Student ID: 4222077
Course: Introduction to sustainability
Critical Analysis of two published works
As the resources are tighter, the environment issues are more serious, the question “what is sustainability” has been the most important topic in the field of chemistry. The shortage of non-renewable resources and the rise of environmental issues triggered the quest for alternative sources for fuel and chemicals. As a renewable resource, it is a trend that the biomass becomes the main fuel resource; lots of chemists are studying on this. The purpose of this essay is to make a critical analysis of two published works which use the biomass as the feedstock to produce the intermediate for chemical industry.
The first paper is “Conversion of chitin derived N-acetyl-D-glucosamine (NAG) into polyols over transition metal catalysts and hydrogen in water”. This article presents a process that converting the N-acetyl-D-glucosamine (NAG) which derived from the second most abundant biopolymer chitin into smaller C2-4 polyols and N-acetylmonoethanolamine (NMEA), over noble metal catalysis in the presence of hydrogen in water.
The chitin is found in many places throughout the natural world, it is the main component of the cell walls of fungi, the exoskeletons of arthropods and so on. So the chitin is the second most abundant biopolymer. In terms of feedstock, the chitin is natural and renewable resource, it is very sustainable, the substances that it generated are not toxicity to human health and the environment, and this is also one way to prevent waste. The chitin is a polymer that composed of monomeric units of N-acetyl-D-glucosamine (NAG), in this paper, they conducted the conversion of NAG over a series of carbon supported noble metal catalysts in the presence of 40 bar hydrogen at different temperatures in water. NAG was converted to the corresponding amide/amino substituted polyols, C2-4 polyols and N-acetylmonoethanolamine (NMEA), these N-containing polyols productions are very useful in the chemical industry, almost all the productions can be used in other ways, at the end of their function, they do not persist in the environment and break down into innocuous degradation products.
The research of the influence of temperature illustrated that, at higher temperatures, the conversion of NAG increased, reaching 100% at 180℃, and the yield of the smaller (N-containing) polyols increased, In order to maximize the incorporation of all materials, the process should choose the higher temperature, which means there may be higher energy consumption. This is the only point that I think is not green and sustainable. But this high temperature does not lead to any chemical accidents such as explosions and fires.
In terms of catalysts, the Ru/C seems to be the best catalyst for this reaction, which is innocuous when used. In the catalysis of Ru/C, the yield of C2-6 N-containing polyols is the highest. This paper mentioned that under the optimized reaction conditions, the catalyst could be reused for at least three times without any loss of activity. The leaching of Ru in the product and washing solution was lower than the detection limit of ICP-AES.
In the view of metrics for green chemistry, all the products are mostly desired products, so the Atom Economy is nearly 100%. If this process can be conducted under optimized reaction conditions, the mass of waste would be very low, so the E-Factor is very low accordingly, just like the E-Factor of petrochemicals is the lowest less than 0.1. As for Process Mass Intensity (PMI), the catalysts can be reused in at least three times, so the PMI is close to 1, which means this is a good chemical process.
From all above, I think the conversion of chitin derived NAG into polyols over transition metal catalysts and hydrogen in water is green and sustainable chemical process.
The second paper I choose is “One-step propylene formation from bio-glycerol over molybdena-based catalysts”.