Pyrolysis of Polyolefins in a Conical Spouted Bed Reactor: A Way to Obtain Valuable Products

The amount of waste plastic increases every single year, which causes a critical environmental issue. Polyolefins (mainly high‐ and low‐density polyethylene and polypropylene) are the most common types of plastics, accounting for 60 wt% of the plastic waste. Pyrolysis, the thermal degradation in an inert atmosphere, is considered to be one of the most appealing technologies for the recycling of plastic materials. The conical spouted bed reactor is suitable for the pyrolysis of plastic waste due to its ability to avoid agglomeration problems that may be caused by the melted plastic. The pyrolysis process may be carried out at different temperatures and with or without the presence of catalysts in the reaction environment in order to streamline product distribution. The resulting products are hydrocarbons: non‐condensable gases (C1–C4), gasoline fraction, diesel fraction, and waxes. These fractions might be used directly as feed streams for refinery units or as pools to be mixed with other streams from refineries

A CONICAL SPOUTED BED REACTOR FOR THE VALORISATION OF WASTE TIRES

A pilot plant provided with a conical spouted bed reactor has been used for the valorisation of waste tires by thermal pyrolysis in continuous mode. The effect of pyrolysis temperature on product distribution and properties has been studied in the temperature range from 425 to 600 ºC. This variable has proven to have an important effect on product distribution. Thus, pyrolysis oil yield was reduced from 64.3 wt% at 425 ºC to 55.9 wt% at 600 ºC. However, the quality of carbon black was improved operating at high temperatures (increasing BET surface area values). High yields of certain interesting chemicals have been obtained in the liquid fraction, such as limonene (19.3 wt%), isoprene (5.7 wt%) and styrene (6.1 wt%)

Evaluating catalytic (gas-solid) spectroscopic cells as intrinsic kinetic reactors: Methanol-to-hydrocarbon reaction as a case study

Commercial spectroscopic gas-solid cell reactors are routinely used to analyze the dynamics of the catalyst (catalyst pelletized as a disc) structure and retained/adsorbed species using multiple operando techniques. These instruments have revolutionized the understanding of many catalytic reactions, including the methanol-to-hydrocarbon reactions. We propose a reaction engineering framework to evaluate spectroscopic cells based on (a) analyzing the fluid dynamic performance, (b) comparing their performance with a reference packed-bed reactor, and (c) the assessment of the external and internal mass transfer limitations. We have used a Specac HTHP and a Linkam THMS600 cell reactors coupled with the corresponding gas conditioning, spectroscopic, and mass spectrometry apparatuses. Our results reveal that these cells approach a perfect mixing only with several equivalent tanks in series and they are reliable at low catalyst loadings (thin disc) and high flowrates (low spacetimes). Under these conditions, we can avoid external-internal mass transfer limitations and fluid dynamic artifacts (e.g., bypassing or dead/stagnant volume zones), obtaining intrinsic kinetics with the corresponding operando spectroscopic signatures. The proposed methodology allows to understand the influence of process parameters and potential design modifications on the observed kinetic performance.This work was possible due to the financial support of the Ministry of Economy, Industry, and Competitiveness of the Spanish Government (project CTQ2016-79646-P, cofounded with ERDF funds), the Basque Government (projects IT1218-19 and IT1645-22), and the King Abdullah University of Science and Technology (KAUST, project BAS/1/1403). J.V. is grateful for the fellowship granted by the Ministry of Economy, Industry, and Competitiveness of the Spanish Government (BES-2014-069980). The authors are grateful for the technical and human support provided by IZO-SGI SGIker of the University of the Basque Country (UPV/EHU) and European funding (ERDF and ESF)

Poliolefinen pirolisia iturri-ohantze konikoan

The amount of waste plastic increases every single year, which causes a critical environmental issue. Polyolefins (mainly high and low density polyethylene and poly- propylene) are the most common types of plastics, accounting for 60 wt% of the plastic waste. Pyrolysis, the thermal degradation in an inert atmosphere, is considered to be one of the most appealing technologies for the recycling of plastic materials. The conical spouted bed reactor is suitable for the pyrolysis of plastic waste due to its ability to avoid agglomeration problems that may be caused by the melted plastic. The pyrolysis process may be carried out at different temperatures and with or without the presence of catalysts in the reaction environment in order to streamline the product distribution. The resulting products are hydrocarbons: non-condensable gases (C1-C4), gasoline fraction, diesel frac- tion, and waxes. These fractions might be used directly as feed streams for refinery units or as pools to be mixed with other streams from refineries.; Hondakin plastikoen kantitatea gero eta handiagoa da eta horrek arazo larria sortzen du. Hondakin plastikoen artean ugarienak, %60 inguruko masa-proportzioan, poliolefinak dira (dentsitate altuko eta baxuko polietilenoa eta polipropilenoa). Pirolisi bidezko birziklatzea aukera interesgarria da plastikoen materiala berreskuratzeko. Pirolisia atmosfera inertean gauzatzen den degradazio termikoko prozesua da. Iturri-ohantze konikoak propietate egokiak ditu material plastikoen pirolisia egiteko, batez ere plastikozko partikula urtuek eragin ditzaketen aglomerazio-arazoak ekiditeko. Pirolisia tenperatura ezberdinetan, katalizatzailerik gabe edo katalizatzaile ezberdinak erabiliz egin daiteke, lortzen diren produktuen banaketa aldatzeko. Poliolefinen pirolisian lortzen diren produktuak hidrokarburoak dira, hala nola, C1-C4 gasak, gasolina frakzioa, gasolio frakzioa edota ezkoak. Frakzio horiek findegietan ohiko korronteekin elkar daitezke edo bertako unitateetako elikadurak osa ditzakete

Pathways of coke formation on an MFI catalyst during the cracking of waste polyolefins

A study has been carried out on the deposition kinetics of carbonaceous-species on an acid catalyst (containing an MFI zeolite) in the cracking of high-density polyethylene and polypropylene. The initiation of coke deposition occurs on the acid sites, followed by aromatic and aliphatic growth in the micro- and mesopores, respectively.Peer reviewe

Energetic viability of a polyolefin pyrolysis plant

The energetic viability of a polyolefin pyrolysis unit that could be installed in a refinery plant was examined. Thermal pyrolysis at 500 and 700 degrees C, and the catalytic cracking by means of HZSM-5 and HY catalysts were analyzed. The energy requirements for an initial separation of the products by means of distillation towers into four main lumps (gas, gasoline fraction, diesel fraction, and waxes) that could be directly treated in a refinery were calculated as well. An energy balance closure and a sensitivity analysis were also carried out for all cases in order to check the accuracy of the yields of products previously obtained. These results were highly satisfactory for all cases, although the actual heat of combustion might be slightly higher than the values measured experimentally (around 5%). The results of the energetic viability analysis showed that only about 5% of the input mass flow rate is needed to burn to satisfy the energy requirements of the plant. Thus, the heat released in the combustion of the product fraction stream that is in minor proportion in each case proved to be sufficient.Spanish Government CTQ2016-75535-R (AEI/FEDER UE) Basque Government IT748-1

The intrinsic effect of co-feeding water on the formation of active/deactivating species in the methanol-to-hydrocarbons reaction on ZSM-5 zeolite

Water is formed and added in the conversion of methanol-to-hydrocarbons, slowing down both the reaction and deactivation rates. This work aims to clarify the selective nature of water quenching on a ZSM-5 zeolite catalyst in terms of (1) reaction/deactivation using an integral reactor (full range of conversions) and (2) rate of formation/growth of deactivating species using two FTIR and UV-vis in situ differential reactors (conversions lower than 0.15). Our approach assesses the effect of water under comparable conversion conditions while characterizing in detail the products and intermediates of the reaction (by online and in situ analysis, and extraction measurements). The results obtained prove, in an unbiased way, that water quenches more selectively the deactivation than the reaction with moderate amounts of added water (water/methanol = 0.11 g g(-1)). On the other hand, in situ FTIR spectroscopy evidences that co-feeding water sweeps the retained species from the silanol sites and favors the formation of olefins as retained species, while in situ UV-vis spectroscopy proves that the rate of formation/growth of discrete retained species drop by the addition of water and the degree of this decline is severer for coke than for coke precursors or active species

Coke deposition and product distribution in the co-cracking of waste polyolefin derived streams and vacuum gas oil under FCC unit conditions

The effect of co-cracking of high-density polyethylene (HDPE) or its pyrolysis wax together with vacuum gasoil (VGO) has been studied. The aim is to determine the content, nature, and location of coke while analyzing the impact on product distribution in the process. Four different feeds were used (VGO, VGO + 5 wt% HDPE, VGO + 20 wt% of wax, and 100 wt% wax) in experiments performed in a laboratory-scaled riser simulator, with similar conditions to those of the fluid catalytic cracking (FCC) unit: equilibrium catalyst; 530 degrees C; catalyst/feed mass ratio, 5; contact time, 6 s. The results of the different characterization techniques of the deactivated catalyst and the coke indicate that the catalyst fouling decreases notably by incorporating these waste streams, changing its nature to a more aliphatic (olefinic) one and its location towards the zeolite micropores. On the contrary, the coke formed from the VGO is more evolved and mainly constituted by polyaromatic components deposited on the mesopores of the catalyst matrix. Product distribution is also affected, increasing the yield of light cycle oil and keeping a relatively similar gasoline yield, with greater olefinity and lower aromaticity. Thus, the FCC shows great perspectives to valorize polyolefins, present in waste plastics, at great scale.This research was funded by the Ministry of Economy and Competitiveness (MINECO) of the Spanish Government (CTQ2015-67425R and CTQ2016-79646-P), the European Regional Development Fund (ERDF) and the Basque Government (IT748-13). Dr. Rodriguez is thankful to the University of the Basque Country UPV/EHU and Petronor S.A. (Zabalduz Programme). S. Izaddoust is thankful to the MINECO for her grant BES-2017-080077.This research was funded by the Ministry of Economy and Competitiveness (MINECO) of the Spanish Government (CTQ2015-67425R and CTQ2016-79646-P), the European Regional Development Fund (ERDF) and the Basque Government (IT748-13). Dr. Rodriguez is thankful to the University of the Basque Country UPV/EHU and Petronor S.A. (Zabalduz Programme). S. Izaddoust is thankful to the MINECO for her grant BES-2017-080077