Influence of Reaction Parameters on the Catalytic Performance of Alkaline-Treated Zeolites in the Novel Synthesis of Pyridine Bases from Glycerol and Ammonia

Abstract

This work presented a novel route for the synthesis of pyridine bases from glycerol and ammonia. The whole process consisted of the dehydration of glycerol to acrolein and the subsequent condensation of acrolein and ammonia to pyridine bases, with the two reactions being conducted either simultaneously over a single catalyst in a conventional fixed-bed reactor (single-stage reactor mode) or separately over two different catalysts, namely, a catalyst pair, in a series-connected fixed-bed reactor (two-stage reactor mode). Under the optimized conditions, a 32.18% total yield of pyridine bases was achieved over the HZSM-5-At-acid catalyst, while a 62.25% and 60.85% total yield of pyridine bases, without the formation of 4-picoline, could be afforded over the catalyst pairs (HZSM-5-At + ZnO/HZSM-5-At-acid) and (HZSM-22-At-acid + ZnO/HZSM-5-At-acid), respectively. The catalyst pair (HZSM-22-At-acid + ZnO/HZSM-5-At-acid) exhibited the greatest stability with time-on-stream. This was attributed to the fact that the above-mentioned two reactions were affected differently by the texture and acid properties of the catalyst, and they could be simultaneously promoted to the greatest extent over two different suitable catalysts in a two-stage reactor mode but not over a single catalyst in the single-stage reactor mode. This novel route was shown to be more green and efficient relative to those employed currently in both industrial production and the literature.

High-efficiency catalytic performance over mesoporous Ni/beta zeolite for the synthesis of quinoline from glycerol and aniline

“…As a result, the characteristic peak would shi slightly toward lower or higher angle. 36,37 Based on the enlargement of the predominant peaks in the XRD patterns, the diffraction peaks over Hb-At and Ni/Hb-At catalysts shi towards a lower angle, relative to that of the parent Hb one. It indicates that the expansion of the Hb zeolite framework have occurred for the Hb-At and Ni/Hb-At catalysts.…”

“…On one hand, in the former step, the strength and type of acid sites on solid acid catalyst perform a crucial function in formation of intermediate acrolein. For instance, Brønsted acid sites (especially weak/ moderately Brønsted acid sites) were effective active and selective sites of acrolein, 37,[61][62][63][64] whereas strong Brønsted acid sites readily result in acrolein polymerization simultaneously. 65 Contrarily, Lewis acid sites could catalyze glycerol dehydration to produce hydroxyacetone.…”

Cycloamination strategies for renewable N-heterocycles

“…198,199 Considering that acrolein is a key intermediate in the synthesis of pyridines, glycerol as the co-product of biodiesel industry and waste polylactic acid are also explored as starting material for the synthesis of pyridines despite of relatively low yields. [200][201][202][203][204] Zeolite-based catalysts (e.g., HZSM-5) have unique features such as shape selectivity, high surface area, and good thermal stability, and they are highly active for the production of pyridines by promoting C-N condensation and Michael addition. [205][206][207] In most cases, the pore size and acidity of ZSM-5 have to be regulated by treatment with alkali or acids or introduction of metal oxide into their structure, so as to increase picoline yield with increased basicity or acidity in the modified catalysts.…”

Continuous Flow Organic Chemistry: Successes and Pitfalls at the Interface with Current Societal Challenges

“…Chao and co‐workers reported the preparation of pyridines from glycerol under continuous flow conditions . The two‐stage sequence involved the dehydration of glycerol into acrolein ( 208 ), and then the condensation of acrolein with ammonia (Figure ).…”