Catalytic performance of commercial Cu-ZSM-5 zeolite modified by desilication in NH3-SCR and NH3-SCO processes

[EN] In the presented manuscript an influence of the mesoporosity generation in commercial ZSM-5 zeolite on its catalytic performance in two environmental processes, such as NO reduction with ammonia (NH3SCR, Selective Catalytic Reduction of NO with NH3) and NH3 oxidation (NH3-SCO, Selective Catalytic Oxidation of NH3) was examined. Micro-mesoporous catalysts with the properties of ZSM-5 zeolite were obtained by desilication with NaOH and NaOH/TPAOH (tetrapropylammonium hydroxide) mixture with different ratios (TPA+/OH- = 0.2, 0.4, 0.6, 0.8 and infinity) and for different durations (1, 2, 4 and 6 h). The results of the catalytic studies (over the Cu-exchanged samples) showed higher activity of this novel mesostructured group of zeolitic materials. Enhanced catalytic performance was related to the generated mesoporosity (improved Hierarchy Factor (HF) of the samples), that was observed especially with the use of Pore Directing Agent (PDA) additive, TPAOH. Applied desilication conditions did not influence significantly the crystallinity of the samples (X-ray diffraction analysis (XRD)), despite the treatment for 6 h in NaOH solution, which was found to be too severe to preserve the zeolitic properties of the samples. The modified porous structure and accessibility of acid sites (increased surface acidity determined by temperature programmed desorption of ammonia (NH3-TPD)) influenced the red-ox properties of copper species introduced by ion-exchange method (temperature programmed reduction with hydrogen (H-2-TPR). Increased acidity of the micro-mesoporous samples, as well as the content of easily reducible copper species resulted in a significant improvement of Cu-ZSM-5 catalytic efficiency in the NH3-SCR and NH3-SCO processes. (C) 2017 Elsevier Inc. All rights reserved.This work was supported by the National Science Center under grant no. 2011/03/N/ST5/04820. Part of the research was carried out with the equipment purchased thanks to the financial support of the European Regional Development Fund in the framework of the Polish Innovation Economy Operational Program (contract no. POIG.02.01.00-12-023/08). U. D. acknowledges to Spanish Government by the funding (MAT2014-52085-C2-1-P).Rutkowska, M.; Pacia, I.; Basag, S.; Kowalczyk, A.; Piwowarska, Z.; Duda, M.; Tarach, K.... (2017). Catalytic performance of commercial Cu-ZSM-5 zeolite modified by desilication in NH3-SCR and NH3-SCO processes. Microporous and Mesoporous Materials. 246:193-206. https://doi.org/10.1016/j.micromeso.2017.03.017S19320624

Linking the defective structure of Boron-Doped Carbon Nano-Onions with their catalytic properties: Experimental and theoretical studies

Defects are widely present in nanomaterials, and they are recognized as the active sites that tune surface properties in the local region for catalysis. Recently, the theory linking defect structures and catalytic properties of nanocatalysts has been most commonly described. In this study, we prepared boron-doped carbon nano-onions (B-CNOs) by applying an annealing treatment of ultradispersed nanodiamond particles and amorphous boron. These experimental conditions guarantee doping of CNOs with boron atoms in the entire carbon nanostructure, thereby ensuring structural homogeneity. In our research, we discuss the correlations between defective structures of B-CNOs with their catalytic properties toward SO2 and tert-butanol dehydration. We show that there is a close relationship between the catalytic properties of the B-CNOs and the experimental conditions for their formation. It is not only the mass of the substrates used for the formation of B-CNOs that is crucial, that is, the mass ratio of NDs to amorphous B, but also the process, including temperature and gas atmosphere. As it was expected, all B-CNOs demonstrated significant catalytic activity in HSO3– oxidation. However, the subsequent annealing in an air atmosphere diminished their catalytic activity. Unfortunately, no direct relationship between the catalytic activity and the presence of heteroatoms on the B-CNO surface was observed. There was a linear dependence between catalytic activity and Raman reactivity factors for each of the B-CNO materials. In contrast to SO2 oxidation, the B-CNO-a samples showed higher catalytic activity in tert-butanol dehydration due to the presence of Brønsted and Lewis acid sites. The occurence of three types of boron-Lewis sites differing in electron donor properties was confirmed using quantitative infrared spectroscopic measurements of pyridine adsorption

Recovering waste plastics using shape-selective nano-scale reactors as catalysts

Waste plastic composed of low-density polyethylene can be converted into a potential new fuel source. This research describes a new nano-scale catalyst with well-defined and uniform surface openings. This material, called Al-SBA-15, is shape-selective, so it uses only one step to generate a gasoline-type product that requires less additional processing compared to that produced by previous catalysts.This work was supported by the Netherlands Organization for Scientific Research (NWO), under the Vidi grant no. 10284, carried out at the ITM-FWN, Groningen University. We acknowledge the support of the industrial steering committee (Shell, DSM, Norit-Cabot Nederland) and R. Winkler (Dutch Technology Foundation). Special thanks go to M. Rigutto (Shell) for his cooperation. We acknowledge E. Polushkin (Polymer Chemistry and Bioengineering, Zernike Institute for Advanced Materials, University of Groningen) for his technical assistance and the NWO for the financial support for project no. 700.58.103 (Small Angle X-ray Facility). M.R.R. acknowledges the US Department of Energy Office of Science (Basic Energy Sciences) for research funding and the National Energy Research Scientific Computing Center (NERSC), a US Department of Energy Office of Science User Facility operated under Contract No. DE-AC02-05CH11231 for access to supercomputing facilities. K.G-M and K.T. acknowledge the National Science Centre, Poland (grant no. 2015/18/E/ST4/00191). We also thank M. Hadfield (Analytix) for his assistance. D. Wiersma and B. Feringa (Groningen University) are thanked for support in setting a TGA apparatus. M. Makkee and his team (TU-Delft) are thanked for support, and guidance, in setting advanced infrastructure for heterogeneous catalysis research at Groningen University, by endorsing a capital STW research grant