Isah Yakub Mohammed

Insight into catalyst deactivation mechanism and suppression techniques in thermocatalytic deoxygenation of bio-oil over zeolites

Abstract The economic viability of the thermocatalytic upgrade of biomass-derived oxygenates is facing the challenge of low-quality products. This is because of leaching of active species, coking, and concomitant catalyst deactivation. These cumulate into the loss of catalytic activity with time on stream (TOS), which causes low degree of deoxygenation. Thus, this article reviews recent advances aimed at alleviating these setbacks to make the process viable for industrial scale-up. To understand the concept of catalyst deactivation and to offer solutions, the review scrutinized the deactivation mechanism diligently. The review also analyzes deactivation-suppression techniques such as nanocrystal zeolite cracking, hydrogen spilt-over (HSO) species, and composite catalysts (hybrid, hierarchical mesoporous zeolite, modified zeolites, and catalytic cracking deposition of silane). Interestingly, these deactivation-suppression techniques enhance catalytic properties mostly by reducing the signal strength of strong acid sites and increasing hydrothermal stability. Further, the approaches improve catalytic activity, selectivity, and TOS stability because of the lower formation of coke precursors such as polynuclear aromatics. However, despite these many advances, the need for further investigations to achieve excellent catalytic activity for industrial scale-up persists.

Element characteristic tolerance for semi-batch fixed bed biomass pyrolysis

Biomass pyrolysis to bio-oil is one of the promising sustainable fuels. In this work, relation between biomass feedstock element characteristic and crude bio-oil production yield and lower heating value was explored. The element characteristics considered in this study include moisture, ash, fix carbon, volatile matter, C, H, N, O, S, cellulose, hemicellulose, and lignin content. A semi-batch fixed bed reactor was used for biomass pyrolysis with heating rate of 30 °C/min from room temperature to 600 °C and the reactor was held at 600 °C for 1 h before cooling down. Constant nitrogen flow (1bar) was provided for anaerobic condition. Sago and Napier glass were used in the study to create different element characteristic of feedstock by altering mixing ratio. Comparison between each element characteristic to crude bio-oil yield and low heating value was conducted. The result suggested potential key element characteristic for pyrolysis and provide a platform to access the feedstock element acceptance range.

Toward N-nitrosamines free water: Formation,prevention, and removal

ABSTRACT This study elucidates the recent trends in the formation, prevention, and removal of N-nitrosamines such as N-nitrosodimethylamine (NDMA) from wastewater or drinking water. Reports are rife on the occurrence of NDMA in areas such as amine degradation during postcombustion CO2 capture (PCC), chlorinated/chloraminated and ozonated drinking water, smoked or cooked foods personal care, tobacco and pharmaceutical products. The major routes responsible for the formation of NDMA in portable waters include chlorination/chloramination and ozonation. The major NDMA precursors are secondary, tertiary, and quaternary amines such as dimethylamine, diethanolamine, and triethanolamine. Due to the environmental and public health concerns posed by this contaminant, a proactive approach is necessary towards suppressing their occurrence, as well as their removal. Consequently, this study critically reviewed the formation, prevention, and removal of N-nitrosamines. The study discussed NDMA prevention techniques, such as physical adsorption, pre-oxidation, and biological activated carbon. The removal techniques discussed here include physicochemical (such as combined adsorption and microwave irradiation and UV photolysis), bioremediation, catalytic reduction, and dope technology. Irrespective of the effectiveness and seemingly economic viability of some of these technologies, preventing the occurrence of NDMA right from the outset is more potent because the treatments consume more energy.