Determination of integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on solid acid catalysts
TL;DR: In this article, the integrated molar extinction coefficients for infrared absorption bands of pyridine adsorbed on acid sites in Si/Al-based catalysts were determined for infrared spectra of five zeolites and two amorphous silica-aluminas.
About: This article is published in Journal of Catalysis.The article was published on 1993-06-01. It has received 2429 citations till now. The article focuses on the topics: Pyridine & Lewis acids and bases.
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961 citations
TL;DR: An integrated biorefinery that converts 78 weight % of birch into xylochemicals is developed that predicts an economically competitive production process, and a life-cycle assessment estimates a lower carbon dioxide footprint relative to that of fossil-based production.
Abstract: The profitability and sustainability of future biorefineries are dependent on efficient feedstock use. Therefore, it is essential to valorize lignin when using wood. We have developed an integrated biorefinery that converts 78 weight % (wt %) of birch into xylochemicals. Reductive catalytic fractionation of the wood produces a carbohydrate pulp amenable to bioethanol production and a lignin oil. After extraction of the lignin oil, the crude, unseparated mixture of phenolic monomers is catalytically funneled into 20 wt % of phenol and 9 wt % of propylene (on the basis of lignin weight) by gas-phase hydroprocessing and dealkylation; the residual phenolic oligomers (30 wt %) are used in printing ink as replacements for controversial para-nonylphenol. A techno-economic analysis predicts an economically competitive production process, and a life-cycle assessment estimates a lower carbon dioxide footprint relative to that of fossil-based production.
506 citations
TL;DR: A direct stepwise method for converting methane into methanol with high selectivity over a copper-containing zeolite, based on partial oxidation with water, involving methane oxidation at CuII oxide active centers, followed by CuI reoxidation by water with concurrent formation of hydrogen.
Abstract: Direct functionalization of methane in natural gas remains a key challenge. We present a direct stepwise method for converting methane into methanol with high selectivity (~97%) over a copper-containing zeolite, based on partial oxidation with water. The activation in helium at 673 kelvin (K), followed by consecutive catalyst exposures to 7 bars of methane and then water at 473 K, consistently produced 0.204 mole of CH3OH per mole of copper in zeolite. Isotopic labeling confirmed water as the source of oxygen to regenerate the zeolite active centers and renders methanol desorption energetically favorable. On the basis of in situ x-ray absorption spectroscopy, infrared spectroscopy, and density functional theory calculations, we propose a mechanism involving methane oxidation at CuII oxide active centers, followed by CuI reoxidation by water with concurrent formation of hydrogen.
495 citations
TL;DR: In this paper, a scale of acidity and an evaluation of the relative acid strength at different temperatures (373 −773 K) were obtained for both Bronsted and Lewis-acid sites.
Abstract: Pyridine and ammonia have been used as probe molecules for the quantitative analysis of surface acidity of some solid catalysts by FTIR spectroscopy. For pyridine, a scale of acidity and an evaluation of the relative acid strength at different temperatures (373–773 K) were obtained for both Bronsted- and Lewis-acid sites. Correlation was verified between the concentration of Bronsted sites and the catalytic activity of the catalysts examined for the dehydration of 2-(2-hydroxyethyl)pyridine to 2-vinylpyridine. In contrast, ammonia was a much less reliable probe, mainly due to the overlapping of the resulting IR absorption bands. Moreover, it decomposed even at rather low temperatures, when adsorbed onto the catalysts.
456 citations
TL;DR: In this paper, an equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading.
Abstract: The main objective of the present work was the study of different ZSM-5 catalytic formulations for the in situ upgrading of biomass pyrolysis vapors. An equilibrium, commercial diluted ZSM-5 catalyst was used as the base case, in comparison with a series of nickel (Ni) and cobalt (Co) modified variants at varying metal loading (1–10 wt.%). The product yields and the composition of the produced bio-oil were significantly affected by the use of all ZSM-5 catalytic materials, compared to the non-catalytic flash pyrolysis, producing less bio-oil but of better quality. Incorporation of transition metals (Ni or Co) in the commercial equilibrium/diluted ZSM-5 catalyst had an additional effect on the performance of the parent ZSM-5 catalyst, with respect to product yields and bio-oil composition, with the NiO modified catalysts being more reactive towards decreasing the organic phase and increasing the gaseous products, compared to the Co 3 O 4 supported catalysts. However, all the metal-modified catalysts exhibited limited reactivity towards water production, while simultaneously enhancing the production of aromatics and phenols. An interesting observation was the in situ reduction of the supported metal oxides during the pyrolysis reaction that eventually led to the formation of metallic Ni and Co species on the catalysts after reaction, which was verified by detailed XRD and HRTEM analysis of the used catalysts. The Co 3 O 4 supported ZSM-5 catalysts exhibited also a promising performance in lowering the oxygen content of the organic phase of bio-oil.
446 citations