ZSM-5@ceramic foam composite catalyst derived from spent bleaching clay for continuous pyrolysis of waste oil to produce monocyclic aromatic hydrocarbons.

Spent bleaching clay, a solid waste generated during the refining process of vegetable oils, lacks an efficient treatment solution. In this study, spent bleaching clay was innovatively employed to fabricate ceramic foams. The thermal stability analysis, microstructure, and crystal phase composition of the ceramic foams were characterized by TG-DSC, SEM, and XRD. An investigation into the influence of Al2O3 content on the ceramic foams was conducted. Results showed that, as the Al2O3 content increased from 15 wt% to 30 wt%, there was a noticeable decrease in bulk density and linear shrinkage, accompanied by an increase in compressive strength. Additionally, the ceramic foams were used as catalyst supports, to synthesize ZSM-5@ceramic foam composite catalysts for pyrolysis of waste oil. The open pores of the ZSCF catalyst not only reduced diffusion path length but also facilitated the exposure of more acid sites, thereby increasing the utilization efficiency of ZSM-5 zeolite. This, in turn, engendered a significant enhancement in monocyclic aromatic hydrocarbons content from 39.15 % (ZSM-5 powder catalyst) to 78.96 %. Besides, a larger support pore size and a thicker ZSM-5 zeolite coating layer led to an increase in monocyclic aromatic hydrocarbons content. As the time on stream was extended to 56 min, the monocyclic aromatic hydrocarbon content obtained with the composite catalyst remained 12.41 % higher than that of the ZSM-5 powder catalyst. These findings validate the potential of the composite catalyst. In essence, this study advances the utilization of spent bleaching clay and introduces a novel concept for ceramic foam fabrication. Furthermore, it contributes to the scaling up of catalytic pyrolysis technology.

Microwave-assisted catalytic pyrolysis of waste cooking oil to monocyclic aromatics under a bifunctional SiC ball catalyst.

Catalytic pyrolysis technology proves to be a highly effective approach for waste cooking oil management. However, high-pressure drops and easy deactivation of powder catalysts hinder the industrialization of this technology. In this study, a bifunctional SiC ball (ZSM-5/SiC ball structured) catalyst was prepared to produce monocyclic aromatics. Bifunctional SiC ball catalyst demonstrates notable microwave-responsive properties and remarkable catalytic efficacy. Results showed that the content of monocyclic aromatics under BFSB catalysis with microwave heating was the highest. Weight hourly space velocity is no longer one of the main factors affecting microwave-assisted catalytic pyrolysis under bifunctional SiC ball catalyst. Monocyclic aromatics content did not decrease significantly and was still higher than 86% when space velocity increased from 30 h-1 to 360 h-1. The highest space velocity could only be 180 h-1 under Powder ZSM-5, and the content of the monocyclic aromatics dropped rapidly to 67.68%. Furthermore, even after five operating cycles, the content of monocyclic aromatics with bifunctional SiC ball catalyst continues to surpass the initial content observed with Powder ZSM-5 at 500 °C and 180 h-1. Related characterizations revealed that coking is the primary cause of catalyst deactivation for both catalyst types; however, the bifunctional SiC ball catalyst exhibits a 29.1% lower occurrence of polyaromatic coke formation compared to Powder ZSM-5.

Post treatment of swine anaerobic effluent by weak electric field following intermittent vacuum assisted adjustment of N:P ratio for oil-rich filamentous microalgae production.

A weak electric field (EF) was applied to decolorize the swine anaerobic effluent, which was followed by N:P ratio adjustment via intermittent-vacuum stripping (IVS) system for oil-rich filamentous microalgae Tribonema sp. cultivation. A higher electric field strength, higher temperature, and lower pH conditions showed higher efficiency in decolorization and nutrients removal during EF application. In the group of 30:1 (N:P) ratio, Tribonema sp. had the largest biomass accumulation (2.04 g·L-1) after 14 days cultivation. However, the 20:1 group had highest oil accumulation (oil content 55.4 ± 3.4%), while 30:1 (N: P) group was 42.3 ± 1.8%. Under the conditions of sufficient nitrogen (50:1 group), the highest contents of α-linolenic acid (15.5%) and ω-3 fatty acids (21.8%) were reached. The integrated treatment of EF, IVS and microalgae cultivation demonstrated to be effective for nutrients recycling and sustainable biomass production.