Making Ethylene (Refrigerant R1150)

in this video I'll show how to make ethylene gas which I'll use as a refrigerant for the second stage of my vapor compression system from my previous video If done correctly this could bring my second stage evaporator temperature below -100z first off huge thanks to Exotic chem lab for providing me with the info for this project he's already built a DIY cryo cooler of his own so he's been able to give me some good pointers on this build check out his channel in the link below ethylene also called ethene has the formula c2h4 note that this is different from ethane which is c2h6 which confused me a little bit at first ethylene has a lot of uses such as ethylene glycol for antifreeze or pure ethylene gas for accelerating fruit ripening by far its biggest uses and Plastics in the form of polyethylene high and low density polyethylene or HDPE and ldpe are probably the most common types of plastic in the world and also tend to serve as a dietary supplement for sea turtles these days in my case I want pure ethylene gas for use as a face change refrigerant in the world of HVAC is known as r1150 ethylene has a boiling point at one atmosphere of minus 104 C but if I compressed it to about 16 Bar it would condense right at around -37c which is the temperature I achieved in the evaporator of my vapor compression system from my previous video so by having a second phase change system with its condenser thermally anchored to the evaporator of my first stage I could theoretically reach that minus 104c temperature in a second evaporator but that's a discussion for the next video right now I'm going to focus on the chemistry of ethylene production ethylene can be produced by boiling ethanol and passing the ethanol Vapor over an aluminum oxide Catalyst that's heated to around 450 C when the ethanol molecule hits the Catalyst two hydrogens and oxygen atom are ripped off producing ethylene gas and water vapor the Catalyst temperature is really important here because you'll get different outputs depending on the temperature below roughly 200C nothing will happen and you'll just have ethanol recondense from around 200 to 400 the majority of the output will be diethyl ether and and above 400 ethylene will start to be the majority of the output ideally we'd like to hold around 450 to maximize the percentage of the output that's ethylene past about 500 or so the ethanol molecules will turn into hydrogen gas and carbon the carbon will deposit itself as soot on the Catalyst and dirty it up I think there's also a way to produce ethylene by heating a mixture of sulfuric acid and ethanol but I'm not really familiar with the details so I'm not going to cover it in this video all right let's start building I'll begin with the heater for the Catalyst the Catalyst will be in a long tube and I want to make sure it's heated as evenly as possible so I'll be making a propane burner comprised of a pipe with pinholes every inch or so along its length similar to what's in some large grills I start off with this half inch pipe tee that'll serve as an air intake for the burner I drill and tap threads for a 1 8 npt fitting to install the propane nozzle the inlet is a 3 8 flare fitting to attach to the propane hose on one end and a 1 8 npt on the other the tip from a MIG welder press fits tightly into the fitting without any drilling this will serve as a nozzle with the small diameter accelerating the gas and causing it to create a Venturi effect through the pipe t drawing an air with the propane I drilled the fitting at a bit of a weird angle but whatever it should still work a two foot long half inch black iron pipe is connected to the T fitting and capped at the other end the pipe is drilled with a 1 16 inch drill bit every inch or so and these holes will serve as flame Outlets the burner is connected to a propane tank with a 20 psi regulator I added these pipe segments to the side of the T fitting so that the pipe wouldn't turn on one side because the flame needs to point straight up all right the burner looks like it works okay but I went ahead and switched the T fitting to have one inch threads on the sides to let more air in which should hopefully make the flame burn a little cleaner and give a slightly Bluer color no real difference oh well this will still work fine I guess I'll just get some soot on the bottom of the Catalyst pipe next I make the fittings for the Catalyst pipe these are one inch npt to one quarter inch reducers with one quarter inch npt to one quarter inch flare fittings on the ends I also added some stainless steel screen mesh to keep chunks of catalyst from flying out the adapters are screwed onto an aluminum pipe and the pipe is drilled and tapped in the Middle With A 1 8 MPT thread to accept a thermocouple then I get the actual Catalyst substance itself this is just aluminum oxide in the form of three to four millimeter balls it's pretty cheap and easy to find I pour the Catalyst into the pipe and close everything up there's no thread sealant on any of these joints because it would probably just burn off at the temperatures involved however the pressures are never going to be more than a couple PSI so a tight fit should be enough to form a decent seal for the inlet line I've got a quarter inch copper tube with a flare nut on one end the other end will be tightly press fit into a rubber stopper that will go into a glass flask containing the ethanol being boiled the outlet line will look similar but with the addition of a copper coil to condense the water and unreacted ethanol I add some 150 proof Everclear to the flask to do a test run 150 proof is 75 ethanol and 25 Water by volume even with 100 ethanol 39 of the mass becomes water when it reacts to ethylene so with 150 proof around half the Everclear will get converted to water to boil the ethanol I put the flask in a pan on a 1000 watt heater I initially put the flask in a water bath to limit the maximum temperature to 100c and slow the temperature rise to avoid thermal shock but later found that this wasn't really necessary here's the crude setup for a quick test after 10 to 15 minutes I got the Catalyst heated to the Target temperature and the ethanol was boiling as you can see it's flowing a lot of gas through this makeshift bubbler which should be ethylene the output must be pretty good because every few seconds I'm able to light off a pretty decent sized pluma fire okay so the general idea seems to work pretty good but we need a few improvements to the generator for starters I need a clean dry gas output that's not contaminated with water unreacted ethanol or particles this bottle will serve as a bubbler to help filter any particles and catch any liquid that comes over from the condenser this one is the dryer the blue beads inside are silica gel desiccant which will turn pink when they're saturated with water this stuff is awesome at removing moisture but can generate some dust particles so I'm installing this filter in line with a dryer I think this one only filters down to about 50 microns but that should be fine for my application the dryer and the filter are placed in a 3D printed bracket and joined with a silicone tube I'll have to cool the output in a condenser before I can handle it with these materials because it comes out of the Catalyst pipe around 450 C to help with this I grab the 120 volt fan I extracted from a window AC unit in my last video 35 watts should be plenty of power to keep things cool here's a look at the setup after those additions I mounted the burner at Catalyst pipe and aluminum brackets and covered them in aluminum foil this helps keep heat in but its main purpose is to prevent the breeze from extinguishing the flame since it doesn't seem to take much airflow to put it out on the output I've got my 25 foot condenser coil from my last video with the 120 volt fan blowing over it this cools the output enough to pipe it into the bubbler dryer filter assembly and out a silicone tube to a length of copper tubing I use this copper because I'm planning to ignite the gas output for demonstration once the catalyst is up to temperature I light off the output the flame Burns bright yellow and gives off a lot of smoke and soot this is a very obvious indicator that what we're burning is in fact ethylene and not diethyl ether or unreacted ethanol Vapors if we ignited either of those they'd burn a very light blue nearly invisible Flame the suit is apparently from the carbon double bond in the ethylene you see a similar effect from acetylene fire which is a carbon triple bond methane propane methanol ethanol and so forth don't have these multi-bonds from carbon to carbon which is part of the reason they burn with a much clearer flame another indicator is the smell I pick up a sweet but musky sort of pungent Aroma coming off the output pipe when it's not burning which is how the smell of ethylene is typically described if I move close to the pipe and get a really good whip it makes me want to gag it's kind of like what you might expect to smell if you threw a bunch of fruit in your garbage can and left it there for a few days sort of sweet but very very pungent the condenser seems to be doing its job very well because it's extremely hot to the touch on the inlet but perfectly cool on the outlet when I remove the filter dryer assembly you can see the liquid spitting out with the surge of flame this is mostly liquid water but a small percentage of unreacted ethanol and possibly liquid ether the surges occur from so-called bumping or uneven boiling I need to add some boiling chips or sand into my flask to even that out here's a view of the connector tube between the condenser and the filter dryer you can clearly see the liquid water coming through let's try to get some idea of how much ethylene gas we're actually producing to do this I stole my dog's water bowl then I hooked up the output of the generator to another tube and bubbled that tube up into the inverted bottle on his bowl making sure to Mark the water levels at the beginning and the end while running a timer as gas bubbles up into the bottle it displaces the water causing it to be pushed down and out of the bowl after a little over two minutes the water is emptied out and I remove the tube let's do some measurements knowing that fresh water is one gram per CC we can easily measure volumes the initial Air volume in the bottle at the first marking was 393 CC and the final volume I marked when I pulled out the tube was 1991 CC's I subtract the two and find that I added 1598 CC's or about 1.6 liters of ethylene gas to the bottle I bubbled the gas in for 2 minutes and 16 seconds meaning we have an average production rate of about 0.7 liters per minute or 42 liters per hour not bad considering I probably need only 20 or 30 liters to fill the second stage of my Cascade system out of curiosity I added a third bottle specifically for collecting the liquid output of the generator ideally this should be 100 water but in reality I think there's some ether and unreacted ethanol because the bubbler water always ends up smelling like an open can of paint or some sort of intense solvent collecting the liquid here should allow me to analyze it later now it's time to actually collect and store the gas to do this I hook up a beach ball to the output tube same as I did in my dry ice video when I was collecting CO2 gas here's the beach ball after one hour of running fully inflated it carries around 120 liters so I'm guessing there's about 50 or 60 liters in there right now after an hour and a half the bubbler output was looking much weaker because I had pretty much used up all my alcohol I started with 500 cc's in the flask I think we're pretty much tapped out at this point to store the ethylene I got this 2.5 gallon or 9.5 liter air tank that I added pressure and vacuum gauges to and several different fitting types with shut off valves on them to make sure there won't be an explosive mixture I evacuate the tank then flood it with propane then evacuate it again this will sure that any residual gas left in the tank is almost entirely propane which will play nice with the ethylene I initially hook up the beach ball directly to the tank since it's under vacuum and then crack the valve open to let the ethylene gas in now we've got one atmosphere of ethylene gas inside the tank and it's time to put the rest in Under Pressure so I connect the beach ball to the inlet of a fridge compressor and turn it on I run the compressor for a minute or two with the line open so that I can Purge any air out of the hoses and the compressor shell once I can smell the stink of ethylene coming out of the fill hose I hook it up to the tank [Music] now the tank is full so I shut off the valve and disconnect the fill hose here's what the beach ball looks like after all the gas has been sucked out the tank settled out at 80 psi which translates to 6.44 atmospheres of absolute pressure the tank has an internal volume of 9.45 liters so we've collected 60.9 liters of ethylene at standard temperature and pressure that comes out to 69.7 grams of gas or 2.5 moles I started with 500 cc's of Everclear at 75 percent concentration by volume which should mean I had 296 grams of ethanol or 6.43 moles this means I only got a 39 yield from this process not exactly amazing but it's still cheaper than paying over a hundred dollars an ounce and requiring a refrigerant handling license I think the answer to our missing yield can be found in the liquid that came over from the reaction working out the math there should be no more than 241 grams of water in the mystery liquid but the scale gives us 284. this liquid also has that nasty solvent smell so I think there some ether in it in addition to the water that came over let's figure out what the density is I don't have a hydrometer but I can do a crude test by marking the water line on the collection bottle then figuring out what the mass of fresh water at the same water level is with fresh water it's 304 grams but our mystery liquid had 284. this means the average density is 0.934 grams per CC which is noticeably less than the one gram per CC for pure water diethyl ether has a density of 0.713 grams per CC so if we assume that this thing is a mixture of only water and ether with no unreacted ethanol that works out to 77 percent water by volume and 23 percent ether that brings us to 234 grams of water and 50 grams of diethyl ether the Water Mass is pretty close to my theoretical prediction and the amount of ether accounts for most of the missing yield I guess the rest was just minor leaks through the fittings let's see how flammable this stuff is it's mostly water but ether is so incredibly volatile that it should still light up and there it goes quite an impressive display however if this was 100 pure ether I would have incinerated myself and my camera by now as you can see once the flame goes out there's still a good amount of liquid left over that I can't ignite which is the water I stored my tank outside just to be on the safe side but for my own peace of mind I wanted to do a test to verify that I'm not storing an explosive mixture so I Revisited the dog bowl but this time I inserted a 10 Ohm resistor which I'm going to overdrive to act as an igniter if the mixture is pure ethylene to within a few percent it shouldn't combust when I turn on the igniter let's bubble in some ethylene and give it a try the igniter gave off a bunch of soot as it cooked off but the gas didn't ignite this makes me feel a little better about handling the storage tank let's see what happens when I fill the rest of the bottle with air now the mixture should be flammable I set off the second igniter but again nothing happened aside from a small puff of smoke I guess the field air ratio was too rich to ignite make no mistake though this stuff is definitely flammable in air I did another run to produce some more ethylene but this time I reduced the alcohol heater power to reduce the ethanol flow rate and increase the Catalyst temperature to 500c from 450. despite my best attempts to heat the Catalyst as evenly as possible I think the inlet and Outlet size of the pipe are probably cooler than the Middle where the thermocouple is located and this lower temperature could be causing some of the ethanol to turn into ether instead of ethylene so maybe by raising the flame until the temperature reached 500 of the thermocouple the average in the pipe should be closer to 450. I also only put 309 grams of alcohol in my flask this time which was about 367 CC as opposed to the 500 I put in previously the bubbler still goes at a pretty steady rate after about 10 or 15 minutes but it's noticeably slower than before which is what I wanted here's the beach ball after one hour also there's noticeably less liquid in The Collector compared to the previous run after about two hours of running I went ahead and pumped what I had into the storage tank the pressure settled out between 150 and 155 PSI and let's call it about 153 that's a 73 PSI difference from the previous batch of ethylene or 4.97 atmospheres that was added that then comes out to 46.9 liters at standard temperature and pressure or 53.7 grams which comes out to 1.92 moles cool but what about the input we started with 309 grams of alcohol and ended with 129 a difference of 180 grams 127 grams of that should be ethanol while the rest is water that means we used 2.75 moles of ethanol to get 1.92 moles of ethylene that means the yield this time was 70 percent far from perfect but a dramatic improvement over last time my only concern is that the higher temperature might have caused a greater portion of the ethanol to decompose into hydrogen the only way to guarantee the purity of the ethylene would be to liquefy it at cryogenic temperature so that any hydrogen gas would separate out for now I guess I'll have to work with what I've got one really obvious difference this time was that there was a lot less of the mystery fluid in the collector this weighed in at 91 grams that still means there's about 35 grams of mass unaccounted for I'm assuming this is from a combination of leaks and line purges doing my crude density test again I found that this mixture was 0.81 grams per CC suggesting that The Ether concentration was even higher than before I must have made a mistake in my measurements though because when I tried to ignite this mixture it couldn't sustain combustion which suggests that The Ether concentration is much lower than the previous batch which ignited easily and burned for several minutes anyway I'm now the proud owner of about 123 grams of ethylene gas and I've managed to dodge the high costs and refrigerant handling license needed to buy it as r1150 in the next video I'll be using this ethylene in the second stage of my vapor compression refrigerator to hopefully reach below -100c thanks for watching and be sure to subscribe if you don't want to miss the next part of this project

Channel: Hyperspace Pirate

Views: 191,900

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Id: UKFEbYdKdJg

Length: 17min 33sec (1053 seconds)

Published: Fri Apr 21 2023