Synthesis of Porous Clay Heterostructures Modified with SiO2–ZrO2 Nanoparticles for the Valorization of Furfural in One-Pot Process

The layered structure of two smectites (montmorillonite and saponite) are modified by the insertion of SiO2–ZrO2 nanoparticles, with a Si/Zr molar ratio of 5, to form porous clay heterostructures (PCHs). These PCHs exhibit a clear improvement of the textural and acid properties in comparison to the starting clays, due to the formation of a pillared structure and the presence of Zr species, which provide an increase in the amount of Lewis acid sites. These materials are studied in one-pot catalytic processes to transform furfural into valuable products, such as furfuryl alcohol, alkyl furfuryl ethers, alkyl levulinates or γ-valerolactone, depending on the experimental conditions. Thus, the use of milder reaction temperature (110 °C) favors the formation of furfuryl alcohol and alkyl furfuryl ethers, while higher temperatures (170 °C) promote the formation of alkyl levulinate and γ-valerolactone, as well as an increase in nondetected products associated to the formation of humins due to the polymerization of furfural and/or furfuryl alcohol.The authors are grateful for financial support from the Spanish Ministry of Science, Innovation and Universities (RTI2018-94918-B-C44 project), FEDER (European Union) funds (UMA18-FEDERJA-171), and the University of Malaga. C.P.J.-G. and C.G.-S. acknowledge Junta de Andalucía and FEDER funds, respectively, for their postdoctoral contracts. Funding for open access charge: Universidad de Málaga/CBUA

Porous SiO2 Nanospheres Modified with ZrO2 and Their Use in One- Pot Catalytic Processes to Obtain Value-Added Chemicals from Furfural

Porous SiO2 nanospheres have been modified with different proportion of ZrO2 to obtain catalysts with Si/Zr molar ratio between 2.5 and 30. These materials were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, N2 adsorption-desorption at -196 ºC, X-ray photoelectron spectroscopy and pyridine and 2-6-dimethylpyridine thermoprogrammed desorption. The characterization of these catalysts reveals that the incorporation of a high proportion of Zr favors the formation of Lewis acid sites, which are implied in catalytic transfer hydrogenation processes, whereas the low Brönsted acidity promote dehydration reaction, in such a way that it is possible to obtain a wide range of products from FUR through consecutive reactions, such as furfuryl alcohol, i-propyl furfuryl ether, i-propyl levulinate and γ-valerolactone in a range of temperature of 110-170 ºC between 1-6 h of reaction.Spanish Ministry of Science, Innovation and Universities:RTI2018‐94918‐B‐C44; FEDER (European Union) funds: RTI2018‐94918‐B‐C44 and UMA18-FEDERJA-171; University of Malaga; Junta de Andalucía; Funding for open access charge: Universidad de Málaga/CBU

Preparation, characterization and catalytic applications of ZrO2 supported on low cost SBA-15

This work presents some applications of ZrO2 supported over SBA-15 silica as promoter of sulfated zirconia and as support from CuO/CeO 2 catalytic system for preferential oxidation of CO to CO2 in hydrogen rich streams, used as feed for proton exchange membrane fuel cells (PEMFC). Different amounts of ZrO2, from 10 to 30 wt.% were incorporated. These prepared materials were characterized by powder XRD, adsorption-desorption of N2 at 77 K, transmission and scanning electron microscopy (TEM and SEM) and X-rays photoelectron spectroscopy (XPS). The acidity was studied by thermo-programmed desorption of ammonia (NH 3-TPD). These materials were tested, after treatment with H 2SO4, by 2-propanol dehydration and 1-butene isomerization catalytic tests. The samples were found quite good catalyst with strong acid sites, the sample with 20 wt.% of ZrO2 being the better performing sample. Finally this material was successfully used as support for a CuO/CeO2 system, with 6 wt.% of Cu and 20 wt.% of Ce. The resulting catalyst was tested in the preferential oxidation of CO (CO-PROX) attaining conversions close to 100% and high selectivity to CO2

Continuous-Flow Methyl Methacrylate Synthesis over Gallium-Based Bifunctional Catalysts

This paper reports on a systematic study on the catalytic gas-phase synthesis of methyl methacrylate (MMA) by means of the hydroxymethylation and dehydration of methyl propionate (MP) with formaldehyde (FAL), the latter being produced in situ by methanol (MeOH) dehydrogenation. This represents a promising variant of the current industrial Alpha process in which pure FAL is fed, alongside MP, into a gas-phase fixed-bed reactor filled with a supported Cs2O catalyst. In this way, an alternative process avoiding the need to feed carcinogenic FAL has been developed by feeding MeOH vapors onto a catalyst with dehydrogenating properties. For this purpose, an innovative Ga oxide-based bifunctional catalytic system is herein described for the first time for this peculiar application. Its catalytic performance and its chemical\u2013physical features were investigated and evaluated to explain structure\u2013activity relationships. Side reactions, MP ketonization, and MMA hydrogenation via H-transfer were accelerated in the presence of strong basic sites. The commercial, low-surface-area \u3b2-Ga2O3 catalyst showed a strong dehydrogenating activity and the highest selectivity toward MMA due to its weak basicity. However, deactivation was observed due to (i) the deposition of carbonaceous species onto surface acidic sites, as evidenced by means of X-ray photoelectron spectroscopy (XPS) analysis, and (ii) the loss of specific surface area. On the other hand, Ga3+ could be easily incorporated into MgO by means of a simple co-precipitation technique, leading to Mg/Ga mixed oxides with a high specific surface area. When relatively small amounts of Ga3+ were used (e.g., in a Mg/Ga mixed oxide with the Mg/Ga atomic ratio = 10), the catalyst was much more active in MeOH dehydrogenation with respect to pure MgO. Moreover, the presence of Ga3+ ions reduced the density and strength of the basic sites while increasing the selectivity toward MMA by decreasing the occurrence of the H-transfer and ketonization reactions, which, conversely, readily occurred on highly basic MgO. On the other hand, the Mg/Ga mixed oxide with Mg/Ga = 10 showed a weaker acidity compared to \u3b2-Ga2O3 and better stability due to limited coking. These results have shown both the potential and limitations of this alternative strategy. In particular, a more selective transformation of methanol to MMA needs to be achieved to allow the applicability of the proposed strategy on a bigger scale. Therefore, future efforts will be devoted to catalyst and condition optimization, also with the aim of limiting methanol unselective decomposition reactions

Furfuryl alcohol from furfural hydrogenation over copper supported on SBA-15 silica catalysts

Vapor phase furfural hydrogenation has been investigated over Cu supported on SBA-15 silica catalysts. These SBA-Cu catalysts, with variable Cu loadings (8, 15 and 20 wt%), have been prepared by impregnation and characterized by N2 sorption, XRD, XPS, N2O decomposition and TEM techniques. Compared with copper chromite, SBA-Cu catalysts showed a better catalytic performance, reaching a furfural conversion of 54 mol% and a selectivity to furfuryl alcohol of 95 mol%, after 5 h of time-on-stream at 170 °C, with the 15 wt% Cu catalyst. The studies of the used catalysts by CNH analysis and thermo-programmed oxidation (TPO) evidenced a lower amount of carbonaceous deposits on this used SBA-15Cu catalyst. Moreover, the study of the copper dispersion by XPS, before and after the catalytic test, revealed that this intermediate copper loading gives rise to the most stable copper particles. The evaluation of the effect of different reaction parameters, such as reaction temperature (170–270 °C), catalyst loadings and furfural concentration and H2 flow, on the catalytic performance has demonstrated that higher conversion are attained at low reaction temperature, and, as expected, by using high catalyst weight and low furfural feed.The authors are grateful to financial support from Spanish Ministry of Economy and Competitiveness (CTQ2012-38204-C03-02), FEDER funds and Junta de Andalucía (P09-FQM-5070). RMT for the financial support under the Program Ramón y Cajal (RYC-2008-03387) and Consejo Nacional de Ciencia y Tecnología (CONACyT, México) for financial support via scholarships (219821).N