Sustainable Biofuel Production from Sugars: Converting Hydroxymethylfurfural to Dimthethylfurfuran / Dimethyltetrahydrofuran

Marco Balboa, advised by Dr. Jesus Requies

University of Nevada, Reno.

DOI: http://dx.doi.org/10.15629/6.7.8.7.5_6-1_S-2020_4

Citation: M. Balboa, “Sustainable Biofuel Production from Sugars: Converting Hydroxymethylfurfural to Dimthethylfurfuran / Dimethyltetrahydrofuran.” Nevada State Undergraduate Research Journal. V6:I1 Spring-2020. (2020). http://dx.doi.org/10.15629/6.7.8.7.5_6-1_S-2020_4

Abstract

Our focus in this work is the creation of alternative fuel sources. 2,5-dimethylfuran (DMF) and 2,5Dimethyltetrahydrofuran (DMTHF) are used as gasoline additives and/or alternatives to enhance fuel efficiency due to their likeness to conventional gasoline. Both DMF and DMTHF are produced from the hydrogenation of 5-hydroxymethylfurfural (HMF). HMF is derived through the dehydrogenation of sugars and is isolated through high pressure liquid chromatography (HPLC). The production of HMF from glucose, sucrose, fructose, and other similar molecules, is a crucial step toward the production of viable biofuel products. In a fixed-bed reactor, DMF and DMTHF are produced in the presence of multiple metal catalysts. A nickel-copper catalyst with a Carbon backing was being used to add stability to the reaction. Various gas chromatography techniques were also being utilized to check the quality of both the DMF and DMTHF, including the use of a Thermal Conductivity Detector (GC-TCD), Flame Ionization Detector (GC-FID), and Mass Spectrometry (GC- MS).

Introduction

Since the Clean Air Act was passed in the early 1970s, the United States has steadily turned its eyes toward less wasteful and more renewable sources of energy. Despite governmental movement toward more sustainable practices, significant advancements in reducing anthropogenicinduced air pollution have yet to be made. In fact, a large part of human contribution toward air pollution has not been fully dealt with. High rates of air pollution caused by transportation is perpetuated by the continued use of fossil fuels around the world. Nearly a third of the greenhouse gas emissions that contribute to air pollution in the United States is due to transportation (1), as well as a third of the CO2 emissions in India (2) and 13% of Russia’s CO2 emissions (via Worldometer.com). This is mainly due to the continued use of fossil fuels. A 2001 study found that the burning of fossil fuels has become a “major factor in the past increase in concentrations of carbon dioxide,” (3). One viable solution to eliminating the world’s reliance on fossil fuels is the transition to more efficient fuel alternatives (4).

Figure 1 - Series of reactions that HMF goes through.
Figure 1: The series of reactions that HMF goes through within the fixed bed reactor that yields DMF and DMTHF. The chemical transformation that undergoes when it reacts with H2, H2O, and CO produce DMF and DMTHF, viable fuel alternatives.
Figure 2 - Inside of the fixed bed reactor.
Figure 2 - Photo of apparatus.
Figure 2:Panel A shows the inside of the fixed bed reactor along with the flow of reactants and product both represented by the green arrows. The red area in the middle represents the mixture of various metal catalysts used. The grey areas to the top and bottom of the cylinder are silicon particles that are used as a buffer. The catalyst is a mixture of Ni and Cu. Panel B is a photograph of the apparatus.

Dimethylfurfuran (DMF) and Dimethyltetrafurfuran (DMTHF) are effective alternatives and/or additives to conventional fuels due to their high energy densities, higher octane number (compared to conventional gasoline), and the lack of engine modifications required to incorporate this fuel into direct ignition spark ignition (DISI) type engines (5). The chemical similarities between DMF/DMTHF and gasoline allows them to be used as either an additive or an alternative. The properties that made DMF/DMTHF attractive candidates for fuel additives have been studied for nearly 10 years (6). However, DMF/DMTHF have not been integrated into mainstream fuel usage due to their high production costs.

The reactions required to produce DMF/DMTHF begin with the hydrogenation of glucose to produce 5, hydroxymethylfurfural (HMF). In a batch reactor, HMF is exposed to and reacts with various metal catalysts to produce DMF and DMTHF through a series of hydrogenolysis reactions, as seen in Figure 1. Along with hydrogenolysis, decarbonylation and demethylation reactions also take place. This leads to the various intermediate substances produced between the initial reactant of HMF and the final product of DMF/DMTHF. Beginning with a high volume of HMF to start the process is critical in maintaining a cost-efficient means of DMF and DMTHF production. Therefore, the specific study on HMF yield from a glucose solution is a critical initial step.

Methods

The focal point of our lab is to navigate the various hydrogenolysis reactions that take place within a fixed bed reactor. The fixed-bed reactor consists of a single column that is filled with various solid metal catalysts such as carbon, nickel, and copper. There is an inward flow of liquid reactant, HMF, that gets pressed through the column at a controlled temperature and pressure. The outward flow is the liquid product, a mixture of DMF and DMTHF. The fixed bed reactor and the apparatus are illustrated in Figure 2. The products from the fixed bed reactor are analyzed and quantified using a Hewlit Packard gas chromatography flame ionization detector (FID) equipped with Surpawax 280 capillary column.

This study aims to produce the “high grade” HMF needed for the initial reaction by utilizing a batch reactor (Figure 3). The batch reactor consists of a small metal chamber with a pressure gauge and in-flow and out-flow pipes. A pressurized container filled with reactant is placed into a platform with magnetic mixing capabilities and temperature control. These batch reactors allow for precise control of the temperature and pressure of the metal chamber, providing a space for the reaction to take place. Using a mixture of glucose, butanol, and a carbon catalyst set in a 9:1 at a constant pressure (600 kPa) for 30 minutes, HMF was produced to proceed with the following DMF/DMTHF reaction. By varying the temperature, the optimum conditions for producing the most abundant supply of HMF were found.

To analyze the reactants, a high-pressure liquid chromatograph (HPLC) 1260 Infinity machine equipped with HI-Plex H column and an infrared detector was used. A sample is pressed through a coiled wire, its constituent particles will separate and travel faster or slower according to their size. The arbitrary units in which the HPLC measures quantities of various substances in a sample are called absorption units (AU). The time at which the HMF reaches the detector is about 29 minutes and can be viewed as a spike on the resulting chromatograph. The products from the batch reactors at the temperatures of 180, 200, and 220 degrees for both aqueous and organic states of the initial reactants were sampled. The resulting absorption units were recorded at t=29 minutes. 29 minutes is the exact time when HMF was captured by the chromatograph detectors. The HPLC results are detailed in Table 1. The average was taken by adding two trials and dividing by 2. The error was computed by taking the difference between the 2 trials and dividing by 2.

Results

Table 1 shows the numerical values of the area under the curves on the HPLC chromatograph at t=29 minutes, corresponding to the yield of HMF in absorption units (AU). At the highest tested temperature of 220◦C, the conditions yielded the highest amount of HMF, more notably in the organic phase of the reactants. An increase of 20◦C led to nearly twice the yield from 200◦C to 220◦C. The HPLC chromatograph data demonstrates that higher batch reactor temperatures will yield greater quantities of HMF. This experiment serves a crucial preliminary roll toward collecting the HMF needed for the later DMF/DMTHF reactions.

Table 1 - Area of the peaks at 29 min
Table 1: The area of the peaks at 29 minutes from the HPLC chromatograph. These areas coincide with the concentration of HMF.

Discussion

A temperature of 220◦C yielded the most HMF within the fixed-bed reactor. That HMF can then be used by our lab to produce the biofuel additive/alternative DMF/DMTHF. HMF yield is an essential step in creating more efficient fuels, which may provide a solution to the world’s necessity for more sustainable fuels in the face of anthropogenicinduced climate change. The byproducts from burning conventional gasoline, i.e. nitrogen oxides, hydrocarbons, and most notably carbon dioxide, have major implications with respect to the global climate, and have highlighted the necessity for fuel-alternatives to be set in place on a global scale. Though fuel efficiency has most of its implications in the transportation sectors, their implementation can provide benefits in the industrial, agricultural, and economic sectors as well.

To facilitate the production of alternative fuel sources, this study has provided further insight into how to costeffectively produce fuel-additives. The implementation of this pilot plant (small scale experimentation) is the first step toward large-scale production of DMF/DMTHF. By focusing on the most cost-efficient means of production on the small scale, a shorter span of time is needed to acquire results. Utilizing small scale reactions also provides the opportunity to easily manipulate the reaction site with various catalysts. It’s only after the pilot plant has been adjusted to maximum efficiency that the shift into the large-scale is feasible.

The results of the batch reactor show that, of the 3 temperatures that were tested the hottest temperature, 220◦C yielded the greatest quantity of HMF derived from the glucose solution. In future experiments, greater temperatures should be tested to determine if the direct relationship of increasing temperature and increasing quantities of HMF holds true. Furthermore, the limiting factor for this smallscale batch reactor is the maximum temperature that the apparatus can safely achieve. In taking this small-scale experiment to a larger industrial scale, the larger chemical production plants may not be able to reach such high temperatures or pressures.

To further determine the most cost-effective means of manufacturing DMF/DMTHF, various metal catalysts will be tested using the same fixed-bed reactor.

Acknowledgements

I’d like to thank the Nevada State Undergraduate Research Journal for reaching out to me about the work I had done over the summer. The opportunity provided to me by NSURJ has given me the chance to have my work publicly recognized in ways that couldn’t be achieved through oral and poster presentations at the University of Nevada Undergraduate Summer Research Symposium. I’d also like to thank Valeria Nava for providing the revisions needed to clarify my work.

This project was made possible due to my mentor Dr. Jesus Requies. Utilizing students from different universities provides students the opportunity to expand their academic horizons in a way that cannot be matched by oncampus opportunities. Your mentorship has been greatly appreciated. A special thanks also goes out to Dr. Scott Mensing for coordinating the International Research Experience for Undergrads (IREU) Program through the University of Nevada Reno, as well as the Associated Students of the University of Nevada (ASUN), the United Studies Abroad Consortium (USAC), Dr. Grant Mastick for his continual encouragement, and finally the graduate students Paula Diaz Maizcurrena and Nere Viar and the University of the Basque Country (UPV/EHU). A big thanks also goes out to the other grad students in the Chemical Engineering department who helped me get through lab doors every day because I never had a key.

References

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