Aromatic Hydrocarbon Production and Catalyst Regeneration in Pyrolysis of Oily Sludge Using ZSM-5 Zeolites as Catalysts

Abstract

ZSM-5 zeolites were selected as catalysts to promote the aromatization during pyrolysis of oily sludge. The total aromatic yield and product distribution were investigated to evaluate the efficiency of the catalysts and the influence of operating condition. The fresh and used catalysts were characterized by means of scanning electron microscopy, inductively coupled plasma optical emission spectrometry, X-ray diffraction, and ammonia temperature-programmed desorption. Results show that the highest catalytic activity (93.37%) was achieved with ZSM-5-O [the silicon/aluminum ratio (SAR) is 19] at a retention time of 40 s. The total aromatic yield increases with a longer retention time and higher catalyst dosage. An increase in the SAR value of ZSM-5 zeolites will reduce its acid density and aromatization activity. The coke deposition leading to deactivation for zeolites was observed, and calcination was used to regenerate the original catalytic performance. After regeneration, crystallinity was not affected but the acidity was reduced because of dealumination. The regenerated zeolites showed comparable catalytic activity for aromatization, and the tricyclic aromatic hydrocarbon content increased with reaction–regeneration cycles.

Regeneration of pristine HZSM-5 extrudates during the production of deeply deoxygenated bio-oil fromex situcatalytic fast pyrolysis of biomass in a bench-scale fluidised-bed reactor

“…This has been investigated in a variety of scales including micro-scale using pyrolysis-GC/MS systems, 4,[9][10][11] a few grams scale using fixed-bed reactors 1,12,13 and bench or lab scale using continuous biomass feeding systems such as bubbling or circulating fluidised-bed reactors, 8,14-22 conical spouted-bed reactors, 23 a mechanically agitated bed reactor, 24,25 an ablative reactor 26,27 and fixed-bed reactors, [28][29][30][31] where real liquid bio-oil could be produced and analysed. Some important previous studies related to the regeneration of ZSM-5-based catalysts applying other types of raw materials rather than biomass or its pyrolysis vapour include crude glycerol, 32 carinata oil, 33 black liquor, 6 kraft lignin, 30 oil sludge, 34 plastic mixtures, 35 waste tire 36 and model compounds such as furan 37 and ethylene. 20 In addition, the regeneration of ZSM-5 was studied using bio-oil 38 and CaO-catalysed bio-oil 39 in fixed-bed flow reactors.…”

Hybridization of ZSM‐5 with Spinel Oxides for Biomass Vapour Upgrading

“…Nonetheless, the fast pyrolysis intermediate products suffer diffusion limitations on ZSM‐5 crystalline porous framework thereby undergoing over‐cracking and producing coke that results into catalyst deactivation by pore blockage and reduction of available catalytic actives due to coverage (active site poisoning) . Moreover, a large amount of water vapour in bio oils also leads to dealumination of the zeolite materials, which in turn leads to loss of surface area and irreversible deactivation of the zeolite . Therefore, active catalysts with high stability and coke formation resistance with enhanced selectivity towards less reactive oxygenates (alcohols) are desirable for biomass depolymerization into high‐quality bio‐oil.…”

“…[9c,10] Moreover, a large amount of water vapour in bio oils also leads to dealumination of the zeolite materials, which in turn leads to loss of surface area and irreversible deactivation of the zeolite. [11] Therefore, active [ catalysts with high stability and coke formation resistance with enhanced selectivity towards less reactive oxygenates (alcohols) are desirable for biomass depolymerization into high-quality bio-oil. Attempts have been made to create large pores in ZSM-5 that would allow heavy oxygenates to enter, react and exit the catalyst matrix, potentially reducing chances of coke deposition and pore blockage while simultaneously improving carbon efficiency and the quality of the liquid product.…”

Effect of using regenerated combined FAU and MOR zeolites as catalysts during the pyrolysis of kraft lignin

“…They used zeolite Y in the PdCaLaH form and the regeneration process was carried out in hydrogen medium with a specific condition (320 °C temperature and 1.2 MPa pressure) and found that mild hydrocracking of hydrocarbon deposits on the catalyst surface occurs during the course of catalyst regeneration in a hydrogen stream. Although Wang et al (2017) reported that no framework change or damage of the zeolite was caused by the regeneration process, the active acid site decreased when increasing the regeneration cycles (Wang et al 2017). They studied the calcination process in the presence of oxygen to remove the deposited coke on theZSM-5 zeolite.…”