Low Frequency Sound Wave (LFSW) driven reactors for new generation biofuels production and upgrading

化学反应工程的研究对开发高效、可持续的新型反应器起着关键作用。在过去的几十年里，研究人员已经花了大量的精力来研究外部影响过程，即所有的反应，其程度可以通过任何一种外部施加的力场来增强，如光催化、微波辅助过程和声化学。在后一种情况下，高频声波（超声波）被用来产生理想的效果，这些效果是局部集中的高温、高压和随后形成的极具活性的物质（主要是自由基）。这是可能的，因为当超声波在液体介质中传播时，由于声压振荡引起的突然压力变化会产生气体/蒸汽气泡，这些气泡在某些条件下会变大并最终内爆。这种现象被称为空化现象，并从理论和实验的角度进行了深入的研究。虽然超声波的化学效应已经被广泛利用，但很少有人关注使用低频声波来提高化学效率。尽管一些理论研究预测，高波长产生的振幅振荡太慢，使气泡无法绝热，从而导致空化，但缺乏实验证据证明低频声波是否对化学反应有任何影响。事实上，文献中没有报道过这样的实验，无论是与液体批处理系统中低频声波的简单传播有关，还是开发利用声特性的设备，如相消干涉（即产生驻波）。杂质的存在可以增强空腔的形成，但对气泡流存在时压力振荡的影响研究甚少。可以初步得出，低频声波可以成功地对化学反应产生积极影响。考虑到被称为热声发动机的新设备的发展，这种前景甚至更有吸引力，因为它可以产生低频声波。这项新技术可以通过在气体上施加热循环来产生高强度的次声，这些气体的末端分别与热交换器和冷热交换器接触。它可以用来产生负责增强反应活性的力场，从而避免了通常用于生产超声波的昂贵设备，并大大降低了工艺成本。最后，该系统的有效性可以在生物燃料过程中进行评估，其中通过空化促进键断裂和分子量降低可能有助于提高生物燃料的质量。新一代生物燃料的生产是化学工程研究的一个目标，目前，科学界面临着一些重大的限制，如高氧含量，使它们不适合与现有发动机中的原油衍生燃料混合。交付成果——热生成低频声波辅助化学反应器——生物燃料生产和精炼微型中试工厂成果——开启声化学新领域（低频驱动）——开发生物燃料生产工艺并提高其质量

The research concerning the chemical reaction engineering plays a key role in the exploitation of new kinds of reactors able to work in increasingly more efficient & sustainable ways. In the past decades, considerable efforts from researchers have been addressed to the study of externally influenced processes,ie all the reactions whose extent could be enhanced by any kind of externally applied force field such as photocatalysis, microwave-assisted processes & sonochemistry. In the latter case high frequency sound waves (ultrasounds) have been used to generate desirable effects, which are locally concentrated high temperature, pressures & the subsequent formation of extremely reactive species (mainly radicals). This is possible because when ultrasounds propagate in a liquid medium the sudden pressure change due to the acoustic pressure oscillation creates gas/vapour bubbles that under certain conditions can grow in size & finally implode. This phenomenon is well known with the name of cavitation & has been deeply studied from both theoretical & experimental points of view.While chemical effects of ultrasound have been widely exploited there is little focus on the use of low frequency sound waves to increase chemical efficiencies. Whist some theoretical studies predict that high wavelengths generate amplitude oscillations too slow for the bubble to behave adiabatically & hence lead to cavitation there is a lack of experimental evidence demonstrating whether low frequency sound waves have any influence on chemical reactions. In fact, no such experiment has been reported in literature, either related to simple propagation of low frequency sound waves in a liquid batch system or developing devices to exploit sound properties such as constructive interference (i.e. generating standing waves). The presence of impurities can enhance the cavity inception but the effects of pressure oscillation in presence of a gas bubble flow have been poorly investigated. It can be preliminarily concluded that low frequency sound waves can be successfully used to positively influence chemical reactions. This perspective is even more attractive given the development of new devices known as thermos-acoustic engines to produce low frequency sound waves. This new technology allows production of high intensity infrasound by exerting a thermal cycle on a gas in presence of a stack whose extremities are in contact with a hot & a cold heat exchanger respectively. It could be used to generate the force field that is responsible of the enhancement of the reaction activity, thus avoiding expensive devices that are normally used for the production of ultrasounds & drastically cutting the process costs. Finally, the effectiveness of this novel system could be evaluated in biofuel process, where the promotion of bond breakage & molecular weight decrease by cavitation could be useful in improving their quality. The production of new generation biofuels is a target in the chemical engineering research &, currently, the scientific world is facing some significant limitation such as the high oxygen content that makes them not suitable to be blended with crude oil derived fuels in existing engines. Deliverables -- Thermally generated low frequency sound waves-assisted chemical reactor- Biofuel production & refining micro-scale pilot plantOutcomes -- Opening of a new field of sonochemistry (low frequency driven)- Development of processes for production of biofuels & improvement of their quality