Table 4.

Use of co-solvents in heterogeneous alkaline catalysed methanolysis.

Co-solvent	Catalyst	Reactor type	Feedstock	Pre- treatment	Reaction conditions							Yield (wt.%d)	Ref.
					Co-solvent amount (wt.%a, v.%b, mol%c)	Catalyst amount (wt.%a)	MeOH/oil molar ratio	Time (min)	T (°C)	Stirrer (rpm)	Special conditions
Acetone	CaO (River snail shells)	STR	Palm oil	–	10 v.%	5	12:1	120	65	300	–	95.28	[72]
	CaO (scallop shells)	Flask	Beef tallow/ soybean oil (1:1)		36 v.%			150		-e		85.3	[11]
	Ca2Al2O5	STR	WCO	1	92 v.% (20 wt%)	1.2	6:1	25	55	N/S		97.98f	[73]
	Waste cement (calcined with K2CO3; 1:4)	Electrolysis cell	WCO	–	40 v.% (10 wt%)	12	7:1	120	25	300	30 V 2 wt% water	95.5	[74]
	Zeolite/chitosan/ KOH composite	Electrolysis cell	WCO		40 v.% (10 wt%)	1		180	RT	100	40 V 2 wt% water	93	[75]
Crude biodiesel	CaO	STR	Sunflower oil	–	34 vol% (10 wt%)	41.5 g/Ltotal volume	7.1:1	90	52	N/S	–	98.9	[77]
n-hexane	CaO	STR	Sunflower oil	–	110 v.% (20 wt%)	5.82	6:1	240	60	N/S	–	98.8	[60]
	CaO	Microreactor	WCO	3	58 v.%	8.17	51.3 v.%g (1:1.95)	10	62	-e		97.03	[78]
	Na/NaOH/ γ-Al2O3	STR	Soybean oil	–	55 v.%	2.17	9:1	120	60	300		94	[79]
2-propanol	CaO	Packed- microchannel	Palm oil	–	20 v.% (14.5 wt%)	30 mg	20:1	6.5	65	-e	–	98.3	[71]
1-propanol	CaO (River snail shells)	STR	Palm oil	–	10 v.%	5	12:1	120	65	300	–	95.69	[72]
								90				94.44
THF	CaO (waste crab shells)	STR	Fish oil	3	100 v.%	2.5	10:1	90	65	650	–	95	[80]
	CaO (River snail shells)	STR	Palm oil	–	10 v.%	5	12:1	120	65	300		96.68	[72]
	CaO	STR	Rapeseed oil		62 v.% (30 wt%)	2.5	12:1	360	60	600		97	[81]
	ZnO–Sr(NO3)2	STR	Soybean oil		91 v.% (44.5 wt%)	5	12:1	240	65	N/S		96.8f	[82]
	CaO	STR	Sunflower oil		82 v.% (20 wt%)	5.82	6:1	240	60	N/S		98.1	[60]
	Limescale	Microreactor	WCO	3	62 v.%	8.13	50.8 v.%g (1:1.97)	10	64.5	-e		95.21	[78]
	Zeolite/chitosan/ KOH composite	Electrolysis cell	WCO	–	35 v.% (10 wt%)	1	7:1	180	RT	100	40 V 2 wt% water	93	[75]

1: filtrated and dried.

2: filtration, drying and esterification.

3: esterification.

^aregarding the oil weight.

^bregarding the MeOH volume.

^cregarding mole MeOH.

^d%FAME yield.

^eno agitation.

^f% oil conversion.

^gregarding the oil volume.