Description

Hydroquinone / 4-Methoxyphenol CAS 150-76-5

4-Methoxyphenol Usage

1. It is mainly used as polymerization inhibitors, ultraviolet inhibitors, dye intermediates for vinyl monomers, as well as for the synthesis of food fats and cosmetics antioxidant, BHA.

2. It is an important intermediate of fine chemical products such as medicine, perfume and pesticide.It can also be used as polymer inhibitor, anti-aging agent, plasticizer and so on.Mainly used to produce acrylonitrile, acrylic acid and its ester,methacrylic acid and its ester and other allyl monomers polymerization inhibitors.Its greatest advantage is that it can be directly involved in polymerization without removing p-hydroxyphenyl ether when used.It is also used as antiaging agent, plasticizer and food additive (BHA) synthesis.

3.Used as solvents. Acrylic acid and acrylonitrile monomer polymerization inhibitors.Ultraviolet inhibitors.Make antioxidants.Dye preparation.

4.Used as solvents. As a polymerization inhibitor for vinyl monomers;Ultraviolet inhibitors;Dye intermediates and the antioxidant BHA (3-tert-butyl -4-hydroxyphenyl ether) used for the synthesis of edible oils and cosmetics.Its biggest advantage is that the monomer added with MEHQ need not be removed when copolymerizing with other monomers, but can be directly copolymerized with ternary, and can also be used as anti-aging agent and antioxidant.

4-Methoxyphenol Packaging and Shipping

Packing: 25kg/carton drum

Delivery:by sea or by air

4-Methoxyphenol Storage

Stored in cool dry and ventilated warehouse away from oxidants.

Contact Us Now!

If you need price, please fill in your contact information in the form below, we will usually contact you within 24 hours. You could also email me info@longchangchemical.com during working hours ( 8:30 am to 6:00 pm UTC+8 Mon.~Sat. ) or use the website live chat to get prompt reply.

Isomerisation of dihydroxybenzene

Dihydroxybenzenes are a class of aromatic compounds having two hydroxyl groups (-OH) attached to the benzene ring. These molecules play important roles in areas such as pharmaceuticals, agrochemicals, materials science and natural product synthesis. For example, catechol (1,2-dihydroxybenzene) is used in bionic adhesives, corrosion inhibitors, and drug synthesis; resorcinol (1,3-dihydroxybenzene) is used as a preservative in the pharmaceutical industry and as a resin in the rubber industry; and phenylphenol (1,4-dihydroxybenzene) is used in a wide range of applications such as photography, cosmetics, and as a polymerisation inhibitor. The global annual demand for dihydroxybenzene exceeds 200,000 tonnes. However, traditional industrial production processes are complex, difficult to separate and less selective of target products. For example, the industrial route for the synthesis of catechol and hydroquinone is formed by hydroxylation of phenol with hydrogen peroxide catalysed by acid or zeolite catalysts (Figure 1). This process requires a high phenol/hydrogen peroxide ratio (~20) to avoid excessive over-oxidation of phenol. However, the dihydroxybenzene obtained by this process route is usually less selective and yields of hydroquinone are much higher than those of high value-added catechols (catechols). The main reasons for this are as follows: 1) Since phenol is easily over-oxidised to form acids and polymers, this leads to relatively low dihydroxybenzene selectivity. 2) The hydroxylation of phenol is less regioselective, and the product contains more hydroquinone than high value-added catechol. The key to solving these problems lies in finding a way to selectively convert dihydroxybenzene to another isomer, thereby addressing the challenges of product selectivity and overproduction. For example, the isomerisation of xylenes in ZSM-5 zeolites can be achieved by converting the lesser-used m- and o-xylenes to paraxylene to meet the demand for it as a polyester precursor. Herein, we report the isomerisation of dihydroxybenzene over Pt/ZSM-5 catalysts in a hydrogen atmosphere with water as solvent at 400 °C. The optimised catalyst enabled the isomerisation of hydroquinone to catechol with 74% selectivity and up to 50% yield. Mechanistic studies showed that the intermediate carbonaceous deposit (coke) plays a key role in the isomerisation reaction.

Isomerisation properties of dihydroxybenzenes

Isomerisation of dihydroxybenzenes has been carried out in a fixed bed reactor using H-ZSM-5 zeolites with and without Pt. Catechol, hydroquinone or resorcinol have been dissolved in water and fed to the catalyst layer in a hydrogen stream at 400 °C, after which the liquid product at the reactor outlet was analysed. Depending on the dihydroxybenzene reacted, the main products of the reaction were catechol and hydroquinone as isomerisation products and phenol as a dehydroxylation product (Fig. 2a, Fig. S1, SI). The activity of the catalyst was high in the initial stage, but gradually decreased with time due to the deactivation of the active sites (Fig. 2d, Fig. S2, SI). Analysis of the isomerisation of catechol on 0.2% Pt/ZSM-5(30) over time showed that the selectivity for phenol and hydroquinone was similar at 15% in the initial phase. The low selectivity of the liquid-phase product is due to the large formation of carbonaceous deposits on the catalyst surface as a reaction by-product, which prevents the selectivity in Fig. 2 from reaching 100%. It also explains the catalyst deactivation due to the deposition of carbonaceous material. The activity decreases rapidly during the reaction and reaches a stable catalytic performance after about 20 h. The catalytic performance of the catechols is not as good as that of the coke. The selectivity for hydroquinone increased with time to more than 50% due to the reduced condensation of catechol with coke. Pure ZSM-5 showed almost no isomerisation activity of catechol (Fig. 2b).The Pt-modified amorphous aluminosilicates provided only traces of hydroquinone, with phenol as the main product of the reaction, suggesting a key role for Pt in the hydrogenolysis of catechol to phenol. The low acidity of the amorphous aluminosilicates resulted in low isomerisation activity of the catalysts. Furthermore, the work focused on analysing the effect of metal and acid functionality on the catalytic performance of Pt/ZSM-5 in the reaction by varying the amount of Pt and the SiO2/Al2O3 ratio, respectively.

Carbonaceous polymer-assisted isomerisation mechanism

Isomerisation of dihydroxybenzene has been carried out in a fixed bed reactor using H-ZSM-5 zeolites with and without Pt. Catechol, hydroquinone or resorcinol have been dissolved in water and fed to the catalyst layer in a hydrogen stream at 400 °C, after which the liquid product at the reactor outlet was analysed. Depending on the dihydroxybenzene reacted, the main products of the reaction were catechol and hydroquinone as isomerisation products and phenol as a dehydroxylation product (Fig. 2a, Fig. S1, SI). The activity of the catalyst was high in the initial stage, but gradually decreased with time due to the deactivation of the active sites (Fig. 2d, Fig. S2, SI). Analysis of the isomerisation of catechol on 0.2% Pt/ZSM-5(30) over time showed a similar selectivity of 15% for phenol and hydroquinone in the initial phase. The low selectivity of the liquid-phase product is due to the large formation of carbonaceous deposits on the catalyst surface as a reaction by-product, which prevents the selectivity in Fig. 2 from reaching 100%. It also explains the catalyst deactivation due to the deposition of carbonaceous material. The activity decreases rapidly during the reaction and reaches a stable catalytic performance after about 20 h. The catalytic performance of the catechols is not as good as that of the coke. The selectivity for hydroquinone increased with time to more than 50% due to the reduced condensation of catechol with coke. Pure ZSM-5 showed almost no isomerisation activity of catechol (Fig. 2b).The Pt-modified amorphous aluminosilicates provided only traces of hydroquinone, with phenol as the main product of the reaction, suggesting a key role for Pt in the hydrogenolysis of catechol to phenol. The low acidity of the amorphous aluminosilicates resulted in low isomerisation activity of the catalysts. Furthermore, the work focused on analysing the effect of metal and acid functionality on the catalytic performance of Pt/ZSM-5 in the reaction by varying the amount of Pt and the SiO2/Al2O3 ratio, respectively. The fact that dihydroxybenzene undergoes significant condensation on the catalyst surface and produces carbonaceous deposits implies that isomerisation can take place via an intermolecular mechanism in which dihydroxybenzene intermediately polymerises and subsequently depolymerises and produces isomers. To test the hypothesis that the polymeric substances act as intermediates, we treated the washed deactivated catalysts at 400°C in a stream of water vapour and hydrogen. Surprisingly, in addition to catechol, a significant amount of hydroquinone was detected in the liquid sample, with a minor contribution from phenol (Fig. 3). The formation of the product stopped after 3 h of treatment. The catalyst after this treatment showed regeneration of catalytic activity for the second cycle (Fig. 3).

Insights and Perspectives

We present the direct isomerisation of dihydroxybenzene to interconvert phenol hydroxylation products (catechol and hydroquinone). The catalytic results showed that catechol and hydroquinone were successfully and reversibly converted over Pt/ZSM-5 catalyst. The selectivity of the reaction was as high as 74% and the yield was as high as 50%. The reaction was carried out in a hydrogen atmosphere in water vapour at 400°C via a hydrogen borrowing mechanism, with activity decreasing over time due to the formation of carbonaceous deposits, which are formed through the dehydrogenation of dihydroxybenzene to quinone and subsequent condensation at the acid sites. These carbonaceous deposits can be converted to isomerised dihydroxybenzene by treatment in hydrogen and water streams, confirming the role of these substances in the reaction. This mechanism provides new insights into the isomerisation process.