Chemistry

Paraffins


Area of ​​Expertise - Organic chemistry

Paraffins (lat. parum "too little" and affinis "ready to react, no binding") is the term for mixtures of liquid and solid, saturated, aliphatic, branched and unbranched hydrocarbons. The general formula of such a mixture of isoparaffins,n-Paraffins and alkanes is C.nH2n + 2.

Paraffins are flammable, colorless, odorless and tasteless and insoluble in water. They are very inert and electrically insulating. The World Health Organization has classified its toxic potential as so low that it has no value for the tolerable daily intake (ADI1)) has set.

Paraffins are used in the manufacture of ointments, candles, care products, lubricants and precision mechanical products.

Purified parafins are used as paraffin waxes or so-called medicinal white oils in medicine and cosmetics. In the form of the food additive E905, they are used as a coating agent for fruit, vegetables and dried fruits, as well as a coating agent for hard and sliced ​​cheese and as a release agent in the confectionery industry and bakeries.

Learning units in which the term is discussed

Crude oil45 min.

Chemistrytechnical chemistryProduction engineering

The learning unit deals with the production and use of oil in the past and present. The production, composition and classification of the crude oil are discussed in detail.


Paraffin

paraffin (Latin parum affinis, & # 160 »little related« & # 160 or & # 160 »not very reactive«) denotes a mixture of alkanes (saturated hydrocarbons) with the general empirical formula CnH2n + 2. The number n is between 18 and 32, the molar mass thus between 275 and 600 grams per mole. Hard paraffin melts between 50 and 60 ° C, soft paraffin at around 45 ° C. the Micro waxes even have solidification points between 70 and 80 ° C and contain chain lengths (n) of up to 75 carbon atoms. Between the hard paraffins and the micro waxes are the so-called intermediates, which have solidification points of 60 to 70 ° C. Paraffin was discovered in 1830 by the Swabian natural scientist Karl von Reichenbach during a series of tests with regard to the constituents of wood tar.

The heat of fusion is between 200 and about 240 & # 160kJ / kg. Liquid paraffins are listed in the CAS directory under CAS-8012-95-1 or in the EINECS directory under EG 232-384-2.


You can't even tell from an ordinary candle. But paraffin as a fuel can develop unimagined powers if the mixture is right. Together with liquid oxygen, a fuel combination is created that releases enough thrust and energy in a combustion chamber to bring a research rocket weighing 80 kilograms and 3.8 meters long to an altitude of at least 4,000 meters at the speed of sound. Students at the Center for Applied Space Technology and Microgravity (ZARM) at the University of Bremen now want to prove that this can succeed. They worked on their project for around four years.

Fig .: The ZEpHyR team from ZARM with project manager Peter Rickmers (Image: ZARM)

Your self-built and almost environmentally friendly rocket with hybrid drive will start its journey to northern Sweden in two days, on March 24, 2016, where it is expected to be launched on April 12, 2016 from the European spaceport Esrange in Kiruna. In keeping with the research topic and the season, the rocket bears the name "ZEpHyR", which in Greek mythology means something like the herald of spring and the god of wind, but in the context of the project it stands for "ZARM Experimental Hybrid Rocket". For the Bremen students in the Production Technology department, the ZEpHyR flight premiere is the grand finale of the STERN program, which is funded by the German Aerospace Center (DLR) and offers German university teams the opportunity to do space research away from the lecture hall with self-made rockets experience.

The Bremen team looked for the specific task itself. The aim is to develop a new type of rocket that meets the requirements of space travel 4.0: These include factors such as cost reduction, ease of use and risk minimization for people and the environment by doing without the highly toxic and explosive fuels such as hydrazine usually used in space travel. What sounds so simple required a creative approach, a knowledge transfer from the areas of combustion research, mechanical engineering, electrical engineering and chemistry as well as manual skills. “We are the only ones within the STERN program who use a combination of paraffin and oxygen as a propellant. Other European research teams are already following similar paths, which clearly shows that this drive concept has great potential for future space projects. With our expertise, we have our finger on the pulse, ”explains Peter Rickmers, who heads and supervises the ZEpHyR project at ZARM.

The focus of the research and tinkering work in Bremen was on the hybrid drive, which had to be completely redesigned and adapted to the fuel components. Thirty engine tests were necessary to achieve the correct mixing ratio of wax and oxygen for good performance with low system complexity. In order to keep component costs as low as possible, the team pragmatically resorted to the 3D printer, manufactured the thrusters from a mixture of cotton and resin and manufactured expensive valves to regulate the supply of oxygen themselves. The electronics for controlling the rocket were bought in electronics stores and the parachute, which is supposed to bring the rocket back to earth safely after its flight, comes from the outdoor leisure sector. In short, the sources of supply for all rocket components are in principle open to everyone and so ZEpHyR should also make a contribution to making space travel more accessible for the private sector and thus promoting innovative, creative ideas for exploring the space of tomorrow.

Regardless of the outcome of the rocket program, the students on the Bremen team have already won. More than 35 bachelor and master theses were created as part of the ZEpHyR project, which is a model for success from the point of view of university teaching.


Heat storage

Various test series on the subject of thermal insulation and storage are offered. Water and paraffin are used as so-called latent heat storage or as phase change material. As a practical example, a paraffin-filled, double-walled “thermo mug” is produced and the temperature profile as it cools is examined. For better manageability, the paraffin can be encapsulated with alginate in a further experiment.

A flyer gives an overview of the topic of "heat storage".

Because of the necessary equipment, no experiment kits are loaned out.

Suitable i.a. Sec. I (HRS, RS, IGS, Gym)

Physics, grade 7

(Law of conservation of energy, thermodynamics, melting and condensing, heat capacity)

Chemistry, grade 10

(Simple energy conversion, internal energy as a form of energy, atomic bonds, Van der Waals forces, relationship between chain length and melting point in alkanes, heat balance of the earth: buffering of temperature fluctuations through the heat capacity of water - maritime climate)

As part of a project funded by the Deutsche Bundesstiftung Umwelt (DBU), “Sustainable Chemistry in the Agnes Pockels Student Laboratory - New Educational Offers on Material Cycles and Resource Conservation”, we worked closely with RS Maschstraße and others. Experiments on the subject of "heat storage and insulation" developed.

Fabrics conduct heat and do so to varying degrees. If you cannot create a vacuum, as is common in thermos flasks or dewars, a poor heat conductor can be used as an insulating material.
A typical material is polystyrene (Styropor®). Experiments on the material properties of the widespread Styrofoam can be connected here (see our experiments on macromolecules). An essential aspect of the efficient use of energy is to avoid undesired heating or cooling, e.g. B. in rooms or from hot beverages, to prevent or at least to slow down. In addition to simple "insulation", phase change materials (PCM) offer the possibility of storing energy. The change in the aggregate states is at the beginning of the science lesson. It is easy to observe experimentally that the temperature remains constant during the phase transition.

The students get to know two different PCMs, which are suitable for different work areas of latent heat storage in terms of their melting temperatures. Water is omnipresent and its particular suitability for dampening temperature fluctuations is of fundamental importance for the climate. The paraffins are the simplest hydrocarbons. In water one can discuss the hydrogen bonds, in paraffin the hydrophobic interactions and the relationship between carbon number and melting point.
When building a “thermal mug”, the students learn the process of microencapsulation and thus a fascinating technique that is important for many practical applications.
Due to the scarcity of fossil fuels and high pollutant emissions, PCMs have gained in importance as latent heat storage in recent years. Their ability to store the thermal energy supplied for melting and to release it again when it solidifies enables z. B. in the construction sector a more efficient use of energy and thus a reduction in CO2Emissions.
The investigation of “heat pads” based on sodium acetate, the effect of which is based on the formation of a supercooled melt, also fits the topic.

The experiments on the subject of sustainability were developed and tested between 2010 and 2012 in close cooperation with the specialist teachers at RS Maschstraße. The experiences flow back into our work. Visiting the Agnes Pockels Laboratory on these topics is an integral part of the RS Maschstrasse curriculum.


Video: Revlon Paraffin Wax Review u0026 Demo (December 2021).