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New insights for the valorisation of glycerol over MgO catalysts in the gas-phase

机译：维持价格的新见解甘油采用催化剂气相

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摘要

Aqueous glycerol solutions of up to 50 wt% were reacted over magnesium oxide catalysts at temperatures greater than 300 degrees C, the reactivity of which was compared to catalyst-free reactions. Under catalyst-free conditions, modest levels of dehydration to hydroxyacetone were observed at temperatures >400 degrees C in a steel reactor tube and >320 degrees C over silicon carbide. For reactions over MgO, the product distribution becomes more diverse, resulting in the formation of methanol, acetaldehyde, ethylene glycol, 1,2-propanediol and acetic acid. The methanol space-time-yield over MgO catalyst samples (0.5 g) was found to be highest at 400 degrees C (205 g h(-1) kg(cat)(-1)) with a 50 wt% solution of glycerol, or with a glycerol concentration of 10 wt%; 255 g h(-1) kg(cat)(-1) over 0.1 g of catalyst. Despite the high glycerol conversion achieved, the MgO catalyst was found to be stable over 48 h, following a modest decrease in glycerol conversion during the initial 2 h of reaction. Post-reaction characterisation revealed that the level of coking at high glycerol conversions (>90%) was 120 mg g(cat)(-1). The carbon mass balance determined by GC analysis for a typical reaction was 75% and so the carbon lost from catalyst coking only represents a modest quantity of the missing carbon; typically <10%. MgO was also found to promote the formation of high molecular weight products via condensation reactions, which were responsible for the remainder of the missing carbon; ca. 15%. Therefore, the total organic content of the post-reaction mixture and coke was calculated to be 94% of the starting solution. We conclude that the catalyst surface directs the formation of methanol, however, the results indicate that the reaction conditions are crucial to obtain optimum yields.
机译：甘油水溶液的50 wt %在氧化镁反应催化剂温度大于300度反应性catalyst-free相比反应。丙酮醇脱水的水平观察到温度> 400度C钢反应堆管,> 320度C /碳化硅。产品分布变得更加多样化,导致甲醇的形成,乙醛、乙二醇、1,2-propanediol和醋酸。采用催化剂样品(0.5 g)被发现最高在400摄氏度(205 g h (1)公斤(猫)(1))和甘油的50 wt %的解决方案,或甘油浓度10 wt %;h(1)千克(cat)(1)超过0.1克的催化剂。高甘油转换实现,分别催化剂在48小时被发现是稳定的,适度降低甘油转换在最初2 h的反应。Post-reaction描述显示炼焦水平在高甘油转换(> 90%) 120毫克g (cat)(1)。为一个典型的平衡由GC分析反应是75%,所以碳损失催化剂炼焦只代表一个适度的数量那个失踪的碳;还发现促进高的形成分子量的产品通过凝结反应,负责剩下的失踪碳;因此,总有机的内容post-reaction计算混合物和可乐是94%的启动解决方案。催化剂表面指导的形成然而,甲醇,结果表明获得最佳反应条件是至关重要的收益率。

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