Abstract
Producing bio-based aromatic substrates is becoming increasingly of (industrial) interest. In this mechanistic work, the gas phase conversion of the biomass tar chemical model compounds (5 wt% naphthalene/95 wt% 1-methylnaphthalene) over the different pristine/metal-modified zeolites in a continuous flow fixed bed reactor was investigated. Bifunctional redox acid process catalysts were synthesized by wet impregnation method.
The effect of the W (/Ni) metal formulation additives to the pristine H-beta, H-USY, H-Y, and H-ZSM-5 in the hydrocracking, hydrogenation, and isomerization transformation reactions of the mixture under applied ambient pressure was firstly studied. Structure, texture, morphology, acidity, composition and properties were determined by various analytical techniques. Results showed that the highest catalytic activity with a comparison to others was established over the 20 wt% W-beta with 96.0 mol% of the selectivity to 2-methylnaphthalene, the 93.3 mol% reacted total reactant after the 24 h time on stream, where ethylene/propane were predominating (80.5 wt%), and facile manufacturing scalability.
Detailed characterization methodologies have revealed that after the loading of W onto H-beta_support, a uniform functional distribution of particles, the dealumination of framework and strong interaction phenomena were observed, which led to an increase in the amount of Brønsted/Lewis/reduction surface sites, and hence, increase stability of the catalyst. In addition, equilibrium coke formation was detected, decreasing all estimated rates, undergoing also consequent external deactivation, blocking pores, and its burning-off regeneration being needed. While both spent W-modified (20 wt%)/unmodified H-beta/ZSM-5 exhibited the lowest carbon quantity, the same fresh materials possessed the uppermost hierarchy factors.
Abstract
The gas phase selective hydrocracking process of tetralin (biomass tar model chemical compound) into benzene, toluene and xylenes (BTX) was carried out over the H-Beta, H-Mordenite, H-USY, H-Y, and H-ZSM-5 zeolite catalysts in a packed bed reactor under applied atmospheric pressure. To the best of our scientific knowledge, this performed work presents the first systematic investigation, focused on tetralin, cracking to BTX under ambient 1 bar.
The highest catalytic activity and carbon deposition resistance were established over the H-ZSM-5 (SiO2/Al2O3 = 30) with the selectivity to the BTX of 52.2 mol.% in intermediates’ liquid phase, 88.7 mol.% of total conversion yield after the 4 h time on stream, 370 °C and gas hourly space velocity (GHSV) = 530 h–1, and limited site deactivation. The gas phase was analyzed and ethylene, propane, ethane and methane were identified as main gas products in the product mixture at different reaction conditions. All catalysts were characterized by BET, ICP-AES, XRD, HRSEM, NH3-TPD, and pyridine-DRIFT technique.
This high catalytic performance of the H-ZSM-5 catalyst is attributed to the presence the high mesopore volume and mesopore surface area, the mild acidity and the highest Brönsted to Lewis acid sites ratio (BAS/LAS) comparing with other studied zeolite catalysts. Based on the experimental results, the reaction pathway of tetralin transformation into BTX was proposed. Hydrocracking, ring opening, ring contraction, dehydrogenation/hydrogenation, alkylation/dealkylation, isomerization, and overcracking reactions were involved. Results were consistent with the occurrence of the monomolecular reaction mechanism.
Abstract
Gas-phase conversion of a model mixture of biomass tar (5 wt% naphthalene and 95 wt% of 1-methylnaphthalene) into 2-methylnaphthalene liquid product and ethylene and propane gas mixture was carried out over different zeolites and metal promoted zeolites in a packed-bed reactor for the first time.
In the present work, a series of MFI (H-ZSM-5), BEA (H-β), FAU (H-Y, H-USY), and MOR (H-Mordenite) zeolites were investigated. The effect of Ni metal addition on the promotion of parent zeolite catalysts was studied. The most successful catalysts were characterized by BET, ICP-AES, XRD, HRSEM, STEM-HAADF, and STEM-BF with EDXS, NH3-TPD, H2-TPR, TGA, and pyridine-DRIFT techniques. The superior performance in comparison to the other studied catalysts was established over the 5 wt%Ni/H-ZSM-5 (SiO2/Al2O3 = 30) with 96.2 mol% of selectivity to 2-methylnaphthalene in the liquid phase, 90 mol% total conversion with the highest part (82.9 wt%) of ethylene and propane in the gas phase after 24 h time-on-stream.
This high catalytic performance of the 5 wt%Ni/H-ZSM-5 catalyst can be attributed to the presence of the high mesopore volume, pore diameter, and high mesopore surface area, the existence of the redox active sites, and the presence of strong Lewis acid sites due to synergetic interaction between Ni metal species and zeolite acid support. Based on the product distributions observed, the reaction scheme of the conversion of biomass tar model mixture of naphthalene and 1-methylnaphthalene over studied catalysts was proposed. Our catalytic results obtained over pristine and Ni-modified zeolite catalysts shed light on the potential use of these catalysts in the biomass tar valorization process under atmospheric pressure.
Abstract
In this experimental study, various NiMo-promoted (as follows: H-beta, H-mordenite, H-USY, H-Y, and H-ZSM-5) catalysts were prepared, tested, and compared with pristine zeolites for the purpose of the gas phase hydrocracking, hydrogenation, and isomerization in a packed bed reactor at 370 °C under atmospheric relative pressure. 5 wt.% naphthalene/95 wt.% 1-methylnaphthalene were selected as biomass tar model molecule compounds, based on real chemical compositions.
A series of material characterization techniques were applied to determine the physical structural, morphological, textural, redox, and acidic properties of synthesized catalysts. An outstanding catalytic activity and stability were found over the 2.5 wt.% Ni–2.5 wt.% Mo/ZSM-5 with high carbon deposition resistance, 2-methylnaphthalene selectivity (96.0 mol.%) in the liquid with the products with a yielded total conversion of 96.3 mol.% after an 18 h time on stream, where ethylene/propane were main (94.2 wt.%).
The latter can be attributed to the presence of mesopore volume/surface area, existing boundary interface, the amount of medium/strong acid sites, and the synergetic interaction phenomena between metal atom species/supports. Attention should be paid to particle size dimensions, diameters and acidity, which facilitated poly-aromatic hydrocarbon removal. Considering particular obtained distributions, intermediates reaction pathway was proposed. Cracking, synthetic ring opening, alkylation, condensation and disproportionation were additionally involved. Results were consistent with the occurrence of two competing mechanisms, a monomolecular, as well as a bimolecular one.
A detailed MILP formulation for the optimal design of advanced biofuel supply chains
Abstract
The optimal design of a biomass supply chain is a complex problem, which must take into account multiple interrelated factors (i.e the spatial distribution of the network nodes, the efficient planning of logistics activities, etc.). Mixed Integer Linear Programming has proven to be an effective mathematical tool for the optimization of the design and the management strategy of Advanced Biofuel Supply Chains (ABSC).
This work presents a MILP formulation of the economical optimization of ABSC design, comprising the definition of the associated weekly management plan. A general modeling approach is proposed with a network structure comprising two intermediate echelons (storage and conversion facilities) and accounts for train and truck freight transport. The model is declined for the case of a multi-feedstock ABSC for green methanol production tested on the Italian case study. Residual biomass feedstocks considered are woodchips from primary forestry residues, grape pomace, and exhausted olive pomace.
The calculated cost of methanol is equal to 418.7 €/t with conversion facility cost accounting for 50% of the fuel cost share while transportation and storage costs for around 15%. When considering only woodchips the price of methanol increases to 433.4 €/t outlining the advantages of multi-feedstock approach.
A Review of Catalytic Cracking Processes of Biomass-derived Hydrocarbon Tars or Model Compounds to Bio-based Benzene, Toluene and Xylene Isomer Mixtures
Andrii Kostyniuk, Miha Grilc, and Blaž Likozar Ind. Eng. Chem. Res., Just Accepted Manuscript DOI: 10.1021/acs.iecr.9b01219 Publication Date (Web): April 23, 2019 Copyright © 2019 American Chemical Society
Abstract
The gasification of biomass is one of the most prominent technologies for the conversion of the raw material feedstock to polymers, useful chemical substances and energy. The main engineering challenge during the processing of wastes is the presence of tars in gaseous reaction products, which could make this operation methodology unsuccessfully due to the blockage of separating particle filters, fuel line flow and substantial transfer losses.
Catalytic hydrocarbon cracking appears to be a promising developing approach for their optimal removal. However, the enhancement of catalyst activity kinetics, selectivity, stability, the resistance to (ir)reversible coke deposition, and its regeneration solutions are nowadays still highly in demand. The review is dedicated to the comparative systematic evaluation of the various natural, synthetic and hybrid types, converting the model molecular compounds into benzene, toluene, xylene (BTX), (poly)aromatics, syngas and others. The recent scientific progress, including calcite, dolomite, lime, magnesite, olivine, char, non-metallic activated carbons, supported alkali, noble and transition metals, and (metal-promoted) zeolites, is presented.
A special concentrated attention was paid to effectiveness, related to hydrogenation, peculiar pore structure and formulations’ suitable acidity. The role of catalysis is described, the recommendations for perspective catalyzed mechanisms are provided, and future technical feasibility is discussed as well.
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EUBCE 2019 workshop
Take a look at the final report and presentations of the EUBCE 2019 workshop ‘Paving the way towards clean energy and fuels in Europe’, which took place on 29 May 2019 in Lisbon: https://lnkd.in/gJFCt7U