloalkanes and hydroarenes under mild conditions. Interestingly, density functional theory (DFT) calculations indicate that the transfer of biatomic active hydrogen (H…H) and heterogenous H+ from 10%Ni/MZB plays important roles during the CHC of diphenoxybenzene (DPOB). After being recycled 4 times, 10%Ni/MZB is still maintains high activity for CHC of DPOB under mild conditions.

Formation of PCDD/Fs, PCBs and HCl during catalytic combustion of chlorobenzene over supported transition metal (Cr, V and Cu) oxide catalysts

As an efficient scheme, catalytic combustion can be used to eliminate chlorinated volatile organic compounds (CVOCs). To avoid the formation of more toxic by-products, it is essential to reveal the relationship between the chlorine-containing products and redox properties of catalyst. In the present study, the activity for chlorobenzene (CB) oxidation, HCl production, and formation of by-products polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs) and polychlorinated biphenyls (PCBs)were investigated over γ-Al2O3-supported transition metal (Cr, V and Cu) oxide catalysts. The results showed that the 10Cr-Al catalyst with relatively high specific surface areaand more oxygen absorbed than other catalysts exhibited higher catalytic oxidation activity for CB. The temperatures needed for 90% conversion of CB (T90) were 331, 353 and 386 °C for 10Cr-Al, 10V-Al and 10Cu-Al, respectively. The amount and type of acid sites on the surface of catalysts play an important role in the distribution of products and by-products. It was found that the increase of acid sites and the presence of Brønsted acid (B-acid) significantly improve the HCl selectivity of catalysts. More HCl was formed on the 10V-Al catalyst with B-acid sites. Meanwhile PCDD/Fs and PCBs detected in the by-products had a tight relationship with the acidity sites and redox performance of the catalyst. The yields of ∑PCDD/Fs and ∑PCBs were the largest on 10V-Al at T10, reaching 25.60, 66.93 mmol/mol CB, respectively. The obtained results provided theoretical support for the subsequent development of CVOCs catalytic oxidation catalysts and the control of toxic by-products.

Function of Brønsted and Lewis acid sites in xylose conversion into furfural.

In this work, the xylose conversion and the selectivity to furfural were assessed over mesoporous sulfonic silica SBA-15-(X)SO3H catalysts doped with metal ions (X = Al(iii), Ti(iv) or Zr(iv)). The type and amount of acid sites were analyzed by adsorption of pivalonitrile. The SBA-15-(X)SO3H materials show Lewis acid sites (LAS) and two types of Brønsted acid sites (BAS) with different strengths. Type I (BAS I) belongs to terminal silanol groups, type II (BAS II) is ascribed to hydroxyl groups bonded to sulfur or transition metal, and the LAS is related to M-O bonds. Optimal reaction conditions for the most active catalyst (SBA-15-(Zr)SO3H) were 120 minutes of reaction at 160 °C, 20 wt% of catalyst, and 2.5% of xylose/solvent. Additionally, a kinetic study was carried out to calculate the rate constants, the activation energy, and the pre-exponential factor for the xylose dehydration reaction. It was found that the selectivity to furfural in sulfonic silica SBA-15-(X)SO3H catalysts was directly related to the BAS II fraction. While LAS negatively impacts the selectivity to furfural leading to the undesired reaction between furfural and xylose obtaining humins as secondary products.

CATALYTIC HYDROTHERMAL CONVERSION OF BIO-DERIVED SUGARS FOR LACTIC ACID PRODUCTION USING SOL-GEL SYNTHESIZED ZIRCONIA

The hydrothermal conversion of a multiple sugars solution (xylose, arabinose and glucose) was studied using high surface ZrO2-based catalysts to produce lactic acid. The catalysts were synthesized by template-assisted sol-gel method and alternative template removal procedures. Samples obtained by template extraction with solvent reported a specific surface area of 323 m2/g, a pore volume of 0.21 cm3/g and a total amount of acid sites of 359 µmol/g. An experimental design was performed to model lactic acid and by-products obtaining around the selected catalyst. The response surface methodology (RSM) was used to optimize the main operating conditions. A mass selectivity of 35.1 % towards lactic acid was found at 183 °C and 212 min. In addition, the reaction mechanisms involved were proposed based on intermediates and degradation compounds detected by HPLC analysis.